The method of purification of gases from nitrogen oxides

 

(57) Abstract:

Can be used to reduce emissions of oxides of nitrogen in the chemical industry and thermal power generation. In the flow of the purified gas injected water mist, followed by passing through the porous sorbent impregnated with an aqueous solution of urea, and simultaneously with a water mist in the treated stream is injected gaseous ammonia in the amount of 15 - 25% of the entrained mass of oxides of nitrogen. The invention improves the efficiency of the process of gas purification from nitrogen oxides, to ensure business continuity and reduce the cost. table 1.

The invention relates to a process of purification and can be used to reduce emissions of oxides of nitrogen in the chemical industry and thermal power generation.

The main traditional method of trapping of NOx is the absorption of water or alkaline solutions, but the way the recovered nitrogen oxides high concentration (percent or ten percent), and the capture of nitrogen oxides low concentration (conventionally less than 0.2% by vol.) practically does not occur [1].

A known method of purification of NOx adsorption on solid sorbents (activated carbon, Cilicia capacity is not more than 0.03 kg NO_x1 kg of sorbent), which leads to decrease the efficiency of capture.

There is also known a method of purification of waste gases from nitrogen oxides passing through granular porous sorbent impregnated with urea. In this way to reduce energy costs and improve the degree of purification of the exhaust gas injected water mist and put it through a sorbent particle size distribution of 0.5 - 5.0 mm with a speed of 0.1 to 0.3 m/s [3].

This method is chosen as a prototype.

The disadvantage of this method is its frequency. The result of the formation of urea decreases the collection efficiency of nitrogen oxides, and due to the need for periodic irrigation granules dissolved, which increases the resistance of the device, leads to the necessity of replacement granules, increases the cost of the cleanup process gases and complicates the maintenance of the site gas purification.

An object of the invention is to organize the continuity of the process, increasing its stability, efficiency and cost reduction.

The solution of the problem is that in the method of cleaning gases from nitrogen oxides, including the introduction of water mist in the gas stream and passing the last speed sovy the flow of injected gaseous ammonia in the amount of 15 - 25% of the mass of the entrained oxides of nitrogen.

The main reason for the decrease in the efficiency of trapping of NOx by urea is the formation of sediment screening of nitrate of urea, preventing the interaction of urea with the following portions of oxides of nitrogen.

The introduction of ammonia leads to the destruction of nitrate of urea and the formation of ammonium nitrate, which in turn is an additional reducing agent for the following portions of oxides of nitrogen.

The introduction of ammonia in the amount of more than 25% by weight of the entrained oxides of nitrogen may cause leakage of ammonia and pollution of exhaust gases.

The introduction of ammonia in quantities of less than 15% by weight of the entrained oxides of nitrogen leads to a slow obliteration of granules nitrate urea.

The best is to feed ammonia in the amount of 20% by weight of the entrained oxides of nitrogen.

Examples of implementation

A layer of granules of silica gel impregnated with a solution of urea 100 g/l in a column with a diameter of 25 mm layer height is 400 mm. Missed the gas flow with a high content of nitrogen oxides. Saw a rapid production of urea and reduced efficiency, as presented in the tables is solilo to improve efficiency, to stabilize the process of cleaning and extend the life of silica gel (chart, PP. 6-21), i.e., to make the process continuous.

The presence of porous granules sorbing surface and pore volume of nitrate of urea, interacting with an excess of ammonia, prevent leakage of excess ammonia. The content of ammonia in the exhaust gas does not exceed 0.2 mg/m³.

Thus, the introduction of ammonia stabilizes the process of gas purification from nitrogen oxides at higher efficiency, to ensure its continuity. Reducing the destruction of the granules will allow to reduce the cost of the process due to less frequent replacement of sorbent granules.

Sources of information

1. Myagkov B. I., Masons, I., Resnick F.B. Cleaning windowsthe electroplating bath. Survey information. Industrial and sanitary gas cleaning. CONTAINERTYPES, 1978, S. 34.

2. The application of Germany N 3226840, MKI B 01 D 53/04, B 01 D 53/14, Appl. 17.07.82, publ. 16.02.84.

3. Ustinov O. A., Polenov, A. I. and other RF Patent N 1824748 prototype.

The method of purification of gases from nitrogen oxides, including the introduction of water mist into the flow of the purified gas and passing the latter through a porous sorbent impregnated in an aqueous solution of urea is in the amount of 15 - 25% of the entrained mass of oxides of nitrogen.