Effect of Design Parameters

The effects of different parameters can be better explained based on one simple concept, which is momentum exchange, which is captured the best by the equation below  

Vacuum and low-pressure eonditions enhance vapor loading at the expense of liquid loading resulting in a low S p and thus promote spray flow. Valve trays have greater tendency to operate under froth regimes than sieve trays which is indicated by a higher K value. Thus, it is a common practice that valve trays are used for vacuum and low-pressure appheations. At the same time, small valves (for small 4) with increased number of valves (for small u ) are used to increase Sp. 

Sieve trays have wide applications due to lower capital cost and less maintenance required. However, valve trays can promote froth regime and thus achieve distillation efficiency up to 20% higher than sieve trays (Anderdson et ah, 1976). Furthermore, valve trays can achieve 3 1 turndown compared to sieve trays in 2 1. However, the disadvantages of valve trays are higher pressure drop and cost. 

Attempts were made to explore the impact of several parameters on the design of the ETBE system. Convergence issues and frequent Fortran system errors severely limited this investigation. 

Two design specifications were set up to hold the bottoms purity at 99 mol% ETBE and the distillate ethanol impurity at 0.7 mol% by manipulating the bottoms flowrate and reflux ratio. 

Pressure. The base case design pressure is 7.5 atm. Table 9.4 gives results over a small range of pressures around this value. Decreasing pressure reduces energy consumption, but the production of ETBE decreases somewhat because of more losses of reactant in the distillate. The program would not converge for pressures lower than 7.2 atm. 

Pressure (atm) Reboiler Heat Input (MW) Reflux Ratio ETBE Recovered in Bottoms (kmol/h) Isobutene Lost in Distillate and Bottoms (kmol/h) 

Other Parameters. We were unsuccessful in trying to change the reactive tray holdup (Fig. 9.23), the number of reactive trays, the number of stripping trays, or the location of the ethanol fresh feed. The program either would not converge or produced Fortran errors and shut down. 

Before we move on to dynamics and control, it may be useful to explore briefly the impact of some of the design parameters on the yields and the boiling points of the various products. This insight will be used when a control structure is developed to maintain the several specifications in the face of disturbances. 

In setting up the steady-state design, we have specified all of the equipment parameters (the number of stages and locations of feeds and withdrawal points). In addition, we have specified 10 operating variables, that is, there are 10 operating degrees of freedom in this pipestill process. 

The 95% boiling point specification on the heavy naphtha stream is 350 F. 

The four stripping steam flow rates are fixed (one to the base of the column and one to each of the three strippers). 

Let us explore what the steady-state effects are of changing some of these variables and establish some principles of operating a petroleum fractionator. 

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Fig. 11. Simulated bulk concentration profiles for the effect of design parameters on the adsorption of berberine and dopamine on encapsulated adsorbent (o, control condition —, change of Ns , change of R0, —, change of n -., change of Rm —, change of Nc) [18]...

Effect of design parameters, A number of design parameters have a far greater effect on one flooding mechanism than on others. These parameters are listed in Table 6.2. 

In this book, we focus primarily on control structure selection. Interactions between design and control are illustrated by examples, and the effects of design parameters on control are discussed. However, we do not present a synthesis procedure for process design that is capable of generating the most conriollable flowsheet for a given chemistry. This is still very much an open area for further research. 

In a separate parametric study, Mohan and Govind(l)(9) analyzed the effect of design parameters, operating variables, physical properties and flow patterns on membrane reactor. They showed that for a membrane which is permeable to both products and reactants, the maximum equilibrium shift possible is limited by the loss of reactants from the reaction zone. For the case of dehydrogenation reaction with a membrane that only permeates hydrogen, conversions comparable to those achieved with lesser permselective membranes can be attained at a substantially lower feed temperature. 

The UPSR can be used to locate the sources of a system s dynamic modes. For design, this allows the localisation of the effects of design parameters, which can reduce and better define the goals and possibilities for the dynamic design problem. 

EFFECT OF COAL AND MULTIFUEL FIRING ON INDUSTRIAL BOILER DESIGN Effect of Design Parameters on Boiler Sizing Oil/Gas Capability Stoker or Pulverized Coal Furnace Maintenance... 

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