GASIFIERS – Updraft Multi-fuel


Updraft multifuel gasifiersPROCESS


In the updraft gasification process, as the name suggests, the flow of gases in the gasifier reactor is upwards. The fuel is fed through the top and then travels downwards. Ash is removed from the bottom. Gasifying agent is blown into the fuel bed through the bottom.

COSMO Multi-fuel Updraft gasifiers are air-blown (air +steam) and operate at near atmospheric pressure. The output gas contains 40-45% combustible constituents mainly in the form of CO, H2, CH4 and balance inert gases consisting of CO2 & N2. This gas is called producer gas and hence such gasifiers are also known as ‘producer gas plants’.

Producer gas exiting through the top of the fuel bed carries with it the moisture of fuel, particulate matter (dust) and condensable volatiles (tars). While the gasifier is used in “hot gas mode”, the temperature of output gas is maintained such that tar remains in vapour form and gets burnt at the burner. While the gasifier is used in “cold-clean gas mode”, the temperature of output gas is maintained as low as possible so that most of the sensible heat of gases is absorbed by fuel bed. The output gas is then cooled & cleaned before being sent to user equipment.

Ash is in granular form and comes out of gasifier in wet condition. It does not fly around and can be removed from the site conveniently.

Updraft gasifiers are highly efficient, 80-85% in hot gas mode and 70-80% in cold gas mode (depending upon energy transferred to tar collected, which would be fuel specific)


ACCEPTABLE FUELS


Wide variety of carbon containing solid fuels can be gasified in COSMO multi-fuel updraft gasifiers that include biomass, coal and wastes.

Biomass materials, such as wood, agro-residues and agro-industrial-residues are good candidates for our gasifiers, with following limitations:
Size: 25 – 150 mm,     Moisture: <20%,  Ash content: <25%,  Ash fusion temperature: >12500C,  Bulk density: >250 kg/m3

Agro-residues and agro-industrial-residues, which mostly come in low density granular form, need to be agglomerated by briquetting to achieve the desired size & density requirements.

Hard bituminous and sub-bituminous coals of any origin can be gasified, with following limitations:
Size: 20-50 mm,                Moisture: <10%,               Ash content: <45%,         Ash fusion temperature: >13500C

Brown coals, which easily crumble into powder form, are difficult to use as they diminish the porosity of fuel bed, adversely affecting smooth operation of gasifier.

Carbon containing wastes can also be gasified, but they need to be tested in our pilot plant to arrive at appropriate design & operating conditions.


CARANGEPACITY


300 kWth to 30,000 kWth in single reactor modules
(Equivalent to 25 to 2500 litres/hour oil substitution)
With parallel installation of multiple gasifiers, any capacity is feasible

SPECIAL FEATURES
Multi-fuel capability, the same gasifier can run on either coal or biomass
 Automatic fuel feeding & ash removal
 Fully automatic computer controlled plants, appropriately integrated with the user’s equipment, are offered as per requirement
 Semi-automatic, low cost gasifiers are also offered for small-medium-scale applications
 Specially designed for high ash Indian coals
 Special grate design has made scalability possible to virtually any capacity, reactor diameter up to 7.5 m has been tested
 Both ‘Hot gas mode’ and ‘Cold-clean gas mode’ configurations are offered as per the requirement of the application
 Daily start-up and stoppage possible
 Long, trouble-free campaign life, some gasifiers have been operated for 6 months at a stretch without interruption
 Environment friendly technology – invisible stack emissions, lower SO2 as compared FO fired furnace operation