MINIMIZATION OF PHENOL AND AMMONIACAL NITROGEN IN REFINERY WASTEWATER EMPLOYING BIOLOGICAL TREATMENT

Wastewater from refineries is usually characterized by presence of phenol and ammoniacal nitrogen. The aim of this work was to search for a refinery wastewater minimization employing a biological technology to reduce these pollutants. Experimental data was obtained by treating a synthetic wastewater in a sequencing batch reactor (SBR) operating on different operational schemes for batch scheduling. COD, nitrate, ammonia, phosphate and phenol were monitored as well as dissolved oxygen, pH, level and redox potential through a supervisory control software. Reductions of 95 % were achieved for different concentrations of NH4 + and phenol, providing an effluent acceptable by Brazilian environmental legislation

The importance of control considerations for heat exchanger network synthesis: a case study

Cost optimization in the synthesis decision tree often leads to a reduced degree of freedom which degrades the process’s ability to reject disturbances as a consequence of low controllability. In fact, Heat Exchanger Networks (HENs) obtained by traditional synthesis procedures that ignore controllability aspects must be evaluated in this context a posteriori. The aim of this work was to develop a procedure that includes RGA and SVD measures of controllability, which are solely based on steady state information, thereby freeing the synthesis procedure of the cumbersome dynamic analysis. When a structure is defined during a traditional HEN synthesis procedure, a degree of freedom analysis is approached as a simulation problem. Next, an optimization is performed, since new variables are usually added to increase the degree of freedom of the HEN in order to render it controllable. A key point in the proposed procedure is the inference of controllability based on the proposed controllability measures, which also provide a control scheme by pairing controlled and manipulated variables during the process design. A HEN reported in the literature is used to illustrate the proposed procedure. The steady state simulator Aspen Plus and the dynamic simulator Aspen Dynamics (Aspentech, Inc.) were employed