A FOAMED GLASS PELLETS Field of invention:

The present invention relates to a method for manufacturing of rounded foamed glass pellets with a sealed cell structure on the surface, based on recycled glass or other material with a high S1O2 content, and a method to prepare a granulate useful in the method from power mixture into a dry granulate with a given particle distribution size, high compression strength and dimensional stability, before heating and foaming the granulate into the foamed glass pellets with a sealed surface.

Background:

Foamed glass spheres are often made using glass granulate as a starting material. In many applications, the granulate is used in a pelletized form. Traditionally, a pelletized granulate useful as a starting material in a foamed glass method is made by moistening a glass powder mixture and then forming the moistened mixture into pellets for example through extrusion. The pelletized granulate is then further worked by breaking and rounding the extrudate to round pellets through spherization, then drying the finished product, or by the use of a pan-granulator, disk granulator or pellet mixer, to form a moist granulate of a specific size before loading it into a revolving tubular furnace, as shown in US patent applications number 11/817,731 and 10/592,379.

The problem with prior art is that the granulates prepared by the prior art method to be used in a foaming process cannot be stored over time without losing some of its foaming capacity, cannot be transported without the risk of changing the particle sizes due to cracking, and it contains su bstances that can be of danger to people, animals and the environment. Furhermore, the production process is labor intensive and demands significant maintenance to make sure that the quality of the foamed glass product is consistent.

The present invention relates to a method of preparing the granulates that overcomes the disadvantages of prior art and further relates to methods of foaming the granulates and to be able to deliver foamed glass pellets with a wider particle distribution than prior art, at a more cost efficient and environmentally friendly way. Summary of the invention:

The present invention has as one of its objectives to produce foamed silicate-based pellets based on dimensionally stable granulate that can be stored, transported and used to produce various fractions of foamed silicate-based pellets on different types of furnace machinery, but particularly a furnace with downward angled vibrating plates to create an independent and almost horizontal movement of the granulates through the furnace.

The current invention is characterized by the features described in the attached independent claims, with additional embodiments described in claims dependent therefrom.

According to one aspect, the current invention relates to preparing a granulate without any moistening of the powder mixture (fig. 1) before making the granulate through a process of sintering (fig. 2), crushing, and if needed tumbling and coating the granulate (fig. 3) before the expansion of the granulate into a foamed glass pellet (fig. 4) through a heating process in a furnace (expansion oven), making a rounded foamed glass pellets with a porous cell structure on the inside and an essentially sealed cell structure on the outside (fig. 5).

According to another aspect, the method used to make the granulate, and further the foamed glass pellets comprises of the following steps:

1. Crushing recycled glass from container glass, flat glass or fines, into powder with a fraction size from 0-1000 micron, preferably from 0-100 micron. As an alternative to, or in combination to recycled glass, artificial igneous rock produced according to

PCT/EP2017/077766 can be used.

2. Dry mixing of powder with expanding agents.

3. Adding the mixture into a sintering oven at a temperature below the reaction temperature of the expanding agents to form a solid material without activating the expanding agents.

4. Crushing or milling the sintered and solid material into granulates with a desired fraction size from 0.001mm to 25mm.

5. Sieving the granulates and separating them into different fraction sizes.

6. For granulates above 2mm, the granulates can be tumbled to make them more rounded if desired.

7. The granulates or the surface inside of the oven that comes in contact with the granulates can be coated with a dry powder to act as a release agent during foaming to increase the granulates or the surface's non-stick capabilities. 8. Feeding the granulates into an expansion oven to melt the granulate and to activate the expanding agent to form a foamed pellet.

9. Keeping the granulate in constant and independent movement in the oven until the

expanding agent has reacted and the granulate has reached its desired shape.

10. Directing the foamed pellets out of the oven before the cells in the foamed pellets start to interconnect and before the cell structure on the surface starts to burst.

11. Cooling down the foamed pellets for a time according to its size to reduce internal tensions in the pellets.

According to another aspect, the expanding agents may comprise AIN, SiC, Mn02, Na ₂ Co ₃ , alone or in combinations thereof.

According to another aspect, an expansion oven to make rounded pellets from the granulate of the invention is provided. The oven of the invention comprises means for feeding the granulates into the expansion oven, a heat source arranged to heat up the granulates to a temperature above the reaction temperature of the expanding agent and the softening point of the granulates, and means for creating an independent movement for each and all of the granulates through the oven so that the granulates do not stick to each other when they exceed the softening point and while the granulates inside the oven expand and until the resulting foamed glass pellets have reached their desired shape, and means to be able to direct the foamed glass pellets out of the oven when they has reached their desired shape. According to another aspect, the means to create the independent movement of the granulates inside the expansion oven comprises plates subject to a vertical linear vibration or a 3D rotation principle.

According to another aspect, the means to create the independent movement of the granulates inside the expansion oven comprises an electromagnetic or pneumatic vibration principle. According to another aspect, the means to create the independent movement of the granulates inside the expansion oven comprises turbulent air.

According to another aspect, to create the directional movement of the granulates, a vibrating plate with an angle from 0.1-45 degrees can be used.

According to another aspect, various embodiments of an expansion oven to make the rounded foamed glass pellets may comprise: 1) Revolving tubular furnace with radiate heat from electricity or gas (fig. 6)

2) Rotating and vibrating disk through an expansion oven with radiate heat from electricity or gas (fig. 7)

3) Moving and vibrating belt through an expansion oven with radiate heat from electricity or gas (fig. 8)

4) Tubular furnace with gas flame creating a circular heated air-flow (fig. 9)

5) Revolving perforated tu be inside a convection furnace (fig. 10)

6) Vertically spinning conical tube furnace heated from electricity, induction or gas (fig. 11)

7) Vibrating furnace or furnace with vibrating angled plates with radiate heat from electricity or gas (fig. 12-17)

According to another aspect, the loose granulates can be feed into the expansion oven through a pipe with an inside screw, a transport band, pneumatic transport, vibrating pipes, vibrating plates, high pressure air or gravity force.

According to another aspect, as a powder with high Si0 ₂ content, the following types of material can be used either alone or in combinations thereof;

1) Recycled container glass (hollow glass)

2) Fines from processing of recycled glass

3) Recycled flint or bottle glass

4) Recycled flat glass or float glass

5) Artificial igneous rock as produced according to PCT/EP2017/077766 "Manufacturing of an artificial igneous rock material by a sintering process".

6) A sintered material made from 70-90% Si0 ₂ , 5-20% CaO and 5-20% Na ₂ Co ₃ sintered at a temperature between 1000-1500°C.

According to another aspect, the temperature range for the powder mixture to be sintered into a solid material is in the range of 600-900°C, maximum temperature is given by the reaction temperature of the expanding agent and the softening point of the silicate based raw material. The hold time at maximum temperature is given by the volume off the glass powder but should be at least until all glass powder has entered into a sintered state.

According to another aspect, process time in the sintering oven is between 10 to 240 min.

According to another aspect, the size of the foamed glass pellets is given by the size of the granulate feed into the oven and the amount and choice of expanding agent. According to another aspect, the granulates are shaped in a crusher or a mill and sometimes also in a tumbler to reach its desired size and shape.

According to another aspect, the granulates after sintering has a moisture content of less than 0.1%.

According to another aspect, the amount of expanding agent in the powder mixture before sintering is in the range of 0.5 to 15 weight %.

According to another aspect, the size of the granulates feed into the expansion oven can range from 0,001 mm to 25 mm. Typical granulate size categories lie, for example, within the following diameter ranges: 0.005-0.070mm, 0.1-0.25mm, 0.25 to 0.5mm, 0.5 to 1.0 mm, 1.0 to 2.0mm, 2.0 to 4.0 mm and 4.0 to 10.0 mm and 8.0- 14.0mm According to another aspect, the time the granulates remain in the expansion oven in order to form a foamed pellet is determined by the size of the granulate and the temperature in the expansion oven.

According to another aspect, the process time in the expansion oven is between 0,1 seconds to 14 minutes.

According to another aspect, the particle density of the foamed pellet ranging from lOOg/l to 1500g/l, is determined by the choice of silica-based material, the choice and amount of expanding agent, the temperature and time in the expansion oven, and the size of the foamed pellet (due to change in ratio between surface area and volume of the pellet with different pellet sizes, because of different density on the surface and in the core of the foamed pellet).

According to another aspect, the powder used as a release agent for the granulates can comprise 0.5-3% of AI2S1O5 (kaolin), AI2O3, CaCo ₃ . or any other material that has a melting point above the maximum temperature in the expansion oven and do not react with the granulates to form a sticky surface.

Brief descriptions of the drawings:

The invention will now be described with reference to the drawing, wherein:

Fig. 1 shows a powder mixture of glass powder and expansion agent inside a mold and before sintering in an oven.

Fig. 2 shows the sintered block before crushing into desired size of granulates. Fig. 3 shows crushed granulates coated with a kaolin powder before entering into the expansion oven.

Fig 4 shows foamed glass pellets on top of a rotating disk as shown in fig 7, and after being inside the expansion oven at a temperature of 1000°C for 2 min. Fig. 5 shows the foamed glass pellets after cooling at ambient temperature.

Fig 6. Shows a revolving tu bular furnace used as an expansion oven.

Fig. 7 shows a rotating plate used to transport the granulates into the expansion oven and the foamed glass pellets out of the expansion oven.

Fir. 8 shows a moving belt used to transport the granulates into and the foamed glass pellets out of the expansion oven.

Fig. 9 show a gas fire used to heat the granulates and move the foamed glass pellets out of the downward angled expansion oven (tube) using turbulent air.

Fig. 10 shows a rotating perforated tube heated by heated air used to heat the granulates and move the foamed glass pellets out of the downward angled expansion oven (tube) using turbulent air. Fig. 11 shows a vertically conical tube, spinning inside an expansion oven, used to heat the granulates that are fed into from top into the center of the tube, and to move the foamed glass pellets over the top and out of the expansion oven, and on to a moving belt.

Fig. 12 shows the main layout of a vibrating expansion oven

Fig. 13 shows the transformation of granulates into spheres in a vibrating expansion oven Fig. 14 shows the principle of vibrating the oven or the plates inside the oven

Fig. 15 shows the horizontal and downward movement of granulates on angled vibrating plates through the oven

Fig. 16 shows the independent movement of each granulate in the oven on a vibrating plate

Fig. 17 shows the direction of the granulates through the oven Fig. 18 shows sintered granulates in the range from l-6mm before loaded in the expansion oven for foaming and transformation into a sphere.

Fig. 19 shows the granulates in fig 18, after foaming and after entering its spherical shape.

Fig. 20 shows a spherical foamed pellet with a glossy and sealed surface, made from recycled glass. Fig. 21 shows a spherical pellet with a glossy and sealed surface and a cellular structure on the inside made from recycled glass.

Detailed description: According to one aspect, a silica-based powder, for instance recycled glass powder or artificial igneous rock powder, is mixed with expansion agents and then sintered at a temperature from 600- 900°C to form a solid block (fig 2) or any other shapes suitable for further crushing and milling into granulates (1).

According to another aspect, the sintered material is then crushed or milled and sieved into granulates (1) with a desired particle size distribution (fig 18).

According to another aspect, the crushed granulates (1) can be powder coated with 0.5-3% release agent (fig. 3).

According to another aspect, the granulates (1) is then fed into an expansion oven (2) (by the use of a pipe with an internal screw (23), gravity (27) or by a vibrating pipe (15). According to another aspect, the coated granulates (1) is then heated inside an expansion oven (2) at temperature from 780-1280°C, dependent upon the reaction temperature of the expansion agent and the softening point of the powder mixture

According to another aspect, the granulates (1) are arranged to move independently (20) at all times in the expansion oven (2). According to another aspect, the granulates (1) are arranged to move independently in one direction (21) from the feeder (15) to the exit (22).

According to another aspect, the method provides that the granulates (1) stay inside the expansion oven (2) until the granulates (1) have reached its softening point and until the temperature inside the granulates (1) is higher than the reaction temperature of the expanding agents. According to another aspect, the expansion oven (2) can be designed using a vibrating feeder (15) to feed the granulates (1) into the expansion oven (2) and onto a vibrating plate (16) with a certain angle(19) and by using a vibrating engine (18) create an independent movement (20) for each granulate (1) in a one direction (21) through the oven (2) at a temperature and at a time necessary for the granulates (1) to reach its softening point and for the expanding agent to react and to create gas inside the molten granulates (1). The transformed granulate (3) will then be directed (21) out of the oven (2) through the opening (22) as a result of the vibrating angled plates (16) and to be sieved (24) before cooled down (25) ready for handling (26).

According to another aspect, the speed of the granulates (1) in the oven (2) is given by the size of the granulates (1), the density of the granulates (1), the length of the oven (2), the size of the vibrating plate (16), the angle (19) of the vibrating plates, the direction, frequency and stroke of the vibration (29) produced by the vibrating engine (18), the material in the plates (16) and the distance (14) from the vibrating engine (18) to the vibrating plate (16).

According to another aspect, the expansion oven (2) can comprise an oven with radiate heat from electricity or gas (17), involving a revolving tube (4) or a rotating disk with or without vibration (5), or a moving belt (6), or inside a tube (7) with turbulent air (8) from burning of gas (9), or inside a perforate tube (10), inside a convection oven (11) with turbulent hot air (12), or inside a spinning conical bowl (13), or inside a furnace with downward angled vibrating plates (16) inside an oven with radiate heat (14) to create a foamed pellet (3) ready for cooling.

Example:

97% crushed recycled glass with a fraction size of 0-100 micron is mixed with 2% SiC and 1% Mn0 ₂ .

2 I of the mixture is then filled in a mold and placed in a sintering oven at 700°C for 3 hours, (fig. 1)

The sintered block (fig. 2) is then crushed into granulates in the range from 1-4 mm and coated with 2% kaolin powder (fig. 3). The granulates is then placed on a rotating plate and moved into an expansion oven at 1000°C for 2 min.

The foamed glass pellets are then removed from the oven (fig. 4) and cooled down to ambient temperature.

The foamed glass pellets (fig. 5) is measured to be in the range of 4-10mm.

Other aspects of the invention:

Instead of sintering the powder mixture consisting of glass and expansion agent, it can be compressed directly under high pressure and if needed some heat, to form granulates with a particle range from 3mm to 15 mm, or compressed into a block, then cut into granulates. The granulates is then placed on a moving belt/plate or in a mold, before loaded into the expansion oven for the reaction to take place. A release agent such as kaolin can be used.

Instead of using vibrating plates inside an oven (2) for independent (20) and directional (21) movement of granulates (1), the whole oven (2) can be put under vibration with angled plates on the inside to create the same independent movement of granulates.

For granulates (1) below 0.15 mm, high pressure air can be used to feed the granulates into the expansion oven (2).

For granulates (1) below 0.15 mm turbulent hot air can be used to create to create an independent movement (20) of the granulates.

For granulates (1) below 0.15 mm an air pillow or gravity can be used inside the expansion oven in combination with turbulent air to create an independent movement of the granulates in one direction (21).

To reduce the tensions in the pellets (3) by controlling the cooling rate, a vibrating cooling pipe can be used for transport through and out of the cooling zone after a desired time.