Twin screw extruder press for solid/fluid separation

a technology of extruder press and screw extruder, which is applied in the direction of press ram, separation process, filtration separation, etc., can solve the problems of difficult to effectively separate solids from liquids under the high heat and pressure required for cellulose pre-treatment, and unsatisfactory low solids conten

Inactive Publication Date: 2016-08-02
GREENFIELD SPECIALTY ALCOHOLS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013]It is an object of the present invention to obviate or mitigate at least one disadvantage of previous solid / liquid separation devices.

Problems solved by technology

Conventional liquid / solid separation equipment is not satisfactory for the achievement of high liquids / solids separation rates and solids with low liquid content.
It is difficult to effectively separate solids from liquid under the high heat and pressure required for cellulose pre-treatment.
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 leftover moisture being predominantly water.
This unsatisfactory low solids content is due to the relatively low maximum pressure conventional screw presses can handle, which is generally not more than about 100-150 psig of separation pressure.
However, their drawbacks are their inherent cost, complexity and continued filter cake limitation of no more than 50% solids content.
A reduction in pressure, an increase in cake thickness or a decrease in porosity of the filter, will all lower the separation efficiency and result in a decrease in the degree of liquid / solid separation and in the ultimate degree of dryness of the solids fraction.
High separating pressures unfortunately require strong filter media, which are able to withstand the separating pressure, making the process difficult and the required equipment very costly.
This may create a problem, depending on the solids to be retained, since 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 being limited solely by the pore size of the filter media.
Pores that are too large allow a significant amount of suspended particles to collect in the liquid fraction, thereby reducing the liquid / solid separation efficiency.
A higher porosity can also be achieved by providing a higher overall number of pores, but that either weakens the filter media and thus lowers the maximum operating pressure, or unduly enlarges the filter surface.
However, over time, that leads to the filter media becoming plugged with suspended solids, thereby not only reducing the separation efficiency, but eventually leading to failure of the filter.
This is especially the case at the high pressures required for cellulose pre-treatment.
Once a filter becomes plugged, it takes high pressure to backwash the filter media.
This is particularly problematic when working with filter media operating at elevated pressures, for example above 1000 psig, or with a process that is to be continuous.
Conventional single, twin, or triple screw presses are known, but have unacceptable separating capabilities.
Operating pressures of such a screw press are low, due to the low strength of the perforated casing and the relatively low porosity of the casing.
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.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example i

Biofuel Process

[0100]As shown in FIG. 1, a simple continuous cellulosic ethanol pre-treatment system 2 of the present invention consists of only three machines. A first extruder 4 being used as a continuous high pressure plug feeder / mixer for biomass. The extruder 4 feeds the biomass into a vertical reactor 6. The vertical reactor 6 is capable of having a long residence time. The vertical reactor 6 feeds the biomass into a second extruder 8, preferably a twin screw extruder. The pre-treatment process comprises flowing the biomass through the first extruder 4, the vertical reactor 6, and the second extruder 8.

[0101]The extruder 4, which may also be a twin screw extruder, is used to provide a continuous feed into the pressurized vertical reactor 6. Mixing of various chemicals in the extruder 4 is possible depending on the type of feedstock. The extruder 4 has an automatic valve, which closes upon loss of feed to prevent loss of pressure in the case of loss of feedstock.

[0102]Vertical ...

example ii

Feedstock Soybeans

[0113]Soybeans were sourced locally (grown in Chatham-Kent, Southern Ontario, Canada). Content analysis of the soybeans showed the feedstock was composed of 70.7% / wt solids and 29.3% / wt liquids, in the form of 13.8% / wt oil and 15.5% / wt water. The soybeans were fed whole into the extruder without pre-processing. The total amount of soybeans fed into the extruder was 1.384 kg whole soybean and the total operating time of the extruder was one hour. During extrusion of the soybeans, the motor load was 8 times higher than the baseline established with water. The feed rate, solids output rate and filtrate output rate over time are graphically illustrated in FIG. 16 As is apparent from the graph, the filtrate output is constant over the whole hour of operation, thereby indicating zero degree of clogging of the filter block. The overall output of the extruder was 11.5% / wt filtrate, with 5:95% / wt equal recovery through each of filter block #1 and #2, thereby indicating that...

example iii

Feedstock Sugar Beets

[0114]Sugar Beets were sourced locally (grown in Chatham-Kent, Southern Ontario, Canada). Whole sugar beets were received directly off the field after harvest and stored at an outdoor holding depot. Prior to processing, sugar beets required washing to remove debris (dirt, stones, etc.). A hand hatchet was used to split the sugar beets, then these sugar beet slices fed into a food processor using a first pass with the grating blades, followed by a second pass with the cutting blades. This produced a particle size of ˜5 mm×5 mm biomass, which was suitable to be fed into the extruder. Content analysis of the sugar beets showed the feedstock was composed of 16.9% / wt sucrose, 1.4% / wt other soluble solids, 1.3% / wt insoluble solids, and 80.4% / wt water. The total amount of sugar beets fed into the extruder was 3.219 kg chopped sugar beets and the total operating time of the extruder was one hour. During extrusion of the sugar beets, the motor load was 25% higher than th...

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Abstract

Disclosed is a solid / liquid separation apparatus including an extruder press combined with a solid / fluid separation module for separating fluid from a mass of solids compressed by the extruder at elevated pressures. The extruder includes two or more extruder screws with flighting intercalated at least along a part of the extruder barrel. The separation module forms a continuation of the barrel, receives the pressurized mass and at least a portion of the twin screws, and includes a filter pack consisting of a filter plate and a backer plate. The filter plate has a throughgoing filter slot extending away from a core opening and into the filter plate for directing fluid away from the core opening. The backer plate has a core opening shaped and sized equal to the barrel and defines a passage for guiding fluid collected in the filter slot to an exterior of the filter pack.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of priority of U.S. Provisional Patent Application No. 61 / 620,772 filed Apr. 5, 2012, the contents of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to a method for the treatment of different types of solid / fluid mixtures. The present invention is broadly concerned with solid / fluid separation apparatus, in particular improved screw press devices of a highly versatile nature which can be used for the separation of a wide variety of liquid / solid mixtures and slurries of varying densities, solids contents and types of solids and liquids.BACKGROUND OF THE INVENTION[0003]Various process feed or process residue treatment processes for solid / liquid separation are known which require significant residence time, high pressure and high temperature. Generally, liquids must be separated from treated solids at those conditions. Conventional liquid / solid separatio...

Claims

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Application Information

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Patent Type & AuthorityPatents(United States)
IPC IPC(8): B01D29/46B01D29/82B30B1/00B30B9/12B30B9/16B30B9/24B30B9/26B01D33/00B30B11/24
CPCB01D33/009B01D29/46B01D29/828B30B1/00B30B9/12B30B9/16B30B9/26B30B11/24
InventorLEHOUX, RICHARD ROMEOBRADT, CHRISTOPHER BRUCE
OwnerGREENFIELD SPECIALTY ALCOHOLS