硝化细菌脱氨氮预处理对鸡粪和玉米秸秆混合厌氧发酵的影响

在发酵温度为40℃,发酵底物TS含量分别为12%,16%和20%的条件下,将经过硝化细菌脱氨氮预处理的鸡粪以及未经预处理的鸡粪分别与玉米秸秆进行混合厌氧发酵,并研究发酵过程中沼气日产量、沼气累计产量、氨氮浓度、TS和VS降解率等参数的变化规律。研究结果表明:在发酵过程的前15 d,当发酵底物的TS含量分别为12%,16%,20%时,经过预处理的试验组的沼气日产量平均值分别为593.1,550.9,355.1 mL/d,未经预处理的试验组的沼气日产量平均值分别为420.8,379.2,433.4 mL/d;与未经预处理的试验组相比,经过预处理的试验组的累积沼气产量更高;在整个发酵过程中,各试验组的氨氮浓度均呈现出逐渐上升的变化趋势;脱氨氮预处理能够提高发酵前物料的挥发性脂肪酸浓度;当发酵底物的TS含量分别为12%,16%和20%时,相比于未经预处理的试验组,经过预处理的试验组的TS降解率分别提高了1.9%,7.9%和17.4%,VS降解率分别提高了2.2%,3.3%和28.4%,纤维素降解率分别提高了1.1%,4.6%和26.0%,半纤维素降解率分别提高了0.1%,1.3%和25.5%。     

华南地区稻草的厌氧干发酵制取沼气研究

研究了经过C/N调节和白腐菌预处理后的稻草在不同温度条件下的干发酵瓶试实验,并根据瓶试实验结果以及华南地区的气候条件,进行了常温1m3罐试实验.瓶试实验结果表明在35℃条件下秸秆干发酵较为稳定,具有较高的产气率、产甲烷率及沼气质量.1m3罐试实验在常温条件下运行89d,累积产气量22.6m3,且前45d的累积产气量约占总产气量的80.4%.发酵原料产气率为570L/kgVS,产甲烷率为240L/kgVS,甲烷百分含量最高可达62%.从pH值、产气量和甲烷百分含量来看,整个发酵过程均为正常发酵.通过循环发酵液的罐试实验表明,发酵液的循环能有效避免酸中毒并提高产气率和产甲烷率,对稻草干发酵而言,循环发酵液是一种较好的搅拌方式.该工艺可为华南地区稻草秸秆的资源化利用提供依据.     

厌氧消化菌群的筛选及其对高浓度玉米秸秆的厌氧消化

为了提高玉米秸秆类原料厌氧消化的产气率和底物利用率,从环境中筛选出了厌氧降解玉米秸秆产酸和产甲烷的优势菌群,该菌群的最高容积甲烷产率为0.73 m3/(m3.d),气体中的甲烷含量达到85%左右,底物产甲烷量为410 L/kg;以15%高浓度玉米秸秆为原料,该菌群的最大产酸能力为10 g/L,最高容积产气率为3.10m3/(m3.d),平均容积产气率为1.7 m3/(m3.d),平均甲烷含量为55%。研究结果明显高于报导过的相应数据。为高浓度玉米秸秆的高效厌氧消化利用提供了良好的微生物菌群应用基础。     

中药药渣预处理厌氧发酵产沼气初步研究

试验研究了沼液和NaOH用于药渣堆沤预处理对发酵过程的影响,以及接种量、pH值对于产气量的影响。结果表明:药渣经过沼液堆沤预处理后即可在较短的时间内高效发酵产沼气,发酵高峰为第2¹0天,此阶段产气为总产气量的95%以上;以秸秆沼液预处理后的药渣产气量最高,为11 940 mL,原料产气率为54.4L/kg干药渣。药渣发酵过程中无需添加畜禽粪便调节碳氮比,秸秆沼液中驯化富集的利于秸秆类物质分解的微生物可大大提高药渣的降解率。NaOH预处理可显著提高药渣的产气潜力,发酵持久且总产气量高。以质量分数5%的NaOH预处理10 d,原料(干药渣)产气率达196.8 L/kg。     

膨化技术用于玉米秸秆厌氧干发酵的试验研究

研究了膨化技术对玉米秸秆成分和结构的影响,并对膨化后原料进行厌氧干发酵试验研究。研究表明,玉米秸秆经膨化处理后,其还原糖量明显增加,纤维素的结晶度降低了12.68%,秸秆内部结构也发生了明显变化。膨化后玉米秸秆发酵启动快,产气效率和甲烷含量都比未膨化秸秆有所提高,最高产气率为0.916 m3/(m3.d),甲烷含量最高可达80.2%。     

热化学预处理玉米秸秆厌氧消化产气特性研究

以玉米秸秆为原料,对经热化学处理后的秸秆进行发酵试验,设置堆腐预处理和碱预处理玉米秸秆发酵作为对比试验。所得试验结果为:热化学预处理玉米秸秆单位容积最大日产气量为1.122 L/d,发酵30 d的单位容积累计产气量为15.995 L,平均甲烷含量为45.85%;发酵完成后,热化学预处理玉米秸秆总固体与挥发性去除率分别为35.50%与39.32%,比未处理玉米秸秆分别提高14.15%与10.64%。在对比发酵试验中,热化学预处理的处理效果与堆腐预处理相似,但低于碱预处理。     

黑曲霉AS0006预处理玉米秸秆产沼气研究

为了提高玉米秸秆与牛粪混合发酵的产气效率,文章对黑曲霉AS0006预处理后的玉米秸秆进行了研究,考察了不同预处理时间的玉米秸秆在混合厌氧发酵过程中的日产气量、累积产气量、TS和VS去除率以及木质纤维素去除率等发酵特性的变化情况。研究结果表明:黑曲霉AS0006对木质纤维素有较强的降解能力,玉米秸秆经黑曲霉AS0006预处理28 d后,纤维素、半纤维素和木质素的降解率分别为26.86%,11.93%和25.09%;经过黑曲霉AS0006预处理的玉米秸秆与牛粪混合发酵可以提高日产气量并缩短厌氧发酵周期,其中,预处理21 d后的玉米秸秆的产气高峰最大,为523.4 mL/d;经过黑曲霉AS0006预处理的玉米秸秆与牛粪混合发酵后, TS和VS去除率以及木质纤维素去除率均比未经预处理的玉米秸秆高。     

农田秸秆高温好氧堆肥试验研究

高温好氧堆肥是农田废弃物--秸秆资源化处理利用的有效途径之一.农田秸秆富含有机质和农作物生长所需的营养元素,可作为堆肥原料用于生产复合肥.秸秆高温好氧堆肥的关键技术是如何为微生物繁殖生长提供良好的环境.适宜的原料配比、添加微生物菌剂、堆肥发酵阶段温度控制在60℃以上,发酵完成后水分含量在40%以下、pH值为8.0左右,在这些条件下,可加快堆肥的进程和提高堆肥的效率.     

拟康氏木霉和白腐菌混菌发酵处理稻草秸秆的研究

以拟康氏木霉3.3002(Trichoderma pseudokoningii)和白腐菌5.776(Phanerochaete chrysosporium)的混合菌发酵处理稻草秸秆,并对处理结果进行了试验研究.研究结果表明,当接人拟康氏木霉与白腐菌时间间隔为3 d.接种液体积比为2 ml:2 ml,氮源为0.3%(质量分数)的(NH4)2SO4,发酵时间为8 d时,稻草秸秆纤维索降解率和木质素降解率分别为40.38%和31.52%,比单独使用拟康氏木霉(纤维素和木质素降解率分别为24.62%,13.78%)或白腐菌(纤维素和木质素降解率分别为6.96%,20.06%)处理稻草秸秆的效果有显著提高.     

水葫芦汁中温沼气发酵的实验研究

以鲜水葫芦汁为原料,在30℃恒温下,采用批量发酵工艺,进行发酵产沼气实验,测定发酵产沼气与时间的关系.实验结果表明,鲜水葫芦汁COD的降解率达到86%;鲜水葫芦汁发酵在第10天后达到稳定值,并持续产气25 d;对发酵过程中所产气体进行分析,发现甲烷含量最高能达到60%左右.因此,水葫芦是一种良好的发酵原料.     

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.     

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.     

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.     

Decomposition of limestone in a solar reactor

The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m² parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO₂ emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.     

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.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法，这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

Biohydrogen production by Anabaena sp. PCC 7120 wild-type and mutants under different conditions: Light, nickel, propane, carbon dioxide and nitrogen

Increasing awareness of environmental problems caused by the current use of fossil fuel-based energy, has led to the search for alternatives. Hydrogen is a good alternative and the cyanobacterium Anabaena sp. PCC 7120 is naturally able to produce molecular hydrogen, photosynthetically from water and light. However, this H₂ is rapidly consumed by the uptake hydrogenase.This study evaluated the hydrogen production of Anabaena sp. PCC 7120 wild-type and mutants: hupL⁻ (deficient in the uptake hydrogenase), hoxH⁻ (deficient in the bidirectional hydrogenase) and hupL⁻/hoxH⁻ (deficient in both hydrogenases) on several experimental conditions, such as gas atmosphere (argon and propane with or without N₂ and/or CO₂ addition), light intensity (54 and 152 ??Em⁻²s⁻¹), light regime (continuous and light/dark cycles 16 h/8 h) and nickel concentrations in the culture medium.In every assay, the hupL⁻ and hupL⁻/hoxH⁻ mutants stood out over wild-type cells and the hoxH⁻ mutant. Nevertheless, the hupL⁻ mutant showed the best hydrogen production except in an argon atmosphere under 16 h light/8 h dark cycles at 54 ??Em⁻²s⁻¹ in the light period, with 1 ??M of NiCl₂ supplementation in the culture medium, and under a propane atmosphere.In all strains, higher light intensity leads to higher hydrogen production and if there is a daily 1% of CO₂ addition in the gas atmosphere, hydrogen production could increase 5.8 times, related to the great increase in heterocysts differentiation (5 times more, approximately), whereas nickel supplementation in the culture medium was not shown to increase hydrogen production. The daily incorporation of 1% of CO₂ plus 1% of N₂ did not affect positively hydrogen production rate.     

Economie d'énergie en trigénération

Trigeneration is defined as the production of three useful forms of energy—heat, cold and power—from a primary source of energy such as natural gas or oil. For instance, trigeneration systems typically produce electrical power via a reciprocating engine or gas turbine and recover a large percentage of the heat energy retained in the lubricating oil, exhaust gas and coolant water systems to maximize the utilization of the primary fuel. The heat produced can be totally or partially used to fuel absorption refrigerators. Therefore, trigeneration systems enjoy an inherently high efficiency and have the potential to significantly reduce the energy-related operation costs of facilities. In this paper, we describe a model of characterization of trigeneration systems trough the condition of primary energy saving and the quality index, compared to the separate production of heat, cold and power. The study highlights the importance of the choice of the separate production reference system on the level of primary energy saving and emissions reduction.     

Investigation of the thermodynamic and kinetic properties of La–Fe–B system hydrogen-storage alloys

La–Fe–B hydrogen-storage alloys were prepared using a vacuum induction-quenching furnace with a rotating copper wheel. The thermodynamic and kinetic properties of the La–Fe–B hydrogen-storage alloys were investigated in this work. The P–C–I curves of the La–Fe–B alloys were measured over a H₂ pressure range of 10⁻³ MPa to 2.0 MPa at temperatures of 313, 328, 343 and 353 K. The P–C–I curves revealed that the maximum hydrogen-storage capacity of the alloys exceeded 1.23 wt% at a pressure of approximately 1.0 MPa and temperature of 313 K. The standard enthalpy of formation ΔH and standard entropy of formation ΔS for the alloys' hydrides, obtained according to the van't Hoff equation, were consistent with their application as anode materials in alkaline media. The alloys also exhibited good absorption/desorption kinetics at room temperature.     

Mineralogical characterization of the intraseam layers of Lofoi lignite deposits in Florina basin (western Makedonia,northwest Greece)

The mineralogical composition of intraseam layers from Lofoi lignite deposits (northwest Greece) is the subject of the present study. The samples were examined by means of X-ray diffraction (XRD), thermo-gravimetric (TG/DTG) and differential thermal analysis (DTA), and Fourier transform infrared (FT-IR) spectrometry. The clay minerals prevail in most samples, with illite-muscovite being the dominant phase, and kaolinite and chlorite being the other major clay components. No smectite was found. Quartz and feldspars, dominate in two cases. The studied materials are characterized as clays to clayey sands, showing significant similarities with the intraseam layers of the adjacent Achlada lignite deposits.