Q & A > Question Details
What is the difference between hydrogen consumption ratio (makeup gas flow rate/ oil flow rate) and recycle gas-to-oil ratio (recycle gas flow rate / oil flow rate)? What will be the effect on the amount of make-up hydrogen required if we reduce the recycle gas flow rate?
 
Answers
11/02/2017 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
Make up gas requirement is function of : (a) Chemical stoichiometric consumption of H2 for reactions like Hydrogenation. HDS, HDN, conversion (b) H2 going with separator bottom (c) losing H2 from compressors & unit tightness, (d) feed thruput (e) feed & product qualities (f) variation in purity of make up H2 (g) catalyst deactivation (h) deviation in operating parameters. Recycle gas (RG) flow rate impacts catalyst deactivation by coking side reaction, cycle length, linear velocity in reactor & optimum value is designed for operation. There is no direct relationship. Models can predict the influence. If you go through the feed from naphtha to vGO you will find increase in both of them. Objective of your question need additional Elaboration
11/02/2017 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
Make up H2
11/02/2017 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
Make up H2 is required to meet the H2 consumption in the process. It may be chemical stoichiometric requirement, solution losses (quite minor), leakages from the compressor etc also Very little in permissible limits. The make up depends on level of hydrogenation, HDS, HDN, conversion that is operating severity & type of feed stocks.
01/02/2017 A: Ganesh Maturu, Self, maturu.ganesh@gmail.com
Chemical h2 consumption only depends on required conversion. If the feed contains high sulfur and other impurities, chemical h2 cons increases to get same prod properties.. To maintain stable catalyst performance and to ensure always H2 available in reactor, min gas to oil ratio to be provided at inlet of reactor. Typically, we need to circulate recycle gas at min 4-6 times chemical h2 in reactor which will ensure always h2 is available in reactor system. Higher the chemical h2, higher the gas to oil ratio requirement. Too much recirculation of gas to oil ratio will also cause reduction h2 partial pressure and purity at reactor inlet because increased impurities of c1 and c2 range hydrocarbons.
26/01/2017 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
The difference in those ratios are exactly what the words say. They are different streams.
Reducing the recycle gas ratio reduces the H/Oil ratio, which directionally requires higher RIT to achieve the same sulfur and nitrogen removal. They are two of the several dependent variables. If you accept the lower conversion, chemical hydrogen consumption will be reduced and less makeup hydrogen will be required.