Counter-Swirl Air Dryer

Abstract

The utility model relates to technology for drying dispersed materials and can be used in the microbiological, food, chemical, and other industries. In a pneumatic dryer with counter-swirling flows, comprising a drying chamber with a swirl device and a baffle plate, wet dispersed material feeders, a discharge device, a gas supply pipe for the first coolant flow, and a tangential gas inlet for the second flow, optimal ratios are selected for the diameter D1 of the drying chamber and the diameter D2 of the outlet pipe, as well as the height H of the drying chamber and the diameter D2 of its outlet pipe. According to the utility model, the drying chamber is equipped with a perforated shell and a draft device. The technical result of the pneumatic dryer with counter-swirling flows is an increase in the drying intensity. 1 Fig.

Description

[0001] The utility model relates to the technique of drying dispersed materials and can be used in the microbiological, food, chemical and other industries.

[0002] A combined spiral-vortex pneumatic dryer is known, containing a spiral channel, hermetically sealed at the top and bottom, respectively, with a lid and a bottom, forming a vortex chamber, an inlet and an outlet branch [USSR Author's Certificate No. 553424, F26B 17 / 10, published 05.04.1977].

[0003] The reasons that prevent the achievement of the specified technical result include the relatively low drying productivity of the final product.

[0004] A known design of a drying pipe is in which wet material is fed by a feeder into a stream of flue gases rising through a vertical pipe (a cylindrical shell welded from sheet steel), the lower part of which is connected to the furnace, and the upper part is combined with a cyclone [Lykov M.V. Drying in the chemical industry. Moscow: Chemistry, 1970, p. 226].

[0005] Factors that prevent the desired technical result from being achieved include adhesion of the drying material to the inner surface of the pipe above the feed point, which occurs when the wet product comes into contact with the hot wall. The high pipe wall temperature is caused by both the high heat transfer coefficient from the coolant (flue gases) to the wall and the high heat transfer coefficient of the all-metal shell.

[0006] A known design of a drying pipe for heat-resistant salts comprises a vertical pipe ending in a discharge chamber, the lower part of which has a nozzle for the introduction of flue gases from a sliding furnace. The wet material is fed into the coolant flow by two feeders-thrower located on diametrically opposite sides of the pipe [Sazhin B.S., Chuvpilo E.A. Typical dryers with a suspended bed of material. TsINTIKHIMNEFTEMASH, 1975, p. 12].

[0007] The reasons that prevent the achievement of the specified technical result include the complexity of the design and the adhesion of wet material to the heated walls of the pipe above the feed point.

[0008] A pneumatic tube-dryer design is known, comprising a vertical cylindrical pneumatic tube ending with an unloading device, and a device for feeding material, characterized in that the pneumatic tube is made sectional, the lower section of which is connected to a source of atmospheric air (fan) and a feeder, and the middle section, separated from the lower and upper sections (or only from the lower section) by inserts made of heat-insulating material, is made in the form of two coaxially located shells, the inner of which is provided with holes, and into the space between the shells - a spiral channel - a coolant is fed through a tangentially located branch pipe [Patent for invention of the Russian Federation No. 2476792, IPC F26B 17 / 10, published. 02 / 27 / 2013].

[0009] The reasons that prevent the achievement of the specified technical result include the adhesion of wet drying material to the walls of the cylindrical pneumatic tube and the unloading device.

[0010] A known design of a pneumatic dryer with counter-swirling flows, containing a drying chamber with a swirler and a baffle washer, feeders for wet dispersed material and an unloading device, a gas supply pipe for the first flow of the coolant, and a tangential gas inlet for the second flow, while a vibrator is fixed on the body of the drying chamber, the optimal operating parameters of which are: vibration level in the range of 70-85 dB, oscillation frequency in the range of 31.5-125 Hz, exposure time of 5 s with an interval of 30 s, and optimal drying modes are carried out with the following parameters: the ratio of the diameter D1 of the drying chamber to the diameter D3 of the outlet pipe lies in the optimal range of values: D1 / D3 = 1.6-1.8; the ratio of the height H of the drying chamber to its diameter D2 lies in the optimal range of values: H / D2=1.5-5.0 [Patent for invention of the Russian Federation No. 2340849, IPC F26B 17 / 10, published 12 / 10 / 2008].

[0011] The reasons that prevent the achievement of the specified technical result include insufficient drying intensity of the dried particles and the possibility of arching in front of the unloading device.

[0012] The technical result of the proposed design of a pneumatic dryer with counter-swirling flows is an increase in the drying intensity of the particles being dried.

[0013] The technical result achieved is that in a pneumatic dryer with counter-swirling flows, containing a drying chamber with a swirl and a baffle washer, feeders for wet dispersed material and an unloading device, a gas supply pipe for the first flow of the coolant, and a tangential gas inlet for the second flow, and optimal drying modes are achieved with the following ratios of the diameter D1 of the drying chamber and the diameter D2 of the outlet pipe:

[0014] D1 / D2=1.6-1.8; (1)

[0015] where D1 is the diameter of the drying chamber, m;

[0016] D2 - outlet pipe diameter, m;

[0017] and the height H of the drying chamber and its diameter D1:

[0018] H / D1=1.5-5.0; (2)

[0019] where H is the height of the drying chamber, m;

[0020] with a perforated shell and a draft device.

[0021] The design of the drying chamber, equipped with a perforated shell, into which air flows are supplied using a draft device, allows for the processing of materials with increased adhesive capacity, lump and aggregated materials that will not stick to the inner surface of the drying chamber, which will lead to an increase in the drying intensity of the dried particles.

[0022] The figure shows a general view of a pneumatic dryer with counter-swirling coolant flows.

[0023] The counter-swirling coolant flow pneumatic dryer comprises an exhaust pipe 1, a drying chamber 2, a swirler 3, a baffle plate 4, a discharge device 5, a gas supply pipe 6 for the first coolant flow, feeders 7, and a tangential gas inlet 8 for the second flow. A perforated shell 9 and a draft device 10 are fixed to the body of the drying chamber 2, supplying atmospheric air necessary for removing wet or unfinished product adhering to the walls of the drying chamber 2.

[0024] When drying dispersed materials with a long second period, it is advisable to carry out drying in "softer" modes after removing free moisture. To ensure such modes, it is necessary to maintain optimal ratios of the dryer's design parameters, namely: the ratio of the diameter D1 of the drying chamber 2 to the diameter D2 of the outlet pipe lies in the optimal range of values ​​according to relation (1); the ratio of the height H of the drying chamber to its diameter D2 lies in the optimal range of values ​​according to relation (2).

[0025] The counter-swirling air dryer operates as follows.

[0026] The wet dispersed material forms a gas suspension with the coolant supplied to the drying chamber 2, which is swirled by a vane or tangential swirler 3. The first swirled flow of the gas suspension from the gas supply pipe 6 is directed upward along the central portion of the pneumatic dryer, while the second flow from the gas inlet 8, swirling in the same direction, is directed downward. Particles of dispersed material from the internal flow are thrown toward the periphery of the pneumatic dryer under the action of centrifugal forces and transported by the second flow to the lower portion of the drying chamber, from where they are removed through the unloading device 5. The interaction of the two counter-swirling flows creates favorable conditions for the separation of the dispersed and gas phases, which results in high drying and dust collection efficiency in these devices. Through the draft device 10, air is supplied into the cavity of the perforated shell 9, from which all particles adhering to the internal cavity of the drying chamber 2 are removed.

[0027] Example. Let's calculate the process parameters of the drying process in the proposed design of a pneumatic tube dryer operating with an initial capacity for wet material, G н = 1000 kg / hour. Table salt is fed into drying chamber 2 for drying. For convenience, the main initial data and calculation parameters are summarized in Table 1.

[0028] Table 1

[0029] Parameter name Dimension Size Initial wet material capacity, Gн kg / hour 1000 Initial moisture content of the input material, wн1 kgW / kgG 0,06 Final moisture content of the material at the outlet, wk1 kgW / kgCk 0,002 Air temperature, t0 °C 25 Relative humidity of ambient air, φ - 0,5 Air temperature at the dryer inlet, t1 °C 200 Air temperature at the dryer outlet, t2 °C 75 Performance of removing moisture from particles, W kgW / hour 58,12 Productivity of drying material, Gk kgGk / hour 941,88 Performance for absolutely dry particles, G kgG / hour 940,0 The rate of removal of particles of the material being dried, νy m / s 7,43 Average air velocity in the drying pipe, νв m / s 8,92 Reynolds number for the onset velocity of fluidization, Re0 - 15,4 Air velocity for the onset of fluidization, ν0 m / s 0,401 Average flow rate of moist air in the dryer pipe, Lc kg Lc / hour 1463 Calculated diameter of the dryer pipe, Dyt m 0,26 Volume of the dryer pipe, calculated taking into account heat transfer, Vat m3 0,54 Dryer pipe height calculated taking into account heat transfer, Hgt m 10,2 The device's moisture resistance, calculated taking into account heat transfer, At kgW / m3⋅hour 105,9

[0030] Thus, the proposed design of a pneumatic dryer with counter-swirling flows with an installed perforated shell 9 and a draft device 10, allows processing materials with increased adhesive capacity, lump and aggregated materials, as well as a number of products with a fine-porous structure, which will ultimately lead to an increase in the drying intensity of the dried particles.

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