SU1711658A3 - Method of reduction of sulphurous anhydride concentration in flue gases - Google Patents

Abstract

The invention relates to a technology for reducing the concentration of 50 in the flue gases of furnaces when burning coal-containing sulfur or oil, which simplifies the process by: eliminating the recycling of unreacted reagent. Fuel, oxygen-containing gas and pulverized reagent, which is limestone, dolomite or calcium oxide, are supplied to the furnace. Water is sprayed into the kiln separately from the reagent; to quench the Ca or Mg oxide present in the gases and formed in the carbonate kiln. Flue gases with a temperature of 50-800 ° C and neutralization products of SOZ in solid form are removed from the furnace after they are separated from the flue gases. Preferably, the reagent is introduced in excess with respect to the sulfur fed to the fuel furnace. With a Ca / S ratio of 4.0 and a gas temperature before supplying water of 800PC, the decrease in SOg concentration is 12%. 2 hp f-ly, 1 tab. WITH

Description

The invention relates to semi-dry methods for reducing the concentration of 80 in the exhaust flue gases of furnaces in which a fuel containing sulfur is burned - coal or oil.

The purpose of the invention is to simplify the process by eliminating the recirculation of unreacted reagent.

Example 1. Coal with sulfur content of 1.4% is fed at a rate of 70 t / h to a furnace operating on pulverized fuel and. having a heat output of 600 MW, and the furnace works5 with full performance. Excess combustion air is supplied so that the oxygen content in the exhaust gases is 4%. Calcium powder (calcium carbonate,

dolomite or calcium oxide) is served in the oven. For example, calcium carbonate with a calcium content of 90% is fed to the furnace at a certain variable ratio with respect to the amount of sulfur fed to the furnace with the fuel. The theoretical equivalent amount of calcium carbonate is 3.4 tons / c.

Calcium carbonate is decomposed in a furnace at high temperature to calcium oxide and carbon dioxide. which exit the furnace with the waste gases. Part of calcium oxide,. in the furnace, it reacts with the sulfur oxides present in the exhaust gases, resulting in the formation of calcium sulphate or sulphite.

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 , M7 Ox and / or steam are sprayed into the furnace. - The increased moisture content of the waste gases allows the formation of highly reactive calcium hydroxide in the furnace from unreacted calcium oxide, which quickly reacts with the sulfur oxides present in the exhaust gases. The higher the moisture content of the exhaust gases as they exit, the more efficiently sulfur dioxide is removed from the exhaust gases. On the basis of energy saving, the treatment is carried out so that the heat released in chemical reactions is sufficient to evaporate the added amount of an ooda. If it is necessary to increase the final temperature of the flue gases, this is achieved by using external heat or by using additional heat flow from the flue gases before the furnace gases are supplied to the separation of solid particles, which are products of SOX neutralization.

It is important that the compounds entering the reaction zone derived from calcium carbonate or dolomite be in the form of oxides. The gas temperature at the outlet of the furnace is 50-800 ° C.

The table shows the results of the removal of sulfur dioxide from the flue gases (the amount of calcium carbonate is given in molar ratios of: the content of powdered calcium carbonate to the sulfur content of the fuel introduced into the furnace; the flue gas temperatures are measured in flue gases at points just before the point supplying water or steam to the gas passage or reactor after the furnace, at 800 ° C water or steam is introduced directly into the furnace).

Example .. Dolomite containing L $% calcium carbonate, 5 magnesium carbonate and 1P% impurities, in-. d t in the furnace operating on pulverized fuel according to Example 1 using the same operating quantities. In equivalent terms, the amount of dolomite needed is proportional to the amount of sulfur introduced into the furnace, 6.8 t / h.

Calcium and magnesium carbonates contained in dolomite are decomposed in the furnace into calcium oxide, magnesium oxide and carbon dioxide, which are the output; from the furnace with offgas 658 4

Some of the oxides in the furnace react with the sulfur oxides present in the exhaust gases, resulting in the formation of sulphate or sulphite.

Water and / or steam is sprayed into the exhaust gases in the furnace, after which the oxides that have not reacted in the furnace can, due to the increased humidity, form hydroxide, which reacts with the sulfur oxides present in the exhaust gases, resulting in a powder reaction product .

When dolomite is used, the highly reactive calcium hydroxide reacts faster than magnesium hydroxide, which, when there is enough calcium, passes through the reactor almost unreacted. By calculating the process so that it is carried out only on the basis of the calcium present in the dolomite, the equivalent value presented above is achieved.

5 When the molar ratio of calcium to sulfur is 1, the results of the method are consistent with the corresponding values in the table.

PRI me R 3. Calcium oxide, containing 10% of impurities, is fed to the furnace according to step 1 using appropriate operating parameters. The theoretical equivalent amount of calcium oxide in proportion to the amount of sulfur fed to the fuel kiln is about 1.9 tonnes per hour.

Part of the calcium oxide reacts in the furnace with the sulfur oxides present in the exhaust gases, resulting in the formation of sulphate or sulphite

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Water and / or vapor spray in the exhaust gases in the furnace is separate from the reagent.

Due to the increase in moisture oxide, calcium forms a highly reactive

Calcium hydroxide, which reacts quickly with the sulfur oxides present in the exhaust gases. The higher the moisture content in the exhaust gases at the exit, the more efficient the removal

0 sulfur dioxide from waste gases. On the basis of energy saving, it is advisable that the heat released in a chemical reaction is sufficient to evaporate the added amount of water.

When the calcium calcium injected is calculated in a molar ratio of sulfur, the results are as shown in the table.

In contrast to the known method, recirculation of unreacted reagent is not required, which simplifies the process of removing SOg from flue gases, while the decrease in the concentration of 80 liters is 72%.

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Claims (3)

Formula of abbet.  . 1. A method of reducing the concentration of sulfurous anhydride in flue gases, comprising feeding a sulfur-containing fuel, oxygen-containing gas and a dust-like reagent, which is an alkaline earth metal compound with alkaline properties, quenching an alkaline earth metal oxide in flue gases five 0 When water is introduced and solid neutralization products of sulfuric anhydride are separated from the flue gases, characterized in that, in order to simplify the process by eliminating the recirculation of unreacted reagent, water is fed into the furnace when sprayed separately from the reagent and the flue gases are removed from the furnace with a temperature 50-800 ° C. 2. The method according to claim 1, about tl and h and y-; u and with the fact that as a pulverized reagent using calcium carbonate, calcium carbonate-magnesium or the corresponding oxides. 3. Method according to claims 1 and 2, about tl and - h and. that the pulverized reagent is introduced in excess with respect to; to sulfur fed to the fuel stove.