INVESTIGATION OF THE POSSIBILITY OF USING A LAMELLA THICKENER IN THE INITIAL PUMPING SYSTEM OF MINE WATERS IN UNDERGROUND MINES

ABSTRACT

This study presents a detailed design and operational analysis of a lamella thickener as an effective solution for preliminary mine water treatment. The working principle of the device is based on gravity settling enhanced by inclined plates, which significantly increase the effective settling area without requiring large installation volumes. Key parameters influencing the performance of the lamella thickener are analyzed, including particle settling velocity, hydraulic loading rate, flow velocity between plates, and residence time. The relationship between these parameters is established using classical fluid mechanics equations. The proposed system integrates the lamella thickener into the mine water collection process prior to entry into the main sump. Implementation of this technology enables substantial reduction of suspended solids concentration, stabilization of sump operation, and decreased operational costs. As a result, the efficiency of the entire mine water drainage system is improved, while extending the service life of pumping equipment and reducing environmental impact.

АННОТАЦИЯ

В данной работе представлена конструкция пластинчатого сгустителя и проведен анализ его работы как эффективного средства предварительной очистки шахтных вод. Принцип действия устройства основан на гравитационном осаждении частиц, усиленном за счет использования наклонных пластин, которые значительно увеличивают эффективную площадь осаждения при компактных габаритах установки. Рассмотрены основные параметры, определяющие эффективность работы сгустителя, включая скорость осаждения частиц, гидравлическую нагрузку, скорость потока между пластинами и время пребывания жидкости. Установлены зависимости между этими параметрами на основе законов гидродинамики. Предлагаемая схема предусматривает внедрение пластинчатого сгустителя на этапе предварительной очистки перед поступлением воды в основной отстойник. Применение данной технологии позволяет существенно снизить содержание твердых частиц, повысить устойчивость работы водосборных систем, сократить эксплуатационные затраты и увеличить срок службы насосного оборудования.

Keywords: Mine water, lamella thickener, sump, solid particles, settling velocity, hydraulic load.

Ключевые слова: Шахтная вода, пластинчатый сгуститель, отстойник, твердые частицы, скорость осаждения, гидравлическая нагрузка.

1. INTRODUCTION

At present, efficient management and safe discharge of underground mine water is considered one of the key technological processes in the mining industry. As a result of mining operations in underground sections, the generated water becomes highly contaminated with solid particles. These solid particles negatively affect not only the stable operation of the water pumping system but also the service life of pumping equipment. The application of a lamella thickener provides a justified approach to improving the overall efficiency of the water pumping system and extending the operational life of pumps [1, 2].

2. METHODS (MATERIALS AND METHODS)

In underground mines, groundwater continuously flows into excavated workings and production areas. To ensure safe and controlled removal of this water, a drainage channel system is established [3; 18 p.]. However, due to the high level of contamination of water flowing from mine sections into the pump station sump, the main sump tends to fill rapidly. This leads to frequent clogging of the sump, increases the number of cleaning operations, and results in additional consumption of time, energy, and operational resources.

A schematic representation of the transfer of water accumulated in mine sections to the sump of the main pumping station is shown in Fig. 1 below:

Figure 1. Water collection system of mine section workings

1 – mine water; 2 – pump; 3 – pipeline; 4 and 5 – water transfer channels;  6 – primary settling tank; 7 – sump; 8 – gate valve; 9 – pit (sump pit); 10 – pump chamber; 11 – pump; 12 – discharge pipeline

Water accumulated in mine sections (1) is pumped by a pump (2) and conveyed through pipelines (3) and water transfer channels (4, 5) to the primary settling tank (6). After preliminary settling, the water is directed to the sump of the main pumping station (7). From the sump, the water flows into the pump chamber sump (zumpf) (9) and is then pumped to the surface by the main pump (11) through the discharge pipeline (12).

In this scheme, slurry containing abrasive particles should be settled in the primary settling tank (6) and the sump (7). However, due to the high level of contamination of mine water at present, solid particles are not completely removed during settling and are carried upward through the main pump. This leads to hydro-abrasive wear of the pump flow surfaces.

Preliminary clarification of water delivered from mine sections to the sump of the main pumping station-by removing sludge mixtures-significantly improves the efficiency of the water pumping system. The use of lamella thickeners has a positive effect on pump performance. Lamella thickeners are high-efficiency units designed for suspension separation, sludge thickening, and water clarification. They are widely applied in the mining, metallurgical, and chemical industries.

Therefore, separating sludge from mine water in a lamella thickener before it enters the main sump, and subsequently supplying clarified water to the sump, enhances the overall efficiency of the water pumping system. This approach enables effective clarification of mine water, prevents rapid filling of the sump, and reduces the frequency of sludge removal operations.

The design of the lamella thickener used for the preliminary clarification of mine water is shown in Fig. 2 below.

Figure 2. Lamella thickener

1 – shell; 2 – cover; 3 – inlet for suspension; 4 – plates; 5 – clarified liquid outlet; 6 – sludge discharge outlet

In a lamella thickener, the separation process depends on the settling velocity of particles in the liquid. This velocity is determined according to Stokes’ law [4]:

                                                     (1)

where  - the settling velocity (m/s);  - the particle density (kg/m³);  - the fluid density (kg/m³); d - the particle diameter (m); g - the gravitational acceleration (m/s²); and  - the dynamic viscosity (Pa·s).

This expression is valid for particle motion in the laminar flow regime. In a lamella thickener, due to the inclined arrangement of plates, the effective settling area increases significantly. The settling area is determined as follows:

                                            (2)

where  - the effective settling area (m²);  - the geometric base area of the device (m²);  - the plate length (m);  - the distance between the plates (m); and  - the inclination angle of the plates (degrees).

The main parameter determining the operational efficiency of the device is the hydraulic loading rate, which is defined as follows:

                                                           (3)

where  - the surface loading rate (m³);  - the volumetric flow rate of the liquid entering the device (m³/s).

The flow velocity along the channel between the plates is determined by the following expression:

                                                         (4)

where  - the flow velocity (m/s);  - the plate width (m);  - the distance between the plates (m); and  - the number of plates.

The residence time of the liquid in the device affects the separation efficiency and is determined as follows:

                                                          (5)

where  - the residence time (s);  - the volume of the device (m³).

The amount of solid matter entering the device is estimated as follows:

                                                     (6)

where  the mass flow rate of solids (kg/s);  - the initial concentration (kg/m³).

The separation process in a lamella thickener is governed by the relationship between the particle settling velocity and the effective settling area of the device. Inclined plates, which allow multiple increases in the effective settling area, are employed. As a result, high operational efficiency of the device can be achieved.

A high degree of clarification efficiency is attained by selecting the hydraulic loading rate to be lower than the particle settling velocity. Additionally, choosing optimal values for the flow velocity between the plates and the residence time ensures stable operation of the device.

The application of a lamella thickener for settling water coming from mine sections reduces the amount of sludge entering the main sump. A schematic of the preliminary clarification system for water collected in mine sections is shown in Fig. 3 below.

Figure 3. Method of clarification of mine section water

1 – filter valve; 2 – suction pipe; 3 – pump; 4 – high-pressure water supply pipe to the ejector; 5 – ejector; 6 – slurry discharge pipe to the lamella thickener; 7 – lamella thickener; 8 – mine cart (wagon); 9 – clarified water pipeline; 10 – sump of the main pump chamber.

The clarification system of mine section water operates as follows: a filter valve (1) is installed at the upper level of the section sump and connected to the pump (3) through a suction pipe (2). The discharge pipe (4) of the pump (3) is connected to an ejector (5) located at the bottom of the section sump. The discharge side of the ejector is connected via a slurry transport pipe (6) to the lamella thickener (7). The sludge discharge outlet of the lamella thickener (7) is directed into a mine cart (8). The clarified water pipeline (9) is connected to the sump (10) of the main pump chamber.

3. CONCLUSION

The application of this method reduces the frequency of sump cleaning operations, decreases the time and resources required for maintenance, and increases the service life of pumping equipment [5].

The high contamination of mine water with solid particles reduces the efficiency of existing sumps and settling facilities and leads to hydro-abrasive wear of pumping equipment. It has been established that the application of a lamella thickener at the preliminary treatment stage significantly reduces the sludge content in water. The use of inclined plates increases the effective settling area, ensuring rapid and efficient particle separation. As a result, by selecting optimal values of hydraulic loading and flow velocity, a high level of clarification efficiency can be achieved.

References:

1. Александров В.И. Ерофеев H.H. Сгуститель A.С. № 1690811. М.: Б.И. № 16, 1994.
2. Александров В.И., Ерофеев H.H. Пластинчатый сгуститель. A.C. № 1632459. М.: Б.И. № 9, 1991.
3. Кравченко В.П. Очистка шахтных вод. – М.: Недра, 1983.
4. Александров В.И. Расчет камерных и пластинчатых сгустителей противоточного типа. В кн.: Транспорт в горной промышленности. М.: "Недра", 1985, С.36-43.
5. Xatamova D.N., Yuldasheva M.A. “Academic research in modern science” // International conference “Analysis of the effect of a lamella thickener on improving the operational efficiency of centrifugal pumps”. Vol.5. 152-154 pp.