CA2215854A1 - Process for preparing sparingly soluble calcium sulphate anhydrite-ii - Google Patents
Process for preparing sparingly soluble calcium sulphate anhydrite-ii Download PDFInfo
- Publication number
- CA2215854A1 CA2215854A1 CA 2215854 CA2215854A CA2215854A1 CA 2215854 A1 CA2215854 A1 CA 2215854A1 CA 2215854 CA2215854 CA 2215854 CA 2215854 A CA2215854 A CA 2215854A CA 2215854 A1 CA2215854 A1 CA 2215854A1
- Authority
- CA
- Canada
- Prior art keywords
- calcium sulphate
- process according
- anhydrite
- finely divided
- sparingly soluble
- 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.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B11/00—Calcium sulfate cements
- C04B11/05—Calcium sulfate cements obtaining anhydrite, e.g. Keene's cement
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention relates to a process for preparing sparingly soluble calcium sulphate anhydrite-II in which finely divided dry calcium sulphate dihydrate is dehydrated in a calcining unit by appropriate action of heat, is held at the calcination temperature under steam, and the calcined material is ground. During this process, the finely divided calcium sulphate dihydrate is heated to a temperature of from 580 to 650°C and is held at this temperature under steam with a partial steam pressure < 0.2 bar for an adequate residence time, in such a way that a phase mixture of predominantly sparingly soluble calcium sulphate anhydrite-II and a lower proportion of insoluble calcium sulphate anhydrite-II and calcium sulphate anhydrite-III is formed, the resultant phase mixture being ground to a Blaine specific surface area of > 4000 cm2/g.
Description
CA 0221~8~4 1997-09-11 Process for preparing sparingly soluble calcium sulphate anhydrite-II
The invention relates to a process for preparing sparingly soluble calcium sulphate anhydrite-II as described in the basic concept of Claim 1.
Sparingly soluble calcium sulphate anhydrite-II
is a calcium sulphate phase pro~uce~ by calcining calcium sulphate dihydrate under industrial conditions in the t~m~erature range above 250.
The predominant raw material for preparing calcium sulphate anhydrite-II has until now been granular natural gypsum. Currently, finely divided raw materials, such as flue gas desulphurization gypsum and chemical gypsum are increasingly being used, and their proportion will rise markedly in the future.
FY~mr1 es of units which are used for calcination are:
rotary tube furnaces, heated directly and indirectly, milling-firing calciners, carrier gas calciners.
In spite of high temperatures and lonq residence times in the calcining process, the calcination products are generally multiphase mixtures which, ~p~n~ing on the particular process and in addition to sparingly soluble ~lcium sulphate anhydrite-II, contain various amounts of insoluble calcium sulphate anhydrite-II and of highly CA 0221~8~4 1997-09-11 .
reactive, hygroscopic calcium sulphate anhydrite-III, which reacts in air to give calcium sulphate ~-hemihydrate. Calcium sulphate anhydrite-III is not elimin~ted even by an ext~n~ duration of calcination or an increase in the calcination t~m~erature.
However, for the production of modern building materials, for example plaster, it is necessary to produce, as base calcium sulphates, calcination products which have high phase purity, uniformity and stability.
DE-A-2 064 210 discloses the dehydration of finely divided dry calcium sulphate dihydrate in a cal~-i ni ng unit by appropriate action of heat, the finely divided calcium sulphate dihydrate being gradually heated to a t~rerature of above 250~C in a first step, and then being held at a t~mrerature in the range from 250 to 450~C under steam with a partial steam pressure of from 1.14 to 5.1 atmospheres in a second step. Although this gives calcined calcium sulphate, appropriate experiments have shown that this, in contrast to the anhydrite-II
assumed in this document , is in practice not at all phase-pure, but contains from about 20 to 25% by weight of anhydrite-III, this percentage being essential-ly in~p~n~nt of the residence time. The subsequent comminution of the resultant material gives only an increase in the surface area, and this has a correspond-ing effect on the reactivity of the calcium sulphate.
EP-A-0 513 779 discloses the preparation of anhydrite floor plaster from flue gas desulphurization gypsum, the starting material being subjected to a two-step preheating, after drying, and then being brought toa calcination t~mr~rature of from 780 to 900~C in a carrier gas calcination zone, after which the calcined material is cooled and then ground. Rec~l~se of the high calcination temperature, this process gives virtually exclusively insoluble anhydrite-II and no sparingly CA 0221~8~4 1997-09-11 soluble anhydrite-II; the material is ground in order to match the degree of hydration to the requirements of floor plaster.
It is an object of the invention to provide a process according to the preamble of Claim 1, which process makes it possible to obtain sparingly soluble calcium sulphate anhydrite-II which is virtually free of anhydrite-III.
This object is achieved as described in the characterizing clause of Claim 1.
In the process described, finely divided calcium sulphate dihydrate is heated to a t~ rature of from about 580 to 650~C and is held at this temperature under steam with an approximate partial steam pressure of < 0.2 bar for an adequate residence time in such a way that a phase mixture of predominantly sparingly soluble calcium sulphate anhydrite-II and a lower proportion of insoluble calcium sulphate anhydrite-II and calcium sulphate anhydrite-III is formed, the resultant phase mixture being ground to an approximate Blaine specific surface area of > 4000 cm2/g.
It has been established that, on the one hand, even high temperatures do not hin~r the formation of calcium sulphate anhydrite-III, but, on the other hand, that a low partial steam pressure of < 0.2 bar is suit-able to break down calcium sulphate anhydrite-III which has been formed, so that with from about 12 to 30 min residence time in the t~mr~rature range from 580 to 650~C
the resultant phase mixture has a proportion of calcium sulphate anhydrite-III which is under 5% by weight, and is therefore virtually free of calcium sulphate anhy-drite-III. However, treatment at these t~r~ratures also gives rise to not inconsiderable quantities of insoluble calcium sulphate anhydrite-II. It has been found, how-ever, that this is located essentially on the surface of CA 0221~8~4 1997-09-11 the grains. Grin~ing to a Rl ~i n~ specific surface area of > 4000 cm2g, expediently undertaken after cooling the material obtained, breaks up the calcium sulphate grains which have been calcined on the surface to give insoluble calcium sulphate anhydrite-II, opening up their kernels which consist of sparingly soluble calcium sulphate anhydrite-II, with the result that the proportion of grains of sparingly soluble calcium sulphate anhydrite-II
increases correspondingly and is, for example, about 80%
by weight (at a calcium sulphate dihydrate purity of about 97%) after grinding. Grinding to a Blaine specific surface area of > 6000 cm2/g is generally not cost-effec-tive.
Although the process may be carried out in one step, a two-step procedure is preferred because of the considerable saving in energy which it achieves. For this, the finely divided calcium sulphate dihydrate is firstly precalcined in a first step at from 130 to 150~C
in a calcining unit to give the hemihydrate. This can be carried out over a period of from 10 to 120 min, in particular from 30 to 60 min. By this means, only a smaller mass and a significantly lower proportion of water vapours remain to be raised to the calcination t~rature for the actual calcination in the t~n~rature range from 580 to 650~C, and moreover only one third of the water r~m~ins to be driven off. This results in a pronounced saving in energy of the order of about 25%
when co~rison is made with the one-step process.
A particularly suitable starting material is a gypsum with a particle size < 100 um, preferably a synthetic gypsum, such as flue gas desulphurization gypsum, which is already produced with a grain size of this order. The moisture content of the calcium sulphate dihydrate used as starting material here is ~iently < 0.2% by weight. Synthetic gypsums are produced in moist CA 0221~8~4 1997-09-11 condition and therefore must be dried to < 0.2% by weight moisture before calcination.
Cooling of the calcined material before grinding can be undertaken using screws, drums, rotary tube units or fluidized bed units or the like.
This process can be implemented on an industrial s~le, so that large amounts of virtually anhydrite-III-free, sparingly soluble calcium sulphate anhydrite-II can be prepared, with conversion of > 98~ by weight of the calcium sulphate dihydrate present in the raw material.
The process may be carried out, for example, in fluidized-bed or moving-bed units or in rotary tube units, the heating medium being conveyed cocurrently or as cross-current or countercurrent to the material flow.
An appropriate residence time of the material at the required t~ erature for the inten~C~ time periods can be set by appropriate structural configuration of the units, for ~m~le weirs, shutters, helical screws or the like.
In the two-step method of operation, the first step of the process may firstly be carried out in one unit. By means of appropriate provision of different temperature zones in such a unit, a rotary tube furnace for example, the second step of the process may also follow in this unit. If desired, a valve may be provided which serves to divide the unit into two zones for the first and second treatment stages. However, it is prefe-rable to carry out the second step in another unit, in particular continuously in a further unit, such as a rotary tube furnace, in which it is only necessary to hold the appropriate temperature and maintain a defined water vapour atmosphere.
In the first step, on the one hand large amounts of steam are evolved and on the other hand large amounts of dust are raised, so that the water vapours discharged from the first step of the process are severely dust-CA 0221~8~4 1997-09-11 laden. The dust can be deposited using cyclones, for e~ and be fed into the material of the second step.
In order to maintain a defined profile of tem-perature and residence time for the material, it is expedient to convey the material by means of a screw or the like.
Example The starting material is finely divided calcium sulphate dihydrate from flue gas desulphurization, dried to < 0.1% by weight of moisture and having a purity of 98%.
A first calcination step (precalcination) was carried out in a rotary tube furnace over a period of 40 min at 130~C and about 0.2 bar partial steam pressure.
There followed a second calcination step in the rotary tube furnace with a residence time of 15 min at 600~C and a partial steam pressure of 0.2 bar.
The product calcined in this way had the follow-ing phase composition, based on the 98 per cent dihydrate content in the flue gas desulphurization gypsum:
calcium sulphate anhydrite-IIs: 91% by weight calcium sulphate anhydrite-IIu: 9% by weight calcium sulphate anhydrite-III: not detectable.
The invention relates to a process for preparing sparingly soluble calcium sulphate anhydrite-II as described in the basic concept of Claim 1.
Sparingly soluble calcium sulphate anhydrite-II
is a calcium sulphate phase pro~uce~ by calcining calcium sulphate dihydrate under industrial conditions in the t~m~erature range above 250.
The predominant raw material for preparing calcium sulphate anhydrite-II has until now been granular natural gypsum. Currently, finely divided raw materials, such as flue gas desulphurization gypsum and chemical gypsum are increasingly being used, and their proportion will rise markedly in the future.
FY~mr1 es of units which are used for calcination are:
rotary tube furnaces, heated directly and indirectly, milling-firing calciners, carrier gas calciners.
In spite of high temperatures and lonq residence times in the calcining process, the calcination products are generally multiphase mixtures which, ~p~n~ing on the particular process and in addition to sparingly soluble ~lcium sulphate anhydrite-II, contain various amounts of insoluble calcium sulphate anhydrite-II and of highly CA 0221~8~4 1997-09-11 .
reactive, hygroscopic calcium sulphate anhydrite-III, which reacts in air to give calcium sulphate ~-hemihydrate. Calcium sulphate anhydrite-III is not elimin~ted even by an ext~n~ duration of calcination or an increase in the calcination t~m~erature.
However, for the production of modern building materials, for example plaster, it is necessary to produce, as base calcium sulphates, calcination products which have high phase purity, uniformity and stability.
DE-A-2 064 210 discloses the dehydration of finely divided dry calcium sulphate dihydrate in a cal~-i ni ng unit by appropriate action of heat, the finely divided calcium sulphate dihydrate being gradually heated to a t~rerature of above 250~C in a first step, and then being held at a t~mrerature in the range from 250 to 450~C under steam with a partial steam pressure of from 1.14 to 5.1 atmospheres in a second step. Although this gives calcined calcium sulphate, appropriate experiments have shown that this, in contrast to the anhydrite-II
assumed in this document , is in practice not at all phase-pure, but contains from about 20 to 25% by weight of anhydrite-III, this percentage being essential-ly in~p~n~nt of the residence time. The subsequent comminution of the resultant material gives only an increase in the surface area, and this has a correspond-ing effect on the reactivity of the calcium sulphate.
EP-A-0 513 779 discloses the preparation of anhydrite floor plaster from flue gas desulphurization gypsum, the starting material being subjected to a two-step preheating, after drying, and then being brought toa calcination t~mr~rature of from 780 to 900~C in a carrier gas calcination zone, after which the calcined material is cooled and then ground. Rec~l~se of the high calcination temperature, this process gives virtually exclusively insoluble anhydrite-II and no sparingly CA 0221~8~4 1997-09-11 soluble anhydrite-II; the material is ground in order to match the degree of hydration to the requirements of floor plaster.
It is an object of the invention to provide a process according to the preamble of Claim 1, which process makes it possible to obtain sparingly soluble calcium sulphate anhydrite-II which is virtually free of anhydrite-III.
This object is achieved as described in the characterizing clause of Claim 1.
In the process described, finely divided calcium sulphate dihydrate is heated to a t~ rature of from about 580 to 650~C and is held at this temperature under steam with an approximate partial steam pressure of < 0.2 bar for an adequate residence time in such a way that a phase mixture of predominantly sparingly soluble calcium sulphate anhydrite-II and a lower proportion of insoluble calcium sulphate anhydrite-II and calcium sulphate anhydrite-III is formed, the resultant phase mixture being ground to an approximate Blaine specific surface area of > 4000 cm2/g.
It has been established that, on the one hand, even high temperatures do not hin~r the formation of calcium sulphate anhydrite-III, but, on the other hand, that a low partial steam pressure of < 0.2 bar is suit-able to break down calcium sulphate anhydrite-III which has been formed, so that with from about 12 to 30 min residence time in the t~mr~rature range from 580 to 650~C
the resultant phase mixture has a proportion of calcium sulphate anhydrite-III which is under 5% by weight, and is therefore virtually free of calcium sulphate anhy-drite-III. However, treatment at these t~r~ratures also gives rise to not inconsiderable quantities of insoluble calcium sulphate anhydrite-II. It has been found, how-ever, that this is located essentially on the surface of CA 0221~8~4 1997-09-11 the grains. Grin~ing to a Rl ~i n~ specific surface area of > 4000 cm2g, expediently undertaken after cooling the material obtained, breaks up the calcium sulphate grains which have been calcined on the surface to give insoluble calcium sulphate anhydrite-II, opening up their kernels which consist of sparingly soluble calcium sulphate anhydrite-II, with the result that the proportion of grains of sparingly soluble calcium sulphate anhydrite-II
increases correspondingly and is, for example, about 80%
by weight (at a calcium sulphate dihydrate purity of about 97%) after grinding. Grinding to a Blaine specific surface area of > 6000 cm2/g is generally not cost-effec-tive.
Although the process may be carried out in one step, a two-step procedure is preferred because of the considerable saving in energy which it achieves. For this, the finely divided calcium sulphate dihydrate is firstly precalcined in a first step at from 130 to 150~C
in a calcining unit to give the hemihydrate. This can be carried out over a period of from 10 to 120 min, in particular from 30 to 60 min. By this means, only a smaller mass and a significantly lower proportion of water vapours remain to be raised to the calcination t~rature for the actual calcination in the t~n~rature range from 580 to 650~C, and moreover only one third of the water r~m~ins to be driven off. This results in a pronounced saving in energy of the order of about 25%
when co~rison is made with the one-step process.
A particularly suitable starting material is a gypsum with a particle size < 100 um, preferably a synthetic gypsum, such as flue gas desulphurization gypsum, which is already produced with a grain size of this order. The moisture content of the calcium sulphate dihydrate used as starting material here is ~iently < 0.2% by weight. Synthetic gypsums are produced in moist CA 0221~8~4 1997-09-11 condition and therefore must be dried to < 0.2% by weight moisture before calcination.
Cooling of the calcined material before grinding can be undertaken using screws, drums, rotary tube units or fluidized bed units or the like.
This process can be implemented on an industrial s~le, so that large amounts of virtually anhydrite-III-free, sparingly soluble calcium sulphate anhydrite-II can be prepared, with conversion of > 98~ by weight of the calcium sulphate dihydrate present in the raw material.
The process may be carried out, for example, in fluidized-bed or moving-bed units or in rotary tube units, the heating medium being conveyed cocurrently or as cross-current or countercurrent to the material flow.
An appropriate residence time of the material at the required t~ erature for the inten~C~ time periods can be set by appropriate structural configuration of the units, for ~m~le weirs, shutters, helical screws or the like.
In the two-step method of operation, the first step of the process may firstly be carried out in one unit. By means of appropriate provision of different temperature zones in such a unit, a rotary tube furnace for example, the second step of the process may also follow in this unit. If desired, a valve may be provided which serves to divide the unit into two zones for the first and second treatment stages. However, it is prefe-rable to carry out the second step in another unit, in particular continuously in a further unit, such as a rotary tube furnace, in which it is only necessary to hold the appropriate temperature and maintain a defined water vapour atmosphere.
In the first step, on the one hand large amounts of steam are evolved and on the other hand large amounts of dust are raised, so that the water vapours discharged from the first step of the process are severely dust-CA 0221~8~4 1997-09-11 laden. The dust can be deposited using cyclones, for e~ and be fed into the material of the second step.
In order to maintain a defined profile of tem-perature and residence time for the material, it is expedient to convey the material by means of a screw or the like.
Example The starting material is finely divided calcium sulphate dihydrate from flue gas desulphurization, dried to < 0.1% by weight of moisture and having a purity of 98%.
A first calcination step (precalcination) was carried out in a rotary tube furnace over a period of 40 min at 130~C and about 0.2 bar partial steam pressure.
There followed a second calcination step in the rotary tube furnace with a residence time of 15 min at 600~C and a partial steam pressure of 0.2 bar.
The product calcined in this way had the follow-ing phase composition, based on the 98 per cent dihydrate content in the flue gas desulphurization gypsum:
calcium sulphate anhydrite-IIs: 91% by weight calcium sulphate anhydrite-IIu: 9% by weight calcium sulphate anhydrite-III: not detectable.
Claims (11)
1. Process for preparing sparingly soluble calcium sulphate anhydrite-II, in which finely divided dry calcium sulphate dihydrate is dehydrated in a calcining unit by appropriate action of heat, is held at the calcination temperature under steam, and the calcined material is ground, characterized in that the finely divided calcium sulphate dihydrate is heated to a temperature of from 580 to 650°C and is held at this temperature under steam with a partial steam pressure < 0.2 bar for an adequate residence time, in such a way that a phase mixture of predominantly sparingly soluble calcium sulphate anhydrite-II and a lower proportion of insoluble calcium sulphate anhydrite-II and calcium sulphate anhydrite-III is formed, the resultant phase mixture being ground to a Blaine specific surface area of > 4000 cm2/g.
2. Process according to Claim 1, characterized in that a residence time of from 12 to 30 min, in particular from 14 to 18 min, is used.
3. Process according to Claim 1 or 2, characterized in that the resultant phase mixture is ground to a Blaine specific surface area of from 4000 to 6000 cm2/g.
4. Process according to one of Claims 1 to 3, characterized in that calcium sulphate dihydrate having a grain size below 100 µm is used.
5. Process according to Claim 4, characterized in that the calcium sulphate dihydrate used is flue gas desulphurization gypsum.
6. Process according to one of Claims 1 to 5, characterized in that finely divided calcium sulphate dihydrate is firstly precalcined in a first step at from 130 to 150°C.
7. Process according to Claim 6, characterized in that the precalcination is carried out over a period of from 10 to 120 min, in particular from 30 to 60 min.
8. Process according to Claim 6 or 7, characterized in that the finely divided calcium sulphate dihydrate is placed in a rotary tube unit, fluidized-bed unit or moving-bed unit and is precalcined.
9. Process according to Claim 8, characterized in that the unit is heated cocurrently or in cross-current to the material which is conveyed through it.
10. Process according to one of Claims 1 to 9, characterized in that the calcination is carried out in a rotary tube unit, fluidized-bed unit or moving-bed unit.
11. Process according to one of Claims 1 to 10, characterized in that dust which arises during the precalcination, after it has been deposited from the water vapours produced during precalcination, is added to the material which is to be calcined.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19639448.1 | 1996-09-25 | ||
| DE1996139448 DE19639448A1 (en) | 1996-09-25 | 1996-09-25 | Process for the preparation of poorly soluble calcium sulfate anhydrite II |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2215854A1 true CA2215854A1 (en) | 1998-03-25 |
Family
ID=7806887
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2215854 Abandoned CA2215854A1 (en) | 1996-09-25 | 1997-09-11 | Process for preparing sparingly soluble calcium sulphate anhydrite-ii |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0832860B1 (en) |
| JP (1) | JPH10101385A (en) |
| AT (1) | ATE199534T1 (en) |
| CA (1) | CA2215854A1 (en) |
| DE (2) | DE19639448A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4777058B2 (en) * | 2004-12-22 | 2011-09-21 | 太平洋セメント株式会社 | Anhydrous gypsum manufacturing method and anhydrous gypsum firing system |
| WO2007066167A1 (en) * | 2005-12-07 | 2007-06-14 | Gypsmix (Sarl) | Process for preparing a stabilized soluble anhydrite iii-based hydraulic binder, hydraulic binder obtained, use of said binder and industrial installation for implementing the process |
| DK1991509T3 (en) * | 2005-12-07 | 2012-08-13 | Columbeanu Ion | Method for Stabilizing Metastable Soluble Anhydrite III |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2076260A5 (en) * | 1970-01-06 | 1971-10-15 | Progil | |
| FR2235891A1 (en) * | 1973-07-04 | 1975-01-31 | Lafarge Sa | Plaster calcination appts. - for prodn. of close tolerance dimension particles |
| FR2453117A1 (en) * | 1979-04-03 | 1980-10-31 | France Platrieres | Alpha calcium sulphate hemi-hydrate mfr. for plaster - by inexpensive dry roasting of gypsum at just above atmospheric pressure |
| FR2512438A1 (en) * | 1981-09-04 | 1983-03-11 | Dussel Christian | PROCESS FOR PREPARING A NEW PLASTER AND ITS APPLICATIONS |
| SU1183475A1 (en) * | 1984-01-05 | 1985-10-07 | Государственный Всесоюзный научно-исследовательский институт строительных материалов и конструкций им.П.П.Будникова | Method of producing anhydride binder |
| DE3827612A1 (en) * | 1988-08-13 | 1990-02-15 | Viktor Dr Ing Gobiet | Building material for use in underground operation |
| DE4107385C2 (en) * | 1991-03-08 | 1995-02-09 | Knauf Westdeutsche Gips | Dry powder plaster mix and process for its preparation |
| DE4115699A1 (en) * | 1991-05-14 | 1992-11-19 | Krupp Polysius Ag | METHOD AND SYSTEM FOR PRODUCING ANHYDRITE FLOATING SCREED PLASTER |
-
1996
- 1996-09-25 DE DE1996139448 patent/DE19639448A1/en not_active Ceased
-
1997
- 1997-07-16 DE DE59703096T patent/DE59703096D1/en not_active Expired - Fee Related
- 1997-07-16 AT AT97112185T patent/ATE199534T1/en not_active IP Right Cessation
- 1997-07-16 EP EP19970112185 patent/EP0832860B1/en not_active Expired - Lifetime
- 1997-08-29 JP JP9235188A patent/JPH10101385A/en active Pending
- 1997-09-11 CA CA 2215854 patent/CA2215854A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| ATE199534T1 (en) | 2001-03-15 |
| JPH10101385A (en) | 1998-04-21 |
| DE19639448A1 (en) | 1998-04-02 |
| EP0832860A1 (en) | 1998-04-01 |
| EP0832860B1 (en) | 2001-03-07 |
| DE59703096D1 (en) | 2001-04-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP2069243B1 (en) | Process for manufacturing ultra low consistency alpha- and beta- blend stucco | |
| DE4109743C2 (en) | Process for the thermal treatment of moist hydrates | |
| US4533528A (en) | Process for continuously calcining gypsum to low dispersed consistency stucco | |
| EP3541765B1 (en) | Process and apparatus for calcination of gypsum | |
| CN101265042A (en) | Technique for preparing desulfurized gypsum by two-step process | |
| CS41591A2 (en) | Method of plaster treatment | |
| CA2215854A1 (en) | Process for preparing sparingly soluble calcium sulphate anhydrite-ii | |
| WO2011057506A1 (en) | Method for secondarily synthesizing calcium sulphoaluminate mineral in portland cement clinker | |
| CZ281929B6 (en) | Process for producing liquid anhydrite plaster for plaster finishes and apparatus for making the same | |
| US3898316A (en) | Calcination of gypsum | |
| EP1726575A1 (en) | Method for plaster production and plaster product obtained by said method. | |
| CA2209589A1 (en) | Process for preparing virtually phase-pure calcium sulphate .beta.-hemihydrate | |
| US9926228B2 (en) | Method of producing gypsum binder | |
| US4248849A (en) | Process for the continuous dehydration and calcination of hydrated aluminum fluoride for the manufacture of high purity aluminum fluoride | |
| US1966864A (en) | Cementitious material of the high alumina type | |
| SU1733419A1 (en) | Method for production of porous filler | |
| SU798070A1 (en) | Raw mixture for producing porous ceramic materials | |
| JPH07172825A (en) | Production of highly reactive quick lime by hydration-redehydration treatment of quick lime | |
| JP2737872B2 (en) | Processing method of α-type calcium sulfate hemihydrate and its product | |
| GB1493703A (en) | Apparatus and method for calcining gypsum | |
| US2560338A (en) | Chromic oxide production particularly for pigment purposes | |
| RU1794925C (en) | Method for production gypsum biding agent of phosphogypsum | |
| Khalil et al. | Gypsum plasters. I. Preparation of β‐hemihydrates | |
| SU345767A1 (en) | Method for preparing dry inorganic salts | |
| EP0218026B1 (en) | Process for producing shaped articles of alumina and zirconia and shaped articles produced according to the process |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |