A back pressure heating system and method suitable for small circulating water flow

Abstract

The invention discloses a back-pressure heating system and method suitable for small circulating water flow rate. A heat network return pipe is connected to the water inlet of a condenser via a condenser water inlet pipe. The water outlet of the condenser is divided into three paths, wherein the first path is connected to the inlet of a cooling tower regulating bypass, the second path is connected to the heated side inlet of an absorption heat pump, and the third path is connected to the heat source side inlet of the absorption heat pump. The heated side outlet of the absorption heat pump is connected to the heat network water supply pipe via the heat absorption side of a heat network heater, the heat source side outlet of the absorption heat pump is connected to the condenser water inlet pipe via the absorption heat pump regulating bypass, and the bottom outlet of the cooling tower is connected to the condenser water inlet pipe via a cooling tower outlet pipeline. The system and method can effectively solve the difficulty that a large-capacity steam turbine generator set cannot implement back-pressure heating, and at the same time realize the complete consumption of exhaust steam heat load.

Description

Technical Field

[0001] The invention belongs to the technical field of cogeneration of heat and power, and relates to a back-pressure heating system and method suitable for small circulating water flow. Background Art

[0002] With the increasing development of urbanization, people's demand for centralized heating is increasing. In urban centralized heating systems, the most common way is to use cogeneration technology, using the steam extraction or exhaust heat of the steam turbine to heat the circulating water of the heating network.

[0003] High back pressure heating is to heat the heat network circulating water entering the turbine condenser by increasing the exhaust saturation temperature of the steam turbine to supply heat to the outside. The condenser becomes the first-level heat network heater of the heating system, making full use of the vaporization latent heat of the exhaust steam of the unit. It greatly reduces the cold source loss of the unit and improves the energy utilization rate. Usually, the exhaust pressure of the high back pressure unit is designed to be about 40kPa, corresponding to an exhaust temperature of about 75℃, and the outlet temperature of the condenser circulating water is controlled at about 70℃.

[0004] However, in this heating mode, the steam turbine can only determine electricity based on heat, and its ability to participate in the peak load regulation of the power grid has been reduced, and the hydraulic conditions on the heat network side can only be regulated by quality but not quantity. At the same time, for large-capacity units, the design circulating water volume of the condenser is large, much higher than the circulating water flow of the heat network in the central heating system. For example, for a conventional 600MW unit, the design circulating water volume of the condenser is 50,000-60,000 t / h, but the circulating water flow of the heat network in a general central heating system is only about 10,000 t / h. Even if the back pressure of the unit is increased and the load of the unit is reduced, the circulating water flow of the heat network is difficult to meet the needs of the condenser. At the same time, the exhaust flow of large-capacity units is large, and the corresponding central heating system is difficult to fully absorb the exhaust heat load. Therefore, there are almost no implementation cases of high back pressure heating transformation for units of 600MW and above in China. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and to provide a back-pressure heating system and method suitable for small circulating water flow rates. The system and method can effectively solve the difficulty that large-capacity steam turbine generator sets cannot implement back-pressure heating, while achieving complete absorption of exhaust steam heat load.

[0006] To achieve the above-mentioned object, the back pressure heating system suitable for small circulating water flow rate described in the present invention comprises a heat network return pipe, a condenser water inlet pipe, a condenser, a cooling tower regulating bypass, an absorption heat pump, a heat network heater, a heat network water supply pipe, an absorption heat pump regulating bypass, a condenser water inlet pipe, a cooling tower, a steam turbine high and medium pressure cylinder and a steam turbine low pressure cylinder;

[0007] The heat network return pipe is connected to the water inlet of the condenser through the condenser water inlet pipe, and the water outlet of the condenser is divided into three routes, wherein the first route is connected to the inlet of the cooling tower regulating bypass, the second route is connected to the heated side inlet of the absorption heat pump, and the third route is connected to the heat source side inlet of the absorption heat pump. The heated side outlet of the absorption heat pump is connected to the heat network water supply pipe through the heat absorption side of the heat network heater, the heat source side outlet of the absorption heat pump is connected to the condenser water inlet pipe through the absorption heat pump regulating bypass, and the bottom outlet of the cooling tower is connected to the condenser water inlet pipe through the cooling tower outlet pipe;

[0008] The outlets of the high and medium pressure cylinders of the steam turbine are divided into two routes, one of which is connected to the steam inlet of the absorption heat pump and the heat release side inlet of the heat network heater, and the other is connected to the inlet of the low pressure cylinder of the steam turbine. The outlet of the low pressure cylinder of the steam turbine is connected to the steam inlet of the condenser.

[0009] The outlets of the high and medium pressure cylinders of the steam turbine are divided into two routes, one of which is connected to the steam inlet of the absorption heat pump and the heat release side inlet of the heat network heater through the heating steam extraction pipeline, and the other is connected to the inlet of the low pressure cylinder of the steam turbine through the medium and low pressure cylinder connecting pipe of the steam turbine. Among them, a heating regulating valve is arranged on the heating steam extraction pipeline, and a heating butterfly valve of the medium and low pressure cylinder connecting pipe of the steam turbine is arranged on the medium and low pressure cylinder connecting pipe of the steam turbine.

[0010] A cooling tower regulating bypass regulating valve is arranged on the cooling tower regulating bypass.

[0011] A retractable heat pump regulating bypass regulating valve is arranged on the retractable heat pump regulating bypass.

[0012] A cooling tower circulating water regulating valve and a cooling tower circulating water pump are provided on the cooling tower outlet pipe.

[0013] A heating network make-up pump is arranged on the heating network return pipe.

[0014] The back pressure heating method applicable to small circulating water flow rate of the present invention comprises the following steps:

[0015] The exhaust steam from the high and medium pressure cylinders of the steam turbine is divided into two paths, one of which enters the absorption heat pump and the heat network heater to release heat, and the other enters the low pressure cylinder of the steam turbine to do work. The exhaust steam from the low pressure cylinder of the steam turbine enters the condenser to release heat;

[0016] During the heating period, the amount of steam entering the low-pressure cylinder of the steam turbine and the heating extraction pipe is distributed by adjusting the opening of the heating butterfly valve of the medium- and low-pressure cylinder connecting pipe of the steam turbine. The amount of steam entering the low-pressure cylinder of the steam turbine affects the final heat load of the condenser, and the amount of steam entering the heating extraction pipe determines the heat load of the heating network heater and the absorption heat pump. The return water of the heating network is mixed with the water from the cooling tower and the output of the absorption heat pump after being replenished and pressure-regulated by the heating network make-up water pump and then enters the condenser for heating. The heated water is divided into three paths, one of which enters the cooling tower regulation bypass, the second enters the heated side of the absorption heat pump, and the third enters the heat source side of the absorption heat pump. The water output from the heat source side of the absorption heat pump enters the condenser, and the water output from the heated side of the absorption heat pump enters the heat absorption side of the heating network heater for heating, and finally enters the heating network water supply pipe.

[0017] The circulating water flow of the condenser is adjusted by adjusting the bypass regulating valve of the cooling tower and the bypass regulating valve of the absorption heat pump to change the load of the condenser; the water flow on the heated side and the heat source side of the absorption heat pump is adjusted by adjusting the bypass regulating valve of the cooling tower, and then the final circulating water volume of the heat network is adjusted.

[0018] The present invention has the following beneficial effects:

[0019] The back-pressure heating system and method suitable for small circulating water flow described in the present invention, during specific operation, adjusts the circulating water flow of the condenser by adjusting the bypass regulating valve of the cooling tower and the bypass regulating valve of the absorption heat pump to change the load of the condenser; adjusts the water flow on the heated side and the heat source side of the absorption heat pump by adjusting the bypass regulating valve of the cooling tower, and then adjusts the final circulating water volume of the heat network, thereby realizing the decoupling of back-pressure heating and the power generation of the unit, so as to increase the flexibility of the back-pressure heating unit, solve the difficulty that large-capacity steam turbine generator sets cannot implement back-pressure heating, and reduce the heating cost of the unit compared with the conventional steam extraction heating method. At the same time, the present invention adds an absorption heat pump in the circulation system to make full use of the low-quality thermal energy of the unit and further enhance the thermoelectric decoupling characteristics of the unit. In addition, the heating network feed water pump and the cooling tower circulating water pump jointly participate in the heating network system pressure setting. When the conventional heating network feed water pump fails, it will not affect the heating network system pressure setting, so as to enhance the safety and reliability of the heating system, and enable the heating network provided by the back-pressure heating unit to adjust the hydraulic conditions in a quality and adjustment mode, thereby improving the adjustment capacity of the heating system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] Among them, 1 is the heat network feed water pump, 2 is the condenser, 3 is the turbine low-pressure cylinder, 4 is the turbine medium and low-pressure cylinder connecting pipe, 5 is the turbine medium and low-pressure cylinder connecting pipe heating butterfly valve, 6 is the turbine high and medium pressure cylinder, 7 is the heating steam extraction pipeline, 8 is the heating regulating valve, 9 is the absorption heat pump, 10 is the heat network heater, 11 is the heat network water supply pipe, 12 is the heat pump regulating bypass, 13 is the cooling tower regulating bypass, 14 is the cooling tower regulating bypass regulating valve, 15 is the condenser water inlet pipe, 16 is the heat network return pipe, 17 is the heat pump regulating bypass regulating valve, 18 is the cooling tower circulating water regulating valve, 19 is the cooling tower circulating water pump, and 20 is the cooling tower. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0023] refer to Figure 1 The back pressure heating system suitable for small circulating water flow rate described in the present invention comprises a heat network return pipe 16, a condenser inlet pipe 15, a condenser 2, a cooling tower regulating bypass 13, an absorption heat pump 9, a heat network heater 10, a heat network water supply pipe 11, an absorption heat pump regulating bypass 12, a condenser inlet pipe 15, a cooling tower 20, a turbine high and medium pressure cylinder 6 and a turbine low pressure cylinder 3; the heat network return pipe 16 is connected to the water inlet of the condenser 2 through the condenser inlet pipe 15, and the water outlet of the condenser 2 is divided into three paths, wherein the first path is connected to the inlet of the cooling tower regulating bypass 13, the second path is connected to the heated side inlet of the absorption heat pump 9, and the third path is connected to the heated side inlet of the absorption heat pump 9. It is connected with the heat source side inlet of the absorption heat pump 9, the heated side outlet of the absorption heat pump 9 is connected with the heat network water supply pipe 11 via the heat absorption side of the heat network heater 10, the heat source side outlet of the absorption heat pump 9 is connected with the condenser water inlet pipe 15 via the absorption heat pump regulating bypass 12, and the bottom outlet of the cooling tower 20 is connected with the condenser water inlet pipe 15 via the cooling tower outlet pipe; the outlets of the high and medium pressure cylinders 6 of the turbine are divided into two routes, one of which is connected with the steam inlet of the absorption heat pump 9 and the heat release side inlet of the heat network heater 10, and the other is connected with the inlet of the low-pressure cylinder 3 of the turbine, and the outlet of the low-pressure cylinder 3 of the turbine is connected with the steam inlet of the condenser 2.

[0024] The outlets of the high and medium pressure cylinders 6 of the steam turbine are divided into two routes, one of which is connected to the steam inlet of the absorption heat pump 9 and the heat release side inlet of the heat network heater 10 through the heat supply extraction pipe 7, and the other is connected to the inlet of the low pressure cylinder 3 of the steam turbine through the medium and low pressure cylinder connecting pipe 4 of the steam turbine, wherein a heat supply regulating valve 8 is arranged on the heat supply extraction pipe 7, and a heat supply butterfly valve 5 for the medium and low pressure cylinder connecting pipe of the steam turbine is arranged on the medium and low pressure cylinder connecting pipe 4 of the steam turbine.

[0025] A cooling tower regulating bypass regulating valve 14 is arranged on the cooling tower regulating bypass 13; a collectible heat pump regulating bypass regulating valve 17 is arranged on the collectible heat pump regulating bypass 12; a cooling tower circulating water regulating valve 18 and a cooling tower circulating water pump 19 are arranged on the cooling tower outlet pipeline; a heating network feed water pump 1 is arranged on the heating network return pipe 16.

[0026] The back pressure heating method applicable to small circulating water flow rate of the present invention comprises the following steps:

[0027] The exhaust steam of the high and medium pressure cylinders 6 of the steam turbine is divided into two paths, one of which enters the absorption heat pump 9 and the heat network heater 10 to release heat, and the other enters the low pressure cylinder 3 of the steam turbine to do work. The exhaust steam of the low pressure cylinder 3 of the steam turbine enters the condenser 2 to release heat;

[0028] During the heating period, the amount of steam entering the low-pressure cylinder 3 of the steam turbine and the heating extraction pipe 7 is distributed by adjusting the opening of the heating butterfly valve 5 of the medium- and low-pressure cylinder connecting pipe of the steam turbine. The amount of steam entering the low-pressure cylinder 3 of the steam turbine affects the final heat load of the condenser 2, and the amount of steam entering the heating extraction pipe 7 determines the heat load of the heating network heater 10 and the absorption heat pump 9. The return water of the heating network is mixed with the water from the cooling tower 20 and the output of the absorption heat pump 9 after being replenished and pressure-regulated by the heating network replenishment pump 1, and then enters the condenser 2 for heating. The heated water is divided into three paths, one of which enters the cooling tower regulating bypass 13, the second path enters the heated side of the absorption heat pump 9, and the third path enters the heat source side of the absorption heat pump 9. The water output from the heat source side of the absorption heat pump 9 enters the condenser 2, and the water output from the heated side of the absorption heat pump 9 enters the heat absorption side of the heating network heater 10 for heating, and finally enters the heating network water supply pipe 11.

[0029] The circulating water flow of the condenser 2 is adjusted by adjusting the bypass regulating valve 14 of the cooling tower and the bypass regulating valve 17 of the absorption heat pump to change the load of the condenser 2; the water flow on the heated side and the heat source side of the absorption heat pump 9 is adjusted by adjusting the bypass regulating valve 14 of the cooling tower, and then the final circulating water volume of the heat network is adjusted. In this mode, the back-pressure heating under a small circulating water flow can be met, and at the same time, the thermoelectric decoupling characteristics of the back-pressure heating unit are greatly improved.

[0030] The characteristics of the present invention are: when the circulating water flow rate of the condenser 2 of a large-capacity unit of 600MW or above is much higher than the circulating water flow rate of the heating network, the conditions of back-pressure heating can still be met; the heating network provided by the back-pressure heating unit can adopt a quality-adjusting mode for heating; the back-pressure heating is decoupled from the power generation of the unit, and when the electric load is low and the heat load is high, the flow rate of the circulating water shunt on the tower can be reduced, and the other part of the circulating water enters the absorption heat pump 9 and the heating network heater 10 in turn, thereby increasing the amount of steam extraction heat supply; when the electric load is high and the heat load is low, the flow rate of the circulating water shunt on the tower can be increased, and the other part of the circulating water enters the absorption heat pump 9 and the heating network heater 10 in turn, thereby reducing the amount of steam extraction heat supply; when the flow rate entering the heating network heater 10 and the cooling tower 20 is adjusted by bypass, the heating network feed water pump 1 and the cooling tower circulating water pump 19 jointly participate in the constant pressure of the heating network system.

[0031] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A back pressure heating system suitable for small circulating water flow, characterized in that: It comprises a heat network return pipe (16), a condenser water inlet pipe (15), a condenser (2), a cooling tower regulating bypass (13), an absorption heat pump (9), a heat network heater (10), a heat network water supply pipe (11), an absorption heat pump regulating bypass (12), a condenser water inlet pipe (15), a cooling tower (20), a turbine high and medium pressure cylinder (6) and a turbine low pressure cylinder (3); The heat network return pipe (16) is connected to the water inlet of the condenser (2) via the condenser water inlet pipe (15); the water outlet of the condenser (2) is divided into three paths, wherein the first path is connected to the inlet of the cooling tower regulating bypass (13); the second path is connected to the heated side inlet of the absorption heat pump (9); the third path is connected to the heat source side inlet of the absorption heat pump (9); the heated side outlet of the absorption heat pump (9) is connected to the heat network water supply pipe (11) via the heat absorption side of the heat network heater (10); the heat source side outlet of the absorption heat pump (9) is connected to the condenser water inlet pipe (15) via the absorption heat pump regulating bypass (12); and the bottom outlet of the cooling tower (20) is connected to the condenser water inlet pipe (15) via the cooling tower outlet pipe; The outlet of the high and medium pressure cylinder (6) of the steam turbine is divided into two paths, one of which is connected to the steam inlet of the absorption heat pump (9) and the heat release side inlet of the heat network heater (10), and the other is connected to the inlet of the low pressure cylinder (3) of the steam turbine. The outlet of the low pressure cylinder (3) of the steam turbine is connected to the steam inlet of the condenser (2); A cooling tower regulating bypass regulating valve (14) is arranged on the cooling tower regulating bypass (13); An absorption heat pump regulating bypass regulating valve (17) is provided on the absorption heat pump regulating bypass (12).

2. The back pressure heating system suitable for small circulating water flow according to claim 1 is characterized in that: The outlet of the high and medium pressure cylinders (6) of the steam turbine is divided into two routes, one of which is connected to the steam inlet of the absorption heat pump (9) and the heat release side inlet of the heat network heater (10) through a heat supply extraction pipeline (7), and the other is connected to the inlet of the low pressure cylinder (3) of the steam turbine through a medium and low pressure cylinder connecting pipe (4). A heat supply regulating valve (8) is provided on the heat supply extraction pipeline (7), and a heat supply butterfly valve (5) is provided on the medium and low pressure cylinder connecting pipe (4) of the steam turbine.

3. The back pressure heating system suitable for small circulating water flow according to claim 1, characterized in that: A cooling tower circulating water regulating valve (18) and a cooling tower circulating water pump (19) are arranged on the cooling tower outlet pipeline.

4. The back pressure heating system suitable for small circulating water flow according to claim 1, characterized in that: A heating network water supply pump (1) is arranged on the heating network return water pipe (16).

5. A back pressure heating method suitable for small circulating water flow, characterized in that: The back pressure heating system suitable for small circulating water flow rate according to claim 1 comprises the following steps: The exhaust steam of the high and medium pressure cylinders (6) of the steam turbine is divided into two paths, one of which enters the absorption heat pump (9) and the heat network heater (10) to release heat, and the other enters the low pressure cylinder (3) of the steam turbine to perform work. The exhaust steam of the low pressure cylinder (3) of the steam turbine enters the condenser (2) to release heat; During the heating period, the amount of steam entering the low-pressure cylinder (3) of the steam turbine and the heating extraction pipe (7) is distributed by adjusting the opening of the heating butterfly valve (5) of the connecting pipe of the medium- and low-pressure cylinders of the steam turbine. The amount of steam entering the low-pressure cylinder (3) of the steam turbine affects the final heat load of the condenser (2), and the amount of steam entering the heating extraction pipe (7) determines the heat load of the heating network heater (10) and the absorption heat pump (9). The return water of the heating network is replenished by the heating network replenishment pump (1) to a constant pressure and then mixed with the output water from the cooling tower (20) and the absorption heat pump (9). The water is mixed with the water and enters the condenser (2) for heating. The heated water is divided into three paths, one of which enters the cooling tower regulating bypass (13), the second enters the heated side of the absorption heat pump (9), and the third enters the heat source side of the absorption heat pump (9). The water output from the heat source side of the absorption heat pump (9) enters the condenser (2), and the water output from the heated side of the absorption heat pump (9) enters the heat absorption side of the heating network heater (10) for heating and finally enters the heating network water supply pipe (11); The circulating water flow of the condenser (2) is adjusted by means of a cooling tower regulating bypass regulating valve (14) and an absorption heat pump regulating bypass regulating valve (17) to change the load of the condenser (2); the water flow on the heated side and the heat source side of the absorption heat pump (9) is adjusted by means of a cooling tower regulating bypass regulating valve (14), thereby adjusting the final circulating water volume of the heat network.

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