What are good ways to utilize the waste heat from the overhead vapor in an FCC fractionator?
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The overhead vapor from the FCC fractionator needs to be cooled from 120°C to 45°C. Most plants use chilled water to recover some of this heat; additional cooling is achieved through air cooling and heat exchange with circulating water. Some of the heat cannot be recovered. Does anyone have any good suggestions? Everyone’s opinions are welcome.
Heat exchange is carried out using deoxygenated water from the gas separation unit; this allows for the efficient use of low-temperature heat, while also saving the heating source required by the gas separation unit to heat this water. We don’t need air cooling; water cooling is sufficient.
A supply of heat transfer water can be provided for use in heating the bottom of the gas separation unit. It works well here.
Generally, it is not practiced to recover the low-temperature heat here, as there is a concern that the stream at the top of the tower might get contaminated; instead, water cooling and air cooling are used to cool and condense the oil and gas.
Here, two applications are introduced: 1. Using low-temperature heat transfer water to heat heavy oil storage areas is also a traditional method for utilizing waste heat. 2. Install a lithium bromide refrigeration system. Produce refrigerant water to improve the efficiency of the absorption tower
Could you elaborate on this? Last edited by wfme816 on 2009-4-3 10:30]
When the vapor at the top of the fractionation tower is cooled below 70 degrees, it is difficult to achieve this even with low-temperature heat recovery. To recover heat from low-temperature hot water, it is necessary to reduce the temperature of this water to below 45 degrees; it is also very difficult to lower the temperature of low-temperature thermal energy to below 45 degrees, so it’s indeed not easy to handle.
That is, recovering energy between 70 and 45 degrees is the key issue, and there are still no very good solutions for FCC units.
Currently, various plants attach great importance to making use of the low-temperature heat generated by the overhead gas and oil. Catalysis and coking are the main areas where this heat can be utilized; it can serve as a heat source for ethane removal towers and propylene towers, for heating alkaline solutions, and for heating crude oil in storage tanks – all of which are effective approaches. However, using this heat for cooling is not energy-efficient; yet if it is applied in coking absorption stabilization processes, it can significantly reduce the amount of propylene in the dry gas, resulting in substantial economic benefits.
The ORC low-temperature waste heat power generation technology can be used to recover heat while also saving water. Contact number: 15077888059