With the strengthening of people's environmental awareness, environmental standards are becoming more and more strict. In order to reduce investment and cost, and improve desulfurization efficiency, in recent years, countries have invested a lot of manpower and material resources, research and development of economic, efficient and practical desulfurization new technology. The representative new desulfurization technologies are mainly the following:
(1) Deep flue gas desulfurization method
This method is a patented technology developed by Chiyoda Chemical Construction Co., Ltd., Japan. The core is a jet boiling reactor. The flue gas passes through the slurry in a boiling state and reacts. The recirculation pump, atomizing nozzle, oxidation tank and concentration device are omitted, and the investment is 50%~75% lower than the limestone - gypsum system.
(2) Pulse corona plasma method
This method relies on a pulsed high voltage power supply to form a plasma in a conventional reactor to produce high energy electrons. It can eliminate the expensive electron beam accelerator, and has the advantages of simple process equipment and easy operation. At present, a test device of 14000m3/h has been built, and the energy consumption is 12~15kWh/m3.
1. Raw material preparation system dust removal
During the preparation process of the sintered raw materials, a large amount of dust is generated at each process equipment point of the raw materials for the collection, mixing, crushing, screening, transportation and batching.
The dust removal process of the raw material preparation system can be carried out by a wet method or a dry dust removal process. For the raw material field, due to the open operation of the stacker and reclaimer, the dust point cannot be sealed, and the mechanical dust removal device cannot be used. The wet method can be used to remove dust, that is, spray water mist at the dust-producing point to capture part of the dust and humidify the material. Dust flying; set up a closed and exhaust dust removal system for material crushing, screening and tape and transfer points. The dust removal system can be decentralized or centralized. The dust removal equipment of the decentralized dust removal system can be used as an impulse dust collector, a foam dust collector and a pulse bag type dust collector. Cyclone dust collector and cyclone water film dust collector have low efficiency and should not be used; centralized system can centrally control dozens or even nearly 100 vacuum points, and install large-scale high-efficiency dust removal equipment, such as electric precipitators, etc., with high dust removal efficiency.
2, the mixture system dust removal
In the process of transporting, adding water and mixing the mixture, waste gas containing dust and moisture is generated. The hot returning process produces a large amount of dust-water qi symbiotic waste gas, which has high temperature, high humidity and high dust concentration, and is the focus of treatment. Due to the low temperature, the cold returning process does not produce a large amount of water vapor, and only produces dusty exhaust gas at the material transfer point.
The key to solving the waste gas treatment of the mixture system is to use the cold return process as much as possible. The dust removal of the mixing system should be carried out by wet dust removal. The dust removal equipment can be equipped with high-efficiency dust removal equipment such as impulse dust collector.
3, sintering machine waste gas treatment
(1) Sintering machine exhaust dust removal
The sintering of iron-containing raw materials mainly uses a suction belt type sintering machine. The exhaust gas generated by the sintering machine mainly contains dust and harmful substances such as SO2 and NOX.
In the dedusting of the exhaust gas of the sintering machine, a water seal zipper can be arranged outside the large flue, and each ash discharge pipe, dust ash discharge pipe and small ash discharge pipe of the large flue are inserted into the water seal zipper groove, and the ash is After precipitation in the water seal, it is taken out by the pull. Dust removal equipment generally uses large cyclone dust collectors and electrostatic precipitators.
(2) Treatment of sulfur dioxide in sintering machine flue gas
1 The concentration of sulfur dioxide in the flue gas of the high chimney discharge sintering machine is generally 500-1000mL/m3, and the high reaches 4000-7000Ml/m3. The emission of this waste gas is large. If there are some problems in the economic recovery of recycling, most countries still rely on high chimney emissions. According to the needs of sintering production, the height of the chimney can be 100~120m. However, in order to protect the environment, many developed countries adopt higher chimneys, such as the American chimney up to 360m, the United Kingdom 260m, Japan to 230m. China Baotou Steel Sintering Plant currently uses low-sulfur raw materials, combustion, and sintering flue gas does not need to be desulfurized. After 200m high chimney discharge, the maximum concentration of SO2 is below 0.006mL/m3.
2 Flue gas desulfurization In the flue gas generated during sintering of the sintering machine, the concentration of sulfur dioxide is changing. The concentration of SO2 in the head and tail flue gas is low, and the concentration of SO2 in the middle flue gas is high. In order to reduce the scale of the desulfurization device, only the sintering tail gas having a high concentration of SO2 can be introduced into the desulfurization device. The research on desulfurization of sintering machines in various countries in the world has entered a practical stage. Such as Japan's ammonium sulphate method, lime gypsum method, steel slag gypsum method;
The former Soviet Union is the gray gypsum method and the circulating magnesite method, as well as the sulphurous soda sulphate method in China. The method uses ammonium sulfite solution as an absorbent to form ammonium hydrogen sulfite, which is then discharged from the coke oven. The ammonia gas reacts to form ammonium sulfite. Ammonium sulfite is again used as an absorbent and is then reacted with SO2. In this reciprocating cycle, the concentration of ammonium sulfite is getting higher and higher. After reaching a certain concentration, a part of the solution is extracted, oxidized, and concentrated to be recovered by ammonium sulfate.
4, the whole system dust removal
The whole grain system includes the crushing of cold sinter and multi-stage sieving. It has many dust removal points and large air volume, and a special granule dust removal system must be set up. The system is equipped with a centralized dust removal system, which adopts dry high-efficiency dust removal equipment, and generally adopts a high-efficiency large-volume bag type dust collector or electric precipitator.
5, pellet furnace flue gas treatment
(1) Pelletizing furnace flue gas dedusting When the ball is mixed with iron ore fines and additives such as lime, bentonite and coke powder, the flue gas is generated during the roasting process in the shaft furnace. Most of the flue gas is dry dust removal, and the dust removal equipment can be a bag filter or an electric precipitator. The use of cyclone dust collectors and multi-tube dust collectors does not meet national emission standards and should not be used.
(2) The sulfur removal of flue gas from the pellet furnace has not taken effective measures for SO2 in the flue gas of the pellet furnace. The treatment method is mainly for preliminary desulfurization of high sulfur combustion and recovery of sulfur dioxide in flue gas. For example, the Japanese steel company uses (NH4)2SO3 as an absorbent, absorbs the sulfur dioxide in the exhaust gas, and then reacts with NH3 in the coke oven gas to regenerate the absorption liquid and return it to the sintering plant for reuse. A part of the absorption liquid is extracted and oxidized, and then ammonium sulfate is prepared. In the United States, dolomite and other materials are added to the sintering machine exhaust gas, and a bag filter is used together to remove dust and sulfur dioxide.
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