Method for carrying out heterogeneous catalytic exothermic gas phase reactions
View Patent ↗The invention relates to a method for carrying out heterogeneous catalytic exothermic gas phase reactions at a high temperature and high pressure, during which the synthesis gas comprised of a mixture of make-up gas and/or of recycle gas is fed through at least two synthesis stages that are connected in-series to form a synthesis system. The product gases from the synthesis stages, with the exception of the last stage, are separated into at least two partial flows. One partial flow is cooled until the product is condensated out, and the condensate containing the product is separated from the gaseous constituents. Afterwards, the gaseous constituents are combined with the warm portion of the product gas in order to reach the inlet temperature of the next synthesis stage. In addition, the partial flow from which the product was condensated out and removed, can be heated before being remixed with the warm portion of the product gas. After heating, the temperature is less than that of the warm portion of the product gas, and the heat used for heating the partial flow from which the product was condensated out, is extracted, at least in part, from this partial flow during its cooling.
1. A method for carrying out heterogeneous catalytic exothermic gas phase reactions at high temperature and pressure, the method comprising the steps of:
feeding the synthesis gas comprised of a mixture of make-up gas and/or of recycle gas through at least two synthesis stages that are connected in-series to form a synthesis system
separating the product gases from the synthesis stages, with the exception of the last stage, into at least two partial flows;
cooling one partial flow until the product is condensated out, and separating the condensate containing the product from the gaseous constituents; and
subsequently, combining the gaseous constituents with the warm portion of the product gas in order to reach the inlet temperature of the following synthesis stage.
2. Method according to claim 1 , wherein the partial flow, from which the product has been condensated out and removed, is heated before its remixing with the warm portion of the product gas, wherein the temperature after heating is lower than the temperature of the warm portion of the product gas.
3. Method according to claim 2 , wherein the heat used for heating the partial flow, from which the product has been condensated out, is at least partially recovered from the cooling of this partial flow.
4. Method according to claim 1 , wherein from the portion of the product gas to be cooled, most of the heat is recovered by indirect heat exchange with boiler feed water and/or totally desalinated water.
5. Method according to claim 1 , wherein the synthesis gas led into the first synthesis reactor is composed of 16 to 40 mol-% of make-up synthesis gas.
6. Method according to claim 1 , wherein the last reactor of a synthesis system is cooled by indirect heat exchange with synthesis gas.
7. Method according to claim 1 , wherein methanol is obtained from a synthesis gas containing hydrogen, carbon monoxide and carbon dioxide, by conversion on granular, copper containing catalysts, at pressures between 20 and 120 bar and temperatures between 200 and 350° C. and in that, between the first and last synthesis stage, 15 to 50% of the total methanol production is present in the separated methanol containing condensate.
8. Method according to claim 7 , wherein the first synthesis reactor is an adiabatic multiple bed reactor.
9. Method according to claim 7 , wherein the first reactor is a tube reactor with synthesis gas cooling.
10. Method according to claim 7 , wherein the first synthesis reactor is an isothermal reactor.
11. Method according to claim 10 , wherein the catalyst is crossed by tubes, in which water, boiling at elevated pressure, flows.
12. Method according to claim 2 , wherein at least 3 ammonia reactors are connected in series.
13. Method according to claim 1 , wherein downstream of each ammonia reactor a cooling vessel is arranged, which converts part of the reaction heat into working steam.
14. Method according to claim 2 , wherein heating of the partial flow, from which ammonia has condensated out, is supported by heat transfer from a successive reactor.