Produced Water Reuse for Production of Chemicals

Abstract

Abstract Produced water is highly saline. It may be used for soda ash (sodium carbonate) production. That is why its main component is sodium chloride and soda ash industrial process is based in brines. This process, in use since 1861, is also known as Solvay process. It starts when seawater-based brines receive ammonia gas, making up ammoniated brine. In the following step, carbon dioxide is added, precipitating sodium bicarbonate, which is filtered, leaving an ammonium chloride solution. Sodium bicarbonate is pyrolised to soda ash, water and carbon dioxide, which returns to the carbonation step. Produced water will undergo a pre-treatment step designed for removing metals such as calcium, magnesium and iron. After this procedure, produced water will be evaporated until it reaches the brine concentration for Solvay process. This operation also produces high purity water, suitable for many purposes. Carbon dioxide (CO2) used in this process is originally obtained from thermal decomposition of limestone. Soda ash is an important raw material for a wide variety of products, such as glass, soap, cosmetics, etc. Brazil imports all soda ash used by its industries. Using high salinity produced water for producing it may be a very attractive alternative with huge economic and environmental incomes. It may be possible to use CO2 captured from atmospheric emissions, contributing to mitigate global warming. Some laboratory scale experiments are in course now, dealing with Solvay process applied to produced water conversion into soda ash. Present results have shown that the process is feasible, allowing us to scale it up to a pilot scale. Considering the environmental benefits obtained of this process, both in wastewater treatment and carbon sequestration, as well as the production of a valuable commodity, applying Solvay process for treating produced water is a promising technology for the next years.