Cement sampling patent

1, the significance of controlling the fineness of raw materials. For a long time, the fineness of raw materials has not been paid much attention to in cement production process, because this index is relatively easy to achieve and has no influence on the production of the next working procedure. There are also many people who think that the finer the fineness of raw materials, the more benefits can be brought to clinker production in the kiln. Therefore, they didn't pay much attention to this index. In fact, from the perspective of refined operation, the reasonable formulation of this index is quite positive. (1) The fineness of raw meal is not as fine as possible. It is directly related not only to the power consumption and output of raw meal mill, but also to the output and heat consumption of kiln. With the popularization of new dry process, more and more people have realized that superfine raw meal will have the following disadvantages: fine powder has little advantage over coarse powder in heat transfer in preheater, on the contrary, it stays in the pipeline for a short time, which is the most difficult part to separate from hot air flow in preheater, so it is easier to escape from one preheater to the next, and at the same time, it upgrades the received tropical zone to the next, increasing heat consumption; Fine powder is easy to enter the waste gas treatment system, which increases the dust content in the waste gas, wasting both heat energy and electric energy; In the process of raw meal storage, fine powder is easy to agglomerate, which is not conducive to transportation and homogenization, resulting in more uneven particles, and is not conducive to powder selection and heat transfer in preheater and heat transfer and calcination in kiln. (2) The requirements for the particle size range of raw materials are quite different from those of cement, and the narrower the particle size distribution of raw materials, the better. Because raw meal fine powder not only wastes energy in the preparation process, but also has the above-mentioned adverse effects on the next calcination process; However, coarse raw meal will increase the difficulty of calcination, resulting in high fCaO residue in clinker and excessive fuel consumption. The practice of many factories at home and abroad proves that it is less than 200? 0? 8m raw meal can meet the needs of clinker calcination, and its screening allowance is far less than 90? 0? 8m screen margin is more important. The advanced power consumption level of raw material main machine should be: for ball mill, when grinding soft materials, the main motor is about 10 kWh/t, and the hard materials are about 25 kwh/t; For the vertical mill, this range is 4.5 ~ 8.5 kWh/t. Although the power consumption of the fan will increase, the power consumption of the system is still 30% lower than that of the ball mill. There are not many enterprises that can reach this level at present. It should be said that from the formulation of fineness index, we can find a way to narrow this gap. 2 Control standard of raw meal fineness The optimum fineness of raw meal should be determined by raw material experiments and production practices of various factories, and its determination principle is: (1) As long as it is within the allowable range of kiln calcination, the raw meal granularity is suitable for coarsening. Generally speaking, raw meal should be ground to 170# (90? 0? 8m) is 15%, while 50# (300? 0? 8m) is 1.5% ~ 2.5%. Most enterprises have basically mastered this control principle. In fact, according to the above theoretical basis, the fineness can be further enlarged. So some production lines have adjusted the fineness of raw materials to 80? 0? 8m screen margin is 22%, and the effect is very good. Under the condition of satisfying and favorable calcination conditions, the output of the mill is increased and the power consumption is reduced, killing two birds with one stone. (2) an increase of 200? 0? 8m screen margin control index. Most domestic production lines are still controlled at 80? 0? 8m is taken as the assessment index, which is 200? 0? The screen margin of 8m is not checked. The result of such control may be: even 80? 0? 8m screen margin control is relaxed to 15%, which does not mean that it is greater than 200? 0? The 8m screen margin must be very small. Once the kiln calcination is affected, is it because of 200? 0? 8m screen margin is too small, or 80? 0? It is difficult to draw a conclusion whether the 8m screen margin is too large. On the other hand, if 200? 0? The screen allowance of 8m can be controlled below 2%, and the kiln calcination is very good. Can it be 80? 0? The screen margin of 8m is too large, which is necessary for fine operation in order to save energy and increase production. 3 Control method of raw material fineness (1) It is very easy to adjust the classifier speed of vertical mill and closed-circuit ball mill by frequency conversion, thus realizing the control of raw material fineness. But it will be much more difficult to narrow down the fineness range of its products. (2) Promote the use of low-voltage technology. A few years ago, Lv Company used its own patented technology to transform the classifier in the vertical mill. After modification, not only the rising speed of airflow is improved, but also the pressure drop and rotor wear are reduced. Its principle is to design a stator with several LV air chambers, so that the coarse particles carried by the ascending airflow are obviously separated from the fine particles of the finished product, and the coarse particles do not collide with the ascending particles in the process of falling back to the grinding disc, thus avoiding energy loss. Moreover, due to the reduction of collision return, the material thickness on the grinding disc tends to be stable, which can not only increase the feed, but also reduce the material overflow by at least half. Moreover, because the airflow speed through the LV wind chamber can be adjusted according to the control of raw meal granularity, after powder selection, not only the fine powder selected does not contain coarse material, but also the descending coarse material does not contain fine powder, thus narrowing the product granularity range and meeting the requirements of raw meal fineness composition. This technology has been widely promoted abroad, and a few factories in China, such as Yunfu, have been reformed, and the effect is very ideal. In recent years, this technology patent has been purchased by companies such as Fan Fei and Smith, so it is no longer necessary to transform the newly purchased vertical mill. In addition, for the system that uses ball milling to produce raw meal, there is also corresponding LV technology to transform its classifier. 4 Inspection method of raw meal fineness The production of mill should not only be supervised by continuous online analysis system, but also have hourly experimental analysis of instantaneous samples or mixed samples. The fineness test sample can come from the sample that tests the ingredients of raw materials, and the test frequency can be once every 4 hours when the production is stable. Pay attention to the cleanliness of raw materials when sampling, otherwise it will seriously damage the control program of analyzer and affect the test results of fineness. Many foreign laboratories have on-line laser particle size analyzer, which can provide raw meal particle size distribution data, and the attention range is 0. 1 ~ 200? 0? 8m: For vertical mill, the material circulation time is usually less than 1 min, while for ball mill, it takes more than ten minutes. Therefore, the response time of control should be as fast as possible to realize the control of automatic control loop.