CA2236486A1 - Production of commercially useful materials from waste gypsum boards - Google Patents

Production of commercially useful materials from waste gypsum boards Download PDF

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Publication number
CA2236486A1
CA2236486A1 CA 2236486 CA2236486A CA2236486A1 CA 2236486 A1 CA2236486 A1 CA 2236486A1 CA 2236486 CA2236486 CA 2236486 CA 2236486 A CA2236486 A CA 2236486A CA 2236486 A1 CA2236486 A1 CA 2236486A1
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CA
Canada
Prior art keywords
product obtained
waste
gyproc
boards
additive
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
Application number
CA 2236486
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French (fr)
Inventor
Gaetan Marcoux
Alphonse Beshay
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Individual
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Individual
Priority date (The priority date 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 date listed.)
Filing date
Publication date
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Priority to CA 2236486 priority Critical patent/CA2236486A1/en
Publication of CA2236486A1 publication Critical patent/CA2236486A1/en
Abandoned legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
    • B01J20/045—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium containing sulfur, e.g. sulfates, thiosulfates, gypsum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3021—Milling, crushing or grinding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
    • 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
    • C04B11/26—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke
    • C04B11/262—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke waste gypsum other than phosphogypsum
    • 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
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
    • C04B28/142—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements containing synthetic or waste calcium sulfate cements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/42—Materials comprising a mixture of inorganic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/46—Materials comprising a mixture of inorganic and organic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4812—Sorbents characterised by the starting material used for their preparation the starting material being of organic character
    • B01J2220/4825—Polysaccharides or cellulose materials, e.g. starch, chitin, sawdust, wood, straw, cotton
    • B01J2220/4831—Polysaccharides or cellulose materials, e.g. starch, chitin, sawdust, wood, straw, cotton having been subjected to further processing, e.g. paper, cellulose pulp
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4875—Sorbents characterised by the starting material used for their preparation the starting material being a waste, residue or of undefined composition
    • 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)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Analytical Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Processing Of Solid Wastes (AREA)

Abstract

A commercially useful material is produced from waste gyproc boards containing calcium sulfate dihydrate, by a method comprising the steps of (a) grinding the waste gyproc boards to obtain particles having a substantially uniform size; (b) drying the particles obtained in step (a) to obtain moisture-free particles; (c) heating the moisture-free particles obtained in step (b) at a temperature of 128 to 162°C to convert the calcium sulfate dihydrate to calcium sulfate hemihydrate; (d) adding water to the product obtained in step (c) to form a paste;
(e) forming the paste obtained in step (d) into a shaped product of a predetermined size; and (f) drying the shaped product obtained in step (e) at a temperature of 105 to 120°C to obtain a commercially useful material. The materials produced by the method of the invention can be used for a variety of industrial and household purposes.
Typical uses include the absorption of oil, grease and chemicals on floors and elsewhere, in animal toilet applications as a cat box absorbent, as carriers for chemicals, such as pesticides and herbicides, in various agricultural and horticultural applications. They can also be used as fillers for agricultural and horticultural applications. When admixed with an adhesive agent such as Portland cement, epoxy or polyester adhesives, they can be applied onto walls and/or floors to provide a decorative coating.

Description

"Production of Commercially Useful Materials from Waste Gyproc Boards"
The present invention pertains to improvements in the field of waste recycling. More particularly, the invention is directed to a method of producing commercially useful materials from waste gyproc boards.
Waste gyproc boards coming from demolition and :LO gyproc board factories represent a serious threat to t=he environment as they accumulate by thousands to hundred thousands of tons in many dumping sites. They retain humidity and thus promote the formation of undesirable mildew. Degradation of the calcium sulfate contained in :L5 the waste gyproc boards under the influence of infra-red and ultraviolet radiations causes the generation of H2S
and S02 which contaminate the environment.
Gyproc boards contain calcium sulfate dihydrat:e, :?0 silicon dioxide, cellulosic fibers as well as various metal oxides such as aluminum oxide, calcium oxide, ferric oxide and magnesium oxide. Calcium sulfate dehydrate is known to have liquid absorbing properties, as disclosed for example in U.S. Patent Nos. 4,163,674 and 4,264,543.
a?5 However, waste gyproc boards are not suitable for use as absorbents or any other useful products such as fillers for agricultural and horticultural applications.
It is therefore an object of the present ~s0 invention to overcome the above drawbacks and to provide a method of producing a commercially useful material fx-om waste gyproc boards.
According to one aspect of the invention, there .5 is thus provided a method of producing a commercially useful material from waste gyproc boards containing calcium sulfate dehydrate. The method of the invention comprises the steps oi=:
a) grinding the waste gyproc boards to obtain particles having a substantially uniform size;
b) drying the particles obtained in step (a) to obtain moisture-free particles;
c) heating the moisture-free particles obtained in step (b) at a temperature of 128 to 162°C to convert the calcium sulfate dehydrate to calcium sulfate T_0 hemihydrate;
d) adding water to the product obtained in step (c) to form a paste;
e) forming the paste obtained in step (d) into a shaped product of a predetermined size; and J_5 f) drying the shaped product obtained in step (e) at a temperature of 105 to 120°C to obtain a commercially useful material.
The present invention also provides, in another ~'.0 aspect thereof, a commercially useful material derived from waste gyproc boards and produced by the above method.
Applicant has found quite unexpectedly that commercially useful products, particularly liquid 25 absorbing materials, filler materials for agricultural and horticultural applications and decorative coating materials for walls and floors, can be produced at a low cost from waste gyproc boards by converting the calcium sulfate dehydrate contained in the waste gyproc boards to ~:0 calcium sulfate hemihydrate having binding properties and serving to bind the other components of gyproc boards. The waste gyproc boards must first be ground to obtain particles having a substantially uniform size, which are then dried to obtain moisture-free particles, for example, a5 by heating the partic:Les at a temperature of 105 to 120°C
in a circulating air oven for a period of time sufficient to evaporate all traces of water. The moisture-free particles are heated at a temperature of 128 to 162"C, preferably about 145°C, to partially dehydrate the calcium sulfate dihydrate and to thereby convert same to calcium sulfate hemihydrate. Care should be taken to avoid heating the moisture-free particles at a temperature above 162 "C, since at a temperature of 163°C calcium sulfate hemihydrate loses all its water of crystallization and is converted to anhydrous calcium sulfate. Water is added to the resulting product to form a paste. The paste is formed 7_0 into a shaped product of a predetermined size, for example, granules, pellets or balls, and the shaped product is then dried at a temperature of 105 to 120°C to obtain the desired absorbent or filler material. If t:he shaped product is dried at a temperature less than 105°C, 7_5 the evaporation of water is insufficient so that t:he absorption characteristics of the final product are adversely affected. At a temperature above 120°C, on t:he other hand, there is a partial conversion of the hydrated calcium sulfate to calcium sulfate to calcium sulfate ~'.0 hemihydrate, which weakens the final product and leads to the formation of cracker therein.
Various additives can be dry-mixed with t:he product obtained in step (c) with a view to increasing t:he ~~5 absorption characteristics, density, hardness and/or water-resistance of t:he material obtained in step (f);
fungicidal agents and/or coloring agents can also be added. For example, when it is desired to increase t:he absorption characteristics of the final product, wood DSO cellulose fibers, textile fibers, paper pulp, peat fines, mineral fines, charcoal, agricultural waste materials such as corn stalks and peanut shells, or porous plast=ic materials can be added. Use is preferably made of cellulosic fibers in an amount of 0.5 to 30 wt.$. When it ~S5 is desired to increase the density of the final produces, powdered slag can be added it is preferably used in an amount of 5 to 80 wt. g. Since powdered slag exhibits binding properties, it can also be used to increase the hardness of the final product. In such a case, the powdered slag is preferably added in an amount of 1 to 80 wt.~. When using powdered slag, acidified water is preferably added in step (d) to reduce the pH so that t:he final product has a pH of about 7. On the other hand, when it is desired to increase the water-resistance of the final product, gypsum plaster which is also called "Plaster of Paris" can be added. The gypsum plaster is 7.0 preferably used in an amount of 10 to 80 wt.~. A clumping agent such as sodium ~>icarbonate can also be added.
A particularly preferred absorbent material produced in accordance with the invention is derived from 7.5 about 50 wt.~ waste gyproc boards and contains about 25 wt.$ powdered slag, about 20 wt.$ gypsum plaster and about 5 wt.~ cellulosi.c fibers. Such an absorbent material not only exhibits increased hardness and absorption characteristics but is also highly resistant to ~!0 degradation by water.
A particularly preferred filler material produced by the methcrd of the invention is derived from about 50 wt.~ waste gyproc contains about boards and a!5 25 wt.~ gypsum plaster and about 25 wt.~ powdered slag.

Such a filler material. exhibits not only increased density and :hardness but is alsoresistant to degradation by water.

.0 The materials produced in accordance with the invention can be used for a variety of industrial and household purposes. Typical uses include the absorption of oil, grease and chemicals on floors and elsewhere, in animal toilet applications as a cat box absorbent, as a5 carriers for chemical~~, such as pesticides and herbicides, in various agricultural and horticultural applications.
They can also be used as fillers for agricultural and horticultural applications . When admixed with an adhesive agent such as Portland cement, epoxy or polyester adhesives, they can be applied onto walls and/or floors to provide a decorative coating.
The following non-limiting examples illustrate the invention.
EXAMPLE 1:
7.0 120 kg of the waste humid gyproc boards were broken down into small particles and dried at 115°C in an air dryer until the particles became moisture-free. The temperature of the dryer was gradually increased to heat the moisture-free part=icles at a temperature of 150°C for J.5 a duration of 20 minutes. The particles thus obtained which contained hemihydrated calcium sulfate are hereinafter referred t:o "H.H.C.S. particles".
kg of the H.H.C.S. particles were mixed with ~!0 a suitable amount of water to form a paste suitable for shaping into granules. The granules were dried at 115°C
then broken down into different mesh sizes from mesh 5 to 40. '.Che broken granules were then redried in the same dryer at 115°C.
a! 5 EXAMPLE 2:
5 kg of the H.H.C.S. particles obtained in Example 1 were well mixed with 2 kg of gypsum plaster.
Water was added to th.e resulting mixture to form a paste a0 suitable for shaping into granules. The granules were dried at 115°C and then broken down into different mesh sizes from mesh 5 to 40. The broken granules were then redried in the same dryer at 115°C.
.C 5 EXAMPLE 3 Example 2 was repeated, except that the H.H.C.S.
particles were mixed with 3 kg of gypsum plaster.

EXAMPLE 4:
Example 2 was repeated, except that the H.H.C.S.
particles were mixed with 4 kg of gypsum plaster.
EXAMF?LE 5:
Example 2 w.as repeated, except that the H.H.C.S.
part_Lcles were mixed 'with 5 kg of gypsum plaster.
EXAMI?LE 6:
Example 4 was repeated, except that 0.5 kg of defibrated waste hygienic paper was added to the mixture containing the H.H.C.S. particles and gypsum plaster, prior to adding the water.
EXAMPLE 7:
Example 2 was repeated, except that the H.H.C..S.
particles were mixed with 1 kg of powdered slag.
EXAMPLE 8:
Example 2 was repeated, except that the H.H.C.S.
particles were mixed with 2 kg of powdered slag.
EXAMPLE 9:
Example 2 was repeated, except that the H.H.C.S.
particles were mixed with 3 kg of powdered slag.
EXAMPLE 10:
Example 2 was repeated, except that the H.H.C.S.
particles were mixed with 4 kg of powdered slag.
EXANfPLE 11:
Example 2 was repeated, except that the H.H.C.S.
particles were mixed with 5 kg of powdered slag.
EXAMPLE 12:
Example 8 was repeated, except that 1 kg of gypsum plaster was added to the mixture containing the H.H.C.S. particles and powdered slag, prior to adding the water.
EXAMPLE 13:
Example 12 was repeated, except that the amount of pc>wdered slag added was 2 kg.
EXAMPLE 14:
Example 12 was repeated, except that the amount of powdered slag added was 3 kg.
EXAM~?LE 15:
Example 12 was repeated, except that the amount of powdered slag added was 4 kg.
EXAMI?LE 16:
Example 12 was repeated, except that the amount of powdered slag added was 5 kg.
The bulk density, hardness, water absorption and resistance to water of the products obtained in Examples 1 through 16 were tested.
The bulk density was determined by filing a graduated cylinder without tamping. The hardness was determined according to the standard test ASTM # E728-91, and compared with i~he hardness of granules made from 100 wt.o gypsum plaster. The water absorption was determined according to the procedure described in US
Patent No. 4,183,763 (col. 11). The resistance to water was determined by soaking' the granules (2 g) in water for 2-4 hours and compressing with a spatula.
_ 7 _ The results are reported in the following Table:
Ex. Bulk Water Resistance Suitable No. density Hardness absorp- to water application pound / tion feet3 1 46 56$ 0.8 Week Animal litter 2 48 71$ 0.65 Moderate Animal litter 3 49 80$ 0.6 Moderate Animal litter 4 51 86$ 0.55 Moderate Animal litter 5 50.5 99.5$ 0.5 Good Animal litter 6 45.2 83~ 0.75 Moderate Animal litter 7 50 80$ 0.6 Good Animal litter 8 55 92~ 0.5 Good Animal litter 9 58 99$ 0.6 Good Animal litter 10 62 102 0.5 Very good Animal litter &
absorbent 11 69 106$ 0.4 Very good Absorbent 12 56 1259s 0.38 Very good Absorbent 13 58 142$ 0.3 Very good Absorbent 14 63 167$ 0.3 Very good Absorbent 15 68 189$ 0.31 Excellent Absorbent 16 72 207$ 0.29 Excellent Absorbent _ g

Claims (22)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A method of producing a commercially useful material from waste gyproc boards containing calcium sulfate dehydrate, comprising the steps of:
a) grinding the waste gyproc boards to obtain particles having a substantially uniform size;
b) drying the particles obtained in step (a) to obtain moisture-free particles;
c) heating the moisture-free particles obtained in step (b) at a temperature of 128 to 162°C to convert the calcium sulfate dehydrate to calcium sulfate hemihydrate;
d) adding water to the product obtained in step (c) to form a paste;
e) forming the paste obtained in step (d) into a shaped product of a predetermined size; and f) drying the shaped product obtained in step (e) at a temperature of 105 to 120°C to obtain a commercially useful material.
2. A method as claimed in claim 1, wherein step (b) is carried out by heating the particles obtained in step (a) at a temperature of 105 to 120°C.
3. A method as claimed in claim 1, wherein step (c) is carried out at a temperature of about 145°C.
4. A method as claimed in claim 1, further including the step of dry-mixing the product obtained in step (c), prior to adding water, with at least one additive for increasing absorption characteristics of the material obtained in step (f).
5. A method as claimed in claim 4, wherein said additive is selected from the group consisting of wood cellulose fibers, textile fibers, paper pulp, peat fines, mineral fines, charcoal, agricultural waste materials and porous plastic materials.
6. A method as claimed in claim 5, wherein said additive comprises wood cellulose fibers.
7. A method as claimed in claim 6, wherein the cellulosic fibers are added in an amount of 0.5 to 30 wt.%.
8. A method as claimed in claim 1, further including the step of dry-mixing the product obtained in step (c), prior to adding water, with an additive for increasing density of the product obtained in step (f).
9. A method as claimed in claim 8, wherein said additive comprises powdered slag.
10. A method as claimed in claim 9, wherein the powdered slag is added in an amount of 5 to 80 wt.%.
11. A method as claimed in claim 1, further including the step of dry-mixing the product obtained in step (c), prior to adding water, with an additive for increasing hardness of the product obtained in step (f).
12. A method as claimed in claim 10, wherein said additive is powdered slag.
13. A method as claimed in claim 11, wherein the powdered slag is added in an amount of 1 to 80 wt.%.
14. A method as claimed in claim 1, further including the step of dry-mixing the product obtained in step (c), prior to adding water, with an additive for increasing water-resistance of the product obtained in step (f).
15. A method as claimed in claim 14, wherein said additive comprises gypsum plaster.
16. A method as claimed in claim 14, wherein the gypsum plaster is added in an amount of 10 to 80 wt.%.
17. A method as claimed in claim 1, further including the step of dry-mixing the product obtained in step (c), prior to adding water, with an additive selected from the group consisting of fungicidal agents and coloring agents.
18. A method as claimed in claim 1, further including the step of dry-mixing the product obtained in step (c), prior to adding water, with powdered slag, gypsum plaster and cellulosic fibers.
19. A method as claimed in claim 18, wherein the powdered slag, gypsum plaster and cellulosic fibers are added in amounts of about 25 wt.%, 20 wt.% and 5 wt.%, respectively.
20. An absorbent material derived from waste gyproc boards and produced by a method as defined in any of claims 1, 4, 5, 6, 11, 12, 14, 15, 18 and 19.
21. A filler material derived from waste gyproc boards and produced by a method as defined in claim 1, 8 or 9.
22. A decorative coating material derived from waste gyproc boards and produced by a method as defined in any of claims 1, 11, 12, 14, 15 and 17.
CA 2236486 1998-05-01 1998-05-01 Production of commercially useful materials from waste gypsum boards Abandoned CA2236486A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA 2236486 CA2236486A1 (en) 1998-05-01 1998-05-01 Production of commercially useful materials from waste gypsum boards

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Application Number Priority Date Filing Date Title
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105251468A (en) * 2015-10-22 2016-01-20 丁玉琴 Preparation method of environment-friendly indoor poisonous gas adsorbent
CN109701488A (en) * 2018-12-20 2019-05-03 宝钢湛江钢铁有限公司 A method of heavy metal absorbent is prepared using industrial waste
EP3517514A1 (en) * 2018-01-30 2019-07-31 Holcim Technology Ltd. Method of processing plasterboards

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105251468A (en) * 2015-10-22 2016-01-20 丁玉琴 Preparation method of environment-friendly indoor poisonous gas adsorbent
EP3517514A1 (en) * 2018-01-30 2019-07-31 Holcim Technology Ltd. Method of processing plasterboards
WO2019150251A1 (en) * 2018-01-30 2019-08-08 Holcim Technology Ltd Method of processing plasterboards
CN111630016A (en) * 2018-01-30 2020-09-04 霍尔辛姆科技有限公司 Method for treating gypsum boards
CN109701488A (en) * 2018-12-20 2019-05-03 宝钢湛江钢铁有限公司 A method of heavy metal absorbent is prepared using industrial waste

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EEER Examination request
FZDE Discontinued
FZDE Discontinued

Effective date: 20080501

FZDE Discontinued

Effective date: 20080501