Liquids Cracking

Figure 5.1-4 The products from the ionic liquid cracking of high-density polyethylene at 120 °C...

The simplest paraffin (alkane) and the most widely used feedstock for producing ethylene is ethane. As mentioned earlier, ethane is obtained from natural gas liquids. Cracking ethane can be visualized as a free radical dehydrogenation reaction, where hydrogen is a coproduct ... 

Toluene has one xylenes have two. Sources of all three BTXs are the same crude oil, catalytic reforming, heavy liquids cracking in on olefins plant, and, to a declining extent, coking at a steel plant.. ... 

Referring to the hardware in Figure 5—4, there are much larger facilities required for heavier liquids cracking than for ethane or propane. As you saw in Table 5—1, the yield of ethylene from the heavier feeds is much lower than from ethane. That means that to produce the same amount of ethylene on a daily basis, the gas-oil furnaces have to handle nearly five times as much feed as ethane furnaces. As the design engineer scales up these volumes, he or she has to worry about the size of the cubes necessary to heat up that much feed, the residence times best for each kind of feed, and the best pressure/temper-ature/steam mixture conditions. 

Crude oil is heated to temperatures at which it thermally cracks into gasoline and distillate products and lower-molecular-weight gases. This liquid cracking process is referred to as visbreaking. A schematic of the process and the effect of operating variables on performance is shown in Fig. 19-12. 

Furnace effluent, after quench, flows to the gasoline fractionator (3) where the heavy oil fraction is removed from the gasoline and lighter fraction (liquids cracking only). Further cooling of furnace effluents is... 

Carbon on the catalyst is determined by burning in air, after the nitrogen flush and after replacement of the synthetic-crude trap (in which liquid cracked products are collected) with an empty one. The... 

The liquid cracked products collected in the trap are distilled directly from the collecting trap through a low hold-up, 5- to 10-plate column (see Fig. 3) at a rate of about Yi ml. per minute. The final cut point is 410°F. (210°C.) vapor temperature, giving the volume yield of 410°F. end-point gasoline. 

Butadiene. Butadiene pricing seems to have reflected increased supply from both ethylene by-product sources and old plants partially modified to increase yields. The favored route for new direct capacity is probably butane dehydrogenation but the growth of more U.S. ethylene capacity based on gas oil would substantially increase by-product supply. Since butadiene growth is slower than ethylene growth with a heavy shift toward refinery liquids, cracking for ethylene would tend to depress butadiene supply/demand balances and prices. 

When the network of the gel is full of liquid, cracking is always related to the permeability and to the mechanical strength. Note that, as demonstrated be-... 

There are numerous expressions that are useful for representing severity of cracking.(1 ) The most commonly used terms in our work, i.e., for liquids cracking, are shown in Table III, and are discussed below. 

In accordance with the diagram, a mixture of straight-run fuel oil, and of liquid cracking residue produced in the thermal cracking process and containing large quantities of resinous bitumen materials and solid coke particles, is supplied to the debitumination section of the plant. 

In order to further increase the yields of light oil products on the light cracking of fuel oil, and especially of products of the mean fractional composition, we studied the light cracking of fuel oil with recycling of the heavy reflux distilled under vacuum from liquid cracking residue. 

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