Low-pressure heating operation system and method with extraction steam stage complementary coupling and low-pressure saving under cylinder cutting condition

Abstract

The present invention discloses a low-pressure operation system and method for steam extraction and complementary coupling of low-pressure economization under cylinder cutting conditions, wherein the exhaust port of the intermediate-pressure cylinder is connected to the steam side of the first low-temperature heater, the heat extraction outlet of the intermediate-pressure cylinder is connected to the steam side of the second low-temperature heater and the steam side of the third low-temperature heater, the condensate pipeline is connected to the water side of the third low-temperature heater and the water side of the second low-temperature heater in sequence, the water side outlet of the third low-temperature heater is connected to the heat absorption side inlet of the low-temperature economizer, the heat absorption side outlet of the low-temperature economizer is connected to the water side inlet of the first low-temperature heater, the first-stage steam extraction port of the low-pressure cylinder is connected to the steam side of the second low-temperature heater, and the second-stage steam extraction port of the low-pressure cylinder is connected to the steam side of the third low-temperature heater. The system and method can achieve that after the supercritical unit is transformed into a zero-output low-pressure cylinder, under cylinder cutting conditions, the low-temperature heater steam inlet pipeline does not have the problem of superflow velocity.

Description

Technical Field

[0001] The invention belongs to the field of peak regulation of thermal power generation technology, and relates to a low-pressure booster operation system and method with complementary coupling of extraction steam at the critical stage under cylinder cutting conditions. Background Art

[0002] In recent years, the installed capacity of new energy power such as wind power, photovoltaic power and hydropower in my country has continued to grow rapidly. While new energy provides us with a large amount of clean electricity, it also brings huge challenges to the safe operation of the power grid and the guarantee of power supply. In addition, in order to comply with the national policy requirements of energy conservation, emission reduction and comprehensive utilization of energy, a large number of thermal power units are gradually moving towards the cogeneration operation mode, which can maximize the interests of enterprises while expanding the scale of heating. Most domestic heating units choose to implement the low-pressure cylinder zero output (cylinder cutting) transformation.

[0003] For the supercritical units after cylinder cutting transformation, considering the constraints such as the high requirements of boiler on condensate water quality, the water drain from the heat network heater is required to enter the condenser before entering the fine treatment system, resulting in a large amount of condensate with lower temperature entering each stage of low-temperature heater in turn. However, under the cylinder cutting condition, the low-pressure cylinder only retains a very small amount of cooling steam, which is far from meeting the required extraction volume of the corresponding low-pressure heater. As a result, the condensate temperature of the low-pressure heater corresponding to the exhaust steam entering the medium-pressure cylinder is greatly reduced compared with the design value, causing a significant increase in the extraction volume of the corresponding stage, and problems such as pipeline vibration are inevitable, posing serious safety hazards. At the same time, due to the low condensate temperature, the low-temperature economizer cannot be put into operation normally, and there is a serious flue gas heat loss. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a low-pressure operation system and method with complementary coupling of extraction steam at the critical stage under cylinder cutting conditions. The system and method can achieve that after the supercritical unit is transformed into a zero-output low-pressure cylinder, under the cylinder cutting condition, the low-temperature heater steam inlet pipe does not have the problem of superflow velocity, the unit operates safely and stably, and the economy is good.

[0005] To achieve the above-mentioned purpose, the low-pressure operation system of the present invention with extraction steam stage complementary coupling and low-pressure economization under the cylinder cutting condition comprises a medium-pressure cylinder, a low-pressure cylinder, a first low-temperature heater, a second low-temperature heater, a third low-temperature heater and a low-temperature economizer;

[0006] The outlet of the intermediate pressure cylinder is connected with the inlet of the low pressure cylinder, the exhaust port of the intermediate pressure cylinder is connected with the steam side of the first low temperature heater, the heat supply steam extraction outlet of the intermediate pressure cylinder is connected with the steam side of the second low temperature heater and the steam side of the third low temperature heater, the condensate pipe is connected with the water side of the first low temperature heater via the water side of the third low temperature heater and the water side of the second low temperature heater in sequence, the water side outlet of the third low temperature heater is connected with the heat absorption side inlet of the low temperature economizer, the heat absorption side outlet of the low temperature economizer is connected with the water side inlet of the first low temperature heater, the first stage steam extraction port of the low pressure cylinder is connected with the steam side of the second low temperature heater, and the second stage steam extraction port of the low pressure cylinder is connected with the steam side of the third low temperature heater.

[0007] The outlet of the medium-pressure cylinder is connected to the inlet of the low-pressure cylinder via the first valve and the second valve.

[0008] A third valve is provided between the heat supply steam extraction outlet of the medium pressure cylinder and the steam side of the second low temperature heater for communication.

[0009] A fourth valve is provided between the heat extraction steam outlet of the medium pressure cylinder and the steam side of the third low temperature heater.

[0010] The first-stage steam extraction port of the low-pressure cylinder is connected to the steam side of the second low-temperature heater through the fifth valve.

[0011] The second-stage steam extraction port of the low-pressure cylinder is connected to the steam side of the third low-temperature heater through the sixth valve.

[0012] A seventh valve is provided between the water side of the third low-temperature heater and the water side of the second low-temperature heater.

[0013] The water side outlet of the third low-temperature heater is connected to the heat absorption side inlet of the low-temperature economizer through the eighth valve.

[0014] The low-pressure heating operation method of the present invention with extraction steam stage complementary coupling and low-pressure saving under the cylinder cutting condition comprises:

[0015] When the unit is operating in the extraction and condensing condition, the second valve is closed and the opening of the first valve is adjusted. The heat extraction steam volume reaches the maximum output to meet the demand of the heat network system. At this time, the steam inlet volume of the low-pressure cylinder is large enough. The fifth valve and the sixth valve are fully opened. The steam extraction volume of each level of the low-pressure cylinder can meet the normal operation of the second low-temperature heater and the third low-temperature heater. At the same time, the third valve and the fourth valve are closed, and the opening of the seventh valve and the eighth valve is adjusted. Under the condition of meeting the inlet water temperature of the low-temperature economizer, the opening of the seventh valve is reduced and the opening of the eighth valve is increased, so that more condensate enters the low-temperature economizer to recover the waste heat of the flue gas.

[0016] When the unit is running under the cylinder cutting condition, the first valve is closed, and the opening of the second valve is adjusted so that the exhaust steam of the intermediate pressure cylinder enters the first low-temperature heater. At this time, the steam intake of the low-pressure cylinder is very small. The fifth valve and the sixth valve are closed to prevent the drain from flowing step by step, which causes the second low-temperature heater and the third low-temperature heater to produce reverse steam intake of the low-pressure cylinder. The opening of the third valve and the fourth valve are adjusted to extract part of the intermediate exhaust steam and throttle it to the steam intake pressure of the second low-temperature heater and the third low-temperature heater under the extraction and condensation condition, so as to maintain the outlet condensate temperature of the third low-temperature heater basically consistent with that under the extraction and condensation condition, and then reduce the opening of the seventh valve and increase the opening of the eighth valve, so that the low-temperature economizer can be put into operation normally; when the low-temperature economizer fails and needs to be exited, the eighth valve is closed and the seventh valve is fully opened to increase the steam intake of the second low-temperature heater, maintain the inlet condensate temperature of the first low-temperature heater basically consistent with that under the extraction and condensation condition, so that the exhaust steam of the intermediate pressure cylinder enters the steam side of the first low-temperature heater without causing the safety hazard caused by over-flow.

[0017] The present invention has the following beneficial effects:

[0018] The low-pressure heater operation system and method for complementary coupling of extraction and low-pressure saving under cylinder cutting conditions described in the present invention are as follows: when the unit is operating under extraction and condensing conditions, the steam intake of the low-pressure cylinder is large enough to meet the normal operation of each level of low-pressure heaters, and the operation mode of the low-temperature heater and the low-temperature economizer is the same as that under pure condensing conditions; when the unit is operating under cylinder cutting conditions, a large amount of exhaust steam from the intermediate-pressure cylinder enters the first low-temperature heater for heat recovery, and the steam intake of the low-pressure cylinder is very small at this time, so the low-pressure cylinder is prevented from reversely inletting steam, and at the same time, the inlet water temperature of the low-temperature economizer and the first low-temperature heater is maintained basically the same as that under extraction and condensing conditions, and the low-temperature heater steam inlet pipe does not have the problem of over-flow, thereby ensuring the safe and stable operation of the low-temperature economizer and the low-temperature heater system, with a simple structure, convenient operation, strong practicality and good economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention.

[0020] Among them, 1 is the medium-pressure cylinder, 2 is the low-pressure cylinder, 3 is the first low-temperature heater, 4 is the second low-temperature heater, 5 is the third low-temperature heater, 6 is the low-temperature economizer, 7 is the first valve, 8 is the second valve, 9 is the third valve, 10 is the fourth valve, 11 is the fifth valve, 12 is the sixth valve, 13 is the seventh valve, and 14 is the eighth valve. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0022] refer to Figure 1The low-pressure operation system of the present invention with extraction steam stage complementary coupling and low-pressure economization under the cylinder cutting condition comprises an intermediate pressure cylinder 1, a low pressure cylinder 2, a first low-temperature heater 3, a second low-temperature heater 4, a third low-temperature heater 5, a low-temperature economizer 6, a first valve 7, a second valve 8, a third valve 9, a fourth valve 10, a fifth valve 11, a sixth valve 12, a seventh valve 13 and an eighth valve 14;

[0023] The outlet of the intermediate pressure cylinder 1 is connected to the inlet of the low pressure cylinder 2 through the first valve 7 and the second valve 8, the exhaust port of the intermediate pressure cylinder 1 is connected to the steam side of the first low temperature heater 3, the heat supply steam extraction outlet of the intermediate pressure cylinder 1 is connected to one end of the third valve 9 and one end of the fourth valve 10, the other end of the third valve 9 is connected to the steam side of the second low temperature heater 4, the other end of the fourth valve 10 is connected to the steam side of the third low temperature heater 5, the condensate pipeline is connected to the water side of the first low temperature heater 3 through the water side of the third low temperature heater 5, the seventh valve 13, the water side of the second low temperature heater 4 and the water side of the first low temperature heater 3 in sequence, the water side outlet of the third low temperature heater 5 is connected to the heat absorption side inlet of the low temperature economizer 6 through the eighth valve 14, the heat absorption side outlet of the low temperature economizer 6 is connected to the water side inlet of the first low temperature heater 3, the first stage steam extraction port of the low pressure cylinder 2 is connected to the steam side of the second low temperature heater 4 through the fifth valve 11, and the second stage steam extraction port of the low pressure cylinder 2 is connected to the steam side of the third low temperature heater 5 through the sixth valve 12.

[0024] The low-pressure heating operation method of the present invention with extraction steam stage complementary coupling and low-pressure saving under the cylinder cutting condition comprises:

[0025] When the unit is operating in the extraction and condensing condition, the second valve 8 is closed and the opening of the first valve 7 is adjusted. The heat extraction steam volume reaches the maximum output to meet the needs of the heat network system. At this time, the steam inlet of the low-pressure cylinder 2 is large enough, and the fifth valve 11 and the sixth valve 12 are fully opened. The steam extraction volume of each level of the low-pressure cylinder 2 can meet the normal operation of the second low-temperature heater 4 and the third low-temperature heater 5. At the same time, the third valve 9 and the fourth valve 10 are closed, and the opening of the seventh valve 13 and the eighth valve 14 are adjusted. Under the condition of meeting the inlet water temperature of the low-temperature economizer 6, the opening of the seventh valve 13 is reduced as much as possible, and the opening of the eighth valve 14 is increased, so that more condensate enters the low-temperature economizer 6 to recover the waste heat of the flue gas and maximize the economic efficiency of the unit operation.

[0026] When the unit is running under the cylinder cutting condition, the first valve 7 is closed, and the opening of the second valve 8 is adjusted, so that a large amount of exhaust steam from the intermediate pressure cylinder 1 enters the first low-temperature heater 3. At this time, the steam intake of the low-pressure cylinder 2 is very small. The fifth valve 11 and the sixth valve 12 are closed to prevent the drain from flowing step by step, causing the second low-temperature heater 4 and the third low-temperature heater 5 to produce reverse steam intake of the low-pressure cylinder 2. The opening of the third valve 9 and the fourth valve 10 is adjusted to extract part of the intermediate exhaust steam and throttle it to the steam intake pressure of the second low-temperature heater 4 and the third low-temperature heater 5 under the extraction and condensation condition, thereby maintaining the first low-pressure cylinder 2. The outlet condensate temperature of the three low-temperature heaters 5 is basically consistent with that under the extraction and condensation conditions. Then, the opening of the seventh valve 13 is reduced as much as possible, and the opening of the eighth valve 14 is increased, so that the low-temperature economizer 6 can be put into normal operation. When the low-temperature economizer 6 fails and needs to be exited, the eighth valve 14 is closed and the seventh valve 13 is fully opened to increase the steam intake of the second low-temperature heater 4, and maintain the inlet condensate temperature of the first low-temperature heater 3 basically consistent with the extraction and condensation conditions, so that the exhaust steam of the intermediate pressure cylinder 1 enters the steam side of the first low-temperature heater 3 without causing the safety hazard caused by overflow.

[0027] The present invention has the advantages of simple structure, convenient operation and strong practicality. When the unit is cut-cylinder operation, the steam inlet pipes of the low-temperature heaters at each level will not have problems such as over-flow velocity that affect the safe and stable operation of the unit. At the same time, it creates the conditions for the normal operation of the low-temperature economizer 6, further improving the economic efficiency of the unit operation.

Claims

1. A low-pressure heating operation method with extraction steam stage complementary coupling and low-pressure saving under cylinder cutting condition, characterized in that: Based on a low-pressure operation system with complementary coupling of extraction steam and low-pressure saving under cylinder cutting conditions, the low-pressure operation system with complementary coupling of extraction steam and low-pressure saving under cylinder cutting conditions comprises a medium-pressure cylinder (1), a low-pressure cylinder (2), a first low-temperature heater (3), a second low-temperature heater (4), a third low-temperature heater (5) and a low-temperature economizer (6); The outlet of the intermediate pressure cylinder (1) is connected to the inlet of the low pressure cylinder (2), the exhaust port of the intermediate pressure cylinder (1) is connected to the steam side of the first low temperature heater (3), the heat supply steam extraction outlet of the intermediate pressure cylinder (1) is connected to the steam side of the second low temperature heater (4) and the steam side of the third low temperature heater (5), the condensate pipeline is connected to the water side of the first low temperature heater (3) via the water side of the third low temperature heater (5) and the water side of the second low temperature heater (4) in sequence, the water side outlet of the third low temperature heater (5) is connected to the heat absorption side inlet of the low temperature economizer (6), the heat absorption side outlet of the low temperature economizer (6) is connected to the water side inlet of the first low temperature heater (3), the first stage steam extraction port of the low pressure cylinder (2) is connected to the steam side of the second low temperature heater (4), and the second stage steam extraction port of the low pressure cylinder (2) is connected to the steam side of the third low temperature heater (5); The outlet of the medium-pressure cylinder (1) is connected to the inlet of the low-pressure cylinder (2) via the first valve (7) or the second valve (8); A third valve (9) is provided between the heat extraction steam outlet of the medium pressure cylinder (1) and the steam side of the second low temperature heater (4) so ​​as to communicate with each other; A fourth valve (10) is provided between the heat extraction steam outlet of the medium pressure cylinder (1) and the steam side of the third low temperature heater (5); The first-stage steam extraction port of the low-pressure cylinder (2) is connected to the steam side of the second low-temperature heater (4) via a fifth valve (11); The second-stage steam extraction port of the low-pressure cylinder (2) is connected to the steam side of the third low-temperature heater (5) via a sixth valve (12); A seventh valve (13) is provided between the water side of the third low-temperature heater (5) and the water side of the second low-temperature heater (4); The water-side outlet of the third low-temperature heater (5) is connected to the heat-absorbing-side inlet of the low-temperature economizer (6) via an eighth valve (14); include: When the unit is operating in the extraction and condensing condition, the second valve (8) is closed and the opening of the first valve (7) is adjusted. The heat extraction steam volume reaches the maximum output to meet the demand of the heat network system. At this time, the steam inlet volume of the low-pressure cylinder (2) is large enough. The fifth valve (11) and the sixth valve (12) are fully opened. The steam extraction volumes of each level of the low-pressure cylinder (2) can meet the normal operation of the second low-temperature heater (4) and the third low-temperature heater (5). At the same time, the third valve (9) and the fourth valve (10) are closed, and the openings of the seventh valve (13) and the eighth valve (14) are adjusted. When the inlet water temperature of the low-temperature economizer (6) is met, the opening of the seventh valve (13) is reduced and the opening of the eighth valve (14) is increased, so that more condensate enters the low-temperature economizer (6) to recover the waste heat of the flue gas. When the unit is operated under the cylinder cutting condition, the first valve (7) is closed and the opening of the second valve (8) is adjusted so that the exhaust steam of the intermediate pressure cylinder (1) enters the first low temperature heater (3). At this time, the steam intake of the low pressure cylinder (2) is very small. The fifth valve (11) and the sixth valve (12) are closed to prevent the drain from flowing step by step, which may cause the second low temperature heater (4) and the third low temperature heater (5) to generate reverse steam intake of the low pressure cylinder (2). The opening of the third valve (9) and the fourth valve (10) are adjusted to extract part of the intermediate exhaust steam and throttle it to the steam intake pressure of the second low temperature heater (4) and the third low temperature heater (5) under the extraction and condensation condition. The outlet condensate temperature of the third low-temperature heater (5) is thereby maintained substantially consistent with that under the extraction and condensation conditions, and the opening of the seventh valve (13) is then reduced and the opening of the eighth valve (14) is increased, so that the low-temperature economizer (6) can be put into normal operation; when the low-temperature economizer (6) fails and needs to be exited, the eighth valve (14) is closed and the seventh valve (13) is fully opened to increase the steam intake of the second low-temperature heater (4), maintain the inlet condensate temperature of the first low-temperature heater (3) substantially consistent with that under the extraction and condensation conditions, and allow the exhaust steam of the intermediate pressure cylinder (1) to enter the steam side of the first low-temperature heater (3) without causing a safety hazard caused by an over-flow rate.

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