Composite hot water recirculation system and method for full-load denitration of supercritical power station boiler

Abstract

The invention discloses a composite hot water recirculation system for full-load denitration of a supercritical power station boiler. The composite hot water recirculation system comprises a water feeding bypass pipeline; a water inlet end of the water feeding bypass pipeline communicates with a main water feeding pipeline of a boiler located at the upstream of a coal economizer; a water outlet end of the water feeding bypass pipeline is connected with a descending pipeline located at an outlet of the coal economizer; and a gate valve and a regulating valve are arranged on the water feeding bypass pipeline. The flow of water fed by the water feeding bypass pipeline can be adjusted, the flow of cold water entering the coal economizer to participate in flue gas heat exchange is reduced, the heat absorption capacity of the coal economizer is reduced, and therefore the temperature of flue gas at an inlet of a denitration device is increased. The invention discloses a composite hot water recirculation method for full-load denitration of the supercritical power station boiler, which comprises the steps of: shunting the water on the main water feeding pipeline located at the upstream of the inlet of the coal economizer to the descending pipeline located at the outlet of the coal economizer; and adjusting the amount of shunted water. The system and the method disclosed by the invention have the beneficial effects of reducing the flow of cold water entering the coal economizer to participate in flue gas heat exchange, reducing the heat absorption capacity of the coal economizer and increasing the temperature of flue gas at the inlet of the denitration device.

Description

technical field [0001] The invention relates to the field of full-load denitrification. More specifically, the present invention relates to a composite hot water recirculation system and method for full-load denitrification of supercritical power plant boilers. Background technique [0002] At present, most of the denitrification devices of power plant boilers adopt selective catalytic reduction (SCR) technology, and the catalysts used generally require a working temperature range between 300 and 400 °C (related to coal types, catalyst types, etc.). In the design of conventional boilers, there will be the following problems: when the load of the unit is high, the flue gas temperature at the inlet of the denitrification device is just within the normal operating range of the catalyst, and when the load of the unit is low, the flue gas temperature at the inlet of the denitrification device is lower than the normal operating range of the catalyst Operating temperature. If the...

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Problems solved by technology

In the design of conventional boilers, there will be the following problems: when the load of the unit is high, the flue gas temperature at the inlet of the denitrification device is just within the normal operating range of the catalyst, and when the load of the unit is low, the flue gas temperature at the inlet of the denitrification device is lower than the normal operating range of the catalyst Operating temperature

The graded economizer has poor matching between high and low loads and cannot meet the requirements of full-load denitrification; the flue gas bypass has shortcomings such as poor flue gas temperature field distribution and low reliability of the flue gas baffle; the economizer water side bypass has The temperature increase range is limited, the working medium is easy to vaporize and other disadvantages; the above-mentioned conventional solutions cannot meet the strict requirements of the country for deep peak regulation of thermal power units, and cannot achieve a safe and stable increase of the SCR inlet smoke temperature under full load conditions.

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