Engines for Biogas (GTZ, 1988, 133 p.) 10. Overview of Commercially Available Systems 10.1 Engines 10.2 Engine modification kits, other accessories 10.3 Other equipment

Engines for Biogas (GTZ, 1988, 133 p.)

10. Overview of Commercially Available Systems

10.1 Engines

Some manufacturers offer engines for the use of biogas, either diesel gas (dual fuel) or Otto types. Some manufacturers are listed below with specifications of their engines (as far as they were made available to the author) as well as some general comments.

In cases where more detailed specifications were given they will be reproduced in the appendix. Citation of manufacturers' names and specifications has only informative character and should not be regarded as advertising for any of the manufacturers.

(Data as per January 1987)

10.1.1 Smaller Engines up to 15 kW

10.1.1.1 Hirloskar Diesel Gas Engines, India

The Indian diesel engine manufacturers offer some of their standard diesel engines as diesel gas engines also.

- Basic engine type: 4-stroke diesel engine with direct injection.
- Type of modification: Addition of simple hand-controlled mixing chamber. Mounted directly to the inlet manifold. As no other modification is undertaken, the engine remains a fully functioning diesel engine with the option to utilize biogas for up to about 80% of its fuel requirements.
- Type of control: The control mechanism for diesel fuel operation is fully maintained. The biogas is manually controlled with a hand-operated valve at the biogas inlet to the mixing chamber.

Rough control of power and speed is achieved by setting the required speed at the governor lever and then opening the biogas valve to admit the allowable amount of biogas to the mixing chamber. Fine control, if not done manually by an operator, can be taken over by variations of the diesel fuel amount through the governor/ injector.

The amount of biogas admitted must however be less than the maximum possible 80% (see Chapter 5.1.4).

According to information of the company the diesel fuel control is equipped with a minimum fuel adjustment to ensure that sufficient pilot fuel is always supplied. Problems with injector nozzle overheating are said to be unknown.

Engine specification of type TV l G

(Information on other types is available from the manufacturer.)

Bore (mm)	87.5
Stroke (mm)	110
Max. speed (rpm)	2000
Min. idle speed (rpm)	750
Min. operating speed (rpm)	1200
Cooling system	water-cooled

B.H.P. (at 2000 rpm)
B.S. 649: 1958 continuous	8.7
S.F.C. at full load when fully on diesel(g/bhp-h)	176.00
S.F.C. at full load of ignition diesel when on-dual fuel (g/bhp-h)	30
Biogas requirement for dual fuel (m³/bhp-h) (15 cubic feet/bhp-h)	0.425

Biogas specification: The data are based on biogas with

- methane content: 60% Vol
- pressure: 100 mbar (± 50 mbar)
- H₂S content: no data but a value of 0.2% Vol should not be exceeded.

Engine/machine units readily available:

- engines cum electric generator, various types
- engines cum water pumps, various types.

Comments: Kirloskar diesel engines, some of which are based on models of other international manufacturers under license, are widespread in India where they apparently enjoy a goodreputation and a considerable share in the market.

Manufacturer's address:
Kirloskar Oil Engines Ltd.
Luxmanrao Kirloskar Rd.
Khadki, Pune 411003
India

10.1.1.2 Shanghai Bioenergy Engineering Co., China

The Chinese company offers a biogas Otto engine obviously modified from a standard single-cylinder diesel engine.

- Basic engine type: 4-stroke, single-cylinder Otto engine.
- Type of modification: Basic diesel singlecylinder engine modified and equipped with gas mixer (venturi), spark ignition, alternator, etc. (see Chapter 5.3).
- Type of control: no direct information available but obviously mechanical governor acting on venturi throttle valve as engine is designed to work with a generator at constant speed.

Engine specifications (as far as given in manufacturer's leaflet)

-model: S 195 DZ
-type: 4-stroke, horizontal, watercooled

- number of cylinder(s):	1
- displaced volume(l):	0.82
- speed (1/min ):	2000
- power (kW): approx	6

Biogas specifications:

- methane content min.: 70% Vol
- hydrogen content max.: 5% Vol

Engine/machine units readily available:
- engine cum electric generator with Pel = 5 kW

U=220/380V, F=50 Hz
Comments: no further information available.

Manufacturer's address:
Shanghai Bioenergy Engineering Co.
P.O. Box
Shanghai
People's Republic of China

10.1.1.3 Montgomery/Yanmar, Brazil

The Brazilian manufacturer offers smaller Otto engines for generators, pumps, etc. They are built for various fuels such as petrol, alcohol, kerosene and biogas.

- Basic engine type: 4-stroke, single-cylinder Otto engine with standing valves
- Type of modification: The housing of the original carburetor for petrol/alcohol is used to form a venturi type of mixing chamber.

Biogas is introduced through a nozzle pointing into the core of the venturi bottleneck. Timing of valves, ignition and the compression ratio remain unchanged from the basic petrol version and this
version is therefore not optimal for biogas operation.

-Type of control: mechanical speed governor with possibility for manual setting, acts on carburetor throttle valve.

Engine specifications:

- models:	R-137	R-320	R-480
-type:	4-strocke, vertical,	air-cooled	(for all models)
- number of cylinder(s):	1	1	1
- displaced volume (1):	0.14	0.32	0.48
- speed range:	n=1800.3600 1/min	(for all models)
- power (kW at n = 3 600 1/min ):
(approximately)	1.5	4.0	6.5

Biogas specifications:

- methane content:	60 . . .70% Vol
- pressure:	120 . . . 180 mbar

Engine/machine units readily available:

- Engine types R-137 and R-320 with electric generators 0.9 kW and 2.5 kW respectively
- engine types R-137 and R-320 with centrifugal pumps
- engine types R-320 and R-480 with self-priming pumps

Comments: the company has so far only sold about 300 units for biogas, mainly in Brazil. According to the company's own statement the experience is not always positive and some further developments would be required. The engine as such is of an outdated design (standing valves, excentric compression chamber), the compression ratio (about 7: 1) very low for biogas. The reliability of the magnetic ignition system could be improved. The engines, as they are designed presently, do not appear to be recommendable for continuous service but might be useful for occasional operation.

Manufacturer's address:
Cia. Yanmar
Av. Dr. Gastao Vidigal, 2001
Cx. Postal 542
Sao Paulo Bazil

In principle other small direct injection diesel engines can be used with simple modification (mixing chamber) for biogas dual fuel operation even though other manufacturers do not specifically offer biogas versions. The same is true for small Otto engines as long as they can operate on unleaded petrol. They require either a modification of their carburetor, or an adapted venturi/mixing valve. Their performance with biogas will however be significantly (up to 40%) lower than with petrol.

10.1.2 Larger Engines

10.1.2.1 C.A.S./Henkelhause-Deutz, Federal Republic of Germany

The German company specializes in the commercial modification of standard "Deutz" diesel engines into Otto gas engines for natural gas and biogases. Their air-cooled engine series range from 15 kW to 144 kW. The water-cooled series from 122 kW to 500 kW are not included here; specifcations may be obtained from the company.

-Basic engine type: 4-stroke Otto gas engine in "Deutz" module design, air-cooled. Type of modification:
-Engine block cum cylinders, crank- and camshaft, cooling and lubrication system are retained from the diesel engine version.
-Low compression (e = 11.5) pistons, cylinder heads with provision for spark plugs are mounted in exchange for the original parts of the diesel version.
-Ignition system with distributor connected via angular gear to the drive for the obsolete injector pump, ignition coil and 24-V alternator cum batteries are added.
-A suction-pressure-controlled air/gas mixing valve with butterfly throttle for the control is connected to the original air inlet manifold.
-A gas inlet control system with filter, shut-off solenoid valve, constant pressure regulation valve and suction gas pressure manometer is added.
-A separate large lubrication oil tank for extended oil exchange intervals is added.

Type of control: The company offers two types of control according to the future operation of the engine:

-mechanical control, using the original governor for the diesel injector pump. The motion of the control rack is passed on to the butterfly throttle of the gas mixing valve. The precision ("droop") is about 5 . . . 8% of the speed set at the governor lever. The mechanical control is sufficient for less sensitive isolated grids and for the drive of pumps or other machines;
- electronic control, using a magnetic pick-up to sense the engine speed from the flywheel ring gear. The speed pulse signal is transmitted to the electronic control box where the actual and the desired speeds are compared. The correcting pulse is given to the actuator which via a linkage moves the throttle in the gas mixing valve. The precision ("droop") of this unit is less than 1%, hence considerably better than the mechanical unit. The control system is made by Barber Colman, USA.

Safety devices like cut-out at overspeed, low oil pressure, low gas pressure and at too high a temperature are part of the system.

Engine and biogas specifications of naturally aspirated 4-cylinder engine (F 4 L 912): (Information on other types is available from the manufacturer.)

Rated power for continuous operation (10% overload, DIN 6271,
27 °C, 100 m above sea level,

60% ref. Humidity)	28 kW
Speed	1500 rpm
No. of cylinders	4
Cylinder arrangement in line
Bore/stroke	100/120 mm
Swept volume	3.77 l
Mean effective pressure at rated
power	5.90 bar
Mean piston speed 6.00 m/s
Fuel consumption at full load:
- natural gas	8.8 Nm³/h
- biogas	12.6 Nm³/h
Gas pressure	13-20 mbar
Max. Permissible mm H2S 0.15%
Lube oil consumption 60 g/h
Lube oil capacity	10.1 l
Direction of engine rotation anticlockwise
Heat quantities:
- radiation heat of engine 4.0kW
- heat quantity to be dissipated
in cooling air	31.1 kW
- heat quantity to be dissipated
in exhaust gas	23.5 kW
Exhaust quantity (referred to 20 °C)	160 m³/h
Exhaust temperature	460 °C
Air requirement/hour for
- cooling air	1810 m³/h
- combustion air (20 °C) 133 m³/h
Quantity of used air (70 °C) 2234 m³/h
Engine dimensions:
- length	813 mm
- width	661 mm
- height	803 mm
Weight	300 kg
Noise (measured at 1-m distance)	91 dB(A)
Power when using
- refuse dump gas	26 kW
-lean gas	24 kW

Engine machine units readily available:

- engines cum electric generator in accordance with customer's planned operation and specification.

Comments Henkelhausen/Deutz gas Otto engines enjoy a good reputation for reliability and a high service factor. Over two hundred machines are in the field, the majority for electricity generation, hence in continuous service. Biogases from waste water treatment plants, waste disposal fields and producer gas are used in about 60% of the engines; natural gas is used in about 40%.

Manufacturer's address:
G.A.S., Henkelhausen/Deutz
Hafenstrasse 5 1
D-4150 Krefeld 12
Federal Republic of Germany

10.1.2.2 Deutz MWM, Federal Republic of Germany

After the recent merger of the two large diesel and gas engine manufacturers Deutz and MWM the group offers a large range of gas engines in diesel gas (dual fuel) and gas Otto versions, from about 20 kW to 3 000 kW. The gas engines are based on standard stationary diesel engines. Specifications for the larger series with a power of more than 100 kW are not included here but can be obtained from the manufacturers.

- Basic engine type: 4-stroke Otto gas engine, vertical in line and V-type, watercooled.
- Type of modification: basically as described in Chapter 10.1.2.1 above.
- Type of control: electronic control, similar to the system described for 10.1.2.1. Manufacturer of the control system is Bosch, Federal Republic of Germany.

Engine specifications:

-models:G 227-3	G 227-4	G 227-6	G 232 V6	G 232 V8
- types:4-stroke Otto gas engines, water-cooled (for all models)

	vertical in line			V-type
-number of cylinders:	3	4	6	6	8
- displaced volume (1):	2.83	3.77	5.65	8.8	11.8
-compression ratio:	11.6:1 (for all models)
-speed(1/min):	1500/1800 (for all models)
- power (Pel in kW):	18/21	24/28	36/43	65/77	87/103

Biogas specifications:

- methane content min.: 65% Vol
- H₂S content max.: 0.1%Vol

Engine/machine units readily available:

- engine cum electric generator and heat cogeneration according to specifications of the customer
- engine cum pump or blower (for aeration ponds in waste water treatment plants)

Comments: The company has sold several thousand gas engines for natural gases and biogases worldwide. Their engines have a good reputation for reliability and a high service factor. The majority of the driven machines are electric generators, furthermore blowers, pumps and heat pumps, all in continuous service. The greater part of the group's activities lies however in the larger power range.

Manufacturer's address:
MWM Motorenwerke Mannheim
Carl-Benz-Str.
D-6800 Mannheim
Federal Republic of Germany

KHD Klöckner Humboldt Deutz A.G.
P.O. Box 800 509
D-5000 Köln-Deutz
Federal Republic of Germany

10.1.2.3 Volkswagen ( VW) do Brasil, Brazil

The Brazilian VW affiliate has developed Otto engines based on standard vehicle engines for operation with alcohol as a consequence of the Brazilian national alcohol program. Due to the increased compression ratio (e = 12) these engines are suitable for biogas operation. About 50 engines are running in vehicles with purified and compressed biogas; a few others produce electricity in stationary application.

- Basic engine type: 4-stroke Oto gas engines, vertical in line, V-type and opposed arrangement ("boxer") type.
-Type of modification: increase of compression ratio to about 12: 1 with smaller variations according to the engine type. Exchange of (alcohol) carburetor for venturi gas mixer or addition of a simple venturi onto the existing carburetor with possibility of switching back to liquid fuel.

Type of control:

- in vehicles: butterfly throttle is connected to driver's pedal as common in vehicles;
- mechanical: a separate mechanical governor (Franker) is driven by the normal V-belt and acts on the throttle valve of the gas mixer/carburetor. Precision is said to be ± 5% of set speed.

Engine specification:

- models:	318-3F	1600 (boxer)	1600 (in line)
- types: 4-stroke Otto gas engine	V-type	boxer type	in-line type
- number of cylinders:	8	4	4
- displaced volume (1):	5.2	1.6	1.6
- compression ratio:	9.5: 1	10:1	10: 1
- speed, max. (1/min):	4 000	4 000	4 000
- power, max.,
short term (kW):	100	30	40

Biogas specification: purified biogas or natural gas with methane content between 90% and 100% and a calorific value between 32 400 and 36 000 kJ/Nm³; H2S content about zero because
of intensive filtering.

Engine/machine units readily available:

- small pick-up vehicle ("Saveiro" type) with 1.6-1 engine,
- light truck (Type 6 - 140) with 5.2-1 engine,
- combi with 1.6-1 boxer engine.

Comments: The basic engines are taken from standard Otto engine series and are of proven quality. The versions for methane/ purified biogas have only recently been developed but have performed satisfactorily so far. As the engines are mainly projected for use in vehicles the speed and power output are relatively high while engine life will be around 3 000 hours. For continuous service and longer engine life speed and power will have to be reduced to 50% which the company decided to do in one larger stationary application. Engine versions for direct use of untreated biogas are so far not offered by the company but one might consider using them on an individual basis. The power will of course be further lowered according to the actual calorific
value of the untreated biogas.

Manufacturer's address:
Volkswagen do Brasil S.A.
09700 Sao Bernardo do Campo
Sao Paulo
Brazil

10.1.2.4 Ford Motor Company, Federal Republic of Germany

The German Ford affiliate offers Otto gas engines based on their standard vehicle engines.

- Basic engine type: 4-stroke Otto gas engines, vertical in-line type, water-cooled
- Type of modification: increase of compression ratio to 11: 1 for natural gases and biogas. (For LPG compression ratio remains at 8: 1 as for petrol versions.) Exchange of carburetor against gas mixing valve (Impco).

Type of control:

- mechanical: a separately mounted governor acting onto the butterfly throttle of the mixing valve;
- electronic: as described earlier under 10.1.2.1.

Engine specifications:

-models:	2274 HC	Dovergas S.1.4	Dovergas S.1.6
-type: 4-stroke vertical in-line Otto gas engine (for all models)
- number of cylinders:	4	4	6
- displaced volume (1):	1.6	4.15	6.22
-compression ratio (natural gas/LPG):	11:1/8:1 (for all models)
-speed(min-1):	1500/3000	1500	1500
-power (Pel in kW):	12/24	33	50

(Bio)gas specification:

- standard LPG, natural gas (CH₄ > 90%)
- for biogas no data available.

Engine/machine units readily available: The manufacturer supplies the engine alone while other engineering companies use the Ford engines to offer engines cum electric generators and heat cogeneration.

Comments: The basic engines are taken from standard mass production series and are of proven quality' also for stationary purposes. The majority of the engines delivered so far work on LPG and natural gas; for the use of biogas the power data given will have to be reduced by about 30%.

Manufacturer's address:
Ford Werke A.G.
Edsel Ford-Strasse
D-5000 Cologne 71
Federal Republic of Germany

In other countries refer to the local Ford representative.

10.1.2.5 Peugeot, France

The French automobile manufacturers offer gas versions of their standard vehicle engines.

-Basic engine type: 4-stroke Otto gas engine, vertical in-line and V-type, water-cooled.
-Type of modification: increase of compression ratio, exchange of carburetor against gas mixing valve.
-Type of control: electronic, similar to system described under 10.1.2.1.

Engine specifications:

-models:	2 E 1A	X N 1 P	ZN 175
-type:	4-stroke	Otto in line	4-stroke Otto V-type
-number of cylinders:	4	4	6
-displaced volume (1):	1.1	2.0	2.8
-compression ratio:	9.6:1	8.8:1	9.5:1
-speed (1/min):	3000 3000	3000
-power (Pel in kW):	20	32	48

(Bio)gas specifications:

- standard LPG and natural gas
- biogas, methane content min.: 60% Vol H₂S content max.: 0.5% Vol

Engine/machine units readily available:

- engine cum electric generator with cogeneration using the engine's waste heat.

Comments: The basic engines are taken from standard mass production series and are of proven quality. The relatively low compression ratios, while suitable for LPG, will result in a higher fuel consumption for methane gases compared to higher compressed engines. Power data given may have to be reduced by about 30% for operation with biogas.

Supplier's address (in the Federal Republic of Germany): Peugeot Motoren GmbH
Bonner Ring 17
D-5042 Erftstadt-Lechenich
Federal Republic of-Germany

In other countries refer to the local Peugeot representative.

10.2 Engine modification kits, other accessories

10.2.1 Impco Gas/Air Mixing Valves, USA

The US company has long been offering carburetion kits for the modification of Otto petrol engines into Otto gas engines. Such kits include suction pressure-controlled mixing valves with butterfly throttles, constant pressure reduction valves, adapters for manifolds and other ancillaries. Elaborate equipment for alternative dual fuel (gas/ petrol, not diesel) is available but is rather geared to vehicle use.

Originally designed for the use of LPG in vehicles, the equipment also functions for natural gas with a calorific value of not less than 37 000 kJ/m³. For gases with lower calorific values, such as biogas, special valve types can be supplied.

The gas mixing valves are offered in a variety for engines from about 10 kW up to about 500 kW. The normal gas pressure at inlet to the mixer should range from 20 . . . 50 mbar which in some cases is too high for Gobar gas-type biogas plants.

Comments: The standard Impco mixer types for high calorific value gases may produce a mixture with biogas which is too lean (l 1.3) for satisfactory performance even at fully opened gas adjustment throttle. A compensation by throttling the airflow externally before the mixer may result in a better excess air ratio value but lowers the performance and efficiency of the Otto engine because of extra reduced filling. It therefore appears recommendable to only utilize the specifically designed digester gas ("DG") types for biogases with a methane content of 60 . . . 90%. A self-modification of the valve cone in the mixing zone of the valve is not recommended.

Manufacturer's address:
Impco Carburetion Inc.
16916 Gridley Place
Cerritos, CA. 90701
USA

10.2.2 Rodagas,Brazil

The Brazilian company has developed modification kits for vehicle and stationary engines, both for Otto gas and diesel gas (dual fuel) engines. The equipment is based on kits for LPG but was also further adapted to the use of purified biogas and natural gas. The mixers are based on the venturi principle which allows adaptation to the actual calorific value of the gas more easily than in mixing ,valves as explained earlier. Other equipment like constant pressure reduction valves and ancillaries for the modification of diesel engines (dual fuel) are also available. The company participates in the Brazilian research program for the extended use of methane gases in small and large vehicles.

The various kits offered include modifi- cation kits for existing carburetors, mixers to be mounted onto carburetors, mixers with butterfly throttles in exchange for carburetors and all necessary control and safety accessories.

Comments: Even though the equipment is mainly designed for the use of compressed methane in vehicles the mixers are well suited for direct use of biogas in stationary engines also. An existing gas adjustment throttle and the possibility of exchanging or modifying the separate venturi ring (widen holes) offer the possibility to adapt the mixers to low calorific biogases.

Manufacturer's address:
Rodagás
Rua Campante 713/721
(04224 Ipiranga)
Sao Paulo
Brazil

10.2.3 Kromschröder Gas Handling Accessories,
Federal Republic of Germany

The company supplies a variety of equipment for handling of different types of gases. In the field of biogas as a fuel for engines the following selection from their program is particularly useful:

Filters, gas governors, ball valves, safety valves, butterfly valves, magnetic relief valves, pressure switches, flow meters, pressure gauges, fittings and others.

The equipment meets DIN and other international standards. Most of the equipment is resistant to H₂S corrosion, but a gas specification should be sent with enquiries.

Comments: Many suppliers of biogas engines use Kromschröder equipment for their gas preparation and control and have expressed their satisfaction with the quality of the products.

Manufacturer's address:
Kromschröder A.G.
P.O. Box 2809
D-4500 Osnabrück
Federal Republic of Germany

10.3 Other equipment

10.3.1 Barber Colman Electronic Control System, USA

The company offers complete electronic control systems with speed pick-up, electronic control box and actuator. Speed precision is very high, with tolerances as low as 0%. The control system is suitable for grid parallel operation of engine-generator sets.

Comments: The system is widely used in cases where electricity generation with a high degree of frequency stability is required. Under difficult conditions in terms of service and spare part availability, however, a mechanical governor should be preferred if the operation allows slight engine speed fluctuations.

Manufacturer's address:
Barber Colman Company
Precision Dynamics Division
1354, Clifford Ave.
P.O.Box 2940
Loves Park, IL.61132-2940
USA

10.3.2 Fiat Totem, Italy

The company supplies compact cogeneratior units in a standard module version for 15 kW electric power and a heat supply of about 30 kW. The unit is equipped with automatic control and suitable for isolated and grid parallel operation. The cost of the system (about US$ 1 500) is only justified when heat and power are fully utilized. The engine i based on a standard Fiat (127) Otto vehicle type engine. The company has supplied unit for natural gas and biogas. The system can be supplied through the local Fiat representative.

10.3.3 Communa Metall, Federal Republic of Germany

The company supplies cogeneration units in standard module versions in a range from 6 . . . 65 kW electric power combined with 15 . . . 90 kW of heat. The units are equipped with automatic control for isolated and grid parallel operation. The engines are Ford standard types, modified for natural gas and biogas. A high degree of utilization of both power and heat is necessary for economic operation.

Manufacturer's address:
Communa Metall Uhlandstr. 17
D-4900 Herford l Federal
Republic of Germany

10.3.4 Sauer und Sohn, Federal Republic of Germany

The company supplies heat pump and cogeneration units driven by gas engines, based on Ford standard engines as described earlier. It also offers ready-made heat exchangers for waste heat utilization of engines, some of which are designed for straight application to the Ford engine model series 2270, 2700, 2710, 2720.

Manufacturer's address:
Sauer und Sohn
P.O. Box 1240
D-6110 Dieburg
Federal Republic of Germany