Installation and method for purifying and liquefying natural gas

A facility for purifying and liquefying natural gas comprising, arranged in series, an adsorption purification unit, a unit for separating hydrocarbon(s) by refrigeration, and a liquefier, the adsorption purification unit comprising an adsorption purification unit inlet configured to connect to a gas source predominantly comprising natural gas, a first adsorption purification unit outlet for purified gas connected to a refrigeration separation unit inlet, a second adsorption purification unit outlet for effluent gases produced during the purification, the unit for separating hydrocarbon(s) by refrigeration comprising a first refrigeration separation unit outlet for purified gas connected to a liquefier inlet of the liquefier and a second refrigeration separation unit outlet for effluent gases enriched in hydrocarbons produced during purification by cooling, the facility comprising a gas-fired power plant for combined heat and power production by combustion of a hydrocarbon, said power plant comprising a fuel gas inlet connected to the second adsorption purification unit outlet and to the second refrigeration separation unit outlet, the facility comprising at least one electrical member selected from the group consisting of:

• a chiller and the liquefier, the power plant being electrically connected to at least one of the electrical member(s) in order to supply the latter with electric power produced by the combustion of a hydrocarbon introduced at a power plant inlet, the facility comprising a bypass line provided with a valve connecting the absorption purification unit inlet to the power plant inlet, the bypass line being configured to allow the power plant to be supplied with fuel gas directly by the source, and in that said power plant is configured to produce a given electric power as a function of the flow rate and the composition of the fuel gas introduced at the power plant inlet and wherein the adsorption purification unit and the unit for separating hydrocarbon(s) by refrigeration are configured to produce given flow rates of fuel gas at their outlets having compositions liable to fluctuate, the sum of these fuel gas flow rates having a combustion power lower than the combustion power needed to produce the electric power required by all the electrical members electrically powered by the power plant and in that the facility is configured to supply the power plant with the additional combustion power needed via a flow of fuel gas originating directly from the source via the bypass line, and in that the adsorption purification unit comprises several adsorbers which are mounted and parallel and operate in an alternating and staggered manner by carrying out each of the cycles comprising an adsorption phase, a depressurization phase, a regeneration phase, in particular with heating and a cooling phase, the adsorption purification unit comprising a circuit provided with valves that is configured to ensure, during a regeneration phase of each adsorber, a closed-loop circulation in the adsorber with a gas compressed in a circulator heated by a first heating member.