Due to the increasing demand for high-grade ceramic products in the market, iron removal from ceramic slurry has become one of the important processes in the ceramic production process. In order to improve the iron removal effect, many manufacturers do not hesitate to invest a lot of money and purchase a large number of iron removal equipment, but in the end they still have not fundamentally solved this problem. There are three factors affecting the effect of iron removal in slurry: raw materials, equipment, and environment. Iron removal equipment is the core that affects the effect of iron removal, and the three are complementary.
1. Effect of raw materials on iron removal effect
The physical properties of the slurry directly affect the iron removal efficiency of the iron removal equipment. Its main physical properties include the concentration, viscosity, flow rate, particle size, temperature, iron content of the slurry, and the strength of magnetic impurities. These factors are mainly It affects the ability of the magnetic field to attract magnetic substances, and the attractive force F must be greater than the resultant force FC (or competitiveness) that prevents the magnetic particles from being separated to be attracted and separated.
When removing iron from slurry, the attractive force is not only related to the magnetic field strength and its viscosity, but also related to the properties of ferromagnetic impurities. The greater the specific magnetic susceptibility k of impurities, the greater F; the greater the weight of the particle itself, the greater F is. The competitiveness includes the volume of ferromagnetic particles, centrifugal force, inertial force and fluid resistance, etc., and the inertial force and fluid resistance are the main parts of the competitiveness. At this time, the fluid resistance
FC=3ηdν where: η--slurry viscosity ν--slurry flow rate d--mineral particle diameter
It can be seen from the above formula that the viscosity of the slurry, the size of the iron mineral particles and the flow rate of the slurry all affect the competitiveness, thus affecting the iron removal effect. Therefore, when using the iron remover, it is necessary to carefully grasp the "four degrees" (concentration, viscosity, speed, particle size) of the slurry. The maximum particle size should be determined by the aperture selection of the vibrating screen; the speed is directly related to the flow rate; the viscosity is related to the concentration, properties and additives of the slurry; the concentration is determined by the water ratio.
The temperature of the slurry also has a great influence on the efficiency of iron removal. The high temperature of the slurry reduces the strength of the magnetic field, which not only affects the attractive force of the magnetic field but also shortens the service life of the magnetic material. Good magnetic materials can withstand a temperature of about 80°C, but they are expensive, and poor ones can only work at room temperature, so the iron remover should not be used directly after the ball mill as much as possible, because the slurry from the ball mill can be above 80°C . In the production process of ceramic products, it is generally more appropriate to install it on the pouring pool process or on the slurry conveying line.
2. Influence of iron removal equipment on iron removal effect
1. The selection and layout of iron removal equipment are very important.
Before selecting the iron removal equipment, the quality requirements of the product should be positioned first, then the slurry should be physically analyzed, and then the iron removal equipment should be reasonably selected. Different products have different requirements for iron removal efficiency: for example, high-grade daily-use ceramics, light-colored polished tiles and sanitary ware, not only the mechanical iron in the slurry must be removed, but also the weak magnetic impurities in it; in addition, such as glazed tiles, The requirements for removing iron from base materials and glazes are different, the requirements for base materials are low, and the requirements for glazes are high; and the requirements for different types of glazes are also different, such as metal glazed tiles, almost no iron removal is required; for general wall and floor tiles , the requirement for iron removal is lower.
For slurries with high requirements for iron removal, various iron removal equipment can be connected in series or in parallel to remove iron. For example, to remove iron from high-grade daily-use ceramics, you can first use a low-cost automatic magnetic bar iron remover to remove the strong magnetic impurities, and then use it in series with the induction series automatic iron remover to remove the weak magnetic impurities. This kind of series connection can not only improve the efficiency of iron removal, but also save costs. When used in series, the strong magnetic field iron remover should be arranged downstream; the parallel use of the same model is to increase the workload to meet the specifications, and the flow specifications of each model should be Similarly, the control of each machine needs to be synchronized to avoid cleaning multiple machines at the same time. The same type of machine is used in series and parallel to meet the demand for production output. At present, there are iron removers with output ranging from 5t/h to 30t/h in the market, which can basically meet the production requirements. It should be noted that the same model should not be used in series as far as possible. This series makes the downstream machines basically not remove iron.
In the use of iron removal tanks with magnetic rods, the spatial layout of the magnetic rods for iron removal should be reasonably designed. If the arrangement is too dense, it will not only affect the flow rate, but also increase the cost and cleaning labor, and if it is too sparse, the iron removal effect will not be achieved. In order to improve the iron removal effect of the magnetic rods on the surface flow and bottom flow slurry, it is generally adopted in the form of double-layer or multi-layer magnetic rods arranged alternately and alternately. The size of the diameter of the magnetic bar should also be appropriate to make full use of the effective magnetic source surface area. For a magnetic source with the same weight, the more the number of magnetic rods and the larger the effective surface area, the better the effect and the lower the cost. Of course, the mechanical strength and use requirements of the magnetic rods must also be considered.
2. The performance of iron removal equipment and the strength of the working magnetic field are important indicators.
At present, the commonly used slurry iron removal equipment includes iron removal tank, electromagnetic magnetic separator, permanent magnet iron remover and other equipment. The working magnetic field strength, production flow, iron removal efficiency and cleaning are important indicators for judging the iron removal effect of the iron remover. , but the working magnetic field is the core. The highest surface magnetism of the magnetic rod is about 8000Gs; the highest working surface magnetism of the electromagnetic iron remover is about 0.5-15,000 Gs; the superconducting high-power iron remover can reach 15,000-30,000 Gs or even higher; the induction series iron remover The working magnetic field can reach 1.0-18,000 Gs. For iron removers with the same iron removal efficiency, the larger the output, the stronger the required working magnetic field strength, and the increase in field strength and gradient will increase the difficulty and cost of making magnetic materials. Usually, the field strength increases by 10%, and the cost will decrease. Increased by 20%, so we can't blindly pursue high magnetic field.
3. Use of iron removal equipment. Proper cleaning is key.
During the iron removal process, timely and effective cleaning is the most effective way to improve the iron removal effect. After the surface of the magnetic source of the iron removal equipment absorbs certain magnetic impurities, the ability of re-attraction gradually weakens with the increase of the adsorbed substances. It adopts a fully automatic cleaning method, which can adjust the cleaning cycle according to the iron content of the slurry and the output requirements, without manual participation. This type of machine can not only improve the iron removal effect, but also save water. According to the current usage of the factory, it is imperative to use a fully automatic iron remover.
3. Methods to improve the effect of slurry iron removal
Based on the above analysis, we know that there are several ways to improve the iron removal effect of slurry:
1. Optimize the physical properties of the slurry.
①Reduce the temperature of the slurry entering the machine as much as possible, and generally cool it before entering the machine, so that the temperature of the slurry is below 80°C. ②Sieve before entering the machine to ensure the particle size of the slurry particles, so as not to block the iron removal equipment. For example, the induction series requires the slurry to pass through a 60-mesh sieve. ③Reducing the competitiveness, reducing the speed of slurry feeding, reducing the viscosity and concentration of slurry can all improve the iron removal effect.
2. Reasonable selection and use of iron removal equipment.
According to the characteristics of similar and different slurries, optimizing the selection and rational use of iron removal equipment can not only improve the efficiency of iron removal, but also save costs. The steps are as follows: ① Determine the total working flow and analyze the physical properties of the slurry. ② Select practical iron removal equipment according to the ratio of strong and weak ferromagnetic impurities in the slurry and the iron removal effect to be achieved. ③Determine the quantity of this equipment according to the production capacity of the model, and optimize the layout and use to maximize the production capacity of all models.
3. Improve the environment of iron removal work, reduce labor costs, and increase the degree of automation.
The magnetic rod iron removal environment is harsh, and cleaning workers generally work in an environment with high temperature and heavy odor. The heavy and repetitive physical labor can easily affect the work mood of the workers, resulting in illegal operations, and more manpower is used, which increases the cost of use. very big. Only by using a fully automatic iron remover can the magnetic rods be cleaned in a cycle. Moreover, due to the special technology of ceramic products, the production environment of the factory is very poor, and at the same time, higher requirements are put forward for the use and maintenance of the automatic iron remover.
The iron removal effect of slurry is a comprehensive problem. With the iron removal equipment as the core, it is impossible for any iron removal method and iron removal equipment to remove 100% at one time. According to the process requirements of the product, the removal of a certain magnetic impurity The iron rate should reach more than 70%. According to the country's requirements for energy-saving and environmentally friendly production, it is urgent to improve the iron removal effect.