Process and reaction system for the preparation of methanol
A process and reaction system for preparation of methanol. A fresh methanol synthesis gas stream is introduced in a first methanol reaction unit in the presence of a methanol catalyst, resulting in a first effluent stream containing methanol and unconverted synthesis gas. A recycle gas stream containing the unconverted methanol synthesis gas contained in the first effluent stream and unconverted methanol synthesis gas from a second methanol reaction unit is introduced and reacted in the second methanol reaction unit in the presence of a methanol catalyst. The first effluent stream and a part of a second effluent stream containing methanol and the unconverted methanol synthesis gas from the second methanol reaction unit are combined, cooled, and separated into a methanol-containing liquid stream and the recycle stream. The remaining part of the second effluent stream is withdrawn as a purge gas stream prior to combining the first and second effluent streams.
1 . A reaction system for use in a process for the preparation of methanol, the system comprises a first methanol reaction unit and a second methanol reaction unit, each containing a methanol catalyst;
a process gas stream passageway for introducing a process gas stream of a fresh synthesis gas into the first methanol reaction unit and a circulation passageway for circulating unconverted synthesis gas to the second methanol reaction unit;
a first effluent passageway for withdrawing and passing a first methanol containing effluent stream from the first reaction unit to a mixing point in a second effluent passageway for withdrawing a second methanol containing effluent from the second reaction unit;
a separating means arranged downstream the mixing point in the second effluent passageway for separating methanol from the unconverted synthesis gas; and
a circulator arranged in the circulation passageway between the separating means arranged upstream the second methanol reaction unit; and
a purge gas line connected to the circulation passageway and arranged upstream the mixing point in the second effluent passageway.
2 . The reaction system of claim 1 , wherein the purge gas line is connected to a hydrogen recovery unit.
3 . The reaction system of claim 2 , further comprising a passageway connected to the hydrogen recovery unit and to the process gas stream passageway for passing hydrogen to the gas stream of a fresh synthesis gas.
4 . The reaction system of claim 1 , further comprising a split stream passageway for passing a part of the unconverted synthesis gas from the circulation passageway to the process gas stream passageway.
5 . The reaction system of claim 1 , further comprising a split stream passageway for passing a part of the process gas stream of a fresh synthesis gas to the circulation passageway.
6 . The reaction system of claim 1 , wherein the first and second reaction units comprise one or more methanol reactors selected from boiling water cooled reactors, gas cooled reactors, quench reactors and adiabatic operated reactors connected in series and/or in parallel.