Lowering ash slagging and fouling tendency of high-alkali coal by hydrothermal pretreatment

High-alkali species in coal are notorious for causing ash slagging and fouling incidents.In this paper,four high-alkali coals were individually subject to hydrothermal pretreatment(HTP),within a batch-type autoclave at 300 -C for 1 h,and the treated coals were analyzed,along with the oxygen-containing functional groups determined by Fourier transform infrared spectrometer(FT-IR).Then the alkali species and other components in the coal ash were quantified by X-ray fluorescence(XRF)for evaluating the ash slagging and fouling tendency.Apart from this,FactSage was adopted to simulate the occurrence and transformation of alkali species during coal thermal conversion ending at various temperatures.The findings indicate that the treated coals are superior to the parent ones in terms of certain remarkable changes via HTP.The moisture,oxygen and sulfur of the hydrothermally treated coals decline obviously,while the calorific value rises sharply.HTP could reduce the alkali species to less than 2%(%,by weight,equivalent to Na2O in dry ash),with a maximum removal ratio of 88.9%,lowering the ash slagging and fouling tendency.The proposed mechanism of HTP was that the alkali species in coal matrix became released due to the breakage of the coal functional groups and micropores during HTP.

Comparative Study of Water-soluble and Alkali-soluble Hemicelluloses Extracted by Hydrothermal Pretreatment

The purpose of this study was to explore the differences of the hemicelluloses extracted by hydrothermal pretreatment using water and alkaline solutions(Na OH or KOH). The physicochemical properties and structural characteristics of two water-soluble and four alkali-soluble hemicelluloses extracted from the triploid of Populus tomentosa Carr. through the hydrothermal pretreatment were comparatively studied. It was observed that the alkalis(Na OH and KOH) were more effective than distilled water as extractants. Sugar analysis showed that xylose(66.83%~86.49%) was the major constituent, followed by glucose(6.83%~18.49%). Mannose(1.40%~8.42%), galactose(2.17%~4.05%), and arabinose(0.21%~2.26%) were also detected in the hemicellulosic fractions. The results of gelpermeation chromatography(GPC) indicated that the hemicelluloses extracted using the alkaline solutions had relatively higher molecular weights than those solubilized in distilled water. Further, based on spectroscopic ~1Hnuclear magnetic resonance(~1H-NMR) and two-dimensional heteronuclear singular quantum correlation(2D-HSQC) analyses, it was confirmed that the hemicellulosic fractions had a major structure of(1→4)-b-D-xylan and a minor structure of(1→4)-a-D-glucan with small amounts of substituted sugars and glucuronic acid attached.

Microwave-Alkaline Assisted Pretreatment of Banana Trunk for Bioethanol Production

Pretreatment is one of the most important steps in the production bioethanol from lignocellulose materials. Alkaline pretreatment is a common mean of pretreatment but microwave oven could assist its efficiency as it can reduce the pretreatment time and improve the enzymatic activity during hydrolysis. The aim of this paper is to determine lignin removal from banana trunk using microwave-assisted alkaline （NaOH and NH4OH） pretreatments. The best pretreatment conditions were used for mass pretreatment before hydrolysis and fermentation. The result shows that, optimum lignin removal was with microwave-assisted NaOH pretreatment with the removal of up to 98% lignin at 2% （w/v （weight/volum）） sodium hydroxide, 170 W microwave power at 10 rain. Microwave-assisted ammonium hydroxide pretreatment achieved 97% lignin removal at 1% ammonium hydroxide concentration and 680 W microwave power at 5 min. Microwave- alkaline assisted pretreatment increased the yield and quality of fermentable sugar after enzyme hydrolysis with NH4OH and ammonium hydroxide yielding 40% and 39% of ethanol, respectively. This result reveals that, well controlled microwave- alkaline assisted pretreatment of banana trunk could effectively remove lignin and give high bioethanol yield.

Etherification of Alkali-pretreated Sugarcane Bagasse Cellulose in Tetrahydrofuran

Sugarcane bagasse(SCB)is an important by-product in the sugar industry.It is a source of cellulose fibers or cellulose for paper mills and textiles factories.In this study,SCB was ethyl etherified in tetrahydrofuran(THF)after alkali pretreatment.The alkali concentration for the pretreatment,the ratio of ethyl bromide(EtBr)to dried SCB in the reaction,reaction time,and temperature were investigated for the etherification of SCB.The ethoxyl content and characterization of the product were determined using headspace gas chromatography(HS-GC),Fourier Transform Infrared(FT-IR)and 13C-NMR spectroscopy,respectively.It was found that SCB was well-etherified with EtBr in alkali-THF.Upon ethylation of SCB,the ethoxyl content of the product was high when the alkali concentration and the ratio of EtBr to dried SCB were controlled from 50%to 75%and 4:1(V/w)to 6:1(V/w),respectively.The reaction occurred optimally when the temperature was controlled below 110℃;above this temperature,the degree of etherification decreased.The thermal stability of ethylated SCB was higher than that of SCB but slightly lower than that of commercial ethyl cellulose.Ethylated SCB has the potential to form composites with many materials because it is soluble in a wide variety of solvents.

Multi-Scale Structural Studies of Sequential Ionic Liquids and Alkali Pretreated Corn Stover and Sugarcane Bagasse

The complexity of plant cell walls impedes the conversion of cellulosic biomass to sugars. Pretreatment becomes a necessity to increase the digestibility of biomass. An in-depth understanding of the structure and underlying mechanisms governing deconstruction process is important. In the present study, the comprehensive investigation of morphological and structural changes in corn stover and sugarcane bagasse following ionic liquids dissolution and alkaline extraction was done using Fourier transform infrared spectroscopy, Thermogravimetric analysis, Confocal scanning laser microscopy, Atomic force microscopy and Dynamic light scattering studies. Both the substrates were pretreated with ILs 1-ethyl-3-methylimidazolium acetate and 1-butyl-3-methylimidazolium acetate followed by alkaline extraction. The pronounced changes such as lignin, hemicelluloses removal and decreased cellulose crystallinity after the pretreatments lead to the structural transformation of matrix polymers. The enzymatic hydrolysis showed 90% theoretical sugar yield in case of sugarcane bagasse and 80% in corn stover following synergistically combined pretreatments.

Quantitative Extraction of p-Coumaric Acid and Ferulic Acid in Different Gramineous Materials and Structural Changes of Residual Alkali Lignin

Ferulic acid(FA)and p-coumaric acid(pCA)in bagasse,wheat straw,corn straw,and corncob were extracted by alkaline hydrolysis and characterized by gas chromatography(GC)and gas chromatography-mass spectrometry(GC-MS).It was found that the FA and most of the pCA in gramineous biomass could be dissociated and released after being treated with 1 M NaOH at 100℃for 4 h.The yields of pCA/FA in bagasse,wheat straw,corn straw,and corncob determined by GC-FID are 39.8/11.5,13.7/11.0,28.0/11.0,and 35.1/14.5 mg/g,respectively.The raw materials and the treated solid residues were characterized by gel-state 2D Heteronuclear Single Quantum Coherence Nuclear Magnetic Resonance(2D HSQC NMR).It was found that only a small amount of lignin was detected in the residue after alkali treatment,indicating that the alkali treatment conditions can effectively cleave the FA and pCA.Additionally,the lignin in the alkali solution was recovered and characterized by 2D HSQC NMR.The FA was not able to be detected by NMR,whereas a small amount of pCA remained in the alkali lignin.This study reveals the structural change of residual lignins during the quantitative isolation of FA and pCA,which is essential for the selective isolation of pCA/FA and valorization of residual alkali lignin.

亚麻催化氧化与碱煮一浴脱胶工艺及其性能

使用棉纺系统进行亚麻纺纱前需经过脱胶处理,为解决传统碱脱胶工艺得到的亚麻纤维白度低和氧化脱胶时纤维易氧化受损、木质素残留造成纤维断裂伸长率低的问题,采用N-羟基-3,4,5,6-四苯基邻苯二甲酰亚胺(NHTPPI)催化氧化与碱煮一浴的方法对亚麻落麻进行脱胶,研究了pH值,反应温度以及催化剂NHTPPI、助催化剂9,10-蒽醌、双氧水、氢氧化钠质量浓度等因素对脱胶后亚麻纤维断裂强度以及白度的影响,得到了NHTPPI催化氧化与碱煮一浴亚麻脱胶的最佳工艺:pH值为10.5,反应温度为83.6℃,NHTPPI、9,10-蒽醌、双氧水、氢氧化钠质量浓度分别为0.6、0.5、10.35、5.67 g/L,此优化条件下得到的亚麻纤维断裂强度为4.39 cN/dtex,白度为70.53%。将催化氧化与碱煮一浴脱胶、高碘酸钠氧化脱胶以及传统碱脱胶与双氧水漂白3种工艺进行对比,发现3种工艺得到的纤维主体长度在28 mm左右,白度均在70%以上,但催化氧化与碱煮一浴脱胶得到的亚麻纤维断裂强度最高,处理时间最短。

灰分中碱和碱土金属对生物质快速热解生物油组分的影响

生物质灰分中的碱和碱土金属(AAEMs)对快速热解生物油的产率和组分分布具有显著影响。本研究选取玉米秸秆为原料,研究梯级脱灰预处理(蒸馏水、醋酸铵和盐酸)对AAEMs的选择性脱除及其生物油组分的影响,研究了碱和碱土金属类别(K、Ca、Na和Mg)、盐质量分数(0.5%、2.5%、5%)和不同钾盐的酸根(SO_(4)^(2-)、NO_(3)^(-)、CO_(3)^(2-)、HCO_(3)^(-)、AC^(-)、PO_(4)^(3-))对生物油组分的影响。结果表明,在梯级脱灰预处理过程中,随着脱灰溶液酸性程度加深,AAEMs的脱除率逐渐上升,根据AAEMs在梯级脱灰过程中的选择性脱除规律,可将其在生物质中的赋存形态分为水溶性(K)、离子交换性(Ca和Mg)和酸溶性(Na)等形态。经过碱和碱土金属盐浸渍后,AAEMs将起到催化剂的作用,促进热解中间产物左旋葡聚糖的二次降解,导致其相对含量显著降低,形成更多的呋喃和酮类等轻质含氧化合物,导致2,3-二氢苯并呋喃、酮类和长链烷烃等组分的含量显著增加。不同钾盐酸根离子对脱水糖的二次裂解反应及木质素芳基醚键和酚羟基的裂解反应具有较大的影响,根据酸根的酸性强弱,对脱水糖裂解反应的影响大小顺序为HCO_(3)^(-)>CO_(3)^(2-)>AC^(-)>PO_(4)^(3-)>Cl^(-)>NO_(3)^(-)>SO_(4)^(2-),而对木质素芳基醚键和酚羟基的裂解反应影响大小顺序为CO_(3)^(2)->Cl^(-)>HCO_(3)^(-)PO_(4)^(3-)≈AC^(-)>SO_(4)^(2-)≈NO_(3)^(-).

苯氧乙醇耦合酸/碱预处理竹屑中残留木质素对其纤维素酶水解的影响

以竹加工剩余物竹屑为对象,探究苯氧乙醇耦合酸/碱溶液预处理竹屑,分析了预处理后竹屑中残留木质素的结构特性和理化性质,并通过荧光光谱和表面等离子共振技术揭示不同方法预处理后的竹屑中残留木质素对纤维素酶的非生产性吸附机制。结果表明:随着苯氧乙醇体系中酸/碱加入,酶解72 h预处理竹屑的纤维素酶解得率从9.39%提高到67.38%和55.41%。对残留木质素进行表征,发现当温度升高,木质素的紫丁香基/愈创木基结构单元(S/G)的比值增高,且木质素相对分子质量分布更均匀。2D-HSQC NMR、^(31)P NMR、表面电荷及疏水性等测试结果表明:木质素对纤维素酶水解的抑制作用与其酚羟基含量、疏水性和Zeta电位有关。荧光光谱和表面等离子共振技术表明:木质素与纤维素酶作用的主要驱动力类型与预处理温度、苯氧乙醇体系中酸/碱溶液的加入相关。不同预处理竹屑中木质素与纤维素酶的亲和力不同,其中纯苯氧乙醇预处理竹屑中木质素与纤维素酶的亲和力最高,其次为纯酸/纯碱溶液预处理的木质素,而苯氧乙醇与酸/碱耦合预处理竹屑中木质素对纤维素酶的亲和力最低。

低共熔溶剂处理木质素抗菌纸的制备及性能研究

利用对甲苯磺酸/氯化胆碱(TA/CC)制备的低共熔溶剂(DES)处理碱木质素,提取得到富含酚类的木质素精油,将其添加到杨木浆中,制备了抗菌纸。结果表明,DES处理后得到的木质素精油中含有大量酚羟基,制得的抗菌纸对大肠杆菌的抗菌率约100%,在食品包装用纸、医疗用纸等领域具有较大的应用潜力。

化学法预处理剩余污泥制备碳源的研究进展

剩余污泥(WAS)作为城市污水处理厂运行的必然产物,其产量也在逐年增加。WAS中含有大量的未稳定的有机物,针对此类有机物的资源化利用无疑会给污泥的减量化处置带来实际意义。WAS厌氧发酵产生的短链脂肪酸(SCFAs)被公认为优质碳源,但污泥水解是厌氧发酵的限速步骤,需要通过预处理方法促进污泥水解,从而提高SCFAs产量。本文综述了化学预处理剩余污泥中碱解预处理、氧化剂预处理和联合预处理等预处理方法研究进展,为以后以剩余污泥水解液为碳源的工艺提供技术指导。

新型聚酰胺66织物的低碱前处理

针对PA66织物前处理碱剂浓度高、浆料容易反沾、布面白度低、手感差、清洗困难以及耗水量大等问题,通过选用合适的碱剂与精练剂,实现了PA66织物冷轧堆+平幅处理的两步法前处理的短流程工艺,不仅提升了加工效率,而且减少了氢氧化钠的用量,降低了前处理成本以及前处理污水负担。

剩余污泥热碱脱水过程中胞内外抗生素抗性基因丰度变化分析

剩余污泥含有高丰度的抗生素抗性基因(ARGs)。随着剩余污泥的脱水,胞内ARGs(iARGs)可能会逐渐转化为胞外ARGs(eARGs)。为探究ARGs在剩余污泥脱水过程中的分布特征,分析了热碱预处理(TAP)对剩余污泥脱水前后iARGs和eARGs丰度的变化。结果表明,TAP能够有效提高污泥脱水率,并且借助响应曲面法(RSM)确定了最优工况,在pH=11、温度90℃条件下处理80 min后,其脱水率达到41.0%。随着脱水率提升,iARGs不断转化形成eARGs,TAP后污泥滤液中eARGs的绝对丰度常用对数提高了0.2~1.8。eARGs丰度的上升,增加了ARGs传播风险,给污泥脱水技术带来了巨大挑战。

碱蚀剂缓蚀机理研究

配置高浓度碱低比例碱蚀剂、低浓度碱低比例碱蚀剂、高浓度碱高比例碱蚀剂和碱蚀剂失效后补加碱蚀剂的4组碱蚀溶液,对其进行溶铝试验,通过测量溶液Al^(3+)和NaOH的浓度、试验铝块的质量变化情况,研究碱蚀剂对溶铝速率的影响,并结合溶液颜色变化情况,分析碱蚀剂的缓蚀机理。结果表明,碱蚀剂的添加可以提高溶液中溶存铝上限,抑制溶液中NaAlO_(2)水解,间接降低溶液溶铝速率;耗铝量的增加会导致碱蚀剂失效;缓蚀剂失效后,溶液中会产生大量白色沉淀,NaOH浓度大幅度提高,Al^(3+)浓度大幅度降低,导致溶液溶铝速率提高,危害生产。

玉米秸秆中还原糖的预提取及其对制浆性能的影响

本研究通过碱(NaOH)和酸(HCl)预处理以提取玉米秸秆中的还原糖,采用扫描电子显微镜观察玉米秸秆预处理前后的形态变化,探究了预处理前后玉米秸秆的制浆性能及纸张强度性能。结果表明,在150℃,NaOH和HCl用量分别为6%,预处理时间120 min条件下,玉米秸秆的酸、碱抽提的还原糖(Trs)得率分别为34.2%和14.5%。其中,酸预处理玉米秸秆在碱用量为12%蒸煮时,纸浆得率最高,为48.1%。此外,酸和碱预处理后纸张撕裂指数分别降低了18%和13%,抗张指数也呈现下降趋势,分别降低了28%和16%,耐破指数分别降低了60%和41%。因此,预处理过程中半纤维素的损失会导致纸张强度性能降低。

蔗渣预处理发酵产纤维素酶研究

纤维素预处理可以使纤维素与木质素、半纤维素分开,从而提高酶类对纤维素和半纤维素的可及度,提高纤维素水解率。本实验采用蔗渣为原料,将其粉碎后分别用40、60、80、100目的筛子过筛得到各种粗细程度不同的蔗渣。然后用2%稀硫酸和10%氨水联合对其进行预处理,再以预处理过的蔗渣为碳源培养绿色木霉研究其产酶情况。先以10% NH_(4)OH处理,再用2% H_(2)SO_(4)的处理经发酵后滤纸酶活为6.90 U/mL,达到最高。先以2% H_(2)SO_(4)处理再用10% NH_(4)OH的预处理方法滤纸酶活为6.79 U/mL。经过预处理的蔗渣培养所产滤纸酶活力从高到低排列:(碱/酸)预处理>(酸/碱)预处理>酸预处理>碱预处理>未处理。在同种处理方法下过80目筛子所得的蔗渣所产的滤纸酶活力最高,其酶活力从高到低排列:80目>60目>40目>100目。

真空冷冻干燥前预处理改善猕猴桃鲜果片品质的分析

该文以“徐香”猕猴桃为原料,采用“加热+弱碱性盐浸泡”的预处理方法,通过改善真空冷冻干燥前猕猴桃鲜果片的品质,以改善真空冷冻干燥猕猴桃果片的品质。结果表明,升高加热温度和延长加热时间会显著改变鲜果片的外观颜色并增加鲜果片中营养损失。碳酸钠浓度和碳酸钠浸泡时间会显著影响鲜果片中的含酸量和营养物质。用最适浓度的碳酸钠浸泡处理可在显著降低鲜果片中总酸含量的同时,较大限度地保留果片中的营养物质。预处理最适条件为猕猴桃鲜果片在50.00℃下加热10.00min后,用3.00%的碳酸钠浸泡20.00min,预处理后猕猴桃果片外观色泽发生轻微改变,但组织结构物无明显变化。感官评价结果表明,预处理前后猕猴桃果片的口感由“偏酸”变为“微甜中略带酸”,感官评分由7.74提升为8.32。

苎麻的果胶酶/木聚糖酶复合生物酶脱胶

麻脱胶是麻纤维制品加工中的重要工序,试验以失重率、残胶率、白度、束纤维强度、液体芯吸高度等为评价指标,对比了果胶酶、木聚糖酶、果胶酶/木聚糖酶复合脱胶的应用效果。结果表明:热水/机械预处理、碱氧后处理对复合酶脱胶具有协同增效作用;相对于传统碱法脱胶,生物酶复合脱胶法不仅具有节能环保、作用条件温和的优势,同时能更好地保留苎麻固有特性,提高精干麻品质。

碱联合微波预处理污泥及交联聚合回收上清液中有机质和氮磷

从污泥中回收有机组分是实现污泥的妥善处理和资源再利用的理想途径.本研究系统考察了碱联合微波处理下污泥中有机质及氮磷的释放特征,同时使用甲基三乙酰氧基硅烷(methyltriacetoxysilane,MTAC)以絮凝聚合物的形式回收污泥上清液中的营养物质,并探究其内在机制.结果表明,碱联合微波处理能有效加速污泥的溶解和胞内物质释放,最佳处理条件为NaOH剂量1.12 g·L^(−1)污泥、碱处理时间40 min,微波辐射功率640 W、微波辐射时间120 s.碱联合微波处理比单独碱处理SCOD溶出浓度提高了97.6%,TN和TP分别增加了51.35%和25.13%.MTAC与上清液中营养物质通过交联、絮凝和团聚作用,有效地分离回收了营养物质,其中蛋白质、多糖、TN和TP回收率分别高达44.72%、58.49%、76.90%和48.71%.本研究证实了碱联合微波处理污泥,以MTAC为交联剂进行化学聚合,是一种污泥高效处置和资源回收的简单的替代策略.