Sequential differential thermal analyses (S-DTA) of autoclave reactions

The main message of this paper is the description of an analyzing technique about the measuring of the energy budget in pressure vessels on a laborato ry scale. To demonstrate this technique two cases are presented. The first series deals with the oxidation of cellulose and the second series with the co-treatment of jarosite and sludge. Jarosite is a waste product of zinc r efining factories using hydrometallurgical processing routes. The energy budget is always a parameter in process design. A common way to obtain the net energy transfer of reactions occurring at atmospheric pressu re is to obtain the differential thermal analyses (DTA) signal by using a j oule measuring device'. Obtaining the reaction energy at higher pressures i s more complicated. Indirect information was obtained by measuring the temp erature rise produced by the ongoing reaction in an autoclave during heatin g, compared to the temperature profile of the same autoclave during a blank experiment, This method is called here 'Sequential Differential Thermal An alyses', (S-DTA). The disadvantage of such a system is the energy loss to t he environment, since the autoclave is not perfectly isolated. It has been shown that for limited energy increases this effect is negligible, and for stronger exothermic reactions the autoclave should be used with smaller qua ntities of reagents. The wet oxidation of cellulose with varying amounts of oxygen has been used to demonstrate the possibilities and the accuracy of this method. (C) 2001 Elsevier Science Ltd, All rights reserved.