Q & A > Question Details
There are several different options to increase liquid production and reduce coke yield in residue coker units. One of the most widely used is try to operate coker drum at low pressure.
But what are the possible options to reduce further the operating pressure in the coker drum?
Could the minimum pressure limit (alarm) at the wet gas compressor inlet be reduced? We currently operate at 0,4 kg/cm2. Has anyone experience operating at lower pressure at this point?
Has anyone experience installing an on-line water wash in top of main fractionator or condenser to remove salts? In that case, which is the maximum DP reduced with this option?
Has anyone experience implementing any other modifications (increase vapor lines diameter, etc)?
19/12/2015 A: K V PRASAD RAKOTI, INDIANOIL, rkvprasad@yahoo.com
Lowering of suction pressure at WGC depends on compressor design....performance curves...
23/04/2015 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Each situation is different as far as what makes the most sense when trying to reduce coker drum pressure. Compressor constraints usually limit trying to lower the compressor suction pressure. Reducing pressure increases both the actual gas volumetric flow and the compressor head requirement. Unless you have a variable speed drive with room to increase speed, this is not an option without spending a lot of money.
A water wash can reduce ammonium chloride salt fouling DP. How much really depends on what the normal DP in the air coolers is and how badly they are fouled. Installing additional air cooler bays will also decrease DP and can decrease gas production through improving cooling/condensation. Installing structured packing in parts of the fractionator can reduce tower DP as can replacing the transfer lines from the coke drums to the fractionator. Ideally to get he best economics you want to make modifications that get you multiple benefits.
Packing in the fractionator can improve fractionation or increase capacity while it reduces DP whereas replacing the line to the fractionator just reduces DP (however, if you say needed to replace the line due to corrosion then upping the size could make sense since it is being replaced anyway.