Laboratory scale tubular reactor

In an effort to verify the results obtained by Frey and Watts, Professor Viejo Dinosaurio has employed a laboratory scale tubular reactor that can operate isothermaUy at 628 K. For a reactor with an effective volume of 2850 cm and an operating pressure of 1 atm, he reported the data summarized below. Feed composition P = 50% v/v Nj = 50% v/v. 

A laboratory scale tubular reactor was built to obtain data for the thermal cracking of hydrocarbons. However, sufficient data... 

Laboratory studies have shown that omega (MAZ structure type) based paraffin hydroisomerization catalyst shows higher activity than mordenite based catalyst and better selectivity, i.e. higher octane due to higher yield of di-branched paraffins compared to mordenite performance (17). The isomerization of a C5/C6 cut at 15 bar results in a final calculated RON of 80.4 for the alumina bound dealuminated PtH-MOR catalyst supplied by IFP with undisclosed (most likely similar) Si/Al ratio, measured at 265 °C compared to a RON value of 80.9 for an alumina bound dealuminated PtH-MAZ catalyst with bulk Si/Al = 16, measured at 250 °C. Both measurements were performed in a bench-scale tubular reactor with a volume of 50 cm3 of 2 mm diameter extrudates with WHSV of 1.5 h and H2/HC of 4. This... 

Exercise 9,5,4, Laboratory experiments on the dehydration of ethyl alcohol indicate that the reaction, C2H5OH —> C2H4 + H O, is second order with respect to the alcohol concentration. The rate constant is 0.52 1 gm-mole" sec at 150 C. It is proposed to construct a small scale tubular reactor which will operate at 2 atm and 150"C to give 35% conversion of the alcohol when the feed rate is 9.9kg/hr. If the reactor has a diameter of 10cm, what length will be required Ideal gas behavior and piston flow through the reactor may be assumed and... 

Figure 16.1 Different types of MIEC laboratory scale membrane reactors (a) short hollow fiber with Au sealing in the hot zone, (b) short tubular membrane, and (c) disk membrane.

The experience of using small-scale tubular reactors [1], which operate in a quasi-plug flow mode, for fast chemical and many mass exchange physical processes, together with the results of laboratory research and mathematical modelling for processes of... 

Peclet number independent of Reynolds number also means that turbulent diffusion or dispersion is directly proportional to the fluid velocity. In general, reactors that are simple in construction, (tubular reactors and adiabatic reactors) approach their ideal condition much better in commercial size then on laboratory scale. On small scale and corresponding low flows, they are handicapped by significant temperature and concentration gradients that are not even well defined. In contrast, recycle reactors and CSTRs come much closer to their ideal state in laboratory sizes than in large equipment. The energy requirement for recycle reaci ors grows with the square of the volume. This limits increases in size or applicable recycle ratios. 

A continuous MW reactor (CMR), which operates by passing a reaction mixture through a pressurized tubular microwave-transparent coil and a MW batch reactor (MBR), have been developed by CSIRO in Australia and are used for organic synthesis on the laboratory scale [8]. The CMR can be operated at pressures up to 1400 kPa and temperatures up to 200 °C and the MBR at pressures and temperatures up to 10 MPa and 260 °C. 

Five biomass samples (hazelnut shell, cotton cocoon shell, tea factory waste, olive husk and sprace wood) were pyrolyzed in a laboratory-scale apparatus designed for the purpose of pyrolysis (Demirbas, 2001, 2002a). Figure 6.4 shows the simple experimental setup of pyrolysis. The main element of the experimental device is a vertical cylindrical reactor of stainless steel, 127.0 nun in height, 17.0 nun iimer diameter and 25.0 mm outer diameter inserted vertically into an electrically heated tubular furnace and provided with an electrical heating system power source, with a heating rate of about 5 K/s. The biomass samples ground... 

Fig. 1.16. Laboratory-scale reproduction of adiabatic tubular reactor temperature profile...

Metal- and alloy-containing membranes are currently applied mainly in ultrapure hydrogen production. Pilot plants with palladium alloy tubular membrane catalyst were used in Moscow for hydrogenation of acetylenic alcohols into ethylenic ones. In the Topchiev Institute of Petrochemical Synthesis, a laboratory-scale reactor of the same type was tested... 

A novel fermentation system, a tubular loop reactor (Figure 4.3), has been developed at laboratory scale which is capable of producing algal cultures with densities of 20 g dry wt r . This system converts 18% of incident solar energy, far in excess of the 7% in algd ponds and 1-2% in agriculture. Such a system mves a theoretical output in Eurc an climates of 100 )00-150,000 kg protein ha year, and could be operated in arid regions as the water is conserved and can be recycled. 

However, no general correlation is yet available for ki,a and kca in vertical tubular reactors when the two-phase flow regime is different from bubble flow. So for design, scale-up should be based on laboratory data for mass-transfer coefficients and on the ratio of eneigy dissipation terms as in the method defined by Jepsen (J3). For any tubular reactor, great care must be taken with the distributor design and with the size of the inlet section so as to minimize the entrance effects. 

Tubular reactors are commonly used in laboratory, pilot plant, and commercial-scale operations. Because of their versatility, they are used for heterogeneous reactions as well as homogeneous reactions. They can be run with cocurrent or counter-current flow patterns. They can be run in isothermal or adiabatic modes and can be used alone, in series, or in parallel. Tubular reactors can be empty, packed with inert materials for mixing, or packed with catalyst for improved reactions. It is often the process that will dictate the design of the reactor, as discussed in this entry. 

The two most common membrane geometries are the flat plate and the tube. Single flat plate membranes are usually used in laboratory scale investigations due to their ease of fabrication. Tubular membranes are more and more popular due to their much larger ratio of the membrane surface area to the equipment volume than flat plate membranes [4]. OITM reactor configurations with multi-planar or multi-tubular structures are required for commercial use. 

Free-radical polymerizations are exothermic, and so the heat produced during polymerization must be removed. This is not a significant problem in a laboratory scale however, heat transfer problems constitute a restriction for batch processes in an industrial scale. In the case of semibatch and CSTR, the cold monomer and water feed are beneficial for heat removal so that much higher production rates are feasible than for a batch reactor of the same volume. For tubular reactors, their large heat transfer area is advantageous for the strongly exothermic polymerizations. 

A pilot plant scale, tubular (annular configuration) photoreactor for the direct photolysis of 2,4-D was modeled (Martin etal, 1997). A tubular germicidal lamp was placed at the reactor centerline. This reactor can be used to test, with a very different reactor geometry, the kinetic expression previously developed in the cylindrical, batch laboratory reactor irradiated from its bottom and to validate the annular reactor modeling for the 2,4-D photolysis. Note that the radiation distribution and consequently the field of reaction rates in one and the other system are very different. 

Olefin polymerization in batch reactors is not common. Laboratory-scale high-throughput reactors are perhaps one of the few examples of such reactors applied to olefin polymerization. Some olefin polymerization tubular reactors can also be treated as batch reactors, where a polymerization-time to reactor-length transformation can be made and directly applied to the equations derived above if the tubular reactor has plug-flow residence time. 

A successful micromixer-assisted pilot plant was designed by researchers at Axiva (formerly Aventis) [8] for the production of acrylates. In the scale-up of the above-described laboratory-scale experiments, the numbering-up approach was used as the performance of the micromixer is direcfly related to its small dimensions. Therefore, 28 micromixers were used to mix the inlet flows of four tubular reactors (Figure 12.3). A capacity of 2000tons per year was achieved without any fouling problem. Axiva filed a patent [9] on the use of such a micromixer for the continuous production of polymers. 

Figure 4 shows the CO conversion curves (calculated from a mass balance on the amount of carbon in CO and of all the hydrocarbons, revealed by the detector of the gas-chromatograph) vs time for two RU/AI2O3 samples (1% Ru w/w). The runs were performed at 275 C, 5 bar in a tubular continuously fed reactor, with a molar ratio H2/CO = 2. Pd/C catalysts were tested in the hydrogenation of acetophenone in ethanol at 25°C and atmospheric pressure with flowing H2 as reactant in a slurry laboratory-scale plant. The activity values were measured by the consumed hydrogen in mL-min i. 

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