A Composite Control System for Nitrogen Oxide Emissions of Layer Burning Furnace

Abstract

The invention belongs to the technical field of boiler energy conservation and environmental protection, and discloses a compound control system for the nitrogen oxide discharge amount of a grate-fired furnace. The compound control system comprises a grate-fired furnace body, stage combustion devices with flue gas recirculation, an SNCR (selective non-catalytic reduction) denitration device, a multifunctional flue gas online monitor and a PLC (programmable logic controller) control system, wherein the stage combustion devices are uniformly distributed on walls at two sides of a combustion chamber, an air inlet pipe is arranged in the center of an air inlet end of the stage combustion devices, an adiabatic flame stabilization blunt body is arranged at the other end of the air inlet pipe, a secondary wind cyclone is arranged on the wall at the air inlet end, and a combustion stabilization cavity is arranged at one end far from the air inlet end; and an appropriate amount of a mixture of powdered coal or fuel gas, fresh air and circulating flue gas is sprayed into the grate-fired furnace through the stage combustion devices. The compound control system disclosed by the invention can significantly improve the oxidation reaction speed of a fuel and the temperature uniformity of the combustion chamber, and can achieve full combustion and low-nitrogen combustion of the fuel and reduce the coefficient of excess air, thereby realizing double promotion of denitration efficiency and heat efficiency, and achieving the aims of energy conservation and emission reduction.

Description

technical field [0001] The present invention relates to the technical field of boiler energy saving and environmental protection, and more specifically, relates to a composite control system for nitrogen oxide discharge of a layer-burning furnace, which can realize full fuel combustion and low-nitrogen combustion, and realize double improvement of denitrification efficiency and thermal efficiency . Background technique [0002] Coal-fired boilers are divided into two types: floor-burning furnaces and chamber-burning furnaces. Among them, the capacity of floor-burning furnaces is relatively small, but they are widely used because of their simple structure, convenient operation and low requirements for the quality of firemen. According to statistics, their proportion is as high as 60% ~70%, its application covers many industries such as building materials, chemical industry, printing and dyeing, heat treatment, pharmaceuticals, etc. The layer combustion furnace pays more atte...

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Problems solved by technology

[0004] The principle of flue gas recirculation is to add 20 to 30% of the flue gas to the combustion-supporting air, and reduce the temperature of the combustion zone by reducing the oxygen content of the combustion air, thereby inhibiting the formation of NOx. The principle of this technology is simple and the investment is not large. The denitrification efficiency is about 10-30%, but it is limited to the combustion method of the layer combustion furnace. Its combustion intensity is low and the combustion speed is not high. There are certain limitations in the application of the flue gas recirculation technology. The specific performance is as follows: ① Use flue gas In the case of recycling technology, there are problems such as the increase of carbon content in ash and the further reduction of furnace temperature, which leads to the decrease of thermal efficiency of layer combustion furnace

② If the combination technology of flue gas recirculation and SNCR is used, the denitrification efficiency of SNCR will also be reduced due to the low furnace temperature and narrowed reaction temperature window

However, when SNCR technology is applied to the layer-burning furnace, problems such as uneven furnace temperature distribution, limited space and low temperature are often encountered, which lead to difficulties in finding effective ammonia injection points, insufficient reduction reaction time, and increased ammonia escape rate, which in turn affects denitrification. Efficiency, ammonia water consumption increases, and ammonia escape will also cause serious air pollution problems

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