GB2539108A

GB2539108A - Pyrolysis device

Info

Publication number: GB2539108A
Application number: GB1610158.6A
Authority: GB
Inventors: Stein Peter
Original assignee: Green Made Easy Ltd
Current assignee: Green Made Easy Ltd
Priority date: 2016-06-10
Filing date: 2016-06-10
Publication date: 2016-12-07
Anticipated expiration: 2036-06-10
Also published as: GB2539108B; CN106065333A; GB201610158D0; CN106065333B

Abstract

The invention provides a pyrolysis (or gasification) apparatus for the pyrolysis of fuel, comprising: a static pyrolysis chamber comprising an inner surface defining a fuel contact surface, wherein the chamber is configured to be heated such that the fuel contact surface is maintained substantially at a desired temperature; the chamber further comprising a fuel inlet 22 and an outlet 23; and fuel transportation means, for moving fuel from the fuel inlet to the outlet, which means comprise: a shelf 5 located within the chamber, below the fuel inlet and above the outlet, to receive fuel failing from the fuel inlet, the shelf defining a hole 21 adjacent to the fuel contact surface; and a fuel contact member 8 configured to move fuel over the shelf towards the fuel contact surface until the fuel falls through the hole in said shelf. Advantages of the invention include a reduction in manufacturing and maintenance costs, increased levels of safety of a pyrolysis gasifier and an improved gas product quality.

Description

Pyrolysis Device The invention relates to a device for use in the process of gasification of carbonaceous material. Gasification includes performing pyrolysis (also called devolatilisation) on a carbonaceous fuel.

Pyrolysis involves the thermal cracking of hydrocarbon cleans (fuel; in the absence of oxygen. This breaks down the fuel into essentially three parts: gas, oil and carbon char. These products can be used in a multitude of ways. However, pyrolysis units are historically expensive and complex, A common type of pyrolysis unit is a rotating kiln type that requires complex gas seals to prevent air ingress into a rotating pyrolysis chamber to prevent the risk of explosion, flashbacks, etc. In a rotating kiln type unit, which rotates around a substantially horizontally orientated axis, gravity puils the fuel down to the lower part of the kiln so the upper parts of the kiln pick up heat when at the top end lose heat to the fuel at the bottom. Therefore, in this unit a significant temperature gradient results, which may affect the thermochemicai reactions inside the kiln resulting in a poorer quality of the gas produced and may thermally stress the retort materials reducing their useful life expectancy.

An embodiment of the present invention can provide a reduction in manufacturing and maintenance costs. An embodiment of the invention can further provide increased levels of safety of a pyrolysis gasifier and improved gas product quality. An embodiment of the invention may be used to process waste materials. for example waste wood, and other agricultural waste products, andior used car tyres. Any carbonaceous waste product may be processed by en embodiment of the present invention in order to yield bio-fuels which may then be burned directly or gasified for example in order to produce energy.

An embodiment of an aspect of the invention includes a pyrolysis apparatus (device) for the pyrolysis of fuei, comprising: a static pyrolysis chamber comprising an inner surface defining a fuel contact surface, wherein the chamber is configured to be heated such that the fuel contact surface is maintained substantially at a desired temperature; the chamber further comprising a fuel inlet and an outlet; and fuel transportation means, for moving fuel from the fuel inlet to the outlet, which means comprise: a shelf located within the chamber, below Me fuel inlet and above the outlet, to receive fuel falling from the fuel inlet, the shelf defining a hole adjacent to the fuel contact surface; and a fuel contact member configured to move foe: over the sheti towards the fuel contact surface until the fuel falls through the hole in said shelf.

The fuel contact member moves the fuel around the chamber so that the fuel comes into contact with the fuel contact surface. As the fuel comes into contact with the fuel contact surface it is heated to the desired temperature, Inside the chamber the atmosphere is oxygen-deprived. Therefore, the fuel is not combusted, but pyrolysed. This embodiment minimises temperature variation of the inner surface of the chamber's outer wall (fuel contact surface) as the fuel is passed over a large surface thereof so as to transfer the heat more equally, providing a consistent temperature of the outer wall and consistent heating of the fuel. Thus, thennal stresses on the chamber, due to temperature variations, can be reduced or eliminated, By achieving a more consistent temperature of the heated surfaces of the pyrolysis chamber, quality of the gas product can be improved. Examples of suitable materials for the chamber include, among others, stainless steel, weathering steel or basic carbon steel. Stainless steel provides an advantage of high oxidation resistance in air as well as resistance to acids.

Weathering steel and basic carbon steel provide a more cost effective material for lower temperature pyrolysis. In order to monitor temperature and temperature variation of the fuel contact surface and the or each shelf, thermocouples may be attached thereto, Preferably, there will be several such thermocouples distributed over the fuel contact surface to check that the temperature distribution is consistent with the throughput of fuel and the speed of movement of the fuel contact member.

Optionally, the fuel contact member comprises a pusher paddle mounted for rotation relative to the shelf.

The fuel contact member may include one or more paddles (pusher arms) for pushing the fuel around the pyrolysis chamber, along the fuel contact surface, The position of the one or more paddles is set to encourage the fuel to contact the fuel contact surface for the longest possible time for one rotation of the paddle pushing the fuel from the point at which the fuel falls onto a shelf until the fuel falls through the hole in the shelf, Specifically, the fuel falls from, for example, the inlet onto the shelf. A pusher paddle then moves to push the fuel across the shelf until the fuel is pushed into contact with the fuel contact surface. As a practical matter, not all of the fuel may immediately contact the fuel contact surface. However, as the fuel is broken down by the heating process it flows down the fuel contact surface to allow ices processed fuel to contact the fuel contact surface, In a cylindrical pyrolysis chamber, the or each pusher paddle requires minimal adjustment when rotating relative to the shelf, as the distance from the rotational axis of the pusher paddle to the fuel contact surface is constant in all directions.

Preferably, the number off] pusher paddles is set in dependence on the amount of luel to be processed, Fuel tens to collect in front of the or each pusher paddle with the rotation thereof. Therefore, to ensure fuel does not build up to the point where it spills over the pusher paddle, the number of pusher paddles may be increased as appropriate. Control of the number of pusher paddles relative to the amount of fuel allows the fuel to be transported around the pyrolysis chamber in a predictable end repeatable manner Optionally, the shelf is one of a plurality of such shelves within the chamber, a first one of the shelves being positioned to receive fuel from the fuel inlet, and the other one or more shelves of the plurality Sing positioned between the first shelf and the outlet, wherein the hole defined in each shelf is offset from the holes of immediately adjacent shelves and each shelf is provided with a fuel contact member to move the fuel over that shelf.

Under the action of gravity fuel enters the pyrolysis chamber through the fuel inlet and falls onto the first shelf. The fuel is then transported around the first shelf and along the fuel contact surface, adjacent to the shelf, by the fuel contact member until the fuel falls through the hole. The fuel then falls to the next shelf where the fuel is again transported around that shelf and along the fuel contact surface adjacent to the shelf by the fuel contact member. The fuel then falls through the hole in that shelf to either a next (lower) shelf or to the outlet. The offset of the respective holes in the shelves refers to the position when observed in a plan view, Each hole is positioned at a different point on the circumference of the chamber so that the fuel does not fall directly through two holes in two shelves, but the holes are only minimally offset to allow the fuel as much contact =civith the fuel contact surface as possible.

Optionally, the pyrolysis apparatus further comprises a shaft configured to be rotated inside the chamber, wherein the or each fuel contact member is attached to and rotatable with the shaft.

The or each fuel contact member may be attached to a shaft, which is preferably located at the centre of the pyrolysis apparatus (when observed in plan). The speed of rotation of the fuel contact member dictates how fast the fuel will pass through the pyrolysis apparatus and thus dictates the dwell time. The number of shelves is also a factor in determining dwell time. Rotation of the shaft with the or each fuel contact member allows all fuel in the pyrolysis apparatus to be processed at the same speed and to have the same dwell time. The rotational speed of the shaft may be controlled from outside the chamber.

Optionally, the shaft further comprises height adjustment means for adjusting and setting a desired height of the shaft.

It may be desirable to adjust the position of the shaft relative to the chamber (height of the shaft), which also affects the height of the fuel contact member. Preferably. the fuel contact member should be located just above the or each shef, to move the fuel efficiently without increasing friction between the fuel contact member and the or each t=0 shelf.

Optionally: the fuel inlet comprises a first rotary valve, configured to allow the fuel into the chamber while inhibiting oxygen from entering the chamber.

The absence of oxygen is a key part of pyrolysis. It is difficult to prevent any oxygen from entering the pyrolysis chamber. However, the use of a rotary valve at the fuel inlet, to let fuel in and Keep as much oxygen (and any halogens) out as possible, improves the pyrolytic process. An isolation valve may be used in combination with the rotary valve to further reduce the ingress of oxygen into the chamber. Alternatively, or in combination, fuel may be delivered to the chamber using a compaction scroll method, making a solid plug to prevent air ingress, or usng a compactor fuel feed system.

Optionally, the outlet comprises a second rotary valve, configured to allow solid pyrolysis products out of the chamber while inhibiting oxygen lion/ entering the chamber.

In order lo allow the solid products (mainly carbon char, but depending on the fuel, other solid productsfby-products may also be present) of the pyrolysis to be output from the chamber, while preventing the ingress of oxygen, a rotary valve may be positioned at the outlet. At the outlet the carbon char has a consistency of a powder. Again, an isolation valve may be used in combination with the rotary valve to a similar effect. A compaction scroll method may also be used to extract the carbon char. Rotary valves provide the further advantage of allowing the volume of fuel delivered into the chamber, and solid fuel product removed from the chamber, to be regulated.

Optionally, the or each shelf comprises an upper surface configured to direct the fuel towards the fuel contact surface.

Although the movement of the pusher paddles will tend to push the fuel towards the inner surface of the wall of the chamber (fuel contact surface), this tendency can be improved by configuring the upper surface of the or each shelf to direct fuel towards the outer walls. For example, the upper surface may be sloped or curved downwards towards the outer walls, preferably at an angle in a range from about 15 to 30 degrees to the horizontal (when the chamber is orientated vertically) in order to encourage the fuel to move towards the fuel contact surface.

Optionally, the upper surface is substantially dome-shaped, frustum-shaped (e.g frusto-conical) or cortical.

An example of a sloped or curved upper surface is a dome-shaped, frustum-shaper) or conical surface. The fuel contact member may preferably have a shape conforming to the upper surface of the corresponding shelf, so as to push substantially all the fuel on the shelf.

Optionally, the or each fuel contact member is configured to spread the fuel over the fuel contact surface.

The fuel contact member may have a shape and/or length appropriate to spread the fuel over the fuel contact surface. For example, the fuel contact member may have a shape that matches the fuel contact surface, such that when fuel contacts the fuel contact surface it is spread or smeared to coat the fuel contact surface. An advantage of spreading the fuel over the fuel contact surface is the avoidance of temperature differentials in the chamber wall and consistent application of heat to the fuel to improve the pyrolysis process.

Optionally, the pyrolysis apparatus further comprises a muffle furnace configured to heat the fuel contact surface, wherein the muffle furnace is fuelled by a product of the pyrolysis.

The outside surface of the wall of the chamber may be heated by any suitable means to provide a consistent temperature at the fuel contact surface, A muffle furnace, surrounding the outside surface of the chamber, provides one such suitable means. One or more products of the pyrolysis may be fed back into the muffle furnace as another l'uei which is burned (combusted) in the muffle furnace to be converted into heated exhaust. This exhaust then heats the outside surface of the wail of the chamber.

Optionally, the pyrolysis apparatus further comprises a gas outlet totaled towards the top of the chamber, for releasing gaseous products andlor oil vapour produced during pyrolysis of the fuel.

During pyrolysis, gee and oil vapour is produced which may preferably be output from the chamber by means of a gas outlet. Positioning the gas outlet near the top of the chamber ensures that only gaseous products of the pyrolysis pass through this outlet. The gas outlet may include a one-way valve to glow gas and oil vapour to pass out of the chamber, but not allow any gases into the chamber.

Optionally, the chamber is orientated substantially vertically.

To obtain an even distribution of the fuel within the chamber, the chamber may be orientated substantially vertically. Since the fuel is transported partially under the influence or gravity, orientating the chamber substantially vertically ensures that the fuel, at each stage, falls to the appropriate position on the first shelf, subsequent shelves and the outlet, This improves the predictability and consistency of the dwell time of the fuel.

Other advantages of this embodiment include lower cost in manufacturing with improved safety and efficiency, and a reduction in thermal stresses of the pyrolysis chamber materials with a compact overall size of the apparatus.

By fixing the pyrolysis chamber substantially vertically within a muffle furnace and moving the fuel around and down through the chamber via a series of shelves by pushes paddles, the only moving parts are the central shaft and the pusher paddles. This eliminates the requirement for seek on the inlet and outlet shafts of a rotating retort of existing systems and increases the usable surface area, improving the efficiency of the thermochernical reaction of pyrolysis, reducing the size of the chamber and the footprint of the furnace as a whole.

Embodiments of the invention will now be described by way of example only, wth reference to the accompanying drawings, in which.

Figure la shows a perspective view of a pyrolysis apparatus according to an embodiment: Figure 1b shows a side-on cross-sectional view of a muffle furnace and pyrolysis chamber according to an embodiment; Figure 2 shows a plan view of a muffle furnace and pyrolysis chambei; Figures 3a and 3b are plan and elevation views showing an embodiment of a shelf, Figure la shows an example of a pyrolysis apparatus according to an embodiment. In this embodiment, the invention includes a chamber 6', in which the pyrolysis of carbonaceous fuel is carried out. The chamber 6' is non-rotating and includes a fuel inlet 22' at the top and an outlet 23', for solid pyrolysis products, at the bottom.

Between the inlet 22' and the outlet 23', there is positioned a shelf 5' in the chamber 6'.

The shelf 5' extends across the entire chamber 6'. The shelf 5' has a hole 21' through which the fuel may pace to get from inlet side of the shelf 5' to the outlet side of the shelf 5'. In use, fuel enters the chamber 6' through the inlet 22'. The chamber 6', and in particular a wall 20' of the chamber 6', is maintained at a desired temperature to 19 achieve pyrolysis. Therefore, once the fuel enters the chamber 6' it begins to be heated. The fuel falls from the inlet 22' onto the shelf 5'. A fuel contact member 8' is positioned over the shelf 5' and moves to push the fuel, now resting on the shelf 5', over the shelf 5' and towards the wall 20' of the chamber 6'. The wall 20' of the chamber 6', which is kept at a desired temperature, heats the fuel on contact to cause thermal cracking of the hydrocarbon chains in the fuel (pyrolysis). During pyrolysis, the fuel is broken down into three main components (products) gas, oil vapour and carbon char The gas and oil vapour may then be extracted from the chamber by any suitable means. The solid component of the fuel is the carbon char. The fuel (mainly carbon char at this stage) is then moved by the fuel contact member 8' along the wail 20' until reaching the hole 21' in the shelf 5', The hole 21' is positioned next to the wail 20' so that as the fuel is moved along the wall 20'. it moves over the hole and falls to the outlet side of the shelf 5'. The fuel (almost entirely carbon char and any other byproducts at this stage) then falls towards the outlet 23' and exits the chamber 6' through the outlet 23'.

Figure lb shows an exemplary embodiment of the invention including a muffle furnace 7 surrounding a pyrolysis chamber 6. In this embodiment the fuel is delivered by a conveying system 1. The conveying system 'I allows for adjustment of the speed and volume of fuel being delivered to the chamber 6. From the end of the conveying system 1 the fuel drops into and through a fuel inlet 22 which includes a rotary valve 2 and an open isolation valve 3. The fuel drops through the rotary valve 2, which acts to form a gas seal, and then through an open isolation valve 3 and down onto a first shelf 5 within the pyrolysis chamber (retort) 6, The rotary valve 2 has several vanes that rotate to allow fuel to pass from one side of the rotary valve 2 to the other. The rotary valve 2 has a minimum of two tips of the vanes in contact with side walls of an entrance to the chamber 6 in which the rotary valve is located, so that the tips form seals and prevent gases escaping and air entering the chamber 6.

Inside the pyrolysis chamber 6, once the fue has passed through the rotary valve 2 it falls onto a first shelf 5a inside the chamber 6. The pyrolysis chamber 6 is provided internally with a plurality of further shelves 5h, 5c, 5d, 5e and 5f. Each of the shelves 5a to 51 slopes down from the centre of the chamber 6 towards an outer wall 20 (fuel contact surface) of the chamber 6. The fuel slides down the slope of the shelf 5a (5b, 511) and on to the fuel contact surface 20. Within the chamber 6, a paddle. wheel 8 rotates around a central shaft 9. The rotational speed of the central shaft 9 may be adjusted to change the length of time (dwell time) that the fuel spends In the pyrolysis chamber 6. In this embodiment the paddle wheel (fuel contact member) Et includes four arms (only two are depicted in figure lb), over the first shelf Se, each arm having a paddle 24. The paddle wheel S may however have a number of arms greater or fewer than four. As the paddle wheel 8 rotates, the paddles 24 sweep the fuel around the shelf 5a (5b, .", 5f) until the fuel reaches a cut-out section 21 (hole) on the shelf where the fuel drops to the next shelf 5b, (Sc.,,5t) below. The average speed with which the paddies 24 move at their outermost portion (adjacent to the fuel contact surface 20) may for example be 200rrim to 300mm per second. The shelves 5 are preferably welded to the outer wall 20 of the chamber 6. The cut-out sections 21 of the shelves are staggered so:hat the fuel drops forward (in the direction of rotation of the paddle wheel 6) of the hole on the shelf 5b (5c, ..., 5f) below and the paddle 24 sweeps it around about 330 degrees to the out-out section 21 on that shelf, where the process continues until the fuel falls down and cut of the pyrolysis chamber 6 after the last shelf 5f. After the last shelf 51, the fuel falls to an outlet 23. The outlet 23 may comprise a further isolation valve andior a rotary vane, similar to those used at the inlet 22. In this embodiment, the pyrolysis chamber 6 is orientated substantially vertically to allow the fuel to fall under gravity from one shelf to the next when passing over the cut-out section 21 of the current shelf 5. This orientation of the chamber 6 may beneficially increase its structural rigidity, owing to a more even distribution of the fuel across the outer wall 20 when being pushed around the chamber 6 by the paddles 24 which prevents the chamber 6 from bending due to differential temperatures experienced by the outer wall 20. The paddles 24 andlor paddle wheel 8 may be made of stainless steel or other suitable materials.

The paddies 24 of the paddle wheel 8 are on arms driven by the central shaft 9 located by a bearing 10 on a bottom end plate of the pyrolysis chamber 6. This shaft is driven by a gearbox and motor drive assembly 4 fixed on a pyrolysis chamber top plate. The central shaft 9 can be raised and lowered by an adjusting nut 15 on the shaft. The position of the central shaft 9 may be adjusted to minimise wear of the pusher paddles 24 and shelf or shelves. Further, the position of the paddles 24 relative to the shelf or shelves may be adjusted to reduce friction to correspondingly reduce running electrical power required to rotate the paddles 24.

Locating the moving or mechanised parts, such as the gearbox and motor drive assembly 4, outside the chamber 6 has the advantage that those pans are not exposed to the relatively inhospitable environments inside the chamber 6. This provides the further advantage that maintenance may be performed on those parts without affecting the chamber 6.

The pyrolysis chamber 6 is located approximately centrally within the muffle furnace 7, where hot exhaust enters the part of the muffle furnace 7 surrounding the chamber 6 at an inlet 11. Cooler exhaust, that has passed some heat into the fuel through the outer wall 20 of the pyrolysis chamber 6, exits the muffle furnace 7 at an nutlet 12. By controlling the exhaust temperature entering the muffle furnace 7 it is possible to control the pyrolysis temperature of the pyrolysis chamber 6. The outside of the muffle furnace 7 is insulated by a layer of insulation 13 to retain heat within. The material krming the insulation 13 may include high density manufactured mineral fibres (MIFF) andtor calcium silicate and may additionally be aluminium clad. Other suitable materials may be used instead or in addition to these.

Gas products of the pyrolysis, together with oil vapour product, exit the pyrolysis chamber 6 via a pipe 16. The pipe 16 is located near to or at the top of the chamber 6. The gases and oils are cracked off from the char (carbon). They take up more volumetric space than the Fuel, so that the pressure in the chamber 6 rises. The increase in pressure then forces the gas and oil out of the chamber 6 via the pipe 16. Optionally, a fan may be activated which socks the gases and oil out of the chamber 6 through the pipe 16 to maintain a slightly negative pressure of 1 or 2 mbar.

The char produced by the pyrolysis is light and powdery once the outlet 23 is reached, so inert byproducts can be separated easily by magnets or eddy current and/or by density separation.

Figure 2 shows a plan view of the exemplary embodiment shown in figure lb. As shown in figure 2, the outer wall 20 of the pyro his's' chamber 6, the muffle furnace 7 and the insulation layer 13 are all substantially circular in plan (or cylindrical in shape). This shape aids even distribution of the fuel over the outer wail 20, when moved by the pusher paddles 24. Adopting this shape also means that the pusher paddles 24 may have a fixed length, requiring no adjustment after manufacture, reducing the maintenance burden. The cut-out section 21 of the shelf 5a is omitted in this figure.

As shown in figure 2, heated exhaust enters the muffle furnace 7 via the inlet 11. The inlet 11 is positioned offset from the pyrolysis chamber 6 to encourage the heated exhaust to circulate around the pyrolysis chamber 6. This arrangement beneficially also avoids one part of the outer wall 20 of the pyrolysis chamber 6 being positioned in the direct path of the exhaust, close to the inlet 11, hence preventing that part being heated more than other parts of the outer wall 20, resulting In a temperature differential. Similarly, the outlet 12 is offset from the inlet 11 and is positioned lower than the inlet 11 to encourage a level of turbulence within the muffle furnace 7, so that the heated exhaust has more time in the muffle furnace 7 to transfer heat to the outer wall 20. The outlet 12 is positioned lower than the inlet 11 so that it is the cooler exhaust which is passed through the outlet 12_ Figure 2 depicts the pusher paddles 24 positioned to rotate in an anticlockwise direction. The direction of rotation of the paddles 24 may however be clockwise.

Figure 3a shows a plan view of a shelf 5. in this case the first she 5a. As shown, the shelf includes a out-out section 21 (hole}, in this embodiment each of the shelves 5a -51 in the pyrolysis chamber 6 has approximately the same shape. When the pyrolysis chamber includes more than one shelf 5a -51, adjacent shelves will be mounted such that the holes are offset with respect to each other. This offset is intended to prevent the fuel falling through the cut-out section 21 of the higher shelf and then directly through the hole in the lower shelf, which would result in the fuel not being passed over the fuel contact surface 20 at the level of the lower shelf. The fuel would therefore pass through the pyrolysis chamber 6 too quickly to be broken down into the various products of the pyrolysis process. The offset of each adjacent shelf 5a -61 may preferably be about 30*, so that the fuel falls beyond the cut-out section 21 on the next shelf and is pushed 330° around the next shelf. However, the exact amount of offset depends on the size of the cut-out section 21, which is preferably slightly smaller than the offset. The central shaft 9 passes through the middle of the or each shelf. The cut-out section 21 may be of arty suitable size to allow the fuel to pass through easily.

Typically the cut-out section 21 may have a length or diameter of 400 600 mm for a chamber 6 having a diameter of 4.5 in designed to accommodate 10 tonnes of fuel. The or each shelf 5 may optionally include multiple cut-out sections 21. For example, a larger apparatus may benefit from multiple holes in the or each shelf in order to allow the fuel contact member 8 to move at lower speeds and avoid excessive fuel build-up in front of the fuel contact member 8. As an example, it is envisaged that a 4.5m chamber 6 with a paddle wheel of twelve paddles 24 might have four cut-out sections 21 per shelf.

Figure 3b shows a side-on view of the shelf 5a of figure 3a. From this view, it can be seen that the shelf fia is formed in a frusto-conical shape. Alternative sloped-shapes are also envisaged, such as a dome or cone.