Costs reactors

However, the concentration of impurity in the recycle is varied as shown in Fig. 8.5, so each component cost shows a family of curves when plotted against reactor conversion. Reactor cost (capital only) increases as before with increasing conversion (see Fig. 8.5a). Separation and recycle costs decrease as before (see Fig. 8.56). Figure 8.5c shows the cost of the heat exchanger network and utilities to again decrease with increasing conversion. In Fig. 8.5d, the purge... 

Figure 10.7 shows that the tradeoff between separation and net raw materials cost gives an economically optimal recovery. It is possible that significant changes in the degree of recovery can have a significant effect on costs other than those shown in Fig. 10.7 (e.g., reactor costs). If this is the case, then these also must be included in the tradeoffs. 

Net Profit = Value of Product — Cost of Reactant — Investment in Reactor — Cost of Operation ... 

The rest of this chapter is a series of examples and problems built around semirealistic scenarios of reaction characteristics, reactor costs, and recovery costs. The object is not to reach general conclusions, but to demonstrate a method of approaching such problems and to provide an introduction to optimization techniques. 

Why are the CSTRs worth considering at all They are more expensive per unit volume and less efficient as chemical reactors (except for autocatalysis). In fact, CSTRs are useful for some multiphase reactions, but that is not the situation here. Their potential justification in this example is temperature control. BoiUng (autorefrigerated) reactors can be kept precisely at the desired temperature. The shell-and-tube reactors cost less but offer less effective temperature control. Adiabatic reactors have no control at all, except that can be set. 

The cost of specialised equipment, which cannot be found in the literature, can usually be estimated from the cost of the components that make up the equipment. For example, a reactor design is usually unique for a particular process but the design can be broken down into standard components (vessels, heat-exchange surfaces, spargers, agitators) the cost of which can be found in the literature and used to build up an estimate of the reactor cost. 

Whatever the nature of the reaction, the choice of catalyst and the conditions of reaction can be critical to the performance of the process, because of the resulting influence on the selectivity of the reaction and reactor cost. 

Before the details of a particular reactor are specified, the biochemical engineer must develop a process strategy that suits the biokinetic requirements of the particular organisms in use and that integrates the bioreactor into the entire process. Reactor costs, raw material costs, downstream processing requirements, and the need for auxiliary equipment will all influence the final process design. A complete discussion of this topic is beyond the scope of this chapter, but a few comments on reactor choice for particular bioprocesses is appropriate. 

Design of the reactor is no routine matter, and many alternatives can be proposed for a process. In searching for the optimum it is not just the cost of the reactor that must be minimized. One design may have low reactor cost, but the materials leaving the unit may be such that their treatment requires a much higher cost than alternative designs. Hence, the economics of the overall process must be considered. 

From the industrial point of view, it is advantageous to work with minimal amounts of solvents. This minimises the reactor size and thereby reactor cost. The extreme case is to omit the solvent completely. The use of solvent-free systems is attractive also because solvents can cause many problems (for example fire hazards, environmental problems and high costs). It has been proven possible in many cases to carry out bioconversions in solvent-free mixtures of substrates. Since most substrates are organic compounds, these mixtures behave like systems containing organic solvents and the advantages mentioned... 

The air compressor purchase cost was estimated on the basis of power consumption. The oxidation vessel and reactor costs were estimated using correlations appropriate for pressure vessels. Capacity formed the basis of the storage tank purchasing cost. The absorption and stripping column were costed according to diameter, operating pressure and number of trays. 

Total reactor cost = AS66 800 Oxidation unit = As34 000... 

The most important examples of reactive separation processes (RSPs) are reactive distillation (RD), reactive absorption (RA), and reactive extraction (RE). In RD, reaction and distillation take place within the same zone of a distillation column. Reactants are converted to products, with simultaneous separation of the products and recycling of unused reactants. The RD process can be efficient in both size and cost of capital equipment and in energy used to achieve a complete conversion of reactants. Since reactor costs are often less than 10% of the capital investment, the combination of a relatively cheap reactor with a distillation column offers great potential for overall savings. Among suitable RD processes are etherifications, nitrations, esterifications, transesterifications, condensations, and alcylations (2). 

The more expensive the catalyst, the higher the optimum recycle flowrate (and reactor pressure drop). We are trading off recycle costs with reactor costs. No bypass flow is needed when the inlet temperature is 475 K or higher. The optimum y A/y B ratio decreases as recycle flowrate increases because the costs associated with heat transfer and compression are lower with more B in the gas because of its higher molar heat capacity. 

SS316 (3). The same reactor design built of SS316 would cost only 1,670,056 (2000 US ). Reactor costs for carbonic acid pretreatment were calculated by using the reactor wall thickness to determine the volume of metal required to meet the demands of various temperature and pressure conditions. The material volume for fabrication of the reactor was calculated using Eq. 2 ... 

Sensitivity analyses were conducted to address the question of whether there is an optimum pretreatment condition that could be used for carbonic acid pretreatment. Laboratory results from Yourchisin and van Walsum (7) and McWilliams and van Walsum (6) indicate that optimal reaction severity would be in the range of Log(R ) = 4.2, where the severity R0 is as defined by Overend and Chornet (10). Relatively high temperature (220°C) and short retention time (4 min) were chosen to achieve this severity, since reactor costs dominate the economics and longer retention times would increase capital costs significantly. Pretreatment temperatures and pressures were varied for this study to determine the sensitivity of the cost to adjustments in these parameters. 

Dow Chemical in Midland, USA, the microprocess technologist Velocys in Plain City, USA, and PNNL in Richland, USA, as research institute in microreactor technology have a public funded project on high-intensity production of ethylene and other olefins by oxidation such as the formation of ethylene from ethane [1], A two-step reactor engineering is performed, starting with a bench-scale reactor with microchannel dimensions equal to the latter commercial unit and followed by numbering to the latter. An economic analysis with focus on reactor costs and energy consumption completes the project. 

EP4 = EP2 - Reactor costs/Payback time — Cost of separations ... 

If a catalyst in a form of solid cylinders is replaced by hollow cylinders with an optimal internal radius, the reactor productivity will increase although the total mass of catalyst decreases. For example, the use of hollow cylinders with an internal radius of 035RU instead of solid cylinders of the same external size for the water-gas shift reaction at a pressure of 3 MPA and a temperature of 417 °C may increase the effectiveness of the unit reactor volume by 18%. This is particularly important for processes under elevated pressures, because of the strong dependence of the reactor cost on its volume [17]. 

For a stand-alone photobiological (sulfur-deprived, algal) H2-production facility producing 300 kg/day of H2, the total capital investment was estimated to be 5 million with a H2 selling price of approximately 14/kg of hydrogen and a 15% return on investment. This system assumed moderate improvements in the H2-production rate and included PSA purification with high-pressure compressed H2 storage. The total photobioreactor area was 110,000 m with a 10-cm pond depth, 0.2 g/1 cell concentration, and 10/m reactor cost. ... 

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