SynGas production from organic waste using non-thermal-pulsed discharge

The purpose of this study was to develop a technology that can convert biogas to synthesis gas (SynGas), a low-emission substituted energy, using a non-thermal-pulsed plasma method. To investigate the characteristics of SynGas production from simulated biogas, the reforming characteristics in relation to variations in pulse frequency, biogas component ratio (C3H8/CO2), vapor flow ratio (H2O/total flow rate [TFR]), biogas velocity, and pulse power were studied. A maximum conversion rate of 49.1% was achieved for the biogas when the above parameters were 500 Hz, 1.5, 0.52, 0.32 m/sec, and 657 W, respectively. Under the above conditions, the dry basis mole fractions of the SynGas were as follows: H2 = 0.645, CH4 = 0.081, C2H2 = 0.067, C3H6 = 0.049, CO = 0.008 and C2H4 = 0.004. The ratio of hydrogen to the other intermediates in the SynGas (H2/ITMs) was 3.1.     

Long-term evaluation of activated carbon as an adsorbent for biogas desulfurization

ABSTRACT

In this study, granular activated carbon (GAC) was used as an adsorbent for biogas desulfurization. Biogas containing 932–2,350 ppm of H₂S was collected from an anaerobic digester to treat the wastewater from a dairy farm with about 200 cows. An adsorption test was performed by introducing the biogas to a column that was packed with approximately 50 L of commercial GAC. The operation ceased if the effluent gas had an H₂S concentration of over 100 ppm. The GAC was replaced by a given weight of new GAC in a subsequent test. According to the results, for H₂S concentrations in the range of 932–1,560 ppm (average±SD = 1,260 ± 256 ppm), 1 kg of the GAC yielded biogas treatment capacities of 568 ± 112 m³ and H₂S adsorption capacities of 979 ± 235 g. For the higher influent H₂S concentrations of 2,110 ± 219 ppm, the biogas treatment and H₂S-adsorption capacities decreased to 229 ± 18 m³ and 668 ± 47 g, respectively. An estimation indicated a requisite cost of US$16.5 for the purification of 1,000 m³ of biogas containing 2,110 ppm of H₂S. This cost is approximately 5% of US$330, the value of 1,000 m³ of biogas.     

金属铁铝对混凝强化初沉污泥中温厌氧消化的影响简

选取FeCl₃和AlCl₃·6H₂O作为混凝剂对城市污水进行一级强化混凝处理,降低二级生物处理的进水负荷,减少污水生物处理系统的能量消耗。主要研究混凝过程投加的金属盐对一级强化混凝产生的初沉污泥中温厌氧消化的影响。和剩余污泥相比,初沉污泥更适合厌氧消化处理,污泥降解性能和产气性能更高。当采用城市污水一级强化混凝处理时,污泥中的金属和金属盐水解引起的pH降低,使混凝强化初沉污泥的厌氧消化受到一定抑制。随着污泥中铝含量的降低和铁含量的增加,厌氧消化的COD降解率和挥发性固体（VS）降解率逐渐升高,生物气产量逐渐增大,产气速率加快。当混凝强化初沉污泥只含有铁时（铁含量为10.16 mg/L）,混凝强化初沉污泥厌氧消化效果最好,产气稳定,而且产气速率高,生物气产量为237 mL,生物气甲烷含量为55.5%,降解单位VS产气量为0.80 L/g,均高于其他含铝的混凝强化初沉污泥。污泥中的铁对初沉污泥厌氧消化的抑制作用远远小于铝的作用,说明铁盐适合用于城市污水的一级强化混凝处理。     

Zn/Fe体系湿法催化氧化高效脱除沼气中H2S的研究

提出了Zn/Fe体系湿法催化氧化脱除沼气中H₂S新工艺,阐述了反应机理、实验装置和工艺流程,考察了各单因素操作条件对H₂S脱除效率的影响,在此基础上进行的综合条件实验,脱硫效率都维持在99.6%以上,净化后沼气中H₂S含量低于国家标准。过程不消耗任何化工原料,不产生二次污染,体系无降解问题。     

Atrazine removal by ozonation processes in surface waters

Abstract

Atrazine (6‐chloro‐N‐ethyl‐N'‐isopropyl‐1,3,5‐triazinedyl‐2,4‐diamine) was treated with ozone alone and in combination with hydrogen peroxide or UV radiation in three surface waters. Experiments were carried out in two bubble reactors operated continously. Variables investigated were the ozone partial pressure, temperature, pH, mass flow ratio of oxidants fed: hydrogen peroxide and ozone and the type of oxidation including UV radiation alone. Residence time for the aqueous phase was kept at 10 min. Concentrations of some intermediates, including deethylatrazine, deisopropylatrazine and deethyldeisopropylatrazine, were also followed. The nature of water, specifically the alkalinity and pH were found to be important variables that affected atrazine (ATZ) removal. Surface waters with low alkalinity and high pH allowed the highest removal of ATZ to be reached. There was an optimum hydrogen peroxide to ozone mass flow ratio that resulted in the highest ATZ removal in each surface water treated. This optimum was above the theoretical stoichiometry of the process. Therefore, to reach the maximum removal of ATZ in a O₃/H₂O₂ process, more hydrogen peroxide was needed in the surface waters treated than in ultrapure water under similar experimental conditions. In some cases, UV radiation alone resulted in the removal of ATZ higher than ozonation alone. This was likely due to the alkalinity of the surface water. Ozonation and UV radiation processes yield different amounts of hydrogen peroxide. Combined ozonations (O₃/H₂O₂ and O₃/UV) lead to ATZ removals higher than single ozonation or UV radiation but the formation of intermediates was higher.     

Deodorization of Dimethyl Sulfide Using a Discharge Approach at Room Temperature

Abstract

The traditional technologies for odor removal of thiol usually create either secondary pollution for scrubbing, adsorption, and absorption processes, or sulfur (S) poisoning for catalytic incineration. This study applied a laboratory-scale radio-frequency plasma reactor to destructive percentage-grade concentrations of odorous dimethyl sulfide (CH₃SCH₃, or DMS). Odor was diminished effectively via reforming DMS into mainly carbon disulfide (CS₂) or sulfur dioxide (SO₂). The removal efficiencies of DMS elevated significantly with a lower feeding concentration of DMS or a higher applied rf power. A greater inlet oxygen (O₂)/DMS molar ratio slightly improved the removal efficiency. In an O₂-free environment, DMS was converted primarily to CS₂, methane (CH₄), acetylene (C₂H₂), ethylene (C₂H₄), and hydrogen (H₂), with traces of hydrogen sulfide (H₂S), methyl mercaptan (CH₃SH), and dimethyl disulfide. In an O₂-containing environment, the species detected were SO₂, CS₂, carbonyl sulfide, carbon dioxide (CO₂), CH₄, C₂H₄, C₂H₂, H₂, formal-dehyde, and methanol. Differences in yield of products were functions of the amounts of added O₂ and the applied power. This study provided useful information for gaining insight into the reaction pathways for the DMS dissociation and the formation of products in the plasmolysis and conversion processes.     

Four Common Diagnostic Problems that Inhibit Radon Mitigation

Abstract

An activated sludge aeration tank (40 × 40 × 300 cm, width × length × height) with a set of 2-mm orifice air spargers was used to treat gas-borne volatile organic compounds (VOCs; toluene, p-xylene, and dichloromethane) in air streams. The effects of liquid depth (Z), aeration intensity (G/A), the overall mass-transfer rate of oxygen in clean water (K _L a _O2 ), the Henry’s law constant of the tested VOC (H), and the influent gaseous VOC concentration (C ₀) on the efficiency of removal of VOCs were examined and compared with a literature-cited model. Results show that the measured VOC removal efficiencies and those predicted by the model were comparable at a G/A of 3.75–11.25 m³/m²·hr and C ₀ of ～1000–6000 mg/m³. Experimental data also indicated that the designed gas treatment reactor with K _L a _O2 = 5–15 hr^?1 could achieve >85% removal of VOCs with H = 0.24–0.25 at an aerated liquid depth of 1 m and >95% removal of dichloromethane with H = 0.13 at a 1-m liquid depth.     

Development of a chemical kinetic model for a biosolids fluidized-bed gasifier and the effects of operating parameters on syngas quality

In an effort to decrease the land disposal of sewage sludge biosolids and to recover energy, gasification has become a viable option for the treatment of waste biosolids. The process of gasification involves the drying and devolatilization and partial oxidation of biosolids, followed closely by the reduction of the organic gases and char in a single vessel. The products of gasification include a gaseous fuel composed largely of N₂, H₂O, CO₂, CO, H₂, CH₄, and tars, as well as ash and unburned solid carbon. A mathematical model was developed using published devolatilization, oxidation, and reduction reactions, and calibrated using data from three different experimental studies of laboratory-scale fluidized-bed sewage sludge gasifiers reported in the literature. The model predicts syngas production rate, composition, and temperature as functions of the biosolids composition and feed rate, the air input rate, and gasifier bottom temperature. Several data sets from the three independent literature sources were reserved for model validation, with a focus placed on five species of interest (CO, CO₂, H₂, CH₄, and C₆H₆). The syngas composition predictions from the model compared well with experimental results from the literature. A sensitivity analysis on the most important operating parameters of a gasifier (bed temperature and equivalence ratio) was performed as well, with the results of the analysis offering insight into the operations of a biosolids gasifier.

Implications:

As gasification becomes a more prominent waste disposal option, understanding the effects of feedstock composition and gasifier parameters on the production of syngas (rate and quality) becomes increasingly important. A model has been developed for the gasification of dried sewage sludge that will allow for prediction of changes in syngas quality (and energy recovery from the waste), and should be helpful in assessing the benefits of new gasification projects.     

培养方式对废水脱氮与沼气脱硫污泥驯化影响

实验研究了底物、接种污泥和微生物生长方式对猪场废水脱氮和沼气脱硫耦联污泥驯化及活性恢复的影响,以解决快速富集培养废水脱氮与沼气脱硫微生物的问题。研究发现,就脱氮脱硫均达到60%的时间而言,接种厌氧污泥反应器为9 d,比接种好氧污泥反应器(18 d)和不接种污泥加填料反应器(21 d)更短。以含氮含硫废水为底物驯化时,接种厌氧污泥更有利于脱氮脱硫污泥的驯化;而同为接种好氧污泥时,以含氮含硫废水为底物的驯化方式更有利于脱氮脱硫污泥的驯化。污泥活性恢复实验中,以含氮废水+沼气(H2S)为底物培养驯化的污泥,硫转化活性恢复所用的时间为15 d,比含氮含硫废水为底物驯化污泥的活性恢复时间更长。     

Benzene and toluene influence with or without nitrogen dioxide on inorganic pigments of works of art—Part II

Air pollution has a great impact on the social and economic aspects all over the world. In order to account the human interaction with the atmospheric environment, a suitable scientific basis is needed.That is why six physicochemical quantities have been determined in a previous work for each one heterogeneous system between organic volatile pollutants and oxide-pigments of works of art. This investigation is extended in order to determine experimentally five new ones. Thus, a more precise contribution to the elucidation of the mechanism of the deterioration of various works of art in museums is achieved. These physicochemical quantities are: (1) local adsorption energies, (2) local monolayer capacities, (3) local adsorption isotherms, (4) density probability function, and (5) pollutant concentration on the oxide-pigment at equilibrium. All these adsorption parameters mentioned above have been calculated as a function of experimental time for the systems: C₆H₆/TiO_2, C₆H₆/NO₂/TiO_2, C₆H₆/Cr₂O_3, C₆H₆/NO₂/Cr₂O_3, C₆H₅CH₃/TiO_2, C₆H₅CH₃/NO₂/TiO_2, C₆H₅CH₃/Cr₂O_3, C₆H₅CH₃/NO₂/Cr₂O_3, C₆H₆/PbO, C₆H₆/NO₂/PbO, C₆H₅CH₃/PbO, and C₆H₅CH₃/NO₂/PbO for the first time. Thus, in this work we shall stress the recent new aspect of Reversed Flow-(Inverse) Gas Chromatography (RF-GC or RF-IGC), i.e. the time-resolved chromatography related to the evaluation of some important adsorption parameters. Gas Chromatography is a promising meeting place of surface science and atmospheric chemistry.     

臭氧氧化苯乙烯有机气体性能及机制

采用臭氧高级氧化处理高浓度苯乙烯有机废气,研究了进气苯乙烯浓度、臭氧浓度、停留时间、O₃/C₈H₈摩尔比对苯乙烯去除效率的影响。研究结果表明,臭氧氧化能有效净化苯乙烯有机废气,苯乙烯去除效率可达66.6%。适宜运行条件为：停留时间为3.6 s,O₃/C₈H₈摩尔比为0.46。采用GC-MS分析臭氧氧化苯乙烯出口气样,研究结果表明,苯甲醛（C₆H₅CHO）和苯甲酸（C₆H₅COOH）为臭氧氧化苯乙烯的中间产物。臭氧高级氧化苯乙烯机制为苯乙烯气体被臭氧氧化为苯甲醛和苯甲酸,然后继续臭氧氧化为最终产物二氧化碳和水。     

微波-Fenton对沼液中抗生素和激素的高级氧化

采用微波强化Fenton氧化处理系统,研究H2O2浓度、Fe2+浓度、初始pH、微波辐射时间和微波辐射功率对沼液中喹乙醇、土霉素、四环素及金霉素降解效果的影响.结果发现,采用微波强化Fenton氧化降解沼液中抗生素与激素的最优条件是:H2O2浓度为40 mg/L、Fe2+浓度为12 mg/L、初始pH为4、微波辐射时间为2 min、微波辐射功率为中火(445W),沼液中喹乙醇、土霉素、四环素、金霉素和COD的去除率分别达到67％、93％、91％、88％和46％.在水浴条件下,与单独微波辐射和单独Fenton相比,微波强化Fenton氧化有明显的优越性.     

UV/H_2O_2/TiO_2联合水解酸化+MBR工艺处理亚砜废水

二甲基亚砜(DMSO)废水因其COD高、可生化性差的特性而较难处理。本实验以采用硫酸二甲酯法生产DMSO的某化工厂废水为研究对象,设计并建立了组合式光催化氧化装置联合水解酸化+MBR工艺的中试系统,探讨了组合式光催化氧化装置、氧化剂投加量、pH、反应时间和水力停留时间对系统处理效果的影响。结果表明,组合式光催化氧化装置可有效提高DMSO废水的可生化性。最优工艺参数为:按H2O2与原水COD质量浓度比为2∶1投加H2O2,在pH值为4、反应时间为6 h、水力停留时间为4 h的条件下,该系统对原水COD(5 000 mg/L)去除率大于98%,出水COD达到《污水综合排放标准》(GB 8978-1996)一级要求。     

Effect of ethanol addition on soot precursors emissions during benzene oxidation in a jet-stirred reactor

A constant volume reactor model (PSR) was used to investigate the effect of ethanol addition on the formation of some pollutants during benzene oxidation in a jet-stirred reactor. The blended fuels were formed by incrementally adding 4 % wt of oxygen (ethanol) to the neat benzene fuel and by keeping the inert mole fraction (nitrogen) and the equivalence ratio constants. The main objective of this work was to obtain fundamental understanding of the mechanisms through which the oxygenate compound affects soot precursor amounts. The modeling results showed that C₂H₂, C₅H₅, and C₃H₃ mole fractions decreased upon increasing the ethanol percentage in the fuel mixture.     

The Inhibition of Photochemical Smog

Additional inhibitors for the conversion of NO to NO₂ in C3H6—NO—0₂ irradiated mixtures have been tested at 25°C. These mixtures initially contained 16 mTorr C₃H₆, 8 mTorr NO, 0.012 mTorr NO₂, additive, and enough O₂ to bring the total pressure to 100 Torr. The NO₂ pressure was monitored photometrically. In the absence of additive, the NO₂ pressure first increases with irradiation time reaching a maximum conversion at about 15 minutes. As the irradiation time increases beyond 15 min, the NO₂ pressure drops. Before adding the inhibitors, runs were done with 10 Torr of CO added, and in these runs the conversion was speeded so that the maximum in NO₂ pressure occurred at 10 min. This enhancement in conversion rate is considered to be diagnostic for the presence of HO radicals. Next 10-min irradiations were done with various amounts of hexafluorobenzene (C₆F₆), nitrobenzene (C₆H₅NO₂), or naphtha lene (C₁₀H₈) added. The NO₂ pressure was reduced to one-half its value in the absence of inhibitor with 270 mTorr C₆F₆’, 220 mTorr C₆H₅N0₂, or 4 mTorr C₁₀Hg. The C₁₀H₈ is a very efficient inhibitor, but additions of up to 1 8.5 mTorr C₁₀H₈ did not reduce the N0₂ pressure to zero. Studies of the percent conversion of NO to NO₂ vs. irradiation time were done with either 4.2 mTorr C₁₀H₈ or 40 mTorr 2,6-di-ferf-butyl-4-methylphenol (Ph) added. In the former case the peak conversion was delayed from 15 to 22 min, while in the latter case no delay occurred. However, with the Ph added, there appeared to be some reduction in the maximum value of percent conversion.     

Impact of Alternative Fuels on Vehicle Emissions of Greenhouse Gases

Abstract

The conversion of methane to liquid products, hydrogen (H₂), and ammonia (NH₃) was investigated experimentally using microgap discharge plasma at an environmentally friendly condition. The experimental results indicated that H₂ and NH₃ were detected as the main gas products. The highest yield and production rate of H₂ was 14.4% (v/v) and 2974.6 μmol/min, respectively, whereas the highest yield and production rate of NH₃ was 8000 ppm (v/v) and 165.1 μmol/min, respectively. Particularly, the liquid products were collected on the plate and consisted of pyrrole, 2-methyl-1,4-pentadiene, α-amidopyri-dine, 2,5-dimethylpyrrole, methylpyrazine, 1-hexyne, 1,4-heptadiene, and polycyclic organic compounds. Some liquid products were the intermediates of drug, ?avor, dye, and organic synthesis, as well as edible ?avor. The collection efficiency in mass and energy efficiency were 26.3% at once and 22.9 g/kWh, respectively. The whole reaction process was considered to be in line with green chemistry principles.     

Performance of an Innovative Two-Stage Process Converting Food Waste to Hydrogen and Methane

Abstract

This study was conducted to evaluate the performance of an innovative two-stage process, BIOCELL, that was developed to produce hydrogen (H₂) and methane (CH₄) from food waste on the basis of phase separation, reactor rotation mode, and sequential batch technique. The BIOCELL process consisted of four leaching-bed reactors for H₂ recovery and post-treatment and a UASB reactor for CH₄ recovery. The leaching-bed reactors were operated in a rotation mode with a 2-day interval between degradation stages. The sequential batch technique was useful to optimize environmental conditions during H₂ fermentation. The BIOCELL process demonstrated that, at the high volatile solids (VS) loading rate of 11.9 kg/m³-day, it could remove 72.5% of VS and convert VS_removed to H₂ (28.2%) and CH₄ (69.9%) on a chemical oxygen demand (COD) basis in 8 days. H₂ gas production rate was 3.63 m³/m³ ·day, while CH₄ gas production rate was 1.75 m³/m³ ·day. The yield values of H₂ and CH₄ were 0.31 and 0.21 m³/kg VS_added, respectively. Moreover, the output from the post-treatment could be used as a soil amendment. The BIOCELL process proved to be stable, reliable, and effective in resource recovery as well as waste stabilization.     

Variability of SO2, CO,and light hydrocarbons over a megacity in Eastern India: effects of emissions and transport

The Indo-Gangetic plain (IGP) has received extensive attention of the global scientific community due to higher levels of trace gases and aerosols over this region. Satellite retrievals and model simulations show that, in particular, the eastern part IGP is highly polluted. Despite this attention, in situ measurements of trace gases are very limited over this region. This paper presents measurements of SO₂, CO, CH₄, and C₂–C₅ NMHCs during March 2012–February 2013 over Kolkata, a megacity in the eastern IGP, with a focus on processes impacting their levels. The mean SO₂ and C₂H₆ concentrations during winter and post-monsoon periods were eight and three times higher compared to pre-monsoon and monsoon. Early morning enhancements in SO₂ and several NMHCs during winter connote boundary layer effects. Daytime elevations in SO₂ during pre-monsoon and monsoon suggest impacts of photo-oxidation. Inter-species correlations and trajectory analysis evince transport of SO₂ from regional combustion sources (e.g., coal burning in power plants, industries) along the east of the Indo-Gangetic plain impacting SO₂ levels at the site. However, C₂H₂ to CO ratio over Kolkata, which are comparable to other urban regions in India, show impacts of local biofuel combustions. Further, high levels of C₃H₈ and C₄H₁₀ evince the dominance of LPG/petrochemicals over the study location. The suite of trace gases measured during this study helps to decipher between impacts of local emissions and influence of transport on their levels.     

Sorptive Behavior of Sorgoleone in Ultisol in Two Solvent Systems and Determination of Its Lipophilicity

Sorgoleone (SGL) exuded by sorghum roots inhibits the development of some weeds. Due to its high hydrophobicity, it is expected that SGL presents low soil mobility and limited allelopathic activity in the field. This work aims to evaluate the sorptivity of sorgoleone in octanol-water and in soil under two solvent systems. The two solvent systems were methanol:water (60:40) (MeOH:H₂O) and pure methanol (MeOH). These two solvent systems promote different conditions for SGL solubility. Treatments were arranged in a 2 × 6 factorial (solvent systems × equilibrium concentrations in the solution (EC)). For each solvent, the sorption was achieved by shaking 500 mg of soil with 10 ml of 0, 5, 10, 15, 25, 40, and 60 mg L^?1 of SGL solution, during 24 h. After centrifugation, the supernatant was filtered and the SGL concentration was determined by high performance liquid chromatography (HPLC). Data of sorbed amount of SGL were submitted to variance analysis, using a hierarchic factorial model. The data of sorbed amount (x/m) and equilibrium concentration (C) were fitted to the linear (x/m = a + K _d C) and to the Freundlich (x/m = K _f C ^1/n ) models. The isotherm obtained for the MeOH:H₂O system presented linear shape, whereas for the MeOH system a two subsequent linear isotherm was fitted. Sorgoleone is a highly hydrophobic compound, presenting a log K _ow of 6.1. The sorption of sorgoleone to the soil was very high. The organic environment stimulated the sorgoleone sorption to the soil.     

Abatement of Ammonia and Hydrogen Sulfide Emissions from a Swine Lagoon Using a Polymer Biocover

ABSTRACT

The purpose of this research was to determine the efficiency of a polymer biocover for the abatement of H₂S and NH₃ emissions from an east-central Missouri swine lagoon with a total surface area of 7800 m². The flux rate of NH₃, H₂S, and CH₄ was monitored continuously from two adjacent, circular (d = 66 m) control and treatment plots using a nonintrusive, micrometeorological method during three independent sampling periods that ranged between 52 and 149 hr. Abatement rates were observed to undergo a temporal acclimation event in which NH₃ abatement efficiency improved from 17 to 54% (p = <0.0001 to 0.0005) and H₂S abatement efficiency improved from 23 to 58% (p < 0.0001) over a 3-month period. The increase in abatement efficiency for NH₃ and H₂S over the sampling period was correlated with the development of a stable anaerobic floc layer on the bottom surface of the biocover that reduced mass transfer of NH₃ and H₂S across the surface. Analysis of methanogenesis activity showed that the biocover enhanced the rate of anaerobic digestion by 25% when compared with the control. The biocover-enhanced anaerobic digestion process was shown to represent an effective mechanism to counteract the accumulation of methanogenic substrates in the biocovered lagoon.