In 2015 overall economic situation fell significantly, cement industry profits fell to the bottom, in order to use "The Belt and Road" and overseas layout to achieve bottoming out, each cement plant will save production costs and the introduction of green environmental protection equipment as the primary bargaining chip. In the process of cement production, cement clinker, materials, slag can be used after grinding, however, the results show that the best grinding efficiency can be achieved only by different materials separately.
1.      General situation of "one grinding and multi use" vertical mill
Xinxiang Yu Hui Yellow River building materials Co., Ltd. is located in Xinxiang city of Huixian Mengzhuang Town Economic Development Zone, plant height is about 100m. In order to make full use of local blast furnace slag and cement clinker, Yu Hui Huang building materials in April 2014 to start the construction of an annual output of 600 thousand tons of iron ore /100 million tons of cement production, completed and put into production in December 2014. Since the production line has been put into operation, the roller mill has been running smoothly, the production of slag surface area is 450m2/kg, the maximum yield can reach 120t/h; the specific surface area of cement (32.5) is 380m2/kg, the maximum yield was 190 t/h; the specific surface area of concrete admixture is 300~380m2/kg. The maximum yield was 225t/h; This system can be completed in 40 minutes slag, cement clinker, gypsum and other mixed materials between the switch.
In this paper, the process characteristics of the system are briefly introduced for reference
2.Process introduction
2.1 Feeding system
Wet slag, cement clinker, gypsum and other mixed materials are transported to the storage yard by truck transport, and into the hopper by forklift, this product line is provided with 5 feed hopper, in order to meet the requirements of different products. The bottom of each hopper is provided with a quantitative feeding method, through the transfer station into the vertical mill, a vibration screen is arranged at the transfer station, the aim is to remove impurities from raw materials when producing slag, but when producing the cement, this vibrating screen requires short circuit. In order to prevent metal block from entering vertical mill, the conveyor belt is arranged on the separator and metal detector.
2.2 grinding system
The material from the feed into the central millstone mill, motor driven by reducer rotating disc, under the action of centrifugal force to the disc edge and the grinding roller compacted by mobile, the crushed material overflow from the disc edge, at the same time from the nozzle ring (air ring) high efficiency separator of high speed upward hot air flow to the mill and one in the coarse powder separator after separation after the return to the disc, re grinding; fine powder with gas outflow mill, collected in the dust collecting system, which is product. Entering the warehouse storage through the conveying and lifting machine. No metal parts by hot air flow with the coarse particles and accidentally enter the sink from the wind ring, the scraper scraping, the outer loop bucket feed mill for regrinding.
2.3 Finished product storage
At mill end provided with two mixing machine and the external active admixture device, to meet the production requirements of concrete admixture. Qualified finished hoist, chute into the 3 x 26 metres of 15 seat plate stored in the library. The bottom is provided with a charging chute, finished by the bottom unloading equipment, bulk loading machine factory.
3. Main equipment configuration of grinding system
The production line is in accordance with the annual output of 600 thousand tons of iron ore /100 million tons of cement grinding system design, configuration and main equipment performance parameters are shown in table 1:
Table 1 Main equipment configuration and performance parameters of the grinding system
Device name Performance specifications and design specifications Quantity(set)
furnace in fluid bed heat capacity:1600×104kcal/h 1
Roller mill GRM46.41
Grinding particle size:≤40mm
Grinding moisture:≤15%
Production capacity:slag105t/h,cement150t/h
Bag filter Total filtration area:450000m3/h
Net filtration area:7860m2
Filtration rate:0.92m/s
Air volume:433000m3/h
System fan Air volume:450000m3/h
Total pressure:8100Pa
4.Production line design characteristics and Practice
4.1 Control of particle size of grinding material
4.2 Vertical mill feed inlet
Vertical mill grinding system is the core of the whole production line, in order to meet the requirements of a multi-purpose grinding, the Great Wall machinery against the mill feed to do a lot of technical improvements. The Great Wall machinery through multiple powder production line of practical experience, the common vertical upper lateral mill inlet due to water content of raw materials caused by excessive clogging, the inlet to the central screw conveyor feeding. This production line set a total of two mill feed inlet, the upper lateral inlet retention, to ensure the smooth feeding of clinker. According to the production in recent months, the setting of the two materials can ensure that the material is smooth, there is no phenomenon of blanking
4.3 Design of hot air system
In order to ensure the stability of the boiling furnace heating, effective regulation and reduce costs, the project set up a circulating air system, and in the hot blast stove outlet pipe is set with electric high temperature control valve and cold air valve. In order to boiling hot stove and circulating air, cold air can effectively mix. Practice shows that, in the boiling furnace outlet temperature of hot air under controlled conditions, as close as possible to the cold air valve, circulating air to adjust the temperature of the feed gas, to reduce energy consumption.
4.4 Selection of dust collector for finished bag
This project finished collecting selection of air box pulse bag dust collector, used in the design of acrylic waterproof and oil temperature for dust collector polyester needle felt filter material. The filter material has good air permeability, the instantaneous working temperature is 160 ℃, the normal working temperature is 140 ℃. Put into operation since the dust collecting effect is good, the emission concentration is less than or equal to 20mg/Nm3, fully meet the national emission standard.
4.5 Production process control
The DCS control system is used to control and monitor the whole process of the grinding system, the finished product transportation storage and the boiling furnace combustion system. The system adopts the module structure, the program is operated, the modification is convenient, the transmission speed is fast, the interface is simple and intuitive, the operation is reliable, and the productivity is improved.
4.6 Comparison of major economic and technical indicators
After the project is put into operation, the main production actual average and the design index are compared in Table 2.
Table2 Comparison of design value and actual average value of main economic indicators
Main economic indicators design value
actual mean
Output,t/h Slag:105
Specific surface area, m2/kg Slag:≥420
Cement: ≥330
Slag: ≥430
Cement: ≥350
Admixture: ≥350
Total installed capacity of production line High pressure:4550kW
Low pressure:712kW
Comprehensive energy consumption of products kwh/t Slag:40
Slag: 37
Dust emission level mg/Nm3 30 20
5.Concluding remarks
After nearly five months of production practice of Yu Hui building materials, the grinding production line is reliable, its product fineness and specific surface area all meet the requirements.The whole line system power consumption is only 40% of the milling system,can to achieve the purpose of saving energy and reducing consumption. According to the market situation, the product can be adjusted quickly, and has good economic and social benefits.


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