463664 Recovery and Purification of Methane in Biogas Using One-Tower Vpsa-Methane with Integrated Pretreatment Adsorbent Layers

Wednesday, November 16, 2016: 2:10 PM
Cyril Magnin II (Parc 55 San Francisco)
Jun Izumi, Headquarter, ADSOTECH, Ltd., Ohmura, Nagasaki, Japan and Seiji Doi, R&D Center, Dainich Fine Chemicals, Ind., Tokyo, Japan

From the viewpoints of both energy conservation and alternative energy in the context of high-efficiency power generation, it is very useful to consume highly concentrated methane as a gas-engine fuel, purified from biogas. The authors of the present report designed and fabricated a biogas purifier which is compact and has a low energy power consumption rate. This biogas purifier features one-tower VPSA-methane loaded with pretreatment adsorbent layers (H2S, Siloxane, and CO2 from bottom to top). We experimented with bio-gas purification using this one-tower VPSA-methane (inlet gas rate of 400m3N/day, inlet methane concentration of 60vol%), and confirmed the performance thereof in this study as having a methane recovery ratio of 90% and a purified methane concentration of 90vol%. The flow sheet for one-tower VPSA-methane is indicated in Fig.1, while the operating conditions and performance are listed in Table 1.

[Adsorption Stage]

One-tower VPSA-methane consists of an adsorption tower (H2S adsorbent, Siloxane adsorbent, CO2 adsorption), a blower/vacuum pump combination rotary mechanism, valves, tubes and pipes, a pressure equalization tank, a product tank, and a raw material tank. The raw material (methane concentration of 60vol%, H2S concentration of less than 200ppm, Siloxane consisting of 10ppm, and a bio gas rate of 16m3N/h). The raw material (16m3N/h) is supplied at an adsorption pressure of 140kPa-abs and an adsorption period of 60 seconds, such that H2, Siloxane, and CO2 are adsorbed. At the outlet, the purified methane (methane concentration of greater than 90vol%, H2S of less than 1ppm, Siloxane undetected, and a purified 9m methane gas rate of 9m3N/h) is collected.

 

[Desorption Stage]

The adsorption tower saturated with H2S, Siloxane, and CO2 (60 second adsorption period) is connected to the blower and vacuum pump combination rotary mechanism and the internal pressure is reduced to the desorption pressure of 10 kPa-abs. The desorption period is set at 60 seconds, i.e., the same as the adsorption period. During the desorption period, the purified methane can be released from the auxiliary tank containing purified methane product to maintain outlet flow continuity. The above-mentioned one-tower VPSA-methane operation is characterized by a purified methane concentration level of 90vol%, a methane recovery ratio of 90%, and an electric power consumption rate of 0.3kWh/m3N-methane. With a 1m3 adsorption tower, purified methane of 173m3N/h can be recovered. We therefore concluded that the one-tower VPSA-methane in this study demonstrated strong economical performance.

Fig.1 Schematic diagram of VPSA-methane

oTable.1 VPSA-methane performance

Biogas composition

CH4 70vol%

CO2 30vol%

H2O 4vol%

H2S 100ppm

Siloxane 10ppm

Biogas flow volume

5~1500m3N/h

CO2, H2O, H2S, CH3SH,

Siloxane removal

>90%

Methane recovery

>80%

Electric power consumption

1~100kW

Methane recovered

10~100m3N/h

(Methane purity>95vol%)

Energy power consumption

0.16~0.2kWh/m3N-CH4

Energy/Generation ratio

Approx. 4%


Extended Abstract: File Not Uploaded
See more of this Session: PSA/TSA
See more of this Group/Topical: Separations Division