GAS-L: Biomass Gasification and Feeding

["Thomas Koch" <Tk@tke.dk>]

At TK Energi we have been testing bagasse feeding in plug feeders over the last 2 years.

We see no or very litle difference on the physical properties on bagasse and other types of soft biomass eg straw, corn stocks, miscantus etc. Bagasse can succesfully be fed by our biomass feeders developed for straw.
I am not sure where the roumors that "bagasse is the most difficult biomass to feed" had come from.

At TK Energi we say that wet biomass is easy to feed and dry biomass is more difficult to feed.
At TKE we have developed a piston feeder that can feed bagasse into pressurised vessels with up to 40 bar.
Our testrig allows us to feed for half an hour. 
In this period of time we have not seen any problems.
Our screew feeders (for pressures up to 2 bar) have been operating on full scale CFB gasifiers since 1998.

Concerning the comments from Terry about his judgments of our approach judged not to be acceptable for continiuos feeding.
If Terry expects that he can send a guy (an intelligent and nice guy by the way) from Australia to visit me, explaining that he is developing bagasse feeders, and expecting me to release sufficient information for him to evaluate what I am dooing in details, without beeing prepared to sign some sort of agreement ---- He is too naive.
And Terry have operated 2 minutes with a feeder for 5 tons pr hour and based on that he conludes "that it can readily scaled up to 70 tons pr hour". To me there is a few thousand operation hours missing. 

Terry, at a mínimum we Must exchange information. 
So Terry --- what are the technical principle you base your feeder on?
And how continious do you want you feeding?

We at TKE are offering feeders for atmospheric and pressurised plant at commercial conditions. 

A more detailed technical description of a TK Energi AS fuel feeding system for a pressurised 30 MW system is shown below.

The plug feeder 1-2-3 is a 3 stage piston feeder. 
The maximum feeding frequency is 1200 times per hour. 

Power consumption and gas leaks.
 
The average power consumption is 80-100 kW at a leak rate of 5-10 Nm3  gas pr. hour feeding 6000 kg soft wood chips with 20 % moist pr hour against 25 bar. 
The average power consumption is 100-130 kW at a leak rate of 10-15 Nm3 gas pr. hour feeding 6000 kg hard wood chips pr hour against 25 bar.    

Operation, safety and wear

The operation seal is established by forming a plug of the biomass that is fed into the reactor. To obtain a mechanical stable plug with a suitable low gas permeability, this plug must have a density in the range from 1000-1700 kg/m3  depending on the texture of the biomass and the requirements of the operation parameters of the plug. 
The safety seal is established by ensuring that one of the pistons is always in the out position. 
The biomass falls down in front of the first piston. The biomass is pressed into the free space in front of the second piston. In this operation the biomass reaches a density of 4-900 kg/m3