The invention relates to a method for separating air by cryogenic distillation in a column system, comprising a first column operating at a first pressure and a second column operating at a second pressure, in which an argon-enriched flow is sent from an intermediate point of the first column to the tank of the second column and an argon-rich flow is drawn off at the top of the second column, wherein a nitrogen-enriched flow of the first column is compressed in a compressor, the compressed flow is sent to a head condenser of the second column after an expansion step and the vaporized flow is expanded in the condenser in a turbine where it at least partially liquefies.

A method for separating air by cryogenic distillation in a system of columns comprising a first column and a second column operating at a lower pressure than the first column, comprising the steps of compressing all of the feed air in a first compressor to a first output pressure of at least 1 bar greater than the pressure of the first column, sending a first portion of the air under the first output pressure to the second compressor, and compressing the air to a second output pressure, cooling and condensing at least a portion of the air under the second output pressure in a heat exchanger, withdrawal of a liquid from a column of the system of columns, pressurising the liquid and evaporating the liquid by heat exchange in the heat exchanger, and pressure reduction of a portion of the compressed air to a second output pressure, at least partially evaporating said air in the heat exchanger, optionally additional heating of said air in the heat exchanger, and sending at least a portion of this air to the second compressor.

A method for the production of liquefied natural gas (LNG) using a cold fluid provided from a cryogenic unit, such as an air separation unit or nitrogen liquefier, is provided. The method may include the steps of: withdrawing a nitrogen stream from a cryogenic unit, wherein the nitrogen stream is at a temperature between about 155 C. to about 193 C.; and liquefying a natural gas stream in a natural gas liquefaction unit using the nitrogen stream from the cryogenic unit.

A system for storing or producing electricity, which allows stabilization of a power network under conditions of excess availability of electricity or lack thereof and for producing liquefied natural gas is provided.

A novel concept for a high energy and material efficient nitric acid production process and system is provided, wherein the nitric acid production process and system, particularly integrated with an ammonia production process and system, is configured to recover a high amount of energy out of the ammonia that it is consuming, particularly in the form of electricity, while maintaining a high nitric acid recovery in the conversion of ammonia to nitric acid. The energy recovery and electricity generation process comprises pressurizing a liquid gas, such as air, oxygen and/or N.sub.2, subsequently evaporating and heating the pressurized liquid gas, particularly using low grade waste heat generated in the production of nitric acid and/or ammonia, and subsequently expanding the evaporated pressurized liquid gas over a turbine. In particular, the generated electricity is at least partially used to power an electrolyzer to generate the hydrogen needed for the production of ammonia. The novel concepts set out in the present application are particularly useful in the production of nitric acid based on renewable energy sources.

A method for controlling a coupled heat exchanger system having a first heat exchanger block and a second heat exchanger block. A first fluid stream is divided into a first partial current and a second partial current both flowing through the heat exchanger system. A second fluid stream flows through the first heat exchanger block counter to the first partial current. A third fluid stream flows through the second heat exchanger block counter to the second partial current. An intermediate temperature is measured on one of the heat exchanger blocks. The amount of the first partial current and the second partial current is controlled based on the current value of the intermediate temperature. This control reduces the strain on the heat exchangers by changing loads while keeping fluctuations of the intermediate temperature low.

A method for producing liquefied natural gas and a stream of liquid nitrogen including step a): producing gaseous nitrogen in an air separation unit; step b): liquefying a stream of natural gas in a natural gas liquefaction unit including a main heat exchanger and a system for producing cold; step c): liquefying the nitrogen stream resulting from step a) in the main exchanger of the natural gas liquefaction unit in parallel with the liquefied natural gas in step b); wherein all the cold necessary for liquefying the stream of nitrogen and for liquefying the natural gas is supplied by the system for producing cold of the natural gas liquefaction unit.

A liquefier device which may be a retrofit to an air separation plant or utilized as part of a new design. The flow needed for the liquefier comes from an air separation plant running in a maxim oxygen state, in a stable mode. The three gas flows are low pressure oxygen, low pressure nitrogen, and higher pressure nitrogen. All of the flows are found on the side of the main heat exchanger with a temperature of about 37 degrees Fahrenheit. All of the gasses put into the liquefier come out as a subcooled liquid, for storage or return to the air separation plant. This new liquefier does not include a front end electrical compressor, and will take a self produced liquid nitrogen, pump it up to a runnable 420 psig pressure, and with the use of turbines, condensers, flash pots, and multi pass heat exchangers. The liquefier will make liquid from a planned amount of any pure gas oxygen or nitrogen an air separation plant can produce.

A liquefactor for a gas includes a framework (O) containing at one end at least one plate-and-fin heat exchanger (E), each plate having a length and a width, and the plates being arranged with their length parallel to the length of the framework and at the other end a turbine (M) to provide cold to the at least one heat exchanger, the framework being orientated such that the turbine is positioned beneath the at least one exchanger.

This invention is about an air separation apparatus to produce oxygen and nitrogen through isobaric separation, which is based on the Rankine cycle system of similar thermal energy power circulation apparatus at cryogenic side, a liquid pump is used to input work and the cold is made up to the air separation apparatus with refrigerating media, so as to realize the isobaric separation of air to produce nitrogen and oxygen. The air separation apparatus of this invention can save energy by over 30% as compared with the traditional advanced apparatus with the identical refrigerating capacity, and it can also realize centralize gas supply via the air separation apparatus, therefore it constitutes a breakthrough to the traditional air separation technology and refrigeration theory, with substantial economic, social and environmental protection benefits.