A precise desulfurization method for circulating fluidized bed boiler

Abstract

The invention relates to the technical field of desulphurization of circulating fluidized bed boilers, in particular to a precise in-boiler desulphurization method applicable to low-calorific-value fuel such as coal gangue, coal slime and the like in the circulating fluidized bed boiler combustion process, and provides a low-calorific-value coal combustion sulfur fixation technology capable of effectively reducing the calcium-sulfur ratio, effectively utilizing fine limestone powder, reducing the escape rate of limestone powder and improving the sulfur fixation efficiency. The precise desulphurization method of the circulating fluidized bed boiler comprises steps as follows: a, preparing a coal slime type coal sulfur-fixing agent from the fine limestone powder, modified fly ash and coal slime; b, mixing prepared coal slime type coal, coal gangue and coarse limestone powder for combustion; c, monitoring the concentration of SO2 in flue gas and controlling spraying of the coarse limestone powder. The method is mainly applied to desulfurization.

Description

technical field [0001] The invention relates to the technical field of desulfurization of circulating fluidized bed boilers, and more specifically, relates to a precise in-furnace desulfurization method suitable for low calorific value fuels such as coal gangue and coal slime in the combustion process of circulating fluidized bed boilers. Background technique [0002] Coal gangue and coal slime, as one of the largest industrial wastes in my country, produced about 800 million tons in 2013 and accumulated nearly 5 billion tons in stockpiles, causing serious environmental pollution and waste of resources. The use of circulating fluidized bed boilers for combustion power generation is one of the important ways for large-scale utilization of low calorific value coal such as gangue and coal slime. However, the sulfur content in low calorific value coal such as gangue and coal slime is usually high, and the combustion process Medium SO X release is larger. With the implementatio...

AI Technical Summary

Problems solved by technology

Although the invention is easy to adjust and control, and has a high utilization rate of the desulfurizing agent, the cost of equipment modification is relatively high, and the particle size of the desulfurizing agent is strictly required

[0004] Chinese invention patent application (201410466872.7) discloses a method for preparing a mixed desulfurizer for circulating fluidized bed boilers. The mixed desulfurizer is prepared by stirring and mixing coal slime and limestone fine powder. First, the limestone fine powder is passed through a star wheel feeder. 1. After being stirred by the differential turbine, it falls to the coal slime conveyor belt, and then the preliminarily mixed material enters the twin-shaft mixer and is then sent to the briquette forming machine to be pressed into a spherical mixed desulfurizer. This method has simple system, small investment and high utilization rate of desulfurizer. , the proportion of blended coal slime is high, but the molding effect is not good. It is easy to crush before falling into the belt conveyor and entering the furnace. At the same time, it lacks a corresponding adjustment mechanism, and it is difficult to control the desulfurization efficiency.

[0005] At present, circulating fluidized bed boilers in low calorific value coal power plants mainly use limestone powder injection for sulfur fixation in the furnace. The main existing problems are: high calcium-sulfur ratio, high escape rate of limestone powder, serious waste, and low sulfur fixation rate

Circulating fluidized bed boilers have strict requirements on the particle size of limestone powder. The optimum particle size range is 0.2-0.7mm. Fine powder with a particle size of less than 0.2mm will be directly discharged with the wind and smoke after entering the boiler and cannot be effectively used. However, a large amount of limestone fine powder (≤0.2mm, accounting for about 30%) produced in the limestone crushing process has a high escape rate and a high cost of sulfur fixation when used directly with limestone.

Moreover, calcium sulfate, the sulfur-fixed product, is prone to secondary decomposition in a high-temperature reducing atmosphere, and re-releases sulfur dioxide, which greatly reduces the desulfurization rate.

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