Decarbonisation Technology - February 2024 Issue

ENOWA, a subsidiary of NEOM. The scheme will use atmospheric pressure alkaline electrolysers from thyssenkrupp nucera to generate green hydrogen from integrated wind and solar power. Air separation units will produce nitrogen to react with the hydrogen in a Haber-Bosch synthesis loop to make green ammonia for export. The Helios project will be implemented in Tabuk in north-western Saudi Arabia. This is an arid region with less than 2mm of rainfall per month in winter and no precipitation in summer. To support the green hydrogen

project, a purpose-built desalination plant will extract seawater from the Red Sea to produce 500,000 m3 a day of fresh water. The Suez Canal Economic Zone in Egypt lies on the opposite shore of the Red Sea. It stretches from Port Said at the northern end of the Suez Canal to Al Sokhna at the Canal’s southern tip. The zone has attracted many green hydrogen project developers, such as France’s EDF Renewables (through the Green Fuel Alliance), Norway’s Scatec, Australia’s Fortescue Future Industries, and UAE-based AMEA Power.

Process

Function

Impurity removal

Mechanical grate

Remove large debris

Solid debris is physically removed from the grate to be disposed of

Raw water intake

Draw seawater or river waste

N/A

Pre-chlorination and flocculation

Chlorine and AI 2 (SO 4 ) 3

Flocs are removed in the multimedia

precipitate heavy metal ions Remove mud, sludge, sand,

filter bed

Multimedia sand and gravel bed

Backwash with air and water

algae, and flocs

Activated carbon filter

Chlorine and dissolved organic

Spent activated carbon filter cartridge

compound removal

is replaced and disposed of

Water softening

Replace Ca 2 and Mg 2 hard water

Backwash with brine

ions with Na ions Low-pressure reverse osmosis (LPRO)* Remove mono-and multi-valent

Backwash with water frequently, backwash with chemicals occasionally Microbes multiply during storage and ions can dissolve into the water Ions build up in the concentrate discharge Dead organisms are removed during ultrafiltration Backwash with water frequently, backwash with chemicals occasionally Gases are vented to atmosphere

ions and microbes

Pure water buffer tank

Intermediate storage of water

Electro de-ionisation (EDI) Ultraviolet (UV) sterilising lamp

Polishing to removed traces of ions Kill bacteria and other microbes

Ultrafilter

Remove dead organisms

Degassing

Remove dissolved nitrogen and CO 2

Introduce water to electrolyser water/

Top up water in electrolyser to enable Degassing, EDI, and filtration may be used

lye recirculation circuit

hydrogen and oxygen generation

in the electrolyte recirculation circuit to remove impurities generated in the electrolyser

EDI and degassing

Pure water purification in the PEM water recycle loop to remove dissolved ions from corrosion and CO 2 from dissolved hydrocarbon decomposition on the electrolyser Lye filtration to remove precipitated

As above

Filtration and degassing

Lye filter backwash to water treatment

carbonates formed by reaction of CO 2 plant with lye, CO 2 degassing * Thermal desalination may take place here, if required or the reverse osmosis may be operated as high-pressure sea water reverse osmosis (SWRO or HPRO) if desalination is required Table 1 Filtration and purification processes involved in the production of ultrapure water