Ejectors capital cost

Because of the low efficiency of steam-ejector vacuum systems, there is a range of vacuum above 13 kPa (100 mm Hg) where mechanical vacuum pumps are usually more economical. The capital cost of the vacuum pump goes up roughly as (suction volume) or (l/P). This means that as pressure falls, the capital cost of the vacuum pump rises more swiftly than the energy cost of the steam ejector, which iacreases as (1 /P). Usually below 1.3 kPa (10 mm Hg), the steam ejector is more cost-effective. 

Below 1 atm, reduces the costs of creating and maintaining a vacuum (e.g., ejector energy consumption and capital costs). 

The main contributions to the capital cost of the venturi loop system are (i) the special pump and (ii) the patented venturi ejector. Choice of the circulation pump is crucial to stable continuous operation (Dierendonck et al. 1998). The circulating pump cost varies with its rating (pressure developed and flow rate). The pressure rating is fixed by the process conditions. On the other hand, the pump flow rate that directly affects the power required (P=M x P as well as its cost can be varied by choosing appropriate A simple analysis shows that a higher results in lower operating cost (lower P JV). Depending on the requirements of the reaction, suitable may be selected. However, as mentioned earlier, the combined... 

Replacement of the steam-jet ejector with a vacuum pump. The distillation operation will not be affected. The operating cost of the ejector and the vacuum pump are comparable. However, a capital investment of 75,000 is needed to purchase the pump. For a five-year linear depreciation with negligible salvage value, the annualized fixed cost of the pump is I5,000/year. 

The staging efficiency is particularly true for steam jet ejectors because the motive steam for one stage becomes the load for succeeding stages. Interstage condensers can dramatically reduce steam consumption consequently all multistage jets should be provided with intercondensers. The reduction in operating cost completely overshadows the increase in capital investment. 

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