Tar from a Biomass Gasification Plant

I would assume the best way to define which hydrocarbons are causing problems would be to get an analysis of the tars on the exchangers. Once that is available, there are sources for informatioon on the physical/chemical properties of the components. You might also look at the potential for sampling the gases going to the heat exchangers and have FTIR analysis run to define components.

Where in the process is the "tar"laying down?

Can you give a process flow walkthrough.

What is the compositional makeup of the coffee waste and other feed streams?

Please describe the application

A few questions that would help:

1. Is the fluid bed air and gas supported or is it mechanically activated with lower amounts of gas flow?

2. Is combustion occurring in the bed and the tar sticking to the exterior of the tubes being heated? Or do I misunderstand your application?

3. Describe the plenum or plate that the fluidising or feed air is distributed through. Is there tar buildup there also?

4. IF it is a combustion process, describe the fuel, air and feed nozzle arrangement. Is it like a coal slurry injection system?

I suspect that some of the tar you refer to is a composite of stuff. If you may experience some separation, decomposition and worse solidification on heating if that is true. The last I heard, coffee plants had good success with liquid CO2 as a solvent for both decaffeinating and cleaning tar off equipment. Is there an opportunity to either remove the tar first?

Dear All,

Sorry I was away at site to find some solution to my tar problem. Let me explain the process in brief. The feed is the coffee beans after the coffee is extracted and dried as instant coffee. This coffee waste is used as feed to extract produced gas in a fluidised bed gasifier. The gasifier is fluidised with air passed through group of air nozzles. (529 nozzles to be precise) The inert catalyst (sand) used as fluidising media is a Al2 O3. This air is also used for gasification reaction. Initially the sand is heated using diesel burner and there after charcoal is used for further heating the sand. Charcoal is gasified to attain the operating temperature through out the plant before biomass is added.

On attaining the required temp, the biomass is fed in place of charcoal. The biomass gasification is done and the gas initially goes to first heat exchanger (HE) where it heat up the air for gasification. the gas from first HE goes to second HE where the gas gives away the heat to air and this hot air is used for certain process not connected with gasifier. Once the gas temp is brought down to about 220 deg C , it is passed through a fabri filter where the gas is separated from the ash. Then the gas is further cooled in two more HEs before it is used in a produce gas engine to produce electricity.

Now it is in the second HE that certain hydrocarbons are depositing on the tube walls as the HE is tube and shell with gas in tubes. The HE gets clogged and we are forced to stop and clean the HE. The plant is able to run maximum of 36 hrs before we take up HE cleaning.

We are trying to get the condensate analysed to see the melting point. It is difficult to find such labs in India.

Now can some body lead me???