GB2158840A - Anaerobic gas digester - Google Patents

Abstract

An apparatus for continuous fermentation or gas production comprises a series of connected tanks using non-returnable ball valves to create a continuous one-way flow of fluids and gas, main or sole operating force being the gas pressure produced within the apparatus: The tanks may have heating coils or pipes connected to solar panels. The fementation process can be applied to brewing, wine and alcohol production; or any liquid gas producing reaction. Gas pressure is used to perform functions normally done by labour, machines and pumps. The plant may transport manure from source, mix it with water to a liquid suspension, maintain suspension, and prevent sediment and crust formation; heat with solar energy; feed from an open tank continuous increments to a sealed pressurised tank for anaerobic fermentation; and create a continuous circulation and production.

Description

SPECIFICATION The respirating methane gas digester THE SPECIFICATION The specification for this invention is presented in three parts: 1. The introduction.

2. General description of the whole plant and process.

3. Detailed technical explanation.

1. INTRODUCTION This invention is developed mainly for the production of "METHANE GAS" and "NI TROGENOUS FERTILISER" from farm waste and effluent, or indeed town sewage waste, in a way that will be accepted as completely selfmotivated, fully automatic and most economically viable.

Because of the various inventive steps involved it is hoped that the "principles" of this design will surpass anything yet produced, for its novelty, simplicity and efficiency.

Making METHANE GAS from manure or effluent waste is a fairly simple and quite wellknown process. However, because it is not considered to be sufficiently economically viable it has not yet become general practice.

The reasons for this are many and varied. In order to produce the gas the solids require to be mixed with water to form a uniformly suspended slurry with an optimum solids content in the region of 10%-20%, and heated up to a temperature in the range of 80 -1 10 F.

To encourage anaerobic fermentation rather than aerobic fermentation all oxygen must be excluded from the slurry, and so it must be contained in a sealed gas-tight container or tank. During this fermentation the reagents go through at least two stages of reaction. The first one produces mainly carbon dioxide gas until all the oxygen in the reagents and water is consumed. (This produces a primary type of bacteria. This then falls in to decay and forms reagent for the METHANE GAS producing bacteria that develops at this latter stage.) Because of this it is expedient to have a predigestion stage prior to the main methane gas digester tanks. (Fig. 1. B section).

I have also proved by experience that a quantity of slurry will produce its own volume of gas in these early stages, and thus will displace itself within 24 hours. (This will later be shown to have a bearing on the size of tanks to be used in the process.) (See end of technical description).

Normally the reagents are just left in one huge tank and the gas is piped off from the top, and the reaction goes on for days or even weeks depending on the solids content of the slurry. During this fermentation, particularly at the commencement, there is considerable crust and sediment formation in the tank unless provision is made for agitation. Eventually the whole mass has to be emptied out and replaced by fresh reagent for further production.

From the above it can be appreciated that there is a lot of work to be done, either by manual labour or motorised mechanical means. All this involves expense and thus detracts from a profit potential.

In this proposed design or invention, instead of the usual idea of gathering vast quantities of slurry into huge tanks containing thousands of gallons, (which create all the ensuing problems of handling, mixing and pumping), this is a completely new departure by conception.

The invention and method will be based on a multi-tank system, where the tanks will be very much smaller. Thus a circulation of reagent fluids can be more readily created from tank to tank, making it possible to handle each day's production as it comes along, and the turbulence thus created will help to maintain a uniform suspension of solids. Not only will this cut out a lot of the old problems but it will open up possibilities to perform all kinds of other functions hitherto undreamed of.

When the whole system is filled with slurry it will still retain the advantages of amassing a vast quantity of slurry, which by its very collective size will be slow to cool, and at the same time large enough to provide a power strong enough to perform its own mechanical motivation.

To do this it is intended to use the gas pressure that can be developed so easily in this type of reaction, but in order to make this feasible it will be necessary to develop what can only be described as a "Reciprocating Gas Pressure Gradient". In other words, pressure must be developed and released, with as much frequancy as possible, and then liquids can be pushed and disturbed and moved, and pneumatic devices can be plugged in to work conveyor belts and agitating devices in the slurry mixing tanks.

This design has been put together so that it must perform the following functions without the use of labour or motorised mechanical assistance, as follow: a) It must feed a sealed and pressurised tank with incriments of prepared slurry in a continuous manner from an open tank, without having to open the sealed pressurised tank, unaided by a pump.

b) It must take out, and pass on, incriments of reacting slurry from this tank and pass this on to as many other similar tanks until maximum extraction of gas has been achieved, again without using pumps.

c) It must simultaneously take off quantities of gas production from all these tanks during the reaction process, again without opening or using pumps.

d) It must make use of the gas pressure thus produced to act as a motive force to perform various mechanical functions required by the whole process.

e) It must, in order to perform the above requirements, create a reciprocating gas pressure gradient.

So, with the use of "Solar Panels" and radiator heating coils in the tanks, it is hoped to provide most of the heating from the sun, and thus coupled with its own source of power it should then be considered to be more economically viable that any other process in present use.

The apparatus embodying the invention will now be described by way of example with reference to the accompanying drawings, not drawn to scale but in proportion, in which: Figure 1. Represents an outline plan of the whole apparatus as a working unit. The mixing devices, solar heating and heat conserving lagging are not shown, for simplicity.

Figure 2. is a sketch illustrating a means of translating gas pressure into power operated mechanical means to move a conveyor belt.

Figure 3 shows the optimum setting of the nylon cord N.2. to obtain maximum activity in the system.

Figure 4 is a simplified illustration of an E.M.M. unit for reference during its explanation or description.

Figure 5 is a time/volume graph lifted directly from experimental research work done by the inventor, from actual Methane Gas production details recorded in replicate experiments in July 1976, to illustrate how the system would quite substantially reduce the amount of carbon dioxide gas in the Bio-gas production, should it be manufactured by the invented apparatus herein referred to.

2. GENERAL DESCRIPTION OF THE WHOLE PLANT AND PROCESS.

With reference to the drawing Fig. 1, the whole system is made up of a large group of tanks of moderate size. The tanks are all connected together in various ways, and are divided into three main groups. Each of these three groups has its own particular purpose.

For convenience of reference, Fig. 1 will show these groups of tanks as A, B and C, and the tanks in each group will be numbered consecutively.

The tanks grouped as A will be open tanks, or at least fitted with loose-fitting lids, and be subject to atmospheric pressure. Where necessary holes will be made in the lids to admit reagents or mechanical working parts. These tanks are the mixing, refining and storage tanks where the ingredients for the slurry are put together, and accumulated, preparatory to being consumed by the next stage of the system. The A tanks will be connected together at the base with pipes of a reasonable diametre, large enough to discourage blockages and yet small enough to delay transfer while mixing and agitation take place.

A suitable form of conveyor belt, C.B. Fig.

1., will be set up to provide a continuous supply of small incriments of solids to the tank A.1. This conveyor will be powered by gas pressure (to be described later). There will also be a metered supply of water going into this tank, which will be adjusted to give a slurry of the optimum solids content to suit whatever the process demands. Tank A. 1. will have an agitator or mixing device fitted inside, and again this will be gas pressure powered (to be described more fully later). The tank A.2. will then receive a preliminary coarse mixed slurry of the required proportions from tank A. 1. through one or more open-ended tubular pipes connecting these tanks together near the base. Again the tank A.2. will be provided with agitators to maintain uniform suspension of solids, and possibly further refinement of particle size.If required, there can be several more of these A tanks, as described, should it be found necessary or convenient, to improve the quality of the slurry, prior to the preliminary digestion or fermentation which will take place in the next group of tanks, identified as the B section of Fig. 1.

The tanks of group B will be sealed and completely gas-tight up to a point well beyond what will be considered to be the mean working pressure, although this mean working pressure will probably not exceed much more than 10 p.p.s.i., even on the bigger plants of this design. This could be a good point in its favour.

The A group of tanks will be connected to the B group near to and running parallel to the base by one or more tubular pipes (of suitable diameter to discourage blockages) between the last of the A tanks and the first of the B tanks, at B. 1. There will be non-return ball valves fitted to these pipes, and these will be situated on the orifices of these pipes in a perpendicular position, or at right angles on the end of the pipe/s, inside tank B. 1. (Fig.

1. vii).

It may also be convenient to have several tanks in the B section. If so, these will be linked together near to and parallel to the base with open-ended tubular pipes (Fig. 1.), again in the line formation, as A.

As these tanks are sealed and constructed to collecte gas, and thus develop pressure, they will all be connected from one to another at the very top with gas lines or pipes (Fig. 1.

G.P. 1 8 2). The diameter of these would not need to be much greater than one inch. This will uniform the gas pressure and supply in the B section, but the circulation of liquid reagent would still be in line and forward formation.

This description of the invention now comes to a "Special Feature", and probably the most important part of this whole process.

This is where it is made possible to feed incriments of fluid reagent from an open tank,subject to atmospheric pressure, to a sealed and sometimes pressurised tank, without having to open or disturb the seal of this tank at any time.

There is situated between the last of the A tanks and B. 1., the first of the B tanks, a Ushaped tube or modified manometer. For the convenience of this description from now on it will be referred to as the ''Internal Modified Manometer", or the l.M.M. (See Fig. 1.).

This I.M.M. will again be of a suitable size or diameter so as to convey a thin liquid or slurry from the main production without encouraging blockages, and will start inside the tank B. 1., pass down to and through the base of B. 1., carry on for a length at least one and a half times as long as the height of the tanks being used, then turn quite sharply through 1 80', up to and through the base of the tank A.2. In other words, into the same tank from which the slurry passes into B.1. tank. This will then extend up to the top of the A tank and will end up with a 180 down turn as a tap above the maximum fluids level in this tank, so that any returning fluids will flow into this tank A.2.

The beginning of this l.M.M. inside B.1.

will be about four fifths of the way up the length of the B. 1. tank. This will be seen later to establish the fluids level Y (Fig. 1.) thus leaving a working space for gas. Both ends of the l.M.M. will be open-ended without valves.

(The purpose and function of the l.M.M. to be explained later).

At the top of the tank B. 1. there will be a gas outlet of similar dimensions to the other gas pipes, and from this will be derived the source of reciprocating gas pressure to provide a power source to drive the conveyor belt feeding solids into A.1. tank (Fig. 1. G.B. 3.).

Situated on the feed pipe/s in A.2. will be a back-stop ball valve or valves (Fig. 1. V.1.) which will normally hang open on a hinge.

Provision will be made to pull this closed at the required time by gas pressure. (To be described later). (Fig. 1. G.B. 1.).

Finally, with reference to the last of the B tanks, there will be an outlet (Fig. 1. 0. 1.) for reacting liquid slurry to pass into the first of the C group of tanks C. 1., which is the first of the main Methane digester tanks. This will take the form of a long vertical pipe which will commence well down inside the last of the B tanks, and pass up and through the sealed lid of this tank, up over and down into the first C tank, again through the sealed lid of the C tank. All the tanks in B 8 C sections are, of course, closed and gas-tight. This pipe in C.1., identified as D.1., will extend down to the base of the tank. Both ends of this Ushaped tube will be fitted with vertical nonreturn ball valves. The ball valve (Fig. 1. V.iii) in B.3. tank will have a float (F.1.) attached to the ball in the valve by a long nylon cord (N.2.).

The idea of this will be to check the evacuation of the fluids from B section to C section at a predetermined level in the B section, before the level of liquids gets low enough to permit the escape of gas from this section.

(Full explanation later).

The C section will comprise of as many tanks as may be required to retain the reagents moving on a day to day basis, until maximum or optimum gas extraction has been achieved. Connecting all these tanks will be inverted U-shaped pipes, (again of suitable diameter for slurry) for the transfer of slurry from tank to tank, through the tops of the tanks. The outlet ends will be short, and the inlets will be long and be fitted with nonreturn ball valves (Fig. 1. V iv). The effect of this is to take out slurry from the tops of the tanks, and put in slurry at the bottom of the tanks, thus creating some turbulance to help keep solids in uniform suspension. The outlet (0.4.) on the final tank in the C group will have to go deeper and be fitted with a float controlled ball valve (F.2. V.v.), and through this the spend reagents will be finally rejected, or some re-circulated for further use.

The gas from each of the C tanks will be vented or taken off through a modified form of external manometer, hereon to be referred to as the E.M.M. (External Modified Manometer), situated in the last of the C tanks. This again is another "Special Feature" of the invention so that further independent "Reciprocating Gas Pressure Gradients" can be produced, and will be employed as a power source for the agitators and stirring paddles in the mixing and blending stage in the A section of tanks.

All vented gases will be collected and stored in large bags (subject only to atmospheric pressure), or an appropriate gasometer from which the gas can be regulated, and used in the normal way.

It would be opportune at this point to say that because of relatively recent developments of synthetic materials such as P.V.C. and other similar plastics, and the use of various manufacturers have made of this; to produce water and sewage pipes, custom made to be non-corrosive, pressure and heat resistant, and joints that are sealed by chemical action or fusion, it is now very much more feasible to develop an invention or process such as this.

Not only is it much easier to create gas-tight conditions but it provides for the relatively inexpensive production of non-corrosive tanks, tubes and valves, strong enough to withstand the pressures produced, so that in the final reckoning it will at least be possible to market a production plant for this process at a reason- able cost in relation to the benefits it will provide.

3. DETAILED TECHNICAL EXPLANATION.

Having made a brief general description of the whole plant, we now come to a more detailed explanation as to how and why it works.

First of all it must be emphasised that in the construction and assembly of all the units so far described it is vital that where necessary all tanks, pipes and joints must be absolutely gas-tight. The whole system depends upon this. The slightest leak, pin-hole or puncture will definitely, and quite effectively, first interfere with, and then stop, the whole process as described.

This process will depend on a "Starting Up Procedure", in order to get it going; from then on it is intended to be self-motivated. To do this it will, initially, be necessary to prepare a suitable liquid reagent or slurry, and keep pouring this into the first of the A section of tanks, until all the A tanks and all the B tanks are filled. Provision must also be made to have this liquid heated up to required temperature (Preferably before it goes in). This will cut down the development time for crust formation possibilities in the B section; because as soon as the reagents are warm enough, gas production will begin, and this in itself will set the whole process in motion.

As previously mentioned, all the tanks must have heating coils or pipes which will provide heat for the system by being connected to "Solar Panels" on the roof of the building, or wherever else is convenient. Suitable lagging of sufficient thickness, such as straw bales or expanded polystyrene, should be provided to conserve the heat within the system.

As the slurry is introduced to the A. 1. tank it will flow through the other A tanks and then start to exert pressure on the ball valve (vii) in B. 1. tank, depending on the weight or specific gravity of this ball. As soon as sufficient stack height of liquid is developed in the A section to provide enough pressure (possibly only a few inches on the water guage scale) the ball will lift, and slurry will start to enter the B section in the B.1. tank.

Although these tanks are sealed, and thus air contained therein is theoretically trapped, the incoming fluids will be able to displace this air, first by way of the outlet pipe (0.1.) in the last of the B tanks, then when this is covered and water sealed, the air will continue to be displaced through the I.M.M. tube.

Because the B tanks are all connected top and bottom with tubes and pipes, this will proceed in a uniform manner until the incoming liquid attains a surface level up to the top of the l.M.M. in B.1. tanks at (Y). From this point on liquid reagent will then cascade down inside the l.M.M. tube, and will continue to do so until it is full, and level with the surface at (Y) inside the B.1. tank. Atmospheric pressure will hold this level in the part of the l.M.M. inside the A.2. tank. Further transfer of slurry or liquid from A to B will then be halted, and pockets of air will be left in all the B tanks from the surface of the liquid at (Y) upwards to the top of the tanks, and these air pockets will be trapped and have no other apparent outlet.

However, the pocket of air in B. 1. will be connected with an outlet tube to a gas-tight form of bellows (See Fig. 2.). These bellows will have a base and a lid, and will be hinged between the two at one side to form a pivot.

On the lid of these bellows will be fixed two parallel beams joined together with occasional rungs or cross-members, as with a ladder.

From the end cross-member of this, two strong nylon ropes go down to a spindle where they have previously been coiled around several times. This spindle is the drive shaft of the conveyor belt for the solids input of the system, and comes directly from, for example, the battery cages in a hen house or from any other supply of continuous manure production. The spindle rotates around an inner fixed spindle, so that with the use of a dog-type ratchet and a return coil spring, the beam on the bellows, as it rises up, due to inflation from gas pressure, will uncoil the nylon ropes. This will turn the outer spindle and cause the conveyor belt to move in a forward direction until the beam comes to a halt, when the bellows reach a stop point beyond which it cannot move.Then when the gas pressure is released, and the bellows collapse, the ropes should rewind in reverse aided by the action of the recoil spring. The conveyor belt will then be ready to move again at the next development of pressure and expansion of the bellows. Having explained this, it is necessary to go back to the point where the input flow of fluids into the B section comes to a stop, and surface levels are established at (Y). (Fig. 1.). At this stage all the tanks throughout A and B are full to a surface level at (Y), when apparently everything comes to a halt. For want of a better description it will be convenient to call this the "State of Fix", because at this point conditions are fixed preparatory to the commencement of a "Set Sequence of Events".

Presuming now that the slurry is up to a working temperature, gas production will commence and start to exert pressure on the apparently trapped pockets of air or gas. The immediate result will be the performance of the following sequence of events: 1. Gas pressure will expand and lift the pivoted lid of a small pair of bellows (G.B.1), which will pull a nylon cord and close the back-stop ball valve (V.1) situated on the outlet pipe in the A.2. tank. It is now possible to add further supplies of liquid to the A section, raising the levels in these tanks without the resultant extra pressure having any influence on the ball in the ball valve (V.2) in B. 1. tank. This is a very important thing to do as early as possible before too much pressure, or back pressure, is developed from the weight of the liquid accruing in the A section.

Otherwise any further development of gas pressure in the B.1. tank would only serve to displace liquids in reverse from B.1.#to A.2., so that whatever pressure is developed in the B section would be nullified by fluid displacement; and no desirable influences would be exerted on the remaining part of the system.

So everything would come to a halt, and the A sections would probably overflow.

2. Once this back-stop valve is shut, and held, then further development of gas pressure will expand a larger set of bellows, which, as previously described, will move a conveyor belt, and this in turn will deposit a small incriment of solid reagent material into A.1. tank, preparatory to mixing with a metered flow of water to form the required slurry.

3. The bellows will then reach a stop position, and any further gas pressure development will then be exerted on the next point of least resistance, which will be the surface of the liquids in the tanks established at (Y).

Because the float (F. 1) in the tank B.3. has now risen, the outlet ball valve at (V. iii) is now open, and further gas pressure development will now start to transfer fluids up the outlet tube (0.1) in B.3. and down the inlet tube (D.1) in C.1. tank. This will continue until sufficient liquid has been sent to the C section, to lower the level of liquids in the B section to a point where the float (F.1) in B.3.

has come down and shut the ball valve at (V.

iii) in B.3. tank. All this time, of course, the pressure in B section is leaning on the ball valve in B. 1. tank (V. ii) which by its efficiency makes all this possible.

4. Now that the float valve at (V. iii) is closed, the continuing pressure development exerts itself on the next point of least resistance, which is the maniscus of the liquids contained in the tube of the l.M.M., which by now is probably some distance lower down, at a point L (Fig. 1). This will have sent a small amount of fluid up the l.M.M. situated in the A.2. which will overflow, the fall into and blend with the contents of A.2. Pressure developement will continue until the maniscus in the l.M.M. is down the bottom at the Point Q (Fig. 1).The pressure developed or attained at this point can, of course, be predetermined according to the length or depth of the I.M.M., and if this is sufficiently high in proportion to the weight and volume of liquid contained in the A.2 section of the I.M.M., then when the maniscus turns to corner beyond 0 the A.2 part of I.M.M. will be suddenly and violently evacuated of all liquid content. All the gas then so far accumulated under pressure in the B section will follow this liquid out, and be rejected to the atmosphere (Unless collected through a box); until all, or most, of the gas pressure developed so far in the B section will be released.

5. By this time the liquid level Y in the B section will have fallen during liquid displacement to C section, which cannot return because of the non-return ball valve (V. iv) in tank C. 1. Also, the liquid in the A section will have risen to point Z because of the input of new reagents; thus a levels gradient X will have been developed between the levels Z and Y.

Because the I.M.M. is now open and evacuated of fluids, and B section has lost most or all of its pressure, the atmospheric pressure on the surface Z in the A section will initiate a flow and a refill of B section through the backstop valve (V. i), which has now fallen open because of the collapse of the pressure in the small bellows, and on through the valve (V. ii) in B. 1. This is because it is now able to displace and eject the gas via the l.M.M. from the B section to a point where the levels (Y) again attain a level at the top of the l.M.M., and thus developing a water seal, and once more a "State of Fix".

From this point the next "Sequence of Events" starts all over again, and this will continue to reciprocate "States of Fix", and ensuing "Sequences of Events" ad infinitum, as long as fresh reacting reagents are available. The two main claims have now been established, i.e.: a) It has been demonstrated how to refuel a sealed and sometimes pressurised tank without mechanical or extraneous mechanical means, and without having to open this sealed tank-by using gas pressure.

b) How to develop and make use of a pressure gradient which will reciprocate the condition by naturally occurring gas pressure.

Each time the l.M.M. performs the "Sequence of Events" as just described, an incriment of liquid reagent is passed over from the B section of the preliminary digester tanks to the C section of main digester tanks. The size and frequency of this transfer is determined by the length of the nylon cord (N.2) connecting the float (F.1) to the ball in the cage of the ball valve (V. iii). (See Fig. 1 and Fig. 3).

Therefore, in order to obtain the maximum frequency of these events, and all the other events in sequence, (and thus maximum use from this power potential), it would be logical to situate the float (F. 1) on, or near, the surface of the liquids in B section, as determined by the "State of Fix" at Y. From here, the nylon cord (N.2) should be just long enough to be holding the ball valve fully open.

From this point, the amount of travel of the ball from its stop position in the valve cage, down to its seating for the valve closed position, will be directly proportional to the distance the surface, as at Y, would have to travel down the tanks, to a lower level, before the valve closed its seating. Then, depending on the diameter of the tanks, so could the volume of the liquid transfer be calculated. It seems expedient, therefore, to restrict this amount of travel of the float and the surface level of the liquid. But, of course, the float does ot travel beyond its restrictions if the l.M.M.#establishes the surface level at Y, way beyond the length of its nylon cord. It has to wait there until the surface comes down to it, before it can move down, taking the ball valve down in the valve cage to the valve seating, in order to close the valve.From this it can be seen that the setting of the length of the nylon cord (N.2) is quite critical, and this must be calculated from the point Y down to the ball in the fully open position in the valve cage. If this is not controlled, the "Sequence of Events" could take too long to repeat itself, and the system would not get the maximum possible amount of turbulance and agitation that it otherwise could have, to help maintain a uniform suspension of solids in solution in order to discourage sediment and crust formation. (See Fig. 3).

The gas pipes (G.P. 1 and G.P. 2) are shown in the sketch (Fig. 1 ) to feed back gas production and pressure from B.3 to B.2 and from B.2 to B.1, with the pipes extended inside B.2 and B.1 to a point intended to be just below the initial working levels, as at Y.

The purpose of this is to provide some extra turbulance at surface level for discouraging crust development.

Going on now to the main digester section, represented on Fig. 1 as the C section; it has been demonstrated that this is receiving incriments of liquid reagents from the B section.

Eventually, after the performance of several "Sequence of Events" by the l.M.M., the first tank C. 1 will be filled up to a working level.

This level will be established around the orifice of the inverted outlet tube (0.2), (Fig. 1), situated near the top of the tank C. 1, and long enough to create a reasonably sized gas pocket at the top of this tank.

Because gases are more compressable than liquids, it will be possible to establish a liquids surface level in this C. 1 tank a little beyond the orifice of this inverted outlet pipe (0.2), and so trap a pocket of gas. This pipe will go up and over and down into tank C.2, through the sealed lid to form the inlet pipe D.2 inside tank C.2. This pipe goes down to the base of the tank, and is fitted with a non-return ball valve (V. iv) in the vertical position near to the base of the tank C.2; This is, of course, a replicate of tank C. 1 with outlets and inlets 0.1. and D.1. All these C tanks will be of similar pattern except the last one (C.3 in the case of this example). It will be noticed (Fig.

1) that all the non-return valves in the C tanks are identified as (V. iv), because, in fact, they are replicates.

The liquid reagents now in C.1 are producing gas and gas pressure, because the orifice 0.2 is effectively closed by a water seal, this being the surface level of the liquid in this tank. The effect of this pressure will be to push incriments of liquid, and sometimes pockets of gas, up the outlet 0.2 into D.3 and eventually into C.2 tank,until C.2 gets filled up to a working level, again as established by the length or depth of the inverted outlet 0.3.

The pattern of valves and outlet pipes and inlet pipes, as shown in tank C.1., will be repeated in as many C tanks as are required, except the last one, as previously mentioned.

The reason for this is that, as in tank B.3, the outlet is modified with another float (F.2) to form a float modified valve, and again a water seal is created in the tank to prevent gas escape through the outlet 0.4.

The next problem is how to establish a working liquid level in the last tank (in an apparently sealed tank), at a point well above what would be a naturally established lower working level which would be produced once a water seal forms above the ball valve controlled orifice on the final outlet 0.4. To explain how this is done it will be necessary to introduce and explain the use of the "External Modified Manometer" (E.M.M.). this is the second "Special Feature", and "Inventive Step" of the overall design or process. This will, from hereon, be referred to as the E.M.M. unit, and will operate from the last of the C tanks.

The purpose of the E.M.M. unit is twofold: first, to provide a means of extracting gas production from the system in a controlled manner, and will enable the design to be of as many tanks as are required. The second function of the E.M.M. unit is to create a "Reciprocating Gas Pressure Gradient"; this being so useful, and indeed necessary, for the developing pressure to lean on while it motivates the transfer of reagent fluids to the next tank, and provides some turbulance within the system for the uniform suspension of solids in solution.

To explain how the E.M.M. unit works, special reference is now made to Fig. 4. A gas outlet (1) at the top of the digester tank is connected to a long U-shaped tube, which is partially filled with ordinary water, or a thin fluid, which will not be affected by low temperatures. This tube only needs to be of quite small diameter, but must be at least half as long again as the particular tank to which it is attached. This ensures that it will create enough pressure to lift fluids above and out of that tank. On a 300 gallon tank half and inch to one inch should be quite adequate in diameter. The top of the tube that enters the top of the tank should have a good high loop on it (A) before it descends to the base of the other loop of the manometer (B) (See Fig. 4).

At the other end of this manometer is fitted a box or suitable container (4). This box should be sealed and gas tight, with a gas outlet pipe to the gasometer, well to the side and high up in the box (5).

As gas pressure develops in the digester tank pressure is exerted up the tube (1) and then (2), and manifests itself again on the surface of the liquid at (C). As the pressure increases, this maniscus in the tube (2) is pushed further and further down. If the manometer is long enough quite a good pressure will have been developed by the time the maniscus at (C) reaches the base of the manometer at (B), then, as this maniscus turns the corner into tube (3) from point (B), the liquid in this tube will be suddenly and violently ejected into the box (4), and temporarily held there as all the pressure and gas escapes.

Then the liquid falls back and reseals the manometer tube. It is now ready to develop another build-up of pressure as gas production continues.

So, gas is taken off for storage, and a pressure gradient is experienced, which will reciprocate continually as long as gas is in production. These reciprocating gas pressure gradients can each be individually employed as power sources, simply by tapping in a power take-off tube somewhere near the top, marked (P.2) in Fig. 4, and connecting this to a bellows to raise and drop a fairly long beam, which will magnify that movement of the bellows, and lift and drop agitating plungers in the mixing tanks, or turn conveyor belts, or even paddles on spindles in the open tanks.

It is important that the E.M.M. unit should exert a pressure not greater than that exerted by the l.M.M. This will encourage an in-line forward flow of reagents along and through the system.

Going back now to the problem of filling the final tank at the end of the process (Fig.

1. C.3.); as part of the starting up procedure it makes this quite possible if the gas outlet (P.2) to the E.M.M. is left open to the atmosphere until the final working liquid level in C.3 is reached. In this way all the initial air contained by all the tanks can be systematically displaced and discarded so that it does not get mixed with the gas that is stored in the gasometer. This is also a safe and easy way to purge the system of air and, of course, oxygen, which would be highly dangerous if mixed and stored with Methane Gas. Once the required working liquids level in the digester tank (C.3) has been reached the E.M.M. unit should be connected and sealed.

The whole system is now complete for reagent liquid content, and it would be an extra means of safety if gas was then released for a while to complete the oxygen purging of the system, and all pipes, before the final pipe is eventually connected to the gasometer. Assuming now, as just stated, that all tanks are now filled, and the valve at (V. v) in C.3 is now being held open by the float (F.2) on the final outlet pipe, represented by 0.4. (Fig. 1), the first incriments of "SPENT REAGENTS" will be pushed out of the system into a storage area, for further use as a fertiliser. As this continues, the level of liquid reagent in tank C.3., representing the end of the line in the system, will fall until the float (F.2) closes the ball valve (V. v), and then any further development of pressure will exert its force on the gas outlet, which is the E.M.M. unit.

When this is caused to "blow" or evacuate, then gas will be taken off and stored, and pressure in this tank will be released. The pressure in the tank behind, (C.2), will then overcome the pressure in C.3, and incriments of liquid will pass forward from C.2 to C.3. In the same way, this will happen from C. 1 to C.2, and from B.3 to C.1, and maybe all the way back to A. 1. So here will be the first inline circulation of fluid reagents from A.1 to C.3 and beyond. At this point provision is made for (if required) all or some of this to go along a return flow pipe from C.3 to A.2.

There may even be quite a short flush through the whole system, and this works wonders on any sediment and crust formation by stirring up the whole mass.

During this time, small amounts of gas will have been taken from the C section, and the E.M.M. unit will have produced reciprocating gas pressure gradients. By plugging in at the points marked P.1 and P.2 (Fig. 1), pneumatic devices will be made to work. From the time when all the A and B sections had been filled with reagent fluids the plant would have been cleaning out the hen shed, or other animal waste supplies, via the conveyor belt system, and blending this with a controlled water supply, to provide further reagent, fluids, to eventually fill the remaining part of the system, which is the C section. The system is now working and is fully operational, and completely self-motivated and automated; and should continue so unaided provided the sun shines quite often and the animals produce manure.During long periods of cold sun-less conditions, some of the gas now in storage could be used as a temporary form of heating, and this arrangement could easily be designed into the plant.

Before concluding this technical explanation, there is one very important overall factor that must now be revealed.

Going back a few years, prior to the development of this process, I did some research and experiments producing "METHANE GAS" in a sealed 40 gallon drum with 30 gallons of poultry manure slurry under very controlled conditions. All the gas production was very carefully collected and measured by volume on a daily output basis; and tests were made for quality and flamability. Production graphs were drawn, and several replicate experiments were done to prove validity of results. Similar results and curves were produced each time.

With reference to Fig. 5, it is demonstrated that there was a very vigorous production of mainly Carbon Dioxide gas in the first relatively short period of the production time.

Thereafter, the production rate tailed off towards zero at an even rate. It was during this longer and less vigorous period that the better quality, and Mainly "Methane" gas was produced.

With reference now to Fig. 1 which shows the process as a whole; it can be seen that in all probability, the most vigorous mainly Carbon Dioxide producing part of this reaction will take place in the B section of the tanks, or the preliminary digestion stage. This surge of gas production will be used and finally "DIS CARDED" by the l.M.M. The better quality mainly "METHANE GAS", however, should occur in the C section of tanks, or the main digester area, where it is separately taken off by the E.M.M. unit and "STORED FOR USE".

The plant does, therefore, to a certain extent "SEPARATE" these two main productions of gas to the benefit of the producer and consumer. This supports the earlier statement in the general description that the three groups of tanks, B and C-liave their own particular purpose.

By way of conclusion, this is a good time to draw attention to the fact that the concept of this whole idea is designed around the fact that this system should deal with each day's production of waste as it comes along. Therefore, this will govern the size of tank to be used throughout, apart from the A group which should be a little taller to accommodate the "LEVELS GRADIENT". For example, if a 500 bird hen battery unit produces X number of pounds of manure a day, and when mixed with XY gallons of water, it produces XYX number of gallons of slurry at the required solids content, then each tank must be just large enough to accommodate this amount plus a gas space area above.

The solids content percentage of the reagent fluid determines the "DWELL TIME", or total optimum period, required for reagents to produce maximum possible gas extraction. So if a solids content of say 10% gives off all possible gas extraction within say 12 days; then twelve tanks will be required of the appropriate size for the B 8 C sections. As the solids content increases it does require more dwell time.

To design a plant, therefore, to meet any particular need, it is only necessary, after determining the total daily output, to: a) Decide on the optimum solids content to use.

b) Convert this to total gallons of prepared slurry.

c) Construct tanks of this size.

d) Assemble enough tanks or units together to produce maximum or optimum extraction of gas.

This process, apart from farms and sewage works, can also be applied to any other indus- tries with gas producing liquid reagents, such as "Brewing", "Wine Making" or other "Alcohol" productions.

This system should fit in well with present day ideas for renewable energy and alternative energy.

So any potential "Manufacturer" of this plant, with a good computer, could calculate the mathematics, and produce production units at short notice, to serve anyones' purpose from 5 gallons of "Home Brew Beer" to a large "Metropolitan Sewage Works".

Claims (13)

1. The Respirating Methane Gas Digester being an apparatus to run a continuous production system for fermenting or gas producing fluid reagents, in a series of connected tanks (Fig. 1) with the use of non-returnable ball valves strategically situated to create a continuous directional one-way flow of productions of fluids and gas, substantially dependent on the "GAS PRESSURE" self-produced and developed by the system as its main and sole motivating force, without consuming any of its own products, to establish a production of maximum economy and viability.

2. The apparatus as claimed in Claim 1 wherein a means is provided for a series of "GAS PRESSURE GRADIENTS", by the use of modified manometers (I.M.M. and E.M.M.-Fig. 1), or any other suitable gas pressure valves to provide a "PUMPING MEANS" for the system, by developing and releasing incriments of gas and gas pressure in a continuous but intermittant manner during fermentation and gas production.

3. The apparatus feeds a sealed and often pressurised tank/s (B section in Fig. 1) from an open tank/s (A section in Fig. 1) subject only to atmospheric pressure, by the use of a modified internal manometer (I.M.M.) and a transfer tube (T. 1) connecting the A and B sections of tanks, which has a gas pressure controlled "BACK STOP VALVE" (V.1) in the A section of tanks, and a "NON-RETURN BALL VALVE" (V.2) in the B section of tanks, with a continuous supply of incriments of prepared fluid reagents as claimed in Claim 1 and Claim 2 without having to open the sealed tanks.

4. The apparatus as claimed in Claims 1 and 2 wherein power means is provided to drive a gas pressure engine using a set of bellows (G.B.3) and a cog and ratchet drive with ropes (Fig. 2) as an example, or any other form of gas pressure piston connected to any other means of mechanical drive to move conveyor belts (C.B. on Fig. 1) to feed the system with incriments of solid reagent, thereby automatically and continually forming a means for cleaning out systems of intensive animal or bird husbandry units, to aleviate the use of manual labour or other expense involving motorised means, as a means of selfmotivation.

5. The apparatus as claimed in Claims 1, 2 and 4 wherein means is provided as a means to motivate mechanical means such as rotating paddles or pendulum or plunger type stirrers to provide a means to mix or blend solids with liquids to form fluid reagents, using power take-off points as illustrated (P.1 and P.2 on Fig. 1 and 4) and for example a beam (Fig. 2).

6. The apparatus as claimed in Claims 1 and 2 wherein means is provided to feed incriments of fluid reagent from tank to tank throughout the system, thereby creating a regular but intermittent circulation or flow of fluids through the system without the use of mechanical pumps.

7. The apparatus as claimed in Claims 1, 2 and 6 wherein is provided a sole means for regular but intermittent amounts of turbulance of the fluid reagents in the C section of the tanks (Fig. 1), to encourage and facilitate the uniform suspension of solids in solution to discourage the formation of sediment and crust formation, to avoid the development of blockages, to maintain a good circulation throughout the system; wherein is provided a system of transfer tubes which take out incriments of fluid reagent and gases from the tops of the tanks and introduces these to the bottom of the next or succeeding tank in each case (Fig. 1+tubes 0.1 to D.1, 0.2 to D.2, 0.3 to D.3, with 0.4 being shown as the final exit for fluids. This fluid to be then either wholly or partially recirculated or rejected to a collection point for other uses.

8. The apparatus as claimed in Claim 1 wherein is provided a means of disposing of or processing or using a daily production of Bio-Mass or fluid reagents, therein avoiding the problems associated with the storage and handling of vast accumulations of materials or fluid reagents and therein working on a daily and continuous system.

9. The apparatus provides valve lifting floats (Fig. 1, F. 1), first to control the size and volume of each incriment of fluid transfer from the B section of tanks to the C section of tanks, and secondly, (Fig. 1, F.2) (and also in Fig. 3) to control the volume and size of evacuated fluids incriments from the system, and also F.2 provides a water seal to facilitate the separation and transfer or evacuation of fluids and gases from the final tank of the C section, which is the end of the system.

10. The apparatus as claimed in all previous Claims provides a means of controlling the velocity and revolutions of mechanical movements of mechanical means by adjusting the lengths of the connecting Nylon Cords (N.2 on Figs. 1 8 3 and N.3 on Figs. 1 8 4.).

11. As described in the specification, the I.M.M. unit situated in the A and B sections (Fig. 1) in using the mainly CARBON DIOX IDE production of gas in the B section of tanks, as claimed in Claims 1 and 2, evacuates this gas through a separate outlet other than the one provided by the E.M.M. unit, which evacuates only the mainly METHANE GAS content of the Bio-Gas production from the C section of tanks (Fig. 1), when the apparatus is used as a METHANE plant rather than for a alcohol production unit, thus producing a more refined or better quality "Bio Gas" than is usually produced by conventional methods. (See Fig. 5).

12. The apparatus has provision for Solar Heating to raise the temperature of the fluid reagent wherein there is little requirement for the use of the Bio-Gas being produced, or any other fuels for this purpose.

13. The apparatus as claimed in all previous Claims wherein provides for the "Absolute" extraction of gas from the reagent fluids by the provision of sufficient number of tanks in the C section of tanks, this being indirectly related to the percentage of solids in solution of the fluid reagents, and the dwell time thus required.