What is Gasification?
Gasification is a flexible, reliable, and clean energy technology that can
turn a variety of low-value feedstocks into high-value products, help reduce our
dependence on foreign oil and natural gas, and can provide a clean alternative
source of baseload electricity, fertilizers, fuels, and chemicals.
It is a manufacturing process that converts any material containing
carbon—such as coal, petroleum coke (petcoke), or biomass—into synthesis gas (syngas).
The syngas can be burned to produce electricity or further processed to
manufacture chemicals, fertilizers, liquid fuels, substitute natural gas (SNG),
Gasification has been reliably used on a commercial scale
worldwide for more than 50 years in the refining, fertilizer, and chemical
industries, and for more than 35 years in the electric power industry.
There are more than 140 gasification plants operating worldwide. Nineteen of
those plants are located in the United States. Worldwide gasification capacity
is projected to grow 70 percent by 2015, with 80 percent of the growth occurring
Gasification can compete effectively in high-price energy environments to
provide power and products.
In a gasifier, the carbonaceous material undergoes several
Pyrolysis of carbonaceous fuels
Gasification of char
- The pyrolysis (or
devolatilization) process occurs as the carbonaceous particle heats up.
Volatiles are released and char is produced, resulting in up to 70% weight
loss for coal. The process is dependent on the properties of the carbonaceous
material and determines the structure and composition of the char, which will
then undergo gasification reactions.
- The combustion process occurs as
the volatile products and some of the char reacts with oxygen to form carbon
dioxide and carbon monoxide, which provides heat for the subsequent
gasification reactions. Letting C represent a carbon-containing organic
compound, the basic reaction here is
- The gasification process occurs
as the char reacts with carbon dioxide and steam to produce carbon monoxide
and hydrogen, via the reaction
- In addition, the reversible gas phase
water gas shift reaction reaches equilibrium very fast at the temperatures in
a gasifier. This balances the concentrations of carbon monoxide, steam, carbon
dioxide and hydrogen.
In essence, a limited amount of oxygen or air is introduced
into the reactor to allow some of the organic material to be "burned" to produce
carbon monoxide and energy, which drives a second reaction that converts further
organic material to hydrogen and additional carbon dioxide.
How Coal Gasification Power Plants Work
The heart of a gasification-based system is the gasifier. A gasifier converts
hydrocarbon feedstock into gaseous components by applying heat under pressure in
the presence of steam.
A gasifier differs from a
combustor in that the amount of air or oxygen available inside the gasifier is
carefully controlled so that only a relatively small portion of the fuel burns
completely. This "partial oxidation" process provides the heat. Rather than
burning, most of the carbon-containing feedstock is chemically broken apart by
the gasifier's heat and pressure, setting into motion chemical reactions that
produce "syngas." Syngas is primarily hydrogen and carbon monoxide, but can
include other gaseous constituents; the composition of which can vary depending
upon the conditions in the gasifier and the type of feedstock.
Minerals components in the
fuel, which don't gasify like carbon-based constituents leave the gasifier
either as an inert glass-like slag or in a form useful to marketable solid
products. A small fraction of the mineral matter is blown out of the gasifier as
fly ash and requires removal downstream.
Sulfur impurities in the
feedstock are converted to hydrogen sulfide and carbonyl sulfide, from which
sulfur can be easily extracted, typically as elemental sulfur or sulfuric acid,
both valuable byproducts. Nitrogen oxides, another potential pollutant, are not
formed in the oxygen-deficient (reducing) environment of the gasifier; instead,
ammonia is created by nitrogen-hydrogen reactions. The ammonia can be easily
stripped out of the gas stream.
In Integrated Gasification
Combined-Cycle (IGCC) systems, the syngas is cleaned of its hydrogen sulfide,
ammonia and particulate matter and is burned as fuel in a combustion turbine
(much like natural gas is burned in a turbine). The combustion turbine drives an
electric generator. Exhaust heat from the combustion turbine is recovered and
used to boil water, creating steam for a steam turbine-generator.
The use of these two types
of turbines - a combustion turbine and a steam turbine - in combination, known
as a "combined cycle," is one reason why gasification-based power systems can
achieve high power generation efficiencies. Currently, commercially available
gasification-based systems can operate at around 40% efficiencies; in the
future, some IGCC systems may be able to achieve efficiencies approaching 60%
with the deployment of advanced high pressure solid oxide fuel cells. (A
conventional coal-based boiler plant, by contrast, employs only a steam
turbine-generator and is typically limited to 33-40% efficiencies.)
Higher efficiencies mean
that less fuel is used to generate the rated power, resulting in better
economics (which can mean lower costs to ratepayers) and the formation of fewer
greenhouse gases (a 60%-efficient gasification power plant can cut the formation
of carbon dioxide by 40% compared to a typical coal combustion plant).
All or part of the clean
syngas can also be used in other ways:
"building blocks" to produce a broad range of higher-value liquid or gaseous
fuels and chemicals (using processes well established in today's chemical
As a fuel
producer for highly efficient fuel cells or perhaps in the future, hydrogen
turbines and fuel cell-turbine hybrid systems;
As a source of
hydrogen that can be separated from the gas stream and used as a fuel (for
example, in the hydrogen-powered Freedom Car initiative) or as a feedstock for
refineries (which use the hydrogen to upgrade petroleum products).
Another advantage of
gasification-based energy systems is that when oxygen is used in the gasifier
(rather than air), the carbon dioxide produced by the process is in a
concentrated gas stream, making it easier and less expensive to separate and
capture. Once the carbon dioxide is captured, it can be sequestered - that is,
prevented from escaping to the atmosphere, where it could otherwise potentially
contribute to the "greenhouse effect."
The gasification process
Because of the
limitations of state-of-the-art biomass technology, a quest to improve the
efficiency and range of applications has been underway for several decades.
The point of
departure was the recognition that the combustion process actually comprises
several separate thermal processes which, if conducted in a controlled manner,
may considerably improve the result. These processes are:
where free moisture and cell-bound water are removed from the biomass by
evaporation. These processes should ideally take place at a temperature of up to
about 160ºC using waste heat from the conversion process.
where volatile gases are released from the dry biomass at temperatures ranging
up to about 700ºC. These gases are non-condensable vapours (e.g. methane,
carbon-monoxide) and condensable vapours (various tar compounds) and the
residuum from this process will be mainly activated carbon.
where the activated carbon reacts with water vapour and carbon dioxide to form
combustible gases such as hydrogen and carbon oxide. The reduction (or
gasification) process is carried out in the temperature ranging up to about
where part of the carbon is burned to provide heat for the previusly described
The updraft gasification
In the updraft
gasifier, moist biomass fuel is fed at the top and descends though gases rising
through the reactor. In the upper zone a drying
process occurs, below which pyrolysis is taking place. Following this,
the material passes through a reduction zone (gasification) and in the zone
above the grate an oxidation process is carried out (combustion).
supply air for the combustion process and steam for the gasification process,
moist hot air is supplied at the bottom of the reactor. Combustible gas at a low
temperature (because of the evaporation of moisture in the drying zone)
is discharged at the top of the reactor, and inert ash from the heat-generating
combustion process is extracted from the reactor bottom through a water lock.
Woody Biomass Conversion Technologies
There are many ways to generate electricity
from biomass using thermo-chemical pathway. These include directly-fired or
conventional steam approach, co-firing, pyrolysis and gasification.
1. Direct Fired or Conventional Steam Boiler
Most of the woody biomass-to-energy plants use direct-fired system or
conventional steam boiler, whereby biomass feedstock is directly burned to
produce steam leading to generation of electricity. In a direct-fired system,
biomass is fed from the bottom of the boiler and air is supplied at the base.
Hot combustion gases are passed through a heat exchanger in which water is
boiled to create steam.
Biomass is dried, sized into smaller pieces and then pelletized or briquetted
before firing. Pelletization is a process of reducing the bulk volume of biomass
feedstock by mechanical means to improve handling and combustion characteristics
of biomass. Wood pellets are normally produced from dry industrial wood waste,
as e.g. shavings, sawdust and sander dust. Pelletization results in:
- Concentration of energy in the biomass feedstock.
- Easy handling, reduced transportation cost and
- Low-moisture fuel with good burning characteristics.
- Well-defined, good quality fuel for commercial and
The processed biomass is added to a furnace or a boiler to generate heat
which is then run through a turbine which drives an electrical generator. The
heat generated by the exothermic process of combustion to power the generator
can also be used to regulate temperature of the plant and other buildings,
making the whole process much more efficient. Cogeneration of heat and
electricity provides an economical option, particularly at sawmills or other
sites where a source of biomass waste is already available. For example, wood
waste is used to produce both electricity and steam at paper mills.
Co-firing is the simplest way to use biomass with energy systems based on fossil
fuels. Small portions (upto 15%) of woody and herbaceous biomass such as poplar,
willow and switch grass can be used as fuel in an existing coal power plant.
Like coal, biomass is placed into the boilers and burned in such systems. The
only cost associated with upgrading the system is incurred in buying a boiler
capable of burning both the fuels, which is a more cost-effective than building
a new plant.
The environmental benefits of adding biomass to coal includes decrease in
nitrogen and sulphur oxides which are responsible for causing smog, acid rain
and ozone pollution. In addition, relatively lower amount of carbon dioxide is
released into the atmospheres. Co-firing provides a good platform for transition
to more viable and sustainable renewable energy practices.
Pyrolysis offers a flexible and attractive way of converting solid biomass into
an easily stored and transportable fuel, which can be successfully used for the
production of heat, power and chemicals. In pyrolysis, biomass is subjected to
high temperatures in the absence of oxygen resulting in the production of
pyrolysis oil (or bio-oil), char or syngas which can then be used to generate
electricity. The process transforms the biomass into high quality fuel without
creating ash or energy directly.
Wood residues, forest residues and bagasse are important short term feed
materials for pyrolysis being aplenty, low-cost and good energy source. Straw
and agro residues are important in the longer term; however straw has high ash
content which might cause problems in pyrolysis. Sewage sludge is a significant
resource that requires new disposal methods and can be pyrolysed to give
Pyrolysis oil can offer major advantages over solid biomass and gasification
due to the ease of handling, storage and combustion in an existing power station
when special start-up procedures are not necessary.
4. Biomass gasification
Gasification processes convert biomass into combustible gases that ideally
contain all the energy originally present in the biomass. In practice,
conversion efficiencies ranging from 60% to 90% are achieved. Gasification
processes can be either direct (using air or oxygen to generate heat through
exothermic reactions) or indirect (transferring heat to the reactor from the
outside). The gas can be burned to produce industrial or residential heat, to
run engines for mechanical or electrical power, or to make synthetic fuels.
Biomass gasifiers are of two kinds – updraft and downdraft. In an updraft
unit, biomass is fed in the top of the reactor and air is injected into the
bottom of the fuel bed. The efficiency of updraft gasifiers ranges from 80 to 90
per cent on account of efficient counter-current heat exchange between the
rising gases and descending solids. However, the tars produced by updraft
gasifiers imply that the gas must be cooled before it can be used in internal
combustion engines. Thus, in practical operation, updraft units are used for
direct heat applications while downdraft ones are employed for operating
internal combustion engines.
Large scale applications of gasifiers include comprehensive versions of the
small scale updraft and downdraft technologies, and fluidized bed technologies.
The superior heat and mass transfer of fluidized beds leads to relatively
uniform temperatures throughout the bed, better fuel moisture utilization, and
faster rate of reaction, resulting in higher throughput capabilities.
Enhanced Gasification; TurnW2E™
W2E has developed waste-to-energy technology for
utilizing a variety of waste materials to make renewable and alternative
energy products. The technology can process virtually any carbonaceous
material, converting it into forms of usable energy that can be consumed or
sold easily. At the core of the W2E technology is a process known as
gasification. It is a well-known technology for converting materials into a
clean-burning synthesis gas, which is then combusted for power production,
or further processed to produce hydrogen for transportation fuels, or
ammonia for use in fuel cells or as fertilizer. The history of gasification
process goes back many decades. There is significant experience with wood
gasification at various system sizes, and with coal gasification, at
relatively large applications. The W2E technology has incorporated the best
elements of past gasification designs and performances to yield a very
flexible and reliable waste-to-energy system.
WHAT IS GASIFICATION?
Gasification converts any carbon-containing material into a
synthesis gas (syngas). The syngas is a combustible gas mixture, sometimes
known as ‘producer gas’, typically contains carbon monoxide, hydrogen,
nitrogen, carbon dioxide and methane. The syngas has a relatively low
calorific value, ranging from 100 to 300 BTU/SCF. The syngas can be used as
a fuel to generate electricity or steam. Alternatively, it can be used as a
basic chemical building block for a large number of applications in the
petrochemical and refining industries. The overall thermal efficiency of
gasification process is more than 75%. Gasification can accommodate a wide
variety of gaseous, liquid, and solid feed stocks and it has been widely
used in commercial applications for more than 50 years in the production of
fuels and chemicals. Conventional fuels such as coal and oil, as well as
low- or negative-value materials and wastes such as petroleum coke, heavy
refinery residuals, secondary oil-bearing refinery materials, municipal
sewage sludge, hydrocarbon contaminated soils, and chlorinated hydrocarbon
byproducts have all been used successfully in gasification operations.
CHEMICAL REACTION OF GASIFICATION
The chemical reactions in gasification process take
place in the presence of steam in an oxygen-lean,reducing atmosphere.
The ratio of oxygen molecules to carbon molecules is far less than one
in the gasification reactor.
A portion of the fuel undergoes partial oxidation by precisely
controlling the amount of oxygen fed to the gasifier. The heat released
in the first reaction provides the necessary energy for the other
gasification reaction to proceed very rapidly. In the Turn W2E™ system,
gasification temperatures and pressures within the refractory-lined
reactor typically range from 800 Deg C to 1200 Deg C and near
atmospheric pressure to few inches of water respectively.
At higher temperatures the endothermic
reactions of carbon with steam are favored. A wide variety of
carbonaceous feed stocks can be used in the gasification process.
Low-BTU wastes may be blended with high - BTU supplementary fuels such
as coal or petroleum coke to maintain the desired gasification
temperatures in the reactor.
The reducing atmosphere within the gasification reactor prevents the
formation of oxidized species such as SO2 and NOx which are replaced by
H2S (with lesser amounts of COS), ammonia, and nitrogen (N2). These
species are much easier to scrub from the syngas than their oxidized
counterparts before the syngas is utilized for power.
GASIFICATION VS. INCINERATION
While gasification and incineration are both thermal processes,
it is important to point out the advantages of gasificati on over
incineration. Incineration is simply a mass burn technology with heat
recovery to produce steam and/or electricity. It has negative connotations
because during the direct combustion of the waste, dangerous carcinogenic
compounds such as dioxins and furans are formed, which are discharged into
the atmosphere. In contrast, gasification employs the conversion of waste
into syngas, which can then be used for generating steam and/or electricity,
for producing chemicals for high-value products, or for producing liquid
• To produce “town gas” for light & heat
• Gasification of coa - All gas for fuel and light
• To produce synthetic fuel
• To produce liquid fuels and chemicals
• First Integrated Gasification Combined Cycle (IGCC) electric
• US agencies provided fi nancial support for IGCC process
• Turnkey thermal & power Green house gas from biomass
• Renewed focus on reducing GHG emissions
• Biomass to liquid fuel conversion commercialized
The synthesis gas is produced under controlled
conditions, and is generated without the formation of impurities associated
with incinerator flue gas. Gasification emissions are generally an order of
magnitude lower than the emissions from an incinerator.
differences between Gasification and Incineration
Combustion Vs. Gasification
to maximize the
conversion of waste to CO2 and H2O
to maximize the conversion of
waste to CO and H2
large quantities of
under controlled amount of air
flue gas discharged to atmosphere. Flue gas contains dioxins and furans
syngas used for chemical production and / or power production (with
subsequent clean flue gas discharge)
sulfur converted to SOx and discharged with flue gas
of reduced sulfur species in the form of a high purity elemental sulfur
or sulfuric acid byproduct is feasible
and Ash Slag Handling
and fly ash collected and disposed as waste
and fl y ash collected and disposed of as waste
There are many carbonaceous materials that are
suitable for gasification. These include wood, paper, peat, lignite,
coal, including coke derived from coal, saw dust and agro-residues. All
of these solid fuels are composed primarily of carbon with varying
amounts of hydrogen, oxygen, and impurities, such as sulfur, ash, and
moisture.Municipal Solid Waste (MSW) is also a good candidate for
gasification; however, it poses a special challenge for waste
processors, due its non-homogenous characteristics, high moisture
content and unpredictable calorific value.
W2E has overcome this challenge by designing a unique gasifier. Thus, the
TurnW2E™ gasification process presents a new and better method for the
treatment of non-homogenous waste streams. Gasification is fast becoming a
favored technology for recovering energy from MSW and other solid wastes,
and the TurnW2E™ system stands ready to provide this service to the
is dry-fed through the top of a reactor onto a bed – usually a
slow-moving metal grate. As the fuel descends, it reacts with gasifying
agents (steam and oxygen) flowing in a counter-current through the bed.
The syngas has a low temperature (400-500 Deg C) and contains
significant quantities of tars and oils.
Entrained Flow: The fuel and gasifying agents flow in
the same direction (and at rates in excess of other gasifier types). The
feedstock – which may be dry-fed (mixed with nitrogen) or wet-fed (mixed
with water) – goes through the various stages of gasification as it
moves with the steam and oxygen flow.
The fuel, introduced into an upward flow of
steam/ oxygen, remains suspended in the gasifying agents while the
gasification process takes place.
Rotary Reactor: Gasifying agents, air and/or oxygen and
steam are introduced along a rotating horizontal cylindrical reactor vessel.
Gasification takes place along the length of the vessel in stages until
SynGas is released from the end while ash drops out. Rotary reactors, such
as the TurnW2E(TM) developed by W2E, enable complete mixing of the gasifying
agents with air while the process is closely controlled by the rotational
speed and air flow. The lower gas temperatures (800 - 900 Deg C) - while
high enough to volatilize tar and oils – allows easier handling of ash.
Gasification, An Overview of the Process and Products
Gasification Products and
Chemicals and Fertilizers
Modern gasification has been used in the chemical industry since the 1950s.
Typically, the chemical industry uses gasification to produce methanol as well
as chemicals, such as ammonia and urea, which form the foundation of
nitrogen-based fertilizers. The majority of the operating gasification plants
worldwide produce chemicals and fertilizers. And, as natural gas and oil prices
continue to increase, the chemical industry is developing additional coal
gasification plants to generate these basic chemical building blocks.
Eastman Chemical Company helped advance the use of coal gasification
technology for chemicals production in the U.S. Eastman's coal-to-chemicals
plant in Kingsport, Tennessee converts Appalachian coals to methanol and acetyl
chemicals. The plant began operating in 1983 and has gasified approximately 10
million tons of coal with a 98 to 99 percent on-stream availability rate.
Power Generation with Gasification
Coal can be used as a feedstock to produce electricity via gasification,
commonly referred to as Integrated Gasification Combined Cycle (IGCC). This
particular coal-to-power technology allows the continued use of coal without the
high level of air emissions associated with conventional coal-burning
technologies. In gasification power plants, the pollutants in the syngas are
removed before the syngas is combusted in the turbines. In contrast,
conventional coal combustion technologies capture the pollutants after
combustion, which requires cleaning a much larger volume of the exhaust gas.
This increases costs, reduces reliability, and generates large volumes of
sulfur-laden wastes that must be disposed of in landfills or lagoons.
Today, there are 15 gasification-based power plants operating successfully
around the world. There are three such plants operating in the United States.
Plants in Terre Haute, Indiana and Tampa, Florida provide baseload electric
power, and the third, in Delaware City, Delaware provides electricity to a
Substitute Natural Gas
Gasification can also be used to create substitute natural gas (SNG) from
coal and other feedstocks, supplementing U.S. natural gas reserves. Using a "methanation"
reaction, the coal-based syngas—chiefly carbon monoxide (CO) and hydrogen (H2)—can
be profitably converted to methane (CH4). Nearly identical to
conventional natural gas, the resulting SNG can be shipped in the U.S. natural
gas pipeline system and used to generate electricity, produce
chemicals/fertilizers, or heat homes and businesses. SNG will enhance domestic
fuel security by displacing imported natural gas that is generally supplied in
the form of Liquefied Natural Gas (LNG).
Hydrogen for Oil Refining
Hydrogen, one of the two major components of syngas, is used in the oil
refining industry to strip impurities from gasoline, diesel fuel, and jet fuel,
thereby producing the clean fuels required by state and federal clean air
regulations. Hydrogen is also used to upgrade heavy crude oil. Historically,
refineries have utilized natural gas to produce this hydrogen. Now, with the
increasing price of natural gas, refineries are looking to alternative
feedstocks to produce the needed hydrogen. Refineries can gasify low-value
residuals, such as petroleum coke, asphalts, tars, and some oily wastes from the
refining process, to generate both the required hydrogen and the power and steam
needed to run the refinery.
Pyrolysis and Gasification Differ?
the difference between Pyrolysis/Gasification and Incineration?
Both gasification is the overall outcome term for processes which involve
turn wastes into energy rich fuels
by heating the waste under controlled conditions.
incineration fully converts the input waste into energy and ash,
these processes deliberately limit the conversion so that combustion does not
take place directly.
Instead, they convert the waste into valuable intermediate
materials that can be further processed for the prupose of materials recycling
and/or energy recovery:
Thermal degradation of waste in the absence of air
to produce char,
pyrolysis oil and syngas, eg the Conversion of wood to
Breakdown of hydrocarbons into a syngas by carefully controlling the
amount of oxygen present, eg the conversion of coal into town gas.
Explanation of Terms
is created when an organic material—usually wood—is burned in a smothered
environment. Char is the most common freshwater fish in Iceland. Char may also
have the potential to sequester large amounts of carbon in the soil.
is made by burning wood in the absence of oxygen, and lump charcoal is the
product of that. One of the most important applications of wood charcoal is as a
component of gunpowder .
Charcoal is a
black substance that resembles coal and is used as a source of fuel. It is
generally made from wood that has been burnt, or charred, while being deprived
of oxygen so that what's left is an impure carbon residue.
There is a
diagram which was published by Bridgwater which shows the nature of the
difference between incineration and gasification and pyrolysis very clearly, and
we have reporduced it below to show the differences, not only between
gasification and incineration but with other combustion type processes.
Evans with assistance from the Juniper Gasification and Pyrolysis Fact Sheet
Pyrolysis and gasification
– how it works
Like incineration, pyrolysis,
gasification and plasma technologies are thermal processes that use high
temperatures to break down waste. The main difference is that they use less
oxygen than traditional mass-burn incineration.
These technologies are
sometimes are known as Advanced Thermal Technologies or Alternative Conversion
Technologies. They typically rely on carbon-based waste such as paper,
petroleum-based wastes like plastics, and organic materials such as food scraps.
The waste is broken down to
create gas, solid and liquid residues. The gases can then be combusted in a
secondary process. The pyrolysis process thermally degrades waste in the absence
of air (and oxygen). Gasification is a process in which materials are exposed to
some oxygen, but not enough to allow combustion to occur. Temperatures are
usually above 750oC.
In some systems the pyrolysis phase is followed by a second gasification stage,
in order that more of the energy carrying gases are liberated from the waste.
The main product of
gasification and pyrolysis is syngas, which is composed mainly of carbon
monoxide and hydrogen (85 per cent), with smaller quantities of carbon dioxide,
nitrogen, methane and various other hydrocarbon gases.
Syngas has a calorific value,
so it can be used as a fuel to generate electricity or steam or as a basic
chemical feedstock in the petrochemical and refining industries. The calorific
value of this syngas will depend upon the composition of the input waste to the
Most gasification and
pyrolysis processes have four stages:
1) Preparation of the waste
feedstock: The feedstock may be in the form of a refuse derived fuel,
produced by a Mechanical Biological Treatment plant or an autoclave (see links
to briefings on MBT and autoclaving on page 6). Alternatively, the plant may
take mixed waste and process it first through some sort of materials recycling
facility, to remove some recyclables and materials that have no calorific value
2) Heating the waste in
a low-oxygen atmosphere to produce a gas, oils and char (ash)
3) ‘Scrubbing’ (cleaning)
the gas to remove some of the particulates, hydrocarbons and soluble matter
4) Using the scrubbed gas to
generate electricity and, in some cases, heat (through combined heat and
power – CHP). There are different ways of generating the electricity from the
scrubbed gas – steam turbine, gas engine and maybe some time in the future,
hydrogen fuel cells (see page 4).
In plasma technologies the
waste is heated with a plasma arc (6,000º to 10,000º Celsius) to create gases
and vitrified slag. In some cases the plasma stage may follow on from a
INNOVATION FOR Clean- Alternate renewable energy.
(Pyrolyzers) A non-conventional, Co-Generation, Renewable energy source, a
Green Project receiving backing & Subsidies from various Governments the world
over, utilizes any type of Biomass /
Municipal Solid Waste as
fuel, namely- Waste Wood, Saw dust, Furniture waste wood, Bagasse, Rice husk,
Coconut Shells, Poultry Litter, Thermocol, Waste Plastic,
Tyres, Leather, Coal
etc. Max.Output of
a single Unit- 04 Mega Watts. For higher requirements multiple Units
can be commissioned.
It is a thermo-chemical process of cracking that converts solid waste, Biomass
or coal to a low heat value (LHV) gaseous fuel called “Producer Gas”. This
producer gas is fuel for many different applications of shaft power, thermal
power or electricity in the equipment like, Internal Combustion Diesel /
Furn.Oil engines, furnaces, kilns, dryers, rolling mills and heat treatment
The equipment to be utilized is
the new generation modified version using Fluidised Circulating Bed Updraft
Technology Gasifier developed by consistent R&D at Bijendra to get better
viability of Gasifiers & to obtain clean, rich and consistent supply of
Producer Gas which has better calorific values (1000 -1400K.Cal/NM3)
with minimum contents of soots and smoke formed by cracking of Tar with higher
gasification efficiency and low coal consumption rate. Further Volatile
Matter contents of the coal are converted into fix carbon which on
gasification increases the Calorific Value of Gas & reduces fuel consumption and
increases the overall efficiency of gasification. Further, steam is cogenerated
& injected with the air into the Pyrolyzer which dissociates to form more of
Carbon Monoxide, resulting in increase of the calorific value of the Producer
Gas. It is then washed by venturi cyclones & multiple perforated pipe washers &
then Tar & Ash is cleaned by passing through the specially designed Tar & Dust
separators & also dehumidified to be ultra clean for injecting directly into the
I.C. Engines modified for Syn-Gas mode of operation by us.
The in-line ESP’s (Electro
static precipitators) help in total removal of tar developed in the process of
WE modify & Convert HFO /
DIESEL Engines into PRODUCER GAS / NATURAL GAS MODE of OPERATION
To operate the Power Plant, the
ULTRA-CLEAN SYN-GAS IS DIRECTLY FED INTO THE I.C. ENGINE MODIFIED & CONVERTED BY
US from HFO / DIESEL operation mode to Syn-Gas / Producer Gas / Nat.Gas mode of
operation with EXHAUST EMISSIONS WITHIN THE POLLUTION CONTROL NORMS.
Ultra clean gas is fed into the
engines with the help of a Microprocessor based, Furnace Oil to gas conversion
system developed by us. When a Variable / Surge / sudden load viz.- Furnace in a
Steel Plant, or a similar load is activated, dual-fuel mode of operation of the
engine starts automatically at 85% gas and 15% Furnace Oil /L.D.O. for a short
duration only & reverts back to 100% Gas mode when the load becomes constant.
The exhaust emissions of the
engine, can be used for a Waste Heat Recovery Boiler & 800 Kg Steam at 7kg.
pressure per MW per hr. can be obtained & also it can be put to use for other
As such, it is an extremely
viable source of non-polluting Alternative renewable energy
FEATURES & ADVANTAGES
The producer gas generated in
the Pyrolyser / Gasifier has higher Calorific Value in the range of 1000-1400
K.Cal/NM3 suitable for getting high flame temperature in the range of
1200-1400°C as required by most of the thermal processes.
in the gas by pyro-gasification is nil. The gas produced being at high
temp. has higher calorific value & as such enhances gasification efficiency and
lowers consumption of Coal/ MSW /Biomass.
There is no effluent output in
the process. The washing of gas is done with re-circulated water which
separates out the solid impurities & Tar to some extent in liquid form.
The in-line ESP’s or Electro
Static Precipitators innovated by us, help in total removal of Tar &
Ash from the gas produced during the process of pyrolysis. Tar, available
as a by product, can be sold in the market or can be used for heating/burning
in a Furnace.
Due to ultra clean gas, the
occurrence of choking of the burner filter and duct pipes is negligible,
resulting in increase in productivity and minimal cleaning interruptions in the
Extremely Low Particulates and
smoke emission, even lesser than Pollution Control board norms, due to the
complete direct firing of Producer Gas.
subsidized, environment friendly Renewable Energy technology.
Very early payback period.
Advantages of Gasifier
The Gasifier based Power Plants have a
distinct advantage over the coal fired conventional Steam/Gas Turbine Power
The conventional power plants with steam
Turbine are highly polluting as Coal / Bio-mass is burnt to fire the boiler
and toxic gases emitted in the form of smoke are highly polluting whereas in
the Gasifier based Power Plant, the Gas produced by the cracking of coal by
heat in the absence of Oxygen is fed directly into the engine after cleaning
it thoroughly & whole of the process is ecofriendly. The exhaust of the
engine or the flue gases are well within the pollution control norms.
The whole setup with the conventional
Turbines is much more expensive as compared to the Gasifier based Power Plant.
In the conventional Turbine & Boiler type
Power Plant the fuel to be used is generally Coal ONLY. Whereas in the
Gasifier type Power Plant, any type of bio-mass can be used as fuel.
The cost per unit of the Gasifier based
Power Plant after accounting for Maintenance, Operation & other over heads is
close to half the rates of the State Electricity Board rates.
The Fischer-Tropsch process is one of the advanced biofuel conversion
technologies that comprise gasification of biomass feedstocks, cleaning and
conditioning of the produced synthesis gas, and subsequent synthesis to liquid
(or gaseous) biofuels. The Fischer-Tropsch process has been known since the
1920s in Germany, but in the past it was mainly used for the production of
liquid fuels from coal or natural gas. However, the process using biomass as
feedstock is still under development. Any type of biomass can be used as a
feedstock, including woody and grassy materials and agricultural and forestry
residues. The biomass is gasified to produce synthesis gas, which is a mixture
of carbon monoxide (CO) and hydrogen (H2). Prior to synthesis, this
gas can be conditioned using the water gas shift to achieve the required H2/CO
ratio for the synthesis. The liquids produced from the syngas, which comprise
various hydrocarbon fractions, are very clean (sulphur free) straight-chain
hydrocarbons, and can be converted further to automotive fuels. Fischer-Tropsch
diesel can be produced directly, but a higher yield is achieved if first
Fischer-Tropsch wax is produced, followed by hydrocracking. Fischer-Tropsch
diesel is similar to fossil diesel with regard to a.o. its energy content,
density and viscosity and it can be blended with fossil diesel in any
proportion without the need for engine or infrastructure modifications.
Regarding some fuel characteristics, Fischer-Tropsch diesel is even more
favourable, i.e. a higher cetane number (better auto-ignition qualities) and
lower aromatic content, which results in lower NOx and particle emissions.
For the production of Fischer-Tropsch diesel the main technological
challenges are in the production of the synthesis gas (entrained flow gasifier).
These barriers also apply to other gasification-derived biofuels, i.e.
bio-methanol, bio-DME and biohydrogen. The synthesis gas is produced by a
high-temperature gasification, which is already used for coal gasification.
Biomass has different properties than coal and, therefore, several process
changes are necessary. First, the biomass pre-treatment and feeding need a
different process, because milling biomass to small particles is too
Moreover, small biomass particles can also aggregate and plug feeding
lines. Pre-treatment processes like torrefaction or pyrolysis (which produces
a liquid oil) could be developed to overcome these problems. Second, due to
the higher reactivity of biomass (compared to coal) the gasification
temperature might be decreased, resulting in higher efficiencies, but this
will require different gasification and burner design. Third, the ash
composition in biomass is different from that in coal, which results in
different ash and slag behaviour, which is an important factor in the gasifier
and still needs to be studied thoroughly. This ash and slag behaviour is also
important for the cooling of the syngas, for which innovative development is
desired. Other research topics are the cleaning and conditioning of synthesis
gas, development of several types of catalysts, and the utilisation of
by-products such as electricity, heat and steam. In Germany, a pilot
production facility for Fischer-Tropsch liquids from biomass is currently in
For more information visit www.refuel.eu
Coal Gasification by Plasma Gasification