Understanding Refinery Sour Water: Sources, Characteristics and Treatment Challenges
Sulfur- and nitrogen-containing compounds are ubiquitous in crude oil and its derivatives. During refining, process steps such as atmospheric and vacuum distillation, catalytic cracking, delayed coking and catalytic hydrogenation subject these compounds to a series of chemical reactions - high-temperature cracking, catalytic conversion and hydrocracking - producing hydrogen sulfide (H2S) and ammonia nitrogen (NH3-N), which then enter the product streams.
Subsequently, when the product streams undergo condensation and dewatering or water washing, wastewater containing sulfides and ammonia nitrogen is generated. This is what the industry generally refers to as sulfur-containing wastewater, often also called sour water.
Among the sour water produced by all refining processes, that from delayed coking units has the most complex composition and generally higher concentrations of every pollutant, making its treatment notably challenging. Its main characteristics are:
High content of solid suspended solids (mainly coke fines), with a relatively narrow particle size distribution;
High oil content, with very fine oil droplets and severe emulsification, making separation difficult;
High concentrations of sulfides, ammonia nitrogen and organic compounds such as phenols;
Complex water composition, with wide fluctuations in the content of each component.
Such highly emulsified, highly concentrated sour wastewater places extremely high demands on the separation precision, stability and reliability of treatment technology.
