Separation and purification coupled process with high helium yield and diversified products

A separation and purification coupled process, which is implemented based on a helium purification, separation and recovery coupled system, wherein the coupled system comprises:

• a first compressor, a second compressor, a first pretreatment unit, a second pretreatment unit, a first membrane separation unit, a second membrane separation unit, a third membrane separation unit, and a pressure swing adsorption unit;
• the process comprising:
• mixing a helium-containing feed gas and a recycle gas to form a first mixture, passing the first mixture through the first compressor to be pressurized to produce a first pressurized gas, passing the first pressurized gas into the first pretreatment unit to remove liquid mist and dust and to adjust a temperature of the pressurized gas to 40 to 100° C. to produce a first pretreated gas, and passing the first pretreated gas into the first membrane separation unit;
• passing the first pretreated gas through the first membrane separation unit to divide the first pretreated gas into two material flows, the two material flows being a preliminarily concentrated helium-rich permeated gas which is the gas that permeates through the first membrane separation unit preferentially and a first retentate gas, on a basis that different gases have different permeation rates upon passing through a same membrane;
• passing the preliminarily concentrated helium-rich permeated gas through the second compressor to be pressurized to produce a second pressurized gas, a passing the second pressurized gas into the second pretreatment unit to remove liquid mist and dust and to adjust a temperature of the second pressurized gas to 40 to 100° C. to produce a second pretreated gas, passing the second pretreated gas into the second membrane separation unit;
• and passing the first retentate gas into the third membrane separation unit through an inlet of the third membrane separation unit;
• passing the second pretreated gas through the second membrane separation unit to divide the second pretreated gas into two material flows, the two material flows being a second retentate gas and a secondarily concentrated helium-rich permeated gas;
• discharging a first part of the secondarily concentrated helium-rich permeated gas from the coupled system as a product gas with medium helium concentration;
• passing a second part of the secondarily concentrated helium-rich permeated gas into the pressure swing adsorption unit to concentrate helium and to produce a helium above grade A;
• mixing the second retentate gas from the second membrane separation unit and the first retentate gas from the first membrane separation unit to produce a third pretreated gas;
• and
• passing the third pretreated gas through the third membrane separation unit to divide the third pretreated gas into two material flows, the two material flows being a permeated gas and a third retentate gas, returning the permeated gas to an inlet of the first compressor for recycling, mixing the third retentate gas and a desorption gas from the pressure swing adsorption unit to produce a product gas, and discharging the product gas from the coupled system.