Reactants, preheating

Titanium disulfide can also be made by pyrolysis of titanium trisulfide at 550°C. A continuous process based on the reaction between titanium tetrachloride vapor and dry, oxygen-free hydrogen sulfide has been developed at pilot scale (173). The preheated reactants ate fed iato a tubular reactor at approximately 500°C. The product particles comprise orthogonally intersecting hexagonal plates or plate segments and have a relatively high surface area (>4 /g), quite different from the flat platelets produced from the reaction between titanium metal and sulfur vapor. The powder, reported to be stable to... 

In the process the preheated reactants, inerts (diluent methane and recycled CO2), and promoters are fed into the multi-tubular reactor The gas stream leaving the reactor is cooled by an external heat exchanger and sent to the ethylene oxide absorber column. In this column the relatively small amounts of ethylene oxide (concentration 1-2 mol.%) are absorbed in water. A minor part of the gas leaving the top of the absorber is purged to reduce the inerts concentration (mainly CO2, argon, and methane). The rest of the gas stream is sent to the CO2 absorber unit. 

Using a flow reactor lined inside with alumina (Alsint) and equipped with five sequentially mounted thermocouples, the authors of [67] measured the temperature profiles (Fig. 3.49), which turned out to be qualitatively consistent with the results of kinetic simulations. In the absence of an oxygen conversion, the preheated reactants cooled down monoton-ically, whereas when the reaction occurred, an induction period followed by rapid heating was observed. A specific feature of these experiments was the instability and incessant fluctuations of the temperature profile. For example, the maximum heat-up temperature fluctuated up and down by 5 °C. It was also pointed out that the results depended on the spatial position of the maximum heat-up zone, with the best results being obtained when the reaction zone was as close to the water-cooled quenching unit as possible. 

SL/RN Process. In the SL/RN process (Fig. 4), sized iron ore, coal, and dolomite are fed to the rotary kiln wherein the coal is gasified and the iron ore is reduced. The endothermic heat of reduction and the sensible energy that is required to heat the reactants is provided by combustion of volatiles and carbon monoxide leaving the bed with air introduced into the free space above the bed. The temperature profile in the kiln is controlled by radial air ports in the preheat zone and axial air ports in the reduction zone. Part of the coal is injected through the centerline of the kiln at the discharge end. The hot reduced iron and char is discharged into an indirect rotary dmm cooler. The cooled product is screened and magnetically separated to remove char and ash. 

Heat Recovery and Feed Preheating. The objective is to bring the reactants to and from reaction temperature at the least utihty cost, and to recover maximum waste heat at maximum temperature. The impact of feed preheating merits a more careful look. In an exothermic reaction, preheated feed permits the reactor to act as a heat pump, ie, to buy low and sell high. The most common example is combustion-air preheating for a furnace. 

Section 1.5 described one basic problem of scaling batch reactors namely, it is impossible to maintain a constant mixing time if the scaleup ratio is large. However, this is a problem for fed-batch reactors and does not pose a limitation if the reactants are premixed. A single-phase, isothermal (or adiabatic) reaction in batch can be scaled indefinitely if the reactants are premixed and preheated before being charged. The restriction to single-phase systems avoids mass... 

By recognizing this variahon in Equahon 4.1.1, can be perturbed by var3ung either nitrogen dilution level or preheat temperature and, it is of interest to compare the deduced values of using the two different methods. It must be noted that the former method perturbs the reactant concentrations by keeping as constant, while... 

The used raw materials were TiCU, oxygen, Ar and NaOH. The reaction apparatus consisted of gas purifiers, reactant preheaters, reactor, water cooler, separator and an off-gas treatment unit. The reactor was a 27 mm in ID. (32 mm in O.D.), 1430 mm in length quartz tube that was heated by a horizontal electrical furnace. A quartz rod and a ceramic rod, 6 mm... 

The cementition reaction between zinc oxide powder and aqueous zinc chloride was found to be both rapid and extremely exothermic. Although at least four days equilibration was allowed before examining any of the cements in detail, Sorrell found evidence that reaction was complete within 20 to 30 minutes and occurred without observable development of intermediate phases. He also found that, as the concentration of reactants was increased, so reaction rate increased until, at sufficiently high concentrations, reaction occurred too quickly to allow proper mixing of the reactants. Preheating the zinc oxide at 900 °C for 16 hours was found to slow the reaction down, but only slightly. 

Heavy fuel oil feedstock is delivered into the suction of metering-type ram pumps which feed it via a steam preheater into the combustor of a refractory-lined flame reactor. The feedstock must be heated to 200°C in the preheater to ensure efficient atomisation in the combustor. A mixture of oxygen and steam is also fed to the combustor, the oxygen being preheated in a separate steam preheater to 210°C before being mixed with the reactant steam. 

Incoming gas is introduced into the saturator (a packed column) where it is contacted with hot water pumped from the base of the desaturator this process serves to preheat the gas and to introduce into it some of the water vapour required as reactant. The gas then passes to two heat exchangers in series. In the first, the unconverted gas is heated... 

Reaction rate experiments were conducted in NMR tubes sealed with Teflon valves. In an inert atmospere glovebox, catalysts and internal standard, TMS4C, were weighed into the tube, followed by addition of solvents and reactants. The tube was immediately inserted in the preheated (50 °C) probe of a 500 MHz Varian Unitylnova spectrometer. To acquire spectra the sample was irradiated twice with a 30° pulse, 5 sec acquisition time, and 120 sec delay. 

Since operation in an autothermal mode implies a feedback of energy to preheat the feed, provision must be made for ignition of the reactor in order to attain steady-state operation. The ordinary gas burner and many other rapid combustion reactions are examples of autothermal reactions in which the reactants are preheated to the reaction temperature by thermal conduction and radiation. (Back diffusion of free radicals also plays an important role in many combustion processes.)... 

Figures 4.6—4.8 are the results for the stoichiometric propane-air flame. Figure 4.6 reports the variance of the major species, temperature, and heat release Figure 4.7 reports the major stable propane fragment distribution due to the proceeding reactions and Figure 4.8 shows the radical and formaldehyde distributions—all as a function of a spatial distance through the flame wave. As stated, the total wave thickness is chosen from the point at which one of the reactant mole fractions begins to decay to the point at which the heat release rate begins to taper off sharply. Since the point of initial reactant decay corresponds closely to the initial perceptive rise in temperature, the initial thermoneutral period is quite short. The heat release rate curve would ordinarily drop to zero sharply except that the recombination of the radicals in the burned gas zone contribute some energy. The choice of the position that separates the preheat zone and the reaction zone has been made to account for the slight exothermicity of the fuel attack reactions by radicals which have diffused into...

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