GB2554440A

GB2554440A - Waste digester

Info

Publication number: GB2554440A
Application number: GB1616427.9A
Authority: GB
Inventors: Cooper Peter
Original assignee: Tetramec Ltd
Current assignee: Tetramec Ltd
Priority date: 2016-09-28
Filing date: 2016-09-28
Publication date: 2018-04-04
Also published as: GB201616427D0

Abstract

A waste digester 1000 comprising a retort 100 enclosing a chamber 101 to contain digesting waste, a vent 140 through the retort to enable gas produced in the chamber to exhaust the chamber, and a heat pump with a condenser 270 arranged to heat digesting waste in the chamber and an evaporator 160 located in or downstream of the vent arranged to distill a liquid from the exhausted gas. Preferably the digester comprises a plenum 150 in fluid communication with the vent wherein at least a portion of the evaporator is located within the plenum. The digester may comprise a catchment 210 for collecting the distilled liquid. The digester may comprise an agitator to agitate the digesting waste which is driven by a hydraulic motor. The agitator may rock or rotate the retort (fig 2) or may be a rotating stirrer 250. The hydraulic motor is ideally driven by the distilled liquid and comprises a wheel with at least one vane or bucket that is acted upon by the distilled liquid falling from the catchment. A method of digesting waste is also disclosed.

Description

(71) Applicant(s):

Tetramec Limited

20a High Street, GLASTONBURY, Somerset, BA6 9DU, United Kingdom (72) Inventor(s):

Peter Cooper (74) Agent and/or Address for Service:

ipconsult

21A Commercial Road, SWANAGE, Dorset, BH19 1DF, United Kingdom (51) INT CL:

B09B 3/00 (2006.01) B09B 5/00 (2006.01) (56) Documents Cited:

JP 2010046008 A KR 101229156 B

KR 19990073431 JP H11100289 (58) Field of Search:

INT CL B09B

Other: WPI, EPODOC, TXTA (54) Title of the Invention: Waste digester Abstract Title: Waste digestion machine (57) A waste digester 1000 comprising a retort 100 enclosing a chamber 101 to contain digesting waste, a vent 140 through the retort to enable gas produced in the chamber to exhaust the chamber, and a heat pump with a condenser 270 arranged to heat digesting waste in the chamber and an evaporator 160 located in or downstream of the vent arranged to distill a liquid from the exhausted gas. Preferably the digester comprises a plenum 150 in fluid communication with the vent wherein at least a portion of the evaporator is located within the plenum. The digester may comprise a catchment 210 for collecting the distilled liquid. The digester may comprise an agitator to agitate the digesting waste which is driven by a hydraulic motor. The agitator may rock or rotate the retort (fig 2) or may be a rotating stirrer 250. The hydraulic motor is ideally driven by the distilled liquid and comprises a wheel with at least one vane or bucket that is acted upon by the distilled liquid falling from the catchment. A method of digesting waste is also disclosed.

FIG. 1

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WASTE DIGESTER

Field of the Invention

This invention relates generally to a waste digester. In particular it relates to aerobic and non-aerobic digestion machines and methods for breaking down organic material to typically considered rubbish or trash for disposal.

Background

Waste digestion is a process which occurs naturally to all non-living organic material. Waste digestion includes aerobic and non-aerobic digestion. Aerobic digestion uses oxygen to break down organic material (as opposed to anaerobic digestion which carries out digestion in an oxygen free environment). Bacteria or fungi which live on oxygen act on the organic matter, breaking it down into its constituent parts. To aid the bacteria and fungi to digest waste, sophisticated enzymes have been developed. The bacteria and fungi gain energy in doing so enabling the organism to grow. As they grow they produce gases including carbon dioxide and water vapor while reducing the amount solid waste.

Prior Art

A traditional waste digester is machine comprising a chamber in a vessel in which the waste is contained whilst it is digested. The vessel ensures liquids and solids are held securely and allows any odors to be contained.

Solid organic waste is fed into one end of the trough/tube together with enzymes and an accelerant which may include water if the solid organic waste is initially very dry. An agitator is used to transport the waste along the trough/tube as it decomposes.

These traditional machines for carrying out aerobic digestion take up a lot of space and digest waste slowly.

Summary of the Invention

According to one aspect of the present invention there is a waste digester comprising: a retort enclosing a chamber to contain digesting waste; a vent through the retort enables gas to exhaust the chamber; a heat pump which includes a condenser arranged to heat digesting waste in the chamber; and an evaporator located in or downstream of the vent arranged to distill a liquid from the gas.

Advantageously a liquid which is a useful by-product of the waste digestion process is produced and the digesting waste is heated accelerates the rate of waste digestion.

Preferably the evaporator is arranged to distill water from the gas. Water vapor is typically the most plentiful gas which may be condensed from the gas. The distilled water has many uses. Other liquids are distilled to remove noxious odors from the gas vented from the chamber.

Preferably the vent channels the gas in the chamber to a plenum wherein the evaporator is located to distil the liquid.

Preferably the waste digester comprises a pressure relief valve to relieve the gas from the plenum. Advantageously the pressure relief valve provides for safety against over pressure.

Preferably the pressure relief valve has a relief pressure which is adjustable. The pressure of the gas in the plenum may be regulated by the pressure relief valve. The composition of the liquid distilled is thereby adjustable because the composition depends on the pressure during distillation.

Preferably the waste digester comprises an agitator to agitate the digesting waste within the retort. Agitating the contents in the chamber including the digesting waste mixes solid organic material, liquid, gases, enzymes and bacteria to accelerate digestion.

Preferably the agitator is arranged to agitate the retort which in turn agitates the digesting waste. Advantageously the whole retort is simply rotated to mix the digesting waste efficiently to accelerate digestion and move the waste which has been digested to the waste outlet of the retort.

Preferably the agitator comprises a stirring means within the retort to agitate the digesting waste. Advantageously the stirring means is designed specifically to mix the digesting waste efficiently and move the waste which has been digested to the waste outlet of the retort.

Preferably the waste digester comprises a hydraulic motor to operate the agitator, the motor being arranged to be driven by the distilled liquid. Advantageously the liquid which is a by-product of the waste digestion process is used to accelerate the waste digestion process.

Preferably the hydraulic motor comprises a vane or gear arranged to be driven by the distilled liquid. Advantageously the hydraulic motor is a simple mechanism.

Preferably the hydraulic motor is located below the evaporator and liquid is fed by gravity. Advantageously the gas in the chamber rises through the vent to a location above the hydraulic motor where liquid is distilled and then falls under gravity to drive the hydraulic motor.

Preferably the liquid is fed to the hydraulic motor under pressure of the gas in the plenum. Advantageously power produced by the digestion process is harnessed because the digestion process pressurizes the gas in chamber and the pressure is harnessed to efficiently drive the hydraulic motor.

Preferably there is a pressure regulation valve in the plenum to regulate the pressure in the plenum. Advantageously the distillation process rate is increased and the efficiency of the process is improved by control of the pressure provided by the digestion process.

Preferably waste digester comprises a pressure regulation valve to regulate the pressure of the gas in the chamber. Advantageously the retort is protected from over pressurization.

Preferably the plenum comprises a temperature sensor whereby the temperature of the gas inside the plenum may be regulated to adjust the composition of the distilled gas.

Preferably the waste digester comprises a catchment for a reservoir for this distilled 5 liquid located below the evaporator to capture the distilled liquid.

Preferably the catchment comprises a storage tank for the distilled liquid.

Preferably the catchment is located in the plenum. Advantageously the plenum wall serves to contain gas for distillation and to capture the liquid distilled in the catchment.

Preferably the catchment is located above the hydraulic motor. Advantageously the 10 catchment is arranged to feed the distilled liquid to the hydraulic motor under gravity.

Preferably the catchment includes a spout to direct the liquid towards the hydraulic motor. Advantageously the distilled liquid may be simply poured on the hydraulic motor comprising a water wheel.

A large amount of torque is required to turn the agitator when there is a large amount of 15 waste in the chamber because the amount of torque required corresponds to the amount of waste. A large amount of waste gives off a large amount of water vapour as it is digested. The use of the water vapour as distilled water to rotate or rock the agitator is advantageous because an amount of water is produced by the digestion process corresponding to the amount of torque required to provide the necessary torque.

Similarly, a small amount of waste in chamber needs low torque to turn agitator, but small amount of waste gives off small amount of water vapour which in turn gives lower torque to agitator.

Advantageously the hydraulic motor, whether as a water wheel or other type, is 25 provided with an amount of water corresponding to the amount of power required to turn the agitator at a rate that enhances digestion of the waste because the power required by the agitator is directly linked to the water available.

Advantageously the waste digester which distills water to drive an agitator is self-regulating, never needing more water than the waste can release.

Preferably there is a throttle in a passageway to deliver the distilled liquid from the evaporator to the hydraulic motor. Advantageously the throttle is intermediate the evaporator and the hydraulic motor to regulate flow of the liquid to the motor and thereby the speed of the motor.

Preferably the throttle is arranged receive distilled liquid poured from the spout and thereby regulate the flow rate and I or the pressure of distilled liquid which drives the hydraulic motor.

Preferably the passageway is enclosed to withstand liquid and gas pressure.

Preferably via the passageway the distilled liquid is fed from the plenum through to the hydraulic motor whereby the hydraulic motor is driven by the distilled liquid under pressure from the gas within the plenum.

Preferably the passageway includes the catchment and encloses the catchment in so the liquid and gas within the catchment is contained under the pressure of the gas in the plenum. Hence the enclosed passage provides a conduit for the pressure of the gas in the chamber to be delivered via the vent to the plenum and through to the hydraulic motor.

Preferably the enclosed passage includes a tube for channeling the liquid from the catchment to the hydraulic motor.

In high humidity ambient conditions, the efficiency of the digester could be reduced. This is due to the fact that as the incoming 'fresh' air is already loaded with moisture and it is therefore difficult for the air to carry more moisture away from the decomposing waste material.

Preferably the evaporator or portion thereof is arranged in an air duct in fluid communication with the gas inlet of the retort into the chamber. Advantageously all or part of the humid ambient air incoming into the chamber is directed across part of the evaporator and condenses out moisture. The incoming air enters the chamber as 'dry' air where it would be able to efficiently absorb water from the waste material.

Advantageously the heat taken out of the incoming humid air by the evaporator (through the heat pump) goes straight into the waste material and is not be wasted.

Advantageously moisture removed from the incoming humid air is preferably used to power the hydraulic motor which powers the agitator.

Advantageously the moisture from the digesting waste is removed efficiently because ‘dry’ air incomes into the chamber. Hence the moisture removal for the digesting waste is faster.

Preferably the air duct is openable for to access and clean the evaporator.

Preferably the waste digester comprises an air/air heat exchanger wherein the incoming air is warmed by warm gas from within the chamber.

Preferably the waste digester comprises a gas motor to operate the agitator, the turbo being arranged to be driven by gas produced in the chamber by the waste digestion process. Preferably the gas motor comprises a turbo comprising rotating vanes driven by the gas. Preferably the gas motor comprises a piston in a cylinder driven by the gas.

Preferably a tube is provided from to deliver gas under pressure in the chamber generated by the waste digestion process to the gas motor. Preferably the tube is connected between the gas motor the retort or between the gas motor and the plenum.

Preferably a pressure regulation valve is provided along the tube to deliver gas to the gas motor to regulate the gas motor.

Preferably a gear reduction system is provided for increased torque to turn or rock the agitator. Preferably the gear reduction system is connected the hydraulic motor and/or the gas motor.

Advantageously the condenser of the heat pump is arranged as an efficient heater of the digesting waste by utilizing energy derived from the gas generated by the process of digestion.

Preferably the condenser is located inside the chamber. Hence the condenser is proximate the digesting waste in the chamber to heat the digesting waste and accelerate the rate of digestion.

Preferably the condenser is located on or inside the retort. Hence the retort provides protection for the condenser from external operations such as by people working around the retort.

Preferably the condenser is located exterior to the retort. Hence condenser is easy to access for maintenance or replacement. Preferably a fan is provided to blow air across the condenser and onto the retort thereby efficiently warming the retort and hence the digesting waste inside the retort.

Preferably the retort comprises a thermally conductive material such as stainless steel, aluminium, copper, or bronze which is resistant to corrosion by the digesting waste and readily transfers heat from the condenser to the digesting material.

Preferably the vent and/or the vent is openable to provide access to remove or clean the evaporator.

Preferably the retort comprises dividers for dividing the chamber into compartments. Preferably the dividers may be raised or lowered.

According to a second aspect of the invention there is a method of waste digestion using a retort enclosing a chamber containing digesting waste, comprising: operating a heat pump comprising a condenser and an evaporator; heating the waste with the condenser to a preselected temperature; and distilling liquid with the evaporator from gas produced in the chamber by digestion of the waste.

Preferably the method includes feeding the liquid by gravity to a hydraulic motor driving an agitator agitating the waste in the chamber.

Preferably the method includes regulating the humidity in the chamber by directing ambient air over the evaporator so producing dried air, and urging the dried air into the chamber.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Brief Description of the Figures

Figure 1 is a schematic of a waste digester comprising a rotatable agitator according to the invention; and

Figure 2 is a schematic of a waste digester comprising a rotatable retort according to 5 the invention.

Detailed Description of the Invention

Referring to the Figures, there is shown in Figure 1 and Figure 2 a waste digestion machine 1000. The waste digestion machine comprises a retort 100, 1100 enclosing a chamber 101 into which solid waste is placed. A gas and specialized enzymes are also added into the chamber. The waste is digested by bacteria which feed off the waste, enzymes, and accelerant, and breath the gas.

The retort is necessary to allow the waste to be contained whilst it is digested. It ensures liquids and solids are held securely and contains odors.

The retort comprises a trough or a tube. Figure 1 illustrates a retort which is an 15 elongate tube. The waste is fed into one end of the trough or tube together with the enzymes and accelerant through a waste inlet.

The retort 100 comprises a gas inlet 120 through a wall of the retort. The gas is blown into the chamber 101 through the gas inlet. The gas inlet is shown in Figure 1 proximate the top of the retort. The gas inlet may also be located at the bottom of the retort where the gas may be blown into the waste to increase the rate of digestion.

The waste is decomposed by digestion leaving a residue of decomposed waste. The retort comprises a waste outlet 130 for removal of the decomposed waste. The waste outlet 130 is located at an end of the retort which is distal from the waste inlet.

Decomposition of the waste produces waste gases inside the chamber. The waste 25 gases include water vapor.

A gas vent 140 is provide through the retort proximate the top of the chamber. The gases in the chamber exit the chamber through the vent 140.

The gas vent 140 has an outlet into a plenum defined by plenum wall 150. The gases from the chamber 101 pass through the vent 140 into the plenum 150.

A relative humidity (ERH) of 50 % in the chamber promotes fast and efficient digestion of the waste. As the humidity in the chamber rises above the 50 % level, the efficiency is reduced.

The gas inlet 120 is a conduit through which ambient air is urged into the chamber to facilitate digestion of the waste. In high humidity ambient conditions, the efficiency of the digester would be reduced because the humidity of the air drawn into the chamber is already above 50 %.

Incoming air is taken in through ambient air inlet 123. To take moisture out of the incoming air, the incoming air is directed across the evaporator 160 or a portion thereof. .The evaporator 160 or a portion thereof is inside an air duct 122 so that the ambient air is directed across the evaporator.

The incoming air is cooled by the evaporator causing its moisture to condense into water. The water drips into a water collector 171 below the evaporator 160. The incoming air is thereby dried.

The air duct 122 comprises a channel to the gas inlet 120 through the retort so that the dried air enters the chamber 101.

The relative humidity of the incoming air is reduced to 50 % or less to so as to maintain the relative humidity in the chamber at 50 % or in a range of 40 % to 60 %.

A relative humidity sensor is arranged in the chamber for regulating the flow rate and humidity of the incoming air so as to maintain the relative humidity of gas in the chamber at 50 % or in the range of 40 % to 50 %.

In desert dry climates the relative humidity of the relative humidity of the ambient air is below 50 %. The heat pump comprises a means for switching the evaporator 160 or the portion thereof in the air duct 122 off to save energy and increase efficiency when the evaporator is not required to condense moisture from incoming air.

Within the plenum is an evaporator heat exchanger 160. The evaporator heat exchanger is a component of a heat pump.

The gases which enter the plenum from the chamber are cooled by the evaporator heat exchanger. The temperature of the gases is lowered below the dew point. The water vapor in the gases condenses.

A liquid collector 170 is located within the plenum wall 150. The liquid collector is a catchment to capture liquid which is distilled from the gas in the plenum by the cooling action of the evaporator heat exchanger 160.

The liquid which is distilled is primarily water. Other chemicals may be included in the liquid because the liquid is distilled from gas vented from the chamber which may contain chemical which condense at a temperature below the dew point of water.

The liquid collector 170 is arranged partly below the evaporator heat exchanger. Liquid which condenses on fins or coils of the evaporator heat exchanger 160 drips down into the liquid collector 170.

The liquid collector 170 is also arranged to collect liquid which condenses on the plenum wall 150 and drips down into the liquid collector.

The plenum wall comprises an exhaust vent 180. The exhaust vent 180 is located above the evaporator heat exchanger. The exhaust vent is located proximate the top of the plenum. Gases exit the plenum to ambient air through the exhaust vent 180.

The plenum comprises an air inlet 190. The air inlet is located near proximate the top of the plenum. A gate 191 is arranged to close the air inlet.

A first liquid conduit 200 provides a fluid passageway from the liquid collector 170 to a liquid reservoir container 210. An aperture near the bottom of the liquid collector opens into the first liquid conduit.

The liquid reservoir container 210 provides storage for liquid distilled from the gas which is vented from the chamber. The liquid reservoir container encloses liquid stored therein to prevent escape of odors.

Another conduit, not shown in figures, is provided from the air duct 122 to the liquid reservoir so that water condensed from the incoming air is collected in the reservoir.

A second liquid conduit 220 provides a fluid passageway from the bottom of the liquid reservoir container 210 to a throttle 230. The liquid reservoir container is located above the throttle 230.

The throttle 230 provides a means to regulate flow of the liquid through the second liquid conduit 220.

The throttle regulates flow of the liquid to a hydraulic motor 240. The hydraulic motor is located below the throttle.

The hydraulic motor is driven by liquid distilled from gas in the plenum supplied from 10 the chamber and by water condensed in the air duct supplied from the ambient air.

The liquid flows under the influence of gravity because the evaporator heat exchanger 160 is located above the liquid collector 170, and the liquid collector is located above the throttle 230, and the throttle is located above the hydraulic motor 240.

The hydraulic motor comprises a wheel comprising at least a vane 241 or a bucket 15 which is acted upon by the liquid. The hydraulic motor is connected to an agitator shaft 250. The wheel is connected to the agitator shaft and so turns or rocks the agitator shaft.

In the embodiment shown, the wheel is connected directly to the agitator shaft so as to rock or rotate the shaft.

In another embodiment, the wheel is connected to an electricity generator which is arranged to provide electricity for a motor which rocks or rotates the agitator shaft.

In another embodiment the electricity generator is arranged to provide power to operate the heat pump, and in particular to a motor which operates the heat pump compressor. The efficiency of waste digester thereby improved since less electricity has to be provided from an external source to operate the heat pump.

The buckets are arranged on the circumferential periphery of the water wheel. The amount of torque provided by the water wheel corresponds to the amount of water in the bucket.

When the waste digestion process is initially started, the agitator is stationary. As the waste digests liquid is distilled which acts on the hydraulic motor by filling the buckets in turn until the torque from the water wheel over comes the resistance of the waste on the agitator. Hence the agitator will start turning or rocking as soon as enough water is in the buckets. The agitator will not necessarily wait until a bucket is full before starting to move, because the agitator will move as soon as the digestion process provides enough water to provide enough torque for the hydraulic motor to move the agitator.

The buckets containing distilled liquid provide a torque arm giving you the torque to turn the agitator. When chamber has waste in it the arm will remain still until the torque from the water wheel over comes the resistance of the waste on the agitator. Hence the arm will turn as soon as enough water is in the wheel.

The agitator shaft 250 extends into the chamber 101 of the retort. The long axis of the agitator shaft 250 is parallel to the long axis of the retort which is tubular shaped.

The agitator shaft 250 comprises arms 260. The arms are radially oriented from the axis of the shaft.

The arms comprise paddles. In use the paddles extend into the waste, enzymes, accelerant, and gas contained in the chamber 101. The paddles 260 stir and agitate the waste because they are connected to the agitator shaft by the arms, and the agitator shaft rocks or rotates paddles.

The paddles mix the waste, enzymes, accelerant, and gas in the chamber by stirring them together. The waste is agitated by ‘tumbling’ the waste.

The paddles mix the enzyme and accelerant system evenly into the organic waste.

This allows the enzyme and accelerant to work quickly on all areas of the waste. Mixing the waste, enzymes, accelerant, and gas increases the rate of digestion of the waste. The paddles break up any areas of oxygen depleted ‘anaerobic’ bacteria which produce methane and are undesirable in the waste digestion process.

The paddles also transport and push the waste along the long axis of the retort. The waste is pushed to the waste outlet 130. By the time the waste is pushed to the outlet, it has been digested by the bacteria. So much less waste is pushed out of the chamber 101 through the waste outlet 130 than enters the chamber 101 through the waste inlet 110. The waste inlet 110 is closable.

Stirring with paddles releases water vapor trapped within the waste. The majority of the waste organic is converted to water and carbon dioxide. These by-products must be removed quickly from the waste organic to promote digestion of new organic waste.

The throttle 230 is adjustable to regulate the rate that the agitator shaft rocks or rotates.

The throttle thereby regulates the rate of mixing of the waste, enzymes, accelerant, and gas in the container. Since the rate of mixing affects the rate that the waste is digested, the throttle regulates the rate of waste digestion.

Increasing the rate of digestion increases the rate of production of waste gases including water vapor in the chamber.

Increasing the digestion rate increases the amount of water vapor which can be distilled in the plenum by the evaporator.

Increasing the amount of water distilled, increases the amount of water drive the hydraulic motor, and so to increase the speed of the motor.

Increasing the speed of the hydraulic motor turns the agitator more quickly which mixes the waste, enzymes, accelerant, gases so that the waste is digested more quickly and produces more water vapor.

Hence the throttle 230 is available to regulate the rate of waste digestion and water vapor production. The throttle is useable to prevent a runaway reaction of digesting waste in the chamber.

The heat pump comprises a condenser heat exchanger 280. The condenser heat exchanger is arranged to heat the contents within the chamber of the retort. The contents include the waste, enzymes, accelerant, and gases.

The condenser heat exchanger 280 is located proximate the retort 100 to warm the retort and the contents.

A water jacket 280 is located adjacent the retort. The water jacket 280 is external to the retort and contains water which is contact with retort.

The condenser heat exchanger 270 is located adjacent the water jacket. In use the condenser heat exchanger heats the water in the water jacket. In turn the heated water in the water jacket heats retort and its contents.

The heat provided by the condenser heat exchanger raises the temperature of the contents in the chamber to about 50 degrees to 60 degrees Celsius. The bacteria which digest the waste work fastest in the temperature range of 50 to 60 degrees

Celsius.

The heat pump comprises a compressor 300. A temperature sensor 301 is located in the retort and connector to a thermostat 303 by a wire 302. The thermostat turns the compressor on when the temperature in the chamber drops below a preselected minimum of about 52 degrees Celsius. The thermostat turns the compressor on when the temperature inside the chamber exceeds a preselected maximum of about 58 degrees Celsius. In this way the temperature within the chamber is maintained in the range of 50 to 60 degrees Celsius.

The waste digestion machine efficiently uses the heat pump to digest waste quickly.

The evaporator heat exchanger 160 of the heat pump distills water from the waste gas produced by the digestion process and the water is use to drive a hydraulic motor which turns an agitator to stir the mixture of waste, enzyme, accelerant and gas in the retort to increase the rate of digestion.

The condenser 270 of the heat pump heats the contents in the chamber including the waste, accelerant, enzymes, bacteria, and gas. The heat pump compressor is controlled by a thermostat so that the condenser maintains the contents in a temperature range where the rate of digestion is fast.

Figure 2 discloses a waste digestion machine comprising a heat pump. The waste digestion machine shown in Figure 2 comprises a retort 1100 defining a chamber 101 contain waste to be digested.

The retort 1100 of Figure 2 is similar to the retort 100 of Figure 1 in that both retorts comprise a waste inlet 110 and a waste outlet 130. Both retorts comprise a gas inlet 120.

A gas vent 140 is provided to both the retort 1100 of Figure 2 and the retort 100 of Figure for gases in the chamber to escape through. The gases in the chamber comprise air which enters the chamber with waste through the waste inlet, and air which enters through the gas inlet, and gases including water vapor produced by the process of digesting the waste.

The gas vent 140 provides a passage for the gases the chamber to a plenum defined by plenum wall.

In the waste digestions machines of both Figures 1 and 2, water is distilled from the gas which enters the plenum by cooling the gas with the heat pump evaporator heat exchanger 160.

In both of waste machines shown in Figures 1 and 2 the distilled water falls through a throttle 230 to a hydraulic motor.

The hydraulic motor 1240 shown in Figure 2 is arranged to rotate or rock the retort 1100. The hydraulic motor 240 shown Figure 1 differs because it is arranged rotate or rock an agitator shaft 250 while leaving the retort 100 stationary.

The waste digestion machine shown Figure 2 does not comprise an agitator shaft with arms to agitate the waste in the chamber 101. Instead the retort 1100 of the waste digestion machine shown in Figure 2 comprises paddles 1260 or tines which extend into the chamber from the wall of the retort.

The hydraulic motor 1240 rotates or rocks the entire retort 1100 including the paddles

1260 or tines. The paddles or tines 1260 thereby agitate and mix the waste, bacteria, accelerant, enzymes, and gas in the chamber. The rate of digestion of the waste is increased by the agitation.

As shown in Figure 2, the heat pump condenser heat exchanger 1270 is arranged proximate the retort so as to heat the retort 1100 and the contents of the chamber including the waste, bacteria, accelerant, enzymes, and gas in the chamber. Warming the contents increases the rate of digestion. A fan 1272 blows air across the condenser heat exchanger and onto the retort. The condenser warms the air which in turn warms the retort 1100 and its contents.

The retort 1100 is rotated which improves the convection of the warm air on the retort.

A temperature sensor 301 proximate the wall of the retort 1100 detects the temperature corresponding to the temperature inside the chamber. The temperature sensor is connected to a thermostat 303. The thermostat turns the heat pump compressor 300 on and off, and/or the fan 1272 on and off to maintain the temperature of the contents inside the chamber 101 at a temperature which promotes rapid digestion of the waste. A temperature range of 70 degrees Celsius to 80 degrees Celsius is ideal.

As shown in Figure 1, a fan 272 which blows air across the condenser heat exchanger

270 is also included with the waste digestion machine comprising stationary retort.

The fan 272 is similarly controlled by the thermostat 303 to maintain the contents of the chamber in a temperature range which promotes digestion.

The waste digestion machine is devised for use with a method of waste digestion.

In the method of waste digestion, waste to be digested, accelerant, enzymes, and bacteria are loaded into the chamber 101 of the retort 100, 1100 through a waste inlet. Air and/or another gas is provided into chamber through a gas inlet.

The components of the heat pump 300, 160, 270, 272 are activated which condenser warms the contents of the chamber to a temperature in a range maintained by the thermostat 303 and temperature sensor 301.

The method includes distilling liquid from gas which is produced by the waste digestion process. The liquid is primarily water. The method uses the evaporator heat exchanger of the heat pump to cool the gas and thereby distill the liquid.

The method also includes feeding the distilled liquid to the hydraulic motor 240, 1240 by gravity.

The method includes using the hydraulic motor to turn or rock an agitator shaft 250 or the retort 1100 to agitate the waste which is digesting in the chamber.

The method includes ejecting or removing waste which has been digested through the waste outlet 130. The arms 260, 1260 are designed to move the waste toward and out the waste outlet as they are moved by the hydraulic motor.

The method also includes regulating the humidity in the chamber by directing incoming ambient air over the evaporator to dry the incoming air and controlling the humidity and inflow of dried air into the chamber.

The waste digestion machine and method described herein rapidly and efficiently digests waste reducing the time and expense of waste digestion, and reducing reliance on landfills or incineration to dispose of waste.

Index of Labelled Features in Figures

Waste digestion machine............................................................. 1000

Retort.......................................................................................... 100

Chamber................................................................................... 101

Waste Inlet...................................................................................110

Gas Inlet and/or outlet.................................................................... 120

Retort pressure relief valve..............................................................121

Air duct.......................................................................................122

Ambient air inlet............................................................................123

Waste Outlet............................................................................... 130

Gas Vent.................................................................................... 140

Plenum wall................................................................................. 150

Evaporator heat exchanger............................................................ 160

Liquid collector..............................................................................170

Water collector.............................................................................171

Plenum Exhaust vent...................................................................... 180

Plenum Pressure relief valve.......................................................... 181

Plenum Air inlet........................................................................... 190

Liquid conduit...............................................................................200

Liquid reservoir container............................................................... 210

Liquid conduit.............................................................................. 220

Throttle..................................................................................... 230

Hydraulic motor........................................................................... 240

Vane.......................................................................................... 241

Agitator shaft.............................................................................. 250

Agitator arm.................................................................................260

Condenser heat exchanger............................................................ 270

Condenser fan............................................................................. 272

Jacket....................................................................................... 280

Heat pump line..............................................................................290

Heat pump motor, compressor, valve................................................ 300

Temperature sensor.......................................................................301

Wire............................................................................................302

Heat pump line............................................................................ 310

Hydraulic motor............................................................................ 1240

Hydraulic motor vanes....................................................................1241

Agitator arms, paddles, tines fixed to retort......................................... 1260

Condenser heat exchanger............................................................ 1270

Condenser fan........................................................................... 1272

Wire............................................................................................1274

The invention has been described by way of examples only. Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the claims.

Claims

Claims:

1. A waste digester comprising: a retort enclosing a chamber to contain digesting waste; a vent through the retort enables gas to exhaust the chamber; a heat pump which includes a condenser arranged to heat digesting waste in the chamber; and an evaporator located in or downstream of the vent arranged to distill a liquid from the gas.

2. A waste digester according to claim 1, wherein the evaporator is arranged to distill water from the gas.

3. A waste digester according to claim 1 or 2 comprising a plenum in fluid communication with the vent; wherein the evaporator or a portion thereof is located within the plenum.

4. A waste digester according to claim 3 comprising a pressure relief valve to relieve the gas from the plenum.

5. A waste digester wherein the pressure relief valve has a relief pressure which is adjustable.

6. A waste digester according to any preceding claim comprising a catchment located below the evaporator to capture the distilled liquid.

7. A waste digester according to claim 6 as dependent on claim 3, 4, 5, wherein the catchment is located within the plenum.

8. A waste digester according to any preceding claim comprising a hydraulic motor arranged to be driven by the distilled liquid.

9. A waste digester according to claim 8 wherein the hydraulic motor comprises a vane, or bucket, or gear arranged to be driven by the distilled liquid.

10. A waste digester according to claim 9 wherein the hydraulic motor comprises a wheel; the vane or bucket being arranged to receive the distilled liquid.

11. A waste digester according to claim 8, 9, or 10 wherein the hydraulic motor is located below the evaporator for feeding the distilled liquid by gravity to the hydraulic motor.

12. A waste digester according to claim 8, 9, 10, or 11 as dependent on claims 6 or 7 wherein the catchment is located above the hydraulic motor.

13. A waste digester according to claim 12 wherein the catchment includes a spout to direct the distilled liquid to the hydraulic motor.

14. A waste digester according to claim 12 or 13 includes a tube for channeling the liquid from the catchment to the hydraulic motor.

15. A waste digester according to any of claims 8 to 14, comprising a throttle arranged to regulate flow of the distilled liquid from the evaporator to the hydraulic motor.

16. A waste digester according to any of claims 8 to 15 comprising an agitator to agitate the digesting waste within the retort, wherein the agitator is drivable by the hydraulic motor.

17. A waste digester according to claim 16 wherein the agitator is arranged to agitate the retort which in turn agitates the digesting waste.

18. A waste digester according to claim 16 wherein the agitator comprises a stirring means within the retort to agitate the digesting waste.

19. A waste digester according to any of claims 8 to 15 wherein the hydraulic motor is arranged to turn an electricity generator.

20. A waste digester according to claim 19 dependent on any of claims 16 to 18 wherein the electricity generator is arranged to provide power to an electric motor which drives the agitator.

21. A waste digester according to claim 19 wherein the electricity generator is arranged to provide power to operate the heat pump.

22. A waste digester according to any preceding claim wherein the condenser is located inside the chamber.

23. A waste digester according to any of claims 1 to 21 wherein the condenser is located on or inside the retort.

24. A waste digester according to any of claims 1 to 21 wherein the condenser is located exterior to the retort.

25. A waste digester according to any of claims 1 to 21 wherein the retort comprises a heater for heating the retort and the digesting waste in the chamber, the heater deriving energy from the condenser when in use.

26. A waste digester according to any preceding claim comprising a gas inlet through the retort into the chamber.

27. A waste digester according to claim 26, wherein the evaporator or portion thereof is arranged in an air duct in fluid communication with ambient air and the gas inlet of the retort, wherein the air duct is arranged to direct ambient air over the evaporator to dry air flowing into the chamber.

28. A waste digester according to any preceding claim wherein the vent is openable to provide access to remove or clean the evaporator.

5

29. A waste digester according to any preceding claim dependent on claim 3 wherein the plenum is openable to provide access to remove or clean the evaporator.

30. A waste digester substantially as described herein with reference to the accompanying drawings.

31. A method of waste digestion using a retort enclosing a chamber containing digesting 10 waste, comprising: operating a heat pump comprising a condenser and an evaporator; heating the waste with the condenser to a preselected temperature; and distilling liquid with the evaporator from gas produced in the chamber by digestion of the waste.

32. A method according to claim 31 including feeding the liquid by gravity to a hydraulic 15 motor driving an agitator agitating the waste in the chamber.

33. A method according to claims 31 or 32 including regulating the humidity in the chamber by directing ambient air over the evaporator so producing dried air, and urging the dried air into the chamber.

Intellectual

Property

Office

Application No: GB 1616427.9