bluuebunny/crossref_metadata_2025 huggingface dataset:
Processes of Knowledge Production in Social Movements as Multi‐level Power Dynamics
Authors: Esteves Ana Margarida
Published: October 2008

Most literature related to the study of processes of knowledge production within social movements neglects how power relations between participants rooted on structural inequalities shape such processes. It also underestimates how such inequalities and the very dynamics of movements intersect in the setting up of the ‘boundaries’ of ‘insidership’ and ‘outsidership’, as well as of the terms implicit in different forms of participation. This article makes a review of theoretical and methodological literature that is relevant to the study of processes of knowledge production within social movements. Based on that review, it proposes the concept of ‘multi‐level power dynamics’ as a tool for future research on the way in which such processes are shaped by power relations between movement members endowed with, or experiencing a differentiated access to different forms of knowledge, as well as with actors within the state and networks promoting the diffusion of ideas and strategies.
A Benefit‐Cost Analysis of Total Maximum Daily Load Implementation1
Authors: Borisova Tatiana , Collins Alan , D’Souza Gerard , Benson Matthew , Leigh Wolfe Mary , Benham Brian
Published: October 2008

Abstract:  Total Maximum Daily Load (TMDL) implementation generates benefits and costs from water quality improvements, which are rarely quantified. This analysis examines a TMDL written to address bacteria and aquatic‐life‐use impairments on Abrams and Opequon Creeks in Virginia. Benefits were estimated using a contingent valuation survey of local residents. Costs were based on the number and type of best management practices (BMPs) necessary to achieve TMDL pollution reduction goals. BMPs were quantified using watershed‐scale water quality simulation models (Generalized Watershed Loading Function and Hydrological Simulation Program‐FORTRAN). Based on our projections, the costs to achieve TMDL induced pollution reduction goals outweigh the estimated benefits. Benefit‐cost ratios ranged between 0.1 and 0.3.
Riparian Ground‐Water Flow Patterns Using Flownet Analysis: Evapotranspiration‐Induced Upwelling and Implications for N Removal1
Authors: Kellogg D.Q. , Gold A.J. , Groffman P.M. , Stolt M.H. , Addy K.
Published: October 2008

Abstract:  Ground‐water flow paths constrain the extent of nitrogen (N) sinks in deep, stratified soils of riparian wetlands. We examined ground‐water flow paths at four forested riparian wetlands in deep, low gradient, stratified deposits subjected to Southern New England’s temperate, humid climate. Mid‐day piezometric heads were recorded during the high water table period in April/May and again in late November at one site. Coupling field data with a two‐dimensional steady‐state ground‐water flow model, flow paths and fluxes were derived to 3 m depths. April/May evapotranspiration (ET) dominated total outflux (44‐100%) while flux to the stream was <10% of total outflux. ET exerted upward ground‐water flux through shallow carbon‐rich soils, increasing opportunities for N transformations and diverting flow from the stream. Dormant season results showed a marked increase in flux to the stream (27% of the total flux). Riparian sites with deep water tables (naturally or because of increased urbanization or other hydrologic modifications) or shallow root zones may not generate ground‐water upwelling to meet evaporative demand, thereby increasing the risk of N movement to streams. As water managers balance issues of water quality with water quantity, they will be faced with decisions regarding riparian management. Further work towards refining our understanding of ET mediation of N and water flux at the catchment scale will serve to inform these decisions.
IMPACT ON ECONOMIC GROWTH OF DIFFERENTIAL POPULATION GROWTH IN AN ECONOMY WITH HIGH INEQUALITY
Authors: Nordhaus William
Published: October 2008

The economic growth of South Africa has been disappointing over the last quarter century. This note addresses a conceptual problem that arises because of composition effects. Two important features of the South African economy are, first, its extreme inequality (primarily between the white population and the African population). Additionally, the African population has been growing rapidly, while the white population has experienced a declining share. This note derives an explicit equation for the impact of inequality and population‐growth differences on the growth of per capita GDP. It shows that the combination of divergent population growth and high inequality can lead to an apparent drag on measured economic growth even though the components, and a more adequate measure of economic welfare, are growing at a healthy rate.
WHAT'S IN A NAME? RACIAL IDENTITY AND ALTRUISM IN POST‐APARTHEID SOUTH AFRICA
Authors: Van Der Merwe Wilhelm Gerhard , Burns Justine
Published: October 2008

This paper reports the results of an economic experiment which was designed to test the effect of racial identity on generosity in a non‐strategic setting. A sample of undergraduate university students was recruited to participate in a dictator game, where surnames of individuals were revealed to convey information about racial identity. Results indicate that compared to a set of control experiments where participant identity was kept anonymous, revealing racial identity has a significant and positive impact on the size of the offers made. However, while Black participants did not vary their offers based on the racial identity of their partners, White participants were more generous towards White partners than Black partners, exhibiting insider favouritism in their offers.
TO PREY OR NOT TO PREY? WELFARE AND INDIVIDUAL LOSSES IN A CONFLICT MODEL1
Authors: Wittenberg Martin
Published: October 2008

We analyse a generalised form of the Hirshleifer‐Skaperdas predation model. In such a model agents have a choice between productive work and appropriation. We suggest that such a model can usefully be thought of as a continuous form of the Prisoners' Dilemma. We present closed form solutions for the interior equilibria and comparative statics for all Cournot equilibria and analyse the social welfare losses arising from predation. We show that predation is minimised under two quite different regimes, one in which claiming is very ineffective and another in which one of the players becomes marginalised. The worst outcomes seem to arise when claiming is effective, but inequality in power is significant but not extreme. This, arguably, is the situation in a number of transition societies.
STRUCTURE, CONDUCT AND PERFORMANCE ANALYSIS OF THE SOUTH AFRICAN AUTO INSURANCE MARKET: 1980‐2000
Authors: Liebenberg André p. , Kamerschen David R.
Published: October 2008

The traditional structure‐conduct‐performance framework makes the explicit prediction that market structure determines market conduct, performance and power. The primary goal of this study is to evaluate this prediction using the South African (SA) short‐term auto insurance market. The empirical evidence shows that a link between market structure and market conduct, performance and/or power is not present. “Prices” and profits are not statistically significantly related to various sellers’ concentration measure and do not follow any explicit trend over time. By construction, profits are directly related to “prices” and follow a cyclical trend, as observed in other countries. A secondary goal of this paper is to compare the findings for the US auto insurance market with the empirical evidence on the SA auto insurance market. While there are few similarities, there is an underwriting cycle in the SA auto insurance market such as is observed for the US auto insurance market.
REGULATORY ENVIRONMENT ANALYSIS IN THE SOUTH AFRICAN TELECOMMUNICATIONS INDUSTRY
Authors: Sibinda Gershon
Published: October 2008

The regulation of the telecommunications industry in South Africa is, by design, a complex matter, since it is mired with overlaps of mandates between the regulator, Independent Communications Authority of South Africa (ICASA) and the Competition Commission on competition matters, coupled with vetoing powers of the Minister of Communications. The Harvard Business Model is employed in this article to show that there is a lack of coordinated effort between the regulator and its supporting structures. This then compromises efficiency as demanded by Parliament from state enacted bodies. Since ICASA is faced with dynamic economic and regulatory challenges, it is recommended that the regulator be fully resourced and granted regulatory as well as competitive authority in the telecommunications industry.
PRICE FLEXIBILITY IN THE COMMON MONETARY AREA
Authors: Matšaseng Kopano
Published: October 2008

This paper examines the presence of flexibility within the common monetary area (CMA) as compared to a selected group of Southern African Development Co‐operation (SADC) countries. The study tests for the readiness of SADC countries towards macroeconomic convergence and monetary unification. The methods followed examine the concept of (relative) purchasing power parity and test for the speed of adjustment of prices after a shock. The results suggest that the level of price flexibility is high within the CMA as opposed to the control group. The implication is that the CMA arrangement has managed to foster price flexibility among its member countries. Furthermore, Botswana could be a potential candidate for a monetary union with the CMA group.
METROPOLITAN HOUSE PRICES IN SOUTH AFRICA: DO THEY CONVERGE?
Authors: Burger Philippe , Van Rensburg Lizelle Janse
Published: October 2008

The question this paper investigates is whether or not different metropolitan areas each constitute a separate housing market or whether or not there is a single South African housing market. Theory on the Law of One Price suggests that if products or geographic areas belong in the same market, their absolute prices must converge, so that their relative prices are stationary. By using cross‐sectional time series data of five metropolitan areas, the paper tests for the Law of One Price by applying the Im, Pesaran and Shin panel unit root test. The paper finds strong evidence of convergence in large middle‐segment house prices and weaker support for convergence in medium middle‐segment house prices. In addition, the paper finds no evidence for convergence in small middle‐segment house prices. This suggests the existence of a national market for large and possibly middle‐segment houses in metropolitan areas, but separate metropolitan markets for small middle‐segment houses. In addition, the paper estimates the speed of convergence and finds that large middle‐segment house prices converge within two to seven quarters, while the speed of convergence for medium middle‐segment house prices in three of the five areas is five to eight quarters.
SPATIAL BAYESIAN METHODS OF FORECASTING HOUSE PRICES IN SIX METROPOLITAN AREAS OF SOUTH AFRICA
Authors: Gupta Rangan , Das Sonali
Published: October 2008

This paper estimates Spatial Bayesian Vector Autoregressive (SBVAR) models, based on the First‐Order Spatial Contiguity and the Random Walk Averaging priors, for six metropolitan areas of South Africa, using monthly data over the period of 1993:07 to 2005:06. We then forecast one‐ to six‐months‐ahead house prices over the forecast horizon of 2005:07 to 2007:06. When we compare forecasts generated from the SBVARs with those from an unrestricted Vector Autoregressive (VAR) and the Bayesian Vector Autoregressive (BVAR) models based on the Minnesota prior, we find that the spatial models tend to outperform the other models for large middle‐segment houses; while the VAR and the BVAR models tend to produce lower average out‐of‐sample forecast errors for middle and small‐middle segment houses, respectively. In addition, based on the priors used to estimate the Bayesian models, our results also suggest that prices tend to converge for both large‐ and middle‐sized houses, but no such evidence could be obtained for the small‐sized houses.
Expression of the HCRP1 mRNA in HCC as an independent predictor of disease‐free survival after surgical resection
Authors: Lai Ming‐Wei , Huang Shiu‐Feng , Lin Shi‐Ming , Chen Tse‐Ching , Lin Chun‐Yen , Yeh Chun‐Nan , Yeh Ta‐Sen , Chen Miin‐Fu , Yeh Chau‐Ting
Published: October 2008

Aim:  Hepatocellular carcinoma (HCC)‐related protein‐1 (HCRP1) gene was located at chromosome 8p22, a frequently deleted region in HCC. The gene product was a subunit of mammalian Endosomal Sorting Complex Required for Transport (ESCRT)‐I, essential for degradation of epidermal growth factor receptors. In this study, we examined the prognostic role of HCRP1 mRNA expression in HCC.

Methods:  The expression of HCRP1 mRNA in HCC was assessed in 125 patients receiving surgical resection of HCC. Using the adjacent non‐cancerous tissues as a reference, 55 and 70 patients expressing high and low levels of HCRP1 mRNA, respectively, were identified. The predictive value of HCRP1 mRNA expression in postoperative survival was evaluated.

Results:  Expression of HCRP1 mRNA was not associated with any of the baseline clinicopathological parameters. However, univariate analysis showed that it was associated with a better disease‐free survival (P < 0.001) and overall survival (P = 0.032). Stepwise Cox multivariate proportional hazards regression analysis showed that the expression of HCRP1 mRNA (hazard ratio [HR], 0.396; 95% confidence interval (CI), 0.233–0.674; P = 0.001), tumor number (HR, 1.596; 95% CI, 1.221–2.087; P = 0.001), serum aspartate aminotransferase (HR, 1.002; 95% CI, 1.000–1.003; P = 0.031) and the presence of microvascular invasion (HR, 1.852; 95% CI, 1.131–3.032; P = 0.014) were included as independent predictors for disease‐free survival.

Conclusion:  Expression of HCRP1 mRNA served as an independent predictor for postoperative disease‐free survival in HCC patients.
Murid herpesvirus‐4 induces chronic inflammation of intrahepatic bile ducts in mice deficient in gamma‐interferon signalling
Authors: Gangadharan Babunilayam , Dutia Bernadette M , Rhind Susan M , Nash Anthony A
Published: October 2008

Aim:  Infection of gamma interferon receptor defective mice with murid herpesvirus‐4 also known as murine gammaherpesvirus‐68 results in multi‐organ fibrosis. In this paper we characterise the pathological changes occurring in the liver in this model.

Methods:  Standard immunohistochemistry and in situ hybridisation techniques were used to identify the cellular changes and the presence of virus at different times post infection.

Results:  In liver sections from infected gamma interferon receptor defective mice sampled on day 16 to at least day 120, 79% showed proliferating intrahepatic bile ducts associated with a chronic mononuclear cell inflammation. Only 8% of wild type mice showed similar lesions. Coincident with the inflammatory response bile duct epithelial cells were positive for arginase 1. Around day 50 post infection onwards focal fibrotic lesions appeared in approximately 30% of gamma interferon receptor defective mice resulting in destruction of intrahepatic bile ducts. In contrast to the chronic persisting inflammatory response the presence of virus infected cells were only observed between day 12–20 post‐infection.

Conclusion:  Infection of gamma interferon receptor defective mice with a murine gammaherpesvirus initiates a chronic persisting inflammatory response with a pathological profile similar to the human fibrotic liver disorder Primary Sclerosing Cholangitis.
Assessment of liver function for safe hepatic resection
Authors: Seyama Yasuji , Kokudo Norihiro
Published: October 2008

The preoperative assessment of liver function is extremely important for preventing postoperative liver failure and mortality after hepatic resection. Liver function tests may be divided into three types; conventional liver function tests, general scores, and quantitative liver function tests. General scores are based on selected clinical symptoms and conventional test results. Child–Turcotte–Pugh score has been the gold standard for four decades, but the Child–Turcotte–Pugh score has difficulty discriminating a good risk from a poor risk in patients with mild to moderate liver dysfunction. The model for end‐stage liver disease score has also been applied to predict short‐term outcome after hepatectomy, but it is only useful in patients with advanced cirrhosis. Quantitative liver function tests overcome the drawbacks of general scores. The indocyanine green retention rate at 15 minutes (ICG R15) has been reported to be a significant predictor of postoperative liver failure and mortality. The safety limit of the hepatic parenchymal resection rate can be estimated using the ICG R15, and a decision tree (known as the Makuuchi criteria) for selecting patients and hepatectomy procedures has been proposed. Hepatic resection can be performed with a mortality rate of nearly zero using this decision tree. If the future remnant liver volume does not fulfill the Makuuchi criteria, preoperative portal vein embolization should be performed to prevent postoperative liver failure. Galactosyl human serum albumin‐diethylenetriamine‐pentaacetic acid scintigraphy also provides data that complement the ICG test. Other quantitative liver function tests, however, require further validation and simplification.
Role of hepatic iron in non‐alcoholic steatohepatitis
Authors: Sumida Yoshio , Yoshikawa Toshikazu , Okanoue Takeshi
Published: October 2008

Non‐alcoholic fatty liver disease (NAFLD) includes a spectrum of clinical entities ranging from simple steatosis to non‐alcoholic steatohepatitis (NASH) with possible evolution to cirrhosis and hepatocellular carcinoma. Iron is considered a putative element that interacts with oxygen radicals in inducing liver damage and fibrosis. The role of hepatic iron in the progression of NASH remains controversial, but in some patients, iron may have a role in the pathogenesis of NASH. Though genetic factors, insulin resistance, dysregulation of iron‐regulatory molecules, erythrophagocytosis by Kupffer cells may be responsible for hepatic iron accumulation in NASH, exact mechanisms involved in iron overload remain to be clarified. Iron reduction therapy such as phlebotomy or dietary iron restriction may be promising in patients with NASH/NAFLD to reduce insulin resistance as well as serum transaminase activities.
Percutaneous transretroperitoneal direct approach to occlude a major shunt in a patient with extrahepatic portal–systemic encephalopathy
Authors: Murakami Masato , Nishino Keiichirou , Satou Takao , Takaoka Youko , Murakami Shigeto , Murakami Bonpei , Chikamori Fumio , Kokubu Shigehiro
Published: October 2008

A 73‐year‐old woman had sudden dystrophy and amnesia in our hospital. Her serum ammonia level was high. Marked collateral vessels from the splenic vein to the left renal vein around the spleen were seen on a computed tomography (CT) scan with contrast enhancement. An abdominal angiogram showed that the direction of the splenic vein was hepatofugal on superior mesenteric arterial portography, with a marked splenorenal shunt on splenic arterial portography. Hepatic encephalopathy due to a marked extrahepatic portal–systemic shunt was diagnosed. Transjugular retrograde obliteration (TJO) was attempted, but the catheter and guide wire could not selectively approach the splenorenal shunt because of many outflow routes. We punctured the vessels from the left side of the back under ultrasonographic guidance. We injected microcoils and ethanolamine oleate to completely obliterate the shunt. Marked collateral vessels showed no venous flow on a CT scan after treatment. The serum ammonia level was in the normal range. There has been no recanalization of the shunt vessels for 4 years after treatment. Hepatic encephalopathy has not recurred, and no other collateral vessels have developed. To our knowledge, this is the first report to document the use of a percutaneous transretroperitoneal direct approach to occlude a major shunt in a patient with extrahepatic portal–systemic encephalopathy.
The first Japanese case of COACH syndrome
Authors: Mitsui Fukiko , Aikata Hiroshi , Azakami Takahiro , Katamura Yoshio , Kimura Takashi , Kawaoka Tomokazu , Saneto Hiromi , Takaki Shintaro , Hiraga Nobuhiko , Tsuge Masataka , Waki Koji , Hiramatsu Akira , Imamura Michio , Kawakami Yoshiiku , Takahashi Shoichi , Arihiro Koji , Chayama Kazuaki
Published: October 2008

COACH syndrome is a disorder characterized by hypoplasia of cerebellar vermis, oligophrenia, congenital ataxia, coloboma and hepatic fibrosis, and 21 cases have been reported to date. Here we describe the first Japanese case of COACH syndrome, who was diagnosed at the age of 37 years and never progressed to liver failure. The patient was found to have delayed developmental milestones at the age of 5 months and mental retardation at the age of 7 years. She had been treated for hepatopathy of unknown origin from the age of 22 years. She was admitted to Hiroshima University Hospital at the age of 37 years after the identification of esophageal varices on a routine upper endoscopy. Computed tomography of the abdomen revealed portal hypertension and splenomegaly, and liver biopsy showed liver fibrosis. In addition, she had coordination disorder and dysarthria. Brain magnetic resonance images revealed hypoplasia of cerebellar vermis. The final diagnosis was COACH syndrome. She underwent endoscopic injection sclerotherapy for esophageal varices. From that point until her death from ovarian cancer at the age of 41 years, the liver function tests were stable without an episode of hematemesis. Physicians should be aware of COACH syndrome when they examine young patients who present with hepatopathy, portal hypertension of unknown origin and cerebellar ataxia.
A case of well‐differentiated cholangiolocellular carcinoma visualized with contrast‐enhanced ultrasonography using Sonazoid
Authors: Joshita Satoru , Ichijo Tetsuya , Suzuki Fumitaka , Yokoyama Takahide , Sugiyama Yukiko , Fukushima Mana , Kamijo Atsushi , Komatsu Michiharu , Umemura Takeji , Yoshizawa Kaname , Miyagawa Shinichi , Tanaka Eiji
Published: October 2008

We here report the first case of cholangiolocellular carcinoma (CoCC) visualized with contrast‐enhanced ultrasonography (CEUS) using a second‐generation contrast agent, Sonazoid. A 76‐year‐old man was admitted to our hospital for evaluation of a hepatic tumor. The tumor was described as having hyper‐enhancement in the early phase and persistent enhancement in the late phase by contrast‐enhanced computed tomography (CT) and magnetic resonance imaging (MRI), as well as hypervascularity by angiography. CEUS assessment of the nodule showed diffuse and homogeneous enhancement in the pure arterial phase, which became progressively hypoechoic relative to the adjacent liver parenchyma during the portal vein and late phases (mixed vascular phase), and showed a contrast defect with an unclear border in the Kupffer phase. Histologically we diagnosed this hepatic tumor as CoCC. In light of the above findings and the rarity of CoCC, it is helpful to incorporate the results of several imagings, such as CT, MRI, angiography and CEUS with a second‐generation contrast agent when clinically diagnosing CoCC.
B&W IR-CFB: Operating Experience and New Development
Authors: Maryamchik M. , Wietzke D. L.
Published: October 2008

The paper provides an update on B&W Internal Recirculation (IR) CFB boilers featuring a two-stage solids collection system. The paper describes the latest commercial projects, operating experience and developments in boiler design and process. Those concern solids collection system, erosion protection, etc.
Effect of Static Bed Height on the Combustion of Rice Husk in a Fluidized Bed Combustor
Authors: Rozainee M. , Ngo S. P.
Published: October 2008

The combustion process is largely controlled by temperature, turbulence and residence time. When the temperature is sufficiently high so that the reaction is no longer kinetically-controlled, turbulence and residence time play a significant role. The reaction is thus diffusion-controlled. During the combustion of rice husk in a fluidized bed, the turbulence is largely governed by the mixing behavior in the inert sand bed, which in turn is governed by the bubble formation characteristics. Further, the residence time among the reactants (air and rice husk) and the heat source is also dependent on the turbulence in the bed. When all other parameters are held constant, the bubble phenomena vary according to the expanded bed height corresponding to a given static bed height. For high heat and mass transfer rates, small slowly rising bubbles are desired. Thus, the purpose of this study is to investigate the effect of static bed height on the quality of ash during the combustion of rice husk. The degree of rice husk burning in the bed could be deduced from the bed temperature as a higher bed temperature indicated that a higher portion of the rice husk feed is being burnt in the bed. Moreover, the particle size of the resulting ash is also able to give indication of the degree of rice husk burning in the bed as the turbulence arising from the bubbling action of the bed material is known to break down the char skeleton of the rice husk, thereby, resulting in ash with finer size. From this study, the static bed height of 0.5 DC was found to give the lowest residual carbon content in the ash (1.9 wt%) and the highest bed temperature (670°C) among the other range of static bed heights investigated.
Profiles and TEQ Concentrations of PAHs Emission From Fluidized Bed Coal Gasification
Authors: Zhou Hongcang , Jin Baosheng , Zhong Zhaoping , Xiao Rui , Huang Yaji
Published: October 2008

More growing particular attentions are being paid to polycyclic aromatic hydrocarbons (PAHs) generated from coal gasification due to their high mutagenic and carcinogenic. Fluidized bed air and steam gasification of three different rank coals were studied in a bench-scale atmospheric fluidized bed test facility. An extraction and high performance liquid chromatography (HPLC) technique was used to analyze the concentrations of the 16 PAHs specified by US EPA in raw coal, slag, bag house char, cyclone char and fuel gas. The profiles and TEQ concentrations of PAHs emission from fluidized bed coal gasification were discussed. The results indicated that there were mainly three- and four-ringed PAHs in raw coal and fuel gas, but the total PAHs in bag house char and cyclone char were dominated by three-, four- and five-ringed PAHs. The concentrations of three-ringed PAHs in fuel gas were higher than those of four-ringed PAHs, but a reverse phenomenon occurred in bag house char and cyclone char. No PAHs were measured in slag during coal gasification. The total TEQ concentration of five-ringed PAHs mainly dominated in raw coal, fuel gas, bag house char, and cyclone char, and their percentages were about 75–96% by weight. Benzo(a)pyrene (BaP) was the main contributor of TEQ concentration in raw coal and gasified products. In addition, the concentration of PAHs in raw coal increased with the rise of coal rank, and there was not an obvious variation about the concentration of PAHs in gasified products.
Coal Gasification Characteristics in a 2MWth Second-Generation PFB Gasifier
Authors: Rui Xiao , Jin Baosheng , Xiong Yunquan , Duan Yufeng , Zhong Zhaoping , Chen Xiaoping , Huang Yaji , Zhou Hongcang , Zhang Mingyao
Published: October 2008

Coal gasification process and equipment feasibility research were carried out in a 2 MW thermal input pressurized spout-fluid bed pilot-scale gasifier and a long-time-run test was performed to study the effects of operating parameters on coal partial gasification behaviors. The test results have demonstrated the feasibility of the gasifier to provide suitable fuel gas and residual char for downstream system of 2G PFBC-CC. The concentration of methane decreased at higher gasification temperature due to the secondary cracking of methane while the carbon conversion increased, and the concentration of hydrogen increased with an increase of steam flow rate. The main experimental results were compared with those of pilot-scale facilities in the world.
Experimental Investigation of Flow Characteristics in a Spout-Fluid Bed
Authors: Zhong Wenqi , Zhang Mingyao
Published: October 2008

Pressure fluctuation time series were obtained at various bed locations in a spout-fluid bed with its dimension of 300mm × 30mm × 2000mm. Power spectrum and Shannon entropy analyses of pressure fluctuations were developed to characterize the flow characteristics. A multi-channel pressure sampling system was established and a high-resolution digital camera was used to record the flow patterns. The effects of two important operating parameters, i.e. spouting gas velocity and fluidizing gas flow rate on the power spectrum major frequency and Shannon entropy were tested. Shannon entropies of different flow patterns were found to have different characteristics, thus Shannon entropy was developed to identify the flow patterns. The results show that power spectrum and Shannon entropy analyses are two helpful ways to realize the complex gas-solid flow characteristics in spout-fluid beds.
Investigation of the Suitability of Serbian Lignites for Burning in CFBC Boilers
Authors: Oka S. , Grubor B. , Dakic´ D. , Ilic´ M. , Manovic´ V. , Eric´ M. , Paprika M. , Oka N. , Belosˇevic´ S. , Mladenovic´ R. , Crnomarkovic´ N.
Published: October 2008

The results of the detailed investigations of behavior of lignites Kolubara and Kovin, in fluidized bed combustion are presented in the paper. Investigation was carried out due to the interest of the Serbian Electric Power Production Company to use CFBC boilers in the process of refurbishment of old pulverized coal combustion boilers. As a part of a feasibility study for CFBC use in power plants in Serbia, investigation of combustion characteristics of lignites was performed using original methodology introduced many years ago by Laboratory for Thermal Engineering and Energy. Methodology was approved by numerous investigations of more than 20 Yugoslav coals for FBC combustion, with the aim to determine design data for bubbling FBC boilers. The main attention in present investigation was paid to the problem of using methodology developed for bubbling FBC in the conditions present in CFBC boilers. Four samples of Kolubara lignite, with heat capacity from 2.5 to 8.5 MJ/kg, and different ash contents were investigated, and also lignite Kovin in the same range of heat capacity. Investigations were performed in three phases: (1) ultimate and proximate analysis, determination of ash sintering temperature by standard method and in fluidized bed laboratory oven, (2) investigations in laboratory fluidized bed furnace and determination of coal particle fragmentation, burning rate, start-up temperature and self-sulfure-capture and (3) investigation of combustion in pilot-plant in stationary combustion conditions. In conclusion, suitability of results obtained in BFBC conditions is approved, and earlier statement that lignites are suitable for BFBC is confirmed by the statement that lignites are even more suitable for burning in CFBC boilers. Considering differences between combustion and flow conditions in bubbling and circulating FBC boilers, behavior of the lignites in CFBC is discussed in details and optimal regime parameters of the CFBC boilers are determined. The results obtained will be used by Serbian Electric Power Production Company for evaluation of bid for CFBC boiler implementation in refurbishment of old thermal power plants.
Leaching of Phosphorus From Ashes of Co-Combustion of Sewage Sludge and Wood
Authors: Pettersson Anita , Andersson Bengt-A˚ke , Steenari Britt-Marie , A˚mand Lars-Erik , Leckner Bo
Published: October 2008

Municipal sewage sludge has a high concentration of phosphorus, which should be recovered because phosphorus is a limited natural resource. In this work, sewage sludge was co-fired with wood in a FBC boiler. The aim of the investigating was to study the solubility of phosphorus in the ashes, by leaching as an alternative to the phosphorous recovery method of using the ashes directly on farmlands. The fly ashes from the boiler’s secondary cyclone and bag filter were leached at various pH-values and the release of phosphorus was measured. Only acidic leaching was applied. The ashes precipitated with Al2(SO4)3 released nearly all phosphorus at a pH-value of 1, whereas the ashes precipitated with Fe2(SO4)3 did not release all phosphorus even at the very low pH of 0.5. The concentrations of phosphorous in the leachate must be compared with liquid phosphorus sources such as human urine or liquid animal manure used as fertilisers. This may result in that the leachate has to be processed further. A continuation of the work to investigate to what extent the leachate is contaminated with toxic trace elements is necessary.
Sulfidation Experiments in a Pressurized Thermogravimetric Analyzer With Chinese Calcined Limestones
Authors: Song Zhanlong , Zhang Mingyao
Published: October 2008

The sulfidation experiments with two kinds of Chinese calcined limestones were performed in a pressurized thermogravimetric analyzer (PTGA). The effects of reaction temperature (700–950°C), total pressure (0–1MPa), particle size (0.055–2mm), and H2S concentration (0.1–4%) on the sorbent conversions were analyzed. Morphological studies with scanning electron microscope and energy dispersive spectroscopy (SEM-EDS) equipment were made to obtain the pictures of solid surface and of the cross-sectioned samples. Nitrogen adsorption measurements were applied to determine the pore structure properties of the particles. Experimental results show that the sulfidation rate increases with total pressure when the volume fraction of H2S is constant. However, the rate of sulfidation decreases with the increase of total pressure when the H2S partial pressure is constant. Reaction temperature affects the sulfidation greatly, and the reaction rate increases with temperature. The sulfidation is the first order with respect to H2S partial pressure. Moreover, larger particles result in lower conversions and reaction rates. The unreacted shrinking core model was applied to describe the sulfidation to determine the kinetic parameters.
Fouling Tendency of Ash Resulting From Burning Mixtures of Biofuels
Authors: Theis Mischa , Skrifvars Bengt-Johan , Hupa Mikko , Tran Honghi
Published: October 2008

Specified mixtures of peat with bark and peat with straw were burned in a lab-scale entrained flow reactor that simulates conditions in the superheater region of a biomass-fired boiler. Deposits were collected on an air-cooled probe that was inserted into the reactor at the outlet. For both mixtures, the deposition behaviour followed a non-linear pattern, which suggests that physico-chemical interaction between the ashes of the different fuels has taken place. The results indicate that it is possible to burn up to 30 wt-% bark (renewable biofuel and pulp mill waste) and up to 70 wt-% straw (renewable biofuel and agricultural waste) in mixtures with peat without encountering increased deposition rates in the reactor. The deposit composition was compared to the fuel ash composition using chemical fractionation analysis and SEM/EDX. While the composition of deposits obtained from pure fuels resembles the feed composition, a considerable change is observed in deposits obtained from mixtures. K and S compounds are attached to Si spheres and the substrate surface. The deposition rate is significantly lowered when removing K, S, Cl and Na in bark prior to burning by washing and mechanical/thermal dewatering.
An Improved Model of Sulfur Self-Retention by Coal Ash During Coal Combustion in FBC
Authors: Manovic Vasilije , Grubor Borislav
Published: October 2008

During combustion of coal a significant amount of sulfur may be retained in ash due to the reactions between mineral matter in coal and sulfur oxides. This process is known as sulfur self-retention and its significance lies in the fact that a part of sulfur oxides, one of the main pollutants during combustion of coal, is not released in the atmosphere. Sulfur self-retention is influenced by parameters that depend on coal characteristics and combustion conditions. The interest for this process was enhanced with the introduction of fluidized bed combustion (FBC) technology since the temperatures and other conditions are favorable for sulfur self-retention. Investigation of this process, primarily modeling, is the subject of this work. The presented model is based on the previously developed model for the combustion of porous char particles under FBC conditions, along with a changing grain size model of sulfation of the CaO grains dispersed throughout the char particle volume. Incorporating the phenomena of sintering, reduction of the produced CaSO4 with CO, thermal decomposition of the produced CaSO4, as well as allowing for the different reactivity of various forms of calcium make major improvements of the model. A temperature dependent relation for the CaO grain radius takes sintering into account. Reductive and thermal decomposition were taken into account by the corresponding reaction rate constants of the Arrhenius type. The reactivity of the calcium forms in coal was considered by different initial radius of the CaO grains. The model was verified by the experimental results of sulfur self-retention of three Serbian coals during combustion in a fluidized bed combustion reactor. The comparison with the experimentally obtained results showed that the model can adequately predict the levels of the obtained values of sulfur self-retention efficiencies, as well as the influence of temperature, coal type and coal particle size.
The Burning of Automotive Shredder Residue (ASR) Using Fluidised Bed Technology
Authors: Abelha P. , Gulyurtlu I. , Lopes H. , Cabrita I.
Published: October 2008

The objective of this work was to demonstrate the feasibility and the environmental performance of FBC technology to burn a fluff fraction of an ASR from a Portuguese vehicle dismantling plant. The combustion studies were carried out on the pilot installation of INETI. The results obtained suggest that the Portuguese ASR has a very high mineral content (70%) and the combustion had to be sustained with the use of an auxiliary fuel (propane); the combustion efficiency was very high; the gaseous pollutants could easily be controlled below the permitted limits and sulphur and chlorine emissions were low. ASR could give rise to some fluidizing problems due to the accumulation of ashes in the bed, therefore, it is essential that a more efficient metal separation method to be used during dismantling process; there was an enrichment of heavy metals (Pb, Cu, Mn and Zn) on ashes retained in the cyclones, specially in the smaller particle size range (less then 10 μm); however the ashes did not have tendency for leaching.
NO Formation Tendency Characterization for Biomass Fuels
Authors: Konttinen Jukka , Hupa Mikko , Kallio Sirpa , Winter Franz , Samuelsson Jessica
Published: October 2008

When a solid fuel, such as coal, biomass or a mixture of these fuels, enters a hot fluidized bed, the volatile carbon and nitrogen compounds are released, while some nitrogen and carbon remains in the solid char. Volatile nitrogen can form reactive species such as NH3, HCN and tar-nitrogen. These can react in the presence of oxygen to NO (and some N2O). Some part of volatile nitrogen is always reduced to N2. During combustion of the char residue, some part of the char-nitrogen forms NO (or N2O) and the rest is converted to N2. Usually the standard fuel analysis is not enough to allow for accurate NO emission predictions in large scale fluidized bed combustion. This paper presents NO formation tendency characterization results from novel laboratory measurements in a small-scale fluidised bed combustor. The laboratory results of this paper give a good insight into the distribution of fuel nitrogen between reactive and non-reactive (N2) volatile components and char-nitrogen. A NO formation tendency database is formed based on the results, including data on biomass-, waste-, peat- and coal-type fuels. The combustion test results show that the cumulative conversion of fuel nitrogen to NO under lean, non-staged fluidized bed combustion is 20–50% (850°C with O2 in excess). For biomass and peat, nearly all reactive nitrogen (forming NO) is released from the fuel during pyrolysis. NO formation during char combustion is significant with coal. With the help of the database, a reasonable estimate of the maximum non-staged NO emission in fluidized bed combustion can be obtained. Normally, air staging is utilized to reduce NO emissions. Effects of air-staging can be studied by means of modelling. In case of a BFBC boiler, the data can be used as input in the design or modelling of air staging for freeboard. For CFBC, the data can be used as input in the NO prediction where the once formed NO is further reduced by char carbon.
Rice Husk Combustion in a BFBC Using Porous Bed Material
Authors: Shimizu Tadaaki , Nemoto Takumi , Tsuboi Hotaka , Shimoda Toshio , Ueno Syunji
Published: October 2008

Rice husk was burned in a bench-scale fluidized bed combustor (53 mm I.D. and 1.3m height) at 1123 K. Silica sand (average size 0.27 mm) was employed as conventional bed material. As an alternative bed material, a kind of porous alumina (average size 0.69 mm) was employed. Unburned gas (CO) emissions were suppressed by employing porous alumina as bed material. NOx emissions from the alumina bed were also suppressed in comparison to the sand bed. N2O emissions were nearly negligible (less than 10 ppm) for both bed materials. During combustion in the sand bed, sudden temperature rise up to 1450 K and increase in pressure drop across the bed were observed. Agglomerates were found in the bed material after the experiments. For the porous alumina bed, such agglomeration trouble did not occur. As conclusion, the present porous alumina was effective for both reduction of pollutants emissions and stable operation.
Effects of Solid Additives on the Control of Trace Elements During Coal Gasification
Authors: Huang Yaji , Jin Baosheng , Zhong Zhaoping , Xiao Rui , Zhou Hongcang
Published: October 2008

Based on the Modified Geo-chemical Enrichment Factor (MGEF), the contents of As, Cd, Co, Cr, Cu, Mn, Hg, Pb, V, Se, Sr, Zn in coal and coal char were analyzed by using Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS) and Inductively Couple Plasma-atomic Emission Spectroscopy (ICP-AES). Limestone, dolomite and sodium carbonate were studied to control trace elements during coal gasification. Different additives show different performances in the control of trace elements. The adsorbing capacity of coal char to all of trace elements enhances when coal is mixed with limestone and dolomite. Chemical adsorption and physical adsorption of lime, which is decomposition product of limestone under high gasification temperature, are both important for As, Co, Cr, Se and Zn. The effects of limestone on Cd, Cu, Hg, Pb, V and Sr are merely caused by physical adsorption of CaO and the adsorbing capacity to Cd, Cu, V is much stronger than those to Hg, Pb, Sr. Dolomite has stronger adsorbing capacity to most of elements (except Cu, Se, Sr) than limestone. Addition of Na2CO3 decreases the MGEFs of As, Cd, Cr, Pb and Se while increases the MGEFs of Zn in coal char. Na2CO3 has little effect on the MGEFs of Co, Cu, Hg, V and Sr in coal char.
NOx and N2O Emission Characteristics From Circulation Fluidized Bed Combustion of Blends of Paper Mill Sludge and Coal
Authors: Chen Xiao-Ping , Gu Li-Feng , Zhao Chang-Sui , Zhu Ai-Qiang , Sun Xin
Published: October 2008

With the rapid economic development and the increase in population in the whole world, the amount of municipal sewage (MS) is increasing and lead to a rapid increasing in amount of municipal sewage sludge (MSS). Combustion of municipal sewage sludge may be a viable solution for its disposal in some cases and so is its co-combustion with coal. Whereas significant information is available on NOx and N2O emissions characteristics of sludge and coal individually, not much has been reported on sludge/coal blends. In the present paper, investigations in NOx and N2O emission characteristics from circulation fluidized bed combustion of blends of municipal sewage sludge and coal were conducted in a 0.2MWth circulating fluidized bed test facility with cross section of 0.23×0.23m2 and height of 5.9m. Coal sample selected was a kind of lignite, while a kind of paper mill sludge was used as sludge sample. The influences of sludge/coal mixing rate, excess air ratio and second air ratio on NOx and N2O emission characteristics have been studied. Test results show that co-combustion of sewage sludge and coal is feasible. With the increasing in proportion of sludge of the sludge/coal blends, the temperatures in dense bed and freeboard decrease rapidly, and the emissions of NOx decrease while the emission of N2O increases obviously. With the increasing in excess air ratio, the emission concentrations of NOx and N2O increase. While with the increasing in secondary air ratio, the emission concentrations of NOx and N2O decrease.
CFB Refurbishment Opportunities in Russia
Authors: Grammelis P. , Koukouzas N. , Skodras G. , Kakaras E. , Tumanovski A.
Published: October 2008

The paper aims to present the current status of the coal-fired power sector in Russia, the prospects for renovation activities based on the fluidised bed technology and the existing experience on CFB refurbishment projects. The renovation needs of the power sector, among the retrofitting, repowering and reconstruction options, were estimated through a multi-criteria analysis. The most attractive system to renovate a power plant between the Supercritical Combustion (SC) and the Fluidized Bed Combustion (FBC) technology was evaluated. Furthermore, the boiler replacement with a CFB unit in the Shatura power plant was studied and its replication potential in the Russian coal-fired power plant park was examined. Nowadays, the installed capacity of coal-fired power plants in the Russian Federation is 29.3 GWe, while they account for about 19% of the total electricity generation in the area. The low efficiency and especially the advanced age are the determinant factors for renovation applications at the Russian units. Even in the more conservative modernisation scenario, over 30% of the thermoelectric units have to be repowered or reconstructed. CFB is the most promising technology for such modernisation projects, when the renovation potential is high. The main characteristics including high volatile yield, low ash content and a large share of light fractions in the as-fired milled peat were taken into account during the CFB boiler calculations in the Shatura power plant. Upgrading the existing coal-fired power plant equipment with CFB technology, which is known to be environmental friendly and efficient, will open new perspectives to the operating power plants in Russia.