Discussion on the Abnormal Temperature Issue of the Tray in the Texaco Gasifier
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Dear colleagues: Our unit uses a Texaco gasification furnace with a pressure of 6.5 MPa and dimensions of 3.2*3.8 meters. During operation, there have been multiple instances of overtemperature alerts related to the brick support plates in the furnace. Almost every time, it was the thermocouples located above the manhole directly opposite the crude gas outlet of the furnace that triggered these overtemperature alarms. In the past, there were serious problems of dust accumulation at those thermocouples, which led to poor heat exchange and subsequent overtemperature issues. Now, dust accumulation is rare at the thermocouples, but overheating of the support trays still occurs. Inspections during shutdowns have shown that in recent cases this was caused by slag blocking or scale fragments blocking the upward flow channel of the coarse gas between the rising and descending pipes, which led to overheating of the thermocouples on the support trays above that area (our facility has four thermocouples on the support trays, arranged at 90-degree intervals). Also, every time we stop the machine to enter the quenching chamber of the gasifier for inspection, we find severe scaling on the walls surrounding the manhole; whereas there is little scaling on the walls of the quenching chamber at the location of the raw gas outlet opposite the manhole. What’s the reason for this? Could it be due to the different air flow speeds inside the quench chamber? Is it still due to one of the two water inlet pipes at the outlet of the lock-hopper pump being blocked (the outlet at the bottom of the cone of the gasification furnace where air enters the lock-hopper pump has two outlets, which are positioned exactly where the manhole and air outlet of the gasification furnace are located)? The above problems occur both when an adequate amount of quenching water is supplied and when the amount of quenching water is low in the later stages. It doesn’t connect; I hope fellow sailors can help find out the reason. Thank you!
Local ash accumulation or blockage below the support brick tray in the gasifier causes the temperature of the support brick tray to rise.
Overall, it is likely due to too low a discharge volume of the black water from the gasification furnace’s quench chamber and the scrubber tower. However, there are many reasons for such a low water discharge volume, such as water present in the gasification furnace, low temperature of the syngas at the outlet of the gasification furnace or scrubber tower, and a low water-gas ratio; operational factors also play a role. When the discharge volume of the black water from the gasification furnace or scrubber tower is low, a large amount of fine ash cannot be discharged along with this water, resulting in an increasing concentration that can lead to scaling in the system. As for the reduced scaling at the syngas outlet, this is due to the scouring effect of the gas.
The black gas flow rate of the gasification grate is between 150–200 m3/h, while that of the scrubber is above 30 m3/h; both values are higher than the normal designed levels for black gas discharge