High Capacity Tube Digestion Technology Reduces Capital and Operating Cost for Refineries
New refineries are facing twin challenges of rising capital and operating costs, the latter particularly influenced by the rising cost of energy. Since 2001 there has been a large increase in the capital cost of alumina refinery projects from approximately 1,000 USD/t to 1,500 USD/t. This has resulted in an increase in the size and complexity of refinery projects as companies attempt to leverage economies of scale. The required investment for a modern green field refinery today is typically in the range of several billion dollars.
Arresting this trend in increasing project costs requires a concerted effort by the alumina industry to improve efficiencies and to innovate. The use of high capacity single stream tube digestion technology is one such innovation that represents an opportunity to address both challenges by reducing refinery complexity and improving energy efficiency.
Tube digestion replaces the conventional shell and tube heat exchangers with jacketed pipe heaters and, for some bauxites, it can also replace conventional digester vessels with pipe reactors. This simplifies the digestion plant and allows a single stream flowsheet to be employed. This paper describes the use of tube digestion technology and compares its use with the more conventional dual stream technology.