The present invention relates to a process and to a unit for cryogenically separating a mixture of nitrogen and carbon monoxide.
The units for producing carbon monoxide and hydrogen may be separated into two parts:
In the case of a syngas resulting from a steam reforming furnace, for the production of CO and hydrogen under pressure, the most common cryogenic process is methane scrubbing, the residual methane content in the syngas being compatible with the methane scrubbing process. In certain cases, it is necessary to include a CO/N2 separation column in the cold box, especially when the nitrogen content in the natural gas is not compatible with the purity of the CO product without this CO/N2 column.
A methane scrubbing layout with CO/N2 column is described in FR-A-2910603.
In the case of certain coal gasification processes, the syngas produced is treated in a cold box by partial condensation with no cycle, the content of inert species (CH4, Ar and N2) being very low and compatible with the purity of the CO.
A partial condensation layout without a separation column is described in EP-A-1729077 and in FR-A-2930332.
A partial condensation layout with a CO/N2 column is described in U.S. Pat. No. 4,478,621. The reboiling of the CO/N2 column being provided by a direct feed of CO at medium pressure into the bottom of the column coming from the CO compressor.
DE-A-4228784 and DE-A-2147465 describe processes comprising the features of the preamble of claim 1 that are similar to that of
According to
In the case where the methane content in the syngas does not enable a methane scrubbing process in the combined production of CO and hydrogen and where the nitrogen content in the syngas is not compatible with the purity of CO without CO/N2 separation, the unit according to an embodiment of the invention is a partial condensation unit including a CO/N2 column with common integrated cycle for the cooling of the syngas and for the CO/N2 separation energy.
In one embodiment, at least one portion of the CO/N2 column reboiling energy is provided by an external reboiler where the feed gas of the CO/N2 column is completely or partially condensed. This makes it possible to reduce the MPCO stream of the cycle compressor and thus to reduce the energy of the compressor by around 15%.
The process layout may include a CO/N2 distillation column alone or else a CO/N2 column with a CO/CH4 column.
Additionally, an embodiment of the invention may also be applied when it is desired to introduce a CO/N2 separation column treating impure CO coming from a cold box that does not comprise a CO/N2 column. Since the nitrogen content in the CO increases over time, it then becomes useful to add a CO/N2 separation step. The new column is then installed in a dedicated cold box that it is necessary to supply with refrigeration and reboiling energy.
According to one subject of the invention, a process is provided for separating a feed gas containing, as main components, nitrogen and carbon monoxide and optionally hydrogen in a distillation column wherein:
Optionally:
According to another aspect of the invention, a unit is provided for separating a feed gas containing, as main components, nitrogen and carbon monoxide and optionally hydrogen, comprising:
Optionally, the unit can comprise:
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it can admit to other equally effective embodiments.
The invention will be described in greater detail while referring to the figures which represent a unit substantially according to the prior art for separating a gas having, as main components, nitrogen and carbon monoxide for
According to
A stream of nitrogen is removed as a purge 125 and is heated in the heat exchanger 103. The vaporized carbon monoxide 127 is also heated in the heat exchanger 103 and is compressed in the first stage 129 of a compressor. It is cooled in a cooler 131 by water and then divided into two. The stream 133 is cooled to an intermediate temperature in the heat exchanger 103 and is divided into two in order to form the stream 133. This stream 133 is cooled in the heat exchanger 134 against liquid nitrogen 137. The liquid nitrogen 137 is vaporized and heated in the heat exchanger 103. The stream 133 is expanded and mixed with the stream 21 downstream of the valve 119. The stream 145 which is sent to the bottom of the distillation column 15 after cooling in the heat exchanger 103A.
Liquid carbon monoxide 179 is withdrawn from the condenser 123, expanded in the valve 181, sent to the fifth phase separator 183 in order to produce a liquid portion 185 and a gaseous portion 187. The liquid portion is vaporized in the exchange line 103A and the gas 187 is mixed with the carbon monoxide stream 127 intended for the compressor 129.
According to
A stream of nitrogen is removed as a purge 125 and is heated in the heat exchanger 103. The vaporized carbon monoxide-enriched stream 127 is also heated in the heat exchanger 103 and is compressed in the first stage 129 of a compressor. It is cooled in a cooler 131 by water and then divided into two. The stream 133 is cooled to an intermediate temperature in the heat exchanger 103 and is divided into two in order to form the stream 193. This stream 193 is expanded in the turbine 191 in order to form the expanded stream 193 which is mixed with the stream 127 in order to be heated in the heat exchanger 103. The stream 145 originating from the stage 129 is sent to the bottom of the distillation column 115 after cooling in the heat exchanger 103A.
Liquid carbon monoxide 179 is withdrawn from the condenser 123, expanded in the valve 181, sent to the fifth phase separator 183 in order to produce a liquid portion 185 and a gaseous portion 187. The liquid portion is vaporized in the exchange line 103A and the gas 187 is mixed with the carbon monoxide stream 127 intended for the compressor 129.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.
The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.
Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.
Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.
Number | Date | Country | Kind |
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0958305 | Nov 2009 | FR | national |
This application is a §371 of International PCT Application PCT/FR2010/052368, filed Nov. 4, 2010, which claims priority to France Patent Application no. 0958305, filed Nov. 24, 2009, the entire contents of which are incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FR10/52368 | 11/4/2010 | WO | 00 | 7/5/2012 |