Drum dryer with channel nozzle and heat pump

Abstract

The utility model relates to drying equipment, in particular to equipment for processing bulk materials in a rotating drum, and can be used for drying bulk materials in the chemical, food and other industries. In a drum dryer with a channel nozzle, comprising a drum mounted for rotation with profile nozzles forming longitudinal channels, wherein the drum dryer is equipped with a recuperative heat exchanger for heating the air, the coil of which is connected via a discharge line to the outlet of a two-stage compressor, and two recuperative heat exchangers for drying the air with the possibility of their regeneration and condensate drainage, the coils of which are connected via thermostatic valves and three-way valves to the suction line of the said compressor,wherein the coil spaces of the recuperative heat exchangers for dehumidifying air are connected via a three-way valve to a device for removing exhaust moist air from the drum and are provided with condensate drainage lines, and the inter-coil spaces of the recuperative heat exchangers for dehumidifying air are connected via a pump and a three-way valve to the inter-coil space of the recuperative heat exchanger for heating the air for the drum, wherein the duct for supplying additional air is connected via a three-way valve to the recuperative heat exchanger for heating the air for the drum and to a device for supplying air to the drum, in which a heater is additionally installed. The technical result consists in reducing the specific heat consumption for drying by reducing the air consumption by recirculating it and heating it using a heat pump. 1 fig.,

Description

[0001] The invention relates to drying technology, in particular to technology for processing bulk materials in a rotating drum with channel nozzles and can be used for drying bulk materials in the chemical, food and other industries.

[0002] Drum dryer designs are known [A.s. No. 1366824 F 26 B 11 / 04, B.I. No. 2, 1988], in which the drying agent moves through channels along the generatrix of the shell, exits the channels through cracks, passes through a layer of bulk product above the layer and exits the drum. The degree of filling of such drums is 15...25% of the drum volume.

[0003] The disadvantage of the known drums is that when the degree of filling of the drum increases, the bulk product enters the channels for the drying agent, as a result of which drying is suspended, and also that the speed of the drying agent in different channels is not the same, since the cross-sectional shape of the layer is a segment, the thickness of which is not constant.

[0004] A dryer for bulk materials is known [A.s. No. 227916 F 26 B 19 / 01 B.I. No. 30, 1968], containing a rotating drum, on the inner surface of which longitudinal perforated pipes are installed with a hollow cylindrical nozzle located along its axis, as well as supply and discharge pipes for the coolant connected to the ends of the drum.

[0005] The disadvantage is that the coolant travels a different path from the channel where it is fed into the layer to the open surface from which it is removed, which leads to its uneven speed and does not allow its potential to be used most effectively.

[0006] A drum dryer is known [patent no. 2153135 F 26 B 11 / 04, published 2000.07.20], in which the drum is divided by a vertical longitudinal partition into a rising and falling section. In the falling section, gas supply and gas collecting manifolds are fixedly mounted along the entire length of the drum.

[0007] The disadvantage of this device is: low specific moisture removal (kg / s m 3 drum volume), since the blowing and, accordingly, drying of the material occurs only in a part of the drum volume; high specific energy costs, caused by the fact that the amount of heat for heating the air is overestimated relative to the minimum required (due to increased air consumption due to its insufficient saturation with moisture during short-term contact of each of its volumes with the material), as well as high aerodynamic resistance of the air duct of the dryers due to the installation of two collectors with sequentially located holes.

[0008] A drying drum is known [patent no. 1838735 A 3 cl. F 26 B 25 / 16 published on 30.08.93, bulletin no. 32], in which air is supplied under a dense layer of moving material through longitudinal channels located on the inner surface of the drum. Air is supplied only to the channels located under the layer of material, through a device located on the stationary wall of the rotating drum.

[0009] The disadvantage of the known drying drum is the increased heat consumption for drying due to the relatively high air consumption, caused by its incomplete saturation with moisture during passage through the layer of material, as well as the supply of air with the same temperature to all drying zones along the length of the drum, which leads to an increase in energy costs and causes low productivity of the drying drum.

[0010] The closest in technical essence and achieved effect to the intended one is a drum dryer with a channel nozzle [patent No. 2367865 C 1 cl. F26B 11 / 04 published 09.20.2009, Bull. No. 26], comprising a drum with longitudinal channels mounted with the possibility of rotation, fixed devices for loading material and supplying air, as well as a fixed unloading chamber, wherein it is additionally equipped with a fixed device for removing exhaust air, which is a chamber adjacent to the ends of the longitudinal channels and fixedly located at the loading end of the drum, an air supply device, which is a chamber adjacent to the ends of the channels and fixedly located in the unloading chamber, all channels are provided with a solid transverse partition, and a channel for supplying additional air is located inside the drum, the transverse partitions of the channels are designed with the possibility of their longitudinal movement and are provided with clamps,the duct for supplying additional air along its length has openings for air outlet, equipped with control devices in the form of dampers, the duct for supplying additional air along its length is divided by solid partitions into sections, each of which is connected to a separate device for heating the air.

[0011] The disadvantage of the well-known drum dryer with a channel nozzle is high energy consumption due to the high air flow rate, which is not fully saturated with moisture during its passage through the material layer, as well as due to the supply of air at the same temperature to all drying zones along the length of the drum.

[0012] The technical objective of the utility model is to reduce the specific heat consumption for drying by reducing air consumption through its recirculation and heating using a heat pump, as well as its most complete saturation with moisture during its passage through the layer of material and with temperature regulation in different drying zones along the length of the drum.

[0013] The technical result consists in reducing the specific heat consumption for drying by reducing air consumption through its recirculation and heating using a heat pump, as well as its most complete saturation with moisture during the time of passage through the layer of material and with temperature regulation in different drying zones along the length of the drum.

[0014] The technical result of the utility model is achieved in that in a drum dryer with a channel nozzle, containing a drum mounted with the possibility of rotation with profile nozzles forming longitudinal channels, fixed devices for loading material, supplying air and removing exhaust air, wherein the air supply device is made in the form of a chamber adjacent to the ends of the said channels and is fixedly located in the unloading chamber of the drum, and the device for removing exhaust air is made in the form of a chamber adjacent to the ends of the channels at the loading end of the drum; inside the drum there is a channel for supplying additional air, and all longitudinal channels are provided with solid transverse partitions, according to the utility model, the drum dryer is provided with a recuperative heat exchanger for heating the air, the coil of which is connected via a discharge line to the outlet of a two-stage compressor,and two recuperative heat exchangers for air drying with the possibility of their regeneration and condensate drainage, the coils of which are connected through thermostatic valves and three-way valves to the suction line of the said compressor, wherein the coil spaces of the recuperative heat exchangers for air drying are connected through a three-way valve to a device for removing exhaust moist air from the drum and are provided with condensate drainage lines, and the inter-coil spaces of the recuperative heat exchangers for air drying are connected by means of a pump and a three-way valve to the inter-coil space of the recuperative heat exchanger for heating the air for the drum, wherein the duct for supplying additional air is connected by means of a three-way valve to the recuperative heat exchanger for heating the air for the drum and to a device for supplying air to the drum, in which a heater is additionally installed. Fig. 1 shows a diagram of a drum dryer with a channel nozzle and a heat pump.

[0015] A drum dryer with a channel nozzle and a heat pump (Fig. 1) includes a drum 1 with profile nozzles 2 forming longitudinal channels 3, inside which solid transverse partitions 4 are located, which can be configured to allow their longitudinal movement and are equipped with locks (not shown). The drum 1 is mounted so as to be rotatable by means of tires 5 and 6, a support roller 7 and a drive roller 8.

[0016] The drum dryer with a channel nozzle is equipped with a fixed device for loading material 9, passing through a fixed end wall 10 with a device for removing exhaust air 11 fixed to it, which is a chamber adjacent to the ends of the longitudinal channels 3.

[0017] The air supply device 12, which is a chamber, is adjacent to the ends of the channels 3 and is fixedly placed in the unloading chamber 13, into which the open end of the drum enters.

[0018] Inside the drum 1 there is a channel 14 for supplying additional air, which along its entire length can be provided with holes for air outlet and control devices in the form of dampers (not shown).

[0019] The product layer 15 in the drum 1 is located on the surface of the profile nozzles 2.

[0020] The channel 14 for supplying additional air is connected by line 16 to a three-way valve 17. In this case, a heater 18 is installed in line 16. The three-way valve 17 is also connected by line 19 to the air supply device 12 and by line 20 to a recuperative heat exchanger for heating air 21, which has a coil 22, which in turn is connected by line 23 to the discharge side of a two-stage compressor 24, which has a first 25 and a second 26 stage. The two-stage compressor 24 is equipped with a drive 27.

[0021] On the other hand, the coil 22 of the recuperative heat exchanger for heating air 21 is connected by line 28 through a three-way valve 29 with thermostatic valves 30 and 31 of the coils 32 and 33 of the recuperative heat exchangers 34 and 35. In this case, the recuperative heat exchangers for dehumidifying air 34 and 35 have lines 36 and 37 for removing condensate from them. Coils 32 and 33 are connected by line 38 through a three-way valve 39 with the suction side of the two-stage compressor 24. And the inter-coil space of the recuperative heat exchangers for drying air 34 and 35 is connected by line 40 through a three-way valve 41, in which a pump 42 having a drive 43 is installed with the inter-coil space of the recuperative heat exchanger for heating air 21. On the other hand, the coil space of the recuperative heat exchangers for drying air 34 and 35 is connected by line 44 through a three-way valve 45 with a device for removing exhaust moist air 11 from the longitudinal channels 3 of the drum dryer.In this case, in line 44 there is a pump 46 with a drive 47.

[0022] The drum dryer with channel nozzle works as follows.

[0023] The material to be dried enters the drum 1 through the fixed loading device 9 and is placed in a layer 15 to a rational degree of filling the drum (for example, 30%) on the surface of the profile nozzles 2, running along the entire drum 1. When the drive roller 8 rotates (its drive is not shown conditionally), the drum 1 rotates (for example, with an operating speed of 5.7⋅10 -2 With -1)), the bandages 5 and 6 of which interact with the drive 8 and support 7 rollers. Due to the rotation of the drum 1, the material, being mixed, moves from the end wall 10 to the discharge end of the drum, after which it is poured into the discharge chamber 13, from which it is removed outside the dryer. Simultaneously, a coolant in the form of heated air is supplied to the channels 3. Moreover, during the rotation of the drum 1, the longitudinal channels 3 adjoin the stationary devices for the supply 12 and exhaust 11 of air, located in such a way that the supply and exhaust of air occurs only through the channels located under the layer of material 15.

[0024] Air heating is provided as a result of the operation of compressor 24, which compresses the refrigerant first in the first 25, and then in the second 26 stages.

[0025] The temperature and pressure of the refrigerant initially increase to intermediate values ​​t пр and R пр, and then to a temperature corresponding to the discharge pressure. Hot refrigerant vapor (at a temperature of, for example, 70-80°C) after the compressor enters coil 22 of the recuperative air heating heat exchanger 21, through which the dehumidified air passes. The heat of the refrigerant is transferred through the tubes of coil 22 to the air, which is then fed into drum 1 of the dryer.

[0026] The refrigerant in coil 22 cools to the saturation temperature (e.g. 30°C) and condenses back into a liquid. The refrigerant condenses at a constant condensation temperature t к (for example, 30°C) and condensation pressure P к (for example, 1.2 MPa).

[0027] The refrigerant enters the coil 22 of the air heating heat exchanger 21, cools, condenses and enters the coil 33 of the recuperative air drying heat exchanger 35, through the thermostatic expansion valve 31, in which it is throttled from the condensation pressure P к(for example, 1.2 MPa) to boiling pressure P о (for example, 0.045 MPa) at boiling temperature (for example, -18°C).

[0028] Another recuperative air dehumidification heat exchanger 34 operates on the same principle.

[0029] Removal of moisture from exhaust air can be carried out both in the condensation mode and in the freezing mode on the surface of coils 32 and 33 of the recuperative heat exchangers for air dehumidification 34 and 35. In the mode of freezing moisture from exhaust air, the recuperative heat exchangers for air dehumidification 34 and 35 operate alternately to carry out regeneration to remove frozen moisture on the surface of coils 32 and 33.

[0030] Air heated by compressor 24 to temperature T1 (e.g. 60-70°C) enters the supply section of channels 3 and through longitudinal slotted openings between profile nozzles 2 along their length enters under layer of material 15 and under the action of feeding device (e.g. fan) passes through layer of material 15, dries it and exits layer 15 through its upper surface with temperature T2 (e.g. 50-60°C). Such air movement occurs in sections of channels 3 (Fig. 1) between feeding device 12 and transverse partition 4 (supply section of channels). Additional air with temperature T3 (for example, 90-100°C) enters the free upper part of drum 1 through air duct 14, which is further heated to this temperature in heater 18. In this case, a mixture with temperature T4 (for example, 70-80°C) is formed with air with temperature T2.This mixture, under the action of the difference in air pressure in the space above layer 15 and in the discharge part of the channels 3, located under the layer of material 15 between the transverse partitions 4 and the device for removing exhaust air 11, passes through the layer of material 15 in the part of the drum 1 in front of it. In this case, the material loses moisture, and the air is additionally saturated with it, its temperature decreases to T5 (for example, 30-40 °C).

[0031] Thus, in the first section of drum 1, the material is dried at a higher air velocity and lower temperature than in the second section. This drying mode corresponds to the general principles and mechanism of moisture removal (O. Krischer. Scientific Foundations of Drying Techniques. Foreign Literature Publishing House: Moscow, 1961. - 539 p.), ensuring more intensive moisture removal with lower heat consumption than drying at a constant temperature and air velocity.

[0032] The result is achieved as follows. Air supplied under the material layer passes through it, becomes saturated with moisture, mixes with additional air, and passes through the material layer again. Increasing the contact distance between the material and air ensures higher moisture saturation and, consequently, reduces the need for air and heat consumption for heating it. For heat-sensitive materials (e.g., grain crops, particularly quinoa), the maximum supply air temperature is limited by the quality requirements of the dry material; typically, the higher the moisture content, the lower the permissible temperature. Therefore, the supply air temperature in the prototype is the minimum permissible, which leads to a slower drying process and, consequently, a decrease in dryer productivity. In the proposed setup, air is supplied under a layer of material pre-dried in the upstream section of the drum.Air with different temperatures is fed through a product layer with different humidity levels in different zones of the dryer in such a way as to ensure the maximum permissible thermolabile properties of the product (for example, for quinoa, the grain temperature should not exceed 50-60°C).

[0033] After the air has been saturated with moisture and removed from the dryer, it is dried in recuperative heat exchangers and also heated in the recuperative heat exchanger using the heat obtained by compressing the refrigerant in the compressor.

[0034] The advantage of the proposed drum dryer with a channel nozzle over the known one is that its use allows for a reduction in the specific heat consumption for drying, as well as due to:

[0035] - adaptation of the installation to the requirements of the process being carried out with two drying zones, with targeted regulation of the temperature of the air supplied to them, ensuring greater compliance of the drying mode with the requirements of optimal process performance and more complete use of the drying potential of the air;

[0036] - implementation of “soft” drying modes with drying air with reduced moisture content due to its drying in a recuperative heat exchanger, which allows obtaining a high-quality dried product;

[0037] - reduction of energy costs by 10-15% for heating drying air compared to using an electric heater;

[0038] - reducing air consumption due to its recirculation.

Claims

A drum dryer with a channel nozzle, comprising a rotatably mounted drum with profile nozzles forming longitudinal channels, fixed devices for loading material, supplying air and removing exhaust air, wherein the air supply device is designed in the form of a chamber adjacent to the ends of said channels and is fixedly located in the unloading chamber of the drum, and the device for removing exhaust air is designed in the form of a chamber adjacent to the ends of the channels at the loading end of the drum; a channel for supplying additional air is located inside the drum, and all longitudinal channels are provided with solid transverse partitions, characterized in that the drum dryer is provided with a recuperative heat exchanger for heating the air, the coil of which is connected via a discharge line to the outlet of a two-stage compressor, and two recuperative heat exchangers for drying air with the possibility of their regeneration and removal of condensate,the coils of which are connected through thermostatic expansion valves and three-way valves to the suction line of the said compressor, wherein the coil spaces of the recuperative heat exchangers for drying air are connected through a three-way valve to a device for removing exhaust moist air from the drum and are provided with condensate drainage lines, and the inter-coil spaces of the recuperative heat exchangers for drying air are connected by means of a pump and a three-way valve to the inter-coil space of the recuperative heat exchanger for heating air for the drum, wherein the duct for supplying additional air is connected by means of a three-way valve to the recuperative heat exchanger for heating air for the drum and to the device for supplying air to the drum, in which a heater is additionally installed.

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