Category: Gas Generation, Nitrogen, PSA Nitrogen Generators
Cement is a basic material for building and civil engineering construction. Output from the cement industry is directly related to the state of the construction business in general and therefore tracks the overall economic situation closely.
The three basic process steps in cement manufacturing are · Preparation, blending and milling of the raw material to raw meal that is used as kiln feed. · Calcination and burning (sintering). This conversion process takes place within the cement kiln and its associated equipment. · Finish milling, the grinding of clinker to produce cement.
After mining, grinding and homogenization of raw materials; the first step in cement manufacture is calcination of calcium carbonate followed by burning the resulting calcium oxide together with silica, alumina, and ferrous oxide at high temperatures then ground or milled together with gypsum and other constituents to produce cement.
The clinker burning takes place in a rotary kiln which can be part of a wet or dry long kiln system, a semi-wet or semi-dry grate preheater kiln system, a dry suspension preheater kiln system or a preheater/precalciner kiln system. The best available technique for the production of cement clinker is considered to be a dry process kiln with multi-stage suspension preheating and precalcination.
The coal mill takes the coal feed and grinds it to a size suitable for introduction into the burner. It is a good example of the boundary considerations that will accompany isolating the kiln from the atmosphere. The coal is transported to site under atmospheric conditions and enters the kiln, which is isolated. At some point between those extremes a gas boundary must be established, either before or after the mill.
Currently, the coal mill presents a safety hazard as friction from the grinding can heat the coal dust to the point of ignition. To mitigate this risk, ambient air is blown through the mill to control internal temperatures. If the boundary is placed upstream of the coal mill then it would be charged with N2 rather than air. As a result, oxygen is not present to ignite the coal dust; in addition, the endothermic Boudouard or carbon gasification reaction caps the maximum temperature at 700o C. Steam will also be brought in as moisture on the coal. The resultant of N2, steam and heat may lead to gasification if the operating temperature of the mill is allowed to rise. In this manner, some of the electrical energy consumed by the mill can be transferred, as sensible heat, to the kiln. The advantage of this scenario is that the combustion properties of the fuel mixture can be altered to produce the optimum conditions in the clinker formation zone.
Inert gas systems based on fuel burning process were used. However, Nitrogen production using GAZTRON PSA Nitrogen application has many benefits and increasingly cement plants are using Nitrogen gas instead of CO2.
Due to the fact that the main part of the combustion air nitrogen also represents the main part of the exhaust gas. Nitrogen it is not a pollutant.