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.

Preparation of Nanosize Anatase TiO2 Powders by Hydrothermal Synthesis

2007 ◽  
Vol 336-338 ◽  
pp. 2017-2020 ◽  
Author(s):  
Fan Yong Ran ◽  
Wen Bin Cao ◽  
Yan Hong Li ◽  
Xiao Ning Zhang
Keyword(s):  
Grain Size ◽  
Hydrothermal Synthesis ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Reaction Temperature ◽  
Reaction System ◽  
Anatase Tio2 ◽  
Holding Time ◽  
Precursor Concentration

Nanosize anatase TiO2 powders have been synthesized by hydrothermal synthesis by using technical grade TiOSO4 as precursor and urea as precipitating agent. The initial pressure of the reaction system was set at 6 MPa. Stirring speed was fixed at 300r/min. The reaction system reacted at the temperature ranged from 110 to 150°C for holding 2hrs to 8hrs and the concentration of the precursor was ranged from 0.25M to1.5M. XRD patterns show that the synthesized powders are in the form of anatase phase. Calculated grain size is ranged from 6.7 to 8.9nm by Scherrer method from the line broadening of the (101) diffraction peak of anatase. The specific surface area of the powders synthesized under different conditions is ranged from 124 to 240m2/g. The grain size of the powders increases with the increase of the reaction temperature, holding time and precursor concentration, respectively. The specific surface area decreases with the increase of reaction temperature and holding time, and does not obviously change with the change of precursor concentration when the concentration of the precursor is less than 1M. However, when the concentration is higher than 1M, the specific surface area will decrease quickly with the increase of the precursor concentration. XRD and DSC-TG analysis shows that the synthesized anatase TiO2 will begin to transform to rutile TiO2 at about 840°C. When heated to 1000°C for holding 1h, the anatase powders will transform to rutile completely.

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.

Property of Nanoporous Metal-Organic Frameworks at Different Synthesis Temperature

2012 ◽  
Vol 427 ◽  
pp. 123-127
Author(s):  
Yuan Hui Ma ◽  
Lei Zhang ◽  
Cheng Chun Tang
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Reaction Temperature ◽  
Metal Organic Frameworks ◽  
Synthesis Temperature ◽  
Structure Stability ◽  
Nanoporous Metal ◽  
Metal Organic ◽  
Ft Ir

The nanoporous metal-organic frameworks were synthesized under solvothermal conditions using organic solvent dimethylformamide. The samples were characterized by XRD, SEM, TGA, FT-IR and specific surface area for their properties difference. When the reaction temperature rises, the particle size becomes larger. All TGA curves are the basically same, the framework structure begins to be destroyed from 500°C up to around 600°C. The metal-organic frameworks accepted at reaction temperature 190°C have larger specific surface area and better structure stability.

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.

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.

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.

Effects of Change in Fineness of Fly Ash on Air-Entrained Concrete

2010 ◽  
Vol 168-170 ◽  
pp. 2195-2199 ◽  
Author(s):  
Hong Zhu Quan ◽  
Hideo Kasami
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Laboratory Experiments ◽  
Drying Shrinkage ◽  
Test Results ◽  
Air Entrained Concrete

In order to make clear of the effects of the change in fineness of fly ash on air-entrained concrete, 2 series of laboratory experiments were carried out using 6 kinds fly ash with the specific surface area in the range from 2500 to 4400cm2/g. The test results indicated higher slump and lower air-entraining content and higher dosage of air-entraining agent for fly ash with higher specific surface area. Compressive strength was found to increase with the increases of specific surface area of fly ash, while drying shrinkage and carbonation were found to show different tendency with change in fineness of fly ash.

Sign in / Sign up

Export Citation Format

Share Document