DE2404608A1 - METHOD AND DEVICE FOR REGULATING THE TEMPERATURE AND THE MOISTURE CONTENT OF FABRIC PARTICLES - Google Patents

Description

^ ***** ' Patent Attorneys
Dipl. Ing. F. Weickmann,? * ». '
Dipl. Ing. H. Weickmann, Dipl. Phys. Dr. K. Fincke 2 4 OA 6 O 8

Dipl. Ing. F. A. Weickmann, Dipl. Chem. B. Huber

- .. 8 Munich 27, Möhlstr. 22 ^

AMF INCORPORATED

777 V'estchester Avenue

White Plains, New York V.St.A.

Method and device for regulating temperature and the moisture content of particulate matter

The invention relates to an improvement in the regulation of the moisture content in tobacco or in other material particles, which, however, has a large surface area in relation to its volume such as fibrous material such as cut tobacco leaves.

It is necessary during the processing of the tobacco leaves that the tobacco has a constant moisture content, in particular, when the dried and chilled cut tobacco (Schnitzeltabak-rag) delivered to a cigarette factory. It is necessary that every gram of schnitzel tobacco which is used for the manufacture. position of a sigeirette is used, the same moisture content like the nearest 'gram.

There is some variation in the moisture content of the tobacco, ' which is delivered to the cigarette studio, and it becomes a

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minimum cigarette weight and thus a target weight aimed for, so that an appropriate density is achieved to allow this scatter. If the scatter range of the moisture content can be restricted, so can the minimum Cigarette weight and thus the target weight is reduced increasing the cigarette yield per kilo of tobacco.

Reached the most even moisture content of tobacco one then when all tobacco particles are in a state of equilibrium have the same temperature and vapor pressure and all grades are evenly mixed in one pile. The moisture content of each tobacco particle is not the same. The quality, the harvest, the location of the plant, the aftertreatment, etc. are all influences that affect the vapor pressure of a certain moisture content, so that the equilibrium state for all tobacco particles is achieved with changing moisture levels. If the tobacco particles are evenly mixed, then each contains Sample for moisture analysis a uniform mixture with an equal moisture content, so that a the same moisture content is detected. Such an even moisture content depends on the mix as well as on the temperatures and vapor pressures of the equilibrium state away.

Mixing is achieved nowadays by first using sheet mixing containers which contain the various Coarsely mix tobacco qualities by layering them together so that a 100-200 pound filling (45.4 to 90.7 kg) Contains equal proportions of each quality. Second through the system that determines the stem weight of the cut stems

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compensates for by increasing the throughput of the cut sheets a weighing conveyor is measured to pick up 10-20 pounds per unit time (4.5-9 kg). And third through a rotary dryer, obtained by blending about 20 pounds of the shredded tobacco into a foot of cylinder length (9 kg per 30 cm) ensures a pure mixture of the cut fibers, so that every tobacco quantity intended for a cigarette has the same mixture dump.

Only moderately accurate moisture levels are achieved nowadays by checking the moisture level of the tobacco prior to drying and after cooling is measured by means of electrical devices and that the measurement is used to control the dryer added: heat is used to achieve the desired result. But at best, this procedure corrects the long-term ones Changes or the mean moisture content of a TobaccoKienge is very large compared to the weight of a single cigarette.

If the best available equipment is used, the tobacco can, after drying, be about 5 ° relative to the surroundings be cooled, but in general the cooling is worse.

A final balance of humidity and temperature is achieved nowadays by storing the tobacco in storage silos. Adjacent while balancing Tobacco particles takes place, is a compensation of the Zuntandes distant particles in an acceptable time and using an acceptable space is not possible because the Effect of "mixing" through the degree of diffusion of the vapor is limited at a relatively high lump density of the tobacco mass.

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The present invention is directed to providing a device by means of which by means of a sustained, very rapid "Mixing" the momentary changes in moisture content can be balanced and with v / elcher the moisture content and the tobacco temperature with great accuracy on predetermined Values can be brought.

According to the invention there is a method for controlling the temperature and the moisture content of particles of matter suggested, which is characterized in that a stream of air is passed through the material particles, its temperature and relative humidity in equilibrium with the desired moisture content and the temperature of the particulate matter is before the air passes through the fabric particles.

The process of balancing or smoothing and correcting e.g. the tobacco moisture content is carried out by an adiabatic Absorption or desorption that occurs at room temperatures. Heat is absorbed or released through the air. Of the The process is slow, because the only temperature difference available for heat transfer is due to the "modified" Temperature of "wet tobacco" or "reverse temperature" that the tobacco assumes, is formed ("modified wet bulb" or "reverse wet bulb" temperature). The modified temperature, because the water in the tobacco is not in steam, so the steam pressure is reduced, and the temperature reversed, because the tobacco is hotter than the air when it absorbs moisture instead of releasing it or evaporating it. Of the The degree of absorption or degree of desorption is proportional to the difference between the vapor pressure of the tobacco and the air, i.e. proportional to the difference in the moisture content of the Tobacco for a balanced moisture content. Therefore, there is a tobacco whose moisture content depends on the equilibrium moisture

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ity content deviates, according to an exponential function on the State of equilibrium, while a tobacco whose moisture content is close to the state of equilibrium or assumes this state of equilibrium, essentially none Shows reaction.

An air is used to carry out the method according to the invention with a precisely defined relative humidity is required. For example, for a shredded tobacco with 14% moisture content after drying and chilling, a typical equilibrium state of 60% relative humidity 70 ° Fahrenheit (22 ° C) required. A change in relative humidity of 2.5 to 5% corresponds, depending on the Mix one percent tobacco moisture content. The relative humidity should therefore be within a range of + 0.25% can be maintained. Changing the air temperature by 1 ° Fahrenheit changes the relative temperature Humidity of the air with a solid Darapfinhalt by approximately 3.3%, so that the air temperature is also very accurate within a range of + 0.08 ° Fahrenheit must be adhered to. To ensure a constant supply of fresh air, the one has relative humidity and a temperature which exactly correspond to the required values, the air is preferred circulated.

The heat capacity of the circulating air is small compared to the heat capacity of the tobacco on the conveyor, as is the weight of the tobacco in the air. The water vapor present is small in relation to the weight of the water present in the tobacco. In this way, off the tobacco exiting air is the average temperature of the tobacco and again assumes a relative humidity, corresponding to the average moisture of the tobacco.

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The temperature of the air that is returned to the tobacco, can be thermostatically controlled by, for example, heating or cooling the coils so that the tobacco is on the desired temperature is brought. This temperature control does not need to be done very precisely, since the relative humidity of the air affects itself on the equilibrium state regulates by withdrawing or adding a negligible amount of moisture content to the tobacco.

The moisture content of the tobacco is balanced by the air circulation, but the average moisture content does not change. In order to correct the mean moisture content., The circulated air gets water vapor in a certain amount supplied or withdrawn, the amount corresponding to that amount which is withdrawn or supplied to the tobacco got to.

The water vapor can be supplied in vapor form through water nozzles, the water being supplied by pressure, compressed air or a centrifugal force atomizer is atomized and in such a case the water addition from an adiabatic cooling of the air is accompanied. The water can also be supplied in the form of steam by using one or more nozzles Steam flow is initiated or by a water surface, to which water and heat is supplied in a certain amount, is heated, the air temperature being essentially unchanged remain.

The water vapor can be removed by passing a suitable portion of air through the bed of desiccant such as silica gel or cooled pipe coils, so that the water vapor condenses.

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The control of the amount of water vapor that the circulated air added or withdrawn does not have to be very precise. The correction of the moisture of the tobacco usually exceeds not 1% moisture content, so there is a major error of 10% in the amount of steam withdrawn or added to the air makes an error of only 0.1% of the corrected moisture content of the tobacco.

The amount of water vapor can be controlled in two ways take place. Firstly, it is controlled by measuring the moisture content of the tobacco by a continuously responsive one Moisture meter. In the simplest possible form a single measurement is made behind the moisture compensation conveyor, whereupon the measurement signal for the moisture is fed back to a control device, where the signal is compared with the value of the desired humidity, and the control signal is then used for the total measurement of the to be fed or steam to be discharged.

In a more complicated system, additional measurements of the moisture content are made prior to the moisture equalization and the tobacco throughput and .the to be added or the amount of water vapor to be removed is calculated. That calculated Signal is used as a feedforward control through which a corresponding amount of water vapor is supplied or discharged. The feedback control can be matched with the feedforward control can be combined so that any errors that may result from feedforward control are canceled out will.

The method described above depends on the accuracy of the moisture measurements to be carried out on an ongoing basis. There are

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various electrical procedures possible that too are acceptable Results, but no method has the accuracy required by the industry.

In the second method for controlling the water vapor outtake odor removal from the air and thus to control the average moisture content of the tobacco is the relative The humidity of the air is measured and controlled by the steam extraction or steam supply at a constant level Value held. In a good tobacco blend, the balanced relative humidity of the air is a measure of the moisture content of tobacco. The relative humidity can be measured using various known methods, and the measured value is then compared in a control device with the desired value, and the control device outputs in turn then emits a control signal by which the amount of steam to be added or removed is set, so that the relative humidity is kept at a constant value.

In practice, it is generally more common to keep the tobacco while the drying and cooling stage to overdry a little and only add moisture (and remove heat) in the equalizing device. This is done from various Establish:

1. Tobacco absorbs moisture more easily than it gives it off;

2. Cooling coils are required to dissipate the heat of absorption (heating coils would be required for desorption);

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3. Cooling coils are definitely required to remove the to dissipate the heat generated by the fan required for air circulation;

4. The tobacco is generally through the existing cooler insufficiently cooled, so that further cooling is required in the compensation device. It is therefore additional cooling coils are required to dissipate this heat;

5. It is easier to add a certain amount of water with the help of metering pumps or flow meters than one discharge dosed amount of water and

6. There is little hysteresis in the absorption and desorption of moisture in the leaves, so it is preferred will cause the equalizer to either add or remove moisture instead of doing both.

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Further features, advantages and details of the invention are are given in the following description of an exemplary embodiment with reference to the drawing. Show in it:

Fig.1 is a schematic sectional view of a known Construction of a spiral cooler for tobacco;

2 shows a schematic sectional view of an embodiment according to the invention, in which the in the cooler shown in Fig. 1 with a P.rückführsystein is equipped, and

3 shows a plan view of the embodiment shown in FIG.

The device shown in Figure 1 is a spiral cooler, to which the tobacco is fed via a conveying device 10 and then deposited on a spiral-shaped, perforated tray 11 which is supported in its cement by a cylinder 13 forming a central shaft. Filing 11 is provided on its outer circumference with an upwardly projecting edge 14 and has an air duct on its underside 16 (drying chamber), which is connected to the interior of the cylinder 13 via bores 17.

The spiral-shaped tray directs the tobacco upwards by the shelf by means of a drive device 19 (which is not shown in detail) in vibrations and one upwards directed rotary movement is offset, so that the tobacco on the spiral tray in successive steps is shaken upwards until it is removed by a vibrating conveyor 20.

The cooling air enters the scroll cooler through an inlet 22

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a, whereby it is sucked in by a suction fan 23 / which the air in the cylinder. 13 down, through holes 17 in passes through the air duct 16 and from there through the tobacco arranged on the shelf. The air then brushes over the Edge and along the sides of the shelf down and through the exhaust duct 25 to the outside.

To carry out the method according to the invention is the 2 and 3 shown tobacco treatment device with a Equipped spiral cooler, which corresponds essentially to the cooler shown in Figure 1 / but is adapted to the system. A conveyor 26 leads to the lower part of a spiral-shaped, perforated tray 28, which is in its center by a a central duct forming cylinder 29 is carried. The shelf is on its outer periphery with an upward reaching Edge 31 is provided and has an air channel 32 (drying chamber) on its underside, which via bores 34 with the interior of the cylinder 29 is in communication.

A drive device not shown with its details 35 is used to set the spiral tray 28 vibrating and to give it an upward rotary movement to lend. An independent rectilinear vibratory conveyor 37 leads away from the top of the spiral tray. The spiral tray 28 is supported on links 38 and is of a thermally insulated stationary housing 40 enclosed.

A slot 41 which is arranged in the housing base on the circumference of the housing is followed by a screw-shaped slot or rounded duct 42, which is for the inlet of an air cleaning device 43 leads, which in turn has an insulating housing 44, at the lower end of which is a very effective

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Kungsvoll fan 46 is arranged. On the fan 46 is a diverging wind hood 47 is connected, which is inserted into a roller filter 49 arranged above the fan for the air flow opens. Another plate filter 50 is between the roller filter and one of several rows of tubes existing air cooler 51 arranged, the cooling coils from a provided with a control valve 54 main supply line 52 are supplied with cooling water. The outlet 53 of the ventilation device is via an air turner 56 channel 55 provided and connected via a flexible connection 59 to the upper end of the cylinder 29 carrying the tray 28. The channel 55 is equipped with water vapor distribution device in the form of steam nozzles 60, which by a Humidity meter 62 are controlled, which is used to measure the relative humidity and within the channel 55 in the immediate Located near the air inlet in the cylinder 29 and connected to a humidity control device, not shown connected. The steam nozzles 60 are supplied with steam via a feed line 61 and a control valve 65. By doing An air temperature meter 64 is also arranged in duct 55 and is connected to a temperature control device (not shown) and the temperature device is used to control the flow of water through the tubes of the air cooler 51.

The device shown in Figures 2 and 3 works as follows. Dried tobacco whose moisture content is below the desired moisture level and which is on a temperature is cooled, which is above the desired temperature, is with the conveyor on the spiral Filing 28 promoted. Air is introduced into the spiral duct via the central duct by passing through the in the bores located in the cylinder wall is introduced radially into the channel (drying chamber), which is located under the per-

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called storage is located, with a pressure drop in the channel a distribution of air 'favored. The air is drawn from the housing through the circumferential slot 41 to the helical or rounded channel 42 derived. The air rises through the tobacco lying on the shelf, the heat being absorbed by the tobacco and released into the air in one Ratio is transferred, which depends on the temperature difference between the tobacco and the air, and the humidity is absorbed in a ratio that depends on the moisture content of the tobacco and the relative humidity . is dependent. The air drawn through the tobacco is therefore hotter and drier than before.

The hot dry air then flows through channel 42 to the air * * cleaning device 43, where the air-entrained dust is removed from the filters 49 and 50. A measured one Amount of cooling water circulates through the cooling coils of cooler 51 to cool the air and a measured amount of steam gets the air through the nozzles. 60 added. If the air then returns to the spiral shelf then tiba: channel 55 strokes them on the temperature meter 64 and the humidity meter 62 over. The temperature control device compares the measured temperature with a predetermined temperature value for the air and, as a function of the comparison value, adjusts the control valve 54 to regulate the flow of cooling water to the radiator 51 to change. The control device for the relative air - humidity compares the measured value of the relative air, humidity with a predetermined value and represents depending of the comparison value, the control valve 65 is switched on in order to change the amount of steam flowing through the nozzles 60. To this The recirculated air enters the spiral tray with a certain temperature and a certain rela-

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tive humidity.

The temperature and relative humidity of the in the Air entering in a spiral shape is dimensioned in such a way that these values correspond to the desired temperature value and the balance desired moisture content of the tobacco exiting the device.

The upward rotational movement of the shelf causes the tobacco to progressively upward along the shelf spiral vibrated until it is discharged via the vibrating conveyor 37 will.

The above-described system receives its thermal energy by heating the air in three ways, namely Abgabedder heat when cooling the tobacco, releasing heat when absorbing moisture and generating heat when compressing it the air through the blower.

The air cleaner 43 is isolated and the partition conveyor is placed in an insulated housing 40 so that the heat exchange with the ambient air, in case there is this differs from the controlled temperature is negligible. Most of the heat is absorbed by a adiabatic cooling of the air balanced when a water sprinkler is used. The cooling coils are in several Arranged in rows and v / iron a high thermal conductivity, so that the cooling coil temperature does not fall below the dew point which normally falls 5.5 degrees (10 degrees Fahrenheit) below air temperature lies. When such a temperature is reached, the humidity in the air would be withdrawn from the system, in particular in the places where the air in the queues around

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the SamiTielrohre is standing around.

The cooling coils are water cooled using tap water and the tap water is either drained away or put back into circulation by a cooling tower or by a cooling system.

In addition to being simple in structure, the circulating system described above has the advantage that it does not have precise temperature control requires and since the system adjusts itself as a function of the humidity equilibrium, it requires no precise control of the steam supply ..

The distribution conveyor can be a flow layer conveyor, a fabric belt conveyor, or a vibrating, perforated shelf. The main grants exist in a long dwell time of about 5 to 15 minutes and a large ventilation area, thus a maximum amount of air comes into contact with every tobacco component supplied. However, it becomes a perforated, spiral-shaped one Plant preferred because a flow layer is not very good is suitable for tobacco because the surface area is small and the tobacco products cannot be easily swirled. It Belt conveyors can be used, although the air tends to sweep past the deeper or denser parts of the tobacco layer if the tobacco layer is not uniform is what is inevitable.

The most suitable ventilation device is formed by the swinging shelf with the perforated bottom. A special The advantage of this device is that the air resistance of the perforated storage shelf is several times greater as the deepest part of the tobacco layer can be made,

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by using a perforation that is only about 2 1/2% of the entire surface, the perforation e.g. holes 1/16 "diameter (1.6 mm) and an offset of 3/8" (9.5 mm). This way you can get a more even Air flow are generated, which is essentially independent of the depth of the tobacco layer. The efficiency of the The air flow is therefore very large, and a smaller ventilation area can be selected than this during use a fabric tape is required.

A belt ventilation device can also be provided in which a perforated belt is used, the holes of which are used have the same properties as the swinging shelf,

In a preferred embodiment, a spiral shelf is used which provides a very long shelf surface in a small space, e.g. 10 turns 6 foot-9 inch outer diameter 4 foot-9 inch inner diameter 180 feet-0 inch χ 12 inch shelf surface (2.06 m outside diameter χ 1.45 m inside diameter, 54.9 m χ 0.3 m), which with a diverted air flow of 8000 cfm (13600 m ³ / h) and a tobacco dwell time of 5-10 minutes for a treatment of 2000 lb / hour tobacco (907 kg / h) is used, the mean deviation of the moisture content being reduced by a factor of approximately 3.

The air purifier and the connections z "are spiral-shaped around Conveyors are carefully sealed against leaks so that only the housing of the spiral conveyor at the tobacco inlet and the outlet channels is open to the atmosphere, these openings to the environment through one or more curtain seals are sealed. In this way,

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essentially no exchange between the air in the system and. the environment.

It is also possible to use measuring devices for measuring the Temperature and humidity of one of the air purification devices supplied by a separate device To arrange air in the air path of the device according to the invention.

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Claims (17)

Claims 1.) Procedure for regulating temperature and moisture content of particulate matter, characterized in that an air flow through the particulate matter is passed through, its temperature and relative humidity in equilibrium with the desired moisture content and the temperature of the particulate matter before the air passes through the particulate matter. 2. The method according to claim 1, characterized in that the air after passing through the particulate matter is redirected again. 3. The method according to claim 2, characterized in that that the temperature of the redirected air is thermostatically controlled. 4. The method according to claim 2 or 3, characterized in that the relative humidity of the again diverted air is controlled in that the re-diverted air water vapor is supplied or withdrawn. 5. The method according to claim 4, characterized in that that the water vapor is added in a certain amount to the air via a water nozzle. 6. The method according to claim 4, characterized in ', that the steam is added as a certain amount of steam. 409833/0762 - 18 - 7. The method according to any one of claims 1 to 6, characterized in that the water vapor is again diverted air is withdrawn by a controllable amount of the diverted air through a dry substance or through cooled pipe coils. 8. The method according to any one of claims 1 to 7, characterized in that the relative humidity The air is measured before the air passes through the particulate matter and is kept constant by adding or removing a certain amount of water vapor from the air will. 9. The method according to claim 1, characterized in that that the material particles are arranged on a spiral-shaped shelf, that the shelf in upwards directed torsional vibrations is offset so that the particles move up along the shelf that the Air is directed essentially over the length of the shelf up through the S.toffteilchen that the air after the passage through the material particles is cooled and enriched with water vapor that the temperature and the relative humidity of the air can be measured so that the temperature and relative humidity are kept constant by regulating the strength of the cooling and the amount of added water vapor, and that the air is passed through the fabric particles again while they move along the shelf. 10. Device for performing the method according to one of claims 1 to 9, characterized by - 19 409833/0762 a spiral-shaped tray (11), a device (26) for conveying the material particles to the spiral-shaped deposit, a drive device by means of which the spiral-shaped Deposit is set in an upward rotary oscillation, through which the particles of matter on the spiral Move up the tray, a device (37) for removing the particles of material from the upper end of the spiral-shaped Tray, a device (46,47,55,56,59,34) for recirculating the air through the spiral tray, a device (51,60,65), which is used to cool eggs and by means of which the recirculated air water vapor is added, measuring devices (62,64) for measuring the temperature and the relative humidity of the recirculated air and control devices to adjust the amount of cooling and the amount of added water vapor as a function of one between the measured temperature and the relative humidity and the air temperature and the relative humidity occurring difference, whereby these values correspond to the values the particles of matter are in a state of equilibrium, if the air is at the desired temperature and moisture content. 11. Apparatus according to claim 10, characterized r that said means for removing the particulate matter from the upper end of the spiral deposition of a linear vibratory conveyor is formed (37). 12. The apparatus of claim 10 or 11, characterized geke η nzeichnet in that the means for returning the air a fan (46), a channel is performed (42) by means of which the air from the spiral-shaped tray to the fan, and a channel ( 55), by means of which the 409833/0762 - 20 - Air is directed from the fan (46) to the spiral tray will. . ■ 13. Device according to one of claims 10 to 12, characterized in that the device for cooling of the recirculated air has cooling coils which are arranged in the path of the recirculated air and through which a cooling liquid flows. 14. Apparatus according to claim 13, characterized in that marked net that the control device to adjust the amount of cooling has a control valve (54) which is arranged in the supply line (52), by multiplying the cooling liquid is fed to the cooling coils, 15. Device according to one of claims 10 to 14, characterized characterized in that the device means which water vapor is added to the recirculated air, has at least one steam jet nozzle (60) which is in the Path of the recirculated air is arranged. 16. The device according to claim 15, characterized net / that the control device to adjust the amount of the added water vapor has a control valve (65) which is arranged in the feed line (61), via which the steam jet nozzle or nozzles are supplied with the steam will. ■■. 17. Device according to one of claims D to 16, characterized characterized that in the path of the returned Air a filter (49) is arranged. - 21 - 409833/0762 Blank page