Silicate cement production technology in cement production representative, is composed of limestone and clay as the main raw material, crushing, batching, grinding into raw material, and then feeding mature cement kilns burning material, and then cooked add appropriate amount of gypsum materials (sometimes mixed with mixed materials or additives) from Ground.
Preparation of cement raw materials with different methods can be divided into dry (including the semi-dry) and wet (including the semi-wet method) two.
` Dry production.
The raw material drying and grinding the same time, or to dry the raw material powder by grinding into a dry kiln calcination after the feeding method of mature material. But there are also adding an appropriate amount of raw material powder made from raw water ball, into the legislature calcining kiln mature material Boer method, called semi-dry, it is still a dry production.
a wet production.
Add gouache ground into the raw material raw slurry, the feed material mature wet kiln calcination methods. There will be wet slurry prepared dehydrated raw material, made of blocks of raw material mature material calcining kiln method, called wet method, the production of a still wet.
Production of the main advantages of dry heat loss is low (such as with the dry preheater kiln heat consumption is 3140 ~ 3768 J / kg), the disadvantage is not easy even raw ingredients, shop dust large, high power consumption . Wet process is simple, easy to control the raw material composition, product quality, convenient delivery of slurry, a small shop dust and other advantages, disadvantage is the high heat consumption (heat consumption of clinker is usually 5234 ~ 6490 J / kg).
Cement production, the general can be divided into raw material preparation, clinker and cement made of the three processes.
(1) raw material grinding
Sub-dry and wet. Dry closed operating system commonly used, that is after the raw materials mill grinded into the separator sorting, coarse grinding back again into the grinding operation, and most materials used simultaneously in the drying and grinding mill process, the tube mill with the equipment, the unloading and the roller grinding mill. Tube usually wet grinding, grinding, and other baseball back in time through the mill is no longer open system, but there is also curved screen with a grading machine or closed-circuit system.
Clinker calcining kiln and kiln equipment mainly two types of kilns for the production of smaller factories, large and medium-sized plant should adopt the rotary kiln.
Rotating kiln shell is not known in vertical shaft kiln. Common shaft and mechanical sub-shaft. Common shaft is artificial feeding and artificial feeding discharge or mechanical, manual discharge; mechanical shaft mechanical feeding and mechanical unloading. Mechanical shaft kiln is a continuous operation, its production, quality and high productivity than standard shaft. In recent years, foreign majority rotary kiln has been replaced, but in the current Chinese cement industry, kiln still occupy an important position. According to requirements of building materials and technology policy, small mechanized vertical kiln cement plant applications, and gradually replace the normal shaft.
a rotary kiln:
Kiln shell in horizontal (slightly slanted, about 3%), and can be referred to as rotary motion rotary kiln. Sub-calcined raw material powder dry kiln and calcined slurry (water content is usually about 35%) of the wet process kiln.
A, dry kiln
Dry kiln can be divided into hollow kiln, furnace waste heat boiler, suspended suspension preheater kilns and furnaces break down. After 70 years, developed a rotary kiln production can be increased kiln calcining process decomposition technique. Which is characterized by a kiln, it is based suspension preheater kiln, between the preheater and the kiln calciner added. Furnace in the decomposition of the total fuel consumption by adding 50 to 60% of the fuel, the fuel combustion process and the raw material of warm-and carbonate decomposition, and less efficient heat transfer from the kiln to move the zone in the calciner, the raw material In the suspended state or boiling state heat exchange with the hot air to improve heat transfer efficiency, so that raw material into the kiln in the decomposition of **** before the more than 80%, to reduce the kiln's heat load, extend the life of the kiln and the kiln lining operation cycle, the heat capacity of the kiln to keep the case, a substantial increase production purposes.
B, wet process kiln
For wet process cement kiln, said in a wet kiln, wet process is the moisture content of raw material made of 32% to 40% of the slurry. As prepared with liquid mud, so a good mix between the various raw materials, raw material composition uniformity, so that high quality clinker firing, which is the main advantage of wet process.
Long wet kiln kiln can be divided into wet and with the wet slurry evaporator short kiln, widely used long kiln, short kiln is now rarely used. To reduce the long wet kiln heat consumption, kiln equipped with various types of heat exchangers, such as chain, filter the slurry preheater, metal or ceramic heat exchanger.
Fine grinding of cement clinker grinding process usually used ring current (ie, closed operating system). In order to prevent the production of dust flying, the cement plant are equipped with dust collection equipment. Electrostatic precipitator, bag filter and cyclone dust collector such as is commonly used cement plant dust collection equipment.
In recent years, the raw material pre-homogenization, the raw material powder collecting all aspects of transportation and the adoption of new technology and new equipment, especially the emergence of decomposition kiln, a new process of dry follow. With this new technology to dry wet less than the quality of the production of clinker production, also reduced power consumption has become a national trend of cement industry development.