Guanghui Wang

Effects and mechanism of ball milling on torrefaction of pine sawdust

The effects and mechanism of ball milling on the torrefaction process were studied. Ball- and hammer-milled (screen size 1mm) pine sawdust samples were torrefied at three temperatures (230, 260, and 290°C) and two durations (30 and 60min) to investigate into their torrefaction behavior and physicochemical properties. The results showed that, under identical torrefaction conditions, torrefied ball-milled pine sawdust had a higher carbon content and fixed carbon, and lower hydrogen and oxygen contents than torrefied hammer-milled pine sawdust. Torrefied ball-milled pine sawdust produced lower mass and energy yields, but higher heating values than torrefied hammer-milled pine sawdust. Ball milling destroyed the crystalline structure of cellulose and thus reduced the thermal stability of hemicellulose, cellulose, and lignin, causing them to degrade at relatively lower temperatures. In conclusion, biomass pretreated with a combination of ball milling and torrefaction has the potential to produce an alternative fuel to coal.

Co-pelletizing characteristics of torrefied wheat straw with peanut shell

The co-pelletizing characteristics of torrefied wheat straw and peanut shell with adding water were investigated. The physicochemical and friction characteristics of biochar were determined to investigate the mechanism of biochar inter-particle cohesive bonding. Results showed that optimized process conditions were obtained with 15% peanut shell and 10% water content. The volume density, maximum breaking force of pellets initially decreased and then increased, while energy consumption increased with increasing temperature. The main factors contributing to the cohesion of mixing pellet were the peanut shell content, water content and friction characteristics of biochar. The moisture absorption of the pellet was improved significantly, while the water absorption of pellets did not always decrease with increased temperature. Peanut shell is an effective and inexpensive binder in the preparation of good-quality biochar pellets. Biochar pellets derived from torrefaction temperature of 275-300°C showed superior qualities for application as renewable biofuels.

Mechanical Properties of Timothy Hay Node

The mechanical property of timothy hay node was investigated using the Instron testing machine. Unbaled first cut timothy hay of the 2007 crop year was used in the test. Before testing, the stem segments with nodes were equilibrated to moisture contents of 12.19 and 14.13% w.b.. According to its position in the hay stalk, the nodes on each stem were designated as top, middle, or bottom node. The nodes were then separated from the stalk and shaped in cylindrical form using a Dremel cutter. Using the Instron universal testing machine, the force-deformation relationship of the nodes as affected by the node position in the stem, node size, and moisture content was obtained under a constant rate of deformation of 1 mm/min. The Hertz’s theory for convex bodies was employed for calculation of the apparent modulus of elasticity and maximum contact stress of the timothy hay node. The apparent modulus of elasticity and maximum contact stress values increased with node moisture content and decreased with size and its position in the stalk. However, moisture content did not affect mechanical values with respect to nodes with size of >2.00 mm and bottom nodes.

Changes in the physicochemical structure and pyrolysis characteristics of wheat straw after rod-milling pretreatment

Pyrolysis is increasingly used for raw biomass conversion. In this study, the effects of rod-milling pretreatment (RMP) on the physicochemical properties and pyrolysis characteristics of wheat straw (WS) was found. The mechanism behind these changes was further analyzed. RMP appreciably reduced the particle size and cellulose crystallinity, and increased the specific surface area and pore volume of WS. Under RMP, with an increasing conversion rate α, the activation energy E was expressed as a para-curve, whereas it was expressed as a tangent curve for samples that underwent hammer-milling pretreatment (HMP). At the same α, the thermal degradation temperature for RMP was lower than that for HMP. The E value clearly decreased with RMP, and increased following a wave-like pattern with increased rod-milling strength (RMS). The lowest E value (118.69 or 108.97u202fkJ/mol) was obtained with a milling time of 60u202fmin. Hence, RMP is an environmental-friendly and effective method for improving the efficiency of pyrolysis.

The effect of tine geometry during vertical movement on soil penetration resistance using finite element analysis

New tillage and planting tools causing low soil disturbance and minimizing vegetation deterioration are desired in the conservation tillage technology development. This paper attempted to study the effect of tine geometry in its vertical movement on penetration resistance. Four kinds of tines were defined (i.e. rectangle, triangle, crescent and mososeries) based on the geometry of the cutting edge. The effects of tine geometry, thickness, and penetration depth on soil penetration resistance were investigated and side soil disturbance evaluated. Finite element method with a Drucker–Prager elasto-plastic model was introduced to simulate the material behavior of sandy loam soil taken from Hebei province in China. Each tine was considered as a discrete rigid body with a reference point at the top-midpoint of the central plane, at which the vertical force (penetration resistance) was calculated. Results indicated that the rectangle tine obtained the highest penetration resistance as compared to the others. Penetration resistances of all the tines increased with the attack surface area with a power function, nonlinear tendency with thickness and a quadratic function with penetration depth. A crescent soil deformation area existed through the penetration process. It can be concluded that the FEM can maximize the understanding of tine geometry effects on penetration resistance and soil deformation area.

Combined different dehydration pretreatments and torrefaction to upgrade fuel properties of hybrid pennisetum ( Pennisetum americanum ×P. purpureum )

Different dehydrating methods combined with torrefaction were investigated to find the underlying mechanism that how dehydration process influence the degree of hornification. Hybrid pennisetum was selected as the experiment material. Oven-dried sample (ODS), crushed dried sample (CDS), and sun-cured dried sample (SDS) were torrefied under the temperature of 275u202f°C and 300u202f°C with the duration time of 60u202fmin. The results showed that, changes in elevated carbon content and higher heating value (HHV) and reduced oxygen content of SDS were the most obvious under identical torrefaction conditions. Fuel ratio of SDS was enhanced most under 300u202f°C. It also had the highest devolatilization index (Di). The combination of sun-cured dried with torrefaction under 300u202f°C caused lowest degree of irreversible hornification happened during dehydrating process, and different hornification degrees caused by different dehydrating methods effect the enhancement of fuel properties of lignocellulosic biomass material.

Effects of a Soil-gashing and Root-cutting Mechanism on Soil Properties and Crop Yield of Grasslands

Traditionally, overturning soil by tillage tools is popularly used to improve the crop yield of degenerated grassland in Northern China. This method can effectively change soil physical and chemical properties; but, it dramatically increases the risks of wind and water erosion. Field tests were conducted to evaluate the effectiveness of a root-cutting mechanism which was previously designed for the purposes of cutting the grass (Leymus-chinensis) roots and gashing the soil. This mechanism can penetrate into soil to a depth of 200 mm. Measured parameters included soil moisture content, bulk density, porosity, pH value, organic carbon, total nitrogen and crop yield. Test results also indicated that this mechanism could gash soil and break tangled roots with minimum soil disturbance. The results showed that the soil bulk density was reduced, and the soil porosity increased after the field plots were treated with this mechanism. Comparison of measured results from test and control plots indicated that soil moisture contents, soil bulk densities, and soil porosity were numerically increased, but not statistically significant. Soil organic matter and total nitrogen were significantly increased. Soil pH value was reduced to the level the grass growth needed. Crop yield was increased by 110.52%.

Effects of combined pretreatment with rod-milled and torrefaction on physicochemical and fuel characteristics of wheat straw

The mechanism of rod-milling combined with torrefaction as well as its effects on physicochemical and fuel properties of wheat straw were investigated. Rod-milling and hammer-milling samples were torrefied under three temperatures (250, 275, and 300u202f°C) with a duration time of 30u202fmin. The results indicated that combined rod-milling and torrefaction pretreatment (CRT) significantly elevated carbon content, higher heating value, fuel ratio, and reduced oxygen content and atomic H/C and O/C ratios in wheat straw. Moreover, CRT significantly reduced cellulose crystallinity, and increased the specific surface area and pore volume of wheat straw, which lowered the wheat straws degrading pyrolysis temperature. These peak values appeared under 300u202f°C. Devolatilization index (Di) was improved by rod-milling pretreatment under identical torrefaction conditions except 275u202f°C. Therefore, the combination of rod-milling with torrefaction under 300u202f°C has the advantage of enhancing fuel properties of lignocellulosic biomass materials.

Design and test of the device forming grass-braid driven by diesel or electricity

Abstract. The forming device is mainly includes the frame, shaping drum, pulling grass roller and driven roller part. The machine described in this article is mainly used for processing grass into the shape of braid. According to the working principle of the whole machine, the grass plate in two shaping drum provides the grass a rotation movement relative to two rollers. Then, the braided grass is formed by two surge of rotating grass which gathered in the middle of two grass roller. This device is suitable for the braid of alfalfa, elymus, black wheat, etc. which length is 500 mm above. The productivity is 500 kg/h and the braid diameter is 120 mm. This proposed method could meet the requirement of real-time forage processing in Qinghai-Tibet Plateau. The grass braid is convenient to transport and storage.

Optimization of Binder Addition and Compression Load During the Pelletization of Wheat Straw Using Response Surface Methodology

Abstract. Densification is required for efficient handling and transportation biomass as feedstock for biofuel production. Binders can enhance the straw pellet strength and improve pellet performance. The present investigation is to optimize binder addition of wheat straw pelletization process by using a single pelleting unit. Response surface methodology was employed by using a four factor five level Central Composite Design with wood residue, bentonite, crude glycerol addition by mass fraction and compression force as process parameters. Pellet tensile strength, specific energy consumption and pellet density were the response variables. The higher heating value, ash content and the cost of the pellet were also considered when optimized binders. The results showed that the developed model fitted the data and was adequate for binder analysis. Wheat straw pelleted with 30% wood residue, 0.80% bentonite and 3.42% crude glycerol addition and 4000 N compressive force was identified as the optimal process parameter with low ash content (6.13%) and high heating value (18.64 MJ t -1 ). Pellet tensile strength, specific energy consumption and pellet density values were 1.14 MPa, 32.6 MJ t -1 and 1094 kg m -3 , respectively. Confirmation tests indicated high accuracy of the model.