Main Technology of High-Pressure Briquette Machine
Source: internal company
Main Technology of High-Pressure Briquette Machine
In order to make the large and medium-sized ferroalloy reduction electric furnace run better, it is required that the burden should have proper fragmentation and ensure good air permeability. At present, the supply of high-quality lumpy burdens which can be directly used in the furnace is becoming increasingly tight. In order to adapt to this situation, some manufacturers adopt various lumping technologies and use fine ore and concentrate to obtain better smelting indexes. Among them, high-pressure briquette machine pelletizing technology has become a new development direction of ferroalloy pelletizing technology in recent years because of its simple process, fuel-saving, applicability to fine ore, and a wide variety.
1. Principle of the pelletizing method of high-pressure briquette machine
The main equipment of the high-pressure pelletizing method is the high-pressure ball press. Its working principle is that the powder raw materials are pressed into pellets of the corresponding size by using the forming roller of opposite rolls.
2. linear speed of press roller
In order to improve the productivity of the high-pressure ball press, the faster the rotating speed of the two rollers, the better. However, with the extrusion of raw materials between pressing rollers, the internal air between loose raw materials will be gradually discharged. When the rotating speed of pressing rollers is too fast, cracks will be left on the surface of pellets because the air between raw materials is too late to be discharged, which leads to the reduction of pellet strength and even the inability to form pellets.
Because of the different internal air volume and different properties of various raw materials in a loose state, the linear velocity on the surface of the pressing roller is different when pressing pellets. The ball pressing with different raw materials needs many tests to find the suitable linear velocity.
3. Linear pressure between pressing rollers
In order to improve the strength of pellets, there is a misunderstanding in production that the greater the pressure between the two rollers, the higher the strength of pellets. But in fact, the pressure between molecules of materials is limited. When the pressure exceeds this limit, the materials will slip between molecules, which will lead to the crushing of materials. At this time, a large number of hemispheres will appear, which will greatly reduce the pelletizing rate and the strength of pellets.
At present, high-pressure ball presses generally use hydraulic devices to provide back pressure between two rollers, and the pressure is required to be adjustable.
4. Water content of briquette
Except for a few raw materials such as limestone and dolomite, which are pressed with dry powder, most materials are pressed with wet materials. The change of moisture affects the particle size and quality of green pellets. Usually, if the moisture of raw materials is too high, the initial pellet will be formed quickly, but it is easy to cause the green pellets to bond and deform each other and not easy to demould, which leads to uneven particle size distribution and poor strength of green pellets, and at the same time brings difficulties to drying. However, if the moisture content of raw materials is too low, the gap between two hemispheres will easily increase, which will lead to poor bonding strength of powder, too many hemispheres, low pelletizing rate, and even unable to pelletizing.
The proper moisture content of raw materials is the key to pelletizing. It is found in many experiments that different materials have a different water content of ball pressing, so the water content of ball pressing is related to the physical properties of materials (particle size, hydrophilicity, density, particle porosity), mixture composition, the productivity of high-pressure ball pressing machine and pelletizing conditions.
5. Selection of binder
In the process of mixing and milling, a certain amount of binder should be added to the raw materials, which mainly increases the adhesion, adsorption, and dispersion between the raw materials. Adhesives are mainly divided into inorganic adhesives and organic adhesives. Organic adhesives with good performance should have the following characteristics:
(1) The molecular structure has multiple groups and can have strong chemisorption with the concentrated surface.
(2) It has hydrophilic genes that enhance the hydrophilicity of the mineral surface.
(3) It has enough relative molecular mass and viscosity, and its chain frame is not easy to break.
(4) The molecular chain is longer and there are more branched chains.
(5) The aromatic structure is superior to the fatty structure. At the same time, the adhesive should be selected according to the requirements of electric furnaces and products of each company and the local actual situation.
Pelletizing is the key process in the pelletizing process of high pressure briquette machine. In order to exert the production capacity of pelletizing and save resources, it is necessary to grasp the key links in the design and production of pelletizing, so as to produce pelletizing conforming to the smelting index of ferroalloy electric furnace with high energy saving and improve economic benefits.