Arrangement structure of tail flue of a double reheat boiler

Abstract

The invention discloses a tail flue arrangement structure of a secondary reheating boiler. The tail flue is divided into a front flue, a middle flue and a rear flue from front to back, coal economizers, a first low-temperature reheater located in the front flue, a second low-temperature reheater located in the middle flue and a low-temperature superheater located in the rear flue are arranged in the tail flue, the coal economizers comprise an inlet header, a first-stage coal economizer, a second-stage coal economizer and an outlet header, wherein the inlet header, the first-stage coal economizer, the second-stage coal economizer and the outlet header are connected successively in series, the first-stage coal economizer comprises a first-stage coal economizer tube group and a second-stage economizer tube group which are connected in parallel, the first-stage coal economizer tube group is arranged at the lower part of the first low-temperature reheater, the second-stage coal economizer tube group is arranged at the lower part of the second low-temperature reheater, and the second-stage coal economizer acts as a third-stage coal economizer tube group arranged at the lower part of thelow-temperature superheater. According to the tail flue arrangement structure of the secondary reheating boiler, the series-parallel grading arrangement of the coal economizer tube groups is carried out based on the smoke temperature of the flue of each-stage coal economizer tube group, the heat absorption deviation among the coal economizer tube groups in flues at the tail part is eliminated, sothat the minimum under-enthalpy of the working medium in the coal economizers is expanded.

Description

technical field [0001] The invention relates to the technical field of power plant boilers, and more specifically, relates to an arrangement structure of flue gas regulating baffles for a three-flue boiler at the rear. Background technique [0002] The layout structure of the three-flue boiler at the end of the conventional double reheat boiler is as follows: figure 1 As shown, the width of 1000MW and 1300MW boilers is usually about 30m and 38m. If the connecting rod of the flue gas regulating baffle installed in the tail flue is drawn from both sides, the torque will be large and easy to deform, which will affect the temperature adjustment effect. Generally, the form of leading from the front and rear of the tail shaft is adopted. However, for the tail three-flue boiler, there must be a problem that the connecting rod of the flue gas regulating baffle in the middle flue passes through the flue, so the middle flue The connecting rod of the baffle is faced with problems such...

AI Technical Summary

Problems solved by technology

According to this arrangement, the economizer tube group in each flue will have a heat absorption deviation, that is, the economizer tube group at the lower part of the low-temperature superheater absorbs the most heat

In addition, in order to reduce the heat consumption of the turbine and improve the efficiency of the unit, the temperature of the feed water provided by the thermal system of the turbine is generally increased (generally reaching about 330°C), and at the same time, the power plant has higher requirements for boiler efficiency (for bituminous coal, it is generally expected to be about 95%), As a result, the overall heat absorption of the economizer does not decrease but increases, resulting in a further increase in the temperature of the working fluid at the outlet of the economizer and a sharp decrease in the lack of enthalpy

However, the enthalpy deficit of the working fluid in the economizer tube group at the lower part of the low-temperature superheater is extremely small, and it is easy to vaporize under conditions such as load fluctuations and coal quality fluctuations, hindering the flow of working fluid in the economizer, and even affecting the safe operation of the water wall

Once the working fluid of the economizer in the side flue of the low-temperature superheater is vaporized, it will inevitably lead to a further increase in the outlet flue temperature, the boiler exhaust gas temperature will increase, and the boiler efficiency may not meet the standard risk

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