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without affecting the operation of

Cyclar Process the reactor and product recovery

sections.

Hydrogen Fuel

Product Gas The principal Cyclar operating

Stacked

Reactor variables are feedstock composi-

Fresh LPG Feed Gas Recovery

from Driers Section tion, pressure, space velocity, and

Catalyst

Regenerator temperature. The temperature must

Combined Feed be high enough to ensure nearly

Exchanger Light Ends complete conversion of reaction

Separator Drag to

Fuel Gas intermediates in order to produce a

liquid product that is essentially

Fresh free of nonaromatic impurities, but

Catalyst Fired Heaters low enough to minimize nonselec-

Spent Stripper

Catalyst tive thermal reactions. Space

velocity is optimized against con-

version within this temperature

range to obtain high product yields

C6+ Aromatic

Product with minimum operating costs.

Reaction pressure has a big impact

the world for reforming petroleum naphtha. Fresh feed on process performance. UOP currently offers two alter-

and recycle are combined and heat exchanged against native Cyclar process designs. The low-pressure design is

reactor effluent. The combined feed is then raised to reac- recommended where maximum aromatic yield is desired.

tion temperature in the charge heater and sent to the reac- The high-pressure design requires only half the catalyst

tor section. Four adiabatic, radial-flow reactors are and is attractive where minimum investment and operat-

arranged in one or more vertical stacks. Catalyst flows ing costs are the overriding considerations.

vertically by gravity down the stack, while the charge

flows radially across the annular catalyst beds. Between P Q Y

RODUCT UALITY AND IELDS

each reactor, the charge is reheated to reaction tempera- The major liquid products from the Cyclar process are

ture in an interheater. The effluent from the last reactor is benzene, toluene, xylenes, and heavier aromatics. In gen-

split into vapor and liquid products in a separator. The liq- eral, the aromatics yield increases with the carbon number

uid is sent to a stripper where light saturates are removed of the feedstock. In a low-pressure operation, the overall

from the C + aromatic product. Vapor from the separator

6 aromatics yield increases from 61 wt-% of fresh feed

is compressed and sent to a gas recovery section, typically with an all-propane feedstock, to 66% with an all-butane

a cryogenic unit, for separation into a 95% pure hydrogen feed, with a corresponding decrease in fuel gas produc-

product stream, a fuel gas stream of light saturates, and a tion. These yield figures can be interpolated linearly for

recycle stream of unconverted LPG. Hydrogen is not mixed propane and butane feedstocks. The distribution of

recycled. butane species in the feed has no effect on yields. The dis-

As coke builds up on the Cyclar catalyst over time at tribution of aromatic species in the liquid product is also

reaction conditions, partially deactivated catalyst is con- unaffected by feedstock composition. Butane feedstocks

tinually withdrawn from the bottom of the reactor stack produce a product that is leaner in benzene and richer in

for regeneration. The catalyst flows down through the xylenes than that produced from propane. With either

regenerator where the accumulated carbon is burned off. propane or butane feeds, the liquid product contains about

Regenerated catalyst is purged and then lifted with hydro- 91% BTX and 9% heavier aromatics.

gen to the top of the reactor stack. Because the reactor The Cyclar process produces high-quality aromatic prod-

and regenerator sections are separate, each operates at its ucts. Petrochemical grade toluene and xylenes can be

own optimum conditions. In addition, the regeneration obtained by fractionation alone, without the need for sub-

section can be temporarily shut down for maintenance 2


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DETTAGLI
Corso di laurea: Corso di laurea in chimica industriale e tecnologie del packaging
SSD:
Università: Parma - Unipr
A.A.: 2007-2008

I contenuti di questa pagina costituiscono rielaborazioni personali del Publisher Atreyu di informazioni apprese con la frequenza delle lezioni di Chimica industriale II e studio autonomo di eventuali libri di riferimento in preparazione dell'esame finale o della tesi. Non devono intendersi come materiale ufficiale dell'università Parma - Unipr o del prof Moggi Pietro.

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