Natural-gas low-temperature helium extracting system and method

Abstract

The invention discloses a natural-gas flow-temperature helium extracting system and a natural-gas flow-temperature helium extracting method. According to the system and the method, the post-expansion and nitrogen circulating refrigerating two-column separating technology is carried out for fully recovering the cooling capacity of the device in order to pre-cool the natural gas which serves as the raw material, and thereby the system can be applied to the natural gas which has an extremely low content of helium, and has the characteristics of being low in energy consumption, high in helium recovery rate, small in investment, flexible in operation, and high in adaptability to variable working conditions. The system and the method have the positive effects that little helium in the helium-containing natural gas can be extracted by a pre-cooling system and a low-temperature rectifying system, an independent nitrogen circulating refrigerating system is adopted and used for supplying an ultralow-temperature cold source required in helium concentration, and the independent system is rich in adjusting means and cannot be influenced by upstream operations; and a post-expansion refrigerating system is adopted, so that the natural-gas low-temperature helium extracting system has the operation pressure higher than that in conventional technology, and higher concentration of the helium can also be obtained at the same refrigerating temperature.

Description

technical field [0001] The invention relates to a system and method for extracting helium from natural gas at low temperature. Background technique [0002] Because of its unique properties, helium has important uses in national defense and scientific research. With its low boiling point of -268.9°C, liquid helium can be used for ultra-low temperature cooling; used as a cleaning medium and pressurized propellant for liquid hydrogen fuel systems in rockets and aerospace; in superconductor applications that have attracted wide attention in fields such as suspension trains , helium is also indispensable. In addition, helium is used as superconducting electromagnet cooling in MRI equipment in the medical field, as a heat transfer medium in nuclear power plants, as cooling and inert gas protection in optical fiber production, and as a gas phase in instrumental analysis. Chromatography and other aspects of the carrier gas have been widely used. [0003] With the rapid developme...

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Problems solved by technology

[0010] In the low temperature method, although the existing external refrigeration process can co-produce LNG, it has high energy consumption. However, in the pre-expansion refrigeration process, the operating pressure and operating temperature of the helium extraction tower are low High, in the case of reaching the same helium concentration, the demand for cooling capacity is large, the energy consumption is high, and the ability to change working conditions is poor

At the same time, the logarithmic average temperature difference is small, the heat transfer area is large, and the investment is high

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