How is the ore sampling process carried out?

In order to analyze the pulp (for density and degree of viscosity), ore and concentration, a method such as sampling is used. With its help, you can find out what the composition of the product is (mineralogical, chemical, etc.), its condition and characteristics.

The process consists of the following stages: first, samples are taken, then they are processed, and then they are prepared for a detailed analysis of their composition.

In order to perform the procedure correctly, it is important that the sample is representative. This means that the part of the material that has been selected for analysis must accurately express the composition of the whole mass.

The enrichment process depends on the sampling process. If you correctly perform all the calculations, you can determine the quality of the tested and final materials, as well as correctly calculate all technological indicators.

Testing is necessary to find out everything possible about the source material. There are two ways to obtain valuable information. The first is to define the properties of the original array. The second method is to determine a small part of the mass in order to distribute the resulting properties to the entire mass.

There are several types of testing. The classification depends on the purpose of the procedure, i.e. how the results obtained from the analysis will be used.

The following types are distinguished:

• It is carried out to check the ore stored or arriving at the enterprise. When developing a commodity balance, this procedure plays a key role.
• There are balance and operational. The latter facilitates the enrichment process.

Commodity allows you to analyze the initial and final products for the purpose of accounting for the period of time that was established for control (for example, one month). In the case of balance testing, a shorter interval is taken. Usually it is equal to the duration of one shift. As for the operational type of the procedure, the process involves samples from concentrates over a period of time depending on the duration of their preparation and analysis. The time can range from a quarter of an hour to 2 hours.

Sampling allows you to obtain information about the composition of the product and the state of the process directly at the time of sampling. The procedure itself is carried out strictly in accordance with the established scheme.

Sampling is classified according to one more characteristic – sampling frequency. The procedure is performed systematically or periodically.

Periodic testing allows you to control the granulometric composition of materials: sand, discharge from hydrocyclones and mills, ore. The procedure allows you to determine the circulation load.

Systematic testing allows you to become familiar with the following indicators:

• The degree of ore density;
• Pulp alkali concentration;
• The moisture content of the ore used in the production process;
• The degree of dehydration of enrichment products;
• The presence of metals in ore in waste and enrichment products;
• Concentration and consumption of reagents;
• Density of concentration of the enrichment product;
• Thickener drain composition.

If you need to test the TP in order to calculate the water-sludge and qualitative-quantitative schemes, the procedure must be performed periodically. Most often , according to a predetermined schedule. The procedure can also be performed if the technological scheme or reagent regime changes.

Conventionally, the testing process is divided into two stages:

• Point samples are selected;
• A combined sample is compiled from them;
• A laboratory sample is compiled.

In order to understand the testing process, it is important to understand the terminology. A point sample is understood as a part of the source body, which is sampled during one cutoff of the sampler. Point samples are components of a combined sample, which is formed over a certain time, and a combined sample is a laboratory sample, which is used directly during analysis. A test of this type can be monthly, shift, or hourly.

The sample must be collected correctly. The main thing is that it well reflects the properties and composition of the source material. This quality of the sample is called representativeness. That is why it is so important to correctly determine the mass of the sample and decide what method of processing it will be.

The following factors influence weight:

• Physical and chemical properties of the product;
• Dimensions of a piece of material;
• The need for accuracy in the research conducted.

The effect of size on the mass of the material can be expressed using the Chechotte formula:

Q = kd 2 , kg,

where k is a coefficient depending on the metal content in the source material, its homogeneity and value, and d is the size of the maximum piece of material selected for testing.

Table 1 shows how homogeneity affects the coefficient k :

Table 1. Values of coefficient k.

To determine the methods and means of conducting research, you need to pay attention to such indicators as the purpose of testing, the conditions for its conduct, and the properties of the material. If the product being tested is moving, then mechanical samplers are most often used for testing. The precision samples collected in the receiver of the device, produced by cutting off the product by crossing the entire jet at a set time interval, form a combined sample. In order to test the pulp stream, samplers should be used that are characterized by transverse or longitudinal flow crossing methods. Such devices guarantee uniform cutting of material from the entire flow, i.e., at equal time intervals.

The mass of the combined sample relative to the mass of the starting material is equal to:

• For enrichment waste – from 0.0004 to 0.006%;
• For ore — from 0.001 to 0.025%;
• For enrichment products – from 0.002 to 0.2%.

The sample weight from a commercial product is in the range of 0.001-0.00001%.

Processing of combined samples is carried out according to the following schemes:

Processing is a multi-stage procedure. First you need to crush and grind the ore material. For this purpose, a mill and a crusher are used. An important condition: cutting and mixing must be carried out simultaneously and in accordance with the dimensions of the material. In other words, the primary sample is transformed into the final one, but at the same time, its representativeness is preserved. The point of the procedure is to mix the sample before reduction. This allows the material to be averaged in size and composition.

There are several ways to mix samples. If ore materials are larger than 100 mm and their weight exceeds 100 kg, then the cone and ring method is used. If the mass exceeds 25 kg, and there are no large bodies, then rolling will do. In the case of finely crushed samples, the procedure is carried out using a sieve with holes of a certain size. They should be 3 times larger than the largest pieces. Mechanical mixing involves the use of mills and mixers.

The mixing process is followed by reduction. The execution procedure depends on the dimensions and amount of material. The reduction is done manually. This is done in two ways. The first is the cone method followed by quartering. The second is quartering and scooping. If it is necessary to reduce crushed material or a body less than 25 mm, either mechanical reducers or grooved devices are used.

In order to take samples of finely ground materials, you need to turn to squaring. A method is used to determine the chemical composition of the ore. Crushed bodies are tested using sampling and reduction units equipped with reducers, mills and crushers. Pulp samples are processed in several stages. Before this, they need to be dehydrated and dried. The temperature should be between 105 and 100 ℃.

To control the production process at an enterprise as quickly as possible, it is necessary to automate all stages of the procedure. Using special devices, you can quickly select, deliver and prepare samples for research, as well as perform their detailed analysis. You can obtain valuable process information using automatic analyzers. They have significantly expanded the capabilities of the process. However, their implementation is sometimes problematic due to some difficulties of a methodological nature. This may be a lack of funds to purchase modern control systems, a wide variety of properties of the media selected for control, etc.

The emergence of theoretical problems is associated with the characteristics of the most complex type of control — analytical. Its complexity also determines the difficulties associated with developing its main aspects at all stages of the research process. As for technical difficulties, the main problem here is that there are no technical means. This is especially common in the early stages of the process when samples need to be collected, transported and prepared. It also plays a role that not all computing and analytical technology is reliable, which is necessary for the successful completion of the task.