Method for operating a full-gas circulating fluidized bed boiler

Abstract

This invention provides an operation method for a fully coal gas-fired circulating fluidized bed boiler, characterized by the following steps: 1) blocking the circulating return material channel with packing material; 2) boiler startup; 3) boiler operation; 4) boiler shutdown, completing the operation of the fully coal gas-fired circulating fluidized bed boiler. When it is necessary to revert to conventional coal-fired circulating fluidized bed boiler operation, simply start the return material fan to open the return material channel and perform conventional coal-fired circulating fluidized bed boiler operation. No changes are made to the original boiler structure; flexible switching between three operating modes—fully coal-fired, fully coal gas-fired, and mixed coal-fired and coal gas-fired—can be achieved solely through operation, while providing a stable supply of steam. The operation is simple, maintains stable boiler operation, fully utilizes surplus coal gas produced, greatly improves economic efficiency, saves costs for enterprises, and demonstrates significant economic and technical benefits.

Description

Technical Field

[0001] This invention relates to an operating method, and more particularly to an operating method for a coal gas circulating fluidized bed boiler, belonging to the field of coal coking operation technology. Background Technology

[0002] Currently, coal-fired circulating fluidized bed (CFB) boilers still primarily use raw coal as fuel, and the utilization of surplus gas mainly involves co-firing it. However, in operating CFB boilers that co-fire, the amount of co-fired gas is generally limited to no more than 50% of the total boiler heat consumption due to factors such as temperature, making it difficult to fully utilize the surplus gas as fuel. Some enterprises, in order to fully utilize their self-produced surplus gas, have had to convert their coal-fired CFB boilers into CFB boilers that burn only coal gas. However, this involves significant modifications, with investment exceeding 5 million yuan. This increases the economic burden on enterprises while failing to fully utilize their self-produced surplus gas. Therefore, it is necessary to improve the existing technology. Summary of the Invention

[0003] In view of the problems of high modification costs and underutilization of self-produced coal gas in existing technologies, this invention aims to make full use of surplus coal gas and proposes an innovative operation method for achieving full coal gas combustion in circulating fluidized bed boilers without the need for boiler equipment modification or large capital investment.

[0004] Based on the existing circulating fluidized bed boiler with a gas co-firing device, this invention mainly improves the operation method to achieve full gas combustion in the circulating fluidized bed boiler, maintain stable boiler operation, without increasing investment in any modified equipment, and make full use of the self-produced surplus gas, creating favorable conditions for the survival of enterprises.

[0005] This invention is achieved through the following technical solution: a method for operating a fully gas-fired circulating fluidized bed boiler, characterized by comprising the following steps: 1) The packing blocks the circulating return channel. Solid particles smaller than 10mm or return ash are filled into the return feeder on the circulating return channel connected to the boiler. The packing or return ash is filled to the point where the circulating return channel is blocked. This prevents high-temperature flue gas or flame from entering the cyclone separator and tail flue through the circulating return channel, which could cause the boiler superheater heating surface to overheat and rupture the tube. It also prevents the water-cooled wall evaporator surface from absorbing too much heat and reducing the steam generation. The bottom of the return feeder is connected to the return blower via a connecting pipe, and a control valve is installed on the connecting pipe; 2) Boiler Start-up 21) Start the induced draft fan and primary air fan, and control the flue gas outlet pressure at the top of the boiler to be between -150 and 0 Pa. Depending on the amount of air required for combustion, start or stop the secondary air fan. If the secondary air fan is not started, the valve on the secondary air connecting pipe to the furnace needs to be closed to prevent the furnace flame or combustion products from entering the secondary air pipe. 22) Open the valve on the gas blending port pipe connected to the boiler, ignite the gas at the first gas blending port, and control the gas flow rate to 100-200 m³ / h. 3 / h, keep the flame burning continuously and stably for half an hour; 23) Ignite the gas at the second gas mixing port, controlling the gas flow rate to 100-200 m³ / h. 3 / h, continue stable combustion for half an hour; 24) Ignite the gas in the remaining gas mixing port, and control the temperature difference between the left and right walls of the furnace to be ≤150℃, and control the steam drum pressure rise rate to be 0.01~0.03MPa / min; 25) When the steam in the steam drum is heated and pressurized to a level suitable for connection to the steam network, perform the routine steam connection operation to complete the boiler startup; 3) Boiler operation: Adjust the opening of multiple gas blending port valves in a timely manner according to combustion requirements to regulate gas flow and maintain normal boiler operation; 4) Boiler shutdown 41) Disconnection: Operate the valve on the gas co-firing port pipeline connected to the boiler to gradually reduce the gas volume of multiple gas co-firing ports until the steam flow rate is less than 10t / h, and complete the boiler disconnection; 42) Maintain the steam pressure and temperature during normal boiler operation, and continue to reduce the amount of gas at multiple gas co-firing ports until the temperature at the bottom of the boiling layer drops to 400-500℃. If a limestone system is in operation, stop the operation of the limestone system. 43) Close the gas supply to multiple gas blending ports, open the vent valve on the gas blending port pipeline connected to the boiler to release the gas until the blending gas pressure drops to 0 Pa. 44) Adjust the opening of the induced draft fan to maintain the furnace negative pressure of -150 to 0 Pa, keep the steam pressure constant, increase the boiler feed water to raise the steam drum water level to +100 mm to +200 mm above the high water level, and adjust or close the boiler feed water to reduce the temperature in a timely manner according to the steam temperature. 45) After maintaining furnace ventilation for 5 minutes, turn off the secondary air fan and primary air fan in sequence. After 5 minutes, turn off the induced draft fan to complete the boiler shutdown.

[0006] The filling material in step 1) is specifically: the bed material or return ash is sent in through the maintenance manhole at the top of the return feeder, or when bed material or fine ash is generated in the furnace, the primary blower is started to send the bed material or fine ash from the flue gas outlet at the top of the furnace through the separator into the return feeder to form blocking material.

[0007] During the ignition process in steps 22), 23), and 24), the ignition status and the temperature of the boiling layer are observed and confirmed through the observation holes on the boiler to confirm whether the ignition in the furnace is normal.

[0008] In step 23), when the number of gas co-firing ports ignited reaches two or more, the steam boiler pressure rise rate is controlled to 0.01-0.03 MPa / min to prevent the boiler from expanding too quickly.

[0009] Step 1) involves filling the return feeder on the circulating return channel connected to the boiler with bed material or return ash to block the circulating return channel. After the circulating fluidized bed boiler has completed its full coal gas operation, when it is necessary to return to the conventional coal-fired circulating fluidized bed boiler operation, simply open the control valve on the connecting pipe between the bottom of the return feeder and the return fan, start the return fan, and the return channel will be opened to resume the conventional coal-fired circulating fluidized bed boiler operation.

[0010] Compared with the prior art, the invention has the following positive effects and advantages; (1) No changes are made to the original structure of the boiler, that is, zero investment and zero modification. The three operating modes of burning all power coal, burning all gas, and mixed burning of power coal and gas can be flexibly switched through operation, and a stable steam product is provided to the outside.

[0011] (2) The present invention is simple to operate and keeps the boiler running stably, so that the surplus gas produced by the company can be fully utilized, greatly improving economic efficiency and saving costs for the company. The economic and technical effects are significant. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of an existing circulating fluidized bed boiler. Detailed Implementation

[0013] The present invention will be further described below with reference to embodiments. Example 1

[0014] The circulating fluidized bed boiler in this embodiment 1 is a 40t / h coal-fired circulating fluidized bed boiler with a boiler outlet steam pressure of 3.5-3.7MPa and a steam temperature of 400-460℃. It has four gas co-firing ports. The bottom of the return feeder is connected to the return blower through a connecting pipe, and a control valve is installed on the connecting pipe. The operation of this circulating fluidized bed boiler using only coal gas includes the following steps: 1) The packing blocks the circulating return channel. 300 kg of solid particle bed material smaller than 10 mm is sent from the maintenance manhole at the top of the return device into the return device on the circulating return channel connected to the boiler. The bed material is filled until the circulating return channel is blocked to prevent high-temperature flue gas or flame from entering the cyclone separator and tail flue through the circulating return channel, which could cause the boiler superheater heating surface to overheat and rupture the tube. It also prevents the water-cooled wall evaporator surface from not absorbing enough heat and reducing the steam generation. 2) Boiler Start-up 21) Start the induced draft fan and primary air fan in sequence, adjust the induced draft volume and primary air volume until the furnace negative pressure is -150 to 0 Pa, control the primary air volume to 20000 to 25000 Nm3 / h, and after the fan volume is adjusted to be stable, purge the furnace for at least 5 minutes and check that there is no gas in the furnace. 22) Open the valve on the gas blending port pipe connected to the boiler, ignite the gas at the first gas blending port, and control the gas flow rate to 100-150 m³ / h. 3 / h, keep the flame burning continuously and stably for half an hour, slowly increase the furnace temperature, and adjust the furnace negative pressure to -200 to -150 Pa; 23) Ignite the gas at the second gas mixing port, which is diagonally opposite the first gas mixing port, and control the gas flow rate to 100-150 m³ / h. 3 / h, continue stable combustion for half an hour, and maintain the furnace negative pressure at -200 to -150 Pa; 24) Slowly increase the opening of the gas valves of the first and second gas mixing ports that have been ignited until the furnace temperature on the left and right walls of the furnace reaches 500℃. Then ignite the gas in the third gas mixing port. When the pressure rise is not significant, ignite the gas in the fourth gas mixing port. Control the temperature difference between the left and right walls of the furnace to be ≤150℃ and control the steam drum pressure rise rate to be 0.01MPa / min. 25) When the steam in the steam drum is heated and pressurized to a level suitable for connection to the steam network, perform the routine steam connection operation to complete the boiler startup; 3) Boiler operation: Adjust the opening of multiple gas blending port valves in a timely manner according to combustion requirements to regulate gas flow and maintain normal boiler operation; 4) Boiler shutdown 41) Disconnection: Operate the valve on the gas co-firing port pipeline of the boiler to gradually reduce the gas volume of multiple gas co-firing ports until the steam flow rate is less than 10t / h, and complete the boiler disconnection; 42) Maintain the steam pressure and temperature during normal boiler operation, and continue to reduce the amount of gas at multiple gas co-firing ports until the temperature at the bottom of the boiling layer drops to 400℃. 43) Close the gas supply to the four gas blending ports, open the vent valve on the gas blending port pipeline connected to the boiler to release the gas until the blending gas pressure drops to 0 Pa. 44) Adjust the opening of the induced draft fan to maintain the negative pressure in the furnace from -150 to 0 Pa, keep the steam pressure constant, increase the boiler feed water to raise the steam drum water level to the high level, i.e. +100 mm, and adjust or close the boiler feed water to reduce the temperature in a timely manner according to the steam temperature. 45) After maintaining furnace ventilation for 5 minutes, turn off the secondary air fan and primary air fan in sequence. After 5 minutes, turn off the induced draft fan to complete the boiler shutdown. Example 2

[0015] The circulating fluidized bed boiler in this embodiment 2 is a 40t / h coal-fired circulating fluidized bed boiler with a boiler outlet steam pressure of 3.5-3.7MPa and a steam temperature of 400-460℃. It has four gas co-firing ports. The bottom of the return feeder is connected to the return blower through a connecting pipe, and a control valve is installed on the connecting pipe. The operation of this circulating fluidized bed boiler using only coal gas includes the following steps: 1) The packing blocks the circulating return channel. 300 kg of solid particle bed material smaller than 10 mm is sent from the maintenance manhole at the top of the return device into the return device on the circulating return channel connected to the boiler. The bed material is filled until the circulating return channel is blocked to prevent high-temperature flue gas or flame from entering the cyclone separator and tail flue through the circulating return channel, which could cause the boiler superheater heating surface to overheat and rupture the tube. It also prevents the water-cooled wall evaporator surface from not absorbing enough heat and reducing the steam generation. 2) Boiler Start-up 21) Start the induced draft fan and primary air fan in sequence, adjust the induced draft volume and primary air volume until the furnace negative pressure is -150 to 0 Pa, control the primary air volume to 25000 to 30000 Nm3 / h, and after the fan volume is adjusted to be stable, purge the furnace for at least 5 minutes and check that there is no gas in the furnace. 22) Open the valve on the gas blending port pipe connected to the boiler, ignite the gas at the first gas blending port, and control the gas flow rate to 150-200 m³ / h. 3 / h, keep the flame burning continuously and stably for half an hour, slowly increase the furnace temperature, and adjust the furnace negative pressure to -150 to -100 Pa; 23) Ignite the gas at the second gas mixing port, which is diagonally opposite the first gas mixing port, and control the gas flow rate to 150-200 m³ / h. 3 / h, continue stable combustion for half an hour, and maintain the furnace negative pressure at -150 to -100 Pa; 24) Slowly increase the opening of the gas valve of the already ignited co-firing port until the furnace temperature on the left and right walls of the furnace reaches 500℃. Then ignite the gas in the third co-firing port. When the pressure rise is not significant, ignite the gas in the fourth co-firing port. Control the temperature difference between the left and right walls of the furnace to ≤150℃ and control the steam drum pressure rise rate to 0.03MPa / min. 25) When the steam in the steam drum is heated and pressurized to a level suitable for connection to the steam network, perform the routine steam connection operation to complete the boiler startup; 3) Boiler operation: Adjust the opening of multiple gas blending port valves in a timely manner according to combustion requirements to regulate gas flow and maintain normal boiler operation; 4) Boiler shutdown 41) Disconnection: Operate the valve on the gas co-firing port pipeline of the boiler to gradually reduce the gas volume of multiple gas co-firing ports until the steam flow rate is less than 10t / h, and complete the boiler disconnection; 42) Maintain the steam pressure and temperature during normal boiler operation, and continue to reduce the amount of gas at multiple gas co-firing ports until the temperature at the bottom of the boiling layer drops to 500℃. 43) Close the gas supply to the four gas blending ports, open the vent valve on the gas blending port pipeline connected to the boiler to release the gas until the blending gas pressure drops to 0 Pa. 44) Adjust the opening of the induced draft fan to maintain the negative pressure in the furnace from -150 to 0 Pa, keep the steam pressure constant, increase the boiler feed water to raise the steam drum water level to the high level, i.e., +200 mm, and adjust or close the boiler feed water to reduce the temperature in a timely manner according to the steam temperature. 45) After maintaining furnace ventilation for 5 minutes, turn off the secondary air fan and primary air fan in sequence. After 5 minutes, turn off the induced draft fan to complete the boiler shutdown.

[0016] When switching to a coal-fired circulating fluidized bed boiler, simply open the control valve on the connecting pipe between the bottom of the return feeder and the return fan, start the return fan, and the return channel will be opened for regular coal-fired circulating fluidized bed boiler operation.

[0017] Through the operations described in Examples 1 and 2 above, the daily consumption of thermal coal is reduced by 84 tons, saving 84 tons / day × 500 yuan / ton = 42,000 yuan / day in thermal coal costs. At the same time, carbon emissions are reduced by 48.72 tons / day. No changes are made to the original structure of the boiler, and it can be operated as a coal-fired or all-gas circulating fluidized bed boiler as needed, making full use of the surplus coal gas produced by the company, greatly improving economic efficiency, saving costs for the enterprise, and achieving significant economic and technical benefits.

Claims

1. An operation method for a circulating fluidized bed boiler powered entirely by coal gas, characterized in that... Includes the following steps: 1) The packing blocks the circulating return channel. Solid particle bed material or return ash smaller than 10mm is filled into the return feeder on the circulating return channel connected to the boiler until the circulating return channel is blocked. This prevents high-temperature flue gas or flame from entering the cyclone separator and tail flue through the circulating return channel, which could cause the boiler superheater heating surface to overheat and rupture the tube. It also prevents the water-cooled wall evaporator surface from absorbing too much heat and reducing the steam generation. The bottom of the return feeder is connected to the return blower via a connecting pipe, and a control valve is installed on the connecting pipe; 2) Boiler Start-up 21) Start the induced draft fan and primary air fan, and control the flue gas outlet pressure at the top of the boiler to be between -150 and 0 Pa. Depending on the amount of air required for combustion, start or stop the secondary air fan. If the secondary air fan is not started, the valve on the secondary air connecting pipe to the furnace needs to be closed to prevent the furnace flame or combustion products from entering the secondary air pipe. 22) Open the valve on the gas blending port pipe connected to the boiler, ignite the gas at the first gas blending port, and control the gas flow rate to 100-200 m³ / h. 3 / h, keep the flame burning continuously and stably for half an hour; 23) Ignite the gas at the second gas mixing port, controlling the gas flow rate to 100-200 m³ / h. 3 / h, continue burning steadily for half an hour. 24) Then ignite the remaining gas in the combustion port, and control the temperature difference between the left and right walls of the furnace to be ≤150℃, and control the steam drum pressure rise rate to be 0.01~0.03MPa / min. 25) When the steam in the steam drum is heated and pressurized to a level suitable for connection to the steam network, perform the routine steam connection operation to complete the boiler startup; 3) During boiler operation, adjust the opening of multiple gas blending port valves in a timely manner according to combustion requirements to adjust the gas flow and maintain normal boiler operation; 4) Boiler shutdown 41) Disconnection: Operate the valve on the gas co-firing port pipeline connected to the boiler to gradually reduce the gas volume of multiple gas co-firing ports until the steam flow rate is less than 10t / h, and complete the boiler disconnection; 42) Maintain the steam pressure and temperature during normal boiler operation, and continue to reduce the amount of gas at multiple gas co-firing ports until the temperature at the bottom of the boiling layer drops to 400-500℃. If a limestone system is in operation, stop the operation of the limestone system. 43) Close the gas supply to multiple gas mixing ports, open the vent valve on the gas mixing port pipeline connected to the boiler to release the gas until the gas pressure drops to 0 Pa. 44) Adjust the opening of the induced draft fan to maintain the furnace negative pressure of -150 to 0 Pa, keep the steam pressure constant, increase the boiler feed water to raise the steam drum water level to +100 mm to +200 mm above the high water level, and adjust or close the boiler feed water to reduce the temperature in a timely manner according to the steam temperature. 45) After maintaining furnace ventilation for 5 minutes, turn off the secondary air fan and primary air fan in sequence. After 5 minutes, turn off the induced draft fan to complete the boiler shutdown.

2. The operation method of the all-gas circulating fluidized bed boiler according to claim 1, characterized in that... The filling material in step 1) is specifically: the bed material or return ash is sent in through the maintenance manhole at the top of the return feeder, or when bed material or fine ash is generated in the furnace, the primary blower is started to send the bed material or fine ash from the flue gas outlet at the top of the furnace through the separator into the return feeder to form blocking material.

3. The operation method of the all-gas circulating fluidized bed boiler according to claim 1, characterized in that... During the ignition process in steps 22), 23), and 24), the ignition status and the temperature of the boiling layer are observed and confirmed through the observation holes on the boiler to confirm whether the ignition in the furnace is normal.

4. The operation method of the all-gas circulating fluidized bed boiler according to claim 1, characterized in that... In step 23), when the number of gas co-firing ports ignited reaches two or more, the steam drum pressure rise rate is controlled to 0.01-0.03 MPa / min.

5. The operation method of a fully gas-fired circulating fluidized bed boiler according to claim 1, characterized in that... Step 1) involves filling the return feeder on the circulating return channel connected to the boiler with bed material or return ash to block the circulating return channel. After the circulating fluidized bed boiler has completed its full coal gas operation, when it is necessary to return to the conventional coal-fired circulating fluidized bed boiler operation, the control valve on the connecting pipe between the bottom of the return feeder and the return fan needs to be opened, and the return fan needs to be started to open the return channel and resume the conventional coal-fired circulating fluidized bed boiler operation.

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