Multiple reactors

The conversion of aromatic monomers relative to C-5—C-6 linear diolefins and olefins in cationic polymerizations may not be proportional to the feedblend composition, resulting in higher resin aromaticity as determined by nmr and ir measurements (43). This can be attributed to the differing reactivity ratios of aromatic and aHphatic monomers under specific Lewis acid catalysis. Intentional blocking of hydrocarbon resins into aromatic and aHphatic regions may be accomplished by sequential cationic polymerization employing multiple reactors and standard polymerization conditions (45). 

In two processes under development as of 1997, the sulfur dioxide stream reacts with reduciag gas over a proprietary catalyst to form elemental sulfur. Both processes have achieved a sulfur recovery of 96% ia a single reactor. Multiple reactor systems are expected to achieve 99+% recovery of the feed sulfur. The direct sulfur recovery process (DSRP), under development at Research Triangle Institute, operates at high temperature and pressure. A similar process being developed at Lawrence Berkeley Laboratory is expected to operate near atmospheric pressure. 

The Catofin process, which was formerly the property of Air Products (Houdry Division), uses a proprietary chromium catalyst in a fixed-bed reactor operating under vacuum. There are actually multiple reactors operating in cycHc fashion. In sequence, these reactors process feed for about nine minutes and are then regenerated for nine minutes. The chromium catalyst is reduced from Cr to Cr during the regeneration cycle. 

Multiple reactors achieve 95-96% conversion and recovery, and stringent air pollution legislation has now pushed this to 99%. A similar sequence of reactions is used for sulfur production from crude oil except that the organosulfur compounds must first be removed from the refinery feed and converted to H2S by a hydrogenation process before the sulfur can be recovered. 

The multiple reactor capability allows the modelling of up to five CSTRs connected in any possible configuration. This is achieved by simple mass and energy accounting, with the user... 

What type of reactor best meets the process requirements Are there advantages associated with the use of a combination of reactor types, or with multiple reactors in parallel or series ... 

Another advantage of Liquid Recycle is that multiple reactors may be arranged in series with the effluent from one passing on to the next. The alkene concentration is less in the downstream reactors, but reaction conditions can be adjusted to optimize each reactor s performance. In back mixed reactors in continuous operation, the effluent from the reactor is the same as the catalyst solution throughout the reactor. By placing reactors in series, the first reactor can be optimized for high rates and later reactors for high conversion. 

Sclairtech An advanced version of the Sclair ethylene polymerization process, using a Ziegler-Natta catalyst and multiple reactors. Announced in 1996. The first commercial plant will be built in Alberta by Amoco Canada and Nova, and is scheduled for completion in 2000. 

The process is run in a semi-batch mode, and multiple reactors are used. There are several possible causes for a loss of control such as insufficient heat removal and loss of agitation. Overpressurization leading to the bursting of rupture discs takes place several times per year, indicating both the clear need for containment but also a need to consider design and control improvements. The reference describes the autoclave rupture disc assembly, procedures for replacement of the discs, the cleaning of the containment vessels, and the routine maintenance procedures for the containment vessels. 

Multiple reactor processes, 20 170 Multiple screw pumps, 21 73 Multiple spinnerette per bank process,... 

For GB Extend titanium reference liner change-out frequency using multiple reactors or implement Pt wear liner product improvement... 

Researchers at the Chinese Academy of Sciences are developing a scalable methanol autothermal reforming (ATR) reactor. The microchannel reactor will be composed of multiple reactor chips (Figure 21). with each chip able to process enough methanol for approximately 100 We hydrogen. Both aluminum and stainless steel were evaluated for use as the chip... 

When we can predict the response of the reacting system to changes in operating conditions (how rates and equilibrium conversion change with temperature and pressure), when we are able to compare yields for alternative designs (adiabatic versus isothermal operations, single versus multiple reactor units, flow versus batch system), and when we can estimate the economics of these various alternatives, then and only then will we feel sure that we can arrive at the design well fitted for the purpose at hand. Unfortunately, real situations are rarely simple. 

Multiple-Reactor Systems 131 Since =2 = 2Vn=i the ratio of flow rates becomes... 

Figure 6.21 (a) The best multiple reactor scheme, (b) The best scheme when unconverted reactant can be separated and recycled. 

Real processes almost invariably involve multiple reactors. These may be simply reactors in series with different conversions, operating temperatures, or catalysts in each reactor. However, most industrial processes involve several intermediates prepared and purified between initial reactants and final product. Thus we must consider the flow diagram of the overall process along with the details of each reactor. 

These examples all involve multiple reactors with separations between reactors and new feeds added in each stage. As an example of the nitration of toluene, starting with CH4, we write the steps as... 

For single and multiple reactor stages we sketch reactors and separation units as shown in Figure 3-20. We assume a first reactor running the reaction... 

General Concept. The development of the fixed-bed process was based upon the idea of using a static bed of catalyst and maintaining a continuous flow of hydrocarbon vapor by the use of multiple reactors (17). Each reactor was submitted to a cycle of operations consisting of ... 

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