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.     

Energetic optimization of microalgal cultivation in photobioreactors for biodiesel production

Traditionally, algal cultivation in sparged photobioreactors has been optimized to maximize biomass productivity. In this study, an energy-based methodology is presented to maximize the net energy gain of the cultivation process by minimizing the energy input for sparging and by maximizing the energy output. Options for minimizing energy input through optimal gas-to-culture volume ratio and CO₂-air ratio and options for maximizing lipid production through optimal levels of nutrition and CO₂ are presented and validated with results from 900-mL bubble column reactors. In contrast to the traditional practice, the proposed energy-based optimization resulted in positive net energy gains. In single stage approach under optimal conditions (CO₂ enrichment of 0.5%, gas-to-culture volume ratio of 0.18 min⁻¹, and nitrate level of 1 mM), tests with Nannochloropsis salina resulted in positive net energy gain of 20 W/m³. In a test under nitrate starvation, the net energy gain in a reactor sparged with CO₂ enrichment of 0.5% was double that in the reactor sparged with ambient air (8 vs. 19 W/m³).     

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。     

Positioning of PV panels for reduction in line losses and mismatch losses in PV array

Partial shading decreases the power output of PV arrays due to mismatch losses. These losses are dependent on the shading pattern and the relative positions of shaded modules in the array. Various static and dynamic reconfiguration techniques have earlier been proposed to mitigate these losses. In an earlier proposed static reconfiguration technique, the power generation is enhanced by altering the physical location of the PV panels using a random Sudoku configuration without modifying the TCT (Total-Cross-Tied) based electrical connections. However, this arrangement faces drawbacks due to ineffective dispersion of shade and significant increase in wiring required. In this work, an optimal Sudoku arrangement to overcome these drawbacks is formulated. Further analysis indicate that the global peak of the optimal Sudoku based PV array occurs as the right most peak in the curve for most shading conditions, thus evidently obviating the need for complex MPPT (Maximum-Power-Point-Tracking) algorithms. The proposed configuration is compared with various other existing reconfiguration schemes in terms of power output and the comparison is presented. In addition, a general formulation is proposed to expand this pattern to any generic array. A strategy is also proposed to make such an interconnection practicable for very large size PV arrays.     

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.     

A review of advanced optimization strategies for fermentative biohydrogen production processes

The inability of statistical optimization to represent the dynamic interaction of the biohydrogen process, which is highly non-linear and complicated, has been identified. However, incorporating a data-driven black-box model could overcome the limitations of conventional methods to provide correct responses rapidly and cost-effective modeling. Despite significant reports on the optimization of hydrogen production from fermentation, fewer studies have been made for the case using artificial intelligence algorithms. As a result, critical and extensive analyses of previous works are conducted to develop a general methodological framework for advanced response optimization.     

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。     

Robust multi-objective optimization of methanol steam reforming for boosting hydrogen production

Methanol steam reforming (MSR) has been considered as a promising method for producing pure hydrogen in recent decades. A comprehensive two-dimensional steady-state mathematical model was developed to analyze the MSR reactor. To improving high purity hydrogen production, a triple-objective optimization of the MSR reactor is performed. Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is employed as a robust optimization approach to maximize the three objectives, termed as, methanol conversion, CO selectivity, and H₂ selectivity. The Pareto optimal frontier has also been provided and the ultimate solution of the Pareto front has been found by the three decision-making methods (TOPSIS, LINMAP, and Shannon's Entropy). Among the three distinct decision-making approaches, LINMAP presents better results according to the deviation index parameter. It has been shown that a perfect agreement is available between the plant and simulation data. Operating under the optimum values based on the LINMAP method confirms an almost 47.04% enhancement of H₂ mass fraction compared to the conventional industrial MSR reactor. The predicted results advocate that the key superiority of the optimized-industrial reactor is the remarkable higher production rate of hydrogen compared to the conventional MSR reactor which makes optimized-industrial reactor both feasible and beneficial.     

Approach to optimization of electrolyte production process

基于锂离子电池行业的迅猛崛起,锂离子电池电解液市场需求不断扩大,传统的电解液生产工艺不能满足现有的发展需求。寻求新的工艺优化途径,结合传统生产工艺进一步改进,对电解液产能及产品质量的提升尤为重要。本文就关于如何在工艺上提高生产效率,缩短生产周期,降低能耗,结合实际应用中的经验和实验结果做进一步的分析和探讨。     

Application of experimental design methodology for optimization of biofuel production from microalgae

Optimization of biofuel productivity, in terms of lipid content, polysaccharide content, and calorific value, from microalgae was performed by varying four variables (temperature, light intensity, nitrogen content, and CO₂ addition) using a 2⁴ full factorial design. A statistical analysis showing the influence of each variable and their interactions was conducted. The selected variables all influence biofuel productivity, but their importance varies according to the sequence: CO₂ addition > temperature > nitrogen content > light intensity. Interactive effects of temperature with light intensity and nitrogen with CO₂ addition for lipid and polysaccharide productivities were identified, respectively. For calorific value, interactive effects of CO₂ addition with light intensity and nitrogen content were observed. The highest biofuel productivity was obtained at the following conditions: temperature (>25 °C), light intensity (>60 μmol photons m⁻² s⁻¹), nitrogen content (<50 mg L⁻¹), and CO₂ addition (>18 mL L⁻¹ d⁻¹). 10 days was found to be the most favorable cultivation time for lipid production under the investigated conditions.     

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。     

Medium optimization for Chlorella zofingiensis biomass production using central composite design

Fertilizers are major raw materials for microalgae cultivation. This study aims to reduce the cost of fertilizers and to enhance economic viability. The focus is on urea, potassium dihydrogen phosphate, and heptahydrate magnesium sulfate, which provide the main elements for algae cultivation. A central composite design was applied to optimize the medium for Chlorella zofingiensis cultivation, which was considered to be a potential feedstock for biodiesel production. The optimal concentrations were 533.31 mg L^–1 urea, 69.50 mg L^–1 potassium dihydrogen phosphate, and 69.10 mg L^–1 heptahydrate magnesium sulfate, and the corresponding biomass concentration of C. zofingiensis was 2.50 g L^–1 after a 3-day culture.     

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.