Soft capsule raw material conveying device

Abstract

The utility model relates to a soft capsule raw material conveying device which comprises a pill pressing machine, the pill pressing machine is provided with a first suspension liquid conveying pipe, a glue liquid conveying pipe is provided with a first stirring tank, the glue liquid conveying pipe is provided with a second stirring tank, and each of the first stirring tank and the second stirring tank comprises a stirring tank body, a stirring device and a first adjusting valve; a steam coil pipe is arranged on the stirring tank body of the second stirring tank, the glue solution conveying pipe comprises a conveying inner pipe, a heat preservation outer sleeve and a heat preservation cavity, a first steam conveying branch pipe and a steam output branch pipe are arranged on the heat preservation outer sleeve, and a steam conveying header pipe is arranged on the steam coil pipe and the first steam conveying branch pipe; and a second regulating valve and a first pressure sensor are arranged on the steam conveying header pipe. And the glue solution can be kept in a proper temperature range and a reasonable pressure range. The utility model has the advantages of convenient use and wide market prospect.

Description

Technical Field

[0001] The utility model relates to the field of soft capsule raw material conveying equipment, in particular to a soft capsule raw material conveying device. Background Art

[0002] Soft capsule is a new dosage form, which can make various powder, oil, lake, strange smell and other effective substances into oily liquid or suspension. Then quantitative injection and encapsulation in the capsule to form a sealed capsule with regular shape and different sizes. Compared with other dosage forms, soft capsule dosage form has the advantages of accurate content, high bioavailability value, strong uniformity, good drug odor masking, exquisite appearance, etc., and gradually becomes one of the most widely used dosage forms in health care products and pharmaceutical industries. At the same time, it is also of great significance in improving efficacy and easy absorption. The production process of soft capsule includes gelling, batching, pill pressing, drying, pill selection and packaging. Batching is one of the important processes in the production process of soft capsule, and it is the premise of ensuring its overall quality. The batching process is the process of configuring the contents of the capsule. The contents are mainly divided into a mixture of solid materials and oil materials, and pure oil materials. When the amount of pure oily materials is small, they need to be mixed evenly with other oils such as corn oil and salad oil; for materials whose effective substances are solid and non-fat-soluble, the materials need to be crushed to fine powder that can pass through a 100 to 200 mesh sieve. Then mix it with salad oil and other oils to form a colloidal uniform mixture. After colloid grinding, it is made into a uniform and delicate suspension, which can avoid the blockage of the spray body during the production process and prevent problems such as loose joints during the drying process. When the contents of soft capsules are a mixture of oils and solids, stratification often occurs during the production process, which has a great impact on the metering accuracy of the dosage package. This requires the addition of an appropriate amount of suspending agent in addition to mixing in salad oil and other oils.

[0003] In the soft capsule processing process, the mixed suspension is filled in the colloid to form the final soft capsule. The quantitative suspension and glue are gradually transported to the pill press. As the number of soft capsules produced by the pill press increases, the liquid levels of the mixed suspension and glue are gradually reduced. However, as the processing time increases, the temperature of the glue will gradually decrease, and as the liquid level of the glue gradually decreases, the driving force of the glue to move downward by its own weight will decrease. In the prior art, in order to overcome this phenomenon, a booster pump is used. However, since the booster pump blade drives the glue to flow through, the heat exchange between the booster pump blade and the external atmosphere will cause the temperature of the glue in direct contact with the booster pump blade to drop, and the drop in the glue temperature will cause the fluidity of the glue to decrease. Even after excessive cooling, the outermost glue will solidify on the delivery pipe and the blades of the booster pump, which will cause the cavity for the colloid to pass through to become smaller and smaller, so that the delivery amount of the glue cannot completely match the delivery amount of the suspension, which will affect the processing of the raw materials in the pill press. Therefore, there is room for improvement to keep the glue liquid and the glue can keep the reasonable delivery speed of the suspension under the premise of maintaining a suitable driving force to maintain the normal production state of the soft capsule in the pill press to meet market demand. Summary of the invention

[0004] In view of the deficiencies in the prior art, the utility model provides a soft capsule raw material conveying device capable of keeping the glue liquid within a suitable temperature range and keeping the glue liquid within a reasonable pressure range, so as to overcome the defects in the prior art.

[0005] The technical scheme adopted by the utility model is as follows: a soft capsule raw material conveying device comprises a pill press, the pill press is provided with an outlet end of a first suspension conveying pipe and an outlet end of a glue conveying pipe, a first stirring tank is provided on the inlet end of the first suspension conveying pipe, a second stirring tank is provided on the inlet end of the glue conveying pipe, the first stirring tank and the second stirring tank both comprise a stirring tank body, a stirring device arranged on the stirring tank body and a first regulating valve arranged on the bottom end of the stirring tank body; a steam coil is provided on the stirring tank body of the second stirring tank, the glue conveying pipe comprises a conveying inner pipe, a heat-insulating outer sleeve arranged outside the conveying inner pipe and a heat-insulating cavity arranged between the heat-insulating outer sleeve and the conveying inner pipe, a first steam conveying branch pipe and a steam output branch pipe are provided on the heat-insulating outer sleeve, a steam conveying main pipe is provided on the inlet end of the steam coil and the first steam conveying branch pipe, and a second regulating valve and a first pressure sensor are provided on the steam conveying main pipe in sequence along the direction from the inlet end of the steam conveying main pipe to the steam conveying main pipe.

[0006] Preferably, the stirring device comprises a stirring shaft arranged on a stirring tank body, stirring blades arranged on the stirring shaft inside the stirring tank body, and a stirring motor drivingly connected to the stirring shaft.

[0007] Preferably, the inner delivery tube is connected to a nitrogen pressurizing tube, and the nitrogen pressurizing tube is sequentially provided with a temperature sensor, a second pressure sensor, a heat exchanger, a third regulating valve and a nitrogen compressor along a direction from close to the inner delivery tube to far away from the inner delivery tube.

[0008] Preferably, the nitrogen pressurizing pipe between the third regulating valve and the nitrogen compressor is provided with a first buffer tank, the nitrogen pressurizing pipe between the first buffer tank and the nitrogen compressor is provided with a one-way valve, and the first buffer tank is provided with a third pressure sensor.

[0009] Preferably, a low-pressure steam delivery pipe is provided on the outlet end of the steam output branch pipe and the outlet end of the steam coil, a gas-liquid separation tank is provided on the outlet end of the low-pressure steam delivery pipe, a wire mesh coalescer is provided in the gas-liquid separation tank above the low-pressure steam delivery pipe, a desalted water delivery pipe is provided on the bottom end of the gas-liquid separation tank, and a first stop valve is provided on the desalted water delivery pipe.

[0010] Preferably, it also includes a second buffer tank, a first reflux pipe is arranged on the bottom end of the second buffer tank, and the first reflux pipe is provided with a fourth regulating valve, a first booster pump, a colloid mill, a second booster pump and a hydrocyclone separator in sequence along the direction from close to the second buffer tank to far away from the second buffer tank, the first outlet end of the hydrocyclone separator is connected with a second suspension delivery pipe and a filter tank in sequence, the filter tank is connected with the first stirring tank, and the second outlet end of the hydrocyclone separator is connected with the second buffer tank.

[0011] Preferably, the filter tank includes a filter tank body and a filter plate vertically arranged in the filter tank body, the inner cavity of the filter tank body on the side of the filter plate away from the second suspension delivery pipe is connected to the first stirring tank, the inner cavity of the filter tank body on the side of the filter plate close to the second suspension delivery pipe is connected to the second buffer tank through a second reflux pipe, the filter tank is located above the second buffer tank, and a second stop valve is arranged on the second reflux pipe.

[0012] The beneficial effects of the utility model are as follows: firstly, the heat preservation cavity of the glue liquid conveying pipe of the utility model continuously receives steam so that the glue liquid in the conveying inner tube of the glue liquid conveying pipe is kept within a suitable temperature range, and nitrogen is conveyed to the glue liquid in the conveying inner tube of the glue liquid conveying pipe and the nitrogen above the glue liquid in the conveying inner tube of the glue liquid conveying pipe is always maintained within a preset range, so that the glue liquid has stable power when being conveyed to the pill pressing machine.

[0013] Secondly, the vacuum pipe of the utility model is provided with a fourth pressure sensor, a fifth regulating valve and a vacuum pump in sequence along the direction from close to the first stirring tank to far away from the first stirring tank; the installation of the fourth pressure sensor facilitates the feedback of pressure parameters.

[0014] Finally, the inner delivery tube described in the utility model is connected to a nitrogen pressurizing tube, and the nitrogen pressurizing tube is sequentially provided with a pressure relief valve, a temperature sensor, a second pressure sensor, a heat exchanger, a third regulating valve and a nitrogen compressor along the direction from close to the inner delivery tube to far away from the inner delivery tube; installing the temperature sensor is convenient for feedback of temperature parameters, and installing the second pressure sensor is convenient for feedback of pressure parameters.

[0015] The utility model has the advantages of simple structure, convenient operation, ingenious design, greatly improved working efficiency, good social and economic benefits, and is a product that is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the utility model.

[0017] Figure 2 for Figure 1 A partial enlarged schematic diagram of detail A. DETAILED DESCRIPTION

[0018] like Figure 1 and Figure 2As shown, a soft capsule raw material conveying device includes a pill press 1, the pill press 1 is provided with an outlet end of a first suspension delivery pipe 2 and an outlet end of a glue delivery pipe 3, and the glue delivery pipe 3 and the pill press 1 are provided with a sixth regulating valve 47; a first stirring tank is provided on the inlet end of the first suspension delivery pipe 2, and a second stirring tank is provided on the inlet end of the glue delivery pipe 3, and the first stirring tank and the second stirring tank both include a stirring tank body 4, a stirring device provided on the stirring tank body 4, and a first regulating valve 5 provided on the bottom end of the stirring tank body 4; the second stirring tank The mixing tank body 4 is provided with a steam coil 6, the glue delivery pipe 3 includes a delivery inner pipe, an insulation outer sleeve provided outside the delivery inner pipe, and an insulation chamber provided between the insulation outer sleeve and the delivery inner pipe, the insulation outer sleeve is provided with a first steam delivery branch pipe 7 and a steam output branch pipe 8, the inlet end of the steam coil 6 and the first steam delivery branch pipe 7 are provided with a steam delivery main pipe 9, and the steam delivery main pipe 9 is provided with a second regulating valve 10 and a first pressure sensor 11 in sequence along the direction from the inlet end of the steam delivery main pipe 9 to the steam delivery main pipe 9. The stirring device includes a stirring shaft 12 provided on the mixing tank body 4, a stirring blade 13 provided on the stirring shaft 12 inside the mixing tank body 4, and a stirring motor 14 connected to the stirring shaft 12 in a transmission manner. The mixing tank body 4 of the first mixing tank is provided with an exhaust pipe 42, and the exhaust pipe 42 is provided with a fourth pressure sensor 43, a fifth regulating valve 44 and a vacuum pump 45 in sequence along the direction from close to the first mixing tank to far away from the first mixing tank.

[0019] The inner delivery tube is connected with a nitrogen pressurizing tube 15, and the nitrogen pressurizing tube 15 is provided with a pressure relief valve 48, a temperature sensor 16, a second pressure sensor 17, a heat exchanger 18, a third regulating valve 19 and a nitrogen compressor 20 in sequence along the direction from close to the inner delivery tube to far away from the inner delivery tube. The glue liquid that has been quantitatively and sol-geled is gradually added to the inner cavity of the inner delivery tube of the glue liquid delivery tube 3, and the nitrogen heated by the heat exchanger 18 is used as the supplementary gas, which reduces the oxidation of the glue liquid in the oxygen exposed under high temperature, and can make the pressure of the upper layer of the glue liquid entering the inner delivery tube of the glue liquid delivery tube 3 can be maintained within a preset range, so as to maintain the glue liquid in the inner delivery tube of the glue liquid delivery tube 3 continuously delivered to the pill press 1. Furthermore, the nitrogen pressurizing pipe 15 between the third regulating valve 19 and the nitrogen compressor 20 is provided with a first buffer tank 21, the nitrogen pressurizing pipe 15 between the first buffer tank 21 and the nitrogen compressor 20 is provided with a one-way valve 22, and the first buffer tank 21 is provided with a third pressure sensor 23. The first buffer tank 21 is used as a high-pressure gas source of nitrogen to be delivered to the delivery inner tube of the glue delivery pipe 3, and the third pressure sensor 23 is installed to facilitate the feedback of pressure parameters.

[0020] A low-pressure steam delivery pipe 24 is provided at the outlet end of the steam output branch pipe 8 and the outlet end of the steam coil 6, a gas-liquid separation tank 25 is provided at the outlet end of the low-pressure steam delivery pipe 24, a wire mesh coalescer 26 is provided in the gas-liquid separation tank 25 above the low-pressure steam delivery pipe 24, a desalted water delivery pipe 27 is provided at the bottom end of the gas-liquid separation tank 25, and a first stop valve 28 is provided on the desalted water delivery pipe 27. A second steam delivery branch pipe 29 is provided between the inlet end of the steam coil 6 and the steam delivery main pipe 9, and a sixth regulating valve 30 is provided on the second steam delivery branch pipe 29 and the first steam delivery branch pipe 7, respectively. This facilitates the recovery of the liquefied high-pressure steam, and the steam pressure after gas-liquid separation is reduced to form low-pressure steam, which is discharged through the gas-liquid separation tank 25 above the wire mesh coalescer 26, so as to be conveniently delivered to the downstream low-pressure steam user unit.

[0021] In addition, the product also includes a second buffer tank 31, a first reflux pipe 32 is arranged on the bottom end of the second buffer tank 31, and the first reflux pipe 32 is sequentially provided with a fourth regulating valve 33, a first booster pump 34, a colloid mill 35, a second booster pump 36 and a hydrocyclone 37 along the direction from close to the second buffer tank 31 to away from the second buffer tank 31, and the first outlet end of the hydrocyclone 37 is sequentially connected with a second suspension delivery pipe 38 and a filter tank 39, the filter tank 39 is connected to the first stirring tank, and the second outlet end of the hydrocyclone 37 is connected to the second buffer tank 31. The filter tank 39 includes a filter tank body and a filter plate vertically arranged in the filter tank body. The inner cavity of the filter tank body on the side of the filter plate away from the second suspension delivery pipe 38 is connected to the first stirring tank. The inner cavity of the filter tank body on the side of the filter plate close to the second suspension delivery pipe 38 is connected to the second buffer tank 31 through the second reflux pipe 40. The filter tank 39 is located above the second buffer tank 31, and a second stop valve 41 is arranged on the second reflux pipe 40. By adjusting the output power of the hydrocyclone 37, a part of the liquid is always refluxed to return to the second buffer tank 31 with solids with larger particle size. When new materials are added and the circulation is maintained for a preset time, it can be considered that the solid grinding has been completed and transported to the filter tank 39.

[0022] The stirring tank body 4 of the first stirring tank, the stirring tank body 4 of the second stirring tank, the gas-liquid separation tank 25 below the wire mesh coalescer 26, the second buffer tank 31 and the filter tank 39 are respectively provided with liquid level sensors 46; the liquid level sensor 46 is installed to facilitate the feedback of liquid level parameters.

[0023] The usage of this product is as follows: Figure 1 and Figure 2 As shown, the following steps are included:

[0024] S1, putting the weighed and sieved powdered raw materials, soybean oil and olive oil into the colloid mill 35, and turning on the colloid mill 35 to fully grind the materials in the colloid mill 35 to form a suspension;

[0025] S2. After the grinding process is completed, the second booster pump 36 and the hydrocyclone 37 are turned on. The ground suspension in the colloid mill 35 is driven by the second booster pump 36 and sent to the mixed liquid inlet of the hydrocyclone 37. Under the action of the hydrocyclone 37, the feed liquid containing larger particles is sent to the second buffer tank 31 through the waste liquid outlet of the hydrocyclone 37; the remaining feed liquid continues to be transported along the second suspension delivery pipe 38 to the filter tank 39, and after passing through the filter plate of the filter tank 39, a filtered suspension is formed in the filter tank body cavity on the side of the filter plate away from the second suspension delivery pipe 38, and then the filtered suspension is sent to the first stirring tank to form the feed liquid for producing soft capsules by the pill press 1.

[0026] S3, when the delivery is completed, the second stop valve 41 is opened, and the unqualified suspension formed by the large particle materials that have not passed through the filter plate of the filter tank 39 in the inner cavity of the filter tank body near the second suspension delivery pipe 38 of the filter plate is delivered to the second buffer tank 31 through the second reflux pipe 40, and the first booster pump 34 is turned on to feed the colloid mill 35, and the colloid mill 35 is turned on to complete the grinding of the liquid entering the colloid mill 35, and then the step S2 is performed again, and this is repeated for many times to complete the full grinding of the liquid, to form the final liquid and keep it in the first stirring tank, and the stirring device on the first stirring tank is used to continuously stir the liquid in the first stirring tank, thereby completing the preparation of the liquid before being delivered to the pill press 1.

[0027] S4, put the weighed glycerin, gelatin and water into the second stirring tank, open the second regulating valve 10 and the sixth regulating valve 30 on the second steam delivery branch pipe 29, at this time, the high-pressure steam is sequentially delivered to the steam coil 6 through the steam delivery main pipe 9 and the second steam delivery branch pipe 29 to heat the raw materials in the second stirring tank, the steam coil 6 discharges the gas-liquid mixture outward and delivers it to the gas-liquid separation tank 25, the liquid phase of the gas-liquid mixture is collected in the gas-liquid separation tank 25, and the gas phase of the gas-liquid mixture is discharged through the gas-liquid separation tank 25 above the wire mesh coalescer 26 to other steam users; at the same time, turn on the vacuum pump 45 and adjust the opening of the fifth regulating valve 44 until the pressure parameter fed back by the fourth pressure sensor 43 is maintained within the preset range; and turn on the stirring device on the second stirring tank to stir the raw materials in the second stirring tank; the raw materials in the second stirring tank are heated under negative pressure and kept stirred continuously to finally form a glue solution.

[0028] S5, open the pressure relief valve 48, the second stirring tank conveys glue to the inner tube of the glue delivery pipe 3, during this process, the inner tube of the glue delivery pipe 3 receives the glue and the gas displaced is discharged to the outside through the pressure relief valve 48, during which the amount of glue delivered to the inner tube of the glue delivery pipe 3 is judged by the drop of the liquid level sensor 46 on the second stirring tank; then, open the third regulating valve 19, the nitrogen stored in the first buffer tank 21 is delivered to the cold source channel of the heat exchanger 18 and the heat source medium continuously delivered to the heat source channel of the heat exchanger 18, and then is delivered to the inner tube of the glue delivery pipe 3 after completing countercurrent heat exchange to maintain the pressure of the inner tube of the glue delivery pipe 3; at the same time, the steam delivery main pipe 9 delivers steam to the insulation chamber of the glue delivery pipe 3 through the first steam delivery branch pipe 7 to maintain the temperature of the glue in the inner tube of the glue delivery pipe 3 within an appropriate range.

[0029] S6. According to the requirements of the pill press machine 1, the material liquid in the first stirring tank and the glue liquid in the inner tube of the glue liquid delivery pipe 3 are delivered to the pill press machine 1; when the glue liquid in the inner tube of the glue liquid delivery pipe 3 has completed delivery to the pill press machine 1; before the inner tube of the glue liquid delivery pipe 3 receives the glue liquid delivered by the second stirring tank again, it is necessary to open the pressure relief valve 48 again. At this time, the nitrogen replaced by the glue liquid delivered by the second stirring tank is discharged to the outside through the pressure relief valve 48. When the inner tube of the glue liquid delivery pipe 3 has completed receiving the glue liquid delivered by the second stirring tank again, the pressure relief valve 48 is closed and the third regulating valve 19 is opened again to supply nitrogen to the inner tube of the glue liquid delivery pipe 3 using the nitrogen stored in the first buffer tank 21 to maintain the pressure in the inner tube of the glue liquid delivery pipe 3 continuously within an appropriate range.

[0030] Through this embodiment, the insulation chamber of the glue liquid delivery pipe 3 continuously receives steam so that the glue liquid in the delivery inner tube of the glue liquid delivery pipe 3 is kept within an appropriate temperature range, and by delivering nitrogen to the glue liquid in the delivery inner tube of the glue liquid delivery pipe 3 and maintaining the nitrogen above the glue liquid in the delivery inner tube of the glue liquid delivery pipe 3 within a preset range at all times, the glue liquid has stable power when being delivered to the pill press 1.

[0031] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, any equivalent changes or modifications made based on the structures, features and principles described in the patent scope of the present invention should be included in the patent application scope of the present invention.

Claims

1. A soft capsule raw material conveying device, characterized in that: The invention comprises a pill pressing machine (1), wherein the pill pressing machine (1) is provided with an outlet end of a first suspension delivery pipe (2) and an outlet end of a glue delivery pipe (3), a first stirring tank is provided on the inlet end of the first suspension delivery pipe (2), and a second stirring tank is provided on the inlet end of the glue delivery pipe (3), wherein the first stirring tank and the second stirring tank both comprise a stirring tank body (4), a stirring device provided on the stirring tank body (4), and a first regulating valve (5) provided on the bottom end of the stirring tank body (4); the stirring tank body (4) of the second stirring tank is provided with a steam coil (6), and the glue delivery pipe (3) is provided with a steam coil (6). The delivery pipe (3) comprises an inner delivery pipe, an outer insulation sleeve arranged outside the inner delivery pipe, and an insulation cavity arranged between the outer insulation sleeve and the inner delivery pipe. The outer insulation sleeve is provided with a first steam delivery branch pipe (7) and a steam output branch pipe (8). A steam delivery main pipe (9) is provided at the inlet end of the steam coil (6) and the first steam delivery branch pipe (7). The steam delivery main pipe (9) is provided with a second regulating valve (10) and a first pressure sensor (11) in sequence along the direction from the inlet end of the steam delivery main pipe (9) to the steam delivery main pipe (9).

2. The soft capsule material conveying device according to claim 1, characterized in that: The stirring device comprises a stirring shaft (12) arranged on a stirring tank body (4), a stirring blade (13) arranged on the stirring shaft (12) inside the stirring tank body (4), and a stirring motor (14) drivingly connected to the stirring shaft (12).

3. The soft capsule material conveying device according to claim 1, characterized in that: The inner delivery tube is connected to a nitrogen pressurizing tube (15), and the nitrogen pressurizing tube (15) is provided with a temperature sensor (16), a second pressure sensor (17), a heat exchanger (18), a third regulating valve (19), and a nitrogen compressor (20) in sequence along a direction from close to the inner delivery tube to far away from the inner delivery tube.

4. The soft capsule material conveying device according to claim 3, characterized in that: The nitrogen pressurizing pipe (15) between the third regulating valve (19) and the nitrogen compressor (20) is provided with a first buffer tank (21), the nitrogen pressurizing pipe (15) between the first buffer tank (21) and the nitrogen compressor (20) is provided with a one-way valve (22), and the first buffer tank (21) is provided with a third pressure sensor (23).

5. The soft capsule material conveying device according to claim 1, characterized in that: A low-pressure steam delivery pipe (24) is provided at the outlet end of the steam output branch pipe (8) and the outlet end of the steam coil (6); a gas-liquid separation tank (25) is provided at the outlet end of the low-pressure steam delivery pipe (24); a wire mesh coalescer (26) is provided in the gas-liquid separation tank (25) above the low-pressure steam delivery pipe (24); a desalted water delivery pipe (27) is provided at the bottom end of the gas-liquid separation tank (25); and a first stop valve (28) is provided on the desalted water delivery pipe (27).

6. The soft capsule material conveying device according to claim 1, characterized in that: The invention also comprises a second buffer tank (31), a first reflux pipe (32) being arranged at the bottom end of the second buffer tank (31), a fourth regulating valve (33), a first booster pump (34), a colloid mill (35), a second booster pump (36) and a hydrocyclone (37) being arranged in sequence along the direction from close to the second buffer tank (31) to far away from the second buffer tank (31), a first outlet end of the hydrocyclone (37) being connected in sequence to a second suspension delivery pipe (38) and a filter tank (39), the filter tank (39) being connected to the first stirring tank, and a second outlet end of the hydrocyclone (37) being connected to the second buffer tank (31).

7. The soft capsule material conveying device according to claim 6, characterized in that: The filter tank (39) comprises a filter tank body and a filter plate vertically arranged in the filter tank body, the inner cavity of the filter tank body on the side of the filter plate away from the second suspension delivery pipe (38) is connected to the first stirring tank, the inner cavity of the filter tank body on the side of the filter plate close to the second suspension delivery pipe (38) is connected to the second buffer tank (31) through a second return pipe (40), the filter tank (39) is located above the second buffer tank (31), and a second stop valve (41) is arranged on the second return pipe (40).

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