Filter for extruder press

Abstract

A solid / fluid separation module (300) and press comprises at least one filter unit (301) for a solid / fluid separating press having a barrel with a core opening (112) for at least one conveyor screw. The filter unit includes a pair of end plates (321,322) and a plurality of intermediate filter plates (314) placed one behind the other and sealingly compressed into a plate stack (310) between the end plates. Each intermediate plate (314) has at least one drainage perforation (362) separate from the core opening, the core opening and drainage perforation each extending from a front face to a back face of the intermediate filter plate. In the filter unit, all end plates and barrel plates are aligned such that the core openings form the core passage of the filter block and such that the drainage perforations form an internal fluid collection chamber (338) within the filter unit.

Description

[0001]This application claims the benefit of priority from U.S. Provisional Patent Application No. 62 / 330,444, filed May 2, 2016, the entire contents of which are incorporated by reference.FIELD OF THE INVENTION[0002]The present disclosure is broadly concerned with solid / fluid separation devices and methods for the separation of different types of solid / fluid mixtures.BACKGROUND OF THE INVENTION[0003]Solid / fluid or solid / liquid separation is necessary in many commercial processes, for example biomass processing, food processing (oil extraction), reduction of waste stream volume in wet extraction processes, dewatering processes, or suspended solids removal.[0004]Many biomass treatment processes generate a wet fiber slurry from which dissolved compounds, gases and / or 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 ...

AI Technical Summary

Benefits of technology

[0015]It is an object of the present invention to obviate or mitigate at least one disadvantage of previous solid / liquid separation devices and processes.

[0016]In order to improve the operation and maintenance of a solid / fluid separation device, the invention provides a filter unit for a solid / fluid separating press having a barrel with a core opening for containing a solid / fluid mixture and housing at least one conveyor screw for conveying the solid / fluid mixture, the barrel being divided into at least two barrel modules respectively defining an axial portion of the barrel. The filter unit forms at least one of the barrel modules and includes a filter block with an internal fluid collection chamber, rather than an external collection chamber. By providing an internal collection chamber, the distance between the core opening and the collection chamber, and thus the distance and fluids separated from the mixture in the core opening must travel in a filter passage is reduced, which reduces backpressure and fines accumulations and facilitates backwashing.

Problems solved by technology

It is difficult with conventional equipment to effectively separate solids from liquid under pressure and especially the high temperature and pressure conditions required for cellulose pre-treatment.

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.

The thicker the pressure jacket, the longer the drainage perforations, the higher the flow resistance through the perforations and the higher the risk of clogging.

However, increasing the number of perforations weakens the pressure jacket, once again reducing the pressure capacity of the filter unit.

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 to be retained 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.

However, once a filter becomes plugged, it takes a pressure higher than the operating pressure to backwash the media.

This can become problematic when working with filter media operating at pressures above 1000 psig in a process that is to be continuous to maximize the production rate, for example to obtain high cellulose pre-treatment process efficiency.

However, most backwashing requires interruption of the filtering operations, so that increased backwashing reduces the production rate.

Conventional single, twin, or triple screw extruders do not have the residence time necessary for pre-treatment of biomass, and also do not have useful and efficient solid / fluid separating devices for the pre-treatment of biomass, in particular lignocellulosic biomass.

Operating pressures of such a screw press are low, due to the low strength of the perforated 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.

The need for a backer plate for each filter plate limits the filter porosity, since the axial length of the module represented by the cumulative thickness of the backer plates cannot be used for filtering.

Moreover, the use of a filter slot in combination with a drainage passage in the backer plate results in a long, tortuous path of the separated fluids with elevated backpressure and ample opportunity for fines accumulations in the slot and / or the passage.

However, clogging of the filter passage with fines is still possible and removal of such clogging may prove challenging due to the long filter passage.

Clogging of the filter passage with particulates occurs due to the long filter passage extending from the core opening to the outside of the filter block.

The length of the filter passage also makes, removal of such dogging challenging and backwashing is difficult due to significant backpressure.

Moreover, backwashing of a clogged filter block requires the draining of the separated fluids from the collection chamber, supplying backwashing fluid into the chamber and removing the backwashing fluid upon completion of the backwash cycle.

This creates significant down time and cost.

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