초록 ▼

A control system for a process of liquefied natural gas production (LNG) from natural gas using a heat exchanger and a closed loop refrigeration cycle employs independent, direct control of both production and temperature by adjusting refrigeration to match a set production. The control system sets

A control system for a process of liquefied natural gas production (LNG) from natural gas using a heat exchanger and a closed loop refrigeration cycle employs independent, direct control of both production and temperature by adjusting refrigeration to match a set production. The control system sets and controls LNG production at a required production value, and independently controls LNG temperature by adjusting the refrigeration provided to the natural gas stream. One exemplary method employs compressor speed, for example, as a key manipulated variable (MV) to achieve fast and stable LNG temperature regulation. Other compressor variables rather than speed may be key MVs, depending on the type of MR compressors employed, and may be the guidevane angle in a centrifugal compressor or the stator blade angle in an axial compressor. The second exemplary method employs a ratio of total recirculating refrigerant flow to LNG flow as the key manipulated variable to effectively control the LNG temperature.

대표청구항 ▼

[ What is claimed:] [1.] A method for controlling the production of a liquefied natural gas (LNG) outlet stream by refrigeration of the natural gas flowing through a liquefaction process, comprising the steps of:(a) measuring a temperature and a flow rate of the LNG outlet stream; and(b) varying the

[ What is claimed:] [1.] A method for controlling the production of a liquefied natural gas (LNG) outlet stream by refrigeration of the natural gas flowing through a liquefaction process, comprising the steps of:(a) measuring a temperature and a flow rate of the LNG outlet stream; and(b) varying the refrigeration of the natural gas to adjust the temperature value of the LNG outlet stream and independently adjusting the rate of the LNG flowing through the process, thereby to maintain the flow rate of the LNG outlet stream at a predetermined flow value and the temperature at a predetermined temperature value.