DE202022103075U1 - Plant for recovering heat from a synthesis gas containing hydrogen - Google Patents

Abstract

Plant for recovering heat from a synthesis gas containing hydrogen, comprising:
(a) a compact multi-fluid heat exchanger between a hot stream comprising hydrogen-containing synthesis gas (H1) and at least 3 cold streams (C1, C2, C3),
(b) where the heat exchanger is divided into (at least) 4 sections,
(c) where H1 is exchanged with 2 cold streams simultaneously in (at least) 2 sections: C1 and C2 in one section and C1 and C3 in another section,
(d) where C1 exchanges heat with H1 in at least 3 sections,
(e) where H1 never exchanges heat with more than 2 cooling streams simultaneously,
(f) wherein at least one of the cold streams is not introduced at an end of the multi-fluid heat exchanger.

Description

field of invention

Steam methane reforming (SMR) Recovering heat from a hydrogen-containing synthesis gas

State of the art

In steam methane reforming (SMR), the hydrogen-rich synthesis gas stream produced after the reaction is usually cooled with the aid of three tube bundle heat exchangers. Three different coolants are used in each plant: first the hydrocarbon feed stream, then the boiler feed water and finally demineralized water. Thanks to this arrangement, the hydrogen-rich stream reaches a temperature of around 130 °C. However, three apparatuses are required here and the temperature approach during heat exchange is about 20 to 30 °C. The overall efficiency of the heat exchanger unit is low. Mass efficiency is defined as the ratio of the heat transfer rate (in watts) to the equipment mass (in tons) multiplied by the mean temperature difference (in Kelvin; the mean temperature difference is calculated using the composite curves). The higher the efficiency, the better the process is integrated and consequently the more cost-effective it is.

In the patents US7871449A and US8828107A a multi-fluid heat exchanger for hydrogen cooling is proposed, which should reduce the investment costs and reduce the minimum temperature approach. However, the heat exchanger configuration is not optimal as it does not maximize the mass efficiency of the unit. In addition, an exit for the hydrogen flow on a certain length of the plate and fin heat exchanger is also considered; the stream is then cooled in an external heat exchanger and then reintroduced into the plate and fin heat exchanger for final cooling. This configuration is not optimal as it requires additional equipment which reduces overall efficiency.

The use of three shell and tube heat exchangers makes the heat exchange costly as three separate devices have to be installed. In addition, better results and higher mass efficiency are achieved when using equipment that allows a lower minimum start-up temperature in the heat exchange process.

Description of the invention

The object of the present invention is therefore to specify a system which does not have the disadvantages of the prior art mentioned. This object is achieved by a plant for recovering heat from a hydrogen-containing synthesis gas according to the features of the claims.

It is suggested to use a compact multi-fluid heat exchanger, preferably made of stainless steel. This allows the three shell and tube heat exchangers to be replaced by a single unit, making the overall process simpler and less expensive. In addition, compact heat exchangers enable a lower minimum start-up temperature, which means that optimal heat integration can be achieved.

By using a multi-fluid heat exchanger (multi-fluid heat exchanger), the process can be improved through higher mass efficiency.

Optimum heat integration is achieved by arranging the heat exchanger in a specific configuration. The device is divided into at least 3 or 4 sections. A section is defined as part of the heat exchanger where the cold streams exchanging heat with the hot stream are constant. In at least 2 of the above sections, the hot stream must simultaneously exchange heat with more than one cold stream.

Thanks to this special configuration, the overall mass efficiency can be increased fivefold compared to the standard process. In fact, the overall mass efficiency of a value of almost 10 for the standard process can be increased to values of 25 to 45 (depending on the number of cold flows) for the integrated heat integration.

Detailed description of the invention, exemplary embodiments

Further developments, advantages and possible applications of the invention also result from the following description of exemplary embodiments and numerical examples and the drawings. All of the features described and/or illustrated form the invention, either alone or in any combination, regardless of how they are summarized in the claims or how they relate back to them.

• 1 ein erstes Beispiel einer Anlage zum Rückgewinnen von Wärme aus einem Wasserstoff enthaltenden Synthesegas gemäß der Erfindung,
• 2 ein zweites Beispiel einer Anlage zum Rückgewinnen von Wärme aus einem Wasserstoff enthaltenden Synthesegas gemäß der Erfindung.

Show it:

• 1 a first example of a plant for recovering heat from a hydrogen-containing synthesis gas according to the invention,
• 2 a second example of a plant for recovering heat from a hydrogen-containing synthesis gas according to the invention.

the inside 1 and 2 The plate and fin heat exchanger shown is made of stainless steel. This device allows a temperature approach of only 3 °C and a high mechanical strength that withstands 20 - 55 bar of pressure. The streams entering the device are under a pressure ranging approximately from 20 to 55 bar.

A hot, hydrogen-rich stream is introduced into the heat exchanger while three to four cold streams are used for cooling. Optimum heat integration is achieved by using the cold streams at various points along the length of the heat exchanger.

The hot stream exchanges heat with several cold streams simultaneously in several sections of the device.

Numerical examples:

Example 1: Three cold streams Electricity [-] synthesis gas (hot) NG feed (cold) BFW (cold) DMW (cold) Main H2 0.56 0.37 components CO2 0.11 0.01 [mol/mol] H2O 0.26 1.00 1.00 CH4 0.04 0.45 CO 0.03 Flow rate [kg/h] 127,863 31,100 164,218 119.011 T in [°C] 423 42 107 28 T off [°C] 139 360 234 90 P to [bars] 24 36 53 5 Abbreviations: NG natural gas BFW boiler feed water DMW demineralized water (demineralized water) Example 2: Four cold streams Electricity [-] synthesis gas (hot) NG feed (cold) BFW (cold) DMW (cold) steam (cold) Main H2 0.56 0.37 components CO2 0.11 0.01 [mol/mol] H2O 0.26 1.00 1.00 1.00 CH4 0.04 0.45 CO 0.03 Flow rate [kg/h] 127,863 31,100 164,205 118,997 53,576 T in [°C] 423 42 107 28 266 T off [°C] 135 360 234 90 322 P to [bars] 24 36 53 5 52

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US7871449A [0003]
• US8828107A [0003]

Claims (15)

Plant for recovering heat from a synthesis gas containing hydrogen, comprising: (a) a compact multi-fluid heat exchanger between a hot stream comprising hydrogen-containing synthesis gas (H1) and at least 3 cold streams (C1, C2, C3), (b) where the heat exchanger is divided into (at least) 4 sections, (c) where H1 is exchanged with 2 cold streams simultaneously in (at least) 2 sections: C1 and C2 in one section and C1 and C3 in another section, (d) where C1 exchanges heat with H1 in at least 3 sections, (e) where H1 never exchanges heat with more than 2 cooling streams simultaneously, (f) wherein at least one of the cold streams is not introduced at an end of the multi-fluid heat exchanger. plant after protection claim 1 wherein C1 comprises or is formed from a hydrocarbon feedstock. Plant according to one of the preceding claims for protection, in which C2 comprises or is formed from boiler feed water. Plant according to one of the preceding claims for protection, in which C3 comprises or is formed from demineralised water. Plant according to one of the preceding claims for protection, in which the total consumption per unit flow rate of the synthesis gas of the multi-fluid heat exchangers is in the range from 100 to 150 kWh/Nm3. Installation according to one of the preceding protection claims, in which the minimum approach temperature is less than 25 °C. Plant according to one of the preceding claims for protection, in which the outlet temperature of the synthesis gas is less than 150 °C. Plant for recovering heat from a synthesis gas containing hydrogen, comprising: (a) a compact multi-fluid heat exchanger between a hot stream comprising hydrogen-containing synthesis gas (H1) and at least 4 cold streams (C1, C2, C3, C4), (b) where the heat exchanger is divided into at least 5 sections, (c) where H1 is exchanged with 2 cold streams simultaneously in at least 3 sections, where C1 and C2 are exchanged in one section and C1 and C3 are exchanged in another section, (d) where C1 exchanges heat with H1 in at least 4 sections, (e) where H1 never exchanges heat with more than 2 cooling streams simultaneously, (f) wherein at least one of the cold streams is not introduced at an end of the multi-fluid heat exchanger. plant after protection claim 8 wherein C1 comprises or is formed from a hydrocarbon feedstock. Plant after one of Claims for protection 8 until 9 , where C2 comprises or is formed from boiler feed water. Plant after one of Claims for protection 8 until 10 , wherein C3 comprises or is formed from demineralised water. Plant after one of Claims for protection 8 until 11 , where C4 comprises or is formed from vapor. Plant after one of Claims for protection 8 until 12 , where the total consumption per unit flow of synthesis gas of the multi-fluid heat exchangers is in the range of 100 to 150 kWh/Nm3. Plant after one of Claims for protection 8 until 13 , where the minimum approach temperature is less than 25°C. Plant after one of Claims for protection 8 until 14 , where the exit temperature of the synthesis gas is less than 150 °C.

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