Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
  • F27B7/20—Details, accessories or equipment specially adapted for rotary-drum furnaces
  • F27B7/2016—Arrangements of preheating devices for the charge
  • F27B7/2025—Arrangements of preheating devices for the charge consisting of a single string of cyclones
  • F27B7/2033—Arrangements of preheating devices for the charge consisting of a single string of cyclones with means for precalcining the raw material
• • 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
  • C04B7/434—Preheating with addition of fuel, e.g. calcining
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
  • Y02P40/125—Fuels from renewable energy sources, e.g. waste or biomass

Definitions

• the process of producing cement clinker can be divided into three different stages.
• the finely ground raw material is heated to about 600 ° C. Apart from the drainage of the clay minerals, no significant reactions occur at this stage.
• the second process stage is characterized by the strongly endothermic reaction of deacidification of the calcium carbonate.
• the third stage of the process finally includes the further heating of the fired material to the sintering temperature and the weakly exothermic reaction of the clinker mineral formation. From an energetic point of view, deacidification of calcium carbonate is of the greatest importance, since according to H.Kühl "Zementchemie", VEB-Verlagtechnik Berlin 1958, page 354 (volume II), it is associated with a heat tone of 1638 kJ / kg. Since common cement raw meal contains about 75% limestone, the predominant energy share in the cement burning process is needed in the deacidification stage, i.e. in a temperature range of around 650 to 950 ° C.
• secondary fuels in the temperature range between about 650 ° and 1000 ° C i.e. usually introduced in the area between the furnace inlet and the bottom cyclone stage of the heat exchanger. This usually succeeds without high investments.
• Heavy fuel oil, gas, coal dust, but also waste materials with constant heating value, such as used tires, are used as secondary fuels.
• the gaseous, liquid or fine-grained fuels are burned in admixture with the raw meal coming from the heat exchanger, the coarse-grained substances, such as the old tires, burn in the intake device to the furnace or can also be carried into the furnace, where they then burn .
• the amount of secondary fuel that can be used is limited in both cases.
• the second variant which is practically only used in new plants, provides for the combustion of the secondary fuels in a separate combustion chamber, which is often referred to as a calciner.
• a calciner A number of proposals have been made for such calcinators. They are all characterized by an extended residence time of the raw meal, as well as by high investments and a higher expenditure of electrical energy due to the pressure drop in the calciner. Only high-quality fuels are practically possible as secondary fuels; the air required for their combustion is often not released through the furnace to relieve the sintering zone. passed, but fed to the calciner in a separate line, preferably as cooler hot air. With suitable calciners, a degree of calcination of over 80 to about 95% can be achieved.
• An essential feature of the present invention is that at the furnace inlet or in the area between the furnace inlet and the pre-combustion zone of the process, a secondary fuel in a greatly increased either compared to the previously customary procedure or compared to the oxygen available for combustion there
• Amount is supplied so that there is a clear air deficit at this point where the secondary fuel is introduced.
• Flammable gases are released from the secondary fuel, which are then used for the calcination (deacidification) of the raw material.
• the present invention thus relates to a method for producing cement clinker, in which the, preferably finely ground, raw material in one
• Preheating zone preferably a system of cyclone heat exchangers, heated, in a calcining zone with secondary firing, in particular a calcining furnace, with the supply of a secondary fuel and with the supply of tertiary air, at least partially deacidified and then, preferably in a furnace, subjected to a firing process is, after which the clinker provided is cooled in a cooling zone, for example a clinker cooler, which is characterized in that in the area of the introduction of the preheated raw material into the firing process, preferably in the area of the inlet of the kiln, and / or in the area
• flammable constituents preferably coarse, possibly uncrushed, in particular delayed burning substances, preferably waste materials and / or conventional fuels, are added and by supplying the exhaust gas resulting from the combustion of the primary fuel in
• the essence of the invention is therefore that the combustion of the secondary fuel is essentially broken down into two stages.
• the first stage there is incomplete combustion and / or only pyrolysis of the secondary fuel, in which the secondary fuel gas is released, which is then only subjected to complete combustion in the second stage, the calcining stage.
• the split combustion of the secondary fuel which takes place in two stages, in particular the heat developed during the combustion of the secondary fuel gas, is used to deacidify the raw material, in particular raw meal.
• the incomplete combustion if oxygen is available at all, the following reaction occurs:
• the gas supplied to the calcining zone as a whole is composed, on the one hand, of exhaust gas formed during the combustion of the primary fuel in the combustion process and, on the other hand, of the gases which, in the event of incomplete combustion and / or pyrolysis of the secondary fuels, therefore, during their combustion or heating Air deficiency are released, together, which are referred to here as secondary fuel gas.
• the secondary fuel gas consists predominantly of a) carbon monoxide CO (from the combustion of the carbon of the secondary fuels with insufficient air or from the reaction of the water contained in the secondary fuels with carbon) b) hydrogen H 2 (from the reaction of the water contained in the secondary fuels with carbon) c) gases formed by pyrolytic decomposition from the secondary fuels, for example hydrocarbons, and d) if necessary, other volatile compounds, for example sulfur compound, formed by the decomposition of the secondary fuels .
• composition of the secondary fuel gas can naturally fluctuate within wide limits, depending on the type and amount of the secondary fuels used.
• Waste products of all types can be used as secondary fuels.
• waste products of all types can be used as secondary fuels. For example:
• Plastic waste in particular polyethylene, polyvinyl acetate, polyamide, polyvinyl chloride and the like, in particular cords, stockings, tricot residues and the like. hard to shred plastic waste, natural or artificial rubber products, especially car and scrap tires,
• Substances containing combustible constituents which burn within more than 20 s, preferably more than 2 min, in particular more than 10 min, can be added to the process without further notice.
• the calcining zone can also be supplied with a conventional secondary fuel. This is of particular interest and is advantageous if, in the process according to the invention, substances share with varying proportions of combustible material or with strongly varying combustion or
• Pyrolysis speed are used, which ultimately leads to fluctuations in the amount and / or in the calorific value of the secondary fuel gas formed.
• the supply of the additional secondary fuel such as a heating gas or oil
• the additional secondary fuel can be controlled in the calcining zone, so that the calcining zone ultimately has one Amount of Geraisches of secondary fuel gas and conventional secondary fuel is supplied, the total heat output is kept substantially constant and is subject to little fluctuations, although the secondary fuel according to the invention used to produce the secondary fuel gas has relatively high quality and combustion property fluctuations.
• Another advantage of the method according to the invention is that the tertiary air is not, as is usually the case, fed to the calcining zone before the secondary fuels are added, but that the gases leaving the furnace already contain the secondary fuel, namely the secondary fuel gas, and in this way the Tertiary air is only added afterwards, so to speak.
• the secondary fuel gas obtained in the incomplete combustion and / or pyrolysis in the calcining zone with, preferably in the cooling zone, for example in the clinker cooler, preheated tertiary air and / or with optionally preheated oxygen.
• the secondary fuel gas should also contain as little O 2 as possible.
• the CO content of the secondary fuel gas is set to above 3% by volume, preferably above $ 7% by volume, in particular above 15% by volume. Further, it is advantageous to adjust the process in this way result in the CO 2 content of the secondary fuel gas being set to a value which is less than 8% by volume, preferably less than 4% by volume, in particular less than 2% by volume, above the CO 2 - Content of the exhaust gas generated during the combustion of the primary fuel in the combustion process is.
• the Wasserge secondary fuels are limited, preferably to 0 to 15%, in particular 0 to 8% and particularly advantageously 0 to 5%.
• the secondary fuel gas together with the furnace exhaust gases generated during the combustion of the primary fuels in the furnace, is led into the area of the process in which the raw steel is deacidified.
• the secondary fuel gas burns after the following reaction:
• the process according to the invention utilizes the secondary fuel in two stages.
• the combustible substance of the secondary fuels in particular the carbon
• combustible gas in particular carbon monoxide
• the speed at which this conversion takes place is immaterial since there is a lot of time available in the furnace.
• the flammable gases thus generated from the secondary fuels become the fed to the second stage of the process, in which the combustion of the carbon monoxide and optionally the hydrogen and the other volatile constituents takes place.
• This substantial reduction in the gases to be conducted in the furnace decisively reduces the dust cycle and leads to a strong improvement in the energy balance and also a reduction in the formation of deposits in the region of the furnace inlet.
• This redaction of the gases to be conducted in or through the kiln makes it possible either to increase the kiln output with the same flow conditions in the kiln and the same dimensions or to significantly improve the flow conditions with the same output and kiln dimensions, that is to say to reduce the gas velocity in the kiln, or to significantly reduce the diameter of the furnace with the same output and the same flow conditions, which ultimately means less investment and significantly better durability of the furnace lining.
• the combustion of the secondary fuel gas can be carried out under precisely defined and controlled conditions.
• the combustion of the secondary fuel gas is carried out in a separate calcining combustion chamber, which is between the entry point of the secondary fuels and the usual preheating or preheating zone, for example the last one
• Cyclone stage of a heat exchanger is arranged.
• the secondary fuel gas mixed with the heated Rohraehl is burned, preferably in a fluidized bed process. It has been shown that under the given conditions when using inferior secondary fuels, the excess air required for complete combustion could be reduced to half that of the previous one.
• the air required for the combustion of the secondary fuel gas is supplied as tertiary air, see above.
• the invention further relates to a system for carrying out the method, which essentially consists of a system of heat exchangers, in particular cyclone heat exchangers, which is preferably connected to a kiln via a calcining furnace, to which a clinker cooler is connected, and is characterized in that that the calcining furnace and / or the lowest stage of the, optionally multi-strand, cyclone system has a device for introducing, preferably preheated in the clinker cooler, tertiary air and / or oxygen, and optionally a device for introducing a conventional secondary fuel gas, or have and in each case via at least one line for supplying raw material into the kiln and via at least one line for discharging the exhaust gas resulting from the combustion of the primary fuel in the kiln and one having incomplete combustion and / or pyrolysis of combustible components n substances, preferably waste materials, secondary fuel gas obtained is (are) connected to the furnace, in the region of the furnace inlet and
• the pipe material to be burned is passed through the calcining zone 3 via a system equipped with a suction fan 1, optionally a multi-strand system, of cyclone heat exchangers 2, which zone is used for calcining the raw material determined calcining furnace 3a. and a separator 3b.
• the raw material is fed through the feed line 7 to the inlet 9 of the kiln 10, which is shown in the drawing as a rotary kiln.
• the raw material passes through the rotary kiln 10, which is equipped with the burner 11 charged with primary fuel and primary air, passes through its sintering zone and leaves the furnace at the furnace head 12 as a finished, hot clinker, which is then cooled in the clinker cooler 13, after which its refurbishment by grinding, which is no longer shown, Sighting and the like he follows.
• the hot furnace exhaust gases which are produced when the primary fuel is burned in the burner 11 of the furnace 10 are, after they have sintered the raw meal in the furnace, fed via the exhaust gas discharge 6 to the calcining furnace 3 or to a bottom cyclone stage designed as a calcining furnace.
• a device On the line 6, on the line 7 and / or directly at the furnace inlet 9 is a device, in particular one there opening lock 8 arranged for introducing the secondary fuel.
• This fuel for example only coarsely comminuted waste, enters the running area 9 of the kiln and is heated, decomposed and burned by the hot kiln exhaust gases, in which a deficit of air or oxygen is set with regard to the amount of combustible substances in the secondary fuel only incomplete and / or pyrolyzed.
• the gases released such as CO, hydrocarbon cracking gases, CH 4 , H 2 or the like, which form the secondary fuel gas, are fed together with the exhaust gas leaving the furnace 10 through the exhaust gas discharge 6 to the calcining furnace 3 and are there under separately ter supply of tertiary air burned via the supply point 4.
• the heat released serves to complete the deacidification of the raw material.
• the tertiary air required for the combustion of the secondary combustion gas can advantageously be fed to the calcining furnace 3 via the line 14 led through the clinker cooler.
• a conventional secondary fuel can additionally be introduced into the calcining zone 3 via the feed 15 in the calciner 3, 3a, which is particularly advantageous to compensate for fluctuations in the quantity and calorific value of the secondary fuel gas.
• the introduction device 8, in particular lock, for the secondary fuel which is to be incompletely burned and / or gasified in the oxygen deficit, can optionally also be introduced into the pyrolysis zone Pyrolysis zone and a separate calcining zone divided calciner 3 can be entered, which is then also arranged in accordance with the invention between the kiln inlet and the calcining zone.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Structural Engineering (AREA)
• Thermal Sciences (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Furnace Details (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Incineration Of Waste (AREA)

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• 1982
  • 1982-04-16 AT AT0149482A patent/AT378170B/de not_active IP Right Cessation
• 1983
  • 1983-04-15 US US06/556,673 patent/US4913742A/en not_active Expired - Fee Related
  • 1983-04-15 AU AU14782/83A patent/AU560364B2/en not_active Ceased
  • 1983-04-15 EP EP83901305A patent/EP0105322B1/de not_active Expired
  • 1983-04-15 DE DE8383901305T patent/DE3361971D1/de not_active Expired
  • 1983-04-15 WO PCT/AT1983/000010 patent/WO1983003601A1/de not_active Ceased
  • 1983-04-15 JP JP58501409A patent/JPS59500911A/ja active Granted

Patent Citations (3)

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