Looking back more than ten years ago, cement grinding AIDS were unfamiliar to most cement enterprises, and few people contacted them, so few enterprises used them. At that time, there were few companies that could provide grinding AIDS, and it was even more difficult to promote them in the market. But today, grinding AIDS are almost familiar to cement enterprises, and there are hundreds of companies that can provide so-called grinding AIDS. The rapid development is the highest in the world, but there are also many problems that are worrying. Grinding AIDS are a kind of applied nonstandard products. How to choose qualified grinding AIDS and how to use them correctly to maximize the benefits of grinding AIDS in cement enterprises needs further study by grinding aid companies and cement enterprises. Grinding AIDS are small products for cement enterprises, but if advanced grinding AIDS companies and products can be correctly selected and used, grinding AIDS can play a big role. It can make great contributions to energy saving, emission reduction, consumption reduction and efficiency improvement of enterprises, and even turn losses into profits. Based on the author's understanding of the grinding process of cement and the demand of cement products, combined with the research on the research and development and application technology of grinding AIDS for more than ten years, this paper analyzes how to correctly apply grinding AIDS and maximize their use efficiency for your reference.
1, the definition and historical development of grinding AIDS
Cement grinding aid is an additive added in cement grinding, which can improve grinding process and improve grinding efficiency without damaging cement performance. There are corresponding standards at home and abroad, which allow cement grinding AIDS to be added in the process of cement grinding, and the addition amount generally does not exceed 1% of cement quality. In China, due to the illegal operation of some cement grinding AIDS suppliers, a large number of harmful components are added in the name of grinding AIDS. Therefore, according to industry standards and regulations of relevant authorities, the addition of cement grinding AIDS should not exceed 0.5% of cement quality, hoping to reduce the dosage of harmful components. Cement grinding AIDS, also known as cement grinding process additives, are one of the internationally recognized cement additives.
As early as 1930s, people began to use cement grinding AIDS to improve the grinding process of cement. One of the earliest records of the use of cement grinding AIDS and British patents was in 1930, when a small amount of resin was added. In the early 1930s, American Grace Company invented and obtained the patented product TDA, and invented the patented product HEA2 at 1965. These products were widely used in the middle and late 20th century. Subsequently, many countries in the world also carried out a lot of research, such as the former Soviet Union, Canadian, Japanese, China and so on. In China, the research on cement grinding AIDS was mainly carried out in the mid-1980s. With the deepening of research, more and more cement grinding AIDS have been developed and applied. In recent twenty years, the new generation of grinding AIDS has been widely used in cement grinding process, which has all the advantages of traditional cement grinding AIDS and can also improve cement quality. People call it "grinding aid to improve cement quality" or "quality improver" for short. When we add additives to cement, such as slag, fly ash, volcanic ash or limestone, we find that the strength development of this cement is different from that of pure portland cement. In order to reduce this influence, the use of this cement additive, that is, "quality improver", will be very beneficial to improve the quality of cement. These additives can meet a series of different needs by strengthening the strength of cement and concrete, adjusting the setting time of cement and the water demand of concrete. The performance advantages they provide can save more costs than ordinary cement grinding AIDS, for example, because of their use, the dosage of additives can be increased, the production cost can be reduced, and the impact on the environment can be reduced to a greater extent.
The research on grinding AIDS in China was earlier, but its real application began in the 1990s. At the beginning, some foreign cement enterprises used traditional chemical raw materials as grinding AIDS to ensure the unloading fluidity of exported cement after long-distance transportation. Since 1996, I have been promoting grinding AIDS to improve cement quality to many large and medium-sized cement enterprises in China. At that time, Beijing Cement Plant should be the first to use quality improvers in normal production, and the benefits created have reached tens of millions.
At present, there are hundreds of grinding AIDS enterprises in China, most of which are small in scale, poor in technical strength and single in variety, which cannot meet the needs of cement enterprises in all aspects. However, the strength of a few enterprises has reached a considerable level, and some have reached the international level. For example, Beijing Renzhong Innovation Industry and Trade Co., Ltd. has reached or exceeded the international level in product technology and application service technology.
2. The importance of applying grinding aids.
The advantages of cement grinding AIDS have been recognized by more and more people, and have been widely used in cement production. More than 95% cement in North America has used cement grinding AIDS, more than 75% cement in Europe has used cement grinding AIDS, and more than 60% cement in the world has used cement grinding AIDS. The benefits brought by high-quality cement grinding AIDS have far exceeded their own values and become necessary auxiliary products for cement production enterprises. It is an effective technical means adopted by cement enterprises to meet the needs of customers. It is an effective method for cement enterprises to save energy, reduce consumption and increase benefits. We fully understand the importance of cement grinding AIDS to cement production, and adopt a scientific attitude and method of seeking truth from facts, which can be conducive to the correct decision-making of decision makers in cement production enterprises and the correct selection of quality technicians and production users.
Second, the choice of cement grinding AIDS
1, types of cement grinding AIDS
Grinding AIDS can be divided into liquid, solid and gas according to the use state. Some liquid grinding AIDS directly use chemical raw materials, such as triethanolamine, ethylene glycol, pulp waste liquid and glycerol. And some grinding AIDS produced by grinding aid companies, such as CB series, RTD series, PB series, CBA series and TDA series, are widely used in the market. This grinding aid is stably and evenly added to the materials entering the grinding belt through the metering pump, or directly sprayed into the mill for use. Solid grinding AIDS include stearate, coal powder, urea, etc. This kind of grinding aid needs to add more equipment and storage tanks, and the addition amount is generally large, which increases the maintenance and logistics costs, has a certain negative impact on cement performance, or is harmful to human health, and is rarely used. Gas grinding AIDS are rarely used in cement industry. According to chemical composition, grinding AIDS can be divided into organic compounds, inorganic compounds and composite compounds. The most widely used compound.
2, clear the purpose of using grinding AIDS.
The main purpose of using grinding AIDS in modern cement enterprises is to reduce production costs, improve cement quality, or meet the special needs of customers in cement enterprises. Nearly 70 years of research and application practice have proved this point. However, a large number of application practices show that even if similar grinding AIDS are applied to similar production lines, their functions are quite different. Therefore, only by understanding the actual situation of cement enterprises and choosing appropriate cement grinding AIDS can the application be successful and the purpose of cement enterprises be achieved.
To make clear the purpose of using cement grinding AIDS, first of all, cement enterprises should have a good understanding of their own cement and its production technology. Understand the variety, quality and performance requirements of cement, admixture and its proportion, fineness, specific surface area and setting time of cement. Secondly, we should fully understand the production technology, mill specifications, partition design, ball matching and its filling rate, output and gap filling rate in the cement mill system. In the case of closed-circuit grinding, it is necessary to know the model, specification, powder selection efficiency, circulating load and ventilation of the classifier. In addition, combined with cement standards, market demand and marketing positioning of enterprises, the self-demand is defined, and the feasibility analysis of whether the application of cement grinding AIDS can meet their own needs is carried out. Generally speaking, if cement enterprises meet the following conditions, they can consider using grinding AIDS to solve the problem.
In order to make up for the shortage of production capacity and meet the sales demand.
In order to improve the hourly output of the mill.
When the same output is produced, in order to reduce the running time, reduce the maintenance cost of the mill system, or improve the flexibility of maintenance and repair plan.
In order to improve the quality of cement, meet customer needs and enhance market competitiveness; In order to meet product standards, or to solve market complaints about quality; Improve their position in the market; Or make up for the variation and weathering of clinker quality.
In order to improve the fluidity of cement and facilitate the operation of cement, thus reducing transportation and transportation costs; At the same time, the storage capacity and storage time are increased.
In order to increase the use of additives and reduce costs.
In order to improve the utilization rate of industrial waste residue and meet the requirements of emission reduction, when producing the same cement, due to the reduction of clinker
Use less, thus reducing the emissions of carbon dioxide, nitrogen oxides, etc.
In order to produce high-grade cement, high prices are obtained.
In order to produce new varieties of cement and meet the needs of new markets.
3. Criteria and methods for selecting suitable grinding AIDS
The above demand list is the basic motivation to consider using cement grinding AIDS. But what is more critical is the selection of grinding AIDS and the application technology of grinding AIDS. Only by choosing the right grinding AIDS and applying them well can we get real value.
There are many substances that can be used as cement grinding AIDS, and there are many grinding AIDS companies in China to choose from, but the effects are different. The production threshold of grinding AIDS is low, but research and development technology, production technology and application service technology directly affect the use effect of grinding AIDS. Even some products are helpful for grinding, but harmful to the quality of cement or concrete, or to human health or the environment. For example, the content of chlorine (Cl-) and alkali (R2SO4, R2O) exceeds the standard, or aluminate and sulphoaluminate are added, or concrete admixture is simply added to stimulate the strength of cement. This will have a potential adverse effect on the performance of cement and concrete. Therefore, it is very important to choose a good grinding aid. At home and abroad, the corresponding standards of cement grinding AIDS have been revised, such as ASTM C-465 in the United States and EN 197 in Europe. China has also adopted ASTM C-465 in the United States to formulate the corresponding building materials industry standard JC/T667- 1997 to evaluate cement grinding AIDS. Meeting these standards is the most basic quality requirement of cement grinding AIDS, but it is often not enough. This is an applied non-standard product, and it is difficult for the standard to specify the characteristics of grinding AIDS and avoid harmful components. Therefore, in order to be widely used in production, detailed and scientific tests must be carried out in specific cement plants, including laboratory tests and industrial tests. If conditions permit, specific tests are needed. Generally speaking, grinding AIDS companies with large scale and strong research strength have many grinding AIDS to choose from to meet different needs.
It is necessary to carry out laboratory tests on grinding AIDS whose performance and quality are not clear, or to choose the best grinding AIDS. The purpose is to compare the performance and quality of different grinding AIDS, find out the best grinding aid suitable for specific cement, and prepare for industrial test. Laboratory tests can be carried out year-on-year with different grinding AIDS. First of all, it is necessary to screen suitable grinding AIDS from a chemical point of view. The main influence of grinding AIDS on the properties of cement and concrete is chemical action. Some people say that the test is useless and biased. Of course, after laboratory tests, it is found that products with good quality and performance cannot be used in production, because grinding AIDS also have grinding AIDS, which can adjust the particle size distribution of cement to a certain extent, and the particle size distribution of cement has a certain influence on the performance of cement, which we will discuss in detail in the later application technology. But this cannot deny the importance of laboratory testing. Laboratory tests generally use small mill or module tests, or directly use concrete tests.
The industrial test is to apply the selected grinding AIDS to industrial production, which is a comprehensive evaluation of grinding adaptability of grinding AIDS and improvement of cement quality. Some require that the grinding process and the amount of grinding AIDS should be properly adjusted to achieve the effectiveness of the selected cement grinding AIDS in use.
During the industrial test or normal application, high requirements are put forward for the application technical services of grinding AIDS companies. Because raw materials, fuels, ingredients, grinding technology and market are changing, the demand or effect of grinding AIDS is also changing from time to time. Even if the grinding AIDS selected through particle size test, due to the changes of the above factors, it is difficult to absolutely ensure that the mixing ratio and output increase by a few percentage points, which should be a range. If the effect becomes worse for some reasons, it is necessary to analyze the reasons or adjust the grinding AIDS, but only if the grinding AIDS are stable. In order to get customers, some grinding AIDS companies promise absolutely certain results, which is unscientific. I once provided three different products for a cement company to meet the needs of three cement varieties. For the same kind of cement in the same cement factory, I used to change different kinds of grinding AIDS because of its seasonal change, cement market change or performance requirements change to meet its changing needs. It is hard to imagine that a grinding aid company with little knowledge of cement performance, cement technology and customer market demand and no product research and development strength can provide good service and product technical support for cement enterprises. If you use it reluctantly, you will definitely not be able to create maximum value for cement enterprises.