DE3232943A1 - METHOD AND DEVICE FOR BURNING FINE-GRAINED GOODS, IN PARTICULAR CEMENT FLOUR - Google Patents

Description

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Annex to the patent application by

KlcJckner-Humboldt-Deutz

Corporation

Method and device for burning fine-grained material, in particular raw cement meal

OiQ invention relates to a method and a device for burning fine-grained material, in particular cement raw meal, in a WMrmebehamjilungssystem, in which the material is gradually preheated, then largely calcined and then heated in the combustion zone of a furnace to the temperature required for the clinker reaction and until completion the clinker reaction lingers in the firing unit.

With usual modern and! industrially used combustion process and devices for cement production is Rohraeh.1 preheated with hot gases in the suspension gas heat exchanger and then largely calcined with the addition of fuel, whereupon the pretreated material is placed in a rotary kiln abandoned and heated relatively slowly to sintering temperature in the material bed and sintered until it is cooked. Garbrand is usually found in the rotary kiln in Countercurrent between good and gas takes place.

It was recognized early on (DE-PS 337 312, from May 27, 1921) that in order to achieve better and faster utilization to bring about the flame gases, for an intimate touch

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between flame and material not during sintering, but before, namely before entering the furnace up to near must take care of the beginning of sintering.

To solve this, a divided rotary kiln was proposed, the sintered part of which rotates more slowly than the other part, the oven used for heating up close to the sintering point rotates at such a high speed that the material is lifted right up to the top of the oven and released from there falls through the cross-section of the furnace.
However, by introducing the above-mentioned methods and devices for heating raw meal in the suspended gas heat exchanger and in particular in a calciner, this invention has been superseded by the prior art.

The realization that it is very advantageous for energy and reaction kinetic reasons, to carry out the heating margin between the calcination of the raw meal at about 900 ⁰ C and the Garbrand at about 1350 ⁰ C with the highest possible heating gradient, has since led to a number of other proposals .

For example, another possibility for so-called rapid burning of raw material is described in DL-PS 97 409 mentioned, and this consists in the fact that in a reactor the dusty or agglomerated mixture in a fluidized bed is heated up quickly and sintered until it is cooked. Furthermore, it is then known that powdery Well heated very quickly to Garbrandt temperatures in reactors.

However, tempering at the maximum temperatures reached until completely burned out is not possible. this is due in particular to the fact that the temperatures are very close to the formation of alite in the material with the onset of melt formation

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cause strong sticking and thus cause buildup, which prevents the trouble-free operation of the Do not allow reactors.

The prior publication suggests working in the temperature range between about 1100 and 1350 ⁰ C with extremely high heating gradients. A reduction in the cooking firing time by about 7035 is indicated as an advantage, with the resulting positive effects, for example through possible downsizing of the cooking firing reactor or increasing its throughput or carrying out the cooking firing at lower temperatures with customary dwell times. This advantage arises in the case of extremely high heating gradients, preferably by avoiding deactivation of the items to be burned.
How such extremely high heating gradients are to be achieved is not given in the cited document by any specific teaching.

The object of the present invention is to improve the quality of the clinker and reduce the energy requirement by heating up as quickly as possible following the calcination to sintering temperature, with the aim of maintaining the active state of the material following the calcination to be used for a quick, substantial and homogeneously distributed Alitkeimbildung, thereby a significant Verkür wetting d he Garbrandzeit and optionally also to a reduction of Garbrandreaktors as well _as: to reach r reduction of the primary energy.

To solve the problem it is proposed that at least a partial amount of largely calcined material to the firing unit from the side of the firing zone in the form of a suspension abandoned, passed through the combustion zone in cocurrent with combustion gases and with a rapid rise in temperature

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is heated, the sintering reaction begins and at least is partially completed, whereupon the material is separated from the fuel gas and in the material bed until the sintering reaction is complete iiD countercurrent to the combustion gases is returned through the combustion unit.

The method according to the invention has the very advantageous effect that the heating following the calcination to sintering temperature, that is to say in the temperature interval between approximately 900 and 1300 ^° C., proceeds as quickly as possible with very high heating gradients.

This ensures the active state of the material for rapid, extensive and even formation of aluminum used, as a result, recrystallizations are avoided and short diffusion paths are maintained for the formation of alite.

The extremely fast heating succeeds with the invention because radiation and convection affect that in the suspension Finely distributed goods with a maximum active surface act and therefore the heat transfer is multiplied are cheaper than in a good bed bed. On the other hand, there is the risk of caking due to the formation of melt phases thus avoided that such, as is known, circulated in the rotary kiln due to the abrasive action of the cies Gutbettes are prevented from permanent formation.

In the method according to the invention, the heated and, in some cases, even fired material falls at the end of the rotary kiln at relatively low gas velocities down from the suspension or is in a separation device separated from the gas, collects into a bed of material, and becomes the in the rotary kiln due to its inclination and rotary motion Flame fed back against, with the property in well-known

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Conveyed way in countercurrent to the flame gases, thereby is sintered or burned to the end and discharged to the furnace outlet. It then falls into a clinker cooler known design.

The rotary kiln can be very advantageous in the method according to the invention as a result of the more favorable heat transfers the same performance can be significantly reduced in length. In addition, the formation of firm clods becomes more solid Agglomerates in the finished clinker are significantly reduced, which has a further advantage, namely that the grindability of the finished clinker is considerably better is, so that a considerable part of the energy required for grinding the clinker is also saved.

Because of the negligible deactivation of the components of the ware the result is a higher reaction activity and thus better reaction kinetics, which leads to a shortening the cooking firing time and / or lowering the cooking firing temperatures and thus a significant reduction in the specific Primary energy requirement per unit weight of clinker.

As a result of the uniform nucleation of the alite, there is also a very advantageous homogenization that is still present in the distribution Freikalkes instead, the disadvantageous Treioen of which is therefore suppressed.

An expedient embodiment of the method according to the invention provides that the partial amount of the largely calcined Good is at least 50Si of the total amount. However other distributions of amounts should not be excluded when carrying out the method according to the invention.

A great advantage arises with the invention from the fact that it is used as a firing unit in a rotary kiln which is customary at sicn can be carried out, this having a burner whose flame at least partially the burning zone interspersed.

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Because the rotary kiln as a result of the invention as Flue dust heating and burning unit in direct current, as well is also used as a conventional firing unit for firing in the bed of material in countercurrent, the invention avoids the use of additional heating units and at the same time the associated risk of caking in the area local overheating, and achieved with the twofold heat transfer through radiation and convection in equal measure Countercurrent the highest possible heat utilization and thus profitability.

It is also provided that the material with carrier gas in the particle beam is blown into the firing unit approximately parallel to the flame, preferably above the burner.

Another advantage is that raw materials with a high chlorine or alkali content are also used can be. Because as a result of the heating up essentially in the suspension, the pollutants are released quickly, and occur in high concentrations in the furnace exhaust gas, where they cannot condense. Because in addition to a process control according to the invention only a very small part of the total fuel requirement in the rotary kiln is burned, therefore, if necessary, up to 100% of the Oven exhaust gases are discharged in the bypass without the heat consumption of the overall system increasing in an inadmissible manner or the Procedure would become uneconomical.

Normally, however, the heat from the exhaust gases is used either for the process or to generate electricity.

It is also provided that the combustion unit also from the On the gas outlet side, a subset, in particular, of largely calcined material is given up.

This may also facilitate the separation of the material that is burned in suspension from the exhaust gas.

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In the event that the firing unit subsets of goods abandoned on both sides, the measure can be used to advantage that Gutsorten with different Composition of their material components are given separately from one another on each side.

It can further be provided with advantage that the Brerin unit also from the gas outlet side together with the partial amount of the calcined material additional fuel, preferably inferior or substitute fuel is abandoned.

A system for burning fine-grained goods, in particular raw cereal meal, according to the method according to the invention, comprising a heat treatment system with at least one preheating unit, at least one calcine tar and a firing unit with a downstream cooler, is characterized by the fact that a device is located on the burner side of the rotary kiln for the production and introduction of a suspension of calcined material and Trägexgas is provided, and that the Rotary kiln operated in cocurrent as well as in countercurrent has a slope with a gradient in the direction of the erenow nerseite.

This inclination of the rotary furnace is an essential feature in conjunction with the suspension entry of the goods the system according to the invention, which in contrast to the usual Arrangement of a rotary kiln operated in direct current. Such, for example, according to the DE-OS 27 38 987 has a clear slope with a gradient in the direction of the direct current of good and gas. The fact that the rotary kiln of the system according to the invention in the direction of the direct current increases, it not only enables a great deal of the double operation in cocurrent and countercurrent is advantageous, but this position also favors the functionally essential Sedimentation of the material from the carrier gas

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at the end of the firing zone and enables - depending on the dimensions and gas velocity - if necessary, even without a separate separation unit, the solid particles will fail to the extent necessary.

However, it can also be provided that the rotary kiln has a separating unit on the exhaust gas side for separating material and gas assigned.

Further advantageous refinements emerge from claims 10 to! 14th

In the following, the invention is illustrated in greater detail with its advantages on the basis of exemplary embodiments in the drawing and explained.

Show it:

1 shows a cement burning plant according to the prior art, in a block diagram;

2 shows a burning system according to the invention, also in a block diagram;

3 shows a modified burning system according to the invention with alternative links between individual functional elements Q, also in a block diagram.

The cement burning plant according to the prior art according to Figure 1 comprises a suspended gas heat exchanger 1 with the heat exchanger cyclones 2, 3 and 4 and a calciner system consisting of the reaction section 5 with additional firing 6 and separator 7. The kiln also includes the rotary kiln 8 with a main burner 9 and a downstream

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switched grate cooler 10, from which a hot air line, the so-called tertiary air line 11 directly next to the additional firing 6 at the foot of the calcination reaction section 5 joins. Raw meal, indicated by the arrow 12, is given to the suspended gas heat exchanger 1, while finished clinker is discharged from cooler 10 according to arrow 13. The incline of the rotary kiln runs vorti furnace inlet head 14 with a slight incline of approx. 3.5 ° in the direction of the burner 9.

'"_ :) The function of the state-of-the-art distillery is as follows:

Raw meal is fed into the gas line 15 at 12, which connects the preheater-cyclone 3 with the separator-cyclone group 4. Therein the raw meal is heated to about 300 to 350 ° and, after leaving the cyclone Group 4 in the connecting line 16 between cyclone 2 and 3 and is heated to about 450 ⁰ C 500 Dis. The raw meal is then separated from the hot gas flow by the cyclone 3 and entered into the connecting line 17 between the cyclone 2 and the separator 7. The material is further ^{heated therein to approx. 650 °} C.: -. At this temperature it is introduced from the cyclone 2 through the downpipe 18 into the lower area of the calcination reaction section 5, where it is mixed with hot air from the tertiary air line 11 and fuel from the secondary firing system 6 as well as with hot furnace gases, subjected to a flameless combustion with extensive calcination will. The material, largely calcined in this way, reaches ^{the separator 7 at a temperature of approx. 900 °} C., which separates the solid particles from the gas flow and enters the inlet chamber 14 of the rotary kiln 8 with the aid of the downpipe 19. In the rotary kiln 8, the material, which has a temperature of approximately 900 C, is heated to approximately 1300 to 1350 ^° C. over a distance of approximately 3/5 to 4/5 of the length of the rotary kiln. This is the temperature limit of the

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beginning alite formation, also called clinker reaction. The cycle time from the furnace inlet 14 to the specified temperature level is approximately 60 minutes, with an average temperature gradient of approximately 7.5 ° / min _; achieved. In the last part of the rotary kiln 8, in the area of the 4th and 5th parts of its total length, in the area of the flame of the burner 9, the baking to clinker takes place. The material reaches a final temperature of approx. 1450 ^° C. At this temperature, the completely burned clinker is thrown into the cooler 10, cooled therein, releasing a substantial part of its sensible heat, and finally discharged according to arrow 13.

Figure 2 shows a system according to the invention in a block diagram. This largely has the same main elements namely a gas suspension heat exchanger 1, a calciner 5, a rotary kiln 8 and a cooler 10. From the cooler 10, the tertiary air pipe 11 leads 5 for calciner with the compound II ¹ of the flame 29 of the rotary kiln 8 hot secondary air is supplied, whereas clinker is entered into the cooler 10 after the finished fire, indicated by the arrow 21. This receives cooling air through a supply device 20 and discharges cooled clinker according to arrow 13.

According to the invention, largely calcined material is discharged from the calciner 5 with the line 19 and in contrast to the system according to the prior art (Fig. 1) with an injector 27 by means of carrier gas, indicated by the Fan 26, entered in the particle beam according to arrow 28 above the burner 9 in the rotary kiln 8 and in direct current to the flame 29 or the hot gases generated by it through the rotary kiln 8. To the area towards the entry chamber 14, the solid particles, indicated, fall from the gas flow as the speed decreases

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by the arrow 30, from the gas flow and collect in the bottom region of the rotary kiln 8, where they form a bed of material, indicated by the dashed line 31. In the event that the exhaust gas from the rotary kiln 8 should still contain parts of dust, For example, a separator 7 can be connected downstream of the rotary kiln 8 with the exhaust pipe 24, which separates the dust from the gas and enters the rotary kiln 8 with the downpipe 35 into the bed 31 of material. As is known per se, the material bed 31 moves therein in the direction of the burner according to arrow 21 to the furnace discharge, from which the completely burned clinker is thrown into the cooler 10. In the case of a high proportion of pollutants, the exhaust gas separated from the solid is discarded in the bypass according to arrow 25 or, if an accumulation of pollutants in the circuit is not to be feared, passed through the line 26 into the calciner 5 for the purpose of recuperation of the heat contained in the gas. Exhaust gas from the calciner 5 is fed into the suspended gas heat exchanger 1 via line 17, while preheated material is introduced into the calciner via line 18 from the suspended gas heat exchanger 1.
A material divider 19 'can also be assigned to the calciner 5, from which conveying devices 19, 19' for calcined material ^{lead to both ends 8 1} and 14 of the rotary kiln 8, with which largely calcined material is fed to the rotary kiln 8 at both ends 8 ', 14 is abandoned.

FIG. 3 shows a modified system according to the invention with a basic structure similar to FIG. 2. Here too The system is on the side of the burner 9 in the rotary kiln 8, a heat treatment system I with a) floating gas heat exchanger 1 and a downstream calciner 5, from which largely calcined material with the line 19 via an injector 27 with the aid of carrier gas, for example from the fan 26, above the flame 29 is entered in the rotary kiln 8, in the form

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a suspension. The fan 26 can optionally be supplied with warm air from the cooler 10 via ^{the branch line II 11.} In addition to the system according to FIG. 2, however, the modified system according to FIG. 3 has a second heat treatment system II, parallel to the first heat treatment system I, with a suspended gas heat exchanger I ¹ . If the system II does not have its own calciner, a line 32 can be provided with which preheated raw meal is conveyed from the heat exchanger 1 ′ into the calciner 5 of the heat treatment system I on the burner side. If the second heat treatment system II has its own calciner 5 ', this can also be equipped with a material divider 36, of which two goods transport devices 35' and 35 'are connected to both sides 14, 8' of the rotary kiln 8. From the calciner 5 'preferably largely calcined material is introduced into the feed chamber 14 of the rotary kiln 8 via the line 19'. Exhaust gas from the rotary kiln 8 is withdrawn from the inlet chamber 14 via the line 24 and introduced into the calciner 5 ¹ . A cooler exhaust air line 33 can also be provided, with which hot cooler exhaust air is also fed to the calciner 5 '. The device 34 is provided for adding additional fuel. Such additional fuel can be, for example, lumpy coal, car tire waste, garbage and the like. Oily sands and / or shale can also be fed to the rotary kiln 8 as additional fuel 34.

The differently modified versions of a still according to the invention according to Figures 2 and 3 is very advantageous property in common, namely that by giving up the possibly largely calcined material in Powder form and in the form of a suspension with optionally preheated carrier gas when passing through the combustion zone an extraordinarily fast recovery in direct current

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tion is effected with rapid temperature gradients. Assuming an average transport speed of the powder cloud of, for example, 5 m / sec, the dwell time of a solid particle at a furnace length of approx. 50 meters is about 10 seconds. Within this time the heating of about 900 ° is carried out to an average of approximately 1300 ⁰ C. This results in a temperature gradient of 40 ° C / sec. On the other hand, the temperature gradient when heating in the bed of material in the conventional kiln, for example according to FIG active state of the material after calcination and forms the prerequisite for rapid and uniform alite nucleation. Furthermore, recrystallizations are avoided and extremely short diffusion paths are maintained for the alite formation.

The shock-like heating also causes a multiplication the lime binding rate.

The method according to the invention also has the advantage that the rotary kiln is shortened as a result of maximum heat transfer and thus the specific volume output of the system is increased with the invention. Thereby the flame zone of the oven is used twice, including once in the Gleicnstrora and once in countercurrent, and there is no need to connect a heating reactor upstream of the rotary kiln.

By arranging the second heat treatment system II for the thermal pretreatment of the raw meal for the cooking fire it is also possible to improve the overall performance of the system and at the same time the economy through complete To optimize the use of the available heat. This second heat treatment system II - as in the previous example 2 shown -i can in different ways

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in relation to gas and flour transport with the first heat treatment system I can be combined.

When the partially or largely calcined flour is fed from the heat treatment system into the upper end 14 of the rotary kiln 8, the furnace area on the exhaust gas side is first used for residual calcination. In this case, substitute fuel 134 in the form of waste such as car tires, low-quality coal, garbage briquettes, etc. can be used with great advantage to cover the necessary heat requirement, which is quickly calcined together with the hot meal from heat treatment system II, if necessary by means of flameless combustion. On the other hand, however, the calcination of the material 12 'fed to the heat treatment system II can also be carried out in an additional, downstream ca ^ zinator 5', which is connected between the suspended gas heat exchanger 1 'and the furnace 8 and that with the burner 6 ¹ Fuel is abandoned. The flour heated and precalcined in the heat exchanger 1 can, however, also be introduced into the calciner 5 of the heat treatment system I via the line 32 and completely calcined together with the preheated metal from the heat exchanger 1. It would also be possible to feed the flow of flour coming from the heat treatment system II, partly over largely calcined, to the furnace inlet and; Dividing the furnace outlet »This mode of operation allows, for example, the heating and sintering speed of a partial flow to be set as desired. This means that the clinker quality can be optimally adjusted or maintained in accordance with the raw materials available. As an additional fuel, in addition to the usual fuels, oil or coal shale can also be used in all cases, the mineral component of which is also used as the raw meal portion.

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In all these cases, however, the essential feature of the invention is the rapid heating of the partial or largely calcined material in the particle beam and the use of the rotary kiln as a flue dust reactor in cocurrent while maintaining the gas fire in countercurrent with one of the preheated and prebaked Particles formed good bed.

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Claims (15)

Gr / Ju * KHD H 82/43 Claims y. A method for burning fine-grained material, in particular raw cement meal, in a heat treatment system, in which the material is preheated in stages, thus largely calcined and then heated to the temperature required for the clinker reaction in the burning zone of a furnace and remains in the furnace until it is complete, characterized in that: that at least a partial amount of largely calcined material is given to the firing unit from the side of the firing zone in the form of a suspension, passed through the firing zone in cocurrent with fuel gases and heated with a rapid rise in temperature, the sintering reaction begins and is at least partially completed, whereupon the material from Combustion gas is separated and returned in the material bed through the combustion unit in countercurrent to the combustion gases until the end of the sintering reaction. 2. The method according to claim 1, characterized in that the partial amount of the largely calcined material is at least 5036 of the total amount. 3. The method according to claim 1, characterized in that a rotary kiln with a burner is used as the firing unit, the flame of which penetrates the firing zone at least partially. KHD H 82/43 4. The method according to any one of claims 1 to 3, characterized in that the material is blown with carrier gas in the particle beam approximately parallel to the flame, preferably above the burner in the combustion unit. 5. The method according to any one of claims 1 to 4, characterized in that the firing unit is given a subset of preferably largely calcined material from the gas outlet side. 6. The method according to any one of claims 1 to 5, wherein denr firing unit on both sides subsets of good are given, characterized gekennz eichnet that types of goods with different composition of their material components are given separately from each other on each side. 7. The method according to any one of claims 1 to 6, characterized in that the fuel unit is fed from the gas outlet side, additional fuel, preferably inferior and / or substitute fuel. 8. The method according to any one of claims 1 to 6, characterized in that exhaust gas from the firing unit between 0 and 100 % is used for preheating and / or calcining the raw cement meal and / or between 0 and 100 % is withdrawn in the bypass. 9. plant for burning fine-grained material, in particular cement raw meal, according to one of claims 1 to 8, comprising a heat treatment system having at least one preheating unit, at least a calciner and a combustion unit with a downstream cooler, dadur ch in that on the burner side of the rotary kiln (8 ) a device (26, 27) for producing and introducing a suspension H 82/43 largely calcined material and carrier gas (26) is provided, and there is both cocurrent and countercurrent operated rotary kiln (8) has an incline with a slope in the direction of the burner side .. 10. Plant according to claim 9, characterized in that the rotary kiln (8) on the exhaust gas side is assigned a separating unit (7) for separating good and gas. 11 »Plant according to claim 9, characterized in that the device for introducing the goods has an injector (27), which goods from the calciner (5) by means of a transport device (19) and air, preferably warm air (II ¹¹ ) from the coal burner (10 ), optionally after the pressure has been increased by a fan (26), is supplied as carrier gas, and that the injector (27) is arranged on the furnace end wall (8) on the burner side, preferably above the burner (9). 12. Plant according to one of claims 9 to 11, characterized by an exhaust line (24) from the rotary kiln (8) with a separator (7) and a line (26) to the calciner (5), from which a bypass line (25) branches off if necessary is, as well as through a line (35) for returning separated material to the rotary kiln (8). 13. Plant according to one of Claims 9 to 12, characterized in that a material ^{divider (19 1} ) with two good transport devices (19, 19 ') is arranged on both sides ( 8 ¹ , 14) of the rotary kiln (8) are connected, and that if necessary at the discharge of the calciner (5 ¹ ) a material divider (36) with two material transport devices (35 ¹ , 35 '*) is arranged, which on both sides ( 8 ¹ , 14 ') of the rotary kiln (8) are connected. H 82/43 14. Plant according to one of claims 9 to 13, characterized in that a second heat treatment system (II) is arranged in addition to the first heat treatment system (I), which has a second heat exchanger (1) and optionally a second calciner (5 ¹ ), which exhaust gases (24 ¹ ) from the rotary kiln (8) flow through, and the material discharge of which is connected to the gas outlet end (14) of the rotary kiln (8) through a line (35). 15. Plant for burning fine-grain material such as raw cement meal, in particular according to one of claims 9 to 14, characterized in that on both sides (8 ¹ , 14) of the rotary kiln (8) and preferably above the same a heat treatment system (I and II) is arranged for the thermal preparation of the raw meal for the cooking fire, each of which has a heat exchanger (I ¹ , 1) through which the furnace gas or hot cooler exhaust air flows and at least one of the systems (I or II), optionally both systems (I and II), one Have calciner (5, 5 ¹ ).