- Time:Feb 01, 2023
I. What is the mineral composition of high quality silicate cement clinker
The chemical composition and mineral composition of high quality silicate cement clinker should be appropriate. In the basic minerals of clinker, the calculated content of C3S is roughly 45% to 65%, should strive to be higher under the production conditions, but should not exceed 65%;C3A + C4AF calculated content is roughly 19% to 22%, and strive to be lower under the conditions allowed. The rest is the calculated content of C2S. General clinker C3S + C2S contains 70% to 75%, so the calculated content of C2S is roughly 30% to 10%. After the mineral composition is determined, the chemical reaction and rate value components MgO + K2O + Na2O + SO3, etc. The content of this sum is 2% ~ 6%.
II. The influence of CaCO3 content fluctuation in raw material on clinker minerals
Every 1% increase in CaCO3 content in the raw material will result in an increase of about 13% in C3S content and about 11.5% in C2S content. So it is necessary to achieve a stable chemical composition of the raw meal during production. In order to seek the kiln calcination operation, the mineral content of the clinker made and the stability of the performance, the permissible fluctuation of CaCO3 content in the raw meal is not more than ±0.2%.
III. How to ensure the best and stable thermal regime of the kiln system
In order to ensure good fuel and heat transfer conditions of the kiln system, and thus ensure the best thermal regime of the kiln system, it is necessary to achieve stable raw material chemical composition, stable raw material feeding, and stable fuel composition (including ventilation equipment) in production, i.e. "five stable to ensure a stable", which is one of the most important process principles in cement kiln production.
IV. What are the main structural units of precalciner kiln system
The main structural units of the precalciner system are.
(1) Cyclone (tube)
(2) Heat exchange pipes (tubes)
(3) Decomposition furnace (furnace)
(4) Rotary kiln (kiln)
(5) Cooling machine (machine)
V. The decomposition furnace material filling rate, retention time, movement speed calculation method
(1) Filling rate of the kiln f
(2) Material retention time in the kiln t
(3) Velocity of material movement in the kiln Vm
in the formula
f - kiln material filling rate, %
G - the amount of material passing through the kiln per unit time, t/h
Vm - material movement rate in the kiln, m/s
Di - effective inner diameter of kiln, m
r - apparent density of material, t/m³
n - speed of kiln, r/min
β - material resting angle, °
t - material retention time in the kiln, min
L - length of kiln, m
VI. The generation of clinker dry raw material consumption calculation method
(1) The amount of coal ash mixed to generate 1kg of clinker.
in the formula
mA - coal consumption, kg/kg·cl
Ay - coal ash content, expressed as a decimal
a - coal ash incorporation rate, °
(2) The amount of CaCO3 consumed in the raw meal to produce 1kg of clinker:
in the formula
CaOcl--CaO content in clinker, %
CaOA--CaO content in coal ash, %
The corner label "cl" indicates clinker, and the corner label "A" indicates coal ash, same as below.
(3) MgCO3 consumption in the raw meal to produce 1kg of clinker.
(4) Kaolin consumption in the raw material to generate 1kg of clinker.
(5) CO2 consumption in raw meal for the production of 1kg of clinker.
(6) Consumption of chemically combined water in raw meal for the production of 1kg of clinker.
(7) Dry raw material consumption for the production of 1kg of clinker.
The foot mark "gy" means dry material
VII. Briefly describe the production process of the general firing system
(1) Material Raw material homogenization warehouse → conveying equipment → weighing bin → measuring equipment → conveying equipment → preheater → decomposer → rotary kiln → cooler → conveying equipment → clinker warehouse
(2) Coal powder Kiln head (kiln tail) coal powder silo → Kiln head (kiln tail) coal powder metering scale → Rotary kiln (decomposer)
VIII. Briefly describe the working principle of the preheater and decomposer system
Preheater and decomposition furnace system is a kind of raw material suspension preheating and decomposition equipment, raw material in suspension state and high temperature gas fully mixed, rapid heat transfer, large heat transfer area, high thermal efficiency, raw material heating speed. The raw material is fed from the upper part of the preheater, and then it is preheated and decomposed by the cyclone and decomposer at all levels in the opposite direction of the high temperature airflow of the system, and the decomposition rate is about 85%~95%, and finally it is collected into the kiln by the next cyclone, while the high temperature airflow passes through the smoke chamber, shrinkage and mixing chamber of the kiln in order to exchange heat with the raw material at all levels, and the temperature is gradually reduced, and finally it is discharged by the high temperature fan at the end of the kiln. The temperature is gradually reduced and finally discharged by the high temperature fan at the end of the kiln. The powdered coal is sprayed into the decomposing furnace, and the three times air from the cooler is used for combustion, so the oxygen supply is sufficient and the powdered coal burns quickly.
IX. Brief description of the working principle of rotary kiln
Cement rotary kiln is a low-speed rotating circular body, which is used to calcine cement clinker. It relies on the wheel belt of the kiln body at a certain slope and is placed on several pairs of pallets, and is driven by an electric motor, which makes the cylinder rotate within a certain, rotational speed through the large gears of the kiln body. The raw material is fed from the high end (kiln end) and moves to the low end (kiln head), and the fuel is sprayed into the low end to form a flame, which will burn the raw material through four natural zones of complex physicochemical reactions: carbonate decomposition, exothermic reaction, firing and cooling, and the clinker is discharged from the kiln head and the flue gas is discharged from the kiln.
X. Briefly describe the skills and role of clinker cooler
(1) As process equipment
Macrocosm takes on the task of quenching the high temperature clinker. The quench can stop the mineral crystal growth, especially the C3S crystal growth. The quench can also control the conversion of hydration-active β-C2S to non-hydration-active γ-C2S, which is beneficial to the improvement of clinker strength and easy properties. At the same time, sudden cooling can make the liquid phase solidify into glass, so that MgO and C3A are mostly fixed in the glass, which is conducive to the improvement of clinker stability and chemical erosion resistance.
(2) As thermal equipment
While quenching the clinker, it also undertakes the task of heating and warming up the secondary and tertiary air of the kiln. In the precalciner system, heating the second and third air to a higher temperature as much as possible not only effectively recovers the heat in the clinker, but also plays an important role in the burning rate of the fuel (especially medium and low quality fuel) and maintaining an optimal heat distribution in the whole kiln system.
(3) As heat recovery equipment
It undertakes the task of recovering the large amount of enthalpy carried out by the clinker out of the kiln. Generally speaking, the recovered heat is 1250~1650kj/kg·cl. This heat enters the kiln and furnace in two or three times with the high temperature heat, which helps to reduce the calcination heat consumption of the system, and the recovery in the form of low temperature is also beneficial to the waste power generation.
(4) As clinker conveying equipment
It undertakes the task of conveying high temperature clinker. The cooling of high temperature clinker is beneficial for clinker conveying and storage.
XI. Classification of solid fuels for cement kilns
The solid fuels used in cement kilns are: anthracite, poor coal, bituminous coal, lignite, petroleum slag, industrial waste, etc.
(1) Anthracite coal has a fixed carbon content of 93% to 98% and a volatile fraction of <10%, which is a low reactivity fuel and is difficult to ignite and burn.
(2) Poor coal (also called semi-anthracite) Volatile content is between 10% and 20%, which is a sub-reactive fuel.
(3) Bituminous coal Volatile fraction content is generally > 14%, the reaction fraction content increases, the calorific value decreases, and the reaction activity should decrease.
(4) Lignite is a low carbonization fuel with high volatile matter, high moisture and low calorific value, and has a relatively low combustion temperature.
(5) Petroleum coke residue belongs to oil refining waste, generally speaking, its volatile matter and ash content are low, and its sulfur content and calorific value are high. It can reach 6%~7% and more than 33400kj/kg respectively, with poor heat generation capacity and reaction activity.
(6) Industrial wastes such as car tires, household waste combustible materials, etc., are mostly put directly into the kiln at the end of the kiln for use.
XII. What are the requirements for controlling the fineness of coal powder
General coal powder fineness requirement The volatile fraction of coal is related, and it can be controlled coarser when the volatile fraction is high, and it must be controlled some when the volatile fraction is low to ensure a good fuel condition.
The empirical formula for coal powder fineness control are.
in the formula
IVm - volatile component index
Vm - volatile fraction percentage content
W - percent moisture content
A - ash percentage content
XIII. Briefly describe the types of air leakage in the preheater system
There are mainly external and internal air leaks in the preheater system.
(1) External air leakage Mainly check the air leakage at doors, poke holes, flanges, thermal testing holes, etc.
(2) internal air leakage is mainly due to a simple type of lock wind valve, or production deformation damage, action does not work, so that the lower level of hot air material pipe directly into the upper preheater
XIV. Briefly describe the impact of preheater air leakage on the firing system
The effects of preheater leakage on the firing system are.
(1) Higher heat consumption and lower production and quality. For the rotary kiln system, the leakage of cold air reduces the amount of secondary air entering the kiln from the cooler and the total heat returned to the kiln; for the three ducts and the decomposition furnace system, the leakage of cold air also reduces the separation efficiency and heat exchange efficiency of the system, increasing the heat consumption and reducing the effective ventilation capacity of the firing system, leading to unstable operation of the system and reducing the production and quality; the reduction of the effective ventilation capacity also directly leads to The reduction of effective ventilation capacity also directly leads to the increase of electricity consumption per unit of product.
(2) Air leakage is an important reason for the preheater decomposition system bonding blockage, which in turn reduces the system operating rate, increasing operating costs, and manual handling will also bring the system heat consumption rise, increasing labor intensity, bringing environmental pollution. When the system leakage is more serious when the separation efficiency of the preheater system is significantly reduced with the airflow from the inner tube and rising pipeline back to the upper preheater, the amount of internal circulation of materials is large, easy to cause blockage in the cone of the system and the lower material pipe. Leakage of cold air and material contact, easy to cause material condensation, adhesion in the refractory surface caused by crust plugging, and when the fuel is incomplete, and leakage of fresh oxygen re-combustion reaction, resulting in local high temperature and crust plugging.
(3) Air leakage will lead to the emergence of dust leakage, bringing environmental pollution.
XV. Requirements for turning kilns in coal kilns
The requirements for turning the kiln in a coal kiln are shown in the table
| Kiln tail temperature (℃) | Kiln turning volume (volume) | Kiln rotation time interval (min) |
| Under 100 | 0 | No slow rotation |
| 100~250 | 1/4 | 60 |
| 250~450 | 1/4 | 30 |
| 450~600 | 1/4 | 15 |
| 600 or more | 1 | Continuous slow rotation |
ZHENJIN REFRACTORIES is committed to the cement, lime, non-ferrous, steel, glass and chemical industry refractories research and development, technical solutions design, construction and supporting products to provide one-stop turnkey services, set production, marketing, research and export of integrated high-temperature kiln solution service provider. The service chain runs through the entire project life cycle, including preliminary consultation, design, R&D, construction and safety production, etc. Through the optimal combination of various grades of products to meet different process requirements, we can effectively create value for our customers.
