Cemeng Dragon Calcinor technology is a novel and innovative approach for enhancing clinker output of existing dry process cement plants.Most of the so called "mini" cement plants in India or elsewhere based on conventional Suspension Preheater and Rotary kiln have been upgraded by recourse to In-line Precalcinator technology for enhanced productivity, though there may be a few installations still operating without. However, higher capacity plants have installed Precalciners in the hot air stream from the Clinker Cooler, with a separate suspension Cyclone preheater stream in spite of high system pressure drop. Fluidised Advanced Clinkering Kiln technology by M/s Kawasaki. Japan replaces rotary kiln and clinker grate cooler but conventional suspension cyclone preheaters and precalcinator are retained. Cemeng Dragon Calciners would be better choice in place of Cyclone preheater/precalciners and can function equally well with either rotary kiln or Fluid bed Advanced Kiln system.What is a Cemeng Dragon Calciner?Cemeng Dragon Calciner is an apparatus for heating and optimum calcination of powdered raw materials developed employing time tested simultaneous indirect and direct heating principles. The Calciner comprises of a battery of serpentine pipes of heat resisting metal alloys housed within the chimney of a hot gas generator utilizing heat in the exhaust gases, enabling the heating of pipes exteriorly for indirect heat exchange. Simultaneously, direct heating of raw materials in the pipe is achieved by addition of suitable solid fuel while preparing the raw materials. Alternately, superheated steam is injected into the pipes. Steam acts as a catalyst for calcination process.Construction Details of Cemeng Dragon Calciner:The pipe can be of any shape formed as a serpentine, flat or helical spirals arranged in spaced superposed relation. The pipe is continuous and is preferably formed or bent so that the pairs of coils are connected at their inner ends and pairs of the same are connected at their outer ends. This is the preferred construction. The turns in the coiled pipe are staggered or out of alignment providing torturous passages for the ascending heated gases and establish maximum contact with it.. The length of the pipe is not limited but can be as necessary to preheat and precalcine the material contained within. Connected with the upper end of the preheating pipe is a compressed air supply pipe equipped with a cut off valve. The schematic arrangement of the Dragon Calciner is shown in figure below:How Cemeng Dragon Calciner functions:Dry powdered raw material is fed along with compressed air into the intake end of pipe such that it is sealed against back pressure, and the outlet end of the pipe is open for discharge. The powdered solid material has voids between its minute particles, which voids are filled with air. While at atmospheric temperature, it would be impossible to properly force the powdered raw meal through the preheating pipe without injecting air into the same, as it would pack within the pipe, but when heated to a sufficiently high temperature, it flows freely and is converted into a form having the characteristics of a liquid and readily passes through the preheating pipe without injecting air into the same. Satisfactory results can be obtained by heating to a temperature of from 500deg F to 2500 degree F in case of cement raw materials. The expansion of the heated air within the material confined within the pipe as also the liberated carbon dioxide from partial or complete calcination in the pipe propels the material through the pipe, not impairing the fluid properties of the heated materials.Pet coke breeze or fines would be appropriate for simultaneous and combined grinding along with raw materials, as it has high ignition point. The amount of solid fuel forming constituent of powdered raw materials mix or black meal would be to suit preheating of the material and the required degree of calcination .The compressed air injected would be as required for combustion of the fuel in the black meal. along with about five percent of excess air.Superheated steam at high temperature and pressure, when used, could be injected after the preheating stage to provide the heat required for calcinations. Residence time of materials in the calciner is predominantly dependent on amount of compressed air/steam injection, viz. velocity of flow. At the discharge end of the pipe, the calcined material ejects out along with the stream of hot exhaust gases, comprising air/steam and carbon dioxide due to burning of fuel as also that released from raw material from de-carbonization, if so required, facilitating separation of material and gas stream through a separator.Advantages of Cemeng Dragon Calciner:Cemeng Dragon Calciners offer the advantage of flameless combustion of fuel and no additional burner and accessories are required. As the black meal flows through the Pipe calciner, the fuel in meal gets burnt to heat the raw meal progressively to calcining temperature and then calcine the material. Besides, the material conveying airItself would be the combustion air for the fuel, thus no additional blowers are required. Further, after the discharge of calcined material, the hot exhaust gases are deflected to ascend through the calciner to utilize the available heat to the maximum extent, and providing additional heat for the calcination process. It would be necessary to install only a start up burner for the hot gas generator forming part of the Dragon Calciner apparatus. Thus these can be stand-alone units.Cemeng Dragon Calciner has versatility and its geometry is highly flexible in view of different possible shape configurations. The required residence time for the meal in the calciner can be altered by changing the quantum of conveying air or selecting suitable pipe cross-section to maintain requisite flow velocity within wide limits. The large surface area of pipes would be beneficial for exterior heat exchange from exhaust gases. The pressure drop in Calciner will be as low as 250 mm wg. The foot print for Cemeng Dragon Calciner would be considerably less when compared with suspension cyclone preheater/precalciners.Cemeng Dragon Calciner can function equally well with either a rotary kiln or fluidized bed kiln where the calcined material discharged from calciner is subject to clinkerisation. The rotary kiln can now be effectively used up to its furnace capacity limits and the kiln exit gases directed through the Dragon Calciner. Besides, clinker cooler hot air can be gainfully utilized for production of superheated steam by installing a suitable boiler at clinker cooler. The superheated steam generated can be transported to the Cemeng Calciner, thus, eliminating the larger tertiary air ducting set up.Carbon dioxide is considered to be the major source of GHG responsible for global warming; man-made CO2 contributes approximately 63.5% to all greenhouse gases. The cement industry is responsible for approximately 5% of global anthropogenic carbon dioxide emissions emitting nearly 900 kg of CO2 for every 1000 kg of cement produced. Cemeng Dragon Calciner offers a way, when superheated steam is used, to capture CO2 by further processing techniques and reduce CHG emissions.(Courtesy: D.S. Venkatesh,Consultant and D.V. Kaushik, Project Executive, Cemtec Engineering, Bangalore)