RU2755304C1 - Heat and mass transfer device for drying dispersed materials - Google Patents

Abstract

FIELD: heat and mass transfer equipment.

SUBSTANCE: invention relates to the design of continuous heat and mass transfer devices used for drying dispersed materials and for carrying out endothermic catalytic reactions. The heat and mass transfer device includes a single-pass transport screw that performs the function of an electrically conductive heating element, and the screw surface of which is made like a mesh. At the same time, copper busbars equipped with dielectric gaskets are installed on the outer and inner ends of the single-pass transport screw. The body of the heat and mass transfer device is covered with a layer of thermal insulation. The device is equipped with a thermal control system, which includes a power source with a magnetic contactor, a control device, a setting device, heat temperature sensors for the turns of the transport screw, dispersed material, drying agent at the inlet and outlet of the device.

EFFECT: increase in the productivity of the device during the implementation of mass transfer processes in conditions of fine regulation of thermal modes.

1 cl, 4 dwg

Description

The proposed technical solution relates to the design of continuous heat and mass exchangers used for the drying process, as well as for the implementation of endothermic catalytic reactions, and can be used in chemical, petrochemical, oil and gas, metallurgical, construction, food, pharmacological, biochemical and other industries.

Known designs for convective drying apparatus for dispersed materials and gas-phase catalytic nonisothermal reactors of various designs (Timonin A.S., Bozhko G.V., Borshchev V.Ya., Gusev Yu.I., etc. Equipment for oil and gas processing, chemical and petrochemical industries. Book 2 / under the general editorship of A.S. Timonin. - M .: Infra-Engineering, 2019 .-- 476 p., Timonin A.S., Baldin B.G., Borshchev V.Ya., Gusev Yu.I. . Machines and devices of chemical production / under the general editorship of AS Timonin. - Kaluga: Publishing house "Noosphere", 2014. - 856 p.)

The reasons that impede the achievement of the specified technical result include the low efficiency of the drying process associated with the uneven residence time of the granules of the dried material in heat and mass transfer devices, low thermal efficiency of the processes, the structural complexity of machines and apparatus for the drying process of dispersed materials.

The known design of a step-countercurrent fluidized bed dryer containing a wet material loading device with a screw feeder, a drying chamber, a furnace with a mixing chamber, a turbo-gas blower and an exhaust air purification system, the fluidized bed dryer is made in the form of a cylindrical body divided into sections with a conical part in the lower parts and support grids located perpendicular to the axis of the housing, and the feeder is located in the lid of the apparatus housing, moreover, a fluidizing heat carrier from a furnace with a mixing chamber is supplied under the grids, while heat and mass exchangers such as coils are placed in the sections to control the heating temperature in the material layer above the support grids, connected to the coolant lines, the transition from one section to another and the unloading of the dried material is carried out through the overflow pipes, and the dust generated during the drying process is captured in the dust cleaning system (RF Patent No. 2304266, F26B 17/00 2007).

The reasons that impede the achievement of the specified technical result include the uneven residence time in the apparatus for drying the products of mass transfer in connection with the organization of the movement of the dispersed phase through the sections of the mass transfer apparatus through the flow pipes, as well as the uneven heating of dispersed particles and continuous gas phase due to the limited heat transfer surface of the coil heat exchangers.

The known design of a fluidized bed dryer for thermolabile bulk materials, comprising a housing divided by gas distribution grids for a layer of material into belted annular chambers with a central generatrix, communicating by means of overflow windows in the grids and having a partition, and the lower and upper chambers are connected, respectively, to the gas supply and gas outlet boxes , a second partition is installed in each chamber, dividing, together with the first partition, the above-layer volume into two sections, and the gas supply and gas outlet ducts are also divided by vertical partitions into two compartments corresponding to the sections of the chambers for autonomous supply of different-temperature gas to the latter and removal from them, according to the invention of the partitions dividing the above-layer volume into two sections, are located obliquely at an angle equal to the angle of exit of the air flow from the fluidized bed of bulk material, and the central generatrix of the annular chambers is made in the form of a cone (RF Patent No. 2241928, F26B 17/10 2004).

The reasons that impede the achievement of the specified technical result include the uneven residence time of the products of mass transfer due to the organization of the movement of the dispersed phase through the sections of the fluidized bed dryer by means of overflow windows in the grids and the lack of the possibility of fine regulation of the heating temperature of the mass transfer products.

The known design of a fluidized bed dryer for thermolabile polydisperse bulk materials containing a vertical body, divided by gas distribution grids, supporting a layer of material on a belt-arranged annular chambers with a central cylindrical generatrix, communicating with each other by means of pouring windows in the gratings and having a partition in each of them, and the lower and the upper chambers are connected, respectively, to the gas supply and gas outlet ducts, in each chamber a second partition is installed, dividing, together with the first partition, the above-layer volume into two sections, and the gas supply and gas outlet ducts are also divided by vertical partitions into two compartments corresponding to the sections of the chambers for autonomous supply to the latter and the removal of a different-temperature gas from them, while the partitions dividing the over-layer volume into two sections are located behind the pouring windows, are equipped with a sampler of bulk material, and the central the generatrix of the annular chambers is made in the form of a truncated cone (RF Patent No. 44804, F26B 17/10 2005).

The reasons that impede the achievement of the specified technical result include the uneven residence time of the products of mass transfer due to the organization of the movement of the dispersed phase through the sections of the fluidized bed dryer by means of overflow windows in the grids and the lack of the possibility of fine regulation of the heating temperature of the mass transfer products.

The known design of an apparatus for drying bulk materials containing a vertical body with nodes for loading and unloading, along the axis of which are sequentially arranged annular shelves, forming with the body annular gaps, supply and output pipes of the drying agent. The device is equipped with a magnetic vibrator and a nozzle for return of dust-entrainment, the annular shelves are installed alternately with an inclination to the center and to the periphery of the case with the possibility of quick replacement, and the annular shelves, installed with an inclination to the center of the case, are made with a hole in the center, the case is equipped with a heat-insulating layer, a branch pipe for supplying a drying agent is located in the lower part of the housing, while the housing is made with an expansion in the areas of supply and removal of the drying agent (RF Patent No. 2492397, F26B 17/14 2013).

The reasons that prevent the achievement of the specified technical result include the uneven residence time of the mass transfer products due to the organization of the dispersed phase movement along the cascade of the dryer shelves, the presence of stagnant zones in the sections of the mass exchange apparatus due to the configuration of the dryer shelves and the lack of the possibility of fine regulation of the heating temperature of the mass transfer products.

The known design of a heat and mass transfer apparatus consisting of a vertical housing with a gas distribution chamber, pipes for supplying initial substances and removing products of mass transfer, fixed on the hollow shaft of a single-threaded screw screw with a perforated screw surface and radial partitions located on the lower surface of the screw screw with a gap relative to the upper surface of the next a turn of the screw screw, and a perforated lattice separating the gas distribution chamber from the screw screw, while the body is additionally equipped with a jacket, the hollow shaft is equipped with pipes for supplying and removing heat carriers, and the upper surface of the screw screw is ribbed in the tangential direction (RF Patent No. 195502, B01D 53 / 06, 2020).

The reasons that impede the achievement of the specified technical result include the lack of the possibility of fine regulation of the heating temperature and the unevenness of heat transfer throughout the volume of the heat and mass transfer apparatus, due to heating of the mass transfer products using a peripheral jacket and an internal heat exchanger (core of the heat and mass transfer apparatus), as well as the need to use gas (steam) -) or liquid-phase heat carriers, which significantly complicates the implementation of the drying process (especially in the case of thermolabile products), negatively affecting the quality of the drying process and the thermal efficiency of the heat and mass transfer apparatus, as well as the relatively low efficiency of heat transfer, and the low thermal efficiency of the heat and mass transfer apparatus when used as dryers of dispersed materials with a moving fluidized bed.

There is a method of controlling the thermal regime of an aerodynamic heating installation, in which the working space in the working channel is heated to a predetermined temperature and maintained within predetermined limits for a predetermined time by supplying power to the electric motor of a rotary heater, rotating the impeller of a rotary heater and supplying a heated gas coolant to the working channel with the regulation of its flow, while the regulation of the flow rate of the gas heat carrier is carried out by changing the speed of its movement by changing the frequency of the voltage supplying the electric motor, and at the stage of heating, the frequency of the voltage supplying the electric motor is changed so that the magnitude of the electric motor current remains constant and equal to the specified value, and at the stage of maintaining the temperature within the specified limits, the change in the frequency of the voltage supplying the electric motor is carried out in a fixed range, and the requirement for the constant current of the electric motor is removed (Patent RF No. 2 267 724, F26B 21/10, F26B 21/12, F26B 9/06, 2002).

The reasons that impede the achievement of the specified technical result include the lack of the possibility of fine regulation of the heating temperature of the working space of the channel, as a result of heat losses and uneven distribution of temperature fields along the length of the channels.

Known systems for automated control of thermal modes of drying plants (Ilyukhin A.V. Basic principles and methods of automation of thermal processes at the enterprises of the road-building complex: monograph / A.V. Ilyukhin, V.I. Marsov, E.V. Marsova. - M .: MADI, 2018 .-- 112 p.). Presented are the developed automated systems that ensure the rational use of energy resources, reducing the energy consumption of products of the industry of building materials and products. The task of reducing thermal emissions into the atmosphere and the irrational consumption of irreplaceable energy resources is also being solved.

The reasons that impede the achievement of a given technical result include the impossibility to fully realize the advantages of the developed automated control systems for thermal modes of the drying process and systems for optimizing the control of thermal modes of the drying process due to imperfections in the hardware design of the drying process, namely the very designs of heat and mass transfer devices, which were developed by the authors. control systems are oriented. The designs of heat and mass transfer devices for drying dispersed materials presented by the authors of the monograph cannot provide a uniform distribution of temperature fields, and, accordingly, smooth self-adaptive regulation of the thermal modes of the process.

Known systems for automated control of drying processes and designs of heat and mass transfer apparatus for drying food plant materials, presented in the doctoral dissertation of Sergei Alexandrovich Shevtsov "Scientific support of energy-saving drying processes and heat-moisture processing of food plant materials with variable heat supply". Dissertation for the degree of Doctor of Technical Sciences. Voronezh - 2015, 478 p.

The reasons that impede the achievement of the specified technical result include the inability to fully realize the advantages of the developed automated control systems for thermal modes of the drying process and systems for optimizing the control of thermal modes of the drying process due to imperfection of the hardware design of the drying process, namely, the very structures of heat and mass transfer machines and apparatus for which the control systems developed by the authors are oriented.

The closest technical solution in terms of a set of features to the claimed object and taken as a prototype is the design of a mass transfer apparatus, consisting of a vertical body, pipes for supplying initial substances and removing products of mass transfer, a screw screw with a perforated screw surface and radial partitions, fixed on the shaft, while the housing in the lower part contains a gas distribution chamber and a perforated grid separating the gas distribution chamber from the auger screw, and the auger screw is single-threaded, while radial partitions are located on the lower surface of the auger screw, with a gap relative to the upper surface of the next turn of the screw screw (Patent No. 141487, RF B01D53 / 06, B01D11 / 02, 2014).

The reasons that impede the achievement of a given technical result include the inability to finely control the heating temperature of the continuous and dispersed phases (mass transfer products) and low thermal efficiency when using a mass transfer apparatus as a dryer for dispersed materials.

The task is to develop the design of a heat and mass transfer apparatus for drying dispersed materials and gas-phase catalytic endothermic reactions with a wide range of possibilities for regulating technological parameters and the ability to finely control thermal modes during heat and mass transfer processes.

The technical result of the proposed heat and mass transfer apparatus for drying dispersed materials is to increase productivity in the implementation of mass transfer processes in conditions of fine regulation of thermal modes of apparatus for drying dispersed materials and gas-phase catalytic endothermic reactions, which is accompanied by an increase in the efficiency of the drying process.

The technical result is achieved by the fact that a heat and mass transfer apparatus for drying dispersed materials, consisting of a vertical body with a gas distribution chamber, pipes for supplying initial substances and removing mass transfer products, fixed on the hollow shaft of a single-thread screw screw with a screw surface and radial partitions located on the lower surface of the screw screw with a gap relative to the upper surface of the next turn of the screw screw, and the helical surface of the single-threaded screw, performing the function of an electrically conductive heating element, is made of mesh, while copper busbars are installed along the outer and inner ends of the single-threaded screw screw, equipped with dielectric spacers that isolate the single-start screw from the body of the apparatus and the hollow shaft, and the body of the heat and mass transfer apparatus is covered with a layer of thermal insulation, while the apparatus is additionally equipped with a thermal regime control system, which includes It is a power source with a magnetic contactor, a control device, a driver, temperature sensors for heating the turns of a screw screw, particulate material, a drying agent at the inlet and outlet of the apparatus.

Supply of a heat and mass transfer apparatus with a thermal regime control system, which includes a power source with a magnetic contactor, a control device, which can be, for example, an analog circuit or a programmable logic controller, a master device, as well as temperature sensors for heating the turns of a screw screw, dispersed material, drying agent at the inlet and outlet of the apparatus, providing feedback of the apparatus with the control device, allows for self-adaptive automatic control of thermal modes with control of the initial and final temperature and humidity of the drying agent and dispersed material. This scheme of the thermal regime control system allows for fine control of the thermal regimes of the apparatus for drying dispersed materials and endothermic gas-phase catalytic reactions, thereby increasing the productivity of the heat and mass transfer apparatus and its efficiency.

The implementation of the screw surface of a single-threaded screw screw, which performs the function of an electrically conductive heating element, is mesh, and copper busbars are installed on the outer and inner ends of the single-start screw screw, equipped with dielectric gaskets that insulate the single-start screw screw from the body of the apparatus and the hollow shaft, creates the necessary insulation conditions and provides fundamental the operability of the system for controlling the thermal modes of the heat and mass transfer apparatus for drying dispersed materials, thereby ensuring a stable continuous action of the claimed apparatus, a uniform residence time of the dispersed phase in it, uniform smoothly controlled stable thermal modes of operation and a relatively high thermal efficiency. Such a design is capable of finding its industrial application regardless of the operating temperatures of the drying process of dispersed materials and is especially important in cases of large-sized devices (from the point of view of the body manufacturing technology).

Coating the body of the heat and mass transfer apparatus with a layer of thermal insulation ensures the preservation of heat and stability of the thermal regimes of the mass transfer apparatus for drying dispersed materials (and gas-phase endothermic catalytic reactions), which increases the energy efficiency of the heat and mass transfer apparatus and the thermal efficiency of the drying process, increasing the productivity of the apparatus.

In fig. 1 shows a general view of a heat and mass transfer apparatus for drying dispersed materials in section.

In fig. 2 shows an additional view of the screw screw of a heat and mass transfer apparatus for drying dispersed materials in section.

In fig. 3 shows a system for controlling thermal modes of a heat and mass transfer apparatus for drying dispersed materials.

In fig. 4 shows a diagram of a system for controlling thermal modes of a heat and mass transfer apparatus for drying granular materials.

The heat and mass transfer apparatus for drying dispersed materials consists of a vertical housing 1, covered with a layer of thermal insulation (not shown in the drawings), with a gas distribution chamber 2, nozzles for supplying starting materials 3 and removing mass transfer products 4 and nozzles for inlet 5 and outlet 6 of the gas phase. The body 1 is equipped with a hollow shaft 7, on which a single-threaded screw screw 8 is fixed with a mesh screw surface and radial baffles 9 located on the lower surface of the screw screw 8 with a gap 10 relative to the upper surface of the next turn of the screw screw 8. Copper busbars 11 provided with dielectric spacers 12 , insulating a single-threaded screw screw 8 from the body 1 of the apparatus and the hollow shaft 7, installed at the inner and outer ends of the electrically conductive single-threaded mesh screw 8, which performs the function of an electrically conductive heating element, are connected to oppositely charged poles of the power source 13, from which the thermal control system is also powered. modes. The power supply 13 is equipped with a magnetic contactor 14. In addition to the power supply 13, the thermal management system includes a control device 15, which can be, for example, an analog circuit or a programmable logic controller, a driver 16, as well as temperature sensors 17 for heating the turns of the screw 8, dispersed material, a drying agent at the inlet and outlet of the apparatus, providing feedback between the apparatus and the control device 15.

Heat and mass transfer apparatus for drying dispersed materials operates as follows.

Through the branch pipe 3, the supplied dispersed phase (for example, granules of dispersed dried material, catalyst) enters the upper part of the housing 1, then slowly moves from top to bottom under the combined action of gravity and gas flow along the mesh surface of the turns of the screw screw 8 through the gaps 10 and leaves the housing 1 through the nozzle 4. Through the nozzle 5, an ascending gas flow (drying agent, gas-phase reaction products) is fed into the gas-distribution chamber 2, which is evenly distributed over the cross-section of the mass transfer apparatus. The flow of gas (drying agent, mixture of gases, reaction products), passing through the holes in the turns of the mesh screw screw 8, forms a moving fluidized bed with the dispersed phase supplied, in which heat and mass exchange occurs between the supplied dispersed phase and the ascending flow of the continuous gas phase. The flow of the continuous gas phase leaves the housing 1 through the branch pipe 6. Since radial partitions 9 are installed between the turns of the mesh screw screw 8, limiting the layer of liquid or solid dispersed phase, the movement of the continuous gas phase along the helical channel in the housing 1 in the gap 10 between the supplied phase and the lower surface of the turns of the mesh screw screw 8 is hindered, which makes it move vertically through the mesh turns of the screw screw 8.

For the implementation of high-quality control of thermal conditions (fine adjustment of the thermal conditions of the apparatus for drying dispersed materials and endothermic gas-phase catalytic reactions), the apparatus is equipped with a control system.

The system for controlling the thermal modes of the apparatus is shown in Fig. 3.and fig. 4. An electric current passes through the mesh auger screw 8, which performs the function of an electrically conductive heating element, heating the working surface of the screw screw 8 and carrying out uniform, smooth heating of the dispersed material (product of the mass transfer process) moving along the surface of the screw screw 8 and the continuous gas phase of the drying agent ( gas-phase reaction products). To ensure uniform heating of the mesh auger screw 8 along its outer and inner ends, conductive copper buses 11 equipped with dielectric spacers 12 are installed, serving to uniformly supply the supply voltage U _pit from the power source 13 along the entire length of the surface of the auger screw 8. Turning on the power of the auger screw 8 is carried out a magnetic contactor 14 on a signal from a control device 15, which can be an analog circuit or a programmable logic controller. The setting of the required temperature of the dispersed material is carried out using the driver 16. Temperature sensors 17 are used to organize the feedback of the control device 15, measuring the temperature of the turns of the screw 8, the flow of the continuous gas phase and the dried dispersed material leaving the mesh screw surface of the screw 8 and the air flow, t .e. drying agent. The control system also provides for the control of the final temperature and humidity of the dried dispersed material with the current self-adaptive automatic regulation of thermal modes with the control of the initial temperature and humidity of the drying agent.

Copper busbars 11 installed at the ends of the electrically conductive single-threaded mesh auger screw 8 (electrically conductive heating element) are connected to oppositely charged poles of the power source 13. An electric current passes through the mesh auger screw 8, heating its working surface and realizing uniform smooth heating of particles of dispersed material ( product of the mass transfer process) and the continuous gas phase of the drying agent.

This design, in comparison with the prototype, provides a smooth, finely controlled heating of the mass transfer products (dispersed phase and continuous phase of the drying agent). Heat, without the threat of local overheating of the dispersed phase, is transferred to the granules of the dried material due to heat transfer (contact with the heat-exchange surface) and convection (the flow of the drying agent penetrates through the turns of the mesh screw screw, heats up and conveys heat to the dispersed sorbent granules by convective transfer, contributing to the activation of the driving force process (difference in partial pressures)).

This design of a heat and mass transfer apparatus for drying dispersed materials with a moving fluidized bed of the material being dried provides stable continuous action, uniform residence time of the dispersed phase, uniform smoothly controlled stable thermal modes of operation, increasing the productivity of the apparatus and thermal efficiency.

Claims (1)

Heat and mass transfer apparatus for drying dispersed materials, consisting of a vertical body with a gas distribution chamber, branch pipes for supplying initial substances and removing products of mass transfer, fixed on the hollow shaft of a single-thread screw with a screw surface and radial partitions located on the lower surface of the screw with a gap relative to the upper surface of the next turn of the screw screw, characterized in that the screw surface of the single-threaded screw, performing the function of an electrically conductive heating element, is made of mesh, while copper tires are installed along the outer and inner ends of the single-threaded screw screw, equipped with dielectric gaskets that isolate the single-start screw from the body of the apparatus and hollow shaft, and the body of the heat and mass transfer apparatus is covered with a layer of thermal insulation, while the apparatus is additionally equipped with a thermal regime control system, which includes a power source with magnesium with a contactor, a control device, a driver, temperature sensors for heating the turns of a screw screw, dispersed material, a drying agent at the inlet and outlet of the apparatus.

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