Petrographic analysis of clinker

The mineralogical composition of clinker can be determined by various methods: petrographic, chemical and X-ray analysis method.

Petrographic analysis is performed mainly by four techniques: 1) immersion method (powder method); 2) in the transparent sections; 3) in polished sections; 4) transparent - polished sections. The method allows to determine the morphological features of clinker - the number and distribution phases, habit, cleavage, twinning crystals, porosity; details of the internal structure - the refractive index anisotropy, coloring minerals, crystallographic constants, crystal system.

When petrographic analysis of polished sections of the most characteristic clinker granules prepared polished section and view it with a polarizing microscope. Determine the content of minerals, their size, structure, and others.

In Shymkent and Karaganda cement plant was once embedded operating petrographic analysis of quality clinker, developed by staff of the Department HTVM Kazakh Chemical - Technological Institute L.G.Trofimovoy, R.A.Saykulovym and B.T.Taymasovym. It allows you to quickly control the quality of clinker, to predict and regulate its activity on the basis of this work of firing units. Implementation of development at JSC "Karagandatsement" has raised the level of quality clinker for 4... 5 MPa, which increased the slag input 3% of clinker and to reduce consumption. In "ShymkentCement» introduction of the method increased the average mark of 0.5 MPa of cement, increased the productivity of furnaces, reduced fuel consumption and reduced output marriage.

Petrographic analysis shows the actual mineral composition of clinker. Rational chemical analysis of clinker to determine its chemical composition, based on which with the help of the formulas can be determined settlement mineralogical composition of clinker. Estimated and actual structure is slightly different. Reasons for discrepancies include: 1) during firing and cooling, the clinker is not achieved complete phase equilibrium, remain free of CaO and SiO2; 2) the actual composition of the minerals is different from the calculated composition of the compounds, as part of alite and belite different from the composition of trёhkaltsievogo and dicalcium silicates, minerals, and similarly - flooded; 3) minerals form solid solutions; 4) significant changes in the theoretical composition of the clinker making lye.

As a rule, the actual content of alite in the clinker is always greater than the estimated, the actual content of C3A less than its rated amount.

Cement production

Most cement plants begin to feed the quarry where mined limestone (calcium oxide) and clay (oxides of silicon, iron and aluminum). D Depth can reach 100 meters, and the area - several dozen football fields. The raw material is crushed and mixed in a ratio of about 75% lime and 25% clay. The process of mixing the raw material mixture used to occur through mixing with water (slurry preparation - the so-called "wet" mode of production "). Now mainly used in the "dry method" of production, wherein the raw material mixture was prepared without mixing with water. This method can save up to 40 percent of the fuel (which was previously passed on subsequent drying of water), which significantly reduces the manufacturing cost of cement. There is also a combined method, or "semi-dry" method of production.

The obtained mixture was fed into a rotary searing oven where it is baked at 1450 ° C followed by quenching in air cooler. The output is a semi-finished product - the granules of up to 15 mm - so called cement clinker. The dimensions of the kiln at the wet process may be as high as 7 meters in diameter and 200 meters in length. In the dry method, the length of the furnace, typically less than 80 meters. The fuel for the clinker burning is usually natural gas. It is gaining popularity topic of alternative fuels such as used tires and rubber waste. Next is the step of preparing a proper cement from cement clinker - grinding in a grinding mill with the addition of gypsum (up to 5%, for adjusting the timing of cement) and mineral supplements (up to 30% depending on the brand of the resulting cement, slag, tripoli - to reduce costs). Incidentally, the grinding step is sometimes transferred to a separate independent production when purchased cement clinker and transported over long distances.

As a rule, cement factories, there are several production lines. For example, the plant capacity of 1.5 - 2.5 million tons can be up to 4 rotary kilns and cement mills to 6.

Ready cement is supplied to the warehouse - cement silos, and then sent to consumers, either in bulk hopper cars and cement trucks, or packaging - bags of 1 - 1.5 tons (big bags) and bags of 50 kg.