Method And Apparatus For The Production Of Gas From Air In Highly Flexible Gaseous And Liquid Form By Cryogenic Distillation

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 T 4 below −100° C. and above T 2, the second fraction is sent to a turbine where it expands up to a temperature T 5, 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 A liquid product is withdrawn from the column system as final product.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.

1 - 13 . (canceled) 
     
     
         14 . A method of producing at least one air gas using cryogenic distillation in a system of columns comprising at least one medium-pressure column operating at a medium pressure and a low-pressure column operating at a low pressure, said at least one medium-pressure column and low-pressure column being thermally coupled to one another, comprising, in a first and a second operating mode:
 a) raising a compressed air stream to a high pressure, at least 5 bar above the pressure of the medium-pressure column, and purifying said air stream at this high pressure,   b) varying said high pressure according to the demand for said at least one air gas;   c) cooling a first part of the air stream in a heat exchange line to an intermediate temperature, and expanding said cooled first part in at least a first turbine;   d) compressing at least a fraction of the air stream to a higher pressure in a supercharger, wherein said higher pressure is greater than or equal to the high pressure, cooling said higher pressure air stream n the heat exchange line down to a temperature less than or equal to −100° C., and returning the supercharged stream to the heat exchange line in which at least part becomes liquefied at the cold end and is then sent into the system of columns following expansion;   e) vaporizing a pressurized liquid product from the system of columns in the heat exchange line; and   in the first operating mode:   f) admitting a gaseous fraction of the air stream into an auxiliary turbine, said fraction having been cooled in the main heat exchange line;   g) expanding at least part of the air stream rate in the auxiliary turbine, warming said expanded stream in the heat exchange; and   in the second operating mode:   h) reducing the flow rate of the air stream processed in the auxiliary turbine, by comparison with the stream processed in the auxiliary turbine in the first mode; and   i) decreasing the production of liquid by way of end product by comparison with the production of liquid by way of end product in the first mode.   
     
     
         15 . The method of  claim 14 , in which the turbine is braked by an air supercharger. 
     
     
         16 . The method of  claim 14 , in which the supercharger is coupled to one of the turbines, and admits at ambient temperature. 
     
     
         17 . The method of  claim 14 , the supercharger is mechanically coupled to the first turbine and has an admission temperature of below −100° C. 
     
     
         18 . The method of  claim 14 , in which the admission temperature of the first turbine differs by at most 15° C. from the oxygen pseudo-vaporization temperature. 
     
     
         19 . The method of  claim 14 , in which the flow rate of the incoming main air is reduced, during the second mode, preferably by a flow rate at least equal to the reduction in the flow rate of the air sent to the auxiliary turbine during the second mode. 
     
     
         20 . The method of  claim 19 , in which the variation in main air flow rate is afforded by the variable vanes of a compressor. 
     
     
         21 . The method of  claim 19 , in which the variation in main air flow rate is afforded by starting and/or stopping an auxiliary air compressor. 
     
     
         22 . The method of  claim 14 , in which the main air pressure varies between the first mode and the second mode. 
     
     
         23 . The method of  claim 14 , in which the first part of the air is supercharged to a pressure higher than the main pressure upstream of the first turbine so that it enters the first turbine substantially at a pressure higher than the main pressure. 
     
     
         24 . The method of  claim 14 , wherein a second part of the air stream is expanded in at least a second turbine the admission and delivery conditions of which differ by at most 5 bar and by at most 15° C. or are identical in terms of pressure and temperature to those of the first turbine. 
     
     
         25 . The method of  claim 14 , wherein the work provided by the first or a third turbine is used at least in part for the work required by the supercharger. 
     
     
         26 . The method of  claim 14 , wherein the admission pressure of the first turbine is substantially higher than the medium pressure. 
     
     
         27 . The method of  claim 14 , wherein the admission pressure of the first turbine is substantially equal to the medium pressure. 
     
     
         28 . The method of  claim 14 , wherein the delivery pressure of the auxiliary turbine is at least  2  bar greater or substantially equal to the high pressure. 
     
     
         29 . The method of  claim 14 , wherein the delivery pressure of the auxiliary turbine is substantially equal to the high pressure. 
     
     
         30 . The method of  claim 14 , wherein some of the constituents of the air are produced by way of end product in liquid form. 
     
     
         31 . The method of  claim 14 , further comprising reducing the flow rate of the air stream processed in the auxiliary turbine, by comparison with the stream processed in the auxiliary turbine in the first mode, to zero. 
     
     
         32 . The method of  claim 14 , further comprising decreasing the production of liquid by way of end product by comparison with the production of liquid by way of end product in the first mode, to zero. 
     
     
         33 . The method of  claim 14 , wherein the admission temperature of the auxiliary turbine is higher than the admission temperature of the first turbine. 
     
     
         34 . A unit for cooling and heating streams intended for and coming from a system of air separation columns comprising a heat exchange line, a first turbine, an auxiliary turbine, a supercharger, the heat exchange line comprising:
 i) at least one passage for receiving a first purified air stream, the at least one passage for receiving a first purified air stream being connected to the supercharger,   ii) at least one passage connected to the delivery of the supercharger, the at least one passage connected to the supercharger being connected to the first turbine,   iii) at least two passages for receiving at least two fluids ( 35 ,  37 ) which become heated,   iv) at least one passage to receive a second purified air flow rate, the at least one passage for receiving the second purified air stream being connected to the admission of the auxiliary turbine and the delivery of the auxiliary turbine being connected to at least one passage for air to be heated.   
     
     
         35 . The unit of  claim 34 , configured in such a way that, in operation, one of the following conditions is met:
 i) the admission temperature of the auxiliary turbine is greater than the admission temperature of the first turbine;   ii) the admission temperature of the auxiliary turbine is greater than the admission temperature of the supercharger;   iii) the admission temperature of the supercharger is lower than the admission temperature of the first turbine;   iv) the delivery temperature of the supercharger is greater than the admission temperature of the first turbine;   v) the delivery temperature of the supercharger is greater than the delivery temperature of the auxiliary turbine.