Patent Application
20160208181
The present disclosure relates to a churning and stoking ram, in particular to a churning and stoking ram for use in furnaces. The disclosure also relates to a furnace capable of mechanically agitating the contents thereof and a system for low temperature gasification of waste solids. Additionally, the disclosure relates to a method of mechanically agitating the contents of a furnace.
Gasification of carbonaceous materials typically involves a thermal reaction between the carbonaceous material, oxygen and steam to create a mixture of low weight hydrocarbons, such as methane, carbon monoxide and hydrogen (syngas). Gasification is widely used to produce syngas for firing or syngas for refining into chemicals, liquid fuels and hydrogen, and has been identified as a key enabling technology for advanced high-efficiency, low-emission non-fossil fuel and renewable energy power generation.
High temperature gasification and other medium to light combustion air input thermal processes generate turbulent hot gases. In turn, the turbulent hot gases facilitate pneumatic agitation of the contents of a furnace, thus assisting in consumption of the carbonaceous material as “fresh” surfaces are brought into contact with the process reactants.
Pneumatic agitation, however, can result in entrainment of solids, heavy metals and ash in the resulting syngas product stream, which is then treated by downstream filtration techniques and/or scrubbing to remove the entrained solids and ash.
The application of high temperature gasification and other medium to high combustion air input thermal processes to manage municipal waste presents many difficulties, particularly because of the lack of homogeneity of the contents in terms of size and composition compared to other carbonaceous materials such as coal and blomass.
The average moisture content of municipal waste may vary from 20-60%, or higher, and the average incombustible content may vary from 5-30% or higher, with some waste charges having 100% incombustible items (e.g., glass, metals, etc.). A high incombustible content results in a high density charge with concomitant increased accumulation of incombustibles/ash content The larger percentage of inorganic solids and ash that is not consumed by combustion processes leads to an increase in the downstream clean-up processes required to provide a syngas product stream and reduced production efficiency.
Further, the high incombustible or ash content accumulates in the gasification or combustion chamber and depletes the available space in the gasification or combustion chamber. After 6-8 hours of operation under typical conditions, several issues can occur if the volume occupied by incombustible material and ash is not reduced by ejection, including:
Furthermore, complete gasification or combustion of the contents is not always achievable as pneumatic agitation may not prove sufficiently strong to bring larger, heavier particles in the waste solids in contact with the combustion reactants. Waste that has a high moisture content, incombustible content and density can self insulate itself from the gasification or combustion process and form sections or “pockets” of coagulated or partially degraded waste that substantially reduces thermal efficiency, in addition to partially degraded matter being ejected with ash.
In contrast, low temperature gasification relies on thermal degradation of the carbonaceous material in an oxygen-depleted ultra-low sub-stoichiometric environment, rather than combustion reactions, to produce a syngas product stream.
The application of low temperature gasification in the management of heterogeneous mixtures of municipal waste minimizes the problem of entrained solids and ash in the syngas product stream because there is little or no pneumatic agitation of the contents of the furnace in which low temperature gasification occurs. Conversely, however, in the absence of pneumatic agitation, there is little mixing of the waste solids within the furnace, resulting in the stratification of the contents where thermally degraded material overlies unreacted carbonaceous material. Where inorganic material, particularly silica-containing material, thermally degrades to form a slag, a mechanical barrier to further thermal degradation of the underlying contents may form, and many of the problems listed above may also arise.
In its broadest aspect, the disclosure provides a churning and stoking ram for a furnace capable of mechanically agitating the contents therein, and a system for 1 o w temperature gasification of waste solids. The disclosure also provides a method of mechanically agitating the contents of a furnace.
Accordingly, in a first aspect of the disclosure, there is provided a churning and stoking ram for a furnace comprising:
In one embodiment of the disclosure, the churning device and the second actuator are housed in an internal void of the stoking ram. The second actuator is operative to impart translational movement of the churning device along the central longitudinal axis of the stoking ram between the retracted position wherein the churning device is disposed in the internal void of the stoking ram, and the extended position wherein the churning device is disposed externally of the stoking ram in longitudinal alignment therewith.
In one embodiment, the churning device comprises an elongate member having a plurality of paddles outwardly depending therefrom.
In another embodiment, the paddles are equiangularly disposed around a central longitudinal axis of the elongate member. In a preferred embodiment, the paddles extend continuously along a length of the elongate member. In an alternative embodiment, the paddles are configured in discontinuous spiral flutes along the length of the elongate member.
In a further embodiment, the stoking ram is provided with a removable head.
In one embodiment, the churning device and/or the stoking ram are generally horizontally disposed proximal a lower surface of the furnace when the churning device is extended and/or the stoking ram is in the internal position relative to the furnace.
In accordance with a second aspect of the disclosure, there is provided an apparatus capable of mechanically agitating the contents therein, the apparatus comprising a furnace provided with the churning and stoking ram as described above.
In a preferred embodiment of the disclosure, the apparatus is provided with a pair of churning and stoking rams in spaced parallel alignment with one another. The pair of churning and stoking rams may be arranged to operate independently of one another, or in an inter-related sequence of operations determined by the positions of the stoking ram and the churning device of each respective churning and stoking ram.
In accordance with a third aspect of the disclosure, there is provided a system for low temperature gasification of waste solids comprising one or a plurality of furnaces adapted for low temperature gasification of waste solids, adjacent furnaces being disposed in stepped tiers, each furnace being provided with a churning and stoking ram as described above to mechanically agitate the waste solids therein.
In a preferred embodiment of the disclosure, each furnace is provided with a pair of churning and stoking rams in spaced parallel alignment with one another. The pair of churning and stoking rams may be arranged to operate independently of one another, or in an inter-related sequence of operations determined by the positions of the stoking ram and the churning device of each respective churning and stoking ram.
In accordance with a fourth aspect of the disclosure, there is provided a method of pyrolyising solid municipal waste comprising:
The method may further comprise discharging the partially pyrolysed solid municipal waste into an adjacent furnace for further pyrolysis.
In one embodiment of the disclosure the churning device is generally horizontally disposed proximal a lower surface of the furnace when the churning device is inserted into the furnace.
The preferred embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:
Referring to the figures, where like numerals refers to like parts throughout, there is shown a furnace 100 provided with one or more churning and stoking rams 10. In a preferred embodiment of the disclosure, the furnace 100 is a static or fixed hearth, in particular a static or fixed hearth in a low temperature gasification chamber adapted for semi-pyrolysis of municipal solid waste. Typically, the low temperature gasification chamber operates at temperatures in a range of about 500° C. to about 1100° C., in particular in a temperature range of about 700° C. to about 850° C. It will be appreciated, however, that in other embodiments, the furnace 100 may be a high temperature gasifier, an incinerator or a fluidized bed operating in a higher temperature range, such as for example in a temperature range where combustion reactions proceed. The furnace 100 may be directly or indirectly heated, and is of generally conventional design.
In the embodiment shown in
Typically, the solid residues and ash are discharged from the furnace 100 via the discharge port 118, or alternatively, from the first stepped furnace 100′ to an adjacent second stepped furnace 100′ via the discharge port 118 as a result of a stoking action imparted by the churning and stoking ram 10 of the present disclosure. Accordingly, the furnace 100 is also provided with one or more second input ports 122 in the side wall 112 of the furnace for receiving respective churning and stoking rams 10 into the furnace 100. Typically, the one or more second input ports 122 are located below the first input port 110 and spaced apart from a lower surface 122 of the furnace 100 on which the furnace contents will be thermally degraded.
The churning and stoking ram 10 includes a frame 12 disposed externally of the furnace 100, a stoking ram 20 mounted on the frame 12, and a churning device 30 associated with the stoking ram 20.
The frame 12 is disposed in general horizontal parallel alignment with the lower surface 124 of the furnace 100, and has a proximal end 12a which abuts the side wall 112 of the furnace 100 and a distal end 12b with respect to the side wall 112 of the furnace 100, so that the stoking ram 20 is longitudinally aligned with the second input port 122 of the furnace 100.
The frame 12 in this particular embodiment includes a pair of spaced-apart parallel I-beams 14 shown in more detail in
In one embodiment of the disclosure, the first actuator 40 is a hydraulic ram, illustrative examples of a hydraulic ram include a single stroke hydraulic ram or a telescopic hydraulic ram. By locating the hydraulic ram within the frame 12, a full stroke movement between the fully extended position and the fully retracted position is possible along the length of the frame 12.
In another embodiment, the first actuator 40 need not be a hydraulic ram but can be a ratchet wheel that interacts with a pawl to move the associated stoking ram 20 in a sliding manner by manual movement between various fixed positions, for example by being moved along a perforated slide rail. In that sense, the translation of the stoking ram 20 can also mean a non-continuous, incremental transiatory motion, unlike the continuous translation offered by a piston or hydraulic ram. Other types of actuators are also within the scope of the disclosure, such as geared electric motors or even threaded rods.
The upper sections 16 of the frame 12 are also provided with one or more fixed roller assemblies 11 as shown in detail in
The roller assembly 11 comprises a pair of spaced apart brackets 13 fixed to the upper sections 16 of the frame 12 and respective rollers 15 rotatably mounted on each bracket 13. The brackets 13 are spaced apart at a distance to enable the stoking ram 20 to be contiguously disposed on circumferential surfaces of the rollers 15.
In a preferred embodiment of the disclosure, the frame 12 comprises three spaced apart parallel I-beams 14, as shown in
The stoking ram 20 is supported on the frame 12 by the roller assemblies 11 in an arrangement to enable the stoking ram 20 to be positionable relative to the furnace 100 between an external position as shown in
Positioning of the free end 22 of the stoking ram 20 between the external and internal positions with respect to the furnace 100 is effected by the first actuator 40 which is in operative communication with a fixed end 24 of the stoking ram 20, as will be described later. When the first actuator 40 is in a fully extended position, the stoking ram 20 is located in the external position; and conversely, when the first actuator 40 is in a fully retracted position, the stoking ram 20 is located in the internal position.
In one embodiment of the disclosure, the stoking ram 20 is a hollow elongate section, preferably a cylindrical tube, with the free end 22 and the fixed closed end 24. As the free end 22 is subject to most wear throughout the operational life of the stoking ram 20, it is preferable that the free end 22 is provided with a removable head 26. The materials of construction of the removable head 26 of the stoking ram 20 can be any suitable materials that wear appropriately under ambient furnace temperatures of about 500° C. to about 1100° C., and that can be shaped, formed and fitted in tile manner so described, and may include ceramics, and appropriate heat and wear resistant metals and metal alloys, and so on.
The churning device 30 associated with the stoking ram 20 is positionable relative to the stoking ram 20 between a retracted position as shown in
In one embodiment of the disclosure, the churning device 30 and the second actuator 50 are housed in an internal void of the stoking ram 20 in longitudinal alignment with one another.
The second actuator 50 is disposed adjacent the distal end 24 of the stoking ram 20 and the churning device 30 is disposed adjacent the leading end 22 of the stoking ram 20. he second actuator 50 is operative to impart translational movement to the churning device 30 along a longitudinal axis of the stoking ram 20 between the retracted position wherein the churning device 30 is disposed in the internal void 28 of the stoking ram 20, and the extended position wherein the churning device 30 is disposed externally of the stoking ram 20 in longitudinal alignment therewith.
It will be appreciated that the removable head 26 of the stoking ram 20 is provided with an aperture 28 (
In one embodiment of the disclosure, the second actuator 50 is a hydraulic ram. Illustrative examples of a hydraulic ram include a single stroke hydraulic ram or a telescopic hydraulic ram movable between a fully extended and a fully retracted configuration, respectively. When the hydraulic ram is fully extended, it translates the churning device 30 to the extended position and, conversely, when the hydraulic ram is fully retracted it translates the churning device 30 to the retracted position. Other types of actuators are also within the scope of the disclosure, such as geared electric motors or even threaded rods.
Referring to
The paddles 34 are equiangularly disposed around a central longitudinal axis of the elongate member 32. In
An auger-like configuration of two or more paddles 34 in a continuous spiral flute arrangement would be likely, in practice, to compact solid waste material in the furnace 100 rather than mechanically agitate it, and is therefore undesirable. However, a plurality of paddles 34 configured in discontinuous spiral flutes along the length of the elongate member 32 is anticipated to impart advantageous shearing forces to the solid waste material in the furnace 100 leading to improved mechanical agitation.
The churning device 30 may be continuously rotated in a clockwise or a counterclockwise direction. Alternatively, the churning device 30 may be rotated 180° in a clockwise or a counterclockwise direction and then subsequently rotated 180° in the opposing direction. In some embodiments where a pair of churning and stoking rams 10 is configured in parallel alignment with one another, the churning devices 30 may simultaneously rotate in opposing directions to assist in improved mechanical agitation of the contents of the furnace 100.
The churning device 30 is static with respect to rotation relative to the stoking ram 20 and it will be appreciated that the rotational motion of the churning device 30 described above is effected by rotating the stoking ram 20 in a clockwise or counterclockwise direction by means of a third actuator 60 which is in operative communication with the stoking ram 20 in an arrangement to rotate the stoking ram 20 and the churning device 30 associated therewith.
The third actuator 60 is shown in detail in
As will be evident from
For example, a sequence of stoking and churning operations to agitate the contents of the furnace 100 may be performed as follows. A “starting” position is shown in
Alternatively, commencing from the “starting position” of
It will be appreciated that in arrangements where a pair of churning and stoking rams 10 are aligned in parallel, that the pair of rams 10 may pass through the same sequence of operations as described above, either in phase with one another (i.e., performing the same sequence operation at the same time as one another) or out of phase with one another (i.e., one stoking ram 20 may be progressively extended into the furnace 100 in the extended position while the other stoking ram 20 may be progressively retracted from the furnace 100 into the external position).
The materials of construction of the churning and stoking ram 10 described can be any suitable materials that wear appropriately under high temperatures, and that can be shaped, formed and fitted in the manner so described, and include an appropriate temperature resistant metal such as mild steel, metal alloys, or even ceramics, and so on.
In the description of the disclosure, except where the context requires otherwise due to express language or necessary implication, the words “comprise” or variations such as “comprises” or “comprising” are used in an inclusive sense, i.e., to specify the presence of the stated features, but not to preclude the presence or addition of further features in various embodiments of the disclosure.
It is to be understood that, although prior art use and publications may be referred to herein, such reference does not constitute an admission that any of these form a part of the common general knowledge in the art, in any country.
Numerous variations and modifications will suggest themselves to persons skilled in the relevant art, in addition to those already described, without departing from the basic inventive concepts. All such variations and modifications are to be considered within the scope of the present disclosure, the nature of which is to be determined from the foregoing description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013903261 | Aug 2013 | AU | national |
The present application is a U.S. National Stage patent application of International Application No. PCT/AU2014/000842, filed on Aug. 26, 2014, which claims priority to Australian Patent Application No. 2013903261, entitled, “CHURNING AND STOKING RAM,” filed Aug. 27, 2013, also naming Neil Martin as inventor, the disclosures of which are hereby incorporated by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2014/000842 | 8/26/2014 | WO | 00 |
