Small Pump for Biogas

[Samrs]

Hello everyone,
I am trying to find a small pump for use with biogas. This is for a research project being conducted by a chemical engineering PHD researcher at my university. She is building a bioreactor and plans to use some of the biogas to periodically backwash a nanocomposite membrane used for the output of the bioreactor.

Here are the pump specs I am looking for:
[ul]
[li]Media: Biogas (75% methane and 25% CO₂)[/li]
[li]Operating pressure: 2.5 bar[/li]
[li]Operating flow rate: 15 lpm[/li]
[li]Price: Around $200[/li]
[/ul]

I would really appreciate it if some kind individual could point me in the right direction. I have been searching for many hours but haven't found anything that wasn't exorbitantly priced.

 

[TugboatEng]

Your price is unreasonable as it won't even cover the cost of specifying the pump.

With that said, I feel a carbon sliding vane pump would be the best fit for your application.

 

[LittleInch]

This is laboratory scale stuff so you need to search for that equipment.

I assume your 15 lpm is at standard conditions?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Samrs]

Thank you both for the responses.

Your price is unreasonable as it won't even cover the cost of specifying the pump.

What price would be reasonable? That price is what my supervisor gave me to shoot for. I understand the price may be higher since this is a somewhat specialized application, but this is a very small scale pump, isn't it?

...I feel a carbon sliding vane pump would be the best fit for your application.

Thanks for the suggestion. I will look into those. I had been looking more at diaphragm pumps. Any particular supplier I should search for?

I assume your 15 lpm is at standard conditions?

By "standard conditions" do you mean the conditions where it will be running (sorry)? Then yes, 15 lpm and 2.5 bar (~35psi).

 

[Artisi]

How long is the research programme likely to run and what do you see as meaningful outcome, you could possible approach a manufacturer of the equipment required and ask for their assistance ie., loan, gift etc.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[jari001]

LittleInch is asking at what temperature and pressure is the 15 lpm referenced to, since the gas density is a strong function of temperature and pressure. Standard conditions are variously defined (see link below), so it would help to know the required mass flow as that is unambiguous. Once the mass flow is known, the volume flow can be calculated for various temperatures and pressures as needed.

https://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure

 

[Samrs]

How long is the research programme likely to run and what do you see as meaningful outcome...

The experiment will be running for around 6 months. The purpose of this is a proof of concept for a self-regulating system for converting wastewater to useful products. Ideally, the system will run with minimal human interaction and will use components that are inexpensive so that the system can be replicated and used in poorer countries.

LittleInch is asking at what temperature and pressure is the 15 lpm referenced to...

Ah. Gas will be around room temperature (25°C). So mass flow rate of about 0.4 g/s.

 

[EdStainless]

Is there any H2S in this gas? Even a few ppm can be an issue.
Are you worried at all about fire or explosion?
I am sure that you can see how this isn't a simple task.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

For some reason I didn't think diaphragm pumps would meet your pressure requirement and rotary vane would. As it turns out I had it backwards. Here is a an example of a pump that meets your requirements:

https://gastmfg.com/products/daa/daa-p501-eb

MATERIALS OF CONSTRUCTION
• EPDM (Ethylene Propylene Diene Monomer) valve and
diaphragm
• Chemically resistant PPS (Polyphenylene Sulfide) for all
other wetted components

 

[Samrs]

Is there any H2S in this gas? Even a few ppm can be an issue.
Are you worried at all about fire or explosion?

I actually wasn't aware H2S was an issue with biogas until now (the person conducting this experiment likely was aware, but I wasn't). I am checking with her to see what the expected content is. And yes, the risk of fire is a concern. But from what I gather, methane won't ignite unless it is mixed with a significant ratio of oxygen. And this won't be present where the biogas is flowing. Also, we will be running this experiment in a safe location and it will be checked regularly.

Here is a an example of a pump that meets your requirements:

https://gastmfg.com/products/daa/daa-p501-eb

That pump looks great! The specs look right and I see a few places we could purchase it at reasonable prices. The materials of construction concern me though. I may be mistaken, but isn't EPDM not suitable for use with methane?

http://www.ipexna.com/media/1663/epdm-fkm-chemical-resistance-guide.pdf

 

[TugboatEng]

Good catch on EPDM. If you browse their catalog some models use neoprene or nylon which will be compatible.

 

[jari001]

If there is a leak into the atmosphere (e.g. loose connection, membrane housing damage) the methane will likely form a flammable mixture and then all anyone has is hope that there isn't an ignition source somewhere (e.g. static electricity). You should also confirm that there isn't a failure mode that draws air into the system - it's probably not likely but it is best to think about that to be sure. When handling flammable chemicals, the best practice is to have some method of leak detection that automatically shuts off the fuel source and warns people of the dangerous situation (alarm, lights); an administrative control of wearing a personal gas monitor whenever checking on the experiment would be prudent IMO.

H2S has similar safety concerns, so don't forget to plan for that as well.

 

[georgeverghese]

While you may take credit for operating procedures to exclude air/ O2 in this biogas stream to this liquid ring type (??)compressor, due to potential gas leaks to the atmosphere from the compressor rotating shaft seals, it may most likely need to operate in a IP electrical Zone 2 classification area, even if this compressor operates in a well ventilated area. That will have a cost impact on the type of electric motor and nearby electrically powered field instruments used at the least. Classification will get more onerous if not located in a well ventilated area. Check with a technical safety engineer.