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
  • C04B7/60—Methods for eliminating alkali metals or compounds thereof, e.g. from the raw materials or during the burning process; methods for eliminating other harmful components
• • 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

Definitions

• the invention relates to a method for reducing salt cycles, in particular in cement kilns, in that a partial gas stream laden with pollutants is removed from the kiln via a bypass line, these kiln gases are cooled and returned to the manufacturing process.
• the feedstocks for cement production contain secondary components such as: alkalis, sulfur, chlorine, which partially evaporate in the area of the sintering zone and which build up circuits which can considerably disrupt the operation of the kiln due to build-up.
• the disadvantage of using this technology is the increased heat requirement of the system and the raw material losses caused by the dust being warped. It is particularly disadvantageous to install such bypass devices in furnace systems which have high dust cycles, as is the case, for example, in heat exchangers which operate according to the shaft preheater principle. the case is .
• EP-A-0154281 discloses a method and a device for the production of cement which works thereafter, wherein raw material is burned to clinker, this is cooled and ground to a flour-like cement end product. Substances interfering with the burning process / such as alkalis, chlorides and / or heavy metals are branched off from the burning process at least up to the harmless limit by means of a partial gas discharge (bypass). An intermediate product is produced from de clinker with the addition of additives, at least some of the gas and / or substances contained in the partial gas discharge being introduced into the intermediate product. The intermediate product is ground to the final cement product. As already mentioned at the beginning, the branching off of the partial gas stream ultimately does not prevent the formation of salt circuits, rather the intermediate products formed are integrated with their impurities in the end product. Depending on the type of cement, this measure can cause problems during further processing.
• EP-A-0138057 discloses a method and a plant operating for the production of cement clinker which is low in pollutants, in particular low in alkali.
• the reaction gas flow and the exhaust gas flow of the clinker stage are combined to form a single suspension gas flow before being introduced into the lowest heat exchanger zone of the preheating stage. This method is also not able to prevent the effect of the Sa cycle formation.
• the invention is based on the object of designing a method and a device for reducing salt circuits, in particular in cement kilns, which largely avoids the disadvantages of a bypass system mentioned on the one hand, but fulfills the procedural requirements.
• this object is achieved by a multi-stage process of dust separation from the partial gas stream, the gases being cooled between the processes and being returned to the raw meal heat exchanger after the dust separation.
• a two-stage process of dust separation is preferably used, the branched partial gas stream being first fed to a pre-separator, the gases being cooled with air to about 600 ° C. after the dust pre-separation, and the second stage of dust separation being designed with a high degree of separation and separation Cyclone occurs.
• the dust separated from the pre-separator stage and the cyclone is returned to the Sint zone according to a further idea of the invention.
• the purified gases are returned to the raw meal heat exchanger to the location which has approximately the same temperature level of the bypass exhaust gases.
• a device for reducing salt circuits is characterized in that the line is provided in the area of the furnace inlet d combustion system and is connected to a dust separator.
• the dust pre-separator is connected to a high-performance cyclone via a line, fresh air being able to be supplied in the area of this line. It is also proposed to connect the high-performance cyclone to the raw meal heat exchanger via a further line.
• the bypass dust is preferably returned to the inlet area of the combustion system.
• the invention is illustrated using an exemplary embodiment in the Ze tion and is described as follows.
• FIG 1 shows the solution of the bypass system according to the invention
• Figure 2 shows three different bypass variants
• FIG. 1 shows the bypass system according to the invention using a functional diagram.
• the rotary kiln 1 is shown as a sintering stage, a calcining stage 2 and a preheating stage formed from a plurality of heat exchangers 3-7.
• a partial gas stream is removed from the rotary kiln 1 in the region of its inlet point 9 via a bypass line 8.
• This partial gas stream is fed to a dust pre-separator 10, whereby already separated dust particles are returned to the combustion process, the partial gas stream is fed to a high-performance cyclone 12 via a line 11, in the area of this line 11 via blowers 13 or the like. Fresh air is fed.
• the partial gas stream is suddenly cooled to about 600 ° C., at which the salt compounds condense or sublimate on the dust particles. Dust separated in the high-performance cyclone 12 is also returned to the combustion process in the region 9 of the furnace 1.
• the partial gas stream which is still approximately 600 ° C., is fed back into the area of the preheater stage by means of a blower 14.
• a further line 15 is provided, which is led to point 16 of the raw meal heat exchanger, where approximately 600 gas temperatures prevail.
• Figure 2 shows essentially the same system as a functional diagram as shown in Figure 1, with the difference that three bypass variants are included here. The three bypass variants are explained as follows:
• a - Bypass gases are removed and cooled to about 600 ° C with air.
• the dust is removed and the cyclone gases are returned to the heat exchanger.
• the cost / benefit ratio is very unfavorable for the e-filter version.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Environmental & Geological Engineering (AREA)
• Structural Engineering (AREA)
• Public Health (AREA)
• Toxicology (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Organic Chemistry (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Furnace Details (AREA)
• Cyclones (AREA)
• Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
• Treating Waste Gases (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

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ID=6362154

Family Applications (1)

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Cited By (2)

Families Citing this family (8)

Citations (6)

Family Cites Families (11)

• 1988
  • 1988-09-02 DE DE3829853A patent/DE3829853C1/de not_active Expired
• 1989
  • 1989-07-27 US US07/655,449 patent/US5244383A/en not_active Expired - Fee Related
  • 1989-07-27 WO PCT/EP1989/000885 patent/WO1990002915A1/de not_active Ceased
  • 1989-07-27 DE DE8989908988T patent/DE58903844D1/de not_active Expired - Fee Related
  • 1989-07-27 EP EP89908988A patent/EP0442892B1/de not_active Expired - Lifetime

Patent Citations (6)

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