Water Management in Oil Refining and Petrochemical Production

The separation and refinement of petroleum requires sophisticated operational systems, which are optimized in accordance with the properties of the desired product and qualities of the crude oil. Due to the complexity and scale of the processes, refineries can consume vast amounts of water, thus making the water network a key factor in ensuring optimum operative conditions. Identifying the main water consumers and the effluents produced is extremely important for the development and improvement of refinery water management. This chapter provides an overview of oil refinery and petrochemical facility water networks. The main discussion points are water sources, the resulting effluents from diverse petroleum processing steps, and the technologies and treatment system employed. Most importantly, water reuse and recycling within a refinery are also addressed in detail. Surface and groundwater constitute major water sources. Furthermore, many refineries choose to include rainwater and stormwater in their water networks. A topic of increasing importance is the reuse and recycling of refinery effluents to form treated streams as an additional, viable water source. The diversity of refinery water supplies is also further explained with a short example. Owing to their high level of contamination, special emphasis must be placed upon the treatment and handling of oil refinery effluents. This chapter discusses and compares the treatment for these streams and their characteristics in a comprehensive manner. The technologies presented are interlinked with other chapters and thus provide a complete picture of the processes. The refinery effluents addressed include desalter effluent, sour water, spent caustics, oily water, cooling water, and petrochemical effluents. The treatment system consists of numerous technologies, which can be divided up into primary, secondary, and tertiary treatment steps of which the latter is crucial for effluent reuse and recycling. Each of these stages is responsible for the removal of different contaminants. The special treatment of challenging effluents is also discussed. One example in this regard is the handling of spent caustics, in which the effluent frequently undergoes wet air oxidation. This treatment process can be tailored in order to achieve the desired water qualities and in order to illustrate the flexibility of the process within this context, three different wet air oxidation designs are compared. As far as petrochemical processes are concerned, the treatment of the effluent resulting from the production of terephthalic acid and polyethylene terephthalate is described with an example. In addition, this chapter briefly depicts the resemblance between refinery effluent treatment and recycling plants by means of diverse case studies from around the world. Owing to the wish to achieve greater sustainability and a reduction in discharged effluent volumes, the reuse and recycling of effluents down to zero liquid discharge (ZLD) or minimum liquid discharge (MLD) have become a major topic. Zero liquid or minimum liquid discharge systems contain a series of treatment steps, which virtually avoid liquid discharges and produce water (mainly condensates) of the highest quality, thus opening up the possibility of high grade recycling. The scope of refinery effluent reuse is diverse, since the reclaimed water can be implemented in numerous areas. Within this framework, a short case study of an oil refinery in Nigeria is presented. At this refinery, the final reverse osmosis and demineralization units produce high-quality water, which is then reused as boiler makeup. Furthermore, this chapter reviews different technologies and in particular membrane processes such as reverse osmosis and ultrafiltration. Within this context, ceramic membranes are discussed with regard to higher robustness and lower life cycle costs.