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1、操作水泥窑的若干体会（Some experiences of operating cement kiln）Some experience of Gao Yuping reproduced the label operation of cement kiln gradually: Cement TechnologyControl of fuel ratio for kiln and calcinerKiln / decomposition furnace fuel ratio control should be based on the following principles: (1) the
2、 kiln and the gas temperature of decomposing furnace should not be higher than the normal value; (2) ventilation in reasonable circumstances, the oxygen content of the kiln and calciner outlet in the exhaust gas should be kept in a proper range, should as far as possible to avoid the emergence of ca
3、rbon monoxide; (3) the temperature and ventilation could improve the fuel ratio of decomposing furnace. These principles are easy to understand and most of them can be carried out, but there are many people who still have some vague ideas and can not deal with them well when confronted with problems
4、.The fuzzy understanding of the kiln to decomposition temperature, furnace area between the crust that is serious due to the decomposition furnace fuel caused by operation, thus always reduce decomposition furnace fuel, and then increase the kiln fuel, the results of this regional temperature increa
5、sed further, the crust is more serious, kiln condition worsened. In fact, in addition to kiln gas and furnace gas separated from the double series kiln, it is mainly due to excessive fuel in the kiln. As we all know, the decomposition furnace is an efficient heat exchanger, the decomposition furnace
6、 more fuel, the exhaust gas temperature is not too high and the furnace material can obtain a higher decomposition rate. But if this part should be added to the furnace, the decomposition rate of the kiln material will be low, which will increase the burden on the kiln. Because the kiln heat exchang
7、e efficiency is low, in order to ensure the normal burning clinker, it should be added to the fuel in the kiln, but by the combustion space and the heat exchange efficiency limit, to the decomposition temperature of the furnace kiln area between the inevitable high. And this area is just material th
8、in area, and the material is easy to produce in this part of the corner of the loop, there are very good skin conditions, easy to cause serious skin. The material itself does not exceed the temperature equilibrium temperature was in complete decomposition before (usually around 850 degrees), so in c
9、alciner with appropriate fuel will not cause the high exhaust temperature will not cause kiln feed temperature is too high, and only the material in the furnace is not well dispersed and uneven distribution of the case and its exports will cause the high temperature of exhaust gas in the furnace. Th
10、erefore, when the kiln and the ascending pipe temperature is high, can not easily believe that decomposing furnace more fuel, and should carefully analyze the reasons, adopt the correct method of operation. In general, the situation will gradually improve as long as a little of the kiln fuel is redu
11、ced and a portion of its reduction is added to the calciner.Two of the fuzzy knowledge is that the burning temperature is low and the clinker is poor, which is thought to be caused by less fuel. Even when the combustion capacity of kiln has reached the limit, the amount of kiln fuel is increased, an
12、d the kiln head temperature is further lowered, and the temperature of kiln end system is too high. This wrong operation will also lead to a reduction of atmosphere in the kiln, resulting in serious crust formation, long and thick crust and even ring formation. The ventilation and combustion capacit
13、y of kiln has a certain limit. In the case of no excess combustion air, increasing the temperature of the fuel kiln head will not increase but decrease. This truth is generally understand, but some people encounter a kiln head temperature is low but always increase kiln fuel, especially not in the f
14、eeding amount of combustion air is not surplus situation, still more fuel into the kiln. The author believes that there is one simple principle for the increase of kiln fuel, that is, there is no need to increase the kiln fuel until the carbon monoxide in the kiln exhaust is present and the carbon m
15、onoxide is removed before adjusting the system status. So if the kiln head temperature is low, should first analyze the reasons, such as lack of combustion air, should try to increase the amount of ventilation; the wind machine has been opened to the limit, you should analyze whether the large quant
16、ities of material, whether the three brake plates did not adjust well, whether inside the kiln circle, and adjust and suitable treatment when the kiln is: if the decomposition rate is low, should increase the decomposition furnace fuel instead of kiln fuel; such as cooling machine of low efficiency
17、two air temperature is low, with cooling machine for processing. In short, we should analyze the specific situation, but not increase the fuel consumption of the kiln head, but the result is counterproductive.Two 、 control and adjust the system ventilationIn the case of reasonable amount of fuel and
18、 feed in the kiln, the proper control of the combustion air for the fuel is the control principle of the system ventilation. General is to waste gas of kiln, decomposition furnace and preheater exit analysis of ventilation system to control the oxygen content of the three parts should be respectivel
19、y at 2%, 2% 3%, 3% 4%, at the same time should try to avoid the emergence of carbon monoxide. Control methods include adjusting exhaust fan speed (or throttle opening), adjust the three brake plate opening etc. By adjusting the primary air volume, the cooling machine drum, the exhaust air volume and
20、 the bypass air flow, etc., the ventilation of the system can also be adjusted. The authors found that a considerable number of operators had CO in the bypass exhaust when operating a kiln outside the kiln that had a bypass system,When the content needs to be reduced, it is not to increase the bypas
21、s quantity, but instead, the CO in the tail gas of kiln will be further increased. The atmosphere of the kiln will be further increased and the kiln condition will deteriorate further. The CO bypass from the kiln (only when decomposing furnace burning oil nozzle and coking coal and coal or oil feedi
22、ng due to uneven material collapse when CO will bypass from the decomposing furnace, and exhaust gas bypass) because the sampling device is generally installed in the bypass mixing chamber, so the content of CO value than much less in the kiln. When there is CO in exhaust gas that bypass kiln CO mor
23、e, then we should adjust the measures include increasing the amount of bypass, and should not reduce the discharge volume of bypass.Three, kiln outside decomposition kiln is not the output, the lower the better burningOutside kiln precalcing kiln decomposing furnace, kiln preheater and rising pipe a
24、t all levels, connecting pipes are designed according to the flow rate, to ensure that the material can be in a suspended state, with air movement and have higher separation efficiency. The wind speed is dependent on the amount of air and the amount of the system when the equipment specification is
25、set. Corresponding to the optimum wind speed throughout the system, there is a corresponding optimum amount of feed. In this sense, the kilns output is below or above the optimum yield. The effect of excessive production on forced calcination is well known, while low production results in the follow
26、ing consequences due to low wind speed:1. materials in the system of stacking and collapse under appropriate conditionsWhen the wind speed is low everywhere, easy material in preheater, decomposition of some small platform, small angle cone parts inside the furnace stack, accumulated to a certain ex
27、tent when the wind speed changes, the accumulated material will lose stability and collapse into the air. Because the wind speed is low, these materials greatly exceed the normal amount may not be uniformly dispersed in the air, but in the absence of appropriate heat exchange of sinking into the kil
28、n and quickly jumped into the burning zone. Thermal system although this process time is short but it will bring serious interference of kiln, firing temperature suddenly decreased, the short term clinker burning kiln; instantaneous poor ventilation appears reducing atmosphere; the length and positi
29、on of each zone in the kiln, kiln brick changes, caused by skin damage; exothermic reaction zone suddenly moved forward, after the ring and other serious consequences. With the bypass system of the kiln, because the material collapse generally after bypass outlet, so the ash quantity increase and de
30、crease the efficiency of bypass material collapse also cause.When the kiln output is low for other reasons, the kiln condition is easy to fluctuate. The performance of the negative pressure meter fluctuates frequently, the kiln driving current (or torque) can not be stable, and the temperature of bu
31、rning is high and low. These phenomena are caused by the collapse of the material.2. material dispersion is not goodIn the preheater and calciner in the wind pipe material evenly suspended in the air, the heat transfer efficiency is high, but if the feeding amount is low, the ventilation rate, low w
32、ind speed, the dispersion effect is all not good, resulting in system of low heat efficiency, easy accumulation and material collapse. Kiln in low yield when high heat consumption of clinker cooling unit in addition to the proportion of large, another reason is that the material dispersion is not go
33、od, the heat has not been fully utilized.3. the material is easy to overheat, the preheater is easy to jamWhen the feed capacity is low, the equilibrium temperature tends to develop in a high direction due to the small amount of heat absorption in the system. Especially when the system accumulates,
34、the amount of material suspended in the hot air stream is less than that of the fuel at that time, thus the material is easy to overheat and easy to adhere to the preheater or the blanking pipe and so on. When the feed rate is low, in order to cope with the fluctuation of the kiln conditions, the am
35、ount of fuel added is higher than the normal demand, so the system is more likely to overheat, contract or even clog. This is the reason why the blockage of the preheater is easy to occur when the kiln is low production.Therefore, the kiln output should have an optimum value, which varies with the m
36、aterials easy to burn, bypass capacity, combustion quality, etc., and should be decided in operation. Kiln feeding amount should increase gradually in the open kiln feeding stage, but should avoid prolonged low feeding stage. As long as a good grasp of the fuel, feed, air volume relations, so that t
37、he system to achieve a reasonable heat balance, even if large kilns in an hour can also be added to the best yield (sometimes the highest yield). The daily output of 3400 tons of kiln, under the condition of the normal kiln skin, can be completed in 40 minutes from the beginning of feeding to the hi
38、ghest output. The system has no abnormal occurrence. The author also found that, when the maximum yield of 70%, kiln conditions have become easier to stabilize. Such as Nissan 3400 tons of kiln, when the amount of feed is greater than 180 tons / hour, it basically does not occur material collapse ph
39、enomenon. Therefore, the operation of such a kiln shall be avoided as follows.Four, not all crusts are harmfulThe kiln, calciner, preheater and their connecting pipes can produce crusts when the contents of overheating and harmful components are high. The material flow, reduce the crust could effect
40、ively through space,Hinder the flow of material or even cause jam; the crust can also cause the material to enter the kiln channel is not smooth, causing material flying, rising pipe circulation, increasing the skin, and increase the system ventilation resistance. But I think, not all crusts are har
41、mful, but most of the crust is harmful, part of the crust is harmless, and some crusts may also be beneficial.Generally, the crusts on the smooth surface and in the original narrow channel are harmful crusts. The following are the tubes, the preheater cone, the combustion zone and the upper part of
42、the precalciner, the slope at the end of the kiln, and the necking at the end of the kiln. The crusts in these areas impede the flow of material and airflow and can even cause blockages, reducing combustion and heat exchange space. And some parts of the crust, such as the square pipe in the four cor
43、ners of the skin is not very large, the gas pipeline in the air flow, dead area inside the skin, are harmless skin. These crusts have little effect on the flow of gases and materials. The following two kinds of crust are good crust: first, if something is not easy to form a vortex flow of crust in t
44、he region, increase the resistance loss, is the part of the crust is beneficial crusts; second, as a part of the design is too large, the location of wind speed is too low, is the crust part of the crust is useful. For example, a kiln in which the author has operated has a rise in the lining of the
45、pipe that gives rise to cracks, and the hot gas enters the space between the lining and the shell. In order to continue the operation of the kiln, it is decided not to clean up the crust of the place. The purpose is to block the cracks with the crust, prevent the hot gas from permeating and cause th
46、e outer shell to deform and the lining bulge out. Later, the crusts gradually thickened, blocking 1/3 of the cross-sectional area, but the kiln reached a rare high yield and stability. Later, the crust fell off, and the kiln lost the period of gold. The reason is simple. The part is under the pipe d
47、ecomposing furnace. The material is in the upper part of the furnace. When the wind velocity is slightly lower, the material is short circuited into the kiln and the kiln condition fluctuates and the output is not high. Once the node thick, high speed material no longer short circuit, so as to impro
48、ve the decomposition rate of kiln, kiln condition stable, kiln production increased. Therefore, there is a problem that should not be clear about the crust. The harmful crusts must be removed continuously; the harmless crust must not be cleaned up, but the beneficial crust should not be cleaned at a
49、ll.Five, about see fire problemIn the modern cement plant, the kiln operator is to understand, judge and control the parameters and equipment of the kiln system in the central control room by means of various parameter display instruments, PID controllers and even computers. The traditional fire watching has a new meaning in the operation of this kind of modern cement plant.In the process of modernization of cement kiln, firing temperature, clinker liter weight and free calcium, k