Inlet smoke temperature adjusting system and method for SCR denitration device

Abstract

The invention discloses an SCR denitration device inlet smoke temperature adjusting system and method, and the system comprises a venturi mixer, an inlet of which is connected with a primary hot air pipeline or / and a secondary hot air pipeline, an injection port of which is connected with a smoke outlet of a superheater and / or a reheater in a boiler, and an outlet of which is connected with an inlet of the SCR denitration device; wherein a valve is arranged on a connecting pipeline between the venturi mixer and the superheater and / or the reheater; and the tail part of the boiler is connected with an inlet of the SCR denitration device through a flue. According to the system, high-temperature flue gas is adopted, so the inlet flue gas temperature of the SCR denitration device in a low-loadstage can be obviously and effectively increased, and even full-load denitration can be realized; and the smoke temperature of the SCR inlet can be reduced under the condition that the smoke temperature exceeds the smoke temperature high limit in the ultra-high load stage, and therefore it is guaranteed that the unit denitration device can normally work in all load sections.

Description

technical field [0001] The invention belongs to the technical field of power plant boilers, and relates to a system and method for adjusting the inlet smoke temperature of an SCR denitrification device. Background technique [0002] The information disclosed in this background section is only intended to increase the understanding of the general background of the present invention, and is not necessarily taken as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to those skilled in the art. [0003] With the rapid development of my country's national economy and the improvement of people's living standards, while the capacity of major power grids continues to expand, the structure of power consumption is also changing. The proportion of municipal power consumption is increasing year by year, and the proportion of industrial power consumption is relatively declining. The peak-to-valley difference is increasing day by day, ...

AI Technical Summary

Problems solved by technology

[0004] However, deep peak shaving is an unconventional operating condition of the unit. Not only is the economy poor, but the safety is also relatively fragile. The most direct problem is that as the load decreases, the combustion intensity of the boiler decreases, and the flue gas temperature decreases accordingly.

At present, power plant boilers basically use SCR denitrification devices to reduce nitrogen oxides. The catalyst requires the flue gas temperature to be 320-420°C. During the deep peak shaving period, the flue gas temperature drops a lot. Ammonia plant exits, nitrogen oxide emissions exceed standard

In order to solve this problem, the methods currently used are: (1) economizer flue gas bypass technology, this technology has a small investment, but has many disadvantages, such as reducing boiler efficiency, limited improvement, and low failure rate of flue gas baffles. (2) The graded economizer technology has the advantages of better economy and does not reduce the boiler efficiency, but it has a large investment, high space requirements, and old units cannot be changed; (3) The economizer water supply bypass, which This technology generally requires less investment, simple construction, and a small amount of work, but the smoke temperature raising capacity is small, and the economizer has the risk of boiling, which reduces the thermal efficiency of the boiler; (4) Economizer hot water recirculation, this technical system is simple, The temperature increase range is large, but it is only suitable for subcritical forced circulation units. It is necessary to add a high-temperature and high-pressure furnace water circulation pump to reduce the reliability of the boiler and reduce the thermal efficiency of the boiler; Power safety, large investment, the disadvantage is that the range of smoke temperature increase is limited, the steam turbine unit is added with an air extraction port, the transformation is difficult, and the thermal efficiency of the boiler is reduced

From the above analysis, it can be seen that the existing problems in the technical transformation to solve the low flue gas temperature at the inlet of the SCR denitrification device are: technical measures with simple technology and small investment, low reliability of equipment, limited range of raising flue gas temperature, and sacrifice Boiler economy; on the other hand, without sacrificing boiler economy, the obvious technical measures to increase the flue gas temperature require large investment, and the system and equipment are more complicated

[0005] In addition, conventional methods have their own advantages and disadvantages in terms of investment, construction, and effect in terms of adjusting and increasing the smoke temperature at the SCR inlet. Among them, one of the common disadvantages of these existing methods is that the smoke temperature at the SCR inlet needs to be adjusted artificially. , it is necessary to greatly increase the labor intensity of the operating personnel. At the same time, if the operating personnel have many operating tasks and neglect the adjustment and over-adjustment of the SCR inlet smoke temperature, it will cause the SCR ammonia injection device to trip, and the environmental protection indicators will exceed the standard, etc. question

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