Gas-liquefying system including control means responsive to the temperature at the low-pressure expansion turbine

• US 4,582,519 A
• Filed: 08/07/1984
• Issued: 04/15/1986
• Est. Priority Date: 09/14/1983
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Someya, Kazuo, Tasaka, Yasuo
• Primary Examiner(s): Bashore, S. Leon
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/638,580
• Time in Patent Office: 616 Days
• Field of Search: 62/8, 62/9, 62/36, 62/37, 62/38, 62/40
• US Class Current: 62/650
• CPC Class Codes: F25J 1/0015 Nitrogen
• CPC Class Codes: F25J 1/0017 Oxygen
• CPC Class Codes: F25J 1/0037 of a return stream
• CPC Class Codes: F25J 1/0208 in combination with an internal quasi-closed refrigeration loop, e.g. with deep flash recycle loop F25J1/021 takes precedence
• CPC Class Codes: F25J 1/0244 Operation; Control and regulation; Instrumentation F25J1/0279 takes precedence
• CPC Class Codes: F25J 2270/06 with multiple gas expansion loops
• CPC Class Codes: F25J 2270/90 External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration

Abstract

A gas liquefying system of the type in which a compressed gas is divided into a part which is to be used for the generation of cold heat and a part which is to be liquefied, the part of the gas for generation of cold heat being introduced into a high-pressure expansion turbine to generate the cold heat and, after an adjustment of the temperature thereof at the outlet of the high-pressure expansion turbine, supplied to a low-pressure expansion turbine to further generate the cold heat while becoming the returning gas of a low temperature, the returning gas being supplied to a liquefier to liquefy the part of gas to be liquefied. The system comprises a temperature controlling means disposed in a pipe connected between the outlet of the high-pressure expansion turbine and the inlet of the low-pressure expansion turbine and adapted to raise the temperature of the gas at the outlet of the high-pressure expansion turbine, and means for adjusting the flow rate of the gas introduced to the temperature controlling means in response to the gas temperature at the inlet or the outlet of the low-pressure expansion turbine thereby optimumly regulating the gas temperature at the outlet of the low-pressure expansion turbine.

Claims

1. A gas liquefying system of the type in which a gas compressed by a circulation type compressor is cooled in a heat exchanger through a heat exchange with a returning gas of a low temperature, the cooled gas being then divided into a part which is to be used for the generation of cold heat and a part which is to be liquefied, the part of the gas for generation of cold heat being introduced into a high-pressure expansion turbine to generate the cold heat and, after an adjustment of the temperature thereof at the outlet of said high-pressure expansion turbine, supplied to a low-pressure expansion turbine to further generate the cold heat while becoming the returning gas of a low temperature, said returning gas being supplied to a liquefier to liquefy said part of gas to be liquefied and returned to said circulation type compressor after a recovery of temperature through a heat exchanger in said heat exchanger, said system comprising:

a heat exchanger, for gas passing through the turbines, disposed in the pipe between the outlet of said high-pressure expansion turbine and the inlet of said low-pressure expansion turbine and adapted for raising the temperature of the gas coming from said high-pressure expansion turbine;

a first branch pipe and a second branch pipe for the gas to be liquefied, said first and second branch pipes shunting from each other at an upstream portion of said liquefier, said first branch pipe leading through said heat exchanger for gas passing through the turbines and merging in said second branch pipe at the downstream portion of said liquefier;

automatic control valves disposed in said first and second branch pipes, respectively; and

an automatic temperature controlling means for actuating said first and second automatic control valves upon sensing the gas temperature at the inlet or the outlet of said low-pressure expansion turbine.

2. A gas liquefying system of the type in which a gas compressed by a circulation type compressor is cooled in a heat exchanger through a heat exchange with a returning gas of a low temperature, the cooled gas being then divided into a part which is to be used for the generation of cold heat and a part which is to be liquefied, the part of the gas for generation of cold heat being introduced into a high-pressure expansion turbine to generate the cold heat and, after an adjustment of the temperature thereof at the outlet of said high-pressure expansion turbine, supplied to a low-pressure expansion turbine to further generate the cold heat while becoming the returning gas of a low temperature, said returning gas being supplied to a liquefier to liquefy said part of gas to be liquefied and returned to said circulation type compressor after a recovery of temperature through a heat exchange in said heat exchanger, said system comprising:

a heat exchanger, for gas passing through the turbines, disposed in the pipe between the outlet of said high-pressure expansion turbine and the inlet of said low-pressure expansion turbine and adapted for raising the temperature of the gas coming from said high-pressure expansion turbine;

a first branch pipe and a second branch pipe for the gas to be liquefied, said first and second branch pipes shunting from each other at an upstream portion of said liquefier, said first branch pipe leading through said heat exchanger for gas passing through the turbines and merging in said second branch pipe at the downstream portion of said liquefier;

automatic control valves disposed in said first and second branch pipes, respectively;

an automatic temperature controlling means for actuating said first and second automatic control valves upon sensing the gas temperature at the inlet or the outlet of said low-pressure expansion turbine;

a temperature controller disposed in the pipe for introducing the gas for generation of cold heat to said high-pressure expansion turbine and adapted to control the temperature of the gas at the inlet of said high-pressure expansion turbine; and

an automatic controller disposed in the pipe for the gas to be liquefied leading from the outlet of said temperature controller and for automatically adjusting the command temperature set in said temperature controller in response to the temperature of the product liquefied gas.