Compressors, cost

In the formulation above, the discrete optimization on the number of compressors has been transformed into a continuous optimization on suction and delivery pressures. This transformation was made possible by the form of the compressor cost function which vanishes when pd = ps. However, if the compressor costs include a fixed capital outlay, i.e., the cost function is a linear function of horsepower with a nonzero constant term, then a branch and bound procedure must be used in conjunction with the GRG method. 

If we should consider the total transportation cost formula we must at least include the compressor costs. It is easily demonstrated (see for example Dahl and Osmundsen (2002)) that the compressor costs do not invalidate the demonstrated economics of scale. The work done by the compressors depend on the so-called compression ratio Pt (compressor outlet pressure) divided by the pressure at the compressor inlet (the suction pressure). If we keep the compressor ratio fixed, the necessary compressor work per unit gas, and hence the compressor related cost per unit gas, will not increase as the diameter and flow increase.37... 

It should also be noted that the compressor costs together with other operating costs typically make a minor part of total discounted lifecycle cost as the major cost contribution is related to pipeline investment, which is a sunk cost as the pipeline cannot be recovered or converted. 

The air compressor is costed according to the nomographs presented in Ref. CE9 (p.560 and 561). The nomographs match the compressor cost against either power rating or capacity. 

Separation S02/02 requires two absorption columns. Only one column is shown in Figure 2, the second one finishing S02 absorption before exhausting (or valorisation of oxygen which is not taken into account therein). This section also requires heat exchangers and compressors. Cost of installed chemical equipment with piping, instrumentation, buildings, etc. is about EUR 223.8 M. 

A0 = Optimum Approach A0 = Optimum at Minimum Aq = Optimum Above Minimum Ml = Fan Cost Increase Small Ml" = Fan Cost Increase Large M2 = CT Pumping Cost M3 = Chiller Compressor Cost = Total Cost w/expensive CT... 

Pressure Drop, Mass and Heat Transfer Pressure drop is more important in reactor design than in analysis or simulation. The size of the compressor is dictated by pressure drop across the reactor, especially in the case of gas recycle. Compressor costs can be significant and can influence the aspect ratio of a packed or trickle bed reactor. Pressure drop correlations often may depend on the geometry, the scale, and the fluids used in data generation. Prior to using literature correlations, it often is advisable to validate the correlation with measurements on a similar system at a relevant scale. 

The catalyst support may either be inert or play a role in catalysis. Supports typically have a high internal surface area. Special shapes (e.g., trilobed particles) are often used to maximize the geometric surface area of the catalyst per reactor volume (and thereby increase the reaction rate per unit volume for diffusion-limited reactions) or to minimize pressure drop. Smaller particles may be used instead of shaped catalysts however, the pressure drop increases and compressor costs become an issue. For fixed beds, the catalyst size range is 1 to 5 mm (0.04 to 0.197 in). In reactors where pressure drop is not an issue, such as fluidized and transport reactors, particle diameters can average less than 0.1 mm (0.0039 in). Smaller particles improve fluidization however, they are entrained and have to be recovered. In slurry beds the diameters can be from about 1.0 mm (0.039 in) down to 10 Jim or less. 

Compressor costs. Prices includes drive, gear mounting, base plate, and normal auxiliary equipment operating pressure to 1000 psig. 

Admin, Water, and Compressor Cost O Electricity Cost — Total H, Production Cost... 

More isobutane needs to be flashed in Strafco reacfors to provide sufficient temperature differences for adequate heat transfer. Compressor costs in Stratco units tend to be higher. Less... 

Each subsystem could then be optimally selected on the basis of the tradeoff between increased capital expenditure for reducing subsystem irreversibilities on the one hand, and increased power and compressor costs on the other hand. 

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