Single stage recycle

Figure 16.n Hydrocracking catalyst performance in single stage recycle as a function of zeolite content and unit cell size. 

In a single stage, without liquid recycle, the conversion can be optimized between 60 and 90%. The very paraffinic residue is used to make lubricant oil bases of high viscosity index in the range of 150 N to 350 N the residue can also be used as feedstock to steam cracking plants providing ethylene and propylene yields equal to those from paraffinic naphthas, or as additional feedstock to catalytic cracking units. 

In a single stage with liquid recycle, total conversion to products lighter than the feedstock is possible. The yield of kerosene plus diesel is between 70 and 73 weight %. 

Hybrid Crystallization/Adsorption Process. In 1994, IFP and Chevron announced the development of a hybrid process that reportedly combines the best features of adsorption and crystallization (59,99). In this option of the Eluxyl process, the adsorbent bed is used to initially produce PX of 90—95% purity. The PX product from the adsorption section is then further purified in a small single-stage crystallizer and the filtrate is recycled back to the adsorption section. It is reported that ultrahigh (99.9+%) purity PX can be produced easily and economically with this scheme for both retrofits of existing crystallization units as well as grass-roots units. A demonstration plant was built at Chevron s Pascagoula refinery in 1994. 

Figure 12-96 illustrates a single-stage dryer employing a paddle mixer, recycle, and an ABB Raymond cage mill for tine grinding and... 

The oxidation reaction may he carried out in a single-stage or a two-stage process. In the single-stage, ethylene, oxygen, and recycled gas are... 

What effect does recycling have on the operation of a single-stage CSTR Consider the... 

Figure 3-20 Sketch of a single-stage reactor with product separation and recycle and also two stages where reactants from the first stage are separated and recycled into the first reactor while products are mixed with other leactants and fed into a second stage.

Dilution water calculations for a two stage system using recycle are slightly more complicated than for a single stage or two stage without recycle. These problems are better suited tn a computer, as hand calculations require several entries of dilution water variables in order to zero in on the proper balance. 

The single-stage plant (Figure 3) can be used to produce gasoline but is most advantageously used to produce middle distillate from heavy vacuum gas oils. The operation is again extinction recycle above a cut point which can be above 700°F. These two flow schemes represent... 

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