Research upon the Structure and Pyrolysis of Cotton Stalk

[Purpose]To research upon the structure and pyrolysis of cotton stalk.[Method] In this paper thermogravimetric analysis is adopted to study pyrolysis characteristics on the longitudinal direction of cotton stalk（the stick and the root）and on the traverse direction（the cuticle,cortex and medulla）.[Result] Cotton stalk is a material of uneven and irregular texture,and there are great differences in the structure of all these parts on the longitudinal and traverse directions,especially in the contents of different components in each layer.The reaction in the stick and root becomes violent along with the increase in the rising rate of temperature,and carbon yield rate decreases in turn.Besides with the same rising rate of temperature,carbon yield rate of cotton stick is higher than the one of cotton root.Carbon yield rates of cuticle,cortex and medulla decrease in turn while the violence of the reaction in cuticle is less severe than in cortex and medulla.[Conclusion] It has provided theoretical basis for obtaining activated carbon technology of cotton stick.

The Cotton Stalk and Its Utilization as Ruminant Feed Resource in Xinjiang

Two separate experiments were carried out: the first one involved a study of the chemical and some intrinsic feed characteristics of raw cotton stalk( CS) and the efficiency of chemical,biological treatments on the improvement of the feed value of CS. CS was treated with chemical treatment by mixing 3% Ca( OH)2( CS + Ca),3% urea( CS + U),3% urea +3% Ca( OH)2( CS + Ca + U). Moreover,CS was treated with biological treatment by inoculation of either Lentinus edodes( CS + Po) or Pleurotus ostreatus( CS + Pl) or crushing CS by adding minor ingredient processed into pellet feed,samples from all treatment were analyzed for the nutrients,In vitro dry matter digestibility( INDMD) and free gossypol detoxification rate. The second investigated was the use of crushed or granulation CS as a test feed followed by voluntary feed intake and preference test with sheep. CS + Ca + U treatment can reach up the CP and IVDMD to 9% and 36%,respectively. CS + Po decreased the fiber component and improved CP content and IVDMD. The free gossypol content declined and the free gossypol detoxification rate reached more than 50%. By feeding sheep under the same level of concentrate and corn silage,the voluntary feed intake and daily weight gain in granulation group is higher than in crushing group( P < 0. 05). Crushing CS by adding minor ingredient processed into a pellet feed was best in terms of improved nutritional quality,feed intake and preference,and it was safe and practical method that can be widely used in sheep production systems,to promote the CS feed utilization in similar areas.

Sustainable synthesis of 5-hydroxymethylfurfural from waste cotton stalk catalyzed by solid superacid-SO4^2-/ZrO2

A sustainable process was explored for the preparation of 5-hydroxymethylfurfural(HMF) by catalytic degradation of the waste cotton stalk. Solid super-acid(SO_4^(2-)/ZrO_2) was used as an efficient catalyst for the degradation of cotton stalk. Both decomposition experiments and kinetic study were conducted for the exploration of degradation condition and kinetics mechanism. The optimized experimental conditions are reaction temperature 503 K, reaction time 75 min and dosage of catalyst 30%(mass fraction) based on the decomposition experiments, under which a maximum yield of 27.2% for HMF could be achieved. Kinetic study was then carried out in the presence of SO_4^(2-)/ZrO_2. The theoretical results indicate that the activation energies for reducing sugar and HMF with catalyst are 96.71 k J/mol, 84.21 kJ/mol in the presence of SO_4^(2-)/ZrO_2, and they are 105.96 k J/mol and 119.37 k J/mol in the absence of SO_4^(2-)/ZrO_2.

Co-Combustion Characteristics and Kinetics of Cotton Stalk and Polypropylene Blends

The combustion kinetics of biomass-cotton stalk (CS), polymer-polypro-pylene (PP) and blend of polymer/biomass-polypropylene/cotton stalk blends were examined through thermo gravimetric analysis in this study. The experiments were performed under non-isothermal conditions in the 298 - 873 K temperature interval. The heating rate of this research realized under the air atmosphere was designated as 5 K·min-1. The particle size effect on the combustion behavior of cotton stalk was also studied. A decrease in the maximum rate of decomposition and an increase in the temperature of maximum decomposition with increasing particle size were obtained. Three different models based on the Arrhenius method were used to analyze differential thermo gravimetric data. Blending ratio effects of biomass-cotton stalk and polymer-polypropylene on the combustion kinetics were further explored. Additionally, factors and kinetic parameters were also discussed. Activation energies obtained through the Arrhenius method (n = 1) were much lower than that of polypropylene for all blends. As a result of the research, as the weight percentage of polypropylene in the mixture rises, an increase in activation energy values was observed. The minimum value of the activation energy was calculated with PP/CS with 2/3 blending ratio as 35.8 kJ·mol-1.

Design and test of a wheel-belt type cotton stalk puller

During the harvesting process,rigid materials are prone to causing damage to the cotton stalks,which will increase the risk of stalk breakage.A cotton stalk pulling component that blends stiff and flexible materials was devised to lower the breaking rate.The cotton stalk pulling component was made up of rollers and flexible belts that pull the stalks using clamping force and the forward speed of the tractor.The influence of various factors in the equipment on the harvesting effect of cotton stalks were analyzed through response surface experiments,and a multiple quadratic regression response surface model with missing pulling rate and breakage rate as response values was established.The significant of influencing factors on the breaking rate of cotton stalks are in a descending order as:the angle of cotton stalk pulling,tractor’s forward speed,and the clamping speed of the cotton stalk component.The working parameters of the wheel-belt type cotton stalk pulling machine have been optimized using the response surface combination experimental method,and the optimal parameter combination was obtained as:tractor forward speed of 4.5 km/h,cotton stalk pulling angle of 60°,and clamping speed of the cotton stalk pulling component of 349 r/min.The results of validation experiments showed that the missing pulling rate of cotton stalks was 5.06%and the breakage rate was 13.12%,indicating a good harvesting effect of the cotton stalks.The model was reasonable and the performance parameters could meet the relevant inspection requirements.The results can provide a reference for further research on the technology of flexible cotton stalk pulling.

Improved design and test of flexible cotton stalks puller

In Xinjiang,in the process of whole stalk harvesting of cotton stalks,there is a problem that the cotton stalks are easily pulled off,and there is an urgent need to develop flexible stalk-pulling machines.Through literature,patent summary,and field research,it is found that domestic researchers have designed many kinds of machines for the problem of easy breaking of cotton stalks,but there is no flexible cotton stalk-pulling machine for the time being.In this study,two flexible cotton stalk-pulling machines were intended to address the problem of easy breakage of cotton stalks.On the basis of the first-generation machine,the design of the second-generation machine was improved.In order to further improve the operational performance of the flexible cotton stalks pulling tools,the operational mechanism of the core working parts of the tools was analyzed and a comparative test was done in a large field.Analysis and the comparative tests proved that improving the clamping working stroke s of the stalk-pulling components can effectively reduce the cotton stalks leakage rate.By using a flexible clamping process,a part of the deformation of cotton stalks can be transferred to the flexible material.To a certain extent,the deformation length L of the contact surface between the cotton stalk and the stalk pulling part is reduced,and the deformation displacementΔy is correspondingly lower.The toughness of the cotton stalk is not significantly decreased and the cotton stalk does not break easily.The improved second-generation machine has a 3.67% to 3.79% lower cotton stalks leakage rate and a 5.65% to 6.30% lower cotton stalks breakage rate than the first-generation machine.As the land in Xinjiang is clay soil,soil bonding to cotton stalks pulling force F2 is larger,resulting in cotton stalks being more difficult to be pulled out of the machine at once.The test proved that the improved second-generation implements had a significant improvement in the cotton stalk-pulling effect because of the subsequent pulling interval CD.The test results verify the analysis results and the research results can provide a theoretical basis for the subsequent structural improvement and performance enhancement of the flexible cotton stalk-pulling machine,which is of reference significance for solving the problem that the cotton stalks are easily pulled and broken in Xinjiang,China.

Cotton stalk restitution coefficient determination tests based on the binocular high-speed camera technology

The restitution coefficient(RC)of cotton stalks is an important elementary physical parameter that is required to establish the crushing mechanical model and research the film residue separation machinery.In this study,the calculation method of restitution coefficient considering the rotation motion of stalk-shaped agricultural materials was derived based on the principle of kinematics and the energy restitution coefficient method,and a test bench for measuring the RC was designed and built.The effects of collision material,moisture content,length,diameter,release height,and collision angle respectively on the RC were investigated by single-factor experiments and orthogonal experiments,and the regression models between influence factors and the RC were established.The results showed that Q235 showed the highest value of the RC,and it was followed by cotton stalks and soil lumps,sequentially.The RC of cotton stalks decreased with the increase of moisture content and diameter,while it increased at first and then decreased with the increase of length.As the release height was less than 500 mm,the RC increased with the increased release height.As the collision angle was less than 40°,the RC showed a linear increasing trend.The significance of the effects of factors on RC decreased with the following sequence:collision angle,length,release height,diameter,and moisture content.Length,collision angle,and release height were extremely significant.The contrast test results showed that the values based on Newton’s restitution coefficient method were smaller than that based on the energy restitution coefficient method.The verification test showed that the predicted rebound height of cotton stalks calculated based on the energy restitution coefficient method was closer to the actual rebound height,and the relative error was less than 5%.

Enhancement of methane yield from cotton stalks by mechanical pre-treatment

Cotton stalks(CS)are lignocellulosic agricultural by-products,a potential source for biogas production,but pretreatment must be considered since hydrolysis is the rate-limiting stage for lignocellulosic biomass substrates.This study investigates the feasibility of mechanical pretreatment of CS to enhance methane production.Batch anaerobic digestion of CS samples with particle sizes ranging from 0.5 to 65 mm was carried out in 1 L eudiometer batch digesters for 48 days at 37◦C.Results showed that methane yield was inversely proportional to particle size,and the quality of biogas was good(54.0-55.2%CH_(4)).Significant increases in methane yield were observed with 20.3%and 26%for samples with a particle size of 3 mm and 0.5 mm,respectively,compared to untreated CS.The coefficient of anaerobic energy turnover was relatively low(20.2-25.5%).Reduction of the CS particle size to 3 mm or less is recommended to achieve effective methane conversion and decrease the retention time in an anaerobic digester from 31 to about 25 days.However,to offset the high energy demand required for grinding,further research should be conducted in combining size reduction with chemical and physicochemical pretreatment.

Mathematical modeling of microwave drying of crashed cotton stalks for man-made composite material

Drying characteristics,energy consumption and drying kinetics modeling of crashed cotton stalks dried in a microwave dryer were investigated in this research.A microwave dryer with an output power of 1000 W and 2450 MHz was employed,and the effects of material load ranging from 50 g to 250 g on drying time,drying rate,drying efficiency and specific energy consumption were evaluated.The results showed that drying rate decreased with drying duration.A rising rate period was followed by a falling rate period and the overall drying process occurred in the falling rate period.Six mathematical models were used to fit the drying rates data of crashed cotton stalks,and Midilli et al.model was found the best prediction model by comparing R2,RMSE andχ^(2)values between experimental and predicted moisture ratios.With decrease in material load from 250 g to 50 g,effective moisture diffusivity increased from 2.8668×10^(-8)m^(2)/s to 7.9817×10^(-8)m^(2)/s.Results also indicated that drying efficiency and specific energy consumption significantly increased with the increase of the material load.Average drying efficiency and specific energy consumption varied in the range of 7.52%-19.78%and 12.49-35.90 MJ/kg water,respectively.There were a lowest energy consumption of 10.99 MJ/kg water and a highest drying efficiency of 17.13%at the material load level of 250 g.

Influence of the Addition of Cotton Stalk during Co-pyrolysis with Sewage Sludge on the Properties, Surface Characteristics, and Ecological Risks of Biochars

Sewage sludge produced by municipal sewage treatment plants can potentially be used as a biomass energy source because of its high organic content.Presently,the conversion and utilization of rapidly growing amounts of sewage sludge represent an urgent challenge in China.Thermal conversion of sewage sludge to biochar through pyrolysis is a promising solution to this problem.However,biochar produced by pyrolysis of sewage sludge alone has a poor pore structure as a result of its low C content and high ash content.Furthermore,it is enriched in heavy metals that may pose high ecological risks.In this study,we addressed these issues through co-pyrolysis of sewage sludge and cotton stalks(1:1,wt./wt.)at different pyrolysis temperatures ranging from 350℃ to 750℃.The properties and surface characteristics of the biochars were investigated.Meanwhile,the transformation behavior of heavy metals during the co-pyrolysis process was studied,and the potential ecological risks of heavy metals in biochars were assessed.The results showed that elevated pyrolysis temperatures reduced the biochar yield and C content of the biochars,whereas such temperatures increased the pH value and ash content of the biochars.The biochars prepared at different pyrolysis temperatures were all mesoporous materials.The elevated temperatures promoted the transformation of heavy metals from mobile fractions to stable ones,thus resulting in a significant decrease in the ecological risks.In summary,co-pyrolysis of sewage sludge with cotton stalks proved to be a feasible method for the conversion and utilization of sewage sludge.

棉秆和油页岩共热解生物炭的氨氮吸附性能研究

使用棉秆(CS)和油页岩(OS)为原料,采用共热解的方式制备了共热解生物炭,探究了对氨氮的吸附性能。考察了不同热解时间、CS和OS比例、热解温度、CS的粒径对共热解生物炭的氨氮吸附量的影响规律,确定了最佳制备条件,并研究了吸附动力学和吸附等温线模型。研究表明,棉秆和油页岩共热解后生物炭的结构特性和表面形貌有较大改善,对氨氮的吸附能力有明显的提高。最佳的制备条件是热解温度为500℃、m(棉秆)∶m(油页岩)=3∶1、热解时间为30 min和CS的粒径为0.20~0.30 mm。在投加量为10.0 g/L、pH 9.0时,最佳条件所制备炭的吸附量为4.89 mg/g,是棉秆生物炭的2.2倍。吸附过程以准二级动力学和Langmuir等温吸附模型描述。吸附机制主要包括为离子交换、静电吸附和配位作用。

快速和慢速热解对棉秆生物炭理化特性及土壤持水量的影响

以新疆棉秆为原料,在300~700℃下利用快速和慢速热解方式制备了生物炭,研究了快速和慢速热解对棉秆生物炭形貌、表面官能团、pH值、元素组成的影响.利用室内土柱试验,研究了不同条件下制备的生物炭对土壤持水量的影响.结果表明:1)随着热解温度的升高,生物炭产率下降,pH值提高,孔隙度增加.快速热解生物炭具有孔隙发达、芳香性高、稳定性强的优点.2)土壤持水量随着生物炭添加量和热解温度的升高而提高.生物炭添加量为0.03 g/g时,土壤持水量分别为51.7%和49.7%,比未添加生物炭提高了32.5%和27.4%.3)添加生物炭土壤15 d后保水量仍有40.3%,远高于纯土壤,且添加快速热解生物炭的土壤保水量高于慢速热解生物炭.

A Comprehensive Analysis of the Thermo-Chemical Properties of Sudanese Biomass for Sustainable Applications

The chemical composition and thermal properties of natural fibers are the most critical variables that determine the overall properties of the fibers and influence their processing and use in different sustainable applications,such as their conversion into bioenergy and biocomposites.Their thermal and mechanical properties can be estimated by evaluating the content of cellulose,lignin,and other extractives in the fibers.In this research work,the chemical composition and thermal properties of three fibers,namely bagasse,kenaf bast fibers,and cotton stalks,were evaluated to assess their potential utilization in producing biocomposites and bioenergy materials.The chemical composition analysis followed the Technical Association of the Pulp and Paper Industry Standards(TAPPI)methods.The total phenol content was quantified using the Folin-Ciocalteu method,while Fourier Transform Infrared Spectroscopy(FTIR)was employed to assess the light absorption by the bonds.To evaluate thermal stability and higher heating values,Thermogravimetric Analysis(TGA),Differential Scanning Calorimetry(DSC),and bomb calorimetry were performed.The chemical analysis revealed that bagasse contained 50.6%cellulose and 21.6%lignin,kenaf bast fibers had 58.5%cellulose and 10%lignin,and cotton stalks exhibited 40.3%cellulose and 21.3%lignin.The FTIR curves demonstrated a notable similarity among the fibers.The TGA analysis showed degradation temperatures of 321°C for bagasse,354°C for kenaf bast fibers,and 289°C for cotton stalks.The DSC analysis revealed glass transition temperatures of 81°C for bagasse,66.3°C for cotton stalks,and 64.5°C for kenaf bast fibers.The higher heating values were measured as 17.3,16.6 and 17.1 MJ/kg for bagasse,kenaf bast fibers,and cotton stalks,respectively.The three fibers have a high potential for biocomposites and bioenergy material manufacturing.

新疆棉花经济效益及其副产物在动物养殖中的饲用价值

新疆棉花产业蓬勃发展,其副产物棉秆和棉籽粕在动物养殖中扮演着重要角色。棉秆为干旱地区珍贵饲料,可提供必要营养并保障畜群健康。棉籽粕是高质量饲料原料,含丰富的蛋白质和营养成分,助推畜禽生长发育。合理利用这些副产物不仅可以提升饲料品质,也可增强动物生产性能。尽管需进一步加强研发与推广,以提高利用率和降低生产成本,但深入挖掘棉秆和棉籽粕在畜牧业的潜在价值有助于提升经济效益,促进畜牧业可持续发展。

KOH含量对棉秆碳结构特征及锂硫电池正极性能的影响

以棉秆为生物质源、KOH为活化剂、单质硫为储能物质,采用炭化-活化-高压3步法制备高性能碳硫复合材料,并探究KOH用量对活性碳结构以及复合材料电化学性能的影响。结果表明,KOH的活化促进了活性碳中10 nm以下孔的发育,碳碱质量比(棉秆碳化后的碳:KOH质量比)为1∶4时活性碳的比表面积和孔体积达到最大,分别为3068.15 m^(2)/g和1.68 cm^(3)/g。过量的KOH活化导致3~9 nm部分孔的坍塌,使得微孔/小介孔向大介孔或大孔转化,比表面积和孔体积缩小。复合材料的电化学性能和活性碳的孔体积呈正相关,碳碱质量比为1∶4时制备的活性碳与硫进行复合的碳硫复合材料展现出最佳的电化学性能。在0.1 C的电流密度下经过100次循环之后,仍可保留787 mAh/g的放电容量;在2 C的电流密度下也可展现出582 mAh/g的高比容量。

棉秆掺烧对燃煤锅炉燃烧特性影响的数值模拟研究

以某热电公司330 MW锅炉为研究对象,基于Fluent数值模拟软件对煤粉与棉秆混燃特性进行研究。以其结构参数与运行参数为依据,研究纯煤工况以及生物质不同掺烧比例、不同掺烧方式的6种工况。通过分析各个工况时炉膛的速度场、温度场、烟气组分及污染物NO的变化趋势,确定出最佳燃烧方式以提高燃煤效率,减少NO污染物排放。结果显示:相比于纯煤燃烧,掺烧棉秆后炉内主燃区温度降低,炉膛出口O_(2)含量减少,NO排放量随掺烧比例增大而减小。在掺烧方式的比较中,只在D层喷入棉秆有利于减少NO排放,其NO排放率较混合燃烧工况降低了15.2%。

淖毛湖煤和棉秆共热解协同效应分析

煤和生物质共热解过程中,填料方式会显著影响挥发分之间相互作用及产物分布。分析分隔放置(Case 1)、机械混合(Case 2)、煤在棉秆上层(Case 3)和煤在棉秆下层(Case 4)4种填料方式下淖毛湖煤(NMH)和棉秆(CS)共热解产物的分布、组成及性质,并结合分形理论研究共热解半焦的孔隙特征,探究共热解协同效应。结果表明,NMH和CS协同作用因填料方式不同而变化,填料方式对共热解产物分布及性质影响大。用Case 4方式时,共热解焦油产率最高,为15.94%,较理论计算值增加3.89%,正协同效应最显著。此时,CS热解产生的富氢组分及时与NMH热解挥发物发生交互作用,导致H_(2)、CH_(4)和C_(2)~C_(4)产量较理论值降低,共热解焦油产率增加。不同填料方式对共热解焦油中轻油馏分均产生负协同作用。含氧化合物相对含量减少可能是因为共热解过程促进脱氧反应(如脱羧和脱羰基化等),进一步生成脂肪烃,减少含氧官能团发生交联反应;在共热解中,·H自由基与活性含氧基团产生正协同作用,促使焦油中O、N、S原子向固体或气体产物转移。由半焦分形结果可知半焦分形维数D_(1)和D_(2)均在2~3间,说明半焦粗糙度和孔结构均满足分形结构基本特征。对于Case 3和Case 4方式,位于下层样品半焦的表面更粗糙。用Case 3方式所得CS-C孔隙更小;而Case 4方式所得NMH-C孔隙更不均匀,孔结构更复杂。

水热及水热氧化预处理对棉秆基成型炭和活性炭性能的影响

水热及水热氧化预处理可以调整生物质内部组分占比,有效促进生物质资源多元化利用。以棉秆为实验原料,经160℃~260℃水热及水热氧化预处理后制备成型炭和活性炭,并使用范式法、热重分析和X射线光电子能谱等测试手段,分析了水热及水热氧化预处理后生物质内部组分的演变对棉秆基成型炭和活性炭的产率、理化性能的影响。结果表明:水热及水热氧化预处理后棉秆中半纤维素和纤维素的分解有利于成型炭的产率和能量密度的增加;与水热预处理相比,水热氧化预处理进一步提高了成型炭的产率及热值,可在一定程度上降低预处理强度;棉秆基活性炭的总产率受预处理产率和活化产率的综合影响;随着水热及水热氧化预处理温度的升高,活性炭总产率呈现先升高后降低趋势,并在预处理温度为200℃获得的最大产率分别为36.95%和29.17%;与原料活性炭相比,水热及水热氧化预处理棉秆基活性炭的前驱体表面含氧官能团含量显著提升,有利于后续的氯化锌活化,得到的活性炭比表面积显著增加,吸附性能更优;此外,在180℃和200℃下水热氧化后的棉秆基活性炭碘吸附值均达到GB/T 13803.2-1999制净水用活性炭的二级品标准。

基于微型流化床的油页岩与棉秆共热解特性及其动力学

采用微型流化床反应分析仪分析油页岩与棉秆共热解特性,探讨不同热解温度和混合比例对H_(2)、CH_(4)、CO、CO_(2)释放特性的影响,并利用等转化率法求解动力学参数,研究共热解过程中的相互作用。结果表明,油页岩和棉秆的单独热解气体释放特性存在明显差异,而在等温共热解过程中,棉秆的添加能加快反应的转化率,提高气体生成速率。通过Friedman-Reich-Levi方法计算气体生成活化能,结果显示共热解活化能明显低于理论值,表明共热解能提高原料热解反应性,促进气体的生成。

响应面法优化棉秆水热液化生产腐植酸的运行条件

为优化棉秆水热液化生产含腐植酸液态肥的运行条件,确定反应条件间的交互作用及其反应产物的组成,采用三因素三水平的响应面分析方法,探究了反应温度(X1,260~340℃)、反应时间(X2,30~90 min)和物料质量分数(X3,5%~10%)对水溶肥腐植酸产率的影响。回归模型方差分析表明,反应温度、反应时间以及物料质量分数均对腐植酸产率有较大影响。其中,物料质量分数是最重要的参数。腐植酸产率的最佳反应条件为:反应温度300℃,反应时间90 min,物料质量分数10%。在此条件下,腐植酸产率为4.10%,高于国家含腐植酸水溶肥标准(NY 1106—2010)中规定的腐植酸含量(不小于3%),与预测值吻合较好。GC-MS分析表明,棉秆水热液化的水溶性产物主要含有酚类及其衍生物、酮类、醛类、醇类以及有机酸化合物。