CA1175209A - Continuous process for the production of light-weight calcium sulfate - Google Patents
Continuous process for the production of light-weight calcium sulfateInfo
- Publication number
- CA1175209A CA1175209A CA000374609A CA374609A CA1175209A CA 1175209 A CA1175209 A CA 1175209A CA 000374609 A CA000374609 A CA 000374609A CA 374609 A CA374609 A CA 374609A CA 1175209 A CA1175209 A CA 1175209A
- Authority
- CA
- Canada
- Prior art keywords
- calcium sulfate
- slurry
- reactor
- acid
- aqueous slurry
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/46—Sulfates
- C01F11/466—Conversion of one form of calcium sulfate to another
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/10—Solid density
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
I-169- (Fl-8101) ABSTRACT OF THE DISCLOSURE
A continuous process for the production of light-weight calcium sulfate which is fibrous a-type calcium sulfate hemihy-drate. The product may be in the form of spherical particles formed of intertwined fibers of the fibrous a-type calcium sulfate hemihydrate. The said product is obtained by passing an aqueous slurry of calcium sulfate through a tubular reactor and injecting steam into said aqueous slurry in said tubular reactor to hydrothermally convert the feed calcium sulfate into said fibrous a-type calcium sulfate hemihydrate.
A continuous process for the production of light-weight calcium sulfate which is fibrous a-type calcium sulfate hemihy-drate. The product may be in the form of spherical particles formed of intertwined fibers of the fibrous a-type calcium sulfate hemihydrate. The said product is obtained by passing an aqueous slurry of calcium sulfate through a tubular reactor and injecting steam into said aqueous slurry in said tubular reactor to hydrothermally convert the feed calcium sulfate into said fibrous a-type calcium sulfate hemihydrate.
Description
~L752~3 BACKGROUND OF THE INVE;NTIt:)N
.
The present invention providss continuous process for the production of light-weight calcium sulfate. More particularly, it provides a process for continuously producing light-weight and high quality calcium sulfate.
Various methods to produce light-weight ibrous calcium sulfate by subjecting raw calcium sulfate comprising mainly calcium sulfate dihydrate to a hydrothermal reaction are known.
Japanese Patent Laid-Open Gazette (Kokai) No. 152692/1979 discloses a continuous process for the production of needle crystalline calcium sulfate which comprises injecting steam into an aqueous slurry of raw calcium sulfate to heat the aqueous slurry to a temperature of 115C. or more and then injecting - said aqueous slurry into an autoclave. In accordance with this process, the aqueous slurry is heated to above 115C. ~ith the steam in a high performance gas-liquid mixing apparatus and, thereafter, the resulting slurry is introduced into the autoclave. Namely, it is important to adjust the temperature - of`the aqueous slurry to above 115C. before introducing it to the autoclave. Furthermore, in this disclosurel it is pointed out that a stream of the aqueous slurry should be allowed to come near a piskon flow. Accordingly, control of the feed amount of tha aqueous slurry is an important factor as well as thè control of the reaction temperature. It is also disclosed to set the feed amount of the aqueous slurr~ preferably to above 11.7 centimetexs per minute, more preferably to 14 centimeters per minute.
The foregoing process, however, is not always advan-tageous from an economic standpoint with respect to installation cost and productivity because the dispersion of the aqueous -- 1 ~
'~7~9 1 slurry in the autoclaYe requires a stirring device and .the amount of the feea is limited SUMM~RY OF THE: INVENTION
It is an object o~ the presen-t invention to provide a continuous process for the production of light-weight calcium sulfate with excellent productivity It has been f~und that the object can be attained by employing a tubular reactor and introducing.steam directly into a slurry of the raw calcium sulfate in the tu~ular reactor, tO The present invention, therefore~ provides a continuous process for the production of light-weight a-type calcium sulfate hemihydrate which comprises contlnuously introducing an aqueous slurry of raw calci.um sulfate into a tubular reactor and, at the same time, introducing steam directly into the aqueous slurry in the tubular reactor to ~bject the raw calcium sulfate to a hydrothermal reaction, In one of its aspects the present invention provides a continuous process for the production o~ an a-type calcium sulfate hemihydrate in a -fibrous form and/or in a spherical . 20 form in which the fibers o~ the fibrous form are intertwined, the a-type calcium sulfate hemihydrate having a bulk density of from 0.08 to 0~16 gJcc, the process comprising hydrothermally treating an aqueous slurry which.has a solids concentration o from 1 to 30% by weight of a calcium sulfate starting material by.preheating said slurry to a temperature of from about 60C to 100C then passing the slur.ry through a tu~ular reactor equipped with a static mixer,.the linear velocity of the slurry through the reactor being from 90 to 450 centimeters per minute, the heat for the hydrothermal treatment bein~
provided by the introduction of steam into the aqueous slurLy in the tu~ular reactor
.
The present invention providss continuous process for the production of light-weight calcium sulfate. More particularly, it provides a process for continuously producing light-weight and high quality calcium sulfate.
Various methods to produce light-weight ibrous calcium sulfate by subjecting raw calcium sulfate comprising mainly calcium sulfate dihydrate to a hydrothermal reaction are known.
Japanese Patent Laid-Open Gazette (Kokai) No. 152692/1979 discloses a continuous process for the production of needle crystalline calcium sulfate which comprises injecting steam into an aqueous slurry of raw calcium sulfate to heat the aqueous slurry to a temperature of 115C. or more and then injecting - said aqueous slurry into an autoclave. In accordance with this process, the aqueous slurry is heated to above 115C. ~ith the steam in a high performance gas-liquid mixing apparatus and, thereafter, the resulting slurry is introduced into the autoclave. Namely, it is important to adjust the temperature - of`the aqueous slurry to above 115C. before introducing it to the autoclave. Furthermore, in this disclosurel it is pointed out that a stream of the aqueous slurry should be allowed to come near a piskon flow. Accordingly, control of the feed amount of tha aqueous slurry is an important factor as well as thè control of the reaction temperature. It is also disclosed to set the feed amount of the aqueous slurr~ preferably to above 11.7 centimetexs per minute, more preferably to 14 centimeters per minute.
The foregoing process, however, is not always advan-tageous from an economic standpoint with respect to installation cost and productivity because the dispersion of the aqueous -- 1 ~
'~7~9 1 slurry in the autoclaYe requires a stirring device and .the amount of the feea is limited SUMM~RY OF THE: INVENTION
It is an object o~ the presen-t invention to provide a continuous process for the production of light-weight calcium sulfate with excellent productivity It has been f~und that the object can be attained by employing a tubular reactor and introducing.steam directly into a slurry of the raw calcium sulfate in the tu~ular reactor, tO The present invention, therefore~ provides a continuous process for the production of light-weight a-type calcium sulfate hemihydrate which comprises contlnuously introducing an aqueous slurry of raw calci.um sulfate into a tubular reactor and, at the same time, introducing steam directly into the aqueous slurry in the tubular reactor to ~bject the raw calcium sulfate to a hydrothermal reaction, In one of its aspects the present invention provides a continuous process for the production o~ an a-type calcium sulfate hemihydrate in a -fibrous form and/or in a spherical . 20 form in which the fibers o~ the fibrous form are intertwined, the a-type calcium sulfate hemihydrate having a bulk density of from 0.08 to 0~16 gJcc, the process comprising hydrothermally treating an aqueous slurry which.has a solids concentration o from 1 to 30% by weight of a calcium sulfate starting material by.preheating said slurry to a temperature of from about 60C to 100C then passing the slur.ry through a tu~ular reactor equipped with a static mixer,.the linear velocity of the slurry through the reactor being from 90 to 450 centimeters per minute, the heat for the hydrothermal treatment bein~
provided by the introduction of steam into the aqueous slurLy in the tu~ular reactor
-2-~ , ~ . . ..... . ...... .. . ...
~5~(D9 BRIEF DESC~IPTION OF THE DRAWING
The Figure is a schematic diagram of the process of the present i.nvention~
' DETAILED' DES'CRI'PTI'ON OF' TEIE INVENTI'ON
The raw calcium sulfate as used herein is usually calcium sulfate`dihydrate, In additi:on, calcium.sulfate hemi-hydrate, soluble calcium sulfate anhydride, and a mixture thereof can be used. Any of a-type and ~-type calcium sulfate hemi-hydrate can be used. As such raw calcium sul~ate, any natural calcium sulfate, chemically produced calcium sulfate, by-product calcium sulfate produced in a crude oil desulfurization process, etc., can be usea, Water is usually used as a solvent in preparing the ~0 -2a-, :.
75i2~
1 aqueous slurry of a raw calci~n sulEate in accordance with the present invention. In addition, an acidic aqueous solution and a water-soluble org~nlc compoun~-cont~ining aqueous solution can be used.
Organic and inorganic acids can be used as the acid component for the acidic aqueous solution. Examples of such organic acids include acetic acid, tartaric acid, formic acid, malic acid, etc., and examples of such inorganic acids include sulfuric acid, nitric acid, boric acid, etc. Although the concentration of the acid component in the acidic aqueous solution is subject to no particular limitations, it is usually from about 0.1 to 20~ by weight.
Water-soluble organic compounds which are used in preparin~ the water-soluble organic compound-containing aqueous solution include such polyhydroxy compounds as ethylene glycol, diethylene glycol, glycerol, etc. The content of the water-soluble organic compound is usually from about 0.1 to 20 parts by weight per 100 parts by weight of water, although it varies depending on various conditions. Addition of such an acid component or water-soluble organic compound to water makes - calcium sulfate precipitation easier in subsequent s~ep.s.
In the process of the present invention, an aqueous slurry prepared by adding raw, i.e. feed, calcium sulfate to the foregoing solvent is used. Although the solid concentration in the slurry can be appropriately determined according to the type of the solvent used, it is usually from about 1 to 30%
by weight and preferably from about 2 to 20~ by weight. The aqueous slurry may be maintained at room temperature, and is preferably adjusted to from about 60 to 100C. by introd~lcing steam directly into the slurry tank or heating the slurry tank from the outside.
~7~i2~
1 In the process of the present inve~tion, the foregoing aqueous slurry is conti~uously introduced into a tubular reactor and at the same time, steam is introduced directly into the aqueous slurry in the tubular reactor ~o subject the raw calcium sulfate to a hydrothermal reactionO The steam is generally - introdùced into the reactor through the same side through which the aqueous slurry is introduced, and in the same direction as the flow of the aqueous slurry. Alternativelv, the steam may be countercurrently introduced into th~ tubular reactor through the side through which the reaction product is withdrawn. Other positions of the steam introduction into the reactor may also be used.
The tubular reactor as used herein is generally a tower-type reactor as shown in the Figure wherein the tubular reactor is vertically installed. So long as the form of the reactor i5 tubular, the position in which it is installed is not critical.
For example, the tubular reactor may be installed ither horizontally or at an angle. One of the features of the present invention is that in such reactors installed horizontally or at àn angle, no problems arise with respect to the dispersion of the raw calcium sulfate and the reaction product in the aqueous slurry.
Hereinafter, the process of ~he present invention will be explained in detail with reference to the Figure.
Raw calcium sulfate and a solvent are introduced into a slurry tank 1 where an aqueous slurry is prepared. The thus - prepared slurry is continuously sent to a tower-type (tubular) - - reactor 3 by the use of a pump 2. Usually, the aqueous slurry is introduced into the reactor from the bottom thereof, sub-]ected to a hydrothèrmal reaction while moving upwards, and then 1 withdrawn from the top oE the reactor. When the reactor is of the tank type, difficulties are encount~red in carrying out the operation continuously and furthermore stirring is needed. Thus, such tank-type reactors are not suitable for the efficient and continuous production of light-weight calcium sulfate having a uniform quality.
The aqueous sluxry introduced into the foregoing towex-type reactor 3 is heated by introducing steam directly thereinto to per~orm the hydrothermal reaction of the raw calcium sulfate.
Auxiliary heating from the outside of the reactor may also be appl~ed to heat the reactor contents. However, if the reactor is heated only from the outside thereof without the introduction of steam thereinto, scales are formed and attached into the inner walls of the reactor, making the continuous operation mpossible because the reactor itself is heated.
The linear velocity of the aqueous slurry in the for~going tower-type reactor 3 is usually from about 50 to 1,000 centimeters per minute (cm/min) and preferably from about 100 to 500 cm/min. In particular, at a linear velocity of from 2~ about 250 to 350 cm~min, spherical calcium sulfate formed sub~
stantially of intertwined calcium sulfate fibers can be obtained.
The amounts of the aqueous slurry and the steam introduced into ~he reactor 3 are determined depending on the length and diameter of the reactor, reaction temperature, etc., so that the foregoing linear velocity is obtained.
The hydrothermal reaction in the tubular tower is carried out by heating the aqueous slurry to a temperature of between 105C. and 1~0C., and preferably between 110C. and
~5~(D9 BRIEF DESC~IPTION OF THE DRAWING
The Figure is a schematic diagram of the process of the present i.nvention~
' DETAILED' DES'CRI'PTI'ON OF' TEIE INVENTI'ON
The raw calcium sulfate as used herein is usually calcium sulfate`dihydrate, In additi:on, calcium.sulfate hemi-hydrate, soluble calcium sulfate anhydride, and a mixture thereof can be used. Any of a-type and ~-type calcium sulfate hemi-hydrate can be used. As such raw calcium sul~ate, any natural calcium sulfate, chemically produced calcium sulfate, by-product calcium sulfate produced in a crude oil desulfurization process, etc., can be usea, Water is usually used as a solvent in preparing the ~0 -2a-, :.
75i2~
1 aqueous slurry of a raw calci~n sulEate in accordance with the present invention. In addition, an acidic aqueous solution and a water-soluble org~nlc compoun~-cont~ining aqueous solution can be used.
Organic and inorganic acids can be used as the acid component for the acidic aqueous solution. Examples of such organic acids include acetic acid, tartaric acid, formic acid, malic acid, etc., and examples of such inorganic acids include sulfuric acid, nitric acid, boric acid, etc. Although the concentration of the acid component in the acidic aqueous solution is subject to no particular limitations, it is usually from about 0.1 to 20~ by weight.
Water-soluble organic compounds which are used in preparin~ the water-soluble organic compound-containing aqueous solution include such polyhydroxy compounds as ethylene glycol, diethylene glycol, glycerol, etc. The content of the water-soluble organic compound is usually from about 0.1 to 20 parts by weight per 100 parts by weight of water, although it varies depending on various conditions. Addition of such an acid component or water-soluble organic compound to water makes - calcium sulfate precipitation easier in subsequent s~ep.s.
In the process of the present invention, an aqueous slurry prepared by adding raw, i.e. feed, calcium sulfate to the foregoing solvent is used. Although the solid concentration in the slurry can be appropriately determined according to the type of the solvent used, it is usually from about 1 to 30%
by weight and preferably from about 2 to 20~ by weight. The aqueous slurry may be maintained at room temperature, and is preferably adjusted to from about 60 to 100C. by introd~lcing steam directly into the slurry tank or heating the slurry tank from the outside.
~7~i2~
1 In the process of the present inve~tion, the foregoing aqueous slurry is conti~uously introduced into a tubular reactor and at the same time, steam is introduced directly into the aqueous slurry in the tubular reactor ~o subject the raw calcium sulfate to a hydrothermal reactionO The steam is generally - introdùced into the reactor through the same side through which the aqueous slurry is introduced, and in the same direction as the flow of the aqueous slurry. Alternativelv, the steam may be countercurrently introduced into th~ tubular reactor through the side through which the reaction product is withdrawn. Other positions of the steam introduction into the reactor may also be used.
The tubular reactor as used herein is generally a tower-type reactor as shown in the Figure wherein the tubular reactor is vertically installed. So long as the form of the reactor i5 tubular, the position in which it is installed is not critical.
For example, the tubular reactor may be installed ither horizontally or at an angle. One of the features of the present invention is that in such reactors installed horizontally or at àn angle, no problems arise with respect to the dispersion of the raw calcium sulfate and the reaction product in the aqueous slurry.
Hereinafter, the process of ~he present invention will be explained in detail with reference to the Figure.
Raw calcium sulfate and a solvent are introduced into a slurry tank 1 where an aqueous slurry is prepared. The thus - prepared slurry is continuously sent to a tower-type (tubular) - - reactor 3 by the use of a pump 2. Usually, the aqueous slurry is introduced into the reactor from the bottom thereof, sub-]ected to a hydrothèrmal reaction while moving upwards, and then 1 withdrawn from the top oE the reactor. When the reactor is of the tank type, difficulties are encount~red in carrying out the operation continuously and furthermore stirring is needed. Thus, such tank-type reactors are not suitable for the efficient and continuous production of light-weight calcium sulfate having a uniform quality.
The aqueous sluxry introduced into the foregoing towex-type reactor 3 is heated by introducing steam directly thereinto to per~orm the hydrothermal reaction of the raw calcium sulfate.
Auxiliary heating from the outside of the reactor may also be appl~ed to heat the reactor contents. However, if the reactor is heated only from the outside thereof without the introduction of steam thereinto, scales are formed and attached into the inner walls of the reactor, making the continuous operation mpossible because the reactor itself is heated.
The linear velocity of the aqueous slurry in the for~going tower-type reactor 3 is usually from about 50 to 1,000 centimeters per minute (cm/min) and preferably from about 100 to 500 cm/min. In particular, at a linear velocity of from 2~ about 250 to 350 cm~min, spherical calcium sulfate formed sub~
stantially of intertwined calcium sulfate fibers can be obtained.
The amounts of the aqueous slurry and the steam introduced into ~he reactor 3 are determined depending on the length and diameter of the reactor, reaction temperature, etc., so that the foregoing linear velocity is obtained.
The hydrothermal reaction in the tubular tower is carried out by heating the aqueous slurry to a temperature of between 105C. and 1~0C., and preferably between 110C. and
3~ In the tower-type reactor 3, the aqueous slurry is ~L7~
1 continuously introduced and moved, and furthermore turbulent flow is produced by the introduc~ion of the steam so that the aqueous slurry and steam are stirred sufficiently. If necessary or desired, a static mixer 4 may be provided in the reactor 3.
A residence time is set at least 30 seconds. The residence time is determined by taking into consideration of the reaction temperature.
The reaction product, i.e., a-type calcium sulfate hemihydrate, produced in the tower-type reactor 3 by the hydro- ¦
thermal reaction is continuously withdrawn from the reactor and introduced into a reservoir 5. If`necessary, it is further introduced into a solid-liquid separator (not shown) where water is removed, and it is taken out as a wet product. The thus-obtained wet product is dried at ~etween about S0 to 120C. to provide dry a-type calcium sulfate hemihydrate.
The calcium sulfate product thus obtained is a fibrous a-type calcium sulfate hemihydrate and/or a spherical a-type calcium sulfate hemihydrate formed substantially from the calcium sulfate fibers which became intertwined to form spherical particles, and thus is very light-weight. The product is usually a mixture o the product in the form of fibers and the larger spherical particles.
When calcium sulfate hemihydrate, soluble calcium sul-fate anhydride or a powdery inorganic substance is used as part of the raw calcium sulfate, or a solvent containing therein an acid is used, the major portion of the calcium sulfate obtained is spherical.
In accordance with the process of the present invention, as described above, a stirrer is not basically needed, the heat efficiency is high because steam is directly introduced as a ~ 6 --~75~
1 heat source, and the amount of the aqueous slurry fed can be increased, and thus the productivity is very high and the plant and operation costs can be greatly reduced. Furthermore, by controlling the amount of the slurry or the steam fedr or by employing a static mixer, calcium sulfate having various physical properties can be produced. Moreover, since the hydrothermal reaction is performed by the introduction of steam and the reactor itself is not heated, the attachment of scales on the walls of the reactor is prevented and the operation can be continuously performed for long periods o time.
The fibrous calcium sulfa~e product obtained by the process of the present invention has a small diameter and it is very long. The spherical calcium sulfate product formed from such fibrous calcium sulfate has a very low density. Thus, both the fibrous calcium sulfate product and the spherical cal-cium sulfate product are of high quality.
The light-weight calcium sulfate produced by the pro-cess of the present invention is of high and uni-form quality and has high strength. It can be used as a building material, such as ceiling material, a partition material, a heat-insulating material, a core material, a spxay material, etc., and also as a filler for plastics in various fields.
The following Examples urther illustrate the present invention in detail.
Examples 1 to 12 An aqueous slurry of a raw calcium sulfate (calcium sulfate by-product of a process for desulfurization of crude oil) was brought to 75C., and continuously introduced into a tower-type reactor (inner diameter: 8 centimeters; length:
550 centimeters) through the bottom at a predetermined linear ~752~
1 velocity by the use of a pump. ~t the same time, steam was introduced into the reactor through the bottom thereof and directly injected through a gas~liquid mixer provided at the bottom thereof to maintain the resulting mixture at a predetermined reaction temperature. The reaction product was continuously withdrawn from the top of the reactor and introduced into a reservoir, and then it was subjected to a solid-liquid separation by a centrifugal separator. The thus obtained product was dried at 80C. for 3 hours to obtain a light-weight -type calcium sulfate hemihydrate.
` In Examples 6 and 7, a static mixer was placed in an upper portion of the gas-liquid mixer.
In Examples 8 to 12, three static mixers were provided in an upper portion of the gas-liquid mixer.
: The reaction conditions employed and the physical properties of the light-weight calcium sulfate obtained are shown in the following Table.
~L'7~
#
~,_ ~N
~ ~ ~ ~ ~1 In o .~ ~ C) ~_ t` ~
a3 ~ ;~
m u~ ~
~ ~, N U l~i Q) *
1 continuously introduced and moved, and furthermore turbulent flow is produced by the introduc~ion of the steam so that the aqueous slurry and steam are stirred sufficiently. If necessary or desired, a static mixer 4 may be provided in the reactor 3.
A residence time is set at least 30 seconds. The residence time is determined by taking into consideration of the reaction temperature.
The reaction product, i.e., a-type calcium sulfate hemihydrate, produced in the tower-type reactor 3 by the hydro- ¦
thermal reaction is continuously withdrawn from the reactor and introduced into a reservoir 5. If`necessary, it is further introduced into a solid-liquid separator (not shown) where water is removed, and it is taken out as a wet product. The thus-obtained wet product is dried at ~etween about S0 to 120C. to provide dry a-type calcium sulfate hemihydrate.
The calcium sulfate product thus obtained is a fibrous a-type calcium sulfate hemihydrate and/or a spherical a-type calcium sulfate hemihydrate formed substantially from the calcium sulfate fibers which became intertwined to form spherical particles, and thus is very light-weight. The product is usually a mixture o the product in the form of fibers and the larger spherical particles.
When calcium sulfate hemihydrate, soluble calcium sul-fate anhydride or a powdery inorganic substance is used as part of the raw calcium sulfate, or a solvent containing therein an acid is used, the major portion of the calcium sulfate obtained is spherical.
In accordance with the process of the present invention, as described above, a stirrer is not basically needed, the heat efficiency is high because steam is directly introduced as a ~ 6 --~75~
1 heat source, and the amount of the aqueous slurry fed can be increased, and thus the productivity is very high and the plant and operation costs can be greatly reduced. Furthermore, by controlling the amount of the slurry or the steam fedr or by employing a static mixer, calcium sulfate having various physical properties can be produced. Moreover, since the hydrothermal reaction is performed by the introduction of steam and the reactor itself is not heated, the attachment of scales on the walls of the reactor is prevented and the operation can be continuously performed for long periods o time.
The fibrous calcium sulfa~e product obtained by the process of the present invention has a small diameter and it is very long. The spherical calcium sulfate product formed from such fibrous calcium sulfate has a very low density. Thus, both the fibrous calcium sulfate product and the spherical cal-cium sulfate product are of high quality.
The light-weight calcium sulfate produced by the pro-cess of the present invention is of high and uni-form quality and has high strength. It can be used as a building material, such as ceiling material, a partition material, a heat-insulating material, a core material, a spxay material, etc., and also as a filler for plastics in various fields.
The following Examples urther illustrate the present invention in detail.
Examples 1 to 12 An aqueous slurry of a raw calcium sulfate (calcium sulfate by-product of a process for desulfurization of crude oil) was brought to 75C., and continuously introduced into a tower-type reactor (inner diameter: 8 centimeters; length:
550 centimeters) through the bottom at a predetermined linear ~752~
1 velocity by the use of a pump. ~t the same time, steam was introduced into the reactor through the bottom thereof and directly injected through a gas~liquid mixer provided at the bottom thereof to maintain the resulting mixture at a predetermined reaction temperature. The reaction product was continuously withdrawn from the top of the reactor and introduced into a reservoir, and then it was subjected to a solid-liquid separation by a centrifugal separator. The thus obtained product was dried at 80C. for 3 hours to obtain a light-weight -type calcium sulfate hemihydrate.
` In Examples 6 and 7, a static mixer was placed in an upper portion of the gas-liquid mixer.
In Examples 8 to 12, three static mixers were provided in an upper portion of the gas-liquid mixer.
: The reaction conditions employed and the physical properties of the light-weight calcium sulfate obtained are shown in the following Table.
~L'7~
#
~,_ ~N
~ ~ ~ ~ ~1 In o .~ ~ C) ~_ t` ~
a3 ~ ;~
m u~ ~
~ ~, N U l~i Q) *
4~ O S~
t~l rl a) c.) ~1-- o o o ~ .~ \0 3 P:; o u~
,~ , 1 ~rl ~ N ~~) ~~D ~ Il)~1 CO ~ t~l 11 C~ ~ ~ ~ . . . . . ~ . . . . . .
~ a~ ~ o o o o o o o o o o o o a:l ~~
-~::
~1 a~ o ~ ~ O co c)~ Il') ,-1 ~ ~) r~J
~_ 3 ~
O O~ O o O O O O O O O Q
co o ~r cn r~ co = = o ~r ~p o ~ ~ u~ ~n o O
~1 1 a O o o o u~
Q) a) ~o ~1 ~1 ,~ ~1 ~1 h--al r~ ~
:1 tq ~
O ~I X o ~n ~ ~ o-~ Z = ~ = = ~ = = = : : =
~ ~1 q~ ,1 ~
O ~ ~ ~ o ~
.~- ~.q o ~1 U~ ~ ~
U~ ~ rd a) ~ ~
~-,1 ~ ~ p~ = : = : = = : : = : ~-O ~ 1~ ~.
- ~ u ~: a ~ C) t~
,1 ~ : ~1 - h ~
o 1~ ~P ~ ~ a~ ~P ~ ~ a U~
o ,¢ ,¢:~: O f~
X Z ~1 ~ ~ ~ u~ ~ r~ ~ ~
75~9 1 *1: Per 100 paxts by weight of the solvent.
*2: 3 milliliters of light-weight calcium sulfate was placed in a 10 milliliters content vessel a~d ~ashed with methanol to remove the calcium sulfate fibers which are not formed into the spherical particles of calcium sulfate, and thus the weight ratio was de-termined.
*3: To lOO parts by weight of the light-weight calcium sulfate obtained was added 400 to 600 parts by weight of water to provide a slurry. The thus obtained slurry was molded by compression and dehydration into a plate tlO x lO x 2 centimeters), which was then dried at 60C. for 8 hours to obtain a molded pxoduct of light-weight calcium sulfate having a density of 0.4 g/cm3. Then, the strength of the molded product thus obtained was measured.
t~l rl a) c.) ~1-- o o o ~ .~ \0 3 P:; o u~
,~ , 1 ~rl ~ N ~~) ~~D ~ Il)~1 CO ~ t~l 11 C~ ~ ~ ~ . . . . . ~ . . . . . .
~ a~ ~ o o o o o o o o o o o o a:l ~~
-~::
~1 a~ o ~ ~ O co c)~ Il') ,-1 ~ ~) r~J
~_ 3 ~
O O~ O o O O O O O O O Q
co o ~r cn r~ co = = o ~r ~p o ~ ~ u~ ~n o O
~1 1 a O o o o u~
Q) a) ~o ~1 ~1 ,~ ~1 ~1 h--al r~ ~
:1 tq ~
O ~I X o ~n ~ ~ o-~ Z = ~ = = ~ = = = : : =
~ ~1 q~ ,1 ~
O ~ ~ ~ o ~
.~- ~.q o ~1 U~ ~ ~
U~ ~ rd a) ~ ~
~-,1 ~ ~ p~ = : = : = = : : = : ~-O ~ 1~ ~.
- ~ u ~: a ~ C) t~
,1 ~ : ~1 - h ~
o 1~ ~P ~ ~ a~ ~P ~ ~ a U~
o ,¢ ,¢:~: O f~
X Z ~1 ~ ~ ~ u~ ~ r~ ~ ~
75~9 1 *1: Per 100 paxts by weight of the solvent.
*2: 3 milliliters of light-weight calcium sulfate was placed in a 10 milliliters content vessel a~d ~ashed with methanol to remove the calcium sulfate fibers which are not formed into the spherical particles of calcium sulfate, and thus the weight ratio was de-termined.
*3: To lOO parts by weight of the light-weight calcium sulfate obtained was added 400 to 600 parts by weight of water to provide a slurry. The thus obtained slurry was molded by compression and dehydration into a plate tlO x lO x 2 centimeters), which was then dried at 60C. for 8 hours to obtain a molded pxoduct of light-weight calcium sulfate having a density of 0.4 g/cm3. Then, the strength of the molded product thus obtained was measured.
Claims (4)
1. A continuous process for the production of .alpha.-type calcium sulfate hemihydrate in a fibrous form and/or in a spherical form in which the fibers of the fibrous form are intertwined, the .alpha.-type calcium sulfate hemihydrate having a bulk density of from 0,08 to 0,16 g/cc, the process comprising hydrothermally treating an aqueous slurry which has a solids concentration of from 1 to 30% by weight of a calcium sulfate starting material by preheating said slurry to a temperature of from about 60°C to 100°C then passing the slurry through a tubular reactor equipped with a static mixer, the linear velocity of the slurry through the reactor being from 90 to 450 centimeters per minute, the heat for the hydrothermal treatment being provided by the introduction of steam into the aqueous slurry in the tubular reactor.
2. The process of Claim 1 wherein the liquid portion of said aqueous slurry is an acidic aqueous solution which con-tains at least one acid selected from the group consisting of acetic acid, tartaric acid, formic acid, malic acid, sulfuric acid, nitric acid and boric acid,
3. The process of Claim 1 wherein the liquid portion of said aqueous slurry contains an alcohol selected from the group consisting of ethylene glycol, diethylene glycol and glycerol,
4. The process of Claim 1 wherein said tubular reactor is a tower-type reactor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP48037/1980 | 1980-04-14 | ||
| JP4803780A JPS56145116A (en) | 1980-04-14 | 1980-04-14 | Continuous preparation of light gypsum |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1175209A true CA1175209A (en) | 1984-10-02 |
Family
ID=12792108
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000374609A Expired CA1175209A (en) | 1980-04-14 | 1981-04-03 | Continuous process for the production of light-weight calcium sulfate |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS56145116A (en) |
| CA (1) | CA1175209A (en) |
| DE (1) | DE3114363C2 (en) |
| FR (1) | FR2480267A1 (en) |
| GB (1) | GB2076791B (en) |
| IT (1) | IT1170883B (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3239669A1 (en) * | 1982-10-27 | 1984-05-03 | Joh. A. Benckiser Gmbh, 6700 Ludwigshafen | CONTINUOUS PROCESS FOR THE PRODUCTION OF INDUSTRIAL RECYCLABLE PLASTER FROM INDUSTRIAL WASTE PLASTER |
| DE3536321A1 (en) * | 1985-10-11 | 1987-04-23 | Bischoff Gasreinigung | Process and reactor for producing alpha-hemihydrate gypsum from calcium sulphate dihydrate from flue gas desulphurisation plants operating by the wet scrubbing process with lime |
| DE3615739A1 (en) * | 1986-05-09 | 1987-11-12 | Benckiser Gmbh Joh A | CONTINUOUS METHOD AND DEVICE FOR PRODUCING INDUSTRIALLY RECYCLABLE PLASTER FROM INDUSTRIAL WASTE PLASTER |
| DE3711367A1 (en) * | 1987-04-04 | 1988-10-13 | Rwk Rhein Westfael Kalkwerke | Process for preparing calcium sulphate hemihydrate |
| DE3819652C3 (en) * | 1987-05-22 | 1996-08-01 | Pro Mineral Ges | Process for the production of calcium sulfate alpha hemihydrate suitable as a building material from moist, finely divided flue gas desulfurization gypsum and its use |
| EP0416089A4 (en) * | 1989-03-16 | 1991-08-07 | United States Gypsum Company | Process and apparatus for producing calcium sulfate microfibers |
| US7765813B2 (en) * | 2004-07-15 | 2010-08-03 | United States Gypsum Company | Apparatus and process for cooling and de-steaming calcined stucco |
| CN103723757B (en) * | 2012-10-10 | 2015-08-05 | 深圳兰度生物材料有限公司 | Medical grade α-calcium sulphate hemihydrate preparation method |
| EP3782725A1 (en) * | 2019-08-21 | 2021-02-24 | Nederlandse Organisatie voor toegepast- natuurwetenschappelijk Onderzoek TNO | Reactor for the hydrothermal treatment of biomass |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1198807A (en) * | 1963-12-03 | 1970-07-15 | Ici Ltd | Continuous process for the production of calcium sulphate alpha-hemihydrate from gypsum |
| GB1051849A (en) * | 1963-12-03 | |||
| US3977890A (en) * | 1972-08-16 | 1976-08-31 | Johns-Manville Corporation | Method for the preparation of fibrous calcium sulfate hemihydrate |
| JPS5143833A (en) * | 1974-10-11 | 1976-04-14 | Nishida Marine Boiler | KIFUKUGEETOSOCHI |
| JPS5187494A (en) * | 1975-01-31 | 1976-07-31 | Idemitsu Kosan Co | Setsukoisukaano seizohoho |
| JPS5319366A (en) * | 1976-08-06 | 1978-02-22 | Mitsubishi Chem Ind Ltd | Resin compositions |
| JPS5817132B2 (en) * | 1976-11-29 | 1983-04-05 | 出光興産株式会社 | Spherical settsukou and its manufacturing method |
| JPS53128624A (en) * | 1977-04-16 | 1978-11-09 | Idemitsu Kosan Co | Gypsum compound |
| US4152408A (en) * | 1977-11-25 | 1979-05-01 | Certain-Teed Corporation | Fibrous calcium sulfate |
| JPS5857384B2 (en) * | 1978-04-04 | 1983-12-20 | 株式会社クボタ | Gypsum firing method and equipment |
| JPS54152692A (en) * | 1978-05-22 | 1979-12-01 | Kanegafuchi Chem Ind Co Ltd | Continuous manufacture of gypsum needle-like crystal |
-
1980
- 1980-04-14 JP JP4803780A patent/JPS56145116A/en active Granted
-
1981
- 1981-04-03 CA CA000374609A patent/CA1175209A/en not_active Expired
- 1981-04-08 GB GB8111034A patent/GB2076791B/en not_active Expired
- 1981-04-09 DE DE3114363A patent/DE3114363C2/en not_active Expired
- 1981-04-10 IT IT48251/81A patent/IT1170883B/en active
- 1981-04-14 FR FR8107440A patent/FR2480267A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE3114363A1 (en) | 1982-03-04 |
| IT1170883B (en) | 1987-06-03 |
| FR2480267A1 (en) | 1981-10-16 |
| JPS56145116A (en) | 1981-11-11 |
| GB2076791B (en) | 1983-03-09 |
| FR2480267B1 (en) | 1984-12-28 |
| DE3114363C2 (en) | 1985-12-05 |
| JPS6320785B2 (en) | 1988-04-30 |
| GB2076791A (en) | 1981-12-09 |
| IT8148251A0 (en) | 1981-04-10 |
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