DESC:Field of Invention
The present disclosure relates to a filtration system. More particularly, the present disclosure relates to a filtration system for filtration of dope prepared in lyocell process.

Background
In the manufacture of lyocell fibers, before spinning, dope comprising wood pulp dissolved in an aqueous solution of amine oxide is pumped under pressure through a series of filters to multiple spinneret heads. The holes of each spinneret head are typically 150 microns or less. Therefore, it is critical to filter the dope to remove various impurities like undissolved fibers, coarse components, or inorganic compounds from the raw materials to avoid blockages in the spinneret.
The conventional filtration system comprises a series of filter modules, including filters such as candle filters and screen change filters of decreasing mesh sizes.
It is desirable to increase the production capacity of the lyocell process by increasing the filtration capacity of filtration systems. One possible means of increasing the filtration capacity of a filtration system is by increasing the flow rate of the material to be filtered. However, lyocell dope is shear-sensitive, and an increase in flow rate and hence shear rate results in undesirable in-situ heating of flowing dope. Also, since the heat capacity of the dope is low, it is difficult to resort to heat removal for a short duration for safe operation. This may increase the likelihood of a runaway reaction due to the high temperature of the dope. Apart from this in-situ temperature rise and subsequent safety risk, the polymer flux rate, i.e., dope flow per unit area per unit time, will also increase. This will adversely affect the filtration efficiency, and as a result, downstream spinning and fiber quality will also be affected.
An alternate way of increasing the filtration capacity is by increasing the number of filtering candles in the filter module by increasing the size of the housing. However, this results in a non-uniform distribution of dope and an increased likelihood of dead zones in the filter module. Again, this will increase the safety risk of runaway reactions due to the prolonged exposure of the dope in these dead zones to high temperatures.

Summary
A filtration system for filtration of dope formed in a lyocell process is disclosed. Said filtration system comprises of an inlet for dope, said inlet including an inlet valve, an outlet for exit of filtered dope, said outlet including an outlet valve, and a housing defining an interior divided into a plurality of filtration units, each filtration unit including a plurality of filter modules disposed therein, each filter module including a module inlet and a module outlet. The filter modules are configured to allow dope, but not impurities, to pass there through. In said filtration system, the module inlet and the module outlet of each filter module of the plurality of filtration units are in fluid communication with the inlet valve and the outlet valve, respectively. Further, the inlet valve is configured to allow selective passage of the dope through each filter module of one or more filtration units, and the outlet valve is configured to selectively receive the filtered dope exiting from each filter module of the one or more filtration units.
A filtration process for the filtration of dope formed in a lyocell process is also disclosed. Said process comprises passing the dope prepared in the lyocell process through the aforesaid filtration system. In said filtration process, the dope is selectively passed through only a predetermined number of filtration units for filtration while the remaining filtration units are on standby.

Brief Description of Drawings
Figure 1 shows a schematic diagram of the filtration system in accordance with an embodiment of the present disclosure.

Detailed Description
To promote an understanding of the principles of the disclosure, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the disclosed composition and method, and such further applications of the principles of the disclosure therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.
Reference throughout this specification to “one embodiment” “an embodiment” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase “in one embodiment”, “in an embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The present disclosure relates to a filtration system for filtration of dope formed in a lyocell process. Said filtration system comprises of an inlet for dope, the inlet including an inlet valve, an outlet for exit of filtered dope, the outlet including an outlet valve, and a housing defining an interior divided into a plurality of filtration units, each filtration unit including a plurality of filter modules disposed therein. Each filter module includes a module inlet and a module outlet, and is configured to allow dope, but not impurities, to pass there through. In said filtration system, the module inlet and the module outlet of each filter module of the plurality of filtration units are in fluid communication with the inlet valve and the outlet valve, respectively. Further, in said filtration system, the inlet valve is configured to allow selective passage of the dope through each filter module of one or more filtration units, and the outlet valve is configured to selectively receive the filtered dope exiting from each filter module of the one or more filtration units.
A filtration process for the filtration of dope formed in a lyocell process is also disclosed. Said process comprises passing the dope prepared in the lyocell process through the aforesaid filtration system. In said filtration process, the dope is selectively passed through only a predetermined number of filtration units for filtration while the remaining filtration units are on standby.
Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding reference numbers may be used throughout the drawings to refer to the same or corresponding parts, e.g., 1, 1`, 1``, 101, and 201 could refer to one or more comparable components used in the same and/or different depicted embodiments.
Referring to FIG. 1, a filtration system 100 is shown and described. Various alternatives to the configurations of the filtration system 100 are possible, and those that are described here are purely exemplary.
With continued reference to FIG. 1, details related to the filtration system 100 are now described. The filtration system 100 includes an inlet 102. The inlet 102 includes an inlet valve 104.
As shown in FIG. 1, the filtration system 100 further defines a housing 106 (not shown). The housing 106 defines an interior including two filtration units 108, and 110. Each filtration unit 108, and 110 includes at least two filter modules- 108A and 108B, and 110A and 110B, respectively. Each filter module has a module inlet (not shown) and a module outlet (not shown). In an embodiment, each filter module 108A, 108B, 110A, and 110B comprises a filter selected from the group consisting of a candle filter and screen changer filter, and any other similar filter as is now known or in the future developed.
In an embodiment, the filter modules in the filtration unit are connected in parallel between the inlet for dope and the outlet for the filtered dope. Referring to FIG. 1, the filtration unit 108 includes filter modules 108A and 108B connected parallelly. Similarly, the filtration unit 110 includes filter modules 110A and 110B connected in parallel between the inlet 102 for dope and the outlet 116 for the filtered dope.
The module outlet of each of the filter modules 108A, 108B, 110A, and 110B is in fluid communication with the outlet valve 114 positioned in the outlet 116.
In an embodiment, one or both the inlet valve and the outlet valve are a multi-way valve with a single piston, and wherein both the valves collectively allow the selective passage of the dope through each filter module of one or more filtration units. As shown in FIG.1, both the inlet valve 104 as well as the outlet valve 114 are a five-way valve with a single piston. In an embodiment, the five-way valve used as inlet valve includes one inlet port and two pairs of alternate outlet ports and is actuated by a single piston to select one of the two pairs of alternate outlet ports. In an embodiment, the five-way valve used as the outlet valve includes one outlet port and two pairs of alternate inlet ports and is actuated by a single piston to select one of the two pairs of alternate inlet ports. As shown in FIG.1, the inlet valve 104 includes one inlet port 112` and two pairs of alternate outlet ports 108A`and 108B`, and 110A` and 110B` for dope. Similarly, the outlet valve 114 includes one outlet port 112`` for filtered dope and two pairs of alternate inlet ports 108A`` and 108B``, and 110A`` and 110B``. The inlet valve 104 is operated through a single handle to switch between the two pairs of alternate outlet ports 108A`and 108B`, and 110A` and 110B`. Similarly, the outlet valve 114 is operated through a single handle to switch between the two pairs of alternate inlet ports 108A``and 108B``, and 110A`` and 110B``.
Both the inlet valve 104 and the outlet valve 114 are in fluid communication with the filter modules 108A and 108B, and 110A and 110B of the filtration units 108 and 110, respectively. The inlet valve 104 selectively allows the dope to pass through the filter modules 108A and 108B or 110A and 110B of the filtration units 108 and 110, respectively. Similarly, the outlet valve 114 selectively receives the filtered dope from the filter modules 108A and 108B or 110A and 110B of the filtration units 108 and 110, respectively.
The disclosed filtration system allows for the use of at least one filtration unit while the remaining filtration units are on standby for repair or replacement of filters. The five-way valve with a single piston is positioned in such a way that while filter modules 108A and 108B are in operation, filter modules 110A and 110B can be removed and replaced after cleaning without interference in the operation of filter modules 108A and 108B.
The operation of the disclosed filtration system 100 is explained using FIG. 1. During operation, when the filtration unit 108 is in the working state and the filtration unit 110 is kept on standby, the outlet ports 108A` and 108B` of the inlet valve 104 are opened in equal proportion, and the outlet ports 110A` and 110B` of the inlet valve 104 are in the closed state. Accordingly, the inlet ports 108A`` and 108B`` of the outlet valve 114 are in an open state, and the inlet ports 110A`` and 110B`` of the outlet valve 114 are in a closed state. When switching operation from the filtration unit 108 to 110, the outlet ports 108A` and 108B` are closed such that the dope starts flowing simultaneously to filter modules 110A and 110B in equal proportion. When filter modules 110A and 110B are completely filled with dope, the outlet valve 114 is operated using a handle so that the inlet ports 108A`` and 108B`` of the outlet valve 114 are closed and the inlet ports 110A`` and 110B`` are opened simultaneously in equal proportion. Thus, the filtration unit 110 comes into operation, and the filtration unit 108 becomes available for maintenance.
In an embodiment, the inlet 102 of the filtration system 100 is connected to a pump (not shown). The pump is configured to control the pump rate of the dope to match with the desired flow rate of the dope in the filtration system 100.
In an embodiment, the dope has an equal flow rate through each filter module. The flow rate is such that the temperature of the dope does not rise beyond 130°C due to shearing upon contact with the filter media in the filter module.

Industrial Applicability
The disclosed filtration system finds application in the filtration of the dope prepared during the production of regenerated cellulosic fibers, specifically lyocell fibers. The disclosed filtration system allows scaling up the lyocell process and setting up a manufacturing plant with higher production capacity.
The disclosed filtration system provides for selectively passing the dope through only a predetermined number of filtration units for filtration while the filter modules in other filtration units are on standby. This allows the filtration system to operate continuously without downtime and thereby allows continuous manufacturing of lyocell fibers without a pause (for maintenance of the filters), as required in conventional systems. Specifically, the multi-way valve used in the filtration system allows switching operation from one filtration unit to another once a filter in the filtration unit under operation requires repair or replacement.
The disclosed filtration system allows for maintaining a low flux rate and hence the desired temperature of the dope without compromising productivity.
The filtration system eliminates the requirement for additional downstream filtration steps required in conventional systems. Also, this filtration system can be used with existing systems and processes for the manufacture of lyocell fibers.

List of Reference Numeral

100- filtration system
102- inlet
104-inlet valve
106-housing
108, 110-filtration units
108A, 108B-filter modules of filtration unit 108
110A, 110B- filter modules of filtration unit 110
114-outlet
116-outlet valve
112`- inlet port of inlet valve 104
108A`, 108B`, 110A` and 110B`- outlet ports of inlet valve 104
112``- outlet port of outlet valve 114
108A``, 108B``, 110A`` and 110B``- inlet ports of outlet valve 114
,CLAIMS:1. A filtration system (100) for filtration of dope formed in a lyocell process, the filtration system comprising:
- an inlet (102) for dope, the inlet (102) including an inlet valve (104);
- an outlet (116) for exit of filtered dope, the outlet (116) including an outlet valve (114);
- a housing (106) defining an interior divided into a plurality of filtration units (108, 110), each filtration unit (108, 110) including a plurality of filter modules (108A, 108B, 110A, 110B) disposed therein, each filter module (108A, 108B, 110A, 110B) including a module inlet and a module outlet, and configured to allow dope, but not impurities, to pass there through,
wherein the module inlet and the module outlet of each filter module (108A, 108B, 110A, 110B) of the plurality of filtration units (108, 110) are in fluid communication with the inlet valve (104) and the outlet valve (114), respectively, and
wherein the inlet valve (104) is configured to allow selective passage of the dope through each filter module (108A, 108B, 110A, 110B) of one or more filtration units (108, 110), and the outlet valve (114) is configured to selectively receive the filtered dope exiting from each filter module (108A, 108B, 110A, 110B) of the one or more filtration units (108, 110).

2. A filtration system (100) as claimed in claim 1, wherein the filter modules (108A, 108B, 110A, 110B) in the filtration unit (100) are connected in parallel between the inlet (102) for dope and the outlet (116) for the filtered dope.

3. A filtration system (100) as claimed in claim 1, wherein one or both the inlet valve (104) and the outlet valve (114) are a multi-way valve with a single piston, and wherein both the valves (104, 114) collectively allow the selective passage of the dope through each filter module (108A, 108B, 110A, 110B) of the one or more filtration units (108, 110).

4. A filtration system as claimed in claim 1, including two filtration units (108, 110), each filtration unit (108, 110) including two filter modules (108A, 108B, 110A, 110B) connected in parallel between the inlet (102) for dope and the outlet (116) for the filtered dope.

5. A filtration system (100) as claimed in claim 4, wherein the inlet valve (104) is a five-way valve including one inlet port (112`) and two pairs of alternate outlet ports (108A`, 108B`, 110A` and 110B`) and is actuated by a single piston to select one of the two pairs of alternate outlet ports (108A`, 108B`, 110A` and 110B`).

6. A filtration system (100) as claimed in claim 1, wherein the outlet valve (114) is a five-way valve including one outlet port (112``) and two pairs of alternate inlet ports (108A``, 108B``, 110A`` and 110B``) and is actuated by a single piston to select one of the two pairs of alternate inlet ports (108A``, 108B``, 110A`` and 110B``).

7. A filtration system (100) as claimed in claim 1, wherein each filter module (108A, 108B, 110A, 110B) comprises a filter selected from the group consisting of a candle filter and screen changer filter.

8. A process for filtration of dope formed in a lyocell process, said process comprising:
passing the dope prepared in the lyocell process through a filtration system (100) comprising:
- an inlet (102) for dope, the inlet (102) including an inlet valve (104);
- an outlet (116) for exit of filtered dope, the outlet (116) including an outlet valve (114);
- a housing (106) defining an interior divided into a plurality of filtration units (108, 110), each filtration unit (108, 110) including a plurality of filter modules (108A, 108B, 110A, 110B) disposed therein, each filter module (108A, 108B, 110A, 110B) including a module inlet and a module outlet, and configured to allow dope, but not impurities, to pass there through,
wherein the module inlet and the module outlet of each filter module (108A, 108B, 110A, 110B) of the plurality of filtration units (108, 110) are in fluid communication with the inlet valve (104) and the outlet valve (114), respectively, and
wherein the inlet valve (104) is configured to allow selective passage of the dope through each filter module (108A, 108B, 110A, 110B) of one or more filtration units (108, 110), and the outlet valve (114) is configured to selectively receive the filtered dope exiting from each filter module (108A, 108B, 110A, 110B) of the one or more filtration units (108, 110);
wherein the dope is selectively passed through only a predetermined number of filtration units (108, 110) for filtration while the remaining filtration units (108, 110) are on standby.

9. The process as claimed in claim 8, wherein the dope has an equal flow rate through each filter module (108A, 108B, 110A, 110B).