Limestone is transported out of the mine by self-provided cars, crushed by PCF2022 single-stage hammer crusher with production capacity of 500-600t/h, and homogenized in φ80m circular pre-homogenizing field, with storage capacity of 23 100t and storage period of 8.6d.
(2) Storage of clay and iron powder
Clay and iron powder are respectively stored in the storage yard where automobiles enter the factory. The storage capacity of clay is 5600 tons, and the storage period is11.2d.: The reserve of iron powder is1600t, and the storage period is13.1d. Clay and iron powder stored in the stack are transported by forklift to bucket elevator, and then transported to 2-φ5× 10m steel plate warehouse for storage, with reserves of 200 tons and 250 tons respectively.
(3) Storage of raw coal
After entering the factory, the raw coal is stacked on the grate of 30× 160m, with a reserve of 5,000 tons and a storage period of 16.8 days. After pre-crushing, the raw coal is sent to the raw coal bunker of pulverized coal preparation workshop by belt conveyor and bucket elevator.
(4) Preparation of raw materials
Limestone discharged from the pre-homogenizing yard is sent to φ8×20m batching bin by belt conveyor, and clay and iron powder enter φ5× 10m steel plate batching bin by * * crane. The three kinds of raw materials discharged from the batching bin are measured by electronic belt weigher and controlled by QCS system. Mixing after preparation
The mixture is sent to HRM3400 vertical mill by belt conveyor, and there is an air lock valve at the entrance of the mill. The ground raw meal is sampled by a continuous sampler and analyzed by a multi-element analyzer. The analysis results are input into the batching computer and compared with the standard values. After calculation, a modification instruction is issued to readjust the feeding amount of each material to keep the batching accuracy within 2%.
Materials with comprehensive moisture content of about 3.5% are fed into the mill by the wind lock feeder, and hot air is pumped out from the bottom of the mill. The material ground by the grinding roller is taken away by the high-speed airflow at the wind ring, and after being separated by the separator, the coarse material falls back to the mill and continues to be crushed, and the fine powder is ground by the airflow and collected by the dust collector to obtain the finished product.
The high-temperature waste gas of about 320℃ pumped by the preheater at the kiln end is divided into two paths: one path passes through the multi-tube cooler and mixing chamber to the bag dust collector at the kiln end; All the way in and out of the material mill is used as a drying medium. Raw material mill exhaust gas is introduced into the mixing chamber by the main exhaust fan of the mill, mixed with the exhaust gas of the high-temperature fan, and then enters the dust collector at the end of the kiln, and is purified and discharged into the atmosphere. The materials collected by the dust collector together with the raw meal powder enter the φ 15×36m homogenization bin, with a storage capacity of 4,400 tons and a storage period of 1.4 days.
(5) raw meal homogenization
The raw meal from the raw meal mill is lifted to the top of φ 15×36m homogenizing bin by the hoist. There is a distributor at the top of the warehouse, and the raw materials are uniformly discharged into the warehouse from the radial conveying chute. The homogenizing bin has a central bin, and there are six outlets at the bottom of the bin to enter the central bin, and at least two outlets are discharged at a time. The bottom of the central room is inflated, so that the mixed raw materials are mixed again, and then sent to the weightless feeding system through the air duct, and then measured by the raw material metering system, and then sent to the ascending pipeline of the No.2 drum of the preheater by the kiln tail hoist and the wind lock device.
(6) Ignition system
The raw material from the kiln end hoist passes through the double-channel electric air gate valve and enters the ascending pipeline of cyclone No.2 in the precalcining system, and then passes through the processes of cyclone 1 #-5 #, heat exchange, temperature rise and decomposition in the calciner in turn, so that the apparent decomposition rate of the raw material entering the kiln reaches over 90%. The preheated and decomposed materials enter a φ4.0×60m rotary kiln for calcination.
Most of the waste gas (~ ~ 3200c) discharged from cyclone separator 1# enters the vertical raw meal grinding system as a drying medium, and the other part enters the front air chamber of the bag-type dust collector after being cooled by a multi-tube cooler, and then merges with the waste gas from the raw meal grinding and is discharged after being purified by the bag-type dust collector.
The clinker discharged from the kiln falls into the controlled flow grate cooler for cooling, and the clinker enters the crusher at the tail of the cooler through the reciprocating motion of the grate plate. After crushing, it will be sent to φ50m clinker silo with a storage capacity of 25,000 tons. The storage period is12.5d. Part of the hot air from the clinker cooled by grate cooler will enter the kiln as secondary air, and it will be sent to the calciner as tertiary air, and part of it will be used by coal mill to dry raw coal. The excess waste gas will be discharged into the atmosphere after being purified by bag dust collector at kiln head.
In the process of rotary kiln production, raw materials are fed from the kiln tail, and the raw materials in the kiln keep rotating and rolling with the rotation of the kiln body. Because the kiln tail is higher than the kiln head, the raw meal also moves to the kiln head and is finally discharged from the kiln head. The temperature of raw materials in the kiln is also rising gradually, and complex physical and chemical changes have taken place. Because of the rotation of the kiln, the temperature of each section in the kiln is basically the same, so according to the temperature and physical and chemical changes of materials, the rotary kiln can be divided into drying preheating zone, carbonate decomposition zone, exothermic reaction zone, sintering zone and cooling zone. Fuel has little to do with clinker calcination except heating.
① Drying and dehydration of raw materials:
The main raw materials of portland cement are limestone and clay, while the main minerals such as clay are all kinds of hydrated aluminum silicate, usually kaolin (AI2O3 SiO2 2H2O) or montmorillonite (AI2O3 4SiO2 9H2O). When kaolin is heated, it mainly loses its mechanically bound water below 300℃. At the temperature of 450 ~ 600℃, the crystal water in kaolin is removed to form metakaolin (AI2O3 2SiO2), which is further decomposed into amorphous new ecology 2SO2 and al2o 3.
450~600℃
al2o 3·SiO 2·2H2O al2o 3·2 SiO 2+2H2O↑
Alumina and silica
② Carbonate decomposition:
When the temperature rises above 600℃, the carbonate in the raw meal begins to decompose. Magnesium carbonate decomposes violently and rapidly at about 750℃. The decomposition temperature of calcium carbonate is above 900℃, and there will be a rapid decomposition reaction around 1000℃ until the decomposition of calcium carbonate is over.
750℃ magnesium carbonate magnesium oxide+carbon dioxide
9 10℃ CaCO3 CaO3+CO2
After the carbonate decomposition reaction, it enters the exothermic reaction, and the temperature of the burnt material gradually drops to about 320℃, and the material is discharged from the kiln head.
③ solid state reaction:
Active oxides such as SiO2 _ 2, Al _ 2O _ 3, Fe _ 2O _ 3 and CaO appear in raw meal due to dehydration of clay and decomposition of carbonate. The combination reaction between oxides began. With the increase of temperature, the amount of CaO also increases, and the chemical reaction speed between these oxides gradually accelerates.
The chemical reaction at this stage occurs on the surfaces of solid particles in contact with each other, which is realized by ion vibration and exchange of fine crystal surfaces. With the increase of temperature, the vibration amplitude of ions increases, and it is easy to leave the crystal, so the reaction is accelerated. This kind of reaction that depends on the interaction between solid surfaces is called solid reaction.
The solid-state reaction is complex and belongs to multi-stage reaction. The following reaction formula can be used to express the reaction process step by step:
800~900℃: CaO+ Fe2O3 CaO Fe2O3
Calcium oxide+alumina
900 ~ 1000℃:3(CaO·al2o 3)+2·CaO·5·CaO·3al2o 3
Calcium dioxide+silicon dioxide
Calcium oxide fe2o 3+ calcium oxide Fe2O3
(The reaction to form 2cao.sio2 will end at about 1200℃).
1000 ~ 1200℃:5 Cao al2o 3+4 Cao 3(3 Cao al2o 3)
5 CaO 3al2o 3+3(2 CaO fe2o 3)+CaO 3(4 CaO al2o 3 fe2o 3)
④ Sintering of clinker.
When the temperature rises to about 1300℃, C3A and C4AF melt and liquid phase appears in the material. The dissolution of CaO and 2cao SiO2 (C2S) in liquid phase is beneficial to molecular diffusion and further synthesis of 3caosio2 (C3S).
2 calcium oxide silica+calcium oxide 3 calcium oxide silica
This reaction is usually called lime absorption process. Because it is carried out by molecular diffusion in the liquid phase, the quantity and viscosity of the liquid phase have a great influence on the process of C2S absorbing CaO to generate C3S, which is why we always hope that there are proper amounts of C3A and C4AF molten medium minerals in silicate hydraulic clinker. In order to make this reaction as fast and complete as possible, the temperature of the material is controlled to be higher than 1300℃ in actual production, generally within the temperature range of 1350~ 1450℃, which is the so-called "sintering temperature".
When the raw materials react chemically in the rotary kiln, the tail gas of the rotary kiln contains dust of mineral raw materials such as SiO _ 2, dust of SO2 and nitrogen oxides when burning coal, moisture in minerals and other atmospheric pollutants.
(7) Preparation and transportation of pulverized coal
The incoming raw coal is 30m× 160m pile, with a storage capacity of 5,000 tons and a storage period of16.8d. The raw coal enters the raw coal bunker through a pre-homogenizing grate, a coal feeding belt conveyor and a hoist, and the coal leaving the raw coal bunker enters the anthracite fine grinding for drying and grinding through a speed regulating belt scale and an air lock valve.
The pulverized coal from the coal mill enters the cyclone separator with the airflow and is collected by FCM high concentration and high negative pressure explosion-proof bag dust collector. The collected finished products are sent to two pulverized coal bins by the reamer, and the purified gas is discharged into the atmosphere through the exhaust fan. A set of pulverized coal metering and conveying system, consisting of a ring-balanced flow metering machine and a Roots blower, is respectively arranged below the two pulverized coal bins. 40% pulverized coal is sent to kiln head, 60% pulverized coal is sent to calciner, and the dry heat source comes from grate cooler.
(8) Clinker storage
Clinker discharged from grate cooler and dust collected by the dust collector of grate cooler are sent to φ50m clinker warehouse for storage through chain bucket conveyor, with a storage capacity of 25,000 tons and a storage period of 12.5 days.
(9) Cement grinding
Cement grinding has two sets of extrusion grinding systems. Clinker, mixture and gypsum are sent to five Φ φ8×20m batching bins by conveying system respectively, and the batching is measured by two metering systems under the bins. The mixture prepared in proportion is sent to the weighing bin of roller press in each system. The mixture is sent to HFCG 120 roller press through the weighing bin for extrusion, and the extruded material is lifted to the crushing classifier by the cake elevator, and the fine material after crushing and grading is sent to the cement grinding head for grinding, and the coarse material is recycled and extruded in the weighing bin. Φ 3.2×13m open-circuit screening cement mill products are hoisted into the cement silo system by the hoist at the end of the mill. High-efficiency dust removal equipment is set at the dust point of the rolling system to ensure that the exhaust gas reaches the standard. The waste gas from the cement grinding system is discharged after being treated by the dust collector of the cement grinding system.
The grinding system has advanced technology and reliable equipment. Compared with the closed-circuit grinding system, the grinding system has the advantages of simple process, convenient operation and control, low power consumption, reasonable cement particle grading, stable product quality and short payback period.
Gypsum, slag, slag and other mixed materials must be added in cement grinding.
The role of gypsum is to control the setting time of cement, because tricalcium aluminate mineral in clinker is the component that makes cement set quickly. If gypsum is added to cement, tricalcium aluminate and water are added, a new water-insoluble calcium sulphoaluminate hydrate will be generated, so that no coagulant will be generated, or little will be generated, so that cement will not set quickly. It's not good to add too much gypsum or too little gypsum. For portland cement, it is generally controlled at 2.5 ~ 5% of the cement weight.
Adding slag, slag and other mixed materials to cement can improve some of your properties. Improve the corrosion resistance of cement. Due to the chemical changes between ordinary portland cement and water, calcium hydroxide [Ca(OH)2] will be generated. When cement buildings are in contact with water for a long time, calcium hydroxide in hardened cement stone will dissolve in water or react with some chemicals in water, such as carbonate, magnesium salt and chloride. There are many small caves in the cement stone, or new substances with volume expansion are generated in the hardened cement stone to crack the building, or loose things are formed, which eventually destroy the building. This phenomenon is called cement corrosion. Adding slag, slag and other mixed materials can make cement react with water before hardening and generate some useful new substances with calcium hydroxide. These new substances will not destroy the structure of cement paste, but will improve the corrosion resistance of cement.
In addition, free calcium oxide in clinker is one of the important factors affecting cement safety. When calcining clinker, due to the limitation of production conditions, some calcium oxide will remain in clinker more or less. This kind of free calcium oxide is relatively dense in structure and inactive in nature due to high temperature calcination, and its reaction rate with water is slow at room temperature. If the free calcium oxide in the hardened cement paste is still slowly reacting with water to generate calcium hydroxide, with the volume expansion, the volume of the hardened cement paste will change unevenly, twist or crack, and even crack in serious cases. There is too much free calcium oxide in clinker, which leads to poor cement safety and low tensile strength. Adding geo-active mixed materials into cement will react with calcium oxide to form useful hydrate during hydration, thus improving the safety and tensile strength of cement.
Gypsum, slag, slag and other mixed materials, together with clinker, are measured by electronic weighing and sent to cement grinding to make the final cement product.
(10) cement storage, bulk and packaging
Cement storage warehouses are six φ 15×36m circular warehouses with a total reserve of 42,000 tons, which can meet the production needs of 16.8 days. There are six SZ92A-2(F) cement bulk loaders beside the warehouse, with a capacity of 6×100t/h.
It is planned to add a BHYW-8 eight-mouth rotary packaging machine to the packaging machine, including packaging machine, vibrating screen, cleaning machine, package breaking processor, calibration scale, etc. The packing capacity is 120 tons/hour ... The cement discharged from the bottom of the cement silo passes through the zipper conveyor and bucket elevator, and the impurities are removed by the vibrating screen, and then it is loaded into the packaging machine. After the packaged cement is cleaned and weighed, it is sent to the original finished product warehouse or loaded with a belt conveyor. The finished product warehouse covers an area of 4,000 square meters and can store 5,600 tons of cement with a storage period of 2.2 days.
The packaging system is equipped with a bag dust collector, which is responsible for dust removal at the discharge point of the system, and the discharge concentration is lower than 50mg/Nm3.