Furnace Aggregate

Technology Field

This solution deals with new construction of sidewalls and ceilings of furnace aggregates, such as continuous tunnel-type and periodic chamber-type furnaces and applications for ceramic industry, sphere of construction materials.

Existing Conditions of Technology

In the 19 ^th and 20 ^th centuries, firing of construction elements, such as burnt bricks, brick blocks or roof coverings has undergone rapid development from chamber furnace where the original heating medium was wood, via circular furnaces with heating medium coal to continuous tunnel furnaces with heating media coal, furnace oil or gas. Common feature of these firing aggregates was unalterable construction and material used for building these applications. Sidewalls and ceilings of these firing aggregates were built of ceramic firebricks joint by refractory mortar.

Intermediate stage of the development was construction of horizontal, suspended ceiling of these aggregates, which, increased capacity of the plants and facilitated implementation of automation for loading and unloading of goods being fired.

Another stage of development of the firing aggregates construction in the 50s of the 20 ^th century was implementation of refractory concrete for construction of sidewalls using ceramic fiber plates and mats for additional insulation of these aggregates. This development, i.e. implementation of new

materials, resulted in reduced volume of the firing aggregates ¹ sidewalls, accelerated assembly works and overall reduction of costs for building these aggregates.

The most progressive solution is the system of monolithic segments, cast directly on site into metal-sheet trapeze modules where the sidewalls and ceiling form a single unit. This solution is represented by the French company CERIC.

Even though this solution was an indisputable progress, in particular in reducing costs for construction of furnace aggregates, when this solution was adopted in Europe, America and Africa, more than 20 years of experience with operation revealed certain deficiencies. These include especially the lifetime and subsequent problems with repairs of these plants. Despite clear advantages of refractory cements with high content of clay, concretes tend to dehydrate in the course of time and due to harmful pollutants from firing the ceramic materials and repairs using additional concreting or shotcreting (Torkret method) are rather short-lived. Lifetime of these furnace aggregates is limited by the lifetime of refractory cast linings.

Principle of the Invention

Disadvantages mentioned above are eliminated by a furnace aggregate consisting of two sidewalls, ceiling formed by modules of ceramic fiber mats, input and output gates, where this furnace aggregate is in direction from the input gate divided into pre-heating, firing and cooling zones. The subject matter of the new solution is that the sidewalls are in their lower parts, to the height of inserted carriage with material to be fired, formed by lines of alternately laid large-format ceramic blocks equipped vertically and horizontally with interlocking joints and with continuous openings in vertical direction. Distance between centers of these openings is L and distance of centers to the closer

edge of the large-format ceramic block is L/2. Above these lines of blocks is a labyrinth created from minimum one line of sidewall stones with interlocking on both sides or of interlocking plates. Above this labyrinth are again lines of alternately placed blocks with continuous openings.

From the outside of the furnace the labyrinth and lines of blocks created above it are covered by lining made of insulating bricks. Such aligned sidewall is covered with ceramic fiber insulation, insulation plates and outer encasement, all this mutually connected and stabilized by fireproof steel anchors.

Encasement of large-format ceramic blocks, i.e. the furnace sidewalls, is in the cooling zone of the furnace equipped with horizontal inlet piping with fan and has incoming branch pipes to inner space of continuous openings in line of blocks above the labyrinth and outgoing branch pipes from continuous openings in the last, uppermost line of blocks to the horizontal outlet piping. Sidewalls created as described are at their top edge equipped with fireproof reinforcement and inner side of this reinforcement is equipped with interlocking joints for mounting the ceiling onto the sidewalls. Ceiling is formed by module assemblies made of ceramic fiber mats equipped on sides with interlocking joints, which are placed close next to each other and allow mutual connection.

A single module assembly is formed by two modules fitted together by the interlocking joints, which are made of ceramic fiber mats mounted to at least one ceramic anchor. For securing their position the ceramic mats are horizontally traversed by at least one spike, which passes through at least one opening formed in the body of ceramic anchor and through coaxially placed at least one puncture formed in ceramic fiber mat.

Anchors are led outside the ceramic fiber mats by means of a head adjusted for mounting the assembly to a welded structure from pressed profiles located above each line of ceramic fiber mats in direction of longitudinal axis of

such line. Thus created module assemblies have ends adjusted for settling to the interlocking joints on sidewalls reinforcement of the furnace aggregate.

Top surface of module assemblies is in most cases equipped with covering layer of chemically and heat resistant PVC foil, in particular in cases where protection against steam permeability must be ensured, where reducing atmosphere, overpressure in furnace are present, etc. This covering layer also facilitates cleaning of the furnace aggregate ceiling.

As an advantage, the continuous openings in pre-heating and firing zones may be filled with bulk or loosened insulation material.

Outer encasement of sidewalls is made either by lining from facing front bricks attached to the basic support and insulation part of the sidewall by refractory anchors or by "JeM" four-sided profiles anchored to the floor and covered by corrugated or trapeze metal sheet.

In one possible arrangement the ceiling module assemblies are equipped on their bottom part with a layer of protective coating.

In another possible arrangement the ceiling module assemblies are equipped on their bottom part with multilateral mutually interlocking cover plates made of insulation refractory material anchored in the body of module assembly. Cover plates are installed in cases where composition of exhausts formed during the firing process is so aggressive that the exhausts have destructive impact on the ceiling modules, on ceramic fiber mats.

Profiles are advantageously formed by a pair of U-profiles oriented with their backs to each other where the space between them accommodates the anchor heads. Such heads and U-profiles have coaxial openings perpendicular to the longitudinal axis of module assemblies, through which is led a ceramic stick to secure them in position. Conveniently, the profiles of one module

assembly are mutually connected by supporting beams for mechanical handling with the assembly and also the profiles of adjacent module assemblies are mutually connected by tightening bolts.

The advantage of presented solution, considering the sidewalls construction, is in particular the reduction of volume as well as volume mass of these sidewalls - roughly by one half compared to traditional lining and by one third compared to assembly duration. Another advantage of new sidewalls is more effective and faster cooling, exploitation of waste heat and possibility to shorten the cooling zone. Reduced construction costs and energy demands of the plant are also not a negligible advantage. Sidewalls allow fast repairs and re-lining without the need for long downtimes of the furnace and for dismantling its accessories.

Considering the new construction of ceiling, by far the greatest advantage is elimination of demanding support structures for the construction. Quality is increased and on-site labor intensity is reduced because the module assemblies are mounted on welded structures from profiles with anti-chemical and anti-corrosive treatment already at the production plant and on-site they are only settled into reinforced refractory concrete sidewall head lintels into created interlocks and tightened together by tightening bolts.

All this contributes to increased pace of assembly works and to final reduction of costs. As a consequence, new construction of the furnace ceiling ensures also its longer lifetime.

Overview of Figures in Drawings

Example of arrangement of the presented solution is schematically outlined in the attached drawings. Fig. 1A and 1 B show two views of vertically and horizontally interlocking ceramic large-format block and fig. 2A shows

interlocking sidewall stone and fig. 2B shows interlocking plate. Fig. 3A represents cross section through the continuous tunnel furnace and fig. 3B offers axonometric view on part of the sidewall equipped with cooling system. Fig. 4 schematically outlines forming of the ceiling of the continuous tunnel furnace. Fig. 5 outlines front view on module assembly of ceramic mats with anchors led between the U-profiles connected by flat cross beam, fig. 6 then shows construction of sidewalls and ceiling of continuous tunnel furnace.

Example of the Invention Application

Based on experience with operation and repairs of furnace aggregates bodies built upon existing systems, a new system of construction of sidewalls and ceiling of furnace aggregate is designed, in particular for continuous tunnel furnaces for ceramic industry.

Continuous tunnel furnace consists of two sidewalls, ceiling formed by modules made of ceramic fiber mats and finally of input and output gates. In direction from the input gate, the furnace is divided into pre-heating, firing and cooling zones.

Firstly, construction of the furnace sidewalls will be described, where fig. 3A represents cross section through such sidewall and fig. 3B shows axonometric view on part of the sidewall equipped with cooling system. The sidewalls are in their lower parts, to the height of inserted carriage with material to be fired, formed by lines of alternately laid large-format ceramic blocks 1 equipped with vertical and horizontal interlocking joints, hereinafter referred to as the blocks 1, which have continuous openings 2 in vertical direction, as shown in fig. 1 A, 1 B and 3B. Distance between centers of these openings 2 is L and distance of center of given continuous opening 2 to the closer edge of the block 1 is L/2.

Above these lines of blocks 1 one or more lines of both-sided interlocking sidewall stones 3 are created, in this case a single line, see fig. 3A, which in direction to the inside of the furnace is offset by width of insulation brick 4. In presented example this is the 4 ^th line from the sidewall base. The purpose of this line of interlocking sidewall stones 3 is to create a labyrinth, which will decrease ambient temperature and contributes to protection of steel structure of furnace carriage. In tunnel furnaces designed for higher temperatures the labyrinth may be doubled and formed for instance by interlocking plate 3_1, fig. 2B. Above this line of interlocking sidewall stone 3 are again lines of alternately placed blocks 1 with continuous openings 2. Sidewall insulation is provided from outside the furnace where the insulation lining of the line of blocks 1 is made onto the line of interlocking sidewall stones 3. This insulation lining will substantially ensure steep and efficient insulation of the sidewall, in particular in the firing zone of the furnace body. Such aligned sidewall is on the whole of its area covered with ceramic fiber insulation 5, for instance with sibral mat 13 - 30 mm thick for temperature up to 1250 °C. Thickness of the mat is to be determined upon calculation of heat transmission. Onto the ceramic fiber mat 5 are applied insulation plates 6, for instance ROCKWOOL for temperatures ranging from 600 ⁰ C to 700 ⁰ C, which are covered by outer encasement 7. In given example, the outer encasement 7 is realized by lining made of decorative front bricks 16, 115 mm wide. Outer encasement 7 is connected with the base and insulation parts of the sidewall by anchors made of fireproof steel formed for instance by wires or bands with maximum thickness 2 mm. Outer encasement 7 may also be created by other means, for instance by "Jekl" four- sided profiles anchored to the floor and the sidewall finish is then realized by covering using corrugated or trapeze metal sheet. This encasement 7, apart from creating aesthetic finish, serves also as a support for burners, cooling, fans, measuring or regulation devices.

Continuous openings 2 inside the refractory sidewall, in the cooling zone of the furnace sidewalls, serve for heat distraction from these sidewalls, indirectly they also increase cooling effect of this zone.

Encasement 7 is in the cooling zone of the furnace, fig. 3, equipped with horizontal inlet piping 8 with fan, which is not shown in the drawing. Inlet piping 8 has incoming branch pipes 8J., which are usually led perpendicular, to inner space of continuous openings 2 in line of blocks 1 placed above line of sidewall stone 3 and then it is led by outgoing branch pipes 91 from continuous openings 2 in the last, uppermost line of blocks 1 to the horizontal outlet piping 9.

In pre-heating and firing zones of the furnace it is advantageous that the continuous openings 2 are filled with bulk or loosened insulation material, which increases insulation properties of mentioned parts of sidewalls of the furnace aggregate, thus eventually decreasing power consumption.

Binding material for individual vertical layers of sidewalls, it means for ceramic blocks 1, ceramic fiber insulation 5 and insulation plates 6, designed in given example is a sealant maximum 2 mm thick, for instance ALU 1250 or other equivalent. For lining made of insulation bricks 4 was used mortar supplied by manufacturer of these insulation bricks 4.

Basic element of the sidewall is therefore the supporting, mutually vertically and horizontally interlocking ceramic large-format block JL Continuous openings 2 created inside the. block 1 allow faster cooling of sidewalls and products located in the cooling: zone of the furnace aggregate, faster and energetically less demanding heating and firing in pre-heating and firing zones of the furnace.

Size of ceramic large-format blocks 1 is determined as optimum ratio between mass and speed of assembly with respect to stability of sidewalls and it can be adjusted according to specific conditions. The same applies to dimensions of vertical openings 2 and size of mutual interlocking.

Pre-heated air warmed by means of vertical openings 2 in the cooling zone, where cold air is blown in, cools down the sidewalls as well as the goods and simultaneously it serves in the pre-heating zone of the furnace aggregate for drying, or, due to its purity, it may be used as air for burners.

Sidewalls created as described are at their top edge terminated with reinforcement 20 made of refractory concrete and inner side of the reinforcement is equipped with interlock for mounting the ceiling on sidewalls.

Ceiling, fig. 4, is formed by module assemblies made of ceramic fiber mats IQ equipped on sides with interlocking joints, which are placed as completed units by minor mechanization on site onto assembled and reinforced ceiling.

Module assemblies assembled in the production plant consist of welded structures from lightweight steel profiles with anti-chemical and anti-corrosive treatment, on which the modules of ceramic fiber mats 10 are suspended by means of ceramic or steel anchors.

Each module assembly, fig. 5, is formed by two parallel lines of ceramic fiber mats 10 interlocked by interlocking joints traversed by minimum one ceramic anchor 12 located at a given line in parallel with them.

Mutually coaxial ceramic fiber mats 10 forming the modules have in their bodies at least one puncture H and ceramic anchors 12 are equipped with openings Hl located coaxially with these punctures V\_. Given example contains three punctures H and openings Hl, through which spikes 13 are traversed serving for connection of ceramic fiber mats 10.

Ceramic anchors 12 are led outside the ceramic fiber mats 10 by means of a head J4 adjusted for mounting the assembly to a welded structure from pressed profiles 15 located above each line of ceramic fiber mats 10 in direction

of longitudinal axis of such line and having their ends adjusted for settling to the interlocking joints on reinforcement 20. Reinforced interlocking of sidewalls simultaneously prevents heat transmission to the outside environment.

In given example this is realized using profiles 15, which are formed by a pair of U-profiles oriented with their backs to each other and the space between them accommodates the heads 14 of ceramic anchors 12. Each head 14 and U-profiles have coaxial openings perpendicular to the longitudinal axis of module assemblies, through which is led a ceramic, or optionally from also anti- corrosive steel, stick 18 to secure their mutual position. Top surface of module assemblies is already in the production plant equipped with covering layer 21 of chemically and heat resistant PVC foil.

After assembly, the ceiling module assemblies are equipped on their bottom part either with a layer of protective coating of special engobe or with multilateral mutually interlocking cover plates 17 made of insulation refractory material anchored in the body of module assembly. Top parts of individual profiles 15 are mutually connected by supporting beams 19, which allow their easy handling during settling to the interlock of reinforcement 20, see fig. 5.

Mutual connection and sealing as a protection against heat transmission through module assemblies is best solved by mutual tightening and possibly also by other tightening of supporting steel welded structures by tightening bolts, which are not shown in the drawings. These tightening bolts simultaneously allow to regulate required dilatation joints between the module assemblies during operation of furnace aggregates.

Covering layer 21 of module assemblies is formed by PVC foil, mutually glued by plastic sealant. In case of overpressure in the furnace aggregate this solution eliminates possibility of exhausts leaking to the atmosphere and from the other side it covers and prevents the ceramic module assemblies from depositing of wastes. It allows easy regular cleaning of outer surface of the

furnace aggregate ceiling using industrial vacuum cleaner without any problems.

The basis of new construction of the ceiling is therefore implementation of ceramic fiber mats 10 arranged in modules where these ceramic fiber mats 10 have special shape, which allows their mutual interlocking and assembly of module assemblies on a steel structure of surface treated welded structure made of pressed sheet, for instance advantageously in a form of U-profiles. This solution allows that the ceiling module assemblies, assembled already in the production plant, are placed by minor mechanization directly on site onto assembled sidewalls of the furnace aggregate. Such design of the ceiling combines in one unit both refractory construction and insulation protection. Supporting structure for module assemblies may serve for installation of technology for heating, cooling and regulation of furnace aggregates. Fig. 6 schematically shows connection of the ceiling and sidewalls of the furnace aggregate.

Industrial Applicability

Proposed solution of bodies of firing aggregates has greatest usability in ceramic industry, for new constructions, in the sphere of low-cost, fast and efficient repairs and reconstructions, especially for bodies of furnace aggregates designed on the basis of refractory concrete lining. It is a system of tunnel, i.e. continuous and chamber, periodic furnaces.

The system of the ceiling design using module assemblies manufactured in the production plant may be successfully applied also in the sphere of aggregates in metallurgy, foundry and steel industry, which predominantly exploit ceramic modules without interlocking, which are individually assembled and mounted directly into the construction of given aggregates.