15th Five-Year Plan", the compliance production of the cement industry has entered a new stage of normalization. It has become the basic criteria for the development of the industry to strictly follow the approved production capacity to organize production and resolutely put an end to overproduction. To this end, China Cement Network interviewed Qi Yanyong, an associate professor of Southwest University of Science and Technology, to deeply analyze the practical path of low production, high efficiency, compliance and cost reduction.
Qi Yanyong pointed out that in the current cement production process, many enterprises reported that the coal consumption increased when the cement burning system was running at a lower output or using coal with higher calorific value, which directly affected the economic benefits of enterprises. Therefore, it is of great practical significance to discuss the operation optimization measures under low output operation.
In the actual production operation, the firing system has a fixed control logic: the operator adjusts and controls the coal consumption of the calciner according to the outlet temperature of the calciner, and determines the coal consumption of the rotary kiln according to the current of the rotary kiln and the free calcium content of the clinker . Meanwhile, the rotating speed of the high-temperature fan is adjusted according to the oxygen content of the primary cylinder. This control mode is more applicable under the conventional output, but in the low output operation, if the recovery heat of the decomposition furnace and the rotary kiln is not reduced in proportion to the output, or the reduction of the coal consumption of the rotary kiln does not match the change of the air volume, it will lead to the reduction of the coal combustion efficiency of the rotary kiln, such as the lack of oxygen. Finally, it directly leads to the increase of coal consumption in the system.
In view of the operation management and control of low-yield operation, Qi Yanyong believes that two key requirements need to be implemented.
First, the high temperature fan must be reduced in proportion. If the air volume of the high temperature fan is not reduced synchronously with the output, the heat loss of the waste gas will be greatly increased. Taking the actual production data as an example, when the output is 6300 t/d, the rotating speed of the high-temperature fan is 840 rpm; when the output is reduced to 5000 t/d, the rotating speed should be adjusted to 667 rpm according to the proportional calculation. The high-temperature fan is a centrifugal fan, and the rated speed of the motor is 996 rpm. When the rated speed of the motor is reduced from 840 rpm to 100 rpm, the efficiency of the fan is estimated to be reduced by about 2%. Considering the change of the efficiency of the fan, the speed of the high-temperature fan should be controlled within 680 rpm in actual operation.
Second, the front row should be lowered in place. After the air output of the high-temperature fan is reduced, if the air output of the grate cooler remains unchanged and the first row of air output is not reduced in time, the secondary air and tertiary air extracted by the system will be reduced, resulting in a decrease in heat recovery efficiency and ultimately a higher coal consumption of the system.
In addition, on the premise of not changing the structural parameters of the equipment such as the necking area of the smoke chamber and the diameter of the rising pipe of the cyclone, the firing system has a limit of output reduction for normal production. The structural parameters of the equipment determine the basic conditions of airflow circulation, material heat exchange and combustion in the system. Running blindly beyond the limit of production reduction will destroy the balance between the airflow field and material calcination in the system, aggravate the problems of heat loss and insufficient combustion, and also lead to the increase of coal consumption.
To sum up, Qi Yanyong said that the low-yield operation of cement firing system should follow the principle of synchronous matching of output, air volume and coal consumption, accurately regulate and control the high-temperature fan and the first row of air, at the same time, clarify the limit of production reduction under fixed structure, realize the control of coal consumption under low-yield conditions through fine operation, and improve the production economy.
On April 9-10, China Cement Network will hold the 15th China Cement Industry Summit and TOP100 Award Ceremony in Hangzhou. At the same time, the " Cement Economy Fifty People Forum (C50) " was held. The Summit will build a platform for the docking of supply and demand and the collision of ideas, explore the path of green transformation and intelligent upgrading from the dimensions of macroeconomic insight, industrial chain synergy and technological innovation breakthroughs, plan a layout for the "15th Five-Year Plan" green development of the industry, and work together to create a new chapter of high-quality development! At that time, Qi Yanyong, associate professor of Southwest University of Science and Technology, will be invited to attend the " 15th China Cement Industry Summit and TOP100 Award Ceremony " and give a keynote report on the theme of " Optimal Operation of Low Yield (Design Output) Kiln System".
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