CO2 compression

[rvallee]

I am wondering what are the obstacles preventing the compressed storage or combustion gases from automobile engines. CO2 is a non-volatile gas and could be stored safely as there is sure to be much less gas that there is liquid gasoline in the tank.

[Flurfl]

Interesting idea! But you'd be surprised how much CO2 your car produces. 2.31 kg of  CO2 per litre of petrol. So if you could compress it to the same density as petrol you'd need a tank nearly 2.5 times larger than your petrol tank, that's assuming you've condensated off the water seperately. You'd also need some sort of "afterburner" to burn off the volatile hydrocarbons that still exist in the exhaust gases, You could compress them but I imagine it would be dangerous to do so, you'll also need some way of disposing all the excess heat that you are creating and the engine will need to be beefier as it has to do the compression as well as carry around the extra weight. Once you've got it then you'll need some way to dispose of it, probably at the service station where they would have to charge you, probably by increasing the cost of the fuel. To encourage people to install the system and not let the gas escape they could give a rebate of certain amount off the cost of the petrol from every litre of CO2 you return.

[Flurfl]

Here's a link on the processes involved in making compressed CO2, basically how I described:

http://www.toromontprocess.com/co2/tables.asp

Here's a link on what to do with the CO2 once you have it, note they are talking about using CO2 from air so as our CO2 is already compressed we already have an efficency increase.

http://www.groupsrv.com/science/post-680612.html

[rvallee]

Thanks! This is great information!

[Hamish]

great answer flurfl, however there is one further consideration. Given the need for a comressor (two of) then the engine will need to be nore powerful (as said). but it will then be heavier also you will have the weight of the Co2 and the tank to add on, requiring a larger engine. A larger engine will consume more fuel, requiring a larger engine. I estimate aprox 25-30% in weight. So less CO2 is released but more fuel is used. Probably better to plant fast growing trees to help the environment instead.

[Loosehead]

Sorry if I've miss understood, Flurfl. Are you sure about your initial figures? I mean 1 litre of petrol weighs approx a kilo so how can you get 2.31kg of CO2 out of it?

[rja211077]

because, loosehead, the carbon and hydrogen in the fuel combine with the oxygen in the air during combustion to make CO2 and H2O. 1 mole of C results in 1 mole of CO2 - a mass ratio of 44/12. One mole of H2 results in 1 mole of H2O - a mass ratio of 18/2 - so the products of combustion are significantly heavier than the fuel. 

[Loosehead]

I see, thanks

[rvallee]

So basically it would be necessary to do real-time breakup of molecules to separate safe ones (who could be ejected) from the nasty ones with all it implies...?

As we'll run out of cheap oil by then, pointless effort...

Oh well...

[Thunderchild]

why not just use an electric car. do you all know that a fuel battery exists. it combines oxegen and hydrogen making water that is expelled and of couse non poluting and leaves us with some electricity to opwer the motor. there have been some prototypes made and that r in use so why not just do that. the process of getting the two gases to put in the car in called electrolisis with electricity water is split into the two gases and the power can come from solar pannels and so no CO2 problems (how nice eh ?)