Full-scale Municipal Solid Waste Incinerator Research Articles

Indication of PCDD/F formation through precursor condensation in a full-scale hazardous waste incinerator

This paper gives the PCDD/F fingerprint of boiler and fly ash of a full scale hazardous waste incinerator and demonstrates that, when the waste to be incinerated contains high concentrations of PCBs and chlorinated pesticides, heterogeneous precursor condensation is the dominant PCDD/F formation mechanism rather than de novo synthesis. This is in contrast to full-scale municipal solid waste incinerators, where de novo synthesis has been shown to be the dominant PCDD/F formation mechanism. This paper agrees with earlier predictions based on numerous lab scale experiments.

Life cycle assessment of selective non-catalytic reduction (SNCR) of nitrous oxides in a full-scale municipal solid waste incinerator

Selective non-catalytic reduction (SNCR) of nitrous oxides in a full-scale municipal solid waste incinerator was investigated using LCA. The relationship between NO x -cleaning and ammonia dosage was measured at the plant. Un-reacted ammonia – the ammonia slip – leaving the flue-gas cleaning system adsorbed to fly-ash or in the effluent of the acidic scrubber was quantified from the stoichiometric reaction of NO x and ammonia assuming no other reaction products was formed. Of the ammonia slip, 37% was associated with the fly-ash and 63% was in the effluent of the acidic scrubber. Based on NO x -cleaning efficiency, the fate of the ammonia slip as well as the environmental impact from ammonia production, the potential acidification and nutrient enrichment from NO x -cleaning was calculated as a function of ammonia dosage. Since the exact fate of the ammonia slip could not be measured directly, a number of scenarios were set up ranging from “best case” with no ammonia from the slip ending up in the environment to “worst case” where all the ammonia slip eventually ended up in the environment and contributed to environmental pollution. In the “best case” scenario the highest ammonia dosage was most beneficial demonstrating that the environmental load associated with ammonia production is of minor importance. In contrast, in a “worst case” scenario” NO x -cleaning using SNCR is not recommendable at all, since the impacts from the ammonia slip exceed the saved impacts from the NO x removal. Increased dosage of ammonia for removal of NO x is recommendable as long as less than 10–20% of the ammonia slip to the effluent of the acidic scrubber ends up in the environment and less than 40% of the slip to the fly-ash ends up in the environment. The study suggests that the actual fate of the ammonia slip is crucial, but since the release of the ammonia may take place during transport and at the facilities that treat the wastewater and treat the fly-ash this factor depends strongly on local conditions and may be hard to determine. Thus, LCA-modeling proved useful in assessing the balance between ammonia dosage and NO x -removal in flue-gas cleaning from waste incineration.

Influence of variation in the operating conditions on PCDD/F distribution in a full-scale MSW incinerator

Optimizing the operating parameters to minimize polychlorodibenzo- p-dioxins and polychlorodibenzofurans (PCDD/F) emission is the common interest of the municipal solid waste (MSW) incineration industry. In this study, we investigated the distribution of tetra- to octa-CDD/F along the flue gas line in a full-scale reciprocating grate incinerator and evaluated the effects of temperature control and O 2 level on PCDD/F formation. Six runs were laid out and all performed under sufficient burning conditions, in which the combustion efficiency of MSW was more than 99.9%. The total concentration of tetra- to octa-CDD/F measured at the boiler outlet showed an increasing tendency with the increase of boiler outlet temperature ( T B) from 214 °C to 264 °C. When flue gas ran across the semi-dry scrubber and cyclone precipitator, in which the temperature varied from 264 °C to 162 °C, the concentrations of the lower chlorinated dioxins and furans were significantly raised, especially for the TCDF. Increasing O 2 supply from 6.0% to 10.5% essentially led to a higher yield of tetra- to octa-PCDD/F, suggested that under sufficient burning conditions the lower O 2 level was favorable for reducing PCDD/F formation and emission. The variation of O 2 level did not give rise to a systematical change of PCDD/F homologue pattern. For all measurements, the isomer distributions of tetra- to hepta-PCDD/F were more or less the same, nearly independent of variations in the operating conditions and sampling positions. Only the significant increase of the sum of 1,3,7,8-TCDF and 1,3,7,9-TCDF was found in the zone after the boiler section.

Numerical simulation of Municipal Solid Waste incineration in a moving-grate furnace and the effect of waste moisture content

Mathematical equations governing the physical and chemical processes in grate combustion systems are described and a full-scale municipal solid waste incinerator was simulated. The effects of waste moisture content as well as preheated air temperature have been assessed. Combustion efficiency around 98% was obtained for moisture levels less than 30% while moisture over 35% resulted in poor combustion efficiency. Depending on the waste moisture content, the maximum gas temperature ranges from 1240C to 1510C and the maximum solid temperature inside the packed-bed from 980C to 1230C. The main reaction zone thickness ranges from 250 mm to 350 mm along the bed height.

Behavior of PCNs, PCDDs, PCDFs, and dioxin-like PCBs in the thermal destruction of wastes containing PCNs

In the first known study to characterize the emissions of polychlorinated naphthalenes (PCNs), polychlorinated dibenzo- p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (dl-PCBs) from the thermal treatment of wastes containing PCNs, the formation and decomposition behavior of these pollutants was investigated both at laboratory scale and at plant scale. Exhaust gas measurements from laboratory-scale combustion of rubber belts containing PCNs (FB belts) were used as the basis for calculations predicting that the incremental dioxin toxic equivalency (TEQ) emissions from municipal solid waste (MSW) incinerators would be less than 0.1 ng/m 3 N. In order to directly examine co-incineration of FB belts with MSW and to address potential differences between the laboratory experiment and full-scale MSW incinerators, experiments were conducted using a larger scale thermal treatment test facility with sampling and analysis at several points in the thermal treatment process. Congener specific analysis of PCNs clearly showed that both destruction and synthesis simultaneously occurred during combustion in the kiln. Most of the PCNs were destroyed by secondary combustion, and almost all PCNs were removed after flue gas treatment. Almost all PCDDs/DFs were synthesized as by-products of kiln combustion, most of them were destroyed by the secondary combustion, and almost all dioxins (PCDDs/DFs and dl-PCBs) were removed after flue gas treatment. The TEQ emission levels were less than 0.1 ng/m 3 N for all plant-scale tests, and differences in TEQ emission levels were very small. Adding wastes containing PCNs to MSW will not influence thermal treatment emissions to the environment from modern solid waste incinerators.

STUDY ON THE TRANSIENT PROCESS OF WASTE FUEL INCINERATION IN A FULL-SCALE MOVING-BED FURNACE

ABSTRACT The transient process in a full-scale municipal solid waste incinerator was investigated to assess the effect of the grate movement and waste feeding cycles. Inside-bed measurements of temperature and O2 were carried out and an 18-hour record of furnace temperature, airflow, and flue gas compositions was analyzed using discrete Fourier transform. The transient burning process was also simulated numerically by solving the governing equations for both the solid and gas phases. It is found that fluctuations in the furnace temperature and flue gas O2 level correspond to the waste feeding and grate movement cycles, either in phase or out of phase (depending on the length of the cycles), while combustion inside the bed is dominated by a series of big spikes and dips in both local temperature and O2 level. Theoretical calculations indicate that each grate movement causes a surge (by 35%) in the volatile release rate but a depression (by 24%) in the char burning rate. The overall bed-burning rate fluctuates between 90 and 110% of its average.

Dioxin removal in a wet scrubber and dry particulate remover

Chlorinated dioxins and furans (PCDDs and PCDFs), formed by de novo synthesis, can be removed from the flue gas stream by using activated carbon. In a series of tests conducted at full-scale municipal solid waste incinerators, the effects of activated carbon injection on PCDD and PCDF emissions was assessed. Also evaluated was the impact of ammonia on the PCDD and PCDF formation process within these systems.