A
research team from the Gas Processing Center (GPC) at Qatar University
College of Engineering (QU-CENG) has developed a combined approach for
carbon and high salinity water (reject brine) management.
Led by GPC
Qafco chair Prof Muftah El-Naas, the team developed and tested a
modified Solvay process that does not involve the use of ammonia. Reject
brine was mixed with 1% to 2% of calcium oxide to raise the water pH to
above 10 and then contacted with carbon dioxide (CO2)-containing gases.
The CO2 reacts with sodium chloride and calcium hydroxide to form
soluble calcium chloride and insoluble sodium bicarbonate. This process
has the dual benefits of capturing CO2 and storing it in solid sodium
bicarbonate and, at the same time, reducing the salinity of the reject
brine.
In addition to mitigating the negative impact of CO2
emissions, the new process can significantly reduce the salinity of
reject brine, so that it can be used for irrigation purposes or enhanced
oil recovery. An important part of the new process is a novel reactor
system that was especially developed to facilitate the direct contact
between the CO2 gas and the high salinity brine.
Prof El-Naas noted that seawater desalination is a major source of potable water in Qatar and most countries in the region.
He
said: “It is estimated that the Gulf countries contribute in about 44%
of the world production of desalinated water, amounting to about 37mn
cubic metres a day. A similar amount of highly concentrated reject brine
is also produced daily. The management of such large quantities of
reject brine represents major economic and environmental challenges to
most desalination plants, especially those involving thermal
desalination. Conventional management methods such as disposal through
deep well injection, land disposal and evaporation ponds have proved to
be ineffective and often lead to negative impacts on the environment.”
He noted that CO2 emission is yet another environmental concern that is considered a major contributor to global warming.
CO2
is believed to have the greatest adverse impact on the observed
greenhouse effect, he said, adding: “CO2 emissions come predominantly
from the combustion of fossil fuels in power generation, industrial
facilities, buildings and transportation. A different approach for
carbon capture and storage has been proposed as a possible, reliable and
environmentally friendly option for the containment of CO2 emissions.
It involves the reaction of carbon dioxide with high salinity water such
as desalination reject brine or produced water.”
“It is worth
noting here that this new system has the potential to be used for
several industrial applications, such as water desalination, reject
brine management, and produced water treatment as well as natural gas
treatment processes such as gas sweetening. Therefore, several Qatari
industries such as Kahramaa, Qatar Petroleum and Qatargas will be
interested in developing the technology associated with the process or
the reactor system.”
Prof Muftah El-Naas