METHOD FOR THE PRODUCTION OF COLORED GLASS AND COLORED GLASS

Description

[0001] The invention relates to a process for producing green and brown container glass.

[0002] Glass is produced by producing a glass melt from quartz sand. Quartz sand consists almost exclusively of silicon dioxide. Other elements may be present in trace amounts. Various components can be added to the starting material to optimize its performance and production conditions. The mixture of the starting materials (batch) is melted in a furnace and subsequently subjected to refining. The refined melt is then cooled to a desired forming temperature.

[0003] In the production of colored glass, for example brown and green container glass, the color is formed by impurities present in the starting mixture, some of which are deliberately accepted.

[0004] It is also known to add waste glass to the glass melt as glass recycling.

[0005] It is also known that in foundries, molten metal is poured into quartz sand molds to produce castings. The sand is first solidified with various types of binding agents, primarily bentonite and organic resins, for mold construction. After the mold has been used, the sand is usually processed and reused. Despite the processing, it is still contaminated with residues of the binding agents. Some of the used sand is removed from the system and replaced with new sand to maintain the quality of the sand mixture. Most of the removed used sand is disposed of in landfills.

[0006] EP 3 093 082 B1 discloses a process for the processing and reuse of used foundry sand, wherein the used sand is subjected to mechanical disintegration by comminution and subsequent classification. For this purpose, the used foundry sand undergoes a multi-stage disintegration grinding process, during which it is deagglomerated using a hammer mill and partially mechanically separated from the binder, and largely freed from its binder shells using a disk mill. Remaining binder shells are removed using a pin mill.

[0007] The foundry sand thus processed is then subjected to classification, with so-called coarse material being used as regenerated or recycled material and so-called fine material being disposed of.

[0008] DE 196 19 987 A1 discloses a physical and chemical crushed glass obtained from the base material glass and admixed physical crushed glass, whereby foundry molding sand residues can be used.

[0009] Finally, DE 199 00 946 C1 discloses a process for the material recycling of used sand. The used sand is mechanically and / or pneumatically processed and cleaned of foreign and impurities. Iron particles contained in the used sand are magnetically separated.

[0010] US 2003 / 083187 A1 discloses a process for producing vitrified slag from various waste materials and its use as blasting material. Used sand from foundries can be used as a possible waste component.

[0011] The invention is based on the object of creating a process for the production of green or brown container glass that can be carried out in a resource-saving manner.

[0012] According to the invention, this object is achieved by a method having the features recited in claim 1. This is achieved by producing green or brown container glass from a glass melt by adding between 20 and 50 percent by mass of purified or reprocessed foundry sand to the total mineral content. A chemical analysis of the purified and reprocessed foundry sand is performed, and the batch formulation of the glass melt is adjusted based on this analysis. This reduces the use of new quartz sand, while also reducing the landfilling of foundry sand. Both of these processes contribute to the conservation of natural resources.

[0013] In an embodiment of the invention, it is provided that the processed used sand thus provided is examined and evaluated with regard to its chemical and physical properties, and that the usual batch recipe for producing the glass melt is adjusted accordingly to account for any remaining impurities. This advantageously makes it possible to react flexibly and easily to different chemical and physical compositions of the processed used sand quantities. As a result, a colored glass can then be obtained that possesses the properties necessary for the desired application. Lower quality requirements are particularly necessary for the production of brown and green container glass, so that processed used foundry sand can be used particularly preferably in this case.

[0014] According to the invention, in the production of green and brown container glass, the proportion of used sand is between 20 and 50% by mass, in particular between 30 and 40% by mass, of the total mineral mixture.

[0015] In a preferred embodiment of the invention, the used foundry sand is processed according to the requirements of the glass industry for the production of colored glass. For this purpose, it is preferably provided that the used foundry sand is first freed of coarser magnetic components. The used sand, freed of the coarser magnetic components, is then mechanically crushed to remove any lumps and coarse grains with a smaller grain size. Remaining coarse fractions, for example, larger than 0.5 mm, can be separated, in particular sieved, and returned to the used foundry sand after further crushing.

[0016] The used foundry sand is then preferably subjected to an attrition process, i.e., intensive abrasion using mechanical mixing devices. This advantageously separates the shells of used sand grains, which consist primarily of bentonite, resins, carbon, and other impurities present in the used sand.

[0017] Subsequently, in a further preferred embodiment, the now existing foundry sand mixture is freed of any fine particles, for example, smaller than 0.1 mm. This separation can be achieved, for example, by screening or blowing. These separated fine particles contain the majority of the grain shells previously separated in the attrition process.

[0018] In a further preferred embodiment, a subsequent magnetic fine cleaning step is provided, in which any remaining magnetic substances are separated, possibly in several cycles. This can be achieved using suitable magnetic separation devices, for example, magnetic separators with magnetic rods through which the used sand passes. The separated metallic material streams can be subjected to metallurgical recycling.

[0019] In a further preferred embodiment, it is provided that the processed foundry waste sands obtained from several different batches are mixed so that larger quantities with homogeneous chemical and physical properties are available.

[0020] Overall, the process according to the invention offers the advantage of conserving the naturally occurring mineral resource sand. Used foundry sand can be kept in the material cycle while simultaneously minimizing sand consumption (quartz sand) for glass production. Furthermore, disposal and landfill costs for used foundry sand can be significantly reduced.

[0021] The glass industry can reduce its raw material costs by using used foundry sand, as the use of new quartz sand and glass cullet can be optimized and, if necessary, reduced.

[0022] The invention is explained below in an exemplary embodiment with reference to the accompanying drawing, which shows a block diagram for the material cycle.

[0023] In a first step 10, uncleaned foundry sand is provided. Depending on the foundry application, this sand has a different chemical composition. It contains proportions of aluminum oxide (Al2O3), iron oxide (Fe2O3), and carbon (C). The addition of binding agents and reducing agents during use in the foundry causes grain shells to form around the individual grain components of the foundry sand, which contain, in particular, bentonite, resin, carbon, and other materials.

[0024] Foundry sand also has a different grain size distribution and so-called nodules, which make the use of foundry sand in its raw state unsuitable for the production of colored glass.

[0025] In a further step 12, magnetic components are separated from a stream of used foundry sand. For this purpose, the used foundry sand is passed through a magnetic separator to separate out the larger, self-contained magnetic components present in the used foundry sand. If necessary, the passage of the used foundry sand through the magnetic separator can be repeated to increase the cleaning effect. In the next step 14, the used foundry sand, which has been cleaned of the coarse magnetic components, is crushed. For this purpose, the used foundry sand is passed over a crusher, for example, a roller, so that nodules and larger grains (≥ 5 mm) are broken up and subsequently present in a smaller grain size.

[0026] In a next step 16, the used foundry sand is sieved to separate a coarse fraction with a grain size of >0.5 mm. This coarse fraction can be further crushed in a step 18 to a grain size of ≤0.5 mm and returned to the used sand stream. In a next step 20, attrition is then performed. This means that the grain shells of the used foundry sand are mechanically separated from the grain by friction, for example, mixing with a paddle mixer. This breaks up grain shells made of, for example, bentonite, resin, carbon, and other materials.

[0027] In the next step 22, fine particles <0.1 mm are separated from the foundry sand stream. This can be achieved, for example, by air fluidization with a connected dedusting system.

[0028] In a further step 24, the remaining foundry sand stream undergoes a fine magnetic cleaning process. Using one or more magnetic separation devices, and possibly in multiple cycles, any remaining magnetic residues are removed. The attrition process, in particular, may release magnetic components that could not be removed during the initial coarse magnetic cleaning process.

[0029] The separated metallic substances can be subjected to metallurgical recycling in a step 26.

[0030] In the next step 28, the cleaned and separated from magnetic residues from the foundry sand stream is fed to a mixing station. Here, the processed and cleaned foundry sands from several batches can be mixed together, as indicated in the figure by steps 24' and 24". Since each type of foundry sand has specific chemical and physical properties, a uniform chemical and physical composition of the foundry sand available for glass production can be achieved by mixing cleaned foundry sands from different batches.

[0031] The foundry waste sand thus provided can, after storage and transport, be used in a step 30 in the glass industry in a glass melt for the production of coloured glass, in particular coloured container glass, in particular green or brown container glass.

[0032] Before being used in the glass melt, the provided foundry sand undergoes a chemical analysis to determine its constituents, particularly any remaining impurities. This is indicated here by step 32.

[0033] Based on the results obtained in step 32, the batch recipe of the glass melt is adjusted in step 34. Based on the chemical and physical composition of the foundry scrap sand, the percentage of the foundry scrap sand in the total glass melt is also determined.

[0034] The glass melt produced in step 30 is then refined in a conventional manner in a step 36, cooled in a step 38 and subjected to shaping in a step 40.

[0035] The process diagram shows that through appropriate processing of used foundry sand, a raw material can be provided for the glass industry for the production of colored glass, especially colored container glass.

[0036] In step 34, for example, the targeted addition of oxidizing or reducing agents can be determined depending on the composition of the used foundry sand. This allows the altered reduction and oxidation conditions in the glass melt resulting from the use of the purified used foundry sand to be addressed and compensated for.

[0037] The following are concrete examples of implementation that illustrate the composition of the used sand in selected process steps: Table 1: Characteristics of two exemplary used sands before cleaning (step 10) Old sand original no. Al 2 O 3 (%) Cr2O3 (%) Fe 2 O 3 (%) Carbon (%) Percentage of particles ≤ 0.1 mm (%) Percentage of particles ≥ 0.5 mm (%) A 1,38 0,029 0,46 0,57 1,5 5,8 B 0,70 0,001 0,82 1,63 2,5 12,9 Table 2: Characteristics of two exemplary used sands after cleaning (step 24) Recycled sand no. Al 2 O 3 (%) Cr2O3 (%) Fe 2 O 3 (%) Carbon (%) Percentage of particles ≤ 0.1 mm (%) Percentage of particles ≥ 0.5 mm (%) A 0,83 0,002 0,22 0,45 0,1 0,1 B 0,13 0,001 0,38 0,95 0,1 0,1 Table 3: Characteristics of the mixed sand from cleaned used sands (step 28) Used sand processed mixture Al 2 O 3 (%) Cr2O3 (%) Fe 2 O 3 (%) Carbon (%) Percentage of particles ≤ 0.1 mm (%) Percentage of particles ≥ 0.5 mm (%) A+B 0,48 0,002 0,30 0,70 0,1 0,1

Claims

1. A method for producing green or brown container gas from a glass melt, characterized in that the glass melt is obtained by adding between 20 and 50 wt.% of cleaned and processed used foundry sand to the total mineral amount used to produce the glass melt, wherein a chemical analysis of the cleaned and processed used foundry sand is carried out and the composition of the glass melt is adjusted according to this analysis.

2. The method according to Claim 1, characterized in that autonomous magnetic components are separated from the used foundry sand.

3. The method according to any one of the preceding claims, characterized in that the used foundry sand is crushed to break up lumps and larger grains.

4. The method according to any one of the preceding claims, characterized in that the used foundry sand is sieved and a coarse fraction with a grain size > 0.5 mm is separated out.

5. The method according to Claim 4, characterized in that the coarse fraction is crushed to a grain size ≤ 0.5 mm and returned to the used foundry sand.

6. The method according to any one of the preceding claims, characterized in that the used foundry sand is subjected to attrition.

7. The method according to any one of the preceding claims, characterized in that fine particles < 0.1 mm are separated from the used foundry sand.

8. The method according to any one of the preceding claims, characterized in that the used foundry sand is subjected to magnetic fine cleaning.

9. The method according to any one of the preceding claims, characterized in that the cleaned and processed used foundry sand from several batches is mixed together.