Application To Specific Reactors

The purpose of this section is to apply the introductory statistics materials to each of the traditional three reactors. The emphasis is on batch reactors since most of the experimental work conducted for the purpose of generating kinetic models, employs batch reactors. As such, most of the illustrative examples to follow are concerned with this class of reactor. Examples on CSTRs and tubular reactors are also presented in two later subsections. 

As noted in an earlier chapter, the variables affecting the rate of reaction in a reactor are the concentration of the species in the reacting system, temperature, pressure, and catalyst effects. Experimentation and the subsequent analysis of the data involves an attempt to isolate the variables and determine mathematical relationships between them. 

In a very real sense, the development material provided in the section titled Experimental Methods and Analysis of Kinetic Data applies directly to batch 

To summarize, either differential or integral batch reactors are employed during the data gathering process. Differential units operate for short periods of time there is usually one data point per run and the extent of the conversion is low with little or no temperarnre variation problems. The integral unit operates for long reaction times generating either one data point per run or many the extent of conversion will usually be high with temperature variation a potential problem. 

ILLUSTRATIVE EXAMPLE 13.5 Given a homogeneous-phase batch polymerization occurring at a constant temperature, with 20% of the monomer disappearing within 34 minutes for initial monomer concentrations of both 0.04 and 0.8 gmol/L. What can be said about the rate of disappearance of the monomer, i.e., what is the order of the reaction and the reaction velocity constant  

---

APPLICATION TO SPECIFIC REACTORS 331 TABLE 13.12 Calculated k Values n = 2... 

APPLICATION TO SPECIFIC REACTORS 333 TABLE 13.15 Calculations for lllusintive Example 13.14... 

APPLICATION TO SPECIFIC REACTORS 339 TABLE 13.20 Calculated Values of ft n = 0... 

There are a multitude of variations for semibatch operation. Equation (5-22) already includes restrictions that limit its application to specific operating conditions for example, constant mass-flow rates. A frequently encountered case for nonisothermal operation is one in which there is no product stream, one reactant is present in the reactor, and the temperature is controlled by the flow rate of the feed stream containing the second reactant. Figure 4-17 shows this type, and Example 4-13 illustrates the design calculations for isothermal operatioh. The energy balance for this situation reduces to... 

The guidance given in this publication is applicable to research reactors with limited hazard potential to the public and typical characteristics. For addressing the topic in research reactors with several tens of megawatts of power, fast neutron spectrum research reactors or small prototype power reactors, etc., other similar IAEA publications prepared for power reactors may be more appropriate for a number of aspects (see References). No specifications for such a transition to other guidance are presented. 

A Protective Action Guide (PAG) is the projected dose to reference man, or other defined individual, from an unplanned release of radioactive material at which a specific protective action to reduce or avoid that dose is recommended The Environmental Protection Agency (EPA) and Food and Drug Administration (FDA) have established PAGs that are applicable to severe reactor accidents. These PAGs must be considered in licensees emergency plans and decisions as discussed in Sections 5.3 and 5.4. 

Mass transfer across the liquid-solid interface in mechanically agitated liquids containing suspended solid particles has been the subject of much research, and the data obtained for these systems are probably to some extent applicable to systems containing, in addition, a dispersed gas phase. Liquid-solid mass transfer in such systems has apparently not been studied separately. Recently published studies include papers by Calderbank and Jones (C3), Barker and Treybal (B5), Harriott (H4), and Marangozis and Johnson (M3, M4). Satterfield and Sherwood (S2) have reviewed this subject with specific reference to applications in slurry-reactor analysis and design. 

The focus of the examples given in this chapter is clearly on micro reactors for chemical processing in contrast to p-TAS or Lab-Chip systems for bioanalytical applications. In the latter microfluidic systems, the fluidic requirements are somehow different from those in micro reactors. Typically, throughput plays only a minor role in p-TAS systems, in contrast to micro reactors, where often the goal is to achieve a maximum molar flux per unit volume of a specific product. Moreover, flow control plays a much greater role in p-TAS systems than in micro reactors. In... 

A fast-start capability is a key requirement for a compact fuel processor, especially crucial for specific cases such as on-board automotive application. A possible means for the fast start-up of an ATR reactor is starting by feeding to the reactor a mixture with an O2 C molar ratio typical of a rich combustion. The goal of this mode is to raise the reactor temperature quickly and simultaneously avoid catalyst oxidation. Then the reactor will move to the ATR mode through the addition of steam and by decreasing the 02 C feed ratio to the desired value. 

We have chosen to concentrate on a specific system throughout the chapter, the methanation reaction system. Thus, although our development is intended to be generally applicable to packed bed reactor modeling, all numerical results will be obtained for the methanation system. As a result, some approximations that we will find to apply in the methanation system may not in other reaction systems, and, where possible, we will point this out. The methanation system was chosen in part due to its industrial importance, to the existence of multiple reactions, and to its high exothermicity. 

For purposes of plant design and for optimum operation consistent with feed stock availability, it is necessary to be able to predict accurately the octanes of the alkylate produced under varying operating conditions. Such a correlation developed from several hundred pilot plant and commercial plant tests is presented in Figures 7, 8, and 9. This correlation is applicable to sulfuric acid alkylation of isobutane with the indicated olefins, and was developed specifically for the impeller-type reaction system, although it also appears to be satisfactory for use with some other types of reactors. 

Enzymes can be used in several ways in chromatographic applications to improve selectivity or to enhance the detector response. Applications may involve enzymes with either a broad specificity toward a group of related compounds or a high specificity toward a particular compound. In the field of drug residue analysis, most current applications concern enzymatic reactions taking place in separate reactors incorporated in LC systems before or after the analytical column. Reactors with immobilized enzymes have proven to be suitable in such continuous flow systems. 

---