Cumulative exergy losses associated with the production of lead metal

Cumulative exergy losses result from the irreversibility of the links of a technological network leading from raw materials and fuels extracted from nature to the product under consideration. The sum of these losses can be apportioned into partial exergy losses (associated with particular links of the technological network) or into constituent exergy losses (associated with constituent subprocesses of the network). The methods of calculation of the partial and constituent exergy losses are presented, taking into account the useful byproducts substituting the major products of other processes. Analyses of partial and constituent exergy losses are made for the technological network of lead metal production.     

Thermodynamic optimization of biomass gasifier for hydrogen production

A thermodynamic equilibrium model was used to predict the chemical composition of the products of biomass gasification. The effects of temperature, pressure, steam biomass ratio (SBR) and equivalence ratio (ER) on the equilibrium hydrogen yield were studied. Gibbs energy minimization approach was used to determine the product gas composition. Wood (designated by ${\mathrm{CH}}_{1.5}{\mathrm{O}}_{0.7}$) was used as the model biomass compound and Stanjan (v 3.93L) software was used. Gasifier, the most critical component of any biomass gasification system, was modeled as an equilibrium reactor and the energy consumption and thermodynamic efficiency were determined. A first law analysis of the gasifier showed that the optimum conditions for hydrogen production occurred at a gasification temperature of 1000 K, SBR of 3, ER of 0.1. Finally, equilibrium calculations were compared with experimental data from literature which showed that for high gas residence times and high gasification temperatures there is a close match of equilibrium results with experimental ones.     

Screening and optimization of pretreatments in the preparation of sugarcane bagasse feedstock for biohydrogen production and process optimization

This work evaluated the effects of individual alkaline, sodium carbonate (Na₂CO₃ denoted as; NaC), sodium sulfide (Na₂SO₃ denoted as; NaS) and combination of NaC + NaS pretreatment for the saccharification of sugarcane bagasse (SCB). The effects of different pretreatments on chemical composition and structural complexity of SCB in relation with its saccharification were investigated. For enzymatic hydrolysis of pretreated SCB we have utilized the produced crude enzymes by Streptomyces sp. MDS to make the process more cost effective. A enzyme dose of 30 filter paperase (FPU) produced a maximum reducing sugar (RS) 592 mg/g with 80.2% hydrolysis yield from NaC + NaS pretreated SCB under optimized conditions. The resulted enzymatic hydrolysates of each pretreated SCB were applied for hydrogen production using Clostridium beijerinckii KCTC1785. NaC + NaS pretreated SCB hydrolysates exhibited maximum H₂ production relative to other pretreatment methods. Effects of temperature, initial pH of culture media and increasing NaC + NaS pretreated SCB enzymatic hydrolysates concentration (2.5–15 g/L) on bioH₂ production were investigated. Under the optimized conditions, the cumulative H₂ production, H₂ production rate, and H₂ yield were 1485 mL/L, 61.87 mL/L/h and 1.24 mmol H₂/mol of RS (0.733 mmol H₂/g of SCB), respectively. The efficient conversion of the SCB hydrolysate to H₂ without detoxification proves the viability of process for cost-effective hydrogen production.     

Forecasting photovoltaic array power production subject to mismatch losses

The development of photovoltaic (PV) energy throughout the world this last decade has brought to light the presence of module mismatch losses in most PV applications. Such power losses, mainly occasioned by partial shading of arrays and differences in PV modules, can be reduced by changing module interconnections of a solar array. This paper presents a novel method to forecast existing PV array production in diverse environmental conditions. In this approach, field measurement data is used to identify module parameters once and for all. The proposed method simulates PV arrays with adaptable module interconnection schemes in order to reduce mismatch losses. The model has been validated by experimental results taken on a 2.2 kW_p plant, with three different interconnection schemes, which show reliable power production forecast precision in both partially shaded and normal operating conditions. Field measurements show interest in using alternative plant configurations in PV systems for decreasing module mismatch losses.     

Kinetic modeling and optimization of biomass pyrolysis for bio-oil production

Thermo-kinetic models for biomass pyrolysis were simulated under both isothermal and non-isothermal conditions to predict the optimum parameters for bio-oil production. A comparative study for wood, sewage sludge, and newspaper print pyrolysis was conducted. The models were numerically solved by using the fourth order Runge–Kutta method in Matlab-7. It was also observed that newspaper print acquired least pyrolysis time to attain optimum bio-oil yield followed by wood and sewage sludge under the identical conditions of temperature and heating rate. Thus, at 10 K/min, the optimum pyrolysis time was 21.0, 23.8, and 42.6 min for newspaper print, wood, and sewage sludge, respectively, whereas the maximum bio-oil yield predicted was 68, 52, and 36%, respectively.     

免烘干造气型煤生产工艺参数的优化

本文阐述了免烘干造气型煤的生产工艺 ,采用正交试验设计方法对造气型煤的生产工艺主要参数进行优化 ,对试验结果进行了详细分析 ,并确定优化后的造气型煤生产工艺参数。     

产木聚糖酶菌株的筛选及产酶条件优化

通过透明圈法从土壤中筛选到两株产木聚糖酶菌株CS-1和CS-2,CS-2产木聚糖酶的酶活力优于CS-1。CS-2产木聚糖酶最佳发酵培养条件:碳源(甘蔗渣)3.0 g/ml,氮源(NH4Cl)0.5 g/ml,接种量为10%,250 ml三角瓶装液量50 ml,pH=8.0,温度为55℃,转速为160 r/min,发酵时间为3 d。在此发酵条件下,CS-2产木聚糖酶的酶活力达到7.980 U/ml。     

Effects of pretreatment methods on cassava wastewater for biohydrogen production optimization

Batch production of biohydrogen from cassava wastewater pretreated with (i) sonication, (ii) OPTIMASH BG^® (enzyme), and (iii) α-amylase (enzyme) were investigated using anaerobic seed sludge subjected to heat pretreatment at 105 °C for 90 min. Hydrogen yield at pH 7.0 for cassava wastewater pretreated with sonication for 45 min using anaerobic seed sludge was 0.913 mol H₂/g COD. Results from pretreatment with OPTIMASH BG^® at 0.20% and pH 7 showed a hydrogen yield of 4.24 mol H₂/g COD. Superior results were obtained when the wastewater was pretreated with α-amylase at 0.20% at pH 7 with a hydrogen yield of 5.02 mol H₂/g COD. In all cases, no methane production was observed when using heat-treated sludge as seed inoculum. Percentage COD removal was found to be highest (60%) using α-amylase as pretreatment followed by OPTIMASH BG^® at 54% and sonication (40% reduction rate). Results further suggested that cassava wastewater is one of the potential sources of renewable biomass to produce hydrogen.     

基于响应曲面法的厨余发酵产氢条件优化研究

利用响应曲面法优化厨余发酵产氢条件。以初始pH、物料比和碳氮比为自变量,培养7天的产氢量为因变量,采用Box-Behnken(BB)设计,研究各自变量及其交互作用对厨余发酵产氢效果的影响。以模拟得到的二次多项式回归方程的预测模型为基础,得到物料比为10%、50%和90%,最佳反应条件下的产氢量(VS)分别为35.49,49.12,48.39 ml/g,远高于单因素实验的最高值34.21,46.36,45.21 ml/g,试验结果为厨余发酵产氢技术应用提供了技术参数。     

以秸秆和厨余垃圾为原料发酵产甲烷工艺的优化

利用响应曲面法研究了秸秆与厨余垃圾混合厌氧发酵产甲烷的二次回归模型和工艺条件。选取原料配比、原始C/N、TS浓度为参考因素,采用3因素3水平的试验设计手段进行预测,在原料配比(秸秆∶厨余)为1.29∶1,C/N为20.42,TS浓度为10.07%时,甲烷的总产气量达到最高值,为21431.7mL,产气率为126.06mL/g。利用响应曲面法对结论进行优化检验,结果表明,实际值与理论值误差很小,工艺参数可用于实际应用中。     

Thermodynamic analysis of hydrogen tank filling. Effects of heat losses and filling rate optimization

A thermodynamic analysis of the refueling of a gaseous fuel tank and a thermal analysis of heat losses through tank walls is presented. The objective of the thermodynamic analysis is to compare the temperature and pressure evolutions coming from different equations of state and from thermodynamic tables. This comparison is performed with nitrogen and hydrogen and the compression is assumed adiabatic. It is shown that the ideal-gas assumption results in under-prediction of the tank temperature and pressure for hydrogen but in over-prediction for nitrogen. An approximate analytical expression of the Redlich–Kwong equation of state is given which is in very good agreement with thermodynamic tables. To handle heat losses, different approaches are used and compared. First, a global thermal conductance is introduced which allows deriving analytical expressions. Then, a thermal nodal modeling of tank walls is proposed to take into account thermal capacity effects. Finally a 1D semi-infinite modeling of the tank walls is presented. Finally, this model is used to optimize mass flow rate in order to limit the temperature rise during the filling process.     

HXD3型机车的制造工艺改进和生产管理优化

介绍了大连机车车辆有限公司HXD3型机车通过引进消化吸收再创新及实施国产化,最终形成了HXD3型机车的批量生产,并达到年产500台以上生产能力。叙述了通过改进工艺来实现生产管理优化的过程。     

Development and application of BioFeed model for optimization of herbaceous biomass feedstock production

An efficient and sustainable biomass feedstock production system is critical for the success of the biomass based energy sector. An integrated systems analysis framework to coordinate various feedstock production related activities is, therefore, highly desirable. This article presents research conducted towards the creation of such a framework. A breadth level mixed integer linear programming model, named BioFeed, is proposed that simulates different feedstock production operations such as harvesting, packing, storage, handling and transportation, with the objective of determining the optimal system level configuration on a regional basis. The decision variables include the design/planning as well as management level decisions. The model was applied to a case study of switchgrass production as an energy crop in southern Illinois. The results illustrated that the total cost varied between 45 and 49 $ Mg⁻¹ depending on the collection area and the sustainable biorefinery capacity was about 1.4 Gg d⁻¹. The transportation fleet consisted of 66 trucks and the average utilization of the fleet was 86%. On-farm covered storage of biomass was highly beneficial for the system. Lack of on-farm open storage and centralized storage reduced the system profit by 17% and 5%, respectively. Increase in the fraction of larger farms within the system reduced the cost and increased the biorefinery capacity, suggesting that co-operative farming is beneficial. The optimization of the harvesting schedule led to 30% increase in the total profit. Sensitivity analysis showed that the reduction in truck idling time as well as increase in baling throughput and output density significantly increased the profit.     

Analysis of sugars by liquid chromatography-mass spectrometry in Jerusalem artichoke tubers for bioethanol production optimization

Sustainability of biofuels is increasingly taken into account; therefore, sustainable production technologies are needed. There has been a long history of converting Jerusalem artichoke into ethanol. Jerusalem artichoke (Helianthus tuberosus L.) is a low-requirement crop, it has a high carbohydrates yield and, nowadays, it does not interfere with food chain. It is, then, a promising energy crop for sustainable bioethanol production. However, the main storage carbohydrate of Jerusalem artichoke, inulin, can not be directly fermented by classic fermentation yeasts, so, either a hydrolysis followed by fermentation with classical yeast or the use of yeasts with inulinase activity are required to obtain bioethanol. Therefore, it is needed to know not only total sugar content, but also their composition, for the bioethanol production optimization from Jerusalem artichoke tubers. Several methods have been used in literature for carbohydrates analysis present in Jerusalem artichoke tubers. However, for further development of carbohydrate analysis, faster and more reliable identification and peak confirmation, mass spectrometry (MS) detection is required. In this paper, liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS) was used as an alternative technique to analyse sugars content and composition in tubers from Jerusalem artichoke. Two simple, rapid, sensitive and specific LC-ESI-MS methods were developed under the positive ionization mode. Glucose, fructose, sucrose, kestose and inulin were determined. Furthermore, inulin profile can be characterized. Analytical reversed phase LC columns were used using only water as eluent. These methods can be useful to optimize the whole bioethanol production chain from Jerusalem artichoke.     

CFD optimization of horizontal continuous stirred-tank (HCSTR) reactor for bio-hydrogen production

This paper described the design on the lab-scale horizontal continuous stirred-tank reactor (HCSTR) that the effective working volume is relatively large and the performance is stable at lower agitating speed. Using the Computational Fluid Dynamics (CFD) simulation with an ethanol-type fermentation process experiment we determined the optimal agitating speed range for the bio-hydrogen production from analysis on the flow pattern generated at the various agitating speed conditions and select and the suitable three phase separator design has been constructed for gas–liquid–solid three phase separations. The experimental results in the designed bioreactor show that the agitating speeds of 50 rpm is most suited for economical bio-hydrogen production and three phase separation. It was consistent with the prediction from CFD simulation. The information obtained from this study is expected to provide basic knowledge on the optimal design of bioreactor and three phase separator aimed for scale up of the continuous stirred-tank reactor for bio-hydrogen production.     

Design and optimization of reforming hydrogen production reaction system for automobile fuel cell

Mathematical modeling and simulation analysis of the dimethyl ether steam reforming reaction system were carried out in the study. The numerical results of simulation and experiment were consistent. The effects of reaction conditions on the conversion of dimethyl ether and hydrogen production were analyzed. The internal structure of the reforming reactor was adjusted to obtain higher hydrogen production efficiency. The study established the reforming hydrogen production industry system, and analyzed the thermal efficiency of the system. The results show that when the temperature of the conversion bed is 673 K, the inlet flow rate of the mixture gas is 0.5 ms^?1 and the ratio of water to ether is 3, the dimethyl ether steam reforming reaction system could obtain the dimethyl ether conversion rate of 90%, the hydrogen production rate of 88% and system thermal efficiency of 74%.     

Biodiesel production process optimization and characterization to assess the suitability of the product for varied environmental conditions

In this study, both edible (coconut oil, palm oil, groundnut oil, and rice bran oil) and non-edible oils (pongamia, neem and cotton seed oil) were used to optimize the biodiesel production process variables like catalyst concentration, amount of methanol required for reaction, reaction time and reaction temperature. The fuel properties like specific gravity, moisture content, refractive index, acid value, iodine number, saponification value and peroxide value were estimated. Based on the cetane number and iodine value, the methyl esters obtained from palm and coconut oils were not suitable to use as biodiesel in cold weather conditions, but for hot climate condition biodiesel obtained from the remaining oil sources is suitable.     

Process optimization for bioethanol production from cassava starch using novel eco-friendly enzymes

Although cassava (Manihot esculenta Crantz) is a potential bioethanol crop, high operational costs resulted in a negative energy balance in the earlier processes. The present study aimed at optimizing the bioethanol production from cassava starch using new enzymes like Spezyme^® Xtra and Stargen™ 001. The liquefying enzyme Spezyme was optimally active at 90 °C and pH 5.5 on a 10% (w/v) starch slurry at levels of 20.0 mg (280 Amylase Activity Units) for 30 min. Stargen levels of 100 mg (45.6 Granular Starch Hydrolyzing Units) were sufficient to almost completely hydrolyze 10% (w/v) starch at room temperature (30 ± 1 °C). Ethanol yield and fermentation efficiency were very high (533 g/kg and 94.0% respectively) in the Stargen + yeast process with 10% (w/v) starch for 48 h. Raising Spezyme and Stargen levels to 560 AAU and 91.2 GSHU respectively for a two step loading [initial 20% (w/v) followed by 20% starch after Spezyme thinning]/initial higher loading of starch (40% w/v) resulted in poor fermentation efficiency. Upscaling experiments using 1.0 kg starch showed that Stargen to starch ratio of 1:100 (w/w) could yield around 558 g ethanol/kg starch, with a high fermentation efficiency of 98.4%. The study showed that Spezyme level beyond 20.0 mg for a 10% (w/v) starch slurry was not critical for optimizing bioethanol yield from cassava starch, although an initial thinning of starch for 30 min by Spezyme facilitated rapid saccharification-fermentation by Stargen + yeast system. The specific advantage of the new process was that the reaction could be completed within 48.5 h at 30 ± 1 °C.     

Process optimization for PHA production by activated sludge using response surface methodology

A five-level-three factor central composite rotary design was employed to find out the interactive effects of three variables, i.e. static magnetic field intensity, concentration of NH₃–N and initial pH on polyhydroxyalkanoates (PHA) production by activated sludge under the aerobic dynamic feeding (ADF) technique. Response surface methodology (RSM) was utilized for process optimization and a second-order polynomial equation was obtained by multiple regression analysis. A yield of 49.5% of dry cell weight (dcw) was achieved at optimized conditions, i.e. magnetic field 11 mT, NH₃–N 4.8 mg l^?1 (C:N = 60:1)and initial pH 9.0.     

Accounting emergy flows to determine the best production model of a coffee plantation

Cerrado, a savannah region, is Brazil's second largest ecosystem after the Amazon rainforest and is also threatened with imminent destruction. In the present study emergy synthesis was applied to assess the environmental performance of a coffee farm located in Coromandel, Minas Gerais, in the Brazilian Cerrado. The effects of land use on sustainability were evaluated by comparing the emergy indices along ten years in order to assess the energy flows driving the production process, and to determine the best production model combining productivity and environmental performance. The emergy indices are presented as a function of the annual crop. Results show that Santo Inácio farm should produce approximately 20 bags of green coffee per hectare to accomplish its best performance regarding both the production efficiency and the environment. The evaluation of coffee trade complements those obtained by contrasting productivity and environmental performance, and despite of the market prices variation, the optimum interval for Santo Inácio's farm is between 10 and 25 coffee bags/ha.