Final Report: Utilization of Paper Mill Waste in Ceramic Products

EPA Grant Number: R830420C002
Subproject: this is subproject number 002 , established and managed by the Center Director under grant R830420
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Center for Environmental and Energy Research (CEER)
Center Director: Earl, David A.
Title: Utilization of Paper Mill Waste in Ceramic Products
Investigators: Earl, David A. , Sinton, Chris
Institution: Alfred University
EPA Project Officer: Klieforth, Barbara I
Project Period: September 1, 2003 through August 31, 2005
RFA: Targeted Research Center (2002) Recipients Lists
Research Category: Targeted Research , Congressionally Mandated Center

Objective:

The main objectives of this research project were to: 
(1) characterize paper waste material from at least three sources; (2) study the performance of ceramic tile body formulations containing variable amounts of waste materials; and (3) estimate the environmental and economic impacts of using waste materials.  Ceramic tile products, with formulations incorporating boiler fly and bottom ash, were studied to evaluate and quantify composition-processing-properties relationships.  Tile manufacture is used in this investigation because the ash is most readily compatible with the starting materials, production volumes are high, there are multiple manufacturing locations across the United States, and the raw materials specifications are relatively broad.

Summary/Accomplishments (Outputs/Outcomes):

Background

The kraft process for manufacturing paper is one of the most widely used processes in the world.  In this process, wood chips are chemically digested to release the cellulose fibers, which are held together by lignin.  The resulting liquid from this process (black liquor) is concentrated and then burned in a recovery boiler, where organic solids are burned for energy (steam and electric power), and the process chemicals are removed and recovered.  There are four streams of waste from the recovery process:  boiler bottom ash, and fly ash, recaust grit, and dregs.  Bottom ash and fly ash are produced from the combustion of the black liquor in the boiler.

There are 112 kraft-process mills in the United States and 19 in Quebec and Ontario.  Mills can produce 10,000 to 20,000 tons per year of ash and recaust waste, which is placed in landfills.  There is potential to use some of this paper mill waste as a raw material for the ceramic industry.  A study in Thailand has shown the use of paper mill waste to manufacture bricks.  Other studies have shown the use of coal fly ash in the production of glass-ceramics.  Paper mill ash is more desirable for ceramics because of much lower iron and heavy metal concentrations and higher CaO content compared to coal ash.

Preliminary work at Alfred University had identified similarities between paper mill waste and tile raw materials, and some tile prototypes have been produced using bottom ash waste.  The composition and phases of a bottom ash sample indicate potential for partially replacing common whiteware raw materials, including wollastonite, whiting, quartz, clay, and talc.  Replacing wollastonite and whiting would be of particular interest to tile manufacturers as wollastonite is one of the most expensive raw materials used (over $200/ton), and whiting tends to cause glaze bubble defects because of its large loss-on-ignition (~ 50%) above the glaze melting temperature.  The U.S. tile market used about 5.3 million tons of body material last year.  If paper mill waste replaces 25 weight per cent of the raw materials, yearly consumption would be 1.3 million tons for U.S. tile companies.

Methods

Bottom ash and fly ash samples from the International Paper Co. in Ticonderoga, New York, were characterized.  The ash composition was found to have significant variations in SiO2, Al2O3, and CaO, important oxides with respect to ceramic (porcelain) compositions, in samples received over a 4-month period.  Although the composition within single samples was uniform, variations over time (and among sites) could lead to complications in optimizing ceramic body formulations on an industrial scale, unless the ash is blended to a constant composition before shipment or the ceramic formulation is modified each time the ash composition changes.

Particle size distribution analysis was used to determine the amount of milling required to successfully substitute ash for traditional raw materials.

All of the ash samples were examined using qualitative X-ray diffraction (XRD) to identify crystalline phases.  The major phases were quartz (SiO2) and calcite (CaCO3), which are commonly present in raw materials for ceramic products.

The sintering/melting behavior of the ash materials was characterized using a hot-stage microscope (HSM) and the results were compared to typical porcelain batch materials.

Experimental compositions incorporating paper mill ash were calculated and batched for an initial target composition based on industrial porcelain.  An “ideal” batch containing bottom ash was calculated, as well as two other formulations, with higher and lower bottom ash content. Compositions for the experimental formulas are shown below in Table 1.  The compositions were prepared into a slurry, filter pressed, and extruded into rods and bars to be fired and tested.


Table 1.  Calculated Compositions for Experimental Formulas

Raw Material

Weight % Compositions

Porcelain

5% Ash

“Ideal”

8% Ash

Tile Kaolin #6

29

35.5

34.3

33.5

Todd Light Ball Clay

6

15.5

15

14.5

A-400 Nepheline Syenite

21

-

-

-

Alcan C-71 Alumina

10

10

10

10

Silcosil 63 Silica

34

34

34

34

Ash

-

5

6.7

8

Results

Particle Size Distribution.  As-received ash samples were tested for particle size distribution (PSD), then milled to achieve the size range of traditional raw materials.  The PSD of the milled bottom ash samples compares well with traditional ceramic raw materials (D50 = 10-15 µm).  The Androscoggin ash has a smaller mean size because of a smaller and more uniform initial size distribution as received.

XRD.  XRD analysis of bottom ash samples revealed the presence of quartz (SiO2), calcite (CaCO3), corundum (Al2O3), a calcium aluminosilicate, and a sodium aluminosilicate.  Fly ash samples were found to contain quartz, calcite, monticellite (a calcium-magnesium silicate), shortite (a sodium-calcium carbonate), and a sodium aluminosilicate.

XRD of fired samples showed that the ash bodies form most of the same crystalline phases as a typical porcelain.  A significant amount of cristoballite, which does not appear in typical porcelain bodies, forms in the ash bodies as well.  Compared to porcelain compositions, less glassy phase forms in the ash bodies, thereby inhibiting sintering (filling of pores).

HSM.  Comparison of sintering behavior of the ash materials with typical porcelain batch materials using HSM showed lower (by approximately 100°C) sintering temperatures for bottom ash than for feldspars and nepheline syenite (traditional fluxes).

Chemical Analysis.  Results of chemical analysis, shown below in Table 2, reveal that the paper mill ash has higher amounts of “fluxing” oxides and carbon than traditional raw materials, as well as lower SiO2 and Al2O3 levels.  Incorporating ash into traditional ceramic formulations, therefore, will require systematic adjustments of the other batch materials to achieve the target composition.


Table 2.  Analyzed Compositions for Ash and Traditional Raw Materials

Material

SiO2

Al2O3

Fe203

MgO

CaO

Na2O

K2O

TiO2

P2O5

MnO

LOI

TOT

%

%

%

%

%

%

%

%

%

%

%

%

Bottom Ash

1.74

5.93

2.94

2.97

29.51

1.24

3.16

1.86

0.90

0.62

9.0

1.1

Fly Ash

13.18

2.46

1.12

1.65

27.64

0.48

2.27

0.35

1.00

0.74

48.6

30.3

K-200

68.06

16.71

0.12

0.01

0.06

3.52

9.56

<0.01

0.09

<0.01

0.6

0.02

G-200

66.30

18.50

0.08

<0.01

0.81

3.04

10.75

<0.01

0.00

<0.01

0.16

0.02

Nepheline Syenite

60.00

22.42

0.08

0.04

0.36

10.65

5.07

0.01

0.02

<0.01

0.76

0.04

Porosity.  Samples were fired at a typical porcelain firing schedule of 2.5°C per minute with a 2.5 hour soak at maximum temperature.  Fired samples were measured for apparent porosity, water absorption, and bulk density using the Archimedes method.  Measurement data are shown in Table 3.  The ash bodies showed much higher porosity and lower bulk density than the control composition (a typical porcelain).

Table 3.  Measurement of Data of Fired Samples. 


Sample

Samples Fired at 1,290°C

Samples Fired at 1,350°C

Apparent Porosity
(%)

Water Absorption (%)

Bulk Density (g/cm3)

Apparent Porosity
(%)

Water Absorption (%)

Bulk Density (g/cm3)

 

Control

 

0.61

 

0.24

 

2.50

 

 

 

 

5% BA

 

29.17

 

15.51

 

1.88

 

22.24

 

11.28

 

1.97

‘Ideal’ BA

 

29.46

 

15.67

 

1.88

 

19.59

 

9.66

 

2.03

 

8% BA

 

29.12

 

15.43

 

1.89

 

17.71

 

8.67

 

2.04

 

5% FA

 

31.84

 

17.53

 

1.82

 

26.51

 

14.15

 

1.87

 

‘Ideal’ FA

 

32.25

 

18.04

 

1.79

 

24.89

 

13.22

 

1.88

 

8% FA

 

32.80

 

18.52

 

1.77

 

25.81

 

13.80

 

1.87

Laboratory and Pilot Trials (July 2003-December 2004).  Body trials were focused on porcelain, because the ceramic tile industry has moved towards porcelain bodies over the past few years, and other whiteware compositions (dinnerware, high-voltage porcelain, sanitaryware) are porcelain, as well.  Initial experiments using an RO + R2O balancing technique in porcelain bodies show that the ash bodies produce higher porosity (lower glassy phase) than the traditional compositions.  Samples were fired using a typical porcelain firing schedule.  The ash bodies were found to have higher porosity and lower bulk density than the traditional composition.  A significant amount of cristoballite, which does not form in typical porcelain bodies, was found the ash bodies as well.  Scanning electron micrographs of a traditional composition (control body), bottom ash composition, and fly ash composition fired to 1,290°C are shown in Figures 1a-1c.

Figure 1a

Figure 1(a).  Control Body Fired at 1,290°C (1000X)

Figure 1b

Figure 1(b).  Bottom Ash Body Fired at 1,290°C (1000X)

Figure 1c

Figure 1(c).  Fly Ash Body Fired at 1,290°C (1000X)

Experimental Tile Bodies With Bottom Ash Paper Waste. Ash body formulas were designed to increase the amount of glassy phase present.  Bottom ash waste was ground to pass through a
65-mesh screen and ball milled in dry state.  Four batches with different formulas were prepared.   Batch compositions are shown below in Table 4.

Table 4.  Composition of the Batches in Grams


Formula #

1

2

3

4

EPK Kaolin

 

 

100

100

Jackson Ball Clay

140

125

100

125

Talc

285

250

 

 

Custer Feldspar

 

 

50

125

W-30 Wollastonite

25

 

 

 

Minusil 40 Quartz

 

 

125

100

Bottom Ash Waster

50

125

125

50

For each formula, 30 samples (buttons, 1² dia. x 0.3² h., 8 g wt.) were pressed (at 6,370 psi).  The samples of formulas #1 and #2 were heat treated at 1,000°C for 4 hours and then cooled slowly (in the furnace) to 50°C.  The color of samples for both formulas is light gray, with a smooth surface texture.  The samples for formulas #3 and #4 were heat treated at 1,200°C for 8 hours, then cooled slowly to 50ºC.  The surface texture of formula #4 samples is smooth, but for #3 is very porous. The color of samples is gray with dark brown particles (most likely associated with flint pebbles).

For measurement of water absorption, samples with the formulas #1, #2, and #4 were dried and weighed, boiled in water for 5 hours, then weighed again (Table 5).

Table 5.  Percent Water Absorption


Formula #

1

2

4

Percent Water Absorption

17.5 %

20.2 %

2.3 %

Experimental Glazing of Green Body Samples.  First glazing: Dried green samples of formulas #1 and #2 were glazed with 0.6 g of a leaded glaze and then heat treated at 1,100ºC for 8 hours and cooled slowly to room temperature. Surface texture of the glazed samples was smooth with no stress apparent in the glaze layer.  The percent water absorption of the glazed samples was
11 percent for formula #1 and 12 percent for formula #2.

Second Glazing.  Dried green samples of formulas #1, #2, #3, and #4 were glazed and heat treated at 1100ºC for 8 hours.  Samples from formulas #2 and #4 showed smooth surface texture, formula #1 showed a small amount of surface porosity, and formula #3 showed a very porous surface texture.  The percent water absorption for formula #4 was 8 percent.  Shrinkage during heat treatment at 1100ºC was 1 percent for formulas #1 and #2 and 5 percent for formula #4.

Conclusions:

Substituting paper mill ash waste for traditional raw materials in porcelain tile bodies was not proved successful in this study, primarily because of compositional makeup and sintering behavior.

The composition of the ash waste varies significantly over time at the same source.  Because of this variation, raw materials must be continuously tested and blended, based on chemical analysis data, to achieve consistent batching.

The test compositions developed in this study exhibited poor sintering behavior with insufficient glassy phase development and the formation of a cristoballite phase which resulted in a decrease in thermal shock resistance.  The fired samples also showed high porosity and low density when compared with traditional porcelain compositions and did not perform well in glazing trials.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this subproject

Supplemental Keywords:

characterization, fly ash, bottom ash, ash utilization, porcelain, waste materials, tiles, paper mill waste, ceramic products, technology for sustainable environment, glass technology, sustainable industry/business,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Sustainable Industry/Business, POLLUTION PREVENTION, Sustainable Environment, Energy, Technology, Technology for Sustainable Environment, Environmental Engineering, energy conservation, clean energy, cleaner production, sustainable development, clean technologies, environmental conscious construction, boron rich carbon, clean manufacturing, energy efficiency, energy technology, alternative fuel, alternative energy source

Relevant Websites:

http://ceer.alfred.edu/ Exit
http://ceer.alfred.edu/research/paperwaste.html Exit

Progress and Final Reports:

Original Abstract
  • 2004 Progress Report

  • Main Center Abstract and Reports:

    R830420    Center for Environmental and Energy Research (CEER)

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