A Study on the Influencing Factors on the Dry-Shrinkage Performance of Phosphate Cement

2011 ◽  
Vol 99-100 ◽  
pp. 838-841
Author(s):  
Chun Ping Tang
Keyword(s):  
Fly Ash ◽  
Specific Surface ◽  
Surface Area ◽  
Magnesium Oxide ◽  
Influencing Factors ◽  
Specific Surface Area ◽  
Specific Area ◽  
Dry Shrinkage

Aiming at the characteristics of phosphate repairing materials, the influences of retarder, specific surface area of magnesium oxide and content of fly ash on the dry-shrinkage performance of phosphate cement were studied in this paper. The results showed that greater content of retarder would result in greater dry-shrinkage value within a certain range, greater specific area of magnesium oxide would result in greater dry-shrinkage value while the increase of content of fly ash would cause the dry-shrinkage value to be decreased correspondingly within a certain range.

Preparation of Sands Modified by Aluminous Salt and its Adsorption Capability of CD2+

2011 ◽  
Vol 130-134 ◽  
pp. 856-859
Author(s):  
Chun Sheng Ding ◽  
Yang Ping Fu ◽  
Qian Fen Zhu ◽  
Jing Fu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Influencing Factors ◽  
Removal Efficiency ◽  
Specific Surface Area ◽  
Quartz Sand ◽  
Ph Value ◽  
Alkaline Condition ◽  
Initial Concentration ◽  
Adsorption Capability

In this experiment quartz sand was chosen as a carrier to be coated by aluminous salt under alkaline condition, and then the specific surface area was tested, and the adsorption capability and Cd2+ removal influencing factors of modified sand were studied. The investigation results showed that the specific surface area of modified sand was 75.244m2/g which was 9.38 times of that of original sand; the removal efficiency of Cd2+ by aluminous salt modified sand reached 59% contrast to 39% of original sand with pH 7.00. It was also found that the removal efficiency of Cd2+ by the aluminous salt modified sand was reduced with the increase of initial concentration of Cd2+ solution, and was enhanced with the increase of pH value, the Cd2+ removal efficiency was almost 71% with pH 9.0.

scholarly journals Study on Adsorption Mechanism and Failure Characteristics of CO2 Adsorption by Potassium-Based Adsorbents with Different Supports

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2424 ◽  
Author(s):  
Bao-guo Fan ◽  
Li Jia ◽  
Yan-lin Wang ◽  
Rui Zhao ◽  
Xue-song Mei ◽  
...  
Keyword(s):  
Fly Ash ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Reaction Temperature ◽  
Adsorption Mechanism ◽  
Co2 Adsorption ◽  
Carbonation Reaction ◽  
Failure Characteristics ◽  
Boiler Fly Ash

In order to obtain the adsorption mechanism and failure characteristics of CO2 adsorption by potassium-based adsorbents with different supports, five types of supports (circulating fluidized bed boiler fly ash, pulverized coal boiler fly ash, activated carbon, molecular sieve, and alumina) and three kinds of adsorbents under the modified conditions of K2CO3 theoretical loading (10%, 30%, and 50%) were studied. The effect of the reaction temperature (50 °C, 60 °C, 70 °C, 80 °C, and 90 °C) and CO2 concentration (5%, 7.5%, 10%, 12.5%, and 15%) on the adsorption of CO2 by the adsorbent after loading and the effect of flue gas composition on the failure characteristics of adsorbents were obtained. At the same time, the microscopic characteristics of the adsorbents before and after loading and the reaction were studied by using a specific surface area and porosity analyzer as well as a scanning electron microscope and X-ray diffractometer. Combining its reaction and adsorption kinetics process, the mechanism of influence was explored. The results show that the optimal theoretical loading of the five adsorbents is 30% and the reaction temperature of 70 °C and the concentration of 12.5% CO2 are the best reaction conditions. The actual loading and CO2 adsorption performance of the K2CO3/AC adsorbent are the best while the K2CO3/Al2O3 adsorbent is the worst. During the carbonation reaction of the adsorbent, the cumulative pore volume plays a more important role in the adsorption process than the specific surface area. As the reaction temperature increases, the internal diffusion resistance increases remarkably. K2CO3/AC has the lowest activation energy and the carbonation reaction is the easiest to carry out. SO2 and HCl react with K2CO3 to produce new substances, which leads to the gradual failure of the adsorbents and K2CO3/AC has the best cycle failure performance.

scholarly journals Zeolite Synthesis from Brazilian Coal Fly Ash for Removal of Zn2+ and Cd2+ from Water

2011 ◽  
Vol 356-360 ◽  
pp. 1900-1908 ◽  
Author(s):  
Juliana De Carvalho Izidoro ◽  
Denise Alves Fungaro ◽  
Shao Bin Wang
Keyword(s):  
Fly Ash ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Metal Ion ◽  
Raw Materials ◽  
Coal Fly Ash ◽  
Mineralogical Composition ◽  
Batch Process ◽  
Metal Ion Removal

A Brazilian fly ash sample (CM1) was used to synthesize zeolites by hydrothermal treatment. Products and raw materials were characterized in terms of real density (Helium Pycnometry), specific surface area (BET method), morphological analysis (SEM), chemical composition (XRF) and mineralogical composition (XRD). The zeolites (ZM1) from fly ash were used for metal ion removal from water. Results indicated that hydroxy-sodalite zeolite could be synthesized from fly ash sample. The zeolite presented higher specific surface area and lower SiO2/Al2O3ratio than the ash precursor. The adsorption showed that cadmium is more preferentially adsorbed on ZM1 than zinc. The adsorption equilibrium time for both Zn2+and Cd2+was 20 hours in a batch process. The adsorption isotherms were better fitted by the Langmuir model and the highest percentages of removal using ZM1 were obtained at pH 6 and 5 and doses of 15 and 18 g L-1for Zn2+and Cd2+, respectively. Thermodynamic studies indicated that adsorption of Zn2+and Cd2+by ZM1 was a spontaneous, endothermic process and presented an increase of disorder at the interface solid/solution.

Influence of Mixture Proportion and Curing Condition on Contribution of Fly Ash to Strength of Concrete

2006 ◽  
Vol 302-303 ◽  
pp. 235-241 ◽  
Author(s):  
F.-R. Wu ◽  
Yoshihiro Masuda ◽  
S. Nakamura ◽  
S. Sato
Keyword(s):  
Fly Ash ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Cement Content ◽  
Ash Content ◽  
K Value ◽  
Fly Ash Concrete ◽  
Curing Condition ◽  
Strength Difference

To investigate the strength efficiency of fly ash in concrete, the contribution of fly ash to strength, k value was calculated with the equation: the strength difference between fly ash concrete and control concrete with no fly ash due to the different fly ash content divides by the strength difference between both control concrete with no fly ash due to the different cement content which equals to the former different fly ash content. The k values were organized with fly ash specific surface area, concrete curing condition and age of specimens. Based on a large number of data collected from several proceedings and journals published in Japan during 1981 to 2003, the influences of fly ash property, mixture proportion and curing condition on k value were investigated. Within the range of study the following observations were made: (1) When fly ash concrete kept in moist curing, the k value of fly ash with specific surface area from 250 to 500 m2/kg is averagely 0.5 to 0.6 or higher at an age of 91 days and later, whereas that of fly ash with specific surface area from 150 to 250 m2/kg is around 0.4 to 0.5, and with some cases contributing little to the strength. (2) In the range of a portland cement content of 250 to 450 kg/m3, the strength contribution tends to increase as the cement content increases. (3) The contributions of fly ash to strength at 91 and 364 days are 1.44 to 1.97 times as large as those at 28 days, respectively, by standard curing, but conversely decrease to 0.75 to 0.79 times those at 28 days by air curing.

Study of Gamma Alumina Synthesis – Analysis of the Specific Surface Area

2014 ◽  
Vol 87 ◽  
pp. 54-60 ◽  
Author(s):  
A.H. Munhoz ◽  
H. de Paiva ◽  
L. Figueiredo de Miranda ◽  
E.C. de Oliveira ◽  
Raphael Cons Andrades ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ageing Time ◽  
Precursor Solution ◽  
Specific Area ◽  
Gamma Alumina ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dta And Tg

Different samples of pseudoboehmite (PB) were synthesized through the sol-gel process, using aluminum nitrate as precursor. The influence of variables on the synthesis and calcinations of the PB on the specific area of the obtained gamma-Alumina were studied. The variables were the ageing temperature (25 and 130o C), addition or not of polyvinyl alcohol to the precursor solution and the ageing time of the PB. The pH adjustment of the precursor solution was made by using ammonium carbonate. The products, which were obtained on different conditions, were then characterized by x-ray diffraction, specific area measurements through the BET process, and by thermal analysis (DTA and TG). After characterization, the synthesis products were calcined at 500°C; during this process the gamma-Alumina transformation was observed. The calcination products were characterized by the same methods (x-ray diffraction, BET, DTA and TG) and the desorption-absorption curves were obtained as well, in order to measure the pore volume of the samples. Finally, the results were analyzed through an experimental factorial planning, which showed that high specific surface area gamma-Al2O3 (around 330m²/g) can be obtained through this process.

scholarly journals Mercury Migration Behavior from Flue Gas to Fly Ashes in a Commercial Coal-Fired CFB Power Plant

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1040 ◽  
Author(s):  
Xiaohang Li ◽  
Yang Teng ◽  
Kai Zhang ◽  
Hao Peng ◽  
Fangqin Cheng ◽  
...  
Keyword(s):  
Fly Ash ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Flue Gas ◽  
Power Plants ◽  
Bottom Ash ◽  
Migration Behavior ◽  
Boiler Unit ◽  
Cfb Boiler

Mercury (Hg) emissions from coal-fired power plants are of increasing concern around the world. In this study, field tests were carried out to understand the Hg emission characteristics and its migration behaviors in a commercial CFB boiler unit with the electricity generation capacity of 25 MW. This boiler is equipped with one electrostatic precipitator (ESP) and two fabric filters (FFs) in series for removing particulates from the flue gas. The EPA 30B method was used for simultaneous flue gas Hg sampling at the inlet of the ESP and the outlet of the second FF. The Hg mass balance in the range of 104.07% to 112.87% was obtained throughout the CFB unit by measuring the Hg contents in the feed fuel, the fly ash and the bottom ash, as well as in the flue gas at the outlet of the particulate control device (PCD) system. More than 99% of Hg contained in the feed fuel was captured by the fly ash, whilst less than 1% of Hg was remained in the bottom ash or the flue gas after passing the PCD system. The gaseous Hg obviously migrated from the flue gas to the fly ash in the air pre-heater, where the flue gas temperature decreased from 250 °C at the inlet to 120 °C at the outlet. Other gaseous Hg migrated from the flue gas to the fly ash in the PCD system, as the Hg concentrations in the flue gas ranged from 3.14 to 4.14 μg/m3 at the inlet of the ESP and ranged from 0.30 to 0.36 μg/m3 at the outlet of the second FF. The average Hg contents in the fly ash samples collected from the ESP, the first FF and the second FF were 912.3, 1313.6 and 1464.9 ng/g, respectively, while the mean particle diameters of these fly ash samples tend to decrease along the flow pass in the PCD system. Compared to large fly ash particles, smaller fly ash particles exhibit higher Hg capture performance due to their high unburned carbon (UBC) content and large specific surface area. The migration of gaseous Hg from the flue gas to the fly ash downstream of the CFB boiler unit was easier than that downstream of the PC boiler unit due to high UBC content and specific surface area.

Preparation and Structural Analysis of Magnesium Oxide Aerogels

MRS Advances ◽  
2017 ◽  
Vol 2 (57) ◽  
pp. 3505-3510
Author(s):  
Jiankai Zhang ◽  
Xiaohong Chen ◽  
Ran Liu ◽  
Huaihe Song ◽  
Zhihong Li
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Magnesium Oxide ◽  
Specific Surface Area ◽  
Average Pore Size ◽  
Sol Gel ◽  
Average Pore ◽  
X Ray ◽  
Water As Solvent ◽  
Saxs Analysis

ABSTRACTMagnesium oxide aerogels were made by sol-gel process using magnesium methoxide as precursor, methanol and deionized water as solvent with ethanol supercritical fluid drying. The influences of the different factors on the gel time and the specific surface area of magnesium oxide aerogels were studied, and the structure and morphology were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and X-ray diffraction (XRD), and the Small Angle X-ray Scatter (SAXS) was utilized to determine the fractural structure of the magnesium oxide aerogels. The results show that MgO aerogels belong to the typical mesoporous materials with rich network and highly developed pore structure, and the specific surface area is 904.9 m2/g, the apparent density is 0.055 g/cm3, the average pore size is 19.6 nm. The results of SAXS analysis show that the fractal dimension of the MgO aerogels is 2.32 in high q area which proves the existence of rough surface and pore fractal structure.

Removal efficiency of subsurface vertical flow constructed wetlands for different organic loads

2007 ◽  
Vol 56 (3) ◽  
pp. 75-84 ◽  
Author(s):  
G. Langergraber ◽  
C. Prandtstetten ◽  
A. Pressl ◽  
R. Rohrhofer ◽  
R. Haberl
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Constructed Wetlands ◽  
Specific Surface Area ◽  
Nitrogen Concentration ◽  
Specific Area ◽  
Ammonia Nitrogen ◽  
Vertical Flow ◽  
Design Standards ◽  
Vertical Flow Constructed Wetlands

Using subsurface vertical flow constructed wetlands (SSVFCWs) with intermittent loading it is possible to fulfil the stringent Austrian effluent standards regarding nitrification. For small plants (less than 500 persons) standards for ammonia nitrogen concentration have to be met at water temperatures higher than 12 °C, effluent concentrations and treatment efficiencies for organic matter have to be met the whole year around. According to the Austrian design standards the required surface area for SSVFCWs treating wastewater was 5 m2 per person. Within the first part of an Austrian research project the goal was to optimise, i.e. minimise the surface area requirement of vertical flow beds. Therefore, three SSVFCWs with a surface area of 20 m2 each have been operated in parallel. The organic loads applied were 20, 27 and 40 g COD/m2/d, which corresponds to a specific surface area requirement of 4, 3 and 2 m2 per PE, respectively. The paper compares the effluent concentrations and elimination efficiencies of the three parallel operated beds. It could be shown that a specific area demand of 4 m2 per person is suitable to be included in the revision of the Austrian design standard. Additionally it could be shown that during the warmer seasons (May–October) when the temperature of the effluent is higher than 12 °C the specific surface area might be further reduced; even 2 m2 per person has been proven to be adequate.

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