WO2024065975A1

WO2024065975A1 - Low-temperature vacuum concentration device for plant extract

Info

Publication number: WO2024065975A1
Application number: PCT/CN2022/131558
Authority: WO
Inventors: 朱明杰; 易孟杰; 廖书桥
Original assignee: 长沙市惠瑞生物科技有限公司
Priority date: 2022-09-27
Filing date: 2022-11-11
Publication date: 2024-04-04
Also published as: BE1030489B1; CN115253334B; CN115253334A

Abstract

A low-temperature vacuum concentration device for a plant extract, comprising an evaporation tank (1). A liquid inlet pipe (2) passes through and is inserted into the tank wall of the rear side of the evaporation tank (1), a plurality of atomizing nozzles (3) are connected to the end of the liquid inlet pipe (2) located inside the evaporation tank (1), and the plurality of atomizing nozzles (3) are annularly distributed; a heating cover (4) is rotatably sleeved on the part of the liquid inlet pipe (2) located inside the evaporation tank (1), and the rear side of the heating cover (4) fixedly passes through and is inserted into the tank wall of the rear side of the evaporation tank (1); a power assembly (5) driving the liquid inlet pipe (2) to rotate is provided at a side surface position of the end of the liquid inlet pipe (2) located outside the evaporation tank (1), and a connecting pipe (6) is rotatably connected to said end of the liquid inlet pipe (2); a sealing door (7) is mounted on the front side of the evaporation tank (1), an exhaust valve (8) and a blow-down valve (9) are respectively connected to the top and bottom of the evaporation tank (1), and a vacuum pump (10) is also connected to the top of the evaporation tank (1). The device can improve the evaporation efficiency of plant extracts.

Description

Plant extract low temperature vacuum concentration device

Technical Field

The invention belongs to the technical field of plant extraction, and particularly relates to a low-temperature vacuum concentration device for plant extracts.

Background technique

At present, for the concentration of plant extracts, steam-heated internal circulation single-effect low-temperature distillation and concentration equipment is widely used. When working, the vacuum pump will first draw a certain vacuum environment inside the low-temperature distillation and concentration equipment, so as to achieve the purpose of lowering the evaporation boiling point of the material, and when the air pressure inside the low-temperature distillation and concentration equipment increases with the evaporation of the plant extract, the vacuum pump will work intermittently, so that the inside of the low-temperature distillation and concentration equipment is always in a certain vacuum environment, thereby ensuring that the plant extract can be evaporated and concentrated at a lower temperature.

For example, a Chinese patent with the announcement number CN103007557B proposed a low-temperature vacuum concentration device for plant extracts, "composed of a concentration tank, a hot water circulation pump, a heating medium heat exchanger, a circulating hot water pool, and a water jet vacuum system." It is a special low-temperature concentration device that uses circulating hot water as the heating medium, which can effectively avoid the problem of local high temperature of the heater producing charred debris.

Although the plant extract low-temperature vacuum concentrator proposed in the above patent solves the temperature problem in the plant extract concentration process to a certain extent, during use, the existing plant extract low-temperature vacuum concentrator has a long evaporation time and uneven evaporation because the plant extract is evaporated in the concentration tank after heating and there is a lot of plant extract in the concentration tank.

Summary of the invention

In view of the above problems, the present invention provides a low-temperature vacuum concentration device for plant extracts to solve the problems raised in the above background technology.

To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a low-temperature vacuum concentration device for plant extracts, comprising an evaporator, a liquid inlet pipe is inserted through the rear tank wall of the evaporator, one end of the liquid inlet pipe located inside the evaporator is connected to a plurality of atomizing nozzles, and the plurality of atomizing nozzles are distributed in a ring shape, the part of the liquid inlet pipe located inside the evaporator is rotatably sleeved with a heating cover, and the rear side of the heating cover is fixedly inserted through the rear tank wall of the evaporator, a power component for driving the liquid inlet pipe to rotate is provided at the side position of one end of the liquid inlet pipe located outside the evaporator, and the end of the liquid inlet pipe is rotatably connected to a connecting pipe, a sealing door is installed on the front side of the evaporator, the top and bottom of the evaporator are respectively connected to an exhaust valve and a drain valve, and the top of the evaporator is also connected to a vacuum pump.

Furthermore, the power assembly includes a transmission shaft, which is transmission-connected to the rear side of the evaporator, a motor is connected to the rear end of the transmission shaft, a first gear is sleeved on the transmission shaft, a second gear is sleeved at a position of the liquid inlet pipe opposite to the first gear, and the second gear is meshed with the first gear.

Furthermore, the heating hood is funnel-shaped, and the opening of the heating hood gradually decreases from front to back, the end of the liquid inlet pipe located inside the heating hood is of closed design, and a plurality of atomizing nozzles are installed at the edge of the liquid inlet pipe, and a fixed shaft is threadedly connected to the axis of one end of the liquid inlet pipe located inside the evaporator, and the top and bottom of the fixed shaft are symmetrically fixedly connected with fixed rods, and the end of the fixed rod away from the fixed shaft is fixedly connected with a scraper, and the scraper is in contact with the inner wall of the heating hood.

Furthermore, a V-shaped guide plate is provided at the bottom of the heating hood, and both sides of the V-shaped guide plate are inclined downward, the front and rear of the V-shaped guide plate are fixedly connected to the inner walls of the front and rear sides of the evaporator respectively, and there is a gap between the two sides of the V-shaped guide plate and the inner wall of the side of the evaporator, and heating plates are symmetrically fixedly connected to the outer walls of both sides of the evaporator, and the two heating plates are respectively opposite to the two sides of the V-shaped guide plate.

Furthermore, a baffle is provided on the front side of the heating hood, the diameter of the baffle is larger than the diameter of the opening on the front side of the heating hood, the top of the baffle is rotatably connected to a rotating shaft, the two ends of the rotating shaft are respectively fixedly connected to the inner walls on both sides of the evaporator, and a block is provided on the rear side of the baffle, the block is fixedly connected to the top of the V-shaped guide plate, and the block can contact the baffle, and the rear edge of the baffle is fixedly connected to an arc-shaped water retaining strip, and a notch is provided near the bottom of the water retaining strip.

Furthermore, an annular limit groove is opened on the outer wall of the heating hood near the front side, and two limit wheels are arranged in the limit groove. The axis of the limit wheel is rotatably connected to the limit shaft, and the front end of the limit shaft is fixedly connected with an L-shaped rod, and the two L-shaped rods are respectively fixedly connected to the front ends of the two scrapers.

Furthermore, guide strips are symmetrically fixedly connected on both sides of the top of the V-shaped guide plate, and the guide strips are in a V-shape with an angle greater than ninety degrees. The angles of the two guide strips are opposite to each other, and the angle of the guide strip is opposite to the position of the baffle. The guide strip is provided with multiple through holes near the top of the V-shaped guide plate.

Furthermore, a handle is fixedly connected to the front side of the baffle near the bottom and the front side of the sealed door, and the handle is made of stainless steel.

Furthermore, the inner wall of the heating hood is in a continuous and smooth wave shape, and the side of the scraper close to the inner wall of the heating hood matches the shape of the inner wall of the heating hood.

Technical effects and advantages of the present invention:

1. When the plant extract is evaporated, when the plant extract is sprayed on the inner wall of the heating hood through the atomizing nozzle on the liquid inlet pipe, the plant extract becomes very thin due to the atomization effect of the atomizing nozzle, and the atomizing nozzle is in a rotating state driven by the liquid inlet pipe, so that the plant extract sprayed on the inner wall of the heating hood is more uniform, so the heating hood can quickly and evenly evaporate the plant extract sprayed on its inner wall, thereby improving the evaporation efficiency of the plant extract;

2. During the rotation of the liquid inlet pipe, the fixed shaft drives the two scrapers to scrape along the inner wall of the heating cover under the drive of the liquid inlet pipe. As the scrapers scrape, the plant extract remaining on the inner wall of the heating cover that has not yet evaporated can be scraped off by the scrapers, thereby preventing the plant extract from generating burnt debris on the inner wall of the heating cover and ensuring the heating efficiency of the heating cover.

3. When the scraper scrapes the plant extract on the inner wall of the heating cover onto the V-shaped guide plate, the extract can contact the guide strip under the action of gravity. At this time, the plant extract can flow evenly on the top of the V-shaped guide plate through the through holes on the guide strip under the guidance of the guide strip, thereby increasing the heating area of the plant extract. When the plant extract flows along the top of the V-shaped guide plate to the position where the inner wall of the evaporation tank is opposite to the heating plate, the plant extract drips more evenly on the evaporation tank, so that the heating plate can further evaporate the plant extract evenly, thereby improving the evaporation efficiency of the plant extract.

Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a first perspective schematic diagram of the present invention;

FIG2 is a second perspective schematic diagram of the present invention;

Fig. 3 is a three-dimensional cross-sectional view of the present invention;

FIG4 is a perspective schematic diagram of a baffle, a V-shaped guide plate and a guide strip in the present invention;

FIG. 5 is a perspective schematic diagram of the internal structure of the heating cover in the present invention.

In the figure: 1. evaporator; 2. liquid inlet pipe; 3. atomizing nozzle; 4. heating cover; 5. power assembly; 51. transmission shaft; 52. motor; 53. first gear; 54. second gear; 6. connecting pipe; 7. sealing door; 8. exhaust valve; 9. drain valve; 10. vacuum pump; 11. fixed shaft; 12. fixed rod; 13. scraper; 14. V-shaped guide plate; 15. heating plate; 16. baffle; 17. rotating shaft; 18. block; 19. water retaining bar; 20. limiting wheel; 21. limiting shaft; 22. L-shaped rod; 23. guide bar; 24. handle.

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

The present invention provides a low-temperature vacuum concentration device for plant extracts as shown in Figures 1 to 5, comprising an evaporation tank 1, a liquid inlet pipe 2 is inserted through the rear tank wall of the evaporation tank 1, and the end of the liquid inlet pipe 2 located inside the evaporation tank 1 is connected to a plurality of atomizing nozzles 3, and the plurality of atomizing nozzles 3 are distributed in a ring shape, the part of the liquid inlet pipe 2 located inside the evaporation tank 1 is rotatably sleeved with a heating cover 4, and the rear side of the heating cover 4 is fixedly inserted through the rear tank wall of the evaporation tank 1, and the side position of the liquid inlet pipe 2 located at one end outside the evaporation tank 1 is provided with a power assembly 5 for driving the liquid inlet pipe 2 to rotate, the power assembly 5 comprises a transmission shaft 51, the transmission shaft 51 is transmission-connected to the rear side of the evaporation tank 1, the rear end of the transmission shaft 51 is connected to a motor 52, a first gear 53 is sleeved on the transmission shaft 51, a second gear 54 is sleeved on the position of the liquid inlet pipe 2 opposite to the first gear 53, and the second gear 54 is meshed with the first gear 53, and the end of the liquid inlet pipe 2 is rotatably connected to the connecting pipe 6, a sealing door 7 is installed on the front side of the evaporation tank 1, and the top and bottom of the evaporation tank 1 are respectively connected to the exhaust valve 8 and the sewage valve 9, and the top of the evaporation tank 1 is also connected to the vacuum pump 10;

When evaporating the plant extract, the vacuum pump 10 is first started to evacuate the evaporator 1. When the interior of the evaporator 1 reaches a specified pressure, the vacuum pump 10 is turned off (and in the subsequent evaporation process, when the vacuum pump 10 evacuates the evaporator 1, the atomizing nozzle 3 is in a stopped state). Then, the motor 52 is started to drive the second gear 54 to rotate through the first gear 53 on the rotating shaft 17. As the second gear 54 rotates, the liquid inlet pipe 2 can start to rotate together with the second gear 54. When the rotation speed of the liquid inlet pipe 2 is stable, the plant extract is injected into the liquid inlet pipe 2 through the connecting pipe 6. When the plant extract is sprayed on the inner wall of the heating cover 4 through the atomizing nozzle 3 on the liquid inlet pipe 2, the plant extract becomes very thin due to the atomization effect of the atomizing nozzle 3, and the atomizing nozzle 3 is in a rotating state driven by the liquid inlet pipe 2, so that the plant extract sprayed on the inner wall of the heating cover 4 is more uniform. Therefore, the heating cover 4 can quickly and evenly evaporate the plant extract sprayed on its inner wall, thereby improving the evaporation efficiency of the plant extract;

In addition, since the heat emitted by the heating cover 4 can be promptly absorbed by the plant extract sprayed on its inner wall, the utilization rate of the heat of the heating cover 4 is improved;

The evaporated gas can then enter the subsequent condensation device through the exhaust valve 8 for further purification, and the residual solution after evaporation can be discharged from the evaporation tank 1 through the drain valve 9.

As shown in FIGS. 3 and 5 , the heating hood 4 is funnel-shaped, and the opening of the heating hood 4 gradually decreases from front to back. The end of the liquid inlet pipe 2 located inside the heating hood 4 is of a closed design, and a plurality of atomizing nozzles 3 are installed at the edge of the liquid inlet pipe 2. The liquid inlet pipe 2 is located inside the evaporator 1 and is threadedly connected to a fixed shaft 11 at the axis center of one end thereof. The top and bottom of the fixed shaft 11 are symmetrically fixedly connected to fixed rods 12. The end of the fixed rod 12 away from the fixed shaft 11 is fixedly connected to a scraper 13, and the scraper 13 is fitted with the inner wall of the heating hood 4. The inner wall of the heating hood 4 is in a continuous and smooth wavy shape, and the side of the scraper 13 close to the inner wall of the heating hood 4 matches the shape of the inner wall of the heating hood 4;

When the plant extract is sprayed onto the inner wall of the heating cover 4 by atomization, since the inner wall of the heating cover 4 is wavy, the heating cover 4 can have a sufficient heating surface to contact with the plant extract, thereby improving the evaporation efficiency of the plant extract;

During the rotation of the liquid inlet pipe 2, the fixed shaft 11 drives the two scrapers 13 to scrape along the inner wall of the heating hood 4 under the drive of the liquid inlet pipe 2. As the scrapers 13 scrape, the plant extract remaining on the inner wall of the heating hood 4 that has not yet evaporated can be scraped off by the scrapers 13, thereby avoiding the generation of burnt debris on the inner wall of the heating hood 4 by this part of the plant extract, thereby ensuring the heating efficiency of the heating hood 4.

As shown in Figures 3 and 4, a V-shaped guide plate 14 is provided at the bottom of the heating cover 4, and both sides of the V-shaped guide plate 14 are inclined downward, and the front and rear of the V-shaped guide plate 14 are fixedly connected to the inner walls of the front and rear sides of the evaporation tank 1, respectively, and there is a gap between the two sides of the V-shaped guide plate 14 and the inner wall of the side of the evaporation tank 1, and the heating plates 15 are symmetrically fixedly connected to the outer walls of the two sides of the evaporation tank 1, and the two heating plates 15 are respectively opposite to the two sides of the V-shaped guide plate 14, and the guide strips 23 are symmetrically fixedly connected to the two sides of the top of the V-shaped guide plate 14, and the guide strips 23 are V-shaped with an angle greater than ninety degrees, and the angles of the two guide strips 23 are opposite to each other, and the angle of the guide strip 23 is opposite to the position of the baffle 16, and the guide strip 23 is close to the V-shaped A plurality of through holes are provided through the top of the guide plate 14, a baffle 16 is provided on the front side of the heating hood 4, the diameter of the baffle 16 is larger than the diameter of the opening on the front side of the heating hood 4, a rotating shaft 17 is rotatably connected to the top of the baffle 16, and the two ends of the rotating shaft 17 are respectively fixedly connected to the inner walls on both sides of the evaporator 1, a stopper 18 is provided on the rear side of the baffle 16, the stopper 18 is fixedly connected to the top of the V-shaped guide plate 14, and the stopper 18 can contact the baffle 16, an arc-shaped water retaining strip 19 is fixedly connected to the rear edge of the baffle 16, and a notch is provided near the bottom of the water retaining strip 19, and a handle 24 is fixedly connected to the front side of the baffle 16 near the bottom and the front side of the sealing door 7, and the handle 24 is made of stainless steel;

Since the amount of plant extract that can be evaporated by the heating hood 4 per unit time is limited, part of the plant extract that has not been evaporated can fall onto the baffle 16 at the corresponding position on the inner side of the water retaining strip 19 along the direction of the inner wall of the heating hood 4 under the scraping and guiding action of the scraper 13, and then the extract that falls on the baffle 16 falls on the top of the V-shaped guide plate 14 through the gap of the water retaining strip 19 under the action of gravity, and then the plant extract that falls on the top of the V-shaped guide plate 14 can move along the top of the V-shaped guide plate 14 in the direction of the guide strip 23 under the action of gravity. When the plant extract contacts the guide strip 23, the plant extract can flow evenly on the top of the V-shaped guide plate 14 through the through holes on the guide strip 23 under the guiding action of the guide strip 23, thereby increasing the plant extract. When the plant extract flows along the top of the V-shaped guide plate 14 to the position where the inner wall of the evaporation tank 1 is opposite to the heating plate 15, the plant extract drips more evenly on the evaporation tank 1, so that the heating plate 15 can further evaporate the plant extract evenly, thereby improving the evaporation efficiency of the plant extract;

When the inner wall of the evaporator 1 needs to be cleaned, due to the presence of the heating cover 4, the side wall of the evaporator 1 rarely contacts the plant extract, so that the cleaning range of the inner wall of the evaporator 1 is small. In addition, since the baffle 16 is rotatably connected to the inner wall of the evaporator 1 through the rotating shaft 17, when cleaning the inner wall of the evaporator 1, the handle 24 on the baffle 16 can be pulled to deflect it upward, so that the inner wall of the heating cover 4 can be exposed, thereby facilitating the cleaning of the inner wall of the heating cover 4.

As shown in FIG5 , an annular limiting groove is provided near the front side of the outer wall of the heating cover 4, and two limiting wheels 20 are provided in the limiting groove. The limiting wheels 20 are rotatably connected to a limiting shaft 21 at the axis center, and an L-shaped rod 22 is fixedly connected to the front end of the limiting shaft 21, and the two L-shaped rods 22 are fixedly connected to the front ends of the two scrapers 13 respectively;

When the fixed shaft 11 drives the scraper 13 to scrape against the inner wall of the heating hood 4, the limiting wheel 20 can roll along the limiting groove, thereby limiting the free end of the scraper 13 to prevent the scraper 13 from shaking during the process of scraping the inner wall of the heating hood 4.

Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

A low-temperature vacuum concentration device for plant extracts comprises an evaporation tank (1), characterized in that: a liquid inlet pipe (2) is inserted through the rear tank wall of the evaporation tank (1), one end of the liquid inlet pipe (2) located inside the evaporation tank (1) is connected to a plurality of atomizing nozzles (3), and the plurality of atomizing nozzles (3) are distributed in a ring shape; a portion of the liquid inlet pipe (2) located inside the evaporation tank (1) is rotatably sleeved with a heating cover (4), and the rear side of the heating cover (4) is fixedly inserted through the rear tank wall of the evaporation tank (1); a power component (5) for driving the liquid inlet pipe (2) to rotate is provided at a side position of one end of the liquid inlet pipe (2) located outside the evaporation tank (1), and the end of the liquid inlet pipe (2) is rotatably connected to a connecting pipe (6); a sealing door (7) is installed on the front side of the evaporation tank (1); an exhaust valve (8) and a sewage valve (9) are respectively connected to the top and bottom of the evaporation tank (1), and a vacuum pump (10) is also connected to the top of the evaporation tank (1).
The low-temperature vacuum concentration device for plant extracts according to claim 1, characterized in that: the power assembly (5) comprises a transmission shaft (51), the transmission shaft (51) is transmission-connected to the rear side of the evaporation tank (1), the rear end of the transmission shaft (51) is connected to a motor (52), a first gear (53) is sleeved on the transmission shaft (51), a second gear (54) is sleeved on a position of the liquid inlet pipe (2) opposite to the first gear (53), and the second gear (54) is meshed with the first gear (53).
The low-temperature vacuum concentration device for plant extracts according to claim 2 is characterized in that: the heating cover (4) is funnel-shaped, and the opening of the heating cover (4) gradually decreases from front to back, the end of the liquid inlet pipe (2) located inside the heating cover (4) is of a closed design, and a plurality of atomizing nozzles (3) are installed at the edge of the liquid inlet pipe (2), the liquid inlet pipe (2) is threadedly connected to a fixed shaft (11) at the axis center of one end of the liquid inlet pipe (2) located inside the evaporation tank (1), the top and bottom of the fixed shaft (11) are symmetrically fixedly connected to fixed rods (12), and the end of the fixed rod (12) away from the fixed shaft (11) is fixedly connected to a scraper (13), and the scraper (13) is in contact with the inner wall of the heating cover (4).
The low-temperature vacuum concentration device for plant extracts according to claim 3 is characterized in that: a V-shaped guide plate (14) is provided at the bottom of the heating cover (4), and both sides of the V-shaped guide plate (14) are inclined downward, and the front and rear of the V-shaped guide plate (14) are respectively fixedly connected to the inner walls of the front and rear sides of the evaporation tank (1), and there is a gap between the two sides of the V-shaped guide plate (14) and the inner wall of the side of the evaporation tank (1), and heating plates (15) are symmetrically fixedly connected to the outer walls of both sides of the evaporation tank (1), and the two heating plates (15) are respectively opposite to the two sides of the V-shaped guide plate (14).
The low-temperature vacuum concentration device for plant extracts according to claim 4 is characterized in that: a baffle (16) is provided on the front side of the heating hood (4), the diameter of the baffle (16) is larger than the diameter of the opening on the front side of the heating hood (4), the top of the baffle (16) is rotatably connected to a rotating shaft (17), the two ends of the rotating shaft (17) are respectively fixedly connected to the inner walls on both sides of the evaporation tank (1), a stopper (18) is provided on the rear side of the baffle (16), the stopper (18) is fixedly connected to the top of the V-shaped guide plate (14), and the stopper (18) can contact the baffle (16), and the rear edge of the baffle (16) is fixedly connected to an arc-shaped water retaining strip (19), and a notch is provided at a position close to the bottom of the water retaining strip (19).
The low-temperature vacuum concentration device for plant extracts according to claim 5 is characterized in that: an annular limiting groove is provided on the outer wall of the heating cover (4) near the front side, and two limiting wheels (20) are provided in the limiting groove. The limiting wheels (20) are rotatably connected to a limiting shaft (21) at the axis center, and an L-shaped rod (22) is fixedly connected to the front end of the limiting shaft (21), and the two L-shaped rods (22) are respectively fixedly connected to the front ends of the two scrapers (13).
The plant extract low-temperature vacuum concentration device according to claim 5 is characterized in that: guide strips (23) are symmetrically fixedly connected to both sides of the top of the V-shaped guide plate (14), and the guide strips (23) are V-shaped with an angle greater than ninety degrees. The angles of the two guide strips (23) are opposite to each other, and the angle of the guide strips (23) is opposite to the position of the baffle (16), and a plurality of through holes are opened through the guide strip (23) near the top of the V-shaped guide plate (14).
The plant extract low-temperature vacuum concentration device according to claim 7 is characterized in that a handle (24) is fixedly connected to the front side of the baffle (16) near the bottom and the front side of the sealing door (7), and the handle (24) is made of stainless steel.
The low-temperature vacuum concentration device for plant extracts according to claim 6 is characterized in that the inner wall of the heating hood (4) is in a continuous and smooth wavy shape, and the side of the scraper (13) close to the inner wall of the heating hood (4) matches the shape of the inner wall of the heating hood (4).