[ heat transfer ]
Thermal management in green hydrogen production : design considerations
Central cooling systems for large-scale green hydrogen production can be based on wet or dry cooling . But there also exist hybrid solutions . This article discusses three such solutions and considers the factors influencing the selection of cooling technology .
By Roy Niekerk , Director Global Sales & Solutions Hydrogen , and Radhouene Manita , Application Engineer , Kelvion Thermal Solutions
The two most established processes for green hydrogen production are alkaline water electrolysis and polymer electrolyte membrane ( PEM ) electrolysis . In both processes , a liquid is recirculated over an electrolyser stack to form hydrogen and oxygen . During the electrolysis process , heat is released , which needs to be cooled away . This cooling step is normally done in a plate and frame heat exchanger .
But there are more cooling positions in the hydrogen production process . Alternating current electricity is changed into direct current , which releases heat . Two further positions are the formed oxygen and hydrogen , which are cooled before further purification . The deeper the cooling , the more water is ‘ knocked out ’ by means of condensation , reducing the required size of the drying section in the plant . Further downstream , the hydrogen is compressed , which requires compression interstage and aftercoolers . A closed loop of water or water-glycol mixture is used to cool all the different coolers in the hydrogen production process . And the closed loop is cooled in a central system . Electrolyser capacity is normally expressed in megawatts . And as a rule of thumb , roughly 25 – 30 % of that capacity is cooled away in the central cooling system . Different cooling methods exist .
Dry or wet cooling
Air Fin Coolers ( AFC ) are one method of cooling down a closed loop . Typically , an AFC consists of a series of horizontal finned tube bundles with box headers at each end that run either underneath or above axial fans within a plenum chamber , which
Demineralized water
Purification section
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Pump |
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Pump |
Plate heat exchanger |
Filter |
Electrolyser stack |
Moisture
H 2 separator Plate heat separator H exchanger 2
Purge
O Purification
2 separator section
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Plate heat exchanger
Moisture separator
Purge
O 2
Electrolysis process scheme
14 Hydrogen Tech World | Issue 6 | October 2022