| American Fuel & Petrochemical Manufacturers

Question 33: Are there any new technologies to control bromine index in aromatics streams? Do clay towers still provide the best operating value?

UOP has commercialized a selective hydrogenation for this application and Exxon Mobil offers an alternative catalyst that appears to be a direct replacement for clay.

Question 32: What are your best practices for minimizing corrosion in aromatics extraction process from oxygen in the feed? Is the strategy to reduce oxygen ingress or treat the feed? Is the situation different for glycol, Sulfolane, Morpholine, or other solvents?

Udex unit uses Tetra Ethylene Glycol as solvent. The Udex performance w.r.t. corrosion was not so high initially after revamp, but we started experiencing severe corrosion from 2008 onwards in stripper reboiler, severe thinning of stripper bottom tray panels and unit had to be shut down repeatedly in 4-5 months interval for attending reboiler leaky tubes till M&I shut down was taken up.

Question 31: In HF alkylation units, do you have two vent gas or flare gas scrubbing systems, one for normal operation and one for a rapid acid dump system?

Each of our units has one system. Most units only route acid containing reliefs to the Acid Relief Header which has a Neutralizing system as part of that.

Question 30: What is the recommended feed nozzle design for HF alkylation units to provide proper mixing of the feed, HF acid, and isobutane? What are the recommended materials of construction for these nozzles?

The licensor for HF alkylation is UOP and they should be consulted before changing the feed nozzles. Isothermal reactors that have feed injection in the reactor bundle utilize a feed pipe system with nozzles machined into the pipes.

Question 29: The relief valve on the acid storage drum on our HF Alkylation unit was designed to be rotated to relieve to the atmosphere during unit turnarounds when the unit flare system is unavailable. Is this still common practice, or have you made arrangements to provide access to another flare system during turnarounds?

Some refiners do disconnect the outlet of the acid storage drum relief valve from the relief header and align it to atmosphere during turnarounds. This situation is very similar to the acid truck that delivers the fresh acid to site.

Question 28: How is the acid soluble oil (ASO) disposal system operated in an HF alkylation unit? - where / how do you dispose of the ASO? - do you operate the rerun continuously or in batch mode? - do you have problems with the ASO line fouling or plugging? - is there a min velocity, min/max temperature or something else that controls your rate of ASO disposal from the rerun?

The summary response is: Collect the ASO, neutralize it in KOH or NaOH and then dispose of it in another refinery product stream.

Question 27: What are the pros and cons of alkylating delayed coker butylenes (co-processed with FCC butylenes)? Does this require higher isobutane recycle? Should we consider processing them in a separate reactor? What are the economic alternatives to alkylation?

A more specific question is: “What is in Coker olefin that is problematic since a pure olefin is the same whether from a Coker or FCC unit?” A Coker derived olefin stream has more sulfur, diolefins and acetonitrile than FCC olefins.

Question 26: When you test for free HF and organic fluorides in alkylation unit products (alkylate, butane, propane), what are your typical observed levels? After HF breakthrough in our butane product, why does our treater still have plenty of KOH remaining? Is there any way to regenerate KOH during the run? Do others maintain a heel of KOH in the bottom of the alkylate storage tank to neutralize traces of HF?

Our sites vary in the type of testing with most sites testing for combined (organic) fluorides in at least the propane and butane streams. Multiple stream points are typically tested dependent on what the monitoring goals are.

Question 25: How do you manage process hazard analysis (PHA) scenarios related to corrosion?

First, ConocoPhillips has developed generic PHA scenarios for each major technology to determine what scenarios are applicable to a particular unit. These tables contain initiating categories (such as Corrosion), potential causes and consequences, possible safeguards and suggested consequence rankings.

Question 24: Do you use Safety Instrumented Shutdown systems in gasoline units (reformers, alkylation, isomerization, hydrotreaters)? How many of you use DCS-based vs. dedicated hardware shutdown systems?

In order to comply with auto fuel policy of Govt. of India for introduction of Euro-III and Euro-IV in the country and in all major cities in India respectively, all IOC refineries (10 nos.) had to take up MS Quality Improvement Projects which included new units and revamp of existing units including catalytic reformers, isomerization units, selective hydrogenation units, benzene saturation units and hydrotreaters.