While the quest of the human civilization continues towards a more sustainable energy resource, current energy conversion technologies need to be improved such that the rate of environmental impact that has occurred due to the rapid industrialization since the 20th century is mitigated. This search has motivated research into new energy conversion technologies that aim to reduce the environmental impact by either improving the efficiencies of existing technologies, developing new technologies with zero emissions or by improving reliability and reducing the cost of renewable energy. Process intensification through process integration is one of the areas of active research that improves the system efficiency by exploiting the synergies that exist between different processes. This thesis considers the design and operational feasibility of heat integrating two conventional industrial processes – gasification and steam reforming of methane for application in polygeneration. To this end, complex mathematical models that describe the integrated system are developed to study different design prospects and to determine if the device can be safely operated in a plant producing electricity, liquid fuels and hydrogen. The designs proposed in this thesis show that significant methane conversion comparable to industrial reformers can be achieved while providing the required cooling duty to the gasifier. The proposed integrated system produces hydrogen rich reformer synthesis gas (hydrogen and carbon monoxide) that can be blended with the hydrogen lean coal synthesis gas providing flexibility to change the molar H2/CO ratio necessary for different downstream processes in a polygeneration plant. Moreover, the results show that the integration helps improve plant carbon efficiency and reduce CO2 emissions. The major contribution of this thesis is the development of designs based on representative mathematical models that are safe to operate for producing several chemicals in polygeneration plants. / Dissertation / Doctor of Philosophy (PhD)

To examine the effects of operational parameters on syn-gas quality and biouel conversion rate under various running conditions, an experimental study of hardwood chip?s gasification in a downdraft gasifier was conducted. The resulting syn-gas had average low heating value of 5.79 ± 0.52 MJ/ Nm3, tar concentration of 14.06 ± 8.54 mg/Nm³, particulate concentration of 3.05 ± 1.79 mg/Nm³, hardwood conversion rate of 2.37±0.24 Nm³/kg, and carbon conversion rate of 98.01 ± 0.53%. This syn-gas is of acceptable quality to be used as a fuel source for internal combustion engine operations. The gasifier?s grate temperature had no evident effects on syn-gas quality and conversion rate within a range of 740 to 817oC. The particulate contents in preiltered syn-gas significantly increased when the gas flow rate changed from 36 to 56 Nm3/h. When the moisture content of hardwood chips increased, tar content of postiltered syn-gas significantly increased, and CO content significantly decreased.

Biomass energy is increasingly used to reduce the dependence on fossil fuels and reduce the impact of greenhouse gas emissions on global warming. Fluidized bed gasification converts solid biomass into gaseous fuels that can be used for combustion or liquid fuels synthesis. The efficiency of biomass gasification is directly affected by the fluidized bed hydrodynamics. For example, the solids recirculation rate through the system is an important parameter that affects the heat and mass transfer rates. In this study, a cold model of a dual fluidized bed (DFB) biomass gasification plant was designed using scaling laws, and was constructed to investigate the hydrodynamics of industrial DFBs. A DFB consists of a bubbling fluidized bed (BFB), where biomass is gasified to produce syngas, and a circulating fluidized bed (CFB) where the residues of gasification are combusted. The investigation was divided into Phase I and II. In Phase I, an operational map was developed for the CFB to define operational boundaries for steady state operation of the plant. An empirical model was developed to predict the solids mass flow rate out of the CFB riser, which is an empirical function of the exit opening width, the CFB diameter, and a newly introduced aerodynamic factor. The correlation coefficient, R2 for the empirical function was 0.8327. The aerodynamic factor accounts for the particle inertia and clustering effects at the exit of the CFB riser. Results from Phase I also showed that increasing the fluidizing velocities increased the solids circulation rate and affected the pressure drop over various points in the CFB plant due to redistribution of solids with the system. A critical assessment was performed on published correlations found in the literature to determine how accurately they predicted the hydrodynamics in the CFB riser. By comparing predicted and experimental results, the correlations were found to be inaccurate for the conditions and configuration of the CFB tested in this study. For example, the solids velocity was not accurately predicted by published correlations due to unaccounted particle clustering effects. The main issue with the published correlations was a lack of generality, so that the correlations only applied for predicting fluidizing behaviour in the equipment they were developed in. In Phase II, an operational map was developed for the DFB, which incorporated both the CFB and the BFB. Experiments with a binary mixture representing sand and char in an industrial gasifier showed a blocking effect in the connecting chute between the CFB and BFB by the material representing char, which was larger and less dense than the material representing sand. A computational fluid dynamics (CFD) based design tool for modelling the cold model CFB cyclone was developed and validated by comparing the predicted and experimental cyclone pressure drop. The correlation coefficient for the CFD pressure drop prediction was 0.7755. The design tool contained information about the grid resolution and the time step required for modelling the cyclone accurately.

Numerical simulations of coal gasification process inside a generic 2-stage entrainedflow gasifier are carried out using the commercial CFD solver ANSYS/FLUENT. The 3-D Navier-Stokes equations and eight species transport equations are solved with three heterogeneous global reactions, three homogeneous reactions, and one thermal cracking equation of volatiles. Finite rates are used for the heterogeneous solid-gas reactions. Both finite rate and eddy-breakup combustion models are calculated for each homogeneous gas-gas reaction, and the smaller of the two rates is used. Lagrangian-Eulerian method is employed. The Eulerian method calculates the continuous phase while the Lagrangian method tracks each coal particle. Fundamental study is carried out to investigate effects of five turbulence models (standard k-ε, k-ω, RSM, k-ω SST, and k-ε RNG) and four devolatilization models (Kobayashi, single rate, constant rate, and CPD) on gasification simulation. A study is also conducted to investigate the effects of different operation parameters on gasification process including coal mixture (dry vs. slurry), oxidant (oxygen-blown vs. air-blown), and different coal distributions between two stages. Finite-rate model and instantaneous gasification model are compared. It is revealed that the instantaneous gasification approach can provide an overall evaluation of relative changes of gasifier performance in terms of temperature, heating value, and gasification efficiency corresponding to parametric variations, but not adequately capture the local gasification process predicted by the finite rate model in most part of the gasifier. Simulations are performed to help with design modifications of a small industrial demonstration entrained-flow gasifier. It is discovered that the benefit of opening the slag tap on the quench-type gasifier wider by allowing slag to move successfully without clogging is compromised by increased heat losses, reduced gasification performance, downgraded syngas heating value, and increased unburned volatiles. The investigation of heat transfer on fuel injectors shows that blunt tip fuel injector is less likely to fail compared to conical tip fuel injector because the maximum high temperature on the injector is scattered. Two concentric fuel/oxidant injections provide better fuel-oxidant mixing and higher syngas heating value than four separate fuel and oxidant injections.

A mild gasification method has been developed to provide an innovative clean coal technology. The objectives of this study are to (a) incorporate a fixed rate devolatilization model into the existing 2D multiphase reaction model, (b) expand the 2D model to 3D and (c) utilize the improved model to investigate the mild-gasification process and guide modification of the mild-gasifier design. The Eulerain-Eulerian method is employed to calculate both the primary phase (air) and secondary phase (coal particles). The improved 3D simulation model, incorporated with a devolatilization model, has been successfully developed and employed to determine the appropriate draft tube dimensions, entrained flow residence time, The simulations also help determine the appropriate operating fluidization velocity range to sustain the fluidized bed depth without depleting the chars or blowing the char away. The results are informative, but require future experimental data for verification.

<p>Kan man producera brännbar gas av biobränsle i en småskalig anläggning? Kan</p><p>detta göras till en rimlig kostnad? Är det möjligt för en privatperson installera</p><p>förgasningsanläggningen själv eller krävs det en fackman? Skulle man kunna göra</p><p>gas av sitt trädgårdsavfall?</p><p>Svaret på dessa frågor är ja, det går.</p><p>Men om man vill göra det på ett säkert och miljövänligt sätt är svaret tyvärr nej.</p><p>Detta gäller i alla fall den anläggningen som detta arbete handlar om.</p><p>Tack vare Compower i Lund så kunde jag få tillgång till en kinesisk ”stalk gasifier”</p><p>Målet var att med denna panna framställa och analysera den gas som produceras</p><p>från biobränslen (gengas). Gasen skulle i bästa fall kunna användas i Compowers</p><p>microkraftverk för el och värmegenerering.</p><p>Efter installation och uppstart såg det lovande ut. Brännbar gas producerades efter</p><p>ca 20 min och gasen brann fint. Bränslet bestod då av en blandning mellan pellets</p><p>och flis.</p><p>Vid samtliga prov brinner gasen med klarblå låga och ingen synlig rök finns i</p><p>samband med förbränningen.</p><p>Pga. skrubber funktionen blir lågan pulserande</p><p>Det visade sig dock efter en stunds eldning att flisen var för blöt och tjärbildning</p><p>uppstod i pannan.</p><p>Efter nedstängning upptäcktes porositeter i fläkthusets gods och tjära hade läckt ut</p><p>på golvet.</p><p>Vid eldning nr. 2 användes endast pellets och det fungerade bra tills det visade sig</p><p>att askan från pelletsen tillsammans med tjäran bildade en sörja och chokade</p><p>luftgenomströmningen så att ingen gas kunde ta sig igenom utan tvingades ut</p><p>igenom luftintaget.</p><p>När vi senare kom in på emissionsmätningarna så visade det sig att vi inte kunde</p><p>mäta alla ämnena i gasen innan dess att vi förbrände den. Vi fick istället inrikta oss</p><p>på att mäta emissionerna efter det att vi tänt gasen. Detta gav oss rimligare världen</p><p>om än höga. Efter den sista eldningen, eldning nr 3, kunde vi konstatera att så länge</p><p>pannan eldades som den skulle så fungerade den bra, dock var CO-emissionerna</p><p>höga. När det gällde stängning så var det inte lika enkelt och det fanns även en stor</p><p>risk för utsläpp av koloxid vilket alltid bör undvikas.</p>

Den negativa miljöpåverkan från förbrukning av fossila bränslen ökar kravet på förnyelsebara energikällor. Biobränsle är ett speciellt lovande alternativ. Detta projekt vill visa på möjligheten att använda gas från biobränsleförgasning som förbränns utan synliga flammor i glassmältugnar. Med bättre teknik är det möjligt både att upprätthålla produktionen och reducera kväveoxidutsläppen med ekonomiska fördelar. Biobränslena bidrar inte till växthuseffekten. En del av hela projektet är de experiment som utfördes den 1 juni 2004 vid Kosta glasbruk. Experimenten tog 7 timmar och 50 minuter. Den viktigaste uppgiften i detta examensarbete är att utvärdera mass- och energibalanserna på den medströms fastbäddsförgasare som användes vid experimenten. / The negative environmental impact of the consumption of fossil fuels has led to an increased claim for a wider use of renewable energy sources. Biomass appears as a particularly promising option. This project demonstrates the possibility to heat glass furnaces with gas from biofuel gasification combusted without visible flames. By better technique you can both retain production and reduce nitrogenoxide emissions with economical benefit. The biofuel doesn’t contribute to the greenhouse effect. A part of the whole project is the experiments performed on June 1st 2004 in Kosta glass- factory, total 7 hours and 50 minutes. A major effort of this diploma work is to evaluate mass and energy balances of the down – draft fixed bed gasifier used in the experiments.

<p>Den negativa miljöpåverkan från förbrukning av fossila bränslen ökar kravet på förnyelsebara energikällor. Biobränsle är ett speciellt lovande alternativ. Detta projekt vill visa på möjligheten att använda gas från biobränsleförgasning som förbränns utan synliga flammor i glassmältugnar. Med bättre teknik är det möjligt både att upprätthålla produktionen och reducera kväveoxidutsläppen med ekonomiska fördelar. Biobränslena bidrar inte till växthuseffekten. En del av hela projektet är de experiment som utfördes den 1 juni 2004 vid Kosta glasbruk. Experimenten tog 7 timmar och 50 minuter. Den viktigaste uppgiften i detta examensarbete är att utvärdera mass- och energibalanserna på den medströms fastbäddsförgasare som användes vid experimenten.</p> / <p>The negative environmental impact of the consumption of fossil fuels has led to an increased claim for a wider use of renewable energy sources. Biomass appears as a particularly promising option. This project demonstrates the possibility to heat glass furnaces with gas from biofuel gasification combusted without visible flames. By better technique you can both retain production and reduce nitrogenoxide emissions with economical benefit. The biofuel doesn’t contribute to the greenhouse effect. A part of the whole project is the experiments performed on June 1st 2004 in Kosta glass- factory, total 7 hours and 50 minutes. A major effort of this diploma work is to evaluate mass and energy balances of the down – draft fixed bed gasifier used in the experiments.</p>

Kan man producera brännbar gas av biobränsle i en småskalig anläggning? Kan detta göras till en rimlig kostnad? Är det möjligt för en privatperson installera förgasningsanläggningen själv eller krävs det en fackman? Skulle man kunna göra gas av sitt trädgårdsavfall? Svaret på dessa frågor är ja, det går. Men om man vill göra det på ett säkert och miljövänligt sätt är svaret tyvärr nej. Detta gäller i alla fall den anläggningen som detta arbete handlar om. Tack vare Compower i Lund så kunde jag få tillgång till en kinesisk ”stalk gasifier” Målet var att med denna panna framställa och analysera den gas som produceras från biobränslen (gengas). Gasen skulle i bästa fall kunna användas i Compowers microkraftverk för el och värmegenerering. Efter installation och uppstart såg det lovande ut. Brännbar gas producerades efter ca 20 min och gasen brann fint. Bränslet bestod då av en blandning mellan pellets och flis. Vid samtliga prov brinner gasen med klarblå låga och ingen synlig rök finns i samband med förbränningen. Pga. skrubber funktionen blir lågan pulserande Det visade sig dock efter en stunds eldning att flisen var för blöt och tjärbildning uppstod i pannan. Efter nedstängning upptäcktes porositeter i fläkthusets gods och tjära hade läckt ut på golvet. Vid eldning nr. 2 användes endast pellets och det fungerade bra tills det visade sig att askan från pelletsen tillsammans med tjäran bildade en sörja och chokade luftgenomströmningen så att ingen gas kunde ta sig igenom utan tvingades ut igenom luftintaget. När vi senare kom in på emissionsmätningarna så visade det sig att vi inte kunde mäta alla ämnena i gasen innan dess att vi förbrände den. Vi fick istället inrikta oss på att mäta emissionerna efter det att vi tänt gasen. Detta gav oss rimligare världen om än höga. Efter den sista eldningen, eldning nr 3, kunde vi konstatera att så länge pannan eldades som den skulle så fungerade den bra, dock var CO-emissionerna höga. När det gällde stängning så var det inte lika enkelt och det fanns även en stor risk för utsläpp av koloxid vilket alltid bör undvikas.

Made available in DSpace on 2015-03-26T13:23:55Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2015122 bytes, checksum: 8ec88dadf2dfe8f408775040894e047c (MD5) Previous issue date: 2013-07-16 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / In order to maintain coffee quality within the commercialization standards, the post- harvest stages must be very well conducted, especially those related to cleaning, drying and storing, so that quality is not lost during storage.Among these stages, drying is the most important and if poorly conducted could put the quality of the product at risk. Drying requires clean warm air in order not to contaminate the product. Few studies have been performed on gasification, especially application of this process to drying grains. Therefore, the objective of the present study was to apply heated air generated by an automated biomass gasifier (eucalyptus charcoal) in coffee drying. Drying of the ripe coffee cherry in this study was performed in two drying silos attached to an automated biomass gasifier which generates the heated air used in the process. Two treatments were determined to conduct the study: treatment 1 consisted of 8 hours of drying per day, with revolving the grain mass every 2 hours; and treatment 2 consisted of drying the coffee on a suspended terrace and treatment 3 consisted of drying the coffee on concrete. In order to evaluate the influence of coffee drying in the system proposed, the following parameters were analyzed: beverage classification, electrical conductivity, potassium lixiviation and one thousand grain weight. Coffee dried in the proposed system was classified as a soft beverage, obtaining an average grade of 79 points. Based on the results, the following average values were obtained: 146.86 Scm- 1 -1 g for the electrical conductivity; 34.04 ppm.g-1for potassium lixiviation; 160.90 g as the one thousand grain weight. Drying performed using the proposed method showed to be viable since the dry coffee obtained presented good qualitative results regarding the specific mass, electrical conductivity, potassium lixiviation, color and other parameters which indicated that there was no risk of final quality loss in the beverage. / Para a manutenção da qualidade do café dentro dos padrões de comercialização, a etapa de pós-colheita precisa ser muito bem conduzida, principalmente, as relacionadas à limpeza, secagem e armazenamento, para que a qualidade não seja perdida durante o armazenamento. Destas etapas, a secagem é de fundamental importância e se mal conduzida pode comprometer a qualidade do produto. Ainda são poucos os estudos sobre a tecnologia da gaseificação, sobretudo na sua aplicação para secagem de grãos. Dessa forma, esta pesquisa visa contribuir para a aplicação do ar aquecido, proveniente de um gaseificador automatizado de biomassa (carvão de eucalipto), na secagem de café. A secagem do café cereja neste trabalho foi realizada em dois silos secadores acoplados a um gaseificador automatizado de biomassa, do qual provém o ar aquecido utilizado durante o processo. Três tratamentos foram determinados para a condução do trabalho, sendo eles: o tratamento 1 consistiu em 8 horas de secagem por dia com revolvimento da massa de grãos em intervalos de 2h e o tratamento 2 consistiu da secagem de café em terreiros suspenso e o tratamento 3 consistiu da secagem em terreiro de concreto. Para avaliar a influência da secagem do café através do sistema foram analisados os seguintes parâmetros: classificação de bebida, condutividade elétrica, lixiviação de potássio, massa de mil grãos. O café secado no sistema foi classificado quanto à bebida como apenas mole, obtendo nota média de 79 pontos. Com base nos resultados foram obtidos os seguintes valores médios: 146,86 Scm-1g-1 para condutividade elétrica; 34,04 ppm.g-1 para lixiviação de potássio; 160,90 g para o massa de mil grãos. De acordo com os resultados obtidos, o sistema de secagem apresentou-se como uma alternativa aos pequenos produtores de café, pois não houve perda de qualidade na sua bebida e por ser um sistema versátil, uma vez que além do café é possível secar outros grãos. Além disso, a automação do sistema propiciou um controle preciso da temperatura do ar de secagem durante todo o processo, o que é de fundamental importância para uma boa secagem do café.