RU2851560C1 - Ventilation system for long dead-end workings - Google Patents

Abstract

FIELD: mine ventilation.

SUBSTANCE: invention relates to a ventilation system for long dead-end workings. The system comprises a local ventilation fan, ventilation duct sections, and elements for attachment to the mine support. The local ventilation fans (LVFs) are connected to flexible ventilation duct sections with the possibility of removal. A technological gap is formed at the end of each section. Nozzles are attached to each local ventilation fan, except for the first section, with the possibility of removal. The nozzles are made in the form of a ring with a constant or variable cross-section - a confuser or diffuser, with a wall thickness designed to withstand the air pressure created by the local ventilation fan following the nozzle without deformation.

EFFECT: increased ventilation efficiency in long dead-end mine workings.

1 cl, 3 dwg

Description

The invention relates to the field of mining and construction, to devices for ventilation of mine workings and structures, including those of great length.

A known installation for forced ventilation of dead-end faces of mine workings (RU patent No. 2428568, published on 10.09.2011) includes a fan, a discharge pipeline, an ejector water spray device containing a discharge head with an annular discharge slit, a receiver and a nozzle for supplying compressed air, which is installed at the end of the discharge pipeline and serves to release a common stream into the atmosphere of the mine working towards the dead-end face, wherein the water spray device includes a profiled two-stage diffuser formed by a sequential connection of a receiving and main diffusers, wherein the receiving diffuser passes through a toroidal convex surface into the main diffuser, equipped at the outlet with a two-layer fine-mesh mesh, and the length of the receiving diffuser is such that the ejector jet in it has time to increase in transverse size by sucking in air from the discharge pipeline stream to the size of the radius of curvature of the convex surface, which ensures the separation of the ejecting stream from the convex surface, its throwing to the center of the flow and further mixing with the ejected stream in the internal space of the main diffuser.

The disadvantages of the installation include the use of a high-performance local ventilation fan operating at high speeds, which significantly worsens acoustic comfort in workplaces near this installation; the inability to ventilate long dead-end workings due to the limited range of the generated air stream; there is a need to periodically move this bulky structure with its shutdown, which does not ensure a continuous ventilation process of the working and reduces the overall level of safety in the dead-end working.

A device for ventilation of a dead-end mine working is known (USSR Author's Certificate No. 1620646, published 15.01.1991), including a pipeline, one end of which is connected to a blower, and the other is installed at the breast of the face, an air bleed pipe with an air-shutoff element connected to the pipeline, a discharge pipe, a valve made in the form of a lateral surface of a truncated cone, which can move inside the pipes along their axis.

The disadvantages of this device include the use of a pipeline with sections connected by fans containing the impeller and spinner, as well as rigid pipes located on the intake side of the fans. The proposed design completely precludes the ability to quickly reverse the ventilation flow in the event of a fire at the working face and ensure the evacuation of miners in a direction opposite to the fresh air supply. This device does not allow for the effective ventilation of long blind workings due to the limited length of the supply pipeline.

A device is known for supplying air (USSR Author's Certificate No. 188439, published 01.11.1966), having sections connected to rigid pipes that are connected to fans and communicated with free sections of a flexible pipeline, wherein the intermediate flexible pipes are provided with parallel guide rods placed inside the pipes in the plane of their cross-section and made with a diameter equal to the diameter of the flexible pipeline, and having sealing rims located at the free end of the pipes, the internal diameter of which is smaller than the diameter of the flexible pipeline, wherein the free end of each section of the flexible pipeline is provided with a flexible end ring, made with side openings and installed inside the rigid intermediate pipe on the guide rods using the side openings, attached to the walls of the rigid intermediate pipe at two points located diametrically opposite and in plane perpendicular to the guide rods.

The disadvantages of this device include the presence of a flexible end ring with side openings installed at the free end of each section of the flexible pipeline, the connection of the end of each section of the flexible pipeline to the walls of a rigid intermediate branch pipe at two points, and the placement of parallel guide rods within the branches in the plane of their cross-section. These design elements, which characterize this technical solution, do not allow for the rapid change of airflow direction in the through-ventilation section of a blind working when the position of its face relative to the mouth changes.

A device for ventilating long, dead-end workings is known (patent SU No. 1627721, A1, published February 15, 1991). It comprises a pipeline with sections connected to each other via fans. The fans have a housing housing the impeller and spinner, a rigid pipe located on the intake sides of the fans, windows, windows formed on the side surface of the rigid pipes, and elastic elements secured at one end to the inner surface of the rigid pipes and installed so as to be able to overlap the windows. This patent focuses on the fan design with the goal of reducing aerodynamic drag as air moves through the ventilation system and, consequently, increasing ventilation efficiency.

A disadvantage of this device is its limited use of flexible ventilation ducts. Due to the device's continuous design within the mine workings and the absence of breaks, as well as the cascaded arrangement of fans within the duct, vacuum pressure zones may develop, leading to inward deformation of the duct and, consequently, loss of ventilation.

A device for forced ventilation of workplaces (RU Patent No. 2816134, C1, published March 26, 2024) is known as a prototype. It comprises a main air duct, a fan, and a system of dispersed nozzles. The fan is installed in the mixing chamber opposite the junction of the borehole and the mixing chamber. The fan is connected to the main air duct. The device also contains a damper installed in the mixing chamber to ensure the flow of air from the working into the mixing chamber in the winter. In the summer, the damper is closed. The main air duct has openings into which one end of the nozzle is installed. The other end is installed in an opening made in the center of the U-shaped air duct. A damper is mounted on the nozzle and can be opened or closed. The U-shaped air duct is installed above the workplace and is shaped like a hollow cylinder. The ends of the cylinder are not connected to each other, forming a gap for air supply. In the main air duct, dampers are installed after each branch pipe with a U-shaped air duct, designed with the ability to open and close depending on the targeted air supply to the workplace.

The disadvantage of this device is its design features that do not allow for the effective ventilation of long workings due to significant losses due to aerodynamic resistance to the movement of air supplied to the dead-end working, namely the small cross-section of the pipeline, the forced-air supply system using a single fan, as well as insufficient capacity for the flow of air supplied to the end of the dead-end working.

The technical result is an increase in the efficiency of ventilation of long dead-end mine workings.

The technical result is achieved by the fact that local ventilation fans (LVF) are detachably connected to sections of a flexible ventilation duct, while at the end of each section a technological gap is formed, the parameters of which are determined by the formula:

- recirculating mass flow rate from the outgoing jet, kg/s;

- mass flow rate of fresh stream from the mouth of the working, kg/s;

- mass flow rate of fresh stream after pipe rupture taking into account recirculation, kg/s;

- kinematic viscosity of air, ^m2 /s;

- air density, kg/ ^m3 ;

- diameter of the pipeline from the mouth and after the rupture of the ventilation pipe, m;

L – distance between sections of the device, m;

- inlet diameter of the nozzle on the VMP, m,

In front of each VMP, with the exception of the VMP of the first section, nozzles are attached with the possibility of removal, made in the form of a ring of constant or variable cross-section - a confuser or diffuser, with a wall thickness made with the ability to withstand the vacuum of air created by the VMP following the nozzle, without deformation.

The system is illustrated by the following figures:

Fig. 1 - general view of the device;

Fig. 2 - connections of ventilation duct sections;

Fig. 3 - distribution of concentration fields of a harmful component in the area of junction of sections of a ventilation pipeline during established ventilation, where:

1 - local ventilation fan (LVF);

2 - section of flexible pipeline;

3 - technological gap between pipeline sections;

4 - nozzle;

5 - mouth of a dead-end working;

6 - dead-end part of the mine workings;

7 - fresh air stream;

8 - outgoing air stream;

9 - diameter of the ventilation duct;

10 – length of the technological gap between pipeline sections;

11 - input diameter of the nozzle.

The system consists of local ventilation fans (LVF) 1 (Fig. 1) connected by a detachable joint to sections of flexible ventilation duct 2. LVF 1 and sections of flexible duct 2 are secured under the roof of the working by connecting to the support of the mine working. LVF 1 of the first section is installed in front of the mouth of the dead-end working 5 on a fresh air stream 7. Each section of the device ends with a technological break of length 10 (Fig. 2). The parameters of the technological break of the ventilation duct section are determined by a formula based on the characteristics of the air ducts and the configurations of the connections.

- recirculating mass flow rate from the outgoing jet, kg/s;

- mass flow rate of fresh stream from the mouth of the working, kg/s;

- mass flow rate of fresh stream after pipe rupture taking into account recirculation, kg/s;

- kinematic viscosity of air, ^m2 /s;

- air density, kg/ ^m3 ;

- diameter of the pipeline from the mouth and after the rupture of the ventilation pipe, m;

L – distance between sections of the device, m;

- input diameter of the nozzle on the VMP, m.

Upstream of each VMP 1, with the exception of the VMP 1 of the first section, nozzles 4 are attached with removable mountings. These nozzles alter the size of the opening at the VMP 1 inlet. Nozzle 4 is molded in the shape of a ring of constant or variable cross-section—a confuser or diffuser. The nozzle is made of a material, such as metal, with a wall thickness capable of withstanding the vacuum created by the VMP 1 following nozzle 4 without deformation.

The system operates as follows. The first section of the VMP 1 extracts a portion of the fresh air supplied to the mine workings by the general mine ventilation system and delivers it to the mouth of the dead-end mine working 5 through a section of the flexible ventilation pipeline 2. As the length of the dead-end mine working increases, the length of the device increases by increasing the number of sections. The second and subsequent sections of the device deliver air with minimal recirculation rates, flowing from the face of contaminated air into the dead-end section of the mine working 6. Technological gaps 3 between the sections of the device help prevent the formation of zones of low pressure relative to the atmospheric air pressure in the mine working. These zones may arise in front of the VMP 1. The diameter of the inlet section of the nozzle 4 and the length of the technological gap 10 are selected taking into account the mass flow rate of air created by the VMP 1, in front of which the nozzle 4 is attached, in such a way as to minimize the admixture of contaminated air 8, which flows out of the face with its subsequent recirculation into the near-face space 6.

The efficiency of the system is confirmed by mathematical modeling of the ventilation process of an extended dead-end mine working. The modeling is carried out with various shapes and types of pipeline nozzles, as well as with variations in the lengths of the technological break. The modeling is based on a 3D model of the mine working. In all cases, a circular cross-section working with an area of 70 ^m2 is modeled. A ventilation stack with a cross-section of 2.5 ^m2 is placed in the working. The length of the technological break in the ventilation pipeline varies from 1.5 to 2.5 meters. The length of the model is 115 meters. The inlet diameter of nozzles 4 varies and is taken equal to: 1.5; 2.0; 2.5; 3.5 meters. The air temperature in the mined-out space is 24.85 °C. The mass flow rate of air in the pipe to the face varies from 37.675 to 53.75 kg/s. Based on the simulation results, it can be seen that the air flow maintains its speed and a stable process of fresh air movement is observed in the area where the pipeline sections meet without significant admixture of contaminated air. (Fig. 3).

The system is effective in ventilating long dead-end workings due to the cascaded, distributed arrangement of fans, and also makes it possible to prevent the formation of vacuum pressure zones inside the flexible ventilation pipeline, the presence of which leads to the destruction of the pipeline, which increases the safety of work by reducing the likelihood of an emergency situation due to the cessation of ventilation of the dead-end working.

Claims (11)

A ventilation system for long dead-end workings, comprising a local ventilation fan, sections of a ventilation pipeline, and elements for fastening to the support of a mine working, characterized in that the local ventilation fans (LVF) are detachably connected to sections of a flexible ventilation pipeline, and at the end of each section a technological gap is formed, the parameters of which are determined by the formula: - recirculating mass flow rate from the outgoing jet, kg/s; - mass flow rate of fresh stream from the mouth of the working, kg/s; - mass flow rate of fresh stream after pipe rupture taking into account recirculation, kg/s; - kinematic viscosity of air, ^m2 /s; - air density, kg/ ^m3 ; - pipeline diameter from the mouth and after the rupture of the ventilation pipe, m; L – distance between sections of the device, m; - inlet diameter of the nozzle on the VMP, m, In front of each VMP, with the exception of the VMP of the first section, nozzles are attached with the possibility of removal, made in the form of a ring of constant or variable cross-section - a confuser or diffuser, with a wall thickness made with the ability to withstand the vacuum of air created by the VMP following the nozzle, without deformation.