Method And Apparatus For Providing Nitrogen

Abstract

A method and apparatus for providing nitrogen is provided.

1 - 7 . (canceled) 
     
     
         8 . A method for providing nitrogen by means of an apparatus for producing gaseous nitrogen by air separation and by vaporization of liquid nitrogen, wherein:
 a) providing nitrogen to the customer exclusively by vaporization of liquid nitrogen if the customer's requirements for gaseous nitrogen are below a first threshold;   b) providing nitrogen to the customer at least partially by the apparatus for producing nitrogen if the customer's requirements for gaseous nitrogen are greater than a second threshold, the second threshold being greater than the first threshold.   
     
     
         9 . The method for providing nitrogen as claimed in  claim 8 , wherein if the customer's requirements for nitrogen exceed a third threshold, greater than the second threshold, the customer is provided partially by the apparatus for producing nitrogen and partially by vaporization of liquid nitrogen. 
     
     
         10 . The method as claimed in  claim 9 , wherein the customer's requirements are between the second and third threshold, and the customer is provided solely by the apparatus for producing nitrogen. 
     
     
         11 . The method as claimed in  claim 8 , wherein if the customer's requirements for gaseous nitrogen are greater than the second threshold, the customer is provided with nitrogen solely by the apparatus for producing nitrogen. 
     
     
         12 . The method of  claim 9 , wherein at least one of the first, second and third thresholds is variable according to the price of electricity and/or the price of liquid nitrogen and/or the quantity of liquid nitrogen in a storage vessel connected to the means of vaporization and/or the rate of change of the quantity of liquid nitrogen in the storage vessel. 
     
     
         13 . The method of  claim 9 , wherein if the customer's requirements for gaseous nitrogen are greater than the second threshold and as the case may be below the third threshold, the apparatus for producing nitrogen produces gaseous nitrogen with a substantially constant flow rate and
 a) if the customer's requirements for gaseous nitrogen are less than the substantially constant flow rate, the excess part of gaseous nitrogen is discharged to atmosphere and the rest of the gaseous nitrogen is conveyed to the customer.   b) if the customer's requirements for gaseous nitrogen are greater than or equal to the substantially constant flow rate, all the gaseous nitrogen flow is conveyed to the customer.   
     
     
         14 . The method of  claim 8 , wherein the apparatus for producing gaseous nitrogen is a cryogenic air distillation apparatus, and as the case may be liquid nitrogen is conveyed to the apparatus for producing gaseous nitrogen in order to participate in keeping it cold.