CN102767821B - Smoke waste heat deep utilization system of power station boiler for heating supplied water at high pressure - Google Patents

Abstract

The invention discloses a coal-fired power plant boiler flue gas waste heat depth utilization system for heating high-pressure water supply, which belongs to the field of energy-saving equipment utilizing waste heat. In the invention, the flue gas at the tail of the boiler at about 300-400°C enters the high-temperature rotary respectively. type air preheater (2), flue gas condensed water heater (3), and low temperature rotary air preheater (4), and through the dust collector (5), enter the front air preheater (6) , until it drops to about 60-100 ℃, it is discharged from the system, and the higher temperature flue gas is used to heat the high-pressure feed water of the heat recovery system, so as to obtain a higher energy-saving effect. At the same time, through the design of the pipeline, the inlet water of the flue gas feed water heater (3) can be flexibly adjusted to be drawn from the inlets of different high-pressure regenerators, thereby ensuring that the exhaust heat utilization system of the flue gas at the tail of the power plant boiler can be used in various working conditions on the air side and The water supply side is in the best operating condition.

Description

Deep Utilization System of Power Plant Boiler Flue Gas Waste Heat for Heating High Pressure Feed Water

technical field

The invention belongs to the field of energy-saving equipment using waste heat, and in particular relates to a deep utilization system for waste heat of power station boiler flue gas used for heating high-pressure feed water. Specifically, the air preheater is used to heat the air in stages and the flue gas feed water heater is used to heat the main feed water to complete the deep utilization of the waste heat of the flue gas and reduce the coal consumption of the unit.

technical background

In China, coal-fired power plants consume nearly half of the country's coal production. With the continuous rise of coal energy prices in recent years, the cost of coal-based power generation is increasing. All thermal power plants are facing huge energy-saving pressure and are constantly seeking to reduce Coal consumption, new technologies applied in energy conservation, and increase related capital investment.

In order to avoid acid dew point corrosion on the heating surface at the tail, the exhaust gas temperature of boilers in thermal power plants is generally around 120-130 °C; for boilers burning high-sulfur fuel, the exhaust gas temperature is raised to about 150 °C; add heaters The exhaust gas temperature of some boilers can reach 150-180°C, and the exhaust gas temperature of individual boilers can reach above 180°C. Excessive flue gas temperature directly leads to considerable energy in the flue gas being discharged directly to the atmosphere without utilization. In terms of environmental protection desulfurization requirements, in the flue gas limestone wet desulfurization process currently used by most thermal power plants, the optimal desulfurization temperature is about 50°C, and the boiler exhaust temperature is reduced to about 50°C by spraying in the desulfurization tower. Not only consume a lot of water and energy, but also increase the amount of flue gas emissions. Therefore, considering both energy saving and emission reduction and economy, further reducing the exhaust gas temperature has become an inevitable choice for the development of energy saving and emission reduction technology for power plant boilers.

The application prospect of waste heat utilization technology is broad. In foreign countries, equipment that reduces the exhaust gas temperature at the tail and recovers heat has been applied earlier. For the recently developed ultra-supercritical generating units, the German Cologne Nideraussem 1000MW lignite generating units installed waste heat heat exchange equipment in the bypass flue of the air preheater, and adopted a separate flue system to fully reduce the exhaust gas temperature. At the same time, part of the flue gas is introduced into the bypass flue to heat the boiler feed water. The 2×800MW lignite generating units of German Schwarze Pumpe Power Plant installed a flue gas cooler after the electrostatic precipitator, and used the waste heat of the flue gas to heat the boiler feed water. In China, the Shanghai Waigaoqiao Power Plant used waste heat exchangers to recover waste heat from tail flue gas in the third-phase expansion project of the million-kilowatt ultra-supercritical unit project.

At present, it is suitable to use the low-temperature flue gas at the outlet of the air preheater to heat the condensed water directly for the utilization of the waste heat of the flue gas at the tail of the boiler. Since the exhaust gas temperature of the air preheater is about 120-140°C, the temperature utilization space is limited and the form is single. The energy utilization relationship among flue gas, air, and condensed water is not considered from the system point of view. In the present invention, flue gas, air and water supply form a four-stage heating system, and two-stage conventional air preheaters are considered to heat air in stages. A flue gas feed water heat exchanger is arranged between the two conventional air preheaters, and the higher temperature flue gas is used to heat the feed water of the high pressure recuperation system. And considering the low-temperature corrosion of flue gas, install a corrosion-resistant front-end air preheater after the conventional low-temperature air preheater, and consider using a heat pipe air preheater. The system takes into account the flexible connection between the flue gas heat exchanger and the recuperation heater under different loads, ensuring that the exhaust gas waste heat utilization system at the tail of the power plant boiler is at the optimum position on the air side and the condensed water side under various working conditions. Excellent waste heat recovery status.

Contents of the invention

The object of the present invention is to propose a power station boiler flue gas waste heat deep utilization system for heating high-pressure feed water for the deep utilization of smoke exhaust heat of thermal power units. It is characterized in that the system consists of three-stage flue gas air heating system and flue gas Composition of feed water heater; on the exhaust pipe of boiler 1, there are high temperature rotary air preheater 2, flue gas feed water heater 3, low temperature rotary air preheater 4, dust collector 5, front air preheater Heater 6, and induced draft fan 7; Steam turbine high-pressure cylinder 8, steam turbine medium-pressure cylinder 9 and steam turbine low-pressure cylinder 10 are connected in series with generator 11, and the regenerative steam extraction of described steam turbine high-pressure cylinder 8 and steam turbine medium-pressure cylinder 9 is heated by Feedwater in the high-pressure recuperation system composed of 1# high-pressure recuperation heater, 2# high-pressure recuperation heater and 3# high-pressure recuperation heater; the heated feedwater returns to the high-pressure cylinder 8 of the steam turbine through the 1# high-pressure heater; The regenerative steam extraction and exhaust steam of the low-pressure cylinder 10 of the steam turbine enter the condenser and the condensed water low-pressure heating system 12, and heat the condensed water in the condensed water low-pressure heating system 12; the condensed water is sent to the Deaerator and feed water pump 13, through deaerator and feed water pump 13, feed water is sent to 3# high pressure recuperation heater, 2# high pressure regenerating heater, 1# high pressure regenerating heater in sequence. The 2# high-pressure heater or the 3# high-pressure heater are connected in series with the flue gas feed water heater 3 through a valve.

The flue gas feedwater heater 3 can be arranged in parallel with the 2# high-pressure recuperation heater and the 3# high-pressure recuperation heater through the combination of corresponding pipelines and valves; and through the booster pump 14 and the corresponding pipeline The combination of /valve can be connected in series between 2#-3# high-pressure heater, and can be connected in series between 3# high-pressure heater-deaerator

The flue gas waste heat depth utilization method of the power station boiler flue gas waste heat depth utilization system for heating high-pressure feed water is characterized in that, on the flue gas side, the flue gas at 300-400°C at the tail of the boiler 1 passes through a high-temperature rotary air preheating method. The heater 2 enters the flue gas feedwater heater 3, then enters the low-temperature rotary air preheater 4, and then enters the pre-type air preheater 6 through the dust collector 5, and its exhaust gas enters the desulfurization device through the induced draft fan 7; The pre-type air preheater 6 and the low-temperature rotary air preheater 4 make the inlet air temperature of the high-temperature rotary air preheater 2 rise, and the exhaust gas temperature also rises accordingly, and the high-temperature rotary air preheater 2 The exhaust gas temperature is controlled between 220-280°C to ensure that its heat can be used to heat the 3# high-pressure regenerator heater or the feed water at the outlet of the deaerator and feed water pump 13 under different load conditions to squeeze out higher pressure High-grade steam turbine extracts steam, effectively cascades the use of flue gas waste heat, and when the main steam flow rate and fuel consumption rate are basically unchanged, the output power of the steam turbine is maximized and the efficiency of the power plant is improved.

In the air channel, in order to prevent low-temperature corrosion of the flue gas, a pre-type air preheater 6 is arranged in front of the conventional rotary air device. It is recommended to use a heat pipe or shell-and-tube air preheater, and the air at normal temperature is preheated by the pre-type air After the device 6 is preheated to a certain temperature, it is sent in series to the low-temperature rotary air preheater 4, and continues to be heated in the high-temperature rotary air preheater 2 until the temperature required by the boiler hot air is reached.

The beneficial effect of the present invention is that through the ingenious design of flue gas graded heating air, the waste heat of the flue gas can be heated to the high-pressure feed water of the heat recovery system, and the inlet water of the flue gas feed water heater can be adjusted through the valve to form a set of flexible waste heat depth Take advantage of the system. This system can realize the series connection between the flue gas feed water heater between 2# and 3# high-pressure regenerative heater, and between the 3# high-pressure regenerative heater and the deaerator according to the load change of the unit, and discharge 2# or 3 The ## high-pressure heater reheats and extracts steam. Under the condition that the main steam flow remains unchanged, the output power of the steam turbine is maximized, the efficiency of the power plant is improved, and the unit coal consumption is reduced.

Description of drawings

Figure 1 is a schematic diagram of a coal-fired power plant boiler flue gas waste heat depth utilization system for heating high-pressure feed water

Detailed ways

The invention provides and proposes a power station boiler flue gas waste heat deep utilization system for heating high-pressure feed water. The following will be described in conjunction with the accompanying drawings and examples.

Fig. 1 is a schematic diagram of a deep utilization system of flue gas waste heat of a coal-fired power plant boiler for heating high-pressure feed water. In the figure, the system consists of a three-stage flue gas air heating system and a flue gas feed water heater; on the flue gas exhaust pipe of the boiler 1, a high temperature rotary air preheater 2, a flue gas feed water heater 3, and a low temperature rotary air preheater are connected in series. Air preheater 4, dust collector 5, pre-type air preheater 6 and induced draft fan 7; steam turbine high pressure cylinder 8, steam turbine medium pressure cylinder 9 and steam turbine low pressure cylinder 10 are connected in series with generator 11. The regenerative extraction steam and exhaust steam of the low-pressure cylinder 10 of the steam turbine enter the condenser and the low-pressure regenerative heating system 12 to heat the condensed water in the low-pressure regenerating system, and the regenerative extraction steam of the high-pressure cylinder 8 and the intermediate-pressure cylinder 9 of the steam turbine are heated Feed water in the high pressure recuperation system composed of 1# high pressure heater, 2# high pressure heater and 3# high pressure heater. The heated feed water returns to the high pressure cylinder 8 of the steam turbine through the 1# high pressure heater;

This system utilizes the residual heat of flue gas to heat air and high-pressure reheated water in stages, and its principle is as follows: the flue gas at the tail of boiler 1 at 300-400°C passes through high-temperature rotary air preheater 2, enters flue gas feed water heater 3, and then enters Low-temperature rotary air preheater 4, then enters and exits front-type air preheater 6 through dust collector 5, and its exhaust smoke enters desulfurization device through induced draft fan 7; the front-type air preheater 6 and low-temperature rotary air The preheater 4 increases the inlet air temperature of the high-temperature rotary air preheater 2, and the exhaust temperature also increases accordingly. The exhaust temperature of the high-temperature rotary air preheater 2 is controlled between 220-280°C to ensure the The heat of the gas can be used to heat the 3# high-pressure regenerating heater under different load conditions, or the feed water at the outlet of the deaerator and the feed water pump 13, so as to squeeze out steam extraction from the steam turbine with a higher pressure level, and effectively utilize the waste heat of the flue gas in cascades , when the main steam flow rate and fuel consumption rate are basically unchanged, the output work of the steam turbine can be increased to the greatest extent, and the efficiency of the power plant can be improved.

In the air channel, in order to prevent low-temperature corrosion of the flue gas, a pre-type air preheater 6 is arranged in front of the conventional rotary air preheater. It is recommended to use a heat pipe or shell-and-tube air preheater. After the heater 6 is preheated to a certain temperature, it is sent in series to the low-temperature rotary air preheater 4, and continues heating in the high-temperature rotary air preheater 2 until reaching the temperature required by the boiler hot air.

Claims (4)

1., for a coal-fired power station boiler fume afterheat deep exploitation system for heating high-pressure feedwater, it is characterized in that, this system is made up of three grades of flue gas air heating systems and flue gas feed-water heater; The smoke discharging pipe of boiler (1) is in series with high temperature rotating regenerative air heater (2), flue gas feed-water heater (3), low temperature rotary air preheater (4), deduster (5), forward type air preheater (6) and air-introduced machine (7) successively; Steam turbine high-pressure cylinder (8), Steam Turbine Through IP Admission (9) and turbine low pressure cylinder (10) and generator (11) are connected in series, and wherein high temperature rotating regenerative air heater (2), low temperature rotary air preheater (4) and forward type air preheater (6) are three grades of flue gas air heating systems; The regenerative steam of described steam turbine high-pressure cylinder (8) and Steam Turbine Through IP Admission (9) heats the feedwater in the high-pressure extraction system be made up of 1# high-pressure extraction heater, 2# high-pressure extraction heater and 3# high-pressure extraction heater, and the feedwater of this heating returns steam turbine high-pressure cylinder (8) through 1# high-pressure extraction heater again; The regenerative steam of described turbine low pressure cylinder (10) and steam discharge enter condenser and condensate water low-pressure heating system (12), the condensate water in heat-setting water low-pressure heating system (12); Turbine low pressure cylinder (10) delivers to oxygen-eliminating device and feed pump (13) by condensate water low-pressure heating system (12) condensate water, is sent to 3# high-pressure extraction heater, 2# high-pressure extraction heater, 1# high-pressure extraction heater successively through oxygen-eliminating device and feed pump (13) feedwater; 2# high-pressure extraction heater or 3# high-pressure extraction heater to be in series with flue gas feed-water heater (3) by valve and to connect; The regenerative steam of described steam turbine high-pressure cylinder (8) and Steam Turbine Through IP Admission (9) heats the feedwater in the high-pressure extraction system be made up of 1# high-pressure extraction heater, 2# high-pressure extraction heater and 3# high-pressure extraction heater.

2. a kind of coal-fired power station boiler fume afterheat deep exploitation system for heating high-pressure feedwater according to claim 1, it is characterized in that, described flue gas feed-water heater (3) had not only been arranged in parallel with 2# high-pressure extraction heater by the combination of corresponding pipeline and valve, but also to be arranged in parallel with 3# high-pressure extraction heater; And pass through the combination of booster pump (14) and corresponding pipeline and valve, then can be connected on and can be connected between 3# high-pressure extraction heater-oxygen-eliminating device between 2#-3# high-pressure extraction heater, again.

3. a kind of coal-fired power station boiler fume afterheat deep exploitation system for heating high-pressure feedwater according to claim 1, it is characterized in that, in fume side, the flue gas of 300-400 DEG C of boiler (1) afterbody is through high temperature rotating regenerative air heater (2), enter flue gas feed-water heater (3), enter low temperature rotary air preheater (4) again, then enter forward type air preheater (6) through deduster (5), its smoke evacuation enters desulfurizer through air-introduced machine (7).

4. the fume afterheat deep exploitation method of a kind of coal-fired power station boiler fume afterheat deep exploitation system for heating high-pressure feedwater described in claim 1, it is characterized in that, the forward type air preheater (6) arranged and low temperature rotary air preheater (4) make high temperature rotating regenerative air heater (2) entering air temperature raise, delivery temperature also increases, high temperature rotating regenerative air heater (2) delivery temperature controls between 220-280 DEG C, guarantee that exhaust gas heat can be used for heating 3# high-pressure extraction heater under different load condition, or the feedwater through oxygen-eliminating device and feed pump (13) exit, the extracted steam from turbine of exclusion different pressures grade, main steam flow and specific fuel consumption substantially constant time, increase steam turbine output work to greatest extent, by flue gas under different load, feedwater characteristic at different temperatures, select optimum heater connection scheme, reach best waste heat recovery state, improve power plant efficiency, normal temperature air is after preposition regenerative air heater (6) is preheating to uniform temperature, low temperature rotary air preheater (4) is sent in series connection, heating is continued again, until reach the temperature required for boiler hot air in high temperature rotating regenerative air heater (2).