Method for coal slime combustion of circulating fluidized bed boiler

Abstract

The invention discloses a method for coal slime combustion of a circulating fluidized bed boiler. A cellular coal slime pipe orifice is designed to split a stream of coal slime into a plurality of streams, and is positioned below an outlet of a hearth and in the upper part of the hearth in a height direction, the coal slime is horizontally thrown by a reciprocating mechanism leaning against a coal slime pipe section after entering the hearth of the boiler, a layer of upper primary air is arranged on the upper part of the hearth, the thickness of a material layer is properly regulated and controlled to be 450mm to 550mm during the running of the boiler, the volumes of primary air and secondary air are properly regulated and controlled to ensure that the oxygen content of flue gas is 2 to 3 percent, and the negative pressure of the flue gas at the outlet of the hearth is regulated and controlled to be 0 to 50Pa. The method has the advantages that the coal slime flow is prevented from getting close to the outlet of the hearth and a screen type heated surface, the point of fall of the coal slime flow is prevented from being close to a deslagging hole, the concepts of low air volume, low oxygen content, low hearth outlet negative pressure, proper material layer thickness and the like are used for guiding running and regulation, and the operation method is innovative.

Description

technical field [0001] The invention clearly relates to a circulating fluidized bed boiler, in particular to a method for burning coal slime in a circulating fluidized bed boiler. Background technique [0002] my country is currently the country that uses the most circulating fluidized bed boilers (referred to as CFB boilers) in power plants in the world, with a total installed capacity of 100 million kilowatts. There are more than 140 large-scale circulating fluidized bed power plant boilers above h, and more than 100 large-scale circulating fluidized bed power plant boilers above 1025t / h (more than 100 are under construction). [0003] Coal slime is a waste product of coal washing plants in coal mines. Its water content is as high as 30%, its particle size is small, its calorific value is very low, and its ash content is large. Slime method. [0004] The lower part of the furnace of the circulating fluidized bed boiler in the power station is a cone, and the middle and up...

AI Technical Summary

Problems solved by technology

[0006] 1. The cross-sectional diameter of the slime flow vertically downward from the furnace top ranges from 150mm to 300mm. What flows out from the slime pipe is a cylindrical slime fluid, which slowly spreads in the air. The central granules are often only dried with water and the surface is burned to form ash shells without burning through. The unburned granules are deposited on the bed material layer at the bottom of the boiler furnace. The granules burn in the bed material at high temperature and agglomerate and are easy to block when they grow up. The slag outlet causes poor slag discharge

[0007] 2. The coal slime flow vertically down from the furnace top must pass through the furnace outlet and be close to the furnace outlet. The furnace outlet is a negative pressure flue gas, which has an attractive effect on the slime flow. The fine carbon particles in the coal slime have not had time to burn. It is drawn away by the negative pressure airflow at the outlet of the furnace and flows to the tail flue of the boiler, causing fine carbon particles to accumulate in the tail flue

[0008] 3. When the fine carbon particles accumulate heavily at the tail, they will burn and cause damage to the heating surface of the tail, resulting in large direct and indirect losses

[0009] 4. The slime flow vertically down from the furnace top must pass through the panel heating surface, and the vertical slime flow is close to the panel heating surface. The slime particles tend to stick to the panel heating surface and accumulate more and more. Affect heat transfer; the slime flow vertically down from the furnace roof passes between the panel heating surface and the furnace outlet, and it is difficult to keep the slime flow away from both the furnace outlet and the panel heating surface

[0010] 5. The area of ​​the boiler roof is as small as a dozen square meters or as large as hundreds of square meters. Improper selection of the coal slime inlet on the furnace top will cause the vertically downward coal slime to flow down to the bed material at the bottom of the furnace when it is close to the slag discharge port. The completely burned slime coke particles will be discharged along with the slag discharge, which reduces the combustion efficiency

[0011] 6. The thickness of the material layer is not properly controlled during the operation of the boiler. Too small a material layer thickness is not conducive to the collision and shredding of coal slime coke particles and thus affects the degree of burning. If the material layer thickness is too large, the fluidization air volume and wind pressure will increase significantly. A large increase in fan power consumption

[0012] 7. The multi-layer secondary air is arranged in the lower part of the furnace. No air is sent into the upper part of the furnace, that is, no oxygen is sent in. The slime flow vertically down from the furnace top is burned in the air, and the lack of oxygen in the upper part of the furnace makes the slime flow burn incomplete

[0016] The reason why there are so many problems in coal slime combustion in the current CFB boiler is mainly because there is no similar system technology at home and abroad for complete reference, lack of awareness of practitioners and improper operation adjustment.

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