A system for measuring bubble voidage and frequency around tubes immersed in a fluidized bed of particles

Journal ArticleGas-solid fluidized beds are common in chemical processing and energy production industries. These types of reactors frequently have banks of tubes immersed within the bed to provide heating or cooling, and it is important that the fluid dynamics within these bundles is efficient and uniform. This paper presents a simple, low-cost method for quantitatively analyzing the behavior of gas bubbles within banks of tubes in a fluidized bed cold flow model. Two probes, one containing an infrared emitter and one containing an infrared (IR) detector, are placed into adjacent glass tubes such that the emitter and detector face each other. As bubbles pass through the IR beam, the detector signal increases due to less solid material blocking the path between the emitter and detector. By calibrating the signal response to known voidage of the material, one can measure the bubble voidage at various locations within the tube bundle. The rate and size of bubbles passing through the beam can also be determined by high frequency data collection and subsequent analysis. This technique allows one to develop a map of bubble voidage within a fluidized bed, which can be useful for model validation and system optimization

Physical phenomena of char-slag transition in pulverized coal gasification

ManuscriptPerformance of entrained-flow coal gasifiers is in large part dictated by the burnout behavior of coal particles. In particular, the transition from porous, reactive char to molten, low reactive slag affects overall coal conversion. In this work, the physical phenomena associated with char?slag transition were studied for three coals using a laminar entrained-flow reactor under simulated gasification conditions. Partially oxidized particles with various conversions were prepared at temperatures above the ash fluid temperatures. The physical properties of the char and slag particles were characterized, including the particle density, size, internal surface area and morphology. Results show that at a coal-dependent critical conversion, the particles undergo remarkable physical changes, such as density increase, size reduction and surface area decrease. These phenomena indicate the char?slag transition

A pulse-width modulation controlled wire-mesh heater apparatus for investigation of solid fuel pyrolysis

pre-printA novel wire mesh heater apparatus has been developed to study the devolatilization of solid fuels under pressurized conditions at well-controlled heating rates on the order of 1000 K/s. The apparatus combines direct current and pulse-width modulation with a fast-acting and high current-capacity relay to achieve operating frequencies up to 2000 Hz. This frequency allows much quicker feedback and tighter control of temperature than conventional ac-based systems that operate at 50 to 60 Hz. The present apparatus has been successfully operated at 63 bars with final temperatures of 1473 K and heating rates of 1100 K/s

Manslaughter by Fake Artesunate in Asia—Will Africa Be Next?

Fake artesunate could compromise the hope that artemisinin-based combination therapy offers for malaria control in Africa and Asia

Perustilaselvitys direktiivilaitosten ympäristölupaharkinnassa ja pilaantuneen ympäristön puhdistamista koskevassa sääntelyssä

Tutkielman aiheena on teollisuuspäästödirektiiviin perustuva perustilaselvitys, joka on Suomessa pantu täytäntöön ympäristönsuojelulain kokonaisuudistuksen yhteydessä. Perustilaselvityksellä tarkoitetaan ympäristön tilainventaariota, jolla selvitetään direktiivilaitosten toimintaan liittyvien merkityksellisten vaarallisten aineiden maaperälle ja pohjavedelle aiheuttama muutos. Euroopan komission mukaan perustilaselvitys on työkalu, jonka avulla pilaantuneen ympäristön ennallistamisen tavoitetaso voidaan teollisen toiminnan päätyttyä määrittää. Tutkielman tavoitteena on selvittää perustilaselvityssääntelyn aiheuttama oikeustilan muutos sekä arvioida selvityksen soveltuvuutta suomalaiseen ympäristölupaharkintaan ja pilaantuneita alueita koskevaan sääntelyyn. Tutkielmassa on lyhyesti esitelty muissa jäsenvaltioissa valittuja toimeenpanoratkaisuja ja arvioitu Suomessa valitun implementointiratkaisun onnistumista suhteessa sääntelyn tavoitteisiin. Aineistona on teollisuuspäästödirektiivin ja ympäristönsuojelulakia koskevan hallituksen esityksen lisäksi käytetty perustilaselvitystä koskevia komission ja ympäristöministeriön ohjeita ja soveltuvissa määrin oikeuskirjallisuutta, joka pääsääntöisesti on peräisin ajalta ennen ympäristönsuojelulain voimaantuloa 1.9.2014. Kirjallisuuden on katsottu olevan käyttökelpoista, koska pilaantuneen ympäristön puhdistamista koskeva sääntely on ympäristönsuojelulain kokonaisuudistuksessa säilytetty pääosin ennallaan. Tutkielma on luonteeltaan lainopillinen, ongelmakeskeinen esitys, joka sijoittuu tutkimuskysymystensä, metodologiansa ja tavoitteidensa johdosta ympäristöoikeuden alalle. Tutkielman perusteella voidaan todeta, että perustilaselvityssääntely ei täysin sovellu suomalaisen ympäristön pilaantumista koskevaan sääntely-ympäristöön. Perustilaselvityksen laatimista koskeva sääntely ja ohjeistus on toteutettu teollisuuspäästödirektiivin tavoitteiden mukaisesti, mutta sääntely on tulkinnanvaraista. Perustilan palauttamista koskeva sääntely on perustilasääntelyn ongelmakohta eikä toiminnan lopettamisvaiheeseen liittyvästä menettelystä sen perusteella synny selkeää kuvaa. Perustilaselvityksen laatiminen voi olla vaikea tehtävä, koska toiminnanharjoittajilta edellytetään vaarallisten aineiden maaperälle ja pohjavedelle mahdollisesti aiheuttaman pilaantumisriskin syvällistä arviointia. Selvityksen mahdolliset hyödyt liittyvät sen ympäristönsuojelullisiin vaikutuksiin. Toiminnanharjoittajien selvilläolovelvollisuus korostuu ja perustilaselvitysten avulla saadaan ajantasaista tietoa maaperän ja pohjaveden tilasta. Tietojen avulla ennaltaehkäisymenetelmiä ja parempia tekniikoita voidaan edelleen kehittää. Maaperän ja pohjaveden laatuinventaariona perustilaselvityksen laatiminen tukee alueiden ennallistamista niiden yksilölliset tarpeet huomioivalla tavalla. Selvitys tarjoaa lupaharkinnassa käytettäväksi aikaisempaa kattavamman ympäristön tilaa koskevan aineiston

Single nucleotide polymorphism discovery in elite north american potato germplasm

BACKGROUND: Current breeding approaches in potato rely almost entirely on phenotypic evaluations; molecular markers, with the exception of a few linked to disease resistance traits, are not widely used. Large-scale sequence datasets generated primarily through Sanger Expressed Sequence Tag projects are available from a limited number of potato cultivars and access to next generation sequencing technologies permits rapid generation of sequence data for additional cultivars. When coupled with the advent of high throughput genotyping methods, an opportunity now exists for potato breeders to incorporate considerably more genotypic data into their decision-making. RESULTS: To identify a large number of Single Nucleotide Polymorphisms (SNPs) in elite potato germplasm, we sequenced normalized cDNA prepared from three commercial potato cultivars: 'Atlantic', 'Premier Russet' and 'Snowden'. For each cultivar, we generated 2 Gb of sequence which was assembled into a representative transcriptome of (~)28-29 Mb for each cultivar. Using the Maq SNP filter that filters read depth, density, and quality, 575,340 SNPs were identified within these three cultivars. In parallel, 2,358 SNPs were identified within existing Sanger sequences for three additional cultivars, 'Bintje', 'Kennebec', and 'Shepody'. Using a stringent set of filters in conjunction with the potato reference genome, we identified 69,011 high confidence SNPs from these six cultivars for use in genotyping with the Infinium platform. Ninety-six of these SNPs were used with a BeadXpress assay to assess allelic diversity in a germplasm panel of 248 lines; 82 of the SNPs proved sufficiently informative for subsequent analyses. Within diverse North American germplasm, the chip processing market class was most distinct, clearly separated from all other market classes. The round white and russet market classes both include fresh market and processing cultivars. Nevertheless, the russet and round white market classes are more distant from each other than processing are from fresh market types within these two groups. CONCLUSIONS: The genotype data generated in this study, albeit limited in number, has revealed distinct relationships among the market classes of potato. The SNPs identified in this study will enable high-throughput genotyping of germplasm and populations, which in turn will enable more efficient marker-assisted breeding efforts in potato

Design of a Gas-Solid-Solid Separator to Remove Ash from Circulating Fluidized Bed Reactors

Cyclones are one of the most common types of gas-solid separators used in circulating fluidized bed boilers. However, cyclones typically do not allow ash to leave the system through the cyclone exit, causing ash to build up in the fluidized bed and necessitating additional systems to remove ash that builds up in the bed. In this study, an alternative “disengager” gas-solid separator is proposed as a way of inherently separating small and large solids, resulting in a gas-solid-solid separation system where ash is allowed to leave the system along with gas while the desired fluidized bed material is retained. Unlike cyclones, which rely on centrifugal force to separate solids and gas, the disengager separates based on entrainment velocity of the particles. Upwards-flowing gas and particles strike a deflection plate and enter the disengaging chamber where particles with low terminal velocity such as ash fines flow with the gas, while larger particles such as sand fall to the bottom of the separator and are returned to the fluidized bed. In this study, several different proposed disengager configurations are simulated and compared to a typical cyclone using computational fluid dynamic (CFD) simulations. It was found that separation efficiency in the disengager is strongly influenced by the size of the deflection plate, rather than by the size of the unit itself. The predicted separation efficiency showed that compared to a cyclone, the disengager design allows significantly more ash to exit the system but retains a similar amount of desirable material. Additionally, the disengager was predicted to not suffer significantly more erosion that a cyclone

A Simulation-Based Parametric Study of CLOU Chemical Looping Reactor Performance

Chemical looping with oxygen uncoupling (CLOU) is a variant on chemical looping combustion in which the oxygen carrier releases gaseous O2 in the fuel reactor, making it well-suited for solid fuels, since the released gaseous O2 readily reacts with solid char. This study presents several computational fluid dynamic (CFD) simulations of copper-based CLOU in a dual fluidized bed system, each with different operating conditions. The modeling predicted that coal particle sizes as large as 1000 μm did not significantly affect performance. Increased oxygen carrier copper loading resulted in an excess of gaseous oxygen in the product gas stream. Decreasing the oxygen carrier bed mass as well as reducing the air reactor fluidizing velocity did not supply enough oxygen to the fuel reactor to complete combustion of the coal. This generated a failure state in which the temperature continued to decrease in the fuel reactor from the lack of combustion, which in turn reduced the O2 equilibrium partial pressure, further lowering the amount of combustion possible. Sufficient O2 can be maintained in the fuel reactor by ensuring a high enough air reactor velocity and a large enough supply of oxygen carrier inventory to handle the chosen coal feed rate