Material balances/consumption

In a typical balanced plant producing vinyl chloride from EDC, all the HCl produced in EDC pyrolysis is used as the feed for oxychlorination. On this basis, EDC production is about evenly spHt between direct chlorination and oxychlorination, and there is no net production or consumption of HCl. The three principal operating steps used in the balanced process for ethylene-based vinyl chloride production are shown in the block flow diagram in Eigure 1, and a schematic of the overall process for a conventional plant is shown in Eigure 2 (76). A typical material balance for this process is given in Table 2. 

NOTE All boiler plant operators are urged to meter the MU water consumption as an aid to calculating a material balance. Steam generation rates can be reasonably accurately determined from the fuel consumption because records of fuel costs are always maintained. Daily and weekly BD rates usually can be estimated from the use of a measuring bucket or pipe velocity table. The difference between steam production and MU represents a combination ofBD and loss of CR. 

A Galerkin finite element (FE) program simultaneously solved the heat transfer PDE plus the material balance ordinary differential equation (Equation 9) (ODE). Typically, 400 equally spaced nodes were used to discretize half the cross-section. The program solved for the temperature and epoxide consumption at each node. 

The objectives of this study were to compare the yields of cold-pressed essential oil, water consumption, material balance and efficiency of the process in a typical citrus peel oil recovery plant with and without recycling system. The different emulsions and aqueous discharges from these processes were also characterized. 

The material balance is consistent with the results obtained by OSA (S2+S4 in g/100 g). For oil A, the coke zone is very narrow and the coke content is very low (Table III). On the contrary, for all the other oils, the coke content reaches higher values such as 4.3 g/ 100 g (oil B), 2.3 g/ioo g (oil C), 2.5 g/ioo g (oil D), 2.4/100 g (oil E). These organic residues have been studied by infrared spectroscopy and elemental analysis to compare their compositions. The areas of the bands characteristic of C-H bands (3000-2720 cm-1), C=C bands (1820-1500 cm j have been measured. Examples of results are given in Fig. 4 and 5 for oils A and B. An increase of the temperature in the porous medium induces a decrease in the atomic H/C ratio, which is always lower than 1.1, whatever the oil (Table III). Similar values have been obtained in pyrolysis studies (4) Simultaneously to the H/C ratio decrease, the bands characteristics of CH and CH- groups progressively disappear. The absorbance of the aromatic C-n bands also decreases. This reflects the transformation by pyrolysis of the heavy residue into an aromatic product which becomes more and more condensed. Depending on the oxygen consumption at the combustion front, the atomic 0/C ratio may be comprised between 0.1 and 0.3 ... 

Watanabe and Ohnishi [39] have proposed another model for the polymer consumption rate (in place of Eq. 2) and have also integrated their model to obtain the time dependence of the oxide thickness. Time dependent oxide thickness measurement in the transient regime is the clearest way to test the kinetic assumptions in these models however, neither model has been subjected to experimental verification in the transient regime. Equation 9 may be used to obtain time dependent oxide thickness estimates from the time dependence of the total thickness loss, but such results have not been published. Hartney et al. [42] have recently used variable angle XPS spectroscopy to determine the time dependence of the oxide thickness for two organosilicon polymers and several etching conditions. They did not present kinetic model fits to their results, nor did they compare their results to time dependent thickness estimates from the material balance (Eq. 9). More research on the transient regime is needed to determine the validity of Eq. 10 or the comparable result for the kinetic model presented by Watanabe and Ohnishi [39]. 

Energy consumption and material balances for environmental auditing ... 

As shown in Table II, in the presence of polymer, the enclosed nitrous oxide is completely consumed during irradiation. In the place of nitrous oxide, nitrogen and water are formed. The yield of nitrogen or water corresponds stoichiometrically to the loss of nitrous oxide. A large G value, about 2000, is given for the disappearance of nitrous oxide. Estimation of the G value is based on the assumption that the available energy for the consumption is only that absorbed directly by the gas dissolved in the polymer solid. The G values for the formation of water and nitrogen should be equal to 2000. Moreover, the summation of the amount of the excess formation of crosslinks and unsaturation becomes stoichiometrically almost equal to the loss of nitrous oxide, as shown in Table III. The equation of material balance of nitrous oxide, therefore, should be written as follows ... 

Polyisobutylene and Polypropylene. In a similar way, the material balance of nitrous oxide in the case of polyisobutylene was measured as shown in Table IV. In this case, whereas the enclosed nitrous oxide is not completely consumed during irradiation, the consumption proceeds... 

Material balance. To produce 1000 kg of cyclonite, 833 kg of hexamine and 8779 kg of HN03 are required 3482 kg of dilute 55% HN03 are recovered plus 3429 kg of HN03 from the absorption towers. Thus the net consumption of HN03 for nitration is 1868 kg. In addition, 490 kg of H2S04 are used for the concentration of HN03. 

The systems described above all result in the transport of metal cations across a metal-recovery circuit. In many cases this leads to very good materials balances in metal-recovery, especially when the circuit uses acid-leaching of the ore followed by solvent extraction using an organic acid (LH). The extraction then releases protons back into the aqueous phase, regenerating the acid needed for leaching. This underpins the very successful copper recovery operations outlined in Figure 7 in which copper oxide in the crude ore is essentially split into its component elements with the consumption of only electrical power. 

Dissolved oxygen. The structure of the DO material balance in a reactor can be divided into three parts, the hydraulic transport of DO, the production related to the air supply and the consumption (uptake rate) due to organism growth and decay. The hydraulic transport of DO is negligible in comparison with the oxygen transfer (production). 

The preliminary material balance sets the limits for the variables of significance for process performance, namely the minimum material consumption and the maximum yield in products, and from this viewpoint is a kind of ideal material balance. 

The nature and the distribution (Table II) of the ozonolysis products in conjunction with the probable modes of their formation allow also a qualitative rationalization of the observed ozone-olefin stoichiometry. Three reactions compete with ozone for the starting material, trans-2,3-dibromo-2-butene. These reactions are the formation of 3,3-dibromobutanone, 31, and the formation of the brominated products, 34 and 35. On the other hand, hydrogen bromide is oxidized to form bromine and water, which consumes ozone on top of the regular olefin— ozonolysis reaction. An attempt to explain the observed stoichiometry quantitatively did, however, not lead to a satisfactory correlation between the actual ozone consumption and the observed material balance. This... 

The models may be used to compare performance between several units or unit types. For example, a week of production data from the above-mentioned modified cascade unit was compared with simulated Stratco performance. The agreement between Amoco s Stratco simulation model predictions and material balance and performance predictions provided by the Stratford Engineering Corporation had been confirmed earlier. Model adjustments allowed a comparison at constant operating conditions to be made. Table I compares the performance of the modified cascade unit with the Stratco simulation model predictions. Acid consumption is 36% lower in the modified cascade unit. The Stratco unit does show a slight research octane advantage over the cascade. However, overall economics favor the modified cascade. in this case. 

In the derivations of the equations above, V was the volume of the control volume which is composed of the volume of the reactor, secondary clarifier, and the associated pipings. As the effluent from the reactor is introduced into the secondary clarifier, it is true that microorganisms continue to respire. In the absence of aeration in the basin, however, this respiration is but for a few moments and consumption of substrates ceases. It is also true that there will be no respiration and consumption of substrates in the associated pipings. Thus, the only volume of the control volume applicable to the material balance is the volume of the reactor. Therefore, V may be considered simply as the volume of the reactor. 

Table 26.15 shows the heat balance in the plant based on the material balance and consumption figures shown in Tables 26.13 and 26.14, under following conditions ... 

Since the process is at steady stale there can be no buildup of anything in the system, so the accumulation term equals zero in all material balances. In addition, since no chemical reactions occur, there can be no nonzero generation or consumption terms. For all balances, Equation 4.2-2 therefore takes the simple form input = output. 

The occurrence of a chemical reaction in a process brings several complications into the material balance procedures described in the previous sections. TTie stoichiometric equation of the reaction imposes constraints on the relative amounts of reactants and products in the input and output streams (if A B, for example, you cannot start with 1 mol of pure A and end with 2 mol of B). In addition, a material balance on a reactive substance does not have the simple form input = output, but must include a generation and/or consumption term. 

Material Balance. Material balances for a low and high sulfur content gas to the RC/Bahco CTB-100 module are illustrated in Table IV. Operating data from actual installations indicate 93-99% SO2 removal and particulate emissions as low as 0.01 grain/SCFW. Scrubbing reagent consumption is about 1.1 times the stoichiometric amount. 

From the viewpoint of both a mass balance or a mole balance for elements themselves, such as C, H, or O, the generation and consumption terms are not involved in a material balance. Finally, Eq. (2.1) should not be applied to a balance on a volume of material unless ideal mixing occurs (see Sec. 3.1) and the densities of the streams are the same. In this chapter, information about the generation and consumption terms for a chemical compound will be given a priori or can be inferred from the stoichiometric equations involved in the problem. Texts treating chemical reaction engineering describe how to calculate from basic principles gains and losses of chemical compounds. 

Most, but not all, of the problems discussed in this chapter are steady-state problems treated as integral balances for fixed time periods. If no accumulation occurs in a problem, and the generation and consumption terms can be omitted from consideration, the material balances reduce to the very simple relation... 

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