Effect of Different Mixtures on Specific Surface Area of Cement Roll Mill Products
Date：2019-07-03 16:56 Source：未知Views:
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
It can be seen from Table 8 and Figure 3 that the specific surface area of cement finished product is linearly positively correlated with the amount of fly ash. For every 1% increase in fly ash, the specific surface area is increased by 1.64 m2/kg. When fly ash is formed, under the action of surface tension, most of the particles are hollow microbeads. The surface of the microbeads is uneven and extremely uneven, and there are a large number of micropores. Some of the particles are in contact with each other in a molten state to form a surface. Rough and angular honeycomb particles, so the cement added with fly ash will increase the specific surface area of the product when the specific surface area is used to characterize the fineness of the product. In addition, in the test process, in order to maintain the power of the roll grinding force, the output will increase as the fly ash content increases.
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
It can be seen from Table 9 and Table 10 that the specific surface area increase decreases with the increase of volcanic ash content in the case of the same grinding power consumption. In the case of the same amount of volcanic ash, the specific surface area increases as the power consumption of the grinding increases.
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.
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.