GLASS BRIQUETTE AND FORMING SYSTEM

Abstract

A method of producing a glass briquette in which reclaimed glass fines are mixed with a binder material to create a mixture. The mixture is subsequently compressed in a chamber to form a briquette having the shape of the interior of the chamber. The reclaimed glass includes glass fines of a size of smaller than 10 mm. The method is performed without melting the glass fines such that the resulting briquette contains the discrete glass fines held in the binder and may be used as a furnace ingredient for later glass product production. The glass briquette may contain other batch ingredients required in the production of glass.

Claims

1. A method of producing glass briquettes, comprising the steps: a) providing reclaimed glass as glass fines of a size of smaller than 10 mm b) spraying a binder material comprising a lignosulphate and/or sodium silicate onto the glass fines and mixing the binder material and reclaimed glass to create a mixture having 2-5% by weight of the binder material; and subsequently c) compressing said mixture in a chamber to form briquettes having the shape of the interior of the chamber and capable of withstanding a drop test from a height of 1 m; wherein steps b) and c) are performed at a temperature below the melting point of the glass fines, such that the glass fines remain present as discrete, solid particulate material contained with the binder of the mixture in the formed briquettes.

2. A method according to claim 1, wherein the chamber of step b) is formed from a pair of opposing cavities.

3. A method according to claim 2, wherein step b) is performed using a press comprising a pair of counter-rotating rollers, and wherein one of said pair of opposing cavities is provided as a pocket on the outer circumference of each roller.

4. A method according to claim 3, wherein each roller comprises a plurality of pockets.

5. A method according to claim 1, wherein the mixing of step b) comprises mixing in a ploughshare mixer.

6. A method according to claim 1, wherein step a) further comprises crushing the reclaimed glass to provide the glass fines of a size of smaller than 10 mm prior to step b).

7. A method according to claim 1, further comprising the step: d) separating any loose material from the briquettes formed in step c).

8. A method according to claim 1, wherein all steps are performed at a temperature below 500° C.

9. A method according to claim 1, further comprising the step: e) transferring the briquettes formed in step c) to an oven for drying.

10. A glass briquette, comprising: a compressed mixture of reclaimed glass fines of a size of smaller than 10 mm and having 2-5% by weight of a binder material comprising a lignosulphate and/or sodium silicate, wherein the reclaimed glass comprises glass fines are present as discrete, solid particulate material contained with the binder of the compressed mixture and the glass briquette is capable of withstanding a drop test from a height of 1 m.

11. A glass briquette according to claim 10, wherein the mixture comprises 4% by weight of a binder material.

12. A glass briquette according to claim 10, wherein the reclaimed glass comprises glass fines of a size of smaller than 2 mm or 1 mm.

13. A glass briquette according to claim 10, further comprising silicone dioxide, sodium carbonate, calcium oxide, or a source thereof within the compressed mixture.

14. A glass briquette according to claim 13, wherein the glass briquette comprises from 15-60% by weight of reclaimed glass.

15. A glass briquette according to of claim 13, further comprising one or more additional additives.

16. A glass briquette according to claim 15, wherein the one or more additional additives are selected from aluminium oxide, antimony oxide, arsenic trioxide, barium, barium oxide, boron oxide, cerium (IV) oxide, cobalt oxide, copper oxide, ferric oxide, iron, lanthanum oxide, lead oxide, magnesia, magnesium oxide, nickel oxide, selenium oxide, selenites, selenates, silver oxide, sodium chloride, sodium nitrate, sodium sulfate, sulfur trioxide and tellurium oxide.

17. A glass briquette according to claim 15, wherein the glass briquette comprises less than 10% by weight of additional actives.

18. A method of producing glass briquettes, comprising the steps: a) mixing reclaimed glass comprising glass fines of a size of smaller than 10 mm with silicon dioxide, sodium carbonate and calcium oxide; b) spraying a binder material comprising a lignosulphate and/or sodium silicate onto the product of a) and mixing the product of a) with the binder material to create a mixture having 2-5% by weight of the binder material; and subsequently c) compressing said mixture in a chamber to form briquettes having the shape of the interior of the chamber and being capable of withstanding a drop test from a height of 1 m; and wherein the steps are performed at a temperature below 500° C., such that the glass fines remain present as discrete, solid particulate material contained within the binder of the mixture in the formed briquettes.

19. A method according to claim 18, wherein steps a), b) and c) are performed at ambient temperature, and method further comprises: transferring the briquettes formed in step c) to an oven for drying.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Practicable embodiments of the invention are described in further detail below by way of example only with reference to the accompanying drawings, of which:

[0050] FIG. 1 shows a schematic view of an example briquette forming plant according to the present invention.

[0051] FIG. 2 illustrates the form of a briquette formed with the system of FIG. 1; and

[0052] FIG. 3A shows standard projection of the views of the briquette illustrated in FIG. 2.

[0053] FIG. 3B shows standard projection of the views of the briquette illustrated in FIG. 2.

[0054] FIG. 3C shows standard projection of the views of the briquette illustrated in FIG. 2.

DETAILED DESCRIPTION

[0055] The briquette forming plant of FIG. 1 comprises a hopper 1, for receiving raw material, which feeds out onto a weighing/dosing conveyor 2. The raw material comprises crushed glass with a small grain/particle size of less than 10 mm, which would typically be considered glass fines not suitable for processing, silicone dioxide, sodium oxide and calcium oxide or a source thereof. In one particular example the raw material comprises MRF glass that has been crushed to a grain/particle size of less than 2 mm and screened to remove larger pieces of harder or more resilient contaminants that survived the crushing operation.

[0056] A weighing/dosing conveyor 2 transfers the material from the hopper 1 into a ploughshare mixer 3, where it is mixed with a binder material such as sodium silicate or a lignosulfonate (sulfonated lignin) which is sprayed into the mixer 3 from a spraying system 4.

[0057] Once mixed, the raw material and binder material passes into a briquetting press 5 where pressure is applied to form briquettes from the mixture. A further, intermediate, conveyor 6 then transfers the briquettes to a screen 7, across which the briquettes pass before they reach a final conveyor 8 which transfers the briquettes to an oven for drying or simply to a storage or transport container.

[0058] A power drive and control cabinet 9, for driving and controlling the process, is also illustrated.

[0059] The briquetting press 5 takes comprises a gravity feeder 10 and a pair of counter-rotating tyres/rollers 11,12, each of which is provided with a plurality of cavities or pockets around their circumference. In one example, each tyre 11,12 has a diameter of 800 mm and a width of 180 mm, and is provided with five rows of eighty-four pockets. The pockets on the tyres 11,12 align with each other as the tyres 11,12 rotate to produce four hundred and twenty individual chambers for forming individual briquettes for every complete rotation of the tyres 11,12. An off-load gap 13 is provided between the tyres 10,11.

[0060] The mixture from the ploughshare mixer 3 passes into the gravity feeder 10 of the press 5 and is drawn between the tyres 11,12 and compressed into the chambers to form a number of briquettes. As the pockets of the tyres move apart again the briquettes are deposited onto the intermediate conveyor 6, together with any mixture or loose glass fines that passed through the press 5 without being compressed.

[0061] The intermediate conveyor 6 provides time for the briquettes to cure and stabilise once formed. The screen 7 then separates out any loose mixture and glass fines from the briquettes so that only whole briquettes are transferred to the final conveyor 8 while the uncompressed mixture and loose glass fines pass through the screen 7 and are collected below 14.

[0062] Various aspects of the illustrated briquette forming plant can be adjusted if required using the control cabinet 9. For example, the speed of rotation of the tyres 11,12 in the press 5 may be altered, as can the applied pressure and off-load gap 13. The volume of binder applied by the sprayer 4 could also be modified, and the speed of the various conveyors 2,6,8 could be adjusted either to adjust the overall production rate or simply to increase or decrease the curing time on the intermediate conveyor 6.

[0063] FIG. 2 shows the form of an example briquette 20 formed according to the present invention. The briquette 20 has curved upper and lower surfaces 22,24 which correspond to the shape of the opposing pockets provided on the tyres 11,12. The upper and lower surfaces 22,24 are separated by an edge section 26 which is formed as a result of the off-load gap 13 between the tyres 11,12.

[0064] The curved upper and lower surfaces 22,24 and the edge section 26 are more clearly shown in the side view of FIG. 3A. The plan view of FIG. 3B shows that the length 28 and width 30 of the example briquette 20 are 36 mm and 27.8 mm respectively. The depth 32, as shown in the end view of FIG. 3C is 15.5 mm. This represents a briquette volume of 8 cm.sup.3.

[0065] The briquetting process of the invention was tested using a raw product of crushed glass mixed with various amounts of sodium silicate binder. The crushed glass used in the tests had a grain size of <2 mm, a bulk density of 1.38 g cm.sup.−3 and a moisture content of 0.47%.

[0066] All tests were conducted with 100% raw product in the mixture, ie with zero recycled fines, at ambient temperature throughout the forming process.

[0067] The press comprised a gravity feeder and a pair of counter-rotating tyres/rollers, and was similar to the press 5 described with reference to FIG. 1. However, in the experiments the tyres were 600 mm in diameter and 145 mm wide. Two hundred and sixty-eight pockets were provided per tyre, each measuring 36×26×14.5 mm giving a pocket volume of 7 cm.sup.3. The off-load gap, ie the adjustment gap between the tyres in the press to prevent damage to the tyres, was consistently set at 1 mm.

[0068] The adjustment pressure for the press was uniformly 10 kilonewtons per linear centimetre (kN lcm.sup.−1) lower than the listed operating pressure. Although some pressure adjustment is achievable by varying the off-load gap, separate pressure adjustment means were provided.

[0069] In tests 1 to 10 a flap of the gravity feeder was opened 20%. In test 11 the flap of the gravity feeder was opened 35% to provide a difference in throughput/flowrate. Test 12 was a production test of 300 kg of briquettes, and the gravity feeder was opened 35%.

TABLE-US-00001 PRODUCT PRESS CHARACTERISTICS Bulk Moisture Operating Rolls BRIQUETTE PROPERTIES TEST Density Content Pressure Speed Power Weight Volume Density Thickness # (g cm.sup.−3) (% H.sub.2O) (kN lcm.sup.−1) (rpm) (A) (g) (mm.sup.3) (g cm.sup.−3) (mm) 1 0.98 4 60 5 53 25 11.2 2.23 6 2 0.97 3.3 60 5 50 26.7 12.2 2.19 6.5 3 0.98 2.2 60 5 51 26.9 11.9 2.26 7 4 0.99 1.16 60 5 53 26.6 11.7 2.27 7.2 5 0.98 4.2 80 5 65 25.6 11.6 2.21 6 6 0.98 2.5 60 5 50 26.8 12 2.23 6.8 7 0.98 2.4 40 5 46 26.6 12.1 2.2 7 8 0.98 3.3 40 5 45 27 12.5 2.16 6.7 9 0.98 4 60 5 54 27.7 12.6 2.2 6.5 10 0.98 4.37 60 5 50 28.5 12.9 2.21 6.5 11 0.98 4.21 60 10 46 27.7 12.7 2.19 6.5 12 0.98 4.09 60 5 51 27.5 12.5 2.2 6.5

[0070] A drop test was performed, from around 1 m, on briquettes from each of tests 1 to 11. The briquettes were then dried in a variety of different ways, and crush tests were performed on briquettes from tests 6 to 9. The results of the tests are summarised below.

[0071] Test 1—50 kg of Raw Product+8% (by Weight) of Sodium Silicate

[0072] Test 2—50 kg of Raw Product+6% of Sodium Silicate

[0073] Test 3—50 kg of Raw Product+4% of Sodium Silicate

[0074] In each of the first three tests the briquettes obtained were well shaped, particularly in the middle rows, but rather fragile at the drop test. Ten briquettes were dried in an oven at 100° C. for one hour, resulting in very hard briquettes.

[0075] Test 4—50 kg of Raw Product+2% of Sodium Silicate

[0076] Compared to tests 1 to 3 the briquettes produced were more fragile, at the press outlet, with a dry appearance. Ten briquettes were again dried in an oven at 100° C. for one hour, but the briquettes remained less hard and crumbled more readily than in the previous tests.

[0077] Test 5—50 kg of Raw Product+8% of Sodium Silicate

[0078] The results were generally in line with test 1, producing well shaped and good quality briquettes. Despite the higher operating pressure of the press, the briquettes weren't noticeably harder than the briquettes from test 1. Drying ten briquettes in an oven at 100° C. for one hour again produced very hard briquettes.

[0079] Test 6—50 kg of Raw Product+4% of Sodium Silicate

[0080] As expected, well shaped and good quality briquettes were produced as in test 3, which was performed using the same variable values. In test 6, the briquettes were placed in an oven at 100° C. and crush tests were then performed, typically on two briquettes, at the furnace outlet after different time periods. The results were as follows: [0081] 10 min—56 kg, 63 kg [0082] 20 min—100 kg, 98 kg [0083] 30 min—92 kg, 95 kg [0084] 40 min—95 kg, 98 kg [0085] 50 min (1 briquette)—102 kg

TEST 7-50 kg of Raw Product+4% of Sodium Silicate

[0086] Test 7 was performed using the same product and binder amounts as test 6, but with the press at a lower operating pressure. This produced briquettes that were well shaped, but more fragile at the press outlet. As in test 6, the briquettes were then placed in an oven at 100° C. and crush tests were performed on pairs of briquettes at the furnace outlet after different time periods, with the following results: [0087] 10 min—No result [0088] 20 min—No result [0089] 30 min—102 kg, 100 kg [0090] 40 min—94 kg, 97 kg [0091] 50 min—106 kg, 102 kg

TEST 8-50 kg of Raw Product+6% of Sodium Silicate

[0092] This test was performed at the same operating pressure as test 7, but with the amount of binder material increased. The briquettes obtained were again well shaped, but crumbled more easily. The crush test results after periods in 100° C. oven were: [0093] 10 min—58 kg, 56 kg [0094] 20 min—70 kg, 73 kg [0095] 30 min—87 kg, 78 kg [0096] 40 min—53 kg, 55 kg

[0097] Test 9-50 kg of Raw Product+8% of Sodium Silicate

[0098] Test 9 replicated the conditions and variable values used in test 1, and once again good quality briquettes were obtained. Crush tests were performed on cold briquettes both after heating as before and on unheated briquettes as follows: [0099] After 10 min at 100° C. in the oven—66 kg, 65 kg, 68 kg [0100] After 20 min at 100° C. in the oven—101 kg, 94 kg, 120 kg [0101] After 15 hours at ambient temperature (10° C.)-20 kg, 21 kg, 23 kg, 21 kg

[0102] Test 10—50 kg of Raw Product+8% of Sodium Silicate

[0103] The test conditions again matched those of test 1. 20 kg of briquettes were put in the oven at 100° C. for 20 minutes and then crush tests were performed on both warm and cold briquettes for comparison: [0104] Warm briquettes—62 kg, 64 kg, 63 kg, 71 kg [0105] Cold briquettes—106 kg, 94 kg, 100 kg, 96 kg

[0106] Test 11-50 kg of Raw Product+8% of Sodium Silicate

[0107] The test conditions for test 11 matched those for test 1, with the exception that the rotational speed of the press was doubled to 10 rpm. Well shaped and good quality briquettes were still obtained, although a relatively larger percentage (around 10% of the total material) passed through the press as fines without being formed into briquettes.

[0108] The experimental results, particularly from tests 3 and 6, show that the proposed method is quite capable of producing briquettes from glass fines with a particle/grain size of under 2 mm. Indeed, briquettes could similarly be formed from smaller grain sizes of 1 mm or below. Once formed into briquettes, the glass can be handled, stored, transported and used far more easily.

[0109] It is envisaged that the resulting briquettes would generally be processed into products such as glass fibre or glass blocks where a lower purity is required. However, with appropriate sorting and decontamination it would be possible to use the same process to produce higher quality products such as bottles and other containers.

[0110] Although developed primarily to address problems associated with contaminated MRF glass, there is no reason why the method of the present invention could not be used with glass fines from other sources that would otherwise be deemed too difficult to process in a recycling operation, or simply to improve the appearance and/or simplify the handling of the glass cullet. There may be no need to crush the glass as an initial step, for example where the source material consists of clean glass fines that has been separated from larger pieces. Indeed, it would be quite possible for any glass fines 14 collected at the screening stage 7 in FIG. 1 to be fed back into the hopper 1 to minimise waste.

[0111] Various types of glass that would otherwise be discarded or lost to the cycle of glass production can therefore be reclaimed due to the present invention.

[0112] The glass briquettes of the type described above may combine reclaimed glass, or cullet, with the batch ingredients required for making glass. A binder is used to hold the components together in a briquette form. The glass briquette of the invention thus contains all of the components required in the production of glass, and can be used in the glass furnace without the need to include additional ingredients. This removes the need for batch processing of the raw ingredients on site, reducing processing time and the opportunity for errors to be introduced. This results in a more efficient manufacturing process, and a more consistent product. The relative proportions of the different components within the briquette may be adjusted according to the needs of the end user, and the desired properties and function of the glass.

[0113] The process of glass manufacture is well established. Typically, the raw materials (silicone dioxide (silica, SiO2), sodium carbonate (Na2CO3), calcium oxide (lime, CaO) or a source thereof, cullet, and any additives) are combined in the furnace at temperatures of up to 1,600° C., where they are melted, fined (to remove gas bubbles) and homogenised, before being cooled to a working temperature to allow the molten glass to be shaped.

[0114] Within the furnace the molten glass undergoes a redox reaction, the extent of the reaction (and oxidation state of the glass melt) depending on the conditions within the furnace, the recipe used and the composition of the cullet. The oxidation state of the glass melt affects a wide range of factors, including the efficiency of the process, product quality, foaming, heat transfer, forming (moulding) properties and optical properties (eg glass colour). It is believed that the oxygen activity of the glass melt determines the valency state of any multivalent ions in the glass melt, eg iron. Thus, there is a strong relationship between the oxidation state of the glass melt and the ratio of Fe2+ and Fe3+ to Fe in the final glass. As an example of the effect of oxidation state, a more oxidised glass melt will produce a lighter coloured, greener glass, and a more reduced melt will result in darker, amber coloured glass.

[0115] It is also believed that there is a correlation between the temperature of the melt at the bottom of the melting tank, and the redox state of the glass melt. A more reduced melt typically results in higher temperatures at the bottom of the melting tank, which results in better heat transfer, and thus lower energy usage.

[0116] Controlling the redox reaction can therefore help ensure that the glass produced is of the desired quality, and has the required properties. The use of pre-prepared glass briquettes containing all of the ingredients required in the glass production process, and which may be produced according to a specific recipe for an end user, has clear advantages. It may enable combined control of both the cullet composition and batch recipe and their relative ratios, thus ensuring consistency of output throughout production, and enabling better control of the oxidation state of the glass melt within the furnace.