Elohopean ja muiden hivenaineiden höyrystyminen pyrolysoitaessa hiiltä ja jätepolttoaineita leijupetireaktorissa
Bibliographic record
Abstract
The objective of this thesis was to investigate the release of mercury and other trace elements (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Tl, V, Zn, Ti and Se) from coal and waste derived fuels during pyrolysis in a bubbling fluidised bed reactor. The release of mercury was of particular interest, as it is the most volatile, difficult to control and causes greatest public health concern of all trace elements. In addition to this, mercury exists in flue gas in three forms: gaseous elemental mercury, gaseous oxidised mercury and particulate bound mercury. It is imperative to know the speciation of mercury in order to address questions concerning mercury emission control, toxicity, mobility, bioaccumulation, and atmospheric fate and transport because each form has different physical, chemical and biological properties. In the theoretical part of this thesis, the sources, health effects, legislation and behaviour of trace elements during thermal processes are introduced, with special focus on mercury. Measurement of trace elements in and their removal from flue gas are also discussed. The focus of the reviewed literature was placed on the most recent studies conducted. In the experimental part of this thesis, the release of mercury and other trace elements from coal, sewage sludge and automotive shredder residue during pyrolysis in a fluidised bed reactor was examined. Mercury emissions were measured by a manual, wet sampling method, Ontario Hydro Method, which has an ASTM standard. Other trace elements were sampled by directing the flue gas flow through a scrubber tank containing of 15 litres of HNO3/H2O2 liquid, of which samples were taken during the test. The compositions of bed sand, fuel and char were also analysed. FTIR gas analyser was used to measure concentrations of about 20 gaseous species in the flue gas. The release of trace elements and the speciation of mercury were evaluated based on the results of these measurements and analyses. According to previous studies, mercury is completely volatilised during combustion and gasification processes and almost completely vaporised during pyrolysis in temperatures below 600 °C. Other trace elements can be released in gaseous form, enriched in fine particles or stay in the bottom ash depending of the characteristics and of the mode of occurrence of the particular trace element. During the experiments, it was noticed that all of the mercury was vaporised from each of the fuels used already at below 320 °C. The behaviour of other trace elements was dependent of the fuel as both vaporisation and enrichment in the char was detected.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.003 | 0.003 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.007 | 0.004 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.004 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.010 | 0.036 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; both teacher heads agree on what is shown here.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".