Biomass gasification

... in remaining char and increase in oxidant), thus the total amount of hydrogen in the product gas remains roughly constant. ... Bioenergy 84 Vol. 3 Biomass Conversion, 73-79. Durai-Swamy, K., DW Warren, B. Aghamahommadi, and MN Mansour. 1989. ...

Tarım atıkları,  orman atıkları ve enerji bitkileri olarak adlandırılan biyokütle kaynaklarının oldukça geniş kullanımı vardır. Bunlardan organik atıklar gübre, ormancılık ve orman endüstrisinden ağaç atıkları, gıda ve kağıt endüstrisi kalıntıları, belediyelerin yeşil kalıntıları, kanalizasyon çamuru, yıllık kısa rotasyonlu ağaçlıklar (okaliptüs, kavak, söğüt), çayır, şeker bitkileri (şeker kamışı, pancar, süpürge darısı), nişasta mahsülleri (mısır, buğday) ve yağlı mahsüller (zeytin, soya, ayçiçeği, yağ şalgamı, palmiye yağı) atıkları olarak sınıflanabilir. Biyokütle tabanlı bu malzemeler, hem doğrudan biyokütle, hem de biyoyakıt olarak enerji üretimi amaçlı kullanılmaktadır. Ağaç ve diğer tarımsal kalıntılar, endüstride buhar ve elektrik üretmek üzere kojenerasyon santralı yakıtı olarak yakılmakta ve ayrıca mesken ve ticari bina ısıtması amacıyla da kullanılmaktadır. Modern biyokütle enerjisi kullanımına geçilmesi ülke ekonomisi ve çevre kirliliğini önleme açısından önem taşımaktadır.

Birçok ülke bugün kendi ekolojik koşullarına göre en uygun ve en ekonomik tarımsal ürünlerden enerji bitkisi olarak alternatif enerji kaynağı sağlamaktadırlar. Türkiye de tarımsal potansiyeli ile, ekolojik tarımsal yapıya sahip ülkeler arasındadır. Türkiye’de enerji ormancılığı yönünden ekonomik değeri yüksek ve hızlı büyüyen yerli ağaç türleri arasında, akkavak, titrek kavak, kızılağaç, kızılçam, meşe, dişbudak, fıstık çamı, karaçam, sedir ve servi ağalarını saymak mümkündür. Burada kavak, söğüt gibi oldukça fazla su isteyen ağaçların yanı sıra, oldukça kurak alanlarda yetişebilecek ağaçlara da önem verilmesi gerekmektedir. Enerji tarımı üretimine yönelik olarak, gerek Avrupa’da gerek ülkemizde modern biyokütle çevrim teknolojilerinin de kullanıldığı, çalışmalar küçük ölçekli olarak uzun yıllar önce başlamıştır. Bunlara örnek olarak mischantus ve tatlı sorgum, arundo donax bitkileri üzerinde yapılan çalışmalar gösterilebilir. Enerji tarımında ülkemizde henüz çok tanınmayan dünya da ise yavaş yavaş yaygınlaşmaya başlayan C4 enerji bitkileri arasında en çok yetiştiriciliği yapılan Fil Çimeni (Miscanthus), Tatlı Sorgum (Sweet sorghum), Dallı Darı (Switchgrass) 'dır. Biyokütle kaynakları olarak biyokütle, enerji bitkileri, enerji ormanları ve bunlardan türetilen yakıtların kullanılması ile ayrıca, hava kirliliğinden büyük ölçüde etkilenen bir çok şehirde, kükürt dioksit ve benzeri zararlı gazların büyük ölçüde azalacağı da açıktır.

Bu çalışmada, genel biyokütle ve gazlaştırma bilgisi verilmeye çalışıldıktan sonra farklı enerji tarımı bitkilerinin gazlaştırma metodu ile değerlendirilerek syngaz üretimi ve syngazdan da elektrik ve ısı enerjisi üretim metodları farklı örnekleri içeren gazlaştırma teknolojileri tanıtılmaya çalışılacaktır. Gazlaştırma metodu ile biyokütleden ve enerji bitkilerinden  enerji üretimi İspanya, İtalya, İsviçre, Japonya, Almanya, A.B.D. gibi ülkelerde kullanılan sistemlerdir. Avrupa’da uzun yıllardan beri çalıştırılan farklı güçlerdeki biyokütle yataklı gazlaştırıcı tesisleri örnek olarak gösterilebilir. İspanya, İtalya, Fransa ve Bulgaristan’da çalıştırılan akışkan yataklı gazlaştırıcılarla biyokütle 5MWe güçlü gazlaştırıcılar enerji bitkileri için teknolojik ve ekonomik biçimde tasarlanarak bu çalışmada tanıtılacaktır.

Production of biogas from agricultural and animal wastes is one of the viable options to mitigate the scarcity of energy and hazards of fossil fuels to both human and ecology. Therefore, this project work was on generation of biogas using cow dung and rumen fluid as co-substrate. A biogas digester with a capacity of 105 liters was used to produce the gas. The substrate (cow dung and rumen fluid) was mixed in the ratio 3:2 and water to substrate ratio of 2:1 was used. The digester was stirred thrice daily to avoid scum formation in the digester and to allow for easy escape of the gas produced. The retention time used for this experiment was 42 days during which the daily internal temperature readings were taken in order to determine temperature variations and also to determine the effect of heat on the production rate. A rubber hose was connected to the digester gas outlet located at the top of the digester and the other end of the rubber hose was connected to a PVC Tyer tube provided for storing the gas generated. The gas produced was collected and taken to the laboratory for chemical analysis. The results showed that biogas yielded consists of 57.98 % of methane (CH4), 39.99 % of carbon dioxide (CO2), 0.10 % of oxygen (O2), 0.01 % of hydrogen sulphide (H2S) and 0.01% of water vapour. The methane has the highest percentage, which represents the main source of energy and oxygen having 0.10 %, which shows that the process was purely carried out under anaerobic condition. Result of this study showed that methane has the highest percentage and generally cow dung with rumen fluid easily lent itself to process of anaerobic digestion.

A review of older literature on wood gasification with the intention to find some general rules for small downdraft wood gasification units.
It also reflects the practical experience of 2 year experimenting with these gasifiers on location in Indonesia.

CFD analysis is a useful tool that can be used to optimize the design of gasifiers. Although plenty of CFD analysis has been performed on fluidized bed gasifiers, little analysis has been performed on the biomass gasification of solid fuels due to the difficulty in modeling the chemical phenomena in the combustion of solids. In order to
simplify calculations, previous CFD simulations have modeled fuel beds by creating homogenous beds with uniform spacing or beds with simplified shapes like spherical particles. However, in real experimental conditions, fuel beds are non-homogenous and particle position is randomized. This study aimed to fill the gap of research simulations on
realistically modeled fuel beds. In this study, a downdraft gasifier was modeled using cubic woodchips as fuel and air as a gasifying agent. Woodchips were individually placed in the gasifier in random orientation to imitate the positioning of when biomass is fed from the top of a gasifier. CFD analysis was performed on the effect of air flow
rate and feedstock properties on air velocity, air trajectory, and average pressure throughout the gasifier. The applications of these analyses were demonstrated in this paper; they include blower size optimization, pressure drop calculation for non-uniform beds, combustion zone range determination, air inlet design, and velocity and pressure
profile generation and analysis. An optimal flow rate was chosen based on previous experimentation and results of the optimized flow rate for this gasifier were given in this paper.

An application for biomass is the synthesis of liquid fuels such as dimethyl ether, and methanol etc. our effort is intended to explore the syngas production technology from biomass using catalytic gasification process and the various process and technologies involved in the purification of biomass derived syngas. In this context, the characteristic of syngas such as yield, the H2/CO ratio and the different factors affecting H2/CO ration have been studied. This ratio is an important parameter which has an upper effect on our process. The reactors employ are fluidized bed, gasifier and the fixed bed reactor. H2/CO ratio lies between 1.87 & 4.45. Further, text of this report involves the purification of syngas. Three technologies are there for syngas cleanup and are classified according to the temperature of the gas which is leaving clean up device. The Hot Gas Cleanup technology has been discussed in details because of energy efficiency and prevention of reheating and cooling of the gas. Wet scrubbers cyclones, absorbers with varying sorbents are discussed regarding Hot Gas Clean up with new approaches for Chlorine and Tar removal.

The ever growing environmental concern caused by excessive use of fossil fuels in energy and transportation systems triggered considerable investigations on alternative energy sources such as biomass. Furthermore, the availability and security of fossil fuels to meet future global energy need are also subjected to uncertainty. For these reasons, the world's current focus is shifted towards hydrogen-based future economy. Gasification is a proven technology to produce satisfactory yield of hydrogen. Many studies have been performed to increase the production yield. Due to the extensive range of investigations, mathematical and computational approaches have been applied to conduct these studies. Thus, this paper aims to update and broaden the review coverage by incorporating works done to materialize the investigations on the potential of producing hydrogen from biomass via gasification encompassing mathematical modeling, simulation, optimization, process heat integration and cogeneration. Each of these subjects is reviewed and analyzed which helped to identify their respective strength and areas which require further research effort.

The World is facing crucial time for energy due to consumption of fossil fuels (natural gas, coal, and oil), rise in fuel price, and unacceptable environmental effect in recent years. Biomass is a renewable potential energy source which can reduces dependency on fossil fuels. Biomass is available in various forms throughout year in India. It accumulates solar energy by photosynthesis method from sunlight. Gasification is a chemical process that converts carbonaceous material such as biomass and coal into gaseous fuel or chemical feedstock. This gaseous fuel is known as producer gas or syngas which contains CO2, H2, CO, H2O, CH4 and N2 compounds. An attempt has been made to give basic idea about gasification, gasification mechanism, types of gasifier and characteristics of different biomass in this paper.

The need for sustainable alternatives to oil has been of deep concern to many countries around the world, and especially the U.S. due to the rapidly rising cost of oil. As a result, many nations face significant energy security challenges stemming from their dependence on imported oil. To achieve future energy security and independence
and in the long run to prepare for the post-oil energy resources, biomass is considered as one of the most important renewable energy resources in a projected sustainable energy future. The key bottleneck for lignocellulosic-derived biofuels is the lack of technology for efficient conversion of biomass in to readily usable fuel products. Current
work provides a detailed theoretical and experimental analysis of two (air and steam only) gasification technologies which are carbon neutral that can be used to overcome this hurdle.

This work also examines the use of mixed ion-electron conductors (MIEC) membranes as a significant option to enhance the production of H2 from biomass feedstock. Currently there are technologies that produce H2 by using renewable energy sources other than biomass as feedstock but they could not provide a long term solution
because of their adverse effects on eco-system. Thin film SrCe0.7Zr0.2Eu0.1 O3-δ membranes were developed and supported using NiO-SrCe0.8 Zr0.2 O3-δ tubular structure, using Dr. Eric Wachsman’s group’s work at UF. The main advantage of this
membrane setup is that it acts as WGS reactor and also separates the H2 from the gas stream, thus avoiding the need for two stage reactor setup requiring WGS and H2 separation independently. The possibility of sequestering the isolated CO2 stream is also another attribute to such membrane reactors. The overall objective of this current work is to analyze the air gasification and steam only gasification technology in detail and to investigate the performance of proton conducting ceramic membranes at high temperatures. Current research also analyzed a
simplistic model of a concept system, which is a self-sustaining H2 fuel production system that integrates the gasification technology and the MIEC membrane technology. The proposed system enhances the H2 produced from the biomass feed stock by carrying out WGS.

Experimental work on oxygen–steam based entrained flow gasification of Torrefied Karanja Press Seed Cake
(TKPSC) has been carried out in order to evaluate the effect of temperature, Equivalence Ratio (ER), Steam to
Biomass Ratio (SBR) and Particle Size (Dp) on the syngas composition also, Lower Heating Value (LHV), Cold Gas
Efficiency (CGE) and Carbon Conversion (CC). The experimental work was conducted in an entrained flow
gasification unit of 1 kg/h federate designed and installed at Indian Institute of Chemical Technology, India. In
this work, the temperature was varied from 600 °C to 1100 °C. The ER and SBR values were varied between 0.1
and 1 while, Dp was changed from 0.5 to 3.0 mm. The aim here was to understand the effect of different process
parameters and derive relative optimum operating conditions for the entrained flow gasification of the TKPSC.
The results obtained show that operating conditions such as temperature of 1100 °C, ER of 0.3, SBR of 0.4 and
0.5mm Dp were found to be the most relative optimum operating parameters. The highest values of LHV around
∼12 MJ/Nm3, CGE around ∼90% and CC up to 98% were obtained for TKPSC. These values are in agreement
with the results reported in the literature on the other biomass waste materials that pocess similar properties to
TKPSC.

Biomass fuels are considered as alternative fuels for different energy sectors. This thesis project considers three different solid and dry biomass fuels: Rice Husk, Wood Chips and Sugarcane Bagasse. Experiments are carried out to analyze the combustible components of the produced syngas by gasification process of solid Biofuels. The Concentration of the three major components (CO, H2, CH4) of syngas are obtained by locally made gas analyzer system. Three different solid biomass fuels are investigated for different amount of fuel (by mass) and different air flow rates. 
The results indicated that the presence of CO is kept almost constant & obtained highest concentration after the combustion period of syngas. On the other hand, it has found that CH4 concentration of about 400 PPM is required to start the combustion of syngas. The combustion period of different biofuels shows that with the increase of mass of biofuel the combustion period is enhanced & rice husk has longer combustion period over the other biofuels. However, syngas from the sugarcane bagasse shows the highest heating value among others. Another findings is the that rice husk also took the least amount of time to produce combustible syngas. But it was easier for wood chips and sugarcane bagasse to ignite the fuel for the start of gasification process.

In this work, biomass (eucalyptus spp.) gasification has been investigated in a two-stage downdraft reactor by using different gasifying agents such as: air, air + saturated steam, and O 2 + saturated steam. The utilization of low quality saturated steam for gasification in different mixtures with air and O 2 is the main novelty of this paper. Thus, the influence of different gasifying agents was assessed on the concentrations of CO, H 2 and CH 4 and hence, on the lower heating value (LHV), the syngas power and the cold gasification efficiency. Since the type and flow of gasifying agent control the biomass consumption in downdraft gasifiers, the equivalence ratio (ER) and the steam-to-biomass ratio (SBR) were calculated by means of a mass balance. The results showed that low quality steam can increase remarkably the H 2 concentration and the LHV of syngas despite its low temperature. Particularly, when O 2 + saturated steam is fed to the gasifier, the H 2 concentration varied between 27.4 and 35.9 vol.%, while the LHV was between 7.13 and 8.35 MJ/N m 3 , i.e. almost twice the produced when only air or air + saturated steam is used. The optimum ER seems to be below 0.412, while the SBR is found between 0.495 and 1.032. Under this conditions, the cold gasification efficiency was between 70 and 75%. Moreover, the O 2 seems to mitigate in a better way the negative effect of the low temperature of the saturated steam given the lower tar concentration in syngas (58.74–64.18 mg/N m 3) respect to those found with air + saturated steam (91.41–91.95 mg/N m 3). This paper concludes that saturated steam can be used blended either with air or O 2 (being better with O 2) for biomass gasification in two-stage downdraft reactors and therefore, the requirements of superheated steam are not so important as in other gasification processes.

The association of concentrated solar energy and biomass gasification has often been suggested as an interesting alternative to conventional autothermal processes where a significant portion of the biomass has to be used for heat generation to drive endothermic reactions. It is a clean process able to produce high quality synthesis gas with a higher output per unit of feedstock and that allows for the chemical storage of solar energy in the form of a readily transportable fuel, among other advantages. The present paper describes the latest advances in solar thermochemical reactors for gasification of carbonaceous feedstocks. This work is categorized in this paper into patents and research/journal papers.

DOE Scientific and Technical ... Publication Date, 2002 Jun 01. OSTI Identifier, OSTI ID: 802155. Report Number(s), FC26-00NT40937--03. DOE Contract Number, FC26-00NT40937. DOI, 10.2172/802155. Other Number(s), TRN: US200223%%920. Resource Type, Technical Report ...

This paper presents the feasibility study of a sound scientific, engineering, and technological solution for
converting lignocellulosic biomass to electrical power using a trailer-scale downdraft biomass gasification
system coupled with a spark-ignited IC engine/electric generator set for portable power applications
on agricultural farms and in rural areas.
The main objective of this study is to investigate the coupling and integration between the gasification
unit and the power generation unit. Also it is intended to emphasize on the effectiveness of distributed
power generation systems and demonstrate the feasibility of such integrated systems in real world scenarios,
where the lignocellulosic biomass resources are widely available and distributed across the board.
Four feedstock materials, pine, red oak, horse manure and cardboard that represent a wide spectrum of
lignocellulosic biomass resources were chosen for the study. The efficiencies for individual components
and the overall integrated system efficiencies were evaluated using experimental data and a thermal–
chemical model for all four feedstocks.

This work presents an experimental study of the gasification of a wood biomass in a moving bed downdraft reactor with two-air supply stages. This configuration is considered as primary method to improve the quality of the producer gas, regarding its tar reduction. By varying the air flow fed to the gasifier and the distribution of gasification air between stages (AR), being the controllable and measurable variables for this type of gasifiers, measuring the CO, CH4 and H2 gas concentrations and through a mass and energy balance, the gas yield and its power, the cold efficiency of the process and the equivalence ratio (ER), as well as other performance variables were calculated. The gasifier produces a combustible gas with a CO, CH4 and H2 concentrations of 19.04, 0.89 and 16.78% v respectively, at a total flow of air of 20 Nm3 h−1 and an AR of 80%. For these conditions, the low heating value of the gas was 4539 kJ Nm−3. Results from the calculation model show a useful gas power and cold efficiency around 40 kW and 68%, respectively. The resulting ER under the referred operation condition is around 0.40. The results suggested a considerable effect of the secondary stage over the reduction of the CH4 concentration which is associated with the decreases of the tar content in the produced gas. Under these conditions the biomass devolatilization in the pyrolysis zone gives much lighter compounds which are more easily cracked when the gas stream passes through the combustion zone.► Obtained results an important for a better phenomenological understanding of processes occurring in two stage gasification reactors. ► The air flow is the fundamental parameter in the operation of downdraft gasifiers. ► CH4 reduction is associated with a decreases in the tar content. ► An enhancement in the thermal cracking of tar is carried out in the two-air downdraft gasifier.

A circulating fluidized bed biomass gasification model is developed in the present study. The model consists of sub-models for devolatilization, tar cracking and a chemical reaction network of main gasification reactions and nitrogen chemistry. A total of forty global chemical reactions are included in the model, of which twenty-eight reactions belong to fuel-nitrogen reaction network. Individual reaction rates are selected from the literature, wherever possible, based on studies of woody biomass fuels. Volatile nitrogen is assumed to consist of NH3, HCN and N2 with the distribution between three species as input parameters to the model. Modeling of the hydrodynamics of the riser is simplified by using solids concentration profile along the riser as an input to the model. Both gaseous phase and solids phase are assumed to be in plug flow. Modeling results are compared with the experimental results published in the literature. Predicted effects of bed temperature, equivalence ratio and fuel moisture content on main gaseous composition, tar and NH3 emissions generally agree with the literature data. A sensitivity analysis of some reaction rates included in the model on NH3 emissions has also been carried out. It has been revealed that the catalytic activity of bed materials towards the oxidation of NH3 has the greatest influence on the predicted NH3 emissions. In addition, the
predicted NH3 emissions are also affected by the catalytic activity of bed materials towards the decomposition of NH3 and the homogenous reaction rates of NH3 decomposition and the reduction of NO by NH3 in the presence of oxygen.