End-of-pipe strategies

Despite great efforts in the realization of sophisticated end-of-pipe strategies to reduce air pollution such as three-way catalysts (TWCs) [4, 5], surely the solution to... 

Reduced Emissions and Waste Minimization. Reducing harmful emissions and minimizing wastes within a process by inclusion of additional reaction and separation steps and catalyst modification may be substantially better than end-of-pipe cleanup or even simply improving maintenance, housekeeping, and process control practices. SO2 and NO reduction to their elemental products in fluid catalytic cracking units exemplifies the use of such a strategy (11). 

It is interesting to compare the optimal configuration shown in Fig. 7.16 to end-of-pipe solutions. Suppose we retain the identified segregation, mixing, and direct recycle strategies shown in Fig. 7.14, but intercept the wrong stream. For instance, if the CE content of the terminal wastewater stream is to be reduced from 6.5 ppmw... 

All of the strategies examined are alternatives to land disposal of the wastes. The methodologies stressed are those that prevent the generation of hazardous wastes. Pollution prevention is preferable to "end-of-pipe" treatment or recovery. 

The rationale for the application of GCP to the control of organic emissions was that the latter were the products of incomplete combustion. Hence, optimization of combustion conditions to approach as closely as possible the theoretical ideal of complete combustion (i.e. combustion to C02, water, etc), coupled with appropriate end-of-pipe control strategies, should lead to reductions in trace organic emissions. The US EPA recommendations for GCP fell into three categories ... 

Minimize emissions of PCDD/Fs by employing end-of-pipe control strategies. 

In principle, BAT(NEEC) and RACT offer the user flexibility in choosing an emission reduction strategy -choice between a variety of end-of-pipe abatement techniques, low solvent technologies, waste minimisation or any combination of these. It recognises that the most appropriate solution will vary from one application to another with size, product quality required and the age and location of a plant. 

Differentiate between end-of pipe and start-of pipe strategy with respect to their innovation, function and implications. 

As there is a very wide range of applications of electrochemical reactors In metal removal and pollution control. It Is Important first of all to attempt to identify the main approaches or strategies for their use The first of these Is known as "point source" or the treatment of a pollutant at Its point of origin. The second is known as "end of pipe" and describes the use of a treatment technology to process a combination of waste sources, generally before being discharged from the plant Into a sewer or local watercourse. Three examples or case studies will be presented which Illustrate these applications. 

Schematically, CO2 capture can be achieved following three main strategies (Figure 39.1) [12] (1) oxy-combustion (or oxy-fuel combustion) where the fuel combustion is performed with pure or enriched O2 instead of air, so that a CO2/ H2O mixture is produced (2) pre-combustion, where the carbon from the fuel is removed prior to combustion (decarbonization) either as CO2, as coke, or in other forms, and whereby the primary fuel heating value is transformed into H2 through partial oxidation, steam reforming, or autothermal reforming with subsequent water-gas shift (WGS) reaction and (3) post-combustion, where CO2 recovery is performed at the end of pipe from a wet exhaust flue gas, usually at 10-30% (v/v) CO2 concentration. The target separations to achieve in these processes to make them feasible are O2/N2 for oxy-combustion, CO2/H2 for precombustion, and CO2/N2 for post-combustion CO2 capture.

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