GB2056480A - Producer gas apparatus - Google Patents

Abstract

Apparatus for producing producer gas which includes a storage chamber 10 for the fuel which may be particulate wood, mealie cobs or coconut husks, a combustion zone 14 located below the storage chamber and in communication with it, an air inlet passage 30 surrounding the combustion zone and in communication with it, a reduction zone 15 for reducing gases produced in the combustion zone, the reduction zone being located below the combustion zone, and an outlet 52 for the producer gas. The product gas can be passed through a solids-removing cyclone 50, a cooler 81 and a filter 90 prior to fuelling a static or mobile internal combustion engine 106. The combustion zone can be supplied with steam produced at 76 by heat exchange with the hot product gas. <IMAGE>

Description

SPECIFICATION Producer gas apparatus This invention relates to the production of producer gas and particularly to apparatus for producing such gas for use with a conventional diesel or petrol engine.

The current fuel crisis requires no elaboration.

One need only pause for a few seconds to become completely aware of the impact on everyday life of dwindling fuel supplies or spiralling fuel prices.

The fuel crisis has had a particularly pronounced effect on liquid fuels such as petrol and diesel and alternative fuel sources are being sought.

It is an object of the invention to provide improved apparatus for producing producer gas which is particularly suitable for the running of internal combustion engines.

This invention provides apparatus for producing producer gas including: a storage chamber for fuel; a combustion zone located below the storage chamber and in communication with it; an air inlet passage surrounding the combustion zone and in communication with it; a reduction zone for reducing gases produced in the combustion zone, the reduction zone being located below the combustion zone; and an outlet for producer gas.

The storage chamber will generally be provided by a cylindrical vessel, the walls of which slope to the combustion zone at an angle of no greater than 1 50 to the vertical. This is of importance when the fuel is particulate wood or the like to ensure that there is even and consistent flow of fuel to the combustion zone.

The producer gas is produced by inverted combustion. In other words, the gases produced during combustion pass downwardly through a reduction zone where they are reduced to producer gas. In one form of the apparatus, at least a portion of the combustion and reduction zones are located in an open-bottomed chamber having walls which taper inwardly to a waist and then flare outwardly to the open bottom.

Ash will be produced during the combustion and an ash collection zone may be provided below the reduction zone and separated therefrom by a grate. To minimise accumulation of ash on the grate, the grate may be adapted to be rotated.

An important feature of the invention is the fact that the air is heated prior to entering the combustion zone. The air passes through the inlet passage which surrounds the combustion zone and thereafter enters the combustion zone. Any draining of heat from the combustion zone is therefore minimised. The inlet passage may be provided with a plurality of openings which open into the combustion zone.

Further according to the invention the apparatus has an outer casing, a passage being defined between the outer casing and the storage chamber through which the producer gas passes prior to passing through the outlet. The fuel located in the storage chamber is thus heated and converted to charcoal by the action of the hot gases passing through the passage.

Means may be provided to introduce steam into the combustion zone. These means typically comprise a steam producer and a passage for carrying steam from the steam producer to the combustion zone. The steam maybe produced using heat from the producer gas.

The apparatus is particularly suitable for producing producer gas capable of running an internal combustion engine. Thus, the invention provides according to another aspect a system comprising an apparatus as described above and means for carrying the producer gas from the outlet to the inlet manifold of an internal combustion engine.

The system will generally include means to remove coarse particles from the gas and cooling means through which the producer gas passes prior to entering the inlet manifold. The coarse particle removal means is typically a cyclone for removing particulate matter from the gas. The cooling means may comprise a chamber having a series of heat exchange elements over which the gas passes to be cooled. The coarse particle removal means and cleaning means will be provided in series with the cooling means generally being downstream of the coarse particle removal means. The gas may also be caused to pass through a gas filter prior to entering the inlet manifold.

The system may also include a mixing chamber through which the producer gas passes prior to entering the inlet manifold, the mixing chamber having an inlet for air, an inlet for producer gas and an outlet leading to the inlet manifold, means for independently controlling the flow of air and producer gas to the chamber, and a gas/air mixture accelerator valve in the outlet connected to and synchronised with the carburettor accelerator linkage of the engine. The controlling means may comprise a valve on the air inlet and a valve on the producer gas inlet, the valves being independently operable from the vehicle cabin.

Brief Description of the Drawings The invention is further described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates a wood producer gas system according to the invention for use on either a motor vehicle or stationary engine; Figure 2 is a plan view in section, taken on the line 2-2 of Figure 1; Figure 3 is a similar view of the system taken on the line 3-3 of Figure 1; Figure 4 is a sectional view of means for introducing the producer gas and/or air into the inlet manifold of an internal combustion engine; Figures 5 and 6 illustrate diagrammatically two ways of using producer gas on a petrol engine; and Figures 7 and 8 illustrate two ways of using producer gas on diesel engines.

Description of a Preferred Embodiment Figures 1 to 3 illustrate a producer gas system according to the invention. The system includes a fuel storage container 10 which tapers at its lower end 12 to a combustion chamber 14. The combustion chamber tapers to a narrow waist 1 6 and thereafter flares outwardly at 1 8. Below the flared section 1 8 there is provided an ash grate 20 which is mounted in outer casing 22. The outer casing 22 surrounds the combustion chamber and storage container and forms an annular gap 24 between itself and the container 10. The fuel storage container has a spring-loaded hatch 26 fitted to its upper end. This hatch may be opened by releasing catch 28.

The angle of the tapered section 12 is no more than 1 50 to the vertical. This is an important feature to ensure that particulate fuel stored in the container 10 flows freely to the combustion zone during use of the system.

The primary air intake ring 30 surrounds the combustion chamber 10 as a pre-heating duct.

Thus, the air is heated before it is introduced into the combustion zone. This makes for more efficient combustion. Air inlet holes 32 are formed through the wall of the combustion chamber 14 and place the air intake ring 30 into communication with a combustion chamber.

The ash grate 20 is mounted below the flared section 1 8 and is rotatable by means of a handle 34. An ash hatch 36 provided at the base of the outer casing 18 is used for the removal of ash from the apparatus. The outer casing also includes an inspection lid 38.

An igniter sleeve 40 is provided in the region of the primary air intake ring 30.

Air is fed to the ring 30 through primary air intake pipe 42 which is provided with a non-return valve 44. This non-return valve prevents back flashing. A pressure fan 46 which is battery operated and used for initial starting is connected to a tee piece on one side of the back flash valve 44. Alternatively a suction fan connected to the gas outlet near the engine may be used. A damper 48 is used to control air flow into the primary air intake pipe and ring.

A dust-soot removal cyclone 50 is connected to a gas outlet 52 which is formed in the upper end of the outer casing in communication with the gap 24. The cyclone has an external sharply curved outlet bend 54 incorporating a reduced straight vertical bypass gas outlet 56 which is regulated with an air-tight valve 58. This is used during initial starting as well as when the cyclone is cleaned. The cyclone has an air-tight soot removal lid 60 at its bottom. An outlet pipe 62 extending from the cyclone passes through expansion joints 64 to a gas cooler 66. The pipe 62 has cleaning plugs 68, 70.

A water tank 72 has an outlet pipe 74 connected to a steam producer vessel 76 on the hot gas pipe 62. The steam producer vessel 76 is connected through a pipe 78 to the primary air inlet pipe 42. Water is fed from the tank 72 by means of a drop valve 80 combined with a transparent drop counting device or alternatively by means of a micro float switch.

The gas cooler is provided with heat-exchange elements 81, and gas-tight cleaning lids 82 at the bottom and gas-tight plugs 84 at the top for washing the cooler. In addition, there is provided a bottom outlet valve 86 with an internal pipe nipple extending to the desired permanent gas cleaner water level. This valve must be opened from time to time in order to drain off accumulated condensed water.

The gas which passes through the cooler 66 flows through an exit pipe 88 to a gas filter 90.

The filter has a gas-tight removable bottom section 92 and a fixed top 94. The filter media may consist of a standard filter cartridge 96.

Alternatively, the filter media may consist of sisal packed in a number of cakes or layers of cork or synthetic filter material. This filter media may be supported on a bottom mesh screen and held in place with a mesh screen pressed tightly against the top.

The gas emerging from the gas filter 90 flows through a pipe 98 which incorporates an emergency sieve 100. The gas is introduced through a mixing chamber 102 into the inlet manifold 104 of a petrol engine 106. The engine is fitted with a conventional carburettor 108 and air filter 110. Use is made of a secondary air inlet connected to air filter 110 and a shut-off valve 112 for the carburettor air, a gas control valve 114, an air control valve 1 16 and a control cable 118 which controls the operation of two ganged throttles 120 and 122.

In operation of the apparatus fuel is placed in the storage container 10 through the hatch 26.

The fuel may be wood, mealie cobs, coconut husks or the like. It is important that the fuel is dry and that it be provided in the form of blocks or chips which do not exceed 100 mm in length and 75 mm in maximum side width. For the initial starting of the gas producer it is necessary to have a layer of charcoal positioned at the base 1 8 of the combustion chamber extending to the top of the funnel section 1 5. The charcoal is lighted either from the ash hatch 36 leaving the top hatch 26 open or with a small lighted torch pushed into the centre of the combustion zone through the igniter sleeve 40 with either the fan 46 running with the ash hatch 36 and the upper hatch 26 open, or with the engine 106 running with the two hatches closed and the gas throttle partly open. It may be added in passing that the gas producer can be refuelled while the engine is running. When the engine is started on petrol the gas producer can be lighted without the starter fan.

The gas-producer system of the invention is based on the inverted reduction principle.

Combustion takes place in the combustion zone 14. This zone does extend into the funnel section 1 5. Once combustion is under way, the carbon dioxide produced in the combustion zone is optimally reduced as are the by-product gases which result from the carbonisation of the wood.

The correct size of the burning zone is of importance for the correct performance of the gasproducer and the gas-producer must be designed to suit a particular engine size.

Reduction takes place in that the gases are forced through the high temperature centre reduction zone immediately below the combustion zone in the region of the flared section 1 8 and below it. The raw producer gas flows past the bottom of the flared section 1 8 as indicated by the arrows and then upwardly through the gap 24 to the outlet 52. In the producer gas process, carbon dioxide is generated by burning charcoal in the burning or oxidation zone of the combustion chamber with air from the primary intake pipe and ring. This air on passing through the ring is heated prior to combustion. The pre-heating of the air is important and produces more efficient burning.

In the burning zone distillates such as tars and methyl-carbon acids which could bring about clogging or corrosion of engine parts, are disintegrated and rendered harmless when they pass through the glowing charcoal reducing zone.

The vacuum which exists on the gas intake pipe to the engine when the engine works, or when an over pressure is created by means of the fan 46, causes the carbon dioxide to flow downwardly through the charcoal layer and at this point the carbon dioxide is reduced to carbon monoxide.

In the reduction zone the amount of heat released is sufficient to reduce practically all the carbon dioxide to carbon monoxide. However the amount of carbon monoxide which is created depends upon a specific equilibrium between the concentrations of carbon dioxide and carbon monoxide and this in turn depends on the temperature. At 1 0000C the ratio is 99% carbon monoxide to 1% carbon dioxide. The quantity of carbon dioxide which is reduced also depends on the speed of the reaction at which the reduction process takes place. It is possible that the gas mixture can leave the reduction zone before equilibrium is reached. Thus the height of the charcoal layer is critical to the production of an equilibrium condition.Consequently special care is required by the driver of the vehicle to ensure that the height of the charcoal layer is not lowered by slag accumulating on the grate 20 for this will prevent cinder and ash from falling through the grate. Thus the grate should be cleaned regularly.

The upwardly flowing raw gas in the annular gap 24 heats the fuel in the storage vessel 10, and together with the heat produced by the combustion process itself converts the fuel into charcoal before it reaches the combustion chamber.

To increase the efficiency of the combustion and reduction process, steam may be introduced into the combustion zone at a controlled rate from the steam producer 76. The amount of steam which is added depends, inter alia, on the moisture content of the fuel.

The gas rises upwardly in the annular gap 24 at a relatively slow velocity and the separation of primary coarse dust particles at the lower part of the gas producer is thereby aided. The gas is further cleaned by the cyclone 50 and is cooled, principally in the cooler 66 from an outlet temperature of approximately 5000C to about 1 O00C before entering the filter 90.

The right-hand part of Figure 1 illustrates one way in which producer gas may be supplied through a petrol driven engine. The gas pipe 98 is fitted directly beneath the conventional carburettor 108 or through an orifice directly on the inlet manifold 104. The secondary air intake from the air filter 110 is connected to the junction point 102 which acts as a mixing chamber. The air control valve 11 6 is used to adjust the air intake to the mixing chamber and can be set as required or can be used to shut off the air supply completely.

This valve is operated from inside the vehicle by means of a Bowden cable in order to achieve the best air/gas mixture setting.

The gas control valve 114 provided in the pipe 98 immediately before joining the mixture chamber is used to shut off the gas supply completely when necessary. This may also be operated from inside the vehicle.

The valve 120 is a normal accelerator or throttle valve for the gas/air mixture which is connected to and in synchronisation with the existing accelerator valve 122 of the vehicle.

Leading from the mixing chamber is a bypass outlet 124 which is fitted with a gas-tight valve 126 and which by means of a flexible coupling is connected to a pipe terminating outside the body of the vehicle. The bypass outlet 124 is used only if the engine is started with the aid of the fan on pure gas without first starting on petrol.

The valve arrangement shown in Figure 1 is such that the vehicle's engine may be started on petrol and subsequently the engine may be run on producer gas only. The engine may be switched back to running on petrol if necessary to obtain maximum power for example on steep inclines.

The power output can also be increased, when running on a gas/air mixture, by means of a supercharger.

To enable the engine to run satisfactorily on producer gas it is necessary to advance the engine timing since the producer gas/air mixture has a lower combustion rate than a petrol/air mixture.

The advance of the engine timing ensures complete combustion of the producer gas. On the other hand the timing must not be advanced to the extent that the engine cannot run smoothly on petrol. For the best results the timing should be manually controllable by means of a Bowden cable which extends to a calibrated knob located on the console of the vehicle at a point where it is accessible to the driver.

Figure 4 illustrates an alternative and preferred mixing manifold for the air and producer gas. The air inlet 11 2 from the filter and the producer gas inlet 98 intersect in the mixing chamber 210. The amount of air entering the mixing chamber is controlled by valve 212. Valve 214 is always open except when starting and stopping the engine.

Air/producer gas mixture enters the manifold inlet 104 through pipe 21 6. Flow of this mixture is controlled by valve 21 8 which is connected to and synchronised with the carburettor accelerator linkage of the engine. When the engine runs on producer gas partially or completely the flow of air to the carburettor is restricted or stopped.

Figure 5 illustrates a purpose made shunt change over valve which is fitted below the carburettor throttle mechanism and which can be operated by the driver from his console. The valve has a port 128 which is connected to the carburettor, an air inlet 130 which is connected to the air pipe 112, a fan bypass port 132 which is similar to the port 124 of Figure 1, and a gas inlet port 134. The port 130 has an air regulator valve 1 36 and an air gas throttle 138 is used to control the passage of the gas/air mixture to the engine.

A petrol/air mixture or a gas/air mixture may be selected by means of a valve 140 which places either the port 128, or the remainder of the ports which are associated with the producer gas system, in communication with the engine manifold.

Figure 6 illustrates diagrammatically the connection system where the engine is operated purely on producer gas. The engine manifold 142 is connected to a gas pipe 144 through a gas control valve 146. An air control valve 148 is located between an air filter 1 50 and the pipe leading to the manifold 142. A throttle valve 1 52 which is operated by means of a conventional pedal mechanism 1 54 is used to control the passage of the gas/air mixture to the manifold. As in the arrangements of Figures 1 and 4, the engine is fitted with a fan bypass port 156 (similarto the fan bypass 124 of Figure 1).

Figures 7 and 8 illustrate the modifications required to use producer gas on a diesel engine.

Referring firstly to Figure 7 use is made of a twoway valve 160 which is connected to an air intake 162 and to a gas supply 1 64. As with the petrol engine the gas supply pipe 1 64 has a starter fan outlet or bypass 1 66.

The outlet port of the valve 160 terminates in a larger diameter pipe 1 68 which is connected to the engine. A secondary air intake 1 70 is connected to the pipe 1 68 which acts as a mixing chamber.

Ganged throttles 1 72 and 1 74 are connected in the air pipe 1 70 and the outlet pipe of the valve respectively. A second throttle 1 76 which functions as an air regulator is connected in the air pipe 1 70. This throttle is used to obtain the best gas/air mixture continuously and is connected by means of a Bowden cable and a calibrated lever to a convenient position in front of the driver or operator. A small diameter quick-start booster inlet pipe 1 80 with insulating valve is connected to the mixing chamber in the vicinity of the discharge end of the pipe 1 70. This is connected to a manual "quick-start" booster pump for injecting minute quantities of "quick-start" (ether) to facilitate initial starting.

The two-way valve has a handle which is movable between a first position marked "producer gas" at which the gas is applied directly to the engine and a second position marked "diesel" at which the valve admits pure air to the engine.

With the arrangement of Figure 7, for starting, the two-way valve is moved to the "diesel" position. At this position air only would be introduced into the engine. The gas producer is then ignited with the aid of the starter fan. Once the gas is produced with a satisfactory quality the air regulator valve 1 76 is set at the approximate correct position and the engine is started on 100% diesel by using the "cold starter" on the fuel pump. Thereafter the two-way valve is changed over to the position marked "producer gas". At this position the engine should run on 80% producer gas with the remaining 20% fuel required for ignition being obtained from diesel supplied by the fuel pump.The fuel pump must be adjusted prior to conversion for running on producer gas to allow for only 20% of the normal diesel output while the "cold start" setting remains at 100% output.

As the engine warms up the air mixture valve setting is adjusted to the best position by means of the calibrated lever. For starting a cold engine the auxiliary "quick start" injector pump may be used to inject "quick start" into the inlet manifold via the injection pipe 1 80.

The arrangement of Figure 8 is suitable for a producer gas conversion of a diesel engine with an external pump adjustment. The gas is admitted through a port 190 and mixed with air introduced through a port 1 92. The gas control valve 194 controls the amount of gas and an air regulator 1 96 is used to control the volume of air. A throttle 1 98 controls the passage of the gas/air mixture through a port 200 to an engine. As before, a starter fan outlet or bypass 202 is provided. With this arrangement the engine is started with the fuel pump pumping to its maximum capacity.

Subsequently the pump output is reduced so that the engine runs on 20% diesel and 80% producer gas.

A small diameter "quick start" booster inlet pipe with isolating valve is connected to the air/gas mixing pipe after the engine throttle. For starting a cold engine the auxiliary "quick start" injector pump may be used to inject "quick start" into the inlet manifold via the injection pipe.

The preceding description has been made with particular reference to wood, mealie cobs or coconut husks as the fuel used for the production of the gas. Where lignite or anthracite is used as a fuel the design and the method of operation is essentially the same as when wood is used.

However a modification to the combustion unit may be called for to facilitate the removal of slag.

In addition the gas cooling, washing and cleaning system may be enlarged.

Claims (23)

1. Apparatus for producing producer gas including: a storage chamber for fuel; a combustion zone located below the storage chamber and in communication with it; an air inlet passage surrounding the combustion zone and in communication with it; a reduction zone for reducing gases produced in the combustion zone, the reduction zone being located below the combustion zone; and an outlet for producer gas.

2. Apparatus according to claim 1 wherein the storage chamber is provided by a cylindrical vessel, the walls of which slope to the combustion zone at an angle of no greater than 150 to the vertical.

3. Apparatus according to claim 1 or claim 2 wherein at least a portion of the combustion and reduction zones are located in an open-bottomed chamber having walls which taper inwardly to a waist and then flare outwardly to the open bottom.

4. Apparatus according to any one of the preceding claims wherein the ash collection zone is provided below the reduction zone and is separated therefrom by a grate.

5. Apparatus according to claim 4 wherein the grate is adapted to be rotated to minimise accumulation of ash thereon.

6. Apparatus according to any one of the preceding claims wherein the air inlet passage is provided with a plurality of openings which open into the combustion zone.

7. Apparatus according to any one of the preceding claims having an outer casing, a passage being defined between the outer casing and the storage chamber through-which the producer gas passes prior to passing through the outlet.

8. Apparatus according to any one of the preceding claims wherein means are provided to introduce steam into the combustion zone.

9. Apparatus according to claim 8 wherein the means comprises a steam producer and a passage for carrying steam from the steam producer to the combustion zone.

10. Apparatus according to claim 8 or claim 9 wherein the steam is produced using heat from the producer gas.

11. Apparatus according to any one of the preceding claims wherein the fuel is particulate wood, mealie cobs, coconut husks or the like.

12. Apparatus according to claim 11 wherein the particulate fuel is in the form of chips or blocks which do not exceed 100 mm in length and 75 mm in maximum side width.

13. Apparatus according to any one of the preceding claims wherein the producer gas is used for running an internal combustion engine.

14. A system comprising apparatus according to any one of the preceding claims and means for carrying the producer gas from the outlet to the inlet manifold of an internal combustion engine.

1 5. A system according to claim 14 including means for removing coarse particles from the gas and cooling means through which the producer gas passes prior to entering the inlet manifold.

16. A system according to claim 15 wherein the coarse particle removal means comprises a cyclone for removing particulate matter from the producer gas.

17. A system according to claim 15 or claim 16 wherein the cooling means comprises a chamber having a series of heat exchange elements over which the producer gas passes.

18. A system according to any one of claims 15 to 17 wherein the cooling means is provided downstream of the coarse particle removal means.

19. A system according to any one of claims 14 to 18 including a gas filter through which the producer gas passes prior to entering the inlet manifold.

20. A system according to any one of the claims 14 to 1 9 including a mixing chamber through which the producer gas passes prior to entering the inlet manifold, the mixing chamber having an inlet for air, an inlet for producer gas and an outlet leading to the inlet manifold, means for independently controlling the flow of air and producer gas to the chamber, and a gas/air mixture accelerator valve in the outlet connected to and synchronised with the carburettor accelerator linkage of the engine.

21. A system according to claim 20 wherein the controlling means comprises a valve on the air inlet and a valve on the producer gas inlet.

22. Apparatus for producing producer gas substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.

23. A system of claim 14 substantially as herein described with reference to any one of Figures 1 to 8 of the accompanying drawings.