Causes and Countermeasures of waste gas emission in cement production Henan Hongxing

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Causes and Countermeasures of waste gas emission in cement production

There will be waste gas emission in the production process of cement enterprises, especially Rotary kiln In the calcination stage, the problem of exhaust gas emission is serious. In view of the increasingly serious environmental problems in China, waste gas management has become a very important work in cement enterprises. Below, we analyze the causes and explain the prevention countermeasures for the two kinds of problems of organized emission and unorganized emission of waste gas.

 Cement production process

1、 Organized emission of waste gas

1. Organized emission of waste gas

There are many organized exhaust emission points in cement production enterprises, and the amount of waste gas emission is very large. Many enterprises that used constant voltage source electrostatic precipitator to deal with dust pollution can not meet the requirements of the new cement industry emission standard, especially the particles in kiln tail gas exceed the standard seriously. When the electrostatic precipitator is used to remove dust, the amount of electric field in the precipitator is small, which directly leads to the excessive emission of particles. The daily operation time of raw material drying mill is different from that of rotary kiln, so 2 and SO2 in waste gas are easy to exceed the standard. When ammonia and other reducing agents are used for denitrification by SNCR method, the concentration of ammonia, denitration temperature and the addition amount of reducing agent are insufficient, which easily leads to 2 exceeding the standard. When fluorite is added and high fluorine raw materials are used in cement production process, fluoride in waste gas exceeds the standard seriously.

2. Causes and Countermeasures of organized emission of waste gas

Reasons: the constant voltage source electrostatic precipitator is not very high in dust removal, which is difficult to meet the requirements of the new standard; generally speaking, the more electric fields are, the higher the dust removal efficiency is. However, in order to save investment and reduce operating costs, many enterprises only use three electric fields and five electric fields for dust removal, and excessive emission will occur when the first level electric field fails. It is suggested that the constant voltage source electrostatic precipitator should be replaced by the constant current source electrostatic precipitator, and the electric field quantity of the electrostatic precipitator should be increased as far as possible, so that the discharge can still meet the standard when the primary and secondary electrostatic precipitators fail.

Prevention measures: the production time of dryer and ball mill in many cement production enterprises is 20 hours per day, while that of rotary kiln is 24 hours per day. The dryer has good desulfurization and denitrification during operation, but when the dryer is shut down, SO2 and SO2 in kiln tail gas are often caused Therefore, when the dryer is shut down, desulfurizer such as fine lime should be put into the decomposition kiln, and the dosage of denitrification agent (such as ammonia water) in SNCR process should be increased to ensure that the exhaust gas can meet the discharge standard. At the same time, the concentration of ammonia water of denitration agent should be increased to about 25%, and enough ammonia water should be added to control the denitration temperature within 860 ℃ - 880 ℃, so as to improve the denitration efficiency and ensure that the concentration of 2 in the waste gas meets the requirements of the new emission standard.

As fluorite and high fluorine raw materials are easy to produce a large amount of hydrogen fluoride and other pollutants during the reaction in the rotary kiln, which leads to the serious emission of fluoride in the waste gas. Therefore, the use of fluorite and high fluorine raw materials should be controlled to ensure that the fluoride in the waste gas can meet the discharge standard.

2、 Unorganized emission of waste gas

1. Unorganized emission of waste gas

In the process of cement production, the unorganized emission of waste gas pollution is relatively serious, mainly including the dust generated by ore loading and unloading, raw meal pre homogenization, raw material and clinker transportation, cement packaging and loading, and vehicle transportation, which lead to the unorganized waste gas emission of cement enterprises exceeding the standard, and the particulate matter pollution around the cement plant is serious.

2. Causes and Countermeasures of unorganized emission of waste gas

(1) Many cement production enterprises do not take spray dust and dust collection measures during ore loading and unloading. Some enterprises have dust suppression and dust collection devices. In order to reduce production costs, they do not use them and do not maintain them after failure, resulting in unorganized dust emission.

(2) The design of rectangular pre homogenization field is not conducive to airtight homogenization. When the spray device on the belt conveyor is not in use, it is easy to cause pre homogenization dust pollution. Therefore, it is necessary to design a circular pre homogenizing field as far as possible, strengthen the maintenance of the spray device, and use the spray device normally can effectively reduce the unorganized emission of dust in the pre homogenization field.

(3) Raw material and clinker conveying facilities and cement packaging room should be sealed, and air exhaust system should be built to make it in micro negative pressure state to prevent unorganized emission of dust; when loading bagged cement, mobile dust collector should be used to collect dust and handle it with care; when loading bulk cement, dust collector should be opened synchronously; only one manhole cover of bulk truck should be opened; loading speed should be controlled; multiple opening is strictly prohibited Manhole and rapid loading can effectively reduce the dust production and emission.

(4) Maintain the roads in the plant regularly, limit the vehicle speed, prevent the materials on the transport vehicles from falling, and increase the frequency of dust cleaning vehicles and watering vehicles to control dust pollution.

Through the classification and analysis of waste gas emission problems, and targeted to develop preventive measures, cement production gradually towards pollution-free environmental protection production road, to protect the ecological environment.

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