Q&A

(2016) Question 6: What is your experience with having a vent depropanizer off-gas unit in order to manage tower pressure, and what might be the cause of and solution to the problem?

The typical and probably most obvious driver for the need to vent from a depropanizer column is the presence of non-condensable gases. Most commonly, this is ethane and ethylene that come in with the feed.

(2016) Question 7: How is propane content in the refrigeration loop optimized against the compressor capacity to minimize contractor temperature? Do you have a good process model to predict the optimum propane content?

There is an optimum propane concentration in the refrigerant that will allow the alkylation unit to operate at a maximum alkylate throughput when the unit is up against limitations of both the compressor and the reaction zone heat removal capability. That optimum concentration of propane will vary from unit to unit and can be different seasonally. It can also be different from night to day or if exchangers are fouled, etc.

(2018) Question 1: What are the benefits of alumina treating in sulfuric acid alkylation and HF alkylation? Has this technology been proven commercially?

In the sulfuric acid alkylation process, droplets of acid are found in the effluent stream from the reactor. These droplets, which are formed primarily from the alkylation chemistry itself and the formation of intermediates, are small and stable and cannot be removed by gravity settling and / or coalescing alone.

(2018) Question 2: What metallurgy works well and does not work well for use in alkylation units? In what applications does the alternate metallurgy perform better/worse?

The standard metallurgy for use throughout HF alkylation units is carbon steel. Showing a high degree of corrosion resistance in both low and very high acid concentrations, carbon steel is also useful for its relatively low cost compared to more exotic materials.

(2018) Question 3: What type of release mitigation safety systems do you use for sulfuric acid and HF alkylation units?

Sulfuric acid alkylation units do not require the robust safety systems as the HF Alky units since sulfuric acid is a liquid at atmospheric conditions. The release mitigation safety systems typically used are curbed and/or diked areas to contain the liquid sulfuric acid in event of a leak.

(2018) Question 26: How do you monitor furnace convection section fouling? What mitigation steps do you implement?

Monitoring the flue gas temperature leaving the process convection section is a simple method of tracking the heat transfer in the convection section. The excess air needs to be taken into consideration as a higher O2 concentration will shift heat transfer into the convection section and causes the total quantity of flue gas to increase.

(2018) Question 27: What is your experience with chemical treatment to reduce furnace coking?

For conventional fouling, which is the result of asphaltene destabilization due to temperature, chemical treatment programs have not been effective for Coker heaters. For premature asphaltene precipitation due to resid compatibility concerns, chemical treatment programs have been effective in reducing or eliminating fouling.

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