Ore washability

When choosing a washing facility and developing a washing process, it is first necessary to understand the washability of the mud-containing material (ore). The washability of the mud-containing material (ore) can be divided by the physical and mechanical properties of the mud-containing material itself, the parameters of the washing process and the washability factor.
(1) Plasticity, expansion and looseness of mud-containing materials
1. Plastic clay materials have different humidity (or moisture content) due to different water absorption. The plastic limit and the yield point are the characteristic constants of the humidity of the clay material. The plastic limit refers to the humidity when the clay material changes from the solid state to the plastic state. The yield point refers to the humidity when the plastic state changes to the fluid state, and the plasticity index and plasticity can be used. Strength to characterize the plasticity of clay materials. The plasticity index can be calculated according to the following formula:
K _S =B _S -B _H (1-1)
Where K _S - plasticity index, %;
B _S - the moisture content of the clay when it begins to flow, %;
B _H - the moisture content of the clay when it is crushed (solid), %.
The greater the plasticity index, the harder it is to wash the material. vice versa.
Plastic Strength The clay material in the plastic state can be measured by a specific cone measuring instrument. Expressed in Pascal (or kilopascals). Calculated according to the following formula:

Where Ï„ - plastic strength, Pa (kPa);
G — cone weight, N;
h — the depth of the cone trapped in the clay, cm
a — cone angle of the cone, (°).

Easy to wash, moderately washable, difficult to wash plasticity index, % <5 5~15 >15
Plastic strength, kilopascal <15 5~35 35~80

2. Swelling From the viewpoint of washing, the process in which the water-absorbing material of the clay-based material and the bond between the binding substances are broken and broken, is a process in which the clay-based material expands. The washability should be classified by the expansion rate of the clay material.
There are two methods for determining the swelling property of clay:
The first method is called soaking. It was measured by the instrument shown in Fig. 1.

Figure 1. Apparatus for determining clay swelling 1. Glass cylinder; 2. Sheet; 3. Pointer; 4. Vertical rod;
5. Roller; 6. Clockwork; 7. Rotating sprocket [next]

A small cubic clay sample with a length of 5 cm on each side was placed on a sieve having a mesh size of 1*1 cm and placed in a container filled with water to soak. The sample was swollen by water and shattered and passed through the screen until the sample completely disappeared. This period of time is used to determine the rate of expansion of the clay material. Divide the washability of the material according to the expansion time of the clay material:

Washability degree expansion time (hours)
Easy to wash 5
Medium washable 5~8
Hard to wash >8

The second method is called the indentation method. It was measured by the balance cone shown in Fig. 2.

Figure 2 Balance cone meter for determining clay swelling
1. a cone; 2. a handle;
3. clay-like; 4. balance ball

The balance cone weighs 76 grams and the cone angle is 30°. The indentation depth is calculated using the following formula:

Where h is the indentation depth, mm;
d — indentation width, mm.

Washability degree Cone indentation depth, mm Easy to wash 8~10
Medium washable 6~8
Difficult to wash 3~6

3. Looseness factor For some sand deposits, the degree of looseness of the gravel layer can be used to assess the washability of the material. The loose coefficient can be calculated as follows:

Where V ₁ - the sampling volume of the pit, the geometric volume of the sample obtained by taking the pit section and taking the thickness, m ³ ;
V ₂ — the loose volume measured with the container after the sample is taken, m ³ .[next]
This value is recorded in the usual geological report. In diamond sand ore, the looseness coefficient is less than 1.2, which is easy to wash. The looseness coefficient is between 1.2 and 1.3, which is moderately washable. If the looseness coefficient is greater than 1.3, it is difficult to wash.
(2) Parameters of the washing process - washing time and unit power consumption
The washing time required to completely remove mud impurities and the electricity consumption during washing are the main parameters of the washing process. They can only be obtained by washing. In the laboratory, the relative washability factor (K ₁ ) can be determined by the like grinding test:

Where t _E - the required washing time for the standard material, min;
t — the time required for the analyte to be measured in the same equipment, min.
According to the relative washability coefficient K1, the unit power consumption (q) required for the material to be measured can be calculated:

Where q _E — the unit power consumption of known standard materials during washing, kW•h/t.
The relative washability factor, washing time and unit power consumption of the material to be measured or the known standard material can be measured in a standard washing drum to which a fixed amount of water is fed. Only the effective power and washing time of the washing cylinder operation are recorded during the measurement. At the same time, the washing efficiency can be calculated according to a certain particle size. The longer the washing time, the greater the unit power consumption of the washing, and the more difficult it is to wash the mud-containing materials.

Washability according to the parameters of the washing process

Easy to wash, medium washable, difficult to wash

Washing time, points <1 1~2 2~6

Unit power consumption, kilowatts per ton <0.25 0.25~0.75 0.75~2

(3) Washability coefficient

The washing kinetics study shows that the parameters of the washing process (washing time and unit power consumption) are consistent with the washing intensity. The maximum recovery rate ε ₀ in the overflow with mud impurities (which can be bounded by a certain particle size) indicates the washing intensity. The time t ₀ required at this time is called the representative washing time, and the washability coefficient K As a washable feature of mud-containing materials, their relationship is as follows:

K=0.5t ₀ ε ₀ +6(t ₀ ε ₀ ) ²

Where ε ₀ - the maximum recovery of a certain particle size in the washing overflow, decimal;

t ₀ - the maximum recovery charge wash time in the overflow, s.

Washability by washing dynamics

Easy to wash, medium washable, difficult to wash

Representative washing time boring t ₀ , seconds _   <50 50～150 150～300

Washability coefficient K, >1 1~0.5 <0.5

The determination of the washability of the mud-containing material by determining the physical and mechanical properties of the material is indirect and inaccurate, but can be used as a preliminary understanding of the washability of the material.
The washability of the mud-containing material can be objectively and accurately assessed using the parameters of the washing process and the washability coefficient characterized by the washing kinetics. However, a certain scale of washing test must be carried out.