�focused on process simulation

Page 1 of 2

CHEMCAD helps to clean bio gas without chemicals

The Pressurized Water Process is used to remove carbon dioxide and hydrogen sulfide from bio

gas in order to upgrade it to natural gas quality.

The good thing: No chemicals besides water are required for this gas treatment processes.

Besides CO2 and H2S, the methane is also absorbed in the pressurized water. In order to reduce

the loss of methane the rich water coming from the absorber is flashed at an intermediate

pressure. The pressure is chosen to be the pressure in between the two compressors used for

the feed compression. This helps to reduce the power consumption of the first compressor.

Have a look at the CHEMCAD flowsheet of the gas treatment process and the specified design

variables on the next page! Our solution has an exergetic efficiency of 50.09%.

However, there are still many degrees of freedom left!

• Which pressure levels (absorber pressure and intermediate pressures), which

temperatures (gas and liquid feed temperatures), and which flowrates (water cycle and

stripping air) lead to the optimal process by means of exergy conversion?

• Is it good to produce more methane at the costs of higher electricity consumption?

• Can the stripping air flowrate be reduced when more cycle water is circulated or

different pressures are used?

• How does the purge effect process performance?

Optimize the exergetic efficiency and send us your solution in the Process Simulation Cup 2016!

© Berthold Werkmann

�focused on process simulation

Page 2 of 2

Participants of the Process Simulation Cup 2016 can download CHEMCAD and the flowsheet

from this website and be a monthly or the overall winner.

Design

Variable Name

Unit Op /

Stream Value Unit

Lower

Bound

Upper

Bound

1 Intermediate Pressure U 1 2.6

bar abs. 1.1 20

2 Absorber Pressure U 4 17.5 bar abs. 1.1 25

3 Gas Feed Temperature U 5 50 °C 20 80

4 Liquid Feed Temperature U18 32 °C 20 80

5 Stripping Air Flowrate S 13 850 stdVm³/h 10 1000

6 Cycle Water Flowrate U 14 236 stdLm³/h 5 500

7 Purge Ratio U 11 3.00% - 1% 10%

8 Intermediate Pressure 2 U 20 7.5 bar abs. 1.1 20