Linear Hourly Space Velocity

The key differences are presented in Table 14. Hydrocrackers tend to operate at higher pressure, using different catalysts, and with lower linear hourly space velocity (LHSV). LHSV is equal to the volume of feed per hour divided by the catalyst volume. A lower required LHSV means that a given volume of feed requires more catalyst. In terms of process conditions and conversion, mild hydrocracking lies somewhere between hydrotreating and full-conversion hydrocracking. 

It has been shown that when fatty acid methyl esters are pyrolysed over activated alumina at 400 C at a weight-hourly space velocity of 0.45, they are completely deoxygenated to form linear hydrocarbons. These are completely compatible with petrodiesel with which they can be blended in all proportions. Because the blending of biodiesel with petrodiesel is one strategy for addressing the CFPP, the pyrolytic deoxygenation offers several options for the use of waste fats and oils as biodiesel precursors. 

Figure IB shows how veil the data fits the relationship with a zero intercept. Most runs, however produced non-zero intercepts the value of which was difficult to reproduce. This was probably due to erratic coking during the first 2 hours for inknown reasons. Despite this initial uncertainty the slope of the line was surprisingly repeatable. It is esclmaced that over 90% of runs gave slopes with an accuracy of 10%, Little change in coking rates was observed on varying linear space velocities indicating the absence of mass diffusion restrictions.

Figure 28.8 shows three cells in the right hand figure. These can be product-centric or customer-centric. One line is linear. Others are arranged in the U shape characteristie of many cell designs. The U shape allows for rapid hand-offs in the cell and a eommon area for flow into and out of the eell. Velocity is up as well as density. Parts move through in minutes or hours rather than days or weeks. There is little work in process on the shop floor to waste space. 

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