CN104534439A - System and method for indirectly heating air heater through extracted low-level steam in waste heat cascade utilization mode - Google Patents

Abstract

A low-energy extraction steam indirect heating air heater system and method for waste heat cascade utilization, the system includes a flue gas heat exchanger installed between the flue air preheater and the electrostatic precipitator at the tail of the boiler, and installed on the air side of the air preheater The air heater in front of the inlet is connected to the flue gas heat exchanger, the air heater and the circulating water pipeline of the condensed water; the condensed water at the outlet of the No. 7 low-pressure heater is used to heat the primary and secondary cold air in the air heater, and the air heater The return water from the outlet is sent back to the inlet of No. 8 low-pressure heater, and the condensate flow of No. 8 low-pressure heater and No. 7 low-pressure heater increases, which increases the flow rate of 8 extraction steam and 7 extraction steam, and realizes the utilization of 8 extraction steam and 7 extraction steam The purpose of the indirect heating heater; part of the condensed water drawn from the inlet of the No. 6 low-pressure heater is sent to the flue gas heat exchanger to absorb heat, and is led back to the heat recovery system from the outlet of the No. 6 low-pressure heater, and flows through the No. 6 low-pressure heater The condensed water flow of the device is reduced, so that the steam flow of the 6 extraction steam is also reduced correspondingly, and the displaced part of the 6 extraction steam is sent to the steam turbine to do work, and the economy of the unit is improved.

Description

System and method for indirect heating heater system and method for low-energy steam extraction in cascade utilization of waste heat

technical field

The invention relates to the technical field of thermal power generation, in particular to a low-energy extraction steam indirect heating air heater system and method for cascaded utilization of waste heat.

Background technique

With the rising global energy prices and the deteriorating climate around the world, the country has more stringent requirements for energy conservation and consumption reduction. How to deeply tap the energy-saving potential of existing power plant units and reduce the production and operation costs of enterprises has become a common concern of every enterprise. important question.

Most power plant boiler units in northern my country are equipped with heater systems to solve the problems of low-temperature corrosion at the cold end of the air preheater and clogging of dust accumulation caused by low air temperature at the inlet of the air preheater in winter or low exhaust gas temperature under low load . The current heater system mostly adopts 4-exhaust steam heating or 6-exhaust steam heating, and the energy level of the heat source is relatively high, which is uneconomical. If the heat of extraction steam with a lower energy level is used for direct heating, steam extraction is required under negative pressure, and the density of extraction steam is low, the volume flow rate is large, thicker steam transmission pipelines are required, and there are many problems. Therefore, it is necessary to consider other more economical heat sources to heat the air heater to improve the economy of the unit.

The exhaust gas temperature of boilers in my country's active thermal power units is generally maintained at around 125-150 °C, which is higher than the design value. Generally, every 20°C increase in exhaust gas temperature will increase the heat loss of exhaust gas by 0.6% to 1.0%, which will have a negative impact on the economy of the unit. As the temperature of the cold air at the outlet of the heater increases, the exhaust gas temperature of the boiler will further increase. In order to ensure that the economy of the unit does not decrease with the operation of the heater, it is necessary to recover and utilize the waste heat of the boiler flue gas. Installing the flue gas heat exchanger after the air preheater can effectively recover the waste heat of the flue gas, and reduce the temperature and flow of the flue gas entering the subsequent electrostatic precipitator, desulfurization tower and induced draft fan, so as to ensure that the economical efficiency of the unit will not be affected by the operation of the heater. reduce.

Contents of the invention

In order to overcome the above-mentioned problems in the prior art, the object of the present invention is to provide a low-energy-level extraction steam indirect heating air heater system and method for cascaded utilization of waste heat, using low-energy extraction steam to indirectly heat the air heater, and at the same time using smoke The gas heat exchanger recovers the waste heat of the flue gas and uses it to replace the higher energy level extraction steam, so as to realize the optimal arrangement of the heat source of the heater and the cascaded utilization of low energy level heat.

In order to realize the above-mentioned purpose of the invention, the technical scheme that the present invention takes is:

The low-energy steam extraction indirect heating air heater system utilizing the waste heat cascade includes the flue gas heat exchanger 2 installed between the flue air preheater 1 and the electrostatic precipitator 3 at the tail of the boiler, and the air preheater 1 installed in the air The air heater 10 in front of the side entrance connects the flue gas heat exchanger 2 and the air heater 10 with the circulating water pipeline of condensed water. The connection relationship between the air heater 10 and the circulating water pipeline of condensed water is: No. The condensate outlet of the heater 8 is divided into two routes, one of which is connected to the inlet of the heater 10, and the outlet of the heater 10 is connected to the No. One way is connected to the condensed water inlet of No. 6 low-pressure heater 7; the connection relationship between the flue gas heat exchanger 2 and the condensed water circulating water pipeline is: No. 6 low-pressure heater 7 condensed water inlet leads one way to the flue gas heat exchanger 2. The condensed water outlet of the flue gas heat exchanger 2 is connected to the heat recovery system through the outlet 7 of the No. 6 low-pressure heater.

The method for indirect heating of the air heater and cascade utilization of exhaust waste heat in the above-mentioned system is as follows: part of the condensed water is drawn from the outlet of the No. 7 low-pressure heater 8 to heat the primary and secondary cold air in the air heater 10, and the air preheater 1 Inlet air temperature; the condensed water released by No. 8 low-pressure heater 9 in the air heater is led back to the heat recovery system by the inlet of No. 8 low-pressure heater 9, so that the flow of condensed water flowing through No. 8 low-pressure heater 9 and No. 7 low-pressure heater 8 increases, As the thermal power increases, the flow rates of the 8 extraction steam 11 and the 7 extraction steam 12 respectively connected to the No. The heat indirectly heats the primary and secondary air in the heater 10; part of the condensed water drawn from the inlet of the No. 6 low-pressure heater 7 is sent to the flue gas heat exchanger 2 to absorb heat, and is discharged from the outlet of the No. 6 low-pressure heater 7 Leading back to the heat recovery system, the flow of condensed water flowing through the No. 6 low-pressure heater 7 decreases, and the steam flow of the 6 extraction steam 13 connected to the No. 6 low-pressure heater 7 also decreases accordingly, and the displaced part 6 extraction steam 13 is sent to the steam turbine Work; because the energy level of 6 extraction steam extraction 13 is higher than 8 extraction steam extraction 11 and 7 extraction steam extraction 12, the working ability of the displaced 6 extraction steam extraction 13 is higher than that of 8 extraction steam extraction 11 and 7 extraction steam extraction 12 flow increase loss function power, the economy of the unit is improved.

Compared with the prior art, the present invention has the following advantages:

After adopting the system of the present invention, the heat source of the air heater can be indirectly used to extract steam at a low energy level, and the heat source has been rationally optimized, and at the same time, the energy level of the exhaust heat of the boiler is improved, so that it can be used in a higher energy level low-pressure heater , to realize the cascade utilization of exhaust heat. The present invention adopts the scheme of heating the condensed water by low-energy level steam extraction, and then uses the condensed water to heat the air heater, which not only reduces the energy level of the heating heat source, but also avoids the need to be in a negative pressure state when using low-energy level steam extraction to directly heat the air heater The lower extraction steam and the large volume flow rate of the extraction steam improve the economical efficiency of the unit.

Description of drawings

Accompanying drawing is the structural representation of the present invention.

Among them, 1 is the air preheater, 2 is the flue gas heat exchanger, 3 is the electric precipitator, 4 is the induced draft fan, 5 is the desulfurization tower, 6 is the chimney, 7 is the No. 6 low-pressure heater, and 8 is the No. 7 low-pressure heater. Heater, 9 is No. 8 low-pressure heaters, 10 is air heater, 11 is 8 extractions, 12 is 7 extractions, and 13 is 6 extractions.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in the drawings, the low-energy-level steam extraction indirect heating air heater system for waste heat cascade utilization of the present invention includes a flue gas heat exchanger 2 installed between the flue air preheater 1 at the boiler tail and the electric precipitator 3, The air heater 10 installed in front of the air side inlet of the air preheater 1 connects the flue gas heat exchanger 2 and the air heater 10 with the circulating water pipeline of the condensed water, and the air heater 10 is connected with the condensed water circulating water pipeline The connection relationship is as follows: No. 7 low-pressure heater 8 condensate outlet is divided into two routes, one way is connected to the inlet of heater 10, and the outlet of heater 10 is connected to No. 8 low-pressure heater 9 and the heat recovery system in turn, and No. The other path of the condensed water outlet of heater 8 is connected to the condensed water inlet of No. 6 low-pressure heater 7; the connection relationship between the flue gas heat exchanger 2 and the condensed water circulating water pipeline is: the condensed water inlet of No. One way is connected to the flue gas heat exchanger 2, and the condensed water outlet of the flue gas heat exchanger 2 is connected to the heat recovery system through the outlet 7 of the No. 6 low-pressure heater.

As shown in the accompanying drawings, the method for indirect heating of the air heater and cascade utilization of exhaust waste heat in the system of the present invention is as follows: part of the condensed water is drawn from the outlet of No. 7 low-pressure heater 8 to heat the primary and secondary cold air in the air heater 10 , to increase the air temperature at the inlet of air preheater 1; the condensed water after the heat released by 10 in the air heater is led back to the heat recovery system from the inlet of No. 8 low-pressure heater 9, so that it flows through No. 8 low-pressure heater 9 and No. 7 low-pressure heater The condensed water flow rate of 8 increases, the thermal power increases, and the flow rate of 8 extraction steam 11 and 7 extraction steam 12 connected to No. 8 low-pressure heater 9 and No. 7 low-pressure heater 8 respectively increases, thereby realizing 8 extraction steam 11 and 7 extract the heat of steam extraction 12 to indirectly heat the purpose of the primary and secondary air in the air heater 10.

As shown in the figure, due to the increase of the temperature of the primary and secondary air at the outlet of the air heater 10, the temperature of the exhaust gas at the outlet of the air preheater 1 increases, and the energy level of the waste heat of the flue gas increases. The flue gas heat exchanger 2 after the heater 1 absorbs. Part of the condensed water drawn from the inlet of No. 6 low-pressure heater 7 is sent to the flue gas heat exchanger 2 to absorb heat, and is led back to the heat recovery system by the outlet of No. 6 low-pressure heater 7, and the condensed water flowing through No. 6 low-pressure heater 7 As the flow rate decreases, the steam flow rate of the 6 extraction steam 13 connected to the No. 6 low-pressure heater 7 also decreases accordingly, and the displaced part 6 extraction steam 13 is sent to the steam turbine for work; the flue gas at the outlet of the flue gas heat exchanger 2 passes through the electric precipitator in turn Device 3, induced draft fan 4, desulfurization tower 5 and chimney 6 are emptied.

Because the energy level of the 6 extraction steam extraction 13 is higher than the 8 extraction steam extraction 11 and the 7 extraction steam extraction 12, the working ability of the displaced 6 extraction steam extraction 13 is higher than the working ability of the 8 extraction steam extraction 11 and the 7 extraction steam extraction 12 flow rate increase loss, In the above-mentioned system layout plan, since the temperature of the primary and secondary air in the heater 10 is indirectly heated by the 8 extraction steam extraction 11 and the 7 extraction steam extraction 12, the temperature of the exhaust gas is increased, and the exhaust gas with a higher energy level is generated. The waste heat is used to displace 6 and extract steam 13, thereby achieving the purpose of using low-grade extraction steam heat to replace high-grade extraction steam heat, and the overall economic efficiency of the unit is improved.

Claims (2)

1. the low-lying level of exhaust heat stepped utilization is drawn gas indirect steam air heater system, it is characterized in that: comprise the flue gas heat-exchange unit (2) be arranged between boiler back end ductwork air preheater (1) and electric cleaner (3), be arranged on the steam air heater (10) before air preheater (1) air side entrance, connect the circulating water line of flue gas heat-exchange unit (2) and steam air heater (10) and condensate water, described steam air heater (10) with the annexation of the circulating water line of condensate water is: No. 7 low-pressure heater (8) condensate water export a point two-way, the entrance on one tunnel access steam air heater (10), the outlet of steam air heater (10) connects No. 8 low-pressure heaters (9) and heat regenerative system successively, another road of No. 7 low-pressure heater (8) condensate water outlets connects the condensate water import of No. 6 low-pressure heaters (7), described flue gas heat-exchange unit (2) with the annexation of the circulating water line of condensate water is: the condensate water import of No. 6 low-pressure heaters (7) is drawn a road and accessed flue gas heat-exchange unit (2), and the condensate water outlet of flue gas heat-exchange unit (2) is by No. 6 low-pressure heater (7) outlet access heat regenerative systems.

2. described in claim 1, the method for system indirect steam air heater and smoke discharging residual heat cascade utilization is: it is characterized in that:

Export first and second cold wind in extension condensate water heating steam air heater (10) by No. 7 low-pressure heaters (8), improve air preheater (1) entering air temperature, condensate water in steam air heater after (10) release heat leads back heat regenerative system by No. 8 low-pressure heater (9) entrances, the condensing water flow flowing through No. 8 low-pressure heaters (9) and No. 7 low-pressure heaters (8) is increased, thermal power increases, corresponding draw gas with 8 of the connection of No. 8 low-pressure heaters (9) and No. 7 low-pressure heaters (8) respectively (11) and 7 the draw gas flow of (12) increases, thus achieve 8 draw gas (11) and 7 draw gas (12) heat indirect steam air heater (10) in one, the object of Secondary Air,

The partial coagulation water of being drawn by No. 6 low-pressure heater (7) entrances sends into heat absorption in flue gas heat-exchange unit (2), and lead back heat regenerative system by the outlet of No. 6 low-pressure heaters (7), the condensing water flow flowing through No. 6 low-pressure heaters (7) reduces, connect to No. 6 low-pressure heaters (7) the 6 steam flow amount also corresponding minimizings of drawing gas (13), by the part 6 squeezed draw gas (13) send into steam turbine acting; Due to 6 draw gas (13) energy level higher than 8 draw gas (11) and 7 draw gas (12), increased the acting ability of loss by the 6 acting abilities of drawing gas (13) squeezed higher than 8 (11) and 7 (12) flows that draw gas that draw gas, the economy of unit improves.