Large Amounts Of CO2 Research Articles

Tree species suitable for roadside afforestation and carbon sequestration in Bilaspur, India

The CO2 stocks in roadside trees in Bilaspur, India, were estimated using a systematic sampling method on 30 sample plots. The sampling plots covered a total area of 3 ha. The region housed 438 trees of 37 species and 17 families, with an accumulated biomass of 101.44 t, 48.18 t of carbon and 176.64 t of CO2. Delonix regia had the largest amounts of species-specific biomass and CO2 stocks, followed by Tamarindus indica, Ficus religiosa, Albizia lebbeck and Ficus benghalensis. Azadirachta indica, Peltophorum pterocarpum, Samanea saman and Senna siamea had the highest numbers and relative abundances in roadside plantations. The 10 tree species that sequestered more than 80% of Bilaspur’s CO2 were, in order of highest to lowest sequestration, Delonix regia, Samanea saman, Tamarindus indica, Azadirachta indica, Ficus religiosa, Peltophorum pterocarpum, Albizia lebbeck, Terminalia catappa, Ficus benghalensis and Terminalia arjuna. These tree species are therefore recommended for roadside plantations to sequester large amounts of CO2 from the city and contribute to offsetting warming and mitigating the impact of climate change.

Ignition and Extinction of n‐Butyl Nitroxyethylnitramine‐Plasticized Polyethylene Glycol Propellants

AbstractThe ignition and extinction of n‐butyl nitroxyethylnitramine (BuNENA)‐plasticized polyethylene glycol (PEG) propellants were investigated with respect to the concentration of binder and the ratio of plasticizer to polymer (pl/po). A distinctive change in the ignition delay time (tign) of the propellants was found at a low pressure of 0.03 MPa, where tign increases as the binder concentration increases from 24 % to 32 % and decreases when the pl/po ratio reaches from 1 to 6. The kinetic analysis shows that the ignition delay of BuNENA‐PEG propellants is due to a high activation energy of a condensed phase accompanied by the reduction of NO in the gas phase that plays an important role in the formation of luminous flames. Furthermore, the BuNENA‐PEG propellants with a high concentration of binder or a low ratio of pl/po were found to result in a relatively high value of the pressure deflagration limit (PDL) under which steady combustion cannot occur. With regard to combustion stability, it seems that the BuNENA‐PEG propellants producing relatively large amounts of CO and H2 are easy to extinguish and exhibit significant delay in ignition at low pressure.

A multifunctional anti-inflammatory drug that can specifically target activated macrophages, massively deplete intracellular H2O2, and produce large amounts CO for a highly efficient treatment of osteoarthritis

Specifically inhibiting the proliferation of activated macrophages and clearing the high levels of reactive oxygen species (ROS) secreted by macrophages is crucial for osteoarthritis (OA) treatment. Moreover, if the clearance of these high levels of ROS can be simultaneously used to induce oxidation-responsive release of anti-inflammatory drugs, the therapeutic effect of OA may be further improved. Here, a multifunctional anti-inflammatory drug (CPHs) based on a peptide dendrimer nanogel was constructed by physically encapsulating CORM-401 and wrapping its surface with folic acid (FA)-modified hyaluronic acid (HA). CPHs is capable of efficiently entering activated macrophages via FA- and HA-mediated specific targeting effects and then rapidly release large amounts of CO by massive consumption of H2O2. The generated CO effectively suppresses the secretion of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α by inhibiting cell proliferation; inducing the activation of heme oxygenase (HO-1), and downregulating the expression of p38 MAPK, NF-kB (p50/p65) and TLR-2. In vivo experiments further confirmed that CPHs can massively deplete ROS in OA joints and effectively suppress the degradation of articular cartilage and their extracellular matrix. More importantly, CPHs is non-toxic to normal macrophages, and the high levels of CO generated in the joints do not result in notable changes in the HbCO levels in blood. Together, these results show that CPHs is an effective and safe anti-inflammatory drug and has essential application prospects in OA treatment.

Influence of vegetation cover and soil features on CO2, CH4 and N2O fluxes in northern Finnish Lapland

Understanding the drivers affecting SOM decomposition, GHG emissions and feedback to climate change in subarctic fragile and highly patterned landforms is crucial nowadays. A field campaign was conducted at catchment scale in Finnish Lapland, aiming at detecting differences in GHG fluxes in a mosaic of subarctic landforms: pine, mixed, birch and open birch forest, alpine tundra, alpine palsa, non-mire wetland, palsa mires and wetland mires. Soil profiles were described and analyzed for chemical and physical properties. CO2, CH4 and N2O fluxes from vegetated soil surface were measured by static chamber method.The largest amount of CO2 was emitted by birch forests>palsa mires>tundra and pine forest>wetlands and was driven by organic layer thickness in palsas and by priming effect mechanisms when environmental conditions favored the mineralization of organic matter stored in birch forest. Depth and organic matter content of humified organic layer, vegetation development and permanent flooding conditions triggered CH4 emissions, with 6-fold higher emissions from wetland than palsa mires and net uptake in the other landform types. N2O emissions in tundra and birch forests derived mainly from nitrification, sustained by oxygen and N availability. Differently, the higher C/N ratio and lower pH in pine and mixed forests caused N2O uptake in the soil.Possible feedbacks to climate change in the next few years or decades were identified: i) huge CH4 emissions in case of seasonally frozen soil or permafrost disappearance and ii) an increase of CO2 and N2O emissions in response to birch forest expansion.

Cement production with pozzolans from residual tropical soils formed from paragneiss with a high silicon oxide content

The manufacture of cement demands a lot of energy and gives off large amounts of CO2. Calcined clays need less energy and emit water instead of CO2, which has drawn attention to them, especially those rich in kaolinite. However, their use has been discouraged due to their location and high market price. Hence, the present study focuses on calcined clays with a low kaolinite content, specifically those derivedfrom paragneiss. In Colombia they are located in weathering horizons with depths of up to 40 meters. The results showed contents of 20%Al2O3, less than 14% Fe2O3, more than 60% SiO2, less than 40% kaolinite, 20% illite and more than 30% quartz. Calcined at 750 °C, they were used in mortars, obtaining SAI values of between 80 and 100% after 28 days, which, added to the results of Frattini tests, show that their use as a supplementary cementing material is feasible.

Electrochemical Hydrogen Separation from Reformate Using High-Temperature Polybenzimidazole (PBI) Membranes: The Role of Chemistry

Various phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes, para-PBI, m/p-PBI, and meta-PBI, were prepared via the poly(phosphoric acid) (PPA) process. These three membranes showed high levels of PA (10–32 PA/PBI repeat unit (r.u.)) and proton conductivity (0.14–0.26 S/cm at 180 °C) as compared with a conventionally imbibed meta-PBI membrane (6 PA/PBI r.u. and 0.08 S/cm at 180 °C). By controlling chemistry and increasing the polymer solid content to ∼18 wt %, m/p-PBI and meta-PBI membranes exhibited significantly improved creep resistance (<2 × 10–6 Pa–1) compared to para-PBI (10 × 10–6 Pa–1). In this work, various chemistries of PBI have been investigated to understand how the chemistry affected the electrochemical hydrogen separation (EHS) performance, including voltage requirement, power consumption, efficiency, hydrogen purities, and also long-term durability of the MEAs. Reformate streams containing H2, N2, and CO were used to validate the increased utility of this technique when operating at 160–200 °C due to the increased Pt tolerance to CO. The EHS device based on PBI membranes synthesized via the PPA process can be operated using dilute hydrogen feed streams with large amounts of CO (1–3%), producing fairly pure hydrogen products (>99.6% with <0.4% nitrogen crossover and ppm levels of CO) with very high power efficiencies of up to ∼72%.

Fate of 4-bromodiphenyl ether (BDE3) in soil and the effects of co-existed copper

The quantitative fate of polybrominated diphenyl ethers (PBDEs) in soil is unknown. Furthermore, the effects of co-contamination by toxic copper on the behavior of PBDEs have not been investigated. Using a 14C-tracer, we studied mineralization, metabolism, and formation of non-extractable residues (NERs) of one PBDE congener, i.e., the 4-bromodiphenyl ether (BDE3) in oxic soil for 50 days, without and with amendment of Cu (400 mg kg−1 soil dw). BDE3 rapidly dissipated with a half-life of 5.5 days and large amounts of CO2 (38.8 ± 0.3% of initial applied amount at the end of incubation) and NERs (42.5 ± 0.4%) were rapidly produced. One hydroxylated metabolite (4′-HO-BDE3) was formed (8.1 ± 0.6%) at the beginning of the incubation, but then decreased to 2.2 ± 0.4%. Only BDE3 occurred in physico-chemically entrapped NERs, amounting to 9.2 ± 0.7%, while only 4′-HO-BDE3 in ester-linked NERs (10.9 ± 0.7%). The addition of Cu strongly reduced the kinetics constants of the transformations (including dissipation, mineralization, and NER-formation), the predicted maximal amounts of mineralization, as well as covalent binding of 4′-HO-BDE3 to soil. The results provide first quantitative insights into the fate of low-brominated congeners of PBDEs in soil and indicate that co-contamination by Cu may increase the environmental risks of biodegradable PBDEs in soil by increasing their persistence.

Energy Consumption Analysis of Cryogenic-membrane Hybrid Process for CO2 Capture from CO2-EOR Extraction Gas

ABSTRACT CO2-EOR (CO2-enhanced oil recovery) is an effective method to increase oil recovery. With more and more exploitation of oilfields, a large amount of CO2 will spill out the surface, which can cause serious environmental problems. At present, high energy consumption, low CO2 purity and recovery are still the main challenges of single CO2 capture technology. Therefore, the combination of different CO2 capture technology is a reasonable choice to overcome these bottlenecks. In this work, a cryogenic-membrane hybrid process for the CO2 capture from extraction gas was proposed. In detail, the main parameters of cryogenic-membrane hybrid process (i.e., CO2 content in feed gas, compression pressure, membrane area, liquefaction temperature) which effect on CO2 properties were investigated. The simulation results indicated that the CO2 purity and recovery rate of cryogenic-membrane hybrid process can achieve 99% and 96%, respectively, and the energy consumption of the whole system was less than 850 MJ t–1 CO2. Compared with membrane and cryogenic process, cryogenic-membrane hybrid process can save about 10% energy consumption. The results of this work indicate that cryogenic-membrane hybrid process has great potential for practical application.

Effects of algal-detritus accumulation on the mineralization characteristics of lake sediment

蓝藻水华暴发形成的大量有机碎屑，沉降到沉积物表面，影响沉积物有机质矿化，进而影响碳氮磷循环.本实验选择于桥水库湖心区作为沉积物采样点，通过设置不同密度藻屑添加组（×1倍组和×20倍组）及空白对照组，研究藻屑堆积对沉积物矿化特征的影响及其环境效应，为蓝藻水华影响下的饮用水环境修复和科学管理提供一定的理论依据.结果表明：（1）藻屑添加降低了上覆水pH值，改变了沉积物生物酶活性.藻屑添加密度越大，上覆水pH值越低、波动越大，反映了培养过程异养微生物活性的变化.×1倍组的转化酶活性较高；×20倍组蛋白酶活性和碱性磷酸酶活性较高.（2）藻屑添加对沉积物的矿化途径和沉积物产物的释放速率产生了显著影响.藻屑添加密度越大，有机质矿化速率越大.其中，×1倍组主要增强好氧矿化，释放CO₂；×20倍组主要增强厌氧产甲烷矿化，释放CH₄.（3）不同密度的藻屑添加组，其氮磷扩散、释放通量存在明显差别.×1倍组以沉积物吸附为主，其上覆水NH₄⁺和PO₄^3-平均释放速率与对照组差异较小；×20倍组的NH₄⁺在第0~10天以沉积物吸附为主，之后和PO₄^3-均以向上覆水中释放为主，其NH₄⁺和PO₄^3-平均释放速率（分别为0.223）和0.075 mg/（L·d））明显大于其他实验组.因此，大量蓝藻堆积明显促进沉积物的碳氮磷矿化，释放大量CO₂、CH₄和氮磷营养盐至上覆水中，对湖泊水环境造成污染，为蓝藻的生长繁殖作贡献.;A large amount of organic algal-detritus after cyanobacterial bloom settled on the surface of the sediment, which has an effect on the mineralization characteristic of sedimentary organic matter, and then the biogeochemical cycle of carbon, nitrogen, and phosphorus. In this study, the central area of Yuqiao Reservoir was selected as the sediment sampling point. By the addition treatments of different densities of algal-detritus (×1 and×20 treatments) and blank controls, the effects of algal-detritus accumulation on the mineralization and their environmental effects were studied to provide some theoretical basis for drinking water environmental restoration and scientific management under the influence of cyanobacteria bloom. The results showed that the addition of algal-detritus lowered the pH value of overlying water and changed the activity of biological enzymes in the sediments. The higher the density of algal-detritus, the lower the pH value of the overlying water and the greater the fluctuation were. The×1 treatment had higher invertase activity, meanwhile the×20 treatment had higher protease activity and alkaline phosphatase activity. Secondly, the addition of algal-detritus had a significant effect on sedimentary mineralization pathways and release rates of mineralization products. The higher the density of algal-detritus, the greater the mineralization rate of sedimentary organic matter was. Moreover, the×1 treatment mainly enhanced aerobic mineralization with the increasing release of CO₂; the×20 treatment mainly enhanced anaerobic methanogens mineralization with the increasing release of CH₄. Thirdly, the diffusion and release fluxes of nitrogen and phosphorus were significantly different in algal-detritus addition treatments with different densities. Sediment adsorption was dominated in the×1 treatment, in which the average release rates of NH₄⁺ and PO₄^3- in overlying water differed slightly from the blank controls. In the×20 treatment, the flux of NH₄⁺ showed the tendency of sediment adsorption in the initial ten days and transferred to releasing potential in the remained time, while the releasing flux of PO₄^3- to overlying water was existed during the whole incubation period. The average release rates of NH₄⁺ and PO₄^3- in the×20 treatment (0.223 mg/(L·d) and 0.075 mg/(L·d), respectively) were significantly higher than those of the other treatments. In general, the accumulation of high density of algal-detritus promotes the mineralization of organic carbon, nitrogen, and phosphorus, releasing a large amount of CO₂, CH₄, and nutrients to the overlying water, which decreases water quality and contributes to the growth and reproduction of cyanobacteria.

Properties of Geopolymer Cement Mortar and Blocks with Calcium Carbonate

During manufacture of cement, a major constituent of concrete, large amount of CO2 is released and waste/by-product materials are produced. Protection of environment from greenhouse gases and dumping of waste/ by-product materials in an un-controlled manner has become very important. Constituents of concrete can be replaced partially or fully with alternate materials to make geopolymer concrete where CO2 emission is significantly low. The present study focuses on manufacture of geopolymer cement by varying the constituents with calcium carbonate. The geopolymer mortar and blocks are cast with different variables and tested for their compressive strength, water absorption, IRAanddensity.

Experimental study on the characteristics of formation and dissociation of CO2 hydrates in porous media

Geologic carbon sequestration (GCS) has been pursued as a feasible strategy to store the large amount of CO2 to curb its emission to the atmosphere in an effort to mitigate the greenhouse effects. CO2 hydrate, which can form when the pressure and temperature satisfy its stability condition, can provide a self-trapping mechanism for an offshore CO2 geologic storage. For example, direct sequestration of CO2 in the form of hydrate crystals can be achieved in the storage aquifer under the seafloor. Besides, the formation of CO2 hydrates in an upper layer of the CO2 storage zone can potentially provide a secondary caprock. These applications, however, require a thorough understanding of the formation and dissociation of CO2 hydrates in porous media, which are largely unknown yet. In this manuscript, a laboratory study on the formation and dissociation of CO2 hydrates in two different environments, a two- (CO2-water) or three-phase (CO2-water in glass beads) condition, is presented. Based on the experimental results, it can be anticipated that the pressure and temperature change will be negligible when the formation of CO2 hydrate is induced for GCS in the actual soil/rock layers. Besides, the formation of CO2 hydrate in porous media may be faster, compared to the two-phase bulk condition that has been typically used in many laboratory studies, as solid grains help accelerate the hydrate formation by providing nucleus sites of crystals. Further elaborations on the role of solid grains would bring a clear path for the feasible application in the subsea area.

CO2 geological storage: Microstructure and mechanical behavior of cement modified with a biopolymer after carbonation

Large amounts of CO2 could be stored underground in deep rock reservoirs and could help reducing emissions into the environment. Carbon geo-storage technologies have several years in development and new techniques and materials are being studied to make this procedure more effective and less expensive. The risk of leakage from geological reservoirs to other rock formations or even towards the surface means that long-term behavior must be carefully studied. The carbonation of the cement used for sealing the wellbore may compromise the borehole integrity. In light of this problem, this work aims to analyze the poromechanical behavior of cement with and without a new additive in a CO2 environment. Bacterial nanocellulose is a biopolymer that modifies important cement properties such as compressive strength, thermal behavior and hydration degree. Two cement types were studied: class G cement and modified class G cement with bacterial nanocellulose. These samples were submitted to a supercritical CO2 environment (temperatures higher than 32 °C and pressures higher than 8 MPa) during 30 days. Mercury intrusion porosimetry and uniaxial compressive strength tests were performed on these samples to study the effect of carbonation. Both types of cement are affected after carbonation by reducing compressive strength and Young’s modulus (E), however, the strength of modified cement was reduced by 8%, while non-modified cement was reduced by 20%.

The Preparation and Characterization of Co–Ni Nanoparticles and the Testing of a Heterogenized Co–Ni/Alumina Catalyst for CO Hydrogenation

Samples of well-controlled nanoparticles consisting of alloys of cobalt and nickel of different atomic ratios were synthesized using wet chemical methods with oleylamine as the solvent and the reducing agent. These materials were characterized by a variety of techniques, including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Small amounts of heterogenized catalysts were prepared using alumina as the support. However, the potential for use of Co–Ni catalysts in CO hydrogenation was explored using a larger amount of Co–Ni/alumina catalyst prepared from standard aqueous impregnation methods and tested in a continuously stirred tank reactor (CSTR) for Fischer–Tropsch synthesis (FTS). Results are compared to a reference catalyst containing only cobalt. The heterogenized catalysts were characterized using synchrotron methods, including temperature programmed reduction with extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge spectroscopy (TPR-EXAFS/XANES). The characterization results support intimate contact between Co and Ni, strongly suggesting alloy formation. In FTS testing, drawbacks of Ni addition included decreased CO conversion on a per gram catalyst basis, although Ni did not significantly impact the turnover number of cobalt, and produced slightly higher light gas selectivity. Benefits of Ni addition included an inverted induction period relative to undoped Co/Al2O3, where CO conversion increased with time on-stream in the initial period, and the stabilization of cobalt nanoparticles at a lower weight % of Co.

Targeted synthesis of Zn-based porous aromatic framework for enhancing fire safety and anti-corrosion performance of wood substrate

Loading metal guests within porous aromatic frameworks (PAF-50) via secondary functional groups is a promising route for introducing or enhancing PAF performance in various applications. Herein, a quaternary pyridinium-type porous aromatic frameworks (PAF-50) and their composites (Zn-PAF-50), are successfully synthesized and incorporated into the wood matrix to effectively realize fire prevention and anticorrosion. More remarkable, PAF micro-nano additives are well dispersed in wood matrix by self-assembly strategy with in situ polymerization, and settled the problem of compatibility. Results show that the treated wood had a strong self-extinguishing ability and passed the UL-94 V-0 burning test. The char residue rate of the treated wood is significantly increased by 112.2%, and the activation energy calculated according to the FWO method has been reduced by 26.3% due to its high pyrolysis and char-forming reactivity. Meanwhile, instead of combustible gases such as methane, large amounts of CO2 and H2O appeared in the degradation products of treated wood. Besides, a more stable and complete char layer is obtained in the treated wood after combustion, and a value of nO/nC is improved by 71.9%. The treated wood exhibited a mass loss rate of 0.5% compared to 32.3% for the untreated wood after the anti-brown-rot fungus tests. Further, this work provides a new direction for the application of PAF particles with expected structure in endowing material with versatility.

On the Development Concept for a New 718-Type Superalloy with Improved Temperature Capability

The superalloy 718 stands out for its excellent manufacturability and strength at ambient temperature. However, its application temperature is limited to about 650 °C due to the instability of the γ’’ precipitates. Here, we provide an in-depth account of an alloy development concept, allowing for the design of superalloys with 718-type properties, yet with a significantly improved microstructural stability. The article begins with a detailed discussion on how the microstructural and chemical composition must be altered to achieve this objective. Then, model alloys were used to explore and validate the outlined strategy. Finally, it is shown how these considerations ultimately led to a new 718-type superalloy with far more improved microstructural stability— namely, VDM Alloy 780. The introduction of a large amount of Co as a substitute for Fe (and partially Ni) is the most important element of our alloy development concept in terms of chemical composition. The most important microstructural feature is the introduction of low solvus temperature, high misfit γ´-strengthening, replacing γ´´-hardening.

Growth of Single-Walled Carbon Nanotubes with Different Chirality on Same Solid Cobalt Catalysts at Low Temperature.

Currently, designing solid catalysts at high temperature is the main strategy to realize single-walled carbon nanotubes (SWNTs) with specific chirality, meaning it is very hard and challenging to create new catalysts or faces to fit new chirality. However, low temperatures make most catalysts solid, and developing solid catalysts at low temperature is desired to realize chirality control of SWNTs. A rational approach to grow SWNTs array with different chiralities on same solid Co catalysts at low temperature (650 °C) is herein put forward. Using solid Co catalysts, near-armchair (10, 9) tubes horizontal array with ≈75% selectivity and (12, 6) tubes array with ≈82% are realized by adopting a small amount of ethanol and large amount of CO respectively. (10, 9) tubes are enriched for thermodynamic stability and (12, 6) tubes for kinetics growth rate. Both kinds of tubes show a similar symmetry to the Co (1 1 1) face with threefold symmetry for the symmetry matching nucleation mechanism proposed earlier. This method provides a new strategy to study the nucleation mechanism and more possibilities for preparing new solid catalysts to control the structure of SWNTs.

Continuous pyrolysis of organosolv lignin and application of biochar on gasification of high density polyethylene

In the pyrolysis of lignin, lignin tends to agglomerate during the feeding stage, and the char produced can expand easily to form foam that prevents continuous operation. To solve this problem, a new bench-scale rotary kiln reactor with alumina balls was used for the pyrolysis of organosolv lignin. Also, a bench-scale fixed-bed reactor was used as a reference reactor to gain an insight on the pyrolysis phenomena from rotary kiln reactor. Compared to the fixed bed reactor, the rotary kiln reactor resulted in a higher yield of organic phase oil with high selectivity to monomeric phenolic compounds. Moreover, a larger amount of CO2 was obtained from the rotary kiln reactor, which strongly suggests that decarboxylation is main deoxygenation path. Furthermore, a char without agglomeration and foaming inside the reactor was generated from the rotary kiln reactor. The catalytic properties of the chars produced from both reactors with nickel impregnation were tested for the gasification of high-density polyethylene to produce H2. Among the four different catalysts (Ni/Rotary Kiln char, Ni/Fixed Bed char, Ni/Al2O3, Ni/Activated carbon) tested, the Ni/Fixed Bed char exhibited the highest yield of H2 (~two times higher H2 generation) from the gasification process of high-density polyethylene. X-ray photoelectron spectroscopy and scanning electron microscopy offers that the high dispersion/distribution of Ni occurred when the fixed bed char was used as a support. All experimental findings from this study significantly suggest that Ni supported on char could be an economically viable catalyst for producing H2 from gasification of high-density polyethylene.

Shock Tube and Kinetic Study on the Effects of CO2 on Dimethyl Ether Autoignition at High Pressures

First-stage and overall ignition delay times of dimethyl ether (DME) were measured in a high-pressure shock tube for various mixtures containing high amounts of CO2. The data are available for DME/air mixtures diluted with 40% CO2 as well as for the mixture of DME and oxidizer containing 20.5% O2 and 79.5% CO2. As a reference, data were also collected for mixtures containing the corresponding amounts of N2. Measurements were conducted for pressures of 15, 35, and 50 bar and a range of temperatures (744–1316 K). For the DME/air mixture diluted with CO2, the equivalence ratio was varied in the range of 0.5–2.0. The results demonstrate that CO2 dilution has a strong effect on ignition delay times in the NTC (negative temperature coefficient) region. The kinetic study that was conducted showed that this phenomenon can be attributed to a thermal effect resulting from the high heat capacity of CO2. In low and high temperature ranges, the effect of CO2 is less pronounced. Additionally, a chemical effect was identified. At high temperatures this effect can be attributed mostly to the influence of CO2 on third-body reactions and leads to slight acceleration of ignition. Various chemical-kinetic models available were evaluated with respect to their accuracy in prediction of ignition delay times for mixtures containing DME and large amounts of CO2.

Chromatographic Procedure for the Determination of Products of the Direct Synthesis of Dimethyl Ether

We developed an original gas chromatographic procedure for determining the products and reagents for the catalytic synthesis of dimethyl ether (DME) from synthesis gas, which enables the simultaneous detection of СН3ОН, DME, СО, СО2, Н2, Н2О, N2, and hydrocarbons to С6. The gas circuit includes four detectors, three packed columns, two precolumns (to prevent water and organic compounds from entering molecular sieve columns) in combination with two relief valves and two pressure regulators for the implementation of the back purging of precolumns. The system is assembled based on a Khromatek-Kristall 5000 chromatograph. The determination is carried out at a constant temperature of 140°C. The duration of analysis is not more than 12 min. Because of the presence of a flame ionization detector, it is possible to detect trace amounts of hydrocarbons, as well as ethane in the presence of large amounts of CO2.

Influence of near-wall air position on the high-temperature corrosion and combustion in a 1000 MWth opposed wall-fired boiler

Low NOx burner together with air-staging system are commonly used in coal-fired power plants in China to reduce NOx emission. However, severe high-temperature corrosion on the water-cooled wall have occurred frequently, because this combustion system result in fuel-rich atmosphere in the main combustion zone and generates a large amount of CO and H2S, which is the main reason for the high-temperature corrosion in the furnace. Near-wall air (NWA) is an economical and effective way to reduce the concentration of CO and H2S. There are two common NWA arrangement, one position is on the side walls, the other is on the front and rear walls. This study numerically investigated the effects of NWA positions on the high-temperature corrosion and combustion of a 1000 MWth opposed wall-fired boiler for better solution of the high-temperature corrosion. The numerical models were validated by the measured data of CO concentration on the side walls. Then the effect of NWA position and NWA ratios (0–1%) on the reducing atmosphere, combustion, and NO generation were numerically studied. The results show that both NWA positions have no effect on the reducing atmosphere and combustion condition when the NWA ratio is lower than 0.5%, but it works when the ratio increase to more than 0.5%. Moreover, it is recommended to arrange NWA on the side walls with the NWA ratio at 1% for better controlling the high-temperature corrosion problems and maintaining good combustion conditions simultaneously, since the concentrations of CO and H2S near side walls were significantly decreased.