Chemical Engineering @ChemengFiles.Com

Methanol is produced in large capacity units of production (2000 t / a and older) from synthesis gas by catalytic reaction of hydrogen with CO and CO2 pressure of about 50 ties and relatively low degrees of conversion , so must recycle the unconverted gas reactor, once separated by condensing the product of the reaction in aqueous solution of methanol.

The process consists of four distinct units: the steam reforming of natural gas, synthesis gas compression, the so-called loop synthesis and distillation. No need for CO conversion unit, for the most appropriate relationship between hydrogen and carbon oxides is achieved by suitably operating the reforming furnace.

The unit is powered steam reforming natural gas, which may contain CO2 and recycling of light that are separated in a first distillation flash raw methanol. The outgoing gas is cooled and condensed water is separated. The compressor provides the synthesis gas loop which is the reactor with multiple beds of catalyst and intermediate cooling gas injection current from cold to bed earlier.

In the synthesis loop, the compressed gas is heated in a heat exchanger with the outgoing gas from the reactor before entering it. On departure cools the feed gas first, and finally with cooling water, separating the aqueous solution of methanol to be rolled into a pressure reducing valve. The condensate of the crude methanol is distilled to concentrate and, where appropriate, to debug. The vapors from the distillation "flash" give up their energy in an expander and join the reforming furnace feed. The fraction of non-condensed gas at the outlet of the reactor is recirculated through a compressor (which is called the recirculation pump) to compensate for pressure losses in this loop. At the exit of the second compressor is incorporated gas from the reforming unit.

To minimize power consumption generates high pressure steam after reheating in the convective section of the reformer, is expanded in turbines that drive compressors counter. Exhaust steam pressure must be greater than the gas in the oven so that it can incorporate as a reagent.

The synthesis loop purge, necessary to prevent the progressive increase of the concentration of inerts (primarily methane) is expanded in a turbine and, if free of nitrogen, is recycled to food.