Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B7/00—Hydraulic cements
  • C04B7/36—Manufacture of hydraulic cements in general
  • C04B7/364—Avoiding environmental pollution during cement-manufacturing
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B7/00—Hydraulic cements
  • C04B7/36—Manufacture of hydraulic cements in general
  • C04B7/364—Avoiding environmental pollution during cement-manufacturing
  • C04B7/365—Avoiding environmental pollution during cement-manufacturing by extracting part of the material from the process flow and returning it into the process after a separate treatment, e.g. in a separate retention unit under specific conditions
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B7/00—Hydraulic cements
  • C04B7/36—Manufacture of hydraulic cements in general
  • C04B7/43—Heat treatment, e.g. precalcining, burning, melting; Cooling
  • C04B7/432—Preheating without addition of fuel
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B7/00—Hydraulic cements
  • C04B7/36—Manufacture of hydraulic cements in general
  • C04B7/43—Heat treatment, e.g. precalcining, burning, melting; Cooling
  • C04B7/44—Burning; Melting
  • C04B7/4407—Treatment or selection of the fuel therefor, e.g. use of hazardous waste as secondary fuel ; Use of particular energy sources, e.g. waste hot gases from other processes
  • C04B7/4446—Treatment or selection of the fuel therefor, e.g. use of hazardous waste as secondary fuel ; Use of particular energy sources, e.g. waste hot gases from other processes the fuel being treated in a separate gasifying or decomposing chamber, e.g. a separate combustion chamber

Definitions

• the invention relates to a method for operating a plant for producing cement clinker from raw meal, having viewed in the material flow direction, at least one calciner for deacidifying the raw meal, and at least one rotary kiln for sintering the deacidified raw meal to cement clinker, wherein the deacidified raw meal after passage of the calciner over a cyclone preheating stage flows into the rotary kiln.
• a mixture of calcareous rock and silicate-containing rock is ground and subjected to a heat treatment in which the lime is formally freed from carbon dioxide (CO 2 ) and converted into burnt lime (CaO).
• CO 2 carbon dioxide
• CaO burnt lime
• the raw meal deacidified by the CO 2 release which consists of the deacidified calcareous rock and of the as yet unchanged silicate-containing rock, is sintered in the heat to various calcium silicate phases.
• the deacidification and also the sintering of raw meal are endothermic processes that require heat energy for their implementation.
• This heat energy can be obtained from high quality fuels.
• the cement plant In addition to the classic, primary fuels such as coal, the cement plant increasingly uses alternative fuels as energy sources for cost reasons, which are often obtained from municipal or industrial waste.
• the nitrogen oxides escape with the exhaust air of the rotary kiln into the free atmosphere, where they are hydrolysed with the humidity to nitric acid (HNO3), nitrous acid (HNO 2 ) and others, be converted acidic nitric oxide hydrates.
• HNO3 nitric acid
• HNO 2 nitrous acid
• the nitric oxides (NO x ) which react with humidity in the air, are the cause of undesirable acid rain, which reduces the natural pH of forest soils and weakens their resistance to disease.
• various measures are known.
• German Offenlegungsschrift DE 10 2005 057 346 A1 discloses a plant for the production of cement which, in addition to the calciner, has a combustion chamber which is fed with tertiary air as combustion air.
• the reduction properties of the exhaust gases produced in the combustion chamber can be set very accurately in the system disclosed therein, in order to reduce the nitrogen oxides originating in the calciner from the rotary kiln in the calciner section.
• a disadvantage of the process disclosed therein is that the deacidification of the raw meal in the calciner on the one hand and the reduction of nitrogen oxides in the calciner on the other hand find their desired chemical equilibrium at different temperatures. The deacidification and the reduction of nitrogen oxides interfere with each other.
• German Offenlegungsschrift P 35 38 707 A1 discloses a straight-line calciner which has two reaction sections in the form of gas strands which rise next to one another inside the calciner, of which a first gas stripe flows from the rotary kiln into the calciner and an adjacent gas scrubber flows from one second inlet of the tertiary air flows into the calciner.
• the gas strands have different reduction potentials and the gas strands from the tertiary air to reduce the nitrogen oxides in the gas flow from the rotary kiln.
• a relatively short time is available for burnout of the nitrogen oxides, so that the requirement for controlling the flow conditions within the calciner is very high. Since the flow conditions in the calciner may vary with minor changes in operating parameters, this mode of operation is not always in the optimum state.
• German published patent application DE 199 03 954 A1 discloses a principle similar thereto, wherein a reactor for adjusting the redox potential of the gases to be produced is present in the tertiary air section. This mode of operation also requires a high standard of control of the flow conditions in the calciner. Since, even with this system, the flow conditions in the calciner can vary with slight changes in the operating parameters, this operating mode is also not always in the optimum state.
• the pyrolysis gases and hot air generated by the carbonization are blown into the calciner to aid in the heat input to the deacidification performed in the calciner.
• the carbonization gases have a reductive effect and can be used to reduce the nitrogen oxides in the calciner that originate from it.
• the operation of a second rotary kiln is associated with high construction costs and requires constant control of the always hot during operation mechanics.
• a plant for the production of cement clinker from raw meal with utilization of waste materials containing waste is known in which used as a secondary fuel waste materials after drying in a operated with rotary kiln exhaust gas and a partial flow of tertiary air carbonization furnace for pyrolysis, but at least partially combusted thermally be treated.
• the pyrolysis gas of this combustion is introduced into the calciner and the solid pyrolysis residues are at least partially introduced into the rotary kiln after their preparation and homogenization.
• the carbonization furnace can also be designed as a rotary kiln.
• DE-A-33 20 670, DE-A-34 1 1 144 and DE-A-35 20 447 it is also known in a plant for the production of cement clinker with utilization of waste containing waste materials to fumigate the waste in a separate rotary kiln or to burn and to use the carbonization / offgas in the thermal raw meal treatment.
• the object of the invention is therefore to provide a method for operating a plant for the production of cement, in which the denitration is better controllable.
• the inventive task is solved by passing the exhaust gases of the rotary kiln into a reactor which is arranged between rotary kiln and calciner, wherein in the reactor with respect to the residence time of the exhaust gases in the reactor superstoichiochemically fuel is added, so that contained in the exhaust gases carbon dioxide ( CO 2 ) is reduced to carbon monoxide (CO).
• CO 2 carbon dioxide
• CO carbon monoxide
• a method for operating a plant for the production of cement clinker from raw meal having seen in material flow direction at least one calciner for deacidifying the raw meal, and at least one rotary kiln for sintering the deacidified raw meal to cement clinker, wherein the deacidified raw meal after passage of the calciner over a Cyclone preheater flows into the rotary kiln.
• the exhaust gas of the rotary kiln of a plant for the production of cement is no longer, as is customary in the art, passed directly into the calciner, where it entrains raw meal and thereby deacidified the raw meal and at the same time in the exhaust gas contained nitrogen oxide ( ⁇ x ) is reduced by formed in the calciner carbon monoxide (CO) in a staged combustion. Rather, it is provided to feed the raw meal from the calciner as before through a raw meal line from the lowest Zyklonvoricarmlab a preheating the rotary kiln.
• the exhaust gas from the rotary kiln inlet chamber initially flows through a specially designed for the exhaust gas duct or pipe into a reactor before the exhaust gas is passed to deacidify the raw meal into the calciner.
• this reactor which is advantageously higher than a rotary kiln inlet chamber, which is arranged between rotary kiln and Cal- cinatorfuß, fuel is added stoichiometrically with respect to the Boudouard reaction and the present in the rotary kiln exhaust gas carbon dioxide (CO 2 ) - concentration.
• the reaction essential in the reactor is determined not by the combustion of the fuel by residual oxygen in the rotary kiln exhaust gases, but by an endothermic Boudouard reaction.
• up to 25% of the carbon dioxide contained in the exhaust gas (CO 2 ) with the carbon (C) of the fuel to carbon monoxide (CO) is implemented.
• the fuel is thus oxidized in the heat by the carbon dioxide (CO 2 ), wherein the carbon (C) from the fuel to carbon monoxide (CO) is oxidized and the carbon dioxide (CO 2 ) in the oxidation of the fuel itself to carbon monoxide (CO) is reduced.
• This pathway of the known Boudouard reaction is endothermic.
• carbon dioxide (CO 2 ) is the better reaction control compared to the simultaneous reaction of deacidification of the raw meal, reduction of carbon dioxide (CO 2 ) to carbon monoxide (CO) and the reduction of nitrogen oxides ( NO x ) to elemental nitrogen (N 2 ) and oxygen (O 2 ) by the formed carbon monoxide (CO).
• the temperature in the reactor can be controlled or even regulated by the addition of fuel to avoid an undesirable increase in temperature in the reactor, in the undesirable further nitrogen oxides ( NO x ) could arise from the added fuel.
• the temperature in the reactor by the addition of superstoichiometric fuel, wherein by the Boudouard reaction in the endothermic reduction of carbon dioxide (CO 2 ) with carbon (C) from the fuel to carbon monoxide (CO), the temperature is reduced in the reactor.
• the reactor always a certain amount of deacidified raw meal supplied to catalytically support the denitrification taking place in the reactor.
• the supply of the deacidified raw meal can be entrained in the rotary kiln stirred up raw meal with the exhaust gases.
• the exhaust system of the exhaust gases from the rotary kiln can thus be provided so that the fluidized raw meal passes into the reactor and is not filtered out by cyclone traps. Alternatively or cumulatively, it may also be provided to feed freshly deacidified raw meal from the lowest or second lowest cyclone preheating stage to the reactor.
• Proper sizing of the reactor is advantageous for ideal combustion management.
• a flap system can control the flow of air through the reactor, so in an advantageous embodiment of the invention, a dimensioning of the reactor, which is so large, the exhaust gases originating from the rotary kiln and containing nitrogen oxides (NO x ) are reduced by the carbon monoxide (CO) formed.
• the reactor is therefore so large that during normal operation, the exhaust gas entering the reactor from the rotary kiln lingers in it until the nitrogen oxides (NO x ) contained in the exhaust gas from the rotary kiln are completely reduced as far as possible.
• a low (NO x ) is not necessarily avoidable, but the low concentration of nitrogen oxides (NO x ) is further reduced in the Calcinator- stretch that follows the reactor.
• An advantage of the method according to the invention is the possibility of combustion of fuel in the rotary kiln with a high excess of atmospheric oxygen.
• a complex solid-state reaction takes place in the heat, which requires an oxidative environment for the preparation of a mixture of calcium silicate phases of different stoichiometry.
• controlling or regulating the amount of exhaust gas in the reactor by a flap system in the supply lines from the rotary kiln to the reactor and in the tertiary air line, wherein the control unit, the total amount of air, which comes from a rotary kiln downstream clinker cooler, so divided that the residence time of the exhaust gas from the rotary kiln in the reactor is so long that a maximum possible reduction of nitrogen oxides (NO x ) happens in the reactor.
• NO x nitrogen oxides
• the residence time of the exhaust gas can be increased in the reactor to suspend the nitrogen oxides contained in the exhaust gas from the rotary kiln (NO x ) a longer exposure time of carbon monoxide concentration in the reactor.
• NO x nitrogen oxides
• a cooling of undesirably high temperature peaks in the reactor by introducing raw meal, wherein excess raw meal from the reactor is discharged through a drain in a rotary kiln inlet chamber, which is arranged between rotary kiln and calciner.
• the discharge of the raw meal into the rotary kiln inlet chamber prevents the reactor from becoming clogged.
• the raw meal is then deacidified and sintered to clinker.
• the fuel supplied burns very badly or forms slag, and the fuel residues, which optionally fall as a solid in the reactor, can be derived by the same line as the raw meal residues for cooling the reactor in the rotary kiln inlet chamber.
• the discharge of excess fuel in a rotary kiln inlet chamber which is arranged between rotary kiln and calciner.
• a pot reactor is suitable, which by means of a corresponding volume accommodates the requirement for the residence time of the exhaust gas to be expected from the rotary kiln or it is possible to use a gooseneck reactor, which is arranged as a burnout between calciner and rotary kiln and vice versa constructed U-shaped.
• Fig. 1 shows a plant according to the invention for the production of cement clinker.
• FIG. 1 shows a plant 1 for the production of cement clinker from raw meal 2, having viewed in the material flow direction at least one calciner 3 for deacidifying the raw meal 2, and at least one rotary kiln 4 for sintering the deacidified raw meal 2 to cement clinker 5, wherein the deacidified raw meal after passage of the calciner 3 via a Zyklonvor-heat stage 1 .4 in the rotary kiln 4 flows.
• the heated raw meal flows from the second lowest Zyklonvor- heat stage 1 .2 via a line 1 .3 in the base of the calciner.
• the raw meal 2 is entrained by the hot exhaust gases 9, which originate from the reactor 7, and deacidified in the heat of the exhaust gases 9 in the calciner.
• the resulting CO 2 is slid off via the heat exchanger 1 .1.
• the deacidified raw meal 2 is separated in the lowermost Zyklonvoricarmissue 1 .4 and introduced via its own line 1 .5 in the rotary kiln inlet chamber 16, where it then flows into the rotary kiln 4 for further thermal treatment.
• the exhaust gas 6 produced in the rotary kiln 4 by the combustion of fuel is conducted via its own exhaust pipe 13 created for this purpose into a reactor 7, where the exhaust gas 6 initially remains and is subjected to a Boudouard reaction with the addition of superstoichiometric fuel 8.
• carbon dioxide (CO 2 ) from the combustion in the rotary kiln 4 is chemically reduced together with the carbon (C) of the fuel 8 to carbon monoxide (CO).
• This Boudouard reaction is thermally influenced by the amount of added of fuel 8, as with increasing fuel supply the Boudouard reaction reacts with cooling.
• the denitrification of the carbon monoxide formation taking place in the reactor 7 takes place in an advantageous manner largely in the reactor 7.
• tertiary air 1 1 is fed to the calciner 3 via a tertiary air line 10 in addition to the exhaust gas from the reactor.
• the high carbon monoxide concentration in the exhaust gas 9 of the reactor 7 ensures a chemical reduction of the nitrogen oxide formed in the calciner 3.
• a flapper system 12 which controls the amount of gas from the clinker cooler 14 in the form of secondary air flowing through the rotary kiln 4 and in the form of tertiary air 1 1, which flows through the Tertiär Kunststofftechnisch 10, divided into different Operastrommnegen per unit time.
• the exhaust gas amount supplied to the reactor 7 can be controlled, so that the exhaust gas composition of the exhaust gas 9 from reactor 7 has a predetermined composition.
• the idea of the invention is aimed at not guiding the exhaust gas 6 of the rotary kiln 4 directly via the rotary kiln inlet chamber 16 into the calciner 3, where the high nitrogen oxide concentration of the exhaust gas 6 in the short calciner section has to be reduced, but it is intended to To reduce the carbon dioxide (CO 2 ) in the exhaust gas 6 from the rotary kiln 4 first in a reactor 7 to carbon monoxide (CO), wherein in the reactor 7 by a Boudouard reactor so much carbon monoxide (CO) is generated that the high nitrogen oxide concentration in the exhaust gas 6 of the rotary kiln 4 is largely chemically reduced in the reactor.
• CO 2 carbon dioxide
• CO carbon monoxide
• pre-acidified raw meal can be passed through a raw meal conduit 17 from the second lowest cyclone preheating stage 1 .2 into the reactor 7.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
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• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Biodiversity & Conservation Biology (AREA)
• Life Sciences & Earth Sciences (AREA)
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• Ecology (AREA)
• Environmental & Geological Engineering (AREA)
• Environmental Sciences (AREA)
• Public Health (AREA)
• Combustion & Propulsion (AREA)
• Muffle Furnaces And Rotary Kilns (AREA)
• Treating Waste Gases (AREA)
• Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Furnace Details (AREA)

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• 2013
  • 2013-04-11 DE DE102013006237.3A patent/DE102013006237B4/de active Active
• 2014
  • 2014-04-04 EP EP14716778.7A patent/EP2984054A1/de not_active Ceased
  • 2014-04-04 WO PCT/EP2014/056777 patent/WO2014166822A1/de active Application Filing
  • 2014-04-04 CN CN201811538602.7A patent/CN109516702A/zh active Pending
  • 2014-04-04 US US14/782,400 patent/US10479727B2/en active Active
  • 2014-04-04 JP JP2016506856A patent/JP6366679B2/ja active Active
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