Abstract: An apparatus and method of separation of LOX and other commercially valuable components, such as LAr from liquefied air, which consists primarily of LN2. Strong magnetic field gradient and gravity are used to separate LOX from liquefied air, based upon the different magnetic properties of LOX and LN2. The apparatus and method employ a magnetic field gradient to levitate the LN2 and LAr diamagnetic components of liquid air while accelerating the paramagnetic LOX component toward the bottom to achieve oxygen separation. In other embodiments, a leak valve system can be used.

Abstract: A process for cryogenic separation of a feed stream containing methane and air gases in which: the feed stream is cooled in order to produce a cooled stream, at least one portion of the cooled stream is sent to one level of a distillation column, a bottom stream is drawn off from the distillation column, the bottom stream being enriched in methane relative to the feed stream, a stream enriched in oxygen and in nitrogen relative to the feed stream is drawn off from the distillation column, at least one noncombustible dilution stream that is more volatile than oxygen is introduced into the distillation column at at least one level lower than the one at which the cooled stream is introduced. The dilution stream is extracted from the feed stream. Facility for producing biomethane by purification of biogases derived from non-hazardous waste storage facilities (NHWSF) implementing the process.

Abstract: An apparatus for producing a purified, pressurized liquid carbon dioxide stream includes a distillation column (B) having packing (C) therein and a sump (D) below the packing, the distillation column in fluid communication with the liquid carbon dioxide supply tank for receiving the liquid carbon dioxide stream and the packing stripping volatile impurities from the liquid carbon dioxide stream; a heater (E) in contact with the liquid carbon dioxide stream in the sump (D) for vaporizing the liquid carbon dioxide stream in the sump; a vent in the distillation column (B) from which a first vaporized portion (G) of carbon dioxide vapor in the sump (D) is withdrawn from the distillation column: and a conduit (I) in fluid communication with the sump (D) and from which a second vaporized portion (H) of the carbon dioxide vapor in the sump is withdrawn into the conduit (I) to be introduced into the carbon dioxide vapor feed stream.

Abstract: 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.

Abstract: A method and the apparatus for the cryogenic separation of air in an air separation plant which has a main air compressor, a main heat exchanger and a distillation column system with a high-pressure column and a low-pressure column. All of the feed air is compressed in the main air compressor to a first air pressure which is at least 3 bar higher than the operating pressure of the high-pressure column. A first part of the compressed total air flow, as first air flow at the first air pressure, is cooled and liquefied or pseudo-liquefied in the main heat exchanger, then expanded and introduced into the distillation column system. A second part of the compressed total air flow, as second air flow, is post-compressed in an air post-compressor to a second air pressure and at least part is further compressed in a first turbine-driven post-compressor to a third air pressure.

Abstract: A method for improving the capacity of an existing air separation unit employing a lost air turbine is provided in which the capacity is increased by operating the existing air separation unit as previously operated, with the exception of collecting the lost air from the lost air turbine, and instead of venting said lost air to the atmosphere, the lost air is compressed in a supplemental air compressor and returned to the air separation unit at a location downstream a front-end purification unit and upstream a booster. This setup advantageously allows for increased production without having to adjust the sizing of the front-end purification unit or main air compressor.

Abstract: A method for desulfurizing molten steel comprising taking a sample out from molten steel after tapping from a converter or during secondary refining and analyzing the sample rapidly with high accuracy by a method comprising a high frequency induction heating step wherein the sample is combusted and oxidized under the high frequency induction heating in an oxygen atmosphere having an oxygen purity of 99.5 vol % or more to convert S in the sample into SO2 and an analyzing step wherein SO2-containing gas produced in the high frequency induction heating step is analyzed through an ultraviolet fluorescence method to quantify S concentration of the sample.

Abstract: A method for the production of air gases with variable liquid production by the cryogenic separation of air can include the steps of sending a purified and compressed air stream to a cold box under conditions effective for cryogenically separating the air stream into an oxygen product and nitrogen using a system of columns, wherein the purified and compressed air stream is at a feed pressure when entering the system of columns; withdrawing the oxygen product at a product pressure; delivering the oxygen product at a delivery pressure to an oxygen pipeline, wherein the oxygen pipeline has a pipeline pressure; wherein during the second mode of operation, the method can include monitoring the pipeline pressure; reducing the difference between the pipeline pressure and the delivery pressure; and adjusting liquid production from the cold box. By operating the method in a dynamic fashion, additional liquid production can be realized in instances in which the pipeline pressure deviates from its highest value.

Abstract: A multiple-input/multiple-output control routine in the form of a model predictive control (MPC) routine operates with wireless or other sensors that provide non-periodic, intermittent or otherwise delayed process variable measurement signals at an effective rate that is slower than the MPC controller scan or execution rate. The wireless MPC routine operates normally even when the measurement scan period for the controlled process variables is significantly larger than the operational scan period of the MPC controller routine, while providing control signals that enable control of the process in a robust and acceptable manner. During operation, the MPC routine uses an internal process model to simulate one or more measured process parameter values without performing model bias correction during the scan periods at which no new process parameter measurements are transmitted to the controller.

Abstract: A compressed air stream is cooled in an exchanger to form a compressed cooled air stream. The stream is then cryogenically compressed in a first compressor to form a first pressurized gas stream. The first pressurized gas stream is further cooled in the exchanger, cryogenically compressed in a second compressor, and then it is cooled and partially liquefied. The cooled and partially liquefied product is then fed to a system of distillation columns. A liquid product is removed from the system of distillation columns. This product is then pressurized, vaporized and warmed in the exchanger to yield pressurized gaseous product.

Abstract: A computer-implemented system and method for producing and distributing at least one product from at least one plant to at least one customer where discretized plant production data, filtered customer sourcing data, forecasted customer demand data, and forecasted plant electricity pricing data are input into a modified genetic algorithm and an electronic processor solves the modified genetic algorithm and outputs the solution to an interface. The system and method is flexible and can incorporate data as it becomes available to yield intermediate solutions for quick decision making.

Abstract: A method and apparatus for producing carbon monoxide by cryogenic distillation is presented.

Abstract: Contemplated NGL plants include a feed gas bypass circuit through which a portion of the feed gas is provided downstream to a vapor portion of the feed gas to thereby increase turbo expander inlet temperature and demethanizer temperature. Contemplated configurations are especially advantageous for feed gases with relatively high carbon dioxide content as they entirely avoid carbon dioxide freezing in the demethanizer, provide additional power production by the turboexpander, and recover C2+ components to levels of at least 80% while achieving a low carbon dioxide content in the NGL product.

Abstract: The invention relates to a method for operating a refrigerating installation, according to which the cooling liquid temperature is controlled and stabilized upstream of the expansion valve, and the suction vapor temperature is controlled and stabilized upstream of the condenser in dry expansion systems, thermosyphon installations, two-stage evaporation installations, dry expansion installations having a downstream internal heat exchanger (IWT), and all other refrigerating systems.

Abstract: A method of producing at least one air gas using cryogenic distillation is provided. The expanded streams coming from the two turbines are combined and then split into two fractions. The first fraction is sent to the medium-pressure column of the system in gaseous form, whereas the second fraction is returned to the cold end of the heat exchange line. At a temperature T4 below ?100° C. and above T2, the second fraction is sent to a turbine where it expands up to a temperature T5, forming an air stream. This air stream is then warmed in the heat exchange line before being discharged into the atmosphere, so that the distillation is not disturbed. A liquid product is withdrawn from the column system as final product. The sole liquid product from the apparatus is liquid oxygen, but of course other products may be produced.

Abstract: An air distillation unit comprises an air distillation column (10) suitable for producing a nominal flow of gaseous nitrogen, the top of said column being connected to a liquid nitrogen source (8), and operates by carrying out the following steps: a flow of compressed, cooled and purified air is sent to an exchanger (11) and then to the column, a flow of gaseous nitrogen is withdrawn from the column, the level of liquid at the bottom of the column is controlled; and injection liquid (20), sent from the source to the column, is no longer sent if the required production reduces to at most the nominal production. Application to the separation of air by cryogenic distillation.

Abstract: There is provided a method of generating nitrogen which includes cryogenically separating compressed air introduced into a high-pressure column 11, storing liquid air 13 in a bottom portion of the high-pressure column 11 and taking nitrogen in gaseous form from an upper portion of the high-pressure column 11, introducing the liquid air 13 stored in the bottom portion of the high-pressure column 11 into a low-pressure column 12, cryogenically separating the liquid air 13 introduced into the low-pressure column 12 and storing oxygen-enriched liquid air 22 in a bottom portion of the low-pressure column 12 and taking nitrogen in gaseous form from an upper portion of the low-pressure column 12 as a product gas. Liquid air 13 taken through an extraction pipe 20 is introduced into a portion of a rectification part 12a of the low-pressure column 12 in which the number of theoretical plates from a column bottom side is set within the range of one to ten.

Abstract: A method of producing a liquid product stream, for example, a liquid nitrogen product stream, at a production rate that is selectively varied. This variation is produced in either a waste expansion or air expansion process by increasing the pressure and flow rate of the feed stream during periods in which a high rate of liquid production is desired without substantially increasing the pressure of the exhaust stream produced by a variable speed turboexpander. This increases the expansion ratio across the turboexpander and therefore the refrigeration supplied to increase liquid production. At the same time, the increase in flow rate prevents a decrease in the performance of the variable speed turboexpander.

Abstract: A system includes an air separation unit configured to separate air into an oxygen rich stream and a nitrogen rich stream and a purity control system configured to receive input indicative of a target diluent level. The purity control system is configured to control the air separation unit to adjust an oxygen percentage and a nitrogen percentage of the oxygen rich stream based on the target diluent level.

Abstract: Method and arrangement for adjusting nitrogen and oxygen concentrations within regions of an aircraft. The method includes separating nitrogen from ambient air onboard an aircraft thereby establishing a high-concentration nitrogen supply and then dispensing high-concentration nitrogen from the supply to a fire-susceptible, non-habitable region of the aircraft where the high-concentration nitrogen is reservoired thereby decreasing the capability for the atmosphere therein to support combustion. Oxygen is also separated from the ambient air thereby establishing a high-concentration oxygen supply that is dispensed to an occupant cabin of the aircraft thereby increasing the level of oxygen concentration within the cabin to a level greater than the naturally occurring concentration of oxygen at the experienced internal cabin pressure.

Abstract: In a process for supplying a pressurized gas, a pressurized gas at a high production pressure is produced as an end product by separating a gaseous mixture in a separator apparatus (3, 5), a liquid to be pressurized is stored in a store (9), storing liquid is tapped, and it is pressurized with a pump (11) and at least part of the pressurized liquid is sprayed in a sprayer (27) to produce the pressurized backup gas (29) having substantially the same pressure or a pressure higher than the pressurized gas to be produced, liquid is circulated in a substantially vertical duct (13), optionally within the cold box (33) of the separator apparatus, and at least part of the duct length is at a level above the sprayer and before and/or after starting up the pump (11), liquid is sent from the duct to the sprayer where the liquid is sprayed to provide pressurized backup gas having substantially the same purity or a purity higher than the pressurized gas to be produced (31).

Abstract: A method for controlling a cryogenic distillation unit, for example an air separation unit or a unit for separating a mixture having hydrogen and carbon monoxide as its main components is presented.

Abstract: The method of adding heat to refrigerated rich liquid that accumulates in a reservoir in a distillation column, to prevent the column from flooding, that includes the steps sensing a rise in rich liquid level to predetermined level in the reservoir, removing rich liquid from the reservoir in response to said sensing, to flow to vaporizer apparatus outside a cold box containing said column, adding heat to the removed rich liquid and converting the removed rich liquid into gas, in said vaporizer apparatus, returning said gas to the distillation column, and utilizing heat from the returned gas in the column to remove excess refrigeration from the rich liquid remaining in the column, thereby stabilizing the column against flooding.

Abstract: Method for controlling the production of one or more liquid products produced by one or more plants, that can be an air separation plant, that has a liquid storage capacity and that consumes electrical power. Linguistic values related to current liquid inventory, a rate of change of liquid inventory, projected demand requirements and projected unit power costs are inputted into a expert system controller having one or more rule sets that apply such input linguistic values to produce output linguistic values that are converted back to an output numerical value of a forecasted differential production rate to be applied during a forecast period. The output numerical value of differential production is added to the current production rate of the plants to obtain a new production rate which is applied during the forecast period.

Abstract: A method which include an air intake into an air separation unit; extracting from the separation unit at least a gas stream, essentially consisting of an air gas, in particular oxygen or nitrogen, and directing one or more of these gas streams towards the combustion chamber of a gas turbine; controlling at least one parameter related to the or each gas stream, by acting on a compressor in each gas stream arranged downstream of the air separating unit; assigning to one or more parameter a variable setpoint value, based on a value representing the load of the gas turbine.

Abstract: A cryogenic air separation plant and method of operation wherein, after an interruption in operation, liquid from the sump of a lower pressure column and liquid from the sump of a higher pressure column is passed to a condenser, preferably an argon column top condenser, prior to the restarting of the plant.

Abstract: Method for controlling the production of one or more liquid products produced by one or more plants, that can be an air separation plant, that has a liquid storage capacity and that consumes electrical power. Linguistic values related to current liquid inventory, a rate of change of liquid inventory, projected demand requirements and projected unit power costs are inputted into a expert system controller having one or more rule sets that apply such input linguistic values to produce output linguistic values that are converted back to an output numerical value of a forecasted differential production rate to be applied during a forecast period. The output numerical value of differential production is added to the current production rate of the plants to obtain a new production rate which is applied during the forecast period.

Abstract: A cryogenic air separation system that optimizes the recovery of argon includes an air intake, a high-pressure distillation column, a low-pressure distillation column, a crude argon distillation column, and a controller that automatically controls the composition of the raw argon stream to decrease the concentration of oxygen in the stream while preventing the concentration of nitrogen in the crude argon stream from exceeding a selected value. In addition, the controller also controls the composition of the crude argon stream until an oxygen concentration of the crude argon stream reaches a selected value. The controller may include a multivariable predictive controller.

Abstract: A back-up quantity of a “first” gas is supplied temporarily to maintain the level of production of the first gas from a cryogenic separation of a gaseous mixture comprising the first gas and at least one other gas in the event of reduction in the level of production of said first gas from the separation. In the event of reduction in the level of production of said first gas from the separation, liquefied first gas inventory is withdrawn from the or at least one of said cryogenic distillation systems and vaporised to produce said back-up quantity of first gas. The invention has particular application to the production of gaseous oxygen (“GOX”) from the separation of air.

Abstract: In a method of producing a high-pressure gas in an air separation unit, all the air intended for distillation is compressed in a compressor (1), the compressed air is purified, at least a first portion of the air is supercharged to a high pressure, the compressed and purified air is sent into a heat exchange line (6) of the unit where it cools, the compressed, purified and cooled air is separated in a system of columns of the unit comprising at least one distillation column (8, 9), a fluid (16) is withdrawn in the liquid state from one column of the system of columns, the said fluid is brought in the liquid state to the high pressure, it is vaporized by heat exchange with the air and the vaporized liquid at this high pressure is warmed in the heat exchange line of the installation, at least one portion of the supercharged air is expanded in an expansion turbine (4) from the high pressure to a second pressure, the expanded air then being sent into one column of the system of columns and during start-up of the

Abstract: The invention concerns a method which consists in: intake (through 18) of air into said separation unit (16); extracting from said separation unit at least a gas stream (through 20, 26), essentially consisting of an air gas, in particular oxygen or nitrogen, and in directing the or each gas stream towards a combustion chamber (8) of the gas turbine (2); controlling at least one parameter related to the or each gas stream, by acting on a compressor (22, 28) of said gas stream arranged downstream of said air separating unit (16); assigning to the or each parameter a variable setpoint value, based on a value representing the load of the gas turbine (2).

Abstract: Controlling the production of a liquefied natural gas (31) comprises measuring the temperature (50) and the flow rate (55) of the liquefied natural gas (31); maintaining the flow rate of the heavy mixed refrigerant (60a) at an operator manipulated set point (80), and determining the flow rate of the light mixed refrigerant (86) from (i) the flow rate of the heavy mixed refrigerant (80) and (ii) an operator manipulated set point for the ratio of the flow rate of the heavy mixed refrigerant to the flow rate of the light mixed refrigerant (81); determining a dependent set point (91) for the ratio of the flow rate of the liquefied natural gas to the flow rate of the heavy mixed refrigerant such that the temperature (50) of the liquefied natural gas is maintained at an operator manipulated set point (90); determining a dependent set point (95) for the flow rate of the liquefied natural gas (95) from (i) the dependent set point (91) for the ratio of the flow rate of the liquefied natural gas product stream to the f

Abstract: A back-up quantity of a “first” gas is supplied temporarily to maintain the level of production of the first gas from a cryogenic separation of a gaseous mixture comprising the first gas and at least one other gas in the event of reduction in the level of production of said first gas from the separation. In the event of reduction in the level of production of said first gas from the separation, liquefied first gas inventory is withdrawn from the or at least one of said cryogenic distillation systems and vaporised to produce said back-up quantity of first gas. The invention has particular application to the production of gaseous oxygen (“GOX”) from the separation of air.

Abstract: A method for operating a cryogenic plant using an online real-time monitoring and diagnostic system that continually compares actual versus expected plant key performance indicators, alerts operating personnel to any significant performance shortfall, assists in required diagnostics, and suggests corrective actions, preferably using a top-down diagnostic tree methodology that presents calculated key performance indicators to the operator in a manner which logically flows from plant overview to detailed breakdown by plant area and equipment component.

Abstract: A method for controlling the operation of a plant such as a cryogenic rectification plant wherein process parameters are quantitatively determined and then are qualitatively categorized to establish by reference to a rule set the general adjustment required for a plant element prior to determining the numerical adjustment for that element.

Abstract: An air separation unit including an air intake, a high pressure cryogenic distillation column receiving air from the air intake and producing an oxygen rich liquid reflux, and a low-pressure cryogenic distillation column. An adaptive controller controls the flow rate of the oxygen-rich liquid from the first distillation column into the second distillation column, wherein during plant upsets, the adaptive controller maintains the level of oxygen-rich liquid in the first distillation column at a substantially constant level by adjusting a flow rate of the oxygen rich liquid into the second distillation column, and wherein the argon content of the argon-rich output stream from the second distillation column remains substantially constant.

Abstract: The process and the apparatus serve for separating a gas mixture in a separation plant. A feed gas (18) is introduced into a compressor system (6, 16) and then into the separation plant. In the event of loss or partial loss of the compressor system (6, 16) of the first feed gas compressor (6), a first auxiliary stream (91, 92) which has approximately the composition of the first product stream or approximately the composition of the feed gas is compressed (78, 89) to at least approximately the first pressure and is recirculated to the separation plant.

Abstract: An air separation unit including an air intake, a high pressure cryogenic distillation column receiving air from the air intake and producing an oxygen rich liquid reflux, and a low-pressure cryogenic distillation column. An adaptive controller controls the flow rate of the oxygen-rich liquid from the first distillation column into the second distillation column, wherein during plant upsets, the adaptive controller maintains the level of oxygen-rich liquid in the first distillation column at a substantially constant level by adjusting a flow rate of the oxygen rich liquid into the second distillation column, and wherein the argon content of the argon-rich output stream from the second distillation column remains substantially constant.

Abstract: For adjusting the capacity of a low-temperature rectification unit having a high pressure column and a low pressure column in which a fluid is introduced into the high pressure column (1) and in which liquid from the bottom of the high pressure column is directed into the low pressure column (2), the amount of liquid that is removed from the bottom of high pressure and fed to the low pressure column (2) is controlled via flow adjustment (4), wherein a nominal value for flow adjustment (4) is set to a desired amount of flow, and the liquid level of the liquid at the bottom of column (1) that operates at higher pressure is fixed without a set nominal value corresponding to the amount of liquid that is removed.

Abstract: In a single column distillation system for obtaining gaseous and liquid nitrogen with a variable proportions of liquid product by low-temperature separation from air, a first portion (12, 13) of nitrogen-rich fraction (5, 7, 8) is fed downstream of circulation compressor (9) to the liquefaction chamber of a condenser-evaporator (14) associated with the single column and condensed under a pressure higher than the operating pressure of the single column (4). A liquid oxygen-enriched fraction (228, 231) from the distillation column system is at least partially evaporated in the evaporation chamber of condenser-evaporator (14). A portion (18) of nitrogen-rich liquid (15, 16) from condenser-evaporator (14) is drawn off at least at times as liquid product. A second oxygen-enriched gas (221, 521) is removed from one of columns (546) of the distillation system and/or from the evaporation chamber of condenser-evaporator (14), machine expanded(23), and heated in main heat exchanger (2).

Abstract: A method of producing a gaseous product, for instance gaseous oxygen in accordance with a cyclical demand pattern having high and low periods of demand. During periods of high demand, liquid is vaporized against condensing air which is in turn stored. During low demand periods, product is accumulated and previously stored liquid air is introduced into the column. During both high and low periods of demand liquid product is drawn to reduce the percentage variance in the required flow rate to the booster compressor used in producing the air to be liquefied. Preferably, during periods of high demand, a turbine used in generating refrigeration can be turned down to increase the amount of air available for condensation and with a reduction in production of liquid product.

Abstract: A method for automatically setting a target production level for at least one air separation unit in a network of air separation units. Each air separation unit has a plurality of field elements and at least one regulatory controller associated with one of the field elements, and has an energy usage level corresponding to a level of production. The method includes receiving a production level requirement for the network of air separation units and generating a production target level for at least one of the air separation units which minimizes and/or optimizes the sum of the ASU energy usage levels. The ASUs then can automatically ramp the plant production to the appropriate production target levels via the use of advanced process control (multivariable process controllers and/or advanced feedforward controllers), advanced regulatory control, and regulatory control means.

Abstract: A film-type vaporizer in a vaporization enclosure, for example the upper column of a double air-distillation column, is associated with a measurement and analysis box where a polished surface and a spillway reconstruct the flow of liquid in the vaporizer in order to check for the absence of the deposition of impurities in the liquid that is to be evaporated. If deposition occurs, the impurities involved are quantified and analyzed and appropriate action taken on the settings of the machine.

Abstract: A system for re-starting an air separation plant after an interruption in operation wherein descending liquid is collected in a non-operating distillation column and passed back to the separation section of that column before or upon re-start. The invention may employ a collection device situated in the column above the sump. Upon interruption in operation, the collection device accumulates descending liquid. From the collection device, liquid may be passed outside of the column and transferred to a holding vessel to re-inventory internal material of the column upon resumption in operation.

Abstract: In a process for the production of a pressurized gaseous product by low-temperature separation of air, which is at times done in a gas operation and at times in a combined operation, whereby in the gas operation and in the combined operation (a) purified charging air is cooled under pressure, partially liquefied, and subjected to rectification to produce gaseous and liquid fractions, (b) extremely cold liquid of at least one of the liquid fractions from the rectification is evaporated under elevated pressure by indirect heat exchange with feed air, heated, and obtained as a pressurized gaseous product, whereby in combined operation, (c) the cold that is required for this purpose is generated in an air-refrigeration cycle, by air being compressed in the refrigeration cycle and work expanded, in which case heat is removed from the air, and the actively depressurized air that is partially in countercurrent is heated again with the charging air that is to be cooled and then repressurized, (d) extremely cold liqui

Abstract: The plant comprises, on site, a compressed-air provision and distribution system (L.sub.A) with at least one dedicated air compressor (CO2, CO3), an air-gas production and provision system (L.sub.G) comprising an air treatment unit (S), with a reservoir R of the said air gas and normally fed by a compressor (CO1). In temporary operating mode, with one air compressor (CO2) off-line, the compressed air from the compressor (CO1) of the air gas provision system (S) is at least in part diverted (C), typically with pressure reduction (D), to sustain the production of the compressed air system (L.sub.A), the air gas then being at least in part provided by the reservoir (R).

Abstract: In a process for the cryogenic separation of air and recovery of argon in a distillation system having at least one distillation column that produces a nitrogen-enriched stream, an oxygen enriched stream, and an argon-enriched stream, and at least one sidearm column which receives the argon-enriched stream from the distillation column, controlling argon recovery by manipulating the total amount of argon inventory within the system at a given time.

Abstract: A process for separating mixtures which comprise oxygen, nitrogen, and argon by cryogenic distillation in a distillation system where the system is comprised of a distillation column that produces a nitrogen-enriched stream, an oxygen-enriched stream, and an argon-enriched stream, and a sidearm column which has a sump and receives the argon-enriched stream from the distillation column. During an interruption of flow of the argon-enriched stream into the sidearm column, the liquid inventory in the sidearm column is collected at a point above the sump and recirculated through the sidearm column during re-startup of the sidearm column.

Abstract: A cryogenic air separation system which is subject to periods of significant changes in product demand is controlled during such periods to minimize the impact of transient operation on product purity. A double-column distillation system is utilized in which a nitrogen-rich liquid is withdrawn from the higher-pressure column and introduced into the lower-pressure column as reflux. An inventory of this liquid is maintained in a holdup tank for storage or withdrawal during periods of transient operation. In addition, nitrogen vapor product from the lower-pressure column is recycled to the higher-pressure column, and the nitrogen vapor recycle rate is controlled as a function of the liquid level in the holdup tank. The flow rate of nitrogen-rich liquid withdrawn from the higher-pressure column is controlled as a function of its composition.

Abstract: The plant comprises, on site, a compressed-air provision and distribution system (LA) with at least one dedicated air compressor (CO2, CO3), an air-gas production and provision system (LG) comprising an air treatment unit (S), with a reservoir R of the said air gas and normally fed by a compressor (CO1). In temporary operating mode, with one air compressor (CO2) off-line, the compressed air from the compressor (CO1) of the air gas provision system (S) is at least in part diverted (C), typically with pressure reduction (D), to sustain the production of the compressed air system (LA), the air gas then being at least in part provided by the reservoir (R).