Four factors that affect the forming rate and strength of cold-pressed briquettes

Cold-pressed briquettes?are briquettes?made in the metallurgical industry by evenly mixing all the required materials with binders and for cold-pressing, followed by low-temperature drying. The commonly used equipment is a double-roller press machine, which has the characteristics of low engineering investment, simple process, and low pollution. The raw materials can be composed of dust, metallurgical sludge, powder ore, reducing agents, and have a wide range of applications.

The feeding methods of the roller press machine are gravity feeding and forced feeding (also called pre-pressing). Generally, the feeding method is determined according to the material density. Materials with high density (such as iron concentrate) can use gravity feeding, while materials with low density (such as coal powder) require forced feeding.

There are many factors that affect the briquetting process, mainly including material properties, pressing process conditions,binder properties and dosage.

Material particle size:

Materials with too fine particle size have a small bulk density, and the strength of briquettes?will decrease; materials with too large particle size have a large individual particle volume, and it is difficult to move and deform during pressing, making it difficult to press. Mixing mainly fine particles with a certain amount of coarse particles, where the coarse particles act as aggregates and the fine particles act as base materials, can achieve a compact arrangement, increasing the density and strength of the briquettes.

Process conditions:

1. Avoid large hard objects from entering the roller press machine, and set up screens or other iron removal and impurity removal facilities during the material conveying process to protect the roller press machine;

2. Extend the mixing time to 6-10 minutes, which is also a condition for improving the forming rate and strength.

Selection of Binders:

Add a certain amount of binder to the raw materials during mixing to increase the adhesion, adsorption, and dispersion between the materials.

Good-performing organic binders should have the following conditions:

1. The molecular structure has multiple polar groups;

2. Has hydrophilic genes that enhance the hydrophilicity of mineral surfaces;

3. Has sufficient relative molecular weight and viscosity, and the chain link is not easy to break;

4. The molecular chain is long, and there are many branches.

Jianjie binders have the above advantages, and the amount added is small, the forming rate is high, and the cold-pressed strength and drop strength are excellent.

Speed of the roller :

In order to improve the productivity of the briquetting, the faster the speed of the two rollers, the better. However, as the loose materials are squeezed between the pressing rollers, the internal air between the loose materials will gradually be expelled. When the roller speed is too fast, cracks will be left on the surface of the briquettes?due to the gas between the materials not being discharged in time, resulting in a decrease in the strength of the briquettes?or even the failure to form briquettes.

Due to the different internal air volumes of loose materials in various raw materials and different material characteristics, the speed of the roller on the roller press machine is also different.

Briquette?moisture content:

Most materials use wet pellet pressing, and changes in moisture content affect the particle size and quality of the briquettes. Generally, if the raw material moisture content is too high, the initial pellet forming rate is fast, but it is easy to cause the briquettes?to stick to each other and deform, making it difficult to demold, resulting in uneven particle size distribution and poor strength.

At the same time, it brings difficulties to drying; If the raw material moisture content is too low, the gap between the two halves of the briquettes will increase, resulting in poor binding strength, too many half briquettes, low forming rate, or even failure to form briquettes.

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