JP2014149148A - Mercury removal system and mercury removal method from high-temperature exhaust gas containing mercury - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mercury removal system having high mercury removal performance and capable of reducing an operation cost, and to provide a mercury removal method from high-temperature exhaust gas containing mercury.SOLUTION: A mercury removal system for removing NOx and Hg included in high-temperature exhaust gas 12 from a boiler 11 includes: an NHCl supply unit 15A that sprays an NHCl solution 14 into a gas flue 13 of the boiler 11; a reduction denitrification device 16 that includes a denitrification catalyst which reduces NOx in the high-temperature exhaust gas 12 with NHand oxidizes Hg under coexistence of HCl; and a wet desulfurizer 20 that removes Hg oxidized in the reduction denitrification device 16 with a lime gypsum slurry 19.

Description

  The present invention relates to a mercury removal system for removing mercury contained in high-temperature exhaust gas discharged from a boiler or the like, and a mercury removal method for mercury-containing high-temperature exhaust gas.

The high-temperature exhaust gas generated when burning coal-fired exhaust gas or heavy oil may contain metal mercury (Hg ⁰ ) in addition to soot, sulfur oxide (SOx), and nitrogen oxide (NOx). In recent years, various devices have been devised for a method and apparatus for treating metallic mercury in combination with a denitration apparatus that reduces NOx and a wet desulfurization apparatus that uses an alkaline absorbent as an SOx absorbent.

As a method of treating metallic mercury in high-temperature exhaust gas, ammonium (NH ₃ ) is sprayed in the upstream process of high-temperature denitration equipment in the flue to reduce and denitrate, and chlorinating agents such as hydrochloric acid (HCl) are sprayed. A system has been proposed in which mercury is oxidized (chlorinated) on a denitration catalyst to form water-soluble mercury chloride, and then mercury is removed by a wet desulfurization apparatus installed on the downstream side (for example, Patent Document 1). reference.).

FIG. 11 shows a schematic diagram of an exhaust gas treatment system including a mercury removal system. As shown in FIG. 11, in the exhaust gas treatment system 100 including the mercury removal system, the high-temperature exhaust gas 102 containing nitrogen oxides and mercury discharged from the boiler 101 is supplied to the reductive denitration device 103 to reduce nitrogen oxides. To do. Thereafter, the high-temperature exhaust gas 102 is heat-exchanged with the air by the air heater 104 and is heat-recovered by the heat recovery device 105 and then supplied to the dust collector 106. After the sulfur oxide is removed by the desulfurizer 107, the high-temperature exhaust gas 102 is discharged as the purified gas 108, heated by the reheater 109, and then discharged from the chimney 110.
Further, there is an NH ₃ injection point 111 in the upstream of the reductive denitration apparatus 103, and nitrogen oxides are reduced by NH ₃ supplied from the NH ₃ tank 112.

  Further, the concentration of hydrochloric acid (HCl) used as a mercury chlorinating agent is measured by the hydrochloric acid concentration measuring means 113 installed on the upstream side of the desulfurization device 107 in the flue, and installed on the downstream side of the desulfurization device 107. The mercury concentration measuring means 114 measures the concentration of mercury (Hg). Based on the measured concentration values of hydrochloric acid and mercury (Hg), the arithmetic unit 117 calculates the initial concentration of the aqueous hydrogen chloride (HCl) solution 116 supplied from the hydrochloric acid solution tank 115. Based on the calculated initial concentration, the control means 118 controls the supply amount of vaporized hydrochloric acid (vaporized HCl) supplied from the hydrochloric acid solution tank 115 into the flue from the HCl injection point 119.

  Further, as a method of spraying HCl from the HCl injection site 119, a method of removing mercury by combining a hydrogen chloride (HCl) vaporizer has been proposed (for example, see Patent Document 2).

FIG. 12 shows a schematic view of a mercury chlorinating agent supply apparatus equipped with an HCl vaporizer. As shown in FIG. 12, in the mercury chlorinating agent supply device 120, a normal temperature aqueous HCl solution 115 stored in a hydrochloric acid solution tank 115 is supplied to the HCl vaporizer 122 side using a solution supply pump 121, and HCl and water vapor are supplied. The mixed gas 123 is supplied into the piping 127 through which the diluted heating air 126 supplied from the diluting means 125 is passed through the gas-liquid separator 124, and is supplied to the hydrogen chloride / water / air mixed gas 128 having a predetermined concentration. adjust. The temperature of the hydrogen chloride / water / air mixed gas 128 is usually 70 to 80 ° C. The obtained hydrogen chloride / water / air mixed gas 128 is dispersed in the flue 139 at a hydrochloric acid injection point 119 using a disperser 130 having the same configuration as that for NH ₃ spraying, and contains mercury. Spray uniformly into the hot exhaust gas 102.

Further, as a method for supplying HCl, a method for removing mercury by combining an ammonium chloride (NH ₄ Cl) solid sublimation apparatus has also been proposed (see, for example, Patent Document 3).

FIG. 13 shows a schematic view of an exhaust gas treatment apparatus using NH ₄ Cl solid. As shown in FIG. 13, in the exhaust gas treatment device 140, in the vicinity of the entrance of the economizer 144 provided in the flue 143 of the boiler facility through which the high temperature high temperature exhaust gas 142 on the upstream side of the denitration device 141 having the ammonia denitration catalyst passes. Ammonium chloride (NH ₄ Cl) stored in the silo 145 is added to the economizer bypass part 144a as a powder by the feeder 146 and the pulverizer 147, so that the high temperature (550 to 650) passing through the economizer bypass part 144a. NH ₄ Cl is sublimated by the high-temperature ambient temperature of the high-temperature exhaust gas 142), hydrogen chloride (HCl) and ammonium (NH ₃ ) are vaporized, supplied into the flue 143, and supplied to the high-temperature exhaust gas 142 in the economizer 144 Mixed HCl and NH ₃ .

Japanese Patent Laid-Open No. 10-230137 JP 2007-167743 A JP 2008-221087

  However, in the exhaust gas treatment system 100 including the mercury removal system shown in FIG. 11 and the mercury chlorinating agent supply device of the mercury removal system shown in FIG. 12, HCl is a dangerous substance, so it takes time and effort to transport and handle. There is a problem.

  Further, when the HCl vaporizer 122 is used as in the mercury chlorinating agent supply device of the mercury removal system shown in FIG. 12, steam 131 or the like is required as a heat source, and the equipment cost and maintenance cost such as the HCl vaporizer 122 are required. There is a problem that it takes.

In addition, in the case of using NH ₄ Cl as in the exhaust gas treatment apparatus shown in FIG. 13, since it is necessary to finely disperse the particle size, handling is difficult and control of the spray amount is not easy. There is a problem.

  In view of the above problems, an object of the present invention is to provide a mercury removal system and a mercury removal method for mercury-containing high-temperature exhaust gas that have high mercury removal performance and can keep operating costs low.

  A first invention of the present invention for solving the above-mentioned problems is a mercury removal system for removing nitrogen oxides and mercury contained in high-temperature exhaust gas from a boiler, which is vaporized in the boiler flue. A reduction oxidation aid supply unit that sprays a reduction oxidation aid that generates hydrogen chloride and ammonia in a liquid state, nitrogen oxide in the high-temperature exhaust gas is reduced with ammonia, and mercury is added in the presence of hydrogen chloride. The reductive denitration apparatus having a denitration catalyst to be oxidized, and the wet desulfurization apparatus for removing mercury oxidized in the reductive denitration apparatus using an alkali absorbing liquid, and the reductive oxidation sprayed in liquid form in the flue The mercury removal system is characterized in that the auxiliary agent is vaporized and decomposed into hydrogen chloride and ammonium.

  A second invention is the mercury removal system according to the first invention, wherein the reducing oxidation assistant is ammonium chloride.

  A third invention is the mercury removal system according to the first or second invention, wherein the concentration of the reducing oxidation assistant is 43 wt% or less.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the reduction oxidation aid supply unit supplies the reduction oxidation aid in a liquid state into the flue, and a reduction oxidation aid supply pipe; A blow pipe inserted into the flue so as to surround the reducing oxidation aid supply pipe and having an injection hole for injecting the air supplied therein into the flue, and a tip of the reduction oxidation auxiliary supply pipe And a spray nozzle for injecting the reducing oxidation aid, wherein the reducing oxidation assistant is sprayed into the flue along with the air.

  According to a fifth invention, in the fourth invention, the spraying means is a two-fluid nozzle for injecting the reducing oxidation aid and air for spraying the reducing oxidation aid. In the system.

  A sixth aspect of the invention is the reduction oxidation aid supply pipe according to any one of the first to third aspects, wherein the reduction oxidation aid supply unit supplies the reduction oxidation aid in liquid form into the flue; An air supply pipe, which is inserted in the flue so as to surround the reducing oxidation assistant supply pipe, and supplies air for spraying the reducing oxidation assistant into the flue, the reducing oxidation assistant supply pipe, and the air A two-fluid nozzle for injecting the reducing oxidation aid and the air, attached to the tip of a supply pipe, and spraying the reducing oxidation aid into the flue with the air In the mercury removal system.

  According to a seventh invention, in any one of the first to sixth inventions, an average droplet diameter of the reduction oxidation aid sprayed from the reduction oxidation aid supply unit is 1 nm or more and 100 μm or less. It is in the characteristic mercury removal system.

  An eighth invention is the mercury removal system according to any one of the first to seventh inventions, wherein the temperature of the high temperature exhaust gas is 320 ° C. or higher and 420 ° C. or lower.

  According to a ninth invention, in any one of the first to eighth inventions, a nitrogen oxide concentration meter for measuring the concentration of nitrogen oxides in the high-temperature exhaust gas is provided on the upstream side and the downstream side of the reductive denitration device. It is in the mercury removal system characterized by having.

  According to a tenth aspect of the present invention, in any one of the first to ninth aspects, an ammonia supply unit is provided between the reduction oxidation aid supply unit and the reductive denitration device, and supplies ammonia into the flue. It is in a mercury removal system characterized by that.

  An eleventh aspect of the present invention is the hydrogen chloride supply unit according to any one of the first to tenth aspects, wherein the hydrogen chloride supply unit is provided between the reduction oxidation aid supply unit and the reduction denitration device and supplies hydrogen chloride into the flue. In the mercury removal system characterized by having.

  A twelfth aspect of the invention is a mercury removal method for mercury-containing high-temperature exhaust gas that removes nitrogen oxides and mercury contained in the high-temperature exhaust gas from the boiler, and when vaporized in the boiler flue, hydrogen chloride and ammonia A reduction oxidation auxiliary agent supplying step of spraying the reduction oxidation auxiliary in a liquid state, and reduction denitration in which nitrogen oxides in the high temperature exhaust gas are reduced with ammonia by a denitration catalyst and mercury is oxidized in the presence of hydrogen chloride. A treatment step and a wet desulfurization step of removing mercury oxidized in the reductive denitration treatment step using an alkali absorbing liquid, vaporizing the reductive oxidation aid sprayed in liquid form in the flue, It is in the mercury removal method of the mercury-containing high-temperature exhaust gas characterized by decomposing into hydrogen and ammonium.

  A thirteenth invention is the mercury removal method for mercury-containing high-temperature exhaust gas according to the twelfth invention, wherein the reducing oxidation assistant is ammonium chloride.

  In a fourteenth aspect of the invention according to the twelfth or thirteenth aspect of the invention, the reducing oxidation aid supplying step sprays the reducing oxidation aid using a two-fluid nozzle. It is in.

  According to a fifteenth aspect, in any one of the twelfth to fourteenth aspects, the concentration of nitrogen oxide in the high-temperature exhaust gas is measured on the pre-process side and the post-process side of the reductive denitration treatment process. A mercury concentration measurement step for measuring the concentration of mercury in the high-temperature exhaust gas on the subsequent step side of the reduction denitration treatment step, and the measurement step in the high-temperature exhaust gas obtained by the nitrogen oxide concentration measurement step The reduction oxidation aid supplied in the reduction oxidation aid supply step based on one or both of the concentration of nitrogen oxides and the concentration of mercury in the high temperature exhaust gas obtained by the mercury concentration measurement step The method for removing mercury from mercury-containing high-temperature exhaust gas is characterized by adjusting the supply amount of the mercury.

  In a sixteenth aspect of the invention, in any one of the twelfth to fifteenth aspects, the ammonia supply step of supplying ammonia into the flue between the reduction oxidation aid supply step and the reduction denitration treatment step, the smoke It includes either or both of hydrogen chloride supply steps for supplying hydrogen chloride in the road, and is obtained by the nitrogen concentration concentration in the high-temperature exhaust gas obtained by the nitrogen oxide concentration measurement step and the mercury concentration measurement step. One or both of ammonia and hydrogen chloride supplied in one or both of the ammonia supply step and the hydrogen chloride supply step based on either or both of the concentration of mercury in the high temperature exhaust gas The method for removing mercury from mercury-containing high-temperature exhaust gas is characterized by adjusting the supply amount of the mercury.

  According to a seventeenth aspect of the invention, in any one of the twelfth to fifteenth aspects, the respective contents of nitrogen oxides and mercury in the high-temperature exhaust gas are determined from the coal properties of the coal used in the boiler, and the reduction oxidation The method of removing mercury from mercury-containing high-temperature exhaust gas is characterized in that the supply amount of the auxiliary agent is determined.

  In an eighteenth aspect based on the sixteenth aspect, the respective contents of nitrogen oxide and mercury in the high-temperature exhaust gas are determined from the coal properties of the coal used in the boiler, and the reducing oxidation aid, ammonia, chloride The present invention resides in a method for removing mercury from mercury-containing high-temperature exhaust gas, wherein the supply amount of hydrogen is determined.

  According to the present invention, the reduction oxidation aid is sprayed in liquid form upstream of the reduction denitration device in the flue, the sprayed non-gaseous reduction oxidation aid is vaporized, and decomposed into hydrogen chloride and ammonium, Since the mercury in the high temperature exhaust gas can be oxidized and NOx can be reduced, the operation cost can be kept low while maintaining the mercury removal performance in the wet desulfurization apparatus.

FIG. 1 is a schematic diagram illustrating a mercury removal system according to Embodiment 1 of the present invention. FIG. 2 is a graph showing the relationship between the temperature of NH ₄ Cl and the saturation dissolution temperature in water. FIG. 3 is a view showing the vicinity of the flue in which the NH ₄ Cl solution supply pipe and the air supply pipe are inserted. 4 is a partially enlarged cross-sectional view of FIG. FIG. 5 is a partially enlarged cross-sectional view of a blowing pipe using a normal injection nozzle. FIG. 6 is a diagram showing another spraying method of NH ₄ Cl solution using a two-fluid nozzle. FIG. 7 is a diagram illustrating another configuration of the mercury removal system according to the first embodiment. FIG. 8 is a diagram illustrating another configuration of the mercury removal system according to the first embodiment. FIG. 9 is a schematic diagram showing a mercury removal system according to Embodiment 2 of the present invention. FIG. 10 is a schematic diagram showing a mercury removal system according to Embodiment 3 of the present invention. FIG. 11 is a schematic view of a mercury chlorinating agent supply apparatus equipped with an HCl vaporizer. FIG. 12 is a diagram showing a schematic diagram of a mercury chlorinating agent supply device in the mercury removal system. FIG. 13 is a diagram showing a schematic view of an exhaust gas treatment apparatus using NH ₄ Cl solid.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

A mercury removal system according to Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a mercury removal system according to Embodiment 1 of the present invention.
As shown in FIG. 1, a mercury removal system 10A according to the present embodiment is a mercury removal system that removes nitrogen oxides (NOx) and mercury (Hg) contained in high-temperature exhaust gas 12 from a boiler 11, An ammonium chloride (NH ₄ Cl) supply unit 15A for spraying an ammonium chloride (NH ₄ Cl) solution 14 containing ammonium chloride (NH ₄ Cl) as a reducing oxidation aid in a liquid state in a flue 13 downstream of the boiler 11 The NOx in the high temperature exhaust gas 12 is reduced with ammonia (NH ₃ ), and the reduction denitration device 16 having a denitration catalyst that oxidizes Hg in the presence of hydrogen chloride (HCl) and the denitrated high temperature exhaust gas 12 are heat exchanged. Air heater (APH) 17, dust collector 18 for removing dust in denitrated high temperature exhaust gas 12, and Hg oxidized in reductive denitration device 16 are alkalinized. Those having a wet desulfurization system 20 be removed using lime gypsum slurry 19 as Osamueki.
In the mercury removal system 10 according to the present embodiment, NH ₄ Cl is used as the reduction oxidation aid, but the present invention is not limited to this, and the reduction oxidation aid is chlorinated when vaporized. Any material that generates hydrogen (HCl) and ammonia (NH ₃ ) can be used.
In the present invention, the reduction oxidation aid is an oxidation aid used for oxidizing and chlorinating mercury (Hg) in the presence of hydrogen chloride (HCl) and ammonia (NH ₃ ). What functions as a reducing agent.

<Preparation of NH ₄ Cl solution>
First, the NH ₄ Cl solution 14 having a predetermined concentration is prepared. The conveyed ammonium chloride (NH ₄ Cl) powder 21 is supplied to a silo 22 for temporarily storing it. The air 24 is supplied from the blower 23 to the NH ₄ Cl powder 21 in a silo 22, NH ₄ Cl powder 21 prevents drying in the silo 22, from sticking. NH ₄ Cl powder 21 in the silo 22 is supplied from the silo 22 to a predetermined amount every NH ₄ Cl powder delivery passageway 26 by the feeder 25, is fed to the NH ₄ Cl dissolution tank 27. Further, water 29 is supplied from the water supply tank 28 to the NH ₄ Cl dissolution tank 27. The NH ₄ Cl dissolution tank 27 is provided with a stirrer 30-1, and the NH ₄ Cl powder 21 supplied to the NH ₄ Cl dissolution tank 27 is dissolved in water 29 to generate an NH ₄ Cl solution 14 having a predetermined concentration. The concentration of the NH ₄ Cl solution 14 is made uniform by the stirrer 30-1. The supply amount of water 29 supplied from the water supply tank 28 is adjusted by the valve V1.

The concentration of the NH ₄ Cl solution 14 is greater than 0 wt% and preferably 43 wt% or less, more preferably 10 wt% or more and 23 wt% or less, further preferably 18 wt% or more and 23 wt% or less, and most preferably around 20 wt%. This is because the NH ₄ Cl powder 21 needs to be dissolved at least in water 29 at room temperature (for example, around 20 ° C.), and the NH ₄ Cl powder 21 needs to be equal to or lower than the saturated dissolution concentration of NH ₄ Cl in water.

FIG. 2 is a graph showing the relationship between the temperature of NH ₄ Cl and the saturation dissolution temperature in water. As shown in FIG. 2, when the temperature of the solution is around 0 ° C., the saturation concentration at which the NH ₄ Cl powder 21 can be dissolved in the water 29 is about 23 wt%, and when around 100 ° C., the NH ₄ Cl powder 21 is The saturation concentration that can be dissolved in the water 29 is about 43 wt%. Therefore, the concentration of the NH ₄ Cl solution 14 needs to be greater than 0 wt% and not greater than 43 wt%.

<Control of NH ₄ Cl solution concentration>
The NH ₄ Cl solution 14 in the NH ₄ Cl dissolution tank 27 is measured by an ammonium chloride (NH ₄ Cl) concentration meter 31, and the measured concentration value of the NH ₄ Cl solution 14 is transmitted to the arithmetic device 32. The The computing device 32 determines the supply amounts of the NH ₄ Cl powder 21 and the water 29 based on the concentration of the NH ₄ Cl solution 14. The arithmetic device 32 transmits control signals to the feeder 25 and the valve V1 to adjust the supply amounts of the NH ₄ Cl powder 21 and the water 29, respectively. As described above, the concentration of the NH ₄ Cl solution 14 in the NH ₄ Cl dissolution tank 27 is adjusted to be in the range of more than 0 wt% and 43 wt% or less.

In the mercury removal system 10A according to this embodiment, NH ₄ Cl supply unit 15A includes a solution _of NH ₄ Cl 14 NH ₄ supplies the flue 13 in liquid form Cl solution supply pipe 33, flue 13 A blow pipe 36 (see FIGS. 3 and 4) having an injection hole 35 (see FIG. 4) inserted into the NH ₄ Cl solution supply pipe 33 so as to inject the air 34 supplied therein into the flue 13. ) And a two-fluid nozzle 37 that is attached to the tip of the NH ₄ Cl solution supply pipe 33 and injects the NH ₄ Cl solution 14. The NH ₄ Cl supply unit 15A is connected to the two-fluid nozzle 37, and is connected to the air supply pipe 39A for supplying the air 38 for compressing and spraying the NH ₄ Cl solution 14 and the blowing pipe 36 (FIG. 3). And an air supply pipe 40 that supplies air 34 for compressing and spraying the NH ₄ Cl solution 14 into the blowing pipe 36. In FIG. 1, the air supply pipe 40 is inserted into the flue 13 but is actually connected to the blow pipe 36 (see FIG. 3).

FIG. 3 is a view showing the vicinity of the flue into which the NH ₄ Cl solution supply pipe and the air supply pipe are inserted, and FIG. 4 is a partially enlarged sectional view of FIG. As shown in FIG. 3, the blowing pipe 36 is inserted into the flue 13 so as to surround the NH ₄ Cl solution supply pipe 33 and the air supply pipe 39 </ b> A. Further, as shown in FIG. 4, the NH ₄ Cl solution supply pipe 33 is provided adjacent to the air supply pipe 39 </ b> A in the blowing pipe 36. The two-fluid nozzle 37 is provided in the injection hole 35 on the wall surface of the blowing pipe 36 and is connected to the NH ₄ Cl solution supply pipe 33 and the air supply pipe 39A. The NH ₄ Cl solution 14 ejected from the two-fluid nozzle 37 is sprayed by air 38, and the NH ₄ Cl solution 14 is further sprayed into the flue 13 along with the air 34 ejected from the ejection hole 35.

Solution _of NH ₄ Cl in NH ₄ Cl dissolution tank 27 14 are fed to the NH ₄ Cl dissolved feed tank 41, once storing the solution _of NH ₄ Cl in NH ₄ Cl dissolved tank 27. Moreover, to keep NH ₄ the NH ₄ Cl concentration of NH ₄ Cl solution NH ₄ Cl dissolved tank 27 with stirrer 30-2 provided for the Cl dissolution tank 27 uniform. Thereafter, the NH ₄ Cl solution 14 in the NH ₄ Cl dissolution feed tank 41 is fed to the two-fluid nozzle 37 through the NH ₄ Cl solution supply pipe 33 by the feed pump 42. The flow rate of the NH ₄ Cl solution 14 in the NH ₄ Cl solution supply pipe 33 is measured by a flow meter 43-1, and the supply amount of the NH ₄ Cl solution 14 is adjusted by a valve V2. The NH ₄ Cl dissolution feed tank 41 is not essential and may not be provided.

The air 38 is supplied from the air supply unit 46 to the two-fluid nozzle 37 via the air supply pipe 39 </ b> A, and is used as compression air when the NH ₄ Cl solution 14 is sprayed from the two-fluid nozzle 37. Thereby, the NH ₄ Cl solution 14 ejected from the two-fluid nozzle 37 can be sprayed as fine droplets. As shown in FIG. 1, the flow rate of the air 38 supplied from the air supply pipe 39A is measured by the flow meter 43-2 and adjusted by the valve V3. The size of the droplets of the NH ₄ Cl solution 14 sprayed from the two-fluid nozzle 37 can be adjusted by the flow rate of the air 38 supplied from the air supply pipe 39A.

Moreover, it is preferable that the flow rate of the air 38 injected from the two-fluid nozzle 37 is, for example, an air-water ratio of 100 to 10,000 (volume ratio). This is because the NH ₄ Cl solution 14 ejected from the two-fluid nozzle 37 is sprayed into the flue 13 as fine droplets.

The air 34 is supplied from the air supply unit 46 to the blowing pipe 36 through the air supply pipe 40 and compressed air for dispersing the droplets of the NH ₄ Cl solution 14 sprayed from the two-fluid nozzle 37. Used as As shown in FIG. 1, the flow rate of the air 34 supplied from the air supply unit 46 is measured by a flow meter 43-3 and adjusted by a valve V4. As shown in FIG. 4, the air 34 is injected from a gap 44 between the injection hole 35 of the blowing pipe 36 and the two-fluid nozzle 37. For this reason, by injecting the air 34 from the gap 44, the droplets of the NH ₄ Cl solution 14 sprayed from the two-fluid nozzle 37 can be further dispersed in the flue 13.

Further, the air 34 injected from the injection hole 35 prevents the NH ₄ Cl solution 14 injected from the two-fluid nozzle 37 from adhering to the blowing pipe 36 and suppresses the temperature rise in the blowing pipe 36. And used to prevent boiling of the NH ₄ Cl solution 14 and precipitation of ammonium chloride particles.

Further, since the air 34 flows between the blowing pipe 36 and the NH ₄ Cl solution supply pipe 33, it works as air for cooling the NH ₄ Cl solution 14, and the heat of the high temperature exhaust gas 12 in the flue 13 blows. Transmission from the outside of the inlet tube 36 into the NH ₄ Cl solution supply tube 33 can be prevented. For this reason, it is possible to prevent the NH ₄ Cl solution 14 from boiling in the blowing pipe 36 by preventing the temperature rise in the blowing pipe 36 and preventing the NH ₄ Cl solution 14 from being heated. The liquid state can be maintained until immediately before the NH ₄ Cl solution 14 is jetted. Moreover, corrosion of the two-fluid nozzle 37 can also be prevented.

Moreover, since the temperature rise in the blowing pipe 36 can be prevented, a metal material can be used as a material constituting the NH ₄ Cl solution supply pipe 33 and the air supply pipe 39A. As materials constituting the NH ₄ Cl solution supply pipe 33 and the air supply pipe 39A, for example, the NH ₄ Cl solution supply pipe 33 includes a corrosion resistant metal such as a nickel-based heat and corrosion resistant alloy such as Hastelloy C, a resin lining steel pipe (low temperature portion). ). Examples of the air supply pipe 39A include carbon steel and stainless steel. The material constituting the NH ₄ Cl solution supply pipe 33 and the air supply pipe 39A is not particularly limited to a metal material.

Further, since the NH ₄ Cl solution 14 can be supplied from the NH ₄ Cl dissolution feed tank 41 into the flue 13 at room temperature, the material constituting the NH ₄ Cl solution supply pipe 33 and the blowing pipe 36 is inexpensive. Resins or resin-lined piping can also be used.

Further, in the mercury removal system 10A according to the present embodiment, the two-fluid nozzle 37 is provided with, for example, several to several tens or less nozzles in the flue 13. Conventionally, for example, hundreds to thousands of NH ₃ grids that are normally used have been provided in the flue 13. On the other hand, the two-fluid nozzle 37 has only a few to several tens or less in the flue 13 and is fixed by the flange portions 51 and 53, so that the nozzle can be easily replaced. . In FIG. 3, two two-fluid nozzles 37 are provided, but the present invention is not limited to this, and a plurality of two-fluid nozzles 37 may be provided as appropriate according to the installation area in the flue 13. Good.

  As shown in FIG. 3, the blowing pipe 36 is outside the flue 13, and a flange portion 51 is provided on the outer periphery of the blowing pipe 36, and the flange portion 51 is an end of the opening 52 of the flue 13. It is formed so as to correspond to the flange portion 53 provided in the portion 52a. By connecting the flange portion 51 of the blowing pipe 36 to the flange portion 53 provided in the flue 13, the blowing pipe 36 is attached to the flue 13. For example, the flange portion 51 of the blowing pipe 36 and the flange portion 53 of the flue 13 may be provided with a plurality of holes on the outer periphery of the flange portion 51 and the flange portion 53 and fixed with bolts. By making the flange portion 51 and the flange portion 53 detachable, the blowing pipe 36 can be easily inserted into and removed from the flue 13, so that the maintenance inside the blowing pipe 36 and the flue 13 is easily performed. be able to.

Further, although the two-fluid nozzle 37 is used for spraying the NH ₄ Cl solution 14, the present invention is not limited to this, and a normal spray nozzle for spraying liquid may be used.
FIG. 5 is a partially enlarged cross-sectional view of a blowing pipe using a normal injection nozzle. As shown in FIG. 5, when it is not necessary to adjust the droplet size of the solution _of NH ₄ Cl 14, is injected a solution _of NH ₄ Cl 14 from the injection nozzle 54, the air 45 injected from the injection hole 47 You may make it spray in the flue 13 with it.

Further, the NH ₄ Cl solution supply pipe 33 and the air supply pipe 39A are provided in the blowing pipe 36, and the NH ₄ Cl solution 14 is sprayed into the flue 13 from the two-fluid nozzle 37. It is not limited to this. If the NH ₄ Cl solution 14 in the NH ₄ Cl solution supply pipe 33 can be prevented from being heated, the NH ₄ Cl solution supply pipe 33 and the air supply pipe 39A are connected to the two-fluid nozzle 37 without using the blowing pipe 36. And the NH ₄ Cl solution 14 may be sprayed into the flue 13.

FIG. 6 shows another spraying method of NH ₄ Cl solution using a two-fluid nozzle. As shown in FIG. 6, the NH ₄ Cl supply unit 15B has a double tube structure in which the NH ₄ Cl solution supply pipe 33 is an inner pipe and the air supply pipe 39B is an outer pipe, and the NH ₄ Cl solution supply pipe 33 and The air supply pipe 39B is connected to the two-fluid nozzle 37.
That is, as shown in FIG. 6, NH ₄ Cl supply unit 15B, a solution _of NH ₄ Cl 14 NH ₄ supplies the flue 13 Cl solution supply pipe 33, solution _of NH ₄ Cl supply tube into the flue 13 33 is inserted so as to surround the air supply pipe 55 for supplying the air 38 for spraying the NH ₄ Cl solution 14 into the flue 13, and attached to the tips of the NH ₄ Cl solution supply pipe 33 and the air supply pipe 39B. And a two-fluid nozzle 37 for injecting the NH ₄ Cl solution 14 and the air 38. By so by the air supply pipe 39B to surround the solution _of NH ₄ Cl supply tube 33, solution _of NH ₄ Cl 14 solution _of NH ₄ Cl in the supply pipe 33 by the air 38 supplied into the air supply pipe 39B flue 13 The NH ₄ Cl solution 14 can be sprayed into the flue 13 together with the air 38 while being prevented from being heated by the high-temperature exhaust gas 12 therein. Further, since the NH ₄ Cl supply unit 15B is not provided with the blowing pipe 36 as shown in FIGS. 3 to 5, the NH ₄ Cl solution supply pipe 33, the air supply pipe 39B, and the two-fluid nozzle are provided in the flue 13. The attachment of 37 can be simplified. Further, since there is no blowing pipe 36, the NH ₄ Cl solution supply pipe 33, the air supply pipe 39B, and the two-fluid nozzle 37 can be easily replaced.

  Further, the air 38 is supplied from the air supply unit 45 and the air 34 is supplied from the air supply unit 46, and the air is supplied from separate supply sources. However, the present invention is not limited to this. Instead, air may be supplied from the same supply source. That is, the air 34 may be air supplied from the air supply unit 45. The air 38 may be air supplied from the air supply unit 46.

Moreover, the temperature of the high temperature exhaust gas 12 in the flue 13 is 320 degreeC or more and 420 degrees C or less, for example, and is high temperature. The NH ₄ Cl solution supply pipe 33 is provided in the blowing pipe 36, and air 34 is used for cooling the NH ₄ Cl solution 14. For this reason, the NH ₄ Cl solution 14 is maintained in a liquid state until immediately before being jetted from the two-fluid nozzle 37, and the NH ₄ Cl solution 14 is sprayed from the two-fluid nozzle 37 in the form of droplets, so that the high-temperature exhaust gas 12 has a high temperature. The droplets of the NH ₄ Cl solution 14 sprayed according to the atmospheric temperature can be vaporized.

In other words, the sprayed droplets of the NH ₄ Cl solution 14 temporarily generate fine NH ₄ Cl solid particles by evaporating due to the high temperature atmosphere temperature of the high temperature exhaust gas 12, and as shown in the following formula (1), HCl It decomposes into NH ₃ and sublimates. Therefore, HCl and NH ₃ can be generated from the droplets of the NH ₄ Cl solution 14 sprayed from the two-fluid nozzle 37 and supplied into the flue 13.
NH ₄ Cl → NH ₃ + HCl (1)

  Moreover, although the temperature of the high temperature exhaust gas 12 in the flue 13 also depends on the combustion conditions of the boiler 11, it is preferably 320 ° C or higher and 420 ° C or lower, more preferably 320 ° C or higher and 380 ° C or lower, and 350 ° C or higher and 380 ° C or lower. Is more preferable. This is because the NOx denitration reaction and the Hg oxidation reaction can occur simultaneously on the denitration catalyst.

The NH ₃ concentration and the HCl concentration of the high temperature exhaust gas 12 in the flue 13 are the ratio of the number of moles of NH _{3 to} the number of moles of NO x of the high temperature exhaust gas 12 (NH ₃ / NOx mole) with respect to the NOx concentration of the high temperature exhaust gas 12. Ratio) is set to a value of 1 or less according to the required denitration performance.

Although depending on the NOx concentration of the high-temperature exhaust gas 12, the NH ₄ Cl solution 14 may be sprayed so that the NH ₃ concentration and the HCl concentration are several tens to several hundred ppm, preferably several tens to 200 ppm. This is because NH ₃ and NOx react with each other at a molar ratio of 1: 1, so that when NH ₃ is supplied in excess, a surplus of NH ₃ remains after the reaction. From this NH _3, acidic sulfate is generated from the components in the high-temperature exhaust gas 12, and damage due to corrosion in the flue 13, air heater 17, dust collector 18, etc., blockage due to ash adhesion, or from the damaged flue 13 This is to prevent the high temperature exhaust gas 12 from leaking.
The Hg concentration of the high-temperature exhaust gas 12 is preferably 0.1 μg / m ³ N or more and several tens of μg / m ³ N or less, and the molar ratio with respect to the HCl concentration in the high-temperature exhaust gas 12 is preferably 1/1000 or less.

  Further, the hole diameter of the two-fluid nozzle 37 is preferably 0.01 mm or more and 10 mm or less, and more preferably 0.1 mm or more and 5 mm or less.

The droplet diameter of the NH ₄ Cl solution 14 sprayed from the two-fluid nozzle 37 is preferably a fine droplet having an average of 1 nm and 100 μm or less. By generating fine droplets with an average of 1 nm and 100 μm or less on average, NH ₄ Cl solid particles generated from the droplets of the sprayed NH ₄ Cl solution 14 are converted into NH ₃ and HCl in the high-temperature exhaust gas 12 with a short residence time. Can be decomposed and sublimated. Thereby, since it is not necessary to heat the NH ₄ Cl solution 14 in advance, lowering and corrosion of the flue 13 and the two-fluid nozzle 37 can be prevented.

Therefore, according to the mercury removal system 10A according to the present embodiment, the NH ₄ Cl solution 14 in a liquid state is sprayed from the two-fluid nozzle 37, so that the NH ₄ Cl solution 14 is HCl, It can be decomposed into NH ₃ and supplied into the flue 13. For this reason, the hydrogen chloride vaporizer 122, the spray grid, the hydrochloric acid solution tank 116, etc. of the mercury chlorinating agent supply device in the conventional mercury removal system as shown in FIG. 12 can be omitted.

Moreover, NH ₄ Cl powder 21 used during the adjustment of the solution _of NH ₄ Cl 14 for a neutral salt, to handle it is easy, can be cheap and readily available to be used in fertilizer. Further, since NH ₃ can be generated from the NH ₄ Cl solution 14, the amount of NH ₃ used can be reduced. In addition, since HCl is a hazardous material, handling costs such as transportation costs, legal approval costs, equipment costs for safety management measures, etc. will be costly, but NH ₄ Cl powder 21 will greatly reduce the costs required for handling. Can do.

Further, since the NH ₄ Cl solution 14 is dissolved in water and vaporizes to NH ₃ and HCl, solid particles of NH ₄ Cl do not remain, and the denitration catalyst provided on the flue 13 or the downstream side is not used. Accumulation of NH ₄ Cl solid particles and deterioration of the denitration catalyst can be prevented.

Further, since the NH ₄ Cl solution 14 uses the high temperature exhaust gas 12 as a heat source and is vaporized into NH ₃ and HCl, a sublimation facility that becomes a new heat source such as steam to vaporize the NH ₄ Cl solution 14. Can be omitted, and the residence time required for the NH ₄ Cl solution 14 to vaporize in the high temperature exhaust gas 12 can be shortened.

Further, the flow rate at which the NH ₄ Cl solution 14 is sprayed from the two-fluid nozzle 37 is only a few t / h while the high-temperature exhaust gas amount is 1,500,000 m ³ N / h. The decrease in the gas temperature of 12 can be almost eliminated, for example, several degrees C. or less. Therefore, it is possible to prevent the SO ₃ in the high temperature exhaust gas 12 from condensing, and to prevent the ash in the high temperature exhaust gas 12 from accumulating and adhering to the flue 13 or the like.

Also, as in the conventional high-temperature exhaust gas treatment apparatus shown in FIG. 13, by grinding of NH ₄ Cl solid compared to spraying, the mercury removal system 10A according to the present embodiment, such as solution _of NH ₄ Cl 14 In the case of a liquid, the liquid particles of the NH ₄ Cl solution 14 can be easily miniaturized, and solid particles having a sprayed fine droplet diameter or less can be generated. Therefore, the time required for the decomposition of the NH ₄ Cl solution 14 can be reduced. It can be greatly shortened.

Further, since the NH ₄ Cl powder 21 is used as the NH ₄ Cl solution 14, it can be stored in a pellet form without being finely pulverized as in the prior art, and can be used as needed.

In addition, supplying NH ₄ Cl alone is less expensive than purchasing NH ₃ and HCl separately as in the conventional case, so that the operating cost of the apparatus can be suppressed and the equipment cost required for installation is also reduced. It can be easily recovered.

Moreover, NH ₄ Cl NH ₄ Cl powder 21 based on the concentration of the solution 14, it is possible to adjust the supply amount of each of the water 29, NOx in the hot flue gas 12, NH ₄ Cl solution 14 in accordance with the concentration of Hg Can be adjusted.

Further, HCl and NH ₃ generated from the droplets of the NH ₄ Cl solution 14 are sent to the reductive denitration device 16 along with the high temperature exhaust gas 12 as shown in FIG. NH ₃ produced by the decomposition of NH ₄ Cl is used for reducing denitration of NOx by the reducing denitration device 16, and HCl is used for oxidizing Hg to remove NOx and Hg from the high temperature exhaust gas 12.
That is, the reduction denitration device 16 is filled with a denitration catalyst. On the denitration catalyst, NH ₃ reductively denitrates NOx as in the following formula (2), and HCl oxidizes Hg with mercury as in the following formula (3).
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (2)
Hg + 1 / 2O ₂ + 2HCl → HgCl ₂ + H ₂ O (3)

  Further, as shown in FIG. 1, the high temperature exhaust gas 12 is subjected to wet desulfurization after passing through an air heater 17 and a dust collector 18 after reduction of NOx and oxidation of Hg in the high temperature exhaust gas 12 in the reductive denitration device 16. To the device 20. Further, a heat recovery device may be provided between the air heater 17 and the dust collector 18. HgCl in the high temperature exhaust gas 12 is absorbed in the lime gypsum slurry 19 used as an alkali absorbing liquid in the wet desulfurization apparatus 20, separated and removed from the high temperature exhaust gas 12, and the high temperature exhaust gas 12 is purified. The purified high temperature exhaust gas is discharged from the chimney 57 as the purified gas 56. Moreover, although the lime gypsum slurry 19 is used as an alkali absorption liquid, as long as it can absorb HgCl in the high temperature exhaust gas 12, another solution can also be used as an alkali absorption liquid.

Further, a mixer for mixing NH ₃ and HCl may be provided downstream of the two-fluid nozzle 37 and upstream of the reductive denitration device 16. As a mixer, a static mixer etc. can be used, for example. When the degree of dispersion of NH ₃ and HCl generated by vaporization of the NH ₄ Cl solution 14 sprayed from the two-fluid nozzle 37 is insufficient, high-temperature exhaust gas is produced by the mixer provided upstream of the reductive denitration device 16. The degree of dispersion of NH ₃ and HCl in 12 can be made uniform.

Further, a flow meter 61 for measuring the flow rate of the NH ₄ Cl solution 14 sprayed from the two-fluid nozzle 37 may be provided on the downstream side of the two-fluid nozzle 37. Thereby, the flow rate of the NH ₄ Cl solution 14 sprayed from the two-fluid nozzle 37 is measured. Further, the flow rate of the high temperature exhaust gas 12 in the flue 13 can be measured.

Further, NOx concentration meters 62-1 and 62-2 are provided on the inlet side and the outlet side of the reductive denitration device 16. The reduction ratio of NOx in the reduction denitration device 16 can be confirmed from the value of the NOx concentration in the high temperature exhaust gas 12 measured by the NOx concentration meters 62-1 and 62-2. Therefore, by controlling the NH ₄ Cl concentration and the supply flow rate of the NH ₄ Cl solution 14 from the value of the NOx concentration in the high temperature exhaust gas 12 measured by the NOx concentration meters 62-1 and 62-2, the two-fluid nozzle 37 The NH ₄ Cl concentration of the NH ₄ Cl solution 14 to be sprayed can satisfy a predetermined denitration performance.

  The mercury (Hg) concentration meter 63 that measures the Hg content in the processing gas discharged from the reductive denitration device 16 and the high-temperature exhaust gas 12 discharged from the dust collector 18 and supplied to the wet desulfurization device 20 And a hydrogen chloride (HCl) concentration meter 64 for measuring the HCl content. The Hg concentration meter 63 may be provided on the downstream side of the wet desulfurization device 20 to measure the mercury (Hg) content in the process gas discharged from the wet desulfurization device 20.

From the values of the HCl concentration and the Hg concentration in the high temperature exhaust gas 12 measured by the Hg concentration meter 63 and the HCl concentration meter 64, the oxidation rate of Hg in the reducing denitration device 16 can be confirmed. The NH ₄ Cl solution 14 is sprayed from the two-fluid nozzle 37 by controlling the NH ₄ Cl concentration and supply flow rate of the NH ₄ Cl solution 14 from the Hg concentration value in the high temperature exhaust gas 12 measured by the Hg concentration meter 63 and the HCl concentration meter 64. NH ₄ NH ₄ Cl concentration of Cl solution 14, the supply flow rate satisfies a predetermined denitration performance so as to maintain the oxidation performance of Hg.

In addition, the amount of NH ₄ Cl solution 14 added can be controlled by controlling the mercury oxidation rate (Hg ²⁺ / Hg ^T ) at 90% or more at the outlet of the reductive denitration device 16 or the mercury oxide concentration (Hg ²⁺ ) to 1 μg / Nm ³ or less. Hg ^T refers to the total mercury concentration and is represented by the sum of the metal mercury concentration (Hg ⁰ ) and the mercury oxide concentration (Hg ²⁺ ) as shown in the following formula (4).
Hg ^T = Hg ⁰ + Hg ²⁺ (4)

Further, the contents of NOx and Hg contained in the high-temperature exhaust gas 12 may be obtained from the coal properties of the coal used in the boiler 11 to determine the supply amount of the NH ₄ Cl solution 14. That is, the contents of NOx and Hg contained in the high temperature exhaust gas 12 are determined by burning the coal properties in the boiler 11. The maximum amount of NOx and Hg contained in the high temperature exhaust gas 12 can be obtained from the combustion amount of the boiler 11 by maximizing the combustion of coal in the boiler 11. Therefore, the respective contents of NOx and Hg contained in the high-temperature exhaust gas 12 can be obtained from the coal properties of the coal used in the boiler 11, and the supply amount of the NH ₄ Cl solution 14 can be determined.

Further, as will be described later, when facilities for supplying NH ₃ and HCl are provided in the flue 13, NOx, Hg, and HCl contained in the high-temperature exhaust gas 12 from the coal properties of the coal used in the boiler 11. It is also possible to determine the supply amount of each of the NH ₄ Cl solution 14, NH ₃ , and HCl.

<Configuration of mercury removal system equipped with facilities for supplying NH ₃ and HCl>
Moreover, FIG. 7 is a figure which shows the other structure of the mercury removal system which concerns on a present Example.
As shown in FIG. 7, the mercury removal system 10A according to the present embodiment, the NH ₃ supply unit 71 for supplying NH ₃ to the flue 13 between the NH ₄ Cl supply unit 15A and the reducing denitration apparatus 16, You may make it provide the HCl supply part 72 which supplies HCl in the flue 13. FIG. When the concentration balance of NOx and Hg in the high-temperature exhaust gas 12 discharged from the combustion equipment such as the boiler 11 is different from usual, the required amount of HCl or NH ₃ is adjusted and supplied into the flue 13 can do.

Also, if having a NH ₃ supplying unit 71 for spraying the NH ₃ into the flue 13, the supply amount of nitrogen oxides of the NH ₃ supplied from the NH ₃ supply unit 71 (NOx) concentration meter 62-1 and 62-2 Control using the value of.

Further, when the NH ₃ supply unit 71 is, for example, an existing facility in the flue 13 or the like, if the required HCl amount is less than the required NH ₃ amount, the NH ₄ Cl solution 14 is supplied up to the required HCl amount. If the amount of HCl exceeds the required amount, NH ₃ is added.

NH ₃ concentration, HCl concentration in the flue 13 is provided with NH ₃ to be dissociated from the solution _of NH ₄ Cl 14, together with NH ₃ to be added, in the same manner as described above, NH ₃ / NOx molar ratio required denitration performance Control is performed so that the value is 1 or less.

Further, the Hg concentration meter 63 and the HCl concentration meter 64 installed in the downstream of the reductive denitration device 16 are used to measure the Hg concentration and the HCl concentration in the high temperature exhaust gas 12 to confirm the oxidation rate of Hg in the reductive denitration device 16. The supply amount of HCl supplied by the HCl supply unit 72 is also controlled using the values of the Hg concentration meter 63 and the HCl concentration meter 64.
The amount of HCl added is the mercury oxidation rate (Hg) at the outlet of the reductive denitration device 16 in the same manner as described above by combining HCl dissociated from the NH ₄ Cl solution 14 and HCl added from the HCl supply unit 72. ^{2 +} / Hg ^T ) is 90% or more, or the mercury oxide concentration (Hg ²⁺ ) is 1 μg / Nm ³ or less.

<When NOx and Hg concentrations are different>
Further, when the balance of NOx and Hg concentration in the high temperature exhaust gas 12 discharged from the combustion equipment such as the boiler 11 is different from usual, HCl or NH in the flue 13 is corresponding to this. _This can be done by supplying the required amount of ₃ .
That is, when the HCl concentration required for oxidizing Hg is different from the NH ₃ concentration required for reducing NOx, either one of HCl or NH ₃ is supplied.

For example, if the amount of HCl required to oxidize Hg is greater than the amount of NH ₃ required to reduce NOx, the HCl is insufficient. In this case, as shown in FIG. 7, HCl is supplied from the HCl supply unit 72 into the flue 13 and the NH ₄ Cl solution 14 is sprayed from the two-fluid nozzle 37.

Further, when the amount of HCl required for oxidizing Hg is less than the amount of NH ₃ required for reducing NOx, NH ₃ is insufficient. In this case, as shown in FIG. 7 supplies the NH ₃ from the NH ₃ supply unit 71 to the flue 13, so as to spray the solution _of NH ₄ Cl 14 from the two-fluid nozzle 37. Further, urea ((H ₂ N) ₂ C═O) may be sprayed instead of supplying NH ₃ .

Position supplies HCl and from HCl supply unit 72, a position for supplying the NH ₃ from the NH ₃ supply unit 71, but the order of the position of the two-fluid nozzle 37 for spraying a solution _of NH ₄ Cl 14 can either, NH ₄ The position where the Cl solution 14 is sprayed is preferably upstream of the position where NH ₃ and HCl are supplied. This is because the NH ₄ Cl solution 14 takes longer to evaporate and vaporize than NH ₃ and HCl.

Therefore, for example, when the HCl and NH ₄ Cl solution 14 is supplied into the flue 13, the NH ₄ Cl solution 14 is sprayed from the upstream side by the two-fluid nozzle 37, and then HCl is sprayed from the HCl supply unit 71. preferable.

Spraying or, when supplying NH _3, solution _of NH ₄ Cl 14 to the flue 13, after supplying the solution _of NH ₄ Cl 14 from the upstream side in the two-fluid nozzle 37, the NH ₃ or urea from NH ₃ supply unit 71 It is preferable to do this.

Or, HCl, when supplying NH ₃ into the flue 13, after supplying the HCl from the HCl supply unit 72 from the upstream side, preferably sprayed NH ₃ or urea from NH ₃ supply unit 71.

Thereby, in the mercury removal system 10A according to the present embodiment as shown in FIG. 7, since NH ₃ and HCl are separately supplied, fluctuations in the NOx or Hg concentration in the high temperature exhaust gas 12 may occur. Appropriate response is possible even in cases.

In the mercury removal system 10A according to the present embodiment, NH ₄ Cl is used as a reduction oxidation aid, but ammonium bromide (NH ₄ Br) other than NH ₄ Cl, ammonium iodide (NH ₄ I). ) Or the like may be used as a reduction oxidation aid, and a solution dissolved in water may be used.

Further, in the mercury removal system 10A according to the present embodiment, either or both of a solution containing a reducing agent and a solution containing a mercury chlorinating agent may be mixed with the NH ₄ Cl solution 14 and used. . A mixture of an NH ₄ Cl solution 14, an ammonium (NH ₃ ) solution in which ammonia (NH ₃ ) is dissolved as a reducing agent, and a hydrogen chloride (HCl) solution in which hydrogen chloride (HCl) is dissolved as a mercury chlorinating agent A configuration using the liquid is shown in FIG.

As shown in FIG. 8, the mercury removal system 10 </ b> A according to the present embodiment uses a two-fluid nozzle 37 to add a mixed solution 83 obtained by mixing an NH ₄ Cl solution 14, an NH ₃ solution 81, and an HCl solution 82 to the flue 13. It is intended to spray inside. NH ₄ and Cl dissolution tank 27 NH ₄ Cl solution 14 in ammonia (NH ₃₎ dissolved and NH ₃ solution 81 in the tank 84, mixing tank and a HCl solution 82 in the hydrogen chloride (HCl) dissolution tank 85 86 Are mixed in the mixed solution tank 86. The obtained mixed solution 83 is fed to the two-fluid nozzle 37 and sprayed into the flue 13 from the two-fluid nozzle 37. Thereby, since NH ₃ and HCl can be separately supplied, appropriate measures can be taken according to the concentration of NOx or Hg in the high temperature exhaust gas 12. The NH ₃ dissolution tank 84 and the HCl dissolution tank 85 are provided with stirrers 30-3 and 30-4 so that the NH ₃ concentration of the NH ₃ solution 81 is uniform in the NH ₃ dissolution tank 84. The HCl concentration of the HCl solution 82 is made uniform in the HCl dissolution tank 85.

Although NH ₃ is used as the reducing agent, a solution having a reducing action such as urea ((H ₂ N) ₂ C═O) may be used as the reducing agent and a solution dissolved in water may be used. Further, when adjusting the solution _of NH ₄ Cl 14, in addition to NH ₄ Cl powder 31, a mixture of urea _{((H 2 N) 2 C} = O) is dissolved in water 39, NH ₄ Cl powder 31 and urea You may use the aqueous solution which mixed. Since the NOx concentration fluctuates in the boiler facility, in such a case, urea may be added together with NH ₄ Cl to increase the supply amount of NH ₃ .
In addition, HCl is used as the mercury chlorinating agent, but hydrogen halides other than HCl, such as hydrogen bromide (HBr) and hydrogen iodide (HI), are used as the mercury chlorinating agent, and a solution dissolved in water is used. It may be used.

As described above, according to the mercury removal system 10A according to the present embodiment, the NH ₄ Cl solution 14 that is non-gaseous at normal temperature and pressure is sprayed in the liquid state on the upstream side of the reductive denitration device 16 in the flue 13. By vaporizing the sprayed NH ₄ Cl solution 14 and decomposing it into HCl and NH ₃ , Hg in the high temperature exhaust gas 12 can be oxidized and NOx can be reduced on the denitration catalyst. For this reason, the removal performance of Hg in the high temperature exhaust gas 12 can be maintained. In addition, equipment such as HCl vaporizer, spray grid, storage tank, etc. can be omitted, NH ₄ Cl powder 21 can be handled easily, and the legal and licensing costs and equipment costs for safety management measures should be greatly reduced. Can do. Furthermore, the NH ₄ Cl powder 21 has low chemical costs and is used to sublimate NH ₄ Cl generated from the droplets of the NH ₄ Cl solution 14 sprayed using the high temperature exhaust gas 12 as a heat source, so no new sublimation equipment is required. Therefore, the operation cost can be reduced.

A mercury removal system according to Embodiment 2 of the present invention will be described with reference to the drawings.
FIG. 9 is a schematic diagram showing a mercury removal system according to Embodiment 2 of the present invention. In addition, about the member which overlaps with the structure of the mercury removal system which concerns on Example 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

As shown in FIG. 9, the mercury removal system 10B according to the present embodiment has an NH ₄ Cl solution supply pipe from an NH ₄ Cl dissolution feed tank 41 by a feed pump 42 according to the concentration of NH ₄ Cl in the NH ₄ Cl solution 14. The flow rate of the NH ₄ Cl solution 14 flowing in 33 is adjusted by the valve V2.

Arithmetic unit 32 calculates the feed rate of the solution _of NH ₄ Cl 14 based on the value of the concentration of the NH ₄ Cl concentration meter 31 solution _of NH ₄ Cl 14 was measured by. The feed rate of the solution _of NH ₄ Cl 14 calculated by the arithmetic unit 32 is transmitted to the valve V2, the flow rate of the solution _of NH ₄ Cl 14 flowing a solution _of NH ₄ Cl supply tube 33 by adjusting the opening and closing degree of the valve V2 Can be adjusted. For example, when the flow rate of the NH ₄ Cl solution 14 when the concentration of the NH ₄ Cl solution 14 is about 20 wt% is used as a reference, and the concentration of the NH ₄ Cl solution 14 is higher than 20 wt%, the NH ₄ Cl solution When the flow rate of 14 is decreased and the concentration of the H ₄ Cl solution 14 is lower than 20 wt%, the flow rate of the NH ₄ Cl solution 14 is increased.

Therefore, it is possible to supply the NH ₄ Cl dissolution tank depending on the concentration of solution _of NH ₄ Cl 14 in 27 solution _of NH ₄ Cl 14 flue 13 from the two-fluid nozzle 37 at an appropriate flow rate. As a result, NH ₄ Cl can be vaporized more reliably, and powder residue caused by NH ₄ Cl can be reliably prevented.

A mercury removal system according to Embodiment 3 of the present invention will be described with reference to the drawings.
FIG. 10 is a schematic diagram showing a mercury removal system according to Embodiment 3 of the present invention. In addition, about the member which overlaps with the structure of the mercury removal system which concerns on Example 1, 2, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

As shown in FIG. 10, the mercury removal system 10 </ b> C according to the present embodiment sends the NH ₄ Cl powder 21 in the silo 22 to the NH ₄ Cl dissolution tank 27 in accordance with the concentration of NH ₄ Cl in the NH ₄ Cl solution 14. The supply amount to be supplied, the supply amount of water 29 to be supplied from the water supply tank 28 to the NH ₄ Cl dissolution tank 27, and the NH ₄ Cl solution supply pipe 33 from the NH ₄ Cl dissolution feed tank 41 to flow into the NH ₄ Cl solution supply pipe 33. The flow rate of the NH ₄ Cl solution 14 is adjusted.

Based on the concentration value of the NH ₄ Cl solution 14 measured by the NH ₄ Cl concentration meter 31 by the arithmetic unit 32, the NH ₄ Cl dissolution tank 27 is fed by the feeder 25 in accordance with the NOx concentration and Hg concentration in the high temperature exhaust gas 12. and the supply amount of NH ₄ Cl powder 21 to deliver within, with the valve V1 NH ₄ by adjusting the supply amount of Cl dissolution tank feeding into 27 Kyusuru water 29 NH ₄ Cl solution 14 concentrations of any The concentration can be adjusted. Further, it is possible to the feed rate of the solution _of NH ₄ Cl 14 corresponding to the density of the solution _of NH ₄ Cl 14 adjusted to adjust the flow rate of the solution _of NH ₄ Cl 14 flowing a solution _of NH ₄ Cl supply tube 33 by a valve V2 .

Therefore, NOx concentration in the hot flue gas 12, with a concentration of solution _of NH ₄ Cl 14 in accordance with the Hg concentration can be arbitrarily adjusted, a solution _of NH ₄ Cl 14 depending on the concentration of solution _of NH ₄ Cl 14 adjusted properly The flow rate can be supplied from the two-fluid nozzle 37 into the flue 13. Thus, corresponding to the concentration of NOx and Hg in the hot exhaust gas discharged from combustion equipment such as a boiler, it is possible to supply necessary amount of NH ₄ Cl in hot flue gas 12, more reliably NH ₄ Cl It is possible to vaporize the powder, and it is possible to reliably prevent the powder from remaining due to NH ₄ Cl.

As described above, the mercury removal system according to the present invention sprays NH ₄ Cl in a liquid state into the flue, and is generated from the sprayed NH ₄ Cl fine droplets by the high-temperature exhaust gas passing through the flue. NH ₄ Cl can be vaporized and decomposed into HCl and NH ₃ , respectively, and the operating cost can be suppressed while maintaining the Hg removal performance.

10A to 10C Mercury removal system 11 Boiler 12 High temperature exhaust gas 13 Flue 14 Ammonium chloride (NH ₄ Cl) solution 15 Ammonium chloride (NH ₄ Cl) supply unit 16 Reductive denitration device 17 Air heater (APH)
18 Dust Collector 19 Lime Gypsum Slurry 20 Wet Desulfurizer 21 Ammonium Chloride (NH ₄ Cl) Powder 22 Silo 23 Blower 24 Air 25 Feeder 26 NH ₄ Cl Powder Supply Path 27 NH ₄ Cl Dissolution Tank 28 Water Supply Tank 29 Water 30 -1 to 30-4 Stirrer 31 Ammonium chloride (NH ₄ Cl) concentration meter 32 Arithmetic unit 33 NH ₄ Cl solution supply pipe 34, 38 Air 35 Injection hole 36 Blow pipe 37 Two-fluid nozzle 39A, 39B, 40 Air supply Pipe 41 NH ₄ Cl dissolution feed tank 42 Feed pump 43-1 to 43-3 Flow meter 44 Gap 45, 45 Air supply part 51, 53 Flange part 52 Opening part 54 Injection nozzle 56 Purified gas 57 Chimney 61 Flow meter 62-1 , 62-2 Nitrogen oxide (NOx) concentration meter 63 Mercury (Hg) concentration meter 4 Hydrogen chloride (HCl) densitometer 71 ammonia (NH ₃₎ supplying unit 72 hydrogen chloride (HCl) supply unit V1~V4 valve

Claims (18)

A mercury removal system for removing nitrogen oxides and mercury contained in high-temperature exhaust gas from a boiler,
An injection nozzle for supplying an ammonium chloride solution that generates hydrogen chloride and ammonia when vaporized into the flue of the boiler;
An ammonium chloride supply pipe for supplying an ammonium chloride solution to the spray nozzle from a feed tank;
An ammonium chloride solution for dissolving an ammonium chloride solution to be supplied to the feed tank from an ammonium chloride powder;
An ammonium chloride concentration meter for measuring the concentration of the ammonium chloride solution in the ammonium chloride dissolution tank;
A flow rate valve provided in the ammonium chloride supply pipe for adjusting the flow rate of the ammonium chloride solution;
A reducing oxidation aid supply unit comprising an arithmetic unit that calculates the supply rate of the ammonium chloride solution based on the value of the concentration of the ammonium chloride solution measured by the ammonium chloride concentration meter;
A reduction denitration apparatus having a denitration catalyst that reduces nitrogen oxides in the high-temperature exhaust gas with ammonia and oxidizes mercury in the presence of hydrogen chloride;
A wet desulfurization device that removes mercury oxidized in the reductive denitration device using an alkali absorbing solution;
Based on the value of the concentration of the ammonium chloride solution measured by the ammonium chloride concentration meter, the supply rate of the ammonium chloride solution is calculated, and the calculated supply rate of the ammonium chloride solution is transmitted to the flow valve. Mercury removal system characterized by adjusting the flow rate of ammonium chloride solution flowing into the ammonium chloride solution supply pipe by adjusting the opening and closing state. In claim 1,
According to the concentration of ammonium chloride in the ammonium chloride solution, the supply amount for feeding ammonium chloride powder to the ammonium chloride dissolution tank, the supply amount of water for dissolving ammonium chloride, and flowing from the feed tank to the ammonium chloride solution supply pipe A mercury removal system characterized by adjusting the flow rate of the ammonium chloride solution. In claim 1 or 2,
The mercury removal system, wherein the concentration of the ammonium chloride solution is 43 wt% or less. In any one of Claims 1 thru | or 3,
The reducing oxidation aid supplier is
An ammonium chloride solution supply pipe for supplying the ammonium chloride solution into the flue;
A blowing pipe inserted into the flue so as to surround the ammonium chloride solution supply pipe and having an injection hole for injecting the air supplied into the flue;
A spray nozzle attached to the tip of the ammonium chloride solution supply pipe and spraying the ammonium chloride solution;
A mercury removal system characterized in that the ammonium chloride solution is sprayed into the flue with the air. In claim 4,
The mercury removing system, wherein the spraying means is a two-fluid nozzle that sprays the ammonium chloride solution and air for spraying the ammonium chloride solution. In any one of Claims 1 thru | or 3,
The reducing oxidation aid supplier is
An ammonium chloride solution supply pipe for supplying the ammonium chloride solution into the flue;
An air supply pipe inserted into the flue so as to surround the ammonium chloride solution supply pipe, and supplying air for spraying the ammonium chloride solution into the flue;
A two-fluid nozzle that is attached to the tip of the ammonium chloride solution supply pipe and the air supply pipe and that injects the ammonium chloride solution and the air;
A mercury removal system characterized in that the ammonium chloride solution is sprayed into the flue with the air. In any one of Claims 1 thru | or 6,
The mercury removal system, wherein a droplet diameter of the ammonium chloride solution sprayed from the spray nozzle is 1 nm to 100 μm on average. In any one of Claims 1 thru | or 7,
The mercury removal system, wherein the temperature of the high-temperature exhaust gas is 320 ° C or higher and 420 ° C or lower. In any one of Claims 1 thru | or 8,
A mercury removal system comprising a nitrogen oxide concentration meter for measuring the concentration of nitrogen oxide in the high-temperature exhaust gas on the upstream side and the downstream side of the reductive denitration apparatus. In any one of Claims 1 thru | or 9,
A mercury removal system comprising an ammonia supply unit that is provided between the reduction oxidation aid supply unit and the reduction denitration apparatus and supplies ammonia into the flue. In any one of Claims 1 thru | or 10,
A mercury removal system comprising a hydrogen chloride supply unit that is provided between the reduction oxidation aid supply unit and the reduction denitration device and supplies hydrogen chloride into the flue. A mercury removal method for removing nitrogen oxides and mercury contained in high-temperature exhaust gas from a boiler,
An injection step of supplying an ammonium chloride solution that generates hydrogen chloride and ammonia when vaporized in the boiler flue;
An ammonium chloride solution supply step of supplying an ammonium chloride solution to the spray nozzle from a feed tank;
An ammonium chloride dissolving step of dissolving an ammonium chloride solution supplied to the feed tank from ammonium chloride powder;
An ammonium chloride concentration measurement step for measuring the concentration of the ammonium chloride solution in the ammonium chloride dissolution step;
A flow rate adjusting step for adjusting the flow rate of the ammonium chloride solution;
A reduction oxidation aid supply step comprising a calculation step of calculating the supply rate of the ammonium chloride solution based on the value of the concentration of the ammonium chloride solution measured in the ammonium chloride concentration measurement step;
A reduction denitration treatment step having a denitration catalyst that reduces nitrogen oxides in the high-temperature exhaust gas with ammonia and oxidizes mercury in the presence of hydrogen chloride; and
A wet desulfurization step of removing mercury oxidized in the reductive denitration apparatus using an alkali absorbing solution,
Calculate the supply rate of the ammonium chloride solution based on the value of the concentration of the ammonium chloride solution measured by the ammonium chloride concentration measurement, and transmit the calculated supply rate of the ammonium chloride solution to the flow valve. A method for removing mercury from mercury-containing high-temperature exhaust gas, comprising adjusting an opening / closing condition and adjusting a flow rate of an ammonium chloride solution flowing into an ammonium chloride solution supply pipe. In claim 12,
According to the concentration of ammonium chloride in the ammonium chloride solution, the supply amount for feeding ammonium chloride powder to the ammonium chloride dissolution tank, the supply amount of water for dissolving ammonium chloride, and flowing from the feed tank to the ammonium chloride solution supply pipe A method for removing mercury from a mercury-containing high-temperature exhaust gas, characterized by adjusting a flow rate of the ammonium chloride solution to be produced. In claim 12 or 13,
The method for removing mercury from mercury-containing high-temperature exhaust gas, wherein the reducing oxidation auxiliary agent supplying step sprays the ammonium chloride solution using a two-fluid nozzle. In any one of Claims 12 thru | or 14,
A nitrogen oxide concentration measuring step for measuring the concentration of nitrogen oxide in the high temperature exhaust gas on the pre-process side and the post-process side of the reductive denitration treatment process;
A mercury concentration measurement step for measuring the concentration of mercury in the high-temperature exhaust gas on the subsequent step side of the reduction denitration treatment step;
Based on one or both of the concentration of nitrogen oxide in the high-temperature exhaust gas obtained by the nitrogen oxide concentration measurement step and the concentration of mercury in the high-temperature exhaust gas obtained by the mercury concentration measurement step The method for removing mercury from mercury-containing high-temperature exhaust gas, characterized in that the supply amount of the ammonium chloride solution supplied in the reducing oxidation aid supplying step is adjusted. In any one of Claims 12 thru | or 15,
Either or both of an ammonia supplying step for supplying ammonia into the flue and a hydrogen chloride supplying step for supplying hydrogen chloride into the flue between the reducing oxidation assistant supplying step and the reducing denitration treatment step. Including
Based on one or both of the concentration of nitrogen oxide in the high-temperature exhaust gas obtained by the nitrogen oxide concentration measurement step and the concentration of mercury in the high-temperature exhaust gas obtained by the mercury concentration measurement step A method for removing mercury from mercury-containing high-temperature exhaust gas, wherein the supply amount of either one or both of ammonia and hydrogen chloride supplied in either or both of the ammonia supply step and the hydrogen chloride supply step is adjusted. In any one of Claims 12 thru | or 15,
Mercury of mercury-containing high-temperature exhaust gas, wherein the contents of nitrogen oxide and mercury in the high-temperature exhaust gas are determined from the coal properties of the coal used in the boiler, and the supply amount of the ammonium chloride solution is determined. Removal method. In claim 16,
The contents of nitrogen oxide and mercury in the high-temperature exhaust gas are determined from the coal properties of the coal used in the boiler, and the supply amounts of the ammonium chloride solution, ammonia, and hydrogen chloride are respectively determined. A method for removing mercury from high-temperature exhaust gas containing mercury.

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