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In the early fifties there was a technical revolution. Henan Hongxing built the preheater, a starting point of a new aera of reducing the heat consumption of the clinker pyro-processing system by nearly 50% at this time. Today HXJQ is one of the technical leaders worldwide in this field. The raw meal processed in the kiln first passes through the preheater absorbing the heat content of the kiln.

The suspension preheater is the basis of all modern systems. Rawmix in dry powder form is injected into hot kiln exhaust gas in a vertical duct. The upward gas velocity is sufficient for the powder to be picked up and lifted up the duct "in suspension" in the gas. Because heat exchange occurs over the vast surface area of the individual mineral particles, the gas and rawmix reach a common equilibrium temperature in a fraction of a second. The solids and gas are then separated in a cyclone. This process is repeated a number of times - typically three to six - by stacking "riser" ducts and cyclones on top of one another in a tower. By repeated heat exchange, most of the heat in the kiln exhaust gas can be captured, while heating the rawmix to calcination temperature. Such heat as escapes the preheater is used to heat the rawmill.

Each “stage” consists of a riser pipe and a cyclone. In the riser pipe, hot gas ascends and raw meal is injected into the side and becomes entrained. Passing into the cyclone, the mixture is separated: the heated meal passes to the next stage down, and the cooled gas passes to the next stage up. The more stages are used, the more efficient the preheater is. But each stage increases the pressure drop across which the kiln fan must work, and with more than six stages, the fan power requirement is prohibitive. However, in practice waste heat is needed for the raw mill, and four stages remains the most common setup. Because the rawmix is partially calcined in the preheater, only a relatively short kiln is required. However, the amount of processing that can be achieved in the preheater is limited by the amount of exhaust gas leaving the kiln, the kiln flame being the only source of energy. The most common operational problems with these preheaters are imperfect entrainment of the meal, causing inefficiency, and blockages caused by sticky materials building up in cyclones and bends, causing reduced and unstable flow.

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The action of the cyclone is essentially centrifugal: the dust-laden gas is made to revolve rapidly, so that relatively dense particles concentrate towards the outside edge. On withdrawing relatively clean gas from the central vortex, the solids proceed by conservation of momentum towards the tip, from which they can be withdrawn through an airlock. The term "cyclone" is justified: in a cyclone with transparent walls, a distinct tornado-like vortex can be seen.

In order to avoid extra handling of the dust, dry process kiln cyclones were arranged above the kiln cold end, so that captured dust could be returned to the kiln by gravity alone. It was noticed that , if the rawmix entering the kiln became entrained in the exhaust gas, the exhaust gas temperature was lowered, and hence energy was saved.