Application of Siemens Level Measurement Technology in Cement Plants

With a history of more than 170 years, Lafarge is the world's largest cement manufacturer. Since 1994, Lafarge has been committed to developing a partnership with China, continuously increasing investment in China, and has achieved great development in China's cement industry. In August 2005, it officially announced the merger of the cement business of both parties in China with Shui On Construction, the largest cement manufacturer in southwest China, so that Lafarge Shui On, as a foreign-funded enterprise, will enter the top three in terms of production capacity in the domestic cement industry.

As Lafarge's largest dry process cement production plant in China, Chengdu Dujiangyan Lafarge Cement Plant was officially put into production in February 2002, with a designed annual output of 1.4 million tons of cement. In the early stage of production, Dujiangyan Lafarge Cement Company relied on advanced production technology, high production efficiency and effective cost control, and adopted a low-price strategy to completely break the original competitive pattern of Chengdu cement market.

Lafarge's market expansion strategy, cost control strategy and product technology advantages are all worthy of learning and reference for domestic cement manufacturers.

Challenges

For Lafarge, how to choose reliable and efficient automatic control systems and instrumentation equipment is an important part of the cost control strategy to improve the competitiveness of products. In cement plants, continuous level measurement of various material bins plays a vital role in improving product quality, production efficiency, safety and environmental protection of the entire production line.

Lafarge has tried various level measurement technologies to solve this problem, but none of them have achieved satisfactory results, especially in clinker bins, assimilation bins, finished cement silos and other locations. The dust is very large, which makes many companies' level products daunting.

After using contact level measurement methods such as heavy hammer level meter, capacitive level meter, guided wave radar level meter, it was found that these methods not only have unsatisfactory measurement results, but also have the risk of the steel cable being broken and affecting production. Therefore, the choice of this contact level measurement method has been basically abandoned.

Although the ultrasonic level meter is a non-contact level instrument, it is widely used in many fields. However, in the actual use of finished cement plants, it is found that it is easily affected by dust. When the feeding is stopped, the ultrasonic wave can obtain the measurement signal within the measurement range of 20m; however, when the measurement range is large (when the material level is low) and the dust is serious (continuous feeding and discharging), it is basically in a state of wave loss and cannot work normally.

Lafarge has been looking for a reliable level measurement method that can fully automate the entire production line, so that the staff can be freed from dangerous and harmful working environments, so as to improve production efficiency and reduce production costs.

Solution

In order to select a suitable and reliable level measurement instrument, Chengdu Lafarge consulted a lot of Lafarge factories. The Alpena Cement Production Plant in Michigan, USA is the largest cement plant in North America, with an annual output of 2.7 million tons of cement. Their experience in use has been a great help to us. It is reported that the plant originally had the same problem as us. After trying Siemens' new product Sitrans LR400 in July 2001, it achieved very good results in the measurement conditions of clinker silos, assimilation silos, and finished cement silos.

After careful comparison, among the solutions provided by many international excellent instrument suppliers, Chengdu Lafarge finally adopted Sitrans LR400 provided by Siemens as a continuous level measurement solution.

Sitrans LR400 is a 24GHz high frequency microwave radar level meter with continuous frequency modulation working mode. The maximum range can reach 45 meters, which can fully meet the requirements of various warehouses of different heights in cement plants.

In addition, it has the following characteristics:

1. It can penetrate the influence of severe dust, and even in the measurement applications of media such as clinker, finished cement, flour, fly ash, etc., it can obtain reliable, stable and accurate level measurement.

2. The advanced echo processing technology, acoustic intelligence technology, which inherits Siemens Milltronics' more than 50 years of level manufacturing experience, can distinguish true and false echo signals under various harsh conditions, thereby ensuring the reliability of level measurement. 3.

The use of a longer horn design not only facilitates the needs of on-site installation, but also obtains a smaller microwave emission angle, which is conducive to enhancing the strength of the echo signal and avoiding interference signals within the emission range of the microwave radar level meter. 4. Unique

solid-type algorithm. It has undergone many years of research and repeated field experiments by Siemens, so that it can always maintain outstanding performance in various dusty solid level measurement applications in industries such as cement.

Sturdy aluminum shell design. Can meet various harsh working conditions.

In February 2005, Siemens launched the new solid LR400, which made many improvements on the original basis for the characteristics of solid level measurement. For example: the aimer is used as the standard configuration of the microwave radar level meter, which improves the performance of the instrument without increasing any cost; the bell mouth can be lengthened according to the actual needs of the customer; the range is upgraded to 50 meters, etc. [page]

Use effect

In more than 3 years of use, Sitrans LR400 has always worked stably and reliably, completely solving the problem of continuous level measurement in severe dust conditions. In the measurement applications of clinker silos, cement silos, assimilation silos, etc., in the case of continuous feeding and discharging, the echo graph is read through the software provided by Siemens and found that the echo signal is basically not affected by dust and is still very strong.

The reliable performance of Sitranas LR400 enables Chengdu Lafarge to fully automate the level control system of each important silo. Workers no longer need to use dipsticks to detect the material level in each silo with poor working conditions every day, and there is no need to worry about the risk of breaking the steel cable like contact level meters. This improves the reliability and accuracy of level measurement, greatly saves production costs, and improves production safety. In addition, the design service life of LR400 is 10 years. This design feature also maximizes the investment cost of the cement plant.

Due to the successful application of Sitrans LR400 in Lafarge's cement plants in recent years, it has become a recommended product of Lafarge.

In the process of using SITRANS LR400, we found that there are two points that need special attention, otherwise it may bring unexpected effects.

1. Dust prevention treatment

Fault phenomenon: Although microwaves can penetrate the influence of dust, in some extremely severe dust conditions, the raised dust may adhere to the radar wave transmitting electrode, resulting in attenuation of the transmission signal or even complete loss. Sometimes, the dust is very wet and even forms mud on the bell mouth of the microwave radar level meter (as shown in Figure 4). In general, the normal use of the instrument can be restored by simply removing the dust and mud in the bell mouth.

Solution:

Installing a PTFE dust cover on the bell mouth of the SITRANS LR400 radar level meter can solve this problem. Under normal temperature conditions, the same effect can be achieved by simply covering the bell mouth with an ordinary plastic film.

B. Purge system. In the case of relatively wet dust, even if a dust cover is used, there will still be mud sticking to the dust cover. Regularly replacing the dust cover will increase the workload of employees and reduce production efficiency. After selecting the special option of Siemens LR400 - the purge device, the compressed air can be blown into the bell mouth regularly or continuously to prevent the intrusion of dust and moisture.

2. Installation location.

Fault phenomenon: Avoid installing near the feed port, silo wall, etc. to prevent faults caused by unexpected interference. In the use of a silo in a cement plant, it was found that the indication of the level measuring instrument was always fixed at a certain value. After the Siemens engineer arrived at the site, he used the debugging software to read the echo graph and found that there was a strong false echo in front of the normal echo (as shown in Figure 6). After returning and checking the site, it was found that the instrument had a metal beam on the silo wall that was "detected" by the instrument due to the reasonable installation position. Solution

: A. Replace it to a reasonable installation position. B. Choose a solid LR400 with a sight. Just slightly adjust the angle of the sight to minimize the echo intensity of the fixed interference. C. Use advanced echo processing software to eliminate the fixed interference. However, if the interference echo is strong or the fixed interference position is in the "center" of the measurement range, the fixed interference echo suppression method may bring "side effects" and produce a larger measurement "blind area". In the previous fault, since the interference occurred at a higher position, the echo processing software technology was used to "cut off" the interference. After the fault was eliminated, it has been working stably and reliably, which fully demonstrates the excellent echo processing ability of Sitrans LR400. Conclusion Sitrans LR400 has been working stably and reliably for more than 3 years, completely solving the problem of continuous level measurement in severe dust conditions. Due to the successful application of Lafarge cement plants, Sitrans LR400 radar level meter has become a recommended product of Lafarge. It is widely used in every cement plant, and some cement plants have hundreds of units. The newly launched solid type LR400 has made a greater impact on the solid material measurement market with its advantages of high quality and low price, thus further confirming the leading position of SITRANS LR400 in solid level measurement.