Choice of bed material: a critical parameter in the optimization of dual fluidized bed systems

Dual Fluidized Bed (DFB) gasification is a promising alternative method for the production of biofuels. In the DFB gasification process, the bed material, which is a crucial component of the process, has two possible roles: 1) to provide the heat needed for the gasification reaction; and 2) if it has catalytic properties, to improve the quality of the produced gas. Ash-forming elements that are introduced together with the biomass into the system can interact with the bed material, and therefore have catalytic potential. As they alternate between the different environments, and depending on the nature of the bonds formed between the bed material and ash elements, some of the inorganic compounds may be released in the gas phase, thereby influencing the final composition of the produced gas. The present work advances current understanding of how biomass ash-induced changes alter the impact of the bed material on the performance of a DFB gasifier. Thus, understanding the bed material-biomass ash interactions can be used to improve the performance of the system. By improving the gasification step, which is the main step in the biomass conversion, the costs associated with the downstream processes, and consequently, the overall cost of the biomass to biofuel pathway can be reduced. In addition, utilizing naturally occurring materials as catalytic bed materials is advantageous given their relatively low price and low environmental impact which in terms of disposal of the material post-process. The work for this thesis was conducted at the Chalmers facility. The possibilities for process improvement were investigated by the use of different bed materials in the gasifier, as well as in a secondary upgrading step. When applied to the gasification step, the interactions between inorganics and bed material alter the chemical properties of the bed, thereby influencing the gasification process. Within the investigations presented in this thesis, six naturally occurring materials were tested in the beds. Tests with silica sand, olivine sand, and bauxite were performed in the Chalmers 2–4-MWth gasifier. For each tested material, the process was evaluated with respect to: 1) the composition of the produced gas; 2) the tar content; and 3) the physicochemical properties of the bed material. The key finding is that the transport of alkalis from the boiler to the gasifier, where they are released, is the major factor influencing the gas composition. An improved understanding the importance of potassium transport was crucial in salvaging the commissioning and start-up of the GoBiGas gasification system, which had suffered from the problem of insufficient gas quality. Even though a positive effect of alkali on the gasification is known, high levels of alkali entail a risk for agglomeration. In this regard, a natural ore of iron, ilmenite, was used in the Chalmers 12–MWth boiler as a material for fluidized bed combustion. It was found that ilmenite has the capability to store potassium in a non-releasable form, thereby decreasing the risk of bed agglomeration in fluidized bed boilers. To enable further upgrading of the gas produced by biomass gasification, two naturally occurring materials were tested in a Chemical Looping Reforming system: a manganese ore; and feldspar. Both materials were able to reform tars and persisted throughout the process with negligible decrease in activity

Comparing Active Bed Materials in a Dual Fluidized Bed Biomass Gasifier: Olivine, Bauxite, Quartz-Sand, and Ilmenite

Active bed materials are in this work investigated for in situ gas upgrading of biomass-derived gas. Previous research on in situ gas upgrading has focused on assessing gas quality, in terms of the concentrations of tar and permanent gases. Other aspects of fuel conversion, such as char conversion and the impact of oxygen transport on the final gas, are not as well documented in the literature on gasification. In this paper, the overall biomass conversion in a dual fluidized bed biomass gasifier is investigated in the presence of the catalytic material olivine and the alkali-binding material bauxite. The impact of these materials on fuel conversion is described as the combination of four effects, which are induced by the bed material: thermal, catalytic, ash-enhanced catalytic effect, and oxygen transport. Quartz-sand and ilmenite are here used as the reference materials for the thermal and the oxygen transport effects, respectively. Olivine and bauxite show activity toward tar species compared to quartz-sand. After 1 week of operation and exposure to biomass ash, the activities of olivine and bauxite toward tar species increase further, and the water gas shift reaction is catalyzed by both materials. Additionally, bauxite shows a stronger ability to increase char conversion than olivine. Under the conditions tested, olivine and bauxite have some degree of oxygen transport capacity, which is between those of quartz-sand and ilmenite. The oxygen transport effect is higher for bauxite than for olivine; nevertheless, the catalytic activities of the materials result in higher yields of H-2 than in a similar case with quartz-sand. The implications of the findings for the operation of dual fluidized bed gasifiers are discussed

Analiza kvaliteta vode reke Mlave na osnovu vodenih makroinvertebrata

Cilj rada je da se predstave rezultati ispitivanja kvaliteta vode reke Mlave, zasnovani na prisutnoj zajednici vodenih makroinvertebrata. Mlava, sa dužinom toka od 78 km i površinom sliva od 1885 km², jedna je od značajnijih pritoka Dunava u Srbiji. Kao najvažniji izvori komunalnog i industrijskog zagađenja mogu se izdvojiti gradovi Požarevac (70000 stanovnika; u donjem toku) i Petrovac na Mlavi (8000 stanovnika; srednji tok), kao i Žagubica (2600 stanovnika; gornji tok). Slivno područje, naročito u srednjem delu toka, je i pod uticajem spiranja sa poljoprivrednih površina, kao i komunalnih otpadnih voda iz brojnih manjih naselja. Negativni efekti, ovih antropogenih uticaja mogu biti još izraženiji, zbog specifične hidrologije, odnosno preovlađivanja stanja niskih voda u slivu ove reke. Uzorkovanje je izvršeno u julu 2013. godine. Kao parametri za ocenu kvaliteta vode, korišćeni su sledeći pokazatelji: Saprobni indeks (SI; Zelinka & Marvan), BMWP i ASPT skorovi, broj taksona grupa Ephemeroptera, Plecoptera and Trichoptera (EPT) i indeks diverziteta (SWI; Shannon-Wiener’s indeks). Ukupno 72 taksona makroinvertebrata su identifikovana. Insekti su bili najraznovrsnija komponenta, a u okviru njih najbrojnije su bile grupe Ephemeroptera (13 taksona) i Trichoptera (11 taksona). Najveća raznovrsnost zabeležena je na lokalitetu Leskovac (33 taksona). Većina taksona je tolerantna na određeni stepen organskog zagađenja (β –mezosaprobni i α–mezosaprobni organizmi), naročito u donjem delu toka (Rašanac i Požarevac). Vrednosti SI na svim lokalitetima upućuju na veoma dobar i dobar kvalitet vode (klase I i II). Vrednosti BMWP i ASPT ukazuju na veoma dobar kvalitet vode samo na lokalitetima u srednjem i donjem delu toka (Leskovac i Požarevac), dok je u gornjem delu toka, kvalitet vode, ili loš (BMWP), ili umeren do dobar (ASPT). I preostali pokazatelj (EPT), takođe, ukazuje na bolji kvalitet vode u donjem delu toka. Na osnovu svih korišćenih pokazatelja, kvalitet vode reke Mlave u julu 2013. godine se može oceniti kao dobar (klasa II)

The assessment of health-related quality of life in relation to the body mass index value in the urban population of Belgrade

<p>Abstract</p> <p>Background</p> <p>The association between excess body weight, impairment of health and different co-morbidities is well recognized; however, little is known on how excess body weight may affect the quality of life in the general population. Our study investigates the relationship between perceived health-related quality of life (HRQL) and body mass index (BMI) in the urban population of Belgrade.</p> <p>Methods</p> <p>The research was conducted during 2005 on a sample of 5,000 subjects, with a response of 63.38%. The study sample was randomly selected and included men and women over 18 years of age, who resided at the same address over a period of 10 years. Data were collected by means of a questionnaire and nutritional status was categorized using the WHO classification. HRQL was measured using the SF-36 generic score. Logistic regression analysis was used to compare HRQL between subjects with normal weight and those with different BMI values; we monitored subject characteristics and potential co-morbidity.</p> <p>Results</p> <p>The prevalence of overweight males and females was 46.6% and 22.1%, respectively. The prevalence of obesity was 7.5% in males and 8.5% in females.</p> <p>All aspects of health, except mental, were impaired in males who were obese. The physical and mental wellbeing of overweight males was not significantly affected; all score values were similar to those in subjects with normal weight.</p> <p>By contrast, obese and overweight females had lower HRQL in all aspects of physical functioning, as well as in vitality, social functioning and role-emotional.</p> <p>Conclusion</p> <p>The results of our study show that, in the urban population of Belgrade, increased BMI has a much greater impact on physical rather than on mental health, irrespective of subject gender; the effects were particularly pronounced in obese individuals.</p

Produkcija makrozoobentosa u reci Rači uzvodno i nizvodno od pastrmskog ribnjaka

Biomasa (produkcija) makrozoobentosa je odabrana kao osnovni pokazatelj za praćenje promena kvantitativnog sastava naselja dna na lokalitetima uzvodno i nizvodno od pastrmskog ribnjaka u reci Rači. Istraživanje sekundarne produkcije makrozoobentosa reke Rače sa sedam lokaliteta, obavljeno je u periodu 2011. (april, jun, septembar, oktobar, decembar) i 2012. godine (februar i maj). Dominantne grupe u biomasi makrozoobentosa su Hirudinea (Annelida), Mollusca, Gammaridae (Crustacea) i Trichoptera (Insecta). Vrednosti biomase zoobentosa kretale su se u svim mesecima istraživanja u intervalu od 3,2001 g/m2, na lokalitetu RČ2 (u februaru) ,do 216,7120 g/m2, na lokalitetu RČ3 (u februaru). Biomasa faune dna najveća je u svim mesecima istraživanja na lokalitetu RČ3, koji je lociran nizvodno od pastrmskog ribnjaka. Na ovom lokalitetu biomasa makroinvertebrata se kretala od 87,8643 g/m2 (u aprilu 2011. godine) do 216,7120 g/m2 (u februaru 2012. godine)

Retrospective evaluation of the incidental finding of 403 papillary thyroid microcarcinomas in 2466 patients undergoing thyroid surgery for presumed benign thyroid disease

This research was aimed to describe the effectiveness of discovery learning model to increase student’s fluency thinking skills on chemical equilibrium subject matter.  The method of the research was quasi-experimental with  Non Equivalent Control Group Design.  The population of this research was all students in XI science class of MA Negeri 1 Metro whose sit in odd semester of academic year 2013-2014.  The sample were taken by purposive sampling technique then obtained XI IPA2 dan XI IPA3 class as sample of the research.  The effectiveness of discovery learning model was showed by the significant difference of n-Gain between control and experiment class.The result of research showed that the average n-Gain score for experiment class was  0,32 and the average n-Gain score for control class was 0,21.  Proving the hypothesis showed that discovery learning model is effective to increase student’s fluency thinking skills on chemical equilibrium subject matter. Tujuan penelitian ini adalah untuk mendiskripsikan efektivitas model discovery learning dalam meningkatkan keterampilan berpikir lancar siswa pada materi kesetimbangan kimia.  Metode dalam penelitian ini adalah kuasi eksperimen.  Populasi dalam peneliian ini adalah semua siswa kelas XI IPA MA Negeri 1 Metro semester ganjil Tahun Pelajaran 2013-2014.  Sampel diambil dengan tehnik purposive sampling sehingga diperoleh kelas XI IPA2 dan XI IPA3 sebagai sampel penelitian.  Efektivitas model discovery learning ditunjukan berdasarkan perbedaan nilai n-Gain yang signifikan antara kelas eksperimen dan kelas kontrol. Hasil penelitian menunjukan rata-rata nilai n-Gain untuk kelas eksperimen adalah 0,32 dan rata-rata nilai n-Gain  untuk kelas kontrol adalah 0,21.  Pengujian hipotesis menunjukan bahwa model discovery learning efektif dalam meningkatkan keterampilan berpikir lancar siswa pada materi kesetimbangan kimia. Kata kunci : kesetimbangan kimia, keterampilan berpikir lancar, model discovery learnin

Prinos zrna različitih sorti pšenice u organskoj proizvodnji u zavisnosti od rizosferne mikroflore

The aim of this paper is testing the productivity of various wheat varieties depending on the rhizosphere microflora in terms of organic cultivation technology. The highest yield in the first year was recorded in cv spelt, and in the second year at ordinary soft wheat varieties for which it was established and greater variation in yield compared to alternative types of wheat varieties. The lowest yield was detected among varieties of durum wheat, Dolap, in which it recorded the lowest number of investigated microbial groups. By testing the significance of regression model was found a statistically significant change in the yield of wheat depending on the number of Azotobacter (r = 0.76), but not the total number of microorganisms (r=0,24).Cilj rada je ispitivanje produktivnosti različitih sorti pšenice u zavisnosti od rizosferne mikroflore u uslovima organske tehnologije gajenja. Najveći prinos zrna u prvoj godini zabeležen je kod sorte krupnika, a u drugoj godini kod sorte obične meke pšenice kod koje je ustanovljeno i veće variranje prinosa u poređenju sa ispitivanim sortama alternativnih vrsta pšenice. Najmanji prinos zrna ustanovljen je kod sorte tvrde pšenice, Dolap, kod koje je zabeležen najmanji broj ispitivanih grupa mikroorganizama. Testiranjem značajnosti regresionog modela ustanovljeno je postojanje statistički značajne promene prinosa pšenice u zavisnosti od brojnosti Azotobakter-a (r=0,76), ali ne i od ukupnog broja mikroorganizama (r=0,24)