US 2025/0091869 A1Published application

Mono pressure system for producing nitric acid and method of operating thereof

AssigneeYara International Asa

InventorsBent VIGELAND, Halvor ØIEN, Krzysztof BANASIAK, Andre DE SMET, Peter FAUCONNIER

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Abstract

A system for producing nitric acid at reduced power consumption, including an air compressor producing a compressed air stream; a source of pressurized oxygen-rich gas having a pressure higher than the pressure of the compressed air stream; a mixing apparatus for mixing the oxygen-rich gas/compressed air stream mixture with an ammonia gas stream; an ammonia converter to provide in a NOx gas/steam mixture; a water cooler/condenser for separating and condensing steam from NOx gas in the gaseous NOx gas/steam mixture; an absorption tower downstream the water cooler/condenser, for absorbing NOx gases in water, to provide in a stream of raw nitric acid-containing residual NOx gas and a tail gas including NOx gases. The system further includes a mechanism for splitting the tail gas into a first tail gas stream and a second tail gas stream; and a mechanism for adjusting the amount of tail gas being split.

Claims18

Dependent claims

A system for producing nitric acid at reduced power consumption, comprising:

an air compressor for compressing air to a pressure P1, comprising an inlet and an outlet, to provide in a compressed air stream;
a source of pressurized oxygen-rich gas having a pressure higher than P1, in fluid communication with the compressed air stream, to provide in an oxygen-rich gas/compressed air stream mixture;
a mixing apparatus for mixing the oxygen-rich gas/compressed air stream mixture with an ammonia gas stream, to provide in an ammonia/oxygen-enriched air mixture;
an ammonia converter for oxidising ammonia in the ammonia/oxygen-enriched air mixture, to provide in a NOx gas/steam mixture, comprising water and nitric oxide;
means for measuring a temperature in the ammonia converter;
means for regulating a concentration of ammonia and of oxygen in the ammonia converter;
a steam turbine or an electric motor and means for converting steam into power, in fluid communication with the ammonia converter or the NOx gas/steam mixture;
a water cooler/condenser for separating and condensing steam from NOx gas in the NOx gas/steam mixture, to provide in an aqueous diluted nitric acid mixture and a gaseous NOx stream;
an absorption tower downstream the water cooler/condenser, for absorbing the NOx gases from the gaseous NOx stream in water, to provide in a stream of raw nitric acid-containing residual NOx gas and a tail gas comprising NOx gases, comprising an absorption tower tail gas outlet for evacuating the tail gas;
and
a tail gas expander for expanding the tail gas downstream of the absorption tower comprising a tail gas expander inlet in fluid communication with the absorption tower tail gas outlet, and a tail gas expander outlet;
characterized in that the system further comprises:
means for splitting the tail gas into a first tail gas stream directed to the tail gas expander inlet and a second tail gas stream directed to means for pressurizing for pressurizing the tail gas stream to a pressure of about P1 in fluid communication with the compressed air stream, to provide in a pressurized tail gas stream joining the compressed air stream;
and
means for adjusting an amount of tail gas being split into the tail gas stream directed to the tail gas expander inlet and the tail gas stream directed to means for pressurizing.

12 more elements

A method for producing nitric acid at reduced power consumption, comprising steps of:

a) compressing air in an air compressor, thereby producing a compressed air stream having a pressure P1;
b) mixing pressurized oxygen-rich gas having a pressure higher than P1 with the compressed air stream, thereby obtaining an oxygen-rich gas/compressed air stream mixture;
c) mixing the oxygen-rich gas/compressed air stream mixture with an ammonia gas stream in a mixing apparatus, thereby producing an ammonia/oxygen-enriched air mixture;
d) oxidising ammonia in the ammonia/oxygen-enriched air mixture in an ammonia converter at a temperature ranging from 800 to 950° C., thereby producing a gaseous NOx gas/steam mixture, comprising water and nitric oxide;
e) converting steam generated in the ammonia converter or from the gaseous NOx gas/steam mixture into power;
f) separating and condensing steam from NOx gas in the gaseous NOx gas/steam mixture, thereby generating an aqueous diluted nitric acid mixture and a gaseous NOx stream, in a water cooler/condenser;
g) absorbing the gaseous NOx stream in an absorption tower, thereby producing a stream of raw nitric acid-containing residual NOx gas and a tail gas comprising NOx gases;
and
h) expanding the tail gas or heated tail gas in a tail gas expander;
characterized in that the method further comprises the steps of:
i) pressurizing part of the tail gas obtained from step g) to a pressure about P1, thereby generating a pressurized tail gas;
j) mixing the pressurized tail gas with the compressed air stream;
k) measuring the temperature in the ammonia converter;
and
I) adjusting a gas volume being pressurized in step i) if the temperature measured in step k) is outside a range of 800-950° C., such that the temperature in the ammonia converter is maintained in the range of 800 and 950° C.

12 more elements

Dependencies are inferred from the claim text.