Patent ID: 6258860
Filing Date: 2001-07-10
Classification: C07C,Y02P

Abstract:
A process for the production of methanol which comprises:(A) converting a carbonaceous feedstock in a synthesis gas production plant into a synthesis gas comprising hydrogen and at least one carbon oxide selected from carbon monoxide, carbon dioxide, and mixtures thereof;(B) providing synthesis gas of step (A) at a methanol synthesis pressure as a compressed synthesis gas;(C) supplying compressed synthesis gas of step (B) to a first methanol synthesis zone containing a charge of a methanol synthesis catalyst and maintained under methanol synthesis conditions including use of an elevated methanol synthesis temperature and an elevated methanol synthesis pressure;(D) recovering from the first methanol synthesis zone a first product stream comprising (i) crude methanol and (ii) unreacted gases;(E) separating the first product stream to form (i) a first crude liquid methanol stream and (ii) a first unreacted gas stream;(F) recycling by means of a first gas recycle compressor part of the first unreacted gas stream of step (E) to the first methanol synthesis zone;(G) recovering another part of the first unreacted gas stream of step (E) as a first purge gas stream containing unreacted at least one carbon oxide and hydrogen;(H) depressurizing the first crude liquid methanol stream of step (E) to a refining pressure to produce (i) a degassed first crude liquid methanol stream, and (ii) an off gas;(I) subjecting the degassed first crude liquid methanol stream of step (H) to at least one refining step in a first methanol refining zone to produce a plurality of streams including (i) a methanol product stream, (ii) a fusel oil stream, (iii) a light byproduct containing secondary methanol streamy and (iv) a methanol-containing vent gas stream;(J) supplying material of the first purge gas stream of step (G) to a second methanol synthesis zone containing a charge of a methanol synthesis catalyst and maintained under methanol synthesis conditions including use of an elevated methanol synthesis temperature and an elevated methanol synthesis pressure;(K) recovering from the second methanol synthesis zone of step (J) a second product stream comprising (i) crude methanol and (ii) unreacted gases;(L) separating the second product stream of step (K) to form (i) a second crude liquid methanol stream and (ii) a second unreacted gas stream;(M) recycling by means of a second gas recycle compressor part of the second unreacted gas stream of step (L) to the second methanol synthesis zone;(N) recovering another part of the second unreacted gas stream of step (L) as a second purge gas stream containing unreacted at least one carbon oxide and hydrogen;(O) subjecting material of the second purge gas stream of step (N) to hydrogen recovery in a hydrogen recovery zone to produce (i) a hydrogen enriched gas stream and (ii) a hydrogen depleted gas stream;(P) passing a gas containing liquid stream comprising material of the second crude liquid methanol stream of step (L) through a gas recovery zone maintained under gas recovery conditions effective for recovery of dissolved gas present in the gas containing liquid stream;(Q) recovering from the gas recovery zone of step (P) (i) a substantially methanol free recovered gas stream containing light byproducts and (ii) a degassed second crude liquid methanol stream;(R) subjecting at least one stream selected from the hydrogen enriched gas stream of step (O) and the recovered gas stream of step (Q) to multistage compression in a multistage gas compression zone comprising a plurality of gas compression stages with an interstate cooler between the or each successive pair of gas compression stages;(S) recovering from the multistage gas compression zone (i) at least one liquid condensate and (ii) a compressed recovered gas stream; and(T) passing the recovered compressed gas stream of step (S) to the second methanol synthesis zone.