天然气脱氮工艺评述

Review on natural gas denitrification process

关键词:  天然气  脱氮  劣质天然气  深度冷冻  马拉法  变压吸附  膜分离  混合膜结构

Key words:  natural gas  denitrification  sub-quality natural gas(SQNG)  cryogenic  Mehra process  pressure swing adsorption(PSA)  membrane separation  mix membrane structure

摘要:

为了加速致密油气藏、页岩气和劣质天然气(SQNG)的开发与利用,近年来,天然气脱氮工艺在全球范围内受到普遍关注。当前应用于工业的天然气脱氮工艺包括:深度冷冻、溶剂吸收、变压吸附和膜分离。深度冷冻工艺流程复杂,投资与成本均较高,较适用于氮气含量相对较高的、处理高压天然气的大型脱氮装置。溶剂吸收工艺因溶剂选择困难且循环量大,还需要致冷系统,近年来工业上很少采用。“Molecular Gate”脱氮工艺的关键技术是使用孔径尺寸可以调节和控制的硅酸钛分子筛,此工艺已成为当前中、小型脱氮装置使用工艺的发展主流。随着天然气脱氮用特殊膜分离材料的成功开发,膜分离脱氮工艺也正在迅速发展,但膜材料的性能还有待进一步完善。 

Abstract:

For speeding up the development of compact oil and gas reservoirs, shale gas and sub-quality natural gas(SQNG), the natural gas denitrification process has been received widespread attention all over the world in recent years. At present, four kinds of denitrification process are used in natural gas industry which including cryogenic, solvent absorption (Mahra process), pressure swing adsorption(PSA) and membrane separation. The flow-sheet of cryogenic process is complicated and the investment and cost are high. So it is only suitable for large unit treating high pressure feed gas with high concentration of N₂. The Mahra process is rarely adopted in industry recently as the selection of solvent because Mahra process is difficult and the solvent circulation rate is high, additionally, it needs refrigerating system. The titanium silicate molecular sieve of which the aperture size can be adjusted and controlled was applied to the Molecular Gate denitrification process. The key technology made it become the main technique of medium and small denitrification units. Along with the successful development of special membrane separation material, the membrane separation denitrification process advances very fast, but the properties of the membrane materials need to be further improved.