Calculation for Mineral Phases in the Calcination of Desulfurization

9504

Ind. Eng. Chem. Res. 2010, 49, 9504–9510

Calculation for Mineral Phases in the Calcination of Desulfurization Residue to Produce Sulfoaluminate Cement Wenlong Wang,*,† Peng Wang,† Chunyuan Ma,† and Zhongyang Luo‡ National Engineering Laboratory for Coal-fired Pollutants Emission Reduction, Shandong UniVersity, Jinan, China, and State Key Laboratory of Clean Energy Utilization, Zhejiang UniVersity, Hangzhou, China

The utilization of dry flue gas desulfurization (FGD) residue has become an environmental issue in China. A new method is introduced here to produce sulfoaluminate cement using the dry FGD residue and fly ash without modification of the cement plant equipments. The bench- and pilot-scale experimental studies indicated that the obtained sulfoaluminate cement product had excellent performance. FACTSAGE was improved by a new database and then used for raw material proportion optimization. The mineral phases of a CaO-SiO2-Al2O3-CaSO4 system after calcination were calculated. The theoretical and experimental results are accordant. This technology has good potential to decrease the raw material costs and energy consumption at cement plants. It is also beneficial in CO2 emission reduction and circular economy development. The calculation results may be generally referred in the studies on the chemical processes such as sulfur fixation at high temperature, mineral optimization, and cement production, etc. 1. Introduction For coal-fired power plants, the utilization of flue gas desulfurization (FGD) residue, especially from dry FGD systems, is a big issue. In China, this issue is more of a concern because more dry or semidry FGD systems are applied than in the United States or Europe.1 The dry FGD residue, which is not gypsum as in the case of wet FGD technology, consists of a mixture of desulfurization products and fly ash. The desulfurization reaction products are mainly CaSO3 and a small amount of CaSO4. Unreacted calcic sorbents are also left in the residue in the form of CaO and Ca(OH)2 or CaCO3. The amount of fly ash in the residue depends on whether or not an ash separator is installed in the front part of the desulfurization device and on the efficiency of the separator. This type of FGD residue usually contains a much greater amount of calcium and sulfur than normal fly ash.2,3 Thus, it is difficult to use for the same purposes as fly ash, e.g., in cement or concrete blending materials.4 In recent years, studies on the utilization of this type of residue have been focused on use as cement retarders, in amending soil, in filling mines, or even in constructing artificial reefs.5-10 However, whether or not CaSO3 has a retarding effect has yet to be established. The compositional fluctuation and limited utilization quantity would still be major barriers. Amending acid soils, filling mines, or constructing artificial reefs may be feasible applications, but they strongly depend on transportation conditions. Only a small part of the dry FGD residue produced in China has hitherto been used, mainly in low-grade ways. It has become a new kind of solid waste that is difficult to dispose of, and its high-valued utilization is strongly expected. Our working group just manages to convert this residue to some value-added product. By more than six years of research, using the dry FGD residue to produce sulfoaluminate cement has been proved to be a feasible and highly promising method. * Corresponding author: Wenlong Wang, Energy and Environment Institute, Energy and Power Engineering School, Shandong University, Jinan, China 250061. Tel.: 86-531-88399372-603. Fax: 86-53188395877. E-mail: [email protected]. † Shandong University. ‡ Zhejiang University.

Via calcination at about 1300 °C, this residue can be converted to cement clinker with dicalcium silicate (Ca2SiO4 or 2CaO · SiO2) and calcium sulfoaluminate (Ca4Al6O12SO4 or 3CaO · 3Al2O3 · CaSO4) as the main minerals. In this way, the desulfurization product included in the residue will act as the source of sulfur and some calcium; the fly ash provides the necessary silica and aluminum; the insufficient calcium can be supplemented by limestone; and even the unburned carbon, which usually has a negative effect, can further release its heat during the calcination. All the compositions in the dry FGD residue could be effectively used by this method. It has been found that this method could bring great social benefits in energy conservation and CO2 emission reduction. For instance, compared with Portland cement production, its calcination temperature could be lowered about 100-200 °C and nearly 1/4 CaO consumption could be saved. The reduction of CO2 emission would not only come from the fuel saving but also from the lower CaCO3 consumption. So far, this new technology has attracted much attention, and a patent has already been authorized in China. However, although a series of experiments have been carried out, the modeling of the mineral formation was scarcely conducted and

Figure 1. Bench-scale experimental setup.

10.1021/ie101228h  2010 American Chemical Society Published on Web 08/18/2010

Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010

9505

Table 1. Chemical Compositions of the Raw Materials (Mass %) items

SiO2

Al2O3

Fe2O3

CaO

MgO

SO3

others

loss

total

desulfurization residues fly ashes chemically pure CaCO3 limestone

9.17 50.82

5.24 29.64

1.35 6.58

1.30 0.86

23.32 0.53

2.00

3.46

0.45

0.68

43.16 3.42 55.44 51.20

18.38 8.15 43.56 42.29

100 100 100 98.78

Table 2. Mineral Compositions of the Dry FGD Residue (Mass %) minerals

CaSO3

CaSO4

CaCO3

CaO

others

content

32.49

3.66

27.77

3.28

32.8

Table 3. Burden Sheet of the Three Typical Batches batch ratio (mass %) items

dry FGD residue

fly ash

CaCO3

CaO module

batch 1 batch 2 batch 3

54.1 39.2 28.6

16.2 21.6 25.7

27.9 39.2 45.7

1.265 1.122 1.020

it could not be fully explained yet. With software FACTSAGE as the modeling tool, this paper will give a calculation for the mineral phases when dry FGD residue is calcined to produce sulfoaluminate cement. The goal is to realize the verification between theoretical calculation and the previous experiments.

1.00 0.70

Figures 2-4 show the XRD patterns of the three cement clinker samples. Dicalcium silicate (E) and calcium sulfoaluminate (D) are clearly the dominant crystal minerals under each condition. However, the peaks of CaSO4 (A) and CaO (B) are still strong or clearly resolved in the spectrum of sample 1. Too much CaSO4 indicates incompletion of the solid-phase reactions. The existence of CaO means that it was excessive in the batch proportion. Sample 3 contains too much gehlenite (C), which is a useless mineral with no hydraulic property.14 With only a small amount of CaSO4, no gehlenite, and mainly dicalcium silicate and calcium sulfoaluminate, sample 2 has the mineral composition closest to that of sulfoaluminate cement. The unsuitability of batches 1 and 3 may be attributed to their

2. Typical Experiments To describe the calculation of mineral formation, the typical bench-scale and pilot experiments will be introduced first in brief.Someoftheresultshavealreadybeenreportedpreviously.11-13 2.1. Bench-Scale Experiments. A great number of benchscale experiments were carried out in a rotary furnace, shown in Figure 1. Dry FGD residue and fly ash, obtained from a power plant in Hebei province, China, were used as the main raw materials. CaCO3, as the chemically pure reagent, was also used as a supplement to meet the requirement for calcium. Table 1 shows the chemical compositions of the FGD residue and fly ash, which were determined by a combination of three analytical methods: chemical analysis according to the China national standard GB/T 176-1996, X-ray fluorescence spectrometric analysis, and sulfur/carbon analysis by far-infrared heating. Table 2 shows the mineral compositions of the FGD residue, which were estimated by XRD analysis and calculation. The diverse mineral compositions, including CaSO3, CaSO4, CaCO3, CaO, etc., highlight the reason for difficulty in disposing of this type of residue. The raw materials, including FGD residue, fly ash, and CaCO3, were blended in different proportions and then well mixed in a ball mill. A lot of test batches were calcined to grope for the optimal batch ratio, temperature, and calcination time, etc. Table 3 lists three typical batches. It is found that the optimized calcination temperature was 1300 °C and the residence time was ∼20 min. The product samples were collected after rapid cooling in air. Then, X-ray diffraction (XRD) analysis was employed to ascertain the types of crystalline minerals that have formed to compare the compositions with sulfoaluminate cement clinker. Mechanical strength was analyzed to check the performance of the product samples. CaO module as the important parameter was investigated.

Figure 2. XRD pattern of cement clinker sample 1.


CaO module ) CaO/[0.73 × (Al2O3 - 0.64Fe2O3) + 1.4Fe2O3 + 1.87SiO2] Therein, the relevant constants are deduced according to the mass of CaO that is combined in a certain product mineral.


9506


Table 4. Results of Pure Cement Strength Analysis for the Cement Clinker Samples

Table 6. Results of Pure Cement Strength Analysis for the Cement Clinker from the Pilot-Scale Experiment

compressive strength (MPa)

compressive strength (MPa)

items

water/cement ratio

3 days

28 days

items

water/cement ratio

3 days

28 days

cement sample 1 cement sample 2 cement sample 3

0.29 0.30 0.30

28.2 55.6 10.4

20.6 74.4 37.6

cement clinker

0.30

90.2

94.5

Table 7. Test Results of the Setting Time

Table 5. Burden Sheet in the Pilot-Scale Experiments items

dry FGD residue

fly ash

limestone

CaO module

items

water/cement ratio

percentage/%

38.5

9.6

51.9

1.12

1# 2#

0.285 0.285

inappropriate CaO-module values, whereas a suitable value of CaO module was obtained in batch 2. Table 4 shows the results of mechanical strength analyses for the cement clinker samples. The pure cement strength method was adopted to measure their mechanical strengths. After grinding, the clinkers were formed into cubic blocks of dimensions 20 mm × 20 mm × 20 mm with a water/cement ratio of ∼0.3:1. The blocks were then cured in water at 20 °C over periods of 3 and 28 days. Six blocks were used to measure compressive strength, and the average results are reported. The mechanical strength performances of samples 1 and 3 were clearly not good. However, the result of sample 2 was more attractive, with the compressive strengths after both 3 days and 28 days being fairly high. These data indicate the importance of batch ratio, in accordance with the XRD results. The performance of cement clinker cannot be better if the CaO module value is too high or too low. CaO module ∼1.12 seems to be the best choice. 2.2. Pilot-Scale Experiments. On the basis of bench-scale experiments, pilot-scale experiments were carried out in a Φ1.9 m × 39 m rotary kiln, which is designed for sulfoaluminate cement production. The raw material preparation, given in Table 5, was based on the previous batch 2, which has been proved to be optimized. The pure CaCO3 was replaced by limestone, whose chemical composition was already given in Table 1. Before the experiments, the kiln operation was stopped and the whole production line was cleaned to eliminate the effects of the previous material. About 100 tons of clinker was produced in 2 days. The obtained sulfoaluminate cement clinker was also subjected to XRD analysis and cement performance analysis. Figure 5 shows its XRD pattern, in which the peaks due to calcium sulfoaluminate (D) and dicalcium silicate (E) are even more prominent than in Figure 3 and the peaks due to other minerals are very weak. It can therefore be concluded that this type of clinker has a better mineral composition than that produced in the bench-scale experiment.

retarding agent

initial setting time (min)

final setting time (min)

baric acid none

53 39

63 50

Table 8. Results of Mortar Strength of the Cement Clinker from the Industrial Experiment compressive strength (MPa)

antibuckling strength (MPa)

water/cement ratio

addition agent

3 days

28 days

3 days

28 days

0.45

3%gypsum

33.2

54.5

6.85

8.9

Table 6 shows the compressive strength test results for the clinker obtained by the pure cement method. The results are much better than those in the bench-scale experiments. To evaluate the performance of the clinker, its mortar strength and setting time were also measured. The setting time test was carried out according to China national standard GB/T 13452005. Table 7 shows the test results. The data shows that the product was rapid setting type. When baric acid was added as a retarding agent, the setting times were extended. For sulfoaluminate cement, the initial setting time cannot be shorter than 25 min and the final setting time cannot be longer than 180 min. The present product clearly satisfies these requirements. For the mortar strength measurements, cement, standard quartz sand, and water were mixed into a mortar in accordance with the China national cement standard. Blocks of dimensions 40 mm × 40 mm × 160 mm were formed. The mechanical strengths of these blocks were tested after curing for a certain numbers of days. Table 8 shows the results, while Table 9 shows a classification of strength grades for common silicate cement and sulfoaluminate cement according to the China national standard. By comparing the strength values in Tables 8 and 9, it is clear that the present product can entirely satisfy the highest 52.5R grade of the common Portland cement. However, the early strength after 3 days curing is not high enough to satisfy the standard of 42.5 grade sulfoaluminate cement, even though the later strength after 28 days greatly exceeds this grade and even satisfies the 52.5 grade. The mechanical strength characteristics are determined by the mineral composition of the product. Because of the relatively low calcium sulfoaluminate content and the relatively high dicalcium silicate content, this cement belongs to the high-silica sulfoaluminate type, which is characterized by low early strength and high long-term strength.15 3. Calculation by FACTSAGE

Figure 5. XRD pattern of the cement clinker from the pilot-scale experiment.

3.1. Application of FACTSAGE. FACTSAGE is a typical thermodynamics software combined by two thermochemistry software packages, FACT-Win and ChemSage.16,17 It is based on the multisolution thermochemistry database and multiphase equilibrium calculation. The core module, Equilib, is set up by minimizing the Gibbs free energy, which can work out the type and proportion of each substance under chemical equilibrium condition. The calculation in this article is based on FACTSAGE 5.2.


9507

Table 9. Classification of Strength Grades for Common Silicate and Sulfoaluminate Cements compressive strength (MPa) items Portland cement

sulfoaluminate cement

antibuckling strength (MPa)

strength grade

3 days

28 days

3 days

28 days

32.5 32.5R 42.5 42.5R 52.5 52.5R 42.5 52.5 62.5 72.5

11.0 16.0 16.0 21.0 22.0 26.0 42.5 52.5 62.5 72.5

32.5 32.5 42.5 42.5 52.5 52.5 45.0 55.0 65.0 75.0

2.5 3.5 3.5 4.0 4.0 5.0 6.5 7.0 7.5 8.0

5.5 5.5 6.5 6.5 7.0 7.0 7.0 7.5 8.0 8.5

The high-temperature, solid-phase reaction is a routine study area concerning silicate. Typical multiphase diagrams have been well developed to expatiate on chemical reactions among SiO2, Al2O3, Fe2O3, and CaO.18,19 However, there is no description for reactions in which SO3 participated. SO3 is proven to take great part in the reactions by this article. It is very important for the development of thermochemical calculation method for its relevant solid-phase reactions. Calcium sulfoaluminate (3CaO · 3Al2O3 · CaSO4) is one of the most important resultants of the reaction in which SO3 participated. At the same time, it is the core mineral of sulfoaluminate cement. At present, there is no reference for the thermodynamic data of calcium sulfoaluminate because of the difficulty in pure substance capture. Even in the FACTSAGE, it is a black space. However strong the calculation software could be, the study is limited by the absence of database. The optimization of thermodynamic data of calcium sulfoaluminate has been done via calculation by several methods. It is well explained in another paper.20 The data is listed here. The standard formation enthalpy ∆Hf298K ) -8393.19 kJ/mol; the Gibbs free energy of formation ∆Gf298K ) -7929.54 kJ/mol; the standard entropy S298K ) 450.2 J/K · mol; and the molar heat capacity is Cp ) a + b × 10-3T + c × 105T-2 where a ) 554.05, b ) 143.34, c ) -113.4. The database of FACTSAGE is expanded by these data. Then, it is possible to make the calculation of reactions in which calcium sulfoaluminate is involved. This is the first time to improve FACTSAGE in calcium sulfoaluminate reaction. The calculation has a significant value on the study of hightemperature sulfur fixation, ash utilization, and cement production. 3.2. Calculation Method. In our typical experiments, CaO, SiO2, Al2O3, and SO3 are the main compositions of the raw materials. The calculation can be simplified to a CaOSiO2-Al2O3-SO3 quarternary system because the Fe2O3 is negligible. In the reactions, the S element exists in the form of CaSO3 or CaSO4. In an oxidizing atmosphere, CaSO3 will be oxidized rapidly to CaSO4 when the temperature is >470 °C.4 Thus, the calculation and discussion can finally be carried out in the CaO-SiO2-Al2O3-CaSO4 system. CaO, SiO2, Al2O3, and CaSO4 are set as the initial reactants. CaSO4, CaO, 3CaO · 3Al2O3 · CaSO4, and all the possible existing minerals in the CaO-SiO2-Al2O3 ternary diagram will be treated as the main resultants of the solid-phase reactions. Table 10 lists all the possible resultants that are taken into consideration in this calculation. The calcination temperature is set to 1300 °C. The influences of different proportions of CaO, CaSO4, and Al2O3 on the mineral phases of the final resultants are investigated. In each calculation, the proportions of any two

compositions among CaO, CaSO4, and Al2O3 are set to typical experimental values. 4. Calculation Results and Discussion 4.1. Influence of CaO Proportion. The proportion of CaO has a great influence on the mineral phases of the final calcination products. Its influences in the CaO-SiO2-Al2O3 ternary system have already been specially analyzed.21-23 It can also be indicated in the typical CaO-SiO2-Al2O3 ternary diagram. However, there is no conclusion in the CaOSiO2-Al2O3-SO3 system. During the investigation of CaO influence, the masses of SiO2, Al2O3, and CaSO4 are set to 20, 10, and 19 g, which are decided according to the optimized experimental proportions. Therein, the mass of CaSO4 is calculated from SO3. Figure 6a shows the mineral contribution when the mass of CaO ranges from 10 to 100 g. The curves fluctuation could be divided into three parts. (1) The mass of CaO increases from 0 to 30 g. The lowcalcium minerals, 3Al2O3 · 2SiO2 and CaO · Al2O3 · 2SiO2, become less and less until they disappear. The amount of 2CaO · Al2O3 · SiO2 increases continuously. The minerals transform from CaO · SiO2 to 3CaO · 2SiO2. (2) The mass of CaO increases from 30 to 60 g. It is very clear from the figure that dicalcium silicate becomes the main mineral and its form switches from 3CaO · 2SiO2 into 2CaO · SiO2. 2CaO · Al2O3 · SiO2 disappears in this part and 3CaO · 3Al2O3 · CaSO4 increases from 0 to ∼10 g and then is replaced by 3CaO · Al2O3. The amount of CaSO4 changes when 3CaO · 3Al2O3 · CaSO4 appears and it keeps constant at the initial value at the other part. (3) The mass of CaO increases from 60 to 100 g. The amount of free CaO in the resultants increases continuously because it is excessive. The products are mainly 2CaO · SiO2, 3CaO · Al2O3, CaSO4, and free CaO. Table 10. Minerals Investigated during Calculation by FACTSAGE regimentation initial reactants

probable resultants

mineral CaO SiO2 Al2O3 CaSO4 CaO · SiO2 β-2CaO · SiO2 3CaO · 2SiO2 3CaO · SiO2 CaO · Al2O3 3CaO · Al2O3 12CaO · 7Al2O3 CaO · 2Al2O3 2CaO · Al2O3 · SiO2 CaO · Al2O3 · 2SiO2 3Al2O3 · 2SiO2 3CaO · 3Al2O3 · CaSO4 CaSO4 f-CaO

9508


Figure 6. Influence of CaO proportion on mineral phases of resultants.

As 3CaO · 3Al2O3 · CaSO4 is the most important component in resultants, the influence of CaO was recalculated in the range from 35 to 55 g with a smaller step. Figure 6b shows the results. When the mass of CaO is ∼43 g, the production of 3CaO · 3Al2O3 · CaSO4 is the highest. The main products under this condition are 2CaO · SiO2 and 3CaO · 3Al2O3 · CaSO4, which is exactly the same mineral compositions of sulfoaluminate cement. Considering the CaO existing in CaSO4, the total amount of CaO should be 51 g. This value is approximately the same as the raw material composition in our typical experiments. It indicates that the optimized batch ratio obtained in the experimental way is reliable. Therefore, the modeling and the experiments accord with each other very well, especially for the key CaO proportion. 4.2. Influence of CaSO4 Proportion. It can be found from the calculation about CaO that CaSO4 always exists in resultants. It indicates that the amount of CaSO4 is always excessive. The masses of SiO2, Al2O3, and CaO are set to 20, 10, and 43 g, respectively. The mass of CaSO4 ranges from 0 to 20 g to investigate the influence on final resultants. The mass is further limited in the range of 0 to 8 g. Figure 7 shows the results of calculations. The production of 3CaO · 3Al2O3 · CaSO4 reaches the peak value when the mass of CaSO4 is ∼5 g. Further increase of CaSO4 only leads to a higher amount of free CaSO4 in resultants. In the typical experiment, the actual CaSO4 mass is 19 g, which is indicated excessive by the modeling. Nevertheless, slightly excessive CaSO4 does not have a fundamental influence on the cement characteristics, and usually some CaSO4 must be added in the eventual sulfoaluminate cement products. But the decomposition of CaSO4 during calcination should be taken into account in industrial application. 4.3. Influence of Al2O3 proportion. During the investigation on influence of Al2O3 proportion, the masses of SiO2, CaSO4, and CaO are set to 20, 19, and 43 g, respectively. Figure 8a shows the resultants when the mass of Al2O3 ranges from 5 to 15 g. The amount of 3CaO · 3Al2O3 · CaSO4 increases continuously until the amount of CaO is not enough for further reaction. Then 2CaO · Al2O3 · SiO2 is produced after the mass of Al2O3 is >10 g. At the given masses of SiO2, CaSO4, and CaO, the best mass of Al2O3 is 10 g. Both dicalcium silicate and calcium

sulfoaluminate reach maximum production under this condition. The amount of total calcium sulfoaluminate is 20.56 g. Since the generation of 2CaO · Al2O3 · SiO2 is caused by insufficient CaO, its mass was increased to 45 and 48 g, respectively, and recalculations were done. Figure 8b and c shows the new results. The same tendency is observed as in Figure 8a. However, the optimized point moves forward. When the mass of CaO is 45 g, the optimized point for Al2O3 is 14 g. Figure 8c shows the result with 48 g CaO, where the optimized point for Al2O3 is 20 g. It indicates that, when the proportion of Al2O3 is increased in raw material, the production of calcium sulfoaluminate can be substantial with a slight increase of CaO proportion. This finding gives us an important idea to improve the mineral phases of products. It has great meaning in industrial utilization. Therefore, the modeling by FACTSAGE can not only describe the experimental data well but also provide more choices to better the experiments.

Figure 7. Influence of CaSO4 proportion on mineral phases of resultants.


9509

Figure 8. Influence of Al2O3 proportion on mineral phases of resultants.

5. Conclusions It is feasible and promising to produce sulfoaluminate cement using FGD residue and fly ash. This method has great advantages. No modification of the cement plant equipment is needed. Only the raw materials and the calcination temperature need to be modified. Because the cost of raw material is lowered by using waste and the cost of grinding is greatly reduced owing to the fineness of the FGD residues and fly ash, this technology may have good potential to reduce the production costs at cement plants. This technology is environmentally friendly. The utilization proportion of FGD residues and fly ash can amount to 40-60%. A great deal of resource can be replaced by waste. In particular, compared with the common Portland cement, about one-fourth less CaO is needed and thus the limestone resource can be saved. Owing to the lower consumption of fuel and limestone, the CO2 emission will be reduced accordingly. The software FACTSAGE was improved by a new database. By calculation, the raw material proportion was optimized. The results are in accordance with the experiments. Hence, this technology is proved to be helpful for developing a circular economy, and it will benefit our world greatly. Further efforts and cooperation are needed to promote the utilization of this promising technology. Acknowledgment The authors thank the support of National Natural Science Foundation of China (Grant 50906046) and National High-Tech

Research and Development Program of China (863 Program) (Grant 2009AA05Z303). Literature Cited (1) Yue, T.; Zhuang, D. A.; Yang, M. Z.; Deng, J. L.; Zhang, Y. C. Status quo of technology development of flue gas desulfurization and denitrification for coal-fired power plants in China. Energy Res. Inf. 2008, 24, 125–129. (2) Lecuyer, I.; Bicocchi, S.; Ausset, P.; Lefevre, R. Physico-chemical characterization and leaching of desulfurization and coal fly ash. Waste Manage. Res. 1996, 14, 15–28. (3) Bigham, J. M.; Kost, D. A.; Stehouwer, R. C.; Beeghly, J. H.; Fowler, R.; Traina, S. J.; Wolfe, W. E.; Dick, W. A. Mineralogical and engineering characteristics of dry flue gas desulfurization products. Fuel 2005, 84, 1839– 1848. (4) Wang, W. L.; Cui, L.; Ma, C. Y.; Dong, Y.; Xu, X. R. Study on properties and comprehensive utilization of dry and semi-dry desulfurization residues. Power Syst. Eng. 2005, 21, 27–29. (5) Tzouvalas, G.; Rantis, G.; Tsimas, S. Alternative calcium-sulfatebearing materials as cement retarders. Part II. FGD gypsum. Cem. Concr. Res. 2004, 34, 2119–2125. (6) Moon, D. H.; Dermatas, D. Arsenic and lead release from fly ash stabilized/solidified soils under modified semi-dynamic leaching conditions. J. Hazard. Mater. 2007, 141, 388–394. (7) Clark, R. B.; Zeto, S. K.; Ritchey, K. D.; Baligar, V. C. Growth of forages on acid soil amended with flue gas desulfurization by-products. Fuel. 1997, 76, 771–775. (8) Pickering, H. Artificial reefs of bulk waste materials: a scientific and legal review of the suitability of using the cement stabilised by-products of coal-fired power stations. Mar. Policy 1996, 20, 483–497. (9) Chen, L.; Dick, W. A.; Nelson, S. Flue gas desulfurization byproducts additions to acid soil: Alfalfa productivity and environmental quality. EnViron. Pollut. 2001, 114, 161–168.

9510


(10) Dermatas, D.; Meng, X. G. Utilization of fly ash for stabilization/ solidification of heavy metal contaminated soils. Eng. Geol. 2003, 70, 377– 394. (11) Wang, W. L.; Dong, Y.; Ma, C. Y.; Song, Z. L.; Xu, X. R. Experimental study on the conversion of desulfurization residues into sulfoaluminate cement. Presented at the International Conference on Power Engineering (ICOPE), Hangzhou, China, 2007; pp 733-737. (12) Wang, W. L.; Dong, Y.; Ren, L.; Ma, C. Y. Study of the utilization rate of desulfurization agents and utilization of desulfurized ash during desulfurizatin by dry-method/semi-dry-method. J. Eng. Thermal Energy Power. 2009, 24, 490–493. (13) Ren, L.; Wang, W. L.; Zhang, H. Y.; Fu, J. Z.; Zhang, Y. X. Pilot test of sulfoaluminate cement production using the semi-dry desulfurization residues. J. Power Eng. 2009, 29, 302–306. (14) Shen, W.; Huang, W. X.; Min, P. R. Cement Technology; Wuhan University of Technology Press: Wuhan, China, 1992. (15) Wang, W. L.; Luo, Z. Y.; Shi, Z. L.; Cen, K. F. Experimental study on cement clinker co-generation in pulverized coal combustion boilers of power plants. Waste Manage. Res. 2006, 24, 207–214. (16) Cao, Z. M.; Song, X. Y.; Qiao, Z. Y. Thermodynamic modeling software FactSage and its application. Chin. J. Rare Met. 2008, 32, 216– 219. (17) Kondratiev, A.; Jak, E. Predicting coal ash slag flow characteristics (viscosity model for the Al2O3-CaO-“FeO”-SiO2 system). Fuel 2001, 80, 1989–2000.

(18) Levin, E. M.; McMurdie, H. F.; Hall, E. P. Phase Diagrams for Ceramists; American Ceramic Society: Columbus, OH, 1956. (19) Djuric, M.; Zivanovic, B.; Petrasinovic-Stojkanovic, Lj.; Ranogajec, J. Computerized thermodynamic analysis of reactions during sintering of CaO-Al2O3-SiO2 system. Cem. Concr. Res. 1992, 22, 139–148. (20) Wang, W. L.; Chen, X. D.; Chen, Y.; Ma, C. Y. Calculation and verification for the thermodynamic data of 3CaO · 3Al2O3 · CaSO4. J. Chem. Eng. Data, submitted for publication. (21) Wang, W. L.; Luo, Z. Y.; Shi, Z. L.; Cen, K. F. Thermodynamic study on formation mechanism of coal ash minerals at high calcium content in PCC boilers. Proc. CSEE 2005, 25, 116–120. (22) Liu, H.; Qiu, J. R.; Kong, F. H.; Wu, H.; Zeng, H. C.; Xie, C. S.; Zhou, H. C. Activation of the calcium-added coal combustion solid residues. Asia-Pac. J. Chem. Eng. 2007, 2, 177–181. (23) Zhao, Y. C.; Zhang, J. Y.; Zhang, F. Q.; Wang, Z. H.; Hu, N. W.; Zheng, C. G. Evolution mechanism and chemical composition of high calcium fly ashes from coal combustion. Proc. CSEE 2007, 27, 12–16.

ReceiVed for reView June 5, 2010 ReVised manuscript receiVed July 26, 2010 Accepted August 3, 2010 IE101228H

Calculation for Mineral Phases in the Calcination of Desulfurization

Recommend Documents