May I ask if it is feasible to place the crude benzene section directly behind the horizontal tubes of the cold drum?
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Recently, I visited a coking plant. The chemical processing flow in that plant is as follows: gas — horizontal tube cooler — benzene extraction section — desulfurization section — electrostatic tar collector — cold blower — ammonium sulfate section — gas returned to the furnace. The traditional process is: gas — horizontal tube cooler — electrostatic tar collector — cold blower — desulfurization section — ammonium sulfate section — benzene extraction section. Is it feasible for this plant to place the benzene extraction section directly after the horizontal tube of the cold blower? It is said that some coking plants in Shandong use this process – is it reliable? How effective is it?
I personally think it’s not feasible; the quality of the cleaning oil is hard to guarantee.
As for whether it is suitable, I believe only the entity using the process has the final say. I think this approach will increase benzene recovery and reduce the consumption of washing oil. It would be helpful to have the process parameters specific to enterprise operations; with those parameters, it will be possible to determine whether the process is more reasonable
One set of cross-tube cooling towers can be omitted. Some manufacturers are already in operation, and the oil consumption is a bit high
Washing oil absorbs ammonia more quickly than benzene. Additionally, hydrogen sulfide and hydrogen cyanide cause the washing oil to regenerate various impurity products, which reduces its ability to absorb benzene. Moreover, very high corrosion resistance is required for the equipment and pipelines, resulting in substantial investment costs. This process is not recommended unless constrained by factory construction conditions or forced by subsequent modifications.
Ammonium sulfate is located after the fan; it belongs to a semi-negative pressure process, as per the patent of Ansteel Design Institute； The requirements for benzene washing equipment remain essentially unchanged. For benzene removal equipment, 316L material is required, which results in a slight increase in investment; however, the need for an end-cooling tower is eliminated, so overall investment is still reduced. Additionally, no pre-cooling tower is needed for desulfurization ； The corresponding circulating water volume has also decreased. It belongs to energy conservation and emission reduction patents.
At the moment, our company is still operating normally, as usual
From the perspective of the system’s temperature gradient distribution, it is quite reasonable
The fully negative-pressure process is too large; there are many devices in the negative-pressure area, which increases the requirements for equipment manufacturing, installation, operation, and maintenance. Additionally, the location of crude benzene is not very appropriate, and the acidic and alkaline impurities in the gas can have a significant impact on the quality of the washed oil. Of course, from the perspective of temperature gradients, it is a bit better than the subsequent process configuration.
The main advantage of the post-desulfurization process is the rational utilization of temperature. It reduces the impact of gas temperature rise caused by the blower and eliminates the need for a final cooling unit. It reduces the costs associated with the equipment, as well as the treatment of large amounts of cooling wastewater and pipeline insulation. However, the material selection for equipment before desulfurization should be appropriately improved. In the previous desulfurization process, positive pressure is maintained in the gas stream after the blower, effectively preventing air from entering and ensuring a high safety factor. The desulfurized eluted benzene and the choice of pipeline material can be reduced. However, a final cooling device is required.