A method for reducing start-up time of a water-cooled wall standby furnace

Abstract

The present application relates to a method for reducing the start-up time of a water-cooled wall standby furnace, which uses equipment including a gasifier water-cooled wall, a steam drum and a water-cooled wall circulating water pump. The present application makes full use of the heat of the continuous blowdown of the operating series steam drum, and realizes the maintenance of the standby series water-cooled wall temperature, and the system is simple and the control is convenient; compared with the prior art, the present application can reduce the start-up time of the standby furnace, reduce the impact of the gasifier trip on the device operation load, and reduce the economic loss caused by shutdown. According to the water baking time of 8 hours, the present application can reduce the economic loss of 8 hours caused by unplanned shutdown, and according to the gasification scale of 100,000 standard cubic meters / hour of effective gas production, the economic loss can be reduced by nearly 500,000 yuan.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, specifically to a method for reducing the start-up time of a water-cooled wall-type standby furnace. Background Technology

[0002] Water-cooled wall gasifiers refer to gasifiers whose gasification reaction chamber or gasification waste boiler chamber uses a water-cooled wall structure. Because their maintenance workload is less than that of refractory brick type gasifiers, they are widely used in the chemical industry. Since gasifiers require regular maintenance, a standby gasifier is generally set up to maintain continuous full-load operation of the unit. Currently, when the operating furnace is running and the standby furnace is shut down, the standby furnace steam drum is in a cold state, i.e., at room temperature. If the standby furnace is started up, two stages are required: water drying and gas drying. Water drying preheats the steam drum to accommodate the thermal expansion of the equipment and water-cooled walls, protecting the equipment, and simultaneously increasing the temperature inside the gasifier, shortening the overall drying time. Steam drum preheating is generally achieved through low-temperature boiler water and steam preheating, controlling the heating rate. After reaching a certain temperature, it is maintained for several hours before proceeding to the next gas drying stage. Currently, the drying time is relatively long. To shorten the standby furnace drying time and reduce the start-up time of the standby furnace, this process was developed.

[0003] Current water-cooled wall process systems, such as Figure 1 The system includes water-cooled walls, steam drum, steam drum circulating water pumps, boiler water, by-product steam, preheating steam, and continuous and periodic blowdown systems. During start-up, boiler water is slowly added to the steam drum to a certain level, establishing water circulation in the water-cooled walls. Then, preheating steam is added to heat the boiler water in the steam drum to the operating temperature at a certain rate. The initial heating rate is generally controlled at <15℃ / h (related to the requirements of the refractory material layer of the water-cooled walls). For standby boilers after the initial baking, the heating rate can be appropriately accelerated to <20℃ / h. Taking a steam drum operating pressure of 5.5 MPa and an operating temperature of 271℃ as an example, the initial start-up requires more than 33.4 hours to heat the boiler water from 104℃ to nearly 271℃. It also requires an 8-hour holding period before the next stage of gas baking, i.e., heating by combustion of fuel gas in the gasifier. For subsequent start-ups, i.e., after the refractory material has been baked, the standby boiler water baking time also needs to exceed 8 hours.

[0004] Because the existing equipment operates independently, when the gasification series is not running, the corresponding steam drum is either cold or kept hot by a separate heat source. This results in a long heating time for the standby boiler steam drum, which in turn leads to a long start-up time for the standby boiler. This is especially true when the operating gasifier trips due to an accident, as the long start-up time of the standby boiler affects the operating load of the unit and causes economic losses. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for reducing the start-up time of the standby furnace, reducing the impact of gasifier tripping on the operating load of the unit, and reducing the economic losses caused by shutdown by reducing the start-up time of the water-cooled wall standby furnace, in light of the current state of the technology.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] A method for reducing the start-up time of a water-cooled wall standby boiler, the equipment used includes a gasifier water-cooled wall, a steam drum, and a water-cooled wall circulating water pump; or a steam drum water heat exchange circulation steam generation system with a heat exchange system and a steam drum including forced circulation and natural circulation; there is a connecting pipeline between the steam drum and water-cooled wall systems of series A and series B, and a portion of the heat from the operating steam drum is distributed to the gasifier and water-cooled wall in the standby series by discharging water from the steam drum;

[0008] Using the A series as the operating furnace and the B series as the standby furnace, the water-cooled wall circulation pump of the standby series does not need to be started. However, it is necessary to set up shut-off valves and discharge valves HV01A / B and HV02A / B from the water-cooled wall outlet to the steam drum. By utilizing the pressure difference and designing the discharge path, the gasifier water-cooled wall and steam drum system can achieve full circulation, thereby raising the temperature of the standby series. Alternatively, using the B series as the operating furnace and the A series as the standby furnace, one water-cooled wall circulation pump of the standby series needs to be started for low-flow circulation. However, it is not necessary to set up shut-off valves and discharge valves HV01A / B and HV02A / B from the water-cooled wall outlet to the steam drum. In this method, the connecting valve HV04 between the steam drums is open, the blowdown valve of the operating steam drum is closed, and the blowdown valve of the standby series is used for drainage, thereby achieving full circulation of the gasifier water-cooled wall and steam drum system and raising the temperature of the standby series.

[0009] Using series A as the operating furnace and series B as the standby furnace, the method is as follows:

[0010] The boiler water inlet control valve LV01A of the steam drum V01A is in the operating state, and LV01B is in the closed state. Boiler water enters the steam drum V01A through LV01A.

[0011] The water-cooled wall circulating water pump P01A is controlled to be in operation. The boiler water in the steam drum V01A is pressurized by the water-cooled wall circulating water pump P01A and enters the gasifier water-cooled wall R01A.

[0012] The gasifier water-cooled wall R01A outlet shut-off valve HV01A is controlled to be open, and the gasifier water-cooled wall R01A outlet drain valve HV02A is controlled to be closed. The boiler circulating water carrying steam after passing through the gasifier water-cooled wall R01A returns to the steam drum V01A.

[0013] After being separated inside the steam drum, the steam is sent to the steam pipeline network through a pressure control valve;

[0014] The connecting valve HV04 between steam drums V01A and V01B is controlled to be open, and the saturated water in steam drum V01A is shared with steam drum V01B through the connecting valve.

[0015] The continuous drain valve FV01A of the steam drum V01A is controlled to be closed, and the periodic drain valve HV03A is controlled to be closed; the continuous drain valve FV01B of the steam drum V01B is controlled to be closed, and the periodic drain valve HV03B is controlled to be closed.

[0016] The water-cooled wall circulating water pump P01B is controlled to be stopped, the gasifier water-cooled wall R01B outlet shut-off valve HV01B is controlled to be closed, and the gasifier water-cooled wall R01B outlet drain valve HV02B is controlled to be in operation and open.

[0017] The saturated boiler water in the steam drum V01B passes through the gasifier water-cooled wall R01B and is discharged to the continuous blowdown network through the outlet drain valve HV02B of the gasifier water-cooled wall R01B. The boiler water in the gasifier water-cooled wall R01B flows slowly through the pressure difference between the steam drum V01B and the continuous blowdown network, maintaining the temperature of the water-cooled wall at a constant level.

[0018] The steam pressure control valve PV01B at the outlet of the steam drum V01B can be in the operating state to maintain the pressure of the steam drum V01B stable; or it can be in the closed state. When it is in the closed state, the liquid level of the steam drum V01B will be different from the liquid level of V01B.

[0019] When series B is running and series A is shut down, the process control is as follows:

[0020] Run the water-cooled wall circulating water pump P01B, open the gasifier water-cooled wall R01B outlet shut-off valve HV01B, and close the gasifier water-cooled wall R01B outlet drain valve HV02B.

[0021] Stop the water-cooled wall circulating water pump P01A, open the outlet drain valve HV02A of the gasifier water-cooled wall R01A, and close the outlet shut-off valve HV01A of the gasifier water-cooled wall R01A.

[0022] In this invention, different series of steam drums are equipped with liquid connection valves, and the number of series is not limited to 2 series;

[0023] The water flow in the standby boiler's water-cooled wall is achieved through the pressure difference between the steam drum and the continuous blowdown system;

[0024] The continuous blowdown of the operating series of steam drums is not put into use; the water quality of the steam drums is controlled by the water-cooled wall drainage of the standby series.

[0025] The inlet and outlet pipelines of the water-cooled wall are not limited to a single pipeline.

[0026] When using series A furnaces as operating furnaces and series B furnaces as standby furnaces, the process control is as follows:

[0027] Steam pressure produced by a steam drum is generally between 5.0 and 10.0 MPa, corresponding to the saturated steam temperature at that pressure. However, this patent applies to steam pressures in steam drums that cover the entire pressure and temperature range from a low pressure of 0.2 MPaG to a high pressure of 15 MPaG. Taking two identical or adjacent steam drums and gasifiers producing 5.0 MPaG of steam as an example.

[0028] The boiler water inlet control valve LV01A of the steam drum V01A is in the operating state. The boiler feedwater temperature is usually between 104℃ and 160℃, and the pressure is greater than 5.0MPag. LV01B is in the closed state. Boiler water enters the steam drum V01A through LV01A. The steam drum pressure of V01A is 5.0MPag, and the temperature is 265℃.

[0029] The water-cooled wall circulating water pump P01A is controlled to be in operation. The boiler water in the steam drum V01A is pressurized by the water-cooled wall circulating water pump P01A and enters the gasifier water-cooled wall R01A. The temperature is between 260 and 265℃ and the pressure is above 5.3MPag (depending on the pressure drop of the water-cooled wall system).

[0030] The gasifier water-cooled wall R01A outlet shut-off valve HV01A is controlled to be open, and the gasifier water-cooled wall R01A outlet drain valve HV02A is controlled to be closed. The boiler circulating water carrying steam after passing through the gasifier water-cooled wall R01A returns to the steam drum V01A. It is a gas-liquid two-phase flow with a temperature of 265℃.

[0031] After the steam is separated in the steam drum, it is sent to the steam pipeline network through the pressure control valve. The pipeline network pressure is usually more than 0.3 MPa lower than the steam drum pressure.

[0032] The connecting valve between steam drums V01A and V01B is in the open state. The saturated water in steam drum V01A is shared with steam drum V01B through the connecting valve. The temperature of the saturated water is between 260 and 265°C, and its pressure is the steam drum pressure.

[0033] The continuous drain valve FV01A of the steam drum V01A is controlled to be closed, and the periodic drain valve HV03A is controlled to be closed; the continuous drain valve FV01B of the steam drum V01B is controlled to be closed, and the periodic drain valve HV03B is controlled to be closed.

[0034] The water-cooled wall circulating water pump P01B is controlled to be stopped, the gasifier water-cooled wall R01B outlet shut-off valve HV01A is controlled to be closed, and the gasifier water-cooled wall R01B outlet drain valve HV02B is controlled to be open.

[0035] The saturated boiler water in the steam drum V01B passes through the gasifier water-cooled wall R01B and is discharged to the continuous blowdown network through the outlet drain valve HV02B of the gasifier water-cooled wall R01B. After reaching a steady state of thermal equilibrium, the discharge temperature before continuous blowdown flash evaporation is slightly lower than 265℃. The boiler water in the gasifier water-cooled wall R01B flows slowly through the pressure difference between the steam drum V01B and the continuous blowdown network, maintaining the temperature of the water-cooled wall above 200℃.

[0036] When the B series is running and the A series is shut down, the process control is as described above, and the equipment and valve tag numbers will change accordingly.

[0037] Both of the above methods can achieve online heating and standby of the backup gasifier steam drum and water-cooled wall. The second method is simpler to configure than the first method, but it requires more electrical power.

[0038] Compared with existing technologies, the advantages of this invention are as follows: This invention fully utilizes the heat from the continuous blowdown of the operating series of steam drums to maintain the temperature of the standby series of water-cooled walls. The system is simple and easy to control. Compared with existing technologies, this invention eliminates the need for separate water drying, reducing the start-up time of the standby boiler, minimizing the impact of gasifier tripping on the unit's operating load, and reducing economic losses caused by shutdowns. Based on an 8-hour water drying time, this invention can reduce the economic losses caused by unplanned shutdowns by 8 hours. For a gasification scale producing 100,000 standard cubic meters of effective gas per hour, this can reduce economic losses by nearly 500,000 yuan. Attached Figure Description

[0039] Figure 1 This is a process flow diagram of the background technology of this invention;

[0040] Figure 2 This is a process flow diagram of an embodiment of the present invention. Detailed Implementation

[0041] The following is in conjunction with the appendix Figure 2 The embodiments provide a further detailed description of the present invention.

[0042] This embodiment describes a method for reducing the start-up time of a water-cooled wall-type standby boiler. The equipment used includes a gasifier water-cooled wall, a steam drum, and a water-cooled wall circulating water pump. Specifically, it relates to... Figure 2 The flowchart shown is consistent.

[0043] When using series A furnaces as operating furnaces and series B furnaces as standby furnaces, the process control is as follows:

[0044] The boiler water inlet control valve LV01A of the steam drum V01A is in the operating state, and LV01B is in the closed state. Boiler water enters the steam drum V01A through LV01A.

[0045] The water-cooled wall circulating water pump P01A is controlled to be in operation. The boiler water in the steam drum V01A is pressurized by the water-cooled wall circulating water pump P01A and enters the gasifier water-cooled wall R01A.

[0046] The gasifier water-cooled wall R01A outlet shut-off valve HV01A is controlled to be open, and the gasifier water-cooled wall R01A outlet drain valve HV02A is controlled to be closed. The boiler circulating water carrying steam after passing through the gasifier water-cooled wall R01A returns to the steam drum V01A.

[0047] After being separated inside the steam drum, the steam is sent to the steam pipeline network through a pressure control valve;

[0048] The connecting valve between steam drum V01A and steam drum V01B is controlled to be open, and the saturated water in steam drum V01A is shared with steam drum V01B through the connecting valve;

[0049] The continuous drain valve FV01A of the steam drum V01A is controlled to be closed, and the periodic drain valve HV03A is controlled to be closed; the continuous drain valve FV01B of the steam drum V01B is controlled to be closed, and the periodic drain valve HV03B is controlled to be closed.

[0050] The water-cooled wall circulating water pump P01B is controlled to be stopped, the gasifier water-cooled wall R01B outlet shut-off valve HV01A is controlled to be closed, and the gasifier water-cooled wall R01B outlet drain valve HV02B is controlled to be open.

[0051] The saturated boiler water in the steam drum V01B passes through the gasifier water-cooled wall R01B and is discharged to the continuous blowdown network through the outlet drain valve HV02B of the gasifier water-cooled wall R01B. The boiler water in the gasifier water-cooled wall R01B flows slowly through the pressure difference between the steam drum V01B and the continuous blowdown network, maintaining the temperature of the water-cooled wall at a constant level.

[0052] When the B series is running and the A series is shut down, the process control is as described above, and the equipment and valve tag numbers will change accordingly.

[0053] When using series A furnaces as operating furnaces and series B furnaces as standby furnaces, the process control is as follows:

[0054] Steam pressure produced by a steam drum is generally between 5.0 and 10.0 MPa, corresponding to the saturated steam temperature at that pressure. However, this patent applies to steam pressures in steam drums that cover the entire pressure and temperature range from a low pressure of 0.2 MPaG to a high pressure of 15 MPaG. Taking two identical or adjacent steam drums and gasifiers producing 5.0 MPaG of steam as an example.

[0055] The boiler water inlet control valve LV01A of the steam drum V01A is in the operating state. The boiler feedwater temperature is usually between 104℃ and 160℃, and the pressure is greater than 5.0MPag. LV01B is in the closed state. Boiler water enters the steam drum V01A through LV01A. The steam drum pressure of V01A is 5.0MPag, and the temperature is 265℃.

[0056] The water-cooled wall circulating water pump P01A is controlled to be in operation. The boiler water in the steam drum V01A is pressurized by the water-cooled wall circulating water pump P01A and enters the gasifier water-cooled wall R01A. The temperature is between 260 and 265℃ and the pressure is above 5.3MPag (depending on the pressure drop of the water-cooled wall system).

[0057] The gasifier water-cooled wall R01A outlet shut-off valve HV01A is controlled to be open, and the gasifier water-cooled wall R01A outlet drain valve HV02A is controlled to be closed. The boiler circulating water carrying steam after passing through the gasifier water-cooled wall R01A returns to the steam drum V01A. It is a gas-liquid two-phase flow with a temperature of 265℃.

[0058] After the steam is separated in the steam drum, it is sent to the steam pipeline network through the pressure control valve. The pipeline network pressure is usually more than 0.3 MPa lower than the steam drum pressure.

[0059] The connecting valve between steam drums V01A and V01B is in the open state. The saturated water in steam drum V01A is shared with steam drum V01B through the connecting valve. The temperature of the saturated water is between 260 and 265°C, and its pressure is the steam drum pressure.

[0060] The continuous drain valve FV01A of the steam drum V01A is controlled to be closed, and the periodic drain valve HV03A is controlled to be closed; the continuous drain valve FV01B of the steam drum V01B is controlled to be closed, and the periodic drain valve HV03B is controlled to be closed.

[0061] The water-cooled wall circulating water pump P01B is controlled to be stopped, the gasifier water-cooled wall R01B outlet shut-off valve HV01A is controlled to be closed, and the gasifier water-cooled wall R01B outlet drain valve HV02B is controlled to be open.

[0062] The saturated boiler water in the steam drum V01B passes through the gasifier water-cooled wall R01B and is discharged to the continuous blowdown network through the outlet drain valve HV02B of the gasifier water-cooled wall R01B. After reaching a steady state of thermal equilibrium, the discharge temperature before continuous blowdown flash evaporation is slightly lower than 265℃. The boiler water in the gasifier water-cooled wall R01B flows slowly through the pressure difference between the steam drum V01B and the continuous blowdown network, maintaining the temperature of the water-cooled wall above 200℃.

[0063] When the B series is running and the A series is shut down, the process control is as described above, and the equipment and valve tag numbers will change accordingly.

[0064] Both of the above methods can achieve online heating and standby of the backup gasifier steam drum and water-cooled wall. The second method is simpler to configure than the first method, but it requires more electrical power.

Claims

1. A method for reducing the start-up time of a water-cooled wall-mounted standby boiler, characterized in that: The equipment used includes gasifier water-cooled walls, steam drum and water-cooled wall circulating water pumps; the steam drum includes a steam drum water heat exchange circulation system with forced circulation and natural circulation; there are connecting pipelines between the steam drum and water-cooled wall systems of series A and series B, and the heat of the operating steam drum is distributed to the gasifier and water-cooled walls in the standby series by discharging water from the steam drum. When Series A is used as the operating furnace and Series B as the standby furnace, the water-cooled wall circulation pump of the standby series does not need to be started. However, it is necessary to install shut-off valves and discharge valves HV01A / B and HV02A / B from the water-cooled wall outlet to the steam drum. By utilizing the pressure difference and designing the discharge path, the full circulation of the gasifier's water-cooled wall and steam drum system is achieved, enabling the standby series to heat up. The process control is as follows: The boiler water inlet control valve LV01A of the steam drum V01A is in the operating state, and LV01B is in the closed state. Boiler water enters the steam drum V01A through LV01A. The water-cooled wall circulating water pump P01A is controlled to be in operation. The boiler water in the steam drum V01A is pressurized by the water-cooled wall circulating water pump P01A and enters the gasifier water-cooled wall R01A. The gasifier water-cooled wall R01A outlet shut-off valve HV01A is controlled to be open, and the gasifier water-cooled wall R01A outlet drain valve HV02A is controlled to be closed. The boiler circulating water carrying steam after passing through the gasifier water-cooled wall R01A returns to the steam drum V01A. After being separated inside the steam drum, the steam is sent to the steam pipeline network through a pressure control valve; The connecting valve between steam drums V01A and V01B is controlled to be open. The saturated water in steam drum V01A is shared with steam drum V01B through the connecting valve. Steam drums V01A and V01B maintain the same liquid level, temperature and pressure. The continuous drain valve FV01A of the steam drum V01A is controlled to be closed, and the periodic drain valve HV03A is controlled to be closed; the continuous drain valve FV01B of the steam drum V01B is controlled to be closed, and the periodic drain valve HV03B is controlled to be closed. The water-cooled wall circulating water pump P01B is controlled to be stopped, the gasifier water-cooled wall R01B outlet shut-off valve HV01B is controlled to be closed, and the gasifier water-cooled wall R01B outlet drain valve HV02B is controlled to be in operation. The saturated boiler water in the steam drum V01B passes through the gasifier water-cooled wall R01B and is discharged to the continuous blowdown network through the outlet drain valve HV02B of the gasifier water-cooled wall R01B. The boiler water in the gasifier water-cooled wall R01B flows slowly through the pressure difference between the steam drum V01B and the continuous blowdown network, maintaining the temperature of the water-cooled wall at a constant level. The steam pressure control valve PV01B at the outlet of the steam drum V01B is set to the operating state to separate steam from the boiler water and maintain the pressure stability of the steam drum V01B. When the B series is used as the operating furnace and the A series as the standby furnace, one water-cooled wall circulation pump of the standby furnace needs to be started for low-flow circulation. However, it is not necessary to install shut-off valves and discharge valves HV01A / B and HV02A / B from the water-cooled wall outlet to the steam drum. In this method, the connecting valve HV04 between the steam drums is open, the blowdown valve of the operating steam drum is closed, and the blowdown valve of the standby series is used for drainage, realizing the full circulation of the gasifier water-cooled wall and steam drum system, and achieving the heating of the standby series; the process control is as follows: Run the water-cooled wall circulating water pump P01B, open the gasifier water-cooled wall R01B outlet shut-off valve HV01B, and close the gasifier water-cooled wall R01B outlet drain valve HV02B. Stop the water-cooled wall circulating water pump P01A, open the outlet drain valve HV02A of the gasifier water-cooled wall R01A, and close the outlet shut-off valve HV01A of the gasifier water-cooled wall R01A.

2. The method for reducing the start-up time of a water-cooled wall-type standby boiler according to claim 1, characterized in that: When using series A furnaces as operating furnaces and series B furnaces as standby furnaces, the process control is as follows: The steam pressure produced by the steam drum is between 5.0 and 10.0 MPa, and the corresponding temperature is the saturated steam temperature corresponding to the steam pressure. The boiler water inlet control valve LV01A of the steam drum V01A is in the operating state, with the boiler feedwater temperature between 104℃ and 160℃ and the pressure greater than 5.0MPag; LV01B is in the closed state, with boiler water entering the steam drum V01A through LV01A, and the steam drum pressure of V01A is 5.0MPag and the temperature is 265℃. The water-cooled wall circulating water pump P01A is controlled to be in operation. The boiler water in the steam drum V01A is pressurized by the water-cooled wall circulating water pump P01A and enters the gasifier water-cooled wall R01A. The temperature is between 260~265℃ and the pressure is above 5.3MPag. The gasifier water-cooled wall R01A outlet shut-off valve HV01A is controlled to be open, and the gasifier water-cooled wall R01A outlet drain valve HV02A is controlled to be closed. The boiler circulating water carrying steam after passing through the gasifier water-cooled wall R01A returns to the steam drum V01A. It is a gas-liquid two-phase flow with a temperature of 265℃. After the steam is separated in the steam drum, it is sent to the steam pipeline network through the pressure control valve. The pipeline network pressure is more than 0.3 MPa lower than the steam drum pressure. The connecting valve between steam drums V01A and V01B is controlled to be open. The saturated water in steam drum V01A is shared with steam drum V01B through the connecting valve. The temperature of the saturated water is between 260 and 265°C, and its pressure is the steam drum pressure. The continuous drain valve FV01A of the steam drum V01A is controlled to be closed, and the periodic drain valve HV03A is controlled to be closed; the continuous drain valve FV01B of the steam drum V01B is controlled to be closed, and the periodic drain valve HV03B is controlled to be closed. The water-cooled wall circulating water pump P01B is controlled to be stopped, the gasifier water-cooled wall R01B outlet shut-off valve HV01B is controlled to be closed, and the gasifier water-cooled wall R01B outlet drain valve HV02B is controlled to be open. The saturated boiler water in the steam drum V01B passes through the gasifier water-cooled wall R01B and is discharged to the continuous blowdown network through the outlet drain valve HV02B of the gasifier water-cooled wall R01B. After reaching a steady state of thermal equilibrium, the discharge temperature before continuous blowdown flash evaporation is slightly lower than 265℃. The boiler water in the gasifier water-cooled wall R01B flows slowly through the pressure difference between the steam drum V01B and the continuous blowdown network, maintaining the temperature of the water-cooled wall above 200℃.

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