NOVELTY - Producing (M1) dimethyl ether using dimethyl ether (DME)-floating, production, storage and offloading (FPSO) system comprises: separating crude oil and gas, and storing separated crude oil; pretreating separated gas by saturation and desulfurization; reforming desulfurized gas with carbon dioxide and steam to produce synthetic gas; removing carbon dioxide from synthetic gas; reacting synthetic gas with carbon dioxide to produce dimethyl ether; producing electric power by operating fuel cell using synthetic gas or hydrogen with water and carbon dioxide; and producing steam.    USE - The method is useful for producing dimethyl ether using dimethyl ether-floating, production, storage and offloading system that is used for offshore oil fields and offshore stranded gas fields (all claimed).    ADVANTAGE - The method: provides improved catalytic performance, enhanced carbon monoxide conversion and dimethyl ether yield; minimizes cost of carbon dioxide disposal while minimizing the size of the DME-FPSO system; provides carbon dioxide and water that are recycled as source materials for reforming of the natural gas; and converts associated gas from oil fields and natural gas from stranded gas fields into dimethyl ether without emission of carbon dioxide. Surplus hydrogen or synthetic gas from the DME-FPSO process may be utilized to produce electric power, thus the power required for the DME-FPSO process for producing clean synthetic fuel is produced offshore without environmental pollution. The designing of the DME-FPSO system is optimized in consideration of safety issue related with the wave motion of the FPSO facility.    DETAILED DESCRIPTION - Producing (M1) dimethyl ether using dimethyl ether (DME)-floating, production, storage and offloading (FPSO) system comprises: separating crude oil and gas at an FPSO facility and storing the separated crude oil in a crude oil storage; pretreating the separated gas by saturation and desulfurization; reforming the saturated and desulfurized gas with carbon dioxide and steam to produce a synthetic gas comprising carbon monoxide and hydrogen; removing carbon dioxide from the synthetic gas and returning the removed carbon dioxide to be used as a reaction source of the reforming; chemically reacting the synthetic gas with carbon dioxide removed by the reaction (comprising (a) reacting 3 moles hydrogen and 3 moles carbon dioxide to give dimethyl ether and carbon dioxide and (b) reacting 4 moles hydrogen and 2 moles carbon dioxide to give dimethyl ether and water) to produce dimethyl ether; producing electric power by operating a fuel cell using the synthetic gas or hydrogen, with water and carbon dioxide being produced during the process; and producing steam using the water produced by the fuel cell as cooling water and returning the same to a reforming reactor (203) along with the produced carbon dioxide. An INDEPENDENT CLAIM is also included for producing (M2) dimethyl ether using a DME-FPSO system for offshore stranded gas fields, comprising: pretreating stranded gas by saturation and desulfurization; reforming the saturated and desulfurized gas with carbon dioxide and steam to produce the synthetic gas comprising hydrogen; removing carbon dioxide from the synthetic gas and returning the removed carbon dioxide to be used as a reaction source of the reforming; chemically reacting the synthetic gas with carbon dioxide removed by the reaction (a) or (b) to produce dimethyl ether; producing electric power; and producing steam.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of process of producing dimethyl ether using a dimethyl ether-floating, production, storage and offloading system for offshore oil fields via a direct method.    Separator (200)    Gas desulfurizer (201)    Reforming reactor (203)    Dimethyl ether fuel storage (213)    Methanol fuel storage (214)