Development of CO2 blasting technology
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(1) Technology introduction
Carbon dioxide fracturing and rock breaking technology started in the 1950s and was developed in the United States in the 1980s. It was mainly developed for coal mining faces in high-gas mines to avoid explosion accidents caused by flames generated by explosive blasting. It was introduced to my country in the 1970s and started to be applied in China in the 1990s.
In the process of introducing and researching this technology, due to the strict control of explosives by the country, it is difficult for mines to apply for explosives, which further promoted the development of this technology. Relevant domestic experts valued its broad market prospects and developed related patented technologies on this technology, and obtained authorization from the Patent Office.
(2) Understanding of blasting industry associations and experts
On March 22, 2016, the "Non-Explosive Blasting Symposium" was held in Beijing. Academician Wang Xuguang, academician of the Chinese Academy of Engineering and director of the Expert Committee of the China Blasting Industry Association, and other experts affirmed that gas blasting technology is a promising technology. On October 31, 2019, Academician Wang wrote an article in Guangming Daily, "Industry Associations to Promote Technological Innovation and Development Must Not Be Absent", which again mentioned "a blasting technology that uses liquid carbon dioxide to heat gasification and expand to do work, which has no high temperature and no open flame. , Small vibration and low pollution, etc., especially in the underground coal mine top coal mining blasting and coalbed methane extraction and blasting operations with high safety and irreplaceability, in the underwater blasting operations, the protection of aquatic organisms is obvious. "
In 2018, "Rock Drilling Machinery Pneumatic Tools" Issue 02 published the article "Application of Carbon Dioxide Fracturing Device in Earthwork Engineering" by Lu Guanghai, introducing: "Carbon dioxide gas fracturing technology" is a comprehensive supporting equipment, including "Fracturing Explosive device (also known as expansion tube), activator (a kind of heating tube) and activator. It is a blasting technology with advanced concept, safe method and significant effect. It belongs to physical fracturing technology. It has the advantages of no spark exposure during the cracking process, high cracking power, no gun inspection, simple operation, not a civilian explosive product, and its transportation, storage and use are exempt from approval, and it is widely used in many stonework projects."
(2) Device composition and working principle
Its working principle is: carbon dioxide exists as a liquid when it is lower than 31°C or the pressure is greater than 7.23MPa, and starts to gasify when it exceeds 31°C, and the pressure is constantly changing with the change of temperature. Carbon dioxide fracturing technology is to use liquid carbon dioxide to generate high pressure when its volume is rapidly expanded during endothermic gasification, causing coal (rock) to break or crack.
From Lu Guanghai’s introduction, it can be seen that the carbon dioxide gas fracturing device includes a "cracker", "heating tube" and "activator".
1. Cracker: It is a steel pipe used to contain liquid carbon dioxide;
2. Heating tube: It is a kind of heating device installed in the fracturing tube. Its function is to make the heating tube stimulate the gasification of liquid carbon dioxide through a series of operations, thereby generating expansion gas, achieving the effect of fracturing the rock;
3. The activator is part of the substance filled in the heating tube, such as potassium perchlorate and other powders. It is the main component of the heating tube. It is activated by a conductive device and its function is to make the heating tube generate heat.
In addition to other supporting devices, the above is the core combination of carbon dioxide gas fracturing devices. The method used is to install the heating tube into the rupture device and complete the assembly on site. The work is a physical change, and does not produce shock waves, open flames, heat sources, and various toxic and harmful gases generated by chemical reactions; the final generation of strong expansion force to crack the rock is not the heating tube, but the carbon dioxide gas excited by the heating tube.
