Ultra-clean discharge system and method for fluidized bed boiler

Abstract

The invention relates to an ultra-clean discharge method for a fluidized bed boiler. The ultra-clean discharge method comprises the following steps of: carrying out in-furnace primary desulfurization in a dense-phase region of the fluidized bed boiler; carrying out primary denitration based on SNCR on the outlet of a furnace cavity; carrying out high-temperature dust removal on a smoke gas which is subjected to the in-furnace primary desulfurization and the primary denitration, and then carrying out secondary denitration based on SCR; carrying out heat exchange on the smoke gas subjected to the secondary denitration to normal smoke discharge temperature, and introducing the smoke gas into a low-temperature dust remover for secondary dust removal; delivering the smoke gas subjected to the secondary dust removal into a desulfurizing system for secondary desulfurization. The invention also provides a corresponding system. According to the method and the system provided by the invention, two-stage dust removal is performed by adopting high-low temperature dust removal devices, combined denitration is performed by combining SNCR and SCR manners, desulfurizing is realized by adopting in-furnace and out-of-furnace manners and accurate control is carried out through a combustion optimization technology and environmental-friendly system parameter, so that the discharge of NOx and SO2 reaches the discharge standard of a gas turbine unit in a key region of the 'fossil-fuel power plant atmospheric pollutant discharge standard' GB13223-2011; in addition, the corresponding system provided by the invention has the advantages of high denitration efficiency, high desulfurization effect, high system reliability, high working condition adaptability, good NOx and SO2 discharge controllability, long operation period, low operation cost and the like.

Description

technical field [0001] The invention belongs to the technical field of boiler environmental protection, and in particular relates to an ultra-clean discharge system and method for a fluidized bed boiler. Background technique [0002] Circulating popularized 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 fluidiz...

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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