Chemistry of inorganic compounds – Nitrogen or compound thereof – Ammonia or ammonium hydroxide
Reexamination Certificate
1999-02-25
2001-02-20
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Nitrogen or compound thereof
Ammonia or ammonium hydroxide
C075S458000, C252S374000, C252S375000, C252S377000, C423S359000, C422S148000, C422S186220
Reexamination Certificate
active
06190632
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to the production of ammonia and, more particularly, to the production of ammonia synthesis gas from a blast furnace and the use of cryogenic rectification to enable the use of such synthesis gas for ammonia production.
BACKGROUND ART
In the operation of a blast furnace, coke is partially oxidized with air and the resulting reducing gases are used to reduce iron ore to produce iron. Modern furnace operation includes enrichment of the air with oxygen and the addition of other hydrocarbons such as coal or natural gas. The off gases from the blast furnace contain some heating value and are generally used as a fuel for power and steam generation. While this is an effective use for this gas, it is desirable to have a better use for this gas, especially in light of expected reductions in the cost of electricity available through the power grid.
Accordingly, it is an object of this invention to provide a method whereby the off gases from a blast furnace may be effectively employed to produce ammonia.
SUMMARY OF THE INVENTION
In general the invention serves to effectively integrate a blast furnace with an ammonia production plant using cryogenic rectification to effect the integration. The cryogenic rectification improves the blast furnace operation and enables off gas from the blast furnace to be used to produce ammonia.
The above and other objects and advantages, which will become apparent to one skilled in the art upon a reading of this disclosure, are attained by the present invention one aspect of which is:
A method for producing ammonia using cryogenic rectification comprising:
(A) separating air in a cryogenic air separation plant by cryogenic rectification to produce oxygen;
(B) mixing oxygen from the cryogenic air separation plant with air to form blast air comprising from about 22 to 50 mole percent oxygen with the remainder comprised primarily of nitrogen;
(C) passing the blast air into a blast furnace and combusting oxygen of the blast air with hydrocarbon in the blast furnace to produce blast furnace gas comprising nitrogen, carbon monoxide and hydrogen;
(D) reacting the carbon monoxide with steam to produce carbon dioxide and additional hydrogen, and removing the carbon dioxide from the blast furnace gas to produce fortified blast furnace gas comprising nitrogen and hydrogen;
(E) passing the fortified blast furnace gas into a cryogenic rectification plant and separating the fortified blast furnace gas within the cryogenic rectification plant to produce ammonia syntheses gas comprising hydrogen and nitrogen in about at 3 to 1 ratio; and
(F) passing ammonia synthesis gas from the cryogenic rectification plant to an ammonia production plant and reacting hydrogen and nitrogen of the ammonia synthesis gas within the ammonia production plant to produce ammonia.
Another aspect of the invention is:
Apparatus for producing ammonia comprising:
(A) a cryogenic air separation plant and means for passing feed air into the cryogenic air separation plant;
(B) a blast furnace, means for passing oxygen from the cryogenic air separation into the blast furnace, and means for passing fuel into the blast furnace;
(C) a water gas shift reaction section, means for passing blast furnace gas from the blast furnace to the water gas shift reaction section, and means for passing steam into the water gas shift reaction section;
(D) a carbon dioxide removal unit and means for passing gas from the water gas shift reaction section to the carbon dioxide removal unit;
(E) a cryogenic rectification plant and means for passing gas from the carbon dioxide removal unit into the cryogenic rectification plant; and
(F) an ammonia production plant, means for passing gas from the cryogenic rectification plant into the ammonia production plant, and means for recovering ammonia from the ammonia production plant.
As used herein, the term “iron ore” means one or more oxides of iron such as ferric oxide and ferrous oxide.
As used herein, the term “column” means a distillation or fractionation column or zone, i.e. a contacting column or zone, wherein liquid and vapor phases are countercurrently contacted to effect separation of a fluid mixture, as for example, by contacting of the vapor and liquid phases on a series of vertically spaced trays or plates mounted within the column and/or packing elements such as structured or random packing.
As used herein, the term “cryogenic rectification plant” means a separation plant wherein at least part of the operation of the plant is carried out at temperatures at or below 150 degrees Kelvin (K).
As used herein, the term “cryogenic air separation plant” means a cryogenic rectification plant comprising at least one column and wherein feed air is separated to produce at least one of product oxygen and product nitrogen.
REFERENCES:
patent: 3872025 (1975-03-01), Singleton
patent: 4013454 (1977-03-01), Jordan
patent: 4363654 (1982-12-01), Frederick et al.
patent: 4409196 (1983-10-01), Skinner et al.
patent: 5582029 (1996-12-01), Occhialini et al.
patent: 5582036 (1996-12-01), Drnevich et al.
patent: 6045602 (2000-04-01), Shah
patent: 0126961 (1984-12-01), None
patent: 271464 (1988-06-01), None
patent: 9728284 (1997-07-01), None
Drnevich Raymond Francis
Shah Minish Mahendra
Black Donald T.
Griffin Steven P.
Medina Maribel
Praxair Technology Inc.
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