JP2554509B2 - Dryer equipped with high-speed fluidized bed - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drying apparatus that uses superheated steam as a fluid for flowing in a fluidized bed and recompresses evaporated vapor to use as a heat source for self-heating. Further, the present invention is used in processes such as drying of various substances in the chemical industry, drying of various products in the food industry, and drying of various products in the mining industry.

[Conventional technology]

Dryers are roughly classified into a direct heating method and an indirect heating method, depending on the difference in their heat transfer mechanism. In the direct heating method, high-temperature gas (heating air, combustion gas, etc.) is brought into direct contact with the object to be heated to evaporate the liquid component, and the generated vapor is separated and exhausted out of the system together with the supply gas whose temperature has dropped. However, the dew point of the exhaust gas is generally low, and it is difficult to recover and utilize the exhaust heat that is discarded together with the exhaust gas. A high-humidity drying method has been realized in which a part of the exhaust gas is recirculated to increase the dew point of the exhaust gas, but the dew point is still about 70 to 80 ° C.

The indirect heating method indirectly heats the object to be processed through the heat transfer surface, but in order to take out the evaporated vapor out of the system, it is generally necessary to supply the atmosphere to the object to be processed as a carrier gas, The dew point of the exhaust gas is around 80 to 90 ° C, and it is still difficult to fully recover and utilize the exhaust heat.

[Problems to be solved by the invention]

If the object to be treated is directly heated using superheated steam, 100
It is possible to obtain exhaust heat at a dew point of ℃. However, in the case of direct heating with superheated steam, the problem of internal dew condensation of the flowing steam caused by the temperature of the supplied processing product being lower than the dew point, the problem of dew condensation on the inner surface of the device due to heat radiation from the device, and the supply and discharge of raw materials and products. There are many practical problems such as the sealing property with the outside of the system and the method of removing the air leaking into the system.

That is, firstly, when the processed product is supplied into the superheated steam, the temperature of the processed product is generally lower than the saturation temperature (100 ° C.) of the superheated steam, so that the steam is first condensed on the surface of the processed product, and accordingly Evaporation starts after the temperature of the water in the processed product rises due to the temperature rise of the processed product generated. During this period, the water content of the treated product is apparently high, which is different from the physical properties at the time of supply. That is, the fluidity of the treated product is reduced,
Phenomena such as agglomeration and adhesion occur, which is a cause of extremely disturbing the operation of the device.

Secondly, as a measure against this, it is usually effective to increase the superheat degree of superheated steam (for example, 140 ° C. or higher) and accelerate heat transfer to shorten the water content as high as possible. A phenomenon such as denaturation of the processed product and further adhesion due to excessive temperature rise of the product tends to be induced. Further, since it is necessary to raise the temperature of the heat source to be supplied, for example, when the exhaust heat having a saturation temperature of 100 ° C. is heated and boosted by a steam compressor as in the present invention, and is used for heating the high-speed fluidized bed, It is necessary to consume a great deal of power for compression.

Thirdly, the direct superheat drying operation using superheated steam reduces the driving force required for evaporation as compared with the case of using a low steam content gas, and thus the drying speed decreases. Therefore, in order to improve the efficiency of the device, it is necessary to use a method with high heat transfer efficiency.

A fourth problem is that the superheated steam needs to be circulated and used, but a part of the circulatory system may have a negative pressure with respect to the atmospheric pressure, so that the atmospheric air leaks into the circulatory system. In addition, when the raw materials and products are supplied and discharged, some air leaks into the circulation system. Further, depending on the substance to be treated, non-condensable gas may be generated by heating. When such non-condensable gas accumulates in the circulation system, the dew point of superheated steam decreases, so it is necessary to release part of the circulation gas to maintain the concentration of the non-condensable gas below a certain value.
The calorific value of the steam entrained in the released non-condensable gas is lost.

As described above, although direct drying itself by superheated steam is known, there is actually no system that has been determined due to energy efficiency, changes in the physical properties of processed materials, operational problems, and the like.

Therefore, a main object of the present invention is to provide a drying device which has a high drying efficiency per unit energy, does not change physical properties of a material to be dried (processed material), and can be stably operated.

[Means for solving problems]

A first aspect of the present invention for solving the above problems is a high-speed fluidized bed which has a built-in heater and is operated near the terminal velocity of particles by superheated steam as a fluid for fluidization; A gas-solid separator for collecting particles from particle-containing water vapor; a vapor circulation path including a fluid-transporting means for recirculating the water vapor from which particles are discharged from the gas-solid separator to the lower part of the fluidized bed; A vapor compression heating means for compressing a part of the circulating vapor and guiding it to a heater in the high-speed fluidized bed; discharging a part of the particles collected by the gas-solid separator as a dry product to the outside of the system, Further, the residual particles and the wet raw material supplied from outside the system are mixed in an atmosphere in which a part or all of the circulating steam is made to flow, and this mixture is quantitatively supplied together with the circulating steam to the lower part of the high-speed fluidized bed. Means and; And it is characterized in that there was example.

A second aspect of the present invention is a high-speed fluidized bed which has a built-in heater and is operated near the terminal velocity of particles by superheated steam as a fluid for fluidization; A gas-solid separator for collecting; a vapor circulation path including a fluid-transporting means for recirculating the steam, from which particles are removed, discharged from the gas-solid separator to the lower part of the fluidized bed,
And a vapor compression heating means for compressing a part of the circulating vapor and guiding it to the heater in the high-speed fluidized bed; and discharging a part of the particles collected by the gas-solid separator to the outside of the system as a dry product. Further, the residual particles and the wet raw material supplied from outside the system are mixed in an atmosphere in which a part or all of the circulating steam is circulated, and this mixture is quantitatively supplied to the lower part of the high-speed fluidized bed together with the circulating steam. Mixing means; a gas-liquid separator is provided in the condensed steam path discharged from the heater of the high-speed fluidized bed to separate the non-condensed gas in the system, and the non-condensed gas further reduces the latent heat of steam accompanying it. Means for preheating the wet raw material supplied from outside the system by indirect heating.

[Work]

In the present invention, a high-speed fluidized bed with a built-in heater is used,
Since the particles to be treated are brought into contact with superheated steam in a state of being accelerated by superheated steam to a velocity near the terminal velocity, heat transfer between the superheated steam and particles and mass transfer can be maximized, and the circulating superheated steam to the treated substance The heat transfer efficiency can be increased. In addition, since a heater is built in the fluidized bed, superheated steam can be heated by a high heat reflux rate, and heat transfer from the superheated steam to the particles can be performed without decreasing in the tank.

On the other hand, in general, when the raw material is supplied to the high-speed fluidized bed, since the mixing effect in the fluidized bed is great, the raw material is supplied to the high-speed fluidized bed by a means such that the raw material is supplied to the circulating powder stream. The particles are introduced into the mixer and rapidly mixed with the source material, and the heat of the circulating particles is used to raise the temperature of the raw material supplied to the fluidized bed in the previous stage. Further, a part or all of a large amount of superheated steam supplied to the fluidized bed during the mixing is circulated to prevent a local temperature drop of the superheated steam. This minimizes water vapor condensation on the surface of the feed material, prevents aggregation and adhesion in the material supply section and inside the fluidized bed, and prevents changes in the physical properties of the material.

Thus, the high-speed fluidized bed can be operated even if the degree of superheat of superheated steam is reduced, and as a result, the temperature required as a heating source for the fluidized bed can be reduced. Therefore, the power required to disperse the steam equivalent to the amount of vaporization from the treated material by compression and heat from the circulating superheated steam is reduced, and the energy efficiency when used as a heating source for the high-speed fluidized bed is improved and the practicality is increased. .

Further, according to the second aspect of the present invention, the vapor that has been used for heating the fluidized bed by compression heating is released from the heater in the fluidized bed together with the non-condensable gas. If a heat exchanger with the feedstock is provided on the way of releasing the gas to the atmosphere, the heat transfer coefficient of the fluidized bed heater can be reduced if it is used for preheating the calorific feedstock accompanied by the non-condensable gas. In addition, it is possible to prevent troubles and prevent troubles when the raw material is supplied by preheating the raw material.

In a preferred embodiment of the present invention, a multitubular heater is used as the heater incorporated in the high-speed fluidized bed. A normal fluidized bed is operated by fluidizing at a flow rate of about 10 to 20% of the final velocity of particles. In this case, it is possible to heat the fluidized gas and particles by providing a heater (flat plate, tubular) in the fluidized bed, but in order to increase the heat transfer amount per constant fluidized bed cross-sectional area, the heater is used. It is necessary to increase the height of the fluidized bed. Along with this, it is necessary to increase the powder bed thickness of the fluidized bed, resulting in an excessive pressure loss of the fluidized gas in the fluidized bed.

In the high-speed fluidized bed, as described above, the particles flow through the fluidized bed in the vicinity of the terminal velocity of the particles.The particle concentration in the fluidized gas is lower than in a normal fluidized bed, and the pressure loss is also small. Become. Therefore, it is possible to sufficiently increase the amount of heater heat transfer surface equipment per fluidized bed cross-sectional area. It is also important that the high-speed fluidized bed can obtain a heat transfer coefficient several times higher than that of a normal fluidized bed.

The form of the heater in the high-speed fluidized bed can be either flat or tubular like a normal fluidized bed, but in order to minimize the amount of fluidized gas that increases with the speeding up of fluidized gas, The larger the heat transfer surface amount per cross-sectional area of the passage portion of the flowing gas and the powder particles, the more advantageous. From this point of view, it is optimal to introduce a fluidizing gas and powder particles into the tube of the multi-tube heat exchanger and heat them with steam or the like from the outside of the tube to form a high-speed fluidized bed. In this case, it is desirable that the flowing gas and powder particles be evenly distributed in each tube, but if the distribution is likely to be uneven, divide the heater into multiple pieces and connect them in series, and place between each heater. It is suitable to provide voids for redispersion.

Since the high-speed fluidized bed using this multi-tube heater has a shape in which the outside of the heat transfer surface is surrounded by the heating medium, there is very little risk of problems due to heat dissipation in the fluidized bed body. Has become. Also, cleaning the heat transfer surface is relatively easy. Further, it is also possible to easily adjust the flow velocity of the flowing gas to increase by reducing the gas passage cross-sectional area for a certain flowing gas by closing a part of the pipe.

[Specific configuration of the invention]

The basic configuration of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows the first embodiment, and 1 in FIG. 1 is a high-speed fluidized bed in which the treated powder is fluidized and passed by a fluidized gas (superheated steam) near the terminal velocity of the particles. This is equipped with the plate-shaped or tubular heater 2. In order to give a large heat transfer area to the amount of passing gas,
The ratio of the height to the cross-sectional area of the fluidized bed is larger than that of a normal fluidized bed.

The fluidized gas that has passed through the high-speed fluidized bed 1 is introduced into a gas-solid separator 3 composed of a cyclone, a bag filter, etc.
Separated from treated powder. The purified superheated steam is again introduced into the lower part of the high-speed fluidized bed 1 by the steam circulation blower 4, and thus the circulation of the fluidized gas is formed. A part of the flowing gas that has passed through the gas-solid separator 3 (amount corresponding to the amount of water vapor newly generated by drying) is pressurized and heated by the vapor compressor 5 and is supplied to the heater 2 and the passing fluid of 1 is passed. It is used for heating. In the circulating heating steam system, air leaks from the supply and discharge part of the raw material product and from the atmosphere held by the raw material, and depending on the processed material, non-condensable gas is generated due to heating Accumulation of the volatile gas lowers the vapor saturation temperature in the system and hinders heat transfer particularly in the heater 2. Therefore, a gas-liquid separator 6 is provided in the condensate discharge passage from the heater 2, separates and extracts the non-condensed gas, and introduces it into the raw material preheater 7 via the flow rate adjusting valve 8 to accompany the non-condensed gas. The latent heat of the generated steam is recovered by preheating the raw material (material to be dried) 10 and then released to the outside of the system. The opening degree of the flow rate adjusting valve 8 is preferably controlled so that the oxygen concentration contained in the circulating superheated steam is measured by the oxygen concentration analyzer 9 and becomes a constant value.

The raw material preheater 7 is an indirect heating means for heating the feed raw material 10 through the heat transfer surface, and it is suitable to use, for example, a paddle type mixing transporter having a jacket, or a mixing transporter having a disc type heating shaft. However, it is also possible to arrange a tubular or plate-shaped heat transfer surface in the raw material storage tank. The preheated feed material is quantitatively supplied to the mixer 12 by a material supply device 11 such as a screw feeder.

The dried particles collected by the gas-solid separator 3 are fed into the distributor 14 through the sealing mechanism 13 such as a rotary valve, and most of the particles are sent from the distributor 14 to the mixer 12, but some Is taken out of the system as a dry product 15.

In the mixer 12, the wet feed raw material supplied from the raw material supply device 11 is charged into the dry-processed particles supplied from the distributor 14 and mixed. As the mixer 12, a single-screw or double-screw paddle type mixer can be generally used. However, by introducing a part or all of the superheated steam discharged from the circulation blower 4, the gas phase inside the mixer 12 can be increased. Care should be taken to keep all parts overheated.

The mixed treated powder is supplied to the lower part of the high-speed fluidized bed 1 together with the superheated steam introduced, and is heated and dried. Generally, the amount of heat to be supplied to the heater 2 is insufficient with the amount of heat equivalent to the amount of evaporation that can be supplied from the vapor compressor 5, so it is desirable to supply the heating supplemental steam 16.

FIG. 2 shows a second embodiment, in which the high-speed fluidized bed 1 has a third
The heaters 2a, 2b in the form of a shell-and-tube heat exchanger as shown in FIGS. 4 and 5 are also built in two stages in series in this embodiment. The lower stage is heated by the vapor obtained by compressing and heating the evaporated vapor, and the upper stage is heated by the heating replenishment vapor 16. As a result, heating replenishment steam 16
The condensed drain 17 of can be returned to the boiler while being clean. In addition, heating adjustment in the high-speed fluidized bed 1 is performed by heating supplemental steam
It is also possible to control 16 pressures.

The flowing gas and the treated particles pass through the inside of the heating pipe and are introduced into the cyclone 3. The lower part of the cyclone 3 is sealed with a double damper 13A, and the collected powder is sent to the mixer 12.

A part of the steam discharged from the cyclone 3 is pressurized by the circulation blower 4 via the circulation gas heater 18. The circulating gas heater 18 is a device that heats using auxiliary heating steam at the time of startup in order to accelerate the temperature rise of the device, and is generally unnecessary during continuous operation.

The mixer 12 is, for example, a single-screw paddle mixer, has a powder distribution / extraction seat at the lower portion on the upstream side, and a portion of the dry powder supplied from the double damper 13A is quantified as a dry product 15 using a rotary valve 19. It is a mechanism that can be taken out. Downstream thereof, the steam circulation blower 4 is mixed with the wet raw material supplied through the supply rotary valve 11B.
After being charged into the superheated steam flow from the above, it is supplied to the lower part of the high-speed fluidized bed 1. The bypass valve 20 is for adjusting the amount of superheated steam introduced into the mixer 12.

The other part of the circulating steam is a steam cleaning device 21 using a water spray cleaning type scrubber, and after removing the accompanying fine powder,
It is introduced into the vapor compressor 5A at about atmospheric pressure. The compressed and heated steam is used to heat the lower part 1b of the fluidized bed. The generated condensed water and the condensable gas are separated by the gas-liquid separator 6, and the non-condensable gas is introduced into the raw material preheater 7A via the flow rate adjusting valve 8. The condensed water is used as makeup water for the steam cleaning device 21. The cleaning waste water is drained 23 using the cleaning water circulation pump 22.

The raw material preheater 7A is, for example, a paddle transporter with a heat transfer jacket, and is a raw material supply device using a table feeder.
The raw material is quantitatively charged from 11A, and the raw material is preheated by utilizing the latent heat of the vapor accompanying the non-condensable gas from the gas-liquid separator 6. Non-condensable gas exhaust with reduced temperature 24
Is released out of the system.

By the way, the detailed structure example of the high-speed fluidized bed 1 provided with the heaters 2a and 2b formed of the multitubular heat exchanger in the second embodiment is the third embodiment.
As shown in Fig. 4 and Fig. 4, the upper and lower heater cylinders 30A, 30B are connected by a stopper bolt 32 through a spacer ring 31, and the upper and lower parts of the cylinders 30A, 30B have an outlet cone 33A and an inlet for flowing gas. A cone 33B is provided. Further, a large number of heat transfer tubes 34, 34 ... Are provided inside, and a tube plate 35 is provided to separate the upper side area and the lower side area. This allows the heated steam inlet 36 to be divided into upper and lower parts.
A heated steam flow passage chamber is formed from A, 36B to the condensate outlets 37A, 37B. In addition, a spacer ring 31 is sandwiched between the upper region and the lower region to form a space for re-dispersing the flowing gas so that the flowing gas is evenly distributed to each tube.

In such a fluidized bed type, a relatively large heat transfer area can be provided for a constant amount of fluidized gas. Further, by connecting the heaters 2a and 2b in a plurality of upper and lower stages (the number of stages is not limited to two as in the embodiment), it is possible to change the heating condition for each stage, the material of the tube, and the meat. The thickness can be changed.

〔Example〕

Next, examples will be shown to clarify the effects of the present invention. The implemented apparatus is shown in FIGS. 2 to 4, and its specifications are as follows.

A part of the operation result data in this example is shown below.

And it became clear that stable operation can be achieved and efficient drying operation can be performed.

〔The invention's effect〕

As described above, according to the present invention, the drying efficiency per unit energy is increased, the physical property change of the material to be dried can be prevented, and stable operation can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of the device of the present invention, FIG. 2 is a schematic diagram of the second embodiment, FIG. 3 is a longitudinal section of a high-speed fluidized bed used in the second embodiment, and FIG. Is a line IV-IV arrow oblique view. 1 ... High-speed fluidized bed, 2,2a, 2b ... heater, 3 ... gas-solid separator, 4 ... steam circulation blower, 5,5A ... vapor compressor,
6 ... gas-liquid separator, 7, 7A ... raw material preheater, 10 ... feed material (material to be dried), 11, 11A ... raw material feeder, 12 ... mixer, 14 ... distributor, 34 ...... Heat transfer device.

Front Page Continuation (72) Inventor Hajime Nakajima 2-17-15 Tsukushima Machinery, Chuo-ku, Tokyo Within Tsukishima Kikai Co., Ltd. (72) Minoru Morita 2-17-15 Tsukishima Kikai, Chuo-ku, Tokyo In-company (72) Inventor Yasuhiko Kamijo 2-17-15 Tsukushima, Chuo-ku, Tokyo Tsukishima Kikai Co., Ltd. (56) Reference JP-A-60-259883 (JP, A) JP-A-54-143960 (JP) , A) JP 59-15785 (JP, A) JP 62-230911 (JP, A) Actual development 59-178595 (JP, U) JP 49-1502 (JP, B1) JP 50-14385 (JP, Y1) S.K. 50-302 (JP, Y1)

Claims (4)

(57) [Claims] 1. A high-speed fluidized bed having a built-in heater, which is operated near the terminal velocity of particles by superheated steam as a fluid for fluidization; particles are collected from particle-containing water vapor discharged from the upper part of the fluidized bed. A gas-solid separator; a vapor circulation path including a fluid-transporting means for recirculating the water vapor discharged from the gas-solid separator to the lower part of the fluidized bed, and a part of the circulating vapor. A vapor compression heating means for leading to a heater in the high-speed fluidized bed; a part of the particles collected by the gas-solid separator is discharged as a dry product out of the system,
Further, the residual particles and a wet raw material supplied from outside the system are mixed in an atmosphere in which a part or all of the circulating steam is circulated, and this mixture is quantitatively supplied together with the circulating steam to the lower part of the high-speed fluidized bed. A drying device having a high-speed fluidized bed. 2. A high-speed fluidized bed which has a built-in heater and is operated near the terminal velocity of particles by superheated steam as a fluid for fluidization; particles are collected from the particle-containing water vapor discharged from the upper part of the fluidized bed. A gas-solid separator; a vapor circulation path including a fluid-transporting means for recirculating the water vapor discharged from the gas-solid separator to the lower part of the fluidized bed, and a part of the circulating vapor. A vapor compression heating means for leading to a heater in the high-speed fluidized bed; a part of the particles collected by the gas-solid separator is discharged as a dry product out of the system,
Further, the residual particles and a wet raw material supplied from outside the system are mixed in an atmosphere in which a part or all of the circulating steam is circulated, and this mixture is quantitatively supplied together with the circulating steam to the lower part of the high-speed fluidized bed. A means for separating the non-condensable gas in the system from the condensed water vapor flow path discharged from the heater of the high-speed fluidized bed, and the non-condensed gas to remove latent heat of water vapor accompanying it. And a means for preheating the wet raw material supplied from outside the system by indirect heating, the drying apparatus having a high-speed fluidized bed. 3. A multi-tube heater as a high-speed fluidized bed, wherein heating steam is introduced outside the tube, and flowing steam and treated powder particles are introduced into the tube. The device according to the item. 4. A high-speed fluidized bed is constructed by connecting a plurality of multitubular heaters in series, and a void is provided between the heaters to redisperse the steam for flowing and the treated powder particles. The drying device according to claim 3, which enables the above.