FURTHER INVESTIGATION OF REFRACTORY

COMPATIBILITIES WITH SELECTED

INCINERATOR SLAGS

G. H. CRISS

Harbison-Walker Refractories Co.

Pittsburgh, Pennsylvania

ABSTRACT

Incinerator slag adherence to and penetration into re­fractories were investigated in the laboratory. The re­fractory compositions included burned superduty fireclay, high alumina, chrome-magnesite and plastic materials. Two slags obtained from incinerator walls were used. Phosphate-bonded compositions appear to do well resist­ing incinerator slag attack.

INTRODUCTION

In the study, "The Chemistry of Incinerator Slags and Their Compatibility with Fireclay and High-Alumina Re­fractories", [1] a variety of incinerator slags was tested to determine compositional ranges. Two slags that were repre­sentative of batch and continuous-feed operations were studied as to their softening point and their effect on superduty and selected high-alumina refractories at oper­ating temperatures.

In the present work, the same slags were further tested with additional refractory brick and monoliths. This in­vestigation was an attempt to find the best refractory with regard to resistance to slag penetration, mechanical strength and economy.

As covered in the earlier paper, slag samples were obtained from 25 incinerators in the New York, New Jersey and Connecticut areas (Table I). These samples were chosen for their proximity to low, intermediate and high temperature build-up. From the group, two slags

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A.R.OLSEN

Thermal Refractories Co.

North Bergen, New] ersey

were selected for further study: Slag C from a continuous­feed incinerator and Slag F from a batch-type incinerator. (Figs. 1 and 2 show the sampling points, and Tables II, IIA, and III show the analyses of the slags). It should be noted that the several samples showed wide variation in chemistry. Also, using these samples gave continuity or a continuation to the prior work.

SLAG TESTING

Two types of static slag tests were conducted. In the usual static type test, one-inch holes were diamond drilled into the ends of nine-inch brick and the cavity charged with the selected slag. The other test consisted of placing 34-gram cylinders of slag on 4% x 4% x 2% in. pieces of refractory as used by Herbert [2]. Both compositions were then heated for 5 hours at either 2200 F or 2300 F. The cylinder test offered the advantages of ease of prepa­ration and ability to physically check adherence of the slag on a flat refractory surface. The test was also con­venient because it eliminated the need for drilling unfired samples of monolithic refractories. In both of the described tests, measurements can be made of the depth of erosion and degree of penetration of the slag into the refractory. Also chemical and mineral analysis can trace the type of reactions that take place as suggested by Muan [3].

Figs. 3 to 6 show cut sections through super duty fire­clay brick, 60 percent alumina, 75 percent alumina (phos­phate bonded) and 85 percent alumina (phosphate bonded) brick after submitting to the drilled cup slag test at 2200 F.

After heating to this test temperature the cut sections revealed that slag F adhered to the super duty fireclay and 60 percent alumina refractories but there was no penetra­tion of the slag into the refractories. The phosphate bonded 75 percent and 85 percent alumina brick refractories also exhibited no penetration and the slag could be removed by chipping with no damage to the refractory. Slag C, however, penetrated and adhered quite strongly to the superduty fireclay and 60 percent alumina brick. Removal of slag C by chipping caused considerable damage to the superduty and 60 percent alumina brick. Slag C again adhered to the 75 and 85 percent alumina phosphate bonded samples but could be removed with little or no damage to the test specimen. It would appear that the high FeO content of slag C (28.1 percent; Table IIA) had little effect on the phosphate bonded brick. Heating to 2300 F instead of 2200 F accentuated each test in es­sentially the same proportions. Actual field results also have indicated that the 85 percent alumina phosphate bonded brick have done exceptionally well in service.

Six compositions of burned chrome-magnesite and magnesite-chrome brick were tested using slags C and F in the previously described cylinder static test. All brands exchibited strong adherence and penetration when heated to 2300 F. Additional work with basic brick and monoliths for incinerators is suggested.

MONOLIT HS FOR REPAIR

While most initial construction of incinerators entails the careful selection of refractory brick, this same care should be given to the emergency or day-to-day refractory maintenance needed to keep an incinerator operating. In areas where the refractory has been gouged or spalled, monolithic materials should be considered. These mate­rials offer the versatility of being formed on the job site with no need to make special shapes. Many types of mono­liths are available to the general maintenance foreman in­cluding plastics, ramming mixes and refractory castables. Various hydraulic bonded castables can be used and slag tests indicated that they have essentially the same re­sistance to penetration and attack as do their superduty and high alumina brick counterparts.

New types of plastic refractories now offer a novel means for repairing excessive wear zones near the grate and other problem areas. Typically the normal fireclay and high alumina plastic refractories were not strong enough for these zones. With the advent of phosphate bonded plastics, materials are available that when heated to 250 F will be as strong or stronger than most burned

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refractory brick (Table IV). These materials typically have better thermal shock resistance than most burned refrac­tories, and exhibit essentially no linear or volume change at temperatures normally encountered in the incinerator. Unlike many castables that derive most of their adherence _

to a burned refractory by mechanical strength, the phos­phate bonded plastics react slightly with the burned re­fractory and the resulting bond between the two materials can be stronger than the burned refractory. Of course, these plastics are shipped wet, ready to use, and their installation precludes mixillg, as a simple mallet or pneumatic rammer is about all that is needed for their installation in excessive wear areas.

Two phosphate-bonded plastic compositions, a 90 percent alumina mix and a recently developed and more economical 85 percent alumina product were tested with Slags C and F. In the cylinder slag test at 2200 F both plastics exhibited excellent resistance to slag penetration. Slag F did not adhere and Slag C could be readily removed with no damage to the plastics (Fig. 7).

To further check their resistance to penetration, ad­ditional cylinder test samples of slags C and F with 85 and 90 percent high alumina phosphate bonded plastics as well as a typical 85 percent high alumina plastic were heated to 2300 F for 5 hours. At this temperature the slags were extremely viscous. When cooled Slag C had not penetrated the samples and Slag F exhibited only slight penetration. Both slags could be removed by chipping with no damage to the refractory. Note in Fig. 8 the smooth cut cross section of the phosphate bonded plastic as opposed to the typical, weaker bond indicated by the rough cut cross section of the (non-phosphate) high alumina plastic.

CONCLUSIONS

Laboratory tests indicated that phosphate bonded re­fractory brick and plastics appear to do well in resisting incinerator slag attack. The 75 percent alumina phosphate bonded products also appeared to be as resistant to attack as the more expensive 90 percent high alumina refractories.

Superduty fireclay brick still would be an excellent choice in many areas of the incinerator but for problem areas phosphate bonded brick should provide an extended safety margin. For maintenance and emergency repairs the phosphate bonded plastics should definitely be considered.

REFERENCES

[1) Criss, G. H. and Olsen, A. R.o "The Chemistry of Incinera­tor Slags and Their Compatibility with Fireclay and High Alumina

Refractories", presented at ASME 1966 National Incinerator Conference, New York, New York, May 1-4, 1966. P ublished in this volume.

[Z] Herbert, D. B., "The Nature of Incinerator Slags," ASME 1964 National Incinerator Conference, New York, New York, May 18-Z0, 1964. Published in Proceedings of 1966 Conference, p.I91-194.

[3] Muan, Arnulf, "Phase Equilibrium Relationships at Liquidus Temperatures in the System FeO-FeZ03-AlZ03-SiOZ'" Journal of the American Ceramic Society, Vol. 40 (IZ) 19S7, pp. 4Z0-431.

TABLE I

RANGE OF SPECTROCHEMICAL ANALYSIS OF ALL

SLAGS TESTED

Silica (SiOz)

Alumina (AlZ03)

Titania (TiOZ)

Iron Oxide (FeZ03)

Copper Oxide (CuO)

Calcium (CaO)

Magnesia (MgO)

Sulfate (S03)

Zinc Oxide (ZnO)

Lead Oxide (PbO)

Phosphorus Pentoxide (PzOs)

Soda (NazO)

Potash (KzO)

Lithia (LiZO)

Manganese Oxide (MnOz)

Barium Oxide (BaO)

Change on Ignition

Range of Analysis of 9 Incinerators in the N.Y., N.J., and Conn. Area (25 Samples),

20.9-76.0%

0.2-28.3

0.33-4.9

1.8-40.0

T

7.3-17.0

1.1-2.6

0.17-20.4 (Av.6)

0.20-6.3 (Av. 6)

T

0.6-2.2 (Av. 6)

0.6-11.6

0.3-8.1

0.03-0.13

0.04-0.9

T -2.9 to +5.7

* - All samples reported on a calcined basis

T - trace

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TABLE II

Location: New York

Type: Continuous-Feed

Slag Sample No: * A B C

Silica (SiOz) 42.5% 42.3% 37.1%

Alumina (AlZ03) 22.0 20.4 7.0

Titania (TiOz) 3.0 2.7 0.55

Iron Oxide (FeZ03) 12.3 15.2 40.00

Copper Oxide (CuO) T T T

Calcium (CaO) 11.5 11.0 7.7

Magnesia (MgO) 2.3 2.2 1.2

Sulfate (S03) 0.17 0.19 0.55

Zinc Oxide (ZnO) 0.30 0.35 0.20

Lead Oxide (PbO) T T T

Phosphorus Pent oxide (PzOs) 1.8 1.7 0.6

Alkalies (NaZO, KZO, Li2O) 4.45 4.65 5.35

Manganese Oxide (MnOz) 0.27 0.27 0.30

Barium Oxide (BaO) T T T

TOTAL 100.59 100. 96 100.55

Change on Ignition + 0.8 + 5.7 + 2.1

* - All samples reported on a calcined basis

T - trace

TABLE II-A

Location: New York Type: Continuous-Feed

Slag Sample No: A B C

Iron Present as Fe: 0.1% 0.0% 1.5%

Iron Present as FeZ03: 2.6 6.2 6.7

Iron Present as FeO: 8.7 8.1 28.1

Total Iron (as FeZ03): 12.3% 15.2% 40.0%

TABLE III

Location: New York Type: Batch-Feed

Slag Sample No: * D E F

Silica (Si02) 46.7% 40.8% 20. 9%

Alumina (Al203) 18.3 21.7 15.2

Titania (Ti02) 2.3 3.5 2.4

Iron Oxide (Fe203) 5.3 5.5 1. 8

Copper Oxide (CuO) T T 0.3

Calcium (CaO) 13.5 14.8 12. 7

Magnesia (MgO) 2.6 2.6 2.4

Sulfate (S03) 0.22 0.62 20.4

Zinc Oxide (ZnO) 1.1 1.0 6.3

Lead Oxide (PbO) T T 0.2

Phosphorus Pentoxide (P2OS) 2.1 2.2

Alkalies (Na20, K20, Li2O) 6.87 6.07

0. 7

17.23

FIG. 1 CONTINUOUS FEED TYPE INCINERATOR NEW YORK ARE

GENERAL LOCATION OF SLAG SAMPLING

Manganese Oxide (Mn02) 0.60 0. 90 0.44

Barium Oxide (BaO) T T T

TOTAL 99.59 99.69 100. 97

Change on Ignition 0.0 - 0.22 -2.0

* - All samples reported on a calcined basis

T - trace

TABLE IV

PHYSIC A L PROPERTIES OF PHOSPHATE BONDED PLASTICS

COMPARED WITH BURNED REFRACTORIES

Bulk Modulus Density, of Rupture

pounds/cu ft pounds/ sq in

85% Alumina Phosphate Bonded Plastic (Dried at 250 F) 172 1340

90% Alumina Phosphate Bonded Plastic (Dried at 250 F) 178 1520

Super Duty Fireclay Brick (Burned) 148 1000

75% Phosphate bonded Alumina Brick 175 1400

(Unburned)

85% Phosphate bonded Alumina Brick 184 3500 (Burned)

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% Loss in Panel

Spalling Test (3000 F Preheat)

0.0

0.0

2 to 4

E

o

F

FIG. 2 BA TCH FEED TYPE INCINERA TOR NEW YORK AREA

GENERAL LOCA TlON OF SLAG SAMPLING

FIG. 3 CUT SECTION OF SUPERDUTY FIRECLA Y BRICK

SHOWING EFFECTS OF SLAGS AT 2200 F IN THE

DRILLED CUP TEST LEFT, SLAG SAMPLE C,

RIGHT, SLAG SAMPLE F

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FIG. 4 CUT SECTION OF REGULAR 60 PERCENT ALUMINA REFRACTORY

SHOWING EFFECTS OF SLAGS AT 2200 F IN THE PRILL ED CUP

TEST LEFT, SLAG SAMPLE C, RIGHT, SLAG SAMPLE F

FIG. 5 CUT SECTION OF 75 PERCENT ALUMINA PHOSPHATE BONDED REFRACTORY

SHOWING EFFECTS OF SLAGS A T 2200 F IN THE DRILLED CUP TEST LEFT,

SLAG SAMPLE C, RIGHT, SLAG SAMPLE F

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FIG. 6 CUT SECTION OF 85 PERCENT ALUMINA PHOSPHATE BONDED REFRACTORY

SHOWING EFFECTS OF SLAGS A T 2200 F IN THE DRILLED CUP TEST LEFT,

SLAG SAMPLE C, RIGHT, SLAG SAMPLE F

FIG. 7 APPEARANCE OF PHOSPHA TE BONDED PLASTICS SHOWING EXTERNAL EFFECTS

OF SLAGS AFTER HEA TlNG TO 2200 F (SLAG CYLINDERS REMOVED). LEFT 2

BLOCKS, SLAG SAMPLE C, ALUMINA CONTENT OF SAMPLES, 90% 85%, RIGHT

2 BLOCKS, SLAG SAMPLE F

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90� Alumina Phosphate Bonded Plastic

85% Alumina Phospbate Bonded Plastic

851 Alumina Regular Plastio

Superduty fireclay Brick ---------------------------------------------

FIG. 8 CUT SECTIONS OF PLASTICS AND BRICK SHOWING EFFECTS OF SLAGS AT 2300 F

LEFT COL UMN, SLAG SAMPLE C, RIGHT COL UMN, SLAG SAMPLE F

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