Capital investment Compressor

The main consideration in the selection of a compressor plant is the production of an adequate supply of compressed air at the lowest cost consistent with reliable service. The installation of a compressed air system, as with all forms of power transmission, calls for capital investment with consequent operating and maintenance costs. The information on which the selection of plant is based should be as accurate as possible. Important factors to be considered are the following. 

The percentage of monomer costs is higher in the low-pressure plant, owing to the extra costs of butene co-monomer whose price in Western Europe exceeds that of ethylene. The capital investment is lower, mainly because of the lower costs of the compressor and reactor, resulting in a lower depreciation. The low-pressure process requires less electrical energy which explains its lower costs for utilities. 

Reciprocating compressors are also favored over centrifugal machines for temporary installations such as gas and field-well head service. Also, when low initial capital investment is favored over longterm maintenance costs, reciprocating compressors are used. 

Gas recycles usually involve a liquid-vapor phase separation in which the lighter reactants come off the top of the flash drum as vapor and are compressed so that they can be recycled back to the reactor inlet. A gas recycle almost always implies a gas-phase reaction. The major costs with gas recycle are compressor capital investment and compressor work. 

Figure 5.15 illustrates the effect of changing the reactor inlet temperature on the economics. All the costs are in terms of annual costs ( per year) using a payback period of 3 years for capital investment. The only energy cost is compressor work. There is a minimum in the total annual cost (TAC) curve. For the expensive catalyst, the optimum... 

The total capital investments costs was estimated on the basis of the equipment costs plus a specific installation factor and is shown in Table 3. An additional of 20% of the total installed equipment costs was included for engineering and contingency costs. The main part of these costs are due to the extraction column, EC, (this includes the price of steel to be used to make the column and the packing expenses) and the main gas compressor, C. 

Analyses of cryogenic processes, such as air separation or the separation of helium from natural gas, have found that a combination of pressure drops involving heat exchangers and compressors was most economical from the standpoint of capital invested and operating expenses. 

Process flexibility and simplicity are main features of the Integrated Gasoline Synthesis. Yield and quality, cycle length etc. can be adjusted to ensure a desired balance between capital investment and operating costs. Synthesis gas compression can be avoided. This means low investment. Further, the exclusion of the synthesis gas compressor means higher reliability. 

An example of an estimate of the total capital investment for a processing plant is given in Tables 16.14 and 16.15 for an ammonia plant producing 1 billion Ib/yr. The costs are for the year 2000 at a U.S. Midwest location. The plant is part of an integrated complex. The process involves a variety of equipment, including gas compressors, pumps, heat exchangers, a catalytic reactor, a distillation column, an absorber, a flash drum, a gas adsorber, and gas permeation membrane separators. The material of construction is almost exclusively carbon steel. 

There is little opportunity to improve further the Oswald nitric acid process. The overall efficiency of ammonia conversion into acid is in the range of 949fr 96%, The process is self-sufficient in energy supply and can even export steam. Up to 80% of platinum catalyst losses can now be recovered. Capital investments were significantly reduced by the development of high-pressure absorption and with the design of efficient and reliable compressors and expanders. Economies of scale improve little for single-train units with capacities above 1,000 tpd. 

Investment costs If the equipment delivered costs (main items like reactors, heat exchangers, compressors, distillation columns, etc.) are known, the total capital costs, which include additional direct and indirect costs for the erection, piping, engineering, and so on, can be estimated. For a quick estimation of the total capital investment the overall factor method is helpful. The costs of each piece of equipment is estimated and summed and, finally, multiplied by an overall factor of about four. 

The PSU-SARS-HDSCS concept represents an attempt to make deep desulfurization in a future refinery fundamentally more efficient and consumes less hydrogen, which is a significant cost factor for both capital investment (H2S scrubber for recycle H2 gas, compressor) and process operation (consumption of H2). It is known that for current commercial hydrotreater operations, each 1 wt% sulfur removal results in about 18-20 NmVm feed (110-120 SCFB) of H2 consumption each 1000 ppm nitrogen removal results in about 5.9-6.1 Nm /m (35-36 SCFB) of H2 consumption each 1 wt% aromatics removal yields about 5.0-8.4 (use half of these numbers if aromatics are reported as voliune %) each one unit increase in °API gravity requires about 17 NmVm feed (100 SCFB) of H2 consumption, as does each one imit increase in cetane number for diesel stocks . 

The qualitative analysis given above suggests that both Alternatives -B- and -C- are superior to Alternative -A-. This conclusion is consistent with the two heuristics for compressors in Table 6.4 It is better to cool a hot gas prior to conpressing it, and it is usually desirable to keep the conpression ratio less than 3 1. Before a final selection is made, an economic analysis, which must include both the capital investment and the operating costs, should be carried out on each of the conpeting schemes. The equivalent annual operating cost (EAOC), described in Chapter 10. would be a suitable criterion to make such a comparison. 

The fixed capital investment is equal to the total module cost of the compressor (centrifugal), g the compressor drive (electric), and heat exchanger (shell-and-tube, floating head). The... 

As an example, the battery-limits capital cost can be estimated for the production of 10,000 t/yr of ethylene (qv) from ethanol (11). Seven processing blocks, ie, vaporizer, reactor, water quench, compressor, dryer, distillation, and energy recovery, can be identified. The highest temperature is 350°C (reactor), and the highest pressure is about 1.7 MPa (17 atm) (compressor, two towers). If a materials-pressure factor, + of 1.03 is assumed, then for N = 7 0 = 0.87 1/0 = 1 64 and f =0 K = 6.3. This gives the 1981 cost as 4.4 X 10 . The 1991 battery-Hmits investment can be obtained, by updating with the CE Plant Cost Index, as 5.3 x 10 . ... 

For large quantities of hydrogen, pipeline delivery is cheaper than any other option. Pipelines are characterised by very low operating costs, mainly for compressor power, but high capital costs. The investment for pipelines is in proportion to the delivery distance, while the influence of capacity is lower. 

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