Effect of Different Mixtures on Specific Surface Area of Cement Roll Mill Products
Date: 2019-07-03 Views:The roller mill final grinding system has been widely used in cement grinding. Different mixed materials have different effects on cement roller mill products. The limestone fly ash and volcanic ash are used as research objects, and the laboratory semi-industrial roller mill TRM5.6 is used to study. The influence of different mixed materials on the specific surface area of the cement roll mill product leads to the following conclusion: for every 1% increase of limestone, the specific surface area of the cement finished product increases by 2.52~2.75m2/kg for each 1% increase of fly ash, and the specific surface area of the product will be Increased to varying degrees. When using volcanic ash as a mixed material, for every 1% increase in volcanic ash content, when the specific surface area of the finished cement is <400 m2/kg, the contribution of the comparative surface area is ~2.5 m2/kg; when the specific surface area of the finished cement is >400 m2/kg, The contribution of the comparative surface area is ~2.0 m2/kg.
In the past ten years, cement roller grinding technology has matured day by day. More and more cement projects at home and abroad have adopted cement roller grinding technology.
There are many types of cement in China, such as P·I, P·II, P·O, P·S·A, P·S·B, P·P, P·F, P·C, etc. The amount and type of the mixed materials are specified. Taking P·O cement as an example, the amount of the mixed material is specified to be > 5% and ≤ 20%. In order to promote the wide use of all kinds of mixed materials in cement, the state has introduced the enterprise income tax for comprehensive utilization of resources and the preferential value-added tax policy for comprehensive utilization of products, and the building materials products produced by using bulk solid waste such as fly ash and coal gangue as main raw materials. The income earned is reduced by 90% into the total income, and the income tax is exempted. In the world, mixed materials are also an important part of cement, but the physical properties of different mixed materials such as grindability and surface characteristics of powder materials are not the same. Here is a brief list of the operation of TRM roller mill P·C cement. Table 1.
From the current operating results of foreign mills, the effects of different types of mixed materials on the operation of the mill are also very large, taking LM56.2+2C/S as an example:
(1) The Cementos Pacasmayo plant in Peru produces 30% slag cement with blast furnace slag content of 7%, and the output of the 45μm sieve is 7%, and the output can reach 160t/h.
(2) CEMEX in the Dominican Republic produces ordinary Portland cement with a fineness of 380 m2/kg, with a yield of up to 180 t/h.
(3) Indian Madras Cement Company produces fly ash cement with a production capacity of 220t/h.
(4) Sichuan Xingchuan City grinds P·O42.5 cement containing 5% limestone and 13.5% slag, and the output can reach 205t/h with a specific surface area of 376m2/kg.
At present, when we select the design of the roller mill final grinding system, we calculate the influence degree of the mixed material on the specific surface area of the product according to the experience coefficient of the ball mill, and the grinding principle of the ball mill and the roller mill grinding material is different. The applicability of the empirical coefficient is not strong. Therefore, it is necessary to have a calculation coefficient for the cement roller mill to ensure the accuracy of the selection, or to verify the reliability of the original calculation coefficient. Therefore, it is necessary to study the influence of different mixed materials on the specific surface area of the cement roller mill product.
2 Test materials and test contents
2.1 Raw materials
(1) Clinker: taken from Tianjin Zhenxing Cement Factory, Bond Performance Index is 14.47kWh/t, and the grade of grinding materials is shown in Table 2.
2.2 Test system
In 2011, the company established a complete semi-industrial roller mill test system, mainly used for roller grinding test of cement, steel slag, tailings, etc. The main machine specification is TRM5.6 roller mill, the diameter of the disc is 560mm, the grinding disc speed is 70r/min, the power 30kW, two rolls, cement grinding design capacity 1t / h.
2.3 Test plan
From 2013 to 2015, we conducted a correlation study between grinding power consumption and specific surface area of cement products on the TRM5.6 test system. We use the product specific surface area of 320m2 / kg as the benchmark operating parameters, through
The test parameters were changed, the blending amount of the mixed materials was changed, and the influence of the blending amount of the mixed materials on the roller mill grinding cement was studied. In order to test the accuracy of the data, each group of experiments was repeated 2~4 times. The specific test plan and control parameters are shown in Table 5 and Table 6, respectively. During the test, the power should be kept as constant, the power should be controlled by adjusting the feed amount, and finally the production and power consumption of the stage should be calculated by weighing the finished product.
3 test results and analysis
3.1 Influence of limestone on the specific surface area of roller mill cement The specific surface area and reference power consumption of the finished product under different limestone contents were obtained through 25 comparative tests. See Table 7.
3.2 Influence of fly ash on specific surface area of roller mill cement
At Jaiprakash, India, the company's MVR5600C-4 roller mill is used to grind coal ash cement, in which clinker accounts for 65%, gypsum accounts for 4%, dry fly ash accounts for 31%, and all materials are mixed into the mill. The production capacity is 320t/h. After deducting the power consumption of the classifier and the fan, if the influence of the output is not considered, the specific surface area increases by: (390-280) / 31 = 3.5, that is, for every 1% of dry fly ash, the specific surface area of the product increases. 3.5m2/kg, which is quite different from laboratory data.
Chai Xing Teng et al. used clinker and fly ash as raw materials, and used a laboratory ball mill to test different amounts of fly ash in the same grinding time. The results showed that for every 1% increase in fly ash, the finished product The specific surface area increased by 3.2 m2/kg, which was greater than that of the cement roller mill test.
In general, the principle of roller mill and ball mill grinding is different. Different fineness of fly ash is incorporated into cement, and the specific surface area of the finished product increases. When the equipment is selected, when the specific surface area is used as the benchmark, it needs to be adjusted according to the objective conditions.
3.3 Effect of volcanic ash on specific surface area of roller mill cement
According to the test data, when the specific surface area of the finished cement is <400m2/kg, the contribution of the comparative surface area is ~2.5m2/kg for each 1% increase in volcanic ash content; when the specific surface area of the finished cement is >400m2/kg, Increasing the amount of volcanic ash by 1%, the contribution of the comparative surface area is ~2.0m2/kg.
4 Conclusion
In roller mill grinding cement, the amount of limestone mixed material is positively correlated with the specific surface area of cement. For every 1% increase of limestone, the specific surface area of the finished product increases by 2.52~2.75m2/kg. For every 1% increase in fly ash, the specific surface area of the product will increase to varying degrees. When using volcanic ash as a mixed material, for every 1% increase in volcanic ash content, when the specific surface area of the finished cement is <400m2/kg, the contribution of the comparative surface area is ~2.5m2/kg; when the specific surface area of the finished cement is >400m2/kg, The contribution of the comparative surface area is ~2.0 m2/kg.
