Detailed modelling of biomass steam gasification in a dual fluidized bed gasifier with temperature variation

Biomass gasification is a very efficient process to produce clean energy in the form of green hydrogen, synthetic natural gas (methane) and liquid chemicals. The products of biomass gasification process can be employed for energy production in a more efficient way. The modelling of biomass gasification enables the optimization of the process designs, but it is a challenge due to its high complexity. In most cases this process is treated with a black box approach where the sub-processes are neglected and only changes between the input and output are assessed. Here a model for prediction of the performance of a 100-kW dual bed fluidized biomass gasifier is derived and implemented. Detailed pyrolysis modelling is properly addressed, and this is believed to be a key factor of this approach and enables more accurate results. The proposed model and its basic assumptions were extensively validated on a range of operating temperature by conducting experiments using softwood pellets as fuel and fresh olivine sand as bed material. To achieve the objective, experimental tests have been conducted and theoretical models have been developed. The results provide understanding of the conversion processes occurring in the different parts of the gasifier enabling optimization of the system under different conditions. The main achievements are summarized in the following: • The fluid dynamics of the system, i.e. the distribution of gas and solids in different parts of the gasifier, the mixing of fuel with bed particles and the operational range at which the gasifier can be safely operated are calculated and validated against the experimental measurements. • The main fuel conversion processes (devolatilization and char gasification) were studied thoroughly. The former through the literature and the latter by the experiments conducted in a thermogravimetric analyzer (TGA). • Water gas shift reaction as the main and most important homogenous reaction in the process of biomass steam gasification has been investigated experimentally to obtain the proper kinetic parameters. • A reactor model of the DFB gasifier system of TUW was developed using the findings from the experimental studies conducted previously, supported by additional data from literature. Simulations were performed to obtain the main outputs of the biomass gasification process and the results have been validated with the experimental measurements. The overall conclusion of this work is that the proposed model for the DFB gasifier is an interesting method to simulate the thermochemical conversion of biomass in the gasifier and this technology is very suitable for electricity production from biomass and waste. Further research on tar conversion processes is necessary as well as testing the flexibility of the model against various bed materials

Poplar from phytoremediation as a renewable energy source:gasification properties and pollution analysis

Biomass gasification is a very efficient process to produce clean energy in the form of a fuel gas (syngas). Hazelnut shells and poplar have good energy production potential and they are abundant in nature. Hazelnut shells have the characteristics of a very good fuel and poplar is among the fastest growing trees; furthermore, poplar demonstrated the capability to absorb organic contaminants (i.e. heavy metals) from the soil in which they are cultivated. However, poplar is not usually used for biomass gasification and its potential is not fully assessed. Here, 3 types of biomass, hazelnut shells (HS), simple poplar (P) and poplar coming from a phytoremediation procedure (PHYP), were chosen as representative samples to be characterized and tested in a steam gasification process carried out on a bench scale fluidized bed gasifier. A comparison is reported on gasification results, such as gas composition, tar production and gas yield for the biomass feedstocks mentioned above. It was concluded that hazelnut shells and poplar (P and PHYP) could be easily gasified in a fluidized bed gasifier, thus producing a good quality gas with low polluting by-products. The PHYP sample showed lower tar content and higher gas yield. It is guessed that Ca and Mg, found in higher quantities in the PHYP sample, could have had a catalytic effect in tar reforming thus producing lower quantity of heavy hydrocarbons

Introducing a sustainable soil fertility system for chickpea (Cicer arietinum L.)

In order to introduce a sustainable soil fertility system for chickpea, field experiments were carried out in 2007 and 2008 growing seasons. Experiments were arranged in split-split plot arrangements with three replications. Main plots consisted of (G1): establishing a mixed vegetation of vetch and barley, (G2): without green manure. Also, five strategies for obtaining the base fertilizer requirement including (N1): farm manure; (N2): compost; (N3): triple super phosphate; (N4): farm manure + compost and (N5): farm manure + compost + triple super phosphate. Four levels of biofertilizers consisted of (B1): Phosphate solubilizing bacteria; (B2): Trichoderma harzianum; (B3): Phosphate solubilizing bacteria + T. harzianum; and (B4): without biofertilizers were arranged in sub-sub plots. Results showed that green manure increased pod number and number of fertile pods per plant. Integrating biofertilizers (B3) and green manure (G1) produced the highest pod number per plant and grain yield. The highest amounts of yield and yield components were obtained in G1N5 treatment. Comparison of 3-way interactions showed that G1N5B3 was the best treatment. Significant increase of N, P, K, Fe and Mg content in leaves and grains emphasized on superiority of mentioned treatment because each one of these nutrients has an approved role in chlorophyll synthesis and photosynthesis ability of the crop. The N5 treatment in addition to having the highest yield had the best grain quality due to high protein, starch and total sugar contents, low crude fiber and reduced cooking time.Key words: Biofertilizer, chickpea, compost, farm manure, soil fertility system

Biofuel production using thermochemical conversion of heavy metal-contaminated biomass (HMCB) harvested from phytoextraction process

Over the past few decades, bioenergy production from heavy metal-contaminated biomasses (HMCBs) has been drawing increasing attention from scientists in diverse disciplines and countries owing to their potential roles in addressing both energy crisis and environmental challenges. In this review, bioenergy recovery from HMCBs, i.e. contaminated plants and energy crops, using thermochemical processes (pyrolysis, gasification, combustion, and liquefaction) has been scrutinized. Furthermore, the necessity of the implementation of practical strategies towards sustainable phytoextraction and metal-free biofuels production has been critically discussed. To meet this aim, the paper firstly delivers the fundamental concepts regarding the remediation of the brownfields using phytoremediation approach, and then, reviews recent literature on sustainable phytoextraction of heavy metals from polluted soils. Thereafter, to find out the possibility of the cost-efficient production of metal-free biofuels from HMCBs using thermochemical methods, the impacts of various influential factors, such as the type of feedstock and metals contents, the reactor type and operating conditions, and the role of probable pre-/post-treatment on the fate of heavy metals and the quality of products, have also been discussed. Finally, based on relevant empirical results and techno-economic assessment (TEA) studies, the present paper sheds light on pyrolysis as the most promising thermochemical technique for large-scale electricity and heat recovery from HMCBs

Biological profitability of maize inoculation with selected rhizosphere micro organisms (Pseudomonas fluorescens and Glomus intraradices) under Water Deficit Stress

This research focused on evaluating the usefulness of an arbuscular mycorrhizal fungus (Glomus intraradices) and a plant growth-promoting rhizobacterium (Pseudomonas fluorescens) to maize growth under water deficit stress. Field experiment was conducted at Soil and water research institute, Karaj Station, Iran, during 2006 growing season. Biological positive effects of the micro organisms on plant growth, nutrient uptake, grain yield and yield components in maize plants was recorded in the treatment receiving mixed inoculums of G. intraradices and P. fluorescens. Maize shoot P content, grain yield, yield components, harvest index, grain N and P, soil available P, root colonization percentage and water use efficiency increased significantly with the G. intraradices inoculation and P. fluorescens, alone or in combination under water deficit stress. The highest profitability was observed in the combined treatment of inoculation with G. intraradices and P. fluorescens, which synergistically increased plant growth compared with other treatments

Towards utilizing Asteraceae alternative oilseed species on marginal lands: Agronomic performance, fatty acid composition, oil biocompounds, and oil physicochemical properties of Asteraceae species

Including alternative and drought-resilient oilseeds in marginal lands, where conventional oilseed production is threatened, could be an effective measure to restore marginal lands and improve sustainable seed oil production. Based on this approach, the present study aimed to evaluate the potential of some new and neglected Asteraceae species as alternative oil seed crops in marginal lands. The agronomic performance, fatty acid profile, seed oil biocompounds, and physicochemical properties of blessed thistle (Cnicus benedictus), cardoon (Cynara cardunculus), milk thistle (Silybum marianum), niger seed (Guizotia abyssinica), pot marigold (Calendula officinalis) and safflower (Carthamus tinctorius) were studied under a marginal land condition (semi-dry poor soils) in two growing years. Niger seed possessed the highest oil content (39.45%), while the highest oil yield (470.21 kg ha−1) was noted in safflower. The GC and HLPC analysis indicated that all the species of seed oils were rich linoleic acid sources (51.65–73.45%). However, some species, such as safflower, also contained a high amount of oleic acid (25.41%) proportion. Pot marigold seed oils had high levels of calendic acid (more than 50% of total fatty acids). The tocopherol and phenol biocompounds as essential micronutrients for human health were abundant in the species studied, which the highest tocopherol contents recorded for blessed thistle (670.43 mg/kg) and safflower (655.75 mg/kg) oils, respectively. Accordingly, the antioxidant activity of the oilseeds followed the same trends, being the highest in blessed thistle and safflower oils. The high concentration of oleic acid in safflower oil was associated with decreasing oil density, saponification, peroxidase, and increasing viscosity indicating its high oil oxidative stability. According to agronomic and oilseed quality properties, most species, especially safflower and blessed thistle, can be considered promising alternative oilseed crops in marginal lands

English Teacher Education Programs and Professionalism: The case of Iranian Novice/Experienced Teachers

A key issue in language teacher education is what teachers need to learn in language teacher programs and how this learning impacts their language teaching practices. The seeds for teacher professionalism are planted and nourished during teacher education program to develop independently after graduation from pre-service teacher educations. The purpose of this study was to investigate English teacher education programs and their effects on novice/experienced English language teachers' professionalism in Iran. The researchers used purposeful sampling to select 150 participants from five Farhangian University Branches in Iran (2016-2017). For this purpose, a computerized questionnaire was constructed and validated. A one-way ANOVA indicated that out of the four dimensions of professionalism-- professional development, reflection, responsibility, and ethics-- only two-- professional development and reflection-- were statistically significant for both novice and experienced teachers. The programs had positive impact on teachers' professional development and reflection. The study has implications for teacher educators, developers of instructional materials, and syllabus designers in the context of Iran