KR100514348B1 - Apparatus & method for transport of cellulose solution - Google Patents

Abstract

The present invention provides a transfer apparatus for a conventional cellulose solution, comprising: a transfer tube for transferring a cellulose solution; An in-tube stationary continuous mixer installed in the conveying pipe; By providing a cellulose transfer device configured to include, it is to prevent the solution from being uneven due to the temperature gradient and the flow rate gradient in the transfer pipe.

Description

Transfer device of cellulose solution and transfer method {APPARATUS & METHOD FOR TRANSPORT OF CELLULOSE SOLUTION}

The present invention relates to a thermally unstable, highly viscous, coagulating cellulose solution transfer device and a method for transferring the cellulose solution. Specifically, the cellulose solution of the cellulose solution is prevented from being uneven due to the temperature gradient and the flow rate gradient in the transfer tube. It relates to a conveying apparatus and a conveying method.

Methods and properties for preparing cellulose solutions are known in the literature. Graenacher et al., For the first time, present a process for preparing cellulose solutions in tertiary amine oxide solutions in US Pat. No. 2,179,181. Subsequently, more efficient and economic methods were proposed. European Patent No. 356,419 swells cellulose in an N-methylmorpholine-N oxide (hereinafter referred to as 'NMMO') non-binder with a water content of 40% by weight, and distillates under reduced pressure in a screw extruder equipped with a fan-type flight to cellulose solution. The invention to manufacture is disclosed. In addition, in WO 94/06530, a thin film distillator is used as the vacuum distillation machine.

Another method for producing a cellulose solution is a solution production method using a twin screw extruder. A method of mixing and dissolving pulp powder having an apparent size of 20 to 60 μm and a high concentration of NMMO aqueous solution having a water content of 5 to 20% by weight in a twin screw extruder maintained at 50 ° C to 130 ° C is disclosed in Korean Patent No. 280353 and German Patent No. 0906455, US Pat. No. 6,153,003.

In addition, Korean Patent No. 365867 uses a liquid NMMO solvent supercooled to a temperature below the melting point to minimize dissolution of the cellulose by the liquid NMMO solvent and maximize swelling to prepare a cellulose pulp mixed powder swelled in the NMMO solvent. And dissolving it to prepare a highly homogeneous cellulose solution.

The NMMO aqueous solution used to prepare the cellulose solution is in the form of a hydrate as the water content is lowered, and the melting point is increased as the water content is lowered. When the cellulose / NMMO solution discolors at 120 ° C or higher and the temperature increases, gaseous components are expelled and exploded with rapid exothermic reaction due to decomposition of NMMO and thermal decomposition of cellulose. The cellulose dissolved in the NMMO solution also decomposes continuously as the heating time elapses, thereby lowering the degree of polymerization. Metallic components, such as iron, further facilitate this decomposition. According to US Pat. No. 5,890,504, decomposition of the NMMO / cellulose solution begins at about 110 ° C. to about 120 ° C., and gas is continuously generated and deflagration is reported. Some additives, such as propyl gallate, may be used to increase the safety of the cellulose solution.

However, in order to shorten the spinning and molding processing time and to obtain high productivity, the temperature of the cellulose solution should be maintained at about 100 ° C to 110 ° C. In the transfer of the cellulose solution, the prior arts that limit the heat medium temperature and the size of the transfer pipe in consideration of heat transfer by the heat medium and the temperature gradient in the transfer pipe include US Patent Nos. 5,354, 371, US Patent No. 5,401,304, and Korea Patent No. 301788. have.

The above patent proposes a formula for calculating the proper temperature (center and wall) of the fluid when maintaining the temperature of the conveying liquid by removing the heat generated by decomposition of the cellulose solution in the conveying tube using the heat medium. The temperature difference between the center and the outer wall is more than 10 ° C, and the smaller the feed pipe, the higher the temperature of the solution. However, the amount of heat loss to the outside may actually be greater than the amount of heat generated by the decomposition reaction. In order to maintain the temperature at 100 ° C or more, the heating medium is supplied to the transfer pipe made of the double pipe to heat and keep warm.

Therefore, it is best to keep the temperature of the solution in the delivery pipe uniformly at the optimum temperature suitable for processing while minimizing the decomposition of cellulose, and to avoid the temperature gradient between the center and the outer wall.

In the delivery tube, there is not only a temperature gradient between the center and the wall, but also a velocity gradient of the fluid, which varies the transport time of the solution. The difference in the transfer time causes a different degree of polymerization of the cellulose which is changed during the transfer, which in turn causes a decrease in processability during spinning or molding of the solution. When the high viscosity solution flows through the tube, the flow rate at the center can reach about twice the average flow rate, and this difference in residence time becomes a factor that widens the distribution of cellulose polymerization degree during cellulose solution transfer.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a transfer device and a transfer method of the cellulose solution to prevent the solution from being uneven due to the temperature gradient and the flow rate gradient in the transfer pipe.

The present invention and the transfer tube for transferring the cellulose solution in order to achieve the object as described above; An in-tube stationary continuous mixer installed in the conveying pipe; It provides a cellulose transfer device configured to include.

Here, the cellulose solution is preferably a solution of cellulose in N-methylmorpholine-N-oxide aqueous solution.

It is also effective that the elements of the in-tube stationary continuous mixer are helical.

In addition, it is preferable that the tube-type continuous mixer is installed at least every 5 m.

In addition, it is effective that the double pipe is installed on the outer wall of the transfer pipe and the fixed continuous mixer in the pipe.

On the other hand, according to another field of the present invention, there is provided a transport method for transporting a solution that is highly viscous, thermally unstable, and can be solidified by installing a fixed continuous mixer in the pipe.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

However, in describing the present invention, a detailed description of known functions or configurations will be omitted in order not to disturb the gist of the present invention.

1 is a view showing the structure of an embodiment of the present invention, a conceptual diagram of a transfer device.

As shown in Fig. 1, the transfer device for cellulose solution according to one embodiment of the present invention is characterized in that an in-pipe stationary continuous mixer (Line Static Mixer) 2 is installed at appropriate intervals in the transfer pipe 1. In addition, a double pipe 3 is installed on the outer wall of the transfer pipe 1 and the fixed continuous mixer 2.

This in-tube stationary continuous mixer 2 is suitable for a helical mixing element that minimizes the resistance of the fluid so that the pressure loss is small and the fluid does not stagnate in the mixer 2. Commercially available in-tube continuous mixers equipped with Kenics Hellical type are suitable.

The fixed tube mixer 2 as described above reduces the difference between the temperature difference and the feed rate of the fluid flowing in the center and the wall of the transfer pipe (1). The smaller the difference is, the more preferable it is. However, since there is a limit in the actual process, it is appropriate to set it within a range that does not affect the molding process such as spinning. As a result of cellulose solution preparation and spinning, the optimum temperature of the solution is 100 ~ 110 ° C, the average residence time until spinning is about 20 minutes, and the temperature difference between the fluid flowing through the center of the transfer pipe and the wall is less than 5 ° C, and the residence time difference Within 1 minute, it was found to be most suitable in consideration of solution denaturation, processability and economic efficiency.

Cellulose solutions are non-Newtonia® fluids with viscosity ranging from 10,000 poise to 20,000 poise depending on the temperature. In order to calculate the flow velocity in the feed pipe, the flow rate and residence time were calculated assuming a power law fluid. As a transfer pipe, a pipe of about 1 to 10 inches is generally used, so when a cellulose solution (12% cellulose, 77% NMMO, 11% water) is transferred to a 1.25 inch to 6 inch pipe, the average velocity and center point of the fluid The difference between the residence time of the fluid passing through the center point and the average residence time at 5m feed rate was calculated.

Feed tube size (inner diameter mm) Flow rate (kg / hr) Average flow rate (cm / sec) Center Point Fluid Flow Rate (cm / sec) Dwell time difference at 5m transfer (min) 6 inches (143) 2,410 3.7 6.9 1.0 5 inches (121) 2,410 5.1 9.7 0.8 3.5 inches (85) 1,205 5.1 9.7 0.8 1.25 in (33) 150.6 4.3 8.1 0.9

As shown in Table 1, the difference between the average residence time in the 5m long transfer pipe and the residence time of the fluid passing through the center point is about 1 minute, so considering the fluid flowing near the wall, a fixed continuous mixer in the pipe is installed at least every 5m. Mix the fluid flowing through it.

If the installation distance of the fixed continuous mixer exceeds 5m, the difference in residence time becomes more than 1 minute, resulting in poor workability in the spinning process. If the installation interval is narrowed, the mixing effect is better, but the installation cost increases and the pressure loss during transportation increases.

As described above, the present invention can narrow the transfer time distribution of the transfer liquid by installing the fixed continuous mixer in the tube at an optimum interval in the transfer tube of the fluid having high viscosity, such as cellulose solution, which can be solidified and decomposed during transfer. And, it is possible to reduce the temperature difference between the center of the transfer pipe and the wall surface, can achieve the object of the present invention to make the transfer liquid very uniform.

The inventor confirmed the above effects by the two tests mentioned later.

[Exam 1]

2100 kg / hr of solvent quenched completely at 95 ° C. with liquid NMMO (monohydrate composition of 13.3% water content) to 50 ° C. was added to the twinaxial swelling mixture maker. At the same time, a cellulose pulp (using Sappi) powder having a degree of polymerization (DPw) of 1050, an average diameter of 16 µm and an apparent specific gravity of 0.05 was introduced into a twin screw swelling mixture maker using a screw feeder. The screw feeder compresses this powder to an apparent specific gravity of 0.3 and compresses it with a twin-axis variable pitch screw feeder (45 mm in diameter (D), length 315 mm, initial P / D 1.5) with a reduced pitch spacing (P) in the feed direction. The pulp powder at room temperature was fed to the side of a biaxial swelling mixture maker (diameter 60 mm, length 1200 mm) at a rate of 310 kg / hr. The pulp powder and supercooled liquid NMMO monohydrate solvent were transferred and kneaded in a twin screw swelling mixture maker to form a swelling mixture in which the NMMO solvent penetrated to the inside, which was fed into an extruder (diameter 120 mm, length 3.6 m). This swelled body was dissolved in an extruder to form a cellulose solution, which was then transferred to the filter using a gear pump. The diameter of the feed tube was 5 inches (120 mm inner diameter) and a fixed continuous mixer (40 cm length) from Kenics was installed 4.5 m from the pump. In addition, a temperature sensor was installed to measure the temperature of the wall fluid and the center fluid before and after the stationary continuous mixer. The temperature of the solution entering the feed pipe from the Kia pump was 108 ° C. The temperature of the heat medium flowing through the double pipe on the outer wall of the feed pipe and the line mixer was supplied at 95 ° C and discharged at 98 ~ 100 ° C.

Just before the continuous mixer installed at 4.5m from the pump, the wall fluid and center fluid temperatures were 99 ° C and 104 ° C, respectively, with a 5 ° C difference in temperature, and immediately after the continuous mixer, 102 ° C and 103 ° C, respectively. It became. Therefore, the solution was properly mixed by the continuous mixer and the temperature arch could be reduced to within 1 ° C. In addition, the difference in transport time (difference in average residence time and residence time of the fluid passing through the center point) by the flow velocity distribution in the pipe was also calculated to be less than 1 minute to achieve the object of the invention.

[Exam 2]

After the cellulose solution was prepared as in Test 1, the cellulose solution of 2310 kg / hr was divided into two, and each was transferred to the filter using a gear pump. The conveying pipe was 3.5 inches (85mm inside diameter) and a continuous mixer (length 40cm) was installed at 4.5m from the pump. In addition, a temperature sensor was installed to measure the temperature of the wall fluid and the center fluid before and after the continuous mixer. The temperature of the solution discharged from the hunger pump was 103 ° C, and the temperature of the heat medium flowing through the double pipe of the transfer pipe and the continuous mixer was supplied at 95 ° C and discharged at 97 ~ 98 ° C.

Just before the continuous mixer installed at 4.5m from the pump, the wall fluid and center fluid temperatures were 98 ° C and 102 ° C, respectively, with a temperature difference of 4 ° C and immediately after the mixer, at 102 ° C. Therefore, the solution was properly mixed by the continuous mixer and the temperature difference could be 1 ° C or less. In addition, the difference in transport time (difference in average residence time and residence time of the fluid passing through the center point) by the flow velocity distribution in the pipe was also calculated to be 1 minute or less to achieve the object of the invention.

Although the preferred embodiments of the present invention have been described above by way of example, the scope of the present invention is not limited to these specific embodiments, and may be appropriately changed within the scope of the claims.

The present invention provides a method for transferring a cellulose solution in which the solution is prevented from becoming uneven due to a temperature gradient and a flow rate gradient in the transfer pipe.

1 is a view showing the structure of an embodiment of the present invention, a conceptual diagram showing a transfer device of a cellulose solution

** Description of the symbols for the main parts of the drawings **

1: conveying pipeline

2: Stationary Continuous Mixer

3: double tube

Claims (6)

A transfer tube for transferring the cellulose solution; An in-tube stationary continuous mixer installed in the conveying pipe; Cellulose transfer device configured to include. The method of claim 1, The cellulose solution is a cellulose transfer device, characterized in that cellulose is dissolved in an aqueous solution of N-methylmorpholine-N-oxide. The method of claim 1, The element of the in-tube stationary continuous mixer is helical system, characterized in that the cellulose transfer device. The method of claim 1, The in-tube stationary continuous mixer is installed at least every 5 m cellulose transport apparatus. The method according to any one of claims 1 to 4, Cellulose transfer device characterized in that the double pipe is installed on the outer wall of the feed pipe and the fixed continuous mixer in the pipe. A transport method for transporting a highly viscous, thermally unstable, and solidified solution by installing a stationary continuous mixer in a transport tube.