This invention relates to the processing of organic material, in particular this invention relates to improvements in processing of material having an organic content by gasification and/or pyrolysis.

Gasification and Pyrolysis of organic matter are known techniques in which the material is heated in the absence of oxygen (pyrolysis) or in a low oxygen environment (gasification) to produce syngas. One example of this is in waste to energy systems wherein waste material, for example municipal solid waste, is pyrolysed/gasified to produce syngas which is then used to create electricity. However when material having a large amount of organic material with a low calorific value, for example wood (in contrast to materials such as plastics which have a high calorific value), is pyrolysed a carbonic residue remains which is a char or coke like substance referred to collectively herein as char.

After the pyrolysis reaction is complete this char still contains a large amount of unrecovered energy. This can be recovered by increasing the oxygen content to a level sufficient for gasification of the char to occur without combustion (approximately 3% to 12% by volume oxygen content). However, the gasification can take some time and adds to the overall processing time for the waste which reduces overall efficiency of the processing.

EP0822374 describes a rotating drum pyrolysis reactor with therein disposed iron balls with the gas inlet suitable for the introduction of hot gas with no or little oxygen content and a gas outlet suitable as outlet for the produced synthesis gas.

US4676439 describes a ball mill consisting of a rotating drum rotating around an axle having inside ferro-magnetic balls, wherein electromagnets are situated around the outer wall of the rotating reactor, which are controlled in such a way that they trap the metal balls on a lower position of the rotating drum, lift the metal balls as the reactor rotates, and release the metal balls near the top position of the rotating drum, causing the metal balls to fall in a parabolic arc to the bottom of the reactor causing a high impact milling action.

It is the purpose of the present invention to reduce the overall processing time of waste by pyrolysis/gasification.

According to a first aspect of the present invention there is provided an apparatus for pyrolysing or gasifying material containing an organic content; the apparatus comprising: an oven mounted for rotation on at least one support, said oven having an inlet for receiving hot gas having a low or zero oxygen content to heat the material therein so as to process it to produce syngas, and an outlet for said syngas; an electromagnet disposed in or adjacent said oven so as to create a magnetic field therein; a plurality of ferrous elements freely disposed within the oven; and control means for controlling the electromagnet and the rotation of the oven; wherein when activated said electromagnet retains said ferrous elements as the oven rotates, wherein the apparatus further comprises at least one gas analyser configured to analyse the composition of the gas exiting said oven; and wherein the control means is configured to receive signals from said gas analyser and when said signals indicate that processing of the material in said oven is substantially complete, control the electromagnet to release the ferrous elements when they are substantially at the top of the oven's rotation.

The oven may further comprise a first portion and a second portion, wherein said first portion is disposed above said second portion in a first rotational position and wherein said second portion is disposed above said first portion in a second rotational position; wherein said control means is configured to control the oven to rotate it between the first position and the second position.

The control means can be configured to activate the electromagnet to retain the ferrous elements as the oven rotates between the second rotational position to the first rotational position. In one arrangement the electromagnet can be located in the first portion and the control means is configured deactivate the electromagnet in the first position so that the ferrous elements fall, under the influence of gravity, into the second portion and in another arrangement the electromagnet can be located in the second portion and the control means is configured deactivate the electromagnet in the second position so that the ferrous elements fall, under the influence of gravity, into the first portion.

In this manner the ferrous elements can fall from above onto the char, which will be at the lowest point of the rotating oven due to gravity, and will break the char into smaller pieces. This increases the surface area of the char which increases the speed at which it is processed.

The apparatus comprises at least one gas analyser for analysing the composition of the gas exiting said oven. As described below, by analysing the gas exiting the oven the extent of the processing of the material in the oven can be determined, and in particular it can be determined when the majority of the material in the oven has been processed. The control means is configured to receive signals from the gas analysers and when said signals indicate that processing of the material in said oven is substantially complete, the control means controls the electromagnet to release the ferrous elements when they are substantially at the top of the ovens rotation. The control means can optionally also increase the oxygen content of the oven at this stage to gasify the char therein.

The ferrous elements may have a mass of at least 500g. Optionally the ferrous elements may have a mass of at least 1 kg. The ferrous elements comprise steel and/or may be substantially spherical. Optionally the ferrous elements may have one or more groove on their surface.

According to a second aspect of the invention there is provided a method of pyrolysing and/or gasifying material containing an organic content; the method comprising: providing an oven mounted for rotation on at least one support, said oven having an inlet and an outlet; providing a flow of hot gas having a low or zero oxygen content to the oven via the inlet to heat the material therein to process it to produce syngas; providing an electromagnet disposed in or adjacent said oven so as to create a magnetic field therein; providing a plurality of ferrous elements freely disposed within the oven; and activating said electromagnet to retain said ferrous elements as the oven rotates, wherein the method further comprises analysing the composition of the gas exiting said oven to determine when processing of the material in said oven is substantially complete, and when said process is substantially complete, controlling the electromagnet to release the ferrous elements when they are substantially at the top of the ovens rotation.

The oven may comprise a first portion and a second portion, and the method may further comprise: controlling the oven to rotate between a first rotational position in which the first portion is disposed above said second portion and a second rotational position wherein said second portion is disposed above said first portion. In one arrangement the electromagnet can be located in the first portion and the method further comprises activating the electromagnet to retain the ferrous elements as the oven rotates from the second rotational position to the first rotational position. The method then further comprises deactivating the electromagnet in the first rotational position so that the ferrous elements fall, under the influence of gravity, into the second portion. In an alternative arrangement the electromagnet is located in the second portion and the method may comprise activating the electromagnet to retain the ferrous elements as the oven rotates from the first rotational position and the second rotational position. The method then further comprises deactivating the electromagnet in the second position so that the ferrous elements fall, under the influence of gravity, into the first portion.

The method comprises analysing the composition of the gas exiting said oven. By analysing the composition of the gas exiting said oven it can be determined when processing of the material in said oven is substantially complete. The method further comprises, when said process is substantially complete, controlling the electromagnet to release the ferrous elements when they are substantially at the top of the ovens rotation. The method may comprise, when processing of the material in said oven is substantially complete, increasing the oxygen content of the oven. Increasing the oxygen content of the oven may comprise increasing the oxygen content of the oven to between 3 and 12 % volumetric flow rate

Specific embodiments of the invention are described below, without limitation, with reference to the accompanying drawings in which:

• Figure1 shows a schematic diagram of an apparatus of the invention;
• Figure 2 shows a side view of an apparatus of the invention;
• Figure 3 - 5 show the operation of the invention; and
• Figure 6 shows an example of a ferrous element for use in the invention.

Referring to Figures 1 and 2 an oven 10 is shown comprising a first portion 12 and a second portion 14. The second portion 14 is detachable from the first portion 12 to load and unload material to be treated into the oven 10.

The oven is pivotally mounted on two mounts 16 and a drive 18 is provided to rotate the oven between a first rotational position in which the first portion 12 is above the second portion 14 and a second rotational position in which the second portion 14 is above the first portion 12.

A supply of hot gas is provided to the oven via a conduit 20 from a hot gas supply 22, and exits the oven via a further conduit 24. A gas analyser 26 is provided to analyse the composition of the gas exiting the oven. The gas analyser may measure one or more of: hydrogen content, carbon monoxide content and carbon dioxide content, of the gas.

An electromagnet 28 is provided in the oven. The electromagnet may be provided in either the first or the second portion of the oven and is shown in the first portion in Figure 1 for illustration purposes. A plurality of ferrous elements 30 are provided in the oven. The ferrous elements are described in more detail in relation to Figure 6 below.

Referring to Figures 3 to 5 the operation of the oven is shown.

A batch of material to be processed is loaded into the oven and hot gas, containing substantially no oxygen is passed through the oven as it rotates so as to pyrolyse the material therein. As the material pyrolyses hydrogen and carbon monoxide is released and exits the oven via the outlet conduit 24. The gas analyser 26 monitors the composition of the gas as it exits the oven and sends signals to the controller 32. Once the controller determines that the signals from the gas analyser indicate that the pyrolysis of the material is nearing completion it increases the amount of oxygen in the gas so that the reaction in the chamber moves from pyrolysis to gasification. The controller may respond to, for example, the reduction below a specific threshold value of the hydrogen or carbon monoxide level in the gas exiting the oven.

At this stage in processing, when the majority of the material in the oven has been pyrolysed a residue 34 containing inert material and carbonic residue formed from the pyrolysis of low calorific value organic material will remain in the oven. As the oven rotates the electromagnet is activated so that the ferrous elements 30 are attracted to and retained as the oven rotates into the first position (Figure 3). When the oven reaches this position the electromagnet 28 is deactivated and the ferrous elements are therefore released and fall from the top of the oven to the bottom of the oven where they will collide with the char and due to their mass and the more brittle nature of the char will break or crush the char into smaller pieces (Figure 4).

The oven then rotates from the second first position to the second position (Figure 5) and the electromagnet 28 is then activated again to attract and retains the ferrous elements. The oven then continues to rotate back towards the first position (Figure 3) and the process is repeated. Once the gas analysers show that the gasification reaction is substantially complete the process is finished, the oven returned to the first position and the second portion 14 is removed, emptied and recharged with a fresh batch of material.

Breaking the char into smaller pieces increases its surface area available to react with the oxygen in the hot gas passing through the oven and thereby reduces the time taken to gasify the char.

Decreasing the overall processing time increases the efficiency of the waste processing as the amount of time the hot gas needs to be provided is reduced. The gas released as syngas can be used for energy production and accordingly by reducing the amount of that energy that needs to be used for producing the hot gas (by reducing the amount of time the hot gas is needed for) the overall percentage of the energy recovered that is available for export is increased.

Referring to Figure 6 an example of a ferrous element for use in the apparatus is shown. The element 30 is substantially spherical in shape and is made of ferrous steel. Each element preferably weighs above 500g and elements having a mass of 1kg or above may be beneficial in crushing the char. As can be seen the element has a number of grooves 36 around its edge separating the surface into a plurality of raised shapes 38. These raised features improve the friction as the elements impact on the char and assist in preventing them from glancing off large pieces which is more likely if the elements a have a smooth spherical outer surface. It will be appreciated that any surface that gives this effect may be used and the ferrous elements are not limited to the shapes shown.