Methods for extracting and recycling ammonia from MOCVD process exhaust gas by FTrPSA

A method for extracting and recycling ammonia from an MOCVD (Metalorganic Chemical Vapor Deposition) process exhaust gas by FTrPSA (full temperature range-pressure swing adsorption), comprising the following procedures:

• (a) providing a feed gas comprising ammonia, wherein the feed gas is an exhaust gas in an MOCVD manufacturing process for a light emitting diode based on gallium nitride epitaxial wafer growth, the feed gas being at atmospheric pressure or a lower pressure and a temperature of 20-140° C.;
• (b) executing a pretreatment procedure, wherein the feed gas is introduced into a pretreatment unit to remove dust, particles, oil mist and other impurities in sequence to form a pretreated feed gas under operating conditions at a pressure of 0.2-0.3 MPa and a temperature of 20-140° C.;
• (c) executing a medium-shallow temperature PSA (pressure swing adsorption) concentration procedure, wherein the pretreated feed gas from the pretreatment procedure is compressed to 0.3-4.0 MPa, passed into a multi-tower PSA concentration unit with an operating pressure of 1.0-4.0 MPa and an operating temperature of 20-140° C., wherein at least one adsorption tower of the multi-tower PSA concentration unit performs an adsorption step to form an adsorbed phase gas that is an ammonia-rich concentrated gas, wherein remaining adsorption tower(s) of the multi-tower PSA concentration unit are in a desorption and regeneration step;
• (d) executing the desorption and regeneration step on the adsorbed ammonia-rich concentrated gas to form a desorbed ammonia-rich concentrated gas, and executing a condensation and freezing procedure on the desorbed ammonia-rich concentrated gas, wherein the desorbed ammonia-rich concentrated gas is introduced into a condensation and freezing unit to form liquid ammonia;
• (e) executing a liquid ammonia vaporization procedure, wherein the liquid ammonia is introduced into a liquid ammonia vaporization unit to form an industrial ammonia gas;
• (f) executing a PSA ammonia extraction procedure, wherein the industrial ammonia gas from the liquid ammonia vaporization procedure is introduced into at least one adsorption tower of a multi-tower PSA ammonia gas purification unit during an adsorption step with an operating pressure of 0.6-2.0 MPa and an operating temperature of 60-120° C., wherein remaining adsorption tower(s) of the multi-tower PSA ammonia gas purification unit are in a desorption and regeneration step, to form a non-adsorbed phase gas that is an ultra-pure ammonia gas;
• (g) executing an ammonia gas purification procedure, wherein the ultra-pure ammonia gas is decompressed to be introduced to an ammonia gas purification unit to remove trace impurities to obtain a final electronic-level ammonia gas product.