BATCH RUNAWAY REACTION RELIEF - REEVALUATION OF CREDIBLE SCENARIO

Many chemical reactions in the fine chemical and related industries ar e performed in a semi-batch manner under isothermal conditions. Relief system design evaluation for runaway reactions using DIERS methodolog y for example, is frequently studied adiabatically using data derived from batch mode testing. In many cases, however, evaluation of the pro cess isothermally, under the realistic semi-batch mode can be extremel y useful, often helping to greatly reduce the vent size as a result of a better understanding of the process. In some cases, it is even poss ible to eliminate runaway reaction as a viable case for relief sizing. Such evaluations of venting are fully consistent with DIERS methodolo gy. This paper presents the arguments for sizing vents for scenarios o ther than the very worst case, by objective evaluation of trips and in terlocks, so that the level of risk is reduced to an acceptable level without the need for extremely large vents.