Sensors Used in Coal Mining
With the development of China’s social economy, the demand for coal is increasing day by day, and accordingly, coal storage has begun to attract extensive attention. Based on the analysis of fire hazards under various coal storage modes, this paper puts forward targeted prevention and control measures.
Open coal yards in thermal power plants, ports, coal mines, coking plants, coal preparation plants, cement plants, iron and steel plants, etc., as unorganized atmospheric pollution sources, have been listed as key or deadline-bound treatment projects by environmental protection bureaus of various provinces and cities in China due to serious air pollution to the surrounding environment. Full enclosure of coal yards is required. If enterprises fail to effectively control dust from coal yards, they will face huge fines, deadline rectification, relocation, or even shutdown and other environmental legal risks.
However, after full enclosure, the coal yard becomes a closed space with poor ventilation. A large amount of coal dust is generated during coal reclaiming and stacking by stacker-reclaimers. During storage, raw coal volatilizes harmful or flammable gases such as CH₄ and H₂S. Meanwhile, coal cannot be truly stored on a first-in-first-out basis, but on a last-in-first-out basis, which easily forms bottom coal. In summer, when the temperature is high, spontaneous combustion is likely to occur. There are many problems such as dust explosion inside the warehouse, spontaneous combustion of coal, and occupational health risks for operators. Problems such as dust explosion, accumulation of toxic and harmful gases, occupational health of operators, and increased risk of coal spontaneous combustion caused by high temperature inside the warehouse due to poor ventilation still cannot be effectively solved. In summary, the hidden dangers of fully enclosed coal silos should attract sufficient attention from design units and owners.
In places where coal needs to be stored and circulated, such as coal mines, thermal power plants, and cogeneration plants, long-term contact between coal and air will cause oxidation reactions and release heat. Although the heat on the outer layer of the coal pile can be dissipated, the slow air flow and poor ventilation inside the coal pile lead to the accumulation of internal heat. The temperature inside the coal pile keeps rising, and when it exceeds the spontaneous ignition point of coal, spontaneous combustion will occur, causing great damage to personnel and equipment. At the same time, toxic and harmful gases such as carbon monoxide and methane are also produced along with the spontaneous combustion of coal. Under the current national environment governance policy, real-time and effective monitoring of coal pile temperature has huge social and economic benefits. It is an important part of the implementation of the "electronic coal yard" and is highly necessary.
Existing monitoring methods for coal pile temperature
Manual inspection: Manual patrol with hand-held thermometers cannot realize 24-hour real-time monitoring and cannot achieve effective measurement density. Due to the harsh on-site environment and numerous large-scale equipment, it also affects the safety of inspection personnel.
Infrared thermal imager with pan-tilt: Collects surface temperature changes of coal piles with a wide monitoring range.
Plug-in temperature measuring instrument: The probe rod is 2 meters long with 3 built-in temperature measuring points. The monitored temperature data is transmitted to the monitoring host and remote monitoring center wirelessly to realize 24-hour real-time monitoring. If there are many on-site operating equipment or harsh environment, 485 wired transmission can be selected to detect the temperature between coal and the wall. The equipment can be installed on the coal retaining wall.
Embedded temperature measuring cable: Realizes star-point temperature measurement at the bottom of coal in the coal yard. The temperature measuring cable is embedded on the ground according to the actual stacking situation of coal piles to detect the temperature change at the bottom of coal piles. The collector can be fixed on the wall or other convenient wiring positions. All temperature data of collection points are uploaded to the monitoring host via 485 transmission to realize 24-hour uninterrupted monitoring.
Monitoring methods of flammable gases in fully enclosed coal yards
Substances that cause coal dust and gas explosions are often suspended in the air, and explosions occur instantaneously. Therefore, it is very important to take precautions in advance against such disasters.In addition, for operating coal yards, water dust removal devices should be used to reduce dust concentration at the feeding points, and dust concentration detectors should be installed to monitor the dust concentration in the coal yard.In the early stage of spontaneous combustion, low-temperature oxidation produces carbon monoxide and changes oxygen concentration. Therefore, carbon monoxide and oxygen detection devices should be installed for real-time monitoring to detect hazards early and take timely measures.Oxidation of coal or failure of the ventilation system will reduce oxygen concentration. The oxygen concentration should be kept above 18% VOL, and the content of methane (CH₄) in the air should be below 1.5%. Taking advantage of the fact that methane diffuses more easily than air, methane concentration detectors are installed at the upper part of the coal yard where exhaust gas is concentrated for real-time monitoring.
Fully enclosed and semi-enclosed coal yards have become the current development trend. Compared with traditional coal yards, they are more environmentally friendly and can reduce coal loss during storage, achieving two benefits at once.However, during coal storage in enclosed coal yards, various reactions easily occur, producing many harmful gases and substances. For normal coal storage, real-time monitoring of the air inside the coal yard is required to achieve preventive effects.
The coal yard environmental monitoring system mainly consists of
oxygen sensors, carbon monoxide sensors, and other instruments. These instruments can be used to monitor the changes of various gas parameters in the coal yard in real time. The data are processed centrally and transmitted remotely through intelligent collection devices, enabling remote display and monitoring, so that dangers can be detected early and targeted measures can be taken to eliminate hidden dangers.For sensors in the coal yard environmental monitoring system,
Shenzhen Wuliang Sensor Technology Co., Ltd. recommends the O₂ sensor S+4OX and CO sensor GS+4CO.
Oxygen Sensor S+4OX
