Crude oil residue heat exchanger; severe coking of crude oil
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The image below shows the crude oil and residue heat exchanger in the atmospheric and vacuum distillation unit of a petrochemical refinery. Crude oil flows in the tube side; after about 3 years of operation, a considerable layer of scale has formed inside the tubes due to the crude oil, which reduces the efficiency of the heat exchanger. Given this situation, let’s see if there are any good ways to slow down scaling or prevent it from occurring.
Based on the coking issue in the crude oil and residue heat exchanger that you described, the following methods can be considered to reduce or prevent scaling: 1. **Optimize flow velocity**: Increasing the flow rate inside the tubes helps to reduce the deposition of sediments on the tube walls. Adjust the flow rate appropriately so as to maintain efficient heat transfer while avoiding equipment wear caused by excessively high flow rates. 2. **Temperature control**: Strictly control the temperature of the feed and output materials to prevent excessive temperatures from causing the crude oil to decompose within the pipes and produce carbonaceous tar. 3. **Regular cleaning**: Periodically clean the heat exchanger chemically or physically, such as by using cleaning agents for chemical cleaning or high-pressure water jets for physical flushing, in order to remove accumulated oil deposits. 4. **Use scale-inhibiting additives**: Add scale inhibitors to crude oil; these additives can reduce the formation of oil scale. 5. **Material Selection**: Use materials that are more resistant to high temperatures and corrosion for manufacturing the internal components of the heat exchanger, such as nickel-based alloys. 6. **Improve design optimization**: Enhance the design of heat exchangers by using spiral or other types of finned tubes to increase turbulence, thereby reducing scale deposition. Through these comprehensive measures, the coking and scaling of crude oil in heat exchangers can be effectively reduced, thereby improving the operational efficiency and service life of the equipment. .
The service life is quite good; regular cleaning is something normal to do, for reference only.
A 3-year cycle is long enough; it’s time for a cleaning. Additionally, scaling in the crude oil line is mainly caused by the sludge brought in from the electrodialysis unit, and this can be addressed through regular backwashing, for example, once a week or every two weeks.
How to carry out backwashing, and where does the oil used for washing go?
Our ultrasonic descaling and anti-scaling equipment can address scaling in such heat exchangers.
First, there must be a backwashing process. An electrodialysis water injection pump is used to supply water to the backwash nozzles at the bottom of each stage, in order to flush out the sediment accumulated at the bottom. The wastewater generated is discharged through the electrodialysis drainage line to downstream water treatment facilities.