Energetic and exergetic aspects of cotton stalk production in establishing energy policies

Exergy analysis is important for energy resource utilization, because exergy, which is a way to a sustainable future, is a part of the energy analysis. Exergy analysis starts to play a role in several countries in developing energy policy. This paper deals with the exergetic assessment of the cotton stalk (CS) production. In this regard, Turkey, which is one of the eight countries producing 85% of the world's cotton, is given as an application country first. Energy and exergy relations used in the analysis are then presented. Finally, the Turkish CS production in 2003 is evaluated using energy and exergy analyses method, while the results obtained are discussed. The values for the net energy and exergy gained are obtained to be about 49,146 and 59,395 MJ/ha, respectively. Turkey's total energy and exergy are estimated to be 75.45 and 81.87 PJ. It may be concluded that this amount of energy is equal to 7.77% and 2.38% of Turkey's primary energy production and consumption in the same year, respectively. The overall mean energy and exergy efficiencies of the cotton production in the year studied are found to be 33.06% and 33.12%, respectively. It is also expected that the results of this study will be helpful in developing highly applicable and productive planning for energy policies.     

Bio-oil production from hydrothermal liquefaction of waste Cyanophyta biomass: Influence of process variables and their interactions on the product distributions

Hydrothermal liquefaction (HTL) of waste Cyanophyta biomass at different temperatures (factor A, 260–420 °C), times (factor B, 5–75 min) and algae/water (a/w) ratios (factor C, 0.02–0.3) by single reaction condition and Response Surface Method (RSM) experiments was investigated. By single reaction condition runs, maximum total bio-oil yield (29.24%) was obtained at 350 °C, 60 min and 0.25 a/w ratio. Maximum bio-oil HHV of 40.04 MJ/kg and energy recovery of 51.09% was achieved at 350 °C, 30 min, 0.1 a/w ratio and 350 °C, 60 min, 0.25 a/w ratio, respectively. RSM results indicate that effect of AB interaction was significant on light bio-oil yield. Both AC and AB had more remarkable influence than BC on heavy bio-oil yield and aqueous total organic carbon (TOC) recovery whereas BC was noticeable on ammonia nitrogen (NH₃N) recovery in aqueous products. By model-based optimization of highest bio-oil yield, the highest bio-oil yield reached 31.79%, increasing by 8.72% after RSM optimization, and light and heavy bio-oil yield was 17.44% and 14.35%, respectively. Long-chain alkanes, alkenes, ketones, fatty acids, phenols, benzenes, amides, naphthalenes were the main components in light bio-oil. Some alcohols, phenols and aromatics were primarily found in heavy bio-oil. Solid residue after HTL consisted of numerous microparticles (～5 μm) observed by Scanning Electron Microscopy (SEM). Energy Dispersive Spectrometer (EDS) analysis shows these particles primarily contained C, O, Mg, P and microelements, derived from Cyanophyta cells.     

Effects of K2CO3 on pyrolysis characteristics of Xinjiang cotton stalk

The horizontal fixed bed pyrolysis method was used in this study to examine the reaction parameters of K in-situ catalytic pyrolysis of the cotton stalk at 600 °C. The pyrolysis conversion mechanism of cotton stalk under the influence of K was investigated in conjunction with gas chromatography analysis, FT-IR analysis, and GC-MS analysis. According to the findings, the gas production of a mixture of 1 g cotton stalks grew from 215 mL (0.0 %- K₂CO₃) to 275 mL (7.5% -K₂CO₃), but it was inhibited to 263 mL when K₂CO₃ addition was at 10.0%. According to the results of the characterization, K₂CO₃ might accelerate the breakdown of oxygen-containing rings in cellulose and hemicellulose, encourage the conversion of furan structure into ketones, and prevent the transformation of furan into long-chain alkanes. The addition of K₂CO₃ introduces more K into the cotton stalk. Under the influence of K, long-chain alkanes, phenols, and esters will be further cracked and polymerized to create more stable aromatic hydrocarbons. According to quantum chemical calculations, xylose's oxygen-containing ring opened first without the presence of K, then H transfer, dehydrogenation, dehydration, and cyclization to generate the cyclopentanone structure. The oxygen-containing groups in the xylose side chain preferentially bind to K in the presence of K, and the bond length between the O and C rings of the side chain is lengthened, while without K, the C–O bond length of the preferred ring opening is shortened.     

An overview of empty fruit bunch from oil palm as feedstock for bio-oil production

Empty fruit bunch (EFB) from oil palm is one of the potential biomass to produce biofuels like bio-oil due to its abundant supply and favorable physicochemical characteristics. Confirming the assertion, this paper presents an overview of EFB as a feedstock for bio-oil production. The fundamental characteristics of EFB in terms of proximate analysis, ultimate analysis and chemical composition, as well as the recent advances in EFB conversion processes for bio-oil production like pyrolysis and solvolysis are outlined and discussed. A comparison of properties in terms of proximate analysis, ultimate analysis and fuel properties between the bio-oil from EFB and petroleum fuel oil is included. The major challenges and future prospects towards the utilization of EFB as a useful resource for bio-oil production are also addressed.     

Economic tradeoff between biochar and bio-oil production via pyrolysis

This paper examines some of the economic tradeoffs in the joint production of biochar and bio-oil from cellulosic biomass. The pyrolysis process can be performed at different final temperatures, and with different heating rates. While most carbonization technologies operating at low heating rates (large biomass particles) result in higher yields of charcoal, fast pyrolysis (which processes small biomass particles) is the preferred technology to produce bio-oils. Varying operational and design parameters can change the relative quantity and quality of biochar and bio-oil produced for a given feedstock. These changes in quantity and quality of both products affect the potential revenue from their production and sale. We estimate quadratic production functions for biochar and bio-oil. The results are then used to calculate a product transformation curve that characterizes the yields of bio-oil and biochar that can be produced for a given amount of feedstock, movement along the curve corresponds to changes in temperatures, and it can be used to infer optimal pyrolysis temperature settings for a given ratio of biochar and bio-oil prices.     

Investigation on hydrogen production by catalytic steam reforming of maize stalk fast pyrolysis bio-oil

Hydrogen production via catalytic steam reforming of maize stalk fast pyrolysis bio-oil over the nickel/alumina supported catalysts promoted with cerium was studied using a laboratory scale fixed bed coupled with Fourier transform infrared spectroscopy/thermal conductivity detection analysis (FTIR/TCD). The effects of nickel loading, reaction temperature, water to carbon molar ratio (WCMR) and bio-oil weight hourly space velocity (W_bHSV) on hydrogen production were investigated. The highest hydrogen yield of 71.4% was obtained over the 14.9%Ni-2.0%Ce/A1₂O₃ catalyst under the reforming conditions of temperature = 900 °C, WCMR = 6 and W_bHSV = 12 h⁻¹. Increasing reaction temperature from 600 to 900 °C resulted in the significant increase of hydrogen yield. The hydrogen yield was significantly enhanced by increasing the WCMR from 1 to 3, whereas it increased slightly by further increasing WCMR. The hydrogen yield decreased with the increase of W_bHSV. Meanwhile, the coke deposition percentage changed little with increasing W_bHSV up to 12 h⁻¹ and then it increased by 4.5% with the further increase of W_bHSV from 12 to 24 h⁻¹.     

Investigation on the physical properties of the charcoal briquettes prepared from wood sawdust and cotton stalk

The physical properties of the charcoal briquettes prepared from biomass waste are usually poor. In the paper, an alternative approach to the charcoal briquette preparation from the densified biomass briquette by carbonization was addressed. The carbonization process of the biomass briquettes prepared from cotton stalk (CS), wood sawdust (WS) and their blends was performed in a fixed bed at 400~600°C. The variation in the mass and volume of the biomass briquettes before and after the carbonization process and the physical properties of the resulted charcoal briquettes were investigated. The results indicate that the physical properties of the charcoal briquettes including bulk density and compression strength decreased firstly and then increased as the temperature increased. CS charcoal briquettes with better physical properties showed more volume shrinkage than WS charcoal briquettes after the carbonization process. However, the physical properties of the charcoal briquettes from the blends were poorer than expected due to the co-pyrolysis characteristics of CS and WS.     

Experimental studies on cotton stalk combustion in a fluidized bed

The present work reports studies on the mixing and combustion characteristics of cotton stalk (CS) with 10–100 mm in length in a fluidized bed. Effects of length and initial weight percentage of CS, diameter of alumina bed material as well as gas velocity on the mixing characteristics of CS with alumina were investigated. CS can mix well with 0.6–1 mm alumina at fluidization number N=3–8.     

Effects of Fe0 and Ni0 nanoparticles on hydrogen production from cotton stalk hydrolysate using Klebsiella sp. WL1316: Evaluation of size and concentration of the nanoparticles

Fe⁰ and Ni⁰ nanoparticles (NPs) of certain size were synthesized and added to the hydrogen production system from cotton stalk hydrolysate using Klebsiella sp. WL1316. Fe⁰ and Ni⁰ NPs with a size of 50 nm at all concentrations effectively improve hydrogen production during mid to late fermentation stages; particularly, the highest daily hydrogen production obtained following treatment with 50 nm Fe⁰ NPs at 30 mg/L fermented for 96 h significantly increased by 61% comparing to the control treatment. The reducing sugar consumption in cotton stalk hydrolysate and ΔOD₆₀₀ could be improved to some extent by Fe⁰ and Ni⁰ NPs supplementation. Addition of Fe⁰ or Ni⁰ NPs of 50 nm at a concentration of 30 mg/L resulted in enhanced cumulative hydrogen production with improvement of hydrogen yield reached higher than 20%, and the values of Y(H₂/S) were all higher than 90 mL/g _substrate, reflecting good hydrogen production and substrate consumption. The analysis of the main soluble metabolites profile revealed that supplementation with Fe⁰ and Ni⁰ NPs of suitable size and concentration may decrease the metabolic flux in the competitive branch of hydrogen production and increase the metabolic flux of the key node that leads to hydrogen generation, thus promoting biohydrogen synthesis.     

Experimental study on cotton stalk combustion in a circulating fluidized bed

This paper summarizes the results of an experimental study on cotton stalk (CS) combustion in a circulating fluidized bed. The mixing and fluidizing characteristics of binary mixture of CS with 10–100 mm in length and alumina bed material with a certain size distribution in a cold test facility were studied. The results show that CS by itself cannot fluidize, and adding inert bed material can improve the fluidization condition. CS can mix well with alumina at fluidization number N = 3–7. As N is more than 7, there will exist a little more segregation. The study concerning combustion characteristics of pure CS was performed on a circulating fluidized bed with a heat input of 0.5 MW. The effects of fluidizing velocity, secondary air flow and gas flow to the loop seal on the bed temperature profiles were investigated. Although there is a little more segregation at N higher than 7 in the cold tests, the hot experimental results indicate that slight segregation has little effect on the steady combustion of the dense region. In this study, the concentrations of major gaseous pollutants (CO, SO₂ and NO) in flue (stack) gas were measured.     

Study of bio-oil and bio-char production from algae by slow pyrolysis

This study examined bio-oil and bio-char fuel produced from Spirulina Sp. by slow pyrolysis. A thermogravimetric analyser (TGA) was used to investigate the pyrolytic characteristics and essential components of algae. It was found that the temperature for the maximum degradation, 322 °C, is lower than that of other biomass. With our fixed-bed reactor, 125 g of dried Spirulina Sp. algae was fed under a nitrogen atmosphere until the temperature reached a set temperature between 450 and 600 °C. It was found that the suitable temperature to obtain bio-char and bio-oil were at approximately 500 and 550 °C respectively. The bio-oil components were identified by a gas chromatography/mass spectrometry (GC–MS). The saturated functional carbon of the bio-oil was in a range of heavy naphtha, kerosene and diesel oil. The energy consumption ratio (ECR) of bio-oil and bio-char was calculated, and the net energy output was positive. The ECR had an average value of 0.49.     

Upgrading of bio-oil distillation bottoms into biorenewable calcined coke

Depleting fossil fuel sources necessitate renewable substitutes for petroleum-based co-products. Fast pyrolysis of biomass generates a hydrocarbon liquid (“bio-oil”) amenable to distillation and/or hydrotreatment into hydrocarbon blendstocks. Biorefineries must add value through parallel generation of co-products. We demonstrated a straightforward conversion of bio-oil distillate bottoms into calcined coke. The solid residue was subjected to calcination at 1200 °C for 1 h under N₂ atmosphere. The dry calcined product contained 96–99% carbon, was free from sulfur (<0.05% mass fraction), and contained a mass fraction of 0.2–1.1% ash. XRD confirmed steady increases in crystallite size with both devolatilization and calcination. FTIR spectroscopy indicated a loss of functional groups after calcination, except two broad peaks representing C–C and C–O. Temperature programmed oxidation (TPO) of the bottoms before and after calcination illustrates an increasing structural order via the increasing temperature(s) necessary to oxidize the samples. SEM images reveal bubbly morphologies similar to the industrially-favored sponge coke. The electrical resistivity of calcined coke samples measured to be < 1.6 mΩ-m, which closely falls in line with specifications for carbon anodes. Due to the aforementioned qualities and biomass origin, biorenewable calcined coke is an improved alternative to petroleum coke and can find application in carbon anodes, steel carburization, and graphite synthesis.     

农林生物质热裂解制取合成气的研究

以树叶为原料，利用热裂解装置进行了试验。并对裂解产物的组成进行了分析。结果表明：树叶热裂解产物为生物油、合成气和炭，其合成气成分主要由CO、CH4、H2和水蒸气组成。     

Biohydrogen production from Imperata cylindrica bio-oil using non-stoichiometric and thermodynamic model

This paper presents a non-stoichiometric and thermodynamic model for steam reforming of Imperata cylindrica bio-oil for biohydrogen production. Thermodynamic analyses of major bio-oil components such as formic acid, propanoic acid, oleic acid, hexadecanoic acid and octanol produced from fast pyrolysis of I. cylindrica was examined. Sensitivity analyses of the operating conditions; temperature (100–1000 °C), pressure (1–10 atm) and steam to fuel ratio (1–10) were determined. The results showed an increase in biohydrogen yield with increasing temperature although the effect of pressure was negligible. Furthermore, increase in steam to fuel ratio favoured biohydrogen production. Maximum yield of 60 ± 10% at 500–810 °C temperature range and steam to fuel ratio 5–9 was obtained for formic acid, propanoic acid and octanol. The heavier components hexadecanoic and oleic acid maximum hydrogen yield are 40% (740 °C and S/F = 9) and 43% (810 °C and S/F = 8) respectively. However, the effect of pressure on biohydrogen yield at the selected reforming temperatures was negligible. Overall, the results of the study demonstrate that the non-stoichiometry and thermodynamic model can successfully predict biohydrogen yield as well as the composition of gas mixtures from the gasification and steam reforming of bio-oil from biomass resources. This will serve as a useful guide for further experimental works and process development.     

生物质热加工液化技术评述

介绍了生物质热加工液化技术中的各种热裂解液化和高压液化工艺,包括流化床、涡流烧蚀反应器、真空快速裂解反应器以及高压釜、半连续固定床等装置的工作原理和生产工艺,分析它们各自的优点和存在的问题,着重讨论了各种工艺提高生物原油产率的措施以及精制生物原油可替代柴油作为车用轻质燃油的方法,指出降低生物原油的生产成本,扩大生产规模是热加工液化的发展方向。     

Slow, fast and flash pyrolysis of rapeseed

Pyrolysis experiments have been conducted on a sample of rapeseed to determine particularly the effects of pyrolysis temperature, heating rate, particle size and sweep gas flow rate on the pyrolysis product yields and their chemical compositions. The maximum oil yield of 73% was obtained at the final pyrolysis temperature of 550–600 °C, particle size range of +0.6–1.25 mm, and sweep gas flow rate of 100 cm³min⁻¹ (N₂) at flash pyrolysis conditions in tubular transport reactor. Chromatographic and spectroscopic studies on the pyrolytic oil showed that the oil obtained from rapeseed can be used as a renewable fuel and chemical feedstock.     

Biogas production potential from cotton wastes

The anaerobic treatability and methane generation potential of three different cotton wastes namely, cotton stalks, cotton seed hull and cotton oil cake were determined in batch reactors. In addition, the effects of nutrient and trace metal supplementation were also investigated. To this purpose biochemical methane potential (BMP) experiments were performed for two different waste concentrations, namely 30 and 60 g/l. The results revealed that cotton wastes can be treated anaerobically and are a good source of biogas. Approximately 65, 86 and 78 ml CH₄ were produced in 23 days from 1 g of cotton stalks, cotton seed hull and cotton oil cake in the presence of basal medium (BM), respectively. BM supplementation had an important positive affect on the production of biogas.     

Bio-oil production via fast pyrolysis of shrub residues in a fluidized-bed reactor

In this article, the shrub residues as raw materials were produced to fast pyrolysis oil (called bio-oil) in a 5-kg/h fluidized-bed reactor. The optimum conditions were obtained at 500°C, flow rate of fluidizing gas of 4 m³/h, and feed rate of 3 kg/h. The liquid yield was up to 60% at the optimum conditions. The bio-oil was easy to divide into two phases: oil phase and aqueous phase. The high heat value of the oil phase was up to 18.55 MJ/kg, but the high heat value of the aqueous phase was only 0.72 MJ/kg. The oil phase and aqueous phase both have lower pH values. The oxygen content was up to 50%, while the sulfur and nitrogen content were very low. Owing to the higher oxygen content and lower pH value in liquid products, it must be further upgraded to bio-oil before application.     

Characterization of bio-oil and its sub-fractions from pyrolysis of Scenedesmus dimorphus

In the present study, microalgae Scenedesmus dimorphus was reported for pyrolysis in a fixed-bed reactor to determine the effects of temperature on products yield and the chemical compositions of the liquid and solid products. Experiments were carried out at a temperature range of 300–600 °C with heating rate of 40 °C/min and nitrogen flow rate of 100 ml/min. The yield of bio-oil was found to be maximum (39.6%) at the temperature of 500 °C and was further fractionated into n-hexane, toluene, ethyl acetate and methanol sub-fractions by using liquid column chromatography. Various characteristics of bio-oil and its sub-fractions were determined by ¹H NMR, FTIR and GC–MS. The biochar produced as a co-product can be a potential soil amendment with multiple benefits including soil fertility and C-sequestration. The present investigation suggests the suitability of Scenedesmus dimorphus as a potential feedstock for exploitation of energy and biomaterials through pyrolytic conversion.     

Combustion properties of slow pyrolysis bio-oil produced from indigenous Australian species

Bio-oil derived via slow pyrolysis process of two indigenous Australian tree species, red gum (Eucalyptus camaldulensis) from the basin of Murray, Victoria, and blue gum (Eucalyptus globulus) wood from the region of Mount Gambier, South Australia was blended with ethanol and burned in a circular jet spray at atmospheric pressure. Bio-oil flames were shorter, wider and brighter than diesel fuel flames at the same conditions. Adding of flammable polar additives (e.g. ethanol) to bio-oil improved some of the undesired properties of the fuel such as poor atomisation, low calorific value, and high NO_x emission from the flame. Nevertheless, adding of ethanol should be carried out with caution since it leads to a reduction of the heat flux from the flame. Changing the concentration of flammable polar additives in bio-oil can be an optimising factor in achieving the proper balance between the best spray formation and the maximal heat flux from the flame.