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2023
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Expert analysis of hazardous waste rotary kiln coking causes and preventive measures
Hazardous waste in high temperature incineration of non-decomposable solids in the high temperature environment occurs melting into liquid (molten state), with the lowering of the temperature, the mobility of these substances become poor will be adhered to the furnace, the tail of the furnace, the flue, the residual heat boiler and other locations to cause coking. These substances in molten state that cause coking are mainly low melting point hazardous wastes, such as glass, packaging containing aluminum magnesium (ash melting point 650℃), sodium carbonate (ash melting point 854℃) and other inorganic salts. Due to the different substances, the color and composition of the charred material are also different. Usually high salt-containing organic wastes incinerated in the furnace will cause coking of the rotary kiln, while the incineration flue gas generated will block the flue. These high salt-containing organic wastes are mostly HW02, HW04 distillation residues and waste mother liquor produced by pharmaceutical and pesticide manufacturing industries, most of which are semi-solid and paste-like.
Hazardous waste in high temperature incineration of non-decomposable solids in the high temperature environment occurs melting into liquid (molten state), with the lowering of the temperature, the mobility of these substances become poor will be adhered to the furnace, the tail of the furnace, the flue, the residual heat boiler and other locations to cause coking. These substances in molten state that cause coking are mainly low melting point hazardous wastes, such as glass, packaging containing aluminum magnesium (ash melting point 650℃), sodium carbonate (ash melting point 854℃) and other inorganic salts. Due to the different substances, the color and composition of the charred material are also different. Usually high salt-containing organic wastes incinerated in the furnace will cause coking of the rotary kiln, while the incineration flue gas generated will block the flue. These high salt content of organic waste to pharmaceutical, pesticide manufacturing industry HW02, HW04 distillation residues, waste mother liquor, most of the semi-solid, paste-like.
First, rotary kiln coking problem cause analysis:
1, rotary kiln in the combustion of hazardous waste, the heat is mainly concentrated in the rotary kiln entrance and the middle section, this stage of the hazardous waste ash most of the molten state, when entering the kiln end of the combustion section as the temperature decreases, the mobility of these melted ash deteriorates adhering to the furnace, furnace tail and other locations. These bonds look like cement, usually rotary kiln tail is easy to coking parts.
2, rotary kiln burning materials in the low-component organic matter is relatively large, such as high calorific value, low flash point paste distillation residue. Volatile components of such materials into the furnace pyrolysis faster, organic precipitation cracking into combustible CO, CH4, H2 and other gases, encountering open flames quickly catch fire. Under normal circumstances, the rotary kiln kiln head temperature control at about 500 ℃, the above situation occurs when the kiln head temperature can reach 700 ~ 1000 ℃, if the long-term operation, coupled with the rotary kiln supplemented with the contact of the combustion of the cold air, it is easy to localized coking in the kiln head, which can lead to a large area of serious coking, which will lead to operational failures.
3, rotary kiln kiln hood incineration of low calorific value of organic waste liquids, the low calorific value of the waste liquids, the choice of spray gun atomization effect is not good. After spraying the atomized waste liquid, in the front of the rotary kiln to absorb a large amount of heat, due to the low temperature in front of the kiln, the organic material combustion effect is poor, gathered at the top of the atomization, deposited in the refractory material, and gradually formed a coking. In the front of the rotary kiln, about 2.0 meters to form a coking circle, in a raised state.
Second, coking prevention and control measures:
1, in the hazardous waste incineration into the furnace before the inspection of various types of hazardous waste, control the material ash in the alkali metal mass fraction. After matching the material in the alkali metal mass fraction is generally controlled to about 3%, not more than 5%, if necessary, add some with a high melting point of the auxiliary materials, in order to improve the melting point of the ash.
2, if you really need a large number of low melting point high salt hazardous waste incineration disposal, should be in accordance with the batch to a small amount of batch incineration, incineration rotary kiln speed can be increased to extend the combustion time, to avoid the low melting point of high salt hazardous waste in the kiln before reaching the end of the combustion into ash. Select the appropriate refractory materials to avoid the refractory materials and molten alkaline ash combined to form slag, in the burning process should be reasonable air distribution to ensure that the combustion temperature is stable. Control rotary kiln burning temperature, for alkali metal low melting point materials, burning temperature should not exceed 1000 ℃.
3, improve the kiln seal structure. For the universal "composite fish scale + labyrinth two-layer sealing method, so that the air leakage rate reduced to less than 3%, composite fish scale sealing using" wear-resistant plate + high-temperature composite plate + protection plate "3-layer structure.
4, for rotary kiln kiln head coking can take the following measures: ① into the furnace of hazardous waste materials for a reasonable match, control the balance of the calorific value, that is, the calorific value of the control in the design value and flammable materials and materials containing polymers or organic materials or relatively inert materials to match, so that the material has a relative pyrolysis of the ignition process, to avoid the flame forward; ② through the organization of combustion and combustion, control of the kiln's main combustion air and the main By reasonably organizing the combustion, control the rotary kiln main combustion air and air volume and wind speed into the rotary kiln, so that the material in the kiln head in a reducing atmosphere, delay the ignition time, such as the use of a circular air inlet structure, with the kiln head wind multi-functional burner.
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