RU2269079C1 - Device for gas distribution in shaft grin drier - Google Patents

Abstract

FIELD: designed for convection drying of dispersed materials, applicable in agriculture and other branches.

SUBSTANCE: the device has drying, feeding and discharging branches, as well as feeding and discharging ducts or half-ducts located in the drying chamber in alternating rows, part of the area of their side walls is perforated. The feeding ducts by their open end surface are connected to the feeding chamber, and the discharging ducts - to the discharging chamber positioned on the opposite side of the drying chamber. The perforation is made in the lower part of the side walls of the ducts or half-ducts so that the line enveloping the upper boundary of the perforation area in the length of the duct or half-duct is non-linear and is remote from the lower edge of the wall at a distance providing an equality of the average values of gas consumptions along it.

EFFECT: enhanced uniformity of gas distribution along the ducts or half-ducts of the drying chamber, improved quality of drying and enhanced capacity of the drying equipment.

2 dwg

Description

The invention relates to the technique of convective drying of dispersed materials, for example grain, in a dense layer and can be used in agriculture and other industries.

The gas distribution device of shaft grain dryers is known (see Samochetov V.F. et al. Technical base of grain receiving enterprises (grain drying). M: Kolos, 1978, p. 89, fig. 20, a). The device contains a drying, inlet and outlet chambers, as well as inlet and outlet boxes or half-boxes placed in alternating rows in the drying chamber. The inlet and outlet boxes or half-boxes have the same cross section along their length, and the inlet boxes with an open end surface are connected to the inlet chamber, and the outlet boxes with a outlet located on the opposite side of the drying chamber.

The disadvantage of this device is the high degree of unevenness of the gas supply to the grain layer along the length of the boxes. At the same time (see Platonov P.N. et al. Distribution of heat carrier in shaft grain dryers // Grain storage and processing. TsINTI Goskomzag USSR. 1967. No. 1. - C.3-8) the highest gas supply is observed in the initial and final parts basins, and the smallest in their central part. Uneven gas supply leads to uneven heating and drying of grain in the drying chamber, which reduces the quality of drying and productivity of the dryer.

One of the reasons for the unequal gas flow is the uneven distribution along the ducts of the potential difference (pressure difference), which stimulates the gas flow in the drying space.

The results of gas flow modeling and experimental verification of the data obtained (see Izmailov D.A., Andrianov N.M. Study of gas distribution in a shaft grain dryer // Abstracts of reports of graduate students, applicants, students: X Scientific Conference of teachers, graduate students and students of NovSU, 1 -April 7, 2003 - Veliky Novgorod, 2003. - P.8.) It was confirmed that the value of the potential difference between the boundaries of the gas entry into the grain layer and exit from it varies non-linearly along the baskets. Moreover, the nature of the change in the potential difference along the baskets is identical to the nature of the change in the dependence of the gas flow along the basins obtained experimentally (see the article by Platonov PN and others. Distribution of the coolant in shaft grain dryers // Storage and processing of grain. TsINTI Goskomzag USSR. 1967. No. 1 . - C.7. Fig.3.).

This confirms the conclusion that since the potential difference (pressure difference) is the driving force of the particle flow, it is obvious that the nonlinearity of the potential difference function is the reason for the uneven field of gas velocity (flow) along the ducts in the drying chamber.

Based on the mechanism that explains the uneven flow of gas into the grain layer, two possibilities arise for correcting the aerodynamic situation. The first of these involves equalizing the potential difference (pressure difference) between the boundaries of the gas entering the grain layer and exiting it along the ducts in the drying chamber. However, the equalization of potentials along the ducts is a difficult task, the solution of which leads to a significant complication of the gas distribution system.

The simplest way to solve the problem of equalizing gas flow rates along the ducts is the method of changing the aerodynamic drag of the grain layer. To do this, it is necessary to change the resistance of the grain layer along the baskets so that, with the known nature of the nonlinearity of the distribution of the potential difference (pressure difference), to ensure the constancy of the average gas flow rates along them. This can be achieved by changing the path length (streamline length) of the gas flow from the boundary of the gas inlet into the grain layer to the boundary of the exit from it, which is easily realized by performing perforation in the side walls of boxes or half-boxes.

In the analyzed analogue, there is no perforation of the walls of the boxes, therefore, the length of the streamline, and therefore the resistance of the grain layer along the boxes are kept constant. It follows that with an uneven distribution of the potential difference (pressure difference) along the boxes and a constant value of the resistance of the grain layer, the gas flow along the boxes will also be uneven.

The closest to the proposed invention in technical essence and the achieved result is a gas distribution device in a shaft grain dryer (see article Platonov P.N., Lebedinsky V.G., Veremeenko EI. Distribution of coolant in shaft grain dryers // Storage and processing of grain CINTI of the State Committee of the USSR. 1967. No. 1. - C.3. Fig. 1, b.) - prototype. The device contains a drying, inlet and outlet chambers, as well as inlet and outlet boxes or half-boxes placed in alternating rows in the drying chamber. A part of the area of the side walls of the boxes or half-boxes is perforated, the supply boxes with an open end surface are connected to the supply chamber, and the discharge boxes are connected to the discharge chamber located on the opposite side of the drying chamber. Moreover, the perforation on the side walls of the boxes or half-boxes along their length is made uneven.

The disadvantage of this device is the uneven flow of gas into the grain layer along the length of the boxes.

This is explained by the fact that the potential difference (pressure difference) between the boundary of the gas inlet into the grain layer and the outlet from it along the length of the ducts (as shown above) is distributed nonlinearly. The minimum values of the potential difference are observed in the central part of the ducts, and the maximum at the beginning and end of the ducts.

To correct the aerodynamic situation, it is necessary to change the length of the gas flow lines, and, consequently, the resistance of the grain layer along the ducts so as to ensure the constancy of the average values of the gas flow along them. For this, it is necessary to leave unchanged the length of the flow lines in that part of the ducts in which the maximum potential differences are observed, and therefore the maximum values of gas flow rates. In those parts of the ducts where the potential difference, and therefore the gas flow rate is less, it is necessary to reduce the length of the gas flow lines. This will lead to a decrease in the resistance of the grain layer and, accordingly, to an increase in the average gas flow rate in this part of the duct.

In the prototype, although the perforation is made unevenly along the duct, the nature of its implementation does not provide a complete equalization of gas flow along it. In the prototype, approximately 75% of the length of the side walls of the boxes or half-boxes from their beginning (counting from the supply chamber) have uniformly perforated, and part of the length of the walls, approximately 25%, do not have perforations.

With this nature of the perforation along the length of the ducts, a greater length of the gas flow lines in the end part of the ducts and a shorter length of the flow lines in their initial and middle parts are provided. An increase in the length of streamlines in the final part of the ducts (where the potential difference is high) provides greater resistance of the grain layer to the gas flow and, as a result, creates conditions for reducing its average consumption.

In the middle part of the boxes or half-boxes (where the potential difference is less), the length of the streamlines is shorter, and therefore the resistance of the grain layer to the gas flow is less. This provides conditions for increasing gas consumption in the middle of the ducts. Thus, by changing the length of the gas flow lines in the prototype, the alignment of the average gas flow rates in the middle and final parts of the ducts is achieved.

However, in the initial part of the boxes where the potential difference is high (compared with the middle part of the boxes), the prototype has the same perforation as in the middle part of the boxes. This ensures a decrease in the length of the gas flow lines and, accordingly, a decrease in the resistance of the grain layer. Thus, due to the high potential difference and simultaneously low resistance to gas flow in the layer in the initial part of the ducts, conditions are created for even greater gas consumption. This leads to a high non-uniformity of gas flow along boxes or half-boxes.

Increased gas consumption in the initial part of the boxes or half-boxes and smaller in their middle and final parts lead to uneven heating and drying of grain. The danger of grain overheating necessitates a decrease in the drying intensity and leads to a decrease in equipment productivity. The unevenness of drying also leads to poor quality of the process.

The problem to which the invention is directed, is to ensure uniform distribution of gas along the ducts or half-boxes, as a result of which drying quality can be improved and the productivity of drying equipment can be increased.

The solution to this problem is achieved by the fact that in the proposed device, the perforation is made in the lower part of the side walls of the boxes or half-boxes so that the line enveloping the upper boundary of the perforation area along the length of the box or half-box is non-linear and is separated from the lower edge of the wall by a distance ensuring equal average values gas flow along it.

The perforation performance that is uneven along the length of the box or half-box makes it possible to take into account the uneven distribution along the box of the potential difference (pressure difference) between the boundaries of the gas entering and leaving the grain layer. Thus, the alignment of the average gas flow rates along the boxes or half-boxes is achieved.

The fact is that the distribution of the potential difference (pressure difference) between the boundaries of the gas inlet and exit from the grain layer is characterized by a nonlinear change along the ducts of the drying chamber. The potential difference reaches the minimum values in the central part of the ducts, and the maximum in their initial and final parts. Since the potential difference (pressure difference) is the driving force of the flow of gas particles, for this reason, conditions are created in the drying chamber along the ducts for lower gas flow rates in the central part of the ducts and higher costs in their initial and final parts.

The equalization of gas flow along the ducts in the proposed device is achieved by a corresponding change in the aerodynamic drag of the blown grain layer. To reduce the resistance of the layer (in the corresponding part of the box), it is proposed to shorten the length of the flow lines (path length) of the gas from the boundary of its entry into the grain layer to the boundary of its exit. This is achieved by performing perforations in the lower part of the side walls of boxes or half-boxes.

Since the potential difference along the duct varies non-linearly, the length of the gas flow lines must also vary non-linearly along the duct. Therefore, the line enveloping the upper boundary of the perforation region along the duct is non-linear. The distance at which it is located from the lower edge of the side wall of the duct is determined by the necessary length of the gas flow line in the corresponding part of the duct. This distance along the duct is selected in such a way as to ensure equality of the average values of gas flow along it.

Thus, in the proposed device due to the appropriate performance of the perforation of the side walls of the boxes or half-boxes, the alignment of the average values of gas flow along them is achieved. This provides a more uniform heating and drying of grain, improves the quality of the drying process. Due to a more uniform heating of the grain, conditions are created to increase the drying intensity, and therefore, to increase the productivity of drying equipment.

In addition, by increasing the intensity of the drying process, the specific energy intensity of the process can be reduced.

The gas distribution device in the shaft dryer is shown in FIGS. 1 and 2. FIG. 1 shows a part of the shaft dryer, a cross-section BB of FIG. 2; figure 2 is a longitudinal section aa of figure 1.

The device comprises a drying chamber 1, an inlet chamber 2 and a discharge chamber 3. The inlet 4 and outlet 5 gas distribution boxes or half box 6 are arranged in alternating rows in the drying chamber 1, the inlet boxes 4 being connected by an open end surface 7 to the inlet chamber 2, and the outlet boxes 5 open end surface 8 is connected to a discharge chamber 3 located on the opposite side of the drying chamber 1. The lower part of the area 9 of the side walls of both the inlet 4 and the outlet 5 boxes or half boxes 6 perforated by making holes, slots, shutters, etc. in them. Moreover, the line 10, enveloping the upper boundary of the perforation region (area) 9, is non-linear along the length of the duct and is spaced from the lower edge 11 of the wall of the duct 4, 5 or half-box 6 at a distance that ensures the equality of average gas flow rates along it.

The gas distribution of the proposed device is as follows. Heated gas from the inlet chamber 2 enters the inlet gas distribution boxes 4 through their open end surfaces 7. Then, through the open bottom of the boxes 4, it enters the layer of processed grain, heats it and absorbs the evaporated moisture. The exhaust gas enters the exhaust ducts 5 or half-box 6 through their open bottom and through their open end surfaces 8 enters the exhaust chamber 3.

The perforation 9, which is uneven along the length of the box 4, 5 or half-box 6, makes it possible to take into account the uneven distribution along the box of the potential difference (pressure difference) between the boundaries of the gas entering and leaving the grain layer. Due to this, the alignment of the average gas flow rates along the boxes or half-boxes is achieved.

The fact is that the distribution of the potential difference (pressure difference) between the boundaries of the gas inlet and exit from the grain layer is characterized by a non-linear change along boxes 4, 5 or half boxes 6 of the drying chamber 1. The potential difference reaches its minimum values in the central part of baskets 4, 5 or half-boxes 6, and the maximum in their initial and final parts. Since the potential difference (pressure difference) is the driving force of the flow of gas particles, for this reason, conditions are created in the drying chamber 1 along the ducts for lower gas flow rates in the central part of the ducts and higher costs in their initial and final parts.

The equalization of gas flow along the boxes 4, 5 or half boxes 6 in the proposed device is achieved by a corresponding change in the aerodynamic drag of the blown grain layer. To reduce the resistance of the layer (in the corresponding part of the box), it is proposed to shorten the length of the flow lines (path length) of the gas from the boundary of its entry into the grain layer to the boundary of its exit. This is achieved by perforation 9 in the lower part of the side walls of the boxes 4, 5 or half boxes 6.

The gas flow between the perforated boxes is as follows.

Through the perforated region 9 of the walls of the supply duct 4, part of the gas freely penetrates into the grain layer and along a shortened path (the gas path is shown by an arrow in FIG. 1) flows to the open bottom surface of the corresponding exhaust ducts 5 or half-boxes 6 located in the adjacent upper row. Another part of the gas through the open bottom of the box 4 enters the grain layer and moves along a shortened path to the perforated surface 9 of the corresponding outlet boxes 5 or half-boxes 6 located in the adjacent lower row. Thus, for both the upper and lower row of the outlet boxes 5 or half-boxes 6, the condition of gas flow along the shortened path is fulfilled. By shortening the length of the gas flow line, the aerodynamic drag of the grain layer in the corresponding part of the box or half-box is reduced and conditions are created for increasing gas consumption.

Since the potential difference along the box 4, 5 or half-box 6 varies nonlinearly, the length of the gas stream lines must also change nonlinearly along them. Therefore, the line 10, enveloping the upper boundary of the perforation region 9 along the box 4, 5 or half box 6, is non-linear. The distance at which it is separated from the lower edge 11 of the side wall of the box 4, 5 or half box 6 is determined by the necessary length of the gas flow line in the corresponding part of the box. This distance along the duct is selected in such a way as to ensure equality of the average values of gas flow along it.

Thus, in the proposed device due to the appropriate execution of the perforation 9 of the side walls of the boxes 4, 5 or half boxes 6, the alignment of the average values of gas flow along them is achieved. This provides a more uniform heating and drying of grain, improves the quality of the drying process. Due to a more uniform heating of the grain, conditions are created to increase the drying intensity, and therefore, to increase the productivity of drying equipment.

In addition, by increasing the intensity of the drying process, the specific energy intensity of the process can be reduced.

The use of the proposed gas distribution device is possible in various grain dryers of the shaft type, for example, dryers with boxes, louvres, etc. In these dryers, various working bodies for gas distribution are used, for example, boxes and half-boxes (in shaft dryers with boxes) or half-boxes (in louvre dryers). Regardless of the design of the dryer, the following are essential.

The inlet 4 and outlet 5 boxes (or half-box 6) should be located in the drying chamber 1 in rows alternating in height, and the inlet 4 with an open end surface 7 should be connected to the inlet chamber 2, and the outlet 5 with an open end surface 8 should be connected to the outlet chamber 3, located on the opposite side of the drying chamber 1. It is with such a design of the device that the nature of the potential distribution along the boxes of the drying chamber 1 will correspond to the above.

It is possible to use the proposed device in shaft dryers with a movable and fixed layer, as well as in chambers for heating, drying and cooling granular material, since regardless of the state of the layer and the purpose of the chamber, the nature of the distribution of potentials of gas flow between boxes or half-boxes in them is the same.

The method of perforation 9 of the side walls of the boxes 4.5 or half boxes 6 is not significant. Perforation can be made in the form of blinds, small slots, holes, mesh, etc. It is important that the gas permeability is ensured by a certain height of the side walls.

A feature of the proposed solution is its simplicity and manufacturability in the manufacture, since neither a significant change in the shape of the boxes, nor the installation of additional partitions is required.

Thus, in the proposed device due to a more uniform distribution of gas along the ducts or half-boxes, more uniform heating and drying of the material is possible. Due to this, the drying intensity can be increased, the productivity of the equipment is increased, and high quality of the processed material is achieved.

Claims (1)

A gas distribution device in a shaft dryer containing a drying, supply and discharge chambers, as well as supply and exhaust ducts or a half-box located in alternating rows in the drying chamber, with a part of the area of their side walls being perforated, leading with an open end surface connected to the leading chamber, and the outlet with a discharge located on the opposite side of the drying chamber, characterized in that the perforation is made in the lower part of the side walls of the boxes or half-boxes so that The envelope enveloping the upper boundary of the perforation region along the length of the box or half-box is nonlinear and is spaced from the lower edge of the wall at a distance that ensures the equality of average gas flow rates along it.

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