A report on Bio Gasified Coupled engines

Submitted in partial fulfilment of the requirementsFor the term work of the subject

IC EnginesThird Year

Mechanical Engineering Semester V

By

Sr. No Name Roll Number1 Kevin Lobo 562 Nandu Vijay 653 Vishnu RC Vijayan 74

Mechanical EngineeringDon Bosco Institute of Technology

Kurla (West), Mumbai-702015

INDEX

Sr. No Contents Pg

No1 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

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).

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 in power 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.

BIOGASThe 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 of fossil fuels, 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

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.

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.

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.

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.

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

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 released from 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.

Gas Engine Energy Balance

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 therefore is 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.

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

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.

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 selection and evaluation of biomass gasification technologies

The following procedure is recommended for the evaluation of the feasibility of

biomass gasification technologies:

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 electric

efficiency 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 emission limits 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 field of the BIOS BIOENERGIESYSTEME GmbH

Development, comparison as well as technical and economical evaluation of different

biomass gasification technologies as a basis for the selection of an adequate technology

Planning of thermal oil systems for the internal heat supply, heat recovery and power

production based on the ORC process

Feasibility studies

Preliminary plant design

Preparation of permit applications

Detailed design, request for proposals (RFP)

Supervision of plant construction and commissioning

Plant monitoring, process and performance optimization

FIELD OF APPLICATION

The industrial waste heat utilisation is especially relevant for industrial processes with

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)

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)

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