ALTERNATIVE FUEL FOR IC ENGINE

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ALTERNATIVE FUEL FOR IC

ENGINE

FAST PYROLYSIS OF BIOMASS TO BIOOIL FOR

GREEN POWER GENERATION

(OPEN CYCLE GAS TURBINE)

PRESENTED BY,

C.DUSHYANTH (ph no:9994545146)

T.DHIVAHAR

V.M.DHINESH(PH NO:9952893208)

2nd YEAR, B.E (SANDWICH) MECHANICAL,

(TEAM NAME: ZYROXAXIANZ)

P.S.G COLLEGE OF TECHNOLOGY,COIMBATORE-641004

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ABSTRACT

The scientific consensus on global warming is clear. If atmospheric

concentrations of greenhouse gases continue to rise thus it will prove to be a severe

threat to human society. It is also a well-established fact that combustion of fossil

fuels such as coal, oil and natural gas for power generation is a significant contributor

to global warming (1;2;3). On the other hand biomass has long been identified as an

alternate sustainable source of renewable energy.

This paper describes in detail a 'fast pyrolysis' process that has been

developed and used to convert biomass to biofuel to be used as a fuel in open cycle

gas turbine for power generation. The properties of BioOil produced from both forest

and agriculture biomass wastes will be given in detail, particularly in reference to their

application as a fuel for gas turbine engines. Economics of a combined cycle power

generation plant utilizing pyrolysis liquid (BioOil) from biomass in a gas turbine

engine is presented.The nearest term commercial application for BioOil is as clean fuel

for generating power and heat from gas turbines and boilers.

1.INTRODUCTION

Power generation using a solid fuel has had significant limitations with

respect to materials handling requirements and efficient energy conversion.

Converting biomass fuel into a liquid addresses these issues and makes possible the

use of higher efficiency combined cycle systems for power generation. 'Fast

pyrolysis' technology is a unique process that converts these solid biomass waste

materials into a relatively clean burning liquid fuel that is carbon dioxide and

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greenhouse gas (GHG) neutral.

In the sugar production process from cane approximately 30% by weight of the

crop becomes a fibrous residue referred to as bagasse. Traditionally, much of this solidwaste product has been incinerated in stationary boilers to produce steam for the

process. As bagasse contains significant quantities of silica, its application as a fuel

creates many operational problems due to a) the glazing (fouling) of spreader stoker

equipment and high temperature heat transfer surfaces and b) accelerated erosion of

steel tubing exposed to the abrasive particles in the flue gas. As a consequence,

disposal of this residue has been problematic, inefficient and expensive to the industry.

To overcome this problem we opt for fast pyrolysis of biomass to bio oil.

2. FAST PYROLYSIS' OF BIOMASS

Fast pyrolysis (more accurately defined as thermolysis) is a process in which

a material, such as biomass, is rapidly heated to high temperatures in the absence of

air (specifically oxygen). The biomass decomposes into a combination of solid

char, gas, vapors and aerosols. When cooled, most volatiles condense to a liquid

referred to as 'BioOil'. The remaining gases comprise a medium calorific value non-

condensable gas. BioOil is a liquid mixture of oxygenated compounds containing

various chemical functional groups, such as carbonyl, carboxyl and phenolic. BioOil is

made up of the following constituents: 20-25% water, 25-30% water insoluble

pyrolytic lignin, 5-12% organic acids, 5-10% non-polar hydrocarbons, 5-10%

anhydrosugars and 10-25% other oxygenated compounds.

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In this particular fast pyrolysis process, biomass feedstock is introduced into a

thermolysis reactor having a bed of inert material, such as sand, with a height to width

ratio greater than one. The biomass is shredded to sufficiently small dimensions so

that its size does not limit significantly the production of the liquid product fraction.

Simultaneous introduction of pre-heated, non-oxidizing gas at sufficient linear

velocity performs two principal functions: firstly, as a medium for fluidizing the hot

sand bed and secondly, to cause automatic elutriation of the product char from the

fluidized bed reactor. The process includes removing the elutriated char particles from

the effluent reactor stream and rapidly quenching the gas, aerosols and vapors to

produce a high conversion yield of liquid BioOil. For maximum yield of liquid, the

thermolysis reaction must take place within a period of a few seconds at temperatures

ranging from 450C to 500C. The products must then be quenched as soon as

possible to prevent cracking of the newly produced BioOil.

3. FAST PYROLYSIS HEAT AND MASS BALANCE

Feedstock for the fast pyrolysis process can be any biomass waste material

including wood by-products and agricultural wastes. Preparation includes drying the

feedstock to less than 10% moisture content to minimize the water in the BioOil and

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then grinding the feed to small particles to ensure rapid heat transfer rates in the

reactor. When processing wood-derived feedstocks the conversion yield to liquid

BioOil, solid char and non-condensable gas is approximately 70%, 15% and 15% by

weight, respectively, on an as fed basis. When processing bagasse derived feedstocks

(having ash content as high as 10% on an a dry basis), the yields are measured to be

62% BioOil, 26% char and 12% non-condensable gas. These yield rates were identical

to those determined previously in laboratory size apparatus using the same operating

conditions. The heat required for thermolysis is the total heat that must be delivered to

the reactor to provide all the sensible, radiation and reaction heat for the process to

proceed to completion. The heat of reaction for the fast pyrolysis process is marginally

endothermic. When operating the pilot plant using prepared pine/ spruce as feedstock,

the total heat requirement to produce BioOil at a 70% yield rate (including radiation

and exhaust gas losses) is approximately 2.5 MJ per kilogram of BioOil produced.

The net heat required from an external fuel source, such as natural gas, is only 1.0 MJ

per kilogram of BioOil when the non-condensable gas produced in the process is

directly injected into the reactor burner. This represents approximately 5% of the total

calorific value of the BioOil being produced.

4. BIO OIL ANALYSIS

BioOil is a dark brown liquid that is free flowing. It has a pungent smoky odor.

BioOil contains several hundred different chemicals with a wide-ranging molecular

weight distribution.

The following Table I lists the properties of BioOil produced by the

BioTherm pilot plant, derived from three different biomass feedstocks

Table I: BioOil Properties

Biomass

Feedstock

Pine/ Spruce

100% wood

Pine/ Spruce

53%wood

Bagasse

Moisture wt% 2.4 3.5 2.1

Ash Content wt% 0.42 2.6 2.9

BioOil

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PH 2.3 2.4 2.6

Water Content wt% 23.3 23.4 20.8

Lignin Content wt% 24.7 24.9 23.5

Solids Content wt% < 0.10 < 0.10 < 0.10

Ash content wt% < 0.02 < 0.02 < 0.02

Density kg/L 1.20 1.19 1.20

Calorific Value MJ/kg 16.6 16.4 15.4

Kinematic Viscosity

cSt 20C73 78 57

cSt @80C 4.3 4.4 4.0

The density of BioOil is high, approximately 1.2 kg/liter. On a volumetric

basis BioOil has 55% of the energy content of diesel oil and 40% on a weight basis.

The solids entrained in the BioOil principally contain fine char particles that

are not removed by the cyclones. As can be seen, the solids in the BioOil have been

reduced significantly to levels of approximately 0.1% by weight. The ash content in

these solids ranges from 2% to 20%, depending on the ash content in the feedstock

Table II: BioOil Composition

Feedstock Pine/ Spruce 55% wood

45% bark

Bagasse

BioOil Concentrations wt%

Water 24.3 20.8"Lignin" 24.9 23.5

Cellobiosan 1.9 -

Gl oxal 1.9 2.2Hydroxy-acetaldehyde 10.2 10.2

Levo lucosan 6.3 3.0Formaldeh de 3.0 3.4Formic acid 3.7 5.7Acetic acid 4.2 6.6Acetol 4.8 5.8

5. CURRENT BIOMASS CONVERSION TECHNOLOGIES

The most common biomass conversion technology in use today is combustion

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using either stoker fed grates or fluidized bed combustors equipped with a

water/steam cooled boiler utilizing the standard Rankine cycle for electric power

generation. Nominal conversion efficiency for this conversion technology is

approximately 21% based on simple cycle operation and biomass feed supplied at 50%

moisture. By adopting a combined cycle system using a gas turbine engine coupled to

a heat recovery steam generator (HRSG) and steam turbine, the conversion efficiency

can be increased as much as 40% more than that of a simple cycle system.

There have been four main directions of development in utilizing gas turbines for

bioenergy applications:

11 Direct Combustion: Combusting finely ground biomass in a large combustor

and expanding it directly in the turbine.

11 Indirect Combustion: Atmospheric combustion of biomass with the heat

introduced to the turbine through a heat exchanger.

11 Gasification + GT: The conversion of solid biomass to a low or medium

energy gas that is directly combusted in the gas turbine.

11 Fast Pyrolysis + GT: The conversion of biomass to a BioOil that is directly

combusted in the gas turbine.

It is this fourth option that shows significant advantages in its ability to

maintain high efficiency due to direct combustion and the added benefit in the ability

to store the fuel. The advantage of fuel storage is significant since this de-couples the

operation of the engine from the reactor, maximizing the overall availability of the

power generation plant. Downtime of the reactor will not shut down the engine

provided sufficient stores of BioOil are available for continuous operation. As well,

this also permits the economic transportation of fuel as it is in a liquid form and has

a relatively high energy density compared to solid biomass, which has a

significantly lower energy to volume ratio thus making it uneconomical to transport.

6. ECONOMIC ANALYSIS

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Although there are significant technical and logistical advantages to a fast

pyrolysis liquid fueled gas turbine system, the economics of such an installation are

also important. Budgetary numbers have been produced which show the variation in the

cost of electricity (COE) with changing feedstock costs. The flexibility of a gas turbine

installation allows for several types of configurations and for this analysis, the

three most common configurations are considered:

Simple Cycle: Gas turbine turning a generator

Combined Cycle: Configuration 1 + the exhaust heat is used to generate steam

which is expanded through a steam turbine providing more mechanical power to

produce additional electricity.

Co-generation: Configuration 1 + process steam generation for use in industry

or a plant.

The COE is calculated as the ratio of annual expenses to the amount of

energy produced in a given year. The annual expenses are a combination of operating

and maintenance costs and capital costs which are amortized over a 15-year plant

life assuming an 8% net present value. The capital cost includes all equipment to take

'as delivered' biomass and convert it to electricity at the generator terminals. For each

of the configurations, their expected heat and power outputs and efficiencies are

indicated. It is assumed that there are no additional revenues from any charcoal or

chemical products which can also be produced from the fast pyrolysis process.

Typically fast pyrolysis char comprises 15 to 20% of the feedstock, by weight. The

higher heating value is normally in the range of 24 to 28 MJ/kg. From an energy

perspective, if this char were combusted and the gases routed through the HRSG

then the steam turbine generation rate would add to the overall efficiency of thesystem.

These examples represent relatively small installations and, therefore, do

not achieve the economies of scale one would see in a larger plant. However, the

results indicate that the COE is similar to other much larger bioenergy installations.

This is the case for a 30 MWe combined cycle installation where a 20 year plant life

was assumed with an equivalent feedstock cost of 3-4 $US/tonne and the COE was

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estimated to be 0.046 $US/kWhr. As well, there is the potential to reduce the COE

further through a revenue stream from carbon credits. Although not yet clearly

established, this potential commodity could be a significant income source for such a

plant.

7. BIO OIL APPLICATION AS A FUEL IN GAS TURBINE ENGINES

As a clean fuel, BioOil has a number of environmental advantages over fossil

fuels:

CO2 / Greenhouse Gas Neutral - Because BioOil is derived from biomass

(organic waste), it is considered to be greenhouse gas neutral and can generate

carbon dioxide credits.

No SOx Emissions - As biomass does not contain sulfur, BioOil produces

virtually no SOx emissions and therefore, would not be subjected to SOx taxes.

Low NOx - BioOil fuels generate more than 50% lower NOx emissions than

diesel oil in gas turbines.

Renewable and Locally Produced - BioOil can be produced in countries

where there are large volumes of organic waste. As BioOil has unique

properties as a fuel, it requires special consideration and design

modifications. Some of these properties are presented in

Table III: Typical Properties of BioOil Compared to Diesel Fuel

A first generation fuel system and combustion system were designed and

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Parameter BioOil Diesel

Calorific Value MJ/kg 15-20 42.0

Kinematic Viscosity cSt 3 - 980 C

2 - 420 C

Acidity pH 2.3 - 3.3 5

Water wt% 20 - 25 0.05 v%

Solids wt%


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tested, demonstrating the capability to operate a 2.5 MW industrial gas turbine on

BioOil These tests not only revealed the feasibility of operation but also

demonstrated that similar performance could be achieved for BioOil and diesel.

Although CO and particulate emissions were higher than diesel, testing revealed that

NOx emissions were about half that from diesel fuel and the SO 2 emissions levels

were so low as to be undetectable by the instrumentation.

The turbine offers distinct technical advantages over other engines. Unlike

aero-derivative engines, it has been designed as an industrial engine with durability

being one of the main design criteria and not weight. In addition to the ruggedness, the

distinct "silo" type combustion system allows for easy access and modifications to the

entire combustion system, which is one of the critical systems for the adaptation of the

engine to BioOil.

COE VS COST OF FEEDSTOCK

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Figure 5: Application of Pyrolysis Oil to Gas Turbine Operation. BioOil has an energy

density approximately half of diesel fuel. Therefore, to meet the same energy input

requirement, the flow rate must be double.

Design modification

Injection system:

This requires design changes to the fuel system to be able to control higher

flow rates and also modify the fuel nozzle to accommodate this larger flow. This lower

energy density also can affect combustion since physically there must be twice as

much fuel in the combustion chamber as with diesel. This, however, is another

advantage of using an industrial engine in the fact that the combustion chambers are

designed with a significantly longer residence time (and therefore a larger volume) fora given power output. Higher viscosity of the fuel reduces the efficiency of atomization

which is critical to complete combustion. Large droplets take too long to burn. Proper

atomization is addressed in three ways.

The fuel system is designed to deliver a high-pressure flow since atomization is

improved with larger pressure drops across the fuel nozzle.

The fuel is pre-heated to lower the viscosity to acceptable levels.

The most importantly, the fuel nozzle has been redesigned to improve spray

characteristics. These design improvements are important for complete

combustion and effectively reducing CO emissions.

Water as a remedy for viscosity reduction:

Although looked at as a contaminant for diesel fuel, the water content in

BioOil has some advantages. Firstly, it is helpful in reducing the viscosity, since it

is a relatively low viscosity fluid. As well, it is a factor in lowering thermal NOx

Advanced coatings

hot corrosion


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emissions.

Material specification:

Due to its relatively low pH, material selection is also critical for all

components wetted by BioOil. This does not require the use of exotic materials,

however, it does eliminate some standard fuel system materials. Typically, 300 series

stainless steels are acceptable metallic materials and high-density polyethylene

(HDPE) or fluorinated HDPE for polymers

Turbine wash system:

The solids content is a combination of ash and char fines which have carried-

over to the liquid part of the BioOil. The effect of these solids is to cause sticking of

close tolerance surfaces and secondly, they can result in particulate emissions because

of the long residence time required to fully combust. It is important that the solids level

in the BioOil is controlled to be less than 0.1 wt%. The ash content in the fuel

represents the material that cannot be combusted. Depending on the elements in the

ash, it can result as a deposit on the hot gas path components that will reduce the

turbine efficiency. This operational problem is a familiar one with the use of low-grade

fuel oils, which also have a high ash content. The solution is a turbine wash system.

This typically consists of two separate systems in which an abrasive medium is

injected during operation to physically 'scrub' off the deposits. This allows turbine

cleaning without any downtime. The second system is an offline process which injects

a cleaning fluid and allows a soak period to loosen the deposits which are then removed

when the engine is started.

Within the ash are alkali elements, which can result in hot corrosion of the hotgas path components with sodium and potassium being the most critical elements

found in BioOil. These elements form low melting temperature compounds, which,

as a liquid, will stick to the hot gas path components and then react and corrode the

component. This effect can be mitigated through the use of fuel additives. As with the

turbine wash systems, this technology was developed for the use of heavy fuel oils in

gas turbines and has been in use for decades. The concept is to inject specific elements,

which preferentially react with the alkali metals such that they do not liquefy.


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This both reduces the propensity to stick to a surface and also reduces or

completely eliminates its rate of attack. In combination with the additives, hot section

coatings are being developed specifically for the type of attack that may be associated

with BioOil.

Ignition modification:

Due to the poor ignition characteristics of BioOil, one other key design

requirement is a BioOil specific ignition system or process. To overcome this, the

turbine system starts on diesel fuel flowing through the primary channel in the fuel

nozzle. Following a warm-up period, BioOil is fed into the secondary channel at an

increasing rate while the diesel fuel flow is reduced until 100% BioOil flow is achieved.

Polymerization is also a key issue with BioOil. This is the growing of

molecular chains, which can result in an increase in fuel viscosity. This process is

highly dependent on time and temperature. For example, the equivalent change in

properties can be achieved in 6 months at room temperature, compared to 8 hours at

90C .Therefore, as part of the fuel and combustion system design, maximum

temperatures and fuel re-circulating are carefully controlled to ensure

polymerization is maintained at a rate, which is inconsequential to engine operation.

8. GAS TURBINE DEVELOPMENT WORK

'First generation' systems and design modifications have been developed and

tested. This has demonstrated both the feasibility and significant benefits in utilizing

BioOil for the operation of a gas turbine. Efforts are now being placed on the

development of second generation designs to achieve performance and durability

levels required for commercial operation. This means providing high efficiencies,

maintaining high availability, typical time between overhauls and capital cost

comparable with current gas turbine power generating packages. Key to this work is

the use of a variety of BioOils to ensure designs accommodate as wide a range of

fuel characteristics as possible. This will maximize the applicability of the BioOil gas


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turbine system to a variety of bioenergy applications. Technically, this work is

proceeding down two main avenues:

1)Performance:

Optimization of the combustion system and the determination of the improved

engine operating and emission characteristics.

Develop and test a turbine wash system based on current systems being utilized

on the line of other Mashproekt engines.

2) Durability:

Design and test fuel system equipment and components for long term

operation with BioOil.

Develop hot section coatings specific to the BioOil combustion environment.

Develop a fuel treatment system to upgrade the fuel quality through filtering,

additives injection and alkali removal.

This work is now underway and has led to the development of a

preliminary specification for BioOil. The purpose of this specification is to define an

acceptable envelope of critical fuel parameters such that commercial level operation

can be maintained.

9. CONCLUSIONS

The use of a gas turbine utilizing pyrolysis oil (BioOil) as a renewable energy

source has many significant advantages in both its flexibility in operation and theefficiency that can be achieved. As well, the economics of this type of installation are

very competitive with other gas turbine powered bioenergy technologies and further

prove its commercial viability.

This has provided confidence in the capability of this fuel being utilized for gas

turbine applications. This work has also been key in identifying the required

development necessary for commercial level operation with the majority of the


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required technologies already developed from the use of heavy fuels in gas turbines.

Additional testing has been carried out and the development of a second-

generation gas turbine BioOil system is under way. It is sure that biooil will contribute

largely for energy generation.

10. REFERENCES

1. United Nations Development Program Global Environment Facility, Climate

Change Information Kit, http: //www. undp. org/gef/new/ccinfo .htm, updated July

1999.

2. International Energy Agency statistics on world CO2 emissions,

http://www.iea.org/stats/files/key stats/stats_98.htm, 1996.

3. Environment Canada , "The Greenhouse Gas Emissions Outlook to 2020",

http://www.ec.gc.ca/climate/fact/greenhou.html,

Global Climate Change, November 1997.

4. J. Yan, P. Alvors, L. Eidensten and G. Svedberg, "Afuture for biomass", Mechanical

Engineering, Vol.119/No. 10, Oct. 1997, pp. 94-96.

11 P. Gogolek and F. Preto, "Status and Potential of Energy from Biomass in

Canada", Proceedings of Combustion and Global Climate Change, Combustion

Canada, May 1999.

11. ENDNOTES

Ratio of electricity and heat output to BioOil energy input.

This type of similar engines are manufactured by Mashproekt in the

Ukraine who has been designing and building industrial gas turbine engines

for over 45 years and has a line of engines ranging from 2.5-25 MW. Orenda

packages these engines for various industrial needs such as power

generation, pumping and bioenergy applications.

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ALTERNATIVE FUEL FOR IC ENGINE