Abstract:
The present invention is directed to a method and apparatus for controlling the kiln gas stream (90, 138) in a conventional long wet or dry process cement kiln (10). A portion of the kiln gas stream (90) can be withdrawn from the rotary kiln vessel (17) at a point upstream, relative to kiln gas flow of the chain system in the mineral drying zone (24). Alternatively, or in conjuction with bypass formation, the apparatus (256) can be used to add tertiary air to the kiln gas stream (90) to promote combustion efficiency downstream of the clinkering zone (28). Use of the present apparatus (56, 156) to form a kiln gas bypass stream (64) enhances operating efficiencies of long kilns by reducing dust loss, by facilitating isolation of high alkali by-product streams, by reducing alkali content of collected kiln dust, by increasing energy efficiency of long kiln operation, and by allowing greater overall control in the cement manufacturing process.
Abstract:
Both drying and the extraction of water of crystallisation can be performed in a fluidised bed apparatus (A, B) without any danger of overheating. This is attained via complete, uniform fluidisation by indirectly heated hot gas. A substantial quantity of energy is transferred to the fluidised layer via heat exchanger systems (4 and 12). These are heated by heat-conveying media. The structural layout of the fluidised bed apparatuses (A, B), the base plan of which is rectangular, ensures a narrow dwell period spectrum and an excellent temperature/moisture curve without the assistance of various fluidised chambers. Owing to the relatively cold introduction area and gentle heating thus produced, the properties of the crystals are favourably affected. The product is distinguished by very uniform quality. No undesirable modifications to the gypsum occur when moist gypsum is calcined.
Abstract:
The invention relates to a method and an arrangement for producing alpha -calcium sulphate hemihydrate using the gypsum suspension produced during the wet flue gas desulphurization process of a fossil-fired thermal power station. The aim of the invention is to carry out a continuous process of converting and further processing gypsum to produce highly pure end products which is directly linked to the flue gas desulphurization process of a coal-fired power station. To this end, a partial flow is removed from the gypsum suspension taken from the flue gas desulphurization process (1) before dehydration and the solid parts are separated into dihydrate and unwanted constituents by one or more hydrocyclones (5). The thus purified suspension is heated, then mixed with a dispersion of crystallizers and nucleators (11), guided via the outer pipe (13) of a longitudinal, upright double-pipe heat exchanger (14) and after being heated again, is released to an optionally coil-shaped reactor (19) which is located underneath which has mixing screws, using the hydrostatic pressure. The suspension is then delivered to the inner pipe (21) of the double-pipe heat exchanger (14). The resulting alpha -calcium sulphate hemihydrate suspension in this inner pipe (21) is caused to rise to the exit level (22) and then dehydrated, the resulting powder then being dried and screened or ground. The invention also relates to an arrangement for producing alpha -calcium sulphate-hemihydrate using the gypsum suspension produced in the wet flue gas desulphurization plant of a fossil-fired thermal power station.
Abstract:
Lightweight gypsum board product can be produced by modifying the calcined gypsum prior to introduction in a gypsum slurry and introducing a foaming agent by the use of a foam generator and high pressure air. The foaming agent has uniform and stable size and distribution of bubbles. The foam imparts these advantageous void properties and results in a lightweight gypsum product that has adequate strength and nail pull characteristics.
Abstract:
Method of producing hemihydrate plaster by calcining natural or synthetic gypsum in at least one cyclone zone, wherein the gypsum and the hot gases are fed into the top of the first cyclone zone and calcining is carried out in a parallel flow of hot gases and particles of the materials to be dehydrated by circulation in a downward direction along a cyclonic path in each cyclone zone, followed by circulation in an upward direction in the central area of each cyclone zone. A plant for carrying out the method is also disclosed.