Circulating fluidized bed boiler and in-furnace SNCR denitration device and process

Abstract

The invention discloses a circulating fluidized bed boiler and an in-boiler SNCR denitration device and process. The SNCR denitration device comprises an injection system, a medium inlet of the injection system is communicated with a cooling air system, a urea conveying pipeline and a compressed air conveying pipeline; the injection system comprises a plurality of multi-point continuous injectiondevices; the multi-point continuous injection device is coaxially provided with a injection device casing pipe, a compressed air pipeline and a urea solution pipeline from outside to inside; a plurality of injection device atomizing nozzles are arranged in the axis direction of the multi-point continuous injection devices; the injection device atomizing nozzles are communicated with the injectiondevice casing pipe, the compressed air pipeline and the urea solution pipeline; a reducing agent solution and compressed air are distributed and then enter the multi-point continuous injection devices, then atomized and then jetted into the flue gas in a downstream manner to realize section coverage; and meanwhile, the device is cooled, so that the denitration efficiency can be improved, the consumption of a reducing agent and the operation cost are reduced, and the problem that the ultralow emission of nitric oxide of a circulating fluidized bed boiler meets the standard under the medium-lowload condition is solved.

Description

technical field [0001] The invention belongs to the technical field of thermal power denitrification, and in particular relates to a circulating fluidized bed boiler, an SNCR denitrification device in the furnace and a process. Background technique [0002] Since the combustion temperature window of the circulating fluidized bed boiler is around 900°C and the combustion temperature is low, the nitrogen in the air cannot be converted into nitrogen oxides basically, and the original generation of nitrogen oxides is much lower than that of the pulverized coal boiler (more than 1000mg / m 3 ), generally at 200-400mg / m 3 . In addition, because the circulating fluidized bed boiler is equipped with a cyclone separator outside the furnace, the flue gas stays for a long time, and the flue gas is violently turbulent in the separator, and the flue gas mixing effect is good. Therefore, SNCR technology is used in circulating fluidized bed boilers. Higher denitrification efficiency can be...

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Problems solved by technology

However, this process scheme also has the following problems: (1) In the case of medium and low load, the flue gas temperature at the inlet of the separator is lower than 800 °C, and the denitrification reaction efficiency is seriously reduced; (2) The dust concentration is high, and the reducing agent is injected into the flue gas. (3) Due to the limitation of reaction residence time, it is difficult to further improve the denitrification efficiency, and the concentration of nitrogen oxides is higher than 250mg / m 3 For circulating fluidized bed boilers on the left and right, the denitrification efficiency cannot guarantee the ultra-low emission requirements; (4) The flue gas flow rate is high, and the reducing agent injection device wears a lot, so it can only be arranged against the flue wall, resulting in a limited degree of reducing agent mixing; (5) ) Some circulating fluidized bed boilers have limited external space for the inlet flue of the separator, and the injection device cannot be arranged reasonably; (6) Some circulating fluidized bed boilers do not have an external cyclone separator, and the injection device cannot be arranged

[0005] Considering that circulating fluidized bed boilers are faced with the urgent need for deep peak regulation and longer combustion time at medium and low loads; low denitrification efficiency means low urea utilization rate and high ammonia escape concentration, which not only greatly increases the operating cost of denitrification devices, but also Cause blockage and corrosion to boiler follow-up equipment (such as air preheater, low-temperature economizer, etc.); some circulating fluidized bed boilers without external cyclone separators or with limited external space cannot use SNCR technology, and the construction cost of other denitrification technologies and high operating costs

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