A method and system for reducing NOx emissions and stabilizing combustion of utility boilers

Abstract

The invention discloses a method and a system for realizing NOx discharge reduction and stable combustion of a power station boiler, which belongs to the technical scope of coal powder power station environmental protection. In the system, a coal mill is connected to a fluidized bed gasifier and a boiler respectively, and a top syngas outlet of the fluidized bed gasifier is connected to a boiler combustor. The method particularly comprises the following steps: performing fluidized bed gasification of fire coal which is 5-20% of the boiler load, delivering the syngas generated in the fluidized bed to a boiler reburning combustor for reburning so as to reduce NOx discharge, or delivering the syngas to a boiler main fuel combustor so as to allow the syngas to be used as auxiliary fuel and to combust stably when the boiler combusts inferior coal of has a low load; after treatment, delivering the gasified top ash and bottom slag in the fluidized bed to a primary air channel of a boiler coal powder combustor, mixing with coal powder so as to combust the uncombusted components. During the cooling process, the heat of high-temperature bottom slag is taken away by supplying water into the boiler, and the bottom slag is delivered to a heating surface of the boiler for heating. The invention realizes the effect of NOx discharge reduction and stable combustion of a power station boiler.

Description

technical field [0001] The invention belongs to the technical scope of environmentally friendly combustion of pulverized coal in a power station, and in particular relates to a method and system for reducing NOx emissions and stabilizing combustion of a power station boiler. Specifically, the synthetic gas obtained by fluidized bed gasification is used as the reburning fuel or stable combustion fuel of the power plant boiler to achieve the purpose of reducing NOx or stabilizing combustion. technical background [0002] The use of coal has brought a lot of pollution. According to the "Research Report on China's Thermal Power Plant Nitrogen Oxide Emission Control Technology Scheme" issued by the China Environmental Protection Industry Association, the total amount of nitrogen oxides emitted by thermal power plants in 2007 was 8.4 million tons, compared with 2003. An increase of nearly 40.6%, accounting for about 35%-40% of the national nitrogen oxide emissions. [0003] In Fe...

AI Technical Summary

Problems solved by technology

However, the direct use of coal-based fuel as reburning fuel also has certain problems. The use of conventional pulverized coal as reburning fuel has a low burnout rate and high carbon content in fly ash, which affects combustion efficiency and causes secondary pollution.

The ultra-fine pulverized coal is more convenient for power plant boilers with a small-capacity medium-storage pulverizing system (ultrafine pulverized coal in the tertiary air), and the large-capacity boiler adopts the direct blowing pulverizing system for safety and land occupation. Stable source of ultra-fine pulverized coal

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