SE529070C2 - Glass melting, comprises melting, homogenizing, degassing and cooling glass in separate interconnected furnace regions - Google Patents

Abstract

Melting (A), homogenization (B), degassing (C) and cooling (D) are carried out in succession in separate interconnected regions (1A-1D) of the furnace and the total volume of these regions is less than half that of a conventional furnace. Melting glass comprises charging a furnace with crushed glass and/or glass raw materials and then (A) melting the glass using radiant heat generated by burning solid fuel, (B) homogenizing, (C) degassing and (D) cooling the molten glass to the desired temperature. Steps (A)-(D) are carried out in succession in separate interconnected regions (1A-1D) of the melting furnace and the total volume of these regions is less than half the volume of a conventional melting furnace.

Description

20 25 30 539 against the homogenization part of the oven. The homogenization takes a long time because protective gas bubbles are formed around the undigested grain particles, which must grow in size in order to be able to reach rising capacity. The time for homogenization for container glass is estimated at about 24 hours and for float glass production more than 60 hours. However, due to recirculation, glass, with different residence times, is mixed with each other so that the minimum residence time, for some of the glass, is as low as 15-20% of the mean value.

The heat requirement for melting recycled glass (cullet) is not as high as making glass from barley raw materials. This is because the chemical conversion is already done for recycled glass, which corresponds to about 23% of the total useful energy, and that the pure melt from the recycled glass is not unnecessarily mixed with melt from grain raw materials including sand grains and associated gas bubbles, which therefore does not have to be heated the higher homogenization temperature.

The conventional way to heat and melt the glass is with radiant heat from flames from natural gas or oil burners. The air to these burners is preheated in recuperators or regenerators with the exhaust heat. Due to a large leakage of air into the oven, only a part of the air preheating necessary for the preheating air is supplied. that through MyCket exhaust heat is lost or requires to be recovered through additional investments in exhaust boilers. Try to reduce energy consumption by enriching the air with oxygen or with so-called oxy-fuel burners have not led to reduced costs because the benefits (higher flame temperatures and longer residence time of the combustion products in the furnace, and thus lower exhaust temperatures) have not outweighed the costs of producing oxygen. With oxy-fuel burners, more expensive bricks of higher quality must be used.

Due to the long time and high temperature required for homogenization, today's ovens must contain very large amounts of glass and thus a number of inconveniences arise.

The time for switching between different color shades is very long because mixing of the new shade with the old one must take place in the oven's large glass volume. This can last for 60 to 160 hours, depending on which shade changes are desired. Meanwhile, production capacity and energy are lost compared to when the process is in full swing and produces recycled glass.

The furnace body is large and a large part of the added heat is dissipated as cooling losses through the furnace walls. These losses increase with the age of the furnace and can eventually be as large as 60% of the energy supplied. The reason why the furnaces are not rebuilt at more frequent intervals is the high cost of rebuilding the furnace body with regenerators and not least the production loss during the repair period.

The present invention solves the above problems.

The present invention thus relates to a method for melting glass, comprising charging and melting material in the form of crushed glass and / or glass raw material in an oven, where treatment of glass mass takes place by melting the glass, homogenizing the glass, cooling the molten glass to a desired final temperature, which is melted with radiant heat from combustion of fuel- to degas the glass and to smooth, each step of the steps to melt the glass, to homogenize the glass, to degas the glass and to cool the molten glass to a desired final temperature, takes place successively in separate oven spaces, and the glass mass is transported from such an oven space to a subsequent oven space for a subsequent step in the chain of steps and is characterized in that the total volume of an oven space per step is less than half the volume of a conventional melting furnace for melting glass, and that for at least some of said steps bri two or more oven spaces are to be used in parallel.

The invention is described in more detail below, partly in connection with exemplary embodiments shown in the accompanying drawings, in which - figure 1 schematically shows a melting chain comprising four steps A-D in the chain; figure 2 shows a melting chain in figure 1 from the side. figure 3 shows a feed screw; figure 4 schematically shows a melting chain comprising a smaller furnace with oxy-fuel burner.

The present invention relates to a process for melting glass, comprising charging and melting material in the form of crushed glass and / or glass raw material in an oven. Glass pulp is treated by melting the glass, homogenizing the glass, degassing the glass and cooling the molten glass to a desired final temperature. The melting takes place with radiant heat from flames from gas and / or oil burners.

According to the invention, each step of steps A-D to melt the glass A, to homogenize the glass B, to degas the glass C and to cool the molten glass D to a desired final temperature is brought successively into separate furnace spaces IA-1D. The glass mass is transported from such an oven space 1A-1D to a subsequent oven space 1A-1D for a subsequent step in the chain of steps A-D. Furthermore, the total volume of an oven space 1A-1D per step A-D is less than half the volume of a conventional melting furnace for melting glass, see Figure 1.

The first stage is the melting stage A. It has a first with a very low bathing depth, so that no recirculation can take place in the furnace space 1A. Here, about 80% of the energy is added to the process of utilizing the exhaust energy for preheating as much as possible.

Melting of return glass Paral '(cullet) takes place in a separate, light kiln space 1A, so that this part does not need to be heated to the same high temperature and for the same length of time as raw material, for example sand.

Alternatively, the raw material can be placed on top of the molten return glass to more easily melt the raw material and at the same time protect the bottom of the oven.

The second step is the homogenization step B, i.e. mixture of melt from the raw material and recycled glass melting furnaces.

The homogenization step is relatively small because it only uses a maintenance heater with a relatively low power in comparison with the melting furnace spaces 1A. Above all, there is a stirring here, for example by blowing air into the bottom of the oven to intensify the mixture.

The third step is the degassing step C. with over 100 ° C to about 1450 ° C, to facilitate clear- The temperature is increased and the evaporation of gas bubbles in the melt.

Preferably, the melt is not exposed to high flame temperatures in this process step because valuable parts of the composition of the glass can be gasified at the high temperatures in question in step C. Electrical heating by means of electrodes the bottom of the oven is therefore preferable.

The degassing step C is relatively long in order to minimize the thickness of the melt in order to minimize the time for the gas bubbles to penetrate the melt.

In order to achieve minimal quality dispersion, it is important that the thickness of the melt is small so that no recirculation takes place.

In order for the entire melt to be above the temperature at which the catalysts for forced gas formation and clarification are to operate, this step should also have an electrical "boost" with bottom electrodes.

The fourth step is the cooling and further homogenization steps D. where the Cooling with recirculating furnace gases, the cooled gases are used for heat recovery or extraction of electricity, gives' better controllability than. today's free. air inflow.

The homogenization is done one last time by stirring.

According to one embodiment, in at least some of said steps two or more furnace spaces 1A-1D are used.

According to a preferred embodiment, the oven space 1A-1D of each stage is displaceable relative to the other oven spaces 1A-1D. Each stage furnace space 1A-1D can thus be replaced by the furnace spaces 1A-1D being mobile laterally relative to the production line and arranged so that a new furnace space 1A-1D 70 15 20 25 30 52 '9 Ü f) can be used immediately in the process from melting A to cooling D. The displaceable furnace spaces 1A-1D can, for example, be displaced with the furnace spaces 1A-1D displaceably placed on displacement means 2, for example a rail 2. If each function is performed in parallel furnace spaces 1A-1D, they can be easily replaced out during operation, without disturbing the glass production.

Preferably, in at least one position for the respective displaceable furnace space 1A-1D burners 3 are located so as to cause the furnace space 1A-1D in question to be heated.

The preheating of the respective oven space 1A-1D takes place so that the said oven space with optimal conditions can be used in operation.

Figure 2 schematically shows the different steps. A-D from the side.

The furnace spaces 1A for the melting stage A are brought to be located at a higher level than the remaining furnace spaces 1B-1D. The furnace spaces 1B in the homogenization step B are caused to be located at a lower level than the oven spaces 1A. at the melting stage A. The furnace spaces 1C at the degassing stage C are brought to be located at a lower level than the furnace spaces 1A-1B at the melting A and the homogenization stage B. The furnace spaces 1D at the final homogenization stage D are brought to be located at a lower level than the furnace spaces melting A, homogenization B and degassing step C.

Each kiln space 1A-1D is tipped to drain glass mass from the kiln space 1A-1D in question. This can also be done so that the oven spaces 1A-1D can be filled above their normal level. The tipping can take place by means of a tipping member 5, for example hydraulic cylinders. Filling above the normal level takes place when the previous module is to be replaced, and emptying takes place when the module is to be replaced, or production is stopped. Glass mass is transferred between steps A-D with a member 4 designed so that the glass mass is successively moved between steps A-D.

According to a preferred embodiment, the melting step A of glass is preceded by heating of glass in a feed screw, see Figure 3, for charging and melting of material in the form of crushed glass and / or glass raw material. According to this method, the glass material or raw material is caused to be preheated by means of a feed screw 13 for feeding crushed glass or glass raw material into the furnace 11. The feed screw 13 is caused to be heated by means of thermal oil flowing in the feed screw 13, which oil is caused to be heated by: exchanging heat for exhaust gases emanating from the furnace 11.

According to a further preferred embodiment, melting in the melting step A, but also homogenization B and degassing step C, is effected with oxy-fuel burner with so-called direct flame impingement. s.k. flame impingement, The material 19 is hereby melted ll with S.k. by means of oxy-fuel burners directly where a number of said oxy-fuel burners 11 are spaced apart from each other, and where the material 19 is caused to be melted in an oven 13 with a sufficiently low bathing depth X to substantially prevent recirculation of the material 19.

Advantages of the invention When the invention is used for industrial glass production, large cost savings arise due to lower operating costs. 10 15 20 25 30 Recycling of undigested sand particles when the process is modularized is prevented. The melt has a considerably smaller residence time spread in the furnace spaces 1A-1D, especially when the steps are optimized for their purpose. This means that the process time can be shortened to approximately less than 20% of the currently normal process time.

A shortened process time means that production can be increased five times compared to today. This leads to savings in construction costs. It also leads to lower energy costs as each step A-D can be specialized for its task. The possibility of effective quality control increases because unexpected recirculation cannot occur.

With a shorter residence time, and with a modularized melting process, the amount of glass in each step A-D will be small. The process step that takes the longest time is the degassing, which corresponds to approximately 50% of the total time required for all steps. The time it takes to change the color shade is thus reduced to 10% compared to today (20% * 50%).

The shortened time for a small shade change is shortened from 60 hours to six hours, and a large shade change can be carried out in six hours instead of 160 hours. If a small shade change takes place every month and a large one every quarter, productivity will increase by about l4.5% and the specific energy consumption will fall by the same amount.

Today's smelting furnaces have a lifespan of about 10 - 20 years.

Due to the wear of oven walls, energy consumption will increase by about 1% per year, with accelerating energy consumption with the life of the oven through the application of forced cooling. 10 75 20 25 UH ïk- "J vf" - (3 * J CJ 10 The invention with modularized, replaceable, oven parts Reduces the specific energy consumption in several ways. In total, losses through oven walls and regenerator walls can be reduced from 50% to less than 20% of the specific energy consumption.

The losses through furnace walls are constant, independent of the flow of glass through the furnace. This fact reduces these losses to 20% per amount of glass produced. In addition, the losses are limited because each step is specially adapted for its purpose and thus does not have a higher oven temperature than necessary.

Finally, the steps that wear the most, for example the melting step A, can be changed more often so that the lining is kept in good condition.

A number of embodiments and uses have been described above. However, the furnace spaces 1A-1D in the various stages A-D comprising displacement means 2 and burner 3 can be designed in another suitable way without departing from the basic idea of the invention.

Thus, the present invention is not limited to the above embodiments but may be varied within the scope of the appended claims.

Claims (10)

70 75 20 25 30 35 5229 GÉFÜ 11 Patent claim 1. A process for melting glass, comprising charging and melting material in the form of crushed glass and / or glass raw material in an oven, where treatment of glass mass takes place by melting the glass, homogenizing the glass, degassing the glass and cooling it. melting the glass to a desired final temperature, which melting takes place with radiant heat from combustion of fuels, each step of the steps (AD) to melt the glass (A), (B), to cool the molten glass (D) to a desired final temperature, ( 1A-1D), the glass mass is transported from such an oven space to homogenize the glass to degas the glass (C) and and wherein (1A-1D) is successively followed in separate oven spaces to a subsequent oven space (1A-1D) for a step in the chain of step (AD), characterized by, (1A-1D) that the total volume of one furnace space per step (AD) is less than half the volume of a conventional melting furnace for melting glass, and that for at least stone some of said ste g bring two or more oven compartments (1A-1D) to be used in parallel. A method according to claim 1, wherein the characteristics (1A-1D) are aV, respectively the oven space of each step is displaceable relative to the other oven spaces (1A-1D). 3. A method according to claim 1 or 2, characterized in that in at least one position for the respective displaceable furnace space (1A-1D) there are burners (3) placed to heat the furnace space (1A-1D) in question. A method according to claim 1, 2 or 3, (IÄ) is caused to be located at a higher level than the remaining characteristics, that the furnace spaces for the melting step (A) are the furnace spaces (1B-1D). 10 75 20 25 30 5239 0328 12 A method according to any one of the preceding claims, characterized in that the furnace spaces (1B) at the homogenization step (B) are brought to be located at a lower level than the oven spaces (1A) at the melting step (A). A method according to any one of the preceding claims, characterized in that the furnace spaces (1C) at the êVgaS 'step (C) are caused to be located at a lower level than the furnace spaces (1A-1B) at the melting (1A). A) and the homogenization step (B). Process according to any one of the preceding claims, characterized in that the homogenization step (D) of the furnace spaces is placed at a lower level than the furnace spaces (1A-1C) at the melting (A) ), the homogenization (B) and the degassing step (C). A method according to any one of the preceding claims, characterized in that each kiln space (1A-1D) is caused to be tipped to drain glass mass from the kiln space in question (1A-1D). Method according to one of the preceding claims, characterized in that the melting step (A) of glass is caused to be preceded by heating of the glass mass in a feed screw (13). Process according to one of the preceding claims, characterized in that melting in the melting step (A) of glass is effected by means of an oxy-fuel burner (II) with so-called direct flame impingement.