A small description on Bio-gasifier coupled engine

1. A report on
Bio Gasified Coupled engines
Submitted in partial fulfilment of the requirements
For the term work of the subject
IC Engines
Third Year
Mechanical Engineering
Semester V
By
Sr. No Name Roll Number
1 Kevin Lobo 56
2 Nandu Vijay 65
3 Vishnu RC Vijayan 74
Mechanical Engineering
Don Bosco Institute of Technology
Kurla (West), Mumbai-70
2015

2. INDEX
Sr.
No
Contents
Pg
No
1 ABSTRACT 3
2 INTRODUCTION 4
3 WORKING 6
4 PROCESS ZONES 8
5 LIMITATIONS 13
6 CONCLUSION 15
7 FUTURE SCOPE 16
8 REFERENCES 19

3. ABSTRACT
Modern agriculture is an extremely energy intensive process. However high agricultural
productivities and subsequently the growth of green revolution has been made possible only by
large amount of energy inputs, especially those from fossil fuels.
With recent price rise and scarcity of these fuels there has been a trend towards use of alternative
energy sources like solar, wind, geothermal etc. However these energy resources have not been
able to provide an economically viable solution for agricultural applications. One biomass energy
based system, which has been proven reliable and had been extensively used for transportation and
on farm systems during World War II is wood or biomass gasification.
Biomass gasification means incomplete combustion of biomass resulting in production of
combustible gases consisting of Carbon monoxide (CO), Hydrogen (H2) and traces of Methane
(CH4). This mixture is called producer gas. Producer gas can be used to run internal combustion
engines (both compression and spark ignition), can be used as substitute for furnace oil in direct
heat applications and can be used to produce, in an economically viable way, methanol – an
extremely attractive chemical which is useful both as fuel for heat engines as well as chemical
feedstock for industries.
Since any biomass material can undergo gasification, this process is much more attractive than
ethanol production or biogas where only selected biomass materials can produce the fuel. Besides,
there is a problem that solid wastes (available on the farm) are seldom in a form that can be readily
utilized economically e.g. Wood wastes can be used in hog fuel boiler but the equipment is
expensive and energy recovery is low.
As a result it is often advantageous to convert this waste into more readily usable fuel from like
producer gas. Hence the attractiveness of gasification. However under present conditions,
economic factors seem to provide the strongest argument of considering gasification. In many
situations where the price of petroleum fuels is high or where supplies are unreliable the biomass
gasification can provide an economically viable system – provided the suitable biomass feedstock
is easily available (as is indeed the case in agricultural systems).

4. INTRODUCTION
Bio gasified coupled engines:-
Bio means any organic matter which includes life and living organisms, including their
structure, function, growth, evolution, distribution, and taxonomy. Gasification is a process
that converts organic or fossil fuel based carbonaceous materials into carbon
monoxide, hydrogen and carbon dioxide.
Bio gasifier coupled engines is conversion of this bio or organic fuel into producer gas or
syngas fuels (fuel gas mixture consisting primarily of hydrogen, carbon monoxide, and
very often some carbon dioxide) which are coupled to engines to develop power.
These engines range inpower from 0.25 to 4 MW and run on
 Natural Gas
 Biogas
 Landfill Gas
 Coal Mine Gas
 Sewage Gas
 Combustible
 Industrial Waste Gases and Site-Specific Special Gases.

5. BIOGAS
The term "biogas" refers to gases created by the anaerobic fermentation of biological
materials. Their main constituents are methane and carbon dioxide. Considerable quantities
of biogas are produced by sludge digestion in the tanks of sewage treatment plants (sewage
gas) and anaerobic fermentation of agricultural waste and organic residues in garbage tips
(landfill gas). Since biomass is a source of energy with no net carbon dioxide emissions,
its use as a fuel can help reduce the use offossilfuels, thus helping to reduce the greenhouse
effect.
GASIFICATION
Gasification is achieved by reacting the material at high temperatures (>700 °C), without
combustion, with a controlled amount of oxygen and/or steam. The resulting gas mixture
is called syngas (from synthesis gas or synthetic gas) or producer gas and is itself a fuel.
The power derived from gasification and combustion of the resultant gas is considered to
be a source of renewable energy if the gasified compounds were obtained from biomass.
Syngas may be burned directly in gas engines, used to produce methanol and hydrogen, or
converted via the Fischer–Tropsch process (The Fischer–Tropsch process is a collection
of chemical reactions that converts a mixture of carbon monoxide and hydrogen into
liquid hydrocarbons) into synthetic fuel. Biodegradable waste and the high-temperature
process refines out corrosive ash elements such as chloride and potassium, allowing clean
gas production from otherwise problematic fuels

6. WORKING
Biogas Types
 Agricultural
 Distillery waste biogas
 MBT-AD
 Biogas from Food Waste / CHP
Biogas formation
Biogas composition
Biogas consists primarily of methane (the source of energy within the fuel) and carbon
dioxide. It also may contain small amounts of nitrogen or hydrogen. Contaminants in the
biogas can include sulphur or siloxanes, but this will depend upon the digester feedstock.

7. The relative percentages of methane and carbon dioxide in the biogas are influenced by a
number of factors including:
The ratio of carbohydrates, proteins and fats in the feedstock
The dilution factor in the digester (carbon dioxide can be absorbed by water)
GASIFICATION TECHNOLOGIES
The fuel particles in fixed bed gasifier are not moved by the gas flow and thus the fuel in
the gasifier is arranged as fixed bed. The fuel feeding of most reactors is positioned above
the fuel bed while the char coal and the ash are extracted from the bottom of the fuel bed.

8. Process Zones
Four distinct processes take place in a gasifier as the fuel makes its way to gasification.
They are:
a) Drying of fuel
b) Pyrolysis – A process in which tar and other volatiles are driven off
c) Combustion
d) Reduction – Though there is a considerable overlap of the processes, each can be
assumed to occupy a separate zone where fundamentally different chemical and thermal
reactions take place. Figure shows schematically an updraft gasifier with different zones
and their respective temperatures.

9. In the downdraft gasifier there are two types :
a) Single throat and
b) Double throat
Single throat gasifiers are mainly used for stationary applications whereas double throat
are for varying loads as well as automotive purposes.
Reaction Chemistry
The following major reactions take place in combustion and reduction zone.
Combustion zone
The combustible substance of a solid fuel is usually composed of elements carbon,
hydrogen and oxygen. In complete combustion carbon dioxide is obtained from carbon in
fuel and water is obtained from the hydrogen, usually as steam. The combustion reaction
is exothermic and yields a theoretical oxidation temperature of 14500 C14. The main
reactions, therefore, are:
C + O2 = CO2 (+ 393 MJ/kg mole)
2H2 + O2 = 2H2 O (- 242 MJ/kg mole)
Reaction zone
The products of partial combustion (water, carbon dioxide and uncombusted partially
cracked pyrolysis products) now pass through a red-hot charcoal bed where the following
reduction reactions take place.
C + CO2 = 2CO (- 164.9 MJ/kg mole)
C + H2O = CO + H2 (- 122.6 MJ/kg mole)
CO + H2O = CO + H2 (+ 42 MJ/kg mole)
C + 2H2 = CH4 (+ 75 MJ/kg mole)
CO2 + H2 = CO + H2O (- 42.3 MJ/kg mole)
Consequently the temperatures in the reduction zone are normally 800-10000 C.
Lower the reduction zone temperature (~ 700-8000 C), lower is the calorific value of gas.

10. Pyrolysis zone
Wood pyrolysis is an intricate process that is still not completely understood. The products
depend upon temperature, pressure, residence time and heat losses. However following
general remarks can be made about them. Upto the temperature of 2000 C only water is
driven off. Between 200 to 2800 C carbon dioxide, acetic acid and water are given off. The
real pyrolysis, which takes place between 280 to 5000 C, produces large quantities of tar
and gases containing carbon dioxide. Besides light tars, some methyl alcohol is also
formed. Between, 500 to 7000 C the gas production is small and contains hydrogen. Thus
it is easy to see that updraft gasifier will produce much more tar than downdraft one. In
downdraft gasifier the tars have to go through combustion and reduction zone and are
partially broken down.
The four stages of the gasification process take place in a distinguishable –
Reduction or combustion zone.
Figure: Basic process steps of a biomass gasification plant

11. Explanations: The framed rectangles show the process steps while the arrows show the
conversion stages of the fuel during the gasification. The framed rectangles below show
the different technologic options for each process step.
During the thermo-chemical biomass gasification process solid biomass is cracked by
thermal energy and a fumigator and converted into a product gas. The product gas is
cleaned and used for the production of heat and power e.g. by gas engines (biomass CHP).
The image below shows the basics of a stationary gas engine and generator used for the
production of power. It consists of four main components - the engine which is fueled by
different gases. Once the gas is burnt in the cylinders of the engine, the force turns a crank
shaft within the engine. The crank shaft turns an alternator which results in the generation
of electricity. Heat from the combustion process is releasedfrom the cylinders this must be
either recovered and used in a combined heat and power configuration or dissipated via
dump radiators located close to the engine. Finally and importantly there are advanced
control systems to facilitate robust performance of the generator.

12. Gas Engine Energy Balance

13. LIMITATIONS
Gasification is a complex and sensitive process. There exists high level of disagreement
about gasification among engineers, researchers, and manufacturers. Several
manufacturers claim that their unit can be operated on all kinds of biomass. But it is a
questionable fact as physical and chemical properties varies fuel to fuel.
Gasifiers require at least half an hour or more to start the process. Raw material is bulky
and frequent refueling is often required for continuous running of the system. Handling
residues such as ash, tarry condensates is time consuming and dirty work. Driving with
producer gas fueled vehicles requires much more and frequent attention than gasoline or
diesel fueled vehicles.
Getting the producer gas is not difficult, but obtaining in the proper state is the challenging
task. The physical and chemical properties of producer gas such as energy content, gas
composition and impurities vary time to time. All the gasifiers have fairly strict
requirements for fuel size, moisture and ash content. Inadequate fuel preparation is an
important cause of technical problems with gasifiers
Gasifier is too often thought of as simple device that can generate a combustible gas from
any biomass fuel. A hundred years of research has clearly shown that key to successful
gasification is gasifier specifically designed for a particular type of fuel. Hence, biomass
gasification technology requires hard work and tolerance.
Fixed Bed - Updraft fixed bed gasifiers
Major drawbacks are the high amounts of tar and pyrolysis products that occur because the
pyrolysis gas does not pass the hearth zone and thereforeis not combusted. This is of minor
importance if the gas is used for direct heat applications in which the tar is simply burned.
But when the gas is used for engines, extensive gas cleaning is required.

14. Fixed Bed - Downdraft fixed bed gasifiers
High amounts of ash and dust particles remain in the gas because the gas has to pass the
oxidation zone, where it collects small ash particles
Fuel requirements are relatively strict; fuel must be uniformly sized from 4 to 10 cm so as
not to block the throat and allow pyrolysis gases to flow downward and heat from the hearth
zone to flow upward; therefore, pelletization or briquetting of is often necessary.
The moisture content of the biomass must be less than 25 percent (on a wet basis).
The relatively high temperature of the exit flue gas results in lower gasification efficiency.
Fluidized bed gasifiers
High tar and dust content of the producer gas could result in problems while using the gas
in the engines.
High producer-gas temperatures, which leave alkali metals in the vapor state
Incomplete carbon burnout results in lesser energy output
Complex operation because of the need to control the supply of both air and solid fuel
Need for power consumption for the compression of the gas stream.
CONCLUSION

15. Biomass gasification offers the most attractive alternative energy system for agricultural
purposes. Most preferred fuels for gasification have been charcoal and wood. However
biomass residues are the most appropriate fuels for on-farm systems and offer the greatest
challenge to researchers and gasification system manufacturers. Very limited experience
has been gained in gasification of biomass residues.
Most extensively used and researched systems have been based on downdraft gasification.
However it appears that for fuels with high ash content fluidized bed combustion may offer
a solution. At present no reliable and economically feasible systems exist.
Biggest challenge in gasification systems lies in developing reliable and economically
cheap cooling and cleaning trains. Maximum usage of producer gas has been in driving
internal combustion engine, both for agricultural as well as for automotive uses. However
direct heat applications like grain drying etc. are very attractive for agricultural systems.
A spark ignition engine running on producer gas on an average produces 0.55-0.75 kWh
of energy from 1 kg of biomass. 8. Compression ignition (diesel) engines cannot run
completely on producer gas. Thus to produce 1 kWh of energy they consume 1 kg of
biomass and 0.07 liters of diesel. Consequently they effect 80-85% diesel saving. 9. Future
applications like methanol production, using producer gas in fuel cell and small scale
irrigation systems for developing countries offer the greatest potentialities.

16. FUTURE SCOPE
Gas engines are typically applied as stationary continuous generation units but can also
operate as peaking plants & in greenhouses to meet fluctuations in local electricity
demand. They can produce electricity in parallel with the local electricity grid, in island
mode operation, or for power generation in remote areas.
Procedure for the selectionand evaluation of biomass gasification technologies
The following procedure is recommended for the evaluation of the feasibility of
biomass gasificationtechnologies:
Technological evaluation and comparison of different biomass gasification systems –
important, since many systems are still under development and not ready to hit the market
Economical evaluation of the gasification technologies compared to a reference system
(e.g. biomass CHP plant based on combustion) – important, since a high electricefficiency
does not necessarily mean a better economic performance (investment and operation costs
have to be considered as well)
Evaluation of already available reference plants for a particular gasification technology –
important, in order to obtain information regarding reliability and availability
Verification of the emissions (exhaust gas, waste water, ash) of gasification plants
compared to expected emissionlimits and guiding values respectively – important since an
ecological operation based on economically meaningful site constraints is required
Overall evaluation of the systems based on the results of topics 1) to 4)
Working fieldof the BIOS BIOENERGIESYSTEME GmbH

17. Development, comparison as well as technical and economical evaluation of different
biomass gasification technologies as a basis for the selectionof an adequate technology
Planning of thermal oil systems for the internal heat supply, heat recovery and power
production based on the ORC process
Feasibilitystudies
Preliminaryplant design
Preparation of permit applications
Detaileddesign, request for proposals (RFP)
Supervision of plant constructionand commissioning
Plant monitoring, process and performance optimization
FIELD OF APPLICATION
The industrial waste heat utilisation is especiallyrelevant for industrial processeswith high
heat demands. This includes the following industry sectors:
 Iron and Steel industry
 Cement and building material industry
 Food and beverage processing industry
 Pulp and paper industry
 Chemical industry
 Petroleum industry
Realised projects and proposals under design
Waste heat recovery for district heat utilisation and design of pipe network / BIOCHEMIE
Kundl GmbH (Tyrol, Austria)
Waste heat recovery by flue gas condensation / Holzindustrie KAINDL (Salzburg, Austria)
Heat recovery from an existing CHP-plant / Domat (Grisons, Switzerland)

18. Heat and power production by waste heat recovery of industrial flue gas streams based on
an ORC cycle – RHI AG, Radenthein (Carinthia, Austria). Heat and power production by
waste heat recovery of industrial flue gas streams based on an ORC cycle, Wietersdorf
(Carinthia, Austria)
Heat and power production by waste heat recovery of industrial waste heat based on an
ORC cycle, Secunda (Mpumalanga, South Africa. Steam generation with waste heat from
an existing biogas plant with gas engine, Holsworthy (Devon, England)

19. References:
http://www.kogeneracija.rs/english.html
https://www.clarke-energy.com/gas-engines/
http://www.bios-bioenergy.at/en/biomass-gasification.html
https://www.google.co.in/#q=pyrolysis
www.dlbio-dryer.com/Biomass_Gassifier
www.fao.org/docrep/t4470e/t4470e0i.htm
www.nariphaltan.org/gasbook.pdf