JP2005241239A - Drying apparatus with superheated steam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To construct an effective system which reforms steam generated in a dryer into good superheated steam to increase the condensing temperature and improve the heat transfer coefficient as well, and converts the heat energy thereof into power easy to use. <P>SOLUTION: The drying apparatus comprises a dryer 10 which allows a heating medium to flow into a heating medium flow passage to dry an object to be dried by indirect heating, wherein the dryer 10 has a substantially sealed structure, and is configured to allow the superheated steam to circulate and flow therein. The drying apparatus further comprises a temperature raising means 23 for drying in the circulating passage for the superheated steam, a heating means for power generation in an air extracting path for the circulating steam, a steam turbine using the superheated steam as a driving source, and a power generating means 42 which is coupled thereto. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a drying apparatus using superheated steam.

Unlike the operation of evaporating water from the liquid, the drying method that removes moisture from the wet material to be dried has a low evaporation rate because the water moves through the solid material (the material to be dried).
The evaporated gas contains air, and when condensed and reused, the condensation temperature is low and the heat transfer coefficient is low, and if a complicated heat transfer surface is adopted to increase this heat transfer coefficient, The equipment cost per unit heat transfer area is high, and a large heat transfer area is required, which is not economical.

  There are cases of drying operation by indirect heating and direct heating, and various types of dryers are known. Indirect heating (conduction heat transfer) dryers supply heat medium to the heat transfer means (heater) in contact with the material, and contact the heat transfer surface with the material by mechanical stirring or fluid flow stirring of the material with hot air. Drying is performed by applying heat while improving the properties. The driving force of indirect heating and drying is the difference between the temperature of the heat medium and the material and the heat transfer coefficient. Therefore, in principle, a large amount of heated air is not used as in direct heating described later. For this reason, indirect heating (conduction heat transfer) dryers are widely used for reasons such as easy drying operation.

  However, there are the following drawbacks. Indirect heat drying does not use a large amount of air, but the exhaust is taken out of the system together with the air. Usually, since the exhaust contains 20-50% air, the condensation temperature is low, and the heat transfer coefficient of condensation is low (because of gas mixing). Only hot water production. In the reduced rate drying section near the product outlet, there is little circulating gas and it is not in good contact with the material, so the drying rate in the reduced rate drying section where the diffusion of moisture in the material to the gas is rate limiting is slow, and the entire drying The speed is decreasing. The exhaust from the indirect heating (conducting heat transfer) dryer contains solids, and since the humidity of the exhaust is high, corrosive gas derived from the raw material may be diffused.

  On the other hand, a direct heating convection dryer is a device in which heated air is brought into contact with a wet object to be dried, and the object to be dried is heated, the water is evaporated, and the moisture is diffused by heating. The temperature difference at the outlet and the circulation rate of the heated air mainly define the drying efficiency, and it is also important to increase the contact between the heated air and the material to be dried. Drying efficiency is increased by the flow of hot air.

  Recently, in the direct heating drying method, a drying method using superheated steam instead of air is used (Non-Patent Document 1). In the convection drying method, it has been found that if the temperature of the superheated steam is set to a certain reverse temperature (for example, 180 to 200 ° C.) or higher, the drying rate is increased, and the moisture is diffused quickly, so that the dried product is uniform. The application range is expected to increase.

  However, in the drying method using superheated steam, in order to increase the drying rate, it is necessary to increase the circulating superheated steam to a temperature higher than the reversal temperature (for example, 180 to 200 ° C. described above) where the effect appears. In order to increase the temperature, high-pressure steam of 32 MPa to 63 MPa is required, or a high-temperature heat exchanger or the like is required for raising the temperature of the circulating superheated steam by the high-temperature gas.

  As an example of drying with superheated steam, there is drying of beetroot radish extracted from a beet sugar factory (Non-patent Documents 2 and 3). In this example, 2.2 MPa high-pressure steam is used as a heating source for the indirect air heater, and the temperature of the circulating superheated steam for fluidization is raised, and then placed in the lower part of the fluidized bed dryer to fluidize the extractor. The operation pressure of the fluidized bed dryer is 0.2 Mpa, and the generated steam is supplied to a multi-effect can for concentration of sugar solution for heat utilization.

However, this method is a special case in which heat can be utilized by supplying it to a multi-effect can for concentration of sugar solution, and is not general purpose. There is a need for a general use of waste heat.
Nobuchi: “Superheated Steam Drying Method”; Chemical Engineering, 66, 409-413 A. S. Jensen: ZUCKERIND. 113 (1990) 827-833 A. S. Jensen: “Steam drying of beet pull and bagasse”, International Sugar Journal 2003 Vol. 105

  The first problem of the present invention is to improve the drying rate in the reduced rate drying period, which is a disadvantage of the indirect heating dryer. The second problem is that the steam generated in the dryer is reformed to a predetermined quality (good quality superheated steam), thereby increasing the condensation temperature and improving the heat transfer coefficient. The aim is to build an effective system by converting energy into easy-to-use electric power and high-quality steam. Even in a convection dryer, an effective system is constructed by converting the heat of superheated steam into electric power that can be easily used. High temperature steam from the steam boiler as a heat source for drying is used to drive the steam turbine in the process of depressurization, and the steam turbine is also driven by the steam generated in the dryer. .

The present invention that has solved the above problems is as follows.
<Invention of Claim 1>
A structure in which a heating medium is circulated in the heating medium flow path to dry the material to be dried by indirect heating, the inside of the drying machine has a substantially sealed structure, and the space is circulated and circulated in the space. And a heating means for power generation in the extraction path of the circulating steam, a steam turbine using superheated steam as a drive source, and a power generation means connected thereto. A drying apparatus using superheated steam.

<Invention of Claim 2>
2. Drying with superheated steam according to claim 1, further comprising steam generating means, wherein the steam generated by the steam generating means is used as the heating medium for indirect heating, the heating medium for the temperature raising means, and the heating medium for the power generation heating means. apparatus.

<Invention of Claim 3>
A high-pressure steam turbine having a high-pressure steam generating means and a high-pressure steam turbine driven by the high-pressure steam from the high-pressure steam generating means and a power generation means connected thereto; The drying apparatus using superheated steam according to claim 1, wherein the heating medium is a heating medium of the temperature means and a heating medium of the heating means for power generation.

<Invention of Claim 4>
A structure in which a heating medium is circulated in the heating medium flow path to dry the material to be dried by indirect heating, the inside of the drying machine has a substantially sealed structure, and the space is circulated and circulated in the space. and then, the heating device provided in the circulation path of the superheated steam, a part of the circulating steam was then supplied to the heat utilization equipment for a heat source, it drying apparatus with superheated steam, characterized in.

<Invention of Claim 5>
The dryer has a stirring shaft that rotates about a substantially horizontal axis inside the cylinder, receives the material to be dried from one side in the longitudinal direction of the cylinder, and a drying operation is performed during the rotation of the stirring shaft. The superheated steam according to any one of claims 1 to 4, wherein the superheated steam is configured to be discharged from the other side, and the superheated steam is circulated from the other side of the cylindrical body to the one side. By drying equipment.

<Invention of Claim 6>
The inside of the dryer has a substantially sealed structure, the superheated steam is brought into direct contact with the material to be dried, and the superheated steam after contact is circulated and circulated. A drying apparatus using superheated steam, characterized in that a heating means for power generation is provided in a steam extraction path, a steam turbine using superheated steam as a drive source, and a power generation means connected to the steam turbine.

<Invention of Claim 7>
The inside of the dryer has a substantially sealed structure, the superheated steam is brought into direct contact with the material to be dried, and the superheated steam after contact is circulated and circulated. A superheater is provided in an extraction path after dry dedusting of steam, a high temperature gas generation means for the superheated steam temperature rising means and a superheated steam superheater is provided, and a steam turbine using superheated steam as a drive source, and A drying apparatus using superheated steam, comprising: a steam turbine using connected superheated steam as a drive source; and a power generation means connected to the steam turbine.

<Invention of Claim 8>
A high-pressure steam generator having a high-pressure steam generating means connected to the high-pressure steam turbine using the high-pressure steam from the high-pressure steam generating means and a power generation means connected thereto; The drying apparatus using superheated steam according to claim 7, wherein the heating medium is a heating medium for the temperature raising means and a heating medium for the heating means for power generation.

<Invention of Claim 9>
The drying apparatus using superheated steam according to any one of claims 1 to 8, wherein a part or all of the dried product is used as a fuel source in the steam generating means or the high-pressure steam generating means.

<Invention of Claim 10>
Before the dryer, a pressure filter or vacuum filter that performs filtration of the slurry to be filtered is provided, and a part of the circulating superheated steam is supplied and brought into contact with the object to promote drying of the object. The drying apparatus using superheated steam according to any one of claims 1 to 9, wherein a solid content is the material to be dried.

<Invention of Claim 11>
The apparatus for drying with superheated steam according to claim 10, wherein the superheated steam is blown toward the slurry on the filter medium.

<Invention of Claim 12>
The drying apparatus using superheated steam according to claim 10 or 11, wherein the dryer is a fluidized dryer with a built-in heater.

(About indirect heating dryers (conduction heat transfer dryers))
The indirect heating type dryer (conducting heat transfer dryer) of the present invention gives heat to the object to be dried through the heat transfer surface to the object to be dried (wet material). A known dryer can be used, and it is desirable to industrially use a heat transfer surface and an object to be dried to improve the heat transfer rate. 1) Grooving type dryer: A heat transfer board (with a heat medium circulating inside) is attached to a rotating shaft inside a cylinder and brought into contact with a solid by mechanical stirring. 2) Multi-tube rotary dryer: A heating medium heating tube group provided in a rotating cylinder and brought into contact by rolling or rotating and dropping solid materials. 3) Fluidized dryer with built-in heater: A device in which a heat transfer plate (a heat medium is circulated) is inserted into a fluidized bed of a flow medium, and brought into contact with the heat transfer plate due to flow. 4) Heater built-in type high-speed fluidized dryer: A heating medium is passed through the outside of a multi-tubular heating tube, and a fluidizing medium is present in the tube to bring it into high-speed contact with the heat transfer surface.

  According to the present invention, when using an indirect heating dryer, the drying rate during the reduced rate drying period can be improved. The steam generated in the dryer is reformed to a predetermined quality (high-quality superheated steam), thereby increasing the condensation temperature and improving the heat transfer coefficient, making it easy to use the heat energy that it has An effective system can be constructed by converting into high-quality steam for electric power. Even in a convection dryer, an effective system can be constructed by converting the heat of superheated steam into electric power that can be easily used. High-temperature steam from the steam boiler as a heat source for drying is driven by a steam turbine in the depressurization process, and the steam turbine is also driven by steam generated in the dryer, so that heat can be used effectively comprehensively. And so on. In addition, by supplying the dried product to an incinerator with a high-pressure boiler, energy self-sustained biomass power generation is possible.

The present invention will be further described below with reference to the best mode for carrying out the present invention.
<First embodiment: Indirect heating>
In the first embodiment of FIG. 1, the dryer has an agitation shaft that rotates about a substantially horizontal axis inside the cylinder, receives the material to be dried from one side in the longitudinal direction of the cylinder, and A drying operation is performed in the process of rotating the shaft, and the dried product is discharged from the other side. The superheated steam flows from the other side of the cylindrical body to the one side.
Specifically, it has a groove-shaped indirect heating (conduction heat receiving) type dryer 10, and a rotating shaft 11 b that rotates around a substantially horizontal shaft core with a large number of heating plates 11 a mounted in a cylinder 11. A heating steam passage is formed between the steam inlet 11c and the drain outlet 11d. The material to be dried D0 is charged from one side in the cylinder 11 through the material inlet rotary valve 11i and from the inlet 11e, and the dried material D1 is discharged from the outlet 11f on the other side through the dry product outlet rotary valve 11j. Discharged.
Further, a circulating gas inlet 11g and a circulating gas outlet 11h are formed at the upper part of the cylindrical body 11, and the circulating gas is brought into contact with the flow of the material to be dried in countercurrent.
Further, the inside of the dryer 10 has a substantially sealed structure. Specifically, measures such as providing a material supply rotary valve 11i and a dry product outlet rotary valve 11j for sealing between the rotating shaft 11b and the cylinder 11, and sealing the material to be dried D0 and the dry material D1. The inside of the cylinder 11 is set to a pressure of 0.5 to 1.0 KPa in water, for example. By doing so, the amount of air in the exhausted circulating steam gas (circulated superheated steam) can be suppressed to 0.05 to 0.01%, and the quality and thermal characteristics of the steam can be improved.
Exhaust of superheated steam from the circulation gas outlet 11h is sent to the cleaning device 20 by the blower 21, sprayed with an alkaline liquid by the circulation pump 22 in the cleaning device 20, and heated by the heating device 23 after wet dust removal, A superheated steam circulation path is formed which becomes superheated steam and is returned to the circulating gas inlet 11g. Steam for power generation is extracted from E1 from the circulation path.

The exhaust of the dryer 10 includes solid matter derived from the material to be dried D0. Therefore, it can be collected by a dry dust remover, for example, a cyclone or a bag filter. However, normally, the to-be-dried material D0 often contains a corrosive volatile substance. Therefore, when a steam turbine is used in the subsequent process, the removal of the corrosive substance causing the corrosion and the removal of the dust are performed. Need to do. Therefore, as in the embodiment, if necessary, a filler, a shelf or the like is provided inside, brought into contact with rising superheated steam and alkali (for example, caustic soda) liquid, wet dust is removed, and volatile substances ( It is also desirable to remove SO ₂ etc. Since the cleaning temperature in wet dust removal is low in non-condensable gas in the circulating superheated steam, for example, 99 ° C. can be easily maintained. The temperature drop due to the cleaning temperature does not cause a large heat loss because the heating temperature in the required heater 23 is as low as 100 to 120 ° C. Further, in order to actively reduce the rate-of-decreasing drying section near the outlet of the dried product D1 in the dryer, it is necessary to superheat the circulating steam with the heater 23, but the required temperature may be about 120 ° C. In addition, there is no significant heat loss.

  For example, an intermediate pressure boiler 30 as a heating means is provided for heating the dryer 10 and heating with the temperature raising device 23 for circulating steam. A part of the heating steam generated in the intermediate pressure boiler 30 is circulated from the steam inlet 11c into the rotary shaft 11b and the heating panel 11a via the path 31, and then discharged from the drain outlet 11d. The object to be dried D0 is heated by the heating of the rotating shaft 11b and the heating platen 11a, and the evaporated water diffuses into the circulating superheated steam and is discharged from the circulating gas outlet 11h.

  The remaining portion of the heating steam generated in the intermediate pressure boiler 30 is led to the temperature raising device 23 via the path 32A, and the circulating steam from the cleaning device 20 is heated to form superheated steam, and also via the path 32B. After the vapor filtered (dust-removed) by the microfilter 41 described below is introduced to the power generation heater 24 for raising the temperature to a level sufficient for power generation, each steam is heated and heated after power generation. The condensed water is returned to the intermediate pressure boiler 30 by the water absorption pump 34 through the path 33. Here, another external heat source can also be used as a heating source in the heater 23.

  On the other hand, a part of the clean steam from the cleaning device 20 is filtered, for example, by a microfilter 41 having a special filter medium having a pore diameter of 0.5 to 1 μm to remove fine particles (for example, 3 μm average diameter) solids, and the power generation After raising the temperature to a level sufficient for power generation through the heating heater 24, the air is led to a low-pressure steam turbine 43 with a generator 42 connected to a condenser 44. The vacuum pump 45 expands to the pressure of the condenser 44 in which a vacuum is maintained, rotates the turbine, and generates electricity. The drain obtained here is taken out of the system.

  In the above operation, the present inventors set the circulating superheated steam supply temperature at 115 ° C. to 125 ° C. and shortened the circulation superheated steam heated at the end of drying in order to shorten the decreasing rate drying section near the outlet of the dryer 10. It has been empirically found that the reduction rate drying section is significantly reduced if the product and the material to be dried are contacted countercurrently. This temperature guide may be 20 ° C. or more lower than the final product temperature, or 20 to 30 ° C. lower than the vapor temperature of the heat transfer means. Unlike the direct heating dryer, the indirect heating dryer does not have a temperature reversal, so there is no need to increase the inlet temperature. It was also found that if the minimum circulation rate at the dryer inlet is about half of the evaporated vapor, a stable drying operation and an operation for extracting the superheated vapor from the evaporated component are possible. When recovering heat as motive power, it is supplied to the microfilter 41, further removes dust, and supplied to the steam turbine. The exhaust gas is put into a condenser and non-condensable gas is extracted by a vacuum pump. If saturated steam at atmospheric pressure is supplied to the turbine as it is, the wetness at the outlet will be 15% or more, exceeding the allowable wear value of the impeller of the turbine. In this case, since the wetness can be reduced to 10% or less, stable operation is possible.

<Second Embodiment: Indirect Heating>
FIG. 2 shows a second embodiment, in which high-pressure steam generating means, for example, a high-pressure boiler 50 is provided, and a high-pressure steam turbine 63 that uses high-pressure steam from the high-pressure boiler 50 as a drive source, and is connected thereto. The generator 62 is provided, and the exhaust gas from the high-pressure steam turbine 63 is used as a heating medium for indirect heating, a heating device 23 (heating device), and a heating medium for the generator heater 24.

  An example of operation will be described. High-pressure boiler 50 generates high-pressure steam, obtains superheated steam of, for example, 3.2 MPa 350 ° C., sends it to high-pressure steam turbine 63, and sets the exhaust pressure to, for example, 0.4 to 0.8 MPa. After generating electricity, it is supplied to the indirect heating type dryer 10 as a heat source for drying. Even in an indirect heating type dryer that does not use superheated steam, it is a system that is practically sufficient as can be understood from the fact that 0.3 to 0.6 bar saturated steam is generally supplied. . In this example, the first stage is power generation by the high-pressure steam turbine 63 and the generator 62 at high pressure, the second stage is drying by the indirect heating (conduction heat receiving) type dryer 10, and the third stage is the low-pressure steam turbine 43 and generator 42. It becomes a low-pressure power generation system.

<Third embodiment: Indirect heating>
FIG. 3 shows a third embodiment in which a part of the circulating superheated steam is supplied to the heat utilization facility 400 as a heat source. In this case, when a part of the circulating superheated steam is supplied to the heat utilization facility 400, it can also be supplied in parallel to the low-pressure steam turbine 43 with the generator 42 as in the above-described embodiments.
Unlike the case of a general indirect heating type dryer, since the exhaust gas by superheated steam drying has a low air content and high quality steam can be obtained, not only low-pressure power generation but also the heat utilization equipment 400 As a specific example, it is used as a process heat source. For example, it can be used as a driving heat source for heating, reaction, or absorption heat pump of a solution in the process.
As a further specific example, there is an evaporation process of corn steep liquor provided near the drying process of corn fiber, which can be used for the heating steam of the evaporator. As shown in the second embodiment, if the high-pressure boiler 50 is used to generate high-pressure steam, three operations of power generation, drying and evaporation can be performed in a three-stage cascade, and if low-pressure steam is used, two-stage operation is possible. Of heat.
The amount of non-condensable gas mixed in the steam generated in the dryer by superheated steam drying is small. According to the experimental results, the amount of non-condensable gas mixed is about 0.01 to 0.1 vol% of the evaporated vapor. Since this steam has high heat transfer characteristics, it can be used not only for power generation but also as a heating source for process evaporators, reboilers, reactors, steaming and the like.

<Fourth embodiment: direct heating>
FIG. 4 shows a fourth embodiment by direct heating. The direct heating dryer 10A has a substantially hermetically sealed structure, and superheated steam is brought into direct contact with the material to be dried. It is configured to circulate and circulate steam, and a temperature raising means 23 is provided in the superheated steam circulation path, and after removing a part of the superheated steam, the low-pressure steam turbine 43 using the superheated steam as a drive source through the generator heater 24 and The power generation means 42 connected to this is provided. The high-temperature exhaust gas from the high-temperature combustion furnace 70 is used as a heating source for the temperature riser 23 and the power generation heater 24.
In this case, a dry dust remover such as the illustrated cyclone 20A or bag filter can be used as the dust removing means. The dust removal dust can be returned to the supply path of the material to be dried D0.
Since hot gas is used, burning of the raw material and ignition become a problem. However, since superheated steam is an inert gas, its risk is low. Further, even in superheated steam drying, the temperature of the material during drying can be lowered by performing an operation in which the flow of the material and the gas is parallel.

<Fifth embodiment: direct heating>
FIG. 5 shows a fifth embodiment by direct heating. The direct heating dryer 10A has a substantially hermetically sealed structure, and superheated steam is brought into direct contact with the material to be dried. It is configured to circulate and circulate steam, and a temperature raising means 23 is provided in the superheated steam circulation path, and after removing a part of the superheated steam, the low-pressure steam turbine 43 using the superheated steam as a drive source through the generator heater 24 and The power generation means 42 connected to this is provided. Then, a high-pressure steam generating means, for example, a high-pressure boiler 50 is provided, a high-pressure steam turbine 63 using the high-pressure steam from the high-pressure boiler 50 as a drive source, and a generator 62 connected thereto are provided, and exhaust gas from the high-pressure steam turbine 63 is provided. Is used as a heating medium for the temperature raising device 23 (temperature raising means) and the power generation heater 24. In the drawing, the material supply rotary valve 11i and the dried product outlet rotary valve 11j are omitted.

<Sixth embodiment: Indirect heating>
FIG. 6 shows a form that can be used for direct heating as well as indirect heating. That is, when power is generated from agricultural products with high moisture content, forest waste industrial waste, various sludges, wood, etc., preliminary drying is performed to improve thermal efficiency. In general, water vapor generated during preliminary drying is diffused to the atmosphere. Effective utilization of this energy is desired.
For this purpose, an object to be dried (for example, biomass raw material) having a high water content (water content of 75% or more) is supplied to the hermetic dryer 10 and dried, for example, in the same manner as in the second embodiment of FIG. The obtained dried product having a moisture content of 10 to 25% is supplied to the high-pressure boiler 50 through the path 11k to generate high-pressure steam to generate power, thereby further improving the energy of the dried product. It will be available.

<Seventh Embodiment: Pressure Filter>
In continuous filtration operation, saturated steam of about 3 to 6 bar generated in a boiler is sprayed on the slurry surface, and the liquid content of the cake is replaced with drain condensed steam, and the purity (in the case of slurry containing crystal content) Techniques for improving the dehydration and dehydrating properties are known. However, in order to use saturated steam, it is rarely used in terms of cost, for example, it is necessary to install a boiler.
On the other hand, in the following embodiment, superheated steam is used instead of saturated steam, so that cleaning and dewatering efficiency can be further improved and purity can be improved, and the burden on the subsequent dryer is reduced. By doing so, the system is excellent in drying efficiency as a whole.
7 to 9 show a seventh embodiment in combination with a continuous rotary cylindrical pressure filter 100, and the filter 100 has a rotary drum 102 in a pressure-resistant casing 101. The rotating drum 102 is divided by a partition plate 102c in the circumferential direction, and a filter cloth 102b is provided on the filter cloth support member 102a. A filtrate discharge pipe 102d is connected to each partitioned chamber, the other is connected to a rotation switching valve 102e, and filtration, washing, dehydration and discharge operations are performed by valve operation with the outer fixed valve 102f. 104 is a blower.
The slurry S to be filtered is fed by the pressure pump 103, picked up on the rotating drum 102, dehydrated and filtered, and when the cake is formed, the cake is peeled off by blowing back the gas from the back side of the filter cloth. The peeled cake is introduced into the screw conveyor from the inlet 11e via the material supply rotary valve 11i, and then charged into the indirect heating type dryer 10.
The filtrate is guided to the separation tank 105, the separated filtrate is discharged out of the system, and the separated steam is led to the washer 20 after condensing excess steam with cooling water.
A part of the superheated steam after passing through the cleaning device 20 is made into a superheated steam circulation system by the blower 107 in the same manner as described above, and the other part is heated by the heater 106 by the heated steam by the compressor 106. Then, it blows toward the slurry or cake layer on the rotating drum 102.
Another mechanism known as the above rotary cylindrical pressure filter may be used.
In general, it is difficult to increase the thermal efficiency by using low-pressure steam generated in a dryer to process the material to be dried. According to this aspect, it is efficient by passing superheated steam through the filter cake. The load on the dryer is remarkably reduced as the temperature of the material to be dried increases, the adhesion moisture decreases, and the temperature of the material to be dried increases.
By the way, if the case of drying terephthalic acid is taken as an example, in the normal vacuum filtration, the one with 12% moisture becomes the material to be dried with 8% moisture and the temperature of 98 ° C. The area is reduced by about 35%. Since the heat transfer surface is not required in the superheated steam dehydration of the present embodiment, the heat transfer area of the indirect heat dryer can be greatly reduced because the indirect heating dryer relies on physical water removal. And since the to-be-dried material from a pressure filter has a low moisture content and temperature is about 100 degreeC, when it supplies in an indirect heating dryer, drying will progress immediately and it will become a thing with high drying efficiency.

<Eighth embodiment: vacuum filter>
10 and 11 show an eighth embodiment in combination with a continuous rotary cylindrical vacuum filter 100A. The vacuum filter 100A is designed to evacuate the casing 101 by a vacuum pump 110. FIG. is there. 111 is a filtrate pump. Further, the superheated steam is blown into the cake generation surface via the blow box 109. Since the other configuration is found from the configuration shown in the drawing, the description is omitted.
When superheated steam is blown along a circular arc that is long in the circumferential direction, such as the blowing box 109, as shown conceptually in FIG. 11, the section that preheats as the superheated steam condenses and the moisture in the cake are removed. It can be conceptually divided into a drainage section and a drying section where the drying and temperature rise dominate.

<Ninth Embodiment: Combination of Vacuum Filter and Heater Built-in Fluid Dryer>
FIG. 12 shows a ninth embodiment in which a continuous rotary cylindrical vacuum filter 100A and a heater built-in type fluid dryer 10B are combined, and an object to be dried D0 from the vacuum filter 100A is fluidized. The battery is charged into the dryer 10B. In the fluid dryer 10B, a large number of vertical heating tubes are fixed between upper and lower tube plates, and a heater is provided in a built-in state. From the upper part of the heater, for example, by heating steam from an intermediate pressure boiler, Drying is performed. The exhaust gas is guided to the cyclone 20A and separated into a dried product and superheated steam, and the dried product is guided to the screw conveyor through the rotary valve 11j to form a circulating fluidized bed, and the remainder is taken out as a dried product D1.
A part of the exhaust gas from the cyclone 20A is circulated to the lower part of the fluid dryer 10B as superheated steam through the temperature riser 23.

(Other)
In the above embodiment, steam is used as the heat source of the indirect heating dryer, but an organic heating medium or the like can also be used as the heating medium. Further, as in the embodiment of FIG. 4, other heating sources besides steam can be used as the heating source of the temperature raising device. Further, as the indirect heating dryer, a rotary dryer (steam tube dryer) with a built-in heating tube type can be used.
Moreover, a horizontal belt filter can be used as a filter, and a mode in which superheated steam is blown into the upper surface via a blowing box 109 can be employed.
Furthermore, the above embodiments can be combined as appropriate to constitute an apparatus.

An experimental example using a steam tube dryer is shown.
Superheated steam using a closed steam tube dryer multi-tube rotary dryer with a diameter of 450 mm, a total length of 3000 mm, a diameter of 40 mm, and a length of 40 mm × length of 3000 mm, a heat transfer area of 4.5 m ² , and a rotational speed of 12 rpm. Circulating blower; 30 m ³ / hr, steam cleaner; diameter 200 m, height 1000 mm, circulating superheated steam 0.8 kW electric heater, extraction condenser 0.45 m ² , saturation of steam pressure 0.45 Mpa The steam supplied corn fiber moisture of 48.3% at a corn starch factory at 36.0 kg / hr by a sealed rotary valve, dried to 4% moisture and taken out. Operation was performed at a dryer outlet superheated steam temperature of 100 ° C. to 103 ° C., a washer outlet temperature of 98 to 99.5 ° C., and a circulating superheated steam temperature of 120 ° C. at the dryer inlet. About 0.5 kW of steam was used for this temperature increase. The amount of steam used for the dryer was 24.9 kg / hr, the total amount of steam was 16.5 kg / hr, and the drying rate was 3.67 kg / m ² h.
When the outlet moisture is suppressed to 4% with the same heating steam pressure in the conventional aeration method, the maximum supply amount is 33.2 kg / hr, the used steam amount is 22.6 kg / hr, and the drying rate is 3.38 kg / m ^2. hr, and the above-mentioned superheated steam drying has a high capacity of about 10%. It was found that indirect heating does not require the high-temperature circulating steam that has been pointed out in the past, and that the decrease in the drying rate in the rate-decreasing drying section of the indirect heating dryer can be prevented by superheated steam drying and the drying rate can be increased.

An embodiment using a steam tube dryer is shown in the form of FIG.
In the drying process to make corn fiber by-product at corn starch factory, raw material 21.4t / hr, moisture 48% 18%, high pressure boiler accepts 11.2t / hr of superheated steam with 3.2Mpa, superheat degree 320 ℃ Then, the pressure was reduced to 0.6 MPa with a high-pressure steam turbine to generate 813 kW, exhaust steam 9.78 ton / hr was used to dry a steam tube dryer with a diameter of 3400 mm and a total length of 26 m and a heating area of 1423 m ² , and superheated circulating steam was used. It was supplied from the product outlet side and brought into countercurrent contact with the raw material at a temperature of 130 ° C. A product with an evaporation amount of 7830 kg / hr and a moisture content of 18% was obtained. The exhaust from the dryer is set at an outlet temperature of 105 ° C., and the circulating superheated steam is heated by a circulating blower of 470 m ³ / min through a washing tower with a diameter of 3400 mm and a height of 4500 mm, and a part of the circulating superheated steam is heated. It is circulated to a dryer at 130 ° C. in a vessel 140 m ² , and 7280 kg / hr of steam for power generation is extracted from the circulation path, and then put into a filter using a 150 m ² surface filter material, and the inlet dust concentration is 20 mg / m ^3. Was further fed to a power generator heater 180 m ² at 1 mg / m ³ , supplied to a low-pressure steam turbine at 160 ° C., and a power of 480 kW was obtained at a pressure of 0.015 Mpa in the condenser. The vacuum pump used a 30 kw electric motor at 15 m ³ / min. It was found that the total power generation amount was 1397 kW (power generation end), and that the power generation amount in the superheated steam dryer was 480 kW.

An example in which a direct contact dryer is used will be described with reference to the embodiment of FIG.
172 tons / day and 70 to 71% moisture extracted from a sugar beet radish 3100 tons / day processing plant were treated by a steam-superheated drying method using the convection dryer shown in FIG. In addition, as equipment, a bag filter is provided in the rear stage of the cyclone 20A in FIG. 4, and a HEPA filter is used as the precision filter 41.
As a dryer, a rotary dryer having a diameter of 3200 mm and a total length of 24 m, a rotational speed of 8 rpm, a driving power of 22 kW and a stepped contact blade inside was used, and a dried product having a moisture content of 12% was obtained. Circulating superheated steam at the entrance of the dryer is 56,800 kg / hr, inlet temperature is 750 ° C., outlet temperature is 140 ° C., dust is removed by a low-pressure cyclone, and the obtained 370 kg / hr of dust is returned to the raw material, and the decirculated circulating steam Except for power recovery by a blower, it is supplied to a 2500m2 temperature riser and heat-exchanged with 850 ° C hot air from a hot air generator that burns 1170kg / hr of A heavy oil to a 750 ° C outlet temperature to the dryer. A feed drying cycle was completed.
On the other hand, 15.9 tons / hr of superheated steam corresponding to the evaporated moisture is extracted, passed through a bag filter equipped with a surface filter medium of 1200 m ² , further passed through a finishing filter (HEPA filter), and a generator heater 300 m ^2. The steam was supplied to the steam turbine at an inlet pressure of 0.11 MPa and a temperature of 160 ° C., and a power of 1020 kW (power generation end) was obtained at a condensation temperature of 50 ° C. and a condensation pressure of 0.011 MPa. Fuel consumption per ton of beet is 163 kg / ton dry matter, which is about 10% more than hot air recycling, but it will generate 1020 kW without steam boiler from unused energy that was previously discarded. I was able to.

Industrial applicability

  By-product fiber from wet processing process of corn, radish fragment after sugar extraction at sugar beet sugar factory, distillation residue from ethanol fermentation of grain raw material, mash from shochu brewing, waste material as raw material for biomass power generation, pulp sludge, sewage This applies to sludge. In any case, the water content is 50 to 80%, and it is possible to convert the power of unused biomass by effectively using the generated steam and energizing the dried product. In the chemical industry, it can be applied to the baking process of gypsum or the drying process of terephthalic acid. In any case, a combined effect can be achieved by a rational combination of a heat-utilizing treatment process and a power generation device.

It is explanatory drawing which showed the 1st Embodiment of this invention. It is explanatory drawing which showed the 2nd Embodiment of this invention. It is explanatory drawing which showed the 3rd Embodiment of this invention. It is explanatory drawing which showed the 4th Embodiment of this invention. It is explanatory drawing which showed the 5th Embodiment of this invention. It is explanatory drawing which showed the 6th Embodiment of this invention. It is explanatory drawing which showed the 7th Embodiment of this invention. It is the general | schematic cross-sectional view. It is the outline longitudinal cross-sectional view. It is explanatory drawing which showed the 8th Embodiment of this invention. It is a conceptual explanatory view of the principle of drying with superheated steam. It is explanatory drawing which showed the 9th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Indirect heating (conduction heat receiving) type dryer, 10A ... Direct heating type (convection type) dryer, 10B ... Built-in heater type fluid dryer, 11 ... Cylindrical body, 20 ... Washing machine, 20A ... Dry-type dust remover ( Cyclone), 23 ... Temperature raising device, 24 ... Heating heater, 30 ... Medium pressure boiler, 41 ... Precision filter, 42 ... Generator, 43 ... Low pressure steam turbine, 45 ... Vacuum pump, 50 ... High pressure boiler, 62 DESCRIPTION OF SYMBOLS ... Generator, 63 ... High pressure steam turbine, 70 ... High temperature combustion furnace, 100 ... Continuously rotating cylindrical pressure filter, 100A ... Continuously rotating cylindrical vacuum filter.

Claims (12)

  A configuration in which a heating medium is circulated in the heating medium flow path and a drying object is dried by indirect heating, and the inside of the drying machine has a substantially sealed structure, and the space is configured to circulate and circulate superheated steam. A heating means is provided in the circulation path of the superheated steam, a heating means for power generation is provided in the extraction path of the circulating steam, and a steam turbine using the superheated steam as a drive source and a power generation means connected thereto are provided. A drying apparatus using superheated steam.   2. Drying with superheated steam according to claim 1, comprising steam generating means, wherein the steam generated by the steam generating means is used as the heating medium for the indirect heating, the heating medium for the temperature raising means, and the heating medium for the power generation heating means. apparatus.   A high-pressure steam turbine having a high-pressure steam generating means and a high-pressure steam turbine driven by the high-pressure steam from the high-pressure steam generating means and a power generation means connected thereto; The drying apparatus using superheated steam according to claim 1, wherein the heating medium is a heating medium of the temperature means and a heating medium of the heating means for power generation. A structure in which a heating medium is circulated in the heating medium flow path to dry the material to be dried by indirect heating, the inside of the drying machine has a substantially sealed structure, and the space is circulated and circulated in the space. and then, the heating device provided in the circulation path of the superheated steam, a part of the circulating steam was then supplied to the heat utilization equipment for a heat source, it drying apparatus with superheated steam, characterized in.   The dryer has a stirring shaft that rotates about a substantially horizontal axis inside the cylinder, receives the material to be dried from one side in the longitudinal direction of the cylinder, and a drying operation is performed during the rotation of the stirring shaft. The superheated steam according to any one of claims 1 to 4, wherein the superheated steam is configured to be discharged from the other side, and the superheated steam is circulated from the other side of the cylindrical body to the one side. By drying equipment.   The inside of the dryer has a substantially sealed structure, the superheated steam is brought into direct contact with the material to be dried, and the superheated steam after contact is circulated and circulated. A drying apparatus using superheated steam, characterized in that a heating means for power generation is provided in a steam extraction path, a steam turbine using superheated steam as a drive source, and a power generation means connected to the steam turbine.   The inside of the dryer has a substantially sealed structure, the superheated steam is brought into direct contact with the material to be dried, and the superheated steam after contact is circulated and circulated. A superheater is provided in a bleed passage after dry dedusting of steam, a high temperature gas generating means for heating the superheated steam and a superheater of the bleed steam is provided, a steam turbine using superheated steam as a drive source, and A drying apparatus using superheated steam, comprising: a steam turbine using connected superheated steam as a drive source; and a power generation means connected to the steam turbine.   A high-pressure steam generator having a high-pressure steam generating means connected to the high-pressure steam turbine using the high-pressure steam from the high-pressure steam generating means and a power generation means connected thereto; The drying apparatus using superheated steam according to claim 7, wherein the heating medium is a heating medium for the temperature raising means and a heating medium for the heating means for power generation.   The drying apparatus using superheated steam according to any one of claims 1 to 8, wherein a part or all of the dried product is used as a fuel source in the steam generating means or the high-pressure steam generating means.   Before the dryer, a pressure filter or vacuum filter that performs filtration of the slurry to be filtered is provided, and a part of the circulating superheated steam is supplied and brought into contact with the object to promote drying of the object. The drying apparatus using superheated steam according to any one of claims 1 to 9, wherein a solid content is the material to be dried.   The apparatus for drying with superheated steam according to claim 10, wherein the superheated steam is blown toward the slurry on the filter medium.   The drying apparatus using superheated steam according to claim 10 or 11, wherein the dryer is a fluidized dryer with a built-in heater.

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