In this guide, we’ll take a look at:
- Introduction of cold ramming paste
- The raw materials of cold ramming paste
- Applications of cold ramming paste
Introduction of cold ramming paste
What is cold ramming paste?
Cold ramming paste refers to a cathode paste that can be laid at room temperature. It is a carbon-filled raw material for masonry. It is widely used in industrial furnaces such as aluminum reduction cells, iron-making blast furnaces, smelting furnaces, and calcium carbide furnaces. The aggregate of this cathode paste is the same as that of ordinary cathode paste (also called hot stamping paste), such as ordinary calcined anthracite or electrically calcined anthracite, metallurgical coke, graphite scrap, etc. The low softening point of the adhesive is 20℃±5℃.
Cathode cold ramming for aluminum is a cathode carbon block ramming material with a construction temperature of 8℃～25℃. Due to the low construction temperature of cold mashing, it can be used directly without heating at room temperature. Therefore, it significantly improves the damage to the body of workers and the pollution to the environment during construction.
The raw materials of cold ramming paste
Cold ramming paste is a material that fills the gaps between the carbon blocks in the electrolytic cell, so its properties should be the same or similar to those of the carbon blocks. The raw material composition of cold ramming paste is mainly: aggregate, binder, and additives.
Raw materials of cold ramming paste aggregate
- Calcined anthracite, the anthracite used for cathode paste, should be low-ash high-quality anthracite, and the ash content of the anthracite before calcination should be less than 10%. Calcined anthracite coal is divided into ordinary calcined anthracite (calcination temperature is 1200℃～1350℃) and high temperature electric calcined anthracite (calcination temperature is 1500℃-2000℃);
- Metallurgical coke is generally ground into fine powder less than 0.5mm for use. Metallurgical coke has poor resistance to erosion by molten aluminum and electrolyte;
- Graphite block can improve the thermal and electrical conductivity of the cathode paste and improve the corrosion resistance of the electrolyte. The carbon materials with strong to weak sodium corrosion resistance at 960°C are graphite, electric calcined coal, gas calcined coal, metallurgical coke, and petroleum coke. Therefore, domestic cold ramming production plants use calcined anthracite, metallurgical coke, pre-baked anode blocks, raw graphitized electrodes, natural graphite, and some petroleum coke as aggregates.
Raw materials of cold ramming paste binder
- The softening point of high-temperature asphalt is 100℃～110℃. Although high-temperature asphalt has a high softening point, its various indicators are significantly better than medium-temperature asphalt. The use of high-temperature asphalt can not only improve the quality of carbon products, but also facilitate transportation and storage, and improve the working environment and working conditions;
- Medium temperature coal tar pitch, with a softening point of 75℃～95℃. The softening point temperature of medium-temperature asphalt is low, and the quality of the carbon products made is not as good as that of high-temperature asphalt;
- Coal tar or anthracene oil can be used to adjust the softening point of the binder, but they reduce the softening point and at the same time reduce the amount of coking of the binder, thereby reducing the physical and chemical indexes of cold mashing. The binder used for cold ramming is required to have a lower softening point, so coal tar pitch and coal tar or anthracene oil are used as the binder. Commonly used mixed binders have a softening point of 15°C to 46°C.
Types of cold ramming paste additives
There are many types of additives, all of which are used to increase the amount of coking of the ramming paste. The mechanism of action:
- Oxidize coal pitch;
- Associate pitch molecules into larger molecules.
The additives of any of the above action mechanisms can increase the coking capacity of asphalt, and increase the bulk density and compressive strength of cold rammed paste.
Commonly used additives are: styrene and m-dinitrobenzene.
Applications of cold ramming paste
Cold ramming paste is a carbon material used for masonry, widely used in aluminum electrolysis cells, blast furnaces, smelting furnaces, calcium carbide furnaces, and other industrial furnaces. Filling the gap between charcoal and cooling equipment, charcoal and charcoal, charcoal, and firebrick.