Sizing equipment

Preselection of the most suitable equipment for a project can be a desk study and may also include information on prior history and experience of others for 

Unfortunately, agglomeration is not yet an exact science that would allow calculation of equipment type and size. Rather, tests must be carried out, preferably with a representative sample of the material to be treated. In those cases where (sometimes substantial) amounts of preagglomerated material are recirculated, testing must include actual recirculation of comparable amounts or the simulation of recycle addition. 

Scale-ups from small scale, often batch, laboratory investigations to commercially sized, continuously operating equipment, which in addition may 

In some cases, for example, toxic characteristics of the material may prohibit shipment of test quantities to vendors laboratories and/or contamination of laboratory buildings and equipment may be irreversible. In other cases, particularly in hot agglomeration, the material must be tested in statu nascendi because cooling and reheating a sample after shipment does not recreate the original material characteristics and the actual binding mechanisms. In those cases, construction of a pilot plant on the project site or other suitable location must be considered which may be equipped with purchased or rented machinery. If this solution is selected, the above remarks on scale-up must still be kept in mind. 

To rough out line sizes and pressure drop for fan or blower sizing, use the following, quickie method  

Arbitrarily assume air velocity of 5,000 ft/min (good for 90% of conveying situations). 

El = Acceleration losses E2 = Eifting energy E3 = Horizontal losses E4 = Bends and elbows 

H = Vertical lift, ft E = Duct horizontal length, ft R = 90° cell radius, ft 

F = Coefficient of friction and tangent of solids angle of slide or angle of repose. Use 0.8 in lieu of solids data for initial estimating N = Number of 90° ells. For 45°, 30°, etc., express as equivalent 90° ells by direct ratio (Example A 30° ell is 0.33 of a 90° ell) 

The process engineer is often required to design separators or knockout drums for removing liquids from process gas streams. This chapter reviews the design of horizontal and vertical separators and the sizing of partly filled horizontal and cylindrical vessels. The chapter concludes by reviewing the sizing of a cyclone and a solid-desiccant gas dryer. 

Vessels used for processing in the chemical process industries (CPI) are principally of two kinds those that are without internals and those with internals. Empty separators are drums that provide intermediate storage or surge of a process stream for a limited or extended period. Alternatively, they provide phase separation by settling. 

Demister Separators. A demister separator is fitted either with a vane demister package or with a wire mesh demister mat. The latter type is much preferred, although it is unsuitable for fouling service. The wire mesh demister is a widely applied type of separator, and is adequate for all gas-liquid flow regimes over a wide range of gas flow rates. 

A knockout drum or demister separator may be either a vertical or a horizontal vessel. A vertical vessel is generally preferred because its efficiency does not vary with the liquid level. Alternatively, a horizontal 

SIZING OF VERTICAL AND HORIZONTAL SEPARATORS Vertical Separators 

The dynamic response of a flow system depends on the flow rate and the volume. For a given flow rate, the smaller the volume, the faster the transient response. 

The procedure for sizing the distillation column shell (diameter and height) has already been discussed in Chapter 3. The only remaining issues are the sizes of the reflux drum and the column base. A commonly used heuristic is to set these holdups such that there are 5 min of liquid holdup when the vessel is 50% full, based on the total hquid entering or leaving the vessel. For the reflux drum, this is the sum of the liquid distillate and the reflux. For the column base, it is the liquid entering the reboiler from the bottom tray. 

The values are entered by clicking the Dynamics button on the top toolbar (see Fig. 7.2). If this button is not displayed, click the View button, then Toolbar and check the Dynamics 

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Having defined and gathered data adequate for an initial reserves estimation, the next step is to look at the various options to develop the field. The objective of the feasibility study is to document various technical options, of which at least one should be economically viable. The study will contain the subsurface development options, the process design, equipment sizes, the proposed locations (e.g. offshore platforms), and the crude evacuation and export system. The cases considered will be accompanied by a cost estimate and planning schedule. Such a document gives a complete overview of all the requirements, opportunities, risks and constraints. 

Sulfur Compounds. Various gas streams are treated by molecular sieves to remove sulfur contaminants. In the desulfurization of wellhead natural gas, the unit is designed to remove sulfur compounds selectively, but not carbon dioxide, which would occur in Hquid scmbbing processes. Molecular sieve treatment offers advantages over Hquid scmbbing processes in reduced equipment size because the acid gas load is smaller in production economics because there is no gas shrinkage (leaving CO2 in the residue gas) and in the fact that the gas is also fliUy dehydrated, alleviating the need for downstream dehydration. 

The principal methods for preventing criticahty are limitations on the mass of the fuel being handled, the equipment size, the concentration of... 

The efficiency of the Rankine cycle itself can be increased by higher motive steam pressures and superheat temperatures, and lower surface condenser pressures in addition to rotating equipment selection. These parameters are generally optimized on the basis of materials of constmction as well as equipment sizes. Typical high pressure steam system conditions are in excess of 10,350 kPa (1500 psi) and 510 °C. 

For many pieces of equipment, such as heat exchangers and distillation columns, stand-alone programs are available that calculate material and energy balances around that piece of equipment, size the equipment, and calculate or rate its performance. 

The optimum pressure level for gaseous diffusion operation is also determined by comparison at some pressure level the decrease ia equipment size and volume to be expected from increasing the pressure and density is outweighed by the losses that occur ia the barrier efficiency. Nevertheless, because it is weU known that the cost of power constitutes a large part of the total cost of operation of gaseous diffusion plants, it can perhaps be assumed that a practical value of r does not differ gready from the above optimum. Inclusion of this value ia the preceding equations yields... 

Published Cost Correla.tions. Purchased cost of an equipment item, ie, fob at seller s site or other base point, is correlated as a function of one or more equipment—size parameters. A size parameter is some elementary measure of the size or capacity, such as the heat-transfer area for a heat exchanger (see HeaT-EXCHANGETECHNOLOGy). Historically the cost—size correlations were graphical log—log plots, but the use of arbitrary equation forms for correlation has become quite common. If cost—size equations are used in computer databases, some limit logic must be included so that the equation is not used outside of the appHcable size range. 

A great variety of factors are in use, depending on the time available and the accuracy expected. Normally the input information required is the base cost. Determination of this cost usually requires a knowledge of equipment sizes, probably using mass and energy balances for the proposed process. 

Equipment Size Uuit Approximate cost, 000 Size range Exponent... 

With turbulent flow, shear stress also results from the behavior of transient random eddies, including large-scale eddies which decay to small eddies or fluctuations. The scale of the large eddies depends on equipment size. On the other hand, the scale of small eddies, which dissipate energy primarily through viscous shear, is almost independent of agitator and tank size. 

Although they are termed homogeneous, most industrial gas-phase reactions take place in contact with solids, either the vessel wall or particles as heat carriers or catalysts. With catalysts, mass diffusional resistances are present with inert solids, the only complication is with heat transfer. A few of the reactions in Table 23-1 are gas-phase type, mostly catalytic. Usually a system of industrial interest is liquefiea to take advantage of the higher rates of liquid reactions, or to utihze liquid homogeneous cat ysts, or simply to keep equipment size down. In this section, some important noncatalytic gas reactions are described. 

Once the highest steam level is set, then intermediate levels must be established. This involves having certain turbines exhaust at intermediate pressures required of lower pressure steam users. These decisions and balances should be done by in-house or contractor personnel having extensive utility experience. People experienced in this work can perform the balances more expeditiously than people with primarily process experience. Utility specialists are experienced in working with boiler manufacturers on the one hand and turbine manufacturers on the other. They have the contacts as well as knowledge of standard procedures and equipment size plateaus to provide commercially workable and optimum systems. At least one company uses a linear program as an aid in steam system optimization. 

Feasibility (factored) 30% Process Flowsheets, Equipment Size, Regional Location... 

Early in the life of a project, information has not been developed to allow definitive cost estimates based on material takeoff and vendor quotes for equipment. Therefore, it is necessary to estimate the cost of a facility using shortcut methods. The first step is to develop or check flow-sheets, major equipment sizes, and specification sheets as described in earlier chapters. From the equipment specification sheets, the cost of each piece of equipment is estimated, using techniques discussed later. Once the major equipment cost has been estimated, the total battery limit plant cost can he quickly estimated using factors developed on a similar project. 

Woods, D. R., Discovering Short Cut Methods of Equipment Sizing and Selection, ASEE Annual Conference Proceedings, 1985. 

Dr. Woods R. and Kodatsky, W. K., Dept, of Chemical Engineering, McMaster University, Hamilton, Ontario, Discovering Short Cut Methods of Equipment Sizing and Selection, presented at 1985 Annual Conference (Computer Aided Engineering) of American Society For Engineering Education, Atlanta, Georgia, June 16-20, 1985, V ol. 1. 

At the end of this chapter you will find three annexes. The first of these is a list of nomenclature used in the chapter. There are quite a few equations that are sununarized in the foregoing sections and hence, you will need to refer to this annex from time to time. The second annex is a list of recommended references that I have relied on over the years, plus some interesting Web sites for you to visit for vendor-specific information as well as supplemental design and equipment sizing information. The final annex is the Questions for Thinking and Discussing. Remember to refer to the Glossary at the end of the book if you run across any terms that are unfamiliar to you. 

Odor and pollution problems are often experienced due to incomplete combustion when concentrated HjS is flared. When such considerations are expected to be critical, flare system designs should include a fuel gas connection and equipment sizing sufficient to handle an equal volume of fuel gas when flaring H2S at design rate. Where flaring of HjS is intermittent and the fuel gas diluent is continuous then steam injection at the base of the flare may be needed to reduce smoking. 

Table 7-7 summarizes eorrelations for the effeets of equipment size on the rotational speed needed for the same mixing time by various investigators. 

Since activated carbon lies to the left of the extractant and has a lower c, it will be used to remove the remaining load (0.0003 kg toluene/s, as shown by Fig. 3.19b). The flowrate of activated carbon is 0.015 kg/s. For 8000 operating hours per year, the annual operating cost of the system is 96,700/year. The annualized fixed cost can be calculated after equipment sizing (as shown in Example 2.1). 

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