Organochloro compounds in the stack emission

Abstract

To dispose of industrial and municipal wastes and residues without contaminating the environment is one of the major problems today. The most widely used technique for the disposal of this refuse is efficient, controlled incineration or thermal treatment. The aim of the work has been to validate and improve the sampling methods for organochloro compounds, to study, to establish and to compare the emission of the above-mentioned oganochloro compounds in different municipal and hazardous waste combustion processes as well as to examine and establish emission of these compounds in a metal reclamation process. The effect of flue gas cleaning devices as a method to reduce the emission of organochloro compounds has been studied in the process of setting achievable technical design criteria for both stack gas emissions and combustion conditions in different thermal treatment processes of waste. Validation of a number of different sampling systems against the more traditional SNV-sampling method proved successful and showed that all methods tested for measuring the emissions of PCDD's and PCDF's are reliable. However, sampling procedures and methods were and still are time consuming and complicated. Rapid concentration changes of organochloro compounds in the flue gases due to changes in the combustion processes or fuels can not be followed with sampling methods used. Faster sampling and analysis technologies with sufficient accuracy must be developed for the very low concentrations of different types of persistent chlorinated organic compounds in the off-gases from MSW- and HW-incineration and other thermal processes. The results obtained from these analyses must be such that they can be used in process control and development and simultaneously clearly show that the limit values for the impurities applicable in each particular case have been observed. Co-combustion of waste or waste derived fuels with other fuels immediately showed an increase of PCDD's, PCDF's, PCP's and PCBz's in the flue gases when either less efficient combustion technology or high portioning of waste fuels were used in combustion. The data available in the context of present the work suggest that parameters reflecting good combustion conditions, optimization of the general process conditions and efficient process control are likely to result in low organochloro compound emission in MSW- and HW-incineration and metal reclamation. Observed data show that the application of efficient acid gas and particulate emission control facilities will significantly reduce organochloro compound emissions from studied thermal processes. The observed reductions in the combustion and metal reclamation process indicate that more particle-bound (higher molecular size, less volatile, more chlorine-containing) substances were recovered to a higher degree. The analyses which focus only on PCDD/F's and PCB's in different thermal processes may underestimate the range and scale of the PCP- and PCBz-emission and the significance of the emission. Thus far, no commonly accepted TeCDD/TeCDF-type toxicity estimation method has been developed for these compounds. The present results indicate that, in addition to PCP, PCB and PCDD/F emission, emission of chlorobenzene, chloronaphthalene and polychlorinated dibenzothiophenes from thermic metallurgical processes might be of serious environmental concern.