DE102011100736A1 - Method for operating e.g. tunnel furnace used for firing brick, involves directing exhaust gas stream from tunnel furnace to waste heat boiler for generating electric power utilized for drying and heating processes of furnace - Google Patents

Abstract

The method involves directing exhaust gas stream (112) from a tunnel furnace (3) to a waste heat boiler (113) for generating electric power from the exhaust gas stream. The generated electric power is utilized for drying and heating processes of the tunnel furnace in several stages. The waste heat boiler is arranged downstream of the tunnel furnace and connected to steam turbine (115) and generator (116) for generating electric power. An independent claim is included for tunnel furnace.

Description

Coupled method for the production of structural ceramic product using a tunnel furnace with integrated Schwellgasverbrennung and heating with solid fuels, also with high content of volatile components and biogenic solid fuels for continuous, simultaneous generation of electrical energy and drying energy from a high temperature exhaust gas stream of the tunnel furnace by steam process.

Building-ceramic products such as bricks are mass-produced products for the creation of durable, ecologically as well as economically, because durable buildings. The manufacturing plants have undergone a long development to their present state, which takes place in largely mechanized processes and is used as the heating medium oil or gas dominant, in addition to electric power to drive the extensive work machines. As a mass building material, bricks can only be produced laboriously with high energy costs. Thus, the call for outdoor drying already takes place in the professional world, in addition to the discussion about the adverse circumstances of oil and gas firing of tunnel kilns ((( Brick and Tile Industry No. 9/09 - Dr. Ing. Vogt - especially page 28-31 ) and the consequences for the thermal efficiency of the kilns, which too often leads to excess heat for the dry process. Waste heat removal is often a way out or the helpless discussions to store waste heat.

With the invention of the ring furnace by Hoffmann, this continuous, fuel - saving firing process quickly prevailed. The result was an exhaust gas flow of low temperature using mostly coal, peat or wood as scattering. The equilibrium heat balance between the heating zone and the cooling zone was easy to produce since solid fuel scavenging did not require primary air.

With the introduction and development of the tunnel kiln, which was used per se, more and more high-speed burners were used to fire them in order to increase the heat transfer in the furnace chamber and to increase the kiln capacities. This measure had become necessary because the too dense block trimmings of the burning material on the firing cart had too few heat transfer surfaces in most cases. Instead of eliminating the causes and creating larger heat transfer surfaces now the bad heat balances are complained.

With the introduction of steam engines found in the brick production, these also have their entrance next to the continuous ring furnace (Hoffmann). The boil-off heat was used for the drying of bricks in artificial drying plants. This combined heat and power was abandoned in the course of the cost of fuel and replaced by externally sourced electrical energy for cost and convenience reasons. Thus, from today's perspective, the course is worth considering back.

In addition to combined heat and power, but in an advanced way, the introduction of solid fuels, especially renewable or other waste fuels is to be considered, which requires a redesign of the furnace systems and process engineering in general.

The earlier "steam bricks", as they called themselves, had two combustion plants, the "steam boiler" and the "kiln", which required two exhaust gas streams with corresponding exhaust gas losses and also operating effort. Furthermore, relatively good coals were required for operation. In no case these would be with waste fuels such. As paper cellulose, straw or washing mountains to operate.

However, such a task is today to maintain a mechanized, economical brick production in developed emerging and developed countries.

According to the newer state of the art, using the teachings of:
DE 10 2007 003 683 B4
DE 10 2007 003 684 A1
DE 10 2007 003 041 A1
The burning of porosity and nonporous bricks in tunnel kilns and the use of coal, wood and cellulose waste from a paper mill results in primary energy savings of 60-70% of oil and natural gas respectively. The solid fuel is used via the stove device and the Ziegelporosierung. In addition, the integrated, thermal exhaust gas purification with the recuperator device could not prevent a too rapid, premature increase in temperature in the Anwärmzone. Both the Porous Bricks (S. Vogt) and the Cellulose Briquettes in the Stove Device provide early ignition under the conditions of countercurrent in the tunneling zone of the tunnel kiln

Also the EP 2017327 A1 does not expect a higher use of biogenic fuels to avoid the use of oil and gas from this teaching. It is essentially a summary of the three specified documents and z. As the teaching of DBGM 298 20 322.7.

The object of the invention is to specify a tunnel or continuous flow furnace or a dryer-oven line with which it is possible, their heating needs up to 100% with To cover solid fuels. It is also intended to keep high ash from the fuel, so that the achieved quality standard, as otherwise achieved with gas or oil firing in tunnel kilns, is maintained. It must be avoided premature increase in temperature for the fuel in the Anwärmzone, even using high proportions of early-ignition biogenic fuels z. As straw briquettes or cellulose pellets in the stove device DE 10 2007 003 683 B4 ,

In addition, the new tunnel kiln should provide a continuous exhaust gas flow of such high temperature (about 700-800 ° C) that it can be used to heat a waste heat boiler for steam generation, with turbine and generator operation to produce electrical energy for own use and grid feed.

The dry heat for the brick drying and fuel drying should also be obtained from the novel, thermal process process. The new tunnel kiln should also with less fluctuating temperature conditions on different, consecutive kiln car loadings with different brick stock z. B. porosierte and unporosierte bricks react.

Since the energy costs for brick production have already reached 40% with oil and gas, it is necessary to fully operate this level with cheaper, renewable or industrial waste fuels.

The central part of the system will be a suitable, new tunnel kiln, which, in addition to the burning of bricks in a first high-temperature stage at about 1000-1200 ° C, the production of electric energy via a waste heat of about 800-400 ° C. Finally, the waste heat from it is again used in a third temperature stage as a heat source for drying bricks and solid fuels at about 200-100 ° C. Thus, less expensive rejects have about 50% water content at about 14,000 kJ / kg dry matter, which requires considerable dry heat.

The new tunnel kiln now has a double function - namely the production of electric energy and fired bricks, whereby this is largely CO2-free through the use of solid fuels with a low calorific value, as well as with biogenic heating fuels.

The use of the fuels used takes place in 3-stage combined heat and power and that

BURN-ELECTRICITY-DRYING OPERATIONS

The previous, proposed methods and devices of the integrated, thermal emission control are not suitable for the task acc. the invention such. B.
EP 0355 569 A2
DE 3042708 A1
DE 352771 A1
DE 2653118 C2
DE 2643406 C3
DE 2641674 C2
DE 3215209 A1

These do not allow decoupling of exhaust gas quantity and exhaust gas temperature level in relation to the furnace throughput capacity. Furthermore, the use of early-ignitable, biogenic fuels or low-value, fossil solid fuels is thus not possible under previous product standards.

With reference to the accompanying drawings, the invention is exemplified.

It means:

1 : Top view of a tunnel kiln, by way of example with flow pattern and upstream drying channel "A"

2 : Cross section through the heating zone of a tunnel kiln - as an example

3 Flow chart of an entire production plant with fuel preparation and composite production of brick firing and simultaneous generation of electrical energy

4 : Scheme of the 3-stage combined heat and power burning power drying with temperature grading

The well-known tunnel ovens with integrated, thermal exhaust gas purification do not allow to achieve a near 100% use of early flammable fuels, which still has to be heated significantly to oil or natural gas for the main combustion zone. Furthermore, the carbonization gases generated in the tunnel furnace are kept too short in the high-temperature zone and can not develop their energy content enough to increase the temperature in the combustion zone. Also, the exhaust gas paths of high temperature are too short for a good thermal emission control when highest Schwellgasmengen develop in the oven. The external thermal exhaust gas purification device are more widespread in ceramic tunnel ovens than furnace-integrated methods, although the former are energetically and economically disadvantageous, but also on the Encouragement and preference of German brick researchers could have lain.

In the present development step of the replacement of oil and gas for a cost reduction in the production of building materials by cheaper solid fuels emerging gases in the furnace for heating the high temperature zone should be used directly to the greatest extent possible, not in an external combustion plant with inefficiencies and significant losses.

With today's Schwellgasmengen there were repeated tar fires at different external plants, so that the future quantities would be under no circumstances economically to be mastered.

The already in use, connected "Hässler-method" according to:
DE 10 2007 003 041 A1 - pellet device
DE 10 2007 003 684 A1 - Recuperator Vorrrichtung
DE 10 2007 003 683 B4 - Stove device
have z. B. proven in a new tunnel kiln for clinker with coal, eucalyptus wood and sawdust and biogenic heating and on a converted tunnel kiln for pore tile in Vorarlberg; here with pellets from waste of the paper industry as fuel. In both plants, these innovations replaced about 60-70% oil or gas. But to replace higher rates of oil or gas, especially with highly flammable solid fuels such. As renewable wood, straw cellulose, paint residues, rubber, polyethylene waste, materials from land-forestry and Maritimwirtschaft is a development of integrated, thermal waste gas purification required. This development is just as urgent as it is urgent if the complex burning range of building ceramic products is to be sustainably solved.

The primary consideration is always the burning behavior of the various ceramic products and their raw materials in an oven. So it depends on a uniform heating of the products in the heating zone. A countercurrent furnace system according to this requirement in the case of the stove device. DE 10 2007 003 683 B4 when using z. B. straw briquettes or cellulose pellets no longer comply.

This renewable fuel would burn too early in large amounts and cause a steep rise in temperature of the fuel car and Brenngut.

It is also according to the invention to bring about a systematic and easily manageable heating of the kiln under such extreme, but also desired fuel conditions; even under changing Brenngutfolge in the oven z. B. porosierte brick and unporosierte.

To solve this problem proposes the patent application EP 2017327 A1 To coat fuel pellets with a non-flammable material, which should only disintegrate at 600 ° C oven temperature, despite the onset of ceramic solidification in the already higher tempered fuel bed. Such elaborate pellet production would at least remove a significant cost advantage of the fuel by expelling the water from the casing and another drying device that would be required. The problem of a too rapid increase in temperature at the furnace entrance area when firing highly porous brick would not be mitigated anyway.

The problem of premature degassing and inflammation of the porosity substances in countercurrent tunnel kilns already exists today in the production of highly porous lightweight bricks. One then speaks of two fires in the oven, wherein in the second, the main fire, the carbon remaining in the moldings from the porosity z. B. sawdust, cellulose comes to combustion. Warming damage to the kiln are the result of such, unscheduled heating of the moldings

The use of biofuels reduces CO2 enrichment and can cover the fuel needs of brick factories in agricultural areas, even for larger facilities, whether for masonry, tile or stoneware. The example of a plant for 400 tonnes per day brick output and a factory with straw briquettes, which can be produced with a density of 1.0 kg / dm ³ , 40 t of straw briquettes are needed daily. When growing cereals, about 5000 kg of straw per hectare are incurred. Thus, 8 hectares of straw yield are required at 350 days of operation thus: 350 × 8 = 2800 ha = about 28 square kilometers or a circle of about 6000 m. So you have only about 3000 m transport radius to handle the straw transport. With a straw price of EUR 50.00 / to incur annual costs of 50 × 40 × 350 = EUR 700,000, which accrue annually to local agriculture. In this case, the mineral-containing ash in the cycle according to the method back into the arable land. Oil and gas would cost us three times more than a future carbon tax. Thus, there is a need to specify a new plant and process engineering, with a technical implementation is possible.

Many other, combustible waste materials are constantly available from industry, agriculture and forestry, which are otherwise often expensive to dispose of, but profitable to exploit on the well-known pellet and stove device beneficial. Dusting and emissions are thereby largely avoided, to a greater extent than in conventional industrial furnaces, since a much longer burning time is available for ceramic firing. Above the fuel bed there is minimal movement of the furnace atmosphere, so that little dust is taken, if any escapes from the pellets, as a result of their largely fixed structure during the entire firing cycle, while for normal industrial firing at most one hour is available, stand for the inventive Oven about 10 to 20 hours available

In 1 the tunnel kiln according to the invention is shown as an exemplary embodiment in which with moldings ( 1 ) loaded Brennwagen ( 2 ) are inserted in an upstream drying duct (A) and after the end of the drying phase pass through a preheater (B) and then into the heating zone (C) of the tunnel kiln ( 3 ) to get. The moldings ( 1 ) rest on a stove device ( 4 ) of fuel-filled, known, lined-up trough-shaped cassettes ( 5 ) made of refractory material z. B. chamotte exist. The cassettes ( 5 ) must be made of larger shape than known since then to z. B. from straw, cellulose, bark, etc., to accommodate briquettes sufficient for firing therein, at a density of only 0.8 to 1.0 t / m ³ . This applies to a great many agricultural and forestry, renewable, but also industrial, combustible waste with which according to the method is to be expected for a cost-effective ceramic production. Therefore, the cassettes ( 5 ) According to the invention strung together end-to-end with tongue and groove connection to ensure a straight alignment with the larger size to ensure a reliable, automatic filling and ash removal the same. The deashing and filling device can thus be equipped with stationary suction nozzles ( 124 ) or filling organs ( 103 ) over the firing cars ( 2 ), which passes underneath.

The tunnel kiln is divided according to. 1 in the successive zones "B" to "E", with a drying channel (A) is connected directly, but this is not a condition. According to the invention, the heating zone "C" is operated in cocurrent, in a circulation flow with parallel to the heating zone arranged circulation channels ( 6 ) with the hot gas stream ( 7 ) are fed from the fire zone (D).

Together with the direct current from the heating zone results in the circulation channels independent of the exhaust flow volume flow of hot gases (about 700-1000 ° C), with which over circulating fans ( 8th ) The Brenngutaufheizung demand and the temperature curve fair, be heated. Usually this is the multiple amount of exhaust gas required. Thus, the economically smallest possible amount of exhaust gas at about 4-6% O2 content can be achieved, which in their amount of the hot circulation flow ( 7 ) is decoupled for Brenngutaufheizung. This property did not feature previous tunnel ovens. The exhaust gas flow to be discharged into the atmosphere ( 9 ) can be used to preheat the burning material in the zone "A" and the drying channel "A" or other purposes; so z. B. for drying wet solid fuels, which are needed for the Ofenbeheizung. The exhaust stream ( 9 ) is preferably in the Ofenanfangsbereich from the circulation channels ( 6 ) and cooled to the kiln heating on z. B. about 170 ° C, and for recovery in recuperative or regenerative heat exchangers ( 10 ).

Heating of the furnace is via two or more heat sources. One feeds the heat demand from the, in the cassettes ( 5 ) filled, highly flammable solid fuels ( 11 ) under the fuel burn, as a result of gasification and the subsequent burning of coal. A second heat source according to the invention ensures the fuel supply of the combustion zone to achieve a uniform Garbrandtemperatur. These are refractory, metallic or ceramic heating baskets ( 12 ) on the Brennwagen ( 2 ), which are supplied via heating holes in the furnace roof with dimensionally stable refractory solid fuels, controlling the temperature, as known in the art.

Another, third heat source when burning porosierte bricks are the burnout in the brick mass, usually sawdust. This is also early ignitable, so that this heat source, which is often already alone about 30% of the fuel heat demand to cover, together with the fuels in the cassettes ( 5 ) would lead to premature, excessive Brennwäruterhitzung in a countercurrent furnace.

The heating zone "C" with fired pre-combustion zone "D" under a direct current, with circulating gas flow ( 1 ), the volatiles of the solid fuels from the cassettes and moldings ( 1 ) in the direction of pre-combustion zone "D" ( 1 ), where they reach the ignition and combustion at approx. 600 ° C, depending on the CO and H2 content. There they serve the heating of the kiln which, if possible, only in the main firing zone "D" by heating the firing baskets ( 12 ) - as far as necessary.

The heating of the heating zone From about 170 ° C inlet temperature to about 600 ° C takes place mainly by means of circulating hot gas flow with the circulation fans ( 8th ) that the approximately 800 ° C hot gas via stubs ( 13 ) and exhaust nozzles ( 14 ) in the heating zone "C" from top to bottom in the combustion channel between the Brennwagenbesatz blow in heating slots, in known Beschatzweise.

At the same time, on the kiln section up to 600 ° C., swelling gases are already burning at the 800 ° C. gas jets from the exhaust nozzles (FIG. 14 ) and serve there the steady Brenngutaufheizung. The DC movement in the heating zone "C" prevents, despite a high total use of early flammable solid fuels in previously unachievable amount, an early Brennwäruterhitzung. In essence, the emerging in the Anwärmzone threshold gases burn in the temperature range above about 600 ° C where the dangerous quartz jump range of 573 ° C is already exceeded. Sulfur-containing clays are no longer in danger of discoloration due to high dew point and condensation on colder brick surfaces. The thermal degree of purification of the furnace gases is high because the combustion zone for the swelling gases is long and has a large volume; In addition there is the residence time in the circulation channels ( 6 ). Between circulation channels ( 6 ) and the combustion channel in the region of the heating zone "C" are adjustable connection openings ( 15 ), for temperature grading in the circulation channels and precombustion of swelling gases in de circulation channels ( 6 ).

The rising in direct current Schwellgastemperatur prevents Brenngutverfärbung due to condensation from impure, acidic furnace gases.

The heating of the fuel is done in DC, although slower than in countercurrent, but more linear, which is the ceramic burning anyway fair. Furthermore, so can burn larger amounts of solid fuels in the heating and firing zone, which comes in the coupling operation of the generation of electric energy to good.

Gem. 2 In addition to the three methods already mentioned, it is possible to supply solid fuels to the kiln, and another solid fuel briquette (in 1a ) under the moldings ( 1 ) of the brick stock.

The improvement according to the invention of the thermal efficiency of the production line for ceramic production can be improved particularly in climatically colder zones with long frost periods. For this purpose, a clay bearing ( 133 ) for longer storage periods with a heated floor ( 132 ), so that even frozen clay can be thawed and preheated, with a lower temperature of about 30-40 ° C. The heating medium used is the exhaust air flow ( 13 ) via exhaust ports ( 130 ) is removed from the dryer (A) and in a channel system z. B. plastic pipes of the soil ( 132 ) is passed and condensed in part. The condensate is added to the clay preparation as valuable distilled water. The ventilation floors are cooled down over the extractor chimney ( 134 ) dissipated. The condensate is stored in a container ( 135 ) collected and stored. Due to the internal heating of the dryer results in a smaller amount of exhaust air with the higher water vapor content and higher temperature, so that their heat content for the aforementioned use is economical.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007003683 B4 [0009, 0011, 0029, 0030]
• DE 102007003684 A1 [0009, 0029]
• DE 102007003041 A1 [0009, 0029]
• EP 2017327 A1 [0010, 0033]
• EP 0355569 A2 [0018]
• DE 3042708 A1 [0018]
• DE 352771 A1 [0018]
• DE 2653118 C2 [0018]
• DE 2643406 C3 [0018]
• DE 2641674 C2 [0018]
• DE 3215209 A1 [0018]

Cited non-patent literature

• Brick and Tile Industry No. 9/09 - Dr. Ing. Vogt - especially page 28-31 [0002]

Claims (10)

Method for operating a continuous furnace z. B. tunnel kiln, for firing of ceramics, especially brick, with integrated, thermal exhaust gas purification and exhaust combustion using high and low quality fossil, biogenic solid and waste fuels, characterized in that the kiln no service chimney for the discharge of its exhaust gas stream into the atmosphere and the exhaust gas flow ( 112 ) of the kiln instead has high temperature and for the most part in a waste heat plant ( 113 ) is passed to the electric power generation for the purpose of own power generation and power output for the external consumption and thereby the waste heat from the heat recovery system ( 113 ) is used after steam generation with electric power generation for dry and heating purposes in several stages for cogeneration process. A method according to claim 1, characterized in that the, the tunnel furnace downstream heat recovery plant ( 113 ) from steam generator, steam turbine ( 115 ) (Engine) and generator ( 116 ) and the heat of condensation from the evaporation stream for the drying process ( 120 ) of the moldings or fuel drying ( 101 ) is being used. A method according to claim 1 and 2, characterized in that the heating zone (C) of the tunnel kiln ( 3 ) in a circulating direct current ( 109 ), the cooling zone ( 107 ) and adjacent areas of the combustion zone (D) are operated in countercurrent. Method according to claim 1 to 3, characterized in that along the heating zone (C) circulation channels ( 6 ) are arranged in parallel or in the oven, the high temperature of about 600-900 ° C. and from the fire zone (D1) of the tunnel kiln (D1). 3 ) and from which supporting bodies ( 8th ) heated in the DC heating zone (C) for heating the kiln is heated. Method according to claim 4, characterized in that the waste heat plant ( 113 ) with exhaust gas ( 112 ) of the tunnel kiln ( 3 ) from the circulation channels ( 6 ) of the same or other furnace areas of high temperature are fed directly or indirectly or, if necessary, between tunnel kilns ( 3 ) and waste heat plant ( 113 ) an additional heating takes place for the regulation of the steam heating of the waste heat plant ( 113 ). A method according to claim 1-5, characterized in that the exhaust steam of the steam engine ( 115 ) for heat utilization of a drying plant ( 121 ) for molding drying and one for drying solid fuels ( 101 ), via heat exchangers or heating cables arranged directly in the dryer ( 120 ) with subsequent condensate return organs. A method according to claim 1-6, characterized in that the method for firing bricks and electric power generation, according to the flow chart 3 takes place and as the last stage of the combined heat and power cycle to the dryer (A) via its exhaust air openings ( 130 ) the exhaust air flow ( 131 ) is taken to heat the soil ( 132 ) of a tone warehouse ( 133 ) or other heat consumers and the resulting condensate in containers ( 135 ) is collected with removal of the soils via fume stacks ( 134 ) into the atmosphere. Continuous furnace z. B. Tunnel kiln ( 3 ) for firing of ceramics, in particular building ceramics according to claim 1 using high amounts of solid fuels of biogenic or industrial origin with internal furnace, thermal exhaust gas purification and combustion, characterized in that the Anwärmzone (C) gem. 1 of the tunnel kiln ( 3 ) takes place in cocurrent to the Brenngutfluss and in this zone primarily the gasification and ignition of the emerging there emerging gases takes place, from the fuel-containing molding material ( 1 ) itself or from a stove device ( 5 ) ceramic or metallic heaters ( 12 ) Fuel briquettes ( 1a ) in trolleys or heaters ( 105 ) via a ceiling lighting the tunnel kiln ( 3 ) are supplied for heating. Tunnel kiln ( 3 ) according to claims 7 and 8, characterized in that the exhaust gases ( 9 ) thereof from the circulation channels ( 6 ) preferably in the furnace entrance area into the chimney ( 9 ) and via regenerative or recuperative heat exchangers ( 19 ) is fed to a dryer (A). Tunnel kiln ( 3 ) according to claims 7-9, characterized in that from the circulation channels ( 6 ) Hot gas by means of funding z. B. fans or blowers ( 8th ) zone by zone in the heating zone "C" of the tunnel kiln ( 3 ) and this, fed gas quantity regardless of the amount of exhaust gas discharged ( 9 ) is controlled according to the heating requirement of the heating zone "C", depending on the requirements of the firing stock and this consist of moldings with different fuel content European Patent No. 0 975 925 ,

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