Impact of excessive temperature at the outlet of the Shell syngas cooler?
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[The syngas outlet temperature must not exceed 380 °C, as exceeding this value would result in the mechanical design temperatures of both the syngas cooler outlet and the downstream equipment being exceeded.] Based on the design coal, under normal operating conditions, the calculated outlet temperature of the syngas should be less than 340 °C. However, what are the effects when the temperature exceeds 340 °C but remains below 380 °C?
If the temperature remains between 340 and 380 for an extended period, it will have a negative impact on subsequent equipment and reduce its lifespan. Steam production will also decrease, water usage in the wet scrubber will increase, and ceramic filters are prone to accumulating dust.
It seems that there is no clear conclusion as to what the outlet temperature of the syngas cooler can be in order to avoid damaging downstream equipment. After discussing this with SHELL’s technical staff, they also said that the temperature at 18 o’clock had not yet been finalized, so I think 380 degrees is likely a safety value provided by them. If the temperature exceeds 340 degrees, it is mainly due to scale accumulation on the inner walls; this reduces the heat exchange efficiency and leads to a decrease in steam production. If the operations are not adjusted in time, the scaling may become more severe, the outlet temperature at 18 o’clock will continue to rise, and ultimately this will result in the shutdown of the gasification furnace.
A high outlet temperature of the syngas cooler is definitely caused by scaling on the heat exchange tubes, which leads to poor heat transfer efficiency. Specific reasons: 1. Coal quality issues: It is necessary to consider factors such as the silicon-aluminum ratio in the ash composition of the coal, the amount of iron, and its cohesiveness. 2. Limestone issue: Excessive amounts of limestone added, especially when coal powder is conveyed using carbon dioxide, can lead to scaling in the lower-temperature areas downstream. 3. Air flow issue: At low load and high system pressure control, scaling can occur due to weak air flow. 4. The rapping frequency can also be increased appropriately.
A high outlet temperature of the syngas cooler is definitely caused by scaling on the heat exchange tubes, which leads to poor heat transfer efficiency. Specific reasons: 1. Coal quality issues: It is necessary to consider factors such as the silicon-aluminum ratio in the ash composition of the coal, the amount of iron, and its cohesiveness. 2. Limestone issue: Excessive amounts of limestone added, especially when coal powder is conveyed using carbon dioxide, can lead to scaling in the lower-temperature areas downstream. 3. Air flow issue: At low load and high system pressure control, scaling can occur due to weak air flow. 4. The rapping frequency can also be increased appropriately. ************************************************************************************************** That’s a very constructive suggestion. In my opinion, the most fundamental issue is still the quality of coal. Along with higher outlet temperatures, scaling of SGC often occurs, while the causes of structural issues are currently considered to be varied. This friend mentioned that an excessive amount of limestone leads to increased scaling, and I completely agree. However, we still lack theoretical validation. Theoretical certification is important; it allows us to see the internal essence of things. However, this is truly a very important experience! :victory: