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(2014) Question 75: Do you draw liquid hydrocarbon from the overhead system in the vacuum tower after the pre-condenser? What is the operating temperature of the tower overhead? What issues do you observe?

At vacuum tower top temperatures over 135-150°F some material heavy enough to condense after the pre-condenser goes overhead. In units with extremely paraffinic feeds the hydrocarbon can form wax in the pre-condenser, leading to reduced heat transfer and higher vacuum tower pressures.
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(2014) Question 76: What is considered industry Best Practices with respect to the control of thermal cracking in vacuum tower bottoms? If quench is not available, what other parameters do you monitor and control? How do you establish the target control points?

Thermal cracking of liquid in the vacuum tower bottoms depends upon time and temperature. The higher the temperature, the higher the cracking rate. The longer the residence time, the more cracking. The key to reduced cracking in the vacuum tower bottoms is to keep the bottoms temperature down and the residence time low.
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(2011) 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.
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(2011) 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.
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(2011) 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.
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