JPH03504596A - Calcium sulfate microfiber manufacturing method and device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Calcium sulfate microfiber manufacturing method and equipment (technical field) The present invention relates to a method and apparatus for continuously producing calcium sulfate microfibers, particularly The present invention relates to a manufacturing method and apparatus that can accurately control the dimensional growth of microfibers.

(Background technology) Until now, artificial calcium sulfate microfibers were called whisker fibers (whisker fibers). Ker fibers) are used for various purposes, such as fillers in plastics. Or used as reinforcement, asphalt, mineral cement, paper, paint There is. Generally, microfibers are aspect recrystallized from pressure-calcined gypsum. Consists of high ratio alpha hemihydrate or anhydrous calcium sulfate crystals. It takes Microfiber is a trademark from the Gypsum Company in the United States. It is marketed under the name “FRANl [LIN FIBER]”. It is.

Basic methods for making calcium sulfate microfibers and their uses , U.S. Pat. No. 3,822,340 and U.S. Pat. No. 4,152,508.

II, calcium sulfate microfiber is calcium sulfate dihydrate (gypsum ) is made by heating a slurry dilute aqueous solution containing particles under pressure. dilution When added to the solution, one dihydrate molecule and 1 1/2 water molecules recrystallize and form sulfuric acid. Long lucium alpha hemihydrate (becomes a thin crystal. Hemihydrate microfiber is Once recovered from the slurry and dried, it is further heated to remove the remaining chemically bound Water is removed and coated to stabilize it under moisture. Microfa Regarding the stabilization of fibers, U.S. Pat. It is disclosed in No. 05.

Calcium sulfate microfibers have so far been manufactured in batches using one of two manufacturing methods. Manufactured on a commercial basis by law.

According to this batch manufacturing method, a certain amount of ground gypsum is mixed with enough water to dilute A slurry is created. This slurry is heated in a pressurized vessel to transform the gypsum into alpha semi-hydrated water. is substantially converted to hydrate crystals and then discharged to a filter/separator where it is The microfibers are separated from the slurry solvent, dried, and stabilized as desired.

Although high quality microfibers can be produced by the above batch production method, This batch manufacturing method has proven to be expensive. A manufacturing facility For example, a batch manufacturing method produces a predetermined amount of microfiber, e.g., about 35 pounds. produced per cycle (typically 45 minutes). Manufacturing output is solid content of slurry It can be increased by increasing the concentration, but in this case the microfiber aspect It has been found that the ratio of Although the aspect ratio of microfibers produced is higher, the manufacturing output per cycle is Output is low (results). Increasing the scale of the batch reactor will further increase the cost. We need to offset this with productivity.

In addition, calcium sulfate microfiber is produced by another one of the two manufacturing methods. Continuously produced on a commercial basis. This manufacturing method uses finely ground gypsum particles and Water is mixed to create an approximately 30% by weight slurry. The slurry has a gradual cavity Continuously agitated tank reactor via pump with or several connected in series Sent to Nori actor. A typical reactor is disclosed in U.S. Patent No. 3.579.300. A cylindrical pressure vessel with 3 to 6 processing stages connected in series with each other so that It is a vessel.

Steam is introduced either pre-mixed with the slurry or introduced separately into the initial processing stage. The slurry temperature is brought to the desired conversion temperature and pressure. Each stage of the reactor has A separate stirrer is provided to keep the calcium sulfate particles in suspension. 4 slurry Pass sequentially through each stage of the reactor with a residence time in the range of ~lO min, then at atmospheric pressure. Depressurize to level. Microfibers are separated from the slurry solvent and optionally further processed.

This continuous manufacturing method significantly improves productivity compared to the batch method. For example, normal manufacturing The facility has a microfiber production rate of over 1200 pounds per hour. . However, the ratio between the maximum length and diameter of the microfiber obtained by this method is Up to now, it has been limited to a maximum of approximately 45, while higher aspect ratio Since microfiber is required, we have developed a chain that can produce longer lengths of microfiber. A continuous manufacturing method is desired.

In order to meet this demand, the plug flora method has recently been proposed. (disclosed in U.S. Patent Application No. 324.158).

In this method, an aqueous slurry solution containing finely ground gypsum particles is preheated. The so-called continuous hollow conduit with a smooth inner surface is mixed with steam and pumped It is moved under pressure in a plug/flora state. The length of this plug flow reactor is 2 The residence time is determined to be such that the hydrate is substantially converted into hemihydrate crystals.

The nearly laminar flow in the plug-flow reactor is free from turbulence or agitation. , dissolved calcium sulfate alpha hemihydrate nucleates into long needle-shaped seed crystals. .

For example, a plug flow reactor with a residence time of approximately 90 to 100 seconds may be used. Continued production.

The plug-flora method described above uses microfabrication with a satisfactorily high aspect ratio. However, as disclosed in U.S. Pat. No. 3,579,300, The diameter of the microfibers obtained using the manufacturing method may in some cases be somewhat larger. Although some diameters are visible, they generally do not exceed about 1.0 micron.

Furthermore, since there is no turbulence and the slurry is hardly mixed, It is difficult to completely convert the supplied gypsum.

Therefore, a larger diameter, e.g. 1.5 to 4.0 microns, and an aspect ratio of 45 or more It is desirable to provide calcium sulfate microfibers, preferably 65 or higher. It will be done. Furthermore, it virtually completely converts the supplied gypsum material into microfiber, reducing manufacturing costs. To produce fibers that are comparable to filled fibers or supplementary fibers with minimal It is hoped that

(Disclosure of invention) The main purpose of the present invention is to convert substantially all of the supplied gypsum material to achieve an economical production rate. Continuous production of calcium sulfate microfiber with high aspect ratio using An object of the present invention is to provide a method and apparatus.

Another objective is to be able to control the dimensional growth of microfibers at the expense of high aspect ratios. A method and apparatus capable of producing microfibers with large diameters without It is about providing.

Another object of the present invention is to combine the plug-flora method and the continuously stirred reactor method. This is achieved by

The manufacturing apparatus of the present invention includes a feed pump having a gradual cavity that increases pressure, and a feed pump that increases pressure. Rari/steam mixing valve, continuous plug flow reactor, and continuous stirring tank It comprises a reactor and a feed pump with a graduated cavity to reduce the pressure.

The new plug flow reactor is constructed as a long pipe-like conduit with a cross-section. It has a substantially constant, smooth, uncut interior. plug flow reactor is connected between the slurry/steam mixing valve and the tank reactor. stir continuously A tank reactor consists of one or more cylindrical vessels connected in series, each with one The diameter of the vessel is substantially larger than that of the plug flow reactor, and the solids content of the slurry, respectively. It has a stirrer to keep the particles in suspension and improve particle-to-particle contact. stirring tank The clearer is a plug/flow reactor and the pressure is left down. connected between the pump and the pump. All constituent members and each member of the manufacturing apparatus according to the present invention The connecting members between the It has a structure that can withstand force and maintain slurry.

According to the production method of the present invention, a preheated diluted slurry aqueous solution of about 12 to 15% by weight is heated under pressure. The power is sent to an ascending feed pump where it is conditioned and mixed with saturated steam for extremely rapid The temperature quickly rises to about 285°F (about 140°C). Next, this high temperature turbulent slurry is Plug long pipe reactors into laminar flow and maintain desired temperature and pressure. ・Transfer in flora state and convert gypsum particles to calcium sulfate alpha hemihydrate . The dissolved hemihydrate nucleates to form thin needle-like seed crystals. Also plug flow The residence time in the Ureactor is usually on the order of 30 seconds.

Stones that were not converted with alpha hemihydrate high aspect ratio seed crystals at this time The slurry of plaster particles is sent directly into the larger volume stirred tank reactor. child Since the volume of the reactor is large, the overall flow of the slurry is slow (and the stagnation inside the reactor is The residence time will be on the order of 4 to 10 minutes. During this residence time, the slurry must be constantly agitated. The solids remain in suspension and contain unconverted gypsum particles or seed crystals. The suspended particles are brought into contact with each other. Therefore, the seed crystal is encouraged to grow in the radial and axial directions. microfibers with larger diameters (higher aspect ratios). Become.

As the slurry progressively moves through successive processing stages of the stirred tank reactor, it is substantially All gypsum particles are converted. This slurry is counter-rotated from the stirred tank reactor. The slurry is fed to a graded cavity pump where it is subjected to atmospheric pressure. This slurry Further, the water is dehydrated using a filter or the like to obtain a microfiber cake. The cake is disassembled It is then dried and packed into packages.

As an additional component, the microfiber is further fired and coated as in the conventional method. It can also be stabilized and packaged to prevent moisture absorption.

The manufacturing method and manufacturing apparatus according to the present invention have many advantages over conventional ones. By greatly increasing the production speed, the cost is lower than that of the batch production method, and sulfuric acid calcium sium microfibers can be produced. In addition, conventional continuous stirring tank reactors Compared to the manufacturing method, gypsum particles are completely converted only by Beplug 70 Ureactor, Microfibers with high aspect ratios can be manufactured. Furthermore, the asperity is higher than that of the conventional method. microfibers with high efficiencies and large diameters can be produced. In particular, By taking into account a number of control parameters to clarify, the manufacturing method according to the invention effectively control the nucleation and growth of microfibers within a predetermined size range. Can be built.

Although the present invention has been briefly described above, more detailed description and features or advantages may be required. This will be described later in conjunction with the attached drawings.

(Brief explanation of the drawing) FIG. 1 is a simplified diagram illustrating a method for producing calcium sulfate microfibers according to the present invention. A schematic diagram, FIG. 2, shows one plug flow reactor preferably used in the manufacturing method shown in FIG. FIG. 3 is a cross-sectional view taken along line 3--3 in FIG. 2, and FIG. A part of the multi-stage glue actor that is suitably used in the manufacturing method shown in Figure 1 and that continuously stirs. 5 is a cross-sectional side view taken along line 5--5 of FIG. 4; FIG.

(Best form for carrying out the invention @) The manufacturing method shown in Figure 1 involves mixing crushed gypsum and water in a mixing tank IQ. Start and create a diluted slurry. For example, terra alha is substantially pure gypsum that has been ground to 99.9% and 100 mesh; Preferably, the gypsum is mixed with sufficient water to have a solid content in the range of 1/2% to 15% by weight. Create a slurry of approximately 12%. Also preferably, the slurry is mixed in a mixing tank for about 200 ml. Heat to O'F (approximately 93°C).

The slurry is then sent from the mixing tank to the inlet of feed pump 12.

Gradual cavity feed pump 12 increases slurry pressure to approximately 80 psi The slurry and steam are discharged into a slurry/steam mixing valve 20 which mixes the slurry and steam. Ma As shown in Figure 2, saturated steam at about 350°F (about 177°C) is added to the slurry/ The steam is supplied to the mixing valve 20 and directly into the metered hot slurry.

Referring to FIG. 2, the mixing valve 20 includes a housing 22, a steam introduction part 23, It includes a slurry introduction part 24, a needle valve, and a discharge part 28, and the needle valve has a valve seat. 25 and a valve stem 26, the valve stem 26 is axially adjustable and includes a It is equipped with a plug 27, and a discharge part 28 is a plug flora (plug-Nov). It can be directly connected to the reactor 30. The high temperature steam is introduced into the steam introduction part 23, It is delivered through the opening between the valve stem 26 and the valve seat 25. At this time, the needle valve The amount of steam supplied can be adjusted more easily. On the other hand, the slurry restricts the orifice 29 The slurry is introduced from the slurry introduction section 24 having a slurry introduction section 24.

The slurry is pumped between the feed pump 12 and the orifice 29 to a pressure of approximately 80 psi. the pressure is substantially higher than the pressure downstream of the orifice 29. subordinate Therefore, the slurry is finely atomized when the needle is passed through the slurry/steam mixing valve. It is ejected directly into the steam jet channel introduced through the valve. Using this configuration The introduced slurry is continuously metered and mixed with hotter steam. directly collided. As a result, heat is transferred instantaneously, and the temperature of the slurry becomes extremely high. The calcium sulfate particles contained in this slurry are quickly raised to a predetermined processing temperature. For example, the temperature may be raised to about 280'F (about 140°C). This type of heating produces needle-like This is considered to be an extremely preferable step when making seed crystals.

The hot slurry is passed through the discharge section 28 and directly from the slurry/steam mixing valve 20 to the plug. It is sent to the flow reactor 30. The plug flow reactor 30 is a long hollow conduit. Constructed as. Fast enough to hot slurry to prevent settling of suspended particles Determine the diameter of the plug/70 urector to provide flow velocity and cause turbulence. Ru. The length of the conduit mainly consists of calcium sulfate dihydrate and calcium sulfate alpha hemihydrate. to give sufficient residence time to transform into hydrate crystals or microfibers. determined. Another important point is that surface defects can lead to nucleation or crystal formation. Plug flow will cause deposits to form and eventually clog the conduit. It is particularly desired that the inner surface 31 of the reactor be as smooth as possible and have as little friction as possible.

Of course, the plug flow reactor 30 can handle temperatures above 285°F (approximately 140°C). Must be strong enough to withstand the pressure generated by temperature (typically 40-50 psi) It is necessary to It is also desirable to insulate the reactor to reduce heat loss. .

The high-temperature and high-pressure slurry flows through the plug-flow reactor 30 as a plug-flow reactor. move. Plug flora means that each incremental portion of this liquid flows almost like a solid. Refers to being held in place by the surrounding solid matter. In other words, liquid steam is essentially It will flow without significant shear or mixing effects. like this In this state, dissolved calcium sulfate hemihydrate nucleates and forms long (high aspect ratio) can grow seed crystals.

On the other hand, due to this plug flora, nucleation occurs in some calcium sulfate dihydrates. Plaster does not adhere to other crystals, so a plug/flow reactor alone is not enough to aluminate gypsum. grains that cannot be completely converted into hemihydrate crystals, but according to the present invention, The sample is moved into a continuously agitated tank reactor 40 and treated in a second processing stage. The advantage is that it becomes a building block. It is clear that

There is one tank reactor 40 that continuously stirs, as shown in FIGS. 4 and 5. Or, it has multiple processing stages 41a, 41b, 41c, and the volume of each processing stage is large. It is a pressurized cylinder container and is equipped with stirring means such as a rotary impeller 42. Tan Processing stage 41, in a typical example of a reactor, has a diameter of about 15 inches and a height of about 15 inches. Inches. The treatment stages of the tank reactor are vertically stacked and flange 4 3 are connected to each other in series. The hot slurry from the plug flow reactor is is moved upward from the inlet 45 at the bottom of the first treatment stage of the successive tank reactor. , preferably from an outlet 46 at the top of the final processing stage. Also, the tank tank Actor 40 is constructed to withstand internal processing temperatures or the resulting pressures. will be accomplished.

Since the tank reactor 40 has a large capacity, the amount of water flowing through the tank reactor 40 is The flow rate in the Rari is substantially lower than in a pipe reactor. Therefore, slurry solvent The solid content will settle.

On the other hand, since the rotary impeller 42 of each processing stage sufficiently stirs, a moderate amount of turbulence occurs. Subsidence is prevented. This not only keeps the solids in suspension, but also keeps the gypsum particles Particle mixing and particle-particle contact is promoted. As a result, seed crystals from the pipe reactor Particles that are not attached to the surface attach and grow in size and in the radial and axial directions. child This creates large diameter microfibers without sacrificing aspect ratio. can.

A series of vertically extending baffle members 44 extend along the length of tank reactor 40. The baffle member 44 is typically shaped as a rectangular baffle member. will be accomplished. Further, the baffle member 44 is spaced apart around the inside of the reactor, and The rotor action prevents flow only in the radial direction, and also creates turbulence. Keeps gypsum particles in suspension.

Alternatively, additionally gypsum particles, crystal growth agents such as potassium sulfate, or anhydrous amber. A nucleation inhibitor such as silicic acid is directly injected into a continuously stirred reactor to form seed fibers. Physical growth can be controlled.

The turbulent flow caused by the thermally rotating impeller causes shearing or shearing of the long seed crystal. Otherwise, destruction will occur. This phenomenon is also caused by the drag coefficient (drag coe4rient ) or by controlling the speed of the rotating impeller and adjusting the crystal length to meet desired product specifications. It has been found that it is more preferable to After leaving the final treatment stage of tank reactor 40, the slurry is subjected to atmospheric pressure and is let down. (let down) is sent to the pump 50. The pump 50 also has a graduated capacitance. However, in this example, it can be reversed to maintain upstream pressure.

After the slurry is returned to atmospheric pressure, it is transferred to rotary pressure Kafiltalo 0 or other dewatering equipment. A large amount of free water is removed and a microfiber buff of approximately 40-50% by weight is Filter cake is left behind.

The water dehydrated by the rotary pressure filter 0 is circulated to the mixing tank 10. this The microfibers are decomposed and separated from the filter cake obtained by drying. The remaining moisture is further removed by being sent to a dryer 62.

As an additional step, as shown by the dotted line in Figure 1, dried calcium sulfate hemihydrate The microfibers are sent to a hardening furnace 64 to remove any remaining chemically bound moisture. to convert hemihydrate to soluble or insoluble anhydrite. In either case, the fiber is After-treatment with a paint well known to those skilled in the art, it is stabilized so that it does not absorb moisture.

The finished calcium sulfate microfibers are collected in the collecting section 66 and placed in a bag 7G. Alternatively, it may be packaged and distributed in other suitable packaging.

The above-mentioned manufacturing method and manufacturing equipment have been greatly improved compared to the conventional batch continuous method, and many improvements have been made. It has advantages. In other words, high aspect ratio calcium sulfate microfibers can be produced at a good production rate with almost complete conversion of raw materials, and therefore at low cost. Become. More flexibility or control allows operators to control the growth of microfiber products. I can control it.

For example, the operating parameters of the first processing stage, i.e. the plug-flow reactor, are Slurry concentration, steam pressure, control temperature, diffusion of steam into feed slurry stream, plug -Residence time in the flow reactor and dimensions of the reactor. These parameters This determines the length and degree of conversion of the initial alpha hemihydrate seed crystal.

Furthermore, in the second processing stage, i.e. the continuous tank reactor, the stirring energy is used as a parameter. The microfibers are grown not only in the radial direction but also in the final axial direction. dimensions are controlled. The stirring energy is controlled by the propulsion coefficient and rotation speed of the rotary impeller. This can be done by adjusting the In addition, in the second treatment stage, gypsum and crystal modifier are added. Alternatively, nucleation inhibitors can be introduced to control seed crystal growth from the first processing stage. can.

In order to produce microfibers with large diameters and high aspect ratios, the present invention A test manufacturing plant was built using the manufacturing method and equipment described above. Slurry/ Connect the steam mixing valve to approximately 32 feet of pipe with a nominal diameter of 1 to 172 inches. directly connected to the plug flow reactor. To ensure space, the pipe reactor is It is constructed as four 7-foot processing stages arranged parallel to each other as shown in Figure 2. The processing stages were connected in a smooth and curved manner. Plug flow reactor outlet was directly connected to the inlet of a continuous tank reactor consisting of three treatment stages.

Each processing stage of the tank reactor is a cylindrical pressure volume with an inner diameter of 15 inches and a height of 15 inches. It was constructed as a container, and an impeller was placed in the center so that it could rotate along a vertical axis. 3 pieces The processing stages are stacked vertically, and the slurry is introduced from the inlet near the bottom of the first processing stage. It was sent to an outlet near the top of the final processing stage.

This test plant uses only the multi-stage continuous tank reactor method and the plug flow method. Microfiber was used for comparison with microfiber produced only by the Ureactor method. manufactured fiber.

The operating parameters for the three processing stages are summarized in Table I below.

Slurry concentration Temperature Residence time Aspect ratio Average diameter - Processing method ( Weight % of solids) (’F) (minutes) (microns) (microns) Continuous stirring tank Link Reactor only 30 285~295 ~5 45 1.75 Plug Flora Reactor only 12 285-295. 75~1.0 >80　　　　. 95 Note 2 The term “aspect ratio” used in this specification refers to each The tap density aspect ratio (T ap Density Aspect Ratio) of a given group. Expressed as the average aspect ratio of the microfibers. tap density aspect ratio Measurements were determined using the following procedures and equipment based on ASTM Standard Test Method 04164. Established.

Step 1. The weight of the 14 gram microfiber sample to be tested is two orders of magnitude (t wo place) Measure to the accuracy.

Step 2: Place this sample in a clean cylindrical body with 1001 scale and seal it to prevent leakage. Seal using raffil.

Step 3. Place this cylinder in the holding part of the tap density device and set the counter to 300. do.

Step 4: Turn on this tap density device and stop automatically after tapping 300 times do.

Step 5: Take out the cylinder and record the volume of the sample inserted without tapping.

Step 6: The aspect ratio of the sample microfiber was determined by the following formula.

Tap density aspect ratio = + [(9,6☆V) + 72]”’-11, 51 where ■ is the final volume expressed in units of 1.

Turbidity survey report +TI+-Electronic-O--AeM+n-xOPCT/US901014 (Co[i

Claims (19)

[Claims] (1) Continuously generate diluted slurry aqueous solution containing particles of calcium sulfate dihydrate at high temperature and high pressure. a supply device that provides a feeder, an inlet portion and an outlet portion connected to the feeder, the cross section being A continuous hollow conduit with a substantially constant and smooth inner surface and an internally smooth conduit. The dihydrate particles become alpha hemihydrate by passing through the Plug the plug to a length that provides sufficient slurry residence time to convert it into needle-like seed crystals. Flow reactor and inlet and outlet connected to outlet of plug/blow reactor and at least one container capable of holding sufficient slurry therein; Includes a slurry agitation device that agitates the slurry and maintains the solid particles in suspension within the slurry. The residence time of the slurry moving in the vessel is controlled by the needle-shaped seed crystals in the radial and axial directions. Continuously stirred tank reactor and tank reactor outlet set up to allow sufficient growth The microfiber containing the slurry is effectively brought to atmospheric pressure by reducing the pressure Continuous production equipment for calcium sulfate microfibers. (2) Claim 1, wherein the plug flow reactor is a continuous pipe. equipment. (3) Claim 2, wherein the pipe has a nominal inner diameter of approximately 1 to 1/2 inches. equipment. (4) The apparatus of claim 3, wherein the length of the pipe is 32 feet. (5) A tank reactor is equipped with two or more containers connected in series and high temperature slurry is supplied to each container. 2. The apparatus according to claim 1, wherein the container is moved with a predetermined residence time. (6) Each container of the tank reactor is stacked vertically, and the slurry is placed in the first container. Enter from the inlet near the bottom of the tank and move the tank reactor upward until it reaches the top of the container. Claim 5, wherein the liquid is disposed so as to be emitted from a nearby outlet. Device. (7) Claim 5, wherein the number of containers in the tank reactor is 3 to 6. Device. (8) Claim 5 further comprising a stirring device provided in each container. equipment. (9) Furthermore, each container is equipped with a rotary stirring device, and all of the stirring devices are attached to a common rotatable shaft that extends vertically within the tank reactor. An apparatus according to claim 6. (10) Mix the crushed particles of calcium sulfate hemihydrate to create a diluted slurry. process and heating the slurry to approximately 285°F (approximately 140°C) using pressure. process, the hot slurry is moved under pressure in a conduit in a plug-flow state to form hemihydrate. The process of converting the majority to alpha hemihydrate nucleated as needle-shaped seed crystals and The tank reactor that continuously stirs the hot slurry is moved under pressure and stirred to remove solids. Axial and radial growth of acicular seed crystals by maintaining them in suspension and promoting interparticle contact A slurry that promotes microfibers with a predetermined average diameter and aspect ratio. a step of moving, a step of reducing the pressure of the microfiber piper containing the slurry, and a step of reducing the pressure of the microfiber piper containing the slurry; A high aspect ratio sulfur solution comprising the step of separating the slurry solvent from the fiber A method for continuously producing calcium acid microfibers. (11) The slurry heating step further includes heating to approximately 350°F (approximately 17°F) in a pressure-sealed mixing valve. It involves the process of mixing slurry and steam at 0°C) and quickly raising the slurry temperature. 11. The method according to claim 10, which comprises: (12) The temperature of the slurry is maintained from the slurry heating process to the microfiber separation process. and maintained at about 285°F (about 140°C) as claimed in claim 10. Law. (13) Calcium nitrate dihydrate particles as the solid content initially contained in the slurry 11. The method of claim 10, wherein the amount is about 1/2 to about 15% by weight. (14) Residence time of high temperature slurry in plug flow reactor conduit approximately 30-60 11. The method according to claim 10, wherein the method is expressed in seconds. (15) The residence time of high-temperature slurry in the tank reactor with continuous stirring is approximately 4 to 6 minutes. The method according to claim 10, which comprises: (16) In the slurry transfer process, finely ground calcium sulfate is also added to the tank reactor. A patent that includes the process of introducing additional particles of aluminum and depositing them on the acicular seed crystal. The method according to claim 10. (17) The slurry transfer process also includes a crystal growth agent or nucleation inhibitor in the tank reactor. The special feature includes a step of controlling the growth of microfibers by introducing an additional inhibitor. The method according to claim 10. (18) Calcium sulfate dihydrate particles as the solid content initially contained in the slurry 11. The method of claim 10, comprising about 12% by weight. (19) Approximately 1/2 to 1/2 finely ground calcium sulfate dihydrate particles as solid content An aqueous slurry solution containing 15% by weight is heated under pressure to about 285°F (about 140°C). , calcium sulfate dihydrate is transferred through a continuous hollow conduit in a plug-flow state. A part of the calcium sulfate alpha hemihydrate is converted into acicular seed crystals, and a seed crystal containing seed crystal is Move the tank reactor that continuously stirs the liquid to grow seed crystals and adjust the average aspect. Create a microfiber with a ratio greater than 45 and an average diameter of 1.5 microns or more. , reduces the pressure on the slurry to atmospheric pressure levels and removes the slurry from the microfiber. Calcium sulfate microfiber obtained by separating the solvent.