CA1312063C - Method of producing an adsorbent from bloating minerals and calcium sulfate hemihydrate - Google Patents
Method of producing an adsorbent from bloating minerals and calcium sulfate hemihydrateInfo
- Publication number
- CA1312063C CA1312063C CA 564667 CA564667A CA1312063C CA 1312063 C CA1312063 C CA 1312063C CA 564667 CA564667 CA 564667 CA 564667 A CA564667 A CA 564667A CA 1312063 C CA1312063 C CA 1312063C
- Authority
- CA
- Canada
- Prior art keywords
- calcium sulfate
- bloating
- adsorbent
- mineral
- weight
- 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 - Lifetime
Links
- 239000003463 adsorbent Substances 0.000 title claims abstract description 42
- 229910052500 inorganic mineral Inorganic materials 0.000 title claims abstract description 36
- 239000011707 mineral Substances 0.000 title claims abstract description 36
- 206010000060 Abdominal distension Diseases 0.000 title claims abstract description 35
- 208000024330 bloating Diseases 0.000 title claims abstract description 35
- ZOMBKNNSYQHRCA-UHFFFAOYSA-J calcium sulfate hemihydrate Chemical compound O.[Ca+2].[Ca+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZOMBKNNSYQHRCA-UHFFFAOYSA-J 0.000 title claims abstract description 25
- 238000000034 method Methods 0.000 title claims abstract description 25
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims abstract description 35
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 31
- 238000001354 calcination Methods 0.000 claims abstract description 25
- 238000001035 drying Methods 0.000 claims abstract description 16
- 239000000203 mixture Substances 0.000 claims abstract description 11
- 239000008187 granular material Substances 0.000 claims abstract description 10
- 238000002156 mixing Methods 0.000 claims abstract description 9
- 230000014759 maintenance of location Effects 0.000 claims abstract description 8
- 238000003756 stirring Methods 0.000 claims abstract description 8
- 239000010451 perlite Substances 0.000 claims description 8
- 235000019362 perlite Nutrition 0.000 claims description 8
- 241001465754 Metazoa Species 0.000 claims description 3
- 230000029142 excretion Effects 0.000 claims description 3
- 239000004566 building material Substances 0.000 claims description 2
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 238000011049 filling Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 238000001179 sorption measurement Methods 0.000 abstract description 16
- 239000002245 particle Substances 0.000 abstract description 9
- 239000011148 porous material Substances 0.000 abstract description 6
- 239000000654 additive Substances 0.000 abstract description 2
- 235000010755 mineral Nutrition 0.000 abstract 6
- 230000000717 retained effect Effects 0.000 abstract 1
- 239000000463 material Substances 0.000 description 9
- 238000005299 abrasion Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- 235000019589 hardness Nutrition 0.000 description 7
- 239000000126 substance Substances 0.000 description 3
- 241000282326 Felis catus Species 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000002594 sorbent Substances 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052925 anhydrite Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- BPOLZZDJHZCCQQ-UHFFFAOYSA-L calcium;sulfite;dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])=O BPOLZZDJHZCCQQ-UHFFFAOYSA-L 0.000 description 1
- 238000007596 consolidation process Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 208000001848 dysentery Diseases 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000011507 gypsum plaster Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 150000005846 sugar alcohols Polymers 0.000 description 1
- 229910052902 vermiculite Inorganic materials 0.000 description 1
- 239000010455 vermiculite Substances 0.000 description 1
- 235000019354 vermiculite Nutrition 0.000 description 1
Landscapes
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Abstract
Abstract The invention relates to a method of producing an adsorbent where an expanded granular bloating mineral and calcium sulfate hemi-hydrate are mixed to form a granulated material where the calcium sulfate hemihydrate is converted in toto into calcium sulfate dihydrate by the addition of a surplus of water, and where the free water is removed by drying. It is desirable that the pro-portion of bloating mineral be reduced, that the adsorption ef-fect be substantially retained and the hardness of the adsorbent be increased without any additives. This is accomplished by mix-ing calcium sulfate hemihydrate and bloating mineral in such proportion that a weight ratio of calcium sulfate : bloating minerals > 5 : 1 and up to 10 : 1 exists in the adsorbent, in that mixing is effected by calcium sulfate hemihydrate and the bloating mineral being poured together into a tank and mixed there together by a stirring tool to form a granulated mixture, in that the granulated mixture after the addition of the water and before drying is allowed a retention time of at least 4 minutes, and in that the dry calcium sulfate dihydrate is con-verted by calcining at 120 - 150°C in such a proportion into calcium sulfate hemihydrate that the adsorbent has a total water content of 1 % by weight to 16 % by weight. The adsorbent pro-duced in this manner comprises, on the one hand, open-pore smaller particles which consist only of calcium sulfate and, on the other hand, open-pore larger particles where a bloating min-eral core is coated with calcium sulfate.
Description
This invention relates to a method of producing an adsorbent, typically for animal excretions, from a bloating mineral and calcium sulfate hemihydrate where expanded granular bloating mineral and calcium sulfate hemihydrate are mixed to form a granulated product, where the calcium sulfate hemihydrate is converted by the addition of a surplus of water in toto into calcium sulfate dihydrate and where free water is removed by drying.
In a prior-art method (German Patent 30 21 377) of this type, a weight ratio of calcium sulfate to perlite of 5 : 1 maximum is recommended for the adsorbent and the mixing is effected in a rotating granulating drum whereby substantially round granules are produced with a perlite core and a calcium sulfate dihydrate coating, the granulated product having a total water content of about 18% by weight. The satisfactory adsorption effect of this adsorbent is achieved by the use of a relatively great amount of perlite which is expensive.
Also, adequate hardness and abrasion resistance of the adsorbent manufactured according to the prior art method is obtained bv the addition of polyalcohol.
The present invention provides a method of the type initially referred to by means of which an adsorbent can be made where the percentage of bloating mineral is reduced, the adsorption performance is substantially maintained and its hardness is 13~2063 increased without any additive substance. The method according to the present invention is characterized in that calcium sulfate hemihydrate and bloating mineral are mixed in such proportion that a weight ratio between calcium sulfate and the bloating mineral > 5 : 1 and up to 10 : 1 exi.sts in the adsorbent, in that the mixing is effected by calcium sulfate hemihydrate and the bloating mineral being poured toyether in a tank and stirred there in bulk by means of a stirring mechanism to form a granulated mixture, in that the - la -~i, :~3~2~3 granulated product mixture aEter adding the water and before drying is allowed a retention time of at least 4 minutes, and in that such a proportion of the dry calcium sulfite dihydrate is converted by calcining at 120 - 200C into calcium sulfate hemi-hydrate that the adsorbent has a total water content of 1 ~ by weight to 16 % by weight.
The method according to the invention uses a reduced amount of bloating mineral and represents an adsorbent which, on the one hand, contains particles consisting o~ an bloating mineral core with a calcium sulfate coating and, on the other hand, particle~
which consist only of calcium sulfate. The particles of the ad-sorbent are substantially of a shape other than round and have an open-pore surface. Despite the reduction in the amount of bloat-ing minerals, the total adsorption effect of the adsorbent i~
maintained due to the additional adsorption effect of the cal-cined calcium sulfate. A reduction in the total water content by 1 % by wéight increases the adsorption effect by abt. 3 %. Al-though, in calcining calcium sulfate dihydrate lumps, the hard-ness of the product normally decreases considerably, this is not so in the case of the method according to the invention. The hardness of the manufactured adsorbent is not less than the hardness of the granulated material before calcining and greater than that of the adsorbent made according to the prior art method It is eespecially effective and advantageous if the calcium sulfate hemihydrate and bloating mineral are ~tirred in such proportion that a weight ratio of calcium sulfate to bloating mineral of 6 : 1 to 8 : 1 exists in the adsorbent. ~7ith this weight ratio, there is a favourable saving in the amount of bloating mineral and the specific weight of the adsorbent is still not too high. The granular expanded bloating mineral is included in the adsorbent not only because of its adsorbent ac-tion, but also in order to reduce the specific weight of the ad-sorbent within certain lirnits. In many cases, for instance in producing pet litter, a ratio of 5.5 : 1 - 6.5 : 1, for instance 6 : 1 is preEerred.
~3~20~3 Conservative calcining is important Eor the properties of the adsorbent made by the method according to the invention. It i9 especially effective and advantayeous, thereEore, if calcining is effected at 135 - 1~5C. At the~e calcining temperatures, im-proved adsorption effect and hardnes~ are obtained.
A calcining temperature up to 150~C is in many cases sufficient.
A increase in the calcining temperature to, say, lg0C will ab-breviate the time required for the calcining process. Calcining temperatures of 120- 190C, preferably 160 - 180C have proved to be especially effective and advanta0eous.
It i5 also especially effective and advantageous if the propor-tion converted into calcium sulfate hemihydrate i9 such thak the adsorbent has a total water content of 6 % by weight to 12 % by weight. On the basis of such calcining, the adsorbent calcium sulfate which, in addition to hemihydrate, also comprises di-hydrate and anhydrite III develops an excellent adsorption effect The retention time allowed for the granulated mixture produced with the addition of water after making this granulated mixture and before drying has proved to be specially important for its hardness and abrasion resistance. It is especially effective and advantageous if the granulated mixture i5 allowed a retention time of up to 8 minutes before drying. During this period of time, the reaction of the water with the calcium sulfate hemihydrate can proceed completely without any disturbance. In practice, a retention time of about ~ minutes is as a rule suf-ficient in order to obtain a ~ufficiently hard granulated product and one of up to 5 minutes is still practicable.
The adsorbent made according to the invention can be used for liquids of inorganic or organic origin, e.g. as a binding agent for acids, alkalies or oil which may also be mixed with water.
However, the adsorbent is preferably used as a binding agent for animal excretions, e.g. aq pets litter.
:~ 3 ~ 3 The e~pensive propor-tion o~ bloating minerals in the finlshed product can be reduced by more than 50 % which amounts to a distinct saving in cost. The adsorbent granulated product is of the open-pore type and has a shape other than round which i3 im-portant when used as a pets litter because the granulated product will not roll. It is especially effective and advan-tageous if the adsorbent is produced with A bulk weight of 0.35 - 0.6 kg/liter, preferably 0.~ - 0.5 kg/liter because lighter products would be scratched out by the cats from the litter box. The adsorbent according to the invention is harder and will not powder so that the cat after using the litter box will not leave any traces.
The bloating mineral used for the method according to the inven-tion may, Eor instance, be vermiculite which, in the raw condi-tion is a water-containing mineral in line with the bloating minerals under consideration here. It is especially effective and advantageous, however, if perlite is used as the bloating mineral Perlite is not yellow or brown, but white and is superior in re-spect of the properties which the adsorbent to be produced according to the invention is desired to have.
The adsorbent manufactured according to the invention may be used not only for adsorption purpo~es, but also for other applica-tions, e.g. in the building industry as an aggregate in gypsum-compatible mortar mixtures. It is especially effective and ad-vantageous if the adsorbent made according to the invention is used as granulated building material for filling. This is because this product has positive properties in respect of bulk weight, abrasion, consolidation and strength which ma}ce it suitable as a filler.
The total water content can be reduced by calcining to 1 % by weight, ~I decrease in the total water content improving the ad-sorption effect. It is especially effective and advantageous if a total water content of about 2 % by weight, but not above 8 % by weight, or of a percentage between these two limits is adjusted by calcining. In this case, strength, bulk weight and adsorption capacity will be in a preferred relationship to each other.
~3~2~6~
The size of the expanded granular bloating mineral used is 0 ~ 6 mm and at least 85 % of the granules in the finished adsorbent have a size > 1.25 mm. In this manner, a granulated product i5 obtained with approximately 95 % > 0.8 mm up to 6 mm . As a rule, the adsorbent comprises greater particles which are calcium 9ul-fate-coated bloating mineral particles and smaller particles which con~ist only of calcium sulfate.
~t least 90 ~ of the granules in the bloating mineral used should h~ve a size of 1 - 6 mm, because ~maller dust fractions are undesirable. In the ca~e of the calcium sulfate hemihydrate, at least 80 %, preferably at least 90 %, should be < 63 ~m, For instance, 143 kg of plaster of Paris would be mixed Eor G0 seconds with 20 kg of expanded perlite in size~ of 50 % 0 - 3 mm and 5~ % 3 - 6 mm with 80 liter water added in an Eirich mixer. ~
surplus of water is added. ~s a rule, the water is poured into the mixer as a solid stream or flush. The peripheral ~peed of the stirring mechanism is 6.5 m/s. An open-pore type granulated ma-terial is obtained. The moist granulated material is allowed a retention time on a slow-running conveyor prior to drying and calcining.
The drying and calcining equipment is so conceived that the granulated material is subject to minimum friction movements.
This is important in order to prevent abrasion of the initially moist material and to preserve the open-pore surface. Therefore, a drum dryer is not suitable while a fluidized-bed drying and calcining installation or a drying and calcining apparatus of the grain dryer type is suitable. Excellent results have been ob-tained with drying and calcining equipment using a belt dryer comprising a screen-type perforated belt where the carrying run on which the material is deposited has hot gas blown through from below.
The drying and calcining equipment is of the two-stage type. In the drying stage, the free moisture is removed at 80 - 100C, typically 90C. In the ca]cining stage, the granulated material ~3~L2~3 is treated with hot air at abt. 130C in order to reduce t~e wa-ter of crystallization from abt. 20 ~ to abt. 8 ~. This step im-proves the adsorption effect of the f inished adsorbent by up to 30 % without the hardness and, consequently, abrasion re~istance of the f inished product being noticeably impaired.
Generally, any suitable mixing apparatus using a ~tirring tool may be used. It is especially effective and advantageou~ i~ mix-ing is carried out in a rotating container and with the stirring tool arranged eccentrlcally and rotating in the opposite direc-tion and if the stirring tool is ~ubstantially formed by a plu-rality of wire-type rods which substantially e~tend in the di-rection of the rotating a~i~ and are arranged about the rotating axis at a distance from the latter. This configuration enables improved mixing to be achieved in a reduced period of time with-out too many particles of the material being disintegrated.
The following table is intended to illustrate the influence of the calcination and the perlite proportion on adsorption:
Perlite Total HzO Adsorp- Bulk Fracture Abra-content of content of tion density resistance sion finished finished after product product Heberlein % ~ % HzO g/l N %
17.8 80 ~10 20 - 35 16 10.5 100 380 20 - 32 17 12 17.9 75 ~40 25 ~ ~8 7.5 12 10.1 95 ~30 25 - 46 8.5 12 8.6 105 410 25 - 45 10.~
For a comparison, the granulated product obtained according to German Patent 30 21 377 i9 as follows:
~3L2~3 In order to determine the adsorption (water adsorption capacity), 110 ~ of the substance to be tested was filled in a cyllnder.
This cylinder was closed at the bottom with a sieve. 250 ml water was poured onto the substance to be tested from the top. The amount of water running out was measured in ml. The indication of adsorption of, say, 100 % means that 1 kg of the granulated product material is capable of absorbing 1 kg of water.
The fr~cture resi~tance teat is rnade with the Heberlein 10 type tablet tester. ~ranules of the granulated material to be examirled with diameters of 1.5 - 3.5 mm are tested for resistance to fracture. A mean value is derived from the 10 values obtained and stated in terms of fracture resistance in kgf or N.
Abrasion test:
1. 100 g granulated product material is screened on the aieve rnachine (model Siebtechnik Muhlheim-Ruhr) on 20 cm circular sieves for 5 minutes.
3.5 mm and 250 ~ sieve and pan material >3.5 mm and C 250 is rejected.
In a prior-art method (German Patent 30 21 377) of this type, a weight ratio of calcium sulfate to perlite of 5 : 1 maximum is recommended for the adsorbent and the mixing is effected in a rotating granulating drum whereby substantially round granules are produced with a perlite core and a calcium sulfate dihydrate coating, the granulated product having a total water content of about 18% by weight. The satisfactory adsorption effect of this adsorbent is achieved by the use of a relatively great amount of perlite which is expensive.
Also, adequate hardness and abrasion resistance of the adsorbent manufactured according to the prior art method is obtained bv the addition of polyalcohol.
The present invention provides a method of the type initially referred to by means of which an adsorbent can be made where the percentage of bloating mineral is reduced, the adsorption performance is substantially maintained and its hardness is 13~2063 increased without any additive substance. The method according to the present invention is characterized in that calcium sulfate hemihydrate and bloating mineral are mixed in such proportion that a weight ratio between calcium sulfate and the bloating mineral > 5 : 1 and up to 10 : 1 exi.sts in the adsorbent, in that the mixing is effected by calcium sulfate hemihydrate and the bloating mineral being poured toyether in a tank and stirred there in bulk by means of a stirring mechanism to form a granulated mixture, in that the - la -~i, :~3~2~3 granulated product mixture aEter adding the water and before drying is allowed a retention time of at least 4 minutes, and in that such a proportion of the dry calcium sulfite dihydrate is converted by calcining at 120 - 200C into calcium sulfate hemi-hydrate that the adsorbent has a total water content of 1 ~ by weight to 16 % by weight.
The method according to the invention uses a reduced amount of bloating mineral and represents an adsorbent which, on the one hand, contains particles consisting o~ an bloating mineral core with a calcium sulfate coating and, on the other hand, particle~
which consist only of calcium sulfate. The particles of the ad-sorbent are substantially of a shape other than round and have an open-pore surface. Despite the reduction in the amount of bloat-ing minerals, the total adsorption effect of the adsorbent i~
maintained due to the additional adsorption effect of the cal-cined calcium sulfate. A reduction in the total water content by 1 % by wéight increases the adsorption effect by abt. 3 %. Al-though, in calcining calcium sulfate dihydrate lumps, the hard-ness of the product normally decreases considerably, this is not so in the case of the method according to the invention. The hardness of the manufactured adsorbent is not less than the hardness of the granulated material before calcining and greater than that of the adsorbent made according to the prior art method It is eespecially effective and advantageous if the calcium sulfate hemihydrate and bloating mineral are ~tirred in such proportion that a weight ratio of calcium sulfate to bloating mineral of 6 : 1 to 8 : 1 exists in the adsorbent. ~7ith this weight ratio, there is a favourable saving in the amount of bloating mineral and the specific weight of the adsorbent is still not too high. The granular expanded bloating mineral is included in the adsorbent not only because of its adsorbent ac-tion, but also in order to reduce the specific weight of the ad-sorbent within certain lirnits. In many cases, for instance in producing pet litter, a ratio of 5.5 : 1 - 6.5 : 1, for instance 6 : 1 is preEerred.
~3~20~3 Conservative calcining is important Eor the properties of the adsorbent made by the method according to the invention. It i9 especially effective and advantayeous, thereEore, if calcining is effected at 135 - 1~5C. At the~e calcining temperatures, im-proved adsorption effect and hardnes~ are obtained.
A calcining temperature up to 150~C is in many cases sufficient.
A increase in the calcining temperature to, say, lg0C will ab-breviate the time required for the calcining process. Calcining temperatures of 120- 190C, preferably 160 - 180C have proved to be especially effective and advanta0eous.
It i5 also especially effective and advantageous if the propor-tion converted into calcium sulfate hemihydrate i9 such thak the adsorbent has a total water content of 6 % by weight to 12 % by weight. On the basis of such calcining, the adsorbent calcium sulfate which, in addition to hemihydrate, also comprises di-hydrate and anhydrite III develops an excellent adsorption effect The retention time allowed for the granulated mixture produced with the addition of water after making this granulated mixture and before drying has proved to be specially important for its hardness and abrasion resistance. It is especially effective and advantageous if the granulated mixture i5 allowed a retention time of up to 8 minutes before drying. During this period of time, the reaction of the water with the calcium sulfate hemihydrate can proceed completely without any disturbance. In practice, a retention time of about ~ minutes is as a rule suf-ficient in order to obtain a ~ufficiently hard granulated product and one of up to 5 minutes is still practicable.
The adsorbent made according to the invention can be used for liquids of inorganic or organic origin, e.g. as a binding agent for acids, alkalies or oil which may also be mixed with water.
However, the adsorbent is preferably used as a binding agent for animal excretions, e.g. aq pets litter.
:~ 3 ~ 3 The e~pensive propor-tion o~ bloating minerals in the finlshed product can be reduced by more than 50 % which amounts to a distinct saving in cost. The adsorbent granulated product is of the open-pore type and has a shape other than round which i3 im-portant when used as a pets litter because the granulated product will not roll. It is especially effective and advan-tageous if the adsorbent is produced with A bulk weight of 0.35 - 0.6 kg/liter, preferably 0.~ - 0.5 kg/liter because lighter products would be scratched out by the cats from the litter box. The adsorbent according to the invention is harder and will not powder so that the cat after using the litter box will not leave any traces.
The bloating mineral used for the method according to the inven-tion may, Eor instance, be vermiculite which, in the raw condi-tion is a water-containing mineral in line with the bloating minerals under consideration here. It is especially effective and advantageous, however, if perlite is used as the bloating mineral Perlite is not yellow or brown, but white and is superior in re-spect of the properties which the adsorbent to be produced according to the invention is desired to have.
The adsorbent manufactured according to the invention may be used not only for adsorption purpo~es, but also for other applica-tions, e.g. in the building industry as an aggregate in gypsum-compatible mortar mixtures. It is especially effective and ad-vantageous if the adsorbent made according to the invention is used as granulated building material for filling. This is because this product has positive properties in respect of bulk weight, abrasion, consolidation and strength which ma}ce it suitable as a filler.
The total water content can be reduced by calcining to 1 % by weight, ~I decrease in the total water content improving the ad-sorption effect. It is especially effective and advantageous if a total water content of about 2 % by weight, but not above 8 % by weight, or of a percentage between these two limits is adjusted by calcining. In this case, strength, bulk weight and adsorption capacity will be in a preferred relationship to each other.
~3~2~6~
The size of the expanded granular bloating mineral used is 0 ~ 6 mm and at least 85 % of the granules in the finished adsorbent have a size > 1.25 mm. In this manner, a granulated product i5 obtained with approximately 95 % > 0.8 mm up to 6 mm . As a rule, the adsorbent comprises greater particles which are calcium 9ul-fate-coated bloating mineral particles and smaller particles which con~ist only of calcium sulfate.
~t least 90 ~ of the granules in the bloating mineral used should h~ve a size of 1 - 6 mm, because ~maller dust fractions are undesirable. In the ca~e of the calcium sulfate hemihydrate, at least 80 %, preferably at least 90 %, should be < 63 ~m, For instance, 143 kg of plaster of Paris would be mixed Eor G0 seconds with 20 kg of expanded perlite in size~ of 50 % 0 - 3 mm and 5~ % 3 - 6 mm with 80 liter water added in an Eirich mixer. ~
surplus of water is added. ~s a rule, the water is poured into the mixer as a solid stream or flush. The peripheral ~peed of the stirring mechanism is 6.5 m/s. An open-pore type granulated ma-terial is obtained. The moist granulated material is allowed a retention time on a slow-running conveyor prior to drying and calcining.
The drying and calcining equipment is so conceived that the granulated material is subject to minimum friction movements.
This is important in order to prevent abrasion of the initially moist material and to preserve the open-pore surface. Therefore, a drum dryer is not suitable while a fluidized-bed drying and calcining installation or a drying and calcining apparatus of the grain dryer type is suitable. Excellent results have been ob-tained with drying and calcining equipment using a belt dryer comprising a screen-type perforated belt where the carrying run on which the material is deposited has hot gas blown through from below.
The drying and calcining equipment is of the two-stage type. In the drying stage, the free moisture is removed at 80 - 100C, typically 90C. In the ca]cining stage, the granulated material ~3~L2~3 is treated with hot air at abt. 130C in order to reduce t~e wa-ter of crystallization from abt. 20 ~ to abt. 8 ~. This step im-proves the adsorption effect of the f inished adsorbent by up to 30 % without the hardness and, consequently, abrasion re~istance of the f inished product being noticeably impaired.
Generally, any suitable mixing apparatus using a ~tirring tool may be used. It is especially effective and advantageou~ i~ mix-ing is carried out in a rotating container and with the stirring tool arranged eccentrlcally and rotating in the opposite direc-tion and if the stirring tool is ~ubstantially formed by a plu-rality of wire-type rods which substantially e~tend in the di-rection of the rotating a~i~ and are arranged about the rotating axis at a distance from the latter. This configuration enables improved mixing to be achieved in a reduced period of time with-out too many particles of the material being disintegrated.
The following table is intended to illustrate the influence of the calcination and the perlite proportion on adsorption:
Perlite Total HzO Adsorp- Bulk Fracture Abra-content of content of tion density resistance sion finished finished after product product Heberlein % ~ % HzO g/l N %
17.8 80 ~10 20 - 35 16 10.5 100 380 20 - 32 17 12 17.9 75 ~40 25 ~ ~8 7.5 12 10.1 95 ~30 25 - 46 8.5 12 8.6 105 410 25 - 45 10.~
For a comparison, the granulated product obtained according to German Patent 30 21 377 i9 as follows:
~3L2~3 In order to determine the adsorption (water adsorption capacity), 110 ~ of the substance to be tested was filled in a cyllnder.
This cylinder was closed at the bottom with a sieve. 250 ml water was poured onto the substance to be tested from the top. The amount of water running out was measured in ml. The indication of adsorption of, say, 100 % means that 1 kg of the granulated product material is capable of absorbing 1 kg of water.
The fr~cture resi~tance teat is rnade with the Heberlein 10 type tablet tester. ~ranules of the granulated material to be examirled with diameters of 1.5 - 3.5 mm are tested for resistance to fracture. A mean value is derived from the 10 values obtained and stated in terms of fracture resistance in kgf or N.
Abrasion test:
1. 100 g granulated product material is screened on the aieve rnachine (model Siebtechnik Muhlheim-Ruhr) on 20 cm circular sieves for 5 minutes.
3.5 mm and 250 ~ sieve and pan material >3.5 mm and C 250 is rejected.
2. Of the screened material 250 ~ - 3.5 mm, 50 g plus 300 g ~teel balls of ~ mm dia are filled in the ~ieve pan and shaken for 20 minute~ in the screening machine.
3. Subsequently, the contents of the pan are poured on a 3.5 mm sieve and the steel balls are removed. The screened material is then placed again on a 250 ~ sieve and screened for 5 minutes. The material passing through the 250 ~ sieve is defined as abrasion or attrition.
Abrasion (attrition) = Passed ma erial (q) x_100 = x %
50 g
Abrasion (attrition) = Passed ma erial (q) x_100 = x %
50 g
Claims (13)
- THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
l. Method of making an adsorbent from bloating minerals and calcium sulfate hemihydrate, where an expanded granular bloating mineral and calcium sulfate hemihydrate are mixed to form a granulated material, where the calcium sulfate hemihydrate is converted by the addition of a surplus of water in toto into calcium sulfate dihydrate, and where free water is removed by drying, characterized in that, calcium sulfate hemihydrate and bloating mineral are mixed in such proportion that a weight ratio of calcium sulfate: bloating mineral > 5 : 1 and up to 10 : 1 exists in the adsorbent, in that mixing is effected by calcium sulfate hemihydrate and the bloating mineral being poured together in a tank to be mixed there by means of a stirring tool to form a granulated mixture, in that the granulated mixture after the addition of water and before drying is allowed a retention time of at least 4 minutes and in that the dry calcium sulfate dihydrate is converted by calcining at 120 - 200°C in such a proportion into calcium sulfate hemihydrate that the adsorbent has a tool water content of 1 % by weight to 16 % by weight. - 2. Method as in Claim 1, characterized in that the calcium sulfate hemihydrate and bloating minerals are stirred in such proportion that a weight ratio of calcium sulfate:
bloating mineral of 6 : 1 to 8 : l exists in the adsorbent. - 3. Method as in Claims l or 2, characterized in that calcining is effected at 135 - 145°C.
- 4. Method as in Claim l, characterized in that conversion into calcium sulfate hemihydrate is in such a proportion that the adsorbent has a total water content of 6 % by weight to 12 % by weight.
- 5. Method as in Claim 1, characterized in that the granulated mixture is allowed a retention time of up to 8 minutes prior to drying.
- 6. Method as in Claim 1, characterized in that the adsorbent is made with a bulk weight of 0.35 - 0.6 kg/l.
- 7. Method as in Claim 1, characterized in that perlite is used as a bloating mineral.
- 8. Method as in Claim 1, characterized in that a total water content of abt. 2 % by weight not exceeding 8 % by weight or a value between these two limits is adjusted by calcining.
- 9. Method as in Claim 1, characterized in that a calcining temperature of 120 - 190°C is used.
- 10. Method as in Claim 1, characterized in that the mixing is effected in a rotating container and with eccentrically arranged stirring tool rotating in the opposite direction and in that the stirring tool is essentially formed by a plurality of wire-type rods which substantially extend in the direction of the rotating axis and are arranged and distributed about the rotating axis at a distance from the latter.
- 11. Method as in claim 6, wherein the bulk weight is 0.4 -0.5 kg/l.
- 12. Method as in claim 9, wherein the temperature is 160 to 180°C
- 13. Method as in any one of claims 1, 2 or 4 to 12, adapted to produce an adsorbent for animal excretions or a granulated building material filling.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19873713742 DE3713742A1 (en) | 1987-04-24 | 1987-04-24 | METHOD FOR PRODUCING AN ADSORPTION AGENT FROM PERLITE AND CALCIUM SULFATE SEMI-HYDRATE |
| DEP3713742.5-43 | 1987-04-24 | ||
| EP88103351.8 | 1988-03-04 | ||
| EP88103351A EP0303760B1 (en) | 1987-04-24 | 1988-03-04 | Process for making an adsorbent agent from expanded rocks and calcium sulfate-hemihydrate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1312063C true CA1312063C (en) | 1992-12-29 |
Family
ID=25854931
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 564667 Expired - Lifetime CA1312063C (en) | 1987-04-24 | 1988-04-21 | Method of producing an adsorbent from bloating minerals and calcium sulfate hemihydrate |
Country Status (3)
| Country | Link |
|---|---|
| AT (1) | ATE76782T1 (en) |
| CA (1) | CA1312063C (en) |
| DK (1) | DK171051B1 (en) |
-
1988
- 1988-03-04 AT AT88103351T patent/ATE76782T1/en not_active IP Right Cessation
- 1988-04-12 DK DK200188A patent/DK171051B1/en not_active IP Right Cessation
- 1988-04-21 CA CA 564667 patent/CA1312063C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DK171051B1 (en) | 1996-05-06 |
| DK200188D0 (en) | 1988-04-12 |
| DK200188A (en) | 1988-10-25 |
| ATE76782T1 (en) | 1992-06-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |