Novel lyocell membrane extraction spinning bath system and method

Abstract

The invention relates to a novel lyocell membrane extraction spinning bath system and method.The system comprises a spinning bath barrel, a spinning bath circulating pump, a spinning bath filter, a heat exchanger, a spinning machine, a buffer tank and a concentration membrane set, and the spinning bath output end of the spinning bath barrel is connected to the spinning machine and the buffer tank; a spinning bath from the spinning machine flows back to the spinning bath barrel and the buffer tank; the outlet end of the buffer tank is connected to the concentration membrane group through a pipeline. The method comprises the following steps: conveying a spinning bath to a spinning machine for spinning; part of spinning bath of spinning backflow of the spinning machine flows back to the spinning bath barrel, and the other part flows back to the buffer tank; the spinning bath in the buffer tank is pumped to a concentration membrane module for spinning bath separation, the spinning bath containing low-concentration NMMO enters a spinning bath barrel, the spinning bath containing high-concentration NMMO enters an evaporation workshop, and water separated by the membrane module flows back to a spinning bath circulating system for recycling. The requirement of adjusting the constant range of the operating temperature of the buffer tank is met by controlling the change of the reflux quantity of spinning in a spinning bath of the spinning machine to flow back to the spinning bath barrel and the buffer tank, and the operating temperature requirement of a membrane assembly is met. The steam consumption in the manufacturing process of the finished silk is reduced, and energy is saved.

Description

Technical Field

[0001] The present invention relates to a novel Lyocell film extraction spinning bath system and method, belonging to the technical field of spinning bath water circulation. Background Art

[0002] The concentration of NMMO (N-methylmorpholine-N-oxide) in the Lyocell fiber spinning bath is usually about 5% - 20%.

[0003] In the production of Lyocell fibers, the spinning bath is an aqueous solution containing a certain concentration of NMMO. After the filaments enter the spinning bath, two-way diffusion is achieved through the concentration difference of NMMO between the filaments and the spinning bath, enabling the cellulose to solidify and form a shape. At the same time, it also facilitates the subsequent recovery and utilization of NMMO in the spinning bath.

[0004] The solidifying spinning bath in the spinning bath barrel is usually a low-concentration aqueous solution of NMMO. After the filaments extruded from the spinneret enter the spinning bath barrel, two-way diffusion occurs due to the concentration difference between the high-concentration NMMO in the filaments and the low-concentration NMMO in the spinning bath. The NMMO in the filaments diffuses into the spinning bath, while the water in the spinning bath penetrates into the filaments, causing the cellulose to quickly solidify and form primary fibers with a certain strength and shape.

[0005] In the production of Lyocell fibers, the recovery of the solvent NMMO is crucial. The spinning bath barrel is an important part of the solvent recovery system. By controlling parameters such as the concentration and temperature of the spinning bath, the NMMO in the filaments can be effectively transferred into the spinning bath, facilitating subsequent treatment of the spinning bath to recover the NMMO therein, realizing the recycling of the solvent, reducing production costs, and simultaneously reducing the impact on the environment.

[0006] In the current Lyocell fiber spinning process, the spinning bath with a concentration of 18% - 25% NMMO is concentrated to over 70% by steam evaporation. The current method uses the principle of steam evaporation as the driving force for the water circulation in the spinning bath, resulting in a steam consumption of more than 3 tons / ton of silk in the spinning process.

[0007] The technical problem of the current method is that the steam drives the water circulation in the spinning bath, resulting in high steam consumption and a substantial increase in product cost.

[0008] The reason for the defects is that the water in the spinning bath is evaporated by steam to concentrate the NMMO concentration, and a large amount of water is added to the spinning bath. Summary of the Invention

[0009] In order to solve the above problems, the present invention discloses a novel Lyocell film extraction spinning bath system and method, and its specific technical solutions are as follows: A novel Lyocell film extraction spinning bath system, comprising a spinning bath barrel, a spinning bath filter, a heat exchanger, a spinning machine, a buffer tank and a concentration membrane module. The spinning bath output end of the spinning bath barrel is connected to the spinning machine and the buffer tank through the spinning bath filter and the heat exchanger. The heat exchanger is arranged at the liquid inlet end of the spinning machine and is used to control the temperature of the spinning bath entering the spinning machine. The spinning bath coming out of the spinning machine flows back to the spinning bath barrel and the buffer tank; A branch pipe connected to the buffer tank and a standby pipe sent to the evaporation workshop are arranged on the main pipe between the spinning bath filter and the heat exchanger. The outlet end of the buffer tank is connected to the concentration membrane module through a pipe. The water separated by the concentration membrane module includes three output pipes. One of the output pipes outputs a spinning bath containing high-concentration NMMO and is connected to the evaporation workshop. One of the output pipes outputs a spinning bath containing low-concentration NMMO and flows back to the return pipeline of the spinning bath barrel. One of the output pipes outputs backwater and flows back to the spinning bath barrel; The spinning bath containing high-concentration NMMO refers to a spinning bath with an NMMO mass concentration of 40% to 70%. The spinning bath containing low-concentration NMMO refers to a spinning bath with an NMMO mass concentration of 18% to 27%; The spinning machine is provided with two return ports. The spinning bath generated by the spinning machine flows back to the spinning bath barrel through one return port and flows back to the buffer tank through the other return port for the temperature balance of the buffer tank. A regulating valve is arranged between the two return ports to control the flow distribution between the two return ports.

[0010] Further, the temperature of the spinning bath in the buffer tank is maintained between 18°C and 27°C.

[0011] Further, the spinning bath barrel is provided with a first water replenishment port and a spinning machine return liquid interface, which are respectively connected to a water replenishment pipe and a spinning machine return pipe.

[0012] Further, a second water replenishment port is also arranged on the pipe between the heat exchanger and the spinning bath filter. The second water replenishment port is located on the pipe between the branch pipe to the buffer tank and the heat exchanger and is used to replenish water to the main pipe.

[0013] Further, a valve is arranged at the connection of the branch pipe and the main pipe between the spinning bath filter and the heat exchanger to control the flow direction of the spinning bath or the respective proportions of the spinning bath in two flow directions; The spinning bath containing high-concentration NMMO and the backwater at the output end of the concentration membrane module share an output main pipe, and a switching valve is arranged on the output main pipe. The downstream of the switching valve is connected to the pipe going to the evaporation workshop and the return pipe.

[0014] Further, the concentration membrane group uses a reverse osmosis RO membrane stack to separate water with a molecular weight of 18 from NMMO with a molecular weight of 117. The separated water is allowed to contain low-concentration NMMO.

[0015] Further, N + 1 groups of concentration membrane groups are provided, and the N + 1 groups are connected in parallel. The filtration volume of each concentration membrane group is QNm 3 / h, where N is a positive integer greater than or equal to 1, and Q is 5 - 500.

[0016] Further, a filter and a pretreatment section are provided at the inlet end of the concentration membrane group according to the specific process.

[0017] A method for a novel Lyocell membrane extraction spinning bath system based on the above includes the following steps: The flow direction of the spinning bath in the spinning process: The spinning bath in the spinning bath bucket is pumped to the spinning bath filter by a pump on the outlet pipe of the spinning bath bucket. The filtered spinning bath is transported to the heat exchanger. Then the spinning bath passes through the heat exchanger, is adjusted to the spinning temperature, and is transported to the spinning machine for spinning use; Part of the spinning bath after spinning by the spinning machine flows back to the spinning bath bucket, and part flows back to the buffer tank. The control basis for the reflux ratio is the temperature in the buffer tank; A branch pipe is connected to the buffer tank to supply water to the buffer tank, and cooperate with the spinning bath flowing back to the buffer tank from the spinning machine to keep the temperature of the spinning bath in the buffer tank between 20°C and 28°C; The flow direction of the spinning bath after membrane separation: The spinning bath in the spinning bath bucket is pumped to the spinning bath filter by a pump on the outlet pipe of the spinning bath bucket. At this time, a valve is set between the spinning bath filter and the heat exchanger. After part of the spinning bath enters the buffer tank, it is pumped to the concentration membrane group. Each concentration membrane group works simultaneously to filter the spinning bath. The liquid separated by the reverse osmosis RO membrane stack flows back and is added to the spinning bath bucket. The spinning bath that does not pass through the reverse osmosis RO membrane stack, or the spinning bath whose concentration is monitored by a refractometer and belongs to the return water, goes to the spinning bath bucket. The spinning bath containing high-concentration NMMO goes to the evaporation workshop. At this time, a switching valve is used to switch the flow direction of the spinning bath.

[0018] The beneficial effects of the present invention are: The present invention replaces the steam evaporation system and adding a large amount of water to the spinning bath in the current scheme with a membrane separation process method to separate the water in the spinning bath, and then add the separated water back to the spinning bath system, reducing the water addition amount by more than 90%.

[0019] The present invention uses the membrane system in the concentration membrane module to separate the water in the spinning bath and return it to the spinning bath bucket. The water in the spinning bath can be recycled without steam evaporation, and the beneficial effect is that the water evaporation amount is reduced by more than 90%.

[0020] The present invention reduces the evaporation amount of the evaporation system in the prior art by more than 90%, and the beneficial effect is that the manufacturing cost of the finished silk is reduced by more than 3 tons of steam consumption per ton of silk. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the connection layout of the present invention. List of reference numerals: 1 - spinning bath bucket, 2 - spinning bath filter, 3 - heat exchanger, 4 - spinning machine, 5 - buffer tank, 6 - concentration membrane module. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be further clarified below in conjunction with the drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0023] Combined with the attached Figure 1 drawings, the layout of the novel Lyocell membrane extraction spinning bath system of the present invention is intuitively introduced. The data in the specific embodiment process are given in the drawings. This system includes a spinning bath bucket 1, a spinning bath filter 2, a heat exchanger 3, a spinning machine 4, a buffer tank 5, and a concentration membrane module 6. The connection layout of each component or machine in this system is as follows: The spinning bath bucket is connected to the spinning bath filter through a spinning bath pipeline. The spinning bath filter is connected to the heat exchanger through a spinning bath pipeline. The heat exchanger is connected to the spinning machine through a spinning bath pipeline. This line transports the spinning bath in the spinning bath bucket to the spinning machine, and the spinning bath is used for spinning in the spinning machine. At the same time, there is another source of the spinning bath going to the spinning machine, which is to replenish water to the spinning bath pipeline in front of the heat exchanger to adjust the concentration of the spinning bath. The specific position is: There is also a second water replenishing port on the pipeline between the heat exchanger and the spinning bath filter. The second water replenishing port is located on the pipeline between the branch pipeline to the buffer tank and the heat exchanger, and is used to replenish water to the main pipeline. In order to balance the concentration of the spinning bath in the system, the spinning bath bucket is also provided with a first water replenishing port, which is connected to a water replenishing pipeline and replenishes water into the system, facilitating temperature adjustment and NMMO concentration adjustment.

[0024] There is also a reflux treatment line for the spinning bath after being used by the spinning machine. The specific connection method is as follows: The spinning machine is provided with two reflux ports. The spinning bath generated by the spinning machine flows back to the spinning bath tank through one reflux port and flows back to the buffer tank through the other reflux port for the temperature balance of the buffer tank. A regulating valve is arranged between the two reflux ports to control the flow distribution between the two reflux ports. The buffer tank is connected to the concentration membrane module through a spinning bath pipeline. The clean spinning bath filtered from the concentration membrane module flows back to the spinning bath tank. The high-concentration NMMO obtained by filtration is transported to the evaporation workshop. When it does not meet the requirements (such as when the concentration membrane module is not working or the concentration is not enough to go to the evaporation workshop), it can flow back to the buffer tank or the spinning bath tank.

[0025] The concentration of NMMO in the spinning bath after being used by the spinning machine changes, and the temperature of the spinning bath also changes. The flow direction of the spinning bath after being used by the spinning machine is set in this system. Specifically, part of the spinning bath flowing out of the spinning machine is transported to the buffer tank through a pipeline, and part is transported to the spinning bath tank through a pipeline. This system is in a continuous working state, and the spinning bath reflux treatment process is in a state where the system does not stop working. The proportion of the spinning bath flowing back from the spinning machine into the spinning bath tank in the buffer tank is adjusted according to the temperature in the buffer tank to keep the temperature of the spinning bath in the buffer tank between 20°C and 28°C.

[0026] A branch pipeline connected to the buffer tank and a standby pipeline sent to the evaporation workshop are arranged on the main pipeline between the spinning bath filter and the heat exchanger. A valve is arranged at the connection of the branch pipeline and the main pipeline between the spinning bath filter and the heat exchanger to control the flow direction of the spinning bath or the respective proportions of the spinning bath towards the two flow directions. The outlet end of the buffer tank is connected to the concentration membrane module through a pipeline. The water separated by the concentration membrane module includes three output pipelines. One of the output pipelines outputs a spinning bath containing high-concentration NMMO, which is connected to the evaporation workshop. One of the output pipelines outputs a spinning bath containing low-concentration NMMO, which is connected to the reflux pipeline of the spinning bath tank. One of the output pipelines outputs backflow water, which flows back to the spinning bath tank. The spinning bath containing high-concentration NMMO and the backflow water at the output end of the concentration membrane module share the same output main pipeline, and a switching valve is arranged on the output main pipeline. Downstream of the switching valve, there are pipelines connecting to the evaporation workshop and the reflux pipeline.

[0027] The spinning bath containing high-concentration NMMO refers to the spinning bath with an NMMO mass concentration of 40% to 70%. The spinning bath containing low-concentration NMMO refers to the spinning bath with an NMMO mass concentration of 18% to 27%.

[0028] The concentration membrane module uses a reverse osmosis RO membrane stack to separate water with a molecular weight of 18 from NMMO with a molecular weight of 117. The separated water is a spinning bath containing low-concentration NMMO.

[0029] Four sets of concentration membrane modules are provided, and the four sets are connected in parallel. The filtration volume of each concentration membrane module is 50m 3 / h. It is adjusted and used according to the water volume of the spinning machine. A specific example data is given in this embodiment.

[0030] A filter is provided at the inlet end of the concentration membrane module to filter out particulate matter and large particle impurities in the spinning bath, playing a protective role for the concentration membrane module.

[0031] A method for a novel Lyocell membrane extraction spinning bath system based on the above includes the following steps: The flow direction of the spinning bath in the spinning process: The NMMO concentration of the spinning bath in the spinning bath tank is below 18%. Through the pump on the outlet pipeline of the spinning bath tank, the spinning bath is pumped to the spinning bath filter. After filtration, the spinning bath is transported to the heat exchanger. Then, the spinning bath passes through the heat exchanger, is adjusted to the spinning temperature, and is transported to the spinning machine for spinning use; Part of the spinning bath after spinning by the spinning machine flows back to the spinning bath tank, and part flows back to the buffer tank. The control basis for the reflux ratio is the temperature in the buffer tank; The branch pipeline is connected to the buffer tank for replenishing water to the buffer tank, and cooperates with the spinning bath flowing back to the buffer tank from the spinning machine to keep the temperature of the spinning bath in the buffer tank between 20°C and 28°C; The flow direction of the spinning bath after membrane separation: The NMMO concentration of the spinning bath in the spinning bath tank is above 18%. Through the pump on the outlet pipeline of the spinning bath tank, the spinning bath is pumped to the spinning bath filter. At this time, a valve is set between the spinning bath filter and the heat exchanger. After part of the spinning bath enters the buffer tank, it is pumped to the concentration membrane module. Each concentration membrane module works simultaneously to filter the spinning bath. The water separated by the reverse osmosis RO membrane stack is used as the spinning bath containing low-concentration NMMO. The spinning bath that does not pass through the reverse osmosis RO membrane stack, or the spinning bath whose concentration is monitored by a refractometer and belongs to the return water, goes to the spinning bath tank, and the spinning bath containing high-concentration NMMO goes to the evaporation workshop. At this time, the switching valve is used to switch the flow direction of the spinning bath.

[0032] Those skilled in the art of this technology can understand that unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the art in the field to which this application belongs. It should also be understood that terms defined in general dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as here.

[0033] The meaning of "connection" described in this application can be a direct connection between components or an indirect connection between components through other components.

[0034] Inspired by the above-described ideal embodiments of the present invention, through the above description, relevant staff can make various changes and modifications completely within the scope without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A novel lyocell membrane extraction spinning bath system, characterized in that: It includes a spinning bath barrel, a spinning bath filter, a heat exchanger, a spinning machine, a buffer tank and a concentration membrane group. The spinning bath output end of the spinning bath barrel is connected to the spinning machine and the buffer tank through the spinning bath filter. The heat exchanger is arranged at the liquid inlet end of the spinning machine to control the temperature of the spinning bath entering the spinning machine. The spinning bath coming out of the spinning machine flows back to the spinning bath barrel and the buffer tank. The main pipeline between the spinning bath filter and the heat exchanger is provided with a branch pipeline connected to the buffer tank and a spare pipeline sent to the evaporation workshop. The outlet end of the buffer tank is connected to the concentration membrane group through a pipeline. The water separated by the concentration membrane group includes three output pipelines, one of which outputs a spinning bath containing a high concentration of NMMO and is connected to the evaporation workshop, one of which outputs a spinning bath containing a low concentration of NMMO and flows back to the reflux line of the spinning bath barrel, and one of which outputs reflux water and flows back to the spinning bath barrel; The spinning bath containing high concentration of NMMO refers to a spinning bath with a NMMO mass concentration of 40% to 70%, and the spinning bath containing low concentration of NMMO refers to a spinning bath with a NMMO mass concentration of 18% to 27%; The spinning machine is provided with two reflux ports. The spinning bath generated by the spinning machine refluxes to the spinning bath barrel through one reflux port and refluxes to the buffer tank through the other reflux port for temperature balance of the buffer tank. The two reflux ports are provided with regulating valves for controlling the flow distribution of the two reflux ports.

2. The novel lyocell membrane extraction spinning bath system according to claim 1, characterized in that: The spinning bath temperature in the buffer tank is maintained at a constant value between 18°C ​​and 27°C.

3. The novel lyocell membrane extraction spinning bath system according to claim 1, characterized in that: The spinning bath barrel is provided with a first water replenishment port and a spinning machine reflux liquid interface, which are respectively connected to the water replenishment pipeline and the spinning machine reflux pipeline.

4. The novel lyocell membrane extraction spinning bath system according to claim 1, characterized in that: A second water replenishment port is also provided on the pipeline between the heat exchanger and the spinning bath filter. The second water replenishment port is located on the pipeline between the branch pipeline to the buffer tank and the heat exchanger and is used to replenish water to the main pipeline.

5. The novel lyocell membrane extraction spinning bath system according to claim 1, characterized in that: A valve is provided at the connection between the branch pipe and the main pipe between the spinning bath filter and the heat exchanger, for controlling the flow direction of the spinning bath or the respective ratios of the two flow directions of the spinning bath; The spinning bath containing high concentration NMMO and the reflux water at the output end of the concentration membrane group share a common output main pipeline, and a switching valve is arranged on the output main pipeline, and the downstream of the switching valve is connected to the pipeline to the evaporation workshop and the reflux pipeline.

6. The novel lyocell membrane extraction spinning bath system according to claim 1, characterized in that: The concentration membrane group uses a reverse osmosis RO membrane stack to separate water with a molecular weight of 18 from NMMO with a molecular weight of 117. The separated water is allowed to contain low concentration NMMO.

7. The novel lyocell membrane extraction spinning bath system according to claim 1, characterized in that: The concentration membrane group is set to N+1 groups, N+1 groups are connected in parallel, and the filtration capacity of each concentration membrane group is QNm 3 / h, N is a positive integer greater than or equal to 1, and Q is 5~500.

8. The novel lyocell membrane extraction spinning bath system according to claim 1, characterized in that: The inlet end of the concentration membrane group is provided with a filter and a pretreatment section according to specific process selection.

9. A method based on the novel lyocell membrane extraction spinning bath system according to any one of claims 1 to 8, characterized in that: The following steps are involved: Spinning bath flow direction during spinning process: The spinning bath in the spinning bath barrel is pumped to the spinning bath filter through a pump on the water outlet pipe of the spinning bath barrel, and the filtered spinning bath is transported to the heat exchanger, and then the spinning bath passes through the heat exchanger, is adjusted to the spinning temperature, and is transported to the spinning machine for spinning; After spinning in the spinning machine, part of the spinning bath flows back to the spinning bath barrel, and part flows back to the buffer tank. The proportion of the backflow is controlled based on the temperature in the buffer tank. The branch pipeline is connected to the buffer tank to replenish water to the buffer tank, and the water flows back to the spinning bath in the buffer tank in coordination with the spinning machine, so that the temperature of the spinning bath in the buffer tank is maintained at a constant value between 20°C and 28°C; Spinning bath flow direction after membrane separation: The spinning bath in the spinning bath is pumped to the spinning bath filter through the pump on the outlet pipe of the spinning bath. At this time, a valve is set between the spinning bath filter and the heat exchanger. After part of the spinning bath enters the buffer tank, it is pumped to the concentration membrane group. Each concentration membrane group works at the same time to filter the spinning bath. The liquid separated by the reverse osmosis RO membrane stack is refluxed and added to the spinning bath. The spinning bath that has not passed through the reverse osmosis RO membrane stack, or the one whose concentration is monitored by a refractometer and belongs to reflux water, goes to the spinning bath. The spinning bath containing high concentration of NMMO goes to the evaporation workshop. At this time, a valve is used to switch the direction of the spinning bath.

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