Emissions from processes control methods

The control of carbon dioxide emission from burning fossil fuels in power plants or other industries has been suggested as being possible with different methods, of which sequestration (i.e., collecting CO2 and injecting it to the depth of the seas) has been much talked about recently. Besides of the obvious cost and technical difficulties, this would only store, not dispose of, CO2 (although natural processes in the seas eventually can form carbonates, albeit only over very long periods of time). 

Regulatory control is governmental imposition of limits on emission from sources. In addition to quantitative limits on emissions from chimneys, vents, and stacks, regulations may limit the quantity or quality of fuel or raw material permitted to be used the design or size of the equipment or process in which it may be used the height of chimneys, vents, or stacks the location of sites from which emissions are or are not permitted or the times when emissions are or are not permitted. Regulations usually also specify acceptable methods of test or measurement. 

Control of stationary sources of air pollution requires the application of either the control concepts mentioned in Chapter 28 of the control devices mentioned in Chapter 29. In some cases, more than one system or device must be used to achieve satisfactory control. The three general methods of control are (1) process change to a less polluting process or to a lowered emission from the existing process through modification of the operation,... 

The composition of steels or other metals is commonly analyzed by emission or X-ray spectrometry during and after the production process. Both methods have to be calibrated by solid samples. These are either exactly analyzed samples taken from the same process or synthetic melted mixtures of the matrix with added accompanying elements (RMs). Available CRMs are then used to control the slope of the calibration function. Today, available RMs and CRMs are increasingly and exclusively used in spectral laboratories as the chemical analysis became much restricted and typical control laboratories were totally closed (Slickers 1993). 

Baghouse systems efficiently control particulate emissions from grinding and blending processes. Vents from feed hoppers, crushers, pulverizers, blenders, mills, and cyclones are typically routed to baghouses for product recovery. This method is preferable to using wet scrubbers. However, even scrubber effluent can be largely eliminated by recirculation. 

Fluorescence spectroscopy offers several inherent advantages for the characterization of molecular interactions and reactions. Firstly, it is 100-1000 times more sensitive than other spectrophotometric techniques. Secondly, fluorescent compounds are extremely sensitive to their environment. For example, vitamin A that is buried in the hydrophobic interior of a fat globule has fluorescent properties different from molecules that are in an aqueous solution. This environmental sensitivity enables characterization of viscosity changes such as those attributable to the thermal modifications of triglyceride structure, as well as the interactions of vitamin A with proteins. Third, most fluorescence methods are relatively rapid (less than 1 s with a Charge Coupled Device detector). One particularly advantageous property of fluorescence is that one can actually see it since it involves the emission of photons. The technique is suitable for at-line and on/in-line process control. 

The use of catalysts, furthermore, is required in the processes of wastewater purification by reducing treatments. Catalysts also find also application as complementary technologies to other wastewater treatment methods, such as in the control of odour, VOC, N2O and NOx emissions from wet oxidation treatments (for example, in the wet oxidation of industrial sludges), and of odours and VOC emitted from biological processes (aerobic and anaerobic). Although usually commercial catalysts are used in these cases, there are often unpredicted effects in treating complex mixtures and thus more specific catalysts would be preferable. The same is valid for catalysts used to convert stripped VOC from contaminated groundwater. 

In addition to APCD, metal emissions from waste combustors can be minimized by 1) limiting the metal content of the waste feed via source control 2) designing and operating the combustion process to minimize metal vaporization and 3) designing and operating the primary combustion chamber to minimize fly-ash carryover. From a practical standpoint, the second method is likely to be the most difficult to implement because the objective of the incineration process is to burn all the combustible waste completely and avoid PIC formation, both of which require the use of high temperatures. Therefore, the most-reliable methods of limiting metal emissions are source control and efficient use of APCD. 

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