Manufacturing of an artificial igneous rock material by a sintering process

Abstract

A method of making a porous silicate based material with similar properties as an extrusive or intrusive igneous silicate based rock without being naturally occurring. Quartz sand with a silica content (SiO.sub.2) of more than 75% is mixed with Sodium oxide, Calcium oxide, and Aluminum oxide and heated up to a temperature of more than 960 C. and for the chemical reactions to take place and for the molten mixture to reach an elastic state where the viscosity allows the formed gasses to be dissolved into the melt. The sintering process may be at atmospheric pressure or at positive pressure. The material is then cooled to a solid. The process gives a porous igneous rock with micro cells based on CO.sub.2 bubbles made at a temperature prior to the molten mixture reaching a plastic state. The solid material may be milled and used as a filter material. In one aspect, the solid is milled, mixed with a foaming agent, melted and cooled in order to form an even more porous second solid material.

Claims

1-11. (canceled)

12. A method for making an artificial, silicate-based igneous rock material, comprising the steps of: a. Providing a mixture consisting of 65-85% by weight of Quartz sand with a SiO.sub.2 content of above 75%, 8-20% by weight of Sodium oxide (Na.sub.2Co.sub.3), 8-15% by weight of Calcium oxide (CaCo.sub.3), 2-10% by weight of Aluminum Oxide (Al.sub.2O.sub.3). b. Heating the mixture to a temperature in the range from 960 C. to 1200 C., whereupon the molten mixture enters its elastic state, c. Heating the mixture at atmospheric pressure or under a pressure from 0-3 bar above atmospheric pressure, d. Cooling the sintered mixture until the mixture forms a solid

13. The method according to claim 1, wherein the molten mixture is cooled prior to the mixture entering into a plastic stage at an average temperature of 1150 C., and prior to any significant amount of gaseous bubbles bursting though the surface of the molten mixture.

14. The method according to claim 1, wherein the mixture is heated to a maximum temperature (Tmax) over the course of from 30-120 minutes, preferably from 50-90 minutes, and most preferably over the course of approximately 60 minutes.

15. The method according to claim 1, wherein a vertical orientated furnace is used to create a positive pressure on the molten mixture due to the weight of the mixture.

16. The method according to claim 1, wherein the mixture is heated in a vertically oriented furnace (14) to a molten material (22), said molten material exiting a nozzle (24), wherein the furnace is arranged such that the molten material flows downward at a higher rate than any upward movement of bubbles (20) created during the heating process.

17. The method according to claim 1, wherein the molten material is cooled to ambient temperature within 300 minutes or less.

18. The method according to claim 1, wherein the molten material is held at Tmax from 15-120 minutes.

19. The method according to claim 1, wherein the heating and cooling of the mixture are performed at atmospheric pressure.

20. The method according to claim 1, wherein the heating of the mixture is performed at a positive pressure of from 0.01-3 bar.

21. The method according to claim 1, wherein the mixture further consists of from 10-40% of rock aggregate made according to one of the proceeding claims, milled to a grain size of 1 mm or less.

22. The method according to claim 1, further comprising the steps of milling the solid into powder with fraction size below 800 micron, adding a foaming agent, heating the resultant second mixture of milled solid and foaming agent until said second mixture melts and reacts to form a foamed mineral product, and cooling said second mixture to a more porous and less dense second solid.

23. A rock aggregate material made according to one of the preceding claims.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0025] The invention will now be described with reference to the attached figures, wherein:

[0026] FIG. 1 is a photograph of aggregates of an artificial porous silicate based igneous rock according to the invention made by an extrusive heating and cooling process.

[0027] FIG. 2 shows material of the invention crushed into 0-2 mm sand.

[0028] FIG. 3 shows crushed artificial igneous rock 1.6-2.5 mm prepared for use as filtration media for fresh water treatment.

[0029] FIG. 4 shows the porous surface structure of crushed aggregate made by an extrusive process with cells in the range from 0.1-10 mm.

[0030] FIG. 5 shows milled artificial igneous rock with a fraction size of 0-100 micron.

[0031] FIG. 6 shows mineral foam made at 850 C. from artificial igneous rock powder 0-100 micron mixed with 4% AlN and 1% MnO.sub.2 as foaming agent. Block density 200 kg/l.

[0032] FIG. 7 shows mineral foam (cellular glass) material made from artificial igneous rock powder, with AlN and MnO.sub.2 as foaming agents, further showing the internal cell structure of the cellular glass material.

[0033] FIG. 8 shows a vertical oven used in one embodiment of a method of the invention

[0034] FIG. 9 shows a casted article with milled artificial rock material 0-100 micron heated with a gasifier to form a cellular low density mineral foam product. Foaming agent AlN forming mineral foam/cellular glass at 850 C.

[0035] FIG. 10 show a set up for a high pressure dual filter for fresh water treatment, with 0.8-2.5 mm artificial rock foamed with SiC as gasifier to form a low density filter media for the top layer, and 0.3-0.8 mm crushed igneous rock as the lower layer.

[0036] FIG. 11 shows 0.3-0.6 mm crushed artificial igneous rock as filtration media for fresh water treatment.

[0037] FIG. 12 shows 0.8-1.8 mm foamed and crushed igneous rock as filtration media for fresh water treatment and as pre-treatment for reverse osmosis.

[0038] FIG. 13 shows 1.6-2.5 mm foamed and crushed igneous rock as filtration media for fresh water treatment and as pre-treatment for reverse osmosis.

[0039] FIG. 14 shows 1.6-4.0 mm foamed and crushed igneous rock as filtration media for fresh water treatment.

DETAILED DESCRIPTION

[0040] According to one aspect of the invention, a method for production of an artificial igneous rock, method is described in detail as follows:

[0041] 65-84% by weight of Quartz sand with high SiO.sub.2 content is mixed with 8-20% by weight of Sodium oxide (Na.sub.2Co.sub.3), 8-15% by weight of Calcium oxide (CaCo.sub.3), and 2-10% by weight of Aluminum oxide (Al.sub.2O.sub.3) and heated up to a temperature in the range from 960 C. to 1200 C. The mixture is heated over the course of from 30 to 180 minutes, preferably over the course of 60 to 120 minutes, most preferably over the course of approximately 90 minutes. For lowering of the melting temperature, a portion of ready-made synthetic igneous rock milled down to fraction size below 1 mm may be added (10-40% by weight).

[0042] Example of production of igneous rock by an extrusive process under atmospheric pressure:

[0043] 75% Quarts sand (including 7.5% Aluminum oxide)+15% Sodium oxide+10% Calcium oxide Batch of 2 kg, density 1.6 kg/l.

[0044] Height of mixture: 100 mm

[0045] Positive pressure: 0.016 bar at the bottom of mixture Heating from 20 C. to 1050 C. over 60 minutes

[0046] Hold at Tmax (maximum temperature) 30-90 min (depended upon the grain size), in this example 60 min with a grain size <0.8 mm

[0047] Then temperature is reduced to ambient temperature in a controlled temperature zone to reduce stress in the artificial rock.

[0048] The temperature is lowered before the molten mixture has reached a plastic state and just before any significant amount (preferably zero) gas bubbles start to pair up and burst through the surface of the melt. This can be observed as large craters on top of the surface of the melt.

[0049] The process time will depend on the amount of Sodium oxide in the blend and the maximum temperature used. A higher temperature and/or higher content of Sodium oxide gives a shorter process time.

[0050] In FIG. 1, some samples produced by the process are shown. The method used in this example:

[0051] The blend consists of 75% Silicon dioxide, 15% Sodium oxide and 10% Calcium oxide. Heated up in a furnace to a maximum temperature of 1050 C. and kept at maximum for 60 minutes before cooled down to room temperature, for further processing.

[0052] According to another aspect of the invention, a method for crushing the artificial igneous rock into sand for further use as filtration media for water treatment is possible.

[0053] An Example of Usage:

[0054] As shown in FIGS. 3 and 4, the artificial rock is crushed into fractions of 0-4 mm size, then again sieved into a different fraction sizes in the range between 0.3-4 mm. Because of its porous and large surface with open micro cells in the range of 0.1-0.4 mm the crushed rock material can be used as a filtration media for fresh water treatment, as pre-treatment of salt water and brackish water before reverse osmosis and as filtration for swimming pools.

[0055] If filtration media with small particle size and large surface area is needed, the igneous rock can be made by an intrusive process under positive pressure (preferably from 0.01-3 bar) to create a smaller cell structure, preferable with a cell size down to 0.01 mm. According to one aspect, this can be achieved by performing the process under positive pressure in a pressure chamber. According to another aspect, illustrated in FIG. 8, this can be performed in a vertical oven arrangement. As shown in FIG. 8, a mixture 10 of the ingredients is fed by a supply tube 12 from the top of a vertical oven 14 and onto the top of the molten mixture 18 inside the furnace. The oven is heated by a heat source 16. The mixture is heated to a temperature above 960 C., melting the mixture. The weight of the column 18 of molten mixture creates a positive pressure, preferably of from 0.01-3 bar. As shown, bubble 20 formed in the molten mixture attempts to rise to the surface. The molten material 22 is allowed to exit a nozzle 24 with a given size. The size of the opening of nozzle 24, as well as the maximum temperature to allow the downward rate of flow of the molten material to be equal to or faster than the rate of upward rising of the bubbles, in order to contain as much gas in the molten mixture as possible. The molten material exiting the nozzle is allowed to a solid, porous material.

[0056] According to another aspect of the invention, a method for lowering the density of the filtration media is provided. By milling the igneous rock down to a fraction size below 700 micron, then adding 0.5-5% of a foaming agent such as SiC, MnO2, AlN or a combination of them, then heating up the mixture to a temperature from 820 C. to 1000 C., to create a foamed product with micro cells, then cool down to ambient temperature, then crush the foamed artificial igneous rock into the desired fraction sizes as shown in FIGS. 12, 13 and 14.

[0057] Fraction sizes used for filtration media can be in the range:

[0058] 0.3-0.6 mm, FIG. 11

[0059] 0.8-1.6 mm, FIG. 12

[0060] 1.8-2.5 mm, FIG. 13

[0061] 2.5-4.0 mm, FIG. 14

[0062] Other ranges can be used dependent upon the end user filtration equipment and need.

[0063] Absolute particle density for the filtration media can range from 1.05 kg/l to 1.8 kg/l.

[0064] According to another aspect of the invention, a method of replacing recycled glass as the main raw material for production of cellular glass by methods known in the art is shown in FIGS. 5,6 and 7. According to this aspect of the invention, the artificial igneous rock aggregates is milled down to a powder, normally from 0-800 micron. In some cases larger fractions can be used. The powder is then mixed with foaming agents such as SiC+MnO.sub.2, or AlN+MnO.sub.2, or Na.sub.2SiO.sub.3, or other foaming agents that reacts with the molten igneous rock to create gas bubbles at temperatures from 750 C. to 1000 C. The molten and foamed igneous rock material is then processed into different foam glass products.

[0065] An Example of Usage:

[0066] A powder as shown in FIG. 5, is prepare by milling the rock material of the invention. To the powder is added 4% by weight AlN and 1% by weight MnO.sub.2 (with 95% by weight of artificial igneous rock powder with a fraction size of 0-600 micron). The mixture is melted by being heated to a temperature of 900 C. The melt is then maintained at maximum temperature for 30 minutes before cooled down to room temperature, resulting in a porous foam glass material, a sample is shown in FIG. 6. The foamed igneous rock can be crushed into aggregates with a sealed cell structure of 0.1-3 mm as shown in FIG. 7.

[0067] Some characteristics of the cellular rock product:

[0068] Block density: 300-800 g/l

[0069] Thermal heat capacity: 0.050-0.090 W/mK

[0070] Compression strength: >1.5 MPa

[0071] Average cell size: 1 mm

[0072] Another Example of Usage:

[0073] An artificial igneous rock powder 0-100 micron as shown in FIG. 5 is prepared by milling the rock material of the invention. To the powder is added 2% by weight SIC and 1% by weight MnO2. The mixture is then added to a mold. The mold is then placed in an oven at 900 C. for one hour, then cooled down to room temperature, resulting in a casted mineral form article, a sample shown in FIG. 9.

[0074] Some characteristics of the casted mineral foam product:

[0075] Block density: 400-600 g/l.

[0076] Compression strength: >7.5 MPa