CNG pump compressor DIY home refueling

[P-hack]

another way to minimize the bypass issue:
direct injection pump off a vehicle. Fill an accumulator with methane (no membrane required?), then pump hydraulic fluid in to squeeze it out, refill with methane and repeat. Valve in cheaper higher flow lower pressure pumps to speed things up at lower pressures.

[rmay635703]

This is actually a decent thread, I asked long ago for a list of non-scuba compressors but no one seemed to be familiar with the industrial pump side of things. There are many pumps that operate in various pressure ranges for all different flammable materials and as has been shown in this thread they are cheaper than the stock CNG solution.

If anyone can get in contact with an oversees ANG company I would be very interested in importing one if it is both ANG and has a type one tank (3600psi) at the same time. My reason is that I would also like to refuel cng at low pressure at home but have the ability to top off at local CNG retailers when I need a more expensive but complete fill up.

Key here is we likely DON"T need to DIY an inexpensive 500psi flammable gas pump, they exist but I have never come in direct contact with them to write down models and brands.

Ah well.

[vlad]

As I said yesterday. I tried DIY CNG adsorption. I took 2 1 lb propane bottles. One was just an empty bottle and second I filled with activated carbon. I broke 2 osmosis carbon filters put them into canvas bag and after an hour hammering I got carbon powder. I used refrigerant recovery unit to boost pressure from few inches (I took gas after one of regulators) to 250 Psi. The guinea pig was my propane converted lawnmower. I started it up on propane first and then I started in using CNG without carbon. It ran for 1 minute and 20 seconds. I tried to start it using CNG with carbon but it didn't run. It was starting and dying right away. So, I tried other method. I emptied both bottles and connected one at the time to recovery unit. First bottle without carbon got to 250 Psi in 2 min and 7 sec. Second bottles got to 250 Psi in 1 min and 48 sec. Also I noticed the carbon weight was 560 gram for 1 lb bottle.

I can call this experiment as failed. May be you need special carbon may be something else but at this point I call it FAILED.

[ksa8907]

For what its worth, I work for a large natural gas transmission and distribution utility company and the words directly from thier sr. management about cng were: the equipment is too cost-prohivitive.

I don't want to kill anyone's entrepreneur spirit, but how much will cng cost to implement and how much would it save? I realize ng is currently about $0.40 per therm (1 million btu).

Correct me if my math is wrong, wouldn't you only need 20 cubic feet at 50psig to be of equal btu content as 10 gal of gas?

[P-hack]

Originally Posted by vlad

I can call this experiment as failed. May be you need special carbon may be something else but at this point I call it FAILED.

I researched adsorption carbon a bit more, you do need special carbon from special sources processed in a special way, and the benefit does not seem linear with psi. Still a lot of vehicles moving in that direction, and some tanks in production.

[vlad]

Originally Posted by ksa8907

For what its worth, I work for a large natural gas transmission and distribution utility company and the words directly from thier sr. management about cng were: the equipment is too cost-prohivitive.

I don't want to kill anyone's entrepreneur spirit, but how much will cng cost to implement and how much would it save? I realize ng is currently about $0.40 per therm (1 million btu).

Correct me if my math is wrong, wouldn't you only need 20 cubic feet at 50psig to be of equal btu content as 10 gal of gas?

50 Psi/ 14.7 Psi (normal atmospheric pressure)=3.47 compression ratio

20 cubic feet x 3.47 = 69.4
69.4/127=0.5

So you have only 0.5 GGE or about 2 Liters......not so much

[vlad]

Originally Posted by P-hack

I researched adsorption carbon a bit more, you do need special carbon from special sources processed in a special way, and the benefit does not seem linear with psi. Still a lot of vehicles moving in that direction, and some tanks in production.

I hear you special here special there.... This "problems" can be solved in no time but I doubt they will be solved. Just like first electric vehicles were all scrapped. The automotive industry will only move their asses when somebody is trying to steal a piece of their market....

Just imagine you can buy CNG car for the same price +1k and refuel station cost you another 1k. Are you in? Somebody BIG must do it and everybody will be scared to loose their market share... But at this point everyone is happy.... but what about you? Are you happy to pay almost $4 gallon? But who cares this is your pocket right???

Hey the dream is over. CNG is not going to happen soon. Wait another decade OR ... help yourself.....

Let's move on.....

[vlad]

Originally Posted by rmay635703

Key here is we likely DON"T need to DIY an inexpensive 500psi flammable gas pump, they exist but I have never come in direct contact with them to write down models and brands.

Ah well.

Almost any AC compressor can pump flammable gas. I filled up my home heat pump with dry propane instead of R22 refrigerant. You can pump to 350-400 Psi using just a R22 AC compressor. R410a compressors can pump 500 Psi.

The problem is I have 2 large and heavy type 1 cng tanks. They are huge but only 3 ft3 together. Lets see how much CNG they will hold at 500 Psi:

500/14.7=34 compression
34x3=102 volume uncompressed
102/127=0.8 GGE...... not much......

I need 1200-1300 Psi to get 2GGE

This is why I am thinking about "second stage compression".

What about using hydraulic cylinder to compress gas? First stage can easily compress to 200 Psi and we only need 6 times ratio to get 1200 Psi.

Benefits of using hydraulic cylinders: not expensive, low temperature, low speed, easy to rebuild ($20-$30 seal kit)

[cRiPpLe_rOoStEr]

Originally Posted by euromodder

From what I've been seeing / reading , the CNG is fed into the air intake of a diesel @ low pressure.
(Getting it in along with the diesel would require very high pressures on CR or DP set-ups.)

The amount they feed in, is regulated by the TPS (throttle), and diesel injection is reduced because you need less throttle to keep a given speed or engine load.
(it may be necessary to dampen / reduce throttle input from the pedal to the ECU to keep the car drivable as you're feeding in more fuel than normal - yet not too much as you still want to be able to drive it on diesel alone if you're out of CNG.)

Without throttle input, you can let it run on diesel and the regular idle regulator in the car.

The problem with a fumigation CNG setup is that it displaces Oxygen while depressurizing, so it goes like choking the intake. That's why I'm more favorable to a direct-injection setup such as the one used in those Westport GX engines.

http://www.youtube.com/watch?v=iXcMkw0jHjc

The video is more focused on the Westport HD system and the safety operation with an LNG fuel system, but you might get the idea. BTW there are some all-mechanical mixers that can be used to combine an amount of CNG with Diesel fuel, usually at fixed ratios such as 70% CNG-30% Diesel which at least is still effective to take benefit from the direct injection with CNG.

[P-hack]

wow, looks expensive, and tricky. So re: choking, what is the stoic air fuel ratio for gaseous ch4 at standard pressure/temp?