Simulation of Real Wastewater Supercritical Water Oxidation at High Concentration on a Pilot Plant Scale

Abstract

Supercritical water oxidation (SCWO) has been studied for the past three decades and is now a well-known process. However, the commercial development of this technique is currently delayed due to several drawbacks such as corrosion, salt precipitation, and high costs. In an effort to overcome these constraints several authors have studied and designed new SCWO reactor concepts, but these technical solutions involve the use of special materials and complex designs that increase the process costs. However, conventional SCWO could be commercialized for certain wastewaters that satisfy certain requirements, e.g., very low salt and chloride contents, and it is necessary to continue studying the SCWO process at high concentrations and on the pilot plant scale. At present, simulations based on the SCWO of real wastewaters at high concentrations on the pilot plant scale are scarce in the literature. Process simulation is a powerful tool to study processes in depth and to make advances in the scale-up process. Nevertheless, the use of specific chemical engineering software, such as Prosim Plus or Aspen Plus, is not applicable to simulate a complex wastewater. In addition, the use of the kinetic data available in the literature is not straightforward because these kinetic parameters were obtained from experiments conducted under very different conditions (isothermal, low concentration, etc). In the work described here, the simulation of Biocut 35 cutting fluid SCWO on a pilot plant scale has been conducted satisfactorily. The model was developed using a Microsoft Excel spreadsheet and a kinetic model obtained on the laboratory scale. Fifteen experiments were carried out in order to validate the simulator. These experiments were conducted on a pilot plant scale at a constant pressure of 250 bar and initial temperatures ranging from 388 to 428 °C. The cutting fluid concentration used in these experiments was varied from 19 to 95 g of O 2 /L. Finally, the simulator was used to check the effect of the operational variables such as wastewater concentration, initial temperature, wastewater flow rate, and thermal insulation.