[Gasification] Fluidised bed reactor

[Doug]

Hi GF and Gasification Colleagues,

Having watched this discussion on FB gasifiers, it's easy to see how information can cross pollinate and contaminate the understanding of anyone trying to learn from answers to any questions.

On Sat, 30 Nov 2013 14:45:47 -0500 (EST)
GFWHELL at aol.com wrote:

>The "recycling " of CO2 within the gasifier sounds very interesting because 
> CO2 can be converted into methane under the right conditions, presumably 
>in the  presence of steam and a catalyst at high temperature.

Others can discuss the chemistry GF presumes to be possible.

> I was informed on this site  that IC engines were not able to deal  with an 
> enriched oxygen fuel mix and required large quantities of "energy  
> absorbing" nitrogen to keep them running. or else the valves would burn out or  
> reasons of that nature.

I doubt if that has been offered in discussions on this Forum, as it is totally incorrect. At best, Syngas made with pure oxygen or steam only represents a gas much the same as Natural gas or LPG, both are less than that energy from gasoline or other high energy liquid fuels. Valves burn out for a number of reasons, but if the gas/air/timing ratios are correct, there should be no issues with modern valve systems.

> This is a pity because the exhaust would be of a much  
> higher value for gas making.

Hot CO2 into a charcoal gasifier has the prime benefit of assisting to lower the huge blast temperature of the air nozzle, as traditionally charcoal gasifiers only have one nozzle. It's addition has been well proven to not make more gas, but to reduce the amount of charcoal used to make a fixed amount of gas.

> This would also be true if the input supply of  
> air to the gasifier was devoid of nitrogen.

No surprises there GF,how to reduce or eliminate nitrogen has been dug over many time by this Forum.

> By comparison the gasifier would only need to be 1/5th in size if it  was 
> designed to deal with oxygen only in order to burn its fuel.
> This would require a  pressure/adsorption system for the provision of  
> primary air for combustion, 
> These devices are not that complicated, requiring a compressor and a couple 
>  of pressure vessels containing
> the correct zeolite together with a plumber.

All things are possible if you have the capability,time, and of course money. My suggestion is just do it and show it works(:-)

> A simple test of this process would be to take your plastic welding  
> electrically heated welding torch and connected to a supply of CO 2 .attach  the 
> nozzle to a suitable "reaction chamber" (capped water pipe"containing your  
> Biomass, switch on and vaporize the contents with your electrically heated CO 
>  2

This is the part that becomes interesting. Is your CO2 out of a cylinder so that you know it is pure, or is it from a gasoline or producer gas fuelled engine? Either way, how are you going to bring up the charcoal temperature to at least 900C (has to be a lot more) for the CO2 to reduce into CO via reduction? Remember that the CO2 is a temperature retardant in an oxidizing bed.

> Test the value of the output, then do a second test using compressed air  
> for comparison.

Me thinks you will see it melt in front of your eyes GF, like an overblown forge, so take extreme care if you try this.

Grandchildren just arrived so will rejoin later in the day.
Doug Williams,
Fluidyne.