A clean discharge system and method for a fluidized bed boiler

Abstract

A clean emission method for a fluidized bed boiler. A first desulphurization is conducted in a dense-phase zone in the fluidized bed boiler; a first denitration based on SNCR is conducted in an outlet of the hearth; the flue gas subjected to the first desulfurization and first denitration in the furnace is subjected to dust removal, heating and secondary denitration based on SCR; and the flue gas subjected to the secondary denitration is sent into a desulfurization system for secondary desulfurization. The invention also provides a corresponding system, which uses an SNCR+SCR combined denitrification mode, and an inside and outside desulfurization mode. Through precise control on parameters of combustion optimization technology and environmental protection system, the NOx and SO2 emission meets the gas turbine emissions standards in key areas of Emission standard of air pollutants for thermal power plants GB13223-2011. The invention has the advantages of high denitration efficiency, high desulfurization efficiency, high system reliability, strong condition compatibility, good controllability of NOx and SO2 emission, long operation cycle and low operating cost.

Description

technical field [0001] The invention belongs to the technical field of boiler environmental protection, and in particular relates to a clean discharge system and method for a fluidized bed boiler. Background technique [0002] Circulating fluidized bed boiler technology is a high-efficiency, low-pollution and clean combustion technology that has developed rapidly in the past ten years. It has wide fuel adaptability, high combustion efficiency, efficient desulfurization, and nitrogen oxides (NO X ) low emission, high combustion intensity, small furnace cross-sectional area, large load adjustment range, fast load adjustment, easy to realize comprehensive utilization of ash and slag, simple fuel pretreatment system, and few coal feeding points. Therefore, this technology has been widely used commercially in the fields of power station boilers, industrial boilers and waste treatment and utilization. [0003] Operating experience shows that the NO of circulating fluidized bed bo...

AI Technical Summary

Problems solved by technology

[0006] The advantages of SCR are: high denitrification efficiency (70-90%), mature technology, and many domestic applications; the disadvantages are: high investment cost (requires catalyst, cost is more than 3 times that of SNCR), high operating cost (reductant, catalyst ), the installation method greatly changes the boiler structure, the tail is easy to be stained and corroded, and is suitable for new pulverized coal units

[0007] The advantages of SNCR are: small footprint (arranged on the boiler body), low investment cost (1 / 4-1 / 3 of SCR), low operating cost (0.003-0.004 yuan / kWh), installation and operation Relatively easy, mature technology; adapt to rapid changes in parameters, load, and coal quality; help reduce average cost, do not catalyze the increase of sulfur trioxide (SO 3 ), will not cause blockage or corrosion of the rear heating surface and air preheater; it is especially suitable for the denitrification transformation of CFB units and old units; the disadvantages are: the denitrification efficiency is not high enough, and the amount of ammonia escape is slightly higher than that of SCR

The disadvantages are: less experience in the application of fluidized bed boilers, and there are also problems such as short service life of SCR catalysts

Fluidized bed boiler can reduce SO by adding desulfurizer (limestone, carbide slag, etc.) 2 The emission value is controlled to a low level, but under the new environmental protection standard, the existing desulfurization device in the furnace has problems such as insufficient output, poor economy, and difficulty in desulfurization.

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