Multi-belt fluidized bed dryer

Abstract

The utility model relates to a heat and mass transfer process for drying dispersed materials and can find application in the chemical, mining, microbiological, construction and other industries, as well as in environmental processes for drying bulk waste. The technical result of the proposed design of a multi-belt fluidized bed dryer is an increase in the intensity of mixing of the particles being dried. The stated technical result is achieved in that in a multi-belt fluidized bed dryer containing a drying chamber, the dryer body is made in the form of a rectangular parallelepiped with two boxes located one above the other in it, formed by partitions in the transverse and longitudinal directions, and the lower plane of each box is formed by perforated conveyor belts with rollers, in the upper part of each box along its length, support rollers, longitudinal canopies are uniformly installed,hermetically closing the upper part at the edges of each box and forming a vertical gap between the edges of the support rollers and the lower surface of the canopies, in which the edges of the perforated belts are installed, a branch pipe for feeding wet material from the hopper, a branch pipe for feeding a fluidizing coolant, fixed in the cover, narrowing channels formed by inclined plates placed under each box, a branch pipe for unloading the dry product, located in the lower part of the body, inclined baffle plates for pouring material from one conveyor to another, and under the edges of the support rollers, which have a square cross-section, cylindrical springs are installed, connected to the frame of the dryer, the frequency of forced oscillations of which is determined by the formula where ν is the frequency of forced oscillations of the cylindrical spring, Hz; k = 4 is the number of faces of the support rollers; ω is the angular speed of rotation of the drive, rpm; D is the diameter of the rollers,m; l is the length of the side of the face at the ends of the support rolls, m. 4 fig.,

Description

[0001] The utility model relates to the heat and mass transfer process of drying dispersed materials and can find application in the chemical, mining, microbiological, construction and other industries, as well as in environmental processes for drying bulk waste.

[0002] A fluidized bed belt dryer is known, comprising a loading device for wet material, the body of which is made in the form of a rectangular parallelepiped, a fan, a system for cleaning the spent coolant and a furnace with a mixing chamber, in the body of the dryer two mesh belts are located one above the other, and the upper belt is lubricated with oil, for example, castor oil, and moves faster or slower than the lower belt, and in the body there are two chambers separated by a solid partition, in one of them the product is dried, and in the other it is cooled, and the supply of fluidizing coolant is carried out from the furnace with a mixing chamber through pipes fixed in the bottom of the body, under the belt and support grates, and wet material from a hopper located in the left part of the body is fed to the mesh belt, the unloading of the dry product is carried out through a pipe located at the other end of the belt, and the spent coolant is discharged through pipes,located in the housing cover, into the dust cleaning system [Patent for invention of the Russian Federation No. 2305238, IPC F28B 17 / 04, published on August 27, 2007].

[0003] The reasons that prevent the achievement of the specified technical result include high energy costs associated with the increased consumption of coolant under the belt and support gratings and friction of the belt against the support gratings.

[0004] A multi-belt fluidized bed dryer is known, comprising a loading device for wet material with a screw feeder, a drying chamber, a furnace with a mixing chamber, a turbo gas blower, wherein the dryer body is made in the form of a rectangular parallelepiped with at least two boxes located in it one above the other, formed by partitions in the longitudinal and transverse directions, wherein the upper plane of each box is formed by support gratings, and the lower plane is formed by perforated belts of at least two belt conveyors with rollers, and the supply of fluidizing coolant is carried out from the furnace with a mixing chamber through a branch pipe fixed in the cover, into the box, from which through narrowing channels formed by inclined plates placed under each box, under the belts and support gratings, and wet material from a hopper located in the upper right part of the body is fed to upper conveyor belt,and the dry product is unloaded through a branch pipe located in the lower left part onto the lower conveyor belt, and then onto the conveyor for dry material, and for pouring the material from one conveyor to another, inclined baffle plates are provided in the housing, and the exhaust air is discharged through a dust cleaning system [Patent for invention of the Russian Federation No. 2314471, IPC F26B 17 / 00, published 10.01.2008].,

[0005] The reasons that prevent the achievement of the specified technical result include increased energy costs associated with the friction of the perforated belts with the support gratings and their hydraulic resistance when supplying the coolant through the opening of the gratings of the perforated belts.

[0006] A multi-belt fluidized bed dryer is known, comprising a loading device for wet material with a screw feeder, a drying chamber, a furnace with a mixing chamber, wherein the body of the dryer is made in the form of a rectangular parallelepiped with at least two boxes located therein one above the other, formed by partitions in the transverse and longitudinal directions, wherein the lower plane of each box is formed by perforated belts of at least two belt conveyors with rollers, a branch pipe for feeding wet material from a hopper, a branch pipe for feeding a fluidizing coolant, fixed in the cover, tapering channels formed by inclined plates placed under each box, a branch pipe for unloading a dry product, located in the lower part of the body, inclined baffle plates for pouring material from one conveyor to another and a dust cleaning system for the spent coolant,in the upper part of each box, support rollers with the possibility of rotation are installed uniformly along the length, and the upper part of each box is hermetically sealed with longitudinal canopies, forming a vertical gap between the side surface of the rollers and the lower surface of the canopies, in which the edges of the perforated belts are installed [Patent for Utility Model of the Russian Federation No. 123915, IPC F26B 17 / 04, published 10.01.2013].,

[0007] The reasons that prevent the achievement of the specified technical result include the high consumption of the fluidizing coolant and, accordingly, high energy costs for creating a fluidized bed of the material being dried.

[0008] The closest technical solution to the proposed design in terms of a set of features and adopted as a prototype is a multi-belt fluidized bed dryer containing a drying chamber and a furnace with a mixing chamber, wherein the dryer body is made in the form of a rectangular parallelepiped with at least two boxes located in it one above the other, formed by partitions in the transverse and longitudinal directions, and the lower plane of each box is formed by perforated belts of at least two belt conveyors with rollers, a branch pipe for feeding wet material from a hopper, a branch pipe for feeding a fluidizing coolant fixed in the cover, tapering channels formed by inclined plates placed under each box, a branch pipe for unloading a dry product located in the lower part of the body, inclined baffle plates for pouring material from one conveyor to another, support rollers,installed uniformly along the length in the upper part of each box, longitudinal canopies, hermetically closing the upper part of each box and forming a vertical gap between the side surface of the support rollers and the lower surface of the canopies, in which the edges of the perforated belts are installed, and a system for dust cleaning of the spent coolant, characterized in that each support roller is a rod tapering from the edges to the middle, having an oval cross-section, while the edges of each support roll, located under the longitudinal canopies, have a cylindrical shape [Patent for Utility Model of the Russian Federation No. 138096, IPC F26B 17 / 04, published. 02 / 27 / 2014].,

[0009] The reasons that prevent the achievement of the specified technical result include low productivity of the dried material, as well as high energy costs for creating a fluidized bed on the perforated belt.

[0010] The technical result of the proposed design of a multi-belt fluidized bed dryer is an increase in the intensity of mixing of the particles being dried.

[0011] The technical result achieved is that in a multi-belt fluidized bed dryer comprising a drying chamber and a furnace with a mixing chamber, wherein the dryer body is made in the form of a rectangular parallelepiped with at least two boxes located therein one above the other, formed by partitions in the transverse and longitudinal directions, wherein the lower plane of each box is formed by perforated belts of at least two belt conveyors with rollers, a branch pipe for feeding wet material from a hopper, a branch pipe for feeding a fluidizing coolant secured in the cover, tapering channels formed by inclined plates placed under each box, a branch pipe for unloading a dry product located in the lower part of the body, inclined baffle plates for pouring material from one conveyor to another, support rollers having an oval cross-section,installed uniformly along the length in the upper part of each box, longitudinal canopies, hermetically closing the upper part of each box and forming a vertical gap between the side surface of the support rollers and the lower surface of the canopies, in which the edges of the perforated belts are installed, and a system for dust cleaning of the spent coolant, and under the support rollers, which have a square cross-section, cylindrical springs are installed, the frequency of forced oscillations of which is determined by the formula,

[0012] (1)

[0013] where ν is the frequency of forced oscillations of a cylindrical spring, Hz;

[0014] k = 4 - number of faces of support rolls;

[0015] ω - angular speed of drive rotation, rpm;

[0016] D - roller diameter, m;

[0017] l - length of the side of the face at the ends of the support rolls, m.

[0018] The implementation of cylindrical springs under the support rollers, which have a square cross-section, the frequency of forced oscillations of which is determined by formula (1), makes it possible to increase the intensity of mixing of particles of the material being dried on the perforated belt.

[0019] Figure 1 shows a general view of a multi-belt fluidized bed dryer, Figure 2 shows a cross-section A-A of Figure 1, Figure 3 shows a view A of the edges of the support roller and the perforated belt, Figure 4 shows a cross-section B-B of the support roller with a cylindrical spring.

[0020] A multi-belt fluidized bed dryer comprises a housing 1 in the form of a rectangular parallelepiped with a cover 2 and at least two boxes 3 located therein, one above the other, formed by transverse 4 and 5, as well as longitudinal 6 and 7 partitions. In the upper part of each box 3, support rollers 8 are uniformly mounted along the length and can rotate in bearings 9 and represent a rod tapering from the edges to the middle, having a square cross-section with a side length l at its ends. Support roller 8 with bearing 9 is connected through hub 10 by a cylindrical spring 11 to the frame 12 of the dryer.

[0021] The upper part of each box 3 is hermetically sealed with longitudinal canopies 13. Inside the housing 1, outside the boxes 3, rollers 14 and 15 with a diameter D are installed with two belt conveyors formed by perforated belts 16. The edges of each perforated belt are installed in the gap between the edges of the support rollers 8 and the lower surface of the longitudinal canopies 13 to form a pneumatic seal.

[0022] In cover 2, a branch pipe 17 is installed for feeding wet material from hopper 18, dry material is removed from housing 1 through branch pipe 19. Inclined baffle plates 20 and 21 are provided in housing 1 for pouring material from one conveyor to another. For feeding coolant from furnace 22 to corridor 23, a branch pipe 24 is installed, fixed in cover 2. Under each box 3, inclined plates 25 are installed, forming narrowing channels for feeding coolant from corridor 23 under belt 16. For removing exhaust air of coolant from corridor 23, a branch pipe 26 is installed in cover 2 of housing 1, which is connected by an air duct to dust cleaning system 27.

[0023] The multi-belt fluidized bed dryer works as follows.

[0024] The coolant is supplied from the furnace 22 with a mixing chamber through the branch pipe 24 into the corridor 23, from which, through the narrowing channels formed by the inclined plates 25, it is supplied between the support rollers 8 under each perforated belt 16 and is filtered through the openings of each perforated belt 16.

[0025] Wet material from hopper 18 is fed through branch pipe 17 to each perforated belt 16 of the upper conveyor, and dry product is discharged through branch pipe 19.

[0026] The coolant passes through the holes of each perforated belt 16 at a speed greater than the fluidization speed, forming a fluidized bed of particles of the material being dried.

[0027] The exhaust air of the coolant is discharged through the pipe 26 into the dust cleaning system 27.

[0028] Since each support roller 8 with a spring 11 is a rod tapering from the edges to the middle, having a square shape in cross-section, then when the support rollers 8 rotate, they force the perforated belt 16 resting on them together with the spring 11 to perform mechanical vertical vibrations, which are transmitted to the particles of the material being dried, shaking and mixing them, and the rod tapering from the edges to the middle, having a square shape in cross-section, forces these particles to move from the periphery to the center of the perforated belt 16. The described mechanical movements of the particles of the material being dried transfer them to the vibro-fluidization mode, which significantly intensifies the processes of heat and mass transfer of water vapor from the surface of these particles into the volume of the fluidizing coolant, which also makes it possible to reduce its consumption, and therefore the energy costs of the process drying.

[0029] Example. Let's calculate the performance of a multi-belt fluidized bed dryer. At a drive speed of 2.5 rpm, the length l of the edge at the end of support roll 8, which has a square cross-section (k = 4), is 0.1 m, and the diameter D of rollers 14 and 15 is 0.4 m.

[0030] According to formula (1), we will calculate the frequency of forced oscillations of the support roll 8

[0031] Hz.

[0032] The elasticity of the coil spring 11 is:

[0033] ,

[0034] where a is the elasticity of the coils of a cylindrical spring 11, N / m;

[0035] π is a mathematical constant denoting the ratio of the circumference of a circle to its diameter;

[0036] g - acceleration of gravity, m / s;

[0037] m – weight of support roll 8 with perforated tape and material, kg.

[0038] For a given coil spring elasticity of 11, a spring is selected according to GOST 13766-86. A spring with a wire diameter of d satisfies the requirements.п =1.6 mm, outer diameter of spring D п =16 mm, elasticity 21.53 N / mm.

[0039] Thus, the installation under each support roller 8, which has a square cross-section, of a cylindrical spring 11, the frequency of forced oscillations of which is determined by formula (1), makes it possible to carry out mechanical shaking and mixing of the particles of the material being dried during their movement with the perforated belt 13 in transport, which, in general, makes it possible to increase the intensity of mixing of the particles being dried.

Claims

A multi-belt fluidized bed dryer comprising a drying chamber, wherein the dryer body is made in the form of a rectangular parallelepiped with two boxes located therein one above the other, formed by partitions in the transverse and longitudinal directions, the lower plane of each box is formed by perforated conveyor belts with rollers, in the upper part of each box along its length, support rollers are uniformly installed, longitudinal canopies hermetically closing the upper part at the edges of each box and forming a vertical gap between the edges of the support rollers and the lower surface of the canopies, in which the edges of the perforated belts are installed, a branch pipe for feeding wet material from a hopper, a branch pipe for feeding a fluidizing coolant, fixed in the cover, tapering channels formed by inclined plates placed under each box, a branch pipe for unloading a dry product, located in the lower part of the body,inclined baffle plates for pouring material from one conveyor to another, characterized in that cylindrical springs are installed under the edges of the support rollers, which have a square cross-section, connected to the frame of the dryer, the frequency of forced vibrations of which is determined by the formula, where ν is the frequency of forced oscillations of a cylindrical spring, Hz; k = 4 - number of faces of the support rolls; ω - angular speed of rotation of the drive, rpm; D – roller diameter, m; l is the length of the side of the face at the ends of the support rolls, m.

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