RU2042885C1 - Method of lowering temperature of exhaust gases - Google Patents

Abstract

FIELD: boiler engineering. SUBSTANCE: withdrawing heat by one of the heating surfaces, wherein exhaust gas is cooled, is increased owing to preliminary cooling of fluid to be heated by this surface, supplying water of the boiler being used as the fluid. EFFECT: simplified method. 1 dwg

Description

 The invention relates to a power system and can be used in the design and operation of boilers burning low-calorie fuel, such as blast furnace gas.

 A known method of reducing the temperature of the exhaust gases in boilers, based on the increase in the "tail" heating surfaces. (Styrikovich M.A. Katkovskaya K.N. and Serova E.P. Steam generators of power plants. Energy, second ed., 1966, p. 45).

However, increasing the surface of a more economically optimal limit is impractical and impossible. When the surface of the water economizer increases due to the difference in the heat capacities of water and gases (the heat capacity of the water is several times greater than the heat capacity of the gas), the temperature head (the difference between the gas and water temperature) at the cold end of the economizer (at the gas outlet from the economizer) drops sharply and tends to zero , since the gas is cooled and its temperature tends to the temperature of the water in the economizer. With an increase in the surface of the air heater, the air temperature increases rapidly (the heat capacity of the gas is much greater than the heat capacity of the air) and the temperature head at the “hot” end (hot air exit from the air heater) theoretically approaches zero, i.e. air quickly heats up to gas temperature. Thus, when burning low-calorific gas, the temperature of the flue gases in the “tail” surfaces is relatively high due to the low temperature head at the “cold” end of the water economizer and the “hot” end of the air heater. Moreover, an increase in the surface of the water economizer and an air heater that is more optimal does not allow lowering the temperature of the flue gases due to a decrease in the temperature head at the indicated points. Therefore, in existing boilers designed for the combustion of blast furnace gas, when running on a blast furnace gas is necessary to reduce boiler load due to high temperature exhaust gases, as chimneys not withstand temperatures over 200 ° ^C. Another solution is to add gas to the domain high calorific fuel. All this reduces the efficiency of the boiler.

 There is a known method of operation of a boiler unit, in which, in order to increase efficiency by making better use of the heat of the boiler’s flue gases, heat is transferred to the fuel from flue gases using an additional circuit with an intermediate heat carrier (ed. St. N 950997, class F 23 L 15/00).

 However, the use of additional heat exchangers with an intermediate heat carrier (especially gaseous) dramatically complicates and increases the cost of the design.

 The aim of the invention is to remedy these disadvantages.

 In the proposed method for reducing the temperature of the flue gases in the boiler when burning low-calorific fuel, for example blast furnace gas, which includes cooling the flue gases by passing them through the tail surfaces of the boiler formed by the air heater and economizer, to achieve the goal, they increase the heat perception of the water economizer by cooling the feed water before it enters boiler.

The drawing shows a diagram of the proposed method of reducing the temperature of the exhaust gases in boilers
The feed water enters the heat exchanger 1, is cooled in it by the blast furnace gas entering the burners 2, and enters the water economizer.

 When the boiler operates on blast furnace gas, the feed water entering the boiler after heating it in low and high pressure heaters and a deaerator, before entering the boiler water economizer, passes an additional heat exchanger and is cooled by blast furnace gas, heating it before entering the boiler burners. Cooling the feed water in an additional heat exchanger increases the temperature head and heat perception of the water economizer and reduces the temperature of the flue gases. The heat received by the blast furnace gas in the additional heat exchanger from the feed water is transferred in the form of radiant heat to the furnace screens. Heated blast furnace gas intensifies the combustion process in the furnace.

Claims (1)

 METHOD FOR REDUCING THE EXHAUST GAS TEMPERATURE in the boiler when burning low-calorific fuel, such as blast furnace gas, which includes cooling the exhaust gases by passing them through the boiler tail surfaces formed by an air preheater and economizer, while increasing the heat perception of one of the surfaces by pre-cooling the medium heated in this surface, which that, in order to increase efficiency, pre-cool the blast furnace gas with the medium entering the economizer, as which uses boiler feed water.

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