System and method for blending combustion of sludge by flue gas recirculation in coal-fired power plant

Abstract

The invention relates to a system and method for blending combustion of sludge by flue gas recirculation in a coal-fired power plant. The system comprises a sludge particle preparation system which is used for using a heat source from a sludge drying system to prepare dry sludge, mixing the dry sludge with pulverized coal, and crushing the mixture to prepare granular mixed fuel; a fire coal particle conveying system which is used for conveying the mixed fuel to a combustor mounted on a hearth of a coal-fired boiler; a sludge drying system which comprises a coal economizer; and an adsorbent conveying system. Part of flue gas at an inlet and an outlet of the coal economizer is led out, mixed and then fed into a dryer of the sludge particle preparation system to be used as a heat source for sludge drying; and the adsorbent conveying system is used for heating the flue gas subjected to heat exchange with the dryer and then utilizing the flue gas to carry a mineral adsorbent to enter the furnace so as to inhibit heavy metal emission in the sludge and coal blending combustion process. Existing equipment of a coal-fired power plant is fully utilized, the sludge drying system and the coal-fired power plant system are coupled, the energy consumption of the system is reduced, and the flexibility and economical efficiency of the system are enhanced.

Description

technical field [0001] The invention relates to the technical field of sludge drying and incineration treatment technology and heavy metal discharge control technology, in particular to a coal-fired power plant using flue gas recirculation to blend and burn sludge system and method. Background technique [0002] The sludge heat treatment method can not only kill the bacteria and harmful substances in the sludge, but also can effectively use the heat energy of the combustible components in the sludge, which greatly protects the environment while taking into account the sludge volume reduction and treatment efficiency. , is currently one of the main means and methods of sludge treatment and disposal. However, when sludge is incinerated alone, there are problems such as low calorific value, complicated process, high operating cost, large equipment investment, and unstable effect. Therefore, there are obvious advantages in using coal-blended sludge in coal-fired power plants. B...

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Problems solved by technology

[0003] The following problems still exist in the current sludge disposal system of coal-fired power plants: (1) The moisture content of wet sludge is as high as 80%, and it must be pre-dried, crushed, etc. before entering the combustion system of the power plant. Treatment to meet the operating parameters of the coal-fired boiler in the power plant and ensure combustion efficiency is one of the key links in the blended combustion system

If the wet sludge is dried separately, the operating cost, operation and maintenance cost, etc. will be increased, the integration of the system will be weakened, and the operating efficiency will be reduced; if the boiler exhaust gas is used for direct drying treatment, the organic matter in the sludge will be volatilized. Malodorous gas, malodorous gas will enter the flue gas and cause environmental pollution

(2) The heavy metals in the sludge will be transferred to the flue gas and combustion ash. They are relatively stable and difficult to remove. If they are directly discharged into the environment with the flue gas, they will cause serious heavy metal pollution.

(3) The flexibility of the system operation is not high. The moisture content of sludge and the amount of sludge blended combustion are one of the key parameters of the blended combustion system of coal-fired power plants. It is necessary to provide effective feedback on the sludge drying effect and the blended combustion situation. Actual operation of the power plant to properly regulate the system

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