There have always been problems regarding scale up of a process from laboratory scale to commercial scale plant. In general, scale up is considered in terms of process performance, while safety and environmental issues are considered based on the full scale design. The relation between Safety and Environmental Risk and the size of plant is an important consideration in design but one that is often considered only indirectly. The magnitude of hazards change with scale in ways that depend on their nature, as well as the response time of equipment, process inventories, changes in the ability to control etc. The IMPULSE project aims are to deploy innovative process equipment such as microreactors, thin-film devices and other structured components to attain step-change performance enhancement for whole processes, including intensification, thereby contributing to significant improvements in supply-chain sustainability. One theme pursued is the numbering up (rather than scale-up) of processing devices, so that in IMPULSE the size of commercial devices is the same as in the lab. By this means it is expected to have fewer problems regarding performance change on scale up. Also, it has been widely claimed that process intensification leads to safer manufacture. There is a need of methodology which helps industries to choose the best technology. In this study, CTNT (Comparison of Traditional versus New technology) method is developed. First a list of hazards is provided. The main hazards are fire and explosion, runaway reaction, frequency of leaks, releases of hazardous and toxic material and overpressure. Each of these hazards is quantified for both plant and a comparison is done to see how hazard changes with scale of plant. This methodology is demonstrated for a particular reaction but it is more generally applicable. It seems regardless of running IC plant longer hours compared to batch plant, the hazard declines. The results for pool fires show that the diameter of pool reduces by a factor of 3 by moving from batch to IC for 10000 kg product per hour in hydrogenation unit if the pressure kept at 3 bar by increasing the pressure to lObar the diameter of pool increases by a factor of 2. The probability of death decreases by increasing the distance from the failure point. The Pc (explosion overpressure) in IC plant increases by increasing the scale from 10 kg product per hour to 10000 kg product per hour at 9 bar to 30 bar respectively (considering the distance to failure point 3 m). By increasing the pressure to lObar in IC plant the explosion overpressure increases to 20 bar for 10 kg product per hour. The probability of death increases to 48% and 40 % for batch and IC plant respectively for 10000 kg product per hour with r ==0.5m. It is found by reducing the size of pipe the frequency of leak increases. This sounds reasonable as the frequency of a given hole size is lower in a larger pipe. In general larger pipes tend to be designed and protected more carefully, and tend to have thicker. walls. In part this is a compensation for the fact that the consequences of a given hole size will be greater if the inventory is larger. Conventionally, it is thought that smaller is safer. It is claimed that microstructured plant can be located in a small room. But this study shows that for the hydrogenation example the concentration of hazardous/toxic material is what limits the size of the space required. It is found that in order to get the same concentration of hazardous /toxic material in IC plant as batch the volume of room can be as small as 25 m3 compared to batch at 210m3 It was also found that it is hard to protect the individual microreactors against overpressure.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:515221 |
| Date | January 2010 |
| Creators | Khoshabi, Parastoo |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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