JP2017203558A - Concentration drying apparatus and concentration drying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concentration drying apparatus and a concentration drying method enabling a sprayed dry matter to be obtained from thin fluid dispersion with a high energy efficiency.SOLUTION: A concentration drying apparatus 1 comprises: a membrane distillation cell 10 having a first chamber 10a through which a stock solution flows, and a second chamber 10b separated from the first chamber 10a by a porous membrane 11 which selectively penetrates steam; a first heat exchanger 20 for heating the stock solution by heat exchange between a heat carrier and the stock solution flowing through the first chamber 10a; a spray drier 70 for spraying the stock solution discharged from the first chamber 10a into a hot air to dry it; and a second heat exchanger 30 for heat exchange between exhaust air discharged from the spray drier 70 and the heat carrier. A concentration drying method comprises: heating a stock solution by heat exchange between exhaust air discharged from the spray drier 70 and the stock solution; concentrating the heated stock solution in the membrane distillation cell 10; and spraying and drying the concentrated stock solution in the spray drier 70.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a concentration drying apparatus and concentration drying method by membrane distillation and spray drying.

  In various fields such as production of food and drink, waste liquid treatment, desalination treatment, and chemical industry, operations for concentrating liquids are performed. As a concentration method, an evaporation concentration method using an evaporator or a heating plate is generally used. As other methods, a membrane concentration method using a reverse osmosis (RO membrane), a freeze concentration method, and the like are also used.

  Although the evaporative concentration method is a method that can easily realize a high concentration rate, it has a disadvantage that it takes a large heating cost to evaporate the liquid. Further, the evaporation concentration method volatilizes low-boiling components such as aroma components with heating, and thus is not suitable for the production of food and drink. On the other hand, the freeze-concentration method also requires a high endothermic refrigeration capacity, and has problems such as complicated apparatus and operation and difficulty in concentrating the suspension.

  Under such circumstances, the use of the membrane concentration method is expanding as an alternative technology to replace the evaporation concentration method and the like. In the membrane concentration method, concentration is performed according to the principle of filtration or dialysis using a separation membrane. A reverse osmosis membrane (Reverse Osmosis; RO membrane) is generally used as a separation membrane when low molecules or more are to be concentrated. Conventionally, as disclosed in Patent Document 1, a technique for concentrating a saccharified solution using a reverse osmosis membrane device or a nanofiltration membrane device is known.

  The reverse osmosis method can be carried out at a relatively low cost and has the advantage that the quality of the concentrated liquid is hardly impaired because it is not necessary to volatilize low boiling components. However, in the reverse osmosis method, the concentration rate is limited due to the relationship between the operating pressure and the pressure resistance. Further, even if the reverse osmosis membrane is pretreated as described in Patent Document 1, fouling is still likely to occur. In addition, the material is often easily deteriorated by chemicals and disinfectants used for the cleaning. Therefore, it is not always the best method in consideration of operation and maintenance of the apparatus.

  A membrane distillation method (MD method) is also known as a method using a separation membrane. In the membrane distillation method, a hydrophobic porous membrane is used that does not permeate liquid but permeates gas. In the concentration by the principle of membrane distillation, the liquid is separated with a phase transition to a gas, and the original liquid is concentrated. The membrane distillation method is advantageous as a method for concentrating liquids containing solutes and turbids because it is easy to operate and maintain the apparatus even in consideration of sterilization treatment and the like.

  Mass transfer in membrane distillation is driven by the vapor pressure differential across the membrane. For this reason, the concentration operation is performed by giving a temperature difference between one side of the membrane with which the stock solution is brought into contact and the opposite side of the membrane with which the vapor is emitted, and making the saturated vapor pressure different. Specific forms of the membrane distillation method include the indirect contact method in which the vapor that has permeated the membrane is cooled on a cooling surface remote from the membrane, and the cooling that has passed through the membrane on the opposite side of the membrane. There is a direct contact method in which the liquid is absorbed.

JP 2014-128213 A

  According to the concentration based on the principle of membrane distillation, it is possible to concentrate the liquid at a lower heating cost compared to the evaporation concentration method. However, even in the membrane distillation method, since it is necessary to give a large amount of liquid a heat amount equal to or greater than the heat of evaporation, there is still a high demand for a reduction in heating cost.

  On the other hand, in the field of performing an operation of concentrating a liquid, a process of drying and solidifying the dispersion liquid may be accompanied. For example, in the field of manufacturing food and drink, granular or powdered processed food and drink may be manufactured by concentrating a dilute raw material liquid and spray-drying the concentrated raw material liquid. In spray drying accompanied by heating with hot air, exhaust air that retains heat is exhausted, so it is desired to reduce waste heat and improve energy saving.

  Then, an object of this invention is to provide the concentration drying apparatus and concentration drying method which can obtain a spray-dried material from a diluted dispersion efficiently.

  In order to solve the above problems, a concentration drying apparatus according to the present invention includes a first chamber in which a stock solution is flowed, and a second chamber separated from the first chamber by a porous membrane that selectively transmits vapor. A membrane distillation cell having a first heat exchanger that heats the stock solution by exchanging heat between the heating medium and the stock solution that flows into the first chamber, and the stock solution discharged from the first chamber. A spray dryer that sprays and dries in hot air, and a second heat exchanger that exchanges heat between the exhaust air discharged from the spray dryer and the heat medium.

  Further, the concentration drying method according to the present invention includes a membrane distillation cell having a first chamber in which a stock solution is flowed, and a second chamber separated from the first chamber by a porous membrane that selectively transmits vapor. A spray dryer for spraying and drying the undiluted solution discharged from the first chamber in hot air, and heat is generated between the unwinded air discharged from the spray dryer and the undiluted solution. Exchange is performed to heat the stock solution, the heated stock solution is concentrated in the membrane distillation cell, and the concentrated stock solution is spray dried in the spray dryer.

  ADVANTAGE OF THE INVENTION According to this invention, the concentration drying apparatus and the concentration drying method which can obtain a spray-dried material energy efficient from a diluted dispersion liquid can be provided.

It is a figure which shows schematic structure of the concentration drying apparatus which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the concentration drying apparatus which concerns on the modification of this invention.

  Hereinafter, a concentration drying apparatus and a concentration drying method according to an embodiment of the present invention will be described. In addition, about the structure which is common in each following figure, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

FIG. 1 is a diagram showing a schematic configuration of a concentration drying apparatus according to an embodiment of the present invention.
As shown in FIG. 1, the concentration drying apparatus 1 according to the present embodiment includes a membrane distillation cell 10, a stock solution pump P1, a heater (first heat exchanger) 20, and a gas-liquid heat exchanger (second heat). Exchanger) 30, cooler 40, coolant pump P2, concentrate tank 50, concentrate pump P3, air supply fan F1, air heater 60, spray dryer 70, and powder separation. Device 80, dust collector 90, exhaust fan F2, stock solution passage 110, coolant passage 120, concentrate passage 130, exhaust passage 140, heat transfer pipe 150, first medium A heat medium tank T10, a second heat medium tank T20, a first heat medium pump (flow rate adjusting means) P4, a second heat medium pump (flow rate adjusting means) P5, and a controller (control unit) 200 are provided. ing.

  The concentration drying apparatus 1 is an apparatus that performs a concentration operation for increasing the concentration of a diluted dispersion liquid based on the principle of membrane distillation, and dries the concentrated dispersion liquid by spray drying. In the concentration drying apparatus 1, a dilute dispersion (stock solution) that is a mixture of a liquid and a solid or in which a solid is dissolved is introduced into the membrane distillation cell 10 and subjected to membrane distillation. In the membrane distillation cell 10, a low-boiling component such as a dispersion medium contained in the stock solution is separated, while a concentrated solution in which the solid content contained in the original stock solution is concentrated is generated. Then, the concentrated liquid is introduced into the spray dryer 70 and spray-dried, and a granular or powder spray-dried product from which the dispersion medium has been removed is recovered.

  The membrane distillation cell 10 includes a porous membrane 11, a cooling plate 12, a stock solution chamber (first chamber) 10a, a condensing chamber (second chamber) 10b, and a cooling chamber (third chamber) 10c. Yes. As shown in FIG. 1, the inside of the membrane distillation cell 10 is partitioned into a stock solution chamber 10a, a condensing chamber 10b, and a cooling chamber 10c by a porous membrane 11 and a cooling plate 12.

  The porous membrane 11 is made of a porous material and forms part of the wall portion of the stock solution chamber 10a. The porous membrane 11 has a property of transmitting gas while not transmitting liquid, and exhibits an action of selectively transmitting vapor in the contacted stock solution. That is, the vapor evaporated from the stock solution can pass through the porous membrane 11 and move from the stock solution chamber 10a side to the condensation chamber 10b side. On the other hand, the original stock solution from which the vapor is released is concentrated in the stock solution chamber 10a without passing through the porous membrane 11.

  As the porous membrane 11, various forms such as a flat membrane, a hollow fiber membrane, and a tubular membrane are applied. The method of assembling the porous membrane 11 is not particularly limited, and various forms such as a circular tube type and a spiral type can be adopted. An example of the porous membrane 11 has an average pore diameter of 0.2 μm, an aperture ratio of 60% to 80%, and a thickness of 50 μm to 200 μm.

  A preferred material for the porous membrane 11 is a material having high hydrophobicity. As the organic material, for example, a fluorinated polyolefin such as polytetrafluoroethylene (PTFE), or a polyolefin such as polyethylene (PE) or polypropylene (PP) can be used. Moreover, as an inorganic material, hydrophobic zeolite, silica, carbon, etc. can be used, for example.

  The cooling plate 12 is made of a material having a high thermal conductivity, and forms part of each wall portion of the condensing chamber 10b and the cooling chamber 10c. The cooling plate 12 is cooled by the coolant from the cooling chamber 10c side, and condenses the vapor that has passed through the porous film 11 on the surface on the condensation chamber 10b side.

  Preferred materials for the cooling plate 12 are stainless steel, aluminum, titanium, copper, alloys thereof, synthetic resin with high thermal conductivity, and the like. A more preferable material is a material having both high thermal conductivity and corrosion resistance, such as stainless steel and titanium.

  The stock solution chamber 10a is a compartment through which the stock solution flows. A stock solution passage 110 formed by piping or the like is connected to the inlet of the stock solution chamber 10a. On the stock solution flow path 110, a stock solution pump P1 and a heater 20 are installed. The stock solution is introduced into the stock solution chamber 10a from outside the system by operating the stock solution pump P1, and flows through the stock solution chamber 10a in which the porous membrane 11 is installed.

  The heater 20 is a heat exchanger that heats the stock solution flowing into the stock solution chamber 10a through heat exchange with a heat medium. Mass transfer in the porous membrane 11 is driven by a vapor pressure difference generated between the interface between the stock solution and the porous membrane 11 and the cooling surface of the cooling plate 12. The higher the temperature of the stock solution, the higher the saturated vapor pressure, and the higher the saturated vapor pressure, the larger the permeation flux of the porous membrane 11. Further, as the saturated vapor pressure increases, the transfer ratio of latent heat to sensible heat increases and heat loss decreases. Therefore, the stock solution is heated by the heater 20 to a predetermined temperature and introduced into the stock solution chamber 10a.

  As shown in FIG. 1, a heating medium pipe 150 through which a heating medium flows is connected to the heater 20. The heat medium pipe 150 forms a circulation path between the heater 20 and the gas-liquid heat exchanger 30. As the heat medium, for example, when an aqueous stock solution such as an aqueous dispersion or an aqueous suspension is to be concentrated, pure water, tap water, industrial water, or the like can be used.

  A heat insulating first heat medium tank T <b> 10 is installed in the middle of the heat medium pipe 150 on the outgoing side from the heater 20 toward the gas-liquid heat exchanger 30. The first heat medium tank T10 temporarily stores the heat medium radiated by heat exchange with the stock solution. A heat medium pipe 150 on the downstream side of the first heat medium tank T10 is provided with a first heat medium pump P4 capable of quantitatively transferring the heat medium.

  Further, in the return side heat medium pipe 150 from the gas-liquid heat exchanger 30 to the heater 20, a heat insulating second heat medium tank T <b> 20 is installed in the middle. In the second heat medium tank T20, the heat medium received in the gas-liquid heat exchanger 30 is temporarily stored. A second heat medium pump P5 capable of quantitatively transferring the heat medium is installed in the heat medium pipe 150 on the downstream side of the second heat medium tank T20.

  The cooling chamber 10c is a section through which the coolant flows. The cooling chamber 10 c is separated from the condensing chamber 10 b by the cooling plate 12. From the outlet to the inlet of the cooling chamber 10c communicates with the outside through a pipe or the like, and a coolant channel 120 for circulating the coolant in the cooling chamber 10c is formed. On the coolant flow path 120, a cooler 40 and a coolant pump P2 for circulating the coolant are installed. The coolant channel 120 connects the outlet and the inlet of the cooling chamber 10c via the cooler 40, and circulates the coolant to the cooling chamber 10c in a circulating manner.

  As the cooling liquid, an appropriate fluid having a high heat capacity and latent heat and having an appropriate viscosity and phase transition temperature is applied. For example, when an aqueous undiluted solution such as an aqueous dispersion or an aqueous suspension is to be concentrated, cooling water such as pure water, tap water, and industrial water can be used.

  The cooler 40 cools the coolant that flows into the cooling chamber 10c. The cooling liquid is cooled by the cooler 40 to a temperature at which the vapor in the condensing chamber 10b can be condensed and introduced into the cooling chamber 10c. Usually, the temperature of the cooling liquid is cooled to a substantially constant temperature from the viewpoint of making the vapor pressure difference between the stock solution side and the cooling side constant. As the cooler 40, for example, an open type cooling tower, a closed type cooling tower, a heat exchanger, or the like is used.

  The condensation chamber 10b is a compartment for condensing steam. The condensation chamber 10 b is separated from the stock solution chamber 10 a by the porous membrane 11. The vapor evaporated from the stock solution in the stock solution chamber 10a passes through the porous membrane 11, and then moves from the porous membrane 11 to the cooling plate 12 by natural convection or diffusion. Then, the cooling plate 12 cooled by the coolant flowing in the coolant flow path 120 cools the condensation chamber 10b and condenses the vapor in the condensation chamber 10b. A drainage path for discharging condensate to the outside of the cell and an exhaust path for exhausting steam are connected to the condensation chamber 10b.

  In the membrane distillation cell 10, the low boiling point components are evaporated from the heated stock solution, and the vapor passes through the porous membrane 11 and is cooled on the cooling plate 12 of the condensing chamber 10b to become a condensate. The condensate and the remaining steam are discharged out of the system from the condensing chamber 10b, while the stock solution (concentrated liquid) concentrated by the separation of the steam is discharged from the stock solution chamber 10a.

  A concentrated liquid flow path 130 formed by piping or the like is connected to the outlet of the stock solution chamber 10a. A concentrate tank 50 is installed on the concentrate channel 130. The concentrated liquid concentrated in the stock solution chamber 10 a is received by the concentrated liquid tank 50 through the concentrated liquid channel 130 and is temporarily stored in the concentrated liquid tank 50. Further, a concentrated liquid pump P <b> 3 is installed on the downstream side of the concentrated liquid tank 50, and the downstream end of the concentrated liquid flow path 130 is connected to the spray dryer 70.

  The spray dryer 70 spray-drys the dispersion liquid (concentrated liquid), and granulates a spray-dried product composed of the solid content in the dispersion liquid. The spray dryer 70 includes, for example, a cylindrical casing whose lower side is tapered toward the lower end, and a discharge mechanism that is provided in the casing and discharges droplets toward the inner wall of the casing. Is done. The discharge mechanism is composed of a pressure nozzle and a rotating disk, and is connected to the concentrate flow path 130. The concentrated liquid supplied through the concentrated liquid channel 130 is discharged as droplets by a discharge mechanism. In addition, hot air for drying the concentrate is supplied into the casing from which the concentrate is discharged.

  As shown in FIG. 1, hot air is supplied to the spray dryer 70 after the air sucked by the air supply fan F <b> 1 is heated by the air heater 60 to collect and remove dust. The heating temperature by the air heater 60 is preferably in the range of 100 ° C. or higher and 300 ° C. or lower. In FIG. 1, the method of supplying hot air is a parallel flow type that is parallel to the liquid droplets discharged from the top of the tower, but a countercurrent type that faces the liquid droplets discharged from the top of the tower from below. Alternatively, a co-current flow type may be used in which droplets discharged toward the top of the tower are opposed from above.

  The spray dryer 70 is connected to an exhaust air exhaust path 140 formed by piping or the like in the housing. On the exhaust path 140, the powder separator 80, the dust collector 90, the exhaust fan F2, and the gas-liquid heat exchanger 30 are installed in this order, and the end of the exhaust path 140 is outside the system. Communicate. The hot air that has been deprived of heat by the concentrated liquid is exhausted together with some of the fine spray-dried material through the exhaust air passage 140 by the operation of the exhaust air fan F <b> 2, and is introduced into the powder separator 80.

  The powder separator 80 is a so-called cyclone, and separates gas and powder by the principle of centrifugal separation by forming a vortex. The exhaust air exhausted from the spray dryer 70 forms a vortex in the cylindrical casing of the powder separator 80, and the gas and the fine spray-dried product are separated from each other. The separated spray-dried material is collected from the lower part of the housing, while the exhausted air is exhausted from the upper part of the housing and then introduced into the dust collector 90.

  The dust collector 90 is a device that collects and separates fine particles in a gas. The dust collector 90 includes, for example, a bag filter that collects dust by the principle of filtration. The exhausted air introduced into the dust collector 90 passes through the bag filter, and the remaining fine particles of the spray-dried material are collected and removed. The spray-dried material collected by dust is removed from the bag filter and collected by compressed air pulses, vibrations, and the like. On the other hand, the exhaust air from which the fine particles have been removed is exhausted from the dust collector 90 and introduced into the gas-liquid heat exchanger 30.

  The gas-liquid heat exchanger 30 performs heat exchange between the heat medium of the heater 20 and the exhaust air discharged by the spray dryer 70. The gas-liquid heat exchanger 30 has a heat receiving part constituted by a part of the heat medium pipe 150 and a heat radiating part constituting a part of the exhaust air path 140. The heat-radiating part of the gas-liquid heat exchanger 30 is supplied with exhaust air discharged from the spray dryer 70 and retaining residual heat, and the heat-receiving part is supplied with a heat medium radiated by the heater 20 and is discharged. Liquid heat exchange takes place. The form of the gas-liquid heat exchanger 30 may be an appropriate form such as a fin tube type, a plate fin type, a shell tube type, a finless multi-tube type, and a direct contact type.

  The controller 200 controls the discharge force of the first heat medium pump P4 and the second heat medium pump P5. The controller 200 controls the first heat medium pump P4 and the second heat medium pump P5 to adjust the flow rate of the heat medium, whereby the heat amount (exchange heat amount) given to the undiluted solution by the heater 20 is controlled. The controller 200 acquires, for example, the measurement results of the inlet temperature and outlet temperature of the heat receiving unit of the gas-liquid heat exchanger 30 and the inlet temperature and outlet temperature of the heat radiating unit to obtain a predetermined exchange heat amount and logarithmic average temperature difference. The flow rate of the heat medium is adjusted by controlling the discharge force of the first heat medium pump P4 so that the corresponding heat exchange is performed. In addition, the measurement results of the inlet temperature and outlet temperature of the heating medium of the heater 20 and the inlet temperature and outlet temperature of the stock solution are acquired, and heat exchange corresponding to a predetermined exchange heat amount and logarithm average temperature difference is performed. The flow rate of the heat medium is adjusted by controlling the discharge force of the second heat medium pump P5.

  Next, based on the specific operation method of the concentration drying apparatus 1, the concentration drying method according to the present embodiment will be described.

  The concentration drying method according to the present embodiment includes a condensate chamber (second chamber) separated from a stock solution chamber (first chamber) by a porous membrane that selectively transmits vapor and a stock solution chamber (first chamber) through which the stock solution flows. And a spray dryer for spraying and drying the stock solution discharged from the stock solution chamber (first chamber) in hot air, and then drying the spray solution from the spray dryer. This is a concentration drying method in which heat exchange is performed between the exhausted air and the stock solution to heat the stock solution, the heated stock solution is concentrated in a membrane distillation cell, and the concentrated stock solution is spray-dried in a spray dryer.

  According to the concentration drying method according to the present embodiment, a granular or powdery spray-dried product is recovered by subjecting the dilute dispersion containing solids such as solute and turbidity as a stock solution to the treatment. For example, by performing membrane distillation and spray drying using milk, fruit juice, vegetable juice, pharmaceutical raw material liquid, fragrance raw material liquid, etc. as the original liquid, spray-dried products such as powdered milk, powdered fruit juice, powdered vegetable juice, pharmaceutical powder formulation, fragrance powder, etc. Is obtained.

  In the concentration drying apparatus 1, the stock solution is introduced into the stock solution channel 110 from outside the system by the operation of the stock solution pump P1. Then, the undiluted solution is heated to a target heating temperature by exchanging heat with a heat medium flowing through the heat medium pipe 150 with a predetermined amount of exchange heat in the heater 20. Thereafter, the stock solution flows through the stock solution chamber 10 a of the membrane distillation cell 10 and is concentrated, and the concentrate is received in the concentrate tank 50 through the concentrate channel 130.

In the stock solution chamber 10a of the membrane distillation cell 10, the low boiling point component evaporates from the heated stock solution, and the vapor passes through the porous membrane 11 and is cooled on the cooling plate 12 of the condensation chamber 10b to become a condensate. In the stock solution chamber 10a of the membrane distillation cell 10, membrane distillation is performed so that the stock solution is concentrated to a predetermined concentration rate. The concentration ratio (C _f ) of the concentrated liquid is expressed by the following formula (1) from the material balance in the membrane distillation cell, where Q _f is the amount of the stock solution and Q _p is the amount of the permeate that permeates the porous membrane 11. It can be expressed as
_{/ C f = Q f (Q} f -Q p) ··· (1)

The amount (Q _f ) of the stock solution can be easily grasped as the amount introduced into the membrane distillation cell 10 or the like. For example, the flow rate sensor may be installed in the stock solution flow path 110 and measured, or before the stock solution is introduced into the stock solution flow path 110, it may be measured by a level sensor or a weight sensor provided in a storage tank or the like for storing the stock solution. it can. On the other hand, the amount of permeate (Q _p ) that permeates through the porous membrane 11 can be adjusted to a predetermined amount by controlling the vapor pressure difference generated across the porous membrane 11.

The vapor pressure difference in the membrane distillation cell 10 may be controlled mainly by adjusting the temperature difference between the heating temperature of the stock solution by the heater 20 and the cooling temperature of the cooling plate 12 by the cooler 40. The heating of the stock solution is adjusted by supplying thermal energy, and the cooling of the cooling plate 12 is maintained at a constant temperature using a cooling liquid cooled with water or air in a normal temperature range. For example, the temperature of the stock solution or the coolant may be monitored and the heater 20 or the cooler 40 may be feedback controlled. The temperature difference between the stock solution side and the cooling side may be set to a temperature at which an appropriate vapor pressure difference is secured for the porous membrane 11 in accordance with the target concentration rate (C _f ). The target temperature for heating by the heater 20 can be less than 90 ° C. when an aqueous stock solution is to be concentrated. Alternatively, the amount of condensate generated in the condensing chamber 10b may be monitored to quantitatively control the amount of condensate. This is because the amount of permeate (Q _p ) that permeates through the porous membrane 11 can be considered to be equivalent to the amount of condensate generated in the condensing chamber 10b.

  The concentrate concentrated in the membrane distillation cell 10 is discharged from the stock solution chamber 10a and received in the concentrate tank 50, and is transferred from the concentrate tank 50 to the spray dryer 70 by the operation of the concentrate pump P3. In the spray drier 70, the concentrated liquid sprayed into the casing to which hot air is supplied is dried into a granular or powder spray dried product, while the hot air deprived of heat by the concentrated liquid is used as exhaust air. Exhausted. The spray-dried product is collected from the spray dryer 70, the powder separator 80, and the dust collector 90 and used for various applications.

  In the membrane distillation cell 10 of the concentration drying apparatus 1, the stock solution is concentrated to a predetermined concentration rate set in advance. Therefore, in the spray dryer 70, the concentrate can be discharged at a constant flow rate set in advance and can be almost completely dried stably. Further, since the stock solution is concentrated to a predetermined concentration rate, the air supply fan F1 supplies air sucked at a preset constant flow rate to the air heater 60, and the air heater 60 is supplied with the air supply fan F1. Can be operated so as to heat the air at a constant flow rate supplied from the air to a predetermined temperature set in advance. That is, during the operation of the concentration drying apparatus 1, the amount of heat input through the air heater 60 can be easily controlled to a substantially constant amount within a range where the concentrated liquid with a predetermined concentration rate discharged at a constant flow rate is dried. Is possible. When such a steady operation is performed, the exhaust air is introduced into the heat radiating portion of the gas-liquid heat exchanger 30 while maintaining substantially constant heat energy, and between the heat medium flowing through the heat medium pipe 150. Thus, heat exchange can be performed with a predetermined amount of exchange heat.

  The heat exchange between the heat medium flowing through the heat medium pipe 150 and the undiluted solution flowing into the undiluted solution chamber 10a is performed from the viewpoint of setting the amount of the concentrated solution and the concentration rate obtained in the undiluted solution chamber 10a as desired. It is preferable to control the amount of heat to be constant. Therefore, in the concentration drying apparatus 1, the amount of heat given to the stock solution by the heater 20 is controlled by adjusting the flow rate of the heat medium flowing through the heat medium pipe 150. The amount of heat input from the air heater 60 is set to a substantially constant amount, and the exhaust air exchanges heat with a predetermined amount of exchange heat, so that the stock solution reaches the target heating temperature by indirect heat exchange performed by adjusting the flow rate of the heat medium. Heated.

  Specifically, in the concentration drying apparatus 1, the first heat medium pump P4 is controlled by the controller 200, and the transfer amount of the heat medium of the first heat medium pump P4 is controlled to the adjusted flow rate. The first heat medium pump P4 is stored in the first heat medium tank T10, and introduces the heat medium that has already dissipated heat by heat exchange with the stock solution into the gas-liquid heat exchanger 30 at an adjusted flow rate. As a result, the amount of exchange heat necessary to heat the stock solution to the target heating temperature is obtained by heat exchange with the exhaust air. For example, the controller 200 determines the required amount of exchange heat from the exhaust air based on the exchange heat amount of the exhaust air in the gas-liquid heat exchanger 30 and the heat medium entry / exit conditions obtained in advance under predetermined spray drying conditions. The discharge force of the first heat medium pump P4 is controlled so as to be obtained.

  In the concentration drying apparatus 1, the controller 200 controls the second heat medium pump P5, and the flow rate of the heat medium transferred from the second heat medium pump P5 is controlled to the adjusted flow rate. The second heat medium pump P5 is stored in the second heat medium tank T20, and introduces the heat medium that has already received heat through heat exchange with the exhaust air to the heater 20 at an adjusted flow rate. As a result, the exchange heat necessary for heating the stock solution to the target heating temperature is radiated. For example, the controller 200 may provide the stock solution with an exchange heat amount for realizing the target vapor pressure difference based on the stock solution exchange heat amount and the heat medium entry / exit condition obtained in advance under a predetermined concentration condition. The discharge force of the second heat medium pump P5 is controlled.

  According to the concentration drying apparatus and the concentration drying method according to the above embodiment, the diluted dispersion can be evaporated by using the waste heat of the exhaust air discharged from the spray dryer and concentrated by membrane distillation. Moreover, the dispersion liquid concentrated by membrane distillation can be spray-dried under predetermined conditions, and the heat of exhaust air can be utilized stably. Therefore, the heating cost required for membrane distillation can be reduced, and a spray-dried product can be obtained from a dilute dispersion with high energy efficiency. In addition, the amount of exhaust heat due to exhaust of exhaust air can be reduced, and an environment-friendly concentration drying apparatus and concentration drying method can be provided.

  Next, a concentration drying apparatus and a concentration drying method according to a modification will be described.

FIG. 2 is a diagram showing a schematic configuration of a concentration drying apparatus according to a modification of the present invention.
As shown in FIG. 2, the concentration drying apparatus 2 according to the modification includes a membrane distillation cell 10, a stock solution pump P <b> 1, a heater (first heat exchanger) 20, and the concentration drying apparatus 1. A gas-liquid heat exchanger (second heat exchanger) 30, a cooler 40, a coolant pump P2, a concentrate tank 50, a concentrate pump P3, an air supply fan F1, an air heater 60, Spray dryer 70, powder separator 80, dust collector 90, exhaust air fan F 2, cooling fluid channel 120, concentrate channel 130, exhaust channel 140, and heat transfer medium 150 The first heat medium tank T10, the second heat medium tank T20, the first heat medium pump (flow rate adjusting means) P4, the second heat medium pump (flow rate adjusting means) P5, and the controller (control unit) 200. And.

  The concentration drying apparatus 2 according to the modification differs from the concentration drying apparatus 1 in that a stock solution circulation channel 210 for circulating the stock solution to the stock solution chamber 10a instead of the stock solution channel 110 for introducing the stock solution into the stock solution chamber 10a. It is a point equipped with. In addition, the other structure in the concentration drying apparatus 2 is the same as that of the said concentration drying apparatus 1.

  The stock solution circulation channel 210 communicates from the outlet to the entrance of the stock solution chamber 10a outside the room via a pipe or the like, and forms a channel for circulating the stock solution to the stock solution chamber 10a. On the stock solution circulation channel 210, a stock solution pump P1 and a heater 20 are installed. The stock solution circulation channel 210 is connected to a channel provided with the first valve V10. The stock solution circulation channel 210 is adapted to introduce a stock solution from outside the system by opening the first valve V10. Further, by closing the first valve V10, the flow path for circulating the stock solution is disconnected from the outside of the system.

  The stock solution circulation channel 210 is provided with a second valve V20. In the stock solution circulation channel 210, the channel for circulating the stock solution communicates with the outside by opening the second valve V20, and the channel for circulating the stock solution is closed by closing the second valve V20. Thus, a one-way flow path for discharging the concentrated liquid concentrated in the stock solution chamber 10a to the concentrated liquid flow path 130 is formed. In FIG. 2, the concentrate flow path 130 includes a third valve V30 that opens and closes the flow of the concentrate on the downstream side of the branch connected to the stock solution circulation path 210.

  Next, based on the specific operation method of the concentration drying apparatus 2, the concentration drying method according to the present embodiment will be described.

  The concentration drying method according to the present embodiment includes a condensate chamber (second chamber) separated from a stock solution chamber (first chamber) by a porous membrane that selectively transmits vapor and a stock solution chamber (first chamber) through which the stock solution flows. Chamber), a spray dryer for spraying and drying the stock solution discharged from the stock solution chamber (first chamber) into hot air, and the heat medium and the stock solution chamber (first chamber). And a heat exchanger that heats the stock solution by exchanging heat with the stock solution, wherein the stock solution is circulated between the stock solution chamber (first chamber) and the heat exchanger, and the heat exchanger Concentration by heating the stock solution by exchanging heat between the exhaust air discharged from the spray dryer and the stock solution, concentrating the heated stock solution in a membrane distillation cell, and spray-drying the concentrated stock solution in the spray dryer It is a drying method.

  In the concentration drying apparatus 2, the stock solution is introduced into the stock solution circulation channel 210 from outside the system by the operation of the stock solution pump P1. The stock solution is circulated through the stock solution circulation passage 210 with the first valve V10 and the third valve V30 closed and the second valve V20 opened. While circulating through the stock solution circulation channel 210, the stock solution exchanges heat with the heat medium flowing through the heat medium pipe 150 in the heater 20, and is concentrated by membrane distillation in the stock solution chamber 10a. After that, when the stock solution is concentrated to a predetermined target concentration rate, the concentrate is controlled through the concentrate channel 130 by closing the second valve V20 and opening the third valve V30. Is drained.

  The vapor pressure difference in the membrane distillation cell 10 is controlled mainly by adjusting the temperature difference between the heating temperature of the stock solution by the heater 20 and the cooling temperature of the cooling plate 12 by the cooler 40 as in the case of the concentration drying apparatus 1. do it. For example, the temperature of the stock solution or the coolant may be monitored and the heater 20 or the cooler 40 may be feedback controlled. Further, the integrated amount of condensate generated in the condensing chamber 10b may be monitored to quantitatively control the integrated amount of condensate.

  In the concentration drying apparatus 2, the spray dryer 70 can be steadily operated as in the case of the concentration drying apparatus 1. And the transfer amount of the heat medium of the 1st heat medium pump P4 and the 2nd heat medium pump P5 is adjusted to the flow volume lower than the transfer amount in the said concentration drying apparatus 1. FIG. In the heater 20, the stock solution is heated to an intermediate temperature lower than the target heating temperature by a single circulation, and the stock solution is repeatedly circulated to raise the temperature to the target heating temperature. For this reason, the amount of heat medium discharged by the first heat medium pump P4 and the second heat medium pump P5 is such that the heat exchanged to the extent that the stock solution is heated to an intermediate temperature is heat exchange in the heater 20 and the gas-liquid heat exchanger 30. To be adjusted.

  According to the concentration drying apparatus and the concentration drying method according to the above modification, the heating cost necessary for the membrane distillation is reduced as in the above-described embodiment, and the spray-dried product can be obtained from the diluted dispersion with energy efficiency. It is. Further, since the stock solution is circulated and heated between the stock solution chamber (first chamber) and the heat exchanger, the stock solution can be reliably heated to the target temperature when the stock solution is concentrated to a predetermined concentration rate. . It is also possible to obtain an advantage that a design with a reduced heat transfer area of the heat exchanger is allowed.

  In addition, the concentration drying apparatus 1 which concerns on the said embodiment, and the concentration drying apparatus 2 which concerns on a modification can perform a various deformation | transformation, substitution of a structure, etc. in the range which does not deviate from the meaning of this invention.

  For example, the concentration drying apparatus 1 according to the embodiment and the concentration drying apparatus 2 according to the modification include a cooling chamber (third chamber) separated from the condensation chamber (second chamber) by a cooling plate, and a cooling chamber. A cooling liquid passage for connecting the outlet of the (third chamber) and the inlet of the cooling chamber (third chamber) to circulate the cooling liquid in the cooling chamber (third chamber), and a cooler for cooling the cooling liquid And. However, the means for cooling the condensing chamber (second chamber) is not limited to this form, and any conventionally known form of a membrane distillation cell can be adopted. For example, instead of the cooling plate, the cooling liquid phase may be in direct contact with steam.

  Moreover, in the concentration drying apparatus 1 which concerns on the said embodiment, and the concentration drying apparatus 2 which concerns on a modification, the stock solution introduce | transduced into the stock solution chamber 10a is heated only by the heater 20 which performs heat exchange. However, other heaters may be installed in the stock solution flow path 110 or the stock solution circulation flow path 210 before or after the heater 20 that performs heat exchange. Other heaters are not limited to those that perform heat exchange, and may be in an appropriate form such as a combustion type or an electric heating type. By providing another heater, the stock solution can be heated to the target temperature even in the initial operation of the concentration drying device 1 and the concentration drying device 2 or when the heat energy of the exhaust air is insufficient.

  Moreover, in the concentration drying apparatus 1 which concerns on the said embodiment, and the concentration drying apparatus 2 which concerns on a modification, the 1st heat-medium tank T10, the 2nd heat-medium tank T20, and the 1st A heat medium pump P4 and a second heat medium pump P5 are provided. However, the number of the first heat medium tank T10, the second heat medium tank T20, the first heat medium pump P4, and the second heat medium pump P5 can be set appropriately. Further, the first heat medium tank T10 and the second heat medium tank T20 may not be provided, and the heat medium may be circulated constantly.

  Further, in the concentration drying apparatus 1 according to the embodiment and the concentration drying apparatus 2 according to the modified example, the powder separator 80 and the bag filter type dust collector 90 are provided on the exhaust path 140. Is provided. However, the apparatus which isolate | separates spray-dried material on the exhaust path 140 can be set as an appropriate structure. For example, two powder separators 80 such as cyclones may be connected in series, or an electric dust collector or the like may be arranged in place of the bag filter type dust collector 90.

  Moreover, in the concentration drying apparatus 1 which concerns on the said embodiment, and the concentration drying apparatus 2 which concerns on a modification, the heater 20 is provided in the exterior of the membrane distillation cell 10, and the undiluted | stock solution flow path 110 or undiluted | stock solution circulation flow The undiluted solution flowing through the passage 210 is heated. However, instead of this, the heater 20 may be installed in the stock solution chamber 10a and the stock solution may be heated inside the stock solution chamber 10a.

  Further, in the concentration drying apparatus 1 according to the embodiment and the concentration drying apparatus 2 according to the modified example, a single membrane distillation cell 10 is provided, and the concentrated liquid is discharged through the concentrated liquid flow path 130. Has been. However, instead of this, a plurality of membrane distillation cells 10 may be connected in series, and the concentrate flow path 130 may be connected to the membrane distillation cell 10 of the next apparatus and then connected to the spray dryer 70.

  Moreover, in the concentration drying apparatus 1 which concerns on the said embodiment, and the concentration drying apparatus 2 which concerns on a modification, the heat exchange performed between exhaust air and a stock solution uses the heat medium which flows through the heat medium pipe | tube 150. Has been done indirectly. That is, heat exchange is performed between the exhaust air discharged from the spray dryer and the heat medium, and further, heat exchange is performed between the heat medium and the stock solution, which is then introduced into the stock solution chamber (first chamber). The stock solution is heated. However, the heat exchange performed between the exhaust air and the stock solution may be performed directly without using a heat medium.

1 Concentration drying apparatus 10 Membrane distillation cell 10a Stock solution chamber (first chamber)
10b Condensing chamber (second chamber)
10c Cooling room (third room)
11 Porous membrane 12 Cooling plate 20 Heater (first heat exchanger)
30 Gas-liquid heat exchanger (second heat exchanger)
40 Cooler 50 Concentrated liquid tank 60 Air heater 70 Spray dryer 80 Powder separator 90 Dust collector 110 Stock solution flow path 120 Coolant flow path 130 Concentrated liquid flow path 140 Exhaust air path 150 Heat transfer pipe 200 Controller ( Control part)
F1 Air supply fan F2 Exhaust fan P1 Raw liquid pump P2 Coolant pump P3 Concentrated liquid pump P4 First heat medium pump (flow rate adjusting means)
P5 Second heat medium pump (flow rate adjusting means)
T10 1st heat medium tank T20 2nd heat medium tank

Claims (3)

A membrane distillation cell having a first chamber through which the stock solution is flowed, and a second chamber separated from the first chamber by a porous membrane that selectively permeates vapor;
A first heat exchanger that heats the stock solution by exchanging heat between the heat medium and the stock solution that flows into the first chamber;
A spray dryer for spraying and drying the stock solution discharged from the first chamber in hot air;
A concentration drying apparatus comprising: a second heat exchanger that exchanges heat between the exhaust air discharged from the spray dryer and the heat medium. Flow rate adjusting means for adjusting the flow rate of the heat medium in the second heat exchanger;
A control unit for controlling the flow rate adjusting means,
The concentration drying apparatus according to claim 1, wherein the control unit controls the amount of heat given to the stock solution by the first heat exchanger by adjusting a flow rate of the heat medium. A membrane distillation cell having a first chamber through which the stock solution is flowed, and a second chamber separated from the first chamber by a porous membrane that selectively permeates vapor;
A spray dryer for spraying and drying the stock solution discharged from the first chamber in hot air;
Heat exchange is performed by performing heat exchange between the exhaust air discharged from the spray dryer and the stock solution,
Concentrating the heated stock solution in the membrane distillation cell;
A concentration drying method in which the concentrated stock solution is spray dried in the spray dryer.

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