Scrubbing investment

For continuous processes the catalytic reactor, or a hybrid process if satisfactory chemical dosing equipment is already installed, appear to be a near-optimum solution still for many installations. At moderate hypochlorite concentrations, economic benefit does accrue from using the catalyst in-loop rather than end-of-pipe, but these benefits may be offset by any required investment in heat-exchange capability. At concentrations above 10 wt% the integration of decomposition into the scrubbing process is beneficial to the overall cost base of hypochlorite treatment. 

A variation of the nonregenerable absorption is the spray dry process. Lime slurry is sprayed through an atomizing nozzle into a tower where it countercurrently contacts the flue gas. The sulfur dioxide is absorbed and water in the slurry evaporated as calcium sulfite—sulfate collects as a powder at the bottom of the tower. The process requires less capital investment, but is less efficient than regular scrubbing operations. 

On the basis of this last observation, it is easy to predict that if the catalytic filter technology can penetrate the market more deeply, investment cost will likely lower, due to higher productions, thus further improving the above economic advantages. Moreover, even better results eould be accomplished if higher lime utilization efficiency were achieved in the dry-scrubbing unit, a point addressed by several research programs all over the world [32-35]. 

As shown In Table 10, both the total capital investment and the first-year revenue requirement are the lowest for adipic acid-enhanced limestone scrubbing at low pH (Case 4). The total capital investment is reduced by 4.8 percent, and the first year revenue requirement reduced by 5.8 percent for the limestone/ adipic acid/low pH case (Case 4), compared with the conventional... 

These cost figures are cited as representative of typical scenarios only, and some variation from them would be normally expected. Moreover, the differences in total capital investments and operating costs between these cases are small. The principal conclusion from these evaluations is that adipic acid addition to a limestone scrubbing system decreases cost consistently when compared on the same basis. 

An improved magnesium oxide (MgO) flue gas desulfurization process and its comparative economics are described. Innovations made include the use of a spray dryer, a cyclic hotwater reheater, and a coal-fired fluidized-bed reactor for regeneration of the MgO absorbent. Several technical concerns with the proposed design are addressed, including fly ash and chloride buildup. The economic evaluation shows the process to have a capital investment of about seven percent less than that of a conventional MgO scrubbing process and a 40 percent smaller annual revenue requirement. Finally, a sensitivity analysis is shown relating annual revenue requirements to the byproduct sulfuric acid price credit. 

The capital investment for the spray dryer MgO FGD process is 139.5M ( 279/kW) in mid-1982 dollars while that for a comparable limestone scrubbing/ESP process is 122.0M ( 244/kW) in mid-1982 dollars. The capital investment for the conventional MgO FGD process (including particulate control) is 149.7M ( 299/kW) in mid-1982 dollars. These costs are... 

The capital investment for the spray dryer MgO process is approximately 14K higher than that for the comparable limestone scrubbing process. This is not an unexpected result since the MgO process is a regenerable system while the limestone scrubbing process is a throwaway system. 

There are no comparable areas in the limestone scrubbing process. The 22 million investment for these areas in the MgO process offsets the lower investment for the other processing areas. 

Likewise, the capital investment for the spray dryer MgO process is approximately 7 percent lower than that for the conventional MgO scrubbing process ( 279/kW vs. 299/kW). The conventional MgO scrubbing process has more equipment, and hence larger investment costs, particularly in the areas of chloride purge, slurry drying, and slurry processing equipment which are not needed in the spray dryer-based system. 

The spray dryer MgO process appears to have a slight advantage (about 10 ) over a comparable limestone scrubbing process in terms of both first-year and levelized annual revenue requirements. This new MgO process, however, has a higher capital investment than the limestone scrubbing process. 

EA Patchman, EE Vicker, MJ Brunner. Origin of glass cup scrub. J Invest Dermatol 22 389, 1954. 

All of these changes may account for about 20%-25% of the investment costs of a new installation. Tail-gas scrubbing is the lowest cost option (15% of the total revamping cost) however, this generates a liquid effluent that needs to be processed. 

Looking at TPC for membrane case (Table 14.11), results show that with the assumed permeance and membrane equipment cost, the membrane reactor cost is about 100 M, which corresponds to 20% of the TEC. An improvement of membrane performance and/or a cost reduction are crucial to reduce final investment costs. Moreover, in order to limit the membrane surface area, an oxy-blown auto-thermal reformer was adopted, adding 40 M for the air separation unit. The resulting specific investment cost is higher than post-combustion capture via amine scrubbing (see Table 14.7). 

The cost of incineration must rise in the future to reflect the investment that operators are having to make to scrub the flue gases and monitor the incineration processes more carefully. The NIMBY lobby is also extremely active in preventing the construction of new incinerators. Well maintained and closely controlled incinerators can dispose of waste effectively by reducing its volume by 90% and its weight by 70% while at the same time recovering the calorific value of the waste stream. 

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