Method for integrating cooling in the waste nitrogen of an air separation device with CO2 capture

Abstract

Method for integrating cooling in waste nitrogen from an air separation unit with CO2 capture In a method for integrating cooling in waste nitrogen from an air separation unit (ASU) with CO2 capture, air is compressed to at least 10 bara, purified to reduce its water and CO2 content and separated by cryogenic distillation in a separation unit to produce oxygen gas and nitrogen gas (WN), oxygen gas is sent from the separation unit to an autothermal reforming unit (ATR) which produces a synthesis gas (SG), the synthesis gas is treated to produce hydrogen and a CO2-containing stream, the CO2-containing stream is separated in a CO2 capture unit (CC) and nitrogen is sent from the separation unit to a direct contact tower (T) where it is contacted with water to cool it and the cooled water is sent to the CO2 capture unit.Abstract figure: Figure 1.

Description

Title of the invention: Method for integrating cooling in the residual nitrogen of an air separation device with the capture of CO2

[0001] Autothermal reforming (ATR) is a process for producing synthesis gas. When high purity hydrogen is the desired product of ATR, a process comprising pressure swing adsorption, temperature swing adsorption, membrane separation, and cryogenic treatment can effectively decarbonize the ATR process. This invention relates to improving the efficiency of such processes and reducing the energy intensity for CO2 capture.

[0002] It is known to use a refrigeration unit to produce iced water for an industrial process. Iced water may be used at various points in CO2 capture, for example to cool hot synthesis gas and desorption regeneration gas to reduce their water content, to cool the produced CO2 to a temperature low enough to allow its pumping and / or compression, or to meet the temperature specifications of the CO2 product.

[0003] Some air separation devices do not use an air booster but use a single compressor to compress all the air to be separated to a pressure between 15 to 30 bara depending on the energy required for compression and liquefaction of the products. It is known that the advantage of this process is the investment savings in the absence of an air booster and pre-cooling equipment. Pre-cooling is not used because there is much less water contained in such high pressure air and the volumetric flow rate is much lower. Since there is no pre-cooling, the excess dry N2 from the cold box generally used for pre-cooling the ASU is not used and becomes an available by-product and the waste nitrogen is directly discharged into the atmosphere.

[0004] The present application makes it possible to recover this excess nitrogen from the cold box of an air separation process by cryogenic distillation using the compression of all the air to be separated at a pressure of between 15 and 30 bars.

[0005] The prior art does not fully utilize waste nitrogen, which can be used to generate chilled water in a chilled water tower by evaporative cooling effect. The generated chilled water can be integrated into a CO2 separation process by partial condensation and / or distillation and / or solidification.

[0006] The invention comprising the following steps a. Inject waste nitrogen from the separation device into a chilled water tower to generate chilled water. b. Integrate the chilled water circuit into the CO2 capture process for different users. This invention replaces (totally or partially) the need for a refrigeration unit.

[0007] According to an object of the invention, there is provided a method of integrating the cooling in the residual nitrogen of an air separation apparatus with the capture of CO2 in which: i. Air is compressed to at least 10 bara, purified to reduce its water and CO2 content and separated by cryogenic distillation in a separation apparatus to produce oxygen gas and nitrogen gas, ii. Oxygen gas is sent from the separation apparatus to an autothermal reforming unit which produces synthesis gas, iii. The synthesis gas is processed to produce hydrogen and a stream containing CO2, iv. The CO2-containing stream is separated by partial condensation and / or distillation and / or solidification in a CO2 capture unit and v. Nitrogen is sent from the separation apparatus to a direct contact tower where it is contacted with water to cool it and the cooled water is sent to the CO2 capture unit.

[0008] The key innovative element of this process is to integrate the cooling capacity in the waste nitrogen with the CO2 capture. This integration can effectively reduce the size or even eliminate the refrigeration unit from the CO2 capture unit. This integration increases the overall efficiency of the blue H2 processing line.

[0009] The invention will be described in more detail with reference to the figure in which:

[0010] [Fig-1] represents an integrated method according to the invention

[0011] Air is compressed by a single compressor to a pressure above 10 bara, for example between 15 and 30 bara, is purified to a pressure above 10 bara and cooled and sent as flow 1 to a cryogenic distillation air separation apparatus ASU which produces oxygen gas 02 and nitrogen gas WN. The oxygen is fed with natural gas NG to an autothermal reforming unit ATR which produces a synthesis gas SG. The synthesis gas is treated to remove hydrogen H2 and the remaining gas containing CO2 is separated in a CO2 capture unit CC by partial condensation and / or distillation and / or solidification producing a carbon dioxide CO2 flow.

[0012] Nitrogen WN is sent from the separation apparatus ASU to a direct contact tower T where it is contacted with water CWR to cool the water and the cooled water is sent to the CO2 capture unit CC by a pump P. The water preferably circulates in a cycle.

[0013] Chilled water may be used in various places in CO2 capture, for example, to cool hot synthesis gas and desorption regeneration gas to reduce their water content, to cool product CO2 to a temperature low enough to allow its pumping and / or compression, or to meet the temperature specifications of the CO2 product.

Claims

Claims

1. A method of integrating cooling in the waste nitrogen of an air separation apparatus with the capture of CO2 in which: i. Air is compressed to at least 10 bara, purified to reduce its water and CO2 content and separated by cryogenic distillation in a separation unit (ASU) to produce oxygen gas (02) and nitrogen gas (WN) ii. Oxygen gas is sent from the separation apparatus to an autothermal reforming (ATR) unit which produces synthesis gas (SG) iii. The synthesis gas is processed to produce hydrogen and a stream containing CO2 iv. The CO2-containing stream is separated by partial condensation and / or distillation and / or solidification in a CO2 capture unit (CC) and v. Nitrogen is sent from the separation apparatus to a direct contact tower (T) where it is contacted with water to cool it and the cooled water is sent to the CO2 capture unit.

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