Patent Application
20150343350
The present disclosure is broadly concerned with solid/fluid separation apparatus and methods for the separation of different types of solid/fluid mixtures. In addition, the present disclosure relates to rotary presses, in particular improved screw press devices, which can be used for the separation of a wide variety of solid/fluid mixtures.
Various processes for the treatment of solid/fluid mixtures by solid/fluid separation are known. They generally require significant residence time and high pressure and, at times, high temperature. Conventional solid/fluid separation equipment is not satisfactory for the achievement of high solid/fluid separation rates and for separated solids with low liquid content.
Processes including the washing and subsequent concentration of a liquid slurry under pressure require solid/liquid separation equipment able to operate under pressure without clogging. For example, a key component of process efficiency in the pretreatment of lignocellulosic biomass is the ability to wash and squeeze hydrolyzed hemi-cellulose sugars, toxins, inhibitors and/or other extractives from the solid biomass/cellulose fraction. It is difficult with conventional equipment to effectively separate solids from liquid under the high heat and pressure required for cellulose pre-treatment.
Many biomass-to-ethanol processes generate a wet fiber slurry from which dissolved compounds, gases and liquids must be separated at various process steps to isolate a solids and/or fibrous portion. Solid/fluid separation is generally done by filtration and either in batch operation, with filter presses, or continuously by way of rotary presses, such as screw presses.
Solid/fluid or solid/liquid separation is also necessary in many other commercial processes, such as food processing (oil extraction), reduction of waste stream volume in wet extraction processes, dewatering processes, or suspended solids removal.
Commercially available screw presses can be used to remove moisture from a solid/liquid slurry. The de-liquefied solids cake achievable with conventional presses generally contains only 40-50% solids, the leftover moisture being predominantly water. This level of separation may be satisfactory when the filtration step is followed by another dilution or treatment step, but not when maximum dewatering of the slurry is desired. The unsatisfactory low solids content is due to the relatively low maximum pressure a conventional screw press can handle, which is generally not more than about 100-150 psig of separation pressure. Commercial Modular Screw Devices (MSDs) combined with drainer screws can be used, which can run at higher pressures of up to 300 psi. However, their drawbacks are their inherent cost, complexity and continued filter cake limitation of no more than 50% solids content.
During solid/fluid separation, the amount of liquid remaining in the solid fraction is dependent on the amount of separating pressure applied, the thickness of the solids cake, and the porosity of the filter. The porosity of the filter is dependent on the number and size of the filter pores. A reduction in pressure, an increase in cake thickness, or a decrease in porosity of the filter, will all result in a decrease in the degree of liquid/solid separation and the ultimate degree of dryness of the solids fraction.
For a particular solids cake thickness and filter porosity, maximum separation is achieved at the highest separating pressure possible. Moreover, for a particular solids cake thickness and separating pressure, maximum separation is dependent solely on the pore size of the filter.
High separating pressures unfortunately require strong filter media, which are able to withstand the separating pressure within the press, making control of the filtering process difficult and the required equipment very costly. Filter media in MSDs are generally in the form of perforated pressure jackets. The higher the separating pressures used, the stronger (thicker) the filter media (pressure jacket) need to be in order to withstand those pressures. The thicker the pressure jacket, the longer the drainage perforations, the higher the flow resistance through the perforations. Thus, in order to achieve with high-pressure jackets (thick jackets) the same filter flow-through capacity as with low-pressure jackets (thin jackets), the number of perforations should be increased. However, increasing the number of perforations weakens the pressure jacket, once again reducing the pressure capacity of the filter unit. Another approach to overcome the higher flow resistance with longer perforations is to increase the diameter of the perforations. However, this will limit the capacity of the filter to retain small solids, or may lead to increased clogging problems. Thus, the acceptable pore size of the filter is limited by the size of the fibers and particles in the solids fraction. The clarity of the liquid fraction is limited solely by the pore size of the filter media and pores that are too large reduce the liquid/solid separation efficiency and potentially lead to plugging of downstream equipment.
Over time, filter media tend to plug with suspended solids, reducing their production rate. This is true especially at the high pressures required for cellulose pre-treatment. Thus, a backwash liquid flow is normally required to clear any blockage and restore the production rate. Once a filter becomes plugged, it takes high pressure to backwash the media. This is particularly problematic when working with filter media operating at pressures above 1000 psig with a process that is to be continuous to maximize the production rate, for example to obtain high cellulose pre-treatment process efficiency.
Conventional single, twin, or triple screw extruders do not have the residence time necessary for low energy pre-treatment of biomass, and also do not have useful and efficient solid/fluid separating devices for the pre-treatment of biomass. U.S. Pat. No. 3,230,865 and U.S. Pat. No. 7,347,140 disclose screw presses with a perforated casing. Operating pressures of such a screw press are low, due to the low strength of the perforated casing. U.S. Pat. No. 5,515,776 discloses a worm press having drainage perforations in the press jacket, which increase in cross-sectional area in flow direction of the drained liquid. U.S. Pat. No. 7,357,074 is directed to a screw press with a conical dewatering housing with a plurality of perforations for the drainage of water from bulk solids compressed in the press. Again, a perforated casing or jacket is used. As will be readily understood, the higher the number of perforations in the housing, the lower the pressure resistance of the housing. Moreover, drilling perforations in a housing or press jacket is associated with serious challenges when very small apertures are desired for the separation of fine solids.
Published U.S. Application US 2012/0118517 discloses a solid/fluid separation module with high porosity for use in a high internal pressure press device for solid/fluid separation at elevated pressures. The filter module includes filter packs respectively made of a pair of plates that create a drainage system. A filter plate with cut through slots creates flow channels for the liquid to be removed and a backer plate creates a drainage passage for the liquid in the flow channels. Moreover, the backer plate provides the structural support for containing the internal pressure of the solids in the press during the squeezing action. The filter pore size is adjusted by the thickness of the filter plate and/or the opening width of the slots in the filter plate. To minimize pore size, both the filter plate thickness and the drainage slot width are minimized. However, in this separation module, as well as in all the other conventional separation devices discussed above, backwashing of a clogged separation module or filter may not be sufficient to achieve release of clogged matter or full removal of all matter clogging the separation module or filter. The separation equipment must then be disassembled for a through cleaning of the separation module or filter. However, this disassembly is very time consuming and often requires the removal and installation of the conveyor screws, especially when separation modules with filter plates are used. Thus, an improved solid/fluid separation device is desired.
It is an object of the present invention to obviate or mitigate at least one disadvantage of previous solid/liquid separation devices and processes.
In order to improve the operation and maintenance of a solids/fluid separation device, the invention provides a solid/fluid separation module with a split filter unit for separating fluid from a solid/fluid mixture. The module can be incorporated into a solid/fluid separation device, such as a modular screw device or a screw extruder and allows for assembly or removal of the filter unit without disassembly of the device, in particular without removal of the screw or extruder screw. The module may be used, for example, in a large bore screw extruder and, for example, for compressing the solid/fluid mixture at pressures above 300 psig.
To achieve improved operating flexibility at reduced maintenance cost, the solid/fluid separation module of the invention preferably requires only the stopping of the screw rotation for replacement of the filter block without any disassembly of any part other than the separation module. This is achieved by a split filter unit in accordance with the invention including first and second filter blocks joinable along a longitudinal plane of symmetry of the core passage of the extruder screw, for defining the core passage when joined along the plane of symmetry. The filter blocks are sealably mountable in the housing so that the housing and joined filter sections together define the longitudinal portion of the core passage. At least one of the filter blocks is a stacked block including a plurality of barrel plates having flat front and back surfaces, an inner edge located at the core opening and an outer edge for contact with a fluid collection chamber in the separation module. The plurality of barrel plates are sealingly stacked in a plate stack one behind the other. At least one of the first and second filter blocks includes a filter passage extending from the inner edge to the outer edge.
In a variant embodiment, the separation module includes a filter unit made of a stack of barrel plates which each have a central bore for receiving the extruder screw and are each split into first and second sections along a separation plane extending across a line of symmetry of the central bore. When the barrel plates are stacked into the filter block, the division of the barrel plates into the first and second plate sections leads to a division of the filter block along the separation plane into first and second filter blocks which can be placed about the conveyor screw.
In either embodiment, each filter block including stacked plates also includes a stacking structure for aligning the stacked plates or stacked plate sections and for combining them into the filter blocks. The separation module further includes a clamping structure for clamping the first and second filter blocks about the conveyor screw to form a clamped filter block enclosing the extruder screw and sealing the bore along the separation plane. At least one of the stacked barrel plates is constructed as a filter plate defining a filter passage for liquid to drain away from the central bore.
In addition to the split block filter unit, a separation module in accordance with the invention includes a housing for integration into the barrel of a screw extruder, the housing defining a pressurizable fluid collection chamber for housing the clamped filter block. The housing has opposite lids which are removable while the housing is incorporated into the barrel. The removable lids allow access to and removal of the clamping structure and the first and second filter blocks from the housing. The housing preferably further includes a sealing and compressing structure for movement between an open position wherein the filter blocks can be removed from the housing, to a locked position in which the compressing structure engages and compresses the filter blocks for locking the clamped filter block in the housing and for sealing of the core passage defined by the clamped filter block from the collection chamber.
For removal of the filter unit from the extruder, the opposing lids are removed from the housing, the compressing structure is moved into the open position and the clamping structure is removed from the clamped filter block to allow removal of the first and second filter blocks from the housing. The installation of replacement filter blocks, different filter blocks, or the same filter blocks after cleaning is then achieved in reverse order. A seal is preferably inserted between the first and second filter blocks in the separation plane for improved sealing of the central bore and further seals are preferably provided between the compressing structure and the clamped block and between the housing and the removable lids.
The filter passages can be formed directly in the filter plate by cutting filter slots into the filter plate, or by simply recessing a fluid passage into a surface of the filter plate. This can be achieved much more easily than the conventional approach of drilling holes in a pressure jacket. For example, a recessed filter passage can be produced by etching the passage into the filter plate surface. By only recessing the filter passage into a surface of the filter plate, the overall integrity of the filter plate is affected less than in filter plates having cut through filter slots. Using recessed passages allows for the creation of much smaller filter pores by using very narrow and shallow passages. For example, by cutting a filter passage of 0.01 inch width and 0.001 inch depth into the filter plate, a pore size of only 0.00001 square inch can be achieved (smallest depth of passage*smallest width of passage).
In one embodiment, the first and/or second filter block includes a plurality of stacked barrel plates, each having a flat front face, a flat rear face, an inner edge defining the core opening and extending from the front face to the rear face and an outer edge for contact with the collection chamber. The barrel plates are stacked in the filter unit one behind the other for sealing engagement of the front and rear faces of adjacent barrel plates to form the filter block and to seal the core opening from the fluid collection chamber in the clamped block. At least one of the barrel plates is constructed as a filter plate having a filter passage recessed into the front face, the filter passage extending from the inner edge to the outer edge for draining fluid in the core opening to the collection chamber in the installed condition of the filter block.
In another embodiment, at least two adjacent barrel plates are together constructed to form a filter plate pair in which one functions as the filter plate and includes one or more filter slots cut through the filter place at the inner edge, while the other functions as a backer plate providing a fluid drainage passage from the filter slots to the outer edge.
In still a further embodiment, a large number, or the majority, of the barrel plates in at least one of the filter blocks are constructed as a filter plate. To achieve the highest possible porosity, each barrel plate may be constructed as a filter plate.
In the filter unit of the invention, each filter plate, or filter plate pair includes at least one filter passage. To increase filter porosity, each filter plate can include multiple filter passages. The number of the filter passages in each filter plate or filter plate pair may be chosen to maximize porosity without compromising filter plate or filter block integrity.
In one aspect, the invention provides a filter unit for a solid/fluid separating press with at least one conveyor screw for conveying a solid/fluid mixture, the press having a barrel divided into at least two barrel modules respectively defining a longitudinal portion of a core passage for housing the at least one conveyor screw. At least one of the barrel modules is a filter module having a housing defining a fluid collection chamber. The filter unit includes first and second filter blocks joinable along a longitudinal plane of symmetry of the core passage for defining the core passage when joined along the plane of symmetry. The filter blocks are sealably mountable in the housing for the housing and joined filter sections together defining the longitudinal portion of the core passage. At least one of the filter blocks is a stacked block including a plurality of barrel plates having flat front and back surfaces, an inner edge located at the core opening and an outer edge for contact with the collection chamber. In the stacked block, the barrel plates are sealingly stacked in a plate stack one behind the other. At least one of the filter blocks includes a filter passage extending from the inner edge to the outer edge.
In one embodiment, at least one of the barrel plates is constructed as a filter plate and includes the filter passage. The filter passage may be in the front and/or back surface.
In another embodiment, at least one pair of the barrel plates is constructed as a filter plate pair defining the filter passage.
The filter unit of the invention can be used with a solid/fluid separating press including one or two conveyor screws, wherein when more than one conveyor screw is used, the plane of symmetry of the core passage along which the filter blocks are joined extends through a longitudinal axis of each conveyor screw.
One or both of the first and second filter blocks may be a stacked block. Alternatively, one filter block may be a solid block, while the other filter block is a stacked block.
In the filter unit of the invention, the stacked block may include the stack of barrel plates and/or filter plates and a pair of end plates, the plate stack being compressed between a pair of end plates. The stacked block may also include a stacking structure for aligning the barrel/filter plates in the plate stack and for compressing the plate stack into the stacked block in which the barrel plates are stacked one behind the other and between the end plates.
The filter unit of the invention may further include a clamping structure for clamping the first and second filter blocks together along the plane of symmetry to form a clamped block, defining a portion of the core passage.
Each filter plate, or filter plate pair, can have a preselected pore size, whereby each filter passage has an opening area at the inner edge corresponding to the preselected pore size. Moreover, each plate stack may have a preselected filter pore size and a preselected porosity, whereby each filter passage has an opening area at the inner edge corresponding to the preselected pore size and each filter plate, or filter plate pair, has a plate porosity calculated from a total surface of the core opening, the preselected pore size and the number of filter passages. The plate stack then includes a number of filter plates, or filter plate pairs at least equal to the ratio of preselected porosity/plate porosity.
In another aspect, the invention provides a filter unit for a solid/fluid separating press with at least one conveyor screw for conveying a solid/fluid mixture and a barrel divided into at least two barrel modules respectively defining a longitudinal portion of a core passage for housing the at least one conveyor screw, at least one of the barrel modules being a filter module having a housing defining a fluid collection chamber. The filter unit includes a plurality of barrel plates having flat front and back surfaces, an inner edge defining a core opening of a size and shape equal to the core passage and an outer edge. To allow for disassembly of the filter unit, each barrel plate is divided into first and second split plates along a plane of symmetry of the core passage. This filter unit further includes a stacking structure for aligning the first split plates into a first plate stack and the second split plates into a second plate stack, wherein the first and second split plates are stacked one behind the other in the first and second plate stack respectively, and for compressing the first and second plate stacks into first and second filter blocks wherein the first and second split plates are sealingly engaged with one another in their respective plate stack. This filter unit further includes a clamping structure for clamping the first and second filter blocks together along the plane of symmetry to form a portion of the core passage and a portion of the barrel. At least one of the first and second split plates in at least one of the first and second plate stacks defines a filter passage extending from the inner edge to the outer edge.
In still a further aspect, the invention provides a solid/fluid separating module for a solid/fluid separating press including at least one conveyor screw for conveying a solid/fluid mixture and a barrel defining a core passage for the at least one conveyor screw, the core passage having a longitudinal axis for each extruder screw. The separating module includes a housing for integration into the extruder barrel and for defining a pressurizable fluid collection chamber, the housing having a pair of opposite lids removable from the housing when integrated into the extruder barrel. The module further includes a filter unit in accordance with the invention, which filter unit is sealingly mounted in the housing for sealing the core opening from the collection chamber. In one embodiment of the solid/fluid separating module, the housing includes separate drains for liquids and gases.
In yet another aspect, the invention provides a solid/fluid separating press including at least one conveyor screw for conveying a solid/fluid containing mixture and a barrel defining a core passage for the at least one extruder screw, the core passage having a longitudinal axis for each extruder screw, the barrel including at least two barrel modules of which at least one is a solid/fluid separating module in accordance with the invention. In one embodiment of the solid/fluid separating press, all barrel modules are solid/fluid separating modules in accordance with the invention. In another embodiment, each solid/fluid separating module has a preselected pore size and each filter passage has an opening area at the inner edge corresponding to the preselected pore size. The filter module may have a preselected porosity calculated from a total surface of the core opening divided by the preselected pore size and the number of filter passages in the filter blocks.
In still another aspect, the invention provides a use of the solid/fluid separating press in accordance of the invention for separating fluids from a solid/fluid containing mixture, for example biomass, such as lignocellulosic biomass.
The separation module in accordance with the invention in one embodiment includes a filter unit having a porosity of 5% to 20% (total pore area relative to the total filter surface) and is constructed to withstand operating pressures of 300 psig to 10,000 psig, at a filter porosity of 5 to 20%, or 11 to 20%. Each filter plate may include a plurality of filter passages with a pore size of 0.0005 to 0.00001 square inch.
In another embodiment, the filter unit includes filter pates with passages having a pore size of 0.00001 square inch for the separation of fine solids, a porosity of 5.7% and a pressure resistance of 2,500 psig. In still another embodiment, the filter unit includes pores having a pore size of 0.0005 square inch and a porosity of 20% and a pressure resistance of 5,000 psig. In a further embodiment, the filter unit includes pores of a pore size of 0.00005 square inch and a porosity of 11.4%. In still a further embodiment, the filter unit includes pores having a pore size of 0.00001 square inch and a porosity of 20%.
In the filter unit in accordance with the invention, the pore size can be controlled by varying either one or both of the width and depth of the filter passages. To maintain maximum filter plate integrity, the depth of the filter passage can be maintained as small as possible and pore size controlled by varying the filter passage width. The width of the filter passages may vary from 0.1 inch to 0.01 inch and the depth of the filter passages may vary from 0.001 inch to 0.005 inch. The filter passages in a filter plate may all have the same pore size, or may have different pore sizes.
In the solid/fluid separation press in accordance with the invention, the separation module is mounted to the barrel of the press and the core opening is sized to fittingly receive a longitudinal portion of the extruder screw, or screws, of the press. The conveyor screw preferably has close tolerances to the central bore of the clamped filter block for continually scraping the compressed material away from the filter surface while at the same time generating a significant separating pressure. In the event that a small amount of fibers become trapped on the surface of the filter blocks, the fibers will be sheared by the conveyor screw into smaller pieces and ultimately pass through the filter unit and out with the liquid stream as very fine particles. This provides a solid/fluid separation device, which allows for the separation of solid and liquid portions of a solid/fluid mixture in a high pressure and high temperature environment.
In a further embodiment of the solid/fluid separation press, the press includes twin, intermeshing conveyor screws, the separation module is mounted to the barrel of the twin screw press and the central bore is sized to fittingly receive a portion of the intermeshing conveyor screws. The housing may have separate liquid and gas outlets for separately draining liquids and gases from the collection chamber.
Other aspects and features of the present disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.
For a better understanding of the embodiments described herein, and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings which show the exemplary embodiments and in which:
It will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements or steps. In addition, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Furthermore, this description is not to be considered as limiting the scope of the embodiments described herein in any way, but rather as merely describing the implementation of the various embodiments described herein.
The filter unit of the invention is intended for use with a single screw, twin screw or multi-screw solid/fluid separation press, for example a twin screw extruder assembly having parallel or non-parallel screws with the flighting of the screws intercalated or intermeshed at least along a part of the length of the extruder barrel to define close-clearance spaces between the screws and between each screw and the barrel. However, the filter unit of the invention can also be used with screw extruders having more than two conveyor screws.
The inventors developed a split filter unit for a solid/fluid separating device, or a solid/fluid filtering device for use with a solid/fluid separating device or press, for example a screw press conveyor, or a modular screw device, which filtering device can be installed into and/or removed from the solid/fluid separating device or press without requiring disassembly of the separating device, any assembly or disassembly being limited to a separating module of the separating device, which separating module houses the filter unit. In particular, the filter unit of the invention can be installed or removed from the separating module without removal of the conveyor screw from the separating device.
In addition to this advantage, the filter unit of the invention can include a barrel plate stack filter able to handle very high pressures (up to 20,000 psig). Some or all of the barrel plates can be constructed as filter plates to create a filer plate stack able to generate solids levels from 50-90%, well beyond that of commercially available screw press filtering devices. The filter plate stack can provide the further advantage of a very small pore size filter, so that a liquid portion extracted with this filter can contain little suspended solids. The combination of a high pressure filter unit in accordance with the invention with a twin-screw extruder press can result in a solid/liquid separation device capable of developing virtually dry cake of a solids level above 80%. A twin conveyor screw press in accordance with the invention and including a filter unit in accordance with the invention can process a solid/fluid mixture in a thin layer at pressures exceeding 300 psi while at the same time allowing trapped and bound liquid and water a path to migrate out of the mixture through the filter unit.
Using a screw press or extruder press with a filter unit in accordance with the invention, one can apply significant shear forces/stresses to a solid/fluid mixture, which forces are applied in a thin cake to free up liquid to migrate out through the filter unit. Most importantly, the filter unit is a split block filter unit, which can be installed about the conveyor screw or screws so that disassembly of the screw press, namely removal of the conveyor screw or screws is no longer required for assembly and disassembly of the filter unit. Thus, this split block filter unit when used with a twin-screw extruder press will provide significant benefits by reducing the amount of downtime and repair cost associated with cleaning a clogged filter unit.
Turning now to the drawings,
A perspective view of an exemplary solid/fluid separation module 200 in accordance with the invention is shown in isolation in
As can be seen from
For removal of the split block filter unit 300, upper and lower lids 105, 106 are removed to provide access to the split block filter unit 300. The filter unit sealing arrangement 400 (
The upper and lower filter blocks 302, 304 can each independently be a solid block, a solid block with drilled filtering passages, or a stacked block as discussed in more detail below in relation to
The upper and lower clamping arrangements 340, 330 of the clamping structure as illustrated in detail in
The upper and lower stacked blocks 310, 320 as illustrated in separation in
Other arrangements for holding the barrel plates aligned and compressed in a plate stack can also be used. The alignment structure can also be integrated with the associated clamping arrangement (not shown) to allow handling of the upper and lower filter blocks 310, 320 together with the respectively associated clamping arrangement, thereby possibly facilitating insertion into and removal from the housing. One or more of the barrel plates 314, 324 in the upper and lower stacked blocks 310, 320 can be constructed as a filter plate. The detailed construction of those barrel plates 314, 324 which are constructed as filter plates will be discussed in more detail below in reference to
Turning now to
As illustrated in
In order to achieve a separation of fluids from a pressurized fluid/solids mixture in the core opening 112, one or more of the universal barrel plates 370 in the stacked block 310, 320 can be constructed as a filter plate 372 including one or more filter passages 360 which each define a fluid passage in the filter plate 372 extending away from the inner edge 328. The filter passage 360 may extend all the way from the inner edge 328 to the outer edge 329 or from the inner edge 328 to a location away from the core opening at which it connects with another fluid passage either provided on or in the same plate or on/in a directly adjacent plate for fluid communication with the collection chamber. The filter passages 360 can be provided by cutting, scoring, etching or bending of the barrel plates 314, 324, 370 and the exact manner in which the passage is created will not be further discussed herein, since not of particular significance to the present invention. If the filter passage 360 extends from the inner edge 328 to the outer edge 329 in the front surface of the filter plate, only one type of filter plate is needed, since when this filter plate is stacked one behind the other with other like filter plates, the back surface of one filter plate will always function as a cover for the filter passage 360 in the like filter plate immediately behind. If a first section of the filter passage extending away from the inner edge is provided in one barrel plate and a complementary fluid passage connecting the first section with the outer edge is provided in another barrel plate, those two types of plates will allways have to be used as plate pairs in the stacked block.
In one embodiment, each barrel plate 314, 324, or universal barrel plate 370, is constructed as a filter plate to simplify the filter unit design and to maximize the filtering capacity of the filter unit. To maximize the porosity of a stacked block, each filter plate includes the maximum number of filter passages 360 which can be included in the filter plate without harming the structural integrity and pressure retention capacity of the filter plate and of the stacked block in which it is included. To reduce manufacturing cost and facilitate assembly, all barrel plates used in the separating module 200 can be filter plates 372 of identical construction.
The number of barrel plates 314, 324 included in the separating module 200 can be adjusted according to the plate thickness, the dimensions of the housing 100 and the desired filter porosity. In the illustrated embodiment, each stacked block 310, 320 included 200 filter plates 372 per inch of stacked length, each plate being 0.005 inch thick and having an overall open area of 0.864 square inches. With the illustrated embodiment, a dry matter content of 72% can be achieved at barrel pressures of about 600 psig. On a continuous basis, 100 g of biomass containing 40 g of solids and 60 g of water can be squeezed out in the filter module 300 using 600 psig internal force at a temperature of 100 C to obtain a dry biomass discharge (solids portion of the liquid/solid biomass) containing 39 g of suspended solids and 15 g of water. The filtrate obtained will contain about 95 g of water, which will be relatively clean and contain only a small amount (about 1 g) of suspended solids with a mean particle size equal to the pore size of the filter passages 360.
In the illustrated embodiment of the universal filter plate 372 of
The principle construction of assembling a portion of the barrel 21 from stacked identical barrel plates, which may be constructed as filter plates, allows for significant design variability and even enables the variation of the filtering or separation capacity and behavior of an extruder press by not only varying the filtering capacity of individual separating modules 200, but by converting separating modules 200 into barrel modules 12 by simply replacing the stacked blocks 310, 320 including one or more filtering plates with stacked blocks including only barrel plates and no filter plates, or even blocks of overall solid construction. In one possible embodiment, the complete barrel is constructed using separating modules, some of which have been converted to barrel modules 12 by replacement of the filter plates in the stacked blocks 310, 320 with barrel plates, In another embodiment, each separating module includes a solid filter block and a stacked filter block, whereby the solid block forms the upper filter block of the filter unit and the stacked block forms the lower filter block. It is a significant advantage of an arrangement in which each barrel module is a separating module in accordance with the invention that any part of the barrel can be used as a barrel section or as a filter unit and can be converted from one to the other without requiring disassembly of the barrel, by simply exchanging the filter blocks. Each of the filter blocks along the barrel can be a solid filter blocks, or a stacked block with a particularly selected porosity. Separation modules in which the upper and lower filter blocks are both solid blocks or stacked blocks devoid of any filter passage then function as a regular barrel module 12. Moreover, it is another significant advantage of such an arrangement that a blockage in any part of the barrel, whether in a separating/filtering region or not, can be cleared, without the need for disassembly of the extruder press or removal of the conveyor screws, by simply replacing the clogged filter block with a clean like filter block and/or removing the compacted solids surrounding the conveyor screws and blocking the core passage 112.
Overall, with higher pressure capability, either more liquid can be squeezed from the solids or, for the same material dryness, a higher production rate can be achieved per unit filtration area. The quality of filtration (solids capture) can be controlled depending on plate configurations and thicknesses. The filtration/pressure rating/capital cost can be optimized depending on the filtration requirements of the particular biomass. The plate configurations can be installed in an extruder (single, twin or triple screws) to develop high pressure, high throughput, continuous separation. The solid/fluid separation module can be constructed with sufficiently tight spacing between the conveyor screws themselves and between the conveyor screws and the inner edge to achieve a self-cleaning effect (for twin and triple screws) by a wiping action of the screws and by an cross axial flow pattern. The filtration area is flexible depending on process requirements as the length of plate pack can be easily custom fit for the particular requirements. The module can be used to wash solids in a co current or counter current configuration in single or multiple stages in one machine reducing capital cost and energy requirements. The pressure of the liquid filtrate can be controlled from vacuum conditions to even higher than the filter block internal pressure (2,000 to 3,000 psig), if required. This provides great process flexibility for further separations in the liquid stream (example super critical CO2 under high pressure, ammonia liquid used for washing under high pressure, or release of VOC and ammonia gases in the liquid filtrate chamber using vacuum).
In the exemplary solid/fluid separation device described, the screw elements that transfer the material internally in the separation device have very close tolerances to the internal surface of the filter block and continually scrape the material away from the filter surface. In the event that a small amount of fibers became trapped on the surface of the filter, they will be sheared by the extruder elements into smaller pieces and ultimately pass through the filter and out with the liquid stream. The high back pressure capability of the housing (higher than internal filter block pressure) can be used to back flush the filter during operation in case of plugging or scaling of the filter, minimizing down time. Of course, any plugging which cannot be cleared by backwashing can be removed by disassembly of only the filter unit 300 which is plugged, without removal of the whole separation module 200 from the separating apparatus 20 or removal of the extruder screws.
It will be readily understood that the solid/fluid separation module in accordance with the invention can be used in many different applications to separate solid/fluid portions of a solid/fluid mixture.
Different filter units 100 have been made and tested. In one embodiment, the filter unit 100 included filter pores having a pore size of 0.00005 square inch for the separation of fine solids, had a porosity of 5.7% and had a pressure resistance of 2,500 psig. In another embodiment, the filter unit 100 included filter pores having a pore size of 0.005 square inch and had a porosity of 20% and a pressure resistance of 5,000 psig. In a further embodiment, the filter unit 100 included filter pores of a pore size of 0.00005 square inch and had a porosity of 11.4%. In still another embodiment, the filter unit 100 included filter pores having a pore size of 0.005 square inch and had a porosity of 20%.
The total number of filter plates can vary depending on the type of solid/fluid mixture to be separated, for example biomass, and influences the overall filter area. For the same liquid separation conditions, more plates/more surface area is required for smaller pores. The size of the pores controls the amount of solids which pass to the liquid portion. Each solid/fluid mixture may require a certain pore size to achieve an optimal solids capture (amount of suspended solids in liquid filtrate). By using separation modules in accordance with the invention, the porosity, pore size, total filter area and pressure capacity of the solid/fluid separation device can be varied and adjusted without disassembly of the device or removal of the conveyor screws, making it possible to adjust the separating properties of the separating device ‘on the fly’.
Although this disclosure has described and illustrated by way of certain embodiments, it is also to be understood that the system, apparatus and method described is not restricted to these particular embodiments. Rather, it is understood that all embodiments, which are functional or mechanical equivalents of the specific embodiments and features that have been described and illustrated herein are included. It will be understood that, although various features have been described with respect to one or another of the embodiments, the various features and embodiments may be combined or used in conjunction with other features and embodiments as described and illustrated herein.
The present application claims priority from U.S. Provisional Application Ser. No. 62/005,351, filed May 30, 2014 and entitled Split Filter Block For Extruder Press, the disclosure of which is incorporated herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62005351 | May 2014 | US |
