Gasification of wood pellets in a bench-scale updraft gasifier

Biomass gasification is proving to be an alternative technology to the use of fossil fuels for energy production. The article considers the bench-scale, air-blown updraft gasification of biomass wood pellets. The objective of the study was to understand the characteristics of evolved gases from the gasifier that was built and assembled at the University Laboratory. Wood pellets of diameter 5 mm, length between 5 and 20 mm constitute the feedstock used. The experimental investigation reveals the major gases produced are CO₂, CO, and H₂, while CH₄ and other hydrocarbons are minor. However, the gasifier used is initially preheated to a temperature of about 800°C. This is indicated by the thermo-couple readings (T1–T8) with T6 as the standard thermo-couple. When T6 attains a steady state at 800°C, the gasifier is turned into a self-sustaining gasification condition. The entire experiment takes about four (4) hours to complete and this gives an understanding of evolved gases from the entire gasification process in the inside of the batch-scale updraft gasifier.     

Non-isothermal reduction characteristics of roasted high alumina iron ore pellets

Non-isothermal reduction of roasted Guangxi high alumina iron ore pellets with CO and H₂ was conducted with high temperature synchronisation thermal analyser (NETZSCH STA 409C/CD) to understand the reduction characteristic of the ore. Chemical analysis, X-ray diffraction examination and scanning electron microscope analysis were adopted to analyse the roasted and reduced pellets. The results show that there are three main phases of Fe₂O₃, Al₂O₃ and Al₃Fe₅O₁₂ in the roasted pellets. During reduction process, the iron bonded in hercynite and fayalite is difficult to be reduced by CO so that the final reduction degree is only 35.62% at the setting temperature of 1573?K. But with H₂ atmosphere, the reduction degree can reach 100% at about 1520?K. It suggests that the ferric ion can completely be reduced to metallic iron by H₂.     

碱度对镁质熔剂性球团性能的影响

 为改善镁质熔剂性球团矿质量,以唐钢铁精粉为原料,进行了造球焙烧试验,研究了碱度对镁质熔剂性球团质量的影响,并结合矿相结构进行了分析。结果表明,随着碱度的升高,生球强度呈略微降低趋势,爆裂温度整体呈降低趋势,碱度高于1.2时,爆裂温度急剧下降;球团抗压强度呈升高趋势,但当碱度高于1.2时,抗压强度急剧下降;低温还原粉化性能变化不大,基本为90%以上;球团软化开始温度整体呈升高趋势。随着碱度增加,铁酸钙质量分数增加,晶粒长大,气孔率呈先降低后增加的趋势;球团黏结率呈增加趋势,碱度每提高0.1,黏结率增加1.4%。     

Multiparticulate systems containing 5-aminosalicylic acid for the treatment of inflammatory bowel disease

Background: In recent years, many achievements have been realized in the therapy of inflammatory bowel disease (IBD) although its etiology remains unknown. Thus IBD treatment is symptomatic and targets general inflammatory mechanisms. Oral formulations containing 5-aminosalicylic acid (5-ASA) have become the standard therapy for mild-to-moderate IBD.

Objective: This article is a review of recently published research dealing with new 5-ASA dosage forms. Thus promising candidates for IBD treatment evaluated in vitro are reported; systems tested in vivo in trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats are mentioned; and 5-ASA formulations used in clinical studies are presented. Moreover, all oral dosage forms containing 5-ASA or its prodrugs are reviewed; their characteristics and utilization in IBD treatment are discussed.

Conclusion: In several clinical studies, it has been shown that multiparticulates such as pellets offer more advantages as compared with single unit forms, that is, coated tablets. Prolonged presence close to the site of the action, improved drug bioavailability, and easier administration of large drug doses belong to the benefits of pellets.     

Preparation of the Traditional Chinese Medicine Compound Recipe Heart-Protecting Musk pH-Dependent Gradient-Release Pellets

ABSTRACT

In this study a sustained-release formulation of traditional Chinese medicine compound recipe (TCMCR) was developed by selecting heart-protecting musk pills (HPMP) as the model drug. Heart-protecting musk pellets were prepared with the refined medicinal materials contained in the recipe of HPMP. Two kinds of coated pellets were prepared by using pH-dependent methacrylic acid as film-forming material, which could dissolve under different pH values in accordance with the physiological range of human gastrointestinal tract (GIT). The pellets coated with Eudragit L30D-55, which dissolves at pH value over 5.5, were designed to disintegrate and release drug in the duodenum. The pellets coated with Eudragit L100–Eudragit S100 combinations in the ratio of 1:5, which dissolve at pH value 6.8 or above, were designed to disintegrate and release drug in the jejunum to ileum. The pellets coated with HPMC, which dissolves in water at any pH value, were designed to disintegrate and release drug in the stomach. Finally, the heart-protecting musk sustained-release capsules (HPMSRC) with a pH-dependent gradient-release pattern were prepared by encapsulating the above three kinds of coated pellets at a certain ratio in hard gelatin capsule. The results of dissolution of borneol (one of the active compounds of the TCMCR) in vitro demonstrated that the coating load and the pH value of the dissolution medium had little effect on the release rate of borneol from pellets coated with hydroxypropyl methyl cellulose (HPMC), but had a significant effect on the release rate of borneol from pellets coated with Eudragit L30D-55 or Eudragit L100–Eudragit S100 combinations in the ratio of 1:5. The pellets coated with Eudragit L30D-55 at 30% (w/w) coating load or above had little drug release in 0.1 mol/L HCl for 3 hr and started to release drug at pH value over 5.5. The pellets coated with Eudragit L100–Eudragit S100 combinations in the ratio of 1:5 at 36% (w/w) coating load or higher had little drug release in 0.1 mol/L HCl for 3 hr and in phosphate buffer of pH value 6.6 for 2 hr, and started to release drug at pH value 6.8 or above. The release profiles of lipophilic bornoel and hydrophilic total ginsenoside from HPMSRC, consisting of three kinds of pellets respectively coated at a certain ratio with HPMC, Eudragit L30D-55, and Eudragit L100–Eudragit S100 in the ratio of 1:5, showed a characteristic of pH-dependent gradient release under the simulated gastrointestinal pH conditions and no significant difference between them. The results indicated that various components with extremely different physicochemical properties in the pH-dependent gradient-release delivery system of TCMCR could release synchronously while sustained-releasing. This complies with the organic whole concept of compound compatibility of TCMCR.     

Eudragit NE40–Drug Mixed Coating System for Controlling Drug Release of Core Pellets

This study was aimed at developing a controlled-release coating system around core pellets with aqueous dispersion, along with some water channeling agents. Core pellets of diltiazem were prepared using the extrusion-spheronization technique and subsequently coated with aqueous dispersion of Eudragit NE40 alone, or drug–polymer mixtures using bottom-spray fluidized bed coater. The lag time in drug release profiles increased as the coating levels of Eudragit NE40 were increased, whereas no lag time was observed in core pellets coated with drug–polymer mixtures. Mixed coating at the 7% level exhibited comparatively better release profiles and provided desirable release rates during the 12-hour testing interval. Diltiazem HCl release from mixed coating was fairly independent of pH and drug loading. Curing of coated pellets was found to be an essential step for stable drug release profiles. The selection of core size range had remarkable effect on drug release rate and was considerably reduced by using greater core size.     

Dryout Heat Flux for Core Debris Bed, (III)

Mixture of cylindrical steel pellets and Al₂O₃ balls, which simulated the intact fuel pellets and fragmented claddings, respectively, was inductively heated in a 50 mm I.D. pyrex glass cylinder filled with water, to investigate the coolability of TMI-2 type degraded core debris bed. The size of steel pellets was 11 mm dia. × 11 mm for BWR, 8 mm dia. × 12 mm for PWR and 5.5 mm dia. × 9 mm for FBR and Al₂O₃ balls were about 2 mm in diameter. The height of the debris bed was 25 cm or lower.

The dryout heat flux does not level off up to a bed height of 25 cm or over for the TMI-2 type bed while 8 cm or so in the bed of only steel balls. The dependence of dryout heat flux on the system pressure agrees with the Lipinski's 0-D model by adopting a proper equivalent diameter. When a simple number-weighted average is used as the equivalent diameter, the prediction gives a fairly good agreement with the experiment for FBR type bed but underestimations for the PWR and BWR type beds. It should be noted, that the small balls of less fraction, not the large pellets, substantially govern the dryout. When the coolant flow is allowed from the bottom, however, the dryout heat flux is enhanced up to the level for the complete vaporization of coolant, and small amount of mass flux or circulation head can greatly improve the coolability.     

Calcuiational Method for Neutron Heating in Dense Plasma Systems, (II)

Abstract

The effect of neutron heating on the burn characteristics of inertial confinement fusion pellets is investigated by applying the calcuiational method developed in an earlier paper (Part I). The basic equations are time-dependent transport equations for fusion neutrons and recoil ions, being written in terms of the modified Eulerian coordinates originally proposed by Wienke (1974). After incorporating these equations into the one-dimensional hydrodynamics code MEDUSA, burn simulations are made for isobaric D-T pellets models compressed to 1,000 times the liquid density. It is found that in reactor-grade pellets, the inclusion of neutron heating decreases the fuel gain from the values obtained by neglecting the neutron heating. Calculations neglecting the energy transport by recoil ions overestimate the neutron energy deposition to plasma ions. The energy spectrum of neutrons emitted out of a typical D-T burning pellet is also shown. These neutrons contain fast components whose energies reach more than 20MeV.     

Fission Gas Induced Cladding Deformation of LWR Fuel Rods under Reactivity Initiated Accident Conditions

Behavior of irradiated fuel rods under power burst conditions by accidental reactivity insertion in light water reactors (LWRs) has been studied in the Nuclear Safety Research Reactor (NSRR). In the experiments, cladding hoop deformation, which reached up to about 10%, was much larger than that of the fresh rods. The current LWR fuel behavior analysis codes, which only take account of the thermal expansion of the fuel pellets for the deformation calculation, under-predicted the plastic deformation of the cladding to be less than about 1%. Fission gas release during the pulse irradiation tests reached as high as 22% in the NSRR irradiated fuel tests. In order to describe these test results, a model of grain boundary fission gases to cause the cladding deformation has been developed and installed in a fuel behavior simulation code, FRAP-T6. In the model, the over-pressurized gases by the pulse irradiation cause grain boundary separation and stress the cladding during the tests. The model assumes that the gases remain in the fuel during the early part of pulse irradiation and are released to the open volume in the rod after the cladding deformation. The model, in combination with a fuel thermal expansion model, GAPCON, which was validated through fresh fuel tests, reproduces the NSRR test results reasonably well.     

Sustained-release alginate-chitosan pellets prepared by melt pelletization technique

Context: Alginate-chitosan pellets prepared by extrusion-spheronization technique exhibited fast drug dissolution.

Objective: This study aimed to design sustained-release alginate pellets through rapid in situ matrix coacervation by chitosan during dissolution.

Methods: Pellets made of alginate with chitosan and/or calcium acetate were prepared using solvent-free melt pelletization technique which prevented reaction between processing materials during agglomeration and allowed such reaction to occur only in dissolution phase.

Results: Drug release was retarded in pH 2.2 medium when pellets were formulated with calcium acetate or chitosan till a change in medium pH to 6.8. The sustained-release characteristics of calcium alginate pellets were attributed to pellet dispersion and rapid cross-linking by soluble Ca²⁺ during dissolution. The slow drug release characteristics of alginate-chitosan pellets were attributed to polyelectrolyte complexation and pellet aggregation into swollen structures with reduced erosion. The drug release was, however, not retarded when both calcium acetate and chitosan coexisted in the same matrix as a result of chitosan shielding of Ca²⁺ to initiate alginate cross-linkages and rapid in situ solvation of calcium acetate induced fast pellet dispersion and chitosan losses from matrix.

Conclusion: Similar to calcium alginate pellets, alginate-chitosan pellets demonstrated sustained drug release property though via different mechanisms. Combination of alginate, chitosan and calcium acetate in the same matrix nevertheless failed to retard drug release via complementary drug release pattern.