Why is the outlet temperature of the waste boiler kept rising?
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In the methane-to-hydrogen production unit, the temperature of the conversion gas at the exit of the second furnace is 880°C; after passing through the first furnace, it drops to 580°C. After passing through the E103 gas-gas heat exchanger, the temperature is 460°C, and after passing through the E102 gas-gas heat exchanger, it is 440°C. Subsequently, the gas enters waste heat boiler 104. Over the course of this month, the inlet temperature of the waste heat boiler remained relatively constant, ranging from 440°C to 443°C, while the outlet temperature increased from 340°C to 370°C, resulting in a very high intermediate transformation temperature. The two-stage furnace contains catalysts, castables, and ceramic balls; E103 has castables. There is also a waste boiler 105 whose temperature is normal, and it uses the same water as boiler 104. Scaling in the shell side is unlikely, with a water-to-carbon ratio of 2.8. We suspect there is a problem with tube 104 – recondensate migration and scaling – but E102 and E103 ahead of it are fine. Please analyze what could be the cause.
It is possible that the design margin of the waste heat exchanger is too small; changes in the composition of the conversion gas or an increase in flow rate result in more heat being generated, thereby limiting the ability of the waste heat exchanger to absorb this heat； Or has the pressure for generating steam increased now?
The inlet temperature changed little, rising from 440 to 443, while the outlet temperature increased from 340°C to 370°C. This deviation doesn’t seem to be very large; it’s necessary to determine what’s more important – the temperature of the process gas or the quality and quantity of the steam produced. To maintain the desired outlet temperature, more water can be added; if that doesn’t work, cleaning is required. If there are no problems with these two aspects or if problems occur frequently, then it’s time to consider replacing the boiler with a larger one