Patent Description:
It is known to heat biomass materials to generate synthesis gas. Synthesis gas is a gaseous mixture comprising hydrogen, carbon monoxide and methane, amongst other substances. The treatment process typically entails heating granulated or otherwise comminuted biomass waste material within a kiln. The kiln is generally heated by a heating system. It is also known to add steam to the contents of the kiln, for example to provide a reducing atmosphere within which synthesis gas may be more readily generated and/or the ratio of constituents of the synthesis gas may be controlled. The steam is typically pre-generated by heating water using a further heating system, prior to introduction of the steam into the kiln. The generated synthesis gas can then be sent on for further treatment.

<CIT> discloses a system including a waste incinerator for purifying waste. The waste incinerator comprises a diffusion pipe vertically arranged in a combustion chamber, diffusion holes formed on the diffusion pipe in several stages, a temperature sensor detecting for the temperature in the combustion chamber and a control means for controlling the amount of fuel supplied from a fuel nozzle. Air curtain layers are created by horizontally jetting air from each of the diffusion holes, forming combustion areas among the air curtain. The gas generated by liquefaction and vaporization of the waste is converted into a high-temperature gas in the upper layer.

As will be appreciated by one skilled in the art, the apparatus for generating synthesis gas (and for its further processing) is relatively complex. Furthermore, the treatment process is typically run continuously, for example <NUM> hours a day. Accordingly, the heating system, compression systems and the like require a relatively large quantity of energy. These relatively high energy requirements may result in relatively high operating costs for such apparatus. However, in order for hydrogen (for example) generated from biomass waste material to be economically competitive with hydrogen generated from other sources, the treatment method must necessarily be as inexpensive as possible. Accordingly, it would be advantageous to minimise the running costs of such apparatus for treating waste material.

It would also be beneficial to increase the efficiency of the method, for example relative to prior art methods. It would be beneficial to provide a relative increase in efficiency of the kiln heating method, of the steam production method, of the gasification process and/or of the production of a component of a generated gas (e.g. hydrogen).

In recent years the proliferation of plastic products and packaging has generated (and continues to generate) large volumes of waste material. Plastics waste material has traditionally been delivered to landfill, for natural decomposition. However, such plastics waste material may take a long time to naturally decompose, for example in the order of many hundreds of years. Accordingly, it has been proposed to treat waste plastics material instead of delivering it to landfill, such that by-products of the treated waste may find use. It would be convenient to separate and recycle plastics materials so that they can be reprocessed to produce useful products.

Unfortunately, recycling and recycling technologies are not universal with regards to plastics wastes materials. Further, it is relatively expensive and challenging to process contaminated waste plastics materials, or mixed plastics waste streams. Indeed, there are some plastics materials which currently impossible (or prohibitively expensive) to recycle. Unfortunately, where a waste stream is contaminated it tends to prove too expensive to separate out the recyclable plastics materials from those which are not recyclable and so the entire waste stream may not be processed.

Plastics packaging is a major source of plastics materials which are difficult to recycle, typically because of the functional properties of the plastics, e.g. plastics barrier films used in food packaging. Tyres are another difficult-to-process waste material.

In the circumstance where the waste stream cannot be recycled, the waste stream will typically be diverted to landfill.

It is an object of the current invention to provide ways in which useful work can be extracted from plastics waste materials for example mixed and or contaminated waste plastics materials and vehicle tyres.

Accordingly, a first aspect of the invention provides a method of treating comminuted waste material, in accordance with Claim <NUM>.

Advantageously, the invention provides a relatively more efficient method of treating comminuted waste material compared to prior art methods. For example, supplying at least a portion of the generated combustible gas to the one or more combustion heating means or combustion heater allows for a relatively reduced quantity of external fuel to be supplied to the one or more combustion heating means or combustion heater. In this way, heating of the heating chamber may be effected at relatively reduced expense compared with prior art methods.

The comminuted waste material may comprise plastics waste, for example polyethylene terephthalate, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polyvinylchloride, polypropylene, or the like. The comminuted waste material may comprise rubber, biomass, tyre crumbs or the like. The comminuted waste material may comprise any suitable combination of plastics and or of other materials.

The term 'comminuted' as used herein should be taken to mean a substance which has been reduced to small particles or fragments.

The combustible gas may comprise a combustible hydrocarbon, for example methane or another suitable alkane. The combustible gas may form a component of a gaseous mixture, e.g. a generated gaseous mixture. The gaseous mixture may comprise synthesis gas. The synthesis gas may comprise hydrogen, methane, carbon monoxide. The synthesis gas may comprise one or more further substances.

The method may comprise a step of supplying at least a portion of the generated combustible gas to a generator, for example for generating electrical energy. The generator may supply electrical energy to control or operate one or more component or machine associated with the steps of the method. Additionally or alternatively, the generator may supply electrical energy to the or a electricity grid. Additionally or alternatively, the generator may supply electrical energy to one or more further component or machine.

At least a portion of the generated combustible gas may be sent or supplied to a gas grid. At least a portion of the generated combustible gas may be processed into one or more further chemicals.

The method comprises heating the comminuted waste material in a first zone of the heating chamber to a first temperature T1 to gasify the comminuted waste material.

The first temperature T1 may be sufficiently high to at least partially gasify the comminuted waste material. The first temperature T1 may be sufficiently high to fully gasify the comminuted waste material.

The method comprises heating the gasified material in a second zone of the heating chamber to a second temperature T2 to generate the combustible gas. The second temperature T2 is greater than the first temperature T1.

The method may comprise heating the combustible gas in a third zone of the heating chamber, e.g. to a third temperature T3. The third temperature T3 may be greater than the first temperature T1. The third temperature T3 may be less than the second temperature T2. The third temperature T3 may be greater than the second temperature T2. The third temperature T3 may be equal (e.g. substantially) to the second temperature T2.

One or more of the zones within the heating chamber may be the same size, e.g. have the same length, width and/or radius. One or more of the zones within the heating chamber may be a different size, e.g. have a different length, width and/or radius.

Where three zones are present within the heating chamber the first and second zone may be the same size, e.g. have the same length, width and/or radius. The third zone may be larger or smaller than than the first and second zones, e.g. the third zone may have a larger or smaller length, width and/or radius than the first and second zones. Preferably, the third zone is smaller than the first and second zones, e. g the third zone has a smaller length, width and/or radius than the first and second zones.

Where three zones are present within the heating chamber the first and second zones may be a different size, e.g. have a different length, width and/or radius. The third zone may be the same size, e.g. have the same length, width and/or radius, as the second zone. The third zone may be a different size, e.g. have a different length, width and/or radius, to the second zone. In an embodiment, the third zone is smaller than the second zone, e. g the third zone has a smaller length, width and/or radius than the second zone. In an embodiment the zones have the same width but are of the same or different lengths. Clearly, if the zones have a different length, for a given flow rate along the heating chamber, the residence time in each zone will be different. Where the temperatures are different in the different zones the material will be exposed to different temperatures and/or other conditions (e.g. atmosphere) for different time periods when the zones are of a different length (for a given throughput of material).

The temperature of the heating chamber may be above <NUM> throughout. For example, the temperature of the heating chamber may be above <NUM>, e.g. above <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, in each of the zones, e.g. in each of the three zones.

The first, second and/or third temperature T1, T2, T3 may comprise predetermined temperatures. The first temperature T1 may be set to between about <NUM> and <NUM>, say about <NUM>. The second temperature T2 may be set to between about <NUM> and <NUM>, say between about <NUM> and <NUM>, for example about <NUM>. The third temperature T3 may be set to between about <NUM> and <NUM>, say between about <NUM> and <NUM>, for example about <NUM>.

The temperature in one or more zones, e.g. the first, second and/or third zone, may be controlled or controllable by controlling, e.g. individually controlling, the supply of fuel and/or air to the respective combustion heating means or combustion heaters. Controlling the supply of fuel and/or air may involve increasing or reducing, the mass flow rate of air and/or fuel supplied to one or more combustion heating means or combustion heater at the or each zone, e.g. the first, second and/or third zone.

Fuel may comprise a mixture of two fuel components (e.g. natural gas and synthesis gas). Controlling the mass flow rate of fuel may comprise altering the ratio of the two fuel components. Controlling the temperature in the or each zone may comprise controlling the ratio of two fuel components supplied to the one or more combustion heating means or combustion heaters. Controlling the temperature in the of each zone may comprise controlling the ratio of fuel to air supplied to the combustion heating means or combustion heaters.

The method may comprise measuring or determining the temperature inside the heating chamber. The method may comprise using one or more temperature sensors to measure or determine the temperature in the heating chamber. The method may comprise using one or more temperature sensors which are inside the heating chamber to measure or determine the temperature in the heating chamber. The method may comprise using one or more temperature sensors which are outside the heating chamber to measure or determine the temperature in the heating chamber. The method may comprise using an array of temperature sensors, e.g. inside and/or outside of the heating chamber (for example to measure or determine the temperature in the heating chamber). Where plural zones are defined in the heating chamber, the method may comprise measuring or determining the temperature of one, some or each zone in the heating zone (for example of the first zone, second zone and/or third zone, where provided).

The method may comprise adjusting the heat generated by the, one, some or each of the one or more combustion heating means or combustion heater, for example in response to a measured or determined temperature inside the heating chamber.

The method may comprise a step f) of cleaning the generated combustible gas. Step f) may occur prior to step d), e.g. and may be subsequent to step c).

The heating chamber may be rotatable, in use. For example, the heating chamber may be rotatable about a rotational axis. The method may comprise a step g) of rotating the heating chamber.

The method may comprise a step h) of introducing, e.g. injecting, steam into the heating chamber. The steam may be introduced at a temperature of between about <NUM> and <NUM>, for example between about <NUM> and <NUM>, say between about <NUM> and <NUM>, e.g. approximately <NUM>.

The steam may be produced by a heat exchanger (e.g. a boiler). The steam may be superheated. The heat exchanger may be heated by excess heat from heating the heating chamber (e.g. heated by flue gas). Water may be provided to the heat exchanger. The temperature of the water may be controlled or controllable. The temperature of the water may be dependent on the amount of comminuted waste material fed into the heating chamber.

The volume of water may be controllable. The water may be provided as a continuous flow or it may be an intermitant flow e.g. pulsed.

Benefically, introducing, e.g. injecting, steam into the heating chamber may rapidly increase the temperature of the comminuted waste material.

Steam may be introduced at any point within the heating chamber. For example, steam may be introduced, e.g. injected, at the inlet and/or in any of the zones of the heating chamber, e.g. in the first, second and/or third zone. Steam may be introduced upstream or downstream of the comminuted waste material. Preferably, steam is introduced downstream of the comminuted waste material. Preferably, steam is injected in the first zone of the heating chamber.

The introduction, e.g. injection, of steam may be offset from the rotational axis of the heating chamber.

T the method may comprise further processing the generated combustible gas. This further processing may occur prior to step d). The further processing may comprise removing or separating out one or more components of the generated combustible gas, for example removing or separating out hydrogen from the generated combustible gas.

A further aspect of the invention provides an apparatus for treating comminuted waste material, in accordance with Claim <NUM>.

The apparatus may comprise a generator, e.g. for generating electrical energy. The supply system may be configured or configurable to supply to the generator at least a portion of a combustible gas generated, in use, in the heating chamber.

The one or more combustion heating means or combustion heater are configured or configurable to heat a first zone in the heating chamber to a first temperature T1. The one or more combustion heating means or combustion heater are configured or configurable to heat a second zone in the heating chamber to second temperature T2. The second temperature T2 is greater than the first temperature T1.

The one or more combustion heating means or combustion heater may be configured or configurable to heat a third zone in the heating chamber to a third temperature T3. The third temperature T3 may be greater than the first temperature T1.

The one or more combustion heating means or combustion heater may comprise one or more combustion heaters, for example one or more heaters using a fuel source such as gas. The one or more combustion heating means or combustion heater may comprise one or more gas heaters, e.g. one or more gas burners. The one or more combustion heating means or combustion heater may be located, in use, outside of the heating chamber. The one or more combustion heating means or combustion heater may be arranged to heat the heating chamber.

The one or more combustion heating means or combustion heater comprises plural combustion heating means or combustion heater. A first combustion heating means or combustion heater may be configured or configurable to heat comminuted waste material in a or the first zone of the heating chamber, e.g. to the or a first temperature T1 (where plural zones are defined in the heating chamber). A second combustion heating means or combustion heater may be configured or configurable to heat gasified material in a or the second zone of the heating chamber, e.g. to the second temperature T2. A third combustion heating means or combustion heater may be configured or configurable to heat a third zone of the heating chamber, e.g. to a third temperature T3. The first zone may be at or adjacent the inlet. The third zone may be at or adjacent the outlet. the second zone may be in between the first and third zones.

The combustion heating means or combustion heater may be configured or configurable to heat gasified material in the second and/or subsequent zones. Synthesis gas may be produced in the second and subsequent zones, e.g. the second and third zones.

The apparatus may comprise one or more temperature sensors, for example configured or configurable to measure or determine the temperature inside the heating chamber. The one or more temperature sensors may be arranged or configured to measure or determine the temperature one, some or each of the zones of the heating chamber (where plural zones are defined therein). One or more temperature sensors may be arranged to measure or determine the temperature of the first zone. One or more temperature sensors may be arranged to measure or determine the temperature of the second zone. One or more temperature sensors may be arranged to measure or determine the temperature of the third zone. Where plural temperature sensors are provided they may comprise an array (e.g. plural arrays). One or more of the temperature sensors (or arrays of temperature sensors) may be located inside of the heating chamber. One or more of the temperature sensors (or arrays of temperature sensors) may be located outside of the heating chamber.

The apparatus may comprise a controller, e.g. configured or configurable to control the heating system. The controller may be configured or configurable to adjust or alter the heat generated by one or more of the one or more combustion heating means or combustion heater, for example in response to a temperature measured or determined inside the heating chamber (for example by the one or more temperature sensors). The controller may be configured or configurable to shut down the apparatus, for example if the temperature in the heating chamber exceeds a predetermined threshold (e.g. is higher or lower than a predetermined threshold temperature). The controller may be configured or configurable to alert an operator, for example if the temperature in the heating chamber exceeds a predetermined threshold. The alert may comprise an alarm which may be visual and/or audible.

The gas burners may be present at set locations along the heating chamber. For example, one or more gas burners may be located in each of the zones of the heating chamber. The controller may be configured to control the heat applied by the or each gas burner. The heat applied by each of the gas burners may be independently controlled by the control system, irrespective of the number of burners. For example, the control system may increase or reduce the mass flow rate of air supplied to one, some or each of the gas burners. The control system may also increase or reduce the mass flow rate of fuel to one, some or each of the gas burners. The fuel may comprise a mixture of two fuel components (e.g. natural gas and synthesis gas). Additionally or alternatively, the control system may alter the ratio of the mixture of the two fuel components.

Gas control valves may be present to alter the amount of the first fuel component supplied to the respective gas burners, or prevent any of the first fuel component from being supplied to the respective gas burner. Each gas control valve may alter the amount of the second fuel component supplied to the respective gas burner, or prevent any of the second fuel component from being supplied to the respective gas burner.

The apparatus may comprise a cleaning system, for example for cleaning combustible gas generated in the heating chamber.

The apparatus may comprise a kiln, for example a rotary kiln. The rotary kiln may be of the direct or indirect type. The heating chamber may be provided or defined within the or a kiln. The heating chamber (e.g. the kiln or a portion thereof) may be arranged or configured to be rotatable, in use. The heating chamber may comprise a thermal conversion chamber.

The apparatus may comprise a steam delivery means or steam delivery system, for example which may be configured or configurable to introduce, e.g. inject, steam into the heating chamber. The steam delivery means or system may comprise a source of water. The steam delivery means or system may comprise a boiler, for example arranged or arrangeable to boil water (e.g. from the source of water). The boiler may be a heat exchanger. The steam may be superheated. The heat exchanger may be heated by excess heat from heating the heating chamber (e.g. heated by flue gas).

The temperature of the water for producing steam may be controlled with a controller, control means or control system.

The volume of the water for producing steam may be controlled with a controller, control means or control system.

An adjustment means may be provided to control the location of steam introduced within the heating chamber.

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

Referring now to <FIG>, there is shown a schematic representation of an apparatus <NUM> for treating comminuted waste material according to the invention. In use, the apparatus <NUM> converts waste material feedstock, for example granulated plastics, into synthesis gas (as will be described in greater detail below).

As shown in <FIG>, the apparatus <NUM> comprises a heating chamber <NUM>, which is provided within an indirect rotary kiln <NUM>. The apparatus <NUM> further comprises a waste feed system <NUM>, a heating system <NUM>, a steam system <NUM>, a cleaning system <NUM>, a storage system <NUM> and a further processing system <NUM>. The heating system <NUM> comprises plural combustion heaters <NUM>. The plural combustion heaters <NUM> are arranged to heat, in use, the contents of the indirect rotary kiln <NUM>. The waste feed system <NUM> is arranged to introduce, in use, comminuted waste material into the indirect rotary kiln <NUM>. The steam system <NUM> is arranged to introduce, in use, steam into the indirect rotary kiln <NUM>. The indirect rotary kiln <NUM> is fluidly connected to the heating system <NUM> by a supply system S. The supply system S comprises the cleaning system <NUM> and the storage system <NUM>. However, the supply system S may be absent one or each of the cleaning system <NUM> and the storage system <NUM>.

The cleaning system <NUM> is arranged to receive, in use, generated synthetic gas from the indirect rotary kiln <NUM>. The storage system <NUM> is arranged to receive, in use, cleaned synthetic gas from the cleaning system <NUM>. The storage system <NUM> is arranged to send at least a portion of cleaned synthetic gas to the further processing system <NUM>.

Referring now to <FIG>, there is shown a detailed schematic view of portions of the apparatus for treating comminuted waste material shown in <FIG>.

As shown in <FIG>, the indirect rotary kiln <NUM> comprises an inlet <NUM> and an outlet <NUM>. The inlet <NUM> and outlet <NUM> are disposed at opposite ends of the indirect rotary kiln <NUM>. The indirect rotary kiln <NUM> comprises a drum <NUM>. The drum <NUM> comprises an outer shell 23a. The outer shell 23a surrounds a layer of insulating refractory bricks 23b. The insulating refractory bricks 23b surround a rotatable tube 23c. The rotatable tube 23c extends beyond the ends of the outer shell 23a on either end. A heating space 23d is defined between the insulating refractory bricks 23b and the rotatable tube 23c. In use, the outer shell 23a and insulating refractory bricks 23b are stationary whilst the rotatable tube 23c is rotated. The rotatable tube 23c may have a diameter of about <NUM>. The rotatable tube 23c may have a heated length of about <NUM>.

The indirect rotary kiln <NUM> is installed, for use, at an angle relative to the horizontal of approximately <NUM>°. The indirect rotary kiln <NUM> is arranged such that the inlet <NUM> is relatively higher than is the outlet <NUM>. A variable speed drive motor 26a is provided, which in this embodiment is located adjacent the inlet <NUM> of the indirect rotary kiln <NUM>. A mechanical drive chain 26b is also provided. The mechanical drive chain 26b links the variable speed drive motor 26a to the rotatable tube 23c. In use, activation of the variable speed drive motor 26a causes the mechanical drive chain 26b to move and, hence causes the rotatable tube 23c to rotate. The rotary kiln <NUM> is supported on water cooled bearings (not shown). The rotatable tube 23c is sealed using nitrogen purge sprung seals (not shown).

A discharge hood 22a is provided adjacent the outlet <NUM> of the indirect rotatable kiln <NUM>. The discharge hood 22a is in fluid communication with the outlet <NUM>. An inspection hatch 22b is provided on the discharge hood 22a.

A heating chamber <NUM> is defined within the rotatable tube 23c. The heating chamber <NUM> is divided into a first zone 28a, a second zone 28b and a third zone 28c. The first zone 28a is adjacent the inlet <NUM>. the third zone 28c is adjacent the outlet <NUM>. The second zone 28b is provided between the first and second zones 28a, 28c. In this embodiment, each of the zones 28a, 28b, 28c are of approximately equal length and/or volume. In embodiments, however, this need not be the case and one or more of the zones 28a, 28b, 28c may be of different lengths and/or volumes.

The apparatus <NUM> comprises an array <NUM> of temperature sensors, in this embodiment. The array <NUM> comprises temperature sensors 29a, 29b, 29c, 29d, 29e, 29f located inside of the rotatable tube 23c, in this embodiment. Two of the temperature sensors 29a, 29b, 29c, 29d, 29e, 29f located inside of the rotatable tube 23c are located inside each of the zones 28a, 28b, 28c, in this embodiment. The array <NUM> also comprises temperature sensors <NUM>, <NUM>, 29i, 29j, <NUM>, <NUM> located in the heating space 23d.

The apparatus comprises a pressure sensor <NUM>. The pressure sensor <NUM> is configured or arranged to monitor the pressure in the heating space 23d.

The heating space 23d contains three exhaust vents 25a, 25b, 25c are provided through the outer shell 23a. The exhaust vents 25a, 25b, 25c are in fluid communication with the heating space 23d. One of the exhaust vents 25a, 25b, 25c is located adjacent each of the zones 28a, 28b, 28c of the heating chamber <NUM>, respectively.

The apparatus <NUM> further comprises a first nitrogen supply 21a. The first nitrogen supply 21a is in fluid communication with the inlet <NUM> of the indirect rotary kiln <NUM>. The apparatus <NUM> further comprises a second nitrogen supply 22c. The second nitrogen supply 22c is in fluid communication with the discharge hood 22a. A check valve 21b is provided between the first nitrogen supply 21a and the rotatable tube 23c. A check valve 22d is provided between the second nitrogen supply 22c and the discharge hood 22a.

The feed system <NUM> comprises a feed screw (not shown). However, the feed system <NUM> may comprise any suitable means for feeding waste material into the indirect rotary kiln <NUM>, as will be appreciated by one skilled in the art. As shown in <FIG>, a flow sensor <NUM> is arranged to monitor the amount (e.g. the mass flow rate) of comminuted waste material into the heating chamber <NUM>.

Referring now to <FIG>, the heating system <NUM> comprises plural combustion heaters <NUM> which are gas burners 40a, 40b, 40c, 40d, 40e, 40f, in this embodiment. The gas burners 40a, 40b, 40c, 40d, 40e, 40f are arranged, in use, to heat the heating space 23d. The gas burners 40a, 40b, 40c, 40d, 40e, 40f are lean burn high efficiency gas burners. The gas burners 40a, 40b, 40c, 40d, 40e, 40f are configured to be individually controllable (as will be described in greater detail later). In this embodiment, two of the gas burners 40a, 40b, 40c, 40d, 40e, 40f are located adjacent each of the zones 28a, 28b, 28c. The gas burners 40a, 40b, 40c, 40d, 40e, 40f are equally spaced along the length of the indirect rotary kiln <NUM>. Each gas burner 40a, 40b, 40c, 40d, 40e, 40f is provided with a respective monitoring device <NUM>, <NUM>, 40i, 40j, <NUM>, <NUM>. The monitoring devices <NUM>, <NUM>, 40i, 40j, <NUM>, <NUM> are flame detectors.

The heating system <NUM> comprises a natural gas supply <NUM>. The natural gas supply <NUM> is in fluid communication with gas control valves 44a, 44b, 44c, 44d, 44e, 44f via a natural gas pipeline 41a. The natural gas pipeline 41a has parallel branches 41b, 41c, 41d, 41e, 41f, <NUM>. On each branch 41b, 41c, 41d, 41e, 41f, <NUM> there is located a gas control valve 44a, 44b, 44c, 44d, 44e, 44f, respectively. A flow sensor <NUM> is also provided. The flow sensor <NUM> is arranged to monitor flow through the natural gas pipeline 41a, e.g. flow between the natural gas supply <NUM> and the first branch 41b.

The heating system <NUM> also comprises a synthesis gas supply pipeline 42a in fluid communication with a store of generated synthesis gas <NUM> (as will be described in greater detail later). The synthesis gas supply pipeline 42a is in fluid communication with the gas control valves 44a, 44b, 44c, 44d, 44e, 44f. The synthesis gas pipeline 42a has parallel branches 42b, 42c, 42d, 42e, 42f, <NUM>. A pressure sensor <NUM> is also provided. The pressure sensor <NUM> is configured to measure or determine the pressure of gas in the synthesis gas pipeline 42a, e.g. between the distal branch <NUM> and the store <NUM> of synthesis gas.

The natural gas pipeline 41a is fluidly connected to each gas burner 40a, 40b, 40c, 40d, 40e, 40f by, respectively, a gas pipe 45a, 45b, 45c, 45d, 45e, 45f. The synthesis gas supply pipeline 42a is fluidly connected to each gas burner 40a, 40b, 40c, 40d, 40e, 40f by, respectively, a gas pipe 45a, 45b, 45c, 45d, 45e, 45f. Each gas pipe 45a, 45b, 45c, 45d, 45e, 45f comprises a gas control valve 44a, 44b, 44c, 44d, 44e, 44f. Each gas pipe 45a, 45b, 45c, 45d, 45e, 45f comprises a temperature control valve 42aa, 42bb, 42cc, 42dd, 42ee, 42ff.

Each gas control valve 44a, 44b, 44c, 44d, 44e, 44f is located between the respective branch 41b, 41c, 41d, 41e, 41f, <NUM> of the natural gas pipeline 41a and the respective gas pipe 45a, 45b, 45c, 45d, 45e, 45f. Each gas control valve 44a, 44b, 44c, 44d, 44e, 44f is located between the respective branch 42b, 42c, 42d, 42e, 42f, <NUM> of the synthesis gas pipeline 42a and the respective gas pipe 45a, 45b, 45c, 45d, 45e, 45f.

The heating system <NUM> further comprises a combustion air supply <NUM>. The combustion air supply <NUM> is in fluid communication with a combustion air fan <NUM>, via a combustion air pipeline 43a. The combustion air fan <NUM> comprises an electric drive motor 46a. The combustion air pipeline <NUM> is fluidly connected to each of the gas burners 40a, 40b, 40c, 40d, 40e, 40f, e.g. via branches 43b, 43c, 43d, 43e, 43f, <NUM>, respectively. An air control valve <NUM>, 43i, 43j, <NUM>, <NUM>, <NUM> is provided on the line between each gas burner 40a, 40b, 40c, 40d, 40e, 40f and each respective branch 43b, 43c, 43d, 43e, 43f, <NUM>. Each branch 43b, 43c, 43d, 43e, 43f, <NUM> of the combustion air pipeline <NUM> is connected to the respective gas pipe 45a, 45b, 45c, 45d, 45e, 45f between the temperature control valve 42aa, 42bb, 42cc, 42dd, 42ee, 42ff and the gas burner 40a, 40b, 40c, 40d, 40e, 40f.

Referring now to <FIG>, the steam system <NUM> is provided with a water source <NUM>. The water source <NUM> is in fluid communication with a steam superheater <NUM> via a steam pipeline 51a. A flow sensor 51b is arranged to measure the flow of water from the water source <NUM> to the steam superheater <NUM>. A flow control valve 51c is located in the steam pipeline 51a. The steam superheater <NUM> is in fluid communication with the inlet <NUM> of the rotatable tube 23c via the steam pipeline 51a.

The steam superheater <NUM> is heated by excess heat from the heating space 23d. The exhaust vents 25a, 25b, 25c are in fluid communication with the superheater <NUM>, to provide the excess heat thereto. The excess heat heats the water to provide superheated steam to the inlet <NUM> of the rotateable tube 23c.

Referring now to <FIG>, the discharge hood 22a is in fluid communication with a synthesis gas fan <NUM>, e.g. via an outlet pipe <NUM>. The discharge hood 22a is in fluid communication with a pressure control valve <NUM>, e.g. via the outlet pipe <NUM>. The pressure control valve <NUM> is in fluid communication with the pressure relief system (not shown). The synthesis gas fan <NUM> is in fluid communication with the cleaning system <NUM>. The synthesis gas fan <NUM> comprises a variable speed electric drive motor 60a. A pressure sensor <NUM> is arranged to monitor the pressure inside the rotatable tube 23c at and/or adjacent its outlet <NUM>. A pressure sensor <NUM> is arranged to monitor the pressure inside the discharge hood 22a. A temperature sensor <NUM> is arranged to monitor the temperature of a gas flowing, in use, from the discharge hood 22a to the synthesis gas fan <NUM>. A pressure sensor <NUM> is arranged to monitor the pressure of gas flowing, in use, from the synthesis gas fan <NUM> to the cleaning system <NUM>.

Referring again to <FIG>, the apparatus comprises a residue removal system <NUM> arranged to receive residue from the discharge hood 22a. This residue may be sent on for further processing in a residue processing system (not shown).

The apparatus <NUM> further comprises a control system (not shown). The monitoring devices <NUM>, <NUM>, 40i, 40j, <NUM>, <NUM> are in wired connection to the control system. The check valves 21b, 22d are in wired communication with the control system. The pressure transmitter <NUM> is in wired communication with the control system. The temperature transmitters 29a, 29b, 29c, 29d, 29e, 29f, <NUM>, <NUM>, 29i, 29j, <NUM>, <NUM> are in wired communication with the control system. The variable speed drive motor 26a is in wired communication with the control system. The gas control valves 44a, 44b, 44c, 44d, 44e, 44f are in wired communication with the control system. The flow sensor <NUM> is in wired communication with the control system. The pressure sensor <NUM> is in wired communication with the control system. The temperature control valves 42aa, 42bb, 42cc, 42dd, 42ee, 42ff are in wired communication with the control system. The electric drive motor 46a is in wired communication with the control system. The air control valves <NUM>, 43i, 43j, <NUM>, <NUM>, <NUM> are in wired communication with the control system. The flow sensor 51b and flow control valve 51c are in wired communication with the control system. The variable speed electric drive motor 60a is in wired communication with the control system. The pressure control valve <NUM> is in wired communication with the control system. The pressure sensor <NUM> is in wired communication with the control system. The pressure sensor <NUM> is in wired communication with the control system. The temperature sensor <NUM> is in wired communication with the control system. The pressure sensor <NUM> is in wired communication with the control system. The flow sensor <NUM> is in wired communication with the control system. One some or each of the above-described components may be in wireless communication with the control system, additionally or alternatively.

Referring now to <FIG>, there is shown a method of treating comminuted waste material according to the invention, using the apparatus shown in <FIG>.

In a first step S1, the apparatus <NUM> comprising the heating chamber <NUM> and the plural gas burners 40a, 40b, 40c, 40d, 40e, 40f is provided. The rotatable tube 23c is caused to rotate.

In a second step S2, comminuted waste material is fed by the feed system <NUM> into the rotatable tube 23c through the inlet <NUM> and hence into the heating chamber <NUM>. Without wishing to be bound by any theory it is believed that the angle of incline of the indirect rotary kiln <NUM> encourages feed material to move along the rotatable tube 23c, e.g. by gravity feed, toward the outlet <NUM>.

In a third step S3, steam is injected by the steam system <NUM> into the heating chamber <NUM>. Steam is introduced into the rotating tube 23c through the inlet <NUM> by the steam pipeline 51a. The steam is introduced into the rotating tube 23c at around <NUM>.

Hot water is provided to the steam superheater <NUM> from the hot water source <NUM>. The flow rate of hot water to the steam superheater <NUM> is monitored by the flow sensor 51b and the measurement is sent to the control system. By adjusting the flow control valve 51c, the control system can adjust the flow rate of hot water to the steam superheater <NUM>. The hot water is heated to steam in the steam superheater <NUM> for introduction to the rotatable tube 23c.

Advantageously, the steam provides a reducing atmosphere for the generation of synthesis gas. Accordingly, without wishing to be bound by any particular theory, it is believed that the waste material in the heating chamber <NUM> is more readily and efficiently gasified into synthesis gas in the presence of steam. Furthermore, the steam acts to transfer heat directly to the waste material inside the heating chamber <NUM>. Beneficially, the heat required from the gas burners to reach the required temperatures in the zones 28a, 28b, 28c may therefore be relatively reduced.

In a fourth step S4, the comminuted waste material in the heating chamber <NUM> is heated using the gas burners 40a, 40b, 40c, 40d, 40e, 40f.

As the waste material moves along the rotatable tube 23c it passes through the three zones 28a, 28b, 28c. In an embodiment, the first temperature T1 in the first zone 28a is about <NUM>; the second temperature T2 in the second zone 28b is about <NUM>; and the third temperature T3 in the third zone 28c is about <NUM>. The temperature adjacent the outlet <NUM> of the heating space 23d may be about <NUM>. In embodiments, however the first, second and/or third temperature T1, T2, T3 may be different.

In a fifth step S5, synthesis gas is generated in the heating chamber <NUM>. The synthesis gas comprises a mixture of hydrogen, methane and carbon monoxide, dependent on the comminuted waste material. Additional gaseous substances may also be present, for example carbon dioxide and oxygen, dependent on the comminutued waste material used. The ratio of hydrogen and methane in the generated synthesis gas can be adjusted by adjusting various operating factors of the apparatus <NUM>. For example, it has been found that a relatively greater ratio of hydrogen to methane can be generated by heating to relatively higher temperatures in the second and/or third zones 28b, 28c. Such relatively higher temperatures may be in the range of <NUM> to <NUM>, for example. In this way maximum hydrogen production can be achieved. Conversely, relatively lower temperatures in the second and/or third zones 28b, 28c may result in a relatively higher ratio of methane to hydrogen in the generated synthesis gas. Such relatively lower temperatures may be in the range of <NUM> to <NUM>, for example. Under such relatively lower temperatures relatively more methane may be present in the synthesis gas which is removed from the rotatable tube 23c. This may be advantageous for sending at least a portion of the generated synthesis gas on to the gas burners for heating the heating chamber <NUM>. Additionally or alternatively, at least a portion of the generated synthesis gas may be sent to a generator for generating electrical energy. This electrical energy can be used to power at least part of the apparatus and/or can be sent to the electricity grid and/or to power other machinery.

Heating of the waste material in the heating chamber <NUM> leads to the generation of synthesis gas (which comprises a combustible gas) in the heating chamber <NUM>, e.g. the fifth step S5.

Generated synthesis gas may have a residence time within the kiln <NUM> of about <NUM> seconds. The residence time of the generated synthesis gas can be altered by increasing or reducing the draw generated by the synthesis gas fan <NUM>. Increasing the power to the synthesis gas fan <NUM> may act to relatively increase the flow of synthesis gas from the rotatable tube 23c.

In a sixth step S6, at least a portion of the generated synthesis gas is supplied from the heating chamber <NUM> to the plural gas burners 40a, 40b, 40c, 40d, 40e, 40f. In some embodiments, the fuel used by the plural gas burners 40a, 40b, 40c, 40d, 40e, 40f may be provided mostly or entirely by generated synthesis gas. The generated synthesis gas (or at least a portion thereof) may be treated prior to being supplied to the plural gas burners 40a, 40b, 40c, 40d, 40e, 40f. For example, one or more components (for example hydrogen) of the generated synthesis gas may be removed prior to supply to the plural gas burners 40a, 40b, 40c, 40d, 40e, 40f.

The time between comminuted waste material entering the rotatable tube 23c and the relevant residue being removed by the residue removal system <NUM> is in the range of <NUM> to <NUM> minutes.

Generated synthesis gas exits the rotatable tube 23c through the outlet <NUM>. The synthesis gas is drawn from the rotatable tube 23c by action of the synthesis gas fan <NUM>. The synthesis gas then enters the discharge hood 22a. The synthesis gas is then drawn from the discharge hood 22a to the cleaning system <NUM>. Additionally, internal distributors (not shown) aid in transporting solid residues through the heating zone <NUM> to the discharge hood 22a. These solid residues are then removed and processed in the residue removal system <NUM>. Additionally, advantageously, the internal distributors also introduce turbulence to the gases and steam within the heating zone <NUM>. Without wishing to be bound by any theory it is believed that this turbulence enhances the efficiency of synthesis gas generation, for example through enhanced mixing of gasified waste material with steam. The generated synthesis gas is cleaned in the cleaning system <NUM>. The cleaned synthesis gas is then sent to the storage system <NUM>. At least a portion of the synthesis gas is then sent from the storage system <NUM> to the gas burners 40a, 40b, 40c, 40d, 40e, 40f.

Advantageously, the method and apparatus <NUM> described above provides a relatively more efficient system than prior art systems. For example, by utilizing synthesis gas generated by the apparatus <NUM> as a fuel source for the plural gas burners 40a, 40b, 40c, 40d, 40e, 40f the amount of external fuel is relatively reduced. The cost of heating the heating chamber <NUM> may, accordingly, be relatively reduced with respect to prior art apparatus and methods.

As will be appreciated by one skilled in the art, the various steps described above may occur simultaneously. For example, waste material may be fed into the indirect kiln <NUM> at the same time as previously fed waste material is being heated by the gas burners.

The pressure in the rotatable tube 23c is monitored by the pressure sensor <NUM>. The temperature in the outlet pipe <NUM> is monitored by the temperature sensor <NUM>. The control system receives the monitored pressure and temperature. If the monitored pressure is greater than a predefined threshold then the control system is configured to actuate the pressure control valve <NUM> to allow synthesis gas to escape from the rotatable tube 23c. A pressure increase could be caused by, for example, an incident such as a blockage in the rotatable tube 23c. If the monitored pressure is less than a predefined threshold then the control system increases the draw of the fan <NUM>. The pressure in the rotatable tube 23c may be set to about <NUM> bar, e.g. atmospheric pressure.

The residue removal system <NUM> removes solids residue from the discharge hood 22a to be processed appropriately.

The control system may periodically provide a nitrogen purge to the inlet of the rotatable tube 23c from the first nitrogen supply 21a, by opening the check valve 21b. The control system may also provide a nitrogen purge to the discharge hood 22a from the second nitrogen supply 22c by opening the check valve 22d.

Referring now to <FIG>, there is shown a method of treating comminuted waste material according to the invention.

In a first step S11, comminuted waste material in the heating chamber <NUM> is heated using the gas burners 40a, 40b, 40c, 40d, 40e, 40f.

In a second step S12, the temperature in the heating chamber <NUM> is measured by the temperature sensors 29a, 29b, 29c, 29d, 29e, 29f, <NUM>, <NUM>, 29i, 29j, <NUM>, <NUM>. The measured temperature is sent to the control system. The temperature inside of the heating space 23d is measured by the temperature sensors <NUM>, <NUM>, 29i, 29j, <NUM>, <NUM>. This measured temperature is sent to the control system. As will be appreciated. the temperature in each of the zones 28a, 28b, 28c of the heating chamber <NUM> can be measured or determined individually. Additionally or alternatively, the temperature in the heating space adjacent each of the zones 28a, 28b, 28c can also be measured or determined individually.

Additionally, the monitoring devices <NUM>, <NUM>, 40i, 40j, <NUM>, <NUM> record the presence or absence of a flame at each gas burner 40a, 40b, 40c, 40d, 40e, 40f, respectively. The pressure sensor <NUM> measures the pressure of synthesis gas in supply pipeline 42a. The flow sensor <NUM> measures the flow rate of natural gas through the natural gas pipeline <NUM>.

In a third step S13, the control system compares the monitored or determined temperature in the heating chamber <NUM> with a predetermined temperature range. In particular, the monitored or determined temperature in the first zone 28a of the heating chamber <NUM> is compared with a predetermined temperature range for the first zone 28a. The monitored or determined temperature in the second zone 28b of the heating chamber <NUM> is compared with a predetermined temperature range for the second zone 28b. The monitored or determined temperature in the third zone 28c of the heating chamber <NUM> is compared with a predetermined temperature range for the third zone 28c.

Additionally, the control system uses data received from the monitoring devices <NUM>, <NUM>, 40i, 40j, <NUM>, <NUM>, the pressure sensor <NUM> and the flow sensor <NUM> to monitor the operation of the heating system <NUM>.

In a fourth step S14, the control system adjusts the amount of heat applied by one or more of the gas burners 40a, 40b, 40c, 40d, 40e, 40f to the heating chamber <NUM> if the measured or determined temperature in the heating chamber is outside of the predetermined temperature range. If, for example the measured or determined temperature in the first zone 28a of the heating chamber <NUM> is lower than the predetermined temperature range, then the control system adjusts one or each of gas burners 40a and 40b to increase the amount of heat they are applying to the first zone 28a.

The predetermined temperature range in the first zone 28a may be between <NUM> and <NUM>, say between <NUM>, <NUM>, <NUM> or <NUM> and <NUM>, <NUM>, <NUM> or <NUM>. The predetermined temperature range in the second zone 28b may be between <NUM> and <NUM>, say between <NUM>, <NUM>, <NUM> or <NUM> and <NUM>, <NUM>, <NUM> or <NUM>. The predetermined temperature range in the third zone 28c may be between about <NUM> and <NUM>, say between about <NUM>, <NUM>, <NUM> or <NUM> and <NUM>, <NUM>, <NUM> or <NUM>. The predetermined temperature range may be altered or set dependent on the composition of the waste material (for example the waste material to be fed into the heating chamber <NUM>).

The temperature in each of the zones 28a, 28b, 28c of the heating chamber <NUM> is controlled by controlling the heat applied by each of the gas burners 40a, 40b, 40c, 40d, 40e, 40f. The heat applied by each of the gas burners 40a, 40b, 40c, 40d, 40e, 40f is independently controlled by the control system. For example, the control system can increase or reduce the mass flow rate of air supplied to one, some or each of the gas burners 40a, 40b, 40c, 40d, 40e, 40f. The control system can also increase or reduce the mass flow rate of fuel to one, some or each of the gas burners 40a, 40b, 40c, 40d, 40e, 40f. The fuel may comprise a mixture of natural gas and synthesis gas. Additionally or alternatively, the control system can alter the ratio of the mixture of natural gas to synthesis gas in the fuel. Each gas control valve 44a, 44b, 44c, 44d, 44e, 44f can alter the amount of natural gas supplied to the respective gas burner 40a, 40b, 40c, 40d, 40e, 40f, or prevent any natural gas from being supplied to the respective gas burner 40a, 40b, 40c, 40d, 40e, 40f. Each gas control valve 44a, 44b, 44c, 44d, 44e, 44f can alter the amount of synethisis gas supplied to the respective gas burner 40a, 40b, 40c, 40d, 40e, 40f, or prevent any synthesis gas from being supplied to the respective gas burner 40a, 40b, 40c, 40d, 40e, 40f. In embodiments, only synthesis gas may be supplied to one, some or each of the gas burners 40a, 40b, 40c, 40d, 40e, 40f. In embodiments, only natural gas may be supplied to one, some or each of the gas burners 40a, 40b, 40c, 40d, 40e, 40f. Only natural gas may be supplied to the gas burners 40a, 40b, 40c, 40d, 40e, 40f when, for example, there is insufficient synthesis gas available. Such a situation may occur during initial start-up and running of the apparatus <NUM>.

The temperatures in the three temperature zones 28a-c may additionally be controlled by the control system altering the rotational velocity of the rotatable tube 23c. The control system is configured to control the variable speed drive motor <NUM> to rotate the rotating tube 23c at the desired rotational velocity.

The combustion air fan <NUM> is operable (e.g. by the control system) at a constant speed or at variable speeds. The electric drive motor 46a can be controlled by the control system. Because the flow rate of combustion air to the gas burners 40a, 40b, 40c, 40d, 40e, 40f is determined by the combustion air control valves <NUM>, 43i, 43j, <NUM>, <NUM>, <NUM>, variable control of the electric drive motor 46a on the combustion air fan <NUM> is only provided to improve the operating efficiency of the heating system <NUM>.

Referring now to <FIG>, there is disclosed a further method of treating comminuted waste material.

In a first, optional step S21, a ratio of mass flow of steam to mass flow of comminuted waste material is calculated. This may be calculated by or using the control system. The ratio is calculated to provide a target amount of a component of synthesis gas generated in the heating chamber <NUM>. The ratio may be calculated to provide a target amount of methane or hydrogen. The ratio may be calculated based upon historical operating data. The ratio may be based upon theoretical analysis, or the output of a proprietary process modelling software. The ratio may be calculated based upon a combination of historical operating data and theoretical analysis. The ratio is calculated based upon the specific geometry and operating conditions of the indirect rotary kiln <NUM> and of the type and granularity of the comminuted waste material.

In a second step S22, comminuted waste material is fed into the heating chamber <NUM> in a manner similar to that described with respect to step S2 of the method described in respect of <FIG>. In a third step S23, steam is introduced to the heating camber <NUM>.

In a second step S24, the steam is contacted with the comminuted waste material, which comprises mixing, in this disclosure. Comminuted waste material is fed into the heating chamber <NUM> in a manner similar to that described with respect to step S2 of the method described in respect of <FIG>. Steam is introduced to the heating camber <NUM>. In this disclosure, mixing of steam and comminuted waste material occurs inside of the heating chamber <NUM>. However, in other disclosures, mixing (and, indeed contacting) may occur at least partially external to the heating chamber <NUM>.

In a third step S25, the steam and comminuted waste material are heated inside the heating chamber <NUM> to generate a synthesis gas. This generated synthesis gas then exits the heating chamber <NUM> and enters the cleaning system <NUM> for further processing, as described above.

In a fourth step S26, the ratio of mass flow of steam to mass flow of comminuted waste material is adjusted such that the generated synthesis gas comprises the target amount of the component (e.g. methane or hydrogen) thereof, at a given temperature or temperatures in the zones 28a, 28b, 28c of the heating chamber <NUM>.

The mass flow rate of comminuted waste material fed into the heating chamber <NUM> is measured or determined. This may be accomplished by monitoring the mass of comminuted waste which is fed into the heating chamber <NUM> by the feed screw. This may be accomplished by measuring or determining the angular velocity of the feed screw. The angular velocity of the feed screw can be measured directly (for example via measurement or knowledge of the angular velocity of the motor driving the feed screw rotation) and/or can be measured indirectly (for example using an encoder).

The mass flow rate of steam into the heating chamber <NUM> is measured or determined by monitoring the flow of water via the flow sensor 51b. However, any suitable means for monitoring the mass flow rate of steam into the heating chamber <NUM> may be used.

The feed rate of comminuted waste material into the heating chamber <NUM> can then be controlled by adjusting the angular velocity of the feed screw. Additionally or alternatively, the mass flow rate of steam into the heating chamber <NUM> can be controlled by adjusting (e.g. automatically or manually) the flow control valve 51c. In this way, the mass flow rate of comminuted waste material into the heating chamber <NUM> can be adjusted to reach the calculated ratio of mass flow of steam to mass flow of comminuted waste material. In this way, the target amount of the component (e.g. hydrogen or methane) of the generated synthesis gas is achieved.

As will be appreciated by one skilled in the art, the first, optional step S21 can be carried out at any time prior to or simultaneously (e.g. at least partially) any of the other steps of the method. The steps S22, S23, S24 and S25 maybe continuous (or substantially continuous) during the treatment of the comminuted waste material. The first, optional step S21 may be run a single time or multiple times during the treatment of the comminuted waste material. For example, a different target amount of the component of the generated synthesis gas may be set. Additionally or alternatively, a different component of the generated synthesis gas may be set. Additionally or alternatively, one or more operating characteristics of the heating chamber (e.g. one or more temperatures therewithin and/or a rate of rotation thereof) may be altered and/or the composition and/or type of the comminuted waste material (e.g. a different plastics or mixture of plastics materials and/or a different size or range of sizes of comminuted particles of the waste material) may be used. A new calculation, where performed, may be based on any one or more of the above-identified characteristics and/or target component amounts. The optional step S21 may be carried out once one or more of the other steps has already begun. The sixth step S26 may be carried out subsequent to the optional step S21, for example and may be based on the results from the optional step S21.

Theoretical analysis using a proprietary process modelling software was undertaken to provide calculations of the ratio of mass flow of steam to mass flow of comminuted waste necessary to provide a target amount of a component of generated synthesis gas (e.g. the optional first step S21).

In one example, the comminuted waste material was polypropylene, the operating temperature within the heating chamber <NUM> was set to be <NUM>. The target component was set to be methane and its target amount was set to be <NUM>% v/v of the generated synthesis gas.

Using the theoretical analysis it was determined that the ratio of mass flow of steam to mass flow of comminuted waste material was <NUM>.

It has been surprisingly found that by increasing the ratio of steam to comminuted waste material between a ratio of <NUM> and <NUM> results in a decrease in the amount of hydrogen (on a percentage v/v of the generated synthesis gas) generated. Increasing the ratio of steam to comminuted waste material between a ratio of <NUM> and <NUM>, however, results in an increase in the amount of hydrogen (on a percentage v/v of the generated synthesis gas) generated.

Referring now to <FIG>, there is shown a method of treating comminuted waste material.

The first three steps S31, S32, S33 of the method shown in <FIG> are similar to the first three steps S21, S22, S23, respectively, of the method shown in <FIG>.

The method shown in <FIG> includes a fourth step S34 comprising a feed-back loop (e.g. a closed loop) for controlling the amount of a component contained in generated synthesis gas.

The fourth step S34 comprises a first stage S35 of measuring the amount of the component in generated synthesis gas. This measurement may occur outside or inside the kiln <NUM>, and/or may be achieved through use of a gas analyser, gas analysis means or system (not shown). The gas analyser or gas analysis means or system may comprise a gas chromatograph and/or may use gas chromatography and/or any other suitable technique as known to one skilled in the art. One or more other component of the generated synthesis gas may be measured (e.g. additionally).

In a second stage S36 the controller determines or calculates the difference between the target amount of the component of the generated synthesis gas and the measured amount of the component. If there is a difference then the controller calculates an alteration to the angular velocity of the feed screw and/or an alteration to the flow control valve 51c to, respectively, adjust the feed rate of comminuted waste material and the mass flow rate of steam into the heating chamber <NUM> in order to produce the target amount of the component. This calculation may be at least partially automated or may be performed by an operator.

In a third stage S37a, S37b an adjustment is made to the flow control valve 51c to increase or decrease the mass flow rate of steam entering the heating chamber and/or an adjustment is made to the angular velocity of the feed screw to increase or decrease the feed rate of comminuted waste material into the heating chamber. The adjustment(s) is/are made responsive to the calculation performed in the second stage S36. In one disclosure, only the mass flow rate of steam is adjusted. In another disclosure, only the feed rate of comminuted waste material is adjusted.

The above-described feed-back loop of the fourth step S34 provides for monitoring and control of the generated synthesis gas such that the target amount of the component is generated. Advantageously, this allows for maintaining a target amount of a component of the generated synthesis gas during operation. Further advantageously, this allows the target amount and/or the component to be changed during operation of the method. In this way, changes to end-use requirements can be more rapidly and readily met.

The control system may be automated (e.g. at least partially) or manually monitored and/or controlled (e.g. at least partially). The control system may be located remotely or at or adjacent the apparatus <NUM>. Additionally or alternatively, although a natural gas source <NUM> is described, this could instead be another combustible fuel, such as oil or coal or the like. Additionally or alternatively, although six gas burners are shown there may instead be any suitable number, for example more or less than six. Additionally or alternatively, although a single indirect rotary kiln is shown there may instead be plural indirect rotary kilns. Where more than one indirect rotary kiln is provided there may be a heating system, steam system, supply system, etc. for each indirect rotary kiln. Alternatively, where more than one indirect rotary kiln is provided a heating system, steam system, supply system or the like may be shared between two or more indirect rotary kilns.

Additionally or alternatively, any of the above-described methods may comprise a step of cleaning generated synthesis gas and/or any component thereof. Additionally or alternatively, any of the above-described methods may comprise a step of preparing or delivering generated (and/or cleaned) synthesis gas and/or any component thereof to or for a gas grid. Additionally or alternatively, any of the above-described methods may comprise a step of further processing generated synthesis gas and/or any component thereof, for example to produce a particular component or compound (e.g. methanol or carbon monoxide or the like).

Additionally or alternatively, although the apparatus <NUM> is described as comprising an indirect rotatable kiln <NUM> this need not be the case and, instead, the kiln may be a direct kiln, e.g. a direct rotatable kiln.

Claim 1:
A method of treating comminuted waste material, the method comprising:
a) providing a heating chamber (<NUM>) and one or more combustion heating means (<NUM>) for heating the contents of the heating chamber (<NUM>), the heating chamber (<NUM>) having an inlet (<NUM>) and an outlet (<NUM>) and comprising a first and second zone (28a, 28b),
b) feeding comminuted waste material through the inlet (<NUM>) and into the heating chamber (<NUM>);
c) heating the comminuted waste material in the first and second zone (28a, 28b) of the heating chamber (<NUM>), using the combustion heating means (<NUM>), to generate a combustible gas;
d) supplying at least a portion of the generated combustible gas to the one or more combustion heating means (<NUM>) for heating the first and second zones (28a, 28b) of the heating chamber (<NUM>); and
e) heating the comminuted waste material in the first zone (28a) of the heating chamber (<NUM>) to a first temperature T1 to gasify the comminuted waste material; heating the gasified material in the second zone (28b) of the heating chamber (<NUM>) to a second temperature T2 to generate combustible gas, where the second temperature T2 is greater than the first temperature T1, and adjusting the amount of heat applied by the one or more combustion heating means (<NUM>) to the first and second zones (28a, 28b) of the heating chamber (<NUM>) by altering the ratio of two or more fuel components supplied to the one or more combustion heating means (<NUM>).