Temperatures and LHSV at Naphtha Hydrotreater Reactor

[Hamzaali1999]

Hello, I hope you all are fine.

My question is,
Is there is any importance of reactor inlet temperature while calculating LHSV ? As in LHSV formula/equation there is no any temperature term. Simply we calculated LHSV as,

LHSV = volume of charge per hour / volume of catalyst

As during operation, the reactor inlet temperature is fixed lets say 600F. Usually H2/HC ratio varies due to little fluctuating in recycle gas. For daily changes in LHSV, the reactor inlet temperature is adjusted according to the equation given below:

T2 = T1 – 45 ln (LSHV1/LHSV2)

Temperature is in F. T1 inlet temperature at LHSV1 and T2 inlet temperature at LHSV2.

Lets say we need to calculate LHSV at two different temperature then how we can use above formula ? Please guide in this.

Thanks & Regards,
Hamza

[Nasir Hussain]

LHSV is the liquid hourly space velocity, which is the ratio of liquid volume flow per hour to catalyst volume. LHSV is inversely proportional to residence time. As the flow rate increases, the LHSV increases. In most systems with a fixed catalyst volume & activity, temperature is increased to offset the negative reaction consequences of increasing LHSV. In systems that can replace catalyst and/or regenerate it online, an increase in catalyst make up rate can also be used to offset an increase in LHSV.
It signifies the residence time of feed in the reactor. Higher the value lower the reaction rate. It is dependent on the reaction kinetics.

[Nasir Hussain]

Theoretically you can can calculate either of the one parameter if you know the other 3 parameters but reactor inlet temperature at LHSV2 is adjusted according to the product quality requirement. The actual temperature might not be the same as theoretical. Normally, when feed rates to reactor are adjusted the reactor inlet temperature does no go below the minimum defined temperature by the designer and temperature can be increased at high LHSVs as required to meet the product quality.

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