1) What do you mean by the term “dump and screen of catalystt”?
Dump of the catalyst means removal of the spent catalyst from the reactor. Normally, the catalyst which has been declared spent and is not supporting the desired reactions is removed through dumping nozzles at reactor.
Screening normally involves removing a top layer of the catalyst from a reactor, remove out the underside material or affected catalyst. This may be required due to blocking of the top of the reactor causing pressure drop and flow problems.
2) What do you mean by cycle length means life life of the catalyst.
This is the expected/deigned life of catalyst to operate at required operating conditions and to produce the desired product quality at designed flow rate.In actual, catalyst cycle length is different from the deigned because of the change in flow rates, reaction severity and quality of feed. Normal designed life is ~ 3 years.
3) What do you mean by severity of process ( low severity operation and high severity operation) in catalytic reforming?
Severity of the process shows the operating conditions. In catalytic reforming operating temperature of the reforming reactor depicts the severity. High severity means that catalyst is operating at high temperature and low severity operation means reactor is operating at low temperature, to control the desired product quality. Operating window is between minimum and maximum design operating temperatures.
3) What is difference between in situ and ex situ catalyst regeneration?
In-situ means on-site, locally, or at the same location. If the catalyst is regenerated at the same site or the same location where it has been consumed, is called in situ regeneration.
Ex-Situ means outside, off-site, or away from the plant site. If the catalyst is regenerated away from the plant at some other location or another site built for catalyst regeneration. This regeneration is called ex-situ regeneration of the catalyst.
4) How we can determined when catalyst need regeneration?
When the catalyst is unable to produce the desire product quality,even at the maximum design operating conditions or at highest severity operation, then it needs regeneration. Once the catalyst has completed its life, indicated by the end of run operating conditions and high differential pressure is considered as a “spent catalyst” and is removed from the process.
Further about catalyst regeneration can found my blog Regeneration of “Hydrotreating Catalysts“