How does limestone desulfurize coal? How to desulfurize limestone powder?

Here's how:

1. Limestone powder is added to water to make a slurry as an absorbent, pumped into the absorption tower and fully contacted and mixed with the smoke, the sulfur dioxide in the flue gas and the calcium carbonate in the slurry and the air blown in from the lower part of the tower are oxidized to generate calcium sulfate, and after the calcium sulfate reaches a certain saturation, it crystallizes to form gypsum dihydrate.

2. The gypsum slurry discharged from the absorption tower is concentrated and dehydrated to make its water content less than 10%, and the conveyor is sent to the gypsum storage silo for stacking, and the flue gas after desulfurization is removed by the mist eliminator, and then discharged into the atmosphere by the chimney after heating and heating by the heat exchanger.

3. NID principle stone: the ash powder enters the reactor after being digested by the lime digester (LDH), and the SO in the flue gas undergoes a chemical reaction to generate CASO and CASO, and the SO in the flue gas is removed.

At present, there are generally three desulfurization methods: pre-combustion, combustion and post-combustion desulfurization. With the development of industry and the improvement of people's living standards, the thirst for energy is also increasing, and SO2 in coal-fired flue gas has become the main cause of air pollution. Reducing SO2 pollution has become a top priority in today's atmospheric environment management.

Many flue gas desulfurization processes have been widely used in industry, and their traces are also of great practical significance for the treatment of exhaust gas of various boilers and incinerators.

The desulfurization absorption and product treatment of dry FGD technology are carried out in a dry state, which has the advantages of no sewage waste acid discharge, light corrosion degree of equipment, no obvious cooling of flue gas in the purification process, high flue gas temperature after purification, conducive to chimney exhaust diffusion, and less secondary pollution, but there are problems such as low desulfurization efficiency, slow reaction speed and large equipment.

Semi-dry FGD technology refers to the flue gas desulfurization technology in which the desulfurizer is desulfurized in the dry state and regenerated in the wet state (such as the water-washed activated carbon regeneration process), or the desulfurization is desulfurized in the wet state and the desulfurization products are treated in the dry state (such as the spray drying method).

In particular, the semi-dry method of desulfurization in wet state and treatment of desulfurization products in dry state has attracted widespread attention because of its advantages of fast reaction speed and high desulfurization efficiency of wet desulfurization, as well as the advantages of dry waste-free waste acid discharge and easy treatment of desulfurization products. According to the use of desulfurization products, it can be divided into two types: discarding method and ** method.

Desulfurization methods for coal:

1. Physical method: Iron sulfide (pyrite) in coal is usually removed by gravity separation or magnetic separation method, and the sulfur in this form accounts for about 2 3 of the sulfur in coal.

2. Chemical method: the coal is mixed with the aqueous solution of iron sulfate after crushing, heated to 100 130 in the reactor, and the iron sulfate reacts with pyrite to convert into ferrous sulfate and monomer sulfur, the former is recycled after oxidation, and the latter is used as a by-product.

3. Gasification method: coal is subjected to incomplete oxidation through a gasifier at a high temperature of 1000 to 1300 to become gas. Most of the sulfur in coal becomes hydrogen sulfide when it is gasified, and then it is removed by liquid absorption or solid adsorption.

4. Liquefaction method: The liquefaction of coal includes synthesis method, direct cracking hydrogenation method and hot melt hydrogenation method. In the liquefaction process, sulfur reacts with hydrogen to form hydrogen sulfide and escapes, thus obtaining a fuel with high calorific value, low sulfur and low ash content.

Flue gas desulfurization is divided into dry and wet process. The former uses solid powder or granules as adsorbents, such as lime powder blowing method, activated carbon method and activated manganese oxide method. The latter uses liquids as absorbents, such as ammonia absorption, limestone or lime milk absorption, magnesium oxide absorption, sodium (potassium) absorption, and oxidative absorption.

Fuel desulfurization can improve sulfur content, reduce sulfur oxide pollution, and improve the calorific value of fuel.

The principle of limestone desulfurization is simply explained as using limestone water to wash the sulfur dioxide in the boiler flue gas;

Principle: acid-base neutralization is redox reaction, limestone water is calcium carbonate slurry for alkaline medium, sulfur dioxide is acidic medium, the two through the circulation pump, limestone slurry power source and booster fan containing sulfur dioxide flue gas power source to provide kinetic energy, in the absorption tower for two gas phase macro and liquid phase reverse contact reaction, the reaction product is aqueous calcium sulfate and carbon dioxide, during which oxygen is needed as a catalyst, if there is no oxygen insufficiency, it can be used in the air with 21% oxygen.

The reason is that limestone powder can react with sulfur (SO2) in an acidic or neutral environment to form calcium sulfate or magnesium sulfate, so as to achieve the purpose of desulfurization of lead. Compared with other commonly used desulfurization agents, limestone powder has the advantages of natural, safe and reliable, effective collapsing and removing high-concentration polluting gases, greatly reducing the blowing and washing of the agent, and the economic effect is remarkable. Big nucleus.

Summary. The use of quicklime as a desulfurizer can achieve efficient and cheap desulfurization in the furnace, and the general desulfurization rate is more than 90%. At the same time, due to the lower combustion temperature in the furnace, the NO2 generated in the circulating fluidized bed boiler is mainly composed of fuel N02, that is, the N in the fuel is converted into NO2:

At the same time, the circulating fluidized bed boiler adopts a graded air supply method, that is, the primary air is sent from under the air distribution plate, and the secondary air is sent from the dense phase zone at the bottom of the furnace in three layers, which can effectively inhibit the generation of NOx, so the pollutant emission in the boiler is very low.

The desulfurizer has high desulfurization efficiency, can remove organic sulfur and inorganic sulfur at the same time, the removal rate of H2S is more than 97%, the removal rate of organic sulfur is about 50%, and the removal rate of hydrogen cyanide is more than 90%, with high activity, long life, good regeneration, large suspended particles, and strong ability to resist hydrogen cyanide poisoning. The molecular structure of the desulfurizer is stable, the amount of desulfurization is small, and the cost of desulfurization is low, which can effectively reduce the production cost.

Excuse me, but please go into more detail?

The use of quicklime as a desulfurizer can achieve efficient and cheap desulfurization in the furnace, and the general desulfurization rate is above 90%. At the same time, due to the low combustion temperature in the furnace, the NO2 generated in the source of the circulating fluidized bed boiler is mainly composed of fuel N02, and the N converted into NO2 in the instantaneous hail alarm is mainly composed of fuel N02: while the thermal N02 is the N02 converted into the air The generation amount is small, and the circulating fluidized bed boiler adopts the method of graded air supply, that is, the primary air is sent from under the air distribution plate to the secondary air in three layers and is sent from the dense phase zone at the lower part of the furnace, which can effectively inhibit the generation of NOx, so the pollutant emission in the boiler is very low.