NOVELTY - The process comprises producing hydrogen in a first mode by: periodically/continuously supplying a carbonaceous feedstock, an alkali metal hydromethanation catalyst (31), a steam stream, a feed gas stream and optionally a first oxygen-rich gas stream to a hydromethanation reactor; and reacting the carbonaceous feedstock in the hydromethanation reactor in the presence of carbon monoxide, hydrogen, steam, hydromethanation catalyst and optionally oxygen to produce a char by-product and a methane-enriched raw product stream (50) comprising methane and carbon monoxide.    USE - The process is useful for generating a hydrogen product stream, which is useful as an energy source for hydrogen-based fuel cells, power and/or steam generation and as a reactant in hydrogenation processes such as chemical and petroleum refining industries.    ADVANTAGE - The process is capable of efficiently and economically generating the high-purity hydrogen product stream in a continuous manner without additional equipment or operational complexity.    DETAILED DESCRIPTION - The process comprises producing hydrogen in a first mode by: periodically/continuously supplying a carbonaceous feedstock, an alkali metal hydromethanation catalyst (31), a steam stream, a feed gas stream and optionally a first oxygen-rich gas stream to a hydromethanation reactor; reacting the carbonaceous feedstock in the hydromethanation reactor in the presence of carbon monoxide, hydrogen, steam, hydromethanation catalyst and optionally oxygen to produce a char by-product and a methane-enriched raw product stream (50) comprising methane, carbon monoxide, hydrogen, carbon dioxide, hydrogen sulfide and heat energy; periodically or continuously withdrawing the char by-product and the methane-enriched raw product stream from the hydromethanation reactor; introducing the methane-enriched raw product stream into a first heat exchanger unit to remove heat energy from the methane-enriched raw product stream to generate process steam; sour shifting a predominant portion of the carbon monoxide in the methane-enriched raw product stream in a sour shift unit (700) to produce a hydrogen-enriched raw product stream (72) comprising hydrogen, methane, carbon dioxide, hydrogen sulfide and optionally carbon monoxide; removing a portion of the carbon dioxide and a portion of the hydrogen sulfide from the hydrogen-enriched raw product stream in an acid gas removal unit to produce a sweetened gas stream (80) comprising a portion of the hydrogen, methane and carbon monoxide from the hydrogen-enriched raw product stream; separating a predominant portion of the hydrogen from the sweetened gas stream in a hydrogen separation unit to produce the hydrogen product stream and a hydrogen-depleted sweetened gas stream comprising methane, carbon monoxide and optionally hydrogen; optionally splitting the hydrogen-depleted sweetened gas stream into a recycle gas stream and a methane-rich product gas stream; supplying a portion of the hydrogen-depleted sweetened gas stream, a second oxygen-rich gas stream and an optional supplemental methane gas stream to a partial oxidation reactor (100); and reacting the supplied hydrogen-depleted sweetened gas stream and the supplied supplemental methane gas stream with oxygen in the partial oxidation reactor to generate heat energy and the feed gas stream comprising carbon monoxide, hydrogen and steam, and producing hydrogen in a second mode by: supplying the supplemental methane gas stream and the second oxygen-rich gas stream to the partial oxidation reactor; reacting the supplied supplemental methane gas stream with oxygen in the partial oxidation reactor to generate heat energy and a supplemental gas stream comprising carbon monoxide, hydrogen and steam; introducing the supplemental gas stream into a heat exchanger unit to remove heat energy from the supplemental gas stream; sour shifting a portion of the carbon monoxide in the supplemental gas stream in a sour shift unit to produce a hydrogen-enriched supplemental gas stream comprising hydrogen and carbon dioxide; removing a portion of the carbon dioxide from the hydrogen-enriched supplemental gas stream in an acid gas removal unit to produce a hydrogen gas stream comprising a portion of the hydrogen from the hydrogen-enriched supplemental gas stream; and purifying the hydrogen gas stream in a hydrogen separation unit to produce the hydrogen product stream. The second mode is utilized when the first mode is not operated. The partial oxidation reactor is a non-catalytic partial oxidation reactor and a catalytic partial oxidation reactor. The reaction step in the first mode has a heat demand and a steam demand that is satisfied by the steam stream. The carbonaceous feedstock optionally comprises moisture content. The steam stream and the feed gas stream fed into the hydromethanation reactor comprise heat energy that is sufficient to meet the heat demand of the reaction step. A portion of the withdrawn by-product char is provided to a catalyst recovery operation. The feed gas stream is passed through a second heat exchanger unit to remove heat energy before introduction into the hydromethanation reactor in the first mode. The recycle gas stream comprises 34-60 wt.% of the sweetened gas stream in the first mode. The carbonaceous feedstock is loaded with an amount of the alkali metal hydromethanation catalyst before introduction into the hydro-methanation reactor to provide a ratio of alkali metal atoms to carbon atoms of 0.01-0.10. The first and second modes are operated in continuous manner.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a hydromethanation portion of a process for producing a hydrogen product stream and an optional methane product stream from a carbonaceous feedstock.    Hydromethanation catalyst (31)    Methane-enriched raw product stream (50)    Hydrogen-enriched raw product stream (72)    Sweetened gas stream (80)    Partial oxidation reactor (100)    Sour shift unit. (700)