1,721,021 research outputs found
Modeling and investigation of the channeling phenomenon in downdraft stratified gasifers
No full textDowndraft stratified gasifiers seem to be the reactors which are most influenced by loading conditions.
Moreover, the larger the reactor is, the higher the possibility to stumble across a channeling phenomenon.
This high sensitivity is due to the limited thickness and superficial placement of the flaming pyrolysis
layer coupled with the necessity to keep all the zones parallel for a correct running of this kind of
gasifier. This study was aimed at modeling and investigating the channeling phenomenon generated
by loading condition variations on a 250-kWe nominal power gasification power plant. The experimental
campaign showed great variations in most of the plant outputs. These phenomena were modeled on two
modified mathematical models obtained from literature. The results of the models confirmed the capability
of this approach to predict the channeling phenomena and its dependency on the loading method
Effects of upgrading systems on energy conversion efficiency of a gasifier - fuel cell - gas turbine power plant
Full text linkThis work focuses on a DG-SOFC-MGT (downdraft gasifier - solid oxide fuel cell - micro gas turbine) power plant for electrical energy production and investigates two possible performance-upgrading systems: polyphenylene oxide (PPO) membrane and zeolite filters. The first is used to produce oxygen-enriched air used in the reactor, while the latter separates the CO2 content from the syngas. In order to prevent power plant shutdowns during the gasifier reactor scheduled maintenance, the system is equipped with a gas storage tank. The generation unit consists of a SOFC-MGT system characterized by higher electrical efficiency when compared to conventional power production technology (IC engines, ORC and EFGT). Poplar wood chips with 10% of total moisture are used as feedstock. Four different combinations with and without PPO and zeolite filtrations are simulated and discussed. One-year energy and power simulation were used as basis for comparison between all the cases analyzed. The modeling of the gasification reactions gives results consistent with literature about oxygen-enriched processes. Results showed that the highest electrical efficiency obtained is 32.81%. This value is reached by the power plant equipped only with PPO membrane filtration. Contrary to the PPO filtering, zeolite filtration does not increase the SOFC-MGT unit performance while it affects the energy balance with high auxiliary electrical consumption. This solution can be considered valuable only for future work coupling a CO2 sequestration system to the power plant
Aige conference: A kinetic model for a stratified downdraft gasifier
No full textA model for a stratified downdraft gasifier has been developed. It has been adapted from two different models from literature with appropriate modifications and improvements. The new “interacting” model is able to predict the syngas composition, input and output flow rates and the gasifier cold efficiency under different working condition and with different biomass input. It works assuming a constant biomass consumption. The results of the model has been compared to experimental data taken from a downdraft gasifier power plant system with nominal power output of 200 kWel. The plant has been set at 160 kWel in order to avoid system instabilities related to high power runs.A model for a stratified downdraft gasifier has been developed. It has been adapted from two different models from literature with appropriate modifications and improvements. The new "interacting" model is able to predict the syngas composition, input and output flow rates and the gasifier cold efficiency under different working condition and with different biomass input. It works assuming a constant biomass consumption. The results of the model has been compared to experimental data taken from a downdraft gasifier power plant system with nominal power output of 200 kWel. The plant has been set at 160 kWel in order to avoid system instabilities related to high power runs
Biodiesel and electrical power production through vegetable oil extraction and byproducts gasification: Modeling of the system
No full textAim of this work is to introduce an alternative to the standard biodiesel production chain, presenting an innovative in situ system. It is based on the chemical conversion of vegetable oil from oleaginous crops in synergy with the gasification of the protein cake disposed by the seed press. The syngas from the gasifier is here used to produce electrical power while part of it is converted into methanol. The methanol is finally used to transform the vegetable oil into biodiesel. Through a coupled use of ASPEN PLUS (TM) and MATLAB (TM) codes, a rapeseed, soy and sunflower rotation, with a duration of three year, was simulated considering 15 ha of soil. This surface resulted sufficient to feed a 7 kW(el) power plant. Simulation outputs proven the system to be self-sustainable. In addition, economical NPV of the investment is presented. Finally the environmental, economical and social advantages related to this approach are discussed
Energy and biochar co-production from municipal green waste gasification: A model applied to a landfill in the north of Italy
Full text linkThis work discusses the advantages that can be obtained from the integration of landfill gas with biomass gasification. The case study presented consists of a landfill located in the province of Reggio Emilia, in the north of Italy. Landfill gas from municipal-waste fuels four internal combustion engines with overall nominal power of 2 MW, the electricity is sold back to the grid, while the thermal power is used for the heating of an industrial greenhouse compartment for basil production. Within the same facility, green waste is collected from the surrounding municipalities then chipped and sieved. Fine particles are disposed into a composting plant close by, while the sieved fraction is sold to the market for electricity production in large-scale boiler-based power plants. The idea here presented and discussed consists of the implementation of a gasifier to convert the sieved fraction of green waste into a syngas fuel directly on site. Syngas is blended with the landfill gas and then fed to the gas engines. In this work green waste gasification is tested in a commercial small-scale gasifier, proving that sifted green waste is a suitable fuel for this application. A specific consumption of 1.2 kg/kWh and a total electrical efficiency of 16.22% were measured. The sizing of the full-scale gasification facility is based on both the experimental results and data about the local availability of green waste. The economic return of the investment is then discussed. Finally, a further level of integration between gasification and the existing site is proposed: gasification-derived biochar is investigated as soil amendment for the on site company at the landfill that grows basil commercially. Results of 55 days in vivo tests show an increase in the biomass production of the basil of 53% compared to the control test group
Easy to implement ventilated sunspace for energy retrofit of condominium buildings with balconies
No full textEnergy retrofit of the facade of condominium buildings may be a difficult task because thermal bridges such as those due to balconies, common elements in the architecture of many countries, are often arduous to correct by added insulation due to several constraints. An alternative retrofit approach is therefore analyzed, easy to implement and relatively inexpensive. It consists in changing a balcony into a ventilated sunspace during the cold season, exploiting solar gains to compensate heat loss. More specifically, transparent plastic roll-up sheets are installed along the balcony perimeter, removable in the hot season, to enclose the volume between two superposed balcony slabs. The obtained sunspace is then used as a pre-heating chamber for a single-flow ventilation system that ensures the air changes required indoors. Heat gain to the indoor environment can thus be increased with respect to a simpler sunspace without ventilation, and possibly modulated along the day by proper control of the flow rate. In this work, the proposed approach and a small-scale physical model are presented. The model will serve to validate analyses aimed to forecast and optimize the performance of ventilated sunspaces built around balconies
Which thermochemical conversion process for agricultural waste? Physical and chemical analyses to guide the choice
No full textThis study investigates how physical and chemical analyses may lead the choice of the more suitable thermochemical energy conversion process for agricultural wastes. Four different case study are presented: corn cobs, digestate pellets from anaerobic digestion, wood biomass from river maintenance and seed cake from vegetable oil production. For all the cases analyzed the physical as well as the chemical characterization of the feedstocks are presented and discussed. Outputs of these analyses are: chemical composition, moisture content, ash content, ash softening point and particle size. These outputs, together with logistic considerations about availability and preconditioning of the biomasses allow to properly define the optimal process for each biomass. Three thermochemical processes are taken into account: pyrolysis, gasification and direct combustion
Modeling and simulation of a DG-SOFC-MGT hybrid system
No full textThis paper describes the modeling and the simulation of an advanced gasification power plant composed of a Downdraft Gasifier (DG) and a Solid Oxide Fuel Cells - Micro Gas Turbine unit (SOFC-MGT). The gasifier converts the woodsy biomass into syngas that it is cooled and filtered before entering in a compressed storage tanks sub-system. A hybrid SOFC-MGT unit uses the stored syngas to produce electrical energy that it is sent to the electrical grid.
The system has been modeled starting from literature. The simulations were made for different types of woodsy biomass over a year long period. Poplar, peach tree and vineyards pruning have been adopted with a variable moisture content ranging
from 5% to 30%. The electrical energy produced and the overall electrical efficiency have been calculated setting the biomass consumption to 187 kg/hour for different biomasses and moistures scenarios. Maintenance of the gasifier has taken into account imposing a cycle of 120 hours of operating and 12 hours of maintenance. Starting from that, the storage sub-system has been design to assure the continuous operation of the SOFC-MGT unit all over the annual simulation.
Sensitive analysis of the performance of the system varying the biomass type and the biomass moisture have been developed in order to find the best working conditions. Moreover, the annual energy balance of the system has been evaluated with these conditions to point out where the most relevant energy losses take place.
Results show that the maximum overall electrical efficiency is around 33.5% for poplar biomass with 10% of moisture. In this scenario the average electrical power production is about 223 kW, the annual electrical energy amount sent to the grid is about 1956 MWh. In this conditions, the 42% of the chemical energy of the biomass is lost in the SOFC-MGT unit
Modeling of coupling gasification and anaerobic digestion processes for maize bioenergy conversion
Full text linkThis work estimates the advantages of using maize as fuel in a power plant composed of an anaerobic digester, a gasifier and an Internal Combustion (IC) engine. The digester is fed with maize grains, while, the remaining part of the plant, the stover, is gasified. Then biogas and syngas streams are both used as fuel into the engine. The performance of this plant was evaluated coupling gasification and anaerobic digestion mathematical models. Results of the proposed solution are compared with the performance of a 100 kW biogas power plant fed with the whole crop silaged. Results show that the overall energy yield of the improved solution is 39% higher than the conventional one fed with maize silage. This method will lead to the design of small and cheap digesters as a result of the increased conversion rate. In fact, the solution proposed fully converts the high cellulose-fiber parts of the maize plant that were tough to degrade in anaerobic digesters
Experimental assessment and modeling of energy conversion effectiveness in a gasification power plant
No full textNational and international energy scenarios seem to be rediscovering a new confidence in gasification power plants as a valuable technology for biomass conversion. Their adaptability, in both direct power production and biofuels synthesis, has been manifested into the development of wide varieties of reactor models and sizes. An appropriate modeling of the system, supported by experimental analysis, is necessary to achieve the high level of efficiency of the gasifier and the proper effectiveness of the entire energy plant conversion. This work is aimed at studying a stratified downdraft gasifier coupled to two IC engines with the total nominal power of 250 kWel. The model of the system is based on mass and energy balance; the model outputs are compared here with those coming from the experimental campaign. All the major thermo-chemical parameters are monitored, these include: air and gas flow rate, biomass moisture content, consumption and ultimate analysis, reaction zones temperatures, tars and char production. In this paper, the model outputs have been compared with the data to evaluate the sensitivity of the model. Moreover, the difference between the theoretical data and the experimental data have been exanimate
- …
