CZ2012605A3 - Method of continuous glass melting under controlled convection of glass melt - Google Patents

Abstract

Energy sources operate in the melting space at least one row in the longitudinal axis of the melting space, or parallel to the longitudinal axis, and induce a spiral flow of glass (6) with a circular motion across the melting portion that extends from the front loading wall (2) to the transverse dam walls (7) in the glass (6) or transverse row (9) of energy sources. The transverse temperature gradient of each helical flow is always higher than its longitudinal temperature gradient between the transverse dam wall (7) in the glass (6), the transverse row (9) of the energy sources and the facing front loading wall (2). The ratio of the transverse temperature gradient to the longitudinal temperature gradient is in the range of 1 to 30, preferably 5 to 20. The helical flow of molten glass passes through a melting space whose use for dissolving particles, in particular glass sand, is 0.6 to 0.8 of the total melting space , defined by the height of the glass (6), the length between the transverse dam wall (7) in the glass (6) or the transverse row (9) of the energy sources and the facing base wall (2) and the width between the opposite side walls (4).

Description

Method of continuous glass melting by controlled glass convection

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a process for continuously melting glass by controlled glass convection, in which molten glass containing undissolved particles, in particular glass sand, is present in a horizontally oriented and separated flow melting space of a glass furnace by energy sources such as industrial glass burners and heating electrodes. and other suitable heating energy sources.

BACKGROUND OF THE INVENTION

Continuous melting of glass is a method of preparing traditional material on a mass scale by melting directly associated with the processing of the resulting raw material in many ways. Its foundations date back to the 19th century, when the emerging glass technology was inspired by another melting process, the production of steel. In accordance with this process, the first continuous glass equipment called glass pans was created as covered horizontal spaces lined with refractory materials into which a glass batch was placed at the inlet, most often a mixture of crystalline raw materials with variable proportion of glass cullet. . The devices were heated by means of burners placed above the surface of the melt with the heating medium gas or oil. It was therefore a compact, top-fired single-space device, which was later divided by flow or constriction into the melting section where the glass-forming - homogenization processes were carried out and finished, and into the working section where the melt was primarily temperature homogenized for processing. The flow of the melt through these devices was essentially horizontal, but due to naturally occurring temperature differences by dosing a cold charge to the melt level, the type and location of the heating and various levels of heat loss through the interface, the natural circulation flow always stabilized in the furnace with flow flow created a relatively complicated flow pattern in the furnace space.

Later, other types of glass melting chambers have been developed, mainly heated electrically, and characterized by a substantially vertical melt flow through the melting chamber and with a similar composite melt flow. However, spaces with predominantly vertical flow are not covered by this application.

The problem of melting unusable circulating melt volumes allowed to refine the tests of the so-called transition characteristics of melting spaces [1-3]. In these tests, an indicator was introduced at the inlet of the melter, the indication pattern of which did not change during the melting process and which was identifiable at the outlet of the melter. The most common indicator was suitable radioactive isotopes. Monitoring the character of the dependence of the indicator in the resulting glass over time provided information on the nature of the flow in the melter. It also helped to identify the space in which the melt only circulated. The measured proportion of such spaces, called dead space ratio, was often 0.5 in conventional melting plants, and in some plants it was even larger. Thus, it was clear that the flow pattern plays an important role for the efficiency of the melting process. A little later, Cooper [4] defined, based on flow type and melting process kinetics, a quantity that is the ratio between the rate constant of the controlling melting process and the mass flow rate that provides the degree of termination of the process at a given location or space trajectory. The thesis emphasizes the importance of flow character for melting processes.

The search for an efficient method of melting glass required a very detailed knowledge of the conditions under which the melting process takes place in industrial space. Such knowledge was only provided by mathematical modeling of the melting process in operated glass tanks. The application of mathematical models provided detailed temperature and velocity fields of the melt in the melting spaces and enabled the modeling of the melting processes directly when the mixture flows through a specific melting space [5-24]. The results confirmed the conclusions obtained by previous experience and measurements. A relatively complicated type of flow consisting of combinations of longitudinally and transversely rotating regions and a flow was established in the melting rooms, which was strongly influenced by the melt circulation. The dissolution process took place under relatively unfavorable temperature conditions [20], the fining process was essentially limited to a small region of the melt temperature maximum [19-24] and the melting compartments indicated a high dead space proportion [12]. paths, i.e., melt paths through the melting space, at which the respective homogenization process in time closest to the exit of the space is completed. Often there were short-circuit paths passing through a space with low residence times, moreover under not very favorable temperature conditions, which significantly limited the melting capacity of the space and increased the specific energy consumption for the melting process. Efforts have been made to eliminate such short-circuit paths by influencing the flow [25]. However, the complex natural flow in the melting aggregates has been very difficult to influence substantially in the right direction since the optimum flow pattern in the melting spaces has not been investigated in detail. Cooper [26], however, previously based on a simple mathematical model of the flow of glass melt in a simple model space, characterizes on a separate type of longitudinal and transverse flow some consequences of a given type of flow for melt homogenization (eg acceleration of process homogenization). transverse flow). These results indicate the need to influence the flow in the melting chamber based on a detailed knowledge of the relationship between the individual types of flow and their effect on the respective homogenization process. Recent global challenges to energy, material and environmentally less demanding technologies - including glass technology - have triggered additional activities involving both changes in the necessary melt residence times in the melting space and changes in the overall layout of the melting process [27]. however, it requires the application of new principles to the melting process, including changes in the spatial arrangement of the process, eg in the form of so-called segmental melters in which the sub-processes take place separately, alternative heating characteristics, etc. from commonly modeled existing industrial equipment to simple model spaces operating under precisely defined conditions, where the principles can be sufficiently identified, to find their general laws allowing for later safe application and. Such a process also includes efforts to overcome the disadvantages of naturally established flow in glass melting furnaces.

SUMMARY OF THE INVENTION

These disadvantages of conventional glass melting are eliminated or substantially reduced in a continuous glass melting process by controlled glass convection, in which molten glass containing undissolved particles, in particular glass sand, and located in the horizontally oriented flow melting space of the glass furnace, is operated by energy sources, such as, for example, heating electrodes, industrial glass burners, or other suitable heating energy sources, according to the present invention. The essence of the present invention is that the energy sources act in the melting chamber in at least one row along the longitudinal axis of the melting chamber or parallel to the longitudinal axis. The energy sources cause a spiral flow of glass with a circular motion across the melting portion, which proceeds from the loading wall to the transverse dam wall in the glass or the transverse row of energy sources. The transverse temperature gradient of each spiral flow is always higher than its longitudinal temperature gradient between the transverse dam wall in the molten glass or the transverse row of energy sources and the facing base wall.

• · • ·

The main advantage of the present invention is the noticeable reduction of the space in the melting part, i.e. dead areas, ie places where the melting process does not take place or only with very low to zero efficiency and the glass is unproductively heated in these places and so the heat losses increase. An important advantage of the present invention is the possibility of adjusting the ratio of the transverse temperature gradient to the longitudinal temperature gradient, which is created by a suitable arrangement of energy sources, and which creates favorable conditions for spiral glass flow through the melting space. . This results in a significant reduction in heat loss and a substantial increase in the melting capacity of the glass furnace, which eventually allows for a design to reduce the melting portion and thereby save costs for the construction of the glass melting furnace.

It is preferred that the ratio of the transverse temperature gradient to the longitudinal temperature gradient be in the range of 1 to 30, which represents the real widest limits. Optimally, this ratio is used in the range of 5 to 20. If this ratio is less than 1, the spiral flow of the glass does not occur. If this ratio were higher, a spiral flow would also be advantageous, but the efficiency of adjusting this ratio does not outweigh the technical difficulties in implementation.

The preferred spiral flow of glass passes through a space whose use for dissolving particles, especially glass sand, represents 0.6 to 0.8 of the total space defined by the height h of the glass, length l between the transverse dam wall in the glass or transverse row of energy sources and a wall and a width w between opposite side walls. The spiral flow of the present invention provides the highest previously known defined utilization of the melting space. The utilization of the melting space represents the amount of used part of the melting space to be unused.

The flow of the glass has an excellent homogenizing function and thus the process of dissolving hard-melting particles, especially glass sand or corundum particles, is shortened. The defined arrangement of the energy sources ensures effective achievement of the desired spiral glass flow. The melting chamber exhibits lower heat losses and a high melting capacity, which allows a possible reduction of the melting part and, as a result, construction savings.

The energy sources are arranged in one or both side walls of the melting chamber. When the energy sources are arranged in one side wall of the melting portion, one helical flow occurs across the entire melting portion, which is suitable for narrow melting portions. When the energy sources are arranged in the two side walls, two substantially symmetrical spiral-like arises. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Flow separated by the longitudinal axis of the melting section, which is suitable for melting areas with difficult operator access to the bottom in the event of displacement or replacement of heating electrodes. In larger glass furnaces, ie with a larger melting space and width, it is possible to use bottom heating electrodes in two or more rows in the longitudinal direction of the melting space. In this case, spiral flows occur between each side wall and the row of heating electrodes and between the individual row of electrodes.

The energy sources are arranged at regular intervals. Regular spacing ensures uniform heating of the melt and thus a favorable even flow of the glass.

Energy sources are heating electrodes and / or industrial glass burners. The heating electrodes are the most advantageous for the spiral flow because of the direct supply of energy to the glass and the easy regulation of the heating electrodes. The heating electrodes may be arranged in the bottom as vertical or inclined, or they may act on the glass from above as vertical. Plate electrodes installed in the side walls seem to be suitable. There may be other sources of heating energy, such as microwaves or plasma torches.

The melting portion may be terminated by a transverse row of bottom heating electrodes. This transverse row of heating electrodes creates a transverse thermal barrier, which is an alternative to the transverse dam wall, and moreover allows for better regulation of the heat output depending on the melting capacity of the glass furnace.

For very small melting rooms for special glass, other sources can be used as energy sources, eg microwaves, plasma burners or resistive sources in the side walls, or indirect sources of heating energy in the side walls, super-channel loops.

BRIEF DESCRIPTION OF THE DRAWINGS

The prior art is represented by Figures 1a and 1b, taken from W. Trier, Advances in Glass Technology, Plenum Press, 1962, p. 619, wherein Figure 1a shows a longitudinal axial section of a constant temperature glass furnace, without circulation; 1b shows a longitudinal axial section through a glass furnace in the presence of temperature gradients and hence circulation.

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The invention is described in detail in the following description of the invention, which is generally illustrated in the accompanying schematic drawings, in which FIG. 2 is a perspective view of a simplified basic melting chamber model with full inlet and outlet; Figure 4 is a graph of the maximum utilization of the model melting space, the dissolution time of the glass sand particles, and the length of the model channel of the melting space.

Exemplary embodiments 1 to 4 schematically show, in Figs. 5-24, a vertical longitudinal axial section of a proposed glass pan module with a melting portion of a typical shape and arrangement of heat sources, electrodes, in Figs. 5-22, vertical heating electrodes, and Fig. 23; 24 combinations of vertical heating electrodes with side wall burners.

In more detail, an exemplary embodiment 1 for melting flat glass is shown in Figs. 5-13, schematically showing in Fig. 5 a melting portion of a typical shape and arrangement of vertical electrodes, with a lower inlet and a lower outlet; 5 for the melting of flat glass, with the upper glass inlet and the lower glass outlet; FIG. 7, the resulting velocity distribution, represented by sections of melt trajectories traveled in 30s, in longitudinal axial section through the melting space of FIG. 6 for the reference case, FIG. 9 the resulting velocity distribution in the longitudinal axial section through the melting space, which is shown by the sections of melt trajectories traveled beyond the 30s of the melting space of FIG. 6 For the optimum case, FIG. 10 shows critical track projections and the other slowest trajectories for melting sand grains into a longitudinal axial vertical section through the melting chamber of FIG. 6, for an optimum case; FIG. 11 a melting chamber for melting flat glass with a lower inlet and a lower outlet; 11 shows sections of the melt trajectories traveled in 30s for the optimum case, FIG. 13 shows critical and other slowest trajectories for dissolving the grains of sand into the longitudinal axial vertical section through the space of FIG. 11 for the optimum case.

An exemplary embodiment 2 for the manufacture of spectacle moldings is shown in Figs. 14-16, where the resulting velocity distribution in longitudinal axial section through the melting space shown in sections of melt trajectories traveled in 30s is schematically shown in Fig. 14; trajectories and other slowest trajectories for melting sand grains into longitudinal axial vertical section through space, for reference case, Fig. 15 resulting velocity distribution in longitudinal axial section through melting space shown by melt trajectory sections traveled in 30s, for optimal case; a longitudinal axial section through the melting chamber of a section of melt trajectories traveled in 30 s, FIG. 17 shows projections of critical and other slowest trajectories for dissolving sand grains into a longitudinal axial vertical section through the space, for optimal case.

An exemplary embodiment 3 for producing glass container moldings is shown in Figures 18a-22, schematically showing the melting chamber of Figure 18a in longitudinal section, Figure 18b in cross-section below the glass surface, Figure 19, resulting speed distribution in longitudinal axial section Figures of critical and other slowest trajectories for melting sand grains into a longitudinal axial vertical section through the melting space, for reference case, Fig. 20, the resulting velocity distribution in the longitudinal axial section through the melting space depicted sections of enamel trajectories traveled in 30s, for the first optimized case, Fig. 22 shows projections of critical and other slowest trajectories for dissolving sand grains into a longitudinal vertical vertical section through space, for the first optimized case,

An exemplary embodiment 4 for the production of utility glass is shown schematically in Figs. 23-24, where the melting space is schematically shown in longitudinal axial section, and Fig. 23 with side wall burner heating, for the reference case, and Figs. 24 with vertical electrode and side burner heating, for the optimum case

DETAILED DESCRIPTION OF THE INVENTION

W. Trier, Advances in Glass Technology, Plenum Press, 1962, p. 619 shows a typical longitudinal axial sectional view of the horizontal glass melting furnace without constant temperature circulation in the attached FIG. glass furnace in the presence of temperature gradients, including circulation.

The naturally occurring type of glass flow evident from FIG. 1b has had a significant effect, in particular in the melting portions of glass furnaces, on the melting process and hence on the efficiency of the entire melting apparatus in terms of its performance and energy consumption per melting process. For the melting process, the resulting type had some advantages, in particular the fact that the massive glass return from the temperature maximum to the trunk layer in the initial part of the furnace, as shown by the left circulation circuit in Fig. 1b, brought much needed heat to reaction of raw materials. A second advantage of natural flow was the often present glass return from the flow to the melting temperature region, as shown in Fig. 1b, at the bottom of the right circulation circuit. The return flow returned to the melting process of inhomogeneity, especially the bubbles that were due to the imperfect flow of the melting process. The disadvantage of the established type of flow was the resulting continuous flow of glass from the charge layer to the bottom of the melting furnace, where it moved forward at the lowest temperatures up to the maximum temperature range, where it was only circulated to bring it to high temperatures. The result of this flow was slow homogenization of the glass (dissolution of particles and chemical inhomogeneities) and practical absence of the fining process (bubble output) in a substantial part of the active furnace space at the bottom of the furnace. While the dissolution processes could be completed after the molten glass was brought from the bottom to the surface, the process of removing primary bubbles in the high temperature region at the surface was practically only beginning. Thus, both processes took place in the post-glass reaction region substantially in series, with the dissolution taking place at the bottom of the furnace for most of the time required at low temperatures. The continuity of the processes (instead of their intensive parallel run) and the high proportion of adverse conditions during the dissolution process were reflected in the high heat losses of the melting process and in the small specific melting performance of the aggregates, which required relatively large devices at higher planned outputs. In addition, it has been shown that the established circulation flow at low specific power of the melting compartments creates significant volumes of long-term circulating glass in the compartments, in which the melting process is essentially not performed (dead compartments - overprocessing compartments). This glass is therefore maintained at the melting temperature without its own effect and causes unnecessary heat loss.

More recently, the authors of this application have begun to look in detail at the effect of flow patterns on the two most important melting processes, ie dissolving unreacted glass batch particles, which in most cases represent glass sand and removing bubbles (refining), mostly the slowest melting process [28-35 ], They defined the specific energy consumption and specific melting capacity of a given melting space as quality criteria of the current melting process. They chose a flow-through cuboid-shaped horizontal space with inlet and outlet as the model melter space with all or part of the front walls. Its diagram is shown in Figure 2, the shape of the melting chamber was simple to achieve the most general results, the dimensions of the equipment were small in accordance with the effort to miniaturize the next melting chamber - length lm, width and glass level 0.5 m. apply the results to other dimensions of the real device. The mathematical model of the melting space with the possibility of wide variability of conditions was chosen as a means of investigation.

Figure 2 is a schematic diagram of a simplified model melting chamber with full inlet and outlet. The appropriate flow pattern was set using linear temperature gradients inserted at the enamel level, the bottom and walls of the space were isolated. Because the dissolution process and the bubble removal process are carried out on different principles, the investigation was performed separately for each process, with a compromise between optimal conditions being chosen in applications, or a separate segment of the equipment would be designed for each process.

In order for the results of the monitoring to be well understood, it is necessary to provide a theoretical basis for the investigation, for this application relating to the dissolution of glass sand particles, which is usually a major part of most industrial glasses and is the glass raw material that dissolves most difficultly and last in the glass melt.

For a process without energy recycling, the criteria of specific energy consumption and melting chamber volumetric performance are described by the following equations, which include the process duration (its kinetics) and the flow pattern influence separately. The influence of the flow character is expressed by a newly introduced variable called the use of melting space, for _D [31,33-35]:

(1) •

«· · · · · · · · · · · · · · ·

(2) where H ° _m is the specific energy consumption [Jkg ¹ ]; H'm is the theoretical heat required for chemical reactions, phase and modification conversions, and heating of the incoming mixture and the resulting glass to the melting temperature [Jkg ^-1 ]; fí ^! is the total heat flow through the interfaces into the environment [Js' ¹ ]; is the mean dissolution time of all glass sand particles under different time-temperature regimes applied [s]; p is the specific gravity of glass [kg / m ³ ]; V is the volume of the melting chamber [m ³ ]; F is the volume flow of glass through the space assuming completion of the melting process [mV] and ud is the use of the melting space for dissolution. Here, up expresses the relation between the mean time for the process itself, and the theoretical residence time of the glass in the melting chamber, the so-called geometric residence time, which is equal to the ratio of volume and volume flow 7 through space rG = 7:

(3)

It can be seen from equations (1-2) that the specific energy consumption is inversely proportional and the volumetric power is proportional to the utilization of the melting space.

The term for the use of melting space in the case of dissolving sand grains is composed of two parts of dead space, where mc includes closed circulation and regions of almost static glass (eg corners). This value has been previously determined, for example, by the method of transient characteristics as mentioned above, mp then indicates the area where all grains of sand are already dissolved, but the respective glass is still heated in space (overprocessing). The use of the melting space for the dissolution of sand is then given by:

(4) where f * is the average residence time of the flowing glass through space, the mean dissolution time of the sand grains under isothermal or near isothermal conditions then satisfies: t _d = t _d = ^T ncn _l 'where is the time required to dissolve all sand grains in a given or average temperatures ar _{/ m} , jc the residence time of the glass on the fastest (critical) trajectory. The calculation of the melting space utilization then works with the values of sand grain dissolution times and the results of modeling the melting process in the model melting space under time-temperature modes on the enamel trajectories (thus not considering the slight buoyancy force acting on the sand particles).

In particular, when investigating the effect of flow patterns on power and specific energy consumption, the sand grain dissolution time is constant, or the temperature dissolution time temperature is constant, the effect of the very slow glass convection there is not considered. The dissolution times of the glass sand particles are determined experimentally. In order to compare individual cases, a reference state is established. When the reference state is reached, the last - critical - particle is dissolved at the exit of the melting chamber. Technologically, such a state corresponds to the state of a “no reserve” process and the real performance would actually be lower. The resulting specific modeling value is the space utilization value uq, which is proportional to the space performance (equation 2) and inversely proportional to the specific energy consumption (equation 1) under constant dissolution kinetics. For information, the ud value for a melting chamber of the melting chamber type assuming a piston flow is equal to 1, and for an isothermal melting chamber with a parabolic distribution of the molten glass velocity of 0.445. However, a higher value is only achievable with an ideal liquid, the isothermal flow of the glass is difficult to implement in high temperature melting rooms, where a multi-stage horizontal temperature difference will induce efficient circulating flow and lowering of the model. flow, where pure longitudinal circulating flow in both clockwise and counterclockwise directions (circulations in vertical planes parallel to the main-working direction of flow) and transverse flow where circulations in planes perpendicular to the main-working direction of flow were considered as the basic types of flow . The mixed streams then included the types of streams whose intensity ratio was set by the ratios between the inserted horizontal temperature gradients. Both types of longitudinal flow have been shown to result in large dead spaces, where the utilization of the melting chamber was only 0.1 to 0.2, while the introduction of a net transverse flow yielded recovery values of 0.4 to 0.5 due to the disappearance of part dead space. However, the best results were obtained with the mixed flow type, where the rapid forward flow component at the molten glass level was hampered by a small temperature gradient with a higher temperature at the exit and where a relatively intense transverse flow through the transverse temperature gradient was induced. longitudinal temperature gradient equal to 5 to 10. This optimal type of flow was characterized by 4 · 4 · 4 · 4 · 4 · 4 · 4 · 4 · 4 The helical enamel trajectories, as shown in Figure 3, and the very small dead space value m _G and the partially reduced dead space value mo (see equation (4)).

Further research has shown how this optimal type of flow and its setting conditions change as the independent variables change, such as the ratio of transverse to longitudinal flow, total circulation flow rate, glass sand particle dissolution time, and melting space length. The influence of the glass properties and the glass layer height can then be included in the influence of the overall flow rate. The width of the space, while maintaining temperature gradients, will not substantially affect the utilization. For each pair of dissolution time of the glass sand particles in a given glass and the length of the melting chamber while maintaining the glass layer height, the maximum value of the melting chamber utilization for the dissolving process can then be found. These maximum values ranged above 0.5 over a wide range of sand dissolution times and melting channel lengths; in most cases even between 0.6 and 0.8, which were considerably better than can even be achieved in the isothermal melting space. The dependence of these maximum utilization values on both mentioned quantities in the model melting space is shown in Figure 4. Figure 4 shows the dependence of the maximum utilization value of the melting space on the melting time of glass sand for different lengths of the melting space. It is apparent from the depicted dependencies that the maximum utilization rates of the melting chamber increase with both the dissolution time of the sand and the length of the melting chamber. At the same time, laws have been found governing the temperature gradient values that need to be set to achieve optimal utilization of the melting space.

The obtained results proved that it is possible to find and define the optimal type of spiral flow in terms of the dissolution of glass sand particles and to define the optimal conditions for achieving it. There were also defined patterns of changes in optimum utilization and optimal conditions for changes in input parameters. Thus, the prerequisites for transferring the results to real smelting spaces were obtained.

Example 1 (Figures 5 to 13)

However, in order to apply the results, it is necessary to define a specific melting space, specific energy sources, their distribution and heat output to enable the desired type of spiral flow to be set, which is the object of the present invention.

Achieving the objective is to design a special glass melting space for dissolving glass batch components, especially glass sand, i.e. to design the shape and suitable dimensions of the melting space, its typical material composition, heating method, and the distribution of heat sources in the melting space. energy to the individual heat sources so that the melting process takes place at a predetermined average temperature and to achieve a spiral flow type that ensures high utilization of the melting space for the glass melting process. To achieve this state, the prescribed process 5 of mathematical modeling of the melting space is used together with the calculation of its utilization.

In carrying out the process according to the invention, molten glass containing undissolved glass sand particles and located in a horizontal flow-through melting space, an energy source, typically by heating electrodes or industrial glass burners, is treated so that a temperature distribution is created in the molten glass 10 shows the type of flow in the direction of glass flow through the space, thereby achieving a high utilization of the melting space for the dissolution process, thus also high space performance and low specific energy losses.

A cuboid appears to be a special space, the length of which is generally greater than its width and the level of the glass level in the melting space of the glass furnace. The melting chamber 15 is horizontally oriented, flowable and separated and comprises a base 7, a foundation wall 2 and an opposing rear flow wall 3 and opposed side walls 4, a vault 5 and a transverse dam wall 7 submerged in the glass 6 in the melting chamber. energy sources in at least one row in the longitudinal axis of the melting chamber or parallel to this longitudinal axis, between the loading wall 2 and the transverse dam wall 7 in the glass 6 or a transverse row - 20 9 energy sources in the glass melting part 6 to induce spiral flow the glass 6 having a circular movement across the melting portion. The energy sources are preferably heating electrodes 10 or industrial burners 11.

The mixture of molten glass 6 with inhomogeneities enters the melting chamber through the upper inlet or the lower inlet 12, which may be tapered or occupy the entire width of the melting chamber 25 and may have different heights. However, too narrow an inlet 12 and an outlet 13 affect the set flow pattern in the space, and it is therefore recommended that the inlet 12 or the outlet 13 not occupy less than about 20% of the front loading wall 2 or the rear flow wall 3. The melting space is lined with a refractory lining used in glass melting furnaces. According to modeling results, electrical heating 30 by means of electrodes W, which are generally molybdenum, has proved to be the best heating. However, heating by gas or oil burners 11 can also be used, especially in combination with electric heating. A diagram of a typical electrically heated melting chamber is shown in Figure 5.

· · · · · · · · * · • · • · · · · · · · · · ·

..... ····

The melting process takes place in a range of temperatures suitable and common for melting industrial glass, the specific temperature depends on the type of glass, but for conventional glass the average melting temperatures of 1300 to 1500 ° C are to be expected. Continuous flow is ensured by the inflow of glass mixture with solid and gaseous inhomogeneities from the previous space, where the incoming mixture of glass raw materials is heated and melted and taken to another space where homogenization is completed, bubbles are removed, or temperature is stabilized and finished vitreous glass. The performance of the melting chamber can be adjusted in addition to adjusting the appropriate type of spiral flow object of the present invention by particle size distribution (sand grains), by adjusting the composition of the resulting glass and by the average temperature in the dissolving chamber. In the melting chamber of the glass furnace, the same amount of glass 6 is maintained by inlet and outlet.

A typical shape and arrangement of heat sources, electrodes 10, in the proposed dissolution module is shown in Figure 5.

The basis of the present invention is to achieve a certain type of spiral flow in the flow space by arranging heat sources, or dimensioning the glass furnace insulation so that a transverse circulation flow occurs in the melting space under both factors simulating the optimal type of spiral flow temperature gradients. This transverse circulation flow has a partially suppressed longitudinal longitudinal component of the glass melt movement at the surface in order to reduce the differences between the residence times of the glass 6 on different trajectories. This can be achieved, for example, by a longitudinal row of electrodes 10 positioned generally from the bottom of the glass furnace so as to form a longitudinal thermal barrier either in the longitudinal axis of the melting chamber, where electrodes 60 will also be located, or from the side walls 4 of the melting chamber where a longitudinal row of electrodes 60 would also be located. More than one longitudinal row of electrodes 50 can be accommodated in the melting rooms designed for high power, but this arrangement appears less advantageous for slowing the horizontal velocity component at the surface. In order to better achieve the desired type of spiral flow, it is advisable, but not necessary, to place other sources in the space, for example a transverse row 9 of electrodes 60 to better inhibit the fast forward of the flow component or prevent the longitudinal circulation flow of the glass. the burners 11 need to be arranged above the surface of the glass furnace either by placing the burners in the furnace vault 5 or in the side walls 4 and orienting them so that a temperature barrier is formed in the melting chamber along the longitudinal axis of the glass furnace or When using the burners 11 as heat sources, it is possible to simultaneously use electrodes 10, predominantly in the longitudinal axis of the melting chamber or at any of the walls that promote the formation of a longitudinal temperature barrier. The distribution of energy into heat sources or the necessary insulation of the melting chamber or its parts, ensuring the optimum character of the spiral flow, must be set by targeted mathematical modeling of the melting chamber. For modeling it is necessary to determine experimentally the dependence of the glass melting time on temperature in the expected melting temperature range. The same temperature dependence can be used for glasses of similar composition and the same grain size of glass sand grains. The melting power and the specific energy consumption of the melting chamber operating in the critical mode, i.e. without reserve, are determined by modeling, i.e. the last dissolving particles are dissolved just at the outlet 13 of the melting chamber. The energy distribution on the sources is gradually adjusted so that the calculated value of the utilization of the melting space reaches the maximum achievable value or is the highest value in a technically achievable arrangement. During modeling it is possible to make corrections also in the arrangement of heat sources, but always in order to create the desired type of spiral flow. Required space utilization values should be at least about 0.4, but rather above 0.5.

It is, of course, very useful to estimate how the spiral flow and the corresponding use of the melting chamber will behave at the extreme setting values, i.e. at very low or very high transverse and longitudinal flow intensities ratios with potential return at glass level 6, low or very high. high intensities of glass circulation 6, with very slow or very fast dissolution or with short or very long melting spaces.

A very low transverse flow ratio when there is a longitudinal flow will always result in a decrease in utilization and will approach zero at increasing longitudinal flow intensities. Conversely, at a very high ratio of transverse to longitudinal flow intensities, the value of utilization will approach and then remain around 0.5.

In the region of the ratio between the flow intensities of the glass 6, which is expressed by the transverse to longitudinal temperature gradient of 5 to 20, the utilization will reach a maximum value of 0.6 to 0.8. Here, the technologically advantageous area is characterized by the maximum value of space utilization. In another region of the ratio of flow intensities, it does not make sense to operate at virtually any total flow intensities, dissolution rates or melting chamber lengths.

The maximum utilization rates of the melting space in this ratio range are 0.445 at zero circulating flow rate, with glass 6 flowing through the isothermal rectangular melting space, and gradually increasing to a total circulating flow rate of 0.6 to 0.8 at commonly achievable intensity values. circulation, and they reach. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Values of 0.5 to 0.6 at high circulating intensities, which, however, are not achieved under normal conditions. The maximum utilization values in the region of the optimum ratio between the transverse and longitudinal flow intensities are little dependent on the dissolution rate and are within a wide range between 0.6 and 0.8. The very short melting chamber channels show low utilization rates because they do not suffice to develop a spiral flow pattern, the values decrease to 0.4 at a melting chamber length of 0.5 m, and will approach 0.4 for even shorter spaces. For very long melting chamber channels, the utilization value will be kept relatively high, around 0.6 and above, but the necessary optimum ratio between transverse and longitudinal flow intensities will increase disproportionately.

The specific objective is then to transfer the character of the temperature field created in the model melting space by means of temperature gradients to the proposed specific melting space, differing from the model one in particular by exhibiting temperature losses through interfaces and heated by specific sources such as electrodes 10 or burners 11 in such an assembly. and distributing the supplied energy such that a temperature field is formed within the space that produces the desired spiral type of glass flow 6, characterized by high utilization of the melting space and corresponding flow pattern in the model device. This object is achieved by designing a first melting chamber arrangement based on the knowledge of the original model apparatus by mathematically modeling the temperature and velocity field of the glass melt and the course of sand grain dissolution on the enamel trajectories generated by the inserted energy into ordered heat sources and losses in the proposed variant. The performance of this arrangement is adjusted after the first calculation so that at a predefined and maintained average temperature in the melting chamber, the last glass sand grain melts just at the outlet 13 of the melting chamber, i.e. to operate without the melting margin. This state is called critical.

Calculations are obtained dissolution time of the sand grains thereon disadvantageous critical path VDcrit, space (grain dissolved just at the outlet from the space and the given trajectory determined maximum melting power based on the critical state) and the relevant geometrical time V ^T G.

dwell time V, sand dissolution times on the other trajectories td (of which 10 or more) as well as their mean dissolution time of the glass sand particles, and from the distribution of glass residence times on the monitored trajectories, their mean residence time + in space at critical setting. Using the equation (4), the corresponding use of the up space is then obtained and the specific energy consumption for heat losses is calculated from the power and energy data.

* · · · ···· · · · · · · · · · · · · · · · · ·

The first arrangement may be, but does not necessarily have to be, reference and simulates an arrangement corresponding to a conventionally heated device that exhibits low space utilization value. The results of the calculations with the expected advantageous type of flow with high utilization of the melting space (hereinafter the space) are then compared with the reference ones and the modified further variants are derived from their comparison. As already mentioned, it is not always necessary to calculate the reference setting, and when searching for the optimum spiral flow, the following calculations can be based only on the obtained space utilization values, where good values start at around 0.4. The aim is then to get the highest value of ud utilization of the melting space between about 0.6 to 0.8.

The second arrangement is also based on the results of modeling on the melting chamber with pre-set temperature boundary conditions, however, the location and dimensioning of selected heat sources or the dimensioning of the interface insulation are already set to better achieve the described advantageous type of spiral flow. In the first variant, the use of the melting space in this variant, the capacity of the space and the specific energy consumption are calculated according to the above-mentioned procedure and, if necessary, compared with the reference values of the first arrangement. According to the results, the arrangement of sources, eventually insulation and distribution of supplied energy will be adjusted in the direction in which the utilization is expected to increase. The direction of the adjustment is determined by the general rules already obtained governing the use of the melting space. In the second variant, a second set of recovery, specific energy consumption and power is obtained. Where appropriate, the design of the improved variants is continued until the highest achievable value of space utilization is achieved.

Thus, the process for designing a high utilization melting chamber is broken down into the following steps:

1. Determination of temperature dependence of sand grain dissolution time in laboratory and determination of temperature dependence of average dissolution rate on temperature.

2. Design of basic dimensions and method of heating of the new melting space using common design knowledge and results from the original model space on the basis of performance requirements and observing the necessary melting conditions (average temperature).

3. Calculation of the utilization of the melting space in the reference arrangement corresponding to the conditions in a classically operated plant. This step is not inevitable.

4. Calculation of utilization in the melting chamber with proposed parameters corresponding to the expected desired type of spiral flow.

5. Repeated adjustments of conditions and calculations leading to the arrangement and conditions under which the maximum utilization of the melting chamber and its corresponding melting capacity and specific losses are achieved in terms of theory and practice.

Special melting room for melting of glass sand grains in float glass working at an average temperature of 1400 ° C and with the required output of at least 20t / 24h. In view of the high specific powers obtained in the previous model space with the set temperatures, a relatively small cuboid-shaped melting space with a length of 2m, a width of 1m and a glass level of 6 0.5m was designed. A detailed diagram of this space is shown in Figure 6. The melting space is preceded by a molten glass space which is not the subject of the present invention. The walls of the melting chamber are composed of layers of refractory material, the vault 5 being low, slightly arched. The inlet 12 is located along the entire width of the melting bed at either the bottom 1 or the glass level 6 and occupies 20% of the front loading wall 2. The outlet 13 is then formed by a flow at the glass level 6 over the entire width of the melting space. rear flow walls. The melting chamber is heated by a longitudinal row of 6 molybdenum electrodes 10 positioned from the bottom f along the axis of the melting chamber. The electrodes 10 are connected in a manner wherein the row of electrodes is divided into three pairs, each pair comprising one transformer. This makes it possible to divide the power of the electrodes into three zones and thus set the desired power and therefore temperature gradient. The method makes it possible to regulate the energy supply to the molten glass in the individual parts of the furnace and thus to adjust the nature and intensity of the natural flow in the melting chamber.

Figure 6 is a detailed diagram of the proposed space for melting flat glass with the upper inlet 12. In the first phase of modeling, the energy distribution at the electrodes 10 was simulated to simulate the type of flow common in conventional glass furnaces (reference setting). The inlet 12 to the melting chamber was at the molten glass level 6. By concentrating the energy on electrodes Nos. 5 and 6, a transverse thermal barrier was created which induces the usual longitudinal circulation flow. The distribution of energy on electrodes in% is given in Table 1.

Table 1

Energy distribution on the electrodes 10 according to their numbering in Figure 6 at the reference heating setting and with the upper input 12.

Electrodes 1 + 2 3 + 4 5 + 6 Performance [kW] 0 0 118.6

· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·

The flow pattern was controlled to match that known from conventional glass melting furnaces.

In Figure 7, the resulting velocity distribution in longitudinal axial section through the melting space is shown by sections of glass trajectories traveled in 30 s, representing the reference case.

Critical and other disadvantageous dissolution paths have also been obtained, the projections of which in longitudinal axial vertical section through the melting space are shown in Figure 8, which illustrates a reference case.

The resulting velocity distribution and trajectory shapes correspond to the results obtained on conventional devices, so the reference case is qualitatively set correctly.

For the dissolution of sand, experimental data were obtained by repeated laboratory melting of the glasses and by counting the undissolved grains of sand in the resulting glass samples obtained in time sequence at temperatures of 1300 to 1500 ° C and at intervals of 50 ° C. An empirical equation [36] was obtained for the average dissolution rate of sand grains of initial maximum grain diameter of 0.5 mm: v _Diss = 1.56x10 ^'18 exp (O.O153T) [ms' ¹ ], where T is the temperature in K. This equation was applied to the dissolution process taking place in the melting chamber with temperatures and flow set to the reference case and later to other cases.

The following values were obtained by modeling of the final variant describing the classical setting, complying with the average temperature of 1400 ° C and processing:

Average temperature: 1400 ° C.

Dimensions of the melting chamber 2x1x0,5 m - length, width, height. Input 12: Upper.

Electric heating output E: 118.6 kW.

Critical power F: 6.79x10 ⁵ mV = 13.65 t / 24h = 6.82 t / (24hm ² ).

Average residence time of glass in the space ϋ 13 888 s. Average time of sand grain dissolution 24): 2451 s.

P

Geometric residence time ^r G = Ø: 14724 s.

Dead space fraction by enamel circulation mc, '· 0.050. Dead space fraction after sand grain dissolution ηΐβ: 0.825.

Share of utilization of melting space ud '. 0.166.

h ^l - ^Ετ °

Specific loss Fp _: 751 kJ / kg.

• * 4 · 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

.............

The measured reference power of the melting module 6.82 t / (24hm) is high compared to that of a conventional glass furnace, but it should be noted that in this case the set average temperature of 1400 ° C is relatively high, the highest possible critical performance - when there is no melting reserve in the space and that the given performance is only related to the completion of the dissolution of sand grains. With a 50% margin, the specific power is only 3.41 t / (24hm) and this value is already realistic. The same situation applies to specific losses, which at 50% reserve would be 1502 kJ / kg, which is also a realistic value due to the high average melting temperature of 1400 ° C.

The detected dead space portion mc is much lower than expected for a given type of flow and is measured, for example, by measuring the furnace transition characteristics. However, checking the furnace residence time distribution curve in the furnace did not reveal irregularities on the curve, which could reveal the recycling of some continuous trajectories due to numerical calculation errors (then the + value increases and the calculated ma value decreases). The reason for the low dead space values mc ·. it is the fact that the transverse temperature barrier was only adjusted by the power on the axially positioned electrodes 10. This has already produced a certain amount of transverse flow and consequently reduced the ny value.

Next, the energy was adjusted on the individual electrodes 10 to achieve the desired type of spiral flow.

At the final setting, see Table 2, substantial changes in the glass flow pattern and the typical spiral nature of the critical and close glass trajectories as shown in Figures 9 and 10 are observed. in 30s, and represents the optimal case. Figure 10 shows the projections of critical and other slowest trajectories for dissolving sand grains into a longitudinal axial vertical section through space, and is an optimal case.

Table 2

The energy distribution on the electrodes 10 according to their numbering in Figure 6 at the optimal variant of the heating setting and at the upper input 12.

Electrodes 1 + 2 3 + 4 5 + 6 Performance [kW] 33.5 39.4 46.6

• «··

The final variant with the power distribution shown in Table 2 gave the optimum result:

Average temperature: 1400 ° C.

Dimensions of the melting chamber 2x1x0.5 m- length, width, height.

Input 12: Upper.

Electric heating output E: 119.5 kW.

An average transverse temperature gradient of 45 K / m, an average longitudinal gradient of 8K / m, an average transverse to longitudinal gradient of 5.6.

Critical power: 2.63x10 ' ⁴ mV ¹ = 52.86 t / 24h = 26.43 t / (24hm ² ).

Average residence time of glass in space τ; 3760 s.

Average time of sand grain dissolution * D: 2498 s.

Geometric residence time: 3807 s.

Dead space fraction by enamel circulation mp: 0.012.

Dead space fraction after melting sand grains mp 0.336.

Utilization rate of melting space uq: 0.656.

h ¹ = phase

Specific losses Vp: 196 kJ / kg.

This result already shows a substantial improvement due to the setting of a more efficient type of flow in the melting chamber. Utilization of ud melting space increased 3.95x compared to the reference case, space melting performance increased 3.87x and specific losses decreased 3.83x. Considering 50% of the melting reserve, the space output would be 26.43 t / 24h and the specific dissolution capacity would be 13.22 t / (24hm ² ). The conditions for the required performance of the melting chamber were met.

When operating an optimized glass flow device, the problem arises in the occasional leakage of the unsold batch from the level of the previous space through the upper inlet into the dissolution chamber. This problem was solved by placing the inlet 12 in the area at the bottom 1 of the dissolution chamber, as shown in Figure 11.

In this case, it will be demonstrated to achieve optimum flow settings using two variants, the first and the last variant - optimal. The first setup was based on the results obtained on the original model device with the set temperature field [33-34]. In the first variant, all electrodes 10 were set to practically the same power as shown in Table 3.

· · 4 4 4 * * * 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 · · · ·

Table 3

Energy distribution on the electrodes 10 according to their numbering in Figure 11 at the first variant of the heating setting and at the upper input 12 ·

Electrodes 1 + 2 3 + 4 5 + 6 Performance [kW] 40.6 40.6 41.8

The results of the calculation of the first variant are as follows:

Average temperature: 1400 ° C.

Dimensions of the melting chamber 2x1x0.5 m - length, width, height.

Input 12; Bottom.

Electric heating output E; 122,9 kW.

Average transverse temperature gradient 40 K / m, average longitudinal gradient 8K / m, average transverse to longitudinal gradient 5.

Critical power: 2.49x10 ' ⁴ mV = 50.11 t / 24h = 25.05 t / (24hm ² )

Average residence time of glass in the space ϊ: 3988 s. Average time of sand grain dissolution: 2531 s.

IN

Geometric residence time ^t g = Ø: 4011 s.

Dead space fraction by enamel circulation mcj; 0.006.

Dead space fraction after melting grains of sand mi>; 0.365.

The share of utilization of melting space ud- 0.631.

_h l ₌ ^ g_

Specific loss ^V P: 212 kJ / kg.

The flow pattern with the change in location of the inlet 12 has not changed. Modeling continued until the optimum case was reached.

The optimal case is illustrated by Table 4 and Figures 12 and 13. Figure 12 shows the resulting velocity distribution in longitudinal axial section through the melting space shown by sections of glass trajectories traveled in 30 s as an optimal case. Figure 13 shows the projections of critical and other slowest trajectories for dissolving sand grains into a longitudinal axial vertical section through space, an optimal case.

The energy flow setting in the optimal case is shown in Table 4.

Table 4

The energy distribution on the electrodes 10 according to their numbering in Figure 6 at the optimum heating setting and at the inlet 12 at the bottom f.

Electrodes 1 + 2 3 + 4 5 + 6 Power [kW] 34.8 41.0 48.4

The results of the last - optimal - variant calculation are as follows:

Average temperature: 1400 ° C.

Dimensions of the melting chamber 2x1x0.5 m - length, width, height.

Entry 12: Lower.

Electric heating output £: 124.2 kW.

Average transverse temperature gradient 45 K / m, average longitudinal gradient 7K / m, average transverse to longitudinal gradient 6.4.

Critical power Ě; 2,54xl0 ^'4 mV = 51.05 t / 24h = 25.53 t / (24hm ^2).

Average residence time of enamel in space *: 3915 s. Average time of sand grain dissolution: 2545 s.

IN

Geometric residence time ^t g = Ø: 3943 s.

Dead space fraction by enamel circulation mc .: 0.007.

Dead space fraction after sand grain dissolution mo: 0.350.

Share of melting space utilization 0.646.

Specific losses Vp 210 kJ / kg.

A comparison of the first and optimal variants shows that the first variant envisaged differs little from the optimal variant. Thus, the results are less sensitive to small changes if there is a well-founded idea of what is to be achieved.

For comparison, values from the reference case were used with the inlet located at the surface. According to the calculation, the space utilization increased 3.89x, the melting capacity increased 3.74x and the specific losses decreased 3.58x. Power at 50% melting reserve would reach 25.53 t / 24h and specific power 12.76 t / (24hm). The values are only slightly worse than in the case of a level inflow, the performance of the space exceeds the required 20t / 24h and the last arrangement can be used with both inputs.

· ** ** «** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** · «··» · * ·· ·· ··· ····

Example 2 (Figures 14 to 17)

Special space for melting grains of glass sand in glass for the production of spectacle moldings operating at an average temperature of 1300 ° C and with the required output of at least 8t / 24h. The same special 2m length, 1m width and 0.5m layer height are available for melting as in example 1, the melting chamber inlet 12 is located at the bottom 1 (see Figure 11), but the heating is again electric, but the heat sources allow achieve an average dissolution temperature of only 1300 ° C. Due to the similar composition of the glass and the same raw materials used, the same temperature dependence of sand grain dissolution time was used as in Example 1. A reference case was also solved, although it was assumed that lowering the average temperature would not have a significant effect on melting space utilization [34] The resulting reference variant yielded the following distribution of electrical power over the electrodes 10.

Table 5

Energy distribution on the electrodes 10 according to their numbering in Figure 6 at the reference heating setting.

Electrodes 1 + 2 3 + 4 5 + 6 Power [kW] 0 0 106.5

The resulting type of flow and the course of critical and similar trajectories did not differ substantially from the flow at 1400 ° C at the reference setting, as shown in Figures 14 and 15. s as a reference case. Figure 15 shows projections of critical and other slowest trajectories for dissolving sand grains into a longitudinal axial vertical section through space as a reference case.

The results of the solution of this reference case are as follows:

Average temperature: 1300 ° C.

Dimensions of the melting chamber 2x1x0,5 m - length, width, height.

Entry 12: Lower.

Electric heating output E: 106.3 kW.

Critical power Ø; 3.78x10 ' ⁶ m ³ s'' = 0.76 / 24h = 0.38 t / (24hm ² ) Average residence time of enamel in space «; 63206 s.

• c ···· a ·· • • * 4 • · « « • • · 9 ♦ r • • · ·· • ··· 9 • ··

»· 9 • ·· • 4 • • • ··· · • > « • »» 4 ·

Average time of sand grain dissolution ^τ ΰ: 10131 s.

IN

Geometric residence time ^T G = 7: 264355 s.

Dead space fraction by enamel circulation mc '· 0.761.

The proportion of dead space after melting grains of sand mo '. 0.840.

Utilization rate of melting space uq: 0.038.

Loss specificity P: 12080 kJ / kg.

The case is very disadvantageous, the lower entrance to space plays a big negative role. There has already been a large proportion of mc dead space, also losses are extremely large, critical trajectory and others are moving near the bottom 1 at low temperatures, the power is consequently very low. The case cannot serve as a reference because of its extreme disadvantage, but it shows the extraordinary effect of an inappropriate type of flow on the efficiency of the dissolution process.

In a further procedure, the powers on the electrodes 10 have been adjusted to create the desired type of optimum flow in the melting chamber. The power distribution is shown in Table 6, while the velocity distribution and critical trajectory along with similar ones are shown in Figures 16 and 17.

Table 6

Energy distribution on the electrodes 10 according to their numbering in Figure 6 at optimal heating settings.

Electrodes 1 + 2 3 + 4 5 + 6 Power [kW] 29.4 34.7 41.0

Figure 16 shows the resulting velocity distribution in a longitudinal axial section through the melting space shown by sections of glass enamel trajectories traveled in 30 s, which is the optimal case. Figure 17 shows projections of critical and other slowest trajectories for dissolving sand grains into longitudinal axial vertical section through space, representing an optimal case.

The results of the optimal variant solution are as follows:

Average temperature: 1300 ° C.

Dimensions of melting chamber 2x1x0,5 m - length, width, height.

Entry 12: Lower.

Electric heating output E: 105.2 kW.

Average transverse temperature gradient 50 K / m, average longitudinal gradient 7K / m, average transverse to longitudinal gradient 7.1.

Critical power: 5.59x10 ' ⁵ mV = 11.23 t / 24h = 5.62 t / (24hm ² )

Average residence time of glass in space *: 17025 s.

Average time of sand grain dissolution: 10599 s.

IN

Geometric residence time ^T G = V: 17895 s.

Dead space fraction by enamel circulation mc '0.049 s.

Dead space fraction after sand grain dissolution m / j: 0.378.

Share of utilization of melting space ud '. 0.592.

_H L ₌

Specific losses: 809 kJ / kg.

The resulting values meet the assumption of power, which at the assumed 25% melting reserve reached 8.42 t / 24h for the entire plant, ie 4.21 t / (24hm ² ). The specific losses in kJ / kg are again very low as expected.

Example 3 (Figs. 18-22)

It is necessary to design a special space for dissolving the glass sand in the white container glass, which will achieve a power of at least 300 t / 24 h at an achievable average melting temperature of 1425 ° C. The required energy was to be supplied as needed by both gas burners f and electrodes 10, but it was sufficient to use only electrodes to cover losses

10. A melting chamber of 6.57 m long and 2 m wide with a melt layer thickness of 1 m, with a total volume of 146 m ^3, will be designed for dissolution. A diagram of the space with the proposed heating of the electrodes 10 in both reference and optimized cases and with the inlet 12 at the bottom of the inlet face is shown in Figure 18a (vertical section along the longitudinal axis) and 18b (horizontal section below the surface). In more detail, Figs. 18a, 18b show a schematic of a proposed melting chamber with heating of the electrodes 10 and the location of the electrodes 10 in sections XZ (a) and XY (b).

Table 7 shows the energy distribution of the electrodes 10 according to their numbering in the figure over their sources in the reference arrangement even in the first optimized case.

····· · · ···· · · · · ·

Table 7

The energy distribution on the electrodes according to their numbering in Figure 18 at the reference and first optimized variant of the heating setting.

Elektrodv 1 -2 3-4 5-6 7-8 9 - 10 11 - 12 13 - 14 15-16 20-21 22-23 23-24 25-26 Performance Ref. 0 0 0 0 0 0 0 0 117.7 117.7 117.7 117.7 Odí. 14.8 19.7 24.6 39.4 49.2 49.2 49.2 49.2 49.2 49.2 49.2 49.2

The resulting velocity distribution in the longitudinal axial section through the melting space shown by the enamel trajectory sections traveled in 30 seconds in the reference case is shown in Figure 19 and the projections of critical and other slowest trajectories for dissolving sand grains into the longitudinal axial vertical section through space also in the reference case are in Figure 20.

Figure 19 shows the resulting velocity distribution in longitudinal axial section through the melting space 10 shown by sections of glass trajectories traveled in 30 s as a reference case.

Figure 20 shows projections of critical and other slowest dissolution trajectories,. . sand grains in longitudinal axial vertical section through space as a reference case.

The results of the reference case are as follows:

Average temperature: 1425 ° C.

Entry 12: Lower.

Dimensions of melting chamber 6,57x2x1,0 m - length, width, height.

Heating power: 471.0 kW.

Critical power ΰ 2,20x10 ' ⁴ m ³ s ^_1 = 44,1 t / 24h = 3,35 t / (24hm ³ ) Average time of enamel residence in the space «; 36 450 s.

Average time of sand grain dissolution: 2433 s.

P

Geometric residence time ^r c = Ø: 59 875 s.

Dead space fraction by enamel circulation mc '· 0.391.

Proportion of dead space after melting grains of sand mc. 0.933.

Use of melting space up: 0.041

Specific losses V ^L = 924 _: kJ / kg.

The resulting values characterize well the classic glass melting furnace. The relatively high specific power is again given by the fact that it is the critical (maximum possible) power of the space and the process only involves the dissolution of sand grains.

In the next procedure, based on past calculations on the model melting space and the experience gained, a new distribution of the energy supplied to the electrodes K) was proposed, which is shown in Table 7 for the optimum case. The resultant distribution of velocities in the longitudinal axial section through the melting space shown by sections of the enamel trajectories traveled in 30 s in the first optimized case is shown in Figure 21 and the projections of critical and other slowest trajectories for dissolving sand grains into the longitudinal vertical vertical section through space. also in the first optimized case are shown in Figure 22.

The results of the first optimized case are as follows:

Average temperature: 1425 ° C.

Entry Π: Lower.

Dimensions of melting chamber 6,57x2x1,0 m - length, width, height.

Heating power: 492.3 kW.

An average transverse temperature gradient of 55 K / m, an average longitudinal gradient of 10 K / m, an average transverse to longitudinal gradient of 5.5.

Critical power Ř: 2,97x10 ' ³ mV = 597 t / 24h = 45,4 t / (24hm ³ ).

Average residence time of enamel in space? Average time of sand grain dissolution: 1795 s.

Geometric residence time ^τ 6 = Ø: 4419 s.

Dead space fraction by glass circulation m <j: 0.096.

Proportion of dead space after dissolution of grains of sand mn. 0.551.

The utilization rate of the melting space for _D : 0.406

Specific Loss = 71.2 _: kJ / fcg.

The resulting values provide an unexpectedly high dissolution performance of the melting chamber. This is due to an increase in the utilization of the melting space by one order compared to the reference case. Lower values of the average dissolution time of the sand grains show that the dissolution in the optimized case took place under more favorable temperature conditions. The high performance of the equipment results in very low specific losses. If we add about 16% melting reserve, the space would provide a dissolution capacity of 500 t / 24h. However, a utilization value of 0.41 shows that the space flow can still be optimized.

In subsequent steps, the melting power distribution on the electrodes 10 has been altered to extend the residence time of the glass that corresponds to the critical trajectory. Two other cases with optimized energy distribution to individual electrode pairs were calculated. The second variant achieved a significant improvement in utilization, the third variant differed from the previous 5 very little, so the utilization was close to the optimal value. The third option was thus taken for the final. The distribution in the third optimized variant is in Table 8.

Table 8

The energy distribution on the electrodes 10 according to their numbering in Figure 18 at the third 10 optimized heating adjustment variant.

Electrodes 1 -2 3-4 5-6 7-8 9 - 10 11 - 12 13 - 14 15-16 20-21 22-23 23-24 25-26 Performance Ref. 0 0 0 0 0 0 0 0 25 25 25 25 Oot. 10.0 9 9 8 8 7 7 6 9 9 9 9

The resulting velocity distribution in the longitudinal axial section through the melting chamber and the projections of the critical and other slowest trajectories for dissolving sand grains into the longitudinal axial vertical section through the space are very similar to the first optimized case.

The results of the third optimized case are as follows:

Average temperature: 1425 ° C.

Entry 12: Lower.

Dimensions of melting chamber 6,57x2x1,0 m - length, width, height.

Heating power: 507 kW.

Average transverse temperature gradient 55 K / m, average longitudinal gradient 8 K / m, average transverse to longitudinal gradient 6.9.

Critical power Ø; 4,39x10 ' ³ m ³ s'' = 881 t / 24h = 67 t / (24hm ³ )

Average residence time of enamel in the space «: s.

Average dissolution time of sand grains L): 1782 s.

IN

Geometric residence time = V: 2994 s.

Dead space fraction by glass circulation ιηρ 0.164.

Dead space ratio after sand grain dissolution m /,: 0.288.

Share of utilization of melting space uq '. 0.595

4 • ·

Specific losses: = 49.7 kJ / kg.

The resulting values show extremely high performance and very low specific losses. The proposed space with optimized spiral flow therefore has a very high ability to dissolve glass sand even after considering a considerable melting margin. The case shows that the dissolution of glass sand in a given space under given conditions cannot very likely become an event limiting the intensity of the entire melting process.

Example 4 (Figures 23 to 24)

There is a melting chamber heated by three pairs of cross-burners 11 for melting soda-lime glass and pressing to produce domestic glass products. The device has a length of 6 m and a width of 2 m in the melter. The height of the glass level 6 is 0.6 m. Its required output should be substantially increased to around 30t / 24h. The average melting temperature is about 1400 ° C. A diagram of half of the original apparatus is shown in Figure 21. Figure 21 shows the original glass melting furnace in longitudinal axial section. In the original configuration, the heating energy was distributed to the individual burners 11 according to Table 9. The numbering in the table is from left to right as shown.

Table 9

The energy distribution over the three pairs of burners 11 according to Figure 23 from left to right at the original burner setting 11 and the reference case is as follows:

Output of the first pair of burners 11: 637 kW. Output of the second pair of burners 11: 700 kW. Output of the third pair of burners 11: 750 kW. Total burner output: 2087 kW.

Electrode input: 0 kW.

The results of the reference case are as follows:

Average temperature: 1400 ° C.

Input 12: With surface charge.

Dimensions: length 7.2 m in total, length of melting section 5.2 m, width 1.65 m, enamel depth 6 is

0,6 m.

Critical power É; 6.47x10 ' ⁵ ncs' ¹ = 2.52 bpm (m ³ 24h) = 13 bpm.

IN

Geometric residence time ^τ ο = V ': 79598 s.

Share of melting space utilization uq '· 0.059.

"O _

Specific energy consumption ' ^X P: 13866 kJ / kg.

The resulting values indicate a small space utilization, which is also reflected in the low melting capacity of the plant. In the present arrangement of the burners 11, however, it was not possible to substantially influence the flow pattern in the desired direction. Therefore, the heating system has been reconstructed by placing 14 vertical electrodes 10 from the bottom 1 in the longitudinal axis of the melting chamber. Thus, the necessary longitudinal temperature barrier in the glass melt and the desired type of spiral glass flow have been created. Dissolution of sand grains was considered a critical process. The resulting melting process arrangement is shown in Figure 24 and the energy distribution between the burners 11 and the electrodes in Table 10. By re-setting the transverse spiral flow required in the region of the electrodes 10 was achieved.

Figure 24 shows the arrangement of the burners 11 in the melting chamber in an optimized case.

Table 10

Energy distribution to burners according to their numbering in Figure 22 in optimized torch and electrode settings.

Electrode input: 1400 kW (1-2 -> 308 kW electrodes; 3-4 -> 266kW electrodes; 5-6 -> 210kW electrodes; 7-8 -> 168kW electrodes; 9-10 -> 112kW electrodes; 11- 12 -> 70 kW; electrodes 13-14 -> 70kW; electrodes 15-18 -> 98kW)

Burner output: 16.8 kW

The results of the optimized layout are as follows:

Average temperature: 1425 ° C

Input 12: With surface charge.

Dimensions of the melting chamber: length 7.2 m in total, length of the melting section 5.2 m, width 1.65 m, enamel depth 0.6 m.

Heating output: 1400 kW on electrodes 10, 16.8 kW on burners 11.

Average transverse temperature gradient 55 K / m, average longitudinal gradient 12 K7m, average transverse to longitudinal gradient 4.6.

Critical power É; 1.81x10 ' ⁴ mV = 7.05 t / (m ³ 24h) = 36.3 t / 24h V

Geometric residence time = P: 28453 s.

Share of melting space up. 0.239.

Specific energy consumption * * P: 3335 kJ / kg.

The melting power of 30t / 24h can be achieved at the given setting in Figure 24 and Table 10 at about 17% reserve. This reserve is not too high, but at steady-state operates sufficient. Although the specific melting capacity of 3.02 t / (24hm ² ) is 2.8 times higher than the reference setting, it is relatively low compared to the previously mentioned cases. The problem is in the existence of a layer of trunk on the surface that does not allow the desired spiral flow to develop fully. However, the furnace operates in both cases uneconomically in terms of energy consumption; in the optimized case, the burners 11 can be eliminated and the furnace operated as an all-electric furnace.

In the majority of cases mentioned in the examples, extremely high dissolution rates of the designed space were achieved. However, the results cannot be automatically applied to the entire melting process. It is a realization of only one melting process, the dissolution of sand grains, in a situation where the melting space has no reserve. The performance of such a special melting chamber can then be further reduced, but not substantially [31], considering the refining process as a further process. Essentially, however, the performance of the melting chamber can be reduced if the batch is also converted into glass in the same chamber, which is finally apparent from the results of Example 4. As the melting performance limitations are removed by optimizing the glass flow, the melting process of the charge conversion and the entire dissolution capacity of the space will not be utilized unless the charge conversion rate is increased. Nevertheless, specific melting capacities higher or significantly higher than 10 t / m ³ 24h can be expected. Major efforts should then be made to increase the conversion capacity of the batch to glass.

• ·

Reference plates Base wall Rear flow wall Side walls Vault Enamel Submerged transverse dam wall Transverse row 9 Power sources Heating electrodes Industrial burners Inlet outlet * »

3If. ··

Literature

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$ 5 • ·

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35. Cincibus, P., Nemec, L .: Accepted in: Eur. J. Glass Sci. Technol. A, 53 (2012).

36. Polák, M .: Unpublished Results.

Claims (4)

PATENT CLAIMS A method of continuously melting glass by controlled glass convection, wherein a molten glass comprising undissolved particles, in particular glass sand, is present in a horizontally oriented flow melting chamber of a glass furnace by energy sources such as industrial glass burners, heating electrodes and other suitable heating energy sources, characterized in that the energy sources act in the melting chamber in at least one row along the longitudinal axis of the melting chamber, or parallel to the longitudinal axis, and cause a spiral flow of glass (6) with circular motion across the melting portion which progresses from the front foundation walls (2) to the transverse dam wall (7) in the glass (6) or transverse row (9) of the energy sources, wherein the transverse temperature gradient of each spiral flow is always higher than its longitudinal temperature gradient between the transverse dam wall (7) or a transverse row (9) of energy sources and a facing front loading wall (2). 2. A method according to claim 1, wherein the ratio of the transverse temperature gradient to the longitudinal temperature gradient is in the range of 1 to 30. 3. A method according to claim 2, wherein the ratio of the transverse temperature gradient to the longitudinal temperature gradient is between 5 and 20. Process for continuously melting glass by controlled glass convection according to claim 1 or one of claims 2 to 3, characterized in that the spiral glass flow passes through the melting chamber, whose use for dissolving particles, in particular glass sand, amounts to 0.6 to 0.8 from the total melting space defined by the height of the glass (6), the length between the transverse dam wall (7) in the glass (6) or the transverse row (9) of the energy sources and the facing base (2) and width between opposite side walls (4).