A natural gas pretreatment system includes a heat exchanger having a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet receives a first pressurized gas stream having a first input temperature, and the second inlet receives a second pressurized gas stream having a second temperature. The second temperature is higher than the first temperature. The first outlet outputs the first gas stream; upon exiting the heat exchanger, the first gas stream has a first output temperature higher than the first input temperature. The second outlet outputs the second gas stream; upon exiting the heat exchanger, the second gas stream has a second output temperature lower than the second input temperature. The system further includes a pipeline network operable to receive the first pressurized gas stream.

An apparatus for forming solid carbon dioxide blocks comprises a chamber with an internal cavity, a flow control valve including a variable area orifice, an actuator configured to control the area of the variable area orifice and a controller configured to vary the are of the variable area orifice while liquid carbon dioxide is being flashed to solid carbon dioxide snow through the flow control valve. A method of forming carbon dioxide blocks comprises the steps of varying the area of an orifice while flowing liquid carbon dioxide through the orifice under sufficient pressure to flash the liquid carbon dioxide to solid carbon dioxide snow.

The amount of consumption of gas is reduced when the gas is expanded to be cooled by using a plurality of expansion turbines. A high-pressure expansion turbine includes: a gas supply passage through which bearing gas is supplied to a bearing portion; and a gas discharge passage through which the bearing gas which has been supplied from the gas supply passage to the bearing portion is discharged from the bearing portion. A low-pressure expansion turbine includes: a gas supply passage through which the bearing gas is supplied to a bearing portion; and a gas discharge passage through which the bearing gas which has been supplied from the gas supply passage to the bearing portion is discharged from the bearing portion. The bearing gas discharged from the gas discharge passage of the high-pressure expansion turbine is supplied to the gas supply passage of the low-pressure expansion turbine.

The amount of consumption of gas is reduced when the gas is expanded to be cooled by using a plurality of expansion turbines. A high-pressure expansion turbine includes: a gas supply passage through which bearing gas is supplied to a bearing portion; and a gas discharge passage through which the bearing gas which has been supplied from the gas supply passage to the bearing portion is discharged from the bearing portion. A low-pressure expansion turbine includes: a gas supply passage through which the bearing gas is supplied to a bearing portion; and a gas discharge passage through which the bearing gas which has been supplied from the gas supply passage to the bearing portion is discharged from the bearing portion. The bearing gas discharged from the gas discharge passage of the high-pressure expansion turbine is supplied to the gas supply passage of the low-pressure expansion turbine.

A natural gas pretreatment system includes a heat exchanger having a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet receives a first pressurized gas stream having a first input temperature, and the second inlet receives a second pressurized gas stream having a second temperature. The second temperature is higher than the first temperature. The first outlet outputs the first gas stream; upon exiting the heat exchanger, the first gas stream has a first output temperature higher than the first input temperature. The second outlet outputs the second gas stream; upon exiting the heat exchanger, the second gas stream has a second output temperature lower than the second input temperature. The system further includes a pipeline network operable to receive the first pressurized gas stream.