Boiler feedwater preheater in the conversion section
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What are the reasons for frequent internal leakage in boiler feedwater preheaters? Additionally, what causes the internal leakage that often occurs in the reboilers of the distillation off-gases?
It’s probably due to an excessive temperature difference between the flow in the tube side and the shell side; a large discrepancy between the actual operating parameters and the design parameters is also certainly a contributing factor.
Is it that the material chosen for your heat exchanger is not appropriate? Austenitic stainless steel should be chosen. Since the conversion gas contains a large amount of CO2, once a dew point is reached in the gas, it will cause corrosion to the metal.
Considerations should be given to aspects such as the quality of the boiler water, the composition of the heating gas, and the material of the boiler feedwater preheater
It is likely caused by oxygen corrosion; the deoxygenation was inadequate
The pressure difference between the tube side and shell side fluids is too large. Additionally, I agree with the view from the 4th floor: poor quality of boiler water, which leads to the presence of corrosive substances, could also be a possible cause. The boiler water heat exchanger in our plant is also leaking. Initially, carbon steel was used, but its quality was poor; it could withstand only limited internal and external pressures. Later, a stainless steel tube-type heat exchanger was installed, and it’s working very well now.
It could be one of the following situations: 1. Water is supplied continuously during driving; if the supply is intermittent, it is a water hammer phenomenon in the heat exchanger, with internal leakage caused by thermal expansion and contraction； 2. Heat exchanger material issues ； 3. Issues with boiler feedwater quality ；