Cracking propane

When a mixture is cracked, one or more components in the feed may also be formed as products. Eor example, in the cocracking of ethane and propane, ethane is formed as a product of propane cracking and propane is formed as a product of ethane cracking. Therefore, the "out" term in the above equation contains the contribution or formation from other feed components and hence does not represent tme conversion. Eor simple mixtures, the product formation can be accounted for, and approximate tme conversions can be calculated (29). Eor Hquid feeds like naphtha, it is impractical if not impossible to calculate the tme conversion. Based on measured feed components, one can calculate a weighted average conversion (A) (30) ... 

Propane cracking is similar to ethane except for the furnace temperature, which is relatively lower (longer chain hydrocarbons crack easier). However, more by-products are formed than with ethane, and the separation section is more complex. Propane gives lower ethylene yield, higher propylene and butadiene yields, and significantly more aromatic pyrolysis gasoline. Residual gas (mainly H2 and methane) is about two and half times that produced when ethane is used. Increasing the severity... 

Besides methane and hydrogen, other products observed were mainly ethane, ethylene (probably due to propane cracking), propene which are shown in figure 3. Minor amounts of benzene and toluene were also found but these products could not be quantified because their slow desorption from the zeolite s channels. 

Portable Power Using a Propane Cracking Reactor System... 

The production of ethylene by gas crackers, mostly from C2, C3, and some C4 feeds, amounts to about 40% of the world ethylene capacity. This results in a small coproduction of benzene compared to benzene co-produced in naphtha and gas oil crackers, which account for 60% of the world s ethylene production capacity. A typical overall benzene yield from ethane cracking is on the order of only 0.6% of the ethane feed, and the yield of benzene from propane cracking is on the order of 3% of the propane feed. In contrast, the... 

R.K. Stoecker, A. Rastogi, L.A. Behie, W.Y. Svreck, M.A. Bergougnou, A computer simulation of propane cracking in a spout-fluid bed reactor with draft tube, in K. Ostergaard, A Sorensen (Eds.), Fluidization V, Engineering Foundation, New York, 1986, pp. 465 172. 

Another key point to note is that chain transfer and termination by radical combination leads to radicals and molecules with more carbon atoms than the feed (propane). Subsequent involvement of these moieties in the radical chain propagation leads to larger molecules. In practice this maimer of radical cracking of ethane and propane cracking leads to some C4, C5 and Ce+ products forming pyrolysis gasoline. 

Normal-butane gives very similar yields of ethylene and propylene to propane cracking. Methane is lower and more butadiene, C5 + aliphatic hydrocarbons and BTX are produced. 

Following the same methodology for the cracking of ethane, the production cost of ethylene by propane cracking in an OPEN system is shown in Table 8.2. In this scenario, all of the products are on-sold to downstream operations or valued at an opportunity cost. 

Figure 8.2 Production cost breakdown for propane cracking - OPEN system...

Figure 8.3 Sensitivity of ethylene production cost by propane cracking to oil price...

The basic conversion rate data for the present study are from experiments on propane cracking made several years ago by one of the authors (K. D. Williamson). The conversion/time/temperature data have been published in graphical form (2). We believe these to be superior to any high-temperature cracking rate data available. The range of decompositions covered (0-80%) is extended by recourse to some older propane data available to us but not previously published. These latter data are of somewhat poorer quality. Previously unpublished data on n-butane and n-hexane conversion (0-99% decomposition) from the Williamson study are used to verify the model. 

Thus the high conversion data indicate, at least conditionally, that the EE model is useful even beyond the maximum decompositions used in commercial propane cracking. 

Propane cracks to both ethylene and methane, and to propylene and hydrogen (Eqs. 19.12 and 19.13) with product proportions, which change with the cracking temperature (Fig. 19.2). 

Fig. 4 represents a simplified schematic flow diagram for an ethane and/or propane cracking ethylene plant. The separation sequences are shown as follows ... 

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