A tobacco vacuum rehumidification machine with a composite vacuum device

Abstract

The present invention provides a tobacco leaf vacuum rehumidification machine with a composite vacuum device, which effectively solves the technical problems in the background technology that the water accumulation removal effect is poor during vacuuming, resulting in prolonged vacuuming time, water vapor easily causing rust on the flow-through parts of the mechanical vacuum pump, and increasing the emulsification probability of the lubricating oil, thereby increasing the maintenance cost. When the vacuum pump is vacuuming, the wet vapor extracted from the rehumidification box is first passed through a condensing tower to condense most of the moisture into water, which is temporarily stored in a vacuum water tank. The uncondensed water vapor passes through a demister, a filter, and a steam trap to remove moisture from the air, and then enters the vacuum pump and is discharged. At this time, since the moisture in the air is removed, the load of the vacuum pump is greatly reduced, ensuring the normal operation of the vacuum pump.

Description

Technical Field

[0001] The invention relates to the tobacco industry, in particular to a tobacco vacuum rehumidification machine with a composite vacuum device. Background Art

[0002] The tobacco vacuum rehumidification machine is a main equipment in the tobacco processing process. Its working principle is: put the incoming tobacco leaves with a moisture content of about 12% in a vacuum box, evacuate the box to remove the air in the middle of the tobacco leaves, and after evacuating to the set vacuum degree, fill and release steam into the vacuum box. The tobacco leaves become moist and soft under the action of heat and mass transfer, which is convenient for subsequent processing. According to the process requirements, the evacuation and humidification process may continue several times.

[0003] During normal production, the vacuum rehumidification machine charges and discharges steam into the vacuum box many times, and condensed water above 50°C is always accumulated in the box. When the pressure is evacuated to 16kPa, the condensed water begins to boil, and the evaporated water vapor will inevitably become an additional load on the vacuum unit; when the pressure is evacuated to 0.9kPa, the volume of water vapor increases by about 140,000 times compared with the original liquid volume, and the additional load is undoubtedly huge; therefore, the condensed water in the box of the vacuum rehumidification machine has a great negative impact on the mechanical vacuum pump unit. First, it prolongs the pumping time, and second, water vapor can easily cause rust to the flow-through parts of the mechanical vacuum pump, while increasing the probability of emulsification of the lubricating oil and increasing maintenance costs.

[0004] A patent proposes to remove the accumulated water in the vacuum box by using a mechanical scraper or compressed air spray. However, this method has three disadvantages: (1) the accumulated water is not completely removed; (2) the accumulated water in the box cannot be removed during the second or third evacuation; and (3) the water vapor from the tobacco leaves is also sucked away by the vacuum pump. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a tobacco leaf vacuum rehumidification machine with a composite vacuum device, which effectively solves the technical problems in the background technology that the water accumulation removal effect during vacuuming is not good, resulting in prolonged vacuuming time, water vapor easily causing rust on the flow-through parts of the mechanical vacuum pump, and at the same time increasing the emulsification probability of the lubricating oil, thereby increasing maintenance costs.

[0006] The technical solution of the present invention is: a tobacco leaf vacuum rehumidification machine with a composite vacuum device, comprising a refrigeration unit and a condensation tower structure connected to a rehumidification box through a first pipeline, the upper end of the condensation tower structure is connected to a filter, the filter is connected to a steam trap, the steam trap is connected to a screw vacuum pump through a first-stage Roots pump and a second-stage Roots pump, a first vacuum valve is connected between the second-stage Roots pump and the screw vacuum pump, a second vacuum valve is connected between the outlet of the second-stage Roots pump and the inlet of the first-stage Roots pump, the steam trap is composed of a steam trap shell and a steam trap coil in the steam trap shell, the steam trap coil is connected to the refrigeration unit and the refrigeration unit supplies a cold source, the filter and the first-stage Roots pump are connected in the steam trap shell of the steam trap.

[0007] Preferably, the lower portion of the steam capture shell is connected to a liquid storage tank via a first vacuum shut-off valve, and the side wall and the lower end of the liquid storage tank are respectively connected to a second vacuum shut-off valve and a third vacuum shut-off valve.

[0008] Preferably, the evaporator of the refrigeration unit is placed in a heat exchange shell, the steam capture coil is connected to a first circulation pump via an eighth vacuum shut-off valve, the first circulation pump is connected to the heat exchange shell via a fourth vacuum shut-off valve, and the heat exchange shell is connected to the steam capture coil via a fifth vacuum shut-off valve.

[0009] Preferably, the refrigeration unit includes a compressor, the compressor is connected to a separator, the separator is connected to a condenser, the condenser is connected to a dryer, the dryer is connected to the inlet of a heat exchange tube of a gas-liquid heat exchanger, the outlet of the heat exchange tube of the gas-liquid heat exchanger is connected to the inlet of an evaporator through a thermal expansion valve, the outlet of the evaporator is connected to the inlet of a shell of the gas-liquid heat exchanger, and the outlet of the shell of the gas-liquid heat exchanger is connected to the compressor.

[0010] Preferably, the condensation tower structure includes a condensation tower shell, the rehumidification box is connected to the condensation tower shell through a first pipe, a third vacuum valve is provided on the first pipe, the lower end of the condensation tower shell is connected to a vacuum water tank through a fourth vacuum valve, the vacuum water tank is connected to a second circulation pump through a first one-way valve, the second circulation pump is connected to a second one-way valve through a sixth vacuum stop valve, the second one-way valve is connected to a return water pipe, the return water pipe is connected to the circulating water tank through a cooling tower, the lower end of the circulating water tank is connected to a seventh vacuum stop valve, and the lower part of the side wall of the circulating water tank is connected to a spray device fixed in the upper part of the side wall of the condensation tower shell through a water supply pump, a third one-way valve and a fifth vacuum valve.

[0011] Preferably, a demister is installed in the condensation tower shell at the upper part of the spray device.

[0012] Beneficial effects of the present invention:

[0013] 1. When the vacuum pump is evacuating, the wet steam extracted from the rehumidification box will first pass through the condensation tower to condense most of the moisture into water, which will be temporarily stored in the vacuum water tank. The uncondensed water vapor will pass through the demister, filter, and steam trap to remove the moisture in the air, and then enter the vacuum pump for discharge. At this time, since the moisture in the air is removed, the load of the vacuum pump is greatly reduced, ensuring the normal operation of the vacuum pump.

[0014] 2. The refrigeration unit in the present invention provides a cold source for the steam collector, so that the moisture entering the steam collector is condensed and discharged.

[0015] 3. In the refrigeration unit of the present invention, a gas-liquid heat exchanger is added, and the medium-temperature high-pressure liquid from the dryer is used to heat the low-pressure and low-temperature gas returning from the evaporator, so that the temperature of the gas output from the evaporator to the compressor is increased, and the steam entering the compressor becomes superheated steam, thereby avoiding compressor cylinder flushing. At the same time, the energy of the medium-temperature high-pressure liquid output from the dryer is utilized, saving energy.

[0016] 4. The moisture in the gas is removed through three stages: condensation tower, demister and steam trap, which greatly ensures the dryness of the air and the normal operation of the vacuum pump.

[0017] 5. The gas with water vapor is passed through the filter to filter out the solid matter in the gas, further ensuring the normal operation and service life of equipment such as the vacuum pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the present invention.

[0019] Description of reference numerals: first pipeline 1, rehumidification box 2, filter 3, steam trap 4, first-stage Roots pump 5, second-stage Roots pump 6, screw vacuum pump 7, first vacuum valve 8, second vacuum valve 9, steam trap housing 10, steam trap coil 11, first vacuum stop valve 12, liquid storage tank 13, second vacuum stop valve 14, third vacuum stop valve 15, evaporator 16, heat exchange shell 17, eighth vacuum stop valve 18, first circulation pump 19, fourth vacuum stop valve 20, fifth vacuum stop valve 21, Compressor 22, separator 23, condenser 24, dryer 25, gas-liquid heat exchanger 26, thermal expansion valve 27, condensation tower shell 28, third vacuum valve 29, fourth vacuum valve 30, vacuum water tank 31, first one-way valve 32, second circulating pump 33, sixth vacuum stop valve 34, second one-way valve 35, return water pipe 36, cooling tower 37, circulating water tank 38, seventh vacuum stop valve 39, water supply pump 40, third one-way valve 41, fifth vacuum valve 42, demister 43. DETAILED DESCRIPTION

[0020] The present invention will be further described in conjunction with the accompanying drawings.

[0021] In the present invention, the condensation tower structure is that the lower part of the condensation tower shell 28 is connected to the vacuum water tank 31 through the third vacuum valve 29, and the lower part of the vacuum water tank 31 is connected to the second circulation pump 33 through the first one-way valve 32. When the vacuum pump evacuates the rehumidification box 2, due to the effect of the first one-way valve 32, it can ensure that the vacuum in the box is not broken. When the vacuum is evacuated, the second circulation pump 33 is not opened. At this time, the condensed water flowing out from the lower part of the condensation tower shell 28 flows into the vacuum water tank 31. When the vacuum is stopped, the second circulation pump 33 is opened, and the first one-way valve 32 is opened under the action of water pressure, and the water in the vacuum water tank 31 is pumped out by the second circulation pump 33. The return water pipe 36 is pumped into the circulating water tank 38. The return water pipe 36 is cooled by the cooling tower 37 before entering the circulating water tank 38 to ensure that there is cooling water in the circulating water tank 38. During the vacuum pumping process, the water supply pump 40 is started, so that the cooling water in the circulating water tank 38 is sprayed out through the spray device on the top of the condensation tower. The spray device cools the gas entering from the rehumidification box 2, condenses the water vapor therein into water droplets and then falls. Then the remaining gas is defogged by the demister, the solid impurities therein are filtered out by the filter 3, and the water vapor therein is further condensed by the steam trap 4 to further remove the moisture in the gas, and then discharged through the vacuum pump.

[0022] The steam collector 4 is equivalent to a tubular heat exchanger. By placing the evaporator 16 of the refrigeration unit in the heat exchange shell 17, the medium in the heat exchange shell 17 is cooled. The two ends of the steam collection coil 11 of the steam collector 4 are respectively connected to the heat exchange shell 17. The medium circulates in the steam collection coil 11 and the heat exchange shell 17 through the first circulating pump 19 in the middle, and continuously brings the cooled medium into the steam collection coil 11. The steam collection coil 11 cools the space in the steam collection shell 10, so that the moisture in the gas passing through the steam collection shell 10 is cooled. During the vacuuming process, the first vacuum valve 8 on the upper part of the liquid storage tank 13 is closed and opened, and the second and third vacuum stop valves 15 are closed. At this time, the vacuum state is maintained, and the condensed water in the steam capture shell 10 flows out into the liquid storage tank 13. When it is necessary to drain the water, the upper first vacuum stop valve 12 is closed to ensure the vacuum degree of the upper part of the first vacuum stop valve 12, and the second vacuum stop valve 14 at the side end and the third vacuum stop valve 15 at the lower end are opened. The purpose of the second vacuum stop valve 14 at the side end is to break the air intake, which is conducive to the smooth discharge of condensed water from the third vacuum stop valve 15 below. The separator is an oil separator.

[0023] The first vacuum valve 8 connected between the secondary Roots pump 6 and the screw vacuum pump 7 in the present invention is used to close the vacuum pump after the vacuum is exhausted, so as to maintain the vacuum degree in the circuit, which is beneficial to energy saving. Of course, the vacuum valve can be removed, and the vacuum in the circuit can be obtained by the screw vacuum pump 7. The second vacuum valve 9 connected between the inlet of the primary Roots pump 5 and the outlet of the secondary Roots pump 6 can short-circuit the primary Roots pump 5 and the secondary Roots pump 6, and directly use the screw vacuum pump 7 to evacuate the system circuit.

[0024] When the present invention is used, the rehumidification box 2 is first evacuated to 8 kPa by the screw vacuum pump 7 (at this time, the second vacuum valve 9 is opened, and the first-stage Roots pump 5 and the second-stage Roots pump 6 are short-circuited), and then the second vacuum valve 9 is closed, the second-stage Roots pump 6 is opened, and the vacuum is evacuated to 2-3 kPa, and the first-stage Roots pump 5 is opened to reach a working vacuum degree of 400-1000 Pa.

[0025] When the system is vacuumed for the first time, the above vacuuming action and sequence are used. There is air and accumulated condensed water in the rehumidification box 2. When vacuuming, the air passes through the vacuum valve, condensation tower, demister, filter 3 and steam trap 4, and the vacuum pump to be discharged. In the later stage of vacuuming, a large amount of condensed water in the box is gasified, and the low-temperature and low-pressure water vapor is condensed into condensed water in the steam trap 4, reducing the load of the vacuum pump. The cold water circulation system of the condensation tower is not opened for the first time.

[0026] After the first vacuuming, steam is sprayed into the rehumidification box 2 to moisten the tobacco leaves. After moistening, the second vacuuming is performed. Because there is a large amount of water vapor in the rehumidification box 2, the cold water circulation system is first turned on. The water vapor comes out of the box and is condensed into water in the cooling tower 37 and temporarily stored in the vacuum water tank 31. The uncondensed water vapor is discharged through the demister 43, the filter 3, the steam trap 4, and then through the second vacuum valve 9 and the screw vacuum pump 7. At this time, since the tobacco leaves have been humidified, the primary and secondary vacuum pumps are no longer turned on for the second vacuuming, otherwise the water in the tobacco leaves will evaporate. Secondary moistening and reverse pumping can be performed as needed.

[0027] When it is finally finished, back-pumping is required. The function of back-pumping is to remove excess exhaust steam in the box. Secondly, it can adjust the temperature of the tobacco leaves to ensure temperature balance, and then break the air and output the tobacco leaves.

[0028] The present invention adopts the composite technology of condensation + vacuum, and condenses the low-temperature and low-pressure water vapor generated in the evacuation process into liquid through the steam trap 4, thereby reducing the workload of the vacuum pump, reducing the installed power of the vacuum system, protecting the mechanical vacuum pump group from steam corrosion, and shortening the evacuation time; compared with traditional equipment, achieving the same process parameters can significantly reduce the installed power or save working time, thereby achieving the purpose of saving energy consumption and improving the reliability of equipment operation.

[0029] Steam with a temperature below 33°C is called low-temperature steam, and steam with a temperature of (32-100)°C is called medium-temperature steam.

Claims

1. A tobacco leaf vacuum rehumidification machine of a composite vacuum device, comprising a refrigeration unit and a condensation tower structure connected to a rehumidification box (2) via a first pipeline (1), the upper end of the condensation tower structure being connected to a filter (3), the filter (3) being connected to a steam trap (4), the steam trap (4) being connected to a screw vacuum pump (7) via a first-stage Roots pump (5) and a second-stage Roots pump (6), a first vacuum valve (8) being connected between the second-stage Roots pump (6) and the screw vacuum pump (7), a second vacuum valve (9) being connected between an outlet of the second-stage Roots pump (6) and an inlet of the first-stage Roots pump (5), the steam trap (4) being composed of a steam trap shell (10) and a steam trap coil (11) in the steam trap shell (10), the steam trap coil (11) being connected to the refrigeration unit and supplied with a cold source by the refrigeration unit, the filter (3) and the first-stage Roots pump (5) being connected in the steam trap shell (10) of the steam trap (4); The lower portion of the steam capture housing (10) is connected to a liquid storage tank (13) via a first vacuum stop valve (12); the side wall and the lower end of the liquid storage tank (13) are respectively connected to a second vacuum stop valve (14) and a third vacuum stop valve (15); The evaporator (16) of the refrigeration unit is placed in a heat exchange shell (17); the steam capture coil (11) is connected to a first circulation pump (19) via an eighth vacuum stop valve (18); the first circulation pump (19) is connected to the heat exchange shell (17) via a fourth vacuum stop valve (20); and the heat exchange shell (17) is connected to the steam capture coil (11) via a fifth vacuum stop valve (21); The refrigeration unit comprises a compressor (22), the compressor (22) is connected to a separator (23), the separator (23) is connected to a condenser (24), the condenser (24) is connected to a dryer (25), the dryer (25) is connected to the heat exchange tube inlet of a gas-liquid heat exchanger (26), the heat exchange tube outlet of the gas-liquid heat exchanger (26) is connected to the inlet of an evaporator (16) via a thermal expansion valve (27), the outlet of the evaporator (16) is connected to the shell inlet of the gas-liquid heat exchanger (26), and the shell outlet of the gas-liquid heat exchanger (26) is connected to the compressor (22).

2. The tobacco leaf vacuum conditioning machine of the composite vacuum device according to claim 1, characterized in that: The condensation tower structure comprises a condensation tower shell (28), the rehumidification box (2) is connected to the condensation tower shell (28) via a first pipeline (1), a third vacuum valve (29) is provided on the first pipeline (1), the lower end of the condensation tower shell (28) is connected to a vacuum water tank (31) via a fourth vacuum valve (30), the vacuum water tank (31) is connected to a second circulation pump (33) via a first one-way valve (32), the second circulation pump (33) is connected to a sixth vacuum stop valve (34) via a sixth vacuum stop valve (35), and the second circulation pump (33) is connected to a second circulation pump (33) via a sixth vacuum stop valve (35). ) is connected to a second one-way valve (35), the second one-way valve (35) is connected to a return water pipe (36), the return water pipe (36) is connected to a circulating water tank (38) through a cooling tower (37), the lower end of the circulating water tank (38) is connected to a seventh vacuum stop valve (39), the lower part of the side wall of the circulating water tank (38) is connected to a spray device fixed in the upper part of the side wall of the condensing tower shell (28) through a water supply pump (40), a third one-way valve (41), and a fifth vacuum valve (42).

3. The tobacco leaf vacuum conditioning machine of the composite vacuum device according to claim 2, characterized in that: A demister (43) is installed in the condensation tower shell (28) at the upper part of the spray device.

Images