GB2396315A

GB2396315A - Fuel cleaning for gas fired engines

Info

Publication number: GB2396315A
Application number: GB0229593A
Authority: GB
Inventors: John Hayward
Original assignee: PRO POWER TECHNOLOGIES Ltd
Current assignee: PRO POWER TECHNOLOGIES Ltd
Priority date: 2002-12-19
Filing date: 2002-12-19
Publication date: 2004-06-23
Also published as: GB0229593D0; WO2004056450A1; AU2003292448A1

Abstract

A method of cleaning the fuel gas feed to a internal combustion engine comprises passing the fuel gas through a filter containing activated earth. Preferably the activated earth is acid treated bentonite, a type of clay. The filter may consist of a hollow container having an inlet and outlet, wherein the container is packed with activated earth. The fuel gas may be biogas derived from the decomposition of waste materials. The container may be in the form of a refillable cartridge so that the activated earth can be regenerated as required. Gas fired internal combustion engines which are run on contaminated fuel suffer from the buildup of internal deposits and corrosion. This is a particular problem with engines fuelled by biogas, e.g. from waste decomposition. By filtering the fuel via an activated earth filter, substantial improvements can be obtained.

Description

- 1 Fuel cleaning for gas fired engines This invention relates to fuel

cleaning for gas fired engines, for example reciprocating internal combustion 5 engines and gas turbine engines.

Internal combustion engines and gas turbines suffer from deterioration in performance and corrosion of their internal parts if the gaseous fuel supplied to them 10 contains impurities. This occurs, in particular, where the fuel is, or contains as a principal component, methane. Such fuels are produced, for example, by the decomposition of waste matter on landfill sites, the decomposition of sewage in water treatment plants, the 15 decomposition of manure or from one of several biogas technologies being developed. When the use of such fuels gives rise to a build up of deposits or matrices of carbon, silica and other contaminants within the engine the efficiency of the engine is compromised and the 20 output of the engine deteriorates rapidly until the engine has to be dismantled and the contaminated parts either cleaned or replaced.

The build up of significant deposits on the combustion

-2 surfaces of an engine, besides causing corrosion, reduces the power output of an engine. For instance, with an engine generating electricity the generating power can be reduced by up to 10% typically from low to 5 900Kw. Cleaning the incoming gas can eliminate these losses and allow the engine to run at full power for an extended period of time.

Whilst the build up of contaminants is often quite slow, 10 on certain sites where the levels of silica are high, severe levels of deposits can build up rapidly. One particular example is where diesel engines are used for generating electricity on landfill and sewage sites, fuelled by the methane gas generated by the 15 decomposition of the landfill waste or sewage waste. The engine operating efficiency deteriorates rapidly accompanied by erosion of the engine parts by chemical contaminants derived from the waste. Typically in such circumstances, chlorides, fluorides, silicates and 20 carbons tend to form matrices with atmospheric contaminants and corrode engine parts over short periods of time. In addition the presence of hydrogen sulphide leads to the formation of unwanted acid derivatives that can lead to severe corrosion within the engine, 25 especially where engine parts are in contact with lubricating oil.

It has been appreciated for some time that if the contaminants could be eliminated from the gas fuel feed, 30 the formation of such matrices and acidic deposits can be avoided and thus corrosion of engine parts from these sources eliminated. Up until now, this has been achieved passing the gas through either an activated carbon filter or through a compounded liquid, usually 35 water-based. Known carbon filters are reasonably efficient but their expense is such that payback times

- -3 for the installation and the carbon cartridges are long, making the use of such systems only viable where severe problems exist. The use of compounded liquid systems is quite common, but the amount of contamination removed by 5 such systems is very limited and they are considered to be largely inefficient.

We have now found that effective filtration of impurity-

containing feed gases used to fuel combustion engines 10 can be achieved simply and in a far more cost-effective fashion by the use of an activated earth filter between the gas supply and the engine itself.

Activated earth is a standard well-known commodity. It 15 generally consists of a clay-type mineral, for example bentonite, which has been treated, e.g. by exposure to one or more commercially available acids, then dried and processed into small particles with a large total surface area per unit volume of finished product. The 20 treatment creates electrostatic points within the mineral structure. It is believed that in use in gas filtration, these electrostatic points have the ability to attract various and different elements from a feed gas stream. Because these electrostatic points have 25 different properties, a wide range of contaminants can be eliminated from the gas and held captive by the activated earth.

Clearly for gas filtration, the gas needs to be passed 30 through some sort of filter structure during which it comes into contact with the activated earth. The type of structure may vary widely, but simple arrangements tend to be inexpensive and easy to maintain. For example, a filter structure for use in the present 35 invention may consist simply of a container filled with granules or similar particles of activated earth through

which the incoming contaminated gas fuel stream is passed, i.e. the container is positioned between the engine and the incoming gas supply. As the gas passes through the activated earth. the contaminants within the 5 gas are largely or wholly removed, leaving a purer gas for fuelling the engine. Such a filter structure also removes liquid contaminants and water from the contaminated gas feed and so leaves a more combustible material to fuel the engine Most conveniently, the 10 activated earth filter is presented in the form of a replaceable cartridge.

The invention preferably uses various activated earths derived from a range of mineral deposits. After mining, 15 the appropriate mineral, for example a clay such as bentonite, is treated by acidification with sulphuric acid which modifies the material to allow certain elements to be held captive within the structure of the material. The activated earths used in this invention 20 preferably are types which have particular affinity to carbons, silicas and other elements contained in the feed fuel gas. These impurities are captured as the gas runs through the activated earth filter and held captive by the activated earth, so they do not reach, and thus 25 harm, the engine. The cleaned gas then is fed into the engine as a purer more combustible material that does not contaminate the engine with corrosive or power reducing deposits.

30 After a period, the length of which depends on the levels of contaminants, usually one week to a month, the filter, e.g. a cartridge containing the activated earth, will become saturated and require changing for a new one. This may be done, for example, simply by unbolting 35 an old cartridge from the gas fuel line and inserting the new cartridge. The cartridge is usually fitted into

-5 a bypass line for the gas so that the gas can be redirected during cartridge replacement without the engine being turned off.

5 Preferably the cartridge or like container construction is one which enables the activated earth granules to be removed and disposed of so that the container can then be refilled with fresh uncontaminated activated earth granules. Suitable activated earth granules are available widely in commerce. For example the products made by Rockwell Industries of Widnes in Cheshire under the names Bleached Earth and Bentonite may be successfully used in 15 practicing the present invention.

The following example will serve to illustrate the invention: 20 EXAMPLE

A landfill site was identified, on which was located a l MW capacity generator powered by a Jenbacher 320 engine, the engine running on methane produced by the 25 decomposing household waste at the site. Analysis of the infeeed gas showed it to contain around lO ppm of siloxane. Inspection of combustion surfaces internally of the engine showed substantial deposits of siliceous material, mostly silicon dioxide. Measurement of the 30 power output revealed that despite a rated power output of l MW, the actual operating output was only 860 KW.

A filter was then inserted into the feed line to the engine, following a stripdown and cleaning of its 35 combustion surfaces. The filter consisted of a cylindrical housing of diameter 800 mm and length 400

-6 mm, which was filled with around lO Kg of Fulcat 435 or Fulcat 230(Ex Rockwell Industries). Analysis of the siloxane level in the output stream of fuel gas which constituted the infeed to the engine showed a siloxane S content of less than l ppm. The resultant clean running of the engine enabled a measured power output of l MW to be achieved and maintained for several weeks essentially unchanged.

Claims

\ -7 Claims

1. A method of cleaning the fuel gas feed to an 5 internal combustion engine which comprises passing the fuel gas through a filter, wherein the filter contains activated earth.

2. A method according to claim 1 wherein the activated 10 earth is acid treated bentonite.

3. A method according to claim 1 or 2 wherein the filter consists of a hollow container having a feed port and an outlet port, and wherein the interior of the 15 container is packed with granules of activated earth.

4. A method according to any one of claims 1 to 3 wherein the fduel gas feed is biogas derived from the decomposition of waste materials.

5. A method of operating an internal combustion engine substantially as hereinbefore described with reference to the foregoing specific example.