改性粉煤灰对生活污水磷的吸附研究

采用单因素的试验方法研究各因素对改性粉煤灰吸附性能的影响.对改性粉煤灰处理含磷生活污水进行了正交实验研究,结果表明各因素对磷酸根的去除率的影响顺序为:水灰比>初始磷浓度>吸附时间>pH值,极差R分剐为7.3%、6.6%、3.9%和3.3%.在pH=6.5、水灰比V/M=16.7、吸附时间T=40min、初始磷浓度Co=8.0mg/L时粉煤灰具有最佳的除磷效果.粉煤灰吸附磷的行为符合H等温方程,方程为:Y=0.1092X相关系数:R=-0.99970     

生物质秸秆作为型煤粘结剂的研究

本研究探讨了用氢氧化钠改性生物质秸秆作为型煤粘结剂的可行性,考察了NaOH溶液浓度对生物质改性的影响以及生物质添加量、无机物(MgO和MgCl2)添加量对型煤机械强度、防水性能和着火温度的影响.研究结果表明NaOH改性液的浓度为1.0%～2.0%时,制得的生物质型煤有较高的机械强度;生物质添加量在2%～20%范围内时,随生物质量的增加,机械强度增加,着火温度降低,但防水性较差;而在生物质型煤中加入适量无机粘结剂(MgO和MgCl2)后,型煤有很高的浸水强度,表现出优越的防水性能;最后得出各项性能指标优异的改性生物质粘结剂的配方.     

活性污泥微波热解残余半焦吸附亚甲基蓝

采用活性污泥微波热解所得的残余半焦作为吸附剂,研究了其对亚甲基蓝的吸附效果.试验结果表明,当热解时间为15 min、热解原料中半焦添加量为10％的条件下,污泥半焦的吸附容量达到80.01 mg/g.动力学分析表明,亚甲基蓝在污泥半焦表面的吸附符合准二级动力学模型,吸附速率常数为6.83×10-4 g/(mg·min).分别用Langmuir和Freundlich等温方程对数据进行拟合,等温吸附过程能较好地用Freundlich吸附等温线描述,这表明磷在半焦表面的吸附受多种机制影响.     

污泥与不同生物质共热解制备生物炭及生物炭的土地应用

文章以乙酸钾为催化剂,在城市污泥中分别添加花生壳、玉米杆、玉米芯、稻草,采用间歇式反应釜在400℃下制备多种污泥-生物质生物炭,考察不同种类生物质的添加对生物炭产率及性能的影响,并对生物炭进行表征和分析。研究结果表明:与污泥生物炭相比,不同种类的污泥-生物质生物炭的H/C均减小,芳香性均增大;与污泥生物炭相比,不同种类的污泥-生物质生物炭的比表面积和总孔体积均增大,平均孔径均减小,其中,污泥-玉米杆生物炭的BET比表面积最大,为26.062 m~2/g;与污泥生物炭相比,不同种类的污泥-生物质生物炭的碘吸附性能均有所提高,其中,污泥-玉米芯生物炭的碘吸附值最大,为438.49 mg/g;污泥-生物质生物炭呈碱性并含有一定量的速效氮、速效磷、有机质等营养物质,污泥-生物质生物炭的重金属含量(Zn除外)均远低于农业用地标准值,有作为土壤改良剂或肥料缓释载体的应用前景。     

醋酸酯淀粉粘结生物质炭基肥抗压及缓释性能研究

为探究粘结剂、成肥条件等因素对生物质炭基肥料性能的影响,文章以松子壳为生物质原料,利用实验室自制的生物质连续热解炭化装置在反应温度为500℃、驻留时间为8 min条件下制备生物质炭,以醋酸酯淀粉为粘结剂,利用圆盘造粒的方式制备颗粒状炭基肥。通过测定颗粒肥料抗压性能及养分释放效果,研究粘结剂浓度、生物质炭颗粒度、圆盘倾角、肥料品种4个因素对生物质炭基肥抗压性能以及缓释性能的影响。结果表明:在圆盘倾角为50°,粘结剂浓度为50%,炭粉过100目筛时,抗压性能最强;总体性能上,粘结剂浓度为50%,炭粉过60目筛,圆盘倾角为50°条件下制备的炭基肥缓释性能最佳。该研究可以为生物质炭基肥的制备和应用提供参考。     

原料种类及热解温度对生物质炭理化特性影响的试验研究北大核心CSCD

为探究生物质原料和热解温度对生物质炭理化特性的影响,文章分别对松子壳、油茶壳、木屑和稻壳进行连续热解试验,获得生物质炭产物。通过对生物质炭的产率、工业分析与热值、吸附值、孔隙结构及表面官能团等理化特性的全面表征,研究原料种类及热解温度对生物质炭理化特性的影响。研究结果表明:松子壳炭、油茶壳炭、木屑炭的热值均大于标准热煤的热值;原料的挥发分含量越高,生物质炭的产率就越低,原料的灰分含量与生物质炭的灰分含量的变化趋势相一致;当热解温度为500℃时,4种生物质炭均可以形成较丰富的中、大孔隙结构,但松子壳、油茶壳等硬壳类生物质炭的微孔更为发达;随着热解温度的升高,生物质炭产率不断下降,生物质炭所含官能团的种类发生变化,数量逐渐减少,孔隙数量也减少,生物质炭的吸附能力减弱。     

2021 年 1 期目录

以棉涤废料为炭前驱体,利用醋酸钙为模板剂,采用单因素法考察在不同热解温度、质量比和热解时间下制得的介孔炭对亚甲基蓝和四环素的吸附性能,从而筛选得到最佳制备工艺参数,同时利用氮气吸附?脱附曲线、扫描电镜、X射线衍射、红外光谱进行物化性能分析,并研究其对水中四环素的吸附规律。结果表明,制备棉涤废料基介孔炭的最佳工艺参数为：热解温度为800 ℃、醋酸钙和棉涤废料质量比为1.5∶1、热解时间为1.5 h。醋酸钙模板剂成孔性能优异,制得的介孔炭总比表面积高达1 106.630 m2·g?1,介孔率达到62%,对水中四环素的吸附过程符合Langmuir模型,为自发吸附,最大吸附值为506.40 mg·g?1。     

磁性花椒树枝生物炭对Cr(Ⅵ)的吸附特性研究

原生花椒树枝生物炭(PB)对Cr(Ⅵ)的吸附能力有限(10.91 mg/g),且在反应结束后回收困难。文章通过使用浓度为0.4,0.6,0.8,1.0 mol/L的Fe(NO₃)₃溶液浸渍花椒树枝粉末,然后在500℃的温度下热解制备磁性花椒树枝生物炭(MZB)。通过SEM,XRD,FTIR和BET等表征分析,结合批式吸附试验,研究了MZB的理化特性和对Cr(Ⅵ)的吸附性能。研究结果表明：Fe₃O₄成功地附载在MZB上,与PB相比,MZB表面的羟基数量增多,比表面积和总孔容增大;MZB6对Cr(Ⅵ)的吸附效果最佳,可达32.3 mg/g,低pH值条件有利于MZB对Cr(Ⅵ)的吸附。Langmuir模型和伪二阶动力学模型的拟合结果表明,MZB对Cr(Ⅵ)的去除是通过均相化学吸附进行的。MZB6在第5次吸附-解吸循环后,对Cr(Ⅵ)的去除率仍能达到54%。     

生物质灰渣对甲基橙废水的去除性能及机制

为将资源化生物质灰渣用于甲基橙(MO)废水的处理,在明确MO初始浓度、pH值、反应时间和温度影响的基础上,探讨MO去除的潜在机制和效果提升途径。结果表明,MO的去除随MO初始浓度的增加而增加,并在80 mg/L时趋于平衡。pH值为2时有利于吸附的进行,且MO去除在12 h内较为迅速,24 h后趋于平衡。Langmuir模型可较好地模拟生物质灰渣对MO的吸附过程,表明该吸附过程属于单分子层吸附,且对MO的理论最大吸附量为25.2 mg/g。此外,灰渣吸附MO能较好地被二级动力学拟合,说明化学吸附是MO去除的主控机制。FT-IR光谱进一步表明吸附机制主要由静电、表面络合物或沉淀等共同作用。此外,添加H₂O₂(最终质量浓度4%)可使MO的去除率提高67.2%,是提升灰渣对MO去除性能的有效途径。     

基于正交试验制备废弃原棉活性炭及其吸附亚甲基蓝的研究

以废弃原棉(简称"原棉")为原料,采用FeCl_3/ZnCl_2混合物为活化剂制备活性炭,以活性炭得率和碘吸附值为试验指标,采用正交法考察了活化剂质量比、活化温度以及活化时间的影响,从而得到最优工艺参数:FeCl_3/ZnCl_2质量比为1∶1、活化温度为400℃以及活化时间为1 h。将最优样(AC-Fe/Zn)应用于吸附阳离子有机染料亚甲基蓝实验,结果表明:吸附过程符合Langmuir吸附等温模型,最大吸附量为342.87 mg·g~(-1)。     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.