Q&A

(2017) Question 4: For the isomerization unit, what is your treatment for the streams containing high concentrations of hydrochloric acid (HCl) in the reactor emergency depressurization system?

Honeywell UOP does not include treatment of gas from the reactor effluent as it enters the flare header when using the emergency depressuring system in our Penex™ and Butamer™ process unit designs.

(2017) Question 5: Is the presence of pyrophoric compounds common in feed/effluent exchangers? What neutralization methods do you employ prior to exposing the equipment to the atmosphere?

In 2015, UOP led a Principles & Practices session on the topic of NHT (naphtha hydrotreater) and reforming unit feed/effluent exchanger fouling and cleaning.

(2017) Question 6: What are your typical disposal options for solid phosphoric acid (SPA) catalyst from a catalytic polymerization unit? Are you employing any innovative methods?

Based on input from previous surveys and discussions with Honeywell UOP SPA customers, appropriate catalyst disposal methods are determined by the spent SPA catalyst’s classification, whether hazardous or non-hazardous. If hazardous, the options are hazardous landfill or incineration.

(2017) Question 7: What are your potential strategies to increase refrigeration system capacity and throughput in sulfuric acid alkylation units?

Several options are available to increase capacity and throughput in the refrigeration system of a DuPont STRATCO® effluent refrigerated alkylation unit. Depending on the specific limitation of the system – whether it be the capacity available from the refrigerant compressor, horsepower limitations of the refrigerant compressor driver, refrigerant condenser capacity or reactor tube bundle area, a specific solution may be tailored to help the refiner improve performance of the refrigeration system with minimal capital investment.

(2017) Question 8: What methods are you using to address alkylates’ sulfur contribution to the blend pool for Tier 3 compliance? Is your focus on feed pre-treatment or alkylate post-treatment?

For many, the alkylate’s sulfur contribution to the pool has not been the most economical sulfur to address when targeting Tier 3 compliance. STRATCO completed a survey of the sulfur content of alkylate streams in 2014; and that time, almost 90% of alkylate streams contained less than 10 ppmw of sulfur, with nearly 60% of those containing less than 5 ppmw of sulfur.

(2017) Question 9: What operating conditions in a catalytic polymerization unit are conducive to the formation of esters? What is the main effect that esters have on unit performance?

The mechanism by which oligomerization takes place over the SPA catalyst necessitates that a phosphate ester is formed between the catalyst and the olefin. The temperature required to dissociate the phosphate ester and convert the olefin depends on the olefin in question.

(2017) Question 10: What impact does silicon have on an isomerization catalyst? What are the symptoms that occur as evidence of a breakthrough?

When looking at chlorinated alumina-type catalyst, we have observed silicon will deposit on the catalyst in a similar fashion as other precious metal catalyst, distributing silicon throughout the pores and blocking access to active sites.

(2017) Question 11: In chlorided isomerization units, have you seen evidence of unconverted perchloroethylene (PERC) in the stabilizer bottoms stream?

Axens has evidence of the presence of organic chlorides in the isomerization stabilizer bottoms product. Since testing specifically for organic chlorides is not possible, one must compare the total chloride content of the isomerate against the HCl content to determine derived organic chloride content.

(2017) Question 12: Are you designing or revamping isomerization units’ radial reactor temperature indicators?

Honeywell UOP does not typically design Penex™ or Butamer™ units with radial temperature indicators in the reactors. UOP standard design is to have a single thermocouple at regular intervals in the catalyst bed. We typically show these TIs in a straight line down one side of the reactor.

(2017) Question 13: In chlorided isomerization units, what procedures are you using to shut down caustic-free and make the net gas scrubber safe for maintenance?

Some refiners want to steam out the scrubber to confirm that all caustic has been removed. This step is not necessary if the scrubber has been water-washed since caustic is soluble in water and there is no heavy hydrocarbon present in this vessel.

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