Batch reactors pyrolysis

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

The pyrolysis of the plastics was carried out in a semi-batch reactor which was made of cylindrical stainless steel tube with 80mm in internal diameter and 135mm in height. A schematic diagram of the experimental apparatus is shown in Fig. 1, which includes the main reactor, temperature controller, agitator, condenser and analyzers. 

To illustrate the concepts of determining, non-determining and negligible processes, the mechanism of the pyrolysis of neopentane will be discussed briefly here. Neopentane pyrolysis has been chosen because it has been studied by various techniques batch reactor [105— 108], continuous flow stirred tank reactor [74, 109], tubular reactor [110], very low pressure pyrolysis [111], wall-less reactor [112, 113], non-quasi-stationary state pyrolysis [114, 115], single pulse shock tube [93, 116] amongst others, and over a large range of temperature, from... 

Among the inexhaustible plant resources for the production of activated carbon, we have the nutshell, which can be transformed by pyrolysis and activation with overheated water vapour. In this example, activated carbon has been used to retain some hydrocarbon traces from water using a batch reactor. The interest here is to... 

This chapter focuses attention on reactors that are operated isotherraally. We begin by studying a liquid-phase batch reactor to determine the specific reaction rate constant needed for the design of a CSTR. After iilustrating the design of a CSTR from batch reaction rate data, we carry out the design of a tubular reactor for a gas-phase pyrolysis reaction. This is followed by a discussion of pressure drop in packed-bed reactors, equilibrium conversion, and finally, the principles of unsteady operation and semibatch reactors. 

The physico-chemical properties of the bagasse-derived bio-oil obtained in the large batch reactor are summarized in Table 4. The bio-oil obtained after evaporation contains 13.8 wt.% water. Like the bio-oils originating from diverse biomasses using various pyrolysis techniques, the oil from vacuum pyrolysis of bagasse is heavier (djo = 1.211 g/rnl) than water,... 

A 800 g sample of the milled wood was pyro lysed in a batch reactor under vacuum run G72). A detailed description of the batch pyrolysis reactor system used in this work has been described elsewhere. Two vacuum pumps in series were used to achieve a total pressure of 0.7 kPa and three dry-ice-in-limonene condensers ( 72 C) were used to trap the pyrolysis vapours. When the maximum pyrolysis temperature was reached, it was held for I hour prior to cooling to room temperature. After the pyrolysis in each step, the system was kept under nitrogen until the next pyrolysis step was started. Each pyrolysis step was carried out by using the solid residue from the previous step. Table 1 shows the different pyrolysis steps and product yields. The pyrolysis oils which were... 

The feasibility of using the char generated by tyre pyrolysis as a precursor in the manufacture of activated carbon has been studied by various authors.119,131 Merchant and Petrich131 have obtained carbons with surface areas above 500 m2 g 1 from tyre pyrolysis in batch reactors and subsequent activation of the chars by treatment with superheated steam at temperatures in the range 800-900 °C. Teng et a/.119 have obtained activated carbons with surface areas above 800 m2 g 1 by pyrolysis of tyres up to 900 °C, followed by activation of the resulting chars in C02 at the same temperature. These surface areas are... 

Mean Residence Time of the Vapor Products in the Reactor. One important feature of the vacuum pyrolysis process is the short residence time of the gases and vapors in the reactor. In a previous investigation (4), the residence time of the vapor products in the laboratory scale batch reactor used was estimated to be about 2s. In the present investigation, a different pumping unit and a very large pyrolysis unit have been used, so that a new estimate of the mean residence time was necessary. 

Figure 4 shows the variations of log rQ as a function of log Pq at two temperatures, rQ is the rate of the pyrolysis reaction of neopentane in a batch reactor, extrapolated to zero conversion, and Pq is the initial partial pressure of neopentane in the reactor. Law (58) can be written ... 

Figure 4 Pyrolysis of neopentane in a batch reactor reaction order at conversion equal to zero.

This reaction has been studied using batch reactors, perfectly stirred continuous reactors, tubular continuous reactors, BENSON type reactors, wall-less reactors and shock tubes. The reaction has been carried out at temperatures between 700 and 1300 K, at pressures of 0.1 Pa to 10 Pa and at reaction times of 10 s to 10 s. The effects of the nature and of the area of the reactor walls as well as those of various additives have also been studied. The diversity of the studies carried out by a dozen teams throughout the world, the particularly widespread range of operating conditions (600 K for the temperature, which represents 11 orders of magnitude for the rate of initiation, 8 orders of magnitude for the pressure and reaction duration) make the pyrolysis of neopentane into a model radical reaction. 

The pyrolysis of isopentane has been studied in a batch reactor at constant volume at the temperature T = 480 at an initial isopentane pressure of p = 25 mmHg. Figure 2 shows the variation of the partial pressures of the products formed as a fimction of the reaction time. Very different results are observed according to the operating conditions. 

Figure 2 Pyrolysis of isopentane in a batch reactor. T = 480 °C, = 25 mmHg,...

Fig. 13.4 Products distributions (wt%) of pyrolysis of polypxtpylene at 300, 400, or 500 °C, AICI3 as catalyst in a batch reactor (PR-1) or in a fluidized bed process (LWS-5) [31]...

The products obtained from thermal cracking of plastics depend on the type of plastics, feeding arrangement, residence time, temperatures employed, reactor type, and condensation arrangement [42]. Reaction temperature and residence time have strong influence on the yield of pyrolysis products and the distribution of their components for plastic samples. Jude et al. conducted smdies on thermal cracking of LDPE in a batch reactor resulted in the production of a broad range of hydrocarbon compounds where the yield of aromatics and aliphatics (olefins and paraffins) deeply depended on the pyrolysis temperature and residence time. 

J.A. Onwudili, N. Insura, P.T. Williams, Composition of products from the pyrolysis of polyethylene and polystyrene in a closed batch reactor effects of temperature and residence time. J. Anal. AppL Pyrol. 86(2), 293-303 (2009)... 

The experimental results agree with the kinetic models and the hypothesis of a well micromixed reactor. They are also in good agreement with previous studies conducted in batch reactors (14, 15). Thus one obtains similar values for the main fundamental kinetic parameters, and these are compatible with those already published in the literature (see Table I). The values of the kinetic parameters shown on Table I (this work) were determined by an optimization procedure which indicates the precision of the estimation. However this work shows that the parameters obtained for self-inhibition (pyrolysis of pure neopentane) and inhibition (pyrolysis of a mixture of neopentane and isobutene) at no extent of reaction) are markedly different. We believe that these differences can be explained by the presence, in the reaction mixture, of impurities (essentially ethylenic products). These... 

Even if the above problems can be resolved, batch reactors can measure with accuracy the intrinsic rates of slow pyrolysis reactions. For faster reactions, the time required to heat the sample up to reaction temperature and then cool it down becomes an appreciable fraction of the total, and thus the accuracy with which data can be obtained becomes progressively poorer. If, however, the temperature history is well-defined, the non-isothermal data can be corrected using the "equivalent reaction time" concept (Hougen and Watson, 1947), which can provide, in some cases, a reasonable accuracy. The equivalent reaction time is the time required at a reference temperature to produce the same conversion as that obtained in the actual non-isothermal operation. 

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