Commissioning of the Luchi furnace

Ignition can be carried out once the steam temperature reaches the required level. Ignition and the development of the flame layer after ignition are crucial for ensuring stable high-load operation of the gasification furnace once it is put into use. Pressurized gasification furnaces generally use air for ignition, and switch to oxygen operation once the operating conditions are stable. In recent years, some factories have adopted direct oxygen ignition. (Such as the original **German Black Pump Gas Plant and the Harbin Gasification Plant in China**), this eliminates the need for switching between air and oxygen, thereby reducing the time required to get the gasification furnace up and running. Air ignition is generally recommended because it is safer. The steps for air ignition are as follows. (1) Verify ignition conditions: Heat the coal seam for about 3 hours ； The outlet temperature of the gasifier is greater than 100°C. (2) Close the steam flow control valve feeding into the furnace. (3) Slowly open the start-up air flow control valve to regulate the air flow into the furnace at approximately 1500 m3 (standard) per hour. (4) By using an austen analyzer to analyze the gas composition at the outlet of the gasifier, an increasing CO2 content and a decreasing O2 content indicate that the fire has been ignited. (5) Once it is confirmed that the gasification furnace has been successfully ignited, slightly open the steam inlet control valve to add a small amount of steam to the gasifying agent, ensuring that the temperature of the gasifying agent remains above 150°C. (6) Once the CO2 and O2 contents in the gas exiting the gasifier become relatively stable, the amount of air fed into the gasifier is gradually increased to 3000–4000 m3 (standard) per hour; simultaneously, the amount of steam fed into the gasifier is increased accordingly to maintain the temperature of the gasification agents. (7) Start the furnace grates and operate them at the lowest speed to ensure uniform gas distribution inside the furnace. For gasifiers equipped with coal distribution agitators, they should be started simultaneously. (8) When the oxygen content in the gas at the outlet of the gasifier is less than 0.4% (by volume), the gas is diverted to a thermal flare for venting (if two start-up flares are available); the flare is ignited, and operation with air is maintained for about 4 hours to develop a flame layer. At this stage, the grate should be operated at a low speed in an intermittent manner. It should be noted, however, that less ash is generated during the air operation phase; therefore, the amount of ash discharged by the grate should be less than the amount of slag produced by the gasifier. Otherwise, the ash will accumulate in the ash lock, disrupting the flame layer inside the furnace. Main control parameters during air operation: High-activity coal, Low-activity coal (lignite, bituminous coal, etc.), (lean coal, anthracite). CO2 content in the gas /%: 16–18, 12–16. Temperature of the gasifying agent /°C: 160–180, 120–140. 4. Oxygen supply, pressure increase, and connection to the grid for gas delivery: Once normal air operation is established and a uniform flame layer has formed inside the gasifier, air can be replaced with oxygen along with steam; thereafter, the pressure is increased gradually and the gasifier is connected to the grid. The specific steps are as follows. (1) Verify the oxygen cutting conditions: ① The water level in the jacket and the water level in the waste heat boiler, as well as the water level of the gas and water mixture at the bottom of the waste heat boiler, are all normal. ②The gas-water washing circulation pump is operating normally. ③The hydraulic system that powers the coal and ash lock valves is operating properly. ④Operation of the gasifier with a full load. (2) Oxygen cutting operation: ① Turn the oxygen blind flange to the open position, and open the bypass valve of the main shut-off valve to test for leaks at the flange; at this time, the oxygen electric valve and the oxygen control valve must be in the closed position. ②Confirm that all valves for the coal lock and ash lock are in the closed position, and that ash discharge from the grate has stopped. ③Close the steam inlet control valve; if there is a leak, the steam electric valve should also be closed. Then wait for 5 minutes before closing the air control valve for the furnace. ④Slightly increase the setting value of the gasifier gas pressure regulator (in automatic control mode) so that the gas pressure control valve closes exactly. ⑤First, open the steam electric valve, and then open the oxygen electric valve. If there is a leak at the oxygen control valve after the oxygen electric valve is opened, close the oxygen electric valve first and reopen it once the steam flow has started. ⑥Slowly open the steam control valve to adjust the steam flow to about 5 t/h, then open the oxygen control valve and adjust the oxygen flow based on the designed steam-to-oxygen ratio; strive to supply an oxygen amount with a high steam-to-oxygen ratio in order to avoid slag formation in the vaporization furnace due to excess oxygen. Upon close inspection, the gas pressure control valve of the gasifier should open within a few seconds after oxygen is introduced; otherwise, the gasifier should be shut down. ⑦Use an austenometer to take continuous samples for analyzing the composition of the gas; the CO2 content in the gas should be less than 40% (by volume), and the O2 content should be less than 1% (by volume). Otherwise, the gasification furnace must be stopped immediately. ⑧Once the composition of the gas becomes stable, increase the amount of steam and oxygen fed into the furnace appropriately. When making adjustments, it is necessary to first increase the steam flow rate before increasing the oxygen flow rate; continue to analyze the gas composition and adjust the steam-to-oxygen ratio so that the CO2 content in the gas is close to the designed value. (3) Pressurization operation of the gasifier ① Move the startup air blind flange to the blind position. ②The gasifier was pressurized to 1.0 MPa by gradually increasing the set value of the gasifier gas pressure regulator. The pressure increase process should be carried out slowly, with the rate of pressure increase being less than 50 kPa/minute. ③After the gasification furnace is pressurized to 1.0 MPa, this pressure is maintained; the coal lock and ash lock are used to add coal and remove ash. At the same time, all flanges on the gasification furnace as well as the associated pipelines and equipment are inspected, and thorough hot tightening is carried out. ④The gasifier pressure was increased to 2.1 MPa again, and the discharge of gas water from the waste heat boiler was switched from the startup line to the normal line. Check whether all flanges of the gasifier are tight. ⑤The gasifier is pressurized again to basically balance with the pressure in the main gas pipeline, in preparation for connecting to the grid and supplying gas. (4) Connecting the gasifier to the main pipeline: Gradually close the electric valve that controls the flow of gas to the flare. When the pressure in the gasifier is 50 kPa higher than the pressure in the main gas pipeline, open the electric valve that allows gas to flow into the main pipeline; simultaneously, close completely the electric valve for the flare, so that the gas from the gasifier can be fed into the main pipeline. (5) Increase the load of the gasifier to 50% of the design value (on an oxygen basis), and put the flow control valves for the steam and oxygen fed into the furnace under automatic control. Gradually adjust the steam-to-oxygen ratio to the design value (using the absence of molten slag particles in the ash discharged by the ash lock as a reference), and then adjust the ratio of steam to oxygen flow rates.

Hehe, the main steps are driving to conduct a check, heating the pipes with steam, raising the steam temperature, operating with air, cutting off oxygen supply, increasing pressure, and connecting to the grid. The information above is already quite detailed, so I won’t say more. This post was last edited by wbp on 2009-3-7 22:39.]

Why is it less than 1%? Why does it explode easily when it’s above 1%? What is the basis for setting the oxygen content at 1%?

It is calculated based on the explosion limits of various combustible components in the raw gas, and of course, a margin needs to be left