Enthalpy batch reactors

The experimental method used for this kinetie study is reaetion ealorimetry. In the ealorimeter, the energy enthalpy balance is continuously monitored the heat signal can then be easily converted in the reaction rate (in the case of an isothermal batch reactor, the rate is proportional to the heat generated or consnmed by the reaction). The reaction orders and catalyst stabihty were determined with the methodology of reaction progress kinetic analysis (see refs. (8,9) for reviews). 

The vast majority of the reactions carried out in industrial scale batch reactors involve reactants in condensed phases. Since the specific volumes of both liquids and solids are very small, the difference between internal energy and enthalpy for these materials is usually negligible. Thus one often sees the statement that for batch reactions taking place at constant volume ... 

Simple examination of A Hr of a reaction immediately tells us how much heat will be absorbed or hberated in the reaction. This is the amount of heat Q that must be added or extracted to maintain the reactor isothermal. (This heat is exactly the enthalpy change in any flow reactor or in a batch reactor at constant pressure, and it is close to this for other conditions.)... 

A catalytic hydrogenation is performed at constant pressure in a semi-batch reactor. The reaction temperature is 80 °C. Under these conditions, the reaction rate is lOmmolT s-1 and the reaction may be considered to follow a zero-order rate law. The enthalpy of the reaction is 540 kj moT1. The charge volume is 5 m3 and the heat exchange area of the reactor 10 m2. The specific heat capacity of water is 4.2kJkg 1K 1. 

For a batch reactor, the accumulation of enthalpy results from the production of enthalpy and the transfer of heat from the surroundings ... 

The formal similarity allows us to carry over the equations for mass and energy balances in the tubular reactor, Eqs. (3.4.11)-(3.4.14). The momentum equation has no meaning. Care must be taken however to distinguish between a batch reactor working at constant volume and one that works at constant pressure. The latter has the Eqs. (3.4.12) or (3.4.14) which were derived from an enthalpy balance. In the former case the heat added would be equated to the internal energy change. Thus in this case c should replace Cp and the internal energy of reaction replace the heat of reaction. These... 

The accumulation term represents the energy increase due to the change in composition and the change in temperature of the reactor contents. This involves the heat of reaction Aif and the specific heat c , as described in the development of Eq. (3-11) for batch reactors. Similarly, the enthalpies Hq and depend on both temperature and composition. Let us take the reference temperature as X and the reference composition as that corresponding to the composition of the feed (zero conversion). Then, following the development of Eq. (3-5),... 

As in the batch reactor, for a single-phase system we consider the change in enthalpy due to changes in temperature, pressure and the jnuniber of moles of component j,... 

For a batch reactor, there is no flow across the system boundaries and no transport of enthalpy across the system boundaries. From Eqn. (8-1),... 

Since enthalpy is a point function, it is independent of the path for any process. If heat of reaction determinations are made in a flow reactor, the energy (in the form of heat) transferred across the reactor boundary or surface, with inlet and outlet temperatures equal, is exactly equal to the heat of reaction. This is not the case for batch or nonflow systems. For this reason, heat of reaction is a misleading term. More recently, it had been referred to as the enthalpy of reaction although a more accurate term would be enthalpy change of reaction. The terms heat and enthalpy of reaction are used interchangeably in this subsection. 

The open-loop observer formed by Equations 7.23,7.27, and 7.28 has been successfully used to estimate the unreacted amounts of monomers in different monomer systems under different conditions [25-29]. Once the unreacted amounts of the monomers (Al and A ) are estimated during the course of the polymerization, the conversion and copolymer compositions can be readily estimated for batch and semibatch reactors. The accuracy of the estimation depends on the reactivity ratios and enthalpies of polymerization for each monomer that can be obtained experimentally or are available in the literature. 

Here, heat is added via the enthalpy of polymerization (AH and removed through heat transfer to a jacket or cooling coil. More complex chemistries and/or reactors other than simple batch will add complexity to these equations, as well as adding an additional species balance for each additional chemical species. More complex models will be developed later in this text. 

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