CFBC Ash Research Articles

Greenhouse Gas Emission Reduction and Economic Benefit Evaluation of Carbon Mineralization Technology using CFBC Ash

탄소광물화 기술은 석탄재와 이산화탄소를 반응시켜 건설재료 등으로 활용이 가능한 복합탄산염 등의 부산물을 생산함과 동시에 이산화탄소를 탄산염에 고정화하여 온실가스 감축효과를 얻을 수 있는 기술로, 이산화탄소 감축 및 경제적 잠재력을 고려하면 국가 온실가스 감축 목표를 실현하기 위한 유용한 방안이 될 수 있다. 그러나 아직까지는 해당 기술의 이산화탄소 감축 성능과 환경적인 이점, 경제성 등에 대한 자료가 적어서 기술의 상용화 가능성에 대해서는 명확하지 않은 상태이다. 본 연구는 국내 순환유동층 발전소에서 발생되는 이산화탄소와 석탄재를 이용하는 이산화탄소 투입량 기준 6,000 tonCO2/년 규모의 탄소광물화 설비에 대해 이산화탄소 감축량 및 경제성 분석을 수행했다. 공정 분석 결과 1톤의 복합탄산염 생산 시 실질적인 이산화탄소 감축량은 약 45.8 kgCO2eq, 연간 약 805.3 tonCO2로 산정되었으며, 경제적 편익 분석 시 비용편익분석비(B/C Ratio)는 1.04, 내부수익률(IRR)은 10.65 %, 순현재가치(NPV)는 24,713,465 원으로 나타나, 탄소광물화 설비가 어느 정도 경제성을 확보하고 있는 것으로 분석되었다.

Utilization of Low Activity CFBC Ash in Cemented Paste Backfill Containing Phosphate Tailings

Utilization of Low Activity CFBC Ash in Cemented Paste Backfill Containing Phosphate Tailings

Assessment of a Carbonation-Based CO2 Utilization Process for the Valorization of CFBC Ash

This work assesses a combined accelerated carbonation and wet granulation treatment applied to circulating fluidized bed combustion fly ash with the aim of producing secondary aggregates for civil engineering applications and of achieving a net storage of CO2. The experiments were carried out at both a laboratory scale and larger scale, and the effects of the CO2 content of the gas flow (40 or 100%), temperature (from 25 to 60 °C), and the use of an alkaline activator solution as binder for the granulation process were investigated. Specifically, the particle size distribution, aggregate crushing value, leaching behavior, and CO2 uptake of the products after 28 days curing under ambient air were analyzed. In addition, the energy requirements of the process were estimated on the basis of the results of the larger scale tests and were used to calculate the CO2 emissions of the process to estimate the net CO2 avoided that could be achieved per kilogram of produced aggregate. The carbo-granulation process allowed us to achieve a relevant increase in particle size with respect to the starting material. The conditions that yielded the best performance in terms of product properties (both technical and environmental) and the maximum amount of CO2 avoided (above 75 g of CO2/kg aggregate) was the carbo-granulation treatment performed at 60 °C with water as binder and a gas phase containing 40% CO2. Although the products obtained employing the alkaline activator solution presented a lower mobility of trace elements of potential environmental concern and generally a higher CO2 uptake compared to the granules produced with water as granulation binder, the carbon footprint of the additives (sodium silicate in particular) would make the process carbon positive, even considering the CO2 avoided by replacing natural aggregates.

Investigation on physical properties, strength and phase evolution of binary cementitious materials made of CFBC ash and lime

Circulating fluidized bed combustion ash (CFBC ash) is the wasteof coal-firedcirculating fluidized bed power plant boiler.CFBC ash contains amounts of free limeand anhydrite, which has a self-hardening andexpansion property. This paper studies the influence of CFBC ash fineness and lime or slaked lime dosage on the physical properties, strength and phase evolution of binary cementitious materials (lime or slaked lime-CFBC ash). The experimental results show that when lime or slaked lime dosage is below 30%, throughCFBC ash getting finer, setting timeof binary cementitious materials becomes shorter and compressive strength of that increases, butwater requirement of normal consistency of that decreases to some extent. And when CFBC ash fineness is constant, with the increment of lime dosage, setting timeof binary cementitious materials becomes shorter and water requirement of normal consistency of that increases, butcompressive strength of that declines first and then increases. But when CFBC ash fineness is constant, with the increment of slaked lime dosage, setting timeof binary cementitious materials becomes longer and compressive strength of that declines, butwater requirement of normal consistency of that increases.

Effect of fineness and components of CFBC ash on performance of basic magnesium sulfate cement

The effect of fineness and components of circulating fluidized bed combustion ash (CFBC ash) on compressive strength, setting time and fluidity of basic magnesium sulfate cement was studied. The results showed that with the increment of the fineness of CFBC ash, the fluidity of cement paste increased, the setting time shortened and the compressive strength was slightly enhanced. The effects of the dosage of active SiO2, f-CaO and SO3 in CFBC ash on setting time, compressive strength and softening coefficient were also investigated. The experimental results indicated that with the increment of the active SiO2 dosage in CFBC ash, the setting time would prolong and softening coefficient would reduce. When the f-CaO dosage increased, the setting time would shorten. When the SO3 dosage increased, the setting time would prolong firstly and then shorten. Softening coefficient increased firstly and then reduced with the increment of the f-CaO dosage, but the softening coefficient firstly reduced and then slightly increased when the SO3 dosage increased. With the increment of the active SiO2, f-CaO and SO3 dosage in CFBC ash, compressive strength increased at first and then decreased. CFBC ash still has the filler effect, the morphology effect and the chemical effect. Comprehensive comparison, the superior fineness of CFBC ash is origin ash, and the optimum composition of CFBC ash is active SiO2 < 5%, f-CaO < 3% and SO3 < 1.75%. The results showed that CFBC ash could serve as favorable source materials for preparing basic magnesium sulfate cement, which may promote comprehensive application of basic magnesium sulfate cement and resource utilization of CFBC ash.

Circulating fluidized bed combustion ash as controlled low-strength material (CLSM) by alkaline activation

The present study is aimed at providing a useful means of treating and utilizing the CFBC ash as controlled low-strength material (CLSM). The CLSM in this study was produced by activating a mixture of CFBC fly ash, bottom ash and blast furnace slag with sodium hydroxide (NaOH) solution. The characteristics of the CLSM were evaluated by the main factors such as flow, bleeding and compressive strength as stated in ACI 229, along with initial setting time and XRD patterns. The CLSM showed delayed strength development due to the reactivity of calcium sulfate in CFBC fly ash and bottom ash. This effect is evidenced by the XRD pattern of the CLSM at 7 and 56d which showed the consumption of gypsum asa source of calcium sulfate, to produce the reaction product ettringite.

Experimental Study of Stabilized Soil Utilizing Circulating Fluidized Bed Combustion Desulfurization Ash with Carbide Slag and Desulfurization Gypsum

This paper discusses the feasibility of preparing soil stabilizer which is circulating fluidized bed combustion ash-based, supplemented with carbide slag and desulfurization gypsum, composed entirely of complete industrial wastes. The results show that CFBC ash has better pozzolanic activity than fly ash. When stabilizer total content is 10% and the ratio of CFBC ash : carbide slag : desulfurization gypsum is 7.2 : 1.8 : 1, compressive strength of stabilized soil can reach the maximum of 2.12 MPa at the age of 28 d of curing. Stabilizer can meet the strength requirements of cement-soil mixing pile composite foundation and cement-soil mixing pile waterproof curtain.

Assessment of Scaling Durability of Concrete with CFBC Ash by Automatic Classification Rules

The objective of this investigation was to develop rules for automatic assessment of concrete quality by using selected artificial intelligence methods based on machine learning. The range of tested materials included concrete containing nonstandard waste material—the solid residue from coal combustion in circulating fluidized bed combustion boilers (CFBC ash) used as an additive. Performed experimental tests on the surface scaling resistance provided data for learning and verification of rules discovered by machine learning techniques. It has been found that machine learning is a tool that can be applied to classify concrete durability. The rules generated by computer programs AQ21 and WEKA by using the J48 algorithm provided a means for adequate categorization of plain concrete and concrete modified with CFBC fly ash as materials resistant or not resistant to the surface scaling.

Automatic categorization of chloride migration into concrete modified with CFBC ash

The objective of this investigation was to develop rules for automatic categorization of concrete quality using selected artificial intelligence methods based on machine learning. The range of tested materials included concrete containing a new waste material - solid residue from coal combustion in fluidized bed boilers (CFBC fly ash) used as additive. The rapid chloride permeability test - Nordtest Method BUILD 492 method was used for determining chloride ions penetration in concrete. Performed experimental tests on obtained chloride migration provided data for learning and testing of rules discovered by machine learning techniques. It has been found that machine learning is a tool which can be applied to determine concrete durability. The rules generated by computer programs AQ21 and WEKA using J48 algorithm provided means for adequate categorization of plain concrete and concrete modified with CFBC fly ash as materials of good and acceptable resistance to chloride penetration.

Inhibition of the Expansion of CFBC Ash

The destructive expansion of CFBC ash is the bottleneck problem for its utilization in building materials. The addition of chemical substances and autoclave curing were used to inhibit the expansion in the paper. The results show that the addition of 1% CaCl2 or 1% Na2CO3 can decrease the 28 d linear expansion ratio of CFBC ash-water mortars by about 19%, with no disadvantage influence on the compressive strength. Moreover, the linear expansion ratio of CFBC ash-clinker-water pastes was below 5×10-4 after autoclave curing. The work confirms that the expansion of CFBC ash can be inhibited effectively by the way of autoclave curing.

06/00603 CFBC ash hydration studies: Anthony, E. J. et al. Fuel, 2005, 84, (11), 1393–1397.

06/00603 CFBC ash hydration studies: Anthony, E. J. et al. Fuel, 2005, 84, (11), 1393–1397.

CFBC ash hydration studies

Hydration studies on CFBC ashes have shown that the acetone technique to prevent hydration in stored samples is relatively effective, only allowing some slight degree of hydration over days in the presence of excess water. In the presence of large excesses of water sufficient to control temperature increases, the degree of bulk mixing has no effect on the degree of hydration, which is shown to be relatively slow at ambient conditions, taking hours to complete. Finally, the effect of salt addition on hydration has been shown to be negligible at the low levels typical of wastewater, but there may be effects at ion concentrations typical of seawater. This work suggests that experience gained from lime hydration should be applied with caution to studies on hydration of CFBC ashes.

Steam hydration of CFBC ash and the effect of hydration conditions on reactivation

A detailed study has been carried out on how hydration methods and conditions influence the sulphur capture potential of ash from a 165 MWe circulating fluidized bed combustion boiler firing a petroleum coke and coal blend. Both bed ash and fly ash were hydrated with saturated steam at various saturation conditions for different periods of time. Samples of the hydrated residues were then analyzed for free lime and calcium hydroxide content after the hydration process. Some size fractions of the steam-hydrated samples and those hydrated with liquid water in previous work were re-sulphated for 90 min using synthetic flue gas in a thermogravimetric analyzer at 850 °C to investigate how reactivation conditions affect the final sulphur capture behaviour of the ash. This work confirms that either hydration method is effective for reactivating the bed ash fractions tested but not fly ash, which should either be re-injected directly or reactivated in some other manner to improve its sulphur capture potential.

Experimental Studies on Hydration of Partially Sulphated CFBC Ash

AbstractThe hydration of partially‐sulphated fluidized bed combustor (FBC) ash with water was carried out at laboratory scale. The bottom ash fractions and the as‐received fly ash were hydrated for different lengths of time, at different temperatures between 5°C and 80°C. The free lime and calcium hydroxide content in the samples were analyzed before and after the hydration process. Scanning electron microscopy (SEM) with an energy dispersive X‐ray system (EDX) was employed to investigate the physical characteristics of the samples. X‐ray diffractograms (XRD) were used to obtain information on the phase composition. The current results show that, during the hydration treatment, the unreacted CaO in the partially‐sulphated material can be almost quantitatively converted to Ca(OH)2 but that the free lime content is not constant. It is also clear that effectiveness of the hydration depends on hydration time and temperature. In addition, the behaviour of different particle size fractions is different and there is evidence that the hydration of CaO is not the only reaction occurring in this system.

99/00778 CFBC ash characterization: the case of the Provence 250 MW unit

99/00778 CFBC ash characterization: the case of the Provence 250 MW unit

Physico-Chemical Characterization and Leaching of Desulphurization Coal Fly Ash

Fly ash produced by coal combustion using two types of desulphurization process were studied: a conventional pulverized coal boiler equipped with lime injection (PCL ash), and a circulating fluidized bed combustion boiler with limestone injection (CFBC ash). The ashes were characterized completely: granulometry, morphology, mineralogy, chemical composition and behaviour to water contact. Both PCL ash and CFBC ash present similar features: fine granulometry, presence of anhydrite phase and sulphate content. However, PCL ash also shows lots of spherical particles, unlike CFBC ash, and a much higher lime content, due to the lower desulphurization rate in PC boilers. Unlike CFBC ash, most of the trace elements in PCL ash show an inverse concentration-particle size dependence. Leachates obtained from both samples are rich in soluble salts [CaSO4 and Ca(OH) 2] and arsenic and selenium are prevented from solubilizing by high lime content. In wetted PCL ash, the formation of ettringite crystals stabilizes calcium and sulphate ions. Simultaneously, arsenate, selenate and chromate anions are trapped in the crystal. CFBC ash does not really harden because the lime content is too low. However, the leached selenium concentration is cut down in wetted CFBC ash samples. © 1996 ISWA