Desulfurization gypsum is an industrial by-product produced by the reaction between limestone powder and sulfur dioxide in flue gas desulfurization. The main component is calcium sulfate dihydrate, which is characterized by high purity, stable composition, small particle size, powdery shape, and free water of about 12-17, particle size distribution is uniform, gradation is poor, thick water consumption is large, contains a certain amount of calcium carbonate and more water-soluble salts, depending on the type of coal burned and the dust removal effect of the flue gas. , Desulfurization gypsum shows different colors in appearance. Generally, the most common ones we see are grayish yellow or off-white. High-quality desulfurization gypsum is pure white.
The technical requirements for desulfurization gypsum used as cement retarder are: So3 (sulfur trioxide) content is greater than 40, the content is less than 7.4mg/kg, the attached water content is less than 5, and the loss on ignition is less than 2. Desulfurization gypsum that meets the above requirements can be used as cement retarder. The setting time of cement can meet the standard requirements. Desulfurization gypsum is used in the cement industry. First: high purity, adjustable calcium sulfate dihydrate content, and similar to natural gypsum. It has fewer impurities and is of high quality; secondly: the microstructure of desulfurized gypsum requires less water and has smaller pores after water evaporates, which has mechanical advantages and contains less corrosive impurities such as chlorine ions, thereby improving strength and durability. sex.
Research shows that desulfurized gypsum contains a certain amount of calcium carbonate and a large amount of water-soluble salts. The setting time of cement mixed with desulfurized gypsum is normal and has a positive effect on the mechanical properties and stability of cement. However, the moisture content of desulfurization gypsum is generally 10-17, and it has strong viscosity. Therefore, it is easy to adhere to the equipment during the process of loading, unloading, lifting, and transportation, causing material accumulation and blockage. If it is directly used in cement production, it will cause difficulty in conveying the material. Problems such as smoothness, uneven mixing, and normal production may occur. The wet desulfurization gypsum is first processed into balls to change its physical properties, reduce the adhesion between materials, and increase fluidity, which can completely change the problems of desulfurization gypsum in the cement production process.
The extrusion of desulfurized gypsum is the process of increasing the particle size of the powder. During this process, the powder particles pressurize the powder through mechanical bite to form a spherical shape. After repeated testing, four rolls were used twice. Pressurized, hydraulic, constant pressure double-action (patented) briquetting machine,
can press desulfurized gypsum with high moisture content into balls at one time without adding any adhesive, ensuring purity and directly forming. No subsequent drying process is required, and it is more conducive to the connection and transformation of existing processes. The balling strength is high and suitable for all kinds of transportation, reducing packaging costs and improving product transportation capacity; after the formed desulfurization gypsum is put into the mill, there will be no problems such as sticking and grinding, affecting the output of the mill; the special briquetting machine for desulfurization gypsum has a compact structure , easy maintenance, simple operation, short process flow, low energy consumption, low failure rate, the main roller part is made of high-quality alloy steel material (patented), which greatly improves the wear resistance and pressure resistance, giving the machine a long service life .
The diameter of the pressed pellets is generally between 20-80mm, the pass rate is 85, and the compressive strength is 30N. The pelletized desulfurization gypsum is a product formed by the material process. Its chemical composition is similar to that of wet powder. Desulfurization gypsum is exactly the same. What changes is not just some of its physical properties. For example, pellets of desulfurization gypsum have very good fluidity and will no longer cause adhesion and blockage, making it easy to transport and apply in the cement production process. Therefore, the successful development of this spherical desulfurization gypsum has opened up a new way for the application of desulfurization gypsum in cement production.