1. Closed-cycle for environmental protection in thermal power plants
NATO Advanced Study Institute on
Energy Security
4-11 October 2015, Antalya, Turkey
Faculty of Power Engineering and Power Machines, Department of Thermal and Nuclear Power Engineering
Closed-cycle for environmental protection in thermal power plants
Denitza Zgureva, Silviya Boycheva
Motivation
Syntheses of zeolites from fly ashes
The expected growth of the consumption of electricity between 2010 and 2040 is 56 %. Still the coal combusting TPP are the major producer of energy. Our investigation program is devoted to the realization of closed-cycle for environmental protection in TPP by the conversion of lignite coal fly ash into synthetic zeolites and their applications in the flue gas cleaning systems.
Zeolitization of FA from Bulgarian lignite coal was carried out by two-stage fusion-hydrothermal syntheses with NaOH as an alkaline activator. FA
SiO2 wt%
Al2O3 wt%
Fe2O3 wt%
MgO wt%
SO3
wt%
CaO wt%
ρ kg/m3
Fraction
AES
46.58
23.26
14.73
0.81
2.49
3.01
1940
d50<0.045 mm
МE 2
52.66
23.37
8.72
2.75
2.40
5.75
3070
d100= mm
Production of greenhouse gases
Capturing of CO2
Synthesis of high porous zeolites
Production of fly ash residue
COALS
FA major constituents:
52-90 % aluminosilicates
Post-combustion
capture for existing TPP
Global
warming
Molecular
sieve
Mixed amorphous-crystalline structure in a ratio of 43/57 for ME 2 and 65/35 for AES.
Raw materials
Synthetic zeolite for analyses
Fusion
Magnetic stirring
FA 5g
550 oC, 1 h
16 h
NaOH 10g
From FA to Na-X zeolite
Washing and drying
Hydrothermal activation
90 oC, 2-20 h
105 oC, 1 h
Zeolites - the best adsorbents for post-combustion carbon capture systems
Fundamental process design parameters
Adsorption capacity - surface and porosity
Selectivity
Mass transfer kinetics
Heat of adsorption
BET analyses of the synthesized materials
Adsorption of carbon dioxide onto synthetic zeolites
Micromeritics Instrument Corporation
TriStar II
TriStar II 3020 Version 3.02
Sample:
Sample AES 4 h
Started:
27/08/ :42:17
Analysis Adsorptive:
CO2
Completed:
27/08/ :56:29
Analysis Bath Temp.: K
Sample Mass: g
Warm Free Space:
cm³ Measured
Cold Free Space:
cm³
Equilibration Interval:
5 s
Saturation Pressure (kPa)
BET range limit
p/p0=
Liquid Nitrogen Т = -198 оС
Gaseous Nitrogen p0 = kPa
Sample
SBET,
m2/g
Smicro,
Vmicro,
cm3/g
Vmeso, cm3/g
Yield of Na-X based on FA aluminosilicates, %
AES 2 h
310.61
186.55
0.083
0.158
57.03
AES 4 h
387.75
242.99
0.098
0.173
71.19
AES 21 h
379.20
253.99
0.108
0.153
69.62
ME2 2 h
176.17
94.82
0.039
0.124
29.71
The Na-X zeolite can be synthesized by lignite coal ash with different composition and structure through controllable two stage mechanism.
The highest specific surface area SBET = m2/g is obtained for Na-X zeolite synthesized by FA from TPP AES for 4 h activation.
Adsorption capacity of FA zeolites is measured through experimental adsorption isotherms and it reaches mgCO2/g.
Technical University of Sofia, Department of Thermal and Nuclear Power Engineering, Blvd. Kl. Ohridsky 8, 1000 Sofia, Bulgaria, s: