Background:

Solid-liquid separation is required in various industries and the nature and type of equipment used depends on the economic values and proportions of the phases as well as certain physical properties that influence relative movements of liquids and particles. Solid liquid separation may broadly be classified as follows: 'clarification/settling' for the removal of small contents of undesirable solids from a valuable liquid; 'filtration' for the recovery of valuable solids from slurries and 'expression' for the removal of relatively small content of liquids from compressible sludges by mechanical means. This broad classification for solid-liquid separation may further be elaborated as:

1. Settling
a. by gravity:
i. In thickeners, ii. In classifiers,

b. by centrifugal force;

c. by air flotation;

d. by dense media flotation;

e. by magnetic properties

2. Filtration
a. ori screens, by gravity;
b. on filters:
i. by vacuum,
ii. by pressure,
iii. by centrifugation,

3. Expression
a. with batch presses,
b. with continuous presses:
i. screw presses, ii. rolls, iii. Discs

Many industrial requirements, such as biomass extracts, today require more than one type (clarification/filtration/expression) of solid liquid separation processes. Accordingly, the equipment design for such processes includes equipment for each process step. Moreover, the multiple equipment design makes a continuous process challenging and often impractical. An oil extraction process typically includes drying the biomass, crushing or sizing the biomass, pressing and/ or solvent extraction of oil, followed by oil separation and/or solvent recovery. The waste product of the oil extraction process may be further put through a pressing and/or solvent extraction step. In the case of biomass extracts, the extraction process requires separation of the liquid fraction of the material along with any dissolved solids from the insoluble solid fraction of the material with or without the addition of solvents. Water, oils and fatty acids are all commonly present in biomass with various dissolved minerals, organic and aromatic compounds in them. The solid faction may or may not be useful and accordingly may require further processing. The methods described above do not provide an efficient way for extracting both liquid/oils and solids from the biomass. Further, these processes involve multiple steps, usually performed in multiple systems/devices. The purpose of this disclosure is to overcome these drawbacks of the existing methods, and provide an apparatus and method for more efficient and continuous biomass processing.

Summary

An extruder for separation of liquids and solids is disclosed. The extruder comprises of a housing defining an inlet end and an outlet end and having a first and second bore. A first screw shaft and a second screw shaft are disposed in the first and second bores and are configured for rotation therein. A plurality of extruder processing elements are mounted on the first and second screw shafts and define a clearance between the screw shaft and the housing. The housing defines an extruder inlet proximate the inlet end and an extruder outlet proximate the outlet end. The housing further defines a liquid outlet proximate the inlet end and wherein the housing is inclined at an angle to a horizontal axis such that the liquid outlet is below the horizontal axis and the extruder outlet is above the horizontal axis.

Brief Description of Drawings

FIG. 1 illustrates a schematic illustration of an inclined extruder setup.

FIG. 2 is a schematic illustration of the extruder housing and screw shafts in accordance with an embodiment.

FIG. 3 shows a side view of an inclined extruder in accordance with an embodiment.

Fig. 4 shows isometric view of an inclined extruder in accordance with an embodiment.

FIG. 5 show configuration of an actual screw in accordance with an embodiment.

Detailed Description:

The present disclosure describes an apparatus for separation of liquids from solids. In particular, the present disclosure provides an extruder to deliver a single-step and continuous process for biomass processing to separate liquids from solids. More specifically, the present disclosure provides an inclined extruder, that is, an extruder disposed at an angle relative to a horizontal axis such that the solid material travels uphill with the inlet lower than the outlet. FIG. 1 illustrates a schematic illustration of an inclined extruder setup for separation of liquids and solids in accordance with this disclosure. As illustrated, the extruder (10) comprises of an extruder inlet (44), an extruder outlet (46) and a liquid outlet (48) with the extruder inlet (44) and the liquid outlet (48) positioned below the extruder outlet (46). According to a preferred embodiment, as shown in FIG. 2, the extruder (10) is a co-rotating twin screw extruder having two screw shafts (22,24) which are parallely disposed relative to each other and rotate in the same direction. A counter-rotating twin screw extruder may alternatively be employed, however such an extruder will require greater clearances. The housing (12) defines an inlet end (14) and an outlet end (16) and has a first (18) and second bore (20). A first screw shaft (22) and a second screw shaft (24) are disposed in the first and second bores (18, 20) and are configured for rotation. A plurality of extruder processing elements (26) are mounted on the first and second screw shafts (22, 24) and define a clearance (28) between the screw shaft (22, 24) and the housing (12).

With reference to FIG. 3 and FIG.4, the extruder (10) for separation of liquids and solids in accordance with an embodiment is illustrated. The extruder (10) includes a housing (12), which is in the form of a hollow cylinder, having a linearly extending passage. A motor (30) is coupled to the screw shafts via a coupler (32) and a gear-box (34). The housing (12) along with the gear-box (34) are mounted on a platform (36) that is mounted on the extruder base (38). In the embodiment illustrated, the platform (36) is mounted on the extruder base (38) by means of a hinge assembly (40) at one end and a sliding system (42) that permits inclination of the platform (36) vis-a-vis the extruder base (38) to be varied. The sliding system may be any known mechanism for length extensions and may include a hydraulic cylinder (56) as illustrated in FIG. 4. The extruder (10) defines an extruder inlet (44) proximate the inlet end (14) and an extruder outlet (46) proximate the outlet end (16). The extruder inlet (44) and the extruder outlet (46) may be provided as is conventionally known in the art. The extruder (10) further defines a liquid outlet (48) proximate the inlet end (14). The liquid outlet (48) is positioned such that the extruder inlet (44) is in between the extruder outlet (46) and the liquid outlet (48). In an embodiment, the liquid outlet is positioned as close as practical to the inlet end (14) of the housing. Further, in accordance with an embodiment, the inlet end of a conventional extruder defining an extruder inlet and a side inlet may be rotated such that the extruder inlet and the side inlet are adapted as the liquid outlet and the extruder side inlet.

In accordance with an embodiment, the extruder (10) has a length less than that of conventional extruders. The ratio of length to screw diameter of the extruder (10) is less than 24 and in some embodiments may range between 10 to 24. In the embodiment illustrated in FIG. 5, the extruder (10) has a screw diameter of 95 mm and a length of 1460 mm defining a L/D ratio of 15.36 or approximately 15. In an embodiment of the present disclosure, the extruder is positioned in an inclined manner to a horizontal axis (50). In the embodiment illustrated, the horizontal axis (50) is parallel to the extruder base (38). The horizontal axis (50) typically passes through the center of the extruder (10). That is, the extruder (10) is disposed at an angle such that the solid material travels against gravity with the extruder inlet (44) lower than the extruder outlet (46) and in particular the liquid outlet (48) below the extruder outlet (46) and the extruder inlet (44). The extruder (10) is disposed at an angle of 5 to 90 degrees to the horizontal axis (50). More specifically, the extruder housing (12) is disposed at an angle such that the extruder base (38) may be positioned horizontally or parallel to the ground, as in a conventional manner, and the housing (12) is so placed to be at an angle. In the extruder of FIG. 3, the angle is 23 degrees.

In a further embodiment, as shown in FIG. 2 a clearance (28) between the screws and the housing (12) is maintained. In particular, the clearance (28) is defined between the extruder processing elements (26) mounted on the screw shaft and the inner wall of the housing (12). This clearance (28) allows the liquid/oil extracted out of the biomass or separated from the solids, on account of the crushing action of the screws followed by packing, to flow freely backward towards the liquid outlet (48) that is lower than the extruder inlet (44), while the solid biomass may continue to be conveyed forward by the conveying action of the screws (22, 24) to the extruder outlet (46). The clearance (28) as referred to herein is greater than the standard clearance maintained in extruders. In accordance with an embodiment, the clearance (28) defined by the extruder processing elements (26) proximate the extruder inlet (44) is greater than the clearance defined by the remaining extruder processing elements (26). Proximate the extruder inlet (44) includes at least two extruder processing elements from the inlet end (14), but may also include a larger number of extruder processing elements (26). A greater clearance in this region is required to ensure that the liquid can flow back towards the liquid outlet (48) and not get pushed up along with the solid material. In the extruder (10) illustrated in FIG. 5, the extruder is shown to comprise of four barrels with the first three barrels having a length of 380 mm and the fourth barrel having a length of 285 mm. The first two barrels (Bl, B2) may be considered as forming the intake zone of the extruder (10) or proximate the extruder inlet (44).

In accordance with an embodiment, the clearance (28) between the extruder processing elements (26) and the housing (12) is kept above 1 mm and closer to 1.5 mm or 2 mm. However, the clearance (28) may go as high as 5 mm or as low as 0.15mm based on the inclination of the extruder, the material processed and/or the feed rate of input material. However, clearances less than 1 mm may not be suitable for all materials and all feed rates. In accordance with an embodiment and as illustrated in FIG.6, the extruder processing elements (26) proximate the extruder inlet (44) are spacers (52) that do not define a screw profile and only marginally increase the diameter of the screw shafts. The use of spacers (52) is particularly beneficial when conventional extruders having a length to screw diameter ratio of around 25 to 40 are used, such as the extruder illustrated in FIG. 6, having a L/D ratio of 40. In accordance with an embodiment, the clearance (28) between the screws and the housing (12) wall may be inversely proportional to the inclination angle (54) of the extruder. That is, more the inclination angle (54), lesser the clearance (28) required for the backward flow of the extracted sap, and vice-versa.

The biomass processing method or the method of separation of liquids from solids includes introducing the biomass to the extruder, crushing the biomass by the screws, separating the liquid/oil and the solid biomass on account of the inclined arrangement of the extruder, and discharging the solid biomass towards the extruder outlet, while recovering the separated liquid from a liquid outlet specifically provided for that purpose. For this purpose, as shown in FIG. 1 and FIG. 3, the extruder of the present disclosure includes an inlet, a crushing/separation zone, an outlet for solids, and an exit port for the liquid. The extruder inlet (44) may use feeding of the material or biomass from a side of the extruder using slurry pumps, single or twin-screw side-feeders or stuffers or other force feeding devices. In accordance with an embodiment, the extruder may form an intake zone, a crushing/separation zone and a discharge zone. The intake zone and the crushing/separation zone define larger than standard clearances as described above. The crushing/separation zone of the extruder may include extruder processing elements (26) that perform the crushing/squeezing of the solid material or biomass.

This zone utilizes the inclination for the extracted liquid/oil to flow downwards or backwards towards the liquid outlet (48) that is suitable for liquid/oil collection. The clearance (28) between screw and housing (12) may be changed along the length of the extruder for achieving the required packing and forward conveying of solids. According to an embodiment, the intake zone as well as the crushing/separation zone defining larger than standard clearances may not form more than one half of the length of the extruder, with the rest of the extruder forming a packing and conveying/discharge zone. It may be contemplated that the crushing zone and the separation zone may be two separate zones with some common portion overlapped onto each other. Further, the discharge zone serves to further compact the biomass and convey the same to the outlet.

SPECIFIC EMBODIMENTS ARE DESCRIBED BELOW

The extruder for separation of liquids and solids comprises of a housing defining an inlet end and an outlet end and having a first and second bore. A first screw shaft and a second screw shaft are disposed in the first and second bores and are configured for rotation therein. A plurality of extruder processing elements are mounted on the first and second screw shafts. The extruder processing elements define a clearance between the screw shaft and the housing. The housing further defines an extruder inlet proximate the inlet end and an extruder outlet proximate the outlet end of the housing. The housing also defines a liquid outlet proximate the inlet end. The housing is inclined at an angle to a horizontal axis such that the liquid outlet is below the horizontal axis and the extruder outlet is above the horizontal axis. Such an extruder(s), wherein the clearance defined by the extruder processing elements proximate the extruder inlet is greater than the clearance defined by the remaining extruder processing elements. Such an extruder(s), wherein the clearance proximate the extruder inlet is at least 1.5 mm. Such an extruder wherein the extruder processing elements mounted on the first and second screw shafts proximate the extruder inlet are spacers. Such an extruder as wherein the housing is inclined at an angle of at least five degrees to a horizontal axis.

Such an extruder wherein the first and second screw shafts are configured for rotation in the same direction. Such an extruder wherein the ratio of length to screw diameter of the extruder is not more than 24. Such an extruder, wherein ratio of length to screw diameter is greater than 24 and the extruder processing elements mounted on the first and second screw shafts proximate the extruder inlet are spacers. Such an extruder further defining an intake zone, a crushing or separating zone followed by a discharge zone, wherein the clearances in the intake zone and the crushing or separating zone are larger than the clearances in the discharge zone. Such an extruder, wherein the intake zone and the crushing and separating zone do not form more than one half of the length of the extruder. Such an extruder comprising a sliding system for varying the inclination of the extruder to the horizontal axis.

EXPERIMENTAL DATA

The present invention has been illustrated with the help of following experiments and do not in any way limit the scope of the invention as described and claimed: The extruder for separation of liquids from solids has the following configuration, as illustrated in FIG.3 and FIG.5.:
Length: 1461 mm
Diameter: 95 mm
Inclination: 23 Degree
Extruder processing elements:

Experiment 1:
Total weight of Sea-weed processed - 900 kg.
Feed rate: 400 kg/h
Amount of Liquid collected: 550 litres

Experiment 2:
Total weight of Cucumber processed - 50 kg
Feed rate: 100 kg/h
Amount of liquid collected: 20 litres

INDUSTRIAL APPLICABILITY

The disclosed method, achieved by means of the described extruder, provides a more efficient way for extraction of both liquid/oil and solid biomass Further, the disclosed apparatus and method provides a single step process for biomass treatment. The disclosed equipment and process may also be applicable for extraction of oils/essence from wood and flowers including material such as sandalwood, jasmine flowers etc. As illustrated in the examples above, the disclosed equipment and process may also be used to extract valuable liquid or solid material from materials such as cucumber and sea-weed, as well as from various seeds.

We claim:

1. An extruder for separation of liquids and solids comprising: a housing defining an inlet end and an outlet end and having a first and second bore; a first screw shaft and a second screw shaft disposed in the first and second bores and configured for rotation therein;a plurality of extruder processing elements mounted on the first and second screw shafts and defining a clearance between the screw shaft and the housing;the housing defining an extruder inlet proximate the inlet end and an extruder outlet proximate the outlet end;wherein the housing defines a liquid outlet proximate the inlet end and wherein the housing is inclined at an angle to a horizontal axis such that the liquid outlet is below the horizontal axis and the extruder outlet is above the horizontal axis.

2. An extruder as claimed in claim 1 wherein the clearance defined by the extruder processing elements proximate the extruder inlet is greater than the clearance defined by the remaining extruder processing«lements.

3. An extruder as claimed in claim 1 wherein the clearance proximate the extruder inlet is at least 1.5 mm.

4. An extruder as claimed in claim 1, wherein the extruder processing elements mounted on the first and second screw sha^s proximate the extruder inlet are spacers.

5. An extruder as claimed in claim 1 wherein the housing is inclined at an angle of at least five degrees to a horizontal axis.

6. An extruder as claimed in claim 1 wherein the first and second screw shafts are configured for rotation in the same direction.

7. An extruder as claimed in claim 1 wherein the ratio of length to screw diameter of the extruder is not more than 24.

8. An extruder as claimed in claim 1, wherein ratio of length to screw diameter is greater than 24 and the extruder processing elements mounted on the first and second screw shafts proximate the extruder inlet are spacers.

9. An extruder as claimed in claim 1 defining an intake zone, a crushing or separating zone followed by a discharge zone, wherein the clearances in the intake zone and the crushing or separating zone are larger than the clearances in the discharge zone.

10. An extruder as claimed in claim 9 wherein the intake zone and the crushing and separating zone do not form more than half the length of the extruder.

11. An extruder as claimed in claim 1 comprising a sliding system for varying the inclination of the extruder to the horizontal axis.