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Purpose: To investigate the neuroprotective effect of Shenxiong Drop Pill (SXDP) pretreatment on rats with middle cerebral artery occlusion (MCAO) in rats, and the mechanism involved.Methods: Ninety-nine SD rats were randomly assigned to 4 groups: control group, MCAO group, shamoperated group and SXDP group. The MCAO model was established via thread occlusion. Rats in the SXDP group was administered SXDP 7 days before induction of MCAO. Neurological deficit score (NDS) was determined using Bederson's neurological behavioral scoring method, while cerebral infarction volume was measured using TTC staining. Integrated optical density (IOD) of Nissl Body was evaluated via Nissl staining. Brain water content was measured using dry-wet method. The expression level of AQP4 in brain tissues was determined using immunocytochemistry.Results: The SXDP treatment resulted in significant reduction in NDS, marked improvement in IOD of Nissl Body, and significant reductions in cerebral infarction volume, brain water content, and expression level of AQP4, relative to control (p< 0.05).Conclusion: These results suggest that SXDP pretreatment exerts neuroprotective effect against cerebral ischemia in rats by decreasing in cerebral edema through a mechanism involving downregulation of the expression of AQP4. Keywords: Middle cerebral artery occlusion, Cerebral ischemia, Aquaporins-4, Cerebral edema, Neuroprotection

Biochar is a solid by-product of thermochemical conversion of biomass to bio-oil and syngas. It has a carbonaceous skeleton, a small amount of heteroatom functional groups, mineral matter, and water. Biochar’s unique physicochemical structures lead to many valuable properties of important technological applications, including its sorption capacity. Indeed, biochar’s wide range of applications include carbon sequestration, reduction in greenhouse gas emissions, waste management, renewable energy generation, soil amendment, and environmental remediation. Aside from these applications, new scientific insights and technological concepts have continued to emerge in the last decade. Consequently, a systematic update of current knowledge regarding the complex nature of biochar, the scientific and technological impacts, and operational costs of different activation strategies are highly desirable for transforming biochar applications into industrial scales. This communication presents a comprehensive review of physical activation/modification strategies and their effects on the physicochemical properties of biochar and its applications in environment-related fields. Physical activation applied to the activation of biochar is discussed under three different categories: I) gaseous modification by steam, carbon dioxide, air, or ozone; II) thermal modification by conventional heating and microwave irradiation; and III) recently developed modification methods using ultrasound waves, plasma, and electrochemical methods. The activation results are discussed in terms of different physicochemical properties of biochar, such as surface area; micropore, mesopore, and total pore volume; surface functionality; burn-off; ash content; organic compound content; polarity; and aromaticity index. Due to the rapid increase in the application of biochar as adsorbents, the synergistic and antagonistic effects of activation processes on the desired application are also covered.

Renewable energy sources e.g. biofuels, are the focus of this century. Economically and environmental friendly production of such energies are the challenges that limit their usages. Microalgae is one of the most promising renewable feedstocks. However, economical production of microalgae lipid in large scales is conditioned by increasing the lipid content of potential strains without losing their growth rate or by enhancing both simultaneously. Major effort and advances in this area can be made through the environmental stresses. However, such stresses not only affect the lipid content and species growth (biomass productivity) but also lipid composition. This study provides a comprehensive review on lipid enhancement strategies through environmental stresses and the synergistic or antagonistic effects of those parameters on biomass productivity and the lipid composition. This study contains two main parts. In the first part, the cellular structure, taxonomic groups, lipid accumulation and lipid compositions of the most potential species for lipid production are investigated. In the second part, the effects of nitrogen deprivation, phosphorus deprivation, salinity stress, carbon source, metal ions, pH, temperature as the most important and applicable environmental parameters on lipid content, biomass productivity/growth rate and lipid composition are investigated.

Biochar (BC) generated from thermal and hydrothermal cracking of biomass is a carbon-rich product with the microporous structure. The graphene-like structure of BC contains different chemical functional groups (e.g. phenolic, carboxylic, carbonylic, etc.), making it a very attractive tool for wastewater treatment, CO2 capture, toxic gas adsorption, soil amendment, supercapacitors, catalytic applications, etc. However, the carbonaceous and mineral structure of BC has a potential to accept more favorable functional groups and discard undesirable groups through different chemical processes. The current review aims at providing a comprehensive overview on different chemical modification mechanisms and exploring their effects on BC physicochemical properties, functionalities, and applications. To reach these objectives, the processes of oxidation (using either acidic or alkaline oxidizing agents), amination, sulfonation, metal oxide impregnation, and magnetization are investigated and compared. The nature of precursor materials, modification preparatory/conditions, and post-modification processes as the key factors which influence the final product properties are considered in detail; however, the focus is dedicated to the most common methods and those with technological importance.

Compared to traditional biomass and coal-fired power plants, a process that includes integrated pyrolysis and subsequent gasification is a promising technology to deliver a larger electrical output through the production of high-purity hydrogen with a low carbon footprint. Chemical looping can further enhance the biomass contribution to the global renewable energy demand while fulfilling the stringent CO2 emission cuts needed in the energy sector. This study aims at investigating the feasibility of developing a solar catalytic chemical looping biomass refinery (SCCLBR) power plant for sustainable production of energy using a comprehensive plant modeling and techno-economic assessment. The plant is composed of 7 sequential units: i) biomass preparation (drying, transferring, and grinding), ii) reacting unit (SCCLBR), iii) water gas shift unit and heat recovery, iv) CO2 and H2S separation (Rectisol Process), v) sulfur removal (Claus Process), vi) air separation and vii) catalyst regeneration. The simulation was performed for 1–6 tonne/hour of biomass as input. The effect of key variables (feedstock load, water injection, and temperature) on the economic performance of the plant were analyzed. The simulated results of the chemical looping reactor were validated against the experimental results, while the results of Rectisol and air separation units were validated against the thermodynamic simulation. The results demonstrated that the CCLBR (without solar integration) and integrated SCCLBR can reach the efficiency of 34% and 41% respectively, yet the results have not been optimized. The sensitivity analysis indicated that water injection rate is the most influential parameter, which can even suppress the impact of biomass loading rate. A separate thermodynamic simulation was also performed to investigate the reaction equilibrium of oxygen carrier regeneration (Ca2Fe2O5) using CO2. The results demonstrated that a temperature above 730 °C is required to avoid carbonation (Fe2O3 and CaCO3 production). The maximum greenhouse gas emission in SCCLBR is 10.70, which is significantly lower than traditional coal-to-hydrogen and biomass-to-hydrogen power plants. It has also been found that across varying feedstock input rates, greenhouse gas emissions average 12.8% lower when solar PV supplements refinery power needs; optimization of the steam/biomass ratio may reduce emissions even further.

Potential substitutes of natural gas and lignite fly ash as NO and HCN reducing agents, respectively, for heterogeneous reburning were examined in a bench-scale apparatus equipped with a simulated reburning and a burnout furnace. Selection of NO reducing agent is based on fuel volatility and nitrogen functionality. HCN reducing agent selection is based on literature data. A wide range of waste materials and industrial by-products show overall NO reduction efficiency up to 88% at reburning stoichiometric ratio 0.90 or 0.95. Mixed fuel containing scrap tire and Fe 2 O 3 is particularly effective. Though its cost is constrained by the energy-intensive operation of grinding the tire, the estimated raw-material cost is better than that of natural gas reburning and highly competitive against SCR. A first-level approximation study of the selectivities of nitrogen species to form NO in burnout zone reveals the importance of HCN and char nitrogen reaction mechanisms.

VLSI realization of video compression is the key to real-time high-definition 3D communication systems. The newly established multiview video coding standard, as an extension profile of H.264/AVC, draws more and more attention for its high compression ratio and free-viewpoint support. Besides providing the 3D experience, multiview video can also give users complete scene perception. However, the multiple-viewpoint throughput requirement of MVC increase the complexity and hardware cost dramatically. The system memory bandwidth, on-chip memory size, and processing data throughput of each module all need to be optimized in an MVC encoder. Therefore, efficient hardware solutions for MVC architecture design are needed. In this article an overview of 3D video coding standards developments and design challenges of an MVC encoder are discussed. Then the algorithm and architecture optimization schemes are proposed. For the trade-off between system memory bandwidth and on-chip memory size, a cache-based prediction engine is proposed to ease both design challenges. Moreover, the hybrid open-close loop intra prediction scheme and the frame-parallel pipeline-doubled dual CABAC solve the throughput requirement problem. At the end of this article, based on all the proposed solutions, a prototype single-chip MVC encoder design with processing ability of 4096 × 2160 single-view to 1280 × 720 seven-view is presented.

Multiview video coding (MVC) plays an important role in a 3-D video system. In addition, the resolution of HDTV is increasing to present more vivid perception for users. To realize real-time processing of dozens of TOPS, VLSI solution is necessary. However, ultra high computational complexity, a large amount of external memory bandwidth and on-chip SRAM size, and complex MVC prediction structures are three main design challenges of implementation of MVC hardware architecture. In this paper, an MVC single-chip encoder is proposed for H.264/AVC Multiview High Profile and High Profile for 3-D and quad full high definition (QFHD) TV applications, respectively. The 4096 × 2160 p multiview video encoder chip is implemented on a 11.46 mm2 die with 90 nm CMOS technology. An eight-stage macroblock pipelined architecture with proposed system scheduling and cache-based prediction core supports real-time processing from one-view 4096 × 2160 p to seven-view 720 p videos. The 212 Mpixels/s throughput is 3.4 to 7.7 times higher than previous work. The 407 Mpixels/W power efficiency is achieved, and 94% on-chip SRAM size and 79% external memory bandwidth are saved by the proposed techniques.

Polar solvents are known to swell coal, break hydrogen bonds in the macromolecular structure, and enhance coal liquefaction efficiencies. The effects of the pretreatment of coal using supercritical CO{sub 2} on its physical structure and combustion properties have been studied at the bench-scale level. Emphasis has been placed on NO reburning, NO emissions during air-fired and oxy-fired combustion, and loss on ignition (LOI). Pretreatment was found to increase porosity and to significantly alter the fuel nitrogen reaction pathways. Consequently, NO reduction during reburning using bituminous coal increased, and NO emissions during oxidation of lignite decreased. These two benefits were achieved without negative impacts on LOI.

It is known that polar solvents swell coal, break hydrogen-bonds in the macromolecular structure, and enhance coal liquefaction efficiencies. The effects of drying, interaction with supercritical CO2 and degassing on the physical structure of coal have been studied using gas sorption technique and a scanning electron microscope (SEM). Both drying and interaction with supercritical CO2 drastically change the micropore and mesopore surface area, absolute volume, and volume distribution in both bituminous coal and lignite. Degassing removes debris in the pore space which allows for better analysis of the changes in the morphology that were induced by drying and exposure to supercritical CO2. SEM reveals that interaction of bituminous coal with supercritical CO2 results in an abundance of carbon structures similar to the maceral collinite.

In a recent study, we discovered that oxygen from the gas phase, organic portions of the coal, and minerals in the coal have profound influence on the formation and desorption of stable surface oxides in the early stages of coal combustion. In an attempt to isolate the effects of minerals, demineralized coals (DMC) are oxidized in O{sub 2} with a contact time less than 1 s, and the amount and strength of stable surface oxides are characterized by temperature-programmed desorption (TPD) up to 1650{sup o}C. Young chars derived from both demineralized lignite and bituminous coals show low and flat TPD profiles over a wide temperature range, signifying the minerals' catalytic activities in forming stable surface oxides for both coals. Indeed, the oxidation rates of chars from both bituminous coals and lignite, estimated based on the O{sub 2} concentrations entering and exiting the Al{sub 2}O{sub 3} reactor, were higher than their DMC counterparts. Moreover, graphite, containing no minerals and organically bound oxygen, has an even lower oxidation rate. Similar to those for the raw coals, the combined oxygen balance and elemental analysis of chars from DMC suggests that the oxygen in the organic portion of the lignite activates oxygen turnover andmore » carbon oxidation during its combustion; neither chars from raw nor demineralized bituminous coals possess these properties. X-ray photoelectron spectroscopy (XPS) of raw and demineralized bituminous coals and their char show peaks at around 532.0 eV in the O(1s) difference spectrum, suggesting the possible existence of intercalated stable surface oxides. 35 refs., 7 figs., 4 tabs.« less

To obtain representative temperature-programmed desorption (TPD) profiles of young oxidized chars up to 1650 °C with minimal reactor wall interferences, the chemistry and physics of four ceramic materials has been critically reviewed. A two-staged experimental apparatus is then uniquely designed to produce chars in an Al2O3 flow reactor with 1−21% O2 followed by in situ TPD with a SiC tube. Comparison of TPD profiles of oxidized chars with those from pyrolyzed chars and ashes suggests early-stage char oxidation is profoundly influenced by oxygen from three sources: organics oxygen, mineral matters, and gas phase O2. Young chars oxidized at 1000 °C with less than 0.3 s residence time shows CO desorption peaks during TPD at three distinct temperatures: 730, 1280, and 1560 °C. The peaks at 730 °C are mainly caused by incomplete devolatilization. The peaks at 1280 °C mainly represent desorption of stable surface oxides and incomplete devolatilization. Increasing the gas phase oxidants notably increases the am...

Studies conducted in recent years have indicated that the innovation behaviors of a company is determined by its knowledge attributes. Research conducted on these topics has mainly focused on the manufacturing industry, and limited emphasis is placed on service-oriented industries such as the information service industry. Most of the companies in the information service industry are small and medium-sized enterprises (SMEs). Therefore, this study focused on information service SMEs and aimed to determine the relationship between knowledge attributes and innovation behaviors in information service companies. An exploratory study involving qualitative interviews with five software companies was performed, and the results indicated that 1) knowledge attributes influence innovation behaviors and management in software companies, and 2) R&D personnel autonomy in information service SMEs also influence innovation behaviors and management. The findings of this study have potential applicability in both the theory and practice of knowledge management.

The variables, kinetics, and mechanisms of heterogeneous reburning were studied in a flow reactor with a simulated flue gas. The efficiency of heterogeneous reburning depends on the origin of the char, char preparation history and the presence of oxidants, CO2 and O2, and the reducing agent CO, in reburning. Estimated intrinsic rate constants for surface NO reduction in various gaseous environments were compared with those published. In addition to its large surface area, the effectiveness of lignite char appears to be due to its ability to promote two consecutive reactions: (1) the gasification of char by CO2 and O2 for production of CO; (2) the removal of surface oxygen complexes, including those formed after adsorption of NO, by gaseous CO, for the regeneration of reactive sites. Moreover, lignite ash also catalyzes the decomposition of HCN, a major intermediate of NO conversion during gas reburning. These observations suggest that reburning by a mixed fuel containing natural gas and lignite char can be a potentially attractive route for the in–furnance control of nitrogen oxide.

Isotopically labeled N15O was used to study the interaction of fuel nitrogen from coal with NO in a simulated reburning environment. Experiments were conducted in an alumina flow reactor operated at 1100°C with a reaction time estimated at 0.2 s. A North Dakota lignite and a Pittsburgh #8 bituminous coal were burned with a simulated flue gas containing 1000 ppm of N15O. Stoichiometric ratios ranged from 0.7 to 1.0. Species and isotope separation were accomplished using GC/MS. The ratio of labeled to unlabeled isotopes of each major nitrogen-containing species varied with stoichiometry, but not with coal type. Delayed nitrogen evolution from both coals was evident from the data. Data analysis showed that significant N2 production (i.e., greater than 50%) probably occurred through non-NO pathways. Little N15O was observed, indicating low conversion rates of intermediates to NO after significant nitrogen evolved from the coal.

A 5.877 TOPS/W Reconfigurable Smart-camera Stream Processor is implemented in 90nm CMOS technology. A reconfigurable hardware architecture with heterogeneous stream processing and subword-level parallelism is implemented to accelerate the vision processing for smart-camera applications. The area efficiency reaches 111.329 GOPS/mm2. The power efficiency and area efficiency are 4.5x to 33.0x and 3.8x to 74.2x better than the state-of-the-art works, respectively.

3DTV promises to become the mainstream of next-generation TV systems. Highresolution 3DTV provides users with a vivid watching experience. Moreover, free-viewpoint view synthesis (FVVS) extends the common two-view stereo 3D vision into virtual reality by generating unlimited views from any desired viewpoint. In the next-generation 3DTV systems, the set-top box (STB) SoC requires both a high-definition (HD) multiview video-coding (MVC) decoder to reconstruct the real camera-captured scenes and a free-viewpoint view synthesizer to generate the virtual scenes [1–2].

In recent years, 3D related applications, including 3D movie and 3DTV, are getting more and more attentions. In order to make the real-time 3D applications feasible, efficient multview video coding (MVC) scheme is desired. However, the system throughput requirement on a high definition (HD) MVC encoder is at least two times higher than the current highest throughput H.264/AVC encoder design. In order to meet the target HD MVC specifications, the system scheduling analysis for the HD MVC encoder is performed in this paper. By the 8-stage MB pipeline system architecture with view-parallel MB-interleaved system scheduling and other in-core computation optimizations, the proposed HD MVC encoder design provides about 339% to 1536% higher system throughput than the previous HD H.264/AVC encoder chips[4][5][6] and therefore the real-time HD MVC encoding can be achieved.

Fractional motion estimation (FME) is widely used in video compression standards. In H.264/AVC, the precision of motion vector is down to quarter pixels to improve the coding efficiency. However, FME occupies over 45% of the computation complexity in an H.264 encoder and this high complexity limits the processing capability. In this paper, a single-iteration full search FME is proposed. By the algorithm and architecture co-optimization, the bandwidth to the frame buffer is reduced by 31%. Furthermore, 82% of circuit area for the Hadamard transformation and subtraction are saved from the direct implementation. Compared with prior arts, the proposed design supports 3.39 × higher throughput with only 0.02 dB PSNR drop. Thus, the specification of 4096 × 2160 quad full high definition H.264/AVC FME processing can be achieved.

To provide more vivid perception, more and more advanced features, like the 4k×2k resolution and the multiview functionality, are emerging for TV. For a multiview video coding (MVC) encoder, motion and disparity estimation (ME/DE) take at least half the hardware requirement. To solve these challenges, a cache-based integer ME/DE algorithm is proposed. With a cache memory as the search window buffer, a predictor-centered ME/DE algorithm is presented. The search range can be reduced to ±16 pixels with less than 0.1dB quality drop compared with full search algorithm. Based on this algorithm, an integer ME/DE chip design is realized. It can reduce 82% on-chip SRAM and 39% system bandwidth. Moreover, the search candidate requirement is also reduced by 79%. As the result, an ME/DE chip design for 4k×2k quad-HD H.264 and HDTV MVC is implemented.

A laboratory coal metering device for the entrainment of pulverized coals is described. The system uses controlled aerodynamic stripping of the powder surface by a carrier gas to effect the coal feed. This device has been used for approximately one year in bench‐scale combustion studies requiring exacting feed rates with very satisfactory results.

Multiview video coding (MVC) is getting more and more attention in recent years because of the realistic perception it can bring. However, the current H.264-based coding scheme cannot get enough coding gain in the rate-distortion (R-D) performance. Furthermore, the view synthesis and random access between views are also design challenges. In this paper, a multiview hybrid coding system with texture-depth synthesis is proposed. By sharing the prediction information between texture and depth maps, the depth map can be reconstructed with reduced bitrate overhead. Then, after using matrix-based warping and adaptive disparity compensation, the R-D performance of the proposed system can be about 2 to 4 dB higher than the current MVC coding scheme at low bitrate range.

External memory bandwidth is an important issue in system-on-chip (SoC) systems. Especially in high definition (HD) video coding, the bandwidth requirement of off-chip memory is critical in video processing. In recent researches, embedded compression shows high potential on off-chip memory bandwidth reduction. Works about embedded compression have been done for low power applications. However, there is no suitable efficient embedded compression with good rate-distortion performance for high throughput applications. In this paper, an algorithm and hardware architecture of high performance lossy embedded compression is proposed to ease the bus congestion problem while keeping the latency low. Using the proposed algorithm, not only the high throughput requirement of HD video encoder is met, but also the hardware cost is relatively low. From our simulation, about 70% memory bandwidth is reduced with only 0.1 dB PSNR degradation in 1080p HD video.

3-D video will become one of the most important video technologies in the next generation of television. Due to ultra high data bandwidth requirement for 3-D video, effective compression technology becomes an essential part in the infrastructure. Thus stereo and multiview video coding (MVC) plays a critical role. However, MVC systems require much more computational complexity relative to mono-view video coding systems. Therefore, an efficient prediction scheme is necessary for encoding. In this paper, a new fast motion estimation (ME) algorithm is proposed. By utilizing disparity estimation (DE) to find corresponding blocks between different views, the coding information such as motion vectors can be effectively shared and reused from the coded view channel. Therefore, the computation for ME in most view channels can be greatly reduced. Experimental results show that compared with the full search block matching algorithm applied to both ME and DE, the proposed algorithm saves 95% computation with near-FSBMA quality.

High Definition (HD) video compression enables vivid reproduction of scenes. However, Motion Estimation (ME) requires large memory capacity and huge memory bandwidth, which are undesirable in many platforms including ASIC and SoC. In this paper, an algorithm and architecture design of cache system and fast ME in HD H.264/AVC are proposed. With the proposed cache system and hardware-oriented fast ME algorithm, the rate-distortion performance is maintained within 0.03dB difference, the size of on-chip memory reduced to only 10% to 21% of original size, while the external memory bandwidth from cache refill is also 18% to 56% less than that of level C data reuse scheme with vertical +64 search range.

For the sake of providing 3D contents for up-coming 3D display devices, a real-time automatic depth fusion 2D-to-3D conversion system is needed on the home multimedia platform. We proposed a priority depth fusion algorithm with a 2D-to-3D conversion system which generates the depth map from most of the commercial video sequences. The results from different kinds of depth reconstruction methods are integrated into one depth map by the proposed priority depth fusion algorithm. Then the depth map and the original 2D image are converted to stereo images for showing on the 3D display devices. In this paper, a 2D-to-3D conversion algorithm set is combined with the proposed depth fusion algorithm to show the improved results. With the converted 3D contents, the needs for 3D display devices will also increase. As long as the two technologies evolve, the 3D-TV era will come as soon as possible.

Desulfurization removes elemental sulfur and its compounds from solids, liquids, and gases. Predominantly, desulfurization involves the removal of sulfur oxides from flue gases, compounds of sulfur in petroleum refining, and pyritic sulfur in coal cleaning. This chapter discusses the following topics: 1. Sulfur pollution (sulfur oxides, hydrogen sulfide, and organic sulfur pollutants). 2. The US Air Quality Act. 3. Solid-phase desulfurization (coal cleaning, gasification, and liquefaction). 4. Liquid-phase desulfurization (acid-lake restoration for H2SO4 removal and groundwater decontamination for H2S removal). 5. Gas-phase desulfurization (SO x and H2S removals from air emission streams).

Multiview video coding (MVC) plays a critical role in 3D-TV systems. However, MVC require much more memory bandwidth and computational complexity relative to mono-view video coding. Therefore, an efficient prediction scheme is necessary for computation reduction. In this paper, a new fast prediction algorithm, computation-free motion estimation (ME) with inter-view mode decision, is proposed. By utilizing disparity estimation to find corresponding blocks between different views, the coding information, such as modes and motion vectors, can be effectively reused from the coded view channel. Therefore, the computation for ME can be almost totally neglected in most view channels. Besides, the proposed algorithm also provides the computation scalability. Experimental results show that compared with the full search block matching algorithm (FSBMA), the proposed algorithm not only save 61-72% computation with near-FSBMA quality, but save almost 100% computation with a little quality drop of 0.23-0.36 dB. Thus, computation-free ME is achieved.

Multiview video coding (MVC) systems require much more bandwidth and computational complexity relative to mono-view video systems. Thus, when designing a VLSI architecture for MVC systems, the hardware resource allocation is a critical issue. In this paper, we propose a new system bandwidth analysis scheme for various and complicated MVC structures. The precedence constraint in the graph theory is adopted for deriving the processing order of frames in a MVC system. In addition, current block centric scheduling (CBCS) and search window centric scheduling (SWCS) are proposed for MVC bandwidth analysis. By adopting data reuse schemes, several design points are explored with the aid of the proposed analysis scheme. The suitable hardware resource allocation can be easily determined.

Luminance and chrominance correction (LCC) is important in multi-view video coding (MVC) because it provides better rate-distortion performance when encoding video sequences captured by ill-calibrated multi-view cameras. This paper presents a robust and fast LCC algorithm based on motion compensated linear regression which reuses the motion information from the encoder. We adopt the linear weighted prediction model in H.264/AVC as our LCC model. In our experiments, the proposed LCC algorithm outperforms basic histogram matching method up to 0.4dB with only few computational overhead and zero external memory bandwidth. So, the dataflow of this method is suitable for low bandwidth/low power VLSI design for future multi-view applications.

Reburning is an emerging three-stage combustion technology designed for the reduction of NO by introducing a small amount of reburning fuel above the primary flame where the majority of NO is chemically reduced to nitrogen. While coal, in general, has not been considered an effective reburning fuel, research at the University of Mississippi suggested that lignite has a reburning efficiency even higher than that of methane. Furthermore, heterogeneous mechanisms are more important than homogeneous mechanisms for char/NO reaction. The objectives of this research are to investigate: (1) implications of pore structure analysis, (2) parameters governing heterogeneous reactions, and (3) estimation of rates of NO reduction and mass transfer limitations. Experiments have been performed in a flow reactor with a simulated fuel gas at a stoichiometric ratio (SR) 1.1. Reburning fuels in this study include chars derived from Pittsburgh No.8 bituminous coal and Mississippi lignite. Chars were produced in N{sub 2} by suspending a sample basket in a tube furnace. Pore structure analyses include BET-N{sub 2}, BET-CO{sub 2}, and DR-CO{sub 2} surface pore size distribution, micropore volume, total pore volume, and average pore radius. These studies suggest that neither BET-N{sub 2} nor DR- CO{sub 2} surface area is a normalization factormore » of chars of different origin. Reaction with NO leads to closures of pores, which may be contributed by formation of surface complexes.« less

During this quarter, we have investigated rates and product compositions of NO reduction on chars in gases. N{sub 2} and CO{sub 2} internal surface areas of chars, selected from runs of various pyrolysis and reaction conditions have been measured to assist in interpreting the experimental results. Implications of Langmuir- Hinshelwood mechanisms and mass transfer limitations were examined. Oxidants suppress NO reduction on bituminous coal char more than on lignite char. Observations suggest that NO adsorption and desorption of stable surface oxygen complexes are potentially important rate- limiting steps and may be catalyzed by mineral matter during reburning with lignite char. Relative inert nature of lignite char to CO{sub 2} presence may have potential value in use of fuel system involving both solid and volatile fuels. Lignite char produced at 950 C and zero holding time has higher reactivity than that produced at 1100 C and 5 min holding time. Bituminous coal chars produced at these two conditions, however, have similar reactivity with NO. Internal surface areas of both type chars vary with pyrolysis conditions and gas composition in the subsequent reaction. When oxidants are introduced in the feed, internal surface areas of these two chars vary in opposite directions.

The investigation of this quarter focuses on the rates of NO reactions with chars in various gaseous environments. The results have revealed significant insights into the NO reduction mechanisms on char surface, particularly when the oxidants, O{sub 2} and CO{sub 2}, are introduced into the feed. Indeed, evidences suggest that the formation of stable oxygen complexes is the major cause of differences in NO reactivity on chars of different origins. The oxidants retard the reactivity of char derived fro the bituminous coal more seriously than they affect the char derived from lignite. Furthermore, additions of these oxidants into the reacting stream produce additional yields of CO and CO{sub 2} during NO reaction with lignite char, suggesting gasification of carbon from lignite char. No excess CO and CO{sub 2} were observed when the bituminous coal char was used. These yields of CO and CO{sub 2} also imply that desorption of stable surface oxygen complex is a rate-limiting step which may be catalyzed by the mineral matters during reactions involving lignite char. Surface area evaluated by CO{sub 2} and Dubinin-Radushkevich (D-R) equation is not a normalization factor of char reactivity during reburning. In the absence of oxidants, the bituminous coal char shows drastic increase in activation energy at about 950 {degrees}C indicating transition of desorption to adsorption controlled mechanisms. When CO{sub 2} is introduced, the transition temperature increases. When oxygen is also added, no such transition is observed up to 1100 {degrees}C. Lignite char reactivity increases smoothly over the temperature range 800 to 1100 {degrees}C. It is also observed that char reactivity decreases with increasing pyrolysis temperature which may be caused by closure of pores due to graphitization. The rate of NO reduction on the Pittsburgh {number_sign}8 coal char is then in good accord with that of a West Virginia coal char reported by De Soete (1980).

The susceptibility of a group of US coals to the production of light gaseous and liquid hydrocarbons during flash hydrogenation is examined. Eight coals ranging from lignite to high-volatile A bituminous and representing five provinces, have been flash heated in 101.3 MPa of flowing hydrogen using a bench scale reactor. A 0.6 s gas phase residence time was provided to hydrocrack the vapour products. Temperatures ranged from 750 to 850°C, where maximum yields of ethane and BTX (benzene+toluene + xylene) are found. The carbon conversion decreased with increasing rank at fixed reaction conditions. Methane yields are highest for lignite. Peak ethane yields range from 6.4 to 9% carbon conversion. BTX yields have a shallow maximum at intermediate ranks, decreasing towards high and low rank coals. Total liquid yields range from 14 to 43%. Although a definite variation of yield with rank is evident, the trends, especially total liquid yields, are attended by considerable scatter. Rank is not the only, and indeed may not be the most significant variable in determining the yield of individual species in flash hydrogenation. To establish the significant variables a stepwise regression procedure was applied to the experimental data using information from the elemental, proximate and petrographic compositions of the coals as independent variables. Two variables are adequate in all cases to correlate species yield and coal properties. Exinite appears to be capable of increasing the amount of liquid obtained from other macerals.

An interesting correlation has been observed between the volatile yield for three coal conversion processes and the oxygen and aliphatic hydrogen (Hal) content of the coal. The three processes are: (1) rapid pyrolysis in vacuum, (2) hydropyrolysis at ≈10 MPa hydrogen, and (3) liquefaction with tetralin at 400 °C. The volatile yield for the first two processes and for low sulphur coals studied in the third process may be predicted with the equation: Yield≈0.8 OT+15 Hal where: OT, the organic oxygen concentration measured by ultimate analysis; and Hal is the aliphatic hydrogen concentration determined from Fourier Transform infrared (FTIR) measurements. The similarity of yields for these processes suggests that they are basically controlled by thermal decomposition. Justification for the above equation is offered by considering a recently developed model for thermal decomposition of coal. The correlation does not fit a group of high sulphur coals studied in the liquefaction programme. These coals have extremely high volatile yields which may be a result of catalytic activity.

This program addresses the mechanisms of NO reduction in pulverized coal flames using reburning. Using both thermodynamic and kinetic simulation combined with both pilot and bench scale experimental work, we propose to better define the conditions that lead to the destruction of NO, without the concomitant increase in other nitrogeneous pollutants. Specifically, the interactions between NO and hydrocarbon constituents in the fuel, and the fate of fuel nitrogen are the focal points of this research. Isotope doped 15 NO is used for tracing the reaction pathways.

This program addresses the mechanisms of NO reduction in pulverized coal flames using reburning. Using both thermodynamic and kinetic simulation combined with both pilot and bench scale experimental work, we propose to better define the conditions that lead to the destruction of NO, without the concomitant increase in other nitrogeneous pollutants. Specifically, the interactions between NO and hydrocarbon constituents in the fuel, and the fate of fuel nitrogen are the focal points of this research. Isotope doped 15 NO is used for tracing the reaction pathways.

The study of stoichiometric constraints under equilibrium conditions provides us with the following information related to reburning as a NO reduction technology: (1) The stoichiometry of air to fuel is the most important stoichiometry of air to fuel is the most important stoichiometric variable for reburning; (2) based on equivalent energy production, the comparative reduction efficiencies of the reburning fuels follow the trend: methane > ethane, ammonia > butane > aromatics, coal > CO; (3) the nitrogen in burning coals causes increases in equilibrium NO; (4) equilibrium TFN is not very sensitive in inlet NO concentration; (5) the heat carried by the flue gas in reburning could push the NO reduction toward equilibrium. If so, reburning has a strong correlation with air staging with air preheat. Further experimental verification is required.

During this quarter we continued to develop improved techniques of using aluminum diaphragms in the chemical shock tube and of analyzing reaction products. Tests with wide ranges of shock pressures have provided a set of baseline data for the proper selection of Al diaphgrams thickness. Our pioneer work on the analysis of trace amounts of NO, NO/sub 2/, NH/sub 3/, and HCN with gas chromatography/mass spectrometry were concentrated on column selection, and the use of a cold trap at the GC inlet. The down-fired furnace was completed, and initial confirmatory testing began. Several new sections of refractory had to be built because of damage sustained in transit from Kansas State University to LSU. Additionally, the on-line analyzers for O/sub 2/, CO, CO/sub 2/, and NO/sub x/ had to be calibrated and tested under suitable furnace conditions. Finally, the furnace was successfully fired with natural gas/air flames doped with ammonia to assess the potential performance of the sampling system and analyzer under conditions comparable to those to be employed during the second year of the program. 2 refs., 5 figs., 1 tab.

The study of stoichiometric constraints under equilibrium conditions provides us with the following information related to reburning as a NO reduction technology: (1) The stoichiometry of air to fuel is the most important stoichiometry of air to fuel is the most important stoichiometric variable for reburning; (2) based on equivalent energy production, the comparative reduction efficiencies of the reburning fuels follow the trend: methane > ethane, ammonia > butane > aromatics, coal > CO; (3) the nitrogen in burning coals causes increases in equilibrium NO; (4) equilibrium TFN is not very sensitive in inlet NO concentration; (5) the heat carried by the flue gas in reburning could push the NO reduction toward equilibrium. If so, reburning has a strong correlation with air staging with air preheat. Further experimental verification is required.