RU2051322C1 - Method of processing granular materials - Google Patents

Abstract

FIELD: heat-and-mass exchange technique. SUBSTANCE: in the beginning of process, particles of granular material are brought to suspended state. Then speed of their motion is increased to create maximum concentration, after which speed is reduced till pseudocleaned thin layer is formed and heat-transfer agent is passed through layer of particles in counter flow to their complete coagulation. EFFECT: enhanced efficiency. 3 dwg

Description

 The invention relates to processes of heat and mass transfer between wet or hot granular material, can find application in the chemical, metallurgical, construction and other industries, in particular, when cleaning gas from dust.

 Known methods of processing granular materials [1] which consists in imparting a material to a suspended state, as a result of which large coagulated particles precipitate.

 The disadvantage of these methods is that there is no gas purification from small particles.

 A known method of processing granular materials [2] consisting in the fact that the drying of the material is carried out in suspension.

 The disadvantage of this method is the weak gas purification from fine particles and the low intensity of heat and mass transfer.

 The objective of the invention is to propose a method of processing granular materials, which would be free from these disadvantages, i.e. would have an increased intensity of heat and mass transfer by increasing the residence time of the particles of the material in suspension.

 The problem is solved in that in the method for processing granular materials by transferring particles of granular material to a suspended state after transferring the particles to a suspended state, their speed increases until a maximum concentration of particles is created, then the speed is reduced to a fluidized thin layer, after which a coolant is passed through the particle layer countercurrent to their movement to complete coagulation of the latter.

 In FIG. 1 shows a general view of the installation; in FIG. 2 same, top view; in FIG. 3, section AA in FIG. 1.

 The proposed method is as follows.

 First, the particles of the granular material are put into suspension, the speed of their movement is increased to create the maximum concentration of particles, then the speed is reduced to the formation of a fluidized thin layer, after which the coolant is passed through the particle countercurrent to their movement until the latter coagulates.

 The source material is introduced by the feeder 1 into a vertical pipe 2, where it is picked up by a stream of air and transferred to a suspended state. In the housing 3, the flow rate is set to such a value at which the maximum concentration of particles is achieved. Large particles in this section begin to move by inertia faster than the flow, transferring part of their energy to it. In branch 4 and transition 5, the flow rate decreases to a value that is less than the maximum concentration of particles in the horizontal flow in the dust-collecting chamber 6. Due to the high concentration of closely spaced and slowly moving particles, a large proportion of them begin to fall out of the stream down as individual particles or their aggregates resulting from coagulation. Part of the material immediately falls onto the shelf 8, the other part first slides along the plates making up the shelves 7, falling down through the gaps between the plates forming these shelves.

 The second stage of processing the material on the shelves 8, in contrast to the first stage, is characterized by high productivity, which is formed by the properties of the material, the number and total length of the shelves 8 and 11, as well as their angle of inclination to the horizon.

 If during the first stage of processing, due to the short residence time of the material in the vertical pipe (1-5 s), only part of the heat is removed from it during the heat process or only the surface moisture is removed during drying, then the second process ensures the full flow of these processes. At the beginning of the technological process, when particles are imparted by a speed of movement, the material is treated with gases whose temperature exceeds the thermal stability of the material.

 Due to the short residence time in the particle stream, the temperature of the latter does not exceed the temperature of the wet thermometer, since only part of the moisture will be removed from the material. Further, upon receipt of a thin fluidized bed of particles of granular material through the nozzle 10, the coolant is introduced countercurrently. The dried material before entering the hopper 12 is dusted off with purge atmospheric air on the system of overflow shelves 11.

 As a result of short-term processing, the material, in addition to partial drying, acquires flowability as a result of blowing out fine dust-like particles from it. The gas entering the dust chamber 6 from the pipe 2 together with the gas and air introduced through the nozzles 10 and 13 surrounds the vertical partition 14, where it is additionally cleaned of dust and enters the cyclone 16, and then into the bag filter.

 The method of processing granular materials and the main dimensions of the device for its implementation are illustrated by example.

 An example of the implementation of the proposed method is obtained by calculation according to the operation data of a dryer for drying single potassium with a capacity of M 30 t / h 8.33 kg / s.

 The fractional composition of potassium chloride, the speed of the particles and other parameters are shown in the table.

2,78 кг/с, откуда объемный расход v_чк=

3,12 м³/с. Здесь ρ_t= ρ_o

1,32

0,89 кг/м³ плотность газа на выходе сушилки при t_к 130^оС, μ_т 3 массовая концентрация частиц в потоке (коэффициент смеси).Secondary mass flow rate of gas at the outlet of the dryer
G _hk = v _hk

2.78 kg / s, whence the volumetric flow rate v _hk =

3.12 m ³ / s. Here ρ _t = ρ _o

1.32

0.89 kg / m ^3, density of the gas at the outlet of the dryer at t _to 130 ^{° C,} μ _r 3 mass concentration of particles in the stream (mixture ratio).

0,537 ≈ 0,6 м.The flow rate is set by the soaring speed of the largest fraction according to the empirical formula WK˙W _of 1.5–9.18 13.77 13.8 m / s, in which k is 1.5. Then the diameter of the pipe 2 is equal to D

0.537 ≈ 0.6 m.

6,2 м/с.We increase the pipe cross section at the outlet to D 0.8 m, then the speed in the inlet section of the cone at the pipe outlet will be
W

6.2 m / s.

3,74

3,74-2,18 1,56;
Y _пред.=36,3 г/см³. Здесь а 5,8˙10^{-0,21 (W}в⁾ 5,8˙10^-9,21/1,1 3,74; b 12 (W_в)^1,2 12˙1,1^1,26 13,56. Действительная концентрация частиц этой фракции в потоке
Y

0,614 кг/м³= 614 г/м³ значительно превышает предельную.The value of the maximum concentration of particles of the fraction 0.40 + 0.20 mm (W _in = 1.1 m / s) at the pipe outlet will be
lgY _pre = A-

3.74

3.74-2.18 1.56;
Y _before = 36.3 g / cm ³ . Here a is 5.8˙10 ^{-0.21 (W} in ⁾ 5.8˙10 ^{-9.21 / 1.1} 3.74; b 12 (W _in ) ^1.2 12-1.1 ^1.26 13.56. The actual concentration of particles of this fraction in the stream
Y

0.614 kg / m ³ = 614 g / m ³ significantly exceeds the limit.

2,08 м/с. Величину предельной концентрации фракции 0,10 + 0,05 мм (W_в 0,3 м/с) рассчитываем по формулам для горизонтального потока. Она равна
lgμ 1,84·10

1,84·10

1,46-(-0,18) 1,64; μ= 43,7 г/кг, у μ_оt 43,7 ˙0,89 38,9 г/м³. Эта же величина для фракции 0,20 + 0,10 мм (W_b 0,87 м/с) равна
lgμ 1,84·10×

0,222

0,062
1,15 1,0 г/м³ В поток, поступающим в камеру, концентрация фракций 0,10 + 0,05 мм составляет
Y

0,427 кг/м³ 427 г/м³, а фракции 0,20 + 0,10 мм
Y

0,534 кг/м³= 534 г/м³ Эти данные показывают, что практически вся фракция 0,29 + 0,10 мм, а также все более крупные, а также 90% фракции 0,10 + +0,05 мм могут осесть на перфорированных полках внизу пылеосадительной камеры. Ее длина необходима для осаждения частиц фракции 0,20 + 0,10 мм. Составит l W_ч

2,08

3,58≈4 м. В камере осядут фракция 0,20 + 0,10 мм и более крупная, т.е.

0,75 всего материала, а также некоторая часть более мелких фракций. Основная масса последних выносится в циклон. Более крупные частицы, осевшие вниз камеры, перемещаются и досушиваются на полках внизу камеры. Время их пребывания на одной полке длиной l 3,8 м составит τ

12,7 с. Здесь W_с 0,3 м/с скорость движения слоя материала на наклонной полке. Этого времени вполне достаточно для удаления остатков влаги или для охлаждения материала до конечной температуры в условиях, где эти процессы при малом значении движущей силы протекают медленно. Установка дополнительно еще хотя бы одной полочки или подача теплоносителя в рубашку или непосредственно в слой материала позволит сократить время пребывания материала на первой стадии сушки путем уменьшения высоты сушки или понизить начальную температуру сушильного агента, что важно при сушке термически нестойких материалов. Наиболее целесообразен предлагаемый способ при сушке материалов с большим содержанием влаги.Thus, in the stream, the maximum concentration of this and all larger fractions is achieved, which, however, do not fall out of the stream, but, moving by inertia, are carried out into the dust collecting chamber. We take the width of the dust chamber equal to b 1.0 m, and the height h 1.5 m. Then the gas flow rate will be in it
W

2.08 m / s. The value of the maximum concentration of the fraction 0.10 + 0.05 mm (W _at 0.3 m / s) is calculated using the formulas for horizontal flow. She is equal
lgμ 1.8410

1.8410

1.46 - (- 0.18) 1.64; μ = 43.7 g / kg; for μ _о t, 43.7 ˙ 0.89 38.9 g / m ³ . The same value for the fraction 0.20 + 0.10 mm (W _b 0.87 m / s) is
lgμ 1.8410 ×

0.222

0,062
1.15 1.0 g / m ³ In the stream entering the chamber, the concentration of fractions 0.10 + 0.05 mm is
Y

0.427 kg / m ³ 427 g / m ³ and fractions 0.20 + 0.10 mm
Y

0.534 kg / m ³ = 534 g / m ³ These data show that almost the entire fraction of 0.29 + 0.10 mm, as well as all larger and 90% fractions of 0.10 + + 0.05 mm, can settle on the perforated shelves below the dust chamber. Its length is necessary for the deposition of particles of the fraction 0.20 + 0.10 mm Will be l W _h

2.08

3.58≈4 m. A fraction of 0.20 + 0.10 mm and larger, i.e.

0.75 of the total material, as well as some of the smaller fractions. The bulk of the latter is carried into the cyclone. Larger particles settling down the chamber move and are dried on the shelves at the bottom of the chamber. The time they spend on one shelf of length 3.8 m is τ

12.7 sec Here W _with 0.3 m / s the speed of movement of the material layer on an inclined shelf. This time is quite enough to remove residual moisture or to cool the material to a final temperature in conditions where these processes proceed slowly with a small value of the driving force. Installing at least one additional shelf or supplying a coolant to the jacket or directly to the material layer will reduce the residence time of the material in the first stage of drying by reducing the drying height or lower the initial temperature of the drying agent, which is important when drying thermally unstable materials. The most appropriate proposed method for drying materials with a high moisture content.

≈ 1,0 м где v_чк=

10,6 м³/с Высота пылеосадительной камеры составит при ее ширине b 2,0 м
h

2,54 м, а длина l W_ч

2,08

≈ 6,0 м
Предлагаемый способ обработки зернистых материалов позволяет повысить эффективность взаимодействия фаз в пневмотранспортных сушилках путем двухстадийного воздействия потока газа на материал при различных скоростях и температурах потока газа, при этом первая стадия, обеспечивая интенсивную сушку, является подготовительным этапом, обеспечивающим интенсивное протекание второй стадии.Calculations performed with a lower concentration of material in the flow showed that the dimensions of the dryer are within the available limits. So with μ = 1 kg / kg, its diameter is
D

≈ 1.0 m where v _hk =

10.6 m ³ / s The height of the dust chamber will be at its width b 2.0 m
h

2.54 m and length l W _h

2.08

≈ 6.0 m
The proposed method of processing granular materials allows to increase the efficiency of the interaction of phases in pneumatic conveying dryers by two-stage impact of the gas flow on the material at different speeds and temperatures of the gas flow, while the first stage, providing intensive drying, is a preparatory stage, providing intensive flow of the second stage.

Claims (1)

 METHOD FOR PROCESSING GRAIN MATERIALS by transferring particles of granular material to a suspended state, characterized in that after the particles are transferred into a suspended state, their speed is increased until a maximum concentration of particles is created, then the speed is reduced to the formation of a fluidized thin layer, after which the coolant is passed through the counter-flow through the particle their movement to complete coagulation of the latter.

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