Hydrothermal Liquefaction of Bark-containing Nordic Biomass

Hydrothermal liquefaction (HTL) is a thermochemical process that takes advantage of the water present in the feedstock under process conditions where the water is kept as a liquid solvent using pressurized systems, avoiding energy losses to heat of evaporation and allowing for high carbon conversion to liquid fuels. In the Nordic countries, woody biomass residues, originating from pine and spruce, are seen as an abundant biomass feedstock for biofuels and bioenergy production due to the extensive forest industry and the by-products they generate. By using by-products and wastes as the source material, the fuel product becomes more sustainable. Bark is not often included in woody biomass feedstocks for HTL, therefore investigating its addition can provide opportunities for a more effective use of this waste stream. Spruce and pine stem wood, as well as their bark fractions, received from a Norwegian wood products company was milled and mixed with water to obtain slurries serving as the source material in this study. The stem wood underwent sub- and supercritical HTL conversion, at 350 and 400 °C respectively, in a 1L CSTR reactor operated in batch mode. The bark fractions were mixed with the stem wood at varying percentages to study the effect of bark presence in the slurry at supercritical (400 °C) conditions. Both the proportions of the HTL products (gaseous, liquid, and solid) and the product components displayed differences when the experiments were performed at sub- and supercritical conditions. Bark addition seemed to increase the gas yields and lower the char yields but did not alter the properties of the liquid products significantly. The results show that bark in the feedstock did not affect the investigated properties negatively, which is promising for biofuel production via HTL.Hydrothermal Liquefaction of Bark-containing Nordic BiomasspublishedVersio

Explaining the type Ia supernova PTF 11kx with a violent-prompt merger scenario

We argue that the multiple shells of circumstellar material (CSM) and the supernovae (SN) ejecta interaction with the CSM starting 59 days after the explosion of the Type Ia SN (SN Ia) PTF 11kx, are best described by a violent prompt merger. In this prompt merger scenario the common envelope (CE) phase is terminated by a merger of a WD companion with the hot core of a massive asymptotic giant (AGB) star. In most cases the WD is disrupted and accreted onto the more massive core. However, in the rare cases where the merger takes place when the WD is denser than the core, the core will be disrupted and accreted onto the cooler WD. In such cases the explosion might occur with no appreciable delay, i.e., months to years after the termination of the CE phase. This, we propose, might be the evolutionary route that could lead to the explosion of PTF 11kx. This scenario can account for the very massive CSM within ~1000 AU of the exploding PTF 11kx star, for the presence of hydrogen, and for the presence of shells in the CSM.Comment: MNRAS, in pres

CO2 gasification of chars prepared from wood and forest residue

The CO2 gasification of chars prepared from Norway spruce and its forest residue was investigated in a thermogravimetric analyzer (TGA) at slow heating rates. The volatile content of the samples was negligible; hence the gasification reaction step could be studied alone, without the disturbance of the devolatilization reactions. Six TGA experiments were carried out for each sample with three different temperature programs in 60 and 100% CO2. Linear, modulated, and constant-reaction rate (CRR) temperature programs were employed to increase the information content available for the modeling. The temperatures at half of the mass loss were lower in the CRR experiments than in the other experiments by around 120 degrees C. A relatively simple, well-known reaction kinetic equation described the experiments. The dependence on the reacted fraction as well as the dependence on the CO2, concentration were described by power functions (n-order reactions). The evaluations were also carried out by assuming a function of the reacted fraction that can mimic the various random pore/random capillary models. These attempts, however, did not result in an improved fit quality. Nearly identical activation energy values were obtained for the chars made from wood and forest residues (221 and 218 kJ/mol, respectively). Nevertheless, the forest residue char was more reactive; the temperatures at half of the mass loss showed 20-34 degrees C differences between the two chars at 10 degrees C/min heating rates. The assumption of a common activation energy, E, and a common reaction order, v, on the CO2, concentration for the two chars had only a negligible effect on the fit quality

Initielle multibrensel reaktor forsøk i KRAV prosjektet

Blandinger av to brensler er testet i en multibrensel reaktor. Fire temperaturer ble valgt for å undersøke effekten av blandingsforhold, luftoverskuddstall og temperatur; 700 °C, 750 °C, 800 °C og 850 °C. Resultatene fokuserer på NOx, SO2 og HCl utslipp og hvor mye av brenselets nitrogen, svovel og klormengde som konverteres til hhv. NOx, SO2 og HCl. Utslippene er avhengig av brenselets sammensetning og forbrenningsforholdene. Resultatene viser at temperaturen i det valgte temperaturområdet ikke påvirker hvor mye av brenselets nitrogeninnhold som konverteres til NOx, men for svovel og klor konvertering er temperaturen av betydning. Brenselets sammensetning har en tydelig effekt på graden av nitrogen-, svovel- og klorkonvertering. Videre eksperimentelle studier hvor også aske- og partikkel analyse er inkludert er nødvendig for å kunne analysere og forklare klor og svovel effektene i detalj.Initielle multibrensel reaktor forsøk i KRAV prosjektetpublishedVersio

Hydrothermal liquefaction of organic resources in biotechnology: how does it work and what can be achieved?

Increasing the overall carbon and energy efficiency by integration of thermal processes with biological ones has gained considerable attention lately, especially within biorefining. A technology that is capable of processing wet feedstock with good energy efficiency is advantageous. Such a technology, exploiting the special properties of hot compressed water is called hydrothermal liquefaction. The reaction traditionally considered to take place at moderate temperatures (200–350 °C) and high pressures (10–25 MPa) although recent findings show the benefits of increased pressure at higher temperature regions. Hydrothermal liquefaction is quite robust, and in theory, all wet feedstock, including residues and waste streams, can be processed. The main product is a so-called bio-crude or bio-oil, which is then further upgraded to fuels or chemicals. Hydrothermal liquefaction is currently at pilot/demo stage with several lab reactors and a few pilots already available as well as there are a few demonstration plants under construction. The applied conditions are quite severe for the processing equipment and materials, and several challenges remain before the technology is commercial. In this review, a description is given about the influence of the feedstock, relevant for integration with biological processing, as well as the processing conditions on the hydrothermal process and products composition. In addition, the relevant upgrading methods are presentedHydrothermal liquefaction of organic resources in biotechnology: how does it work and what can be achieved?acceptedVersio

Status på problemer knyttet til bruk av ulike biobrensler

Dagens energibehov øker i en slik takt at bruk av alternative biobrensler i biomasse kraft-varme anlegg i økende grad blir nødvendig for å oppnå kostnadseffektivitet. Disse alternative biobrenslene byr ofte på problemer på grunn av deres lavere brenselkvalitet sammenlignet med f.eks. flis. Den lavere brenselkvaliteten er i stor grad knyttet til brenselets kjemiske sammensetning og problemer enkelte forbindelser skaper i et bioenergianlegg. I denne rapporten er egenskapene for de mest vanlige biobrenslene beskrevet. Brenselets egenskaper påvirker hele prosesskjeden. Brenselets fysiske egenskaper, som energitetthet, partikkelstørrelse og -fordeling og form påvirker biomasselagring og -håndtering samt konverteringsprosessen. Brenselets kjemiske egenskaper påvirker både konverterings-prosessen, energiutnyttelsespotensialet, utslippene og driftsikkerheten. En av de største utfordringene er å hindre korrosjon og beleggdannelse. Det finnes ulike metoder som kan redusere eller eliminere problemene, men per dags dato gjelder disse for større skala anlegg. Hittil har småskala anlegg valgt å fyre med høykvalitets brensler for å unngå de brenselrelaterte utfordringene. Det er derfor viktig å identifisere kostnadseffektive teknologier som kan brukes i småskala (< 10 MW innfyrt) anlegg. For å være kostnadseffektive i det lange løp må også småskala anlegg bruke brensler med lavere og mer ujevn kvalitet. Diverse teknologier er kandidater for småskala kraft-varme anlegg. De ulike teknologiene må vurderes og den eller de beste teknologiene for bruk i Norge må identifiseres. Gassifisering er en aktuell kandidat til å kunne gjøre småskala anlegg kostnadseffektive ved bruk av lavkvalitets brensler, men per i dag dominerer forbrenning. KRAV prosjektets rolle i dette er å fokusere på småskala kraft-varme anlegg basert på biomasse, inkludert lavkvalitets biomasse, som én sannsynlig betydelig bidragsyter til det norske energisystemet i fremtiden.Status på problemer knyttet til bruk av ulike biobrenslerpublishedVersio

Ny teknologi innen avansert forbrenning av avfall og biomasse - Litteraturstudie

publishedVersio

SO2 utslipp ved forbrenning av gipsholdige avfall

I forskningsprosjektet aCOM, er det fra industrideltagerne framsatt ønske om å kartlegge SO2 utslipp fra avfallsforbrenning, hvis avfallet inneholder gips. Innledende forsøk (TR F6615) viste at gips ble spaltet ved en mye lavere temperatur enn hva som er beskrevet i teorien (~1100 °C), og at ved ufullstendig forbrenning kan SO2 utslippet øke ytterligere. Denne gangen ble en mer omfattende forsøksrunde utført, som viser at gipsinnblanding øker SO2-utslippet, og at økende mengde gips gir økende utslipp. Med økende SO2-utslipp øker HCl utslippet også, som indikerer en interaksjon mellom S og Cl i brenselet, via askekomponenter og dannelse av mer alkaliesulfater på bekostning av alkalieklorider. Mer Cl blir derfor tilgjengelig for dannelse av HCl. SO2-utslippet viser avhengighet av luftoverskuddstall og temperatur, men graden av avhengighet er forskjellig for rene brensler og brensler med gipsinnblanding. Dette er forventet siden SO2 dannes både fra brenselet og fra gipsen innblandet i brenselet. SO2 utslipp ved forbrenning av gipsholdige avfallpublishedVersio

Thermogravimetric investigation of four fuels

The KRAV project focuses on small-scale CHP plants running on biomass, included low quality biomass fuels. In order to be more cost efficient, it is a need to be able to burn low quality fuels in small-scale CHP plants. Four fuels (wood pellets, demolition wood, coffee waste and glossy paper) were investigated in this report, with TGA-MS technique. Two atmospheres were used, the combustion experiments were carried out in argon with 21 vol% oxygen and the pyrolysis experiments were carried out in pure argon. Three different heating rates (5, 20 and 100 K/min) were used, to investigate the influence of the heating rate on the fuel conversion. Coffee waste releases volatiles at the lowest temperature, but the release is slowest in this case, followed by wood and demolition wood, and glossy paper releases volatiles at the highest temperature. The volatiles release temperature is not affected by the presence of oxygen but increases slightly with increasing heating rate. The volatiles release is followed by the char conversion process at higher temperatures, and this process is slow. The process is faster in the presence of oxygen. When oxygen is not available in the reactive gas, the char does not convert completely. The char conversion rate decreases with increasing heating rate and the portion of unconverted char in the ash increases. In the combustion experiments, coffee waste ignites at 5 K/min heating rate, all fuels ignite at 20 K/min heating rate and none at 100 K/min heating rate. The results derived in these TGA experiments will together with planned accompanying macro-TGA experiments provide useful fundamental knowledge about the characteristics of the fuels.Thermogravimetric investigation of four fuelspublishedVersio