The method of cleaning flue gases from toxic products of combustion

 

(57) Abstract:

Usage: for cleaning of flue gases of different thermal power units. The essence of the method consists in the treatment of flue gases at a temperature of 850 - 1100oC aqueous solution containing the amino group, and according to the invention produce additional processing of flue gases with a solution of aminecontaining reagent at a temperature of 300 - 800oC, after which produce neutralizing sulfur oxides and absorption of products of neutralization at 40 - 90oC. In a preferred embodiment, additional processing of flue gases aminecontaining reagent is carried out at 500 - 700oC, and neutralized with 70 - 90oC. Preferably by neutralizing sulfur oxides and absorption of products of neutralization to use an aqueous solution of a sulfite-bisulfite salts formed during neutralization of sulfur oxides. The proposed method allows for the simultaneous cleaning of the flue gases from nitrogen oxides and sulfur oxides with the degree of purification respectively 85 - 90% 90 - 95%. 2 C.p. f-crystals, 1 tab., 1 Il.

The invention relates to the field of flue gas and can be used in various thermal power units.

oC, taken in sufficient quantity for the reduction of nitrogen oxides. The degree of purification from nitrogen oxides depending on the process conditions is 35 100% [1]

The closest analogue is the method of cleaning flue gases from nitrogen oxides, including the handling of these gases at 700 1200oC urea or its derivatives, mainly in the form of aqueous solutions, which are first injected into a stream of air or steam, and then this mixture is injected into the stream of exhaust gases [2]

The disadvantages of this method is that it is not possible to clean flue gases from other toxic compounds, in particular oxides of sulfur.

The present invention is to develop a method of cleaning flue gases, which allows to remove not only the oxides of nitrogen and oxides of sulfur.

The problem is solved by the proposed method of cleaning flue gases from toxic combustion products, including the processing of flue gases at a temperature of 850 1100oC aqueous solution of aminecontaining reagent, a distinctive feature of which is that perform additional processing of the flue gas with an aqueous solution of aminecontaining reagent PR is saved at 40 90oC.

Preferably, an additional treatment of flue gases aminecontaining reagent to carry out at 500 700oC.

Preferably the neutralization of sulfur oxides and absorption of products of neutralization to exercise at 70 90oC, and to use an aqueous solution of a sulfite-bisulfite salts formed during neutralization of sulfur oxides.

The proposed method allows you to clean flue gases from nitrogen oxides from level 85 to 90% and sulfur oxides with the degree of 90 to 95%

The drawing shows the General scheme of the installation to implement the proposed method of cleaning flue gases from nitrogen oxides and sulphur.

The solution of aminecontaining reagent concentration of 10 to 40% by weight is mixed with steam and fed to a high-temperature (850 1100oC) the area of the power plant 1 via the distribution nozzle 2 for the reduction of nitrogen oxides. As aminecontaining reagent can be used any known amino compounds reducing agents, for example, an aqueous solution of urea, ammonia, ammonium carbonate, ammonium oxalate and other compounds (the most widespread among aminecontaining reductants finds urea).

Products p is 4NO + O2_ 2CO2+ 4H2O (1)

The solution of aminecontaining reagent such as urea to neutralize sulfur oxides is fed through the nozzle 3 in the zone where the flue gas temperature is 300 800oC, preferably 500 700oC. At these temperatures there is a thermal decomposition of urea, which is excreted ammonia. Flue gases containing ammonia, with a temperature of 180 - 200oC enter the Packed scrubber 4. In the initial period of operation of the scrubber is irrigated by water, the temperature of the gases is reduced to the desired size 40 90oC, preferably 70 to 90oC, and the process of neutralization of sulfur oxides and dissolution of the formed ammonium salts:

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After the scrubber solution with a temperature of 50 80oC using a circulating pump 5 is supplied to heat exchanger 6 where it is cooled to a temperature of 20 30oC due to heat water, which can be used, for example, for hot water or for other purposes. Then, the solution is returned into the cycle. Saturation of the solution is due to its continuous circulation as irrigating fluid, and increasing the salt content of the efficiency of absorption of sulfur oxides increases. saved from the process, is collected in the storage tank 7 and is sent to the consumer. The amount of irrigating fluid output from the process, is compensated by feeding fresh water. Flue gases with a temperature of 70 90oC using the exhauster 8 released into the atmosphere.

Below are examples of flue gases from nitrogen oxides and sulphur furnace thermal treatment of liquid waste.

Example 1. In the process furnace for thermal treatment serves 50 kg/h of a solution containing 15% by weight of ammonium sulfate. As fuel in the furnace is natural gas. The gas flow rate of 45 m3/H. the Total amount of flue gas at the furnace outlet of the furnace 700 m3/H. According to the analytical measurements of the concentration of nitrogen oxides is 530 mg/m3the concentration of sulfur oxides 2450 mg/m3. The temperature of the flue gases at the outlet of the furnace the furnace is equal to 960oC.

In the chimney of the furnace at the furnace outlet serves the urea solution concentration of 10% by weight of 7 kg/h, after which the content of nitrogen oxides at the outlet of the furnace is reduced to 50 mg/m3. The content of sulfur oxides at the outlet is 2300 mg/m3the concentration of ammonia of 100 mg/m3.

Example 2. In the chimney of the furnace described is about the mass of 7 kg/h for the reduction of nitrogen oxides. In the area of the chimney, where the flue gas temperature is 700oC, in the flow of products of combustion of the injected urea solution concentration of 10% by weight in the amount of 20 kg/h Flue gases pass into a Packed scrubber, irrigated in the starting period, water in an amount of 3 m3/h, and further the solution formed in the scrubber as a result of binding of sulfur oxides, products of thermal decomposition of urea and dissolving the resulting sulfite-bisulfite ammonium salts. The temperature of the gases in the scrubber 70oC. research Results are summarized in the table.

Thus, the possibility of implementation of a process for purification of flue gases from nitrogen oxides and sulfur using the same reagent, in this case urea, with an efficiency of 85 to 90% for oxides of nitrogen and 90 to 95% of the sulfur oxides.

During the process of joint cleaning significant decrease of the content of NH3in the flue gases after the second stage through participation in high-temperature unreacted stage ammonia neutralization reactions of sulfur oxides.

1. The method of cleaning flue gases from toxic combustion products, including the processing of flue gases at 850 lnow processing of flue gases with an aqueous solution of the reagent, containing the amino group, at 300 800oC, followed by neutralization of sulfur oxides and absorption of products of neutralization at 40 90oC.

2. The method according to p. 1, characterized in that as a reagent containing an amino group, use urea, ammonia, ammonium carbonate or ammonium oxalate.

3. The method according to p. 1 or 2, characterized in that during the neutralization of sulfur oxides and absorption of products of neutralization using an aqueous solution of a sulfite-bisulfite salts formed during neutralization of sulfur oxides.

 

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