Process and plant for providing a nitrogen product, an oxygen product and a hydrogen product

Abstract

A method for providing a nitrogen product, an oxygen product and a hydrogen product, wherein an air separation installation is used which is designed for the low-temperature separation of feed air and which has a rectification column system, the rectification column system comprising an air-fed rectification column and a main heat exchanger. The provision of the nitrogen product comprises, in particular, subjecting feed air to low-temperature rectification using the air-fed rectification column such that a tops gas is obtained, and using part of the tops gas as the nitrogen product. The provision of the oxygen product and the hydrogen product comprises subjecting water to water electrolysis in an electrolyzer, such that a water-containing oxygen stream and a hydrogen stream are obtained, the water-containing oxygen stream or part thereof being subjected, at least in one operating phase, to drying and, in an unmixed state, to liquefaction in the air separation installation.

1 . A method for providing a nitrogen product, an oxygen product and a hydrogen product, wherein an air separation installation is used which is designed for the low-temperature separation of feed air and which has a rectification column system, the rectification column system comprising an air-fed rectification column and a main heat exchanger for cooling the feed air, the provision of the nitrogen product comprising subjecting feed air to low-temperature rectification using the rectification column system and taking the nitrogen product or a precursor thereof from the rectification column system, wherein the provision of the oxygen product and the hydrogen product comprises subjecting water to water electrolysis in an electrolyzer, such that a water-containing oxygen stream and a hydrogen stream are obtained, the water-containing oxygen stream or part thereof being subjected, at least in one operating phase, to drying and optionally to further purification steps such that a liquid oxygen stream is obtained, and the dried oxygen stream thereafter being introduced into the air separation installation without being mixed with a process stream of the air separation installation, and being subjected in an unmixed state to liquefaction in the air separation installation, and the liquid oxygen stream produced in the process or part thereof being used to provide the oxygen product. 
     
     
         2 . The method according to  claim 1 , wherein the liquefaction of the dried oxygen stream is performed in the main heat exchanger, a supercooling counterflow unit of the air separation, in the supercooling part of a combined main heat exchanger-supercooler or in a separate heat exchanger of the air separation installation independent of the main heat exchanger and optionally the supercooling counterflow unit. 
     
     
         3 . The method according to  claim 1 , wherein the feed air is subjected to the low-temperature rectification using the air-fed rectification column such that a tops gas is obtained, part of the tops gas being used as the nitrogen product or a precursor of the nitrogen product, two material streams with different oxygen contents being formed in a condenser evaporator by evaporating liquid from the air-fed rectification column, and a further part of the tops gas being condensed in the condenser evaporator and returned to the air-fed rectification column . 
     
     
         4 . The method according to  claim 1 , wherein the water-containing oxygen stream is provided using electrolysis, in particular high-pressure electrolysis. 
     
     
         5 . The method according to  claim 1 , wherein the water-containing oxygen stream or part thereof is subjected to compression after drying ( 21 ) and before liquefaction in the main heat exchanger. 
     
     
         6 . The method according to  claim 1 , wherein the provision of the oxygen product comprises purification, in particular rectification for depletion of argon. 
     
     
         7 . The method according to  claim 1 , wherein the liquid oxygen stream is formed only in a first operating phase, the liquid oxygen stream being temporarily stored in the first operating phase for later provision of the oxygen product, and the oxygen product being obtained in a second operating phase using the temporarily stored liquid oxygen stream or part thereof with heating in the main heat exchanger as a gaseous pressurized oxygen product. 
     
     
         8 . The method according to  claim 7 , wherein, in the second operating phase, a gaseous nitrogen stream is subjected to liquefaction in the main heat exchanger so as to obtain a liquid nitrogen stream, the liquid nitrogen stream or part thereof being used as the or a further nitrogen product or being temporarily stored for later provision of the or a further nitrogen product. 
     
     
         9 . The method according to  claim 1 , wherein the liquefaction is performed using liquid air. 
     
     
         10 . The method according to  claim 1 , wherein the air-fed rectification column is operated using a condenser evaporator, in which a first and a second material stream are formed below an operating pressure level of the air-fed rectification column by evaporating liquid from the air-fed rectification column, further tops gas from the air-fed rectification column being condensed in the condenser evaporator and returned to the air-fed rectification column as a return flow. 
     
     
         11 . The method according to  claim 10 , wherein the first material stream is formed with a first oxygen content and the second material stream is formed with a second oxygen content above the first oxygen content, the first material stream or part thereof being subjected to recompression to the first pressure level and being fed into the air-fed rectification column, and the second material stream or part thereof being subjected to a work-performing expansion and being discharged from the installation. 
     
     
         12 . The method according to  claim 10 , wherein a further rectification column fed from the air-fed rectification column is used, wherein bottoms liquid from the second rectification column is used to provide the oxygen product. 
     
     
         13 . The method according to  claim 12 , wherein the liquid oxygen stream is fed into the further rectification column. 
     
     
         14 . An installation for providing a nitrogen product, an oxygen product and a hydrogen product, the installation comprising an air separation installation for low-temperature separation of feed air, which air separation installation in turn has a rectification column system comprising an air-fed rectification column, a main heat exchanger for cooling the feed air, the installation for providing the nitrogen product being designed to subject feed air to low-temperature rectification using the rectification column system and to take the nitrogen product or a precursor thereof from the rectification column system, wherein the installation comprises an electrolyzer designed to subject, for the provision of the oxygen product and the hydrogen product so as to obtain a water-containing oxygen stream and a hydrogen stream, to a water electrolysis, the installation being designed to subject the water-containing oxygen stream or part thereof, at least in an operating phase, to drying ( 21 ), so as to obtain a liquid oxygen stream and without mixing with a process stream of the air separation installation, and thereafter, in an unmixed state, to liquefaction in the air separation installation and to use the liquid oxygen stream produced in this process or part thereof to provide the oxygen product.