Patent Application
20100135851
The present invention relates to the treatment of municipal solid waste and the like. This invention disclosure presents a means of utilizing steam to heat and dry wet heterogeneous solids inside a rotating autoclave with at least one entry and exit door.
The present invention relates to systems and methods for treating process material and, more particularly, to systems and methods for treating municipal solid waste material, medical waste material, reclaimed paper and the like.
This process typically involves sterilizing high density materials such as glass, plastics, metals and recovering others from municipal solid waste (MSW) and converting paper, cardboard, food waste, etc. to a usable fiber and separating it from other recyclable materials.
As a result of increasing scarcity of landfills and more stringent environmental regulations, efforts have been made to reduce the volume of process material, such as municipal solid waste (MSW) and paper material, such as newsprint and other reclaimed and recycled paper products as a step in the process of disposing of the material, either by depositing it in landfills, incinerating it or recycling it.
Systems and methods have been developed to break down such material for disposal, or in the case of paper products, use as insulation, or for further processing to produce a combustible product.
It remains desirable to be able to efficiently dry a treated waste mass within an autoclave as it is beneficial to render the waste mass as a relatively dry mass for further processing, such as into fuel pellets, or as fuel for use in fluidized bed combustors and the like.
One of the disadvantages of the arrangements of the prior art is that many autoclaves feature helical blades that resist material flow when the waste is loaded into the autoclave and when the treated waste mass is removed from the autoclave. Helical blades also create blockages when stringy, fibrous material, such as clothing and rugs, is present.
Another disadvantage of prior systems is that they have not been able to provide efficient in situ drying, and to make efficient and effective use of waste steam for such a process.
In this same regard, the environment surrounding the autoclave upon loading differs from that surrounding the autoclave upon discharge. As these environments differ, it is also desirable to be able to provide a waste treatment autoclave that may be loaded, operated or discharged while maintaining some degree of separation or isolation of the loading environment from the discharge environment.
The present invention accordingly represents an improvement over prior art apparatus and methods, such as those described in U.S. Pat. Nos. 5,540,391; 5,126,363; 5,253,764; 5,190,226; 5,361,994; 5,427,650; 5,407,809; 5,636,449; 5,655,718 and 6,397,492, all of which are incorporated herein by reference. PCT application PCT/US06/16773 and co-pending patent application Ser. No. 11/716,101 are also are incorporated herein by reference.
Recent examples (see, for example, U.S. Pat. No. 5,636,449) provide technology improvements to systems that provide steam for the use of a pipe or pipes situated longitudinally in a configuration known as a tube dryer. Steam, introduced to these tubes, heats the autoclave contents directly, evaporating contained water.
Turbulence introduced by rotating assures that the entire contents (of homogenous wetcake) are properly heated and dried.
In tube dryers, steam is introduced into, and water/steam is exhausted through, a common rotating union on one end of the autoclave. The end of the autoclave provides manifolds to distribute the steam/collect the spent steam to and from the tubes in the autoclave.
The prior art provides for the re-use of spent contact steam via “regeneration.” The spent steam is separated from liquid condensate and is combined with superheated and energetic steam in a thermal vapor recovery (TVR) device, produces a product saturated steam with elevated temperature and pressure for re-use in the dryer. Contact condensate is recirculated to the boiler, and a small (5%) bleed of steam from the TVR removes non-condensibles (with a significant loss of energy). Non-contact condensate is recirculated to the boiler.
Experience with waste autoclaves shows that the contact steam has contaminants such as organic vapors. The current art eventually results in the detrimental release of the vapors to the contact steam condensate. Further, experience shows that spent contact steam has substantial air content, with detrimental consequences to both heat transfer coefficient and to tube/boiler/plumbing material life.
The invention includes apparatus and methods for treating solid waste using an autoclave, and especially for drying waste and recycling the steam from the autoclave system.
Apparatus with Straight Hollow Blades for Steam Conduction
The invention includes an apparatus for processing solid waste products, said apparatus comprising: (a) a rotatably mounted cylindrical autoclave having an interior surface and two ends, at least one end terminating in a hatch that may be opened to allow access to the interior of said autoclave and sealably closed to allow pressurization of said autoclave; (b) an autoclave steam inlet for injecting contact steam into said autoclave so as to come into contact with waste material placed into said autoclave; (c) a plurality of straight hollow blades adapted to conduct non-contact steam and protruding from said interior surface of said autoclave; and (d) at least one blade steam inlet for injecting steam into said blades.
It is preferred that the autoclave additionally comprises a waste steam outlet adapted to conduct waste contact steam from said interior of said autoclave and wherein another waste steam outlet is adapted to conduct said non-contact waste steam from said blades.
It is also preferred that the autoclave steam inlet and the blade steam inlet are each provided with a rotating connector so as to permit the supply of steam therethrough while the autoclave is rotated. Typically and preferably, the steam introduced into the blades at least partially comprises steam reconstituted from non-contact blade condensate obtained from the autoclave.
A variable flow valve may be used to dynamically control the exit steam quality.
The invention also preferably features the autoclave additionally comprising a waste steam outlet adapted to conduct waste steam from the interior of the autoclave and wherein another waste steam outlet is adapted to conduct non-contact waste steam from the hollow blades; and a device that is adapted to reconstitute the waste steam from the hollow blades and to reintroduce reconstituted steam into the autoclave steam inlet and or the inlets of other autoclaves. This embodiment may additionally comprise a steam separator followed by mechanical vapor recompression device for separated steam and a boiler/steam generator for separated water.
The present invention also includes a method of processing solid waste material in an autoclave, comprising: (1) loading the autoclave with a charge of solid waste products, the autoclave comprising: (a) a rotatably mounted cylindrical autoclave having an interior surface and two ends, at least one end terminating in a hatch that may be opened to allow access to the interior of the autoclave and sealably closed to allow pressurization of the autoclave; (b) an autoclave steam inlet for injecting steam into the autoclave so as to come into contact with waste material placed into the autoclave; (c) a plurality of straight hollow blades adapted to conduct steam and protruding from the interior surface of the autoclave; and (d) at least one blade steam inlet for injecting steam into the blades; (2) sealing the autoclave; (3) rotating the autoclave so as to cause the charge of solid waste material to be moved from the bottom of the autoclave to toward the top of the autoclave while introducing steam into the autoclave and into the blades, so as to produce dried processed waste; and (4) thereafter depressurizing the autoclave and unloading the processed waste therefrom.
It is preferred that the steam introduced into the blades is substantially comprised of reconstituted non-contact waste steam obtained from the autoclave, and most preferably that a variable flow valve controls the flow of the waste steam.
It is also preferred that the device adapted to reconstitute the non-contact waste steam is a steam separator followed by mechanical vapor recompression device for separated steam and a boiler/steam generator for separated water, wherein the thermal energy of the contact condensate is recovered by heat transfer to combustion air, to steam generation, and/or by direct mechanical vapor recompression.
The methods of the present invention also include a method of processing solid waste material in an autoclave, comprising: (1) loading the autoclave with a charge of solid waste products, the autoclave comprising: (a) a rotatably mounted cylindrical autoclave having an interior surface and two ends, at least one end terminating in a hatch that may be opened to allow access to the interior of the autoclave and sealably closed to allow pressurization of the autoclave; (b) an autoclave steam inlet for injecting steam into the autoclave so as to come into contact with waste material placed into the autoclave; (c) a plurality of hollow blades adapted to conduct steam and protruding from the interior surface of the autoclave; (d) at least one blade steam inlet for injecting steam into the blades; and (e) a waste steam outlet adapted to conduct waste steam from the interior of the autoclave and wherein another waste steam outlet is adapted to conduct non-contact waste steam from the blades, (2) sealing the autoclave;
(3) rotating the autoclave so as to cause the charge of solid waste material to be moved from the bottom of the autoclave to toward the top of the autoclave while introducing steam into the autoclave, so as to produce processed waste; (4) thereafter depressurizing the autoclave; (5) introducing waste steam into the blades so as to dry the processed waste; and (6) unloading the processed waste from the autoclave.
The present invention also includes a variation of an autoclave for steam treatment and drying comprising: a) a rotating steam tube dryer comprising a plurality of tubes, a rotating input port adapted to supply steam to the plurality of tubes, a rotating output port adapted to accept steam to the plurality of tubes and one or more end doors; b) a source of saturated or supersaturated steam connected to the steam tube dryer; c) a conduit for connecting steam through the rotating input port to the plurality of tubes; d) a conduit for withdrawing condensed steam from the plurality of tubes through the rotating output port; e) a conduit for withdrawing product moisture through a rotating port; f) a valve for controlling product moisture withdrawal through an external and non-rotating valve.
It is preferred that the spent non-contact steam and condensate are recycled back to the steam source.
The present invention also includes a method of modifying the autoclave tilt angle to a slightly off level, so as the liquid condensate within the blades is caused to migrate from the steam supply end to the steam exhaust end, the means provided by leveling actuators as described herein. This may be done for instance by a means for controlling the autoclave tilt that senses the blade steam exhaust condensate conditions and adjusting the tilt to properly regulate the production and exhaust of condensate in the blades.
The present invention represents an improvement upon these systems via a system that heats contents with both contact and non-contact steam (maintaining separation of the contact steam from the non-contact steam) by distributing the non-contact steam for drying of contents via a system of blades that serve to both heat the contents and to mechanically agitate the contents, by maintaining the pressure of the steam in the blades so as to transfer heat released by the condensation of steam in the blades, and by an efficient system of regeneration of non-contact condensate that includes a mechanical vapor recompressor.
Condensate leaving the autoclave consists of contact steam that has been in direct contact with the waste contents. Contact steam has small quantities of particulate, air, and organic vapors. While prior art provides for the removal of non-condensibles by purging a small quantity of steam, such a process loses the energy of the steam. The present invention provides for the condensation of the contact steam (with functional use for the heat of condensation), thus providing for the separation of non-condensibles, and the subsequent purification of the water column.
It is preferred that the steam condensate from the vanes is under medium pressure (typically about 5 bar to about 7 bar), but lower than supply steam pressure (typically about 7 bar to about 8 bar). Non-contact steam condensate from the autoclave is at nearly the supply steam pressure. A standard single stage mechanical vapor recompressor (MVR) is able to lift the steam to supply pressure. The present invention features the inclusion and use of such an MVR in its preferred embodiment, but allows thermal vapor recompression as an alternate.
Various designs, mechanical arrangements and technologies exist to transfer steam across the door of the autoclave and to maintain the non-contact steam.
The doors provide for dual unions, to transfer steam and condensate from fixed locations to the rotating autoclave. A system of transferring steam from the autoclave door (removable) to the autoclave proper is also provided, using an annular groove on both sides of the door seal. This allows the door to be removed and returned without an alignment problem.
In general terms, the invention includes an apparatus, system, waste treatment facility and method of autoclave operation and waste treatment.
The present invention also includes a method of changing the autoclave tilt angle to a slightly off level, such that the liquid condensate within the blades is caused to migrate from the steam supply end to the steam exhaust end. This may be done by any mechanical means, such as through the use of actuators such as those shown in
Apparatus with Straight Hollow Blades for Steam Conduction
The present invention includes an apparatus for processing solid waste products, the apparatus comprising: (a) a rotatably mounted cylindrical autoclave having an interior surface and two ends, at least one end terminating in a hatch that may be opened to allow access to the interior of the autoclave and sealably closed to allow pressurization of the autoclave; (b) an autoclave steam inlet for injecting steam into the autoclave so as to come into contact with waste material placed into the autoclave; (c) a plurality of hollow blades adapted to conduct steam and protruding from the interior surface of the autoclave; and (d) at least one blade steam inlet for injecting steam into the blades.
The apparatus may feature an autoclave that additionally comprises a waste steam outlet adapted to conduct waste steam from the interior of the autoclave and wherein the at least one blade steam inlet is connected to the waste steam outlet.
It is also preferred that the autoclave steam inlet and the blade steam inlet are each provided with a rotating connector so as to permit the supply of steam therethrough while the autoclave is rotated.
The autoclave may also optionally comprise a waste steam outlet adapted to conduct waste steam (contact steam) from the interior of the autoclave and wherein the at least one blade steam outlet is separately provided to conduct non-contact condensate from the blade or blades.
Also preferred, where the steam is introduced into the blades, is the inclusion of a variable flow valve adapted to control the non-contact condensate flow.
In a preferred variation the autoclave additionally comprises (1) a waste steam outlet adapted to conduct waste steam from the interior of the autoclave (2) at least one blade steam outlet for conducting waste steam from the hollow blades, and (3) a device adapted to reconstitute the waste steam from the hollow blades and to reintroduce reconstituted steam into the autoclave steam inlet. The device adapted to reconstitute the waste steam may be any suitable device, such as a mechanical vapor recompression device.
It is preferred that the blades are substantially straight.
The invention also includes methods that may be carried out by the device.
These methods includes a method of processing solid waste material in an autoclave, comprising: (1) loading the autoclave with a charge of solid waste products, the autoclave comprising: (a) a rotatably mounted cylindrical autoclave having an interior surface and two ends, at least one end terminating in a hatch that may be opened to allow access to the interior of the autoclave and sealably closed to allow pressurization of the autoclave; (b) an autoclave steam inlet for injecting steam into the autoclave so as to come into contact with waste material placed into the autoclave; (c) a plurality of hollow blades adapted to conduct steam and protruding from the interior surface of the autoclave; and (d) at least one blade steam inlet for injecting steam into the blades; (2) sealing the autoclave; (3) rotating the autoclave so as to cause the charge of solid waste material to be moved from the bottom of the autoclave to toward the top of the autoclave while introducing steam into the autoclave and into the blades, so as to produce processed waste; and (4) thereafter depressurizing the autoclave and unloading the processed waste therefrom.
It is preferred that the method also involve use of an apparatus as is described above in its preferred and optional variations, and that the method include the additional process steps brought about by those preferred and optional elements and devices.
The present invention also includes a method of processing solid waste material in an autoclave, comprising: (1) loading the autoclave with a charge of solid waste products, the autoclave comprising: (a) a rotatably mounted cylindrical autoclave having an interior surface and two ends, at least one end terminating in a hatch that may be opened to allow access to the interior of the autoclave and sealably closed to allow pressurization of the autoclave; (b) an autoclave steam inlet for injecting steam into the autoclave so as to come into contact with waste material placed into the autoclave; (c) a plurality of hollow blades adapted to conduct steam and protruding from the interior surface of the autoclave; (d) at least one blade steam inlet for injecting non-contact steam into the blades; and (e) a waste steam outlet adapted to conduct contact waste steam from the interior of the autoclave and wherein the at least one blade steam inlet is connected to the waste steam outlet; (2) sealing the autoclave; (3) rotating the autoclave so as to cause the charge of solid waste material to be moved from the bottom of the autoclave to toward the top of the autoclave while introducing steam into the autoclave, so as to produce processed waste; (4) thereafter depressurizing the autoclave; (5) introducing waste steam into the blades so as to dry the processed waste; and (6) unloading the processed waste from the autoclave.
The apparatus and method of the present invention may also feature the use of steam introduced into the blades that is comprised of reconstituted non-contacted waste steam obtained from the autoclave.
The apparatus and method of the present invention may also involve the waste steam being controlled by a variable flow valve.
The apparatus of the present invention may also incorporate a device adapted to reconstitute the non-contact waste steam which is a steam separator followed by mechanical vapor recompression device for separated steam and a boiler/steam generator for separated water, such that the thermal energy of the contact condensate is recovered by heat transfer to combustion air, to steam generation, and/or by direct mechanical vapor recompression.
It is preferred that the method also involve use of an apparatus as is described above in its preferred and optional variations, and that the method include the additional process steps brought about by those preferred and optional elements and devices. It is preferred that the steam introduced into the blades is predominately regenerated condensate, and that the flow of the waste steam is reduced by a controllable variable flow valve during the drying step.
It is also preferred that the steam exiting the blades is reconstituted and reintroduced in the autoclave steam inlet.
The present invention also involves variations of the apparatus and method including the use of method of modifying the autoclave tilt angle to a slightly off level, so as the liquid condensate within the blades is caused to migrate from the steam supply end to the steam exhaust end, such as by leveling actuators as described herein and in the incorporated references.
The present invention also involves variations of the apparatus and method including means of controlling the autoclave tilt by sensing the blade steam exhaust condensate conditions (such as temperature) and adjusting the tilt to properly regulate the production and exhaust of condensate in the blades.
Other embodiments of the present invention include an autoclave for steam treatment and drying comprising: (a) a rotating steam tube dryer comprising a plurality of tubes, a rotating input port adapted to supply steam to the plurality of tubes, a rotating output port adapted to accept steam to the plurality of tubes and one or more end doors; (b) a source of saturated or supersaturated steam connected to the steam tube dryer; (c) a conduit or other means for connecting steam through the rotating input port to the plurality of tubes; (d) a conduit or other means for withdrawing condensed steam from the plurality of tubes through the rotating output port; (e) a conduit or other means for withdrawing product moisture through a rotating port; (f) a valve or other means for of controlling product moisture withdrawal through an external and non-rotating valve.
It is preferred that the spent waste non-contact steam and condensate are condensed and cleansed prior to being recycled back to the steam generator.
The invention also includes a steam cooking and drying apparatus comprising: (a) a rotating steam tube dryer comprising a plurality of tubes and one or more end doors; (b) a source of saturated or supersaturated steam connected to the dryer; (c) a conduit or other means of connecting steam through a rotating port to the plurality of tubes; (d) a conduit or other means of connecting the plurality of tubes to a discharge port, preferably comprising (1) a steam/water separator and (2) a rotating valve; and (e) a conduit or other means of withdrawing spent steam and product moisture through a rotating valve.
The autoclave contents typically are materials to be sterilized and dried, and preferably pulped and dried, such as municipal wastes.
It is preferred that, as the processing of the waste mass proceeds into the operational cycle, the flow of steam through the blades is slowed so as to compensate for the reduced rate of heat transfer as the waste mass dries. For instance, where a treatment cycle is approximately 1 hour from loading to unloading, the reduction in the steam flow rate will begin about 20 minutes from the end of the cycle. The rate of slowing will depend upon the heat transfer rate experienced with different types of waste, having varying in-coming moisture amounts, the amount of water brought in through steam contact during processing and the ambient temperature and pressure.
a is a longitudinal sectioned view, taken along line C-C of
b is a longitudinal sectioned view, taken along line E-E of
a is a sectioned elevation view, taken along line G-G of
a is a sectioned elevation view, taken along line J-J of
b is a detailed sectioned elevation view, taken along line L-L of
In accordance with the foregoing summary, the following provides a detailed description of the preferred embodiment, which is presently considered to be the best mode thereof.
In one embodiment, steam may be introduced into, and water/steam may be exhausted through a common rotating union on each end of the autoclave. The end of the autoclave may be provided with one or more manifolds to distribute the steam and collect the spent waste steam to and from the tubes in the autoclave.
In the instance where autoclave operations require autoclave material to flow through the end of the autoclave, a manifolded door must be provided. The present invention provides one or more manifolded doors, to provide a sealed manifold against a system of tubes.
a is a longitudinal sectioned view, taken along line C-C of
b is a longitudinal sectioned view, taken along line E-E of
a is a sectioned elevation view, taken along line G-G of
a is a sectioned elevation view, taken along line J-J of
b is a detailed sectioned elevation view, taken along line L-L of
The contact condensate is conducted to heat exchanger 34 which includes an air intake. This produces hot combustion gases that are in turn routed to the gasification, combustion and power generation system 31. The condensate from the heat exchanger 34 is directed to a separator, and non-condensable gases are taken therefrom and disposed of in the gasification, combustion and power generation system 31. The remaining liquid from the separator in turn is directed to a boiler water treatment system 35 where it is cleansed for reintroduction into the heat recovery steam generator (HRSG) 32. The HRSG obtains combustion gases from the gasification, combustion and power generation system 31. The HRSG 32 also generates superheated steam that may be routed to the gasification, combustion and power generation system 31. The gasification, combustion and power generation system 31 in turn produces electricity which may be used on site for any industrial purposes, such as in the water treatment system, or to operate the autoclave itself, etc. The process steam produced by the HRSG 32 may then be returned to the autoclave 30. In addition, it is preferred that the process steam be returned to the gasification, combustion and power generation system 31 for operational purposes. Superheated steam generated by the HRSG 32 may then be returned to the gasification, combustion and power generation system 31. An exhaust stack may be used to vent away excess evaporated water from the HRSG 32 as required.
The clean condensate from the non-contact steam coursed through the hollow blades may be recycled through a steam separator which feeds mechanical vapor recompression device 33 that may regenerate process steam for reuse either as contact or non-contact steam.
Clean cellulose obtained from the solid fraction of the treated waste mass may be used for any number of purposes, including for combustion in the gasification, combustion and power generation system 31.
By contrast,
In operation of one embodiment of the present invention, the manifold system may be moved to the autoclave itself. Steam, as before, flows to the end of the autoclave 2, using a door 7, with a rotating union 8. From this rotating connector, steam is routed to a pipe 9 then to the manifold 3. The manifold distributes steam to the pipes and hollow blades within the autoclave. In this manner, the door can be opened and closed while maintaining a sealed steam supply line.
If the exit line or lines from a sealed autoclave (whether steam or water) is/are closed, and the steam is allowed to enter the autoclave, the autoclave contents will heat up, both from the contact with the hot walls of the manifolded tubes and from direct contact with the steam. Pressure in the autoclave will also increase. The temperature and pressure will rise in a dynamic and rapid manner until the autoclave and contents near the saturation temperature/pressure of the supply steam. The water content of the autoclave will also rise, as steam condenses to give up its latent heat.
Effective use of the steam tubes for drying requires that the heating steam be under a higher pressure and temperature than the autoclave contents. Three aspects to the present invention may be used to achieve this end.
In the first aspect of the present invention, one end of the autoclave provides a dual supply and exhaust system, using a commercially available two-port rotating union. Typically, one port distributes steam to a manifold as described above, and the other port receives condensate from a similarly constructed manifold.
Non-contact steam is introduced to one union into the autoclave system 30, and thence into the autoclave vanes 5, whereupon it substantially condenses, yielding its heat of condensation to the autoclave contents. The flow of the non-contact steam is regulated by valves, and the valves are adjusted such that about 15% of the introduced steam does not condense.
After passing through a set of autoclave tubes, the non-contact condensate is captured and discharged through a second rotary union.
Non-contact condensate is led to a separator tank, wherein the steam (about 15% of the total) and liquid (about 85% of the total) is separated.
The clean non-contact steam loses a little pressure through the autoclave transit: the steam is repressurized with a small mechanical vapor recompressor 33 and the regenerated steam is charged to the steam main.
The clean non-contact condensed water is returned to the steam generator 32 to create additional steam to charge to the steam main.
The process creates excess water. The steam generator (32) preferentially provides a superheat loop to generate high temperature steam from the excess water; this energy can be recovered as electrical energy with a turbine. In the preferred embodiment, the superheated steam is injected into the turbine section of a gas turbine in the power generator 31 for energy recovery.
During the cooking cycle, contact steam may be added to the autoclave contents to increase its moisture initially (assisting in the pulping process) and also providing more rapid heating. In the preferred embodiment, the added contact steam raises the autoclave moisture to the preferred pulping moisture content (in excess of 50%), and raised the autoclave interior temperature to cooking temperatures in the range of 149-173° C.
For the drying cycle, the autoclave is initially vented, releasing contact steam and lowering the pressure and temperature of the contents. The autoclave contents are held at or near ambient pressure for the remainder of the drying cycle, thus providing a lower temperature environment to receive heat from the non-contact, higher temperature, drying steam. As the contents dry, additional contact steam is generated within and released by the autoclave.
Contact steam condensate released from autoclave 30 contains a substantial quantity of latent heat. In the preferred embodiment, the contact condensate is cooled and condensed by heat exchange with heat exchanger 34. Intake air (combustion air) is heated by heat exchanger 34, thus capturing the sensible heat from the contact condensate.
Heat exchanger 34 may be a direct heat exchanger, or may be an indirect heat exchanger.
After condensation, non-condensibles are easily separated from the condensed liquid. As the non-condensibles contain volatile organics, the non-condensibles are lead to the turbine in the power generation 31 for combustion/destruction.
Condensed liquids from the heat exchanger 34 and following separator are led to boiler water treatment 35 for cleanup and re-use.
A plurality of heating tubes may be used in order to provide a large heat transfer surface, in accordance with arrangements known in the art. Such a plurality is most effective when the autoclave contents are homogenous and of small size. In the extant application with municipal solid waste, the autoclave contents are heterogeneous and may have bulky items that render prior art unworkable for the MSW autoclave. Thus, the heating must be provided by the wall of the autoclave, and by rigid heat transfer surfaces attached to the wall.
Another invention of this disclosure utilizes non-circular tubes that conform to the interior of the rotating autoclave. In this manner, a high surface area is provided without the interferences of a complex of interior tubes. The tubes may be in the form of hollow blades in order to better distribute heat. It is also preferred that the blades be substantially straight as this best facilitates the loading and un-loading of the waste mass.
The preferred non-circular tubes are integral to the mechanical mixing processes that occur in the autoclave.
After the autoclave is loaded with the charge of waste products, the door through which the charge was loaded is shut, steam is introduced continually into the autoclave, and the autoclave becomes pressurized. Fresh steam may be continuously fed into the autoclave from the loading end, and after a predetermined processing pressure is reached, steam may be allowed to escape the autoclave into the discharge steam line.
The temperature and pressure of the autoclave are monitored, and the flow of steam is regulated to keep the process within predetermined processing ranges (typically around 7 bar, at 173° C.). The autoclave is rotated at a predetermined speed (depending on the size of the autoclave). Following a cooking time interval (which is automatically controlled), the pressure in the autoclave is released, steam is used to flood the steam tubes, and the drying commences. Typical dry times of 30 minutes are experienced in 10-ton autoclaves. After drying the processed waste is removed.
A given charge of waste products may contain a wide variety of constituents, such as wood, paper, organic matter, water, etc. Each charge of waste products presents its own heat capacity and transfer profile, while there is required an overall heat absorption of the mass in order to provide an effective treatment of the waste products charge.
The information from the thermometers or thermocouples may also be used to determine the heat absorption over time as the charge of waste products heats up initially. This allows the operator (or a microprocessor or PLC controller) to extrapolate the energy needs for that charge of waste products and, based upon a comparison of the heat transfer profile, to also determine the approximate qualitative constituent make up of the charge of waste products, and thus allow the determination of the treatment time necessary to treat that particular charge.
According to the invention, steam inlets are connected to one or more saturated or superheated steam supply and to a steam receiver. In this way, the autoclave is pressurized and depressurized from one or more openings. Each opening may be provided with a pressure lock and bidirectional steam flow conduits and valves. The apparatus may also include an optional steam vacuum pump at each opening for rapid depressurizing of the autoclave. Rotating union valves may also be included to enable steam flow in- and out-of the autoclave as the autoclave is rotating or tilting. The temperature range of the autoclave contents is preferred to be in the 149-173° C. temperature range during cooking. This range has been established by the applicant as providing the most rapid pulping of contents, without causing thermal degradation of plastics. Under separate application, the preferred temperature range is claimed as it provides for the inactivation of CJD “prions”.
The temperature of the drying steam may be provided to be higher that the contents temperature, in order to enhance the rate of heat transfer from the blades to the autoclave contents and thereby decrease the drying time.
Alternative configurations are possible. For example, as shown in
As another alternative, as shown in
It is apparent that while specific embodiments of the invention is disclosed, various modifications of the apparatus or parameters of the process may be made which will be within the spirit and scope of the invention. Therefore the spirit and scope of the present invention should be determined by reference to the claims below.
Further, while it is apparent that the specific embodiments as fully disclosed apply to the preferred embodiment of an autoclave system, it is possible and desirable to deploy some of these elements to autoclave systems that do not have all of the preferred embodiments.
