Computers and Chemical Engineering 25 (2001) 745 – 755 An integrated framework of process and environmental models, and EHS constraints for retrofit targeting F. Nourai *, D. Rashtchian, J. Shayegan Chemical Engineering Department, Sharif Uni6ersity of Technology, Azadi A6enue, Tehran 14155 1446, Iran Received 10 May 2000; accepted 5 January 2001 Abstract Stricter environmental regulations posed on chemical process industries (CPI), and the ever-increasing costs of end-of-pipe treatment, explain why chemical process industries have adopted new ‘cleaner production’ approaches in new designs and in retrofits. Finding environmentally clean alternatives for retrofitting existing processes has been addressed with various approaches. In this paper, a previous approach by the same authors is extended to include EHS criteria for targeting waste reduction in chemical processes. The method is applied to an existing local production facility as a case study and risk-based pollution prevention (P2) targets, and the appropriate direction and magnitude of necessary modifications are highlighted in order to improve the environmental conditions of the plant with the regulatory constraints in mind. Solutions are based on a precise, integrated description of the plant and the environment, the modifications are recommended based on their feasibility, and the pollution impacts are defined in accordance with regulations. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: Pollution prevention; Process integrated methodologies; NO x ; EHS criteria www.elsevier.com/locate/compchemeng 1. Introduction Although oil, gas and petrochemical industries of Iran are no less than 60 years old, the abundance of natural raw materials, like gas and oil, planning and implementation of various development projects in downstream industries are still in progress. New and expansion projects each have their share of these activ- ities. Obviously, impact of development on the environ- ment is a major concern now. Product quality, mainly for export, is another concern that adds to the impor- tance of the issue. Considering the fact that Iran is a contributor to international conventions like that of Rio de Janeiro, adds an obligatory dimension to the concerns. The same is true for the world CPI, as a whole, which is moving more and more towards improving its environmental impact as it feels higher pressures from public opinion and governments on a global basis. However, this issue is more important when it comes to retrofit projects. Because, typically, the design basis of the old plants does not necessarily match today’s environmental limitations. At the same time, the old plant is required to produce more and emit less. What makes the problem more difficult is that first, it is usually expensive to modify the flowsheet in an already built plant, and second, there is less scope for improve- ment in these cases. It can be concluded that stricter environmental regu- lations posed on CPI through national, regional or international agreements, and the ever-increasing costs of end-of-pipe treatment, are the main indicators of the extent to which operators and designers can benefit from adopting a pollution prevention approach to the problem. In fact, they are already realizing the benefits of this type of approach. Legislators also appreciate the approach in several countries (Shanley, 1993). Since the principle objective is sustainable development, it is now possible to say that the control technologies are re- garded more as complementary tools for the improve- ments that are needed. * Corresponding author. E-mail addresses: nuraai@mehr.sharif.ac.ir (F. Nourai), davood@sina.sharif.ac.ir (D. Rashtchian), shayegan@che.sharif.ac.ir (J. Shayegan). 0098-1354/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII:S0098-1354(01)00650-0