Patent ID: 7521483

Claim:
A method for coproducing methanol and ammonia from natural gas, which comprises the steps of: (a) mixing natural gas, steam and oxygen which has a purity of 90 to 99.5% in a catalytic partial oxidation reactor in the presence of a catalyst for reforming natural gas to partially oxidize and reform the natural gas into a gas mixture which comprises carbon monoxide, carbon dioxide, hydrogen and steam; (b) dividing the gas mixture obtained in step (a) into two portions, a larger portion for hydrogen production and a smaller portion for methanol synthesis; (c) catalytically converting the carbon monoxide in the larger portion of the gas mixture for hydrogen production to carbon dioxide to obtain a gas mixture rich in hydrogen and carbon dioxide in a one or two stage catalytic converter, and cooling the gas mixture rich in hydrogen and carbon dioxide thus produced; (d) passing the gas mixture rich in hydrogen and carbon dioxide to a purification unit having a molecular sieve and maintained at a pressure of 30 to 100 bar, passing the gas mixture rich in hydrogen and carbon dioxide through the molecular sieve using variable pressure absorption, to separate the carbon dioxide from the hydrogen, splitting the hydrogen into two streams, combining one stream of hydrogen with the smaller portion of the gas mixture obtained in step (b) for synthesis of methanol, and subsequently washing out any residual impurities from the other stream of hydrogen , including methane, carbon monoxide, and argon, with a stream of liquid nitrogen to obtain a pure stream of hydrogen and nitrogen for ammonia synthesis, and returning the washed out residual impurities as a fuel to the catalytic partial oxidation reactor according to step (a); (e) catalytically converting the smaller portion of the gas mixture obtained in step (b) combined with the stream of hydrogen according to step (d) to methanol, and purifying the methanol by distilling the methanol at a pressure between atmospheric pressure and 15 bar; and (f) catalytically converting the pure stream of hydrogen and nitrogen obtained according to step (d) to ammonia, and separating the ammonia by means of partial condensation.