Reduction of polluting effluents in a polymerization process using simultaneous mass and heat integration

Abstract In this paper, we propose a method for process integration where the amount of separation agents, energy demand and consequently the polluting effluents discharged to the environment are simultaneously minimized. This method overcomes some disadvantages of the traditional mass and energy integration techniques (pinch point method), where the main difficulty to implement them in a determined system relies on that the bases of their development have been settled down separately, causing that an optimal scheme of mass integration generally is opposed to the optimal one for energy. When the proposed methodology is applied for counter current systems, simultaneous minimum requirements of mass and heat are obtained, showing differences between 1 to 5% with respect to results obtained by the traditional mass and heat pinch point methods. The methodology consists of a graphical technique based on the analogy between the techniques that are used to separately integrate the interchange of mass and energy. The procedure is developed in two stages; the first one is based on the pinch point method to define the mass interchange network, the interchanges between currents and the definition of minimum service requirements take place by means of pondered concentration gradients with their corresponding gradients of energy. In this stage, the minimum differences of concentration and temperature are adjusted using a similar procedure to the diverse pinch point method. The second stage consists on the heat integration for the interchange network defined in the first stage of the method. As case of study, the technique is applied to the separation systems of an industrial process of suspension polymerization, obtaining a reduction in the operation costs of 39% and in polluting effluents of 40%.