Grinding energy and physical properties of chopped and hammer-milled barley,wheat, oat,and canola straws

In the present study, specific energy for grinding and physical properties of wheat, canola, oat and barley straw grinds were investigated. The initial moisture content of the straw was about 0.13–0.15 (fraction total mass basis). Particle size reduction experiments were conducted in two stages: (1) a chopper without a screen, and (2) a hammer mill using three screen sizes (19.05, 25.4, and 31.75 mm). The lowest grinding energy (1.96 and 2.91 kWh t⁻¹) was recorded for canola straw using a chopper and hammer mill with 19.05-mm screen size, whereas the highest (3.15 and 8.05 kWh t⁻¹) was recorded for barley and oat straws. The physical properties (geometric mean particle diameter, bulk, tapped and particle density, and porosity) of the chopped and hammer-milled wheat, barley, canola, and oat straw grinds measured were in the range of 0.98–4.22 mm, 36–80 kg m⁻³, 49–119 kg m⁻³, 600–1220 kg m⁻³, and 0.9–0.96, respectively. The average mean particle diameter was highest for the chopped wheat straw (4.22-mm) and lowest for the canola grind (0.98-mm). The canola grinds produced using the hammer mill (19.05-mm screen size) had the highest bulk and tapped density of about 80 and 119 kg m⁻³; whereas, the wheat and oat grinds had the lowest of about 58 and 88–90 kg m⁻³. The results indicate that the bulk and tapped densities are inversely proportional to the particle size of the grinds. The flow properties of the grinds calculated are better for chopped straws compared to hammer milled using smaller screen size (19.05 mm).     

Grinding performance and physical properties of non-treated and steam exploded barley, canola, oat and wheat straw

Grinding experiments were conducted on non-treated and steam exploded barley, canola, oat and wheat straw using a forage chopper and a hammer mill (screen sizes of 30, 6.4, 3.2 and 1.6 mm) to determine specific energy requirements, and geometric mean particle size and distribution of ground material. The bulk density of non-treated biomass was significantly higher than bulk density of steam exploded agricultural biomass. For non-treated agricultural straw, the particle density of canola and oat straw significantly increased with a decrease in hammer mill screen size from 30 to 1.6 mm. The particle density of steam exploded barley and oat straw was significantly higher than non-treated straw, except for barley at 6.4 mm hammer mill screen size. The particle density of steam exploded canola straw was not statistically different from non-treated straw. The chopper consumed highest (3.15 ± 0.09 kWh t⁻¹) and lowest (1.96 ± 0.33 kWh t⁻¹) specific energy to chop barley and canola straw, respectively. The highest and lowest specific energy was consumed by wheat (42.57 ± 2.04 kWh t⁻¹) at 1.6 mm and canola (1.46 ± 0.30 kWh t⁻¹) straws ground using 30 mm hammer mill screen size, respectively. For steam exploded agricultural biomass, the highest and lowest specific energy was consumed by oat (33.18 ± 3.10 kWh t⁻¹) at 1.6 mm and canola (2.69 ± 0.26 kWh t⁻¹) straws ground using 6.4 mm hammer mill screen size, respectively. Specific energy required by hammer mill to grind non-treated and steam exploded barley, canola, oat and wheat straw showed a negative power correlation with hammer mill screen sizes.     

Briquetting soda weed (Salsola tragus) to be used as a rural fuel source

Amount of traditional fuel sources in the world has been decreasing and there is a definite need to produce and utilize alternative fuels such as biomass materials. In this study, briquetting conditions of Russian tumbleweed, Salsola tragus, (commonly named soda weed in Turkey) which grows in salty soils were investigated.Soda weeds were first chopped coarsely in a local tresher, then chopped finely in a hammer mill. Weed materials at three moisture levels (7%, 10%, and 13%) were prepared in the lab. Chopped weed materials were filled in cylindrical and square dies and compressed using a hydraulic press at three pressure levels of 15.7, 19.6 and 31.4 MPa. Optimum temperature, moisture rate, and pressure values were determined to produce stable briquettes. Further experiments were conducted to produce briquettes using sawdust and walnut shells as additives in conical dies of two different sizes.Results of a statistical analysis of parameters to produce briquettes in different dies indicated that moisture rates of 7–10%, pressure of 31.4 MPa, and temperatures of 85–105 °C were suitable for briquetting soda weed. Furthermore, sawdust and walnut shells additives increased briquette density without any negative effects on production process and product stability.     

锯末制备生物质成型燃料的试验研究

分别采用冷压成型和炭化成型工艺以锯末制备生物质成型燃料。冷压成型工艺主要考察原料水分、成型压力对燃料的成型性能影响。试验结果表明:原料水分为12%~16%,成型压力为60 MPa的条件下能够制得成型性能较好的生物质成型燃料,其密度与抗跌强度分别能够达到0.94 g/cm3和99%;炭化成型工艺主要考察混合料水分、无烟煤配比、J型粘结剂添加量、成型压力对燃料的成型性能影响。试验结果表明:无烟煤配比为50%、混合料水分为30%、J型粘结剂添加量为8%、成型压力为45 MPa的条件下能够制得成型性能较好的优质生物质成型燃料,其密度与抗跌强度分别为0.93 g/cm3和99.3%。     

秸秆类生物质压块棱角撕裂倒钝过程数值分析

针对生产过程中出现的压块成型设备模孔边角处堵塞原料造成压块棱角撕裂倒钝现象的形成机理进行研究,运用FEA分析软件ANSYS11.0模拟成型过程中原料的流动与塑性形变过程并通过试验对比研究,为压块成型设备结构优化提供技术依据。     

Effects of compressive force,particle size and moisture content on mechanical properties of biomass pellets from grasses

Mechanical properties of wheat straw, barley straw, corn stover and switchgrass were determined at different compressive forces, particle sizes and moisture contents. Ground biomass samples were compressed with five levels of compressive forces (1000, 2000, 3000, 4000 and 4400 N) and three levels of particle sizes (3.2, 1.6 and 0.8 mm) at two levels of moisture contents (12% and 15% (wet basis)) to establish compression and relaxation data. Compressed sample dimensions and mass were measured to calculate pellet density. Corn stover produced the highest pellet density at low pressure during compression. Compressive force, particle size and moisture content significantly affected the pellet density of barley straw, corn stover and switchgrass. However, different particle sizes of wheat straw did not produce any significant difference on pellet density. The relaxation data were analyzed to determine the asymptotic modulus of biomass pellets. Barley straw had the highest asymptotic modulus among all biomass indicating that pellets made from barley straw were more rigid than those of other pellets. Asymptotic modulus increased linearly with an increase in compressive pressure. A simple linear model was developed to relate asymptotic modulus and maximum compressive pressure.     

大容量锅炉尾部烟道空气动力场研究

阐述了北方农村秸秆高效利用技术研究的重要意义;对各种秸秆高效利用技术进行了分析,指出了它们推广应用的技术关键。秸秆固化成型技术在近期已经具备一定推广应用条件。秸秆成型燃料燃烧特性艮好,且便于储存和运输。秸秆成型加工可以作为秸秆燃料的预处理技术,为各种秸秆的高效利用技术特别是直接燃烧技术准备原料。秸秆成型机技术已有较大进步,进一步研究需要在降低能耗和提高成产率方面开展。     

Physical properties of rice husk and bran briquettes under low pressure densification for rural applications

Agriculture generates large amount of by-products that could be used to produce energy and reduce the amount of fuelwood required to meet the daily cooking needs, especially in developing countries. Rice is a major crop grown in West Africa and rice husk is a by-product of the milling process. The goal of this study was to develop a low cost system to produce biomass briquettes from rice husks in the context of a rural village. A manual press generating a pressure of 4.2 MPa was developed and used. The influence of the briquette formulation (type of binder, binder content, water addition, and bran content) was studied. The binders investigated were cassava wastewater, rice dust, and okra stem gum. The physical properties (density, moisture content, calorific value, durability, and compressive strength) were tested to identify the briquettes with the highest quality, i.e. greatest physical integrity. The briquettes made with rice dust had the highest durability (91.9%) and compressive strength (2.54 kN), while the briquettes made with cassava starch wastewater had the greatest density (441.18 kg m⁻³). Water added to the rice husk before densification positively influenced the briquette quality while bran seemed to mostly increase the density, but not necessarily the briquette quality. The briquette formulation did not significantly influence the calorific value. With a higher heating value of 16.08 MJ kg⁻¹ dry basis, rice husk briquettes represent an interesting alternative to fuelwood.     

Comparison of quality and production cost of briquettes made from agricultural and forest origin biomass

This paper presents the quality and cost of small-scale production of briquettes, made from agricultural and forest biomass in north-eastern Poland. The experiment involved production of eight types of briquettes. The highest net calorific value was determined for briquettes made from pine sawdust (18,144 MJ t⁻¹). The value measured for briquettes made from perennial energy plants was over 1500 MJ t⁻¹ lower, and for those made from straw 2000 MJ t⁻¹ lower than for sawdust briquettes. The sawdust briquettes left significantly the lowest amount of ash (0.40% of dry mass). The significantly highest content of hydrogen, sulphur and nitrogen was found in briquettes containing the highest portion of rapeseed oilcake. The quality of briquettes varied and only some of them met the requirements of DIN 51731. Briquettes made from pine sawdust were of the highest quality. The briquette production cost ranged from 66.55 € t⁻¹ to 137.87 € t⁻¹ for rape straw briquettes and for those made from a mixture of rape straw and rapeseed oilcake (50:50), respectively. In general, briquette production was profitable, except for the briquettes made from a straw and rapeseed oilcake mixture.     

Influence of process parameters and biomass characteristics on the durability of pellets from the pruning residues of Olea europaea L.

The present work aims to investigate the influence of the main process parameters (pressure and temperature) and biomass characteristics (moisture content and particle size) on some mechanical properties (density and durability) of olive tree pruning residues pellets. By means of a lab scale pellet press, able to control process parameters, the biomass, ground with three different hammer mill screen sizes (1, 2 and 4 mm) and conditioned at different moisture contents (5, 10, 15 and 20% w.b.), was pelletized at various process temperatures (60, 90, 120 and 150 °C) and pressures (71, 106, 141 and 176 MPa). Compressed sample dimensions and mass were measured in order to calculate pellet density, while compressive strength tests were carried out to estimate the durability of the final biofuel. The relationships between the factor settings and the responses (density, compression strength and modulus of elasticity) were examined by univariate and multivariate statistical analysis.Temperature resulted the most important variable influencing pellet mechanical properties, followed by the initial moisture content and the particle size of the raw material. In particular, high process temperature, low moisture contents and reduced particle sizes allowed obtaining good quality pellets. The effect of compression force resulted scarcely relevant.     

生物质成型系统一体化和自动化设计

为了实现生物质成型系统一体化和自动化运行、降低能耗、提高产率,对生物质成型设备进行了合理配置和整合。采用控制理论和技术,根据进料量、粉碎量、供热量、出料量、物料含水率等条件变化,对生物质成型设备进行自动化设计。实现了生物质成型燃料系统生产过程连续稳定,提高了设备的集成化水平,减少了人工操作,降低了能耗及生产费用。生物质干燥过程采用生物质热风炉提供热量,实现了能源的自循环利用。一体化和自动化的生物质成型系统燃料生产电耗小于100 kWh/t,人工费不超过100元/t,为生物质的规模化利用提供了较为合理的途径。     

生物质型煤的研制与应用

生物质型煤是一种新型型煤,是利用粉煤、生物质等通过一定的生产工艺制作而成,不仅有利于节约能源,同时也可以减少环境污染.文章重点介绍了水分、生物质添加量、粘结剂、原料煤粒度、成型压力、熟化过程、干燥程度对生物质型煤冷强度的影响,添加剂、生物质、配煤量以及煤的种类对生物质型煤热强度的影响.文章还分析了生物质型煤与生物质和煤在燃烧速度和着火性能上的区别,固硫效果与所加固硫剂量之间的关系,并提出了生物质型煤作为气化型煤今后应开展的研究方向与课题.     

Utilization of straw in biomass energy in China

China is a big agricultural country and one of the most abundant straw resources in the world, producing more than 620 million tons of straw in 2002, and representing about 33–45% of energy consumption for livelihood in rural areas. Utilization of straw as energy with high efficiency and rationality not only meets the demands for energy as the economy grows, but also provide a basis for environmental protection and sustainable development of society in China. This paper reviews the present utilized technologies of straw in biomass energy, including improved stove, biogas, straw gasification and straw briquette, which are already commercialized and popularized in China. Other technologies, such as liquefaction, straw carbonization and bio-coal, are also presented. Based on the technology status and potential, the future research and development of straw in the biomass energy portfolio in China are proposed.     

Effect of compressive load and particle size on compression characteristics of selected varieties of wheat straw grinds

In this study, the effect of compressive load and particle size on compression characteristics of four varieties (Strongfield, Blackbird, DT773 and DT818) of wheat straw grown at two different fields was investigated. Particle size, bulk and particle densities of all wheat straw samples were determined after grinding. Ground wheat straw samples were densified in a cylindrical die at 90 °C using an Instron testing machine. The wheat straw samples with 9% moisture content were compressed at five levels of compressive pressures (31.6, 63.2, 94.7, 126.4 and 138.9 MPa) and two levels of particle sizes (1.6 and 3.2 mm). Dimensions and mass of all compressed samples were measured to calculate the pellet density. The specific energy required to compress and eject the pellets was calculated from force-displacement data. Applied compressive force and particle size significantly affected the pellet density of wheat straw samples. The pellet density was in the range of 699–1064 kg m⁻³ increasing with pressure and particle size. The total specific energy required for compression and ejection of pellets varied from 4.35 to 33.64 MJ t⁻¹ that increased with compressive load and particle size. Higher compressive forces and particle size increased the durability of pellets to more than 95%. Blackbird variety was the most compressible of the four varieties of wheat straw.     

Key techniques and parameters for briquetting corn stover sprayed with biogas slurry in a cold region in China

Densification of biomass is often necessary to combat the negative storage and handling characteristics of these low-bulk-density materials. Corn stover is an important feedstock being considered for production of renewable fuels and energy in China. Densification of corn stover would help reduce the problems and costs of bulk transportation, handling, and storage of biomass feedstock. In cold regions, some thermosetting binder will be added when briquette fuel is made with corn stover because of its high water and lignin content. It is important to understand the synthesis mechanism of thermosetting binder under certain temperature and pressure combined with strong alkaline slurry to explore develop ment of a new process of briquetting corn stover based on only alkaline slurry as an environment-friendly binder. In this study, flat-die briquetting machine has been used with a cone-shaped press roller, and a matching die hole on the press plate. At the same time, orthogonal experiments were designed from the results of single-factor experiments to obtain optimal briquetting conditions. The effects of spray quantity of biogas-slurry, size of die hole, and water content of corn stover on the durability and bulk density of corn stover briquettes were investigated. Moreover, the model for whole factors and the model for interaction between factors for indexes have been built, emulated the optimum processing parameters. The results show briquettes of corn stover with durability of 83.33% were produced when the spray liquid flow quantity of biogas-slurry, size of die hole, and water content of corn stover were 0.45 L/kg, 28 mm, and 20%, respectively. Bulk density of 616 kg/m³ was produced when the spray liquid flow quantity of biogas-slurry, size of die hole, and water content of corn stover were 0.3 L/kg, 24 mm, and 25%, respectively. These results have been checked by verification testing. The successful implementation of this project provides theoretical support and test instruction for the development of green biomass energy for sustainable development.     

新型成型机秸秆碎料形变分析及挤压力控制措施

介绍了一种新型秸秆燃料成型机,阐述了其基本机械结构和工作原理．为了便于分析秸秆燃料压缩成型过程中秸秆碎料形变规律,将成型机工作区域动态地划分为供料区、压紧区、压实区、成型区和保型区等五个工作分区．从秸秆碎料宏观体积、微观组织变化以及秸秆碎料的形变情况,分别探讨了每个分区秸秆碎料的形变特点．成型机压辊对秸秆碎料的挤压力过小会降低成型燃料的品质,挤压力过大则会降低秸秆成型机的寿命．通过研究挤压力与秸秆燃料密度的关系,以控制压缩比为措施设计了新型秸秆成型机的挤压力控制方案．     

Tandem-ring mill pulverization benefits for enzymatic saccharification of biomass

A vibration mill, called a “tandem-ring mill”, which has cog-ring media in place of the ball medium of a conventional vibration mill, was developed to achieve high-impact pulverization of lignocellulosic biomass for bio-ethanol production. This study investigated pulverization characteristics of various biomass samples of Japanese cedar, eucalyptus, rice straw, rice husk, and reeds using a batch-type tandem-ring mill for 60 min and 100 min pulverizations. The pulverized biomasses were characterized by the mean particle diameter, crystallinity index, and enzymatic saccharification. The mean particle diameter of biomass was decreased rapidly in the first 20 min. Then the biomass mean particle diameter reached around 40 μm by flocculation. Furthermore, the crystallinity indexes of biomasses were decreased by pulverization. Especially, woody biomasses of cedar and eucalyptus were decreased rapidly around 10%, nearly a non-crystalline state. Woody biomasses, Japanese cedar, and eucalyptus showed high saccharification efficiency. Similarly, grass biomasses, rice straw, and rice husks showed high saccharification, aside from reeds. Therefore pretreatment of various biomasses using a tandem-ring mill was suitable for enzymatic saccharification.     

木屑致密成型燃料微观结构观察与分析

林木生物质在全球生物质储量中占有很大比例,本文以木屑致密成型燃料为研究对象。试验分别对木屑致密成型燃料进行了元素分析、工业分析和燃料组成分析。并在200 kV场发射透射电子显微镜(JEM-2100F)下对木屑致密成型燃料进行观察,分别得到放大倍数为100、500、1 000、2 000倍的微观结构图片。通过对木屑成型燃料的微观结构分析研究能够为生物质成型燃料加工成型设备和燃烧设备的优化设计与改进提供理论基础。     

Microbial changes during the on-farm storage of canola (oilseed rape) straw bales and pellets

The effect of on-farm storage on microbial growth on baled and pelletised Brassica napus (oilseed rape/canola) straw was investigated. Canola straw collected in 2008 and 2009 was stored baled in an open shed for 3, 4, 7, 10 and 20 months in 2008 and for 1 and 3 months in 2009. Pellets were produced from straw stored for 3, 7, and 10 months in 2008 and straw stored for 3 months in 2009, and stored for up to 48 weeks.The moisture content (MC), water activity (a_w), bacterial and fungal colony-forming units (CFU), and carbon-to-nitrogen ratio (C:N) of canola straw bales and pellets were measured during storage. In addition, temporal environmental conditions (ambient temperature and relative humidity) and bale temperature were monitored. The moisture content showed a tendency to stabilise during storage, with an equilibrium moisture content of approximately 155 g kg⁻¹ total weight for straw bales and 110 g kg⁻¹ total weight for straw pellets. Consequently, the water activity of canola straw bales remained below 0.8 and that of pellets below 0.66 during storage, providing an explanation for relatively low microbial growth. The number of bacterial and fungal CFU present in the straw bales and pellets followed the trend of ambient relative humidity and no correlation was found with the C:N ratio of the biomass. Canola straw pellets were considered a superior combustion fuel to straw bales due to lower moisture content and less microbial deterioration during storage.