Powered Powered
Sour Gas
CHP Units
for heat and power
The AJAX engine is designed to last for decades with little maintenance and at very high levels of availability. Just imagine,
- no oil filters to change,
- 2 cheap car spark plugs on a 115kw engine,
- no timing to adjust,
- no exhaust valves
- no turbochargers
- a crankcase full of oversized bearings
- crankcase oil that lasts one to two years without changing
- bearings physically separated from the hot, acidic combustion gases.
- oil industry standard service backup
Utopia?? Don't take our word for it. Contact the UK owners and let them tell you the real life story of the AJAX powered CHP unit operating on sour gas sources. Here are the engine histories (warts and all!), beginning with the first 15kw experimental unit that started it all 7 years ago and including the Canterbury Sewage Works engine that has produced approximately 4.5million Kwh of electricity and its bearings are just nicely polished - the unit should now cruise along generating cash without engine replacement or capital requirement for 35 years with exceptionally low maintenance costs.
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AJAX 22HP (electrical output only ) 15kWe
MAXWELL HOUSE COFFEE COMPANY 1991
KRAFT GENERAL FOODS
BANBURY
OXFORDSHIRE
Contact : PETER SWANN Engineering Director
COMMENT
This was the original experimental high H2S engine in the UK, the fuel gas from a short retention time UASB digester is wet, with condensing water and 12,000-19,000ppm Hydrogen Sulphide. The flare on the site was an inefficient oxidiser of Hydrogen Sulphide and the cause of odour complaints from encroaching housing development. The AJAX engine was the subject of an environmental research programme and was shown to reduce 12,000ppm Hydrogen Sulphide to 4.7ppm at full engine output in a single pass. Further engine tuning reduced the Hydrogen Sulphide in the exhaust to 2.7ppm at the exhaust stack. A conventional exhaust stack reduced the odour level to below the odour threshold at the site boundary a few yards away.
The research findings are published in Gornall L.K. and Rippey B., 1996, Corrosion Resistant Engine for Odour Control with Electricity Generation, Water Research, Vol 30, No.2 pp 351-356 Elsevier Science Ltd. UK .
Gas pre-treatment: Compression to 10psi.
Digester chemicals to reduce H2S - Nil
Current status: Experimental Machine (now out of service).
Downside: The lack of controls on the head temperature caused condensation and high decoking frequency (by ajax standards). Small size could not compete with the 6MW mains gas CHP unit on site. This engine proved that it is possible to generate electricity from a single cylinder two stroke low speed engine.
FARM WASTE DIGESTER 1992
BALLYNABRAGGET ROAD
WARINGSTOWN
CO ARMAGH, NORTHERN IRELAND
CLIENTS: ALAN LYTTLE /MERVYN LYTTLE
COMMENT
The fuel is a highly variable biogas from an agricultural waste digester, initially the digester was fed on pig and laying hen slurry and more recently on cattle manure with broiler hen manure. The digester was designed by Dr. Les. Gornall and works at high solids levels (c. 20- 25% TS Feedstocks) with great efficiency. The H2S level in the wet gas is variable but normally below 10,000ppm. Full heat recovery is installed to heat the digester which can operate at 6 days retention time. Head temperature control has reduced decoking frequency to the annual scheduled service.
Gas Pre-treatment: Fuel is fed from the digester at 0.125inches (3mm) of water gauge and boosted to 0.75 Bar with a small compressor.
Digester chemicals to reduce H2S - Nil
Current status: Fully Operational
Downside: Compressed Fuel Gas buffer tank was subject to occasional flooding over compressor outlet - fuel compressor internals were operated wet on occasions. Operator tilted the tank and improved the drainage significantly to solve the problem. Fuel pressure regulators need adjustment from time to time.
SOUTHERN WATER 1992
CANTERBURY SEWAGE TREATMENT WORKS
STURRY ROAD,
CANTERBURY,
KENT
After a catalogue of disasters with high speed multicylinder engines on biogas, the engineering department of Southern Water decided to test a 105kwe AJAX engine on a new digester at Canterbury Sewage Treatment Works. The H2S level is variable from 3,000 -15,000ppm.
A survey of Southern Water's sewage works indicated several good sites were available for a suitable biogas engine but none of the English, Dutch or American engines tried to date were reliable enough to warrant a repeat purchase. The AJAX was chosen after the performance of the Maxwell House experimental unit had been evaluated. A SCADA connection is fitted for remote performance monitoring, this transmits control system data to the Southern Water Engineering HQ by phone line.
Gas pre-treatment: compression to 1 Bar, conventional mechanical pressure regulator and throttle valve.
Digester chemicals to reduce H2S - Nil
Current status: Fully operational
Downside: The clutch is never used yet requires greasing. The gearbox runs warm and wastes about a kilowatt of heat. The gas supply has a regulator and variable orifice (ball valve) throttle which can jam after a digester foaming incident. Cleaning of these components is now a scheduled maintenance item and after digester foaming.
SOUTHERN WATER 1995/6
HAM HILL SEWAGE TREATMENT WORKS
SNODLAND
KENT, UK
GEORGE SCARROTT , CHIEF ENGINEER,
This is the proof of the success of the Canterbury engine installation
and the first time S.Water has repeated an order for a sour gas engine.
This engine, with a more sophisticated control and more efficient toothed
belt drive power transmission system is also fitted with a larger dry type
air intake which increases the air flow capacity thus extending the capacity
of the engine to burn weak fuel. The effect is to produce more power with
fewer components than previous installations. The engine is packaged on
a single rectangular skid with full heat recovery. 
The
installation into an ancient brick boiler house built on marshland on a
piled foundation required that the whole 25 tonne skid be floated on air
springs to provide 99% isolation of low frequency vibration from the floor.
A very efficient air starting system is also provided to reduce the generator
inrush current on autostart - also full heat recovery and a district heating
scheme for remote digester boilers are fitted.
Gas treatment: Compression to 1 Bar - Practically Green' s Digital Throttle (TM) with no compressed gas storage bottle, no regulator or mechanical throttle valve in the fuel line .
Current status: Fully Operational
Downside: New air intake is noisier than the oil-filled type but highly effective at getting air into the engine which will run even when the flare has shut down. Oil from the pressure lubricated fuel compressor can carry over to the fuel injector and bake on. This can be removed with a knife in a few minutes once every 6-10 weeks during the weekly oiling shutdown .
The engines have been extremely successful and show no corrosion problems after 4.5 million kwh of generation. Ever lower noise levels in the auxiliary systems (which can be noisier than the engine) and yet more reliability is our next goal. AJAX powered biogas fuelled chp engines will be fitted into acoustic enclosures in 1997 and digital throttles will be fitted with oil mist recovery to reduce maintenance times on the fuel injector with the goal of >10,000 hour service interval here. Guards will be fitted with quick release toggles for rapid deployment to enable belt tension to be checked quickly. Rapid belt tensioning systems will be adopted. Air compressors for starting air will be higher pressure system (120psi) and rotary screw type to reduce noise and improve efficiency.
120 kW CHP units will have two cylinder arrangements with almost silent compressed air direct to head starting.
Our goal is simply to make the AJAX the ultimate low maintenance sour gas electricity producer and to continue producing electricity at the world's lowest cost per kWh delivered - long term.
Data Sheet on Current CHP unit Production
Other AJAX Powered compressors / engines world wide - tens of thousands.
For further information contact Dr. Les. Gornall, Director
Environmental Services
Magherafelt,
BT45 6HW,
Northern Ireland, UK
Tel/Fax 01648 32615
International +44 1648 32615
email Les.Gornall@dial.pipex.com
http://www.practicallygreen.com