A method and apparatus of removing heavy hydrocarbons from a natural gas feed stream, the method comprising using first and second hydrocarbon removal systems in series such that the first system processes the natural gas feed stream to produce a heavy hydrocarbon depleted natural gas stream and the second system processes at least a portion of the heavy hydrocarbon depleted natural gas stream from the first system to produce a natural gas stream lean in heavy hydrocarbons, wherein one of said systems is a adsorption system that comprises one or more beds of adsorbent for adsorbing and thereby removing heavy hydrocarbons from a heavy hydrocarbon containing natural gas, and the other of said systems is a gas-liquid separation system for separating a heavy hydrocarbon containing natural gas into a heavy hydrocarbon depleted natural gas vapor and a heavy hydrocarbon enriched liquid.

A liquefaction system that is configured to use a single methane expander to provide primary refrigeration duty. The liquefaction system can include a heat exchanger and a fluid circuit coupled with the heat exchanger, the fluid circuit configured to circulate a process stream derived from an incoming feedstock of natural gas. The fluid circuit can comprise a methane expander coupled with the heat exchanger, a sub-cooling unit coupled with the methane expander, the sub-cooling unit configured to form a liquid natural gas (LNG) product from the process stream, and a first throttling device interposed between the heat exchanger and the sub-cooling unit. The methane expander and the first throttling device can be configured to expand the process stream to a process pressure that is between a first pressure of the incoming feedstock and a second pressure of the process that exits the sub-cooling unit.

Variable N2 content in feed gas ranging from 3 mol % to 50 mol % can be rejected from the process using a feed exchanger that is fluidly coupled with a cold separator and a single fractionation column to produce a nitrogen vent stream and streams that are suitable to be further processed for NGL recovery and LNG production.

A system and method for cooling a gas using a mixed refrigerant includes a compressor system and a heat exchange system, where the compressor system may include an interstage separation device or drum with no liquid outlet, a liquid outlet in fluid communication with a pump that pumps liquid forward to a high pressure separation device or a liquid outlet through which liquid flows to the heat exchanger to be subcooled. In the last situation, the subcooled liquid is expanded and combined with an expanded cold temperature stream, which is a cooled and expanded stream from the vapor side of a cold vapor separation device, and subcooled and expanded streams from liquid sides of the high pressure separation device and the cold vapor separation device, or combined with a stream formed from the subcooled streams from the liquid sides of the high pressure separation device and the cold vapor separation device after mixing and expansion, to form a primary refrigeration stream.

The disclosure provides a method and system for optimizing production of a natural gas liquefaction process, the method comprising the steps of: selecting at least one manipulated variable (MV) for controlling the liquefaction process; selecting at least one control variable (CV), the at least one control variable at least comprising liquefied natural gas (LNG) throughput; providing at least one model, each model providing a dependency of the at least one control variable (CV) on the at least one manipulated variable (MV); using the at least one model to estimate LNG throughput for at least one of the manipulated variables (MV); obtaining process data from the liquefaction process, the process data at least including observed values of LNG throughput; creating a gain matrix based on said interdependencies; and using the gain matrix to optimize a process control system of the liquefaction process.

The liquefaction system comprises a high-temperature refrigerant circuit and a low-temperature refrigerant circuit. The system further comprises a first high-temperature heat exchanger, wherein the feed gas is in heat exchange with a first stream of vaporizing first refrigerant and is cooled thereby, and a second high-temperature heat exchanger, wherein compressed first refrigerant of the first refrigerant circuit and compressed second refrigerant of the second refrigerant circuit are in heat exchange with a second stream of vaporizing first refrigerant and are cooled thereby. A low-temperature heat exchanger is further provided, wherein cooled feed gas from the first high-temperature heat exchanger and cooled second refrigerant from the second high-temperature heat exchanger are further cooled and liquefied in heat exchange with a flow of vaporizing second refrigerant.