DE102004023686A1 - Production of cement clinker, from briquettes and pellets, comprises use of additional primary kiln heating and passing exhaust gas from rotary kiln to dehydrator for constant and optimum heating - Google Patents

Abstract

To produce cement clinker by heating raw cement, a primary kiln (3) is heated additionally and the exhaust gas from the rotary kiln (1) is passed into a dehydrator (2). The fired cement clinker is taken from the rotary kiln through a cooling stage (4). The raw cement is pressed into briquettes or pellets etc., of 5-20 mm to be fed through the dehydrator at least at 600[deg]C and at a maximum of 700[deg]C and transferred to the primary kiln for complete calcination and then passed to the rotary kiln to be converted into clinker. The rotary kiln and the primary kiln have fuel feeds (5, 6).

Description

The The invention relates to a method and a device for thermal Treatment of cement raw meal for the production of cement clinker complete deacidification in the calciner and the reduction of the specific heat expenditure for the Clinker fire.

Under Application of the different precalcinier processes, associated, relatively shorter rotary kilns, the Use of 5-6 stage cyclone preheaters as well as the most modern clinker coolers are today with such systems depending on the type and preparation fuel and fuel specific fuel requirements from about 2930-3140 kJ / kg Clinker reached.

As from the ZKG-10/89, p.510-514 is known, were precalcined with a 2-stage calciner in experiments Vorcalcinierraten of about 98% at temperatures below 850 ° C reached. The high degree of calcination was achieved without increase the temperature of the furnace feed, but at extension of the Dwell time double in the passage through the two calcination stages.

The produce the best cyclone heat exchangers operated today the cement clinker with a specific heat input of approx. 3000 kJ / kg Clinker in exhausted Reduction potential of the specific heat expenditure. This general The opinion is represented by the BDZ / VDZ and also by the leading plant manufacturers. Other fuel systems for cement clinker are higher than the aforesaid value of about 3000 kJ / kg clinker.

Of the Disadvantage of the standard "cyclone heat exchanger" is that he his optimal performance only in the for the design of the gas speed specified sizing can reach the cyclone. When falling below the optimum gas velocity takes the degree of separation of the cyclones and thus the throughput from and the specific heat requirement rises. The disadvantage is the cyclone heat exchanger also, that through the diverse, branched flows one before complex homogenized raw meal in the heat exchanger is homogenized becomes. This process is also known from ZKG-1992 / Nr. 5 p. 225 under 2.1.3., In which it u.a. means that the thermal efficiency the well-known cyclone preheater is reduced by internal dust cycles and throughput. Important is to note that the combustion process with the cyclone heat exchanger a Vorcalcinier method with over 300 ° C hot exhaust gases remains in which at temperatures below about 1040 ° C no total deacidification possible is.

Of the Heating system "waste gas utilization / raw material drying" is only optimal at full utilization of the heat supply and only in this case is the loss of exhaust gas from that in the combustion system spent thermal energy deducted. Disadvantages and problems are further caking and the formation of deposits in the temperature range from about 850 ° C for normal Raw meal into the area before the melt phase formation at all known preheater constructions. Especially critical is the problem of buildup in the temperature range approx. 700-900 ° C with Na-K and Cl-containing Links.

By the patent DE 4315212 a method for the production of cement clinker is known in which the raw meal is completely calcined in the calciner by higher temperatures and only in the rotary kiln is sintered.

Furthermore, it is known in the production of clinker to produce from the starting materials or partially processed materials pellets (pellets, etc.) and to introduce them into the process. According to the DE OS 25 54 989 This is done after preheating, before sintering. This solution is intended to enable sintering in a fluidized bed. According to the DE PS 44 33 049 The wet raw materials are pressed into filter cake and then crushed into pieces smaller than 10 mm. These are now partially calcined and then introduced into the rotary kiln. The use of lumpy material results from the required comminution of the filter cake for processing. The granulation of cement raw meal for the production of cement clinker was carried out for reasons of special procedures, the aspect of hydration and formation of hitherto has not been considered.

OBJECT OF THE INVENTION

The The object of the invention is a combustion process and a Device for its implementation with a flow-throughput independence create an at least constant, or constantly optimal specific heat demand for the Clinker burning, even with considerable reduction of Brenngutdurchsatzes to accomplish. Furthermore, the segregation of the raw meal components prevents and minimizes material caking and buildup in the heat exchanger and rotary kiln, even at temperatures above 1040 ° C in the calciner and raw meals be achieved with a high alkali content.

The object is achieved by the features of claim 1 solved.

The Advantages of the new heat exchanger system across from since over 50 years old and the world's leading cyclone heat exchangers et al the noticeable heat energy savings opposite and those with the energy savings in the same percentage reduction of CO2 and NOX emissions. An important Process for environmental protection.

With the unbranched Gutführung into the sintering zone is a in all individual heat exchange phases thermally and chemically homogeneous Gutzustand achieved and remains the advantage of dividing the processes into small steps is maintained.

• – die strömungstechnische Durchsatzunabhängigkeit,
• – die Vermeidung von Entmischungen der Rohmehlkomponenten und internen Staubkreisläufe,
• – die größere Flexibilität in der Anlagenführung im Hinblick auf die Abnehmererfordernisse aber auch auf das Eigeninteresse des Betreibers,
• – die räumliche Anordnung der verschiedenen Anlagenteile vom Vorwärmer bis zum Kühler, hierdurch erfolgt die Gutführung ausschließlich durch Schwerkraft sowie durch mechanische Wirkprinzipien,
• – ein Anlagenkonzept mit erhöhter Flexibilität in der Betriebsführung zu schaffen, um auf die künftig qualitativ und quantitativ breiter gefächerten Anwenderanforderungen besser und kostengünstiger reagieren zu können,
• – die merkliche Ersparnis an Mahlenergie durch eine optimal grobe Mahlfeinheit des Rohmehls,
• – der Entfall eines Kühler-Abluftfilters,
• – der Entfall einer großen Klinker-Bevorratung mit den umfangreichen Transportmitteln zur Ein- und wieder Auslagerung des Klinkers, (dafür der direkte Weg des Klinkers vom Kühler in den Mühlen-Aufgabebunker), mit Wegfall der durch die Klinkerbevorratung vorweg entstehenden Brennstoffkosten,
• – der Entfall der umfangreichen Entstaubungseinrichtungen für Klinker-Transport und -Lagerung.

The time for the heat exchange from Guteintritt in the preheater to Gutaustritt in the rotary kiln is compared to the cyclone heat exchanger over a thousand times higher. As a result, a more compact design and construction of the new system with much smaller volume conversions and thus low construction costs are possible and also reduce the radiation losses. The significant saving in heat energy is achieved by lowering the exhaust gas temperature, considerably increasing the heat exchange time in the preheater and in the calciner, and by reducing the cooler losses through the pipe cooler. In addition to saving heat energy, the specific electrical energy requirement is also reduced. The main advantages are summarized:

• - the flow-throughput independence,
• The avoidance of segregation of the raw meal components and internal dust cycles,
• - the greater flexibility in plant management in terms of customer requirements but also the self-interest of the operator,
• - The spatial arrangement of the various parts of the system from the preheater to the radiator, thereby the Gutführung takes place exclusively by gravity and by mechanical principles of action,
• - to create a plant concept with increased operational flexibility, in order to be able to react better and more cost-effectively to the future qualitatively and quantitatively broader user requirements,
• The noticeable saving of grinding energy by an optimally coarse grinding fineness of the raw meal,
• The omission of a radiator exhaust filter,
• - The elimination of a large clinker storage with the extensive means of transport for loading and unloading of the clinker, (for the direct route of the clinker from the cooler in the mill-task bunker), with the elimination of the costs incurred by the clinker storage fuel costs,
• - The elimination of extensive dedusting facilities for clinker transport and storage.

According to claim 1, the task of molded from raw meal compacts preferred on a traveling grate in the dehydrator, the compacts are here Temperatures around at least approx. 650 ° C up to max. 750 ° C completely drained and then led to the calciner. In the calciner at temperatures of 1100 ° C and more the material is completely deacidified. In the micro rotary kiln according to the invention (compared to the usual Cyclone preheater method considerably smaller oven volume!), or another sintering device then the residual clinker formation takes place.

According to claim 2, the optimally coarsely ground for the digestion, well-homogenized raw meal before the task in the dehydrator heat exchanger ( 2 ) processed by a special treatment by means of water and / or a binder such as coke dust and / or oils to pellets, wherein the required addition of water takes place exactly over a weight-dependent, automatic dosage of water / raw meal. As a result, no worker / operator on the granulator is required. The pellets are preferably granules with a spherical shape in an average size of 10 mm.

In claim 6, a special device version is claimed for heat recovery. With the arrangement of the components in series ( 1 ) is via the fixed collecting ducts around the components 3 and 1 , as well as on the coats 3 and 1 applied cooling fins sucked fresh air forcibly guided by the screw-like control system to the air outlet and thereby heated for heat recovery.

The invention is illustrated schematically in the appended drawings, and described in more detail below. Compared to the well-known custom is below the rotary kiln 1 because in this process only a 10% share of the total heat demand via the fuel input QI 5 is supplied, also referred to as a secondary furnace. The calciner 3 with 90% fuel content via fuel input QII 6 is accordingly used as a primary oven 3 designated.

In the 1 illustrated plant for the production of cement clinker contains a rotary kiln 1 and is with a dehydrator 2 and a calciner 3 provided as a heat exchanger. The dehydrator 2 is designed in this case as a traveling grate for gentle treatment of the compacts until their curing. The fuel inputs take place With 5 in the rotary kiln 1 and 6 in the calciner 3 , That from the calciner 3 , a rotating, inclined heat exchanger, coming good is in the rotary kiln 1 , the kiln exhaust directly into dehydrator 2 guided.

The 2 shows an opposite arrangement of the system parts 1 and 4 ,

The 3 shows a rotary cooler 4 to 13 from the patent DE 43 00 011 C2 with integrated crushing device.

The 4 shows the components required for heat recovery of the jacket radiation losses, such as the helically mounted on the jackets, snail-shaped sheets (which may also be individual wings) and the fixed, non-co-rotating jacket of the hot air collecting ducts 3 ' and 1' ,

The 5 shows the cross section. The collection channels are free in the area of the respective role stations for the free access of the stations down, this right picture 5 (Air passage in hatched area). From the mill or dryer fan is via the open collecting channel 3 ' , on this left picture 5 (shaded area), fresh air sucked in and over the collecting channel 1' supplied from the heat recovery system of raw meal drying or other heat recovery.

1

Rotary kiln = Secondary oven

1'

Collecting channel too 1

2

dehydrator

3

calciner = Primary oven

3 '

Collecting channel too 3

4

tube cooler

5

Fuel input QI

6

Fuel input QII

Claims (6)

Process for the production of cement clinker, wherein the calciner additionally heated, the exhaust gas of the rotary kiln out in the dehydrator and the burned cement clinker is discharged from the rotary kiln via a cooler, characterized in that the raw meal into pellets (granules, briquettes or moldings ) is formed with a size of 5 to about 20 mm, then the pellets in a dehydrator ( 2 ) for dehydration at least 600 ° C to max. 700 ° C under mechanical agitation, the pellets subsequently in a rotary kiln-shaped calciner ( 3 ) are heated to full calcination and from this into the rotary kiln ( 1 ) are led to the cement clinker. A method according to claim 1, characterized in that the optimally coarsely ground for the digestion, well-homogenized raw meal prior to the task in the dehydrator ( 2 ) is processed by a special treatment by means of water and / or a binder such as coke dust and / or oils to pellets, wherein the required addition of water takes place exactly over a weight-dependent, automatic dosage of water / raw meal. A method according to claim 1 and 2, characterized in that the sintering in the rotary kiln ( 1 ) is carried out at a temperature above 1040 ° C to the sintering temperature, wherein the exothermic reaction to 420 kJ / kg clinker are free and only in the rotary kiln ( 1 ) incurred wall heat loss via the fuel input ( 5 ) is covered and introduced. Device for carrying out the method according to claims 1 to 3, characterized in that the dehydrator ( 2 ) a circumnavigated traveling grate and the calciner ( 3 ) is a rotary kiln with inclined axis of rotation. Apparatus according to claim 4, characterized in that to prevent the formation of deposits in the calciner ( 3 ) the inner wall is lined with approach-reducing material such as ceramic material or high temperature resistant special steel or exists. Apparatus according to claim 4, characterized in that on the coats of the rotating calciner ( 3 ) and the rotary kiln ( 1 ) are mounted in a helical line cooling fins and these in fixed collecting channels ( 1' . 3 ' ) on entry at the calciner ( 3 ) Sucked in cooling air, fed into the calciner and the secondary furnace collecting channel and is fed from here as heated air use of the heat recovery.