Plant energy saving through efficient retrofit of furnaces

Abstract

Tubular process furnaces belong to energy demanding equipment in the process industry, especially in the chemical and petrochemical process plants and refineries. Several ways of energy saving in such plants usually exist. Retrofit of furnaces can be considered as one of the straightforward and efficient ways. However, operational and geometrical constraints of an existing furnace are the reasons due to which the retrofit of a furnace is a very difficult task. Therefore, the process retrofit is usually focused on heat exchanger network (HEN) retrofit considering maximum furnace duty. Nevertheless, the furnace retrofit should be considered wherever possible. In some older plants, the placement of new shells or topology changes in HENs can be expensive due to various reasons and only minimum topology modifications are usually allowed. The furnace retrofit procedure described in this paper is based on an advanced furnace integration approach using some principles of Pinch Analysis and considering furnace limitations. It can bring surprising results. This method combines principles of an effective design of both processes and equipment. An efficient methodology for furnaces retrofit, using optimization of both stack temperature and air preheating system, is applied. An advantage of this approach is demonstrated through a case study — retrofit of furnace in petrol hydrogenation refining plant for energy efficiency improvement.