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Show which offers an advantage of simplicity and lower capital cost at a penalty of lower purity and higher power requirement. Typical power requirements range from as low as 275 Kwh/ton to over 600 Kwh/ton. Active developmental efforts are continuing both in the U. S. and abroad to improve the adsorbent characteristics and to optimize the cycle design. It is expected to result in significant improvement in the PSA economics in the near future. PSA technology due to its simplicity is a lower capital cost option as compared to cryogenic plants. The lower recovery of oxygen usually results in higher unit power consumption as compared to cryogenic cycles producing gaseous oxygen. The membrane systems are newcomers to the oxygen generation industry. These systems employ synthetic membranes which have different permeation characteristics for the constituents of air. Thus, through the use of a pressure difference across the membrane, oxygen enrichment can be attained. The pressure gradient can be created using pressure or vacuum depending on the system desired. The oxygen purity attainable is typically 28-35% for commercial systems. Membrane processes are characteristically simple and continuous in operation which offer the lowest capital cost option for small size systems. The current drawbacks are limited oxygen concentration and higher power requirement per unit amount of equivalent pure oxygen generated. The currently available commercial systems require about 650 Kwh/ton of equivalent pure oxygen. Developmental systems require about 350-400 'Kwh per ton of equivalent pure oxygen (Ref. 6). Active current R&D efforts are expected to improve membrane materials and fabrication techniques which offer potential for significant reduction in the oxygen cost. Table 3 summarizes the characteristics of different oxygen supply options based on the three different air separation technologies. The base case economics are shown in Figures 9a and 9b for a capacity range up to 100 TPD assuming 100% and 70% capacity utilization, 50 mil/Kwh power cost and no product compression. For each air separation process the upper and the lower lines represent the economics of the existing commercial systems and the expected economics of the near term developmental systems respectively. The lowest cost oxygen is provided by the cryogenic process for large capacities due to its inherent energy efficiency and the economy of scale. In the low capacity range, however, the capital cost becomes very significant and the unit cost goes up sharply. Membrane systems offer better economics in the low flow range of less than about 15 TPD. Since membrane systems are fabricated in modular units, the unit cost does not change appreciably with the capacity. PSA offers the best economics in the mid range between 10 to 50 TPD due to its moderate capital cost and relatively low power requirement. The delivered cost of liquid oxygen is in a range between $80/ton to over $130/ton. This wide variation in liquid oxygen cost reflects the diversity of the size and 160 OXYGEN COST VERSUS PRODUCTION 1~ UTILIZATION O~O------------~-------------W~------------7~'------------~ onGIN PMJOUC'1'1OH I&OUN'A&.&NT ...... OX'rOeN) Figure 9a OXYCEN COST VERSUS 'ROOUCTION lOS UTILIZATION Figure 9b Table 3 - Cbcygen/Oxygen Enriched Air S~ly Alternatives Typical Ge. Plwer Supply capacitY(I) Oxygen Pressure Requir_t(l) ~ {TonlDaI} PuritI{\} ~ {~TCID} 1. Liquid 0-50 99.5+ 250(2) 700-800 2. Cryogenic 50-2000+ 70-99.5+ 3 230-250 Plant 250 350-400 3. Pipeline 10-1000 99.5+ 250 400 4. ~n:l~:e_ 10-100 37+ 1 10 150 5. PS& 10-100 80-95 3-20 250-600 6. K8ibrane 1-15 28-35 1 (3) 350-600 COtVIIDITS. 1. BuIlt storage tank and vaporiser required. "uw- fleaibility in use pattern. 2. Low cost oKJgen for large vol_ users. Possible utilization of co-products. 3. Large flow rate available fr_ nearby air separation plant. Good fleaibility in use pattern. 4. R_al of H20/CO2 and pro«ict ca.pre.sioo .ay be required. 5. Bcon-tcs is generally better than cryogenic plants for low capacity range. 6. Lt.ited 02 purity. Very .~le proces •• IIOTBS. (1) Ton of equivalent pure oKJgen . . (2) Typical qas pressure obtaind by vaporising liquid OKJgen. (3) Blower or ca.pre.sor required for .ost applicatiooa. |