The process of cement production
Date：2019-08-29 16:45 Source：cementepcViews:
If you want to produce cement well, you must know the process of cement production.
1. Related concepts
(1) raw materials:
raw materials made of limestone, clay and a small amount of calibration materials are grinded to a certain fineness in proportion, which are called raw cement.
the raw material with appropriate ingredients is burned to partial melting, and calcium silicate is the product of the main component.
(3) calibration of raw materials:
when the raw ingredients obtained by combining calcareous and clay materials cannot meet the requirements of the batting scheme, appropriate raw materials must be added according to the missing components. Such raw materials, which are mainly used to supplement the deficiencies of some components, are called calibration of raw materials.
The limestone raw material (the main ingredient for calcium carbonate, calcium oxide), such as limestone, marl, chalk, shell, etc.
The clay materials (provide silica and alumina and some iron oxide), such as loess, clay, shale, mudstone, siltstone and river mud
Small amount of calibration raw materials (iron calibration raw materials and siliceous calibration raw materials, providing iron oxide and silicon oxide), such as low-grade iron ore, tailings of iron smelting plant and industrial waste residue of sulfuric acid plant, sulfuric acid residue (pyrite slag), etc.;Siliceous correction raw materials such as sandstone, river sand, siltstone, etc.
The raw materials of silicate cement are mainly limestone and clay.Calcareous raw materials mainly provide CaO, often using limestone, chalk, limestone tuff and so on.Clay raw materials mainly provide SiO2, Al2O3 and Fe2O3, and usually use clay, clayey shale, loess, etc.Sometimes the chemical composition of the two raw materials can not meet the requirements, but also need to add a small amount of calibration raw materials to adjust, often using pyrite residue.In addition, gypsum is added to regulate the setting time of the cement.Now cement production often add some active admixture, such as fly ash, slag and so on.
2.Cement kiln and rotary kiln
(1) the calcining method of vertical vertical kiln is a static calcining device. The calcining process of raw materials is not completely the same as that of rotary kiln, and the waste of resources is large and the environmental pollution is serious.
(2) the calcining method of rotary kiln adopts a rotary horizontal calcining equipment. The materials are first decomposed by preheater and outside the kiln and move towards the flame emitted by rotary kiln, so the calcining is more complete and thorough than that of vertical kiln.
3. Production process:
The general steps of Portland cement production are:
First, several raw materials are mixed in an appropriate proportion and then grinded into raw materials in the mill.Then the raw materials are put into the kiln for calcining;Cement is obtained by grinding the clinker in a mill with appropriate gypsum (and mixed materials) to a fine powder.Portland cement production is summed up as "two grinding and one burning".
Raw material preparation:
after crushing calcareous raw material, clay raw material and a small amount of corrected raw material, the raw material should be matched in a certain proportion and ground to a fine level
Calcining of clinker:
raw cement clinker with calcium silicate as the main component obtained by calcining in cement kiln until partial melting
clinker add appropriate amount of gypsum, sometimes add appropriate amount of mixed materials or additives grinding together for cement
(1) dry production raw materials at the same time drying and grinding, or the first drying after grinding raw material powder feed into the dry kiln calcining mature material method.However, there is also a method of adding raw powder to water to make raw pellets and feeding them into libo kiln to calcinate mature materials, which is called semi-dry method and still belongs to one of the dry production methods.
(2) wet production of raw materials add gouache grinding into raw material slurry, feed the wet kiln calcining mature material method.There is also a method to make raw material block into calcinated mature material after dewatering the raw material pulp prepared by wet method, which is called semi-wet method and still belongs to one of the wet production methods.
Dry and wet production characteristics
(1) dry production characteristics: dry method is the raw material powder directly into the kiln calcining, into the kiln raw material moisture content is generally only 1% ~ 2%, saving a lot of heat required by drying raw material.It can not only prepare raw materials with uniform quality but also develop to large scale.Suspension preheating and predecomposing kilns are now collectively referred to as new dry kilns and they become the future development direction of dry production.
(2) wet production characteristics: the raw material is made into the slurry with water content of 32% to 36%, the raw material slurry is dried and the mature material is burned in the rotary kiln.Wet preparation slurry, low energy consumption by grinding, easy to mix slurry, stable raw material composition, good for high quality clinker.However, the steel consumption of the easy grinding parts of the ball mill is large, the temperature of the clinker out of the kiln is low, it is not suitable to burn the clinker with high silica rate and high alumina rate.
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