WO1999003795A1

WO1999003795A1 - Method and apparatus for the processing of phosphate gypsum waste

Info

Publication number: WO1999003795A1
Application number: PCT/GR1997/000030
Authority: WO
Inventors: Jacek Kleszczewski; Marceli Cyrkiewicz
Original assignee: Karageorgis, Ioannis
Priority date: 1997-07-15
Filing date: 1997-07-15
Publication date: 1999-01-28
Also published as: AU3354697A

Abstract

The present invention relates to a method for the wasteless processing of great quantities of phosphate gypsum waste into a form suitable for use as additive in colours, enamels, synthetic resins, and as binding component for especially loose soils for road constructions. The method for processing of phosphate gypsum waste consists of three heating steps in the temperature range of 460-650 K during about 60 minutes until pH over 5,9 is obtained. The process is running in machinery which includes a horizontal rotating chamber (1), on the inside of which on the axis a fixed cylinder (2) is attached, wherethrough a heating factor is passing in opposite direction. The rotating chamber (1) consists of three processing zones (3), (4), (5). The first zone (3) has on the inner periphery loosely set chain units (7), the second zone (4) is equipped with a worm-wheel (8) firmly set on the fixed cylinder (2), and the third zone (5) has on the full length a free hanging chain unit (11) and at least two rows of flat wing units (12).

Description

METHOD AND APPARATUS FOR THE PROCESSING OF PHOSPHATE GYPSUM WASTE

The present invention relates to a method for the processing of phosphate gypsum waste into a form especially suitable for use as additive in colours, enamels and synthetic resins, as well as soil stabilizers especially in road construction, and to the machinery for the processing of phosphate gypsum waste.

The problem of the continuously increasing quantities of phosphate gypsum waste resulting from the production of phosphoric acid from raw material containing phosphoric compounds is well known. During the processing of the main available source of phosphoric acid, that is a necessary ingredient in the production of phosphoric fertilizers, the apatite and phosphorite, large quantities of waste are produced simultaneously, usually called phosphate gypsum. This waste contains mainly calcium sulfate, with various degrees of hydration, and lanthanides, phosphoric compounds, fluorine compounds, chlorine compounds etc., according to the origin of the raw material containing phosphoric compounds, and are practically useless in the bigger part creating a serious ecological problem.

Background Art.

There are known efforts for the exploitation of phosphate gypsum waste. The polish patent application P277084 describes the use of phosphate gypsum waste as binding material in the production of building materials.

Also known from the polish patent 152954 is the use of small quantities of untreated phosphate gypsum waste as mineralizer in ceramic materials. From the polish patent 158532 are known means for obtaining waterproof gypsum derivative additives and other building materials, wherein the phosphate gypsum waste is used as one of the ingredients of the mixture in a quantity limited to 20 % of the total mixture mass. It is obvious that these are not quantities that can influence the exploitation of phosphate gypsum waste significantly.

Also known are methods for recovering the rare-earth elements = lanthanides from the phosphate gypsum waste, as described in the polish patents 129444 and 163042. These methods, however, do not influence very much the problem of phosphate gypsum waste, because their application leaves the quantities of original waste almost unchanged.

According to the polish patent application P285994 in order to obtain slag-sulfate cement the phosphate gypsum waste is mixed until homogenizing with metal sulfates and/or chlorides, followed by dehydration in acidic environment, pH > 7,5, steam wetted, keeping the pressure at 0,2-1,2 MPa, while the process is carried out at a temperature of 400-490 K over 1,5-12 hours, following the whole is dried and shredded and known bonding activators are added.

According to the polish patent application P290377 the obtaining of anhydrite binders is the result of tabletting of untreated phosphate gypsum waste, which is then burned at temperatures of 1015 K, 1115 K and 1270 K for one hour, and after cooling to room temperature they are shredded.

According to the polish patent 163643 gypsum may be produced from phosphate gypsum waste by addition of first small quantities, below 1 % of mass, of also residuals of copperas, after which it is roasted with burnt lime and barium chloride at a temperature of 450-500 K. Also known from literature are methods for the production of binding materials and isolating building materials using phosphate gypsum waste, where this waste is first undergoing treatment by the dry or wet method for the neutralization of the phosphoric salts, sodium fluoride compounds contained therein, so that the dehydration and crystallization process of gypsum proceeds without disturbance. In the wet methods the water consumption is up to 10 tons per 1 ton of phosphate gypsum waste, and in the dry methods the use of large quantities of additives, such as burnt lime or limestone powder, is necessary. The disadvantage of these methods is, as shown in literature, that the building materials containing the thus processed phosphate gypsum waste are characterized by a large degree of absorption.

From the polish patent 108676 is known the process for transforming the phosphate gypsum waste into limestone and ammonium sulfate forcing the cycling of the reaction products and suspension of reacting substance, such as phosphate gypsum waste, ammonia, carbon dioxide, while the process is conducted in the presence of at least 10 % of mass calcium carbonate in order to maintain the pH within the limits 7,5-8.

From the polish patent 119292 is known the process for cleaning phosphate gypsum waste by the use of ozon in order to obtain a bleaching degree of phosphate gypsum up to 75

%, so that it is suitable for use in paper bleaching processes.

The significant disadvantages of these known methods are that unfortunately they consume much time, energy and very often large quantities of water, as well as that they create other waste harmful for the environment.

Also known from the polish patents 170069, P299472 and P299473, and the polish patent application P303058 is the obtaining of ceramic-like materials with very good mechanical qualities and great chemical resistance. In these methods the phosphate gypsum waste is used as anorganic additive, after being heated for at least 1 hour at a temperature of 430-440 K.

Brief description of the invention

The present invention relates to a method for the processing of phosphate gypsum waste into a form especially suitable for use as additive in colours, enamels and synthetic resins, as well as soil stabilizers especially in road construction, and to the machinery for the processing of phosphate gypsum waste (Fig. 1).

It was found that during the heating of phosphate gypsum waste at a temperature of 470-650 K for about 1 hour, the waste is undergoing a processing without further residuals in a form suitable for use especially as additive in colours, enamels and synthetic resins (Fig. 2, 3 and 4), as well as a binding component for especially loose soils for road constructions, useful in reduction of consumption of weel known building material like cement.

Brief description of drawings

Fig. 1 shows the machinery for the processing of phosphate gypsum waste.

Fig. 2 shows a schematic diagram of the machinery and production line for the production of ceramic-like materials from phosphate gypsum waste and synthetic resins.

Fig. 3 shows a diagram of the phosphate gypsum waste treatment line in detail. Fig. 4 shows the ceramic-like material production line in detail.

Fig. 5 shows the schema of chemical reactions occuring in the processing of crude phosphate gypsum waste into gypsum.

Detailed description of invention

According to the present invention the method for processing of phosphate gypsum waste in a form suitable for use especially as additive in colours, enamels and synthetic resins, as well as soil stabilizer, especially in road construction, consists of three heating steps under continuous stirring. In the first step the phosphate gypsum waste is heated for at least 15 minutes at a temperature of 460-480 K. In the second step the heating takes place for 10- 25 minutes raising simultaneously the temperature to 490-540 K. In the third step the heating takes place for 10-25 minutes and the temperature is increased from 550 to 680 K in order to achieve pH higher than 5,9.

The machinery for processing of phosphate gypsum waste (Fig. 1) according to the present invention includes a horizontal rotating chamber, on the inside of which on the axis a fixed cylinder is attached, wherethrough a heating factor is passing in opposite direction to the stirred phosphate gypsum waste. The rotating chamber is equiped with a shute, through which the untreated phosphate gypsum waste is entered, and an outlet for the waste, and at the end there is an outlet for the processed phosphate gypsum. The rotating chamber consists of three processing zones. The first zone has on the inner periphery loosely set chain units in a fish-scale-like slanting arrangement, which collect, stir and shred. The second zone is equiped with a worm-wheel firmly set on the fixed cylinder, wherethrough a heating factor is passing, and may additionaly bear on the outer periphery flat units alternately set, according and slightly in a contrary way to the direction of the worm-wheel spiral, forming concentric circles. The third zone has on the full length of the outer periphery a free hanging chain unit, and also at least two rows of flat wing units parallel to the chain, vertical to the outer periphery and converging towards the axis of the chamber, the most advantageous ratio of length of each zone of the chamber is respectively 2:5:1, with a relation of the outer diameter to the inner 1,5-1,7:1. Furthermore, to intensify the development of the processing of phosphate gypsum waste, the machinery is set at an angle (1/53-1/42)π rad. with respect to the horizontal level.

By processing of phosphate gypsum waste by the method according to the present invention, which permits the removal of water, including the crystallic one, from the compounds existing in the processed phosphate gypsum waste, as a result of simultaneous thermic decomposition of a portion of the compounds in the phosphate gypsum waste, quasi- complexes are created, which are a mixture of the compounds calcium oxide, lanthanides salts, phosphorus pentoxide, as well as anhydrous calcium sulfate, which have a chemical constitution similar to the crystallic constitution, i.e. well- ordered in relation to intermolecular interactions (Fig. 2, 3, 4, 5). It can be presumed that the quasi-complexes, that are created in the place of amorph and non-homogenous in mass mixtures of compounds forming unprocessed phosphate gypsum waste, influence in an advantageous effective way the incorporation of elements of processed phosphate gypsum waste into the matrix of synthetic resins (Fig. 2, 4), so that the matrix of the thus complemented resins becomes after the hardening more homogenous from a physical and chemical point of view. This unexpectedly improves the application qualities and the extent of use, from the production of coverings especially protective on the surfaces of various materials, of jointless floor coatings, even to the production of products that are formed in special forms by the non- pressure method. Furthermore, the processing of phosphate gypsum waste according to the method of the present invention permits its use as in part alternative solution in building materials, such as cement. The change of reaction of the processed phosphate gypsum waste in acidity close to neutral, i.e. pH 5,9-6,3, neutral from the point of chemical influence on the environment, permits the safe use of processed phosphate gypsum waste as filling of exhausted excavations in mines or surface mines in the form of dry material, and also as pulp for the stabilization of underground areas.

Since corrosive qualities of the phosphate gypsum waste are neutralized during processing, the processed phosphate gypsum waste may be used in large scale in road construction. Known is the necessity of soil stabilization in road foundation, particularly for heavy and fast trucking. Commonly these soils are stabilized by using cement with a compression strength of 0,5-5,0 MPa after 28 days of curing. As it happens, the composition of 10-30 parts of weight of treated phosphate gypsum waste, 1-3 parts of weight of Portland cement, 10-27 parts of weight of flue dusts containing mainly 40-60 % of weight of Siθ2, 15-20 % of weight AI2O3, 5-18 % of weight Fβ2θ3, 1-16 % of weight alkaline earths, and 3,5 % of weight of SO3, used in proportion 66,7-73,1 parts of weight for 100 parts of weight of loose soils, can be applied to make the bottom layer of the road foundation or layers of improved subsoils. Utilization of treated phosphate gypsum waste in road constructions simultaneously helps reducing the consumption of natural resources and fully effective, no-waste exploitation of useless and harmful for the environment phosphate gypsum waste. The machinery for the processing of phosphate gypsum waste according to the present invention (Fig. 1) permits continuously processing under conditions of suitably constantly increasing temperature in the following steps of the method, which is carried out in every zone with simultaneous stirring and under conditions of stable temperature in the transversal compartments of the rotating chamber. Due to the inside equipment of the rotating chamber for processing phosphate gypsum waste cloding of the waste during the processing is prevented and simultaneously an advantageous influence on the shredding of phosphate gypsum waste is provided, thanks to which the size of the granules of the processed waste does not exceed 100 μm, being very often below 25 μm, a fact that indeed has an advantageous influence on the application qualities of the processed waste permitting the use, without any further preparation, as additive in colours, enamels and synthetic resins in the production of anticorrosive, protective coverings or plasters resistent to chemically aggresive environment, as well as for industrial constructions and house building. Furthermore, the phosphate gypsum waste processed according to the method and in the machinery of the present invention (Fig. 1, 2, 3), which is used as stabilizer of the soil in road construction, permits due to the very small granular structure a very good binding of the soil for the laying of foundations under the covering of roads designed for heavy and/or high-speed transport.

The machinery for the processing of phosphate gypsum waste by permitting the continuous processing under conditions of permanently increasing temperature without local overheatings, secures stable continuation of processing and change of the mixture of chemical compounds present in the unprocessed waste to the dehydrated chemical compounds (Fig. 5), which transform into the quasi-complexes of anhydrous salts and oxides especially of calcium, lanthanum oxides and phosphorus oxides. It is presumed that the compounds of lanthanides series, which remain and are not removed from the mass of processed phosphate gypsum waste, have a significant influence during the processing on the obtaining of phosphate gypsum waste in a form for broad use. The process of treatment according to the present invention is carried out by the dry method (Fig. 2, 3, 4), not like until today by the wet methods, i.e. by multistage washing, nor by the mixed methods, i.e. first by multistage washing and then drying or heating the washed precipitates at temperatures also over 700 K.

It is presumed that the presence of the lanthanide series in the unprocessed waste, which remain entirely in the processed phosphate gypsum waste, may have an advantageous influence on the creation of the quasi- complexes with a stable and well ordered structure, and this subsequently has an advantageous influence on the possibilities of use of the processed waste as additive in colours, enamels, synthetic resins and in other cases, where this structure has a significant influence on the characteristics of usefulness of the products, in which the processed phosphate gypsum waste has been used.

The present invention is described in detail in the following examples, which are indicative and do not restrict the extent of its application.

Example 1

In the chamber (Fig. 1) rotating at a speed of 1,1 revolutions/minute, which is set horizontally at an angle of 1/48 π rad (1), equiped centrally with a fixed cylinder (2), through which a heating factor is passing in an opposite direction with a temperature of 850-900 K, 600 kg of unprocessed phosphate gypsum waste is entered for one hour through the shute (6) into the first zone (3) of the chamber (1), where there is a temperature of 480-495 K, being heated at first up to 310 K, with pH 2,1 and 12 % of mass of chemically non-bounded water. The rotation of the chamber (1), equiped on its inner periphery with loose chain units (7) set in a slanting way, so that they form a fish-scale-like arrangement, securing the stirring of the phosphate gypsum waste and the removal of 83-85 % of the chemically non- bounded water, permits the movement of the waste towards the second zone within a time period of 22 minutes. In the second zone (4) of the chamber (1) the second step of the processing of the phosphate gypsum waste is carried out at a temperature of 515-550 K within a time period of approximately 20 minutes, i.e. heating and simultaneously stirring by the worm-wheel (8) stably mounted on the fixed cylinder (2), and stirring by the wings (9) set alternately according and in a contrary way to the direction of the worm- wheel spiral (8). Subsequently the phosphate gypsum waste, from which a part of the crystallic water has already been removed, is entered for approximately 15 minutes into the third zone (5) of the chamber (1), in which the temperature in increased towards the outlet (10) from 560 K to 660 K, where additionaly thermic decomposition with simultaneous heating of the waste in the form of quasi-complexes of calcium oxide, calcium sulfate and compounds of lanthanides and phosphorus takes place. To secure a continuous movement of the waste towards the outlet (10) for the processed phosphate gypsum waste from the chamber (1), the third zone (5) is equiped on the full length of the external periphery of the chamber (1) with a chain unit (11) and twelve rows of symmetrically set flat elements (12), nine in each row. The length of the heating zones (3), (4) and (5) is respectively 1,9:4,96:1 and the ratio of the external diameter of the chamber (1) to the inner is 1:1,62. 367 kg of processed phosphate gypsum waste with pH = 6 , 1 , a temperature of 590- 595 K and average granule size 35 μm, after cooling until 350 K in the intermediate chamber (13) (Fig. 2), are packed and were later used for obtaining cement mortar with resistance 1,5 MPa, which contains 89 kg of the processed waste, 140 kg cement, 1,15 m^ sand and 230 kg water, and was used as layer underneath the base of foundations.

Example 2

As in example 1, 600 kg of unprocessed phosphate gypsum waste were processed in the chamber (1)(Fig. 1), containing 14 % of mass chemically non-bounded water and with a pH = 2,7, which were at first heated up to 315 K. After 53 minutes 352 kg of processed phosphate gypsum waste were obtained with pH = 6,2, humidity 0,35 and an average granule size 42 μm, of which 20 kg were added under constant stirring over approximately 15 minutes to 40 kg acrylic resin DEGADUR 410 (Fig. 2). Subsequently, after homogenization of the whole, 40 kg of quartz sand with granules size 0,1-0,4 mm are added under constant stirring, 2 kg of dibenzoyl peroxide are added as hardener and stirred for approximately 8 minutes. Afterwards a smooth, dust-free and dry surface of beton 1,5-2 mm thick is covered. After 35 minutes a flat, shiny surface is obtained, which after examination on the same day under pressure of 283 MPa revealed no deformation whatsoever.

Example 3

5,3 kg of processed phosphate gypsum waste, that were obtained according to example 2, are added under constant stirring to a mixture of 4,6 kg epoxy resin EPIKOTE 828, 0,05 kg of the volatilizer BYK A 530 and 0,05 kg antipyren (Fig. 4). After 15 minutes a composition is obtained, with which, after addition of 3,03 kg of the hardener ANCAMINE 2280, a pipe of the installation for the production of sulphuric acid is covered using a roll. One coat of covering of 185 μm hardened after 3,5 hours and showed no damages after three months.

Example 4

To 23 kg of epoxy resin EPIKOTE 828 are added under constant stirring 0,5 kg of the volatilizer BYK A 530, 0,5 kg of antipyren and 50 kg of quartz sand with granules size 0,06- 0,12 mm (Fig. 4). To the homogenous pulp are added under constant stirring 25,3 kg of processed phosphate gypsum waste, which are obtained according to example 1. Subsequently 16 kg of the hardener ANCAMINE 2280 are added under constant stirring. A material similar to plaster is received, with which holes and cracks that were created due to atmospheric conditions on the external walls of a beton reservoir were filled. After 4 hours the material obtained according to example 3 was covered over the hole with a depth of 12 dm and expanse of 40 dm^ and on the dry plaster. After one year the surface showed no damage.

Example 5

To a homogenized composition of 5,5 kg alkyd resin, 1,5 kg titanium white, 1,5 kg sunflower oil, 0,95 kg ethanol are added under constant stirring 0,5 kg of processed phosphate gypsum waste, which were obtained according to example 2. Subsequently 0,5 kg of 10 % solution of cobalt napthenate are added under stirring. With the colour obtained large surfaces of losses on the protective layer of the protective cover of the grinding machine are covered by brush and after 18 hours a shiny covering of 85 μm is obtained. After 7 days the surface is ready for use. Example 6

A composition of 59,5 parts of weight of river sand, 10,5 parts of weight of flue dusts containing 46 % of weight Siθ2, 19 % of weight AI2O3, 10 % of weight Fβ2θ3, 6 % of weight CaO, 1,5 % of weight MgO, 0,7 % of weight SO3, 30 parts of weight of treated phosphate gypsum waste obtained according to example 2, and 2 parts of weight of portland cement was prepared and samples were made, condensed by a standard Proctor method. One part of the samples was subject to an axial compression inside the press after 28 days of curing in air moisture environment, with previous full saturating with water during the last 14 days, and the average resistance of 3,11 MPa was obtained. The second part of the samples was subject to resistance tests. Previously during the final stage of 28 days of curing, the samples were subject to 14 cycles of freezing and defrosting fully saturated with water, and the average resistance to compression of 1,04 MPa was achieved. These data indicate, that this composition meets the requirements for the bottom layer of road foundations.

Example 7

A composition of 63 parts of weight of river sand, 27 parts of weight of flue dusts containing 55 % of weight Siθ2, 22 % of weight AI2O3, 14 % of weight Fβ2θ3, 6 % of weight CaO, 4,2 % of weight MgO, 3,3 % of weight SO3, 10 parts of weight of treated phosphate gypsum waste obtained according to example 1, and 3 parts of weight of portland cement were processed according to example 6. The resistance of the samples was adequately 3,98 MPa and 1,41 MPa, i.e. this composition is suitable for making the improved subsoils layer or the bottom layer of road foundations.

Claims

1. Method for processing of phosphate gypsum waste in a form suitable for use especially as additive in colours, enamels, synthetic resins and building compositions, which consists of three heating steps under constant stirring, wherein the first step the unprocessed phosphate gypsum waste is heated for at least 15 minutes at a temperature of 460-480 K until 90 % of mass of the original water is removed, in the second step it is heated for 10-25 minutes with simultaneous raising of temperature to 490-540 K, and in the third step it is heated for 15-25 minutes with simultaneous raising of temperature from 550 K to 680 K to obtain pH higher than 5,9.

2. Machinery for processing of phosphate gypsum waste (Fig. 1, 2, 3, 4) in a form suitable for use especially as additive in colours, enamels, synthetic resins and building compositions, which consists of a horizontal rotating chamber (1), in which a fixed cylinder (2) is internally mounted upon the axis, through which a heating factor is passing in an opposite way, the chamber (1) being equiped with a shute (6) through which the unprocessed phosphate gypsum waste is entered and an outlet (14) of the waste, and at the end an outlet for the processed phosphate gypsum waste (10), which machinery is divided into three zones of processing (3), (4), (5), where the first zone (3) has on the outer periphery of the chamber (1) loosely set chain units (7) in a slant fish-scale-like arrangement that collect-stir and shred, the second zone (4) is equiped with a worm-wheel (8) set firmly on the fixed cylinder (2), and in the third zone (5) there are on the full length of the outer periphery of the chamber (1) a freely set chain unit (11), at least two rows of flat wing units (12) parallel to the chain unit (11), vertical to the outer periphery and converging towards the axis of the chamber (1), where the ratio of the length of each zone (3), (4), (5) is advantageously respectively 2:5:1, and the ratio of the external diameter of the chamber (1) to the inner is 1,5-1,7:1.

3. Machinery according to claim 2 (Fig. 1), which is equiped in the second heating zone (4) on the inner periphery of the chamber (1) with flat elements (9) forming circles or set alternately according to and slightly adversely to the direction of the worm-wheel spiral (8).

4. Machinery according to claims 2 and 3 (Fig. 1), where the chamber (1) is set in angle (1/53-1/42) ╧Ç rad with respect to the horizontal level.

5. Cement mortar, which contains phosphate gypsum waste processed by the method according to claim 1 and at a ratio for each 100 parts of cement mass 53,5 parts of mass processed phosphate gypsum waste.

6. Floor covering, which contains phosphate gypsum waste processed by the method according to claim 1, consisting after hardening of 40 parts of mass of acrylic resin, 20 parts of mass of processed phosphate gypsum waste and 40 parts of mass of quartz sand.

7. Protective covering, which contains phosphate gypsum waste processed by the method according to claim 1, consisting after hardening of 40 parts of mass of epoxy resin, 53 parts of processed phosphate gypsum waste and 0,5 parts of mass of antipyren.

8. Plaster, which contains phosphate gypsum waste processed by the method according to claim 1, consisting after hardening of 23 parts of mass epoxy resin, 5 parts of mass antipyren, 50 parts of mass quartz sand and 25,5 parts of mass processed phosphate gypsum waste.

9. Body colour, which contains phosphate gypsum waste processed by the method according to claim 1, consisting after hardening of 55 parts of mass of alkyd resin, 15 parts of mass titanium white, 15 parts of mass sunflower oil, 9,5 parts of mass ethanol and 5 parts of mass processed phosphate gypsum waste.

10. Composition for the stabilization of especially loose soils in bottom layers of road foundations or layers of improved subsoils for roads, consisting of 10-30 parts of weight of treated phosphate gypsum waste, 1-3 parts of weight of portland cement and 10-27 parts of weight of flue dusts, which contain mainly 40-60 % of weight Si╬╕2, 15-25 % of weight AI2O3, 5-18 % of weight F╬▓2╬╕3, 1-16 % of weight of alkaline earths and up to 3,5 % of weight of SO3, used in proportion 66,7-73,1 parts of weight to 100 parts of weight of loose soils.