Methods and apparatus for reducing the content of controlled acidic pollutants in clinker kiln emissions are disclosed. The methods and apparatus include introducing bypass dust produced during production of clinker into one or more locations between the preheater exhaust and the inlet to a dust filter including into a gas conditioning tower. Total bypass dust separated from the kiln exhaust gas may be used. The bypass dust can be separated into a fine and coarse portions. Fine or total bypass dust can be mixed with water to form a bypass dust slurry that can be introduced into the gas conditioning tower. Bypass dust can be used to reduce the content of acidic pollutants such as hydrogen chloride HCl and sulfur oxides SO.sub.x from clinker kiln emissions.

The present invention discloses a method of applying electric arc furnace dust in chemical looping combustion process, and particularly a method of applying electric arc furnace dust in chemical looping combustion process without releasing of zinc vapor. The method of applying electric arc furnace dust in chemical looping combustion process comprises following steps: (1) providing an electric arc furnace dust and an inert support (Al.sub.2O.sub.3) and mixing the electric arc furnace dust and the inert support (Al.sub.2O.sub.3) to obtain a mixture of the electric arc furnace dust and the inert support (Al.sub.2O.sub.3); (2) calcining the mixture of the electric arc furnace dust and the inert support (Al.sub.2O.sub.3) with high temperature to obtain another mixture of Fe.sub.2O.sub.3, ZnAl.sub.2O.sub.4, and Al.sub.2O.sub.3; (3) applying the mixture of Fe.sub.2O.sub.3, ZnAl.sub.2O.sub.4, and Al.sub.2O.sub.3 as oxygen carrier and inert support in a chemical looping combustion process.

A method for calcination includes providing a heated coarse solid particle stream with a carbon dioxide rich sorbent to a reactor having a rotatable container.

An apparatus for producing cement clinker, comprising a kiln for calcining raw materials to form cement clinker, comprising a preheating stage for preheating the raw materials in a counter-flow to kiln off-gases, comprising a clinker cooler for cooling the cement clinker, comprising a denoxing stage for denoxing kiln off-gases, comprising a heat exchanger for heating the kiln off-gases upstream of the denoxing stage by heat exchange with a heat exchange medium, comprising at least one further heat exchanger for heating the heat exchange medium by heat exchange with kiln off-gases or exhaust air of the clinker cooler, wherein the heat exchanger is connected to the further heat exchanger via a line for the heat exchange medium, wherein a hot gas filter is arranged in the flow direction upstream of the further heat exchanger.

The invention relates to a method and a system for producing cement clinker from raw cement mixture, wherein one part of the raw cement mixture is preheated in a calciner preheater, and the other part of the raw cement mixture is preheated in an oven preheater, the preheated raw cement mixture is pre-calcined in a calciner which is operated according to the oxyfuel method, the pre-calcined raw cement mixture is fired in an oven, the fired raw cement mixture is cooled in a cooler, the calciner preheater is operated using exhaust gases of the calciner, the oven preheater is operated using exhaust gases of the oven, an entrained flow reactor is used as the calciner, a part of the calciner exhaust gas being recirculated to the calciner after being used in the calciner preheater, and the oven exhaust gas undergoes a post-combustion CO.sub.2 separation.

The present invention provides a process and system for waste heat grading cyclic utilization and pollutant emission reduction of sintering flue gas, in which the sintering flue gas is divided into low-temperature, high-oxygen, low-humidity section sintering flue gas; middle-temperature, low-oxygen, high-humidity section sintering flue gas; and high-temperature, high-oxygen, low-humidity section sintering flue gas according to the emission characteristics of temperature, oxygen content and humidity of the flue gas. The low-temperature, high-oxygen, low-humidity section sintering flue gas is led into the sintering machine for hot air ignition and hot air sintering; the middle-temperature, low-oxygen, high-humidity section sintering flue gas is subjected to dust removal and desulfurization treatments; the high-temperature, high-oxygen, low-humidity section sintering flue gas is mixed with exhaust gas of a cooler and then is led into the sintering machine for hot air sintering. The present invention can conduct grading utilization to the flue gas and recycle low-temperature sensible heat in flue gas, making the carbon monoxide left in the sintering flue gas burn again and thus saving energy consumption in the sintering process, on the premise that the quality and yield of the sintered ores are ensured. The present invention can also conduct cyclic utilization to the flue gas and thereby reduce pollutant emissions and the total emissions of sintering flue gas per unit of the sintered ores. Thus, the present invention has a very high value on energy saving and emission reduction.

A blast furnace system is used wherein the coke rate is decreased by recycling upgraded top gas from the furnace back into its shaft section (which upgraded top gas is heated in a tubular heater prior to being recycled). The top gas, comprising CO, CO.sub.2 and H.sub.2, is withdrawn from the upper part of the blast furnace; cooled and cleaned of dust, water, and CO.sub.2 for increasing its reduction potential and is heated to a temperature above 850 C. before being recycled thus defining a first gas flow path used during normal operation of the blast furnace. Uniquely, a second gas flow path for continued circulation of top gas selectively through the heater and a cooler during operation interruptions of the blast furnace allows time for gradual controlled cool down of the heater in a manner to avoid heat-shock damage to the tubular heater.

An industrial furnace for heating products such as steel products includes a thermally insulated enclosure, a plurality of burners arranged in the enclosure for heating products passing from one end of the enclosure to the other, the burners being distributed over a plurality of temperature-regulated heating areas, and a recovery system designed for recovering heat energy from recovery fumes, The recovery system includes a rotary regenerator associated with each heating area, each of the rotary regenerators being configured to receive a predetermined flow rate of recovery fumes via a first duct, receive a predetermined flow rate of supply air via a second duct, preheat the supply air in order to supply the burners of the associated heating area with a predetermined flow rate of preheated combustion air via a third duct, and discharge exhaust fumes via a fourth duct.

A thermally efficiency regenerative air preheater 250 extracts more thermal energy from the flue gas exiting a solid fuel fired furnace 26 by employing an alkaline injection system 276. This mitigates acid fouling by selectively injecting different sized alkaline particles 275 into the air preheater 250. Small particles provide nucleation sites for condensation and neutralization of acid vapors. Large particles are injected to contact and selectively adhere to the heat exchange elements 542 and neutralize liquid acid that condenses there. When the deposit accumulation exceeds a threshold, the apparatus generates and utilizes a higher relative percentage of large particles. Similarly, a larger relative percentage of small particles are used in other cases. Mitigation of the fouling conditions permits the redesign of the air preheater 250 to achieve the transfer of more heat from the flue resulting in a lower flue gas outlet temperature without excessive fouling.

Methods and apparatus for reducing the content of controlled acidic pollutants in clinker kiln emissions are disclosed. The methods and apparatus include introducing bypass dust produced during production of clinker into one or more locations between the preheater exhaust and the inlet to a dust filter including into a gas conditioning tower. Total bypass dust separated from the kiln exhaust gas may be used. The bypass dust can be separated into a fine and coarse portions. Fine or total bypass dust can be mixed with water to form a bypass dust slurry that can be introduced into the gas conditioning tower. Bypass dust can be used to reduce the content of acidic pollutants such as hydrogen chloride HCl and sulfur oxides SO.sub.x from clinker kiln emissions.