JPS59230620A - Slurry concentration control method of wet waste gas desulfurization apparatus - Google Patents

Abstract

PURPOSE:To simplify an apparatus by stably controlling the concn. of a Ca-compound slurry, by dividing a Ca-compound suspended slurry into two or more slurries different in a Ca-compound concn. in withdrawing said slurry from an absorbing tower while respectively adjusting the flow amounts of the withdrawn slurries. CONSTITUTION:SO2-containing waste gas 101 is guided to an absorbing tower 102 and brought into contact with Ca-compound suspended slurry to remove SO2 while the purified gas 107 is exhausted. A liquid chamber 115 is formed in a tank 103 by a partition wall 114 of which the lower end is opened and the supernatant liquid in the liquid chamber 115 is discharged from a line 117. The filtrate returned from a separator 11 by a line 13 is downwardly flowed into the lower part of the liquid chamber 115 to prevent the rising of a gypsum crystal and the concn. of the gypsum to be taken out by a pump 119 is enhanced. The flow amount of the supernatant liquid from a line 117 and the flow amount of the slurry from a discharge port 110 are controlled by a microcomputer and the concn. of the Ca-compound in the slurry in the tank 103 is controlled to a desired concn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling slurry concentration in a wet flue gas desulfurization equipment, and further relates to a method for controlling the concentration of slurry in a wet flue gas desulfurization equipment, in which SO2 in flue gas is absorbed using a slurry in which solids are suspended, and solid sulfur is produced as a by-product. The present invention relates to a method for controlling slurry concentration in a wet flue gas desulfurization device for recovering compounds.

Currently, the main stream of flue gas desulfurization is the so-called wet lime method flue gas desulfurization equipment, which uses 0aOO3 and 0a(OH)z as absorbents to recover calcium sulfite and calcium sulfate (gypsum). This is a conventional method that is described in detail in many publications including, for example, Japanese Patent Application Laid-Open No. 57-4S5117.

Here, with reference to FIG. 1, a flue gas desulfurization apparatus using a wet lime method, which is currently widely used industrially, will be explained.

The flue gas 1 containing SO is guided to the absorption tower main body 2. A tank 3 for receiving a slurry in which Oa compounds are suspended is provided at the bottom of the absorption tower body 2, and the slurry is stirred by an agitator 4 to prevent precipitation of solids. The slurry in which the aa compound is suspended is sent to the top of the tower by the absorption tower circulation pump 5, spread inside the tower, flows down while coming into contact with flue gas, and returns to the tank 3 again. The exhaust gas from which SO has been removed by contact with the slurry passes through the mist eli juice inator 6, and then passes through the purified gas 7.
It is discharged as. On the other hand, a slurry of CaCO3 or ca (OH) 2 is supplied to tank 6 in a 2-in-8 format according to the amount of SO2 absorbed, and a slurry containing calcium sulfite produced when the absorbent absorbs SO is supplied in a 2-in-8 format. 9
from there to the oxidation tower 10. In the oxidation tower 10, air 12 is blown through a bubble generator 11 provided at the bottom, and sulfuric acid is supplied from a line 15 to oxidize calcium sulfite to gypsum, and unreacted caco3 and ca(OH)2 to gypsum. converts into The stone/sae slurry coming out of the oxidation tower 10 is led to the thickener 15 through the line 14, and the concentrated gypsum slurry is sent to the line 16, tank 17, pump 18, and centrifugal separator 19 to obtain the gypsum 20 and the filtrate. is led to tank 21 and then to thickener 15 via pump 22 and line 23. On the other hand, the supernatant liquid of the thickener 15 is led from the line 24 to the tank 25, and the pump 2
6, it is used, for example, for the preparation of an absorbent in a flue gas desulfurization device, or it is drained.

The present invention was developed as a result of intensive research to simplify the configuration included in current flue gas desulfurization equipment and make it economically superior.
Based on the data on the reaction rate with 2, the oxidation reaction rate of calcium sulfite produced by absorbing S02, and the sedimentation rate of gypsum, we changed the basic concept of the conventional one-operation-one-step process, which had separate steps for each. The process has been simplified by consolidating the operations of SO, absorption, oxidation, gypsum precipitation concentration, and supernatant liquid recovery in the absorption tower and absorption tower tank.

The wet flue gas desulfurization apparatus according to the present invention will be explained with reference to FIG. Flue gas 101 containing SO, is guided to the absorption tower main body 102. Although FIG. 2 shows a case in which the flue gas and absorption slurry contact in a so-called parallel flow, a countercurrent gas-liquid contact method as shown in FIG. 1 may also be used. However, in the method of the present invention, parallel flow has the advantage of increasing the efficiency of the oxidation reaction to gypsum, as will be described later.

A tank 105 is provided at the bottom of the absorption tower body 102 to receive the slurry in which Ca compounds are suspended.
Stir the slurry to prevent precipitation of solids. Ca
The slurry in which the compound is suspended is passed through the absorption tower circulation pump 10.5
The gas is sent to the top of the tower, dispersed within the plant, flows down while coming into contact with flue gas, and returns to tank 105 again. SO on contact with slurry.

The exhaust gas from which the gas has been removed passes through a mist eliminator 106 and is discharged as purified gas 107.

On the other hand, SO and CaO are supplied to the tank 103 in proportion to the absorbed amount.
Powder of O3 or Oa(OH)x is supplied through a powder transport line 108. Absorbent caco, ca (OH)
z can also be supplied to the tank 105 as a slurry suspended in water. Calcium sulfite, which is produced when the absorbent absorbs SO2, is oxidized by the oxygen contained in the flue gas and converted into gypsum crystals because the slurry is kept in an acidic state in the gas-liquid contact zone of the parallel flow system. I end up.

However, if there is little oxygen in the flue gas, the air nozzle 10
When gas containing oxygen gas is supplied from 9, the absorbed S
O, can be fixed as gypsum.

In this way, slurry in which gypsum crystals as an Oa compound are suspended accumulates in the tank 105, so the slurry discharge port 1
10 and a pump 119, the slurry containing gypsum crystals is introduced into a separator 111 to obtain a gypsum cake 112, and the filtrate is returned to the tank 106 through a line 115.

Inside the tank 106, there is a liquid chamber 115 that extends from above the slurry liquid level to below the liquid level and is isolated from the slurry being stirred.
The partition wall 114 is provided so that the partition wall 114 is formed.
The lower end of the liquid chamber 115 is opened and the slurry stirred by the stirrer 104 is separated by a partition wall 114.
The lower portions of the tubes are arranged so that they can communicate with each other. Further, in FIG. 2, a baffle plate 116 is provided to prevent the supernatant liquid in the liquid chamber 115 from being disturbed by the flow of the stirred slurry.

The supernatant liquid in the liquid chamber 115 is transferred to the supernatant liquid outlet 117 and the pump 11.
8. In addition, the filtrate returned from the line 113 is made to flow downward from above into the lower part of the liquid chamber 115 to prevent gypsum crystals from rising.

Furthermore, the slurry discharge port 110 is provided on an inclined plate 12 at the end of the tank 103 located at the bottom of the liquid chamber 115! ] is provided at a position where gypsum crystals are precipitated and concentrated.

By doing so, the slurry concentration of gypsum crystals taken out by the pump 119 is high, and wasteful energy for transporting the liquid can be saved.

In wet flue gas desulfurization equipment, Oa compound crystals in the mist collected by the mist eliminator 106 adhere and accumulate.
A large amount of water is used, such as washing water flowing in from the washing nozzle 121 to avoid narrowing the gas flow path, and sealing water from the pump flowing in. And these waters are in tank 1
It becomes a disturbance to the slurry concentration accumulated in 03. Changes in slurry concentration make the operational management of wet flue gas desulfurization equipment unstable and induce scale troubles due to fluctuations in seed crystal concentration. Conventionally, these problems have remained unsolved. In particular, prevention of schooling in wet flue gas desulfurization equipment using slurry in which Oa compounds are suspended is an important issue, but according to the research of the present inventors, It was found that the main cause of school troubles was fluctuations in slurry concentration due to water inflow.

The present invention aims to simplify the device configuration compared to the conventional method, and during the course of research, it was realized that preventing the above-mentioned slurry concentration fluctuation is an important issue.

According to the present invention, Ca is removed from the tank of a wet flue gas desulfurization equipment.
By simultaneously and arbitrarily performing the two operations of discharging the slurry in which the compound crystals are suspended and discharging the supernatant liquid with a low concentration of Ca compound crystals from the same tank, without any response delay, It becomes possible to stably control the concentration of Ca compound slurry in the wet flue gas desulfurization equipment. Furthermore, compared to conventional wet flue gas desulfurization equipment, the structure is simplified and the above-mentioned effects can be obtained.

Example The equipment used is shown in Figure 2.

The tank 103 that stores the slurry containing gypsum crystals is 100
It has a cross section of 0@X2000■, and the liquid depth is 200'Ow.
And so. The absorption tower circulation pump 105 sprays sludge at a rate of 50 m”/h from the top of the absorption tower 102, and the tower is filled with a grid to exhaust smoke in a gas-liquid parallel flow system!l, OO
Process ONm37'h, inlet So, + 200 p
Desulfurization was carried out from pm to so at the outlet of 60 Ppm.

SO was supplied to the tank 103 from a line 108 using OaOO3 powder as an absorbent in proportion to the absorbed amount. tank 1
A cylindrical partition wall 114 having an inner diameter of 400 mm and a length of 2500 mm and having an open bottom end was installed inside the 03.

The supernatant liquid from the line 117 that takes out the supernatant liquid from the liquid chamber 115 surrounded by the partition wall 114 contained some solid matter, but the flow rate and the flow rate from the slurry discharge port 110 were By controlling this with a microcomputer, the slurry concentration of the Ca compound accumulated in the tank 103 could be controlled to a desired concentration in the weight range of 1 to 35.

In this experiment, the composition of the solids discharged from the separator 111 was 0.
aSO4・2 H2O97wt%, caco3o, s
wt%, others 2.5 wt%, mostly gypsum, and no calcium sulfite was detected.

Air is not blown from the air nozzle 109 installed in the core. Therefore, when co-current gas-liquid contact is carried out in a grid packed tower, in the wet lime method flue gas desulfurization, the SO absorbed at the top of the tower is completely oxidized by the oxygen in the flue gas as it flows down the grid packed part. Therefore, air oxidation was no longer necessary in tank 103.

During this experiment, the cleaning nozzle 12 of the mist eliminator
Although water was injected from step 1 and pump seal water was further injected, the slurry concentration could be controlled to a desired value by the above-mentioned method and the method of the present invention.

According to the present invention, the oxidation tower, thickener, filtrate tank, and supernatant tank provided in conventional wet flue gas desulfurization equipment, as well as the pumps, valves, and instrumentation equipment associated with these equipment, are unnecessary. We have demonstrated that it is possible to significantly simplify the process.

[Brief explanation of drawings]

FIG. 1 shows a flue gas desulfurization device using a wet lime method that has been conventionally employed industrially, and FIG. 2 shows a configuration diagram of the wet flue gas desulfurization device of the present invention. In Fig. 2, 101.. Flue gas, 102.. Absorption tower main body, 103.. Tank, 104.. Stirrer, 105.. Absorption tower circulation pump, 106.. Mist eliminator, 1107.. Purified gas, 108. - Powder transport line, 109... Air nozzle, 110... Slurry discharge port, 111... Separator, 11
2... Gypsum cake, 113... f filtrate line, 114...
・Partition wall, 115...Liquid chamber, 116...Baffle plate, 117
...Supernatant liquid outlet, 118.. Pump, 119.e pump, 120.1 inclined plate, 121.-washing nozzle.

Claims (1)

[Claims] In an absorption tower that absorbs SO by bringing flue gas containing S02 into contact with a slurry in which a Ca compound is suspended, at least two different aa compound concentrations are The Oa compound concentration in the slurry that comes into contact with flue gas is controlled by dividing the slurry into slurries to obtain a slurry with a high Oa compound concentration and a slurry with a low Ca compound concentration, and adjusting the flow rate of each slurry extracted from the absorption tower. A method for controlling slurry concentration in an absorption tower, characterized by: