Reboiler flow calculation amine scrubber

[thermalvtx]

First of all: I'm sorry if there is already a thread regarding this.

I’m working on a design for a amine scrubber using MDEA. The purpose is to remove about 582 kg/h of CO2 from a CO2/CH4 gas flow. I calculated that I would need 480 kW for my reboiler capacity. Based on a reflux of 1.25 (about 300 kg of H2O). Can anyone confirm that this is correct?

The plan is to use 50% amine with 50% (demi)water. Because of the layout I cannot use a thermosyphon type of reboiler (to complicated piping / not enough height). Instead I’m planning to use a regular plate type heat exchanger for my reboiler with forced circulation (pump). The top of the plates will be below the minimal level in the sump/stripper.

From different literature / internet I understood that in the reboiler about 15-20% evaporation occurs?

Can anyone help to determine how much the flow rate for this pump should be (based on 15-20 % evaporation in heat exchanger).

Thanks ahead. PS: I'm new at this site

 

[maddocks]

We need a lot more info to comment on this unusual design. Can you provide amine circ rate? What about contactor pressure and temp, treated gas specs, regen pressure, heat medium, etc.?

 

[dcasto]

its closer to 730 kW.

There are plenty of pump around direct fired reboilers in operation which is similar to what you are proposing.

so, pick 16.66% evaporation, that means that for every pound (kg) vaporized 5 pounds do no get vaporized. That means you need to circulate 6 times as much as needed. Since you need 2,500,000 BTU/hr and it takes about 1000 btu/lb to vaporize, that means you need 2500 lb/hr times 6 or 15,000 lb per hour and at 9 lb/gallon, that is 30 GPM. you'll be circulating 32 gpm of a 50% solution of MDEA.