Tire and TDF Use in Portland Cement Kilns

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The portland cement production process is extremely energy intensive (from 4 to 6 million Btu's (MMBtu's) are required to make a ton of product); therefore, alternative and cost-effective fuel options are of great interest. Waste tires have been tried as a supplemental fuel in well over 30 cement kilns and in at least one rotary lime manufacturing kiln. Currently, tires are in use, either on a trial or permanent basis, in 11 cement kilns and one lime kiln.

A cement kiln provides an environment conducive to the use of many fuel substances, such as tires, not normally included in the fuel mix. Specifically, the very hot, long, inclined rotary kiln provides temperatures up to 2700*F, long residence time, and a scrubbing action on kiln materials that allows a kiln to accommodate and destroy many problem organic substances. Also, the rock-like "clinker" formed in the kiln can often incorporate the resulting ash residue with no decrease in product quality. Tires are a compact fuel, with very low moisture. Tires have some iron and zinc content, both desirable materials in the raw material mix for cement manufacturing. Further, the materials handling operations already in place at many cement plants require only minimal modification to accommodate TDF feed. For these reasons, cement kilns are one of the most common methods by which energy in waste tires is recovered.

Cement plants attract favorable power rates because the process is so energy intensive; TDF cost per Btu is thus less of a savings. Second, cement kilns can accommodate many alternate fuels,1 such that regional availability and price for these may affect the marginal savings of TDF. For example, on the Southeast Gulf coast, petroleum coke is often less expensive than TDF. Whole tires are cheaper than TDF, but feeding and handling equipment for whole tires is expensive.1

Other alternative fuels of interest to the industry have included organic hazardous waste (e.g., solvents), waste oil, and wood chips. In 1990, seven cement plants reported to the Portland Cement Association (PCA) that their primary fuel included waste; three reported using a combination of coal and waste as primary fuel.2 The type of waste was not specified and, therefore, the number burning tires or TDF specifically could not be determined. The PCA reported that 31 plants utilized waste fuel as an alternate fuel in 1990.2 The number of kilns reporting use of waste fuels is 40 percent higher in 1990 than in 1989.2 There is no record of waste fuel being burned in cement kilns at all in 1972.3 Overall, the number of cement plants with kilns fired by fuels other than coal, natural gas, or oil, has risen from 2.2 percent in 1983 to 15.2 percent in 1990. Figure 4-1 graphs this change.

This chapter describes the use of whole tires and TDF in the cement industry in five sections. First, an industry description is provided. Second, the cement production process is described, including traditional fuel use and use of both whole tires and TDF as supplemental fuel. Third, air pollution implications are discussed in detail, including emissions, control techniques, and control effectiveness. Fourth, other environmental and energy impacts are evaluated. Last, cost considerations of tire use are described.

1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 (a) The types of fuels were not specified for 'other*.

Figure 4-1. Fuel use at cement kilns, 1981-1991.2

4.1 INDUSTRY DESCRIPTION

As of the Summer of 1991, 112 cement plants were operational in the United States.2 Annual U.S. production of clinker in 1990 was approximately 81 million tons per year. Using an average of 5 MMBtu's per ton of clinker produced, some 400 x 1012 Btu's are required nationally by the industry each year. One source estimated that, theoretically, if all waste tires went to the cement industry, waste tires could provide approximately 11 percent of the fuel requirements for the cement industry.4

Many industry-wide changes over the last decade have dramatically affected fuel use and efficiency in the cement industry. First, a trend toward more prevalent use of the dry process of cement manufacture rather than the wet process continues. New technology in conjunction with fuel savings provided by the dry process have made it the process of choice. In fact, no new wet process kilns have been built in over 15 years.2 Second, over the last decade, many plants have converted their kilns to coal firing because of coal's cost effectiveness in comparison to oil and gas. Although both of these trends have had a considerable effect on fuel efficiency and cost in the industry, use of supplemental fuels, such as waste tires, continues to be of high interest to the industry. All fuels are purchased, however, based on regional prices.

Table 4-1 provides a list of cement facilities in the United States that have been reported to be burning tires or to have burned tires in the past. Test data on air emissions while burning tires were obtained for three cement facilities and one lime plant. These facilities comprised both wet and dry process plants, and plants that burned whole tires and TDF. A summary of this test data is presented in this report in section 4.3 below.

Table 4-1. Portland Cement Facilities that have been, or are, Burning TDF or Whole Tires

COMPANY AND LOCATION

KILNS DESCRIPTION*

TDF OR TIRE EXPERIENCE

AIR EMISSIONS TEST OATA

COMMENTS/REFERENCES

Allentown Cement (LeHIgh Portland Ccnent Co.) Allentoun, PA

Aah Grov* Cement Co. Uest Plant Durkee, OR

llu* Circle, Inc. Atlanta, GA

■ox Crow Cement Co., •ox Crow Plant Midlothian, TX

Calavcraa Cement Co. Redding, CA

California Portland Ccnent

(Arizona Portland) Rlltlto, AZ

California Portland

Ccnent

HoJava, CA

Centex

Illinois Cement Co. LaSalle, 1L

Essroc Materials, Inc. Nazareth, PA

2 dry kiln«; coal/coke fired

Dry/1900; PH; ESP; natural gaa/oll co-fire; one four-stage preheater; 500,000 tpy.

2 dry kilns; coal/coke fired

1 dry kiln; PH/PC; coal-flrad; baghouse; 510,000 tpy

4-dry kilns; 1 with PH/PC; coal-fired; 2 kilns Inactive In 1990.

1 planned dry kiln; PC; to be completed 1991

Current use; burned since 6/90, 2"x2"; fed pneuaetlcally Into feed end of kiln; penaltted to burn up to 10X TDF; currently running BX

Past use

Pest use; 2"x6" TDF; 10-12X TDF

Current use; burned since 1985, 2"x2" TDF, Mire-free now; whole by ■Id-1991; about 20X Itu; 65 tons TDF per day (6,000 tires); TDF Into riser duct just above kiln feed housing

Past use; 2"x2" 10X of energy from TDF; TDF since 1986

Extensive testing for PM, SO,, astsls, HC; showed no significant Increase

CEHS only; test burn planned soon

Yes; caission not signifi-csntly different than burning coal

Test use; anticipate 4/91 test bum Applied for test burn permit; plant 4/91 test burn.

Test burn In Novcofcer

References 2 and 5

References 2, 6, and 7

References 2 and 5

References 2, 5, and 7

Usa parait aodlflcatlon froa local agency. References 1, 2, 7, and 6

References 1 and 2

References 2,5, and 7

Conpleted perait application; plans April 1991 test burn. References 2 and 9

References 2, 5, and 7

"O

COMPANY AM) LOCATION

KILNS DESCRIPTION*

TOF OH TIRE EXPERIENCE

Florida Crushed Stona 1 dry kiln; PH; FF; ; Co. coal fired

Giant Resource Recovery Narlayvllla, SC

GIFford Hill Ceaent Co. Nsrley 'Ha, SC (now llua Clrcla)

Holnaai/ldeal Ceaent Dundee, NI

4 wet Kllna; ESP; coal flrad

1 dry kiln; PH; FF; coal flrad

2 uat kllna; coel/coke-flred

Pa«t use; fad TDF Into preheeter; stopped because of prahaatar plugging problems; Installing whole tire feeder; Teat data (10/90) not valid, but tasted for FN, SOj, VOCs, furans, dloxlna, aetata.

Past uae; whole tires; 20X of energy froai TOF during testing; In process of asking aodifIcatlona to Instsll feed equlpatent.

2"x2"

Nolnaa/ideal Coaent 1 wet kiln; ESP; Currant uae; 2' wire-free; test

Seattle, UA coal/coke fired penalt Is for 14* to 2SX; first used

TDF In 1986; discontinued because TDF not price coapetltive with coal; reinstated TOF use In 1990; 20X of energy is froa TOF.

Kosmos Ceaent Co. Kossnsdale, KY

la Farge Corp., ■alcones Plant New Braudels TX

1 dry kiln; PH/PC

Past use; shredded TDF

Current test use; 2* wire-free. Used TDF experlnentally for 2 yrs; completed trials for Mission testing; paraît being Issued to liait TOF to 25X of energy used; planning to test VOC, PAH'«, PCOD/PCOR.

AIR EMISSIONS TEST DATA

COHHENTS/REfEREIICES

Incomplete

References 2 and 10

xn o

H tics

Reference« 2 and 5

References 2 and 11

S fr

•afarancaa 2 and S

Ta«; usine OX, 11X, and UX TDf; conplete data for PN, SOj, NO,, heavy aietals, PNA's, and VOC«».

References 2, S, 12, and 13

References 2, S, and 7

planned

Investigating tire burning on corporate level. References 2, 5, and 7

Tabla 4-1. (Continuad)

COMPANY ANO LOCATION KILNS DESCRIPTION* TDF OR TIRE EXPERIENCE

Lone Star Ceaent, Cape Glrardeu, HO

Medusa Concrete Cllnchflsld, GA

1 Uet Kiln Inactive In 1990; 1 dry kiln w/PH; FF; coil fired.

Medusa Ceaent Charlevoix, MI

Monarch Ceaent Co.

Huifcoldt, KS

River Cement Co., Seine Plant Festus, MO

RNC Lone Star Davenport, CA

Roanoke Cement Co. Cloverdale Plant Roanoke, VA

1 dry kiln; PH/PC; coal-fired

3 dry kilns; 2 with PH; FF; coal/coke

2 dry kilne; FF; coal fired.

1 dry kiln; PH/PC; ESP; coal fired

5 dry kilns; 1 with PH; coal fired; TDF planned In kiln with PH

Current use

Test use; planning use of whole tires, beginning with 4X end Increeslng to 20X tires; tires from retailers and Maybe froa dutpe.

Southdown, Inc. Southwestern Port I end Cement Co. Vlctorville, CA

Southdown, Inc. Southwestern Portland Cement Co. Falrbom, OH

1 dry kiln; PH FF; coal fired.

Current use; test perait; use not continuous; whole end shredded; TDF added et precetclner; whole added Into feed end of kiln by double gate method.

Past peraitted uae; Uhole 3A"; 10-15X; use was successful and ere renewing elternete fuels perait; tires were slid, not rolled, Into feed end of kiln.

AIR EMISSIONS TEST OATA

COMMENTS/REFERENCES

Test burn coon

Reference 7 References 2 and 5

References 2 and 5 RafercncM 2 and S

Rafarancaa 2 and 5

Rafarcncaa 2 and U

Tea, winter 1991; tlraa at 20X

CEHS; new teat data

CEHS; new emissions tests have been done

Hava spent >320,000 for equipment and testing; will be paid a disposal fee for taking tires, and perhaps a state siiieldy based on S0.50 tax on new tires; currently permitting. References 2 and IS

Test permit; final permit pending CEMS data analysis. Uhole Into kiln feed end; TOF Into prcheater at precalciner. References 2, 7, and 16

Tire burning stopped until renew permit to bum whole tires; public opposition to solvent-derived fuels; working their copy through the permit process References 2, 7, 16, and 17

0 ft

Table 4-1. (Continued)

COMPANY ANO LOCATION KILNS DESCRIPTION* TOF M TIRE EXPERIENCE AIR EMISSIONS _TEST DATA_CCHHENU/REFERENCES

Table 4-1. (Continued)

COMPANY ANO LOCATION KILNS DESCRIPTION* TOF M TIRE EXPERIENCE AIR EMISSIONS _TEST DATA_CCHHENU/REFERENCES

Southdown, Inc. (Southwestern) Lyone, CO

1 dry kiln; PH/PC; FF; gaa, coal, waste oil; 1,400 tpd

Current use; 3"x3a TDF; dropped on to feed aheif by acrew conveyor; 1/2 ton/hr 8 5X; sos» feeding problens; plugging of rubber shreds to hopper If shreds have belts and beads.

References 2, 5, 7, and 16

St. Mary's Peerless

Ceawnt

Detroit, Ml

1 wet kiln; coel-flred

References 2 snd 5

Line Manufacture

Uallula, UA

1 rotary llae kiln; freed by gas, oil, and tires; venturl scnfcber controlled.

TDF up to 15X

Tes; 5/86; basstlns gss fired; TDF 1SX

with gas; Matured PAN'S snd aetata

Lias aanufecturlng rotary kiln. Reference 18

' PH > Preheater, PC ■ Preceiclner, ESP ■ electrostatic pracipltator, FF ■ fabric filter

' PH > Preheater, PC ■ Preceiclner, ESP ■ electrostatic pracipltator, FF ■ fabric filter

4.2 PROCESS DESCRIPTION

In the portland cement manufacturing process, three steps occur. First, raw materials are crushed and mixed. The raw materials are powdered limestone, alumina, iron, and silica. Second, the raw materials are fed to an inclined rotary kiln in which they are heated to at least 2700*F. A rock-like substance called clinker is formed, which exits the kiln and is cooled. Third, the cooled clinker is finely crushed, and about 5 percent gypsum is added to produce finished cement. Details of the process are explained below.

4.2.1 Mixing and Grinding

Cement may be made via a wet or a dry process. In the wet process, water is added to the mill while grinding raw materials to form a slurry before entering the kiln. Much of the fuel must be used to evaporate this water from the feed. In the dry process, raw materials are also ground finely in a mill, but no water is added and the feed enters the kiln in a dry state. Therefore, much less fuel is needed in the kiln. Many older kilns use the wet process; in the past, wet grinding and mixing technologies provided more uniform and consistent material mixing, resulting in a higher quality clinker. Dry process technologies have improved, however, to the point that all of the new kilns since 1975 use the dry process. Figure 4-2 diagrams typical wet process material handling, and Figure 4-3 shows typical dry process material handling. Fuel type, or use of tires, does not affect this part of the operations, except that tire use may allow less iron to be added from raw materials. Usually, without an iron supplement, raw materials would contain about 2 percent iron; cement requires about 3 to 3.5 percent iron. Metal in tires is mostly steel and iron. One cement plant estimated that, in one test using whole tires, iron content was raised 0.1 percent by the tires.16

vo 00

CRUSHED RAH MATERIALS FROH STOCKPILE

lila.

WATER

C0AREC1ING SLURRY TANKS BASIH

RAW MATERIALS ARC PROPORTIONED

HAW MATERIALS MILL

C0AREC1ING SLURRY TANKS BASIH

HAW MATERIALS MILL

BS "O

IT tt

o"

Figure 4-2. Typical wet process.material handling during Portland Cement manufacture.3

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Responses

  • carlo
    Did anybody use shreded tire in wet cement process?
    4 months ago
  • Selam
    Can shredded tyres be used on lime kilns?
    22 days ago

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