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
  • C04B33/00—Clay-wares
  • C04B33/32—Burning methods
• • 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 peculiar to 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
• • 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
  • Y02P40/60—Production of ceramic materials or ceramic elements, e.g. substitution of clay or shale by alternative raw materials, e.g. ashes

Definitions

• This invention relates to a process for operating a plant for producing calcined clay.
• cement primarily is made of ground cement clinker, which is, however, very energy-intensive and leads to high CO 2 emissions. Beside the CO 2 emission from the combustion for achieving the clinker temperature as high as about 1450°C, CO 2 is separated and emitted from limestone - the main raw material of clinker production.
• One possibility for reducing CO 2 emissions is the admixture of cement substitutes, such as calcined clay.
• Conventional plants for cement production by the dry or semidry process consist of a precalciner (for instance series-connected cyclone preheaters) and a succeeding rotary kiln, alternatively a grate preheater (Lepol process) in the semiwet process.
• a precalciner for instance series-connected cyclone preheaters
• a succeeding rotary kiln alternatively a grate preheater (Lepol process) in the semiwet process.
• Calcining fine-grained mineral solids such as clay
• rotary kilns or multiple-hearth furnaces This ensures the maintenance of a low temperature with a retention time necessary for treatment in this process.
• U.S. patent 4,948,362 for instance describes a process for calcining clay, in which kaolin clay is treated in a multiple-hearth furnace by means of a hot calcining gas to increase gloss and minimize abrasiveness.
• the calcined clay powder is separated from the waste gas of the calcining furnace and processed to obtain the desired prod- uct.
• the plant for producing cement by the dry or semiwet process is used itself, with a precalciner, for instance comprising at least one line of series-connected preheating stages, such as cyclone preheaters or grate preheaters, and a rotary kiln or roaster, wherein in accordance with the invention the rotary kiln or roaster for producing heating gas is utilized as combustion chamber, replaced by a combustion chamber and/or completed by an additional combustion chamber.
• the heating gases are used for calcining clay and are guided through the preheating stages in counterflow to the solids.
• an existing cement plant thus can be converted to operation for calcining clay at low cost by using the existing precalcining stages.
• the clay preferably is heated by the respective combustion chamber heating waste gases to a temperature of up to 900 0 C, preferably between 650 and 850 0 C; with a corresponding retention time, these temperatures are sufficient to completely calcine the clay.
• preheating is effected in at least two preheating lines, wherein the one preheating line serves for preheating the clay and the other one for heating clinker raw material.
• a particularly flexible operation is possible when beside the rotary kiln or roaster for cement production an additional combustion chamber is operated, to which a separate heating line for the clay possibly is associated.
• a fuel/air mixture can be supplied to the heating gas stream of the respective combustion chamber before entry into the preheating line, so that enough heat is available in the possibly two or more preheating lines.
• the fuel and/or air supply for the respective combustion chamber can be controllable.
• relatively poor fuels such as coal, carbonaceous minerals with sufficiently positive calorific value, biomass, sewage sludge and/or wastes can be used, which further increases the economy of the process.
• combustion residues can be admixed to the mass flow "calcined clay".
• the illustration in the only Figure represents the fundamental principle of the operation of a plant for producing cement.
• the same includes a precalciner 1 with a plurality of preheating stages 2, which for instance can be formed as cyclone preheaters.
• a rotary kiln 3 which in accordance with the invention can, however, (also) be operated as combustion chamber 3 1 by supplying fuel and air.
• a fuel/air mixture can be supplied before entry into the precalciner 1.
• heating of the clay to be calcined which is added as solid in counterflow to the heating gases, can be effected up to 900 0 C, preferably to 650 to 850 0 C.
• Variants of the process shown in the drawing in particular consist in that either to the one rotary kiln 3 with one preheating line a combustion chamber 3 1 additionally is associated or that to the one rotary kiln 3 operated as combustion chamber 3' at least two preheating lines from preheating stages 2 are associated, wherein for instance in the one preheating line clinker raw materials are preheated and in the other preheating line the clay to be calcined is preheated.
• clinker raw materials are preheated and in the other preheating line the clay to be calcined is preheated.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Dispersion Chemistry (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Treatment Of Sludge (AREA)
• Muffle Furnaces And Rotary Kilns (AREA)
• Processing Of Solid Wastes (AREA)

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Publications (1)

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• 2008
  • 2008-07-03 DE DE102008031165.0A patent/DE102008031165B4/de active Active
• 2009
  • 2009-06-13 WO PCT/EP2009/004271 patent/WO2010000383A1/en active Application Filing
  • 2009-06-13 BR BRPI0913910A patent/BRPI0913910B8/pt active IP Right Grant
  • 2009-06-13 AU AU2009266109A patent/AU2009266109B2/en active Active
  • 2009-06-13 EA EA201100137A patent/EA018769B1/ru not_active IP Right Cessation
  • 2009-06-13 UA UAA201101190A patent/UA106588C2/uk unknown

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