3 replies to this topic

[mbaig2007@me.com]

Dear all ,

I want to calculate vapor load for the below situation ,

I have 2 kl reactor with methanol as a solvent qty 1.5kl , it is to be heated by steam in jacket at 1kg pressure

the reactor vapor column size is 6" , what qty of vapors should i receive to the condenser per hr .

how long will the distillation continue.

condenser is shell & tube type , 10 m2 capacity. Brine of -5 deg c can be circulated .

can i have an excel sheet for above calculations

[acer_asd]

Dear all ,

I want to calculate vapor load for the below situation ,

I have 2 kl reactor with methanol as a solvent qty 1.5kl , it is to be heated by steam in jacket at 1kg pressure

the reactor vapor column size is 6" , what qty of vapors should i receive to the condenser per hr .

how long will the distillation continue.

condenser is shell & tube type , 10 m2 capacity. Brine of -5 deg c can be circulated .

can i have an excel sheet for above calculations

Dear M.N.BAIG

your problem is not clear.

If your reactor only contains methanol and nothing else then you can easily calculate the vapor produced from heat balance using the steam flow.

But if your system contains components other than methanol too, then please specify those components.

For condensation purpose, you can again use the standard calculations of heat exchangers to estimate the required flow of brine.

please provide more info and state your problem correctly.

have a nice day

[Jiten_process]

hello Baig

I have come across very similar case in my previous company. It was batch distillation operation employed to recover remaining solvent after completiting the reaction process.

here you havent specified the process. Is level of reactor is constant throughout, i mean methanol is keep coming as boiling from reactor continues ??? is it a pure methanol ??? if it is a solvent remaining after some reaction then there must be some impurities and if you want to recover pure solvent then u must have to employ a distillation operation with some reflux. Ofcourse the requirement of reflux and no. of stages are not so huge as remaining solvent might be almost pure. the 6" column that you are refering is it with trays ??? how did u arrive 6" size without knowing the vapor rate ???

Here I assume it is your batch process and in that case it is unsteady state process. It depends on the time in which you want to recover your solvent. Based on that only you have to decide how long your distillation process take place. We used ChemCad for this analysis. have you carried out any such calculation before arriving the column size and jacket size ??? I guess initial and final vapor loads should be found out by carrying batch distillation column calculation.

Condenser will not receive constant vapor load as vapor rate will keep on decreasing as level goes down. If you treate your case just batch heating not but batch distillation then you can Refer kern for heat transfer rate for unsteady state heat transfer and find out the unsteady state heat transfer coefficient first. Based on that only you can find out peak steam rate and peak vapor load. You may like to size your condenser for peak load but care shuold be taken while thermal designing the condenser to check condenser performance at lowest anticipated vapor load. As duty goes down cooling water requirement and delta T of service fluid also goes down and the performance may get deteriorated.

I am not sure exactly what you are looking for, the shortcut way, an excelsheet or the best way, a well elaborated healthy discussion...!!!

[Madhan Kumar]

Some more insights

I assume that you want to calculate the maximum boil up rate from 2.0 KL reactor operating initially with 1.5 KL of methanol using steam at 1.0 kg/cm2 g.

The boil up rate can be calculated using

Q = U A Delta T

U - is the overall heat transfer coefficient of the reactor ranges from 215 to 420 kcal / hr m2 °C for steam in jacket & light organics in reactor.

A - is the surface area occupied by the reaction mass. Here you need to calculate based on your reactor configuration like diameter and height of the cylindrical portion of the reactor. (surface area of torispherical bottom + surface area of cylinder)

T - is the driving force which is equal to the differential temperature between the jacket (corresponding to steam at 1 kg/cm2 g) and the reactor operating temperature.


With this you can calculate the maximum heat transfer rate possible at a particular operating volume and hence you can calculate the maximum boil up rate, which will become a basis for condenser designing.

Now you can check this boil up rate using your actual steam flow rate.

Cheer's
MK_Chem

Edited by MK_CHEM, 02 May 2011 - 07:59 AM.