JPS6138619A - Purification of flue gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for separating flue gases resulting from the combustion of waste materials and containing solids of various compositions as well as harmful gases and heavy metals into a flue gas by means of a device for separating the main components of the solids. Cleaning the flue gas to remove the gas, collect it as ashes, combine harmful gases and residual solid components, and send the flue gas exiting the separator to a condensation/cleaning device. separating water vapor, H(4') and/or heavy metals contained in the flue gas in the form of steam, and using the condensate to remove soluble heavy metals from the smoke ash;
This invention relates to a method for purifying soluble heavy metals by precipitating them and removing them from the process.

Conventional flue gas purification involves the separation of solid, liquid or gaseous harmful substances from the flue gas in order to reduce environmental damage to an acceptable level. In principle, the separation of harmful dusts from gases is carried out by mechanical and electrical methods and, in the case of wet dedusting, by absorption, adsorption or chemisorption. The basic methods for the separation of harmful gases are absorption, adsorption, condensation and chemical reactions. In the case of wet cleaning, waste mud, salt and waste water are produced.

In flue gas purification systems, a collective method is often obtained by combining several basic methods. One of the most used garbage combustion methods is the purification of waste gases from dust by electric or mesh filters on the flue gas side and the harmful gases in the exhaust by acid or alkali treatment methods before or after the filter device. Partial removal of HC7, SO2 and HF is also taken into account
erTU Berlin), Volume 1, pp. 1-41]. Heavy metals present in gaseous form, such as Hg, can conventionally only be removed by filters in a wet process.

A significant drawback of the conventional method is that approximately 30 kg of halogen-containing dust is generated per 1 ton of burned garbage, and 1 ton of heavy metals are generated in this.
The part is to exist in an easily flowing state. Therefore, the utilization of dust from the removal of dust from the flue gas is no longer carried out, but rather the dust is still deposited under special conditions. Safe removal of heavy metal toxic substances from ecosystems is therefore not guaranteed, especially over long periods of time. Smoke ash or harmful gas and/or harmful substances Hg, cd in waste combustion equipment
There are problems with SI'b, Sb, sn, Zn, etc.

In addition to this, various chemical reactions occur in the waste combustion process due to the composition of the waste. On one side, the combustion temperature is 800°C.
In the case of , many of the products decompose or evaporate, and on the other hand, the products liberated in the gas phase undergo a long process under cooling to about 200 °C, although anticombinatorial reactions occur or new formations occur. Things form. Thus, for example, chlorinated organic compounds (aliphatic as well as aromatic) owe their existence to this mechanism. The organic compounds that occur generally adhere to dust or soot particles present in the crude gas. The smoke ash discharged into a filter, for example an electric filter, therefore contains different compositions and different concentrations of organic chemicals.

A problem arises when this organic compound in the smoke ash is a toxic substance, such as a chlorinated dibenzodioxin or dibenzofuran, which makes the final removal of the smoke difficult or prevents it.

Acid solutions of smoke ash have been found to be particularly favorable in conjunction with the separation of mobile heavy metals. The acid solution does not change the organic content of the hazardous substances, but due to the reduced heavy metal content of the reflux of the treated smoke ash, it passes into the combustion chamber, where the high temperature process further fixes the residual heavy metals.

This invention. Purpose, 1, flue. It is possible to remove toxic substances in the form of thickeners and other toxic substances, as well as in particular heavy metals, which are present dissolved in the air, from the flue gas purification process in the honeyiest possible form, with the addition of HCl, B at the same time.
The object of the present invention is to obtain a method in which sufficient purification of O2 and NOx can be obtained, and even improved.

All other residues can be sent for reuse. However, in addition, the organic hazardous substances contained in the residual substance must still be able to be decomposed or at least converted into non-hazardous components.

According to the invention, this purpose is to send the remaining solids to the combustion chamber and decompose the organic harmful substances contained therein by high temperature treatment or to decompose the organic harmful substances contained in the acid film/wash water. The solution is to separate the dissolved mercury from the solution phase by reaction with the smoke ashes and to bind it in insoluble form to the smoke ashes.

In the method of the present invention, in order to protect the environment, gaseous harmful substances such as HClXSO2, NoX, dust,
Metals that occur in gaseous form, especially Hg, and soluble heavy metal toxic substances that occur in droplets and combustion chamber combustion, remain only as immobile components, which can be combined with combustion embers for a long time. Consideration must be given to time immobility and, with this, removal in such a way that risk-free reuse or removal is guaranteed. By means of the method of the invention, the mercury present dissolved in the acid condensate/wash water can be separated in large quantities from the liquid phase by reaction with precipitated filter dust and bound in insoluble form, i.e. immobile, in the smoke ash. achieved. This smoke ash can be combined directly with the cinders.

If the ash is returned to the combustion chamber for further high temperature reactions, the mercury is preferably separated and recovered by a further thermal pretreatment. The important novelty of the present invention is that, instead of extracting from one ton of garbage, for example, the smoke residue, which is difficult to remove by about 30% in conventional deposits, this amount is reduced to about 1 kg, i.e. The actual heavy metal hazardous substances extracted for the purpose of the process, especially H
The purpose is to obtain the basics of how to reduce g and Cd. For example, recovering mercury, lead, and cadmium from the resulting sulfides,
Completely residue-free removal is possible if

Handling with salt depends on location. Normally salt can be discharged into drains without any problem. This is because it liberates heavy metals. If a suitable drainage channel is not used, smoke ash as well as other advantageous removal materials containing salts may be removed.
Obtained, for example, by bituming.

In method 2 of combustion of this waste, solid residues are present, namely cinders and smoke, but in the second case still a cinder is obtained which no longer contains organic harmful substances due to its high temperature treatment (separated heavy metals are removed). supply for reuse). Furthermore, the new process results in a recycled product of trapped organic pollutants, which, together with the formation of this organic pollutant, also contains its thermal decomposition products. In this way, the discharge of organic hazardous substances into the environment is largely prevented.

In the embodiment shown in FIG. 1, garbage 1 is sent to a combustion chamber 2 and is incinerated. Heat and embers 3 are generated in the flue gases. A portion of the heat is removed from the flue gas in heat exchanger 4 and used elsewhere. After this heat recovery, the flue gases are selectively subjected to a dry prepurification by means of cyclones or electric filters at approximately 180°C, and as in the case of heat recovery, the dew point of the gas, water vapor, etc. It must be noted that there is no

A condensing/cleaning section 6 is connected to the dry purification section 5 for the gas and vapor passing through the filter or cyclone, where water vapor is produced with simultaneous removal of HCl and Hg. Subsequently, the residual flue gas containing the harmful gas components So2, No. 2 is passed through the alkaline cleaning section 7, and the purified gas is sent to the chimney 8.

The washed condensate from the coagulation stage 6 is transferred together with the smoke ash 9 to a dissolution reactor 10 in order to partially dissolve heavy metals from the smoke ash 9.
send to A mechanical mixing step may be considered in this case; the pickled condensate (containing HO1) reacts with the alkaline smoke and adjusts the final pH of about 6. Hg present in this case
is completely engulfed in smoke.

A solid/liquid separation device (eg sedimentation or centrifugation) is connected to this dissolution reactor 10.

A solid residue 11 and a solution 12 are formed, which mainly consist of the washed condensate (among other things <Hct) and the heavy metals removed from the smoke ash 9. However, solid residue 11
also contains Hg and can be fed directly into the cinders 3.

In the case of large amounts of smoke ash 9, one portion of the amount already produced is sufficient to completely bind the Hg.

The solid residue 11 of the solid/liquid separation can be sent to a special heat treatment 27 for recovering the Hg, for example at the temperature of the flue gas, with the Hg being desorbed and collected in 28 .

The solid residue from the special treatment section 27 can be sent further to the combustion chamber 2 or to the cinders 3.

The acid solution 12 preferably undergoes sulfide precipitation in the heavy metal precipitation section 13. After a fresh solid/liquid separation, a heavy metal honey substance 14 is obtained, which is optionally passed through a recirculation section 16.
send. Note that in order to neutralize the acid solution 15 (neutralization device 17
) is combined with the substance in the alkaline cleaning section 7.

The purified sludge formed in the neutralization device 17 is preferably transferred to the combustion chamber 2.
where it is bonded to cinders 3 at high temperatures. The cinders 3 are sent from the recycling section 21 and used for road construction, for example.

If the cinders 3 contain heavy metal components that are still unbound despite suitable assumptions in the temperature treatment and these can be washed, post-treatment is carried out. Considering the weak acid treatment of , this can be done at a pH of about 4.

For after-treatment, in a preferred manner a bath 21 is suitable, in which the cinders 3 are generally slaked or cooled after being discharged from the combustion chamber 2. Bath 21 consists of water.

However, it is also possible to spray the cinders 3 with a mist of weak acids and collect the resulting slaked liquid to liberate the heavy metals.

During neutralization, a solution 19 in which the purified sludge, free (purified), and heavy metal hazardous substances have been purified is discharged into a drainage channel 20.

Example of Hg adsorption Smoke ash/washing condensate ratio = 37.6 kg/l [] []
[] 7=100% Smoke ash (%) Hg in solution (ppm)07
．． 8 55.1 10 2.4 15 0.97 2 D O,4525<0. l Hg0 Example of Thermal Desorption Temperature (° C.) Desorption (%) 2D0 2 The following table shows the experimental results of the dioxin content of the smoke ash and especially of the residual solids before and after treatment.

The process shown in FIG. 2 corresponds to the process in FIG. This is a process in which the disconnected portion has a characteristic, and this is the second embodiment.

In the process from the combustion chamber 2 via the heat exchanger 4 to the electric filter 5, the formation of organic harmful substances takes place. In the electric filter 5, the main amount of the organic pollutants formed is separated from the crude gas together with the smoke ash 9. In the acid leaching step 10, organic hazardous substances are adsorbed onto the resulting residual solids 11. The residual solids 11 containing organic hazardous substances are then returned to the combustion chamber 2, optionally mixed with fresh waste, in which the residual solids 11 are
Decomposes 1 organic harmful substance.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an apparatus for carrying out the method of the invention, and FIG. 2 is a system diagram of another apparatus.

Claims (1)

[Claims] 1. Flue gas generated from combustion of waste materials and containing solids of various compositions as well as harmful gases and heavy metals is obtained by removing the main solid component from the flue gas using a separator and capturing it as smoke ash. cleaning of the flue gas to combine noxious gases as well as residual solid components, and sending the flue gas exiting the separation device to a condensation/cleaning device in which the flue gases contained in the flue gas are Residual solids ( 11) is sent to a combustion chamber (2), and the organic harmful substances contained therein are decomposed by high temperature treatment. 2. Flue gas generated from the combustion of waste and containing solids of various compositions as well as harmful gases and gaseous heavy metals is removed from the flue gas by a separator to remove the main solid components from the flue gas and collected as smoke ash. The flue gas is scrubbed to combine gases and residual solid components, and the flue gas exiting the separator is sent to a condensation/scrubbing device in which the water vapor, HCl and / or in a process in which the heavy metals are separated in vapor form and the condensate is used to extract the soluble heavy metals from the smoke ash, the soluble heavy metals are precipitated and removed from the process for purification; A process for purification of flue gases, characterized in that the dissolved mercury contained therein is separated from the solution phase by reaction with the smoke ashes (9) and is bound to the smoke ashes (9) in insoluble form. 3. The method according to claim 2, wherein the smoke ash (9) is combined with the cinders (3). 4. The method according to claim 2 or 3, wherein mercury is desorbed and recovered by treating the leached smoke ash (9) in a thermal post-treatment section (27). 5. The method according to any one of claims 1 to 4, wherein the smoke ash (9) from which mercury has been liberated is newly sent to the combustion chamber (2).