How To Dry The Biomass 10 Ton Per Hour

The flue gases are already being exhausted to the atmosphere, so it seems they could also be blown through the wood chips. 10 tons/h * 2000 lb *~1000 Bth/lb x (0.45 -0.15) ≈ 6,000,000 Btu/h. Is the quantity of flue gases enough for this?

You did not state the fuel source for the existing flue gasses. IF it is natural gas, the flue gasses must not be cooled below about 70C or you will be condensing the water vapor products of combustion- not good for drying. Similarly, IF the products being "dried" using these gases is less than 70C, you stand the risk of condensing on the products as well.

A better choice might be to use recovered heat from the flue to regenerate a desiccant dryer on the air used to dry the chips and also to warm that air (after drying) to a higher temperature (with a corresponding even lower humidity) and use the "very" dry and warmed air from the dryer to extract the moisture from the chips and/or other bio-wastes.

Warming the "damp" products will also help dry them by increasing the vapor pressure of the water contained in the materials. Passing the products over a set of tubes that have the hot flue gasses inside is one way to do this.

You can also install a coil in the flue exhaust (with a booster fan if necessary) and send the hot water to another coil that will heat the incoming air being used to pre-heat and partially dry the bio-wastes. One advantage of this approach is that you can, and want to, reduce the temperature of the flue gasses below 70C so that you will extract the 14% of input latent heat contained in the water vapor and use it effectively to heat the wood chips or bio-wastes. Since the incoming "drying air" will be at ambient temperatures (which are always less than 70C) you will like have no problem extracting the latent energy.

Another choice is to use an industrial microwave on a belt with the wood or bio-solids passing through the microwave radiation.

For the bio-wastes, consider putting batches into a centrifugal separator before you warm up the solids that remain.

Water moves very quickly- the vapor moves at nearly the speed of sound- from areas of high humidity to areas of low humidity. If you give it the best chance of reaching that condition, all will be wonderful.

Agree with what you stated, this company produces heat exchangers for doing just that type of recovery.

Dear Freind, Can you explain me about the equipment mentioned in your following suggestion. "Another choice is to use an industrial microwave on a belt with the wood or bio-solids passing through the microwave radiation." Ramesh

Dear Friend, If the flue gas is not sufficient, I can add some more heat through other means. Or I will reduce the quantity of wood chips to meet the heat energy supplied by flue gas. Can u suggest how to blow the same through the wood chips i.e., the system so that the condensed flue gas shall not cause environmental problems. Regards Ramesh

You have not informed the BOLER PRESSURE, CAPACITY and the quantity of wood chip to be dried and flue gas temperature.

OPTION 1:

If flue gas temp. is above 160 Deg. C, fabricate a small Heat exchanger to be used for blowing atmospheric air and use a small blower to blow the flue gas in to the heat exchanger so that the atmospheric air is heated to about 90 to 100 Deg.C ( which is well below the ignition temp. of wood chip) and this hot air is to be blown over the wood chips in a thin layer in a 10 to 12 Metre long travelling conveyor and then feed to the boiler. Here the over all heat transfer co-efficient will be very less.

OPTION 2.

If you have difficulty for the above arrangement use the blow-down water from the boiler to heat the air to be blown over the wood chip. For this you have to fabricate a small heat exchanger. This may be simpler but please ensure there is no valve put before the entry of the blow-down water in the blow-down line to the pit. Here the over all heat transfer co-efficient is more than option 1.

DHAYANANDHDAN.S.

Dear Sri. Dhayanandhan My boiler specifications are 65Kg/Cm2, 485 Degree C. The exhaust temp at the outlet of ESP is around 130 to 150. Please explain what if I directly blow the flue gas coming from the ESP through the wood chips or agricultural wastes.

I recommend to look into a rotary heat recovery / heat exchanger. This is a big mainly aluminium mass with holes rotating on one side through your flue gases. The other halv rotates through a duct where a fan blows the exterior air through the holes and transfers the heat to the air used to dry the bio masses.

The designs are very efficient and allow to recover quite an amout of the otherwise wasted energy. These Units are commercially available. Availablity will depend on the location you live.

Hi rameshbabu.

You are talking about removing 3 tonnes of water per hour from the biomass material. To do this in a practical, and safe, manner will require a moving bed type dryer supplied with air heated from some source such as your flue gas system. There is no point in using cooled down flue gases as they are both contaminated and moist. A plate heat exchanger can be used as the transfer agent between the two streams. handling wet and hot chips is a process that requires care and after cooling to avoid problems further down the chain. Therefore there must be an aftercooling section in the bed-dryer.

Each type of material requires a specialised handling mechanism, it is not a case of 'one size fits all'. As has already been stated you must decide whether your existing energy source has sufficient power to produce the required heating/evaporating effect. An auxiliary heat exchanger can be used in series with the flue gas converter to enhance/increase the heat transfer as needed. This could take the form of another heater battery using heat from your process plant or even another fuel burner.

Good luck,

Massey.

Thank you Massey. I will be helpful to me if you can provide the addresses of the manufacturers of such equipment.

If quantity of flue gases is sufficient enough to become a heat source and the exhausting conditions of flue gas permit lower temperatures, the flue gases can be used to dry the bio-mass. Drying systems have been provided for Similar application

in sugar industries. You may contact me at: arunkumar1954@gmail.com for further information.

With Regards/ARUNKUMAR

Items to look at:

http://www.biomasscenter.org/pdfs/Wood-Chip-Heating-Guide.pdf

http://www.globalspec.com/FeaturedProducts/Detail/GEMThermalEnergyInternational/DRYREX_Biomass_Fuel_Dryer/93131/0

There are a number of companies that supply equipment for the use of both chips and

sawdust as alternate fuels.

Thank You for your valuable information. Rameshbabu

Have you looked into systems like this? Perhaps they can be modified to fit your needs.

http://www.graindryers.com/

http://www.grainsystems.com/

the following are a little different:

http://www.kason.com/index.php

http://www.globalspec.com/LearnMore/Processing_Equipment/Heat_Transfer_Equipment/Process_Dryers