EVALUATION OF SECONDARY SHREDDING TO ENHANCE RDF PRODUCTION AS FUEL FOR CEMENT KILNS

Transcription

1 EVALUATION OF SECONDARY SHREDDING TO ENHANCE RDF PRODUCTION AS FUEL FOR CEMENT KILNS A RESEARCH TEST CARL S. WEINBERGER Teledyne Natinal Cckeysville, Maryland ABSTRACT An experimental system was designed and cnstructed t evaluate the effect f series and parallel secndary shredding f trmmeled versize air classified light fractin refusederived fuel (RDF). The system included the material cnveyrs, a U.S. Army wned Heil Mdel42D diesel engine mbile shredder, a Gruendler 5640 shredder, cyclne separatr and cmpactr. Material was prcessed thrugh the system at varius feed rates and cnfiguratins. The effect f the varied parameters was evaluated against utput rate and particle size reductin. Analysis f test results indicated that when the test shredders perated independently r in parallel, a sufficient prductin rate f required material culd nt be sustained. When the tw shredders were perated in series, an ptimum feed cnditin culd be maintained which wuld prduce the required rate and particle SIze. INTRODUCTION In January, 978, the U.S. Envirnmental Prtectin Agency, under EPA Grant R705630, funded a prgram t determine the feasibility f using Refuse Derived Fuel (RDF) as a supplemental fuel in cement kilns. The test plan, as described in the Grant applicatin, called fr installatin f receiving and secndary shredding equipment at the cement kiln site, fllwed by a 30 day burn test. In der t supprt this prgram, RDF fuel prductin required a minimum rate f 0 tns/hr (9 t/h) with a particle size f 95 percent less than inch (25 mm). As a result f preliminary RD F burn tests, it was determined that additinal mdificatins t prductin equipment wuld be required in rder t prduce sufficient RDF f the quality required t burn in the cement kiln. The existing EPA grant was amended t prvide a prgram fr upgrading the capacity f existing secndary shredding equipment by evaluating parallel and sequential shredding. In the case f sequential shredding, with tw shredders in series, the first prduces a carse prduct at a high prductin capacity with minimum pwer requirements. By "presizing" the feed t the secnd shredder, its capacity may increase substantially resulting in a sytem that can prduce fmely shredded RDF at a greater rate, and with less hrsepwer than is pssible with a single stage shredding system. In additin, the sequential system prvides the pssible f further imprvements in capacity by permitting the ptin f screening r trmmeling the utput frm the first stage t minimize "reshredding" f undersize particles, thus reducing the lad n the secnd stage, and als remving lng, unshredded textiles that reduce capacity when using a grate with small penings. It was prpsed that gvernment furnished equipment be used, if pssible, t save csts. Specifically, a mbile, trailer munted, Dieselpwered Heil Mdel #42D secndary shredder, available frm the prperty management ffice, 373

2 . U.S. Crps f Engineers, Cnstructin Engineering and Research Labratry, Champagne, Illinis, culd be transprted frm its lcatin, Rbbins Warner Air Frce Base, Gergia, t the Baltimre Cunty Resurce Recvery Facility (BCRRF), refurbished and suitably mdified t secndary shred RDF cntaining rags. Necessary cnveyrs and pneumatic blwers were prvided t permit feeding this equipment and transferring the resulting secndaryshredded RDF t the existing Gruendler secndary shredder fr sequential shredding. Cnveyrs, a diverter, and a splitter were als prvided t permit parallel peratin f bth shredders. RESULTS In rder t cnduct the test prgram f imprving the technlgy f secndary shredding refuse derived fuel, an additin t the existing prductin facility had t be designed, purchased and installed at the BCRRF. Figure shws the schematic f the additinal system which allwed investigatigatin f the enhancement f fuel pre paratin. As shwn in this schematic, the standard methd f RDF preparatin was t mve primary shredded air classified light fractin thrugh a trmmel t reduce ash cntent. Frm the trmmel, the versize material was mved by the trmmeled RDF cnveyr t the Gruendler secndary shredder. The RDF fed t the Gruendler was shredded thrugh grates with inch (25 mm) diameter hles and mved by fan thrugh a cyclne t an RDF cmpactr where it was cmpacted int packer trucks. This system was limited t a prductin rate f 44 tns/hr (3.64. t/h) f prperly sized material. The additinal equipment prvided under this study pr<]gram allwed the expansin f the shredding capability, thus increasing the ptential prductin capacity. The trmmeled RDF cnveyr was cnverted t a bidirectinal cnveyr, thus allwing feed frm the trmmel t the Gruendler shredder r t the Heil shredder. A feed cnveyr was installed between the trmmeled RDF cnveyr and the Heil shredder where material culd be slu;edded and cnveyed by fan thrugh a diverter valve t either the packer r t the Gruendler fr tertiary shredding. This system allwed the in : d I P/"",q,ey JI;eI!OO All! C/.AS$lp/ir LIGl(r F'RACT"/a'\I FIG. EQUIPMENT SCHEMATIC RDF MODI FICATION 374

3 TABLE TEST PLAN TEST NO. TEST CONDITIONS TEST DATA Heil, di scha rge fu II pen, high feed rate Thrughut (TPH), hrsepwer particle size 'distributin 2 Hail, discharge full pen, Lw Feed Rate 3 Heil, discharge full pen, Gruendler, lw feed rate 4 Heil, discharge full pen, Gruendler, high feed rate 5 Heil, discharge 75 percent pen, Gruendler, lw feed rate 6 Heil, discharge 75 percent pen, Gruandler, high feed rate 7 Heil, discharge 75 percent pen, lw feed rate 8 Heil, discharge 75 percent pen, high feed rate 9 Heil, discharge 50 percent pen, lw feed rate 0 Heil, discharge 50 percent pen, high feed rate Heil, discharge 50 percent pen, Gruendler, lw feed rate 2 Heil, discharge 50 percent pen, Gruendler, high feed rate vestigatin f shredding material thrugh either f tw secndary systems singly, in parallel, r in ' series. The bject f the investigatin was t increase prductin capacity t a rate f 0 tns/hr (9 t/h) while maintaining a fuel particle size distributin equal t that material prcessed thrugh the Gruendler shredder with in. (25 mrn) diameter grate size. T accmplish the prpsed study, a test plan was established which culd investigate the cnditins by which material flw culd be increased while maintaining ptimum particle size. Table 2 shws this plan in which test data f thrughput (TPH), shredding energy (HP) and RDF particle size distributin was mnitred. Prir t testing, the Heil shredder was mdified internally by replacing the existing shredder ham mers with blade type cutters and adding statr plates t the inside f the shredder husing. This prvided a fmer reductin in size f the shredder feed, especially textiles. Preliminary testing had established the limitatin f the Gruendler shredder t prduce the required RDF fuel. Maximum prductin capability was limited t 44* tprns/hr (3.64. t/h) at the required particle size. Limits f this shredder are shwn in Fig. 2 and 3 which give shredding capacity as a functin f grate size and ttal pen area. Part f the test prgram was t determine the effect n the Heil shredder capacity and particle size reductin caused by varying the area f the material discharge thrat. Nrmally, shredded material is discharged by the bttm rtating sweep hammers thrugh an pening 27 in. wide x 2 in. 375

4 TABLE 2 TEST DATA Average Hrsepwer Gruendler Average Thrughput Particle Size Test N. Heil in. (25 mm) Grates Ttal Tns/hr %< in. (25 mm) %<Y:. in. (3 mm) Additinal Tests Average Thrughput Test N. Heil Gruendler Ttal Tns/hr %< in. (25 mm) %<Y:. in. (3 mm) Y:. in. Grates in. Grates in. Grates in. Grates (0.7 X 0.3 m) high. By reducing the height f this pening frm full 2 in. (0.3 m) high (00 percent pen) t 9 in. (0.23 m) (75 percent pen) and 6 in. (0.5 m) (50 percent pen), the effect n particle size reductin and thrughput capacity culd be studied. Figure 4 shws the result f this variatin n shredding capacity in tn/hr. A summary f results f the measured data taken during the test prgram is shwn in Table 2. Shwn is the energy required (hp), average shredding cpacity (tns/hr), and percent particle size reductin less than the required in. (25 mm) size fr each f the planned twleve tests. Als shwn are cmparative results f tests at maximum shredding capacity fr bth the Heil and Gruendler shredders independently. By using the Heil shredder t presize material prir t shredding in the Gruendler (series shredding), it was fund that shredding capacity f the Gruendler increased dramatically with a crrespnding decrease in required hrsepwer. Figure 5 shws this effect... Figure 6 shws the effect f varying the discharge area f the Heil shredder n shredder thrughput capacity and input energy in hp/tn. Material samples f prcessed RDF were taken during each f the tests cnducted in the prgram. These samples were analyzed fr particle size distributin by screening in a Gilsn sizing machine at the Baltimre Cunty Material Testing Lab. Results f the size distributin tests are shwn in. Table 3. The criteria fr particle sizing required t meed the RDF fuel specificatins was 95 percent less than in. (25 mm) diameter. As shwn in Table 3, seven f the twelve tests met this requirement. In rder t determine the quantitative effect n thrughput capacity and particle size f each f 376

5 .. 4 Z H 3 ::s <x: H 02 :r: t< t:j SHREDDING CAPACITY GRUENDLER SHREDDER RD F FEED FROM TROMMEL THROUGHPUT TONS/HR. FIG. 2 H X Z 4 H <x: <x: 3 0 :r: <x: t< 0 t< 2 t< <x: t:j (" HOLES) (" HOLES) (H" HOLES) (2" HOLES) SHREDD ING CAPAC ITY GRUENDLER SHREDDER RDF FEED FROM TROMMEL (4" HOLES) THROUGHPUT TONS/HR. FIG

6 0Q 75 HElL SHREDDER 42D RDF FEED FROM TROMMEL THROUGHPUT VS. DISCHARGE OPENING THROUGHPUT TONS/HR. FIG / CI) / SHREDDING CAPACITY 300 <: / I E< I GRUENDLER SHREDDER WITH " GRATES THROUGHPUT VS. MOTOR CURRENT 8200! RDF FEED FROM TROMMEL... _ RDF FEED FROM HElL O THROUGHPUT TONS/HR. FIG

7 0 HElL SHREDDER 42D RDF FEED FROM TROMMEL «: 0...:l p:: "" "" p:: :x: rn A DISCHARGE 00.% OPEN DISCHARGE 75% OPEN DISCHARGE 50% OPEN 2 " THROUGHPUT TONS/HR. FIG

8 TABLE 3 PARTICLE SIZE DISTRIBUTION SCREEN SIZE (76mm) (5 mm) (25mm) (3mm) (9.5mm) minus 3/8 in. Test N. % PassRetain 3 in. 2 in. in. Y:. in. 3/8 in. (9.5mm) % Retain % Pass % Retain % Pass % Retain % Pass % Retain % Pass % Retain % Pass % Retain % Pass % Retain % Pass % Retain % Pass % Retain % Pass % Retain % Pass % Retain % Pass % Retain % Pass

9 TABLE 4 STATISTICAL ANALYSIS FORM Factrial Test 3 Variables, 2 Cnditins Each Thrughput Analysis Test N. Variable Thrughput Rate Shredder Feed Rate Heil Discharge Opening tns/hr (t/h ) Heil Hi Feed Discharge Full Heil & Gruendler Lw Feed Discharge Yz (5.5) (3.0 ) 3.40 (0.34) 4.6 (.05) (3.52) (0.54 ) (6.6 5) (.93) Particle Size Analysis Test N. Variable Particle Size Shredder Feed Rate Heil Discharge Opening Heil Hi Feed Discharge Full %<Yz in. (3 mm) Heil & Gruendler Lw Feed Discharge *

10 TABLE 5 STATISTICAL ANALYSIS RESULTS Thrughput Analysis Maximum Variable Cnsidered Factr. Heil better than Gruendler Heil with discharge 75 percent pen.5/ 2. Heil better than Gruendler Heil with discharge 50 percent pen.49/ 3. Hi feed rate better than lw feed rate with Heil discharge 75 percent pen 6.25/ 4. Hi feed rate better than lw feed rate with Heil discharge 50 percent pen 4.56/ 5. Heil discharge full pen better than 75 percent pen.30/ 6. Heil discharge full pen better than 50 percent pen.68/ Particle Size Reductin Analysis <'h in. (3 mm). Hei I Gruendler better than Hei I wi ttj discharge 75 percent pen.68/ 2. Heil Gruendler better than Heil with discharge 50 percent pen.34/ 3. Hi feed rate better than lw feed rate with discharge 75 percent pen 2.70/ 4. Hi feed rate better than lw feed rate with discharge 50 percent pen 2.35/ 5. Discharge 75 percent pen better than full pen.52/ 6. Discharge 50 percent pen better than 75 percent pen.06/ 38 2

11 TABLE 6 PARTICLE SIZE DISTRIBUTION OF SECONDARY SHRED LIGHT FRACTION. Gruendler Shredder Particle Size Distributin f Secndary Shred R DF Using 4 in. ( 02 mm) grates. Screen Size (mm) Weight % Retained Weight % Passing 3% in. (89) 3 in. (76) 2in.(5) in. (25) % in. (8) %in. (3) % in. (3) Misture Cntent 29% Screen Size (mm) We ight % Reta i ned Weight % Passing 4 in. (02) 3 in. (76) 2in. (5) in. (25) % in. (8) % in. (3) %in.(3) Misture Cntent 9.4 % TABLE 7 PARTICLE SIZE DISTRIBUTION OF SECONDARY SHRED RDF USING 2 IN. (5 mm) GRATES Screen Size (mm) Weight % Retained Weight % Passing 3% in. (89) 5 2in. (5) 6 89 in. (25) 0 79 % in. (3) 38 4 % in. (3) 4 Misture Cntent 5.8 % 95 TABLE 8 PARTICLE SIZE DISTRIBUTION OF SECONDARY SHRED RDF USING % IN. (38 mm) GRATES Screen Si ze (mm) Weight % Retained Weight % Passing 4 in. ( 02) in. (76) in. (5) 0 00 in. (25) 27 % in. (8) 23 %in. (3) % in. (3) Misture Cntent 6.7%

12 TABLE 9 PARTICLE SIZE DISTRIBUTION OF SECONDARY SHRED RDF USING IN. (25 mm) GRATES Screen Size (mm) Weight % Retained Weight % Passing 2 in. (5) 0 00 in. (25) 5 Y:. in. (3) in. (5) 34 Misture Cntent 4.2 % 95 7 TABLE 0 PARTICLE SIZE DISTRIBUTION OF SECONDARY SHRED RDF USING Y:. IN. (3 mm) GRATES Screen Size (mm) Weight % Retained Weight % Passing 4 in. (02) in. (76) in. (5) 0 00 in. (25) 0 00 * in. (8) 25 Y:. in. (3) Y:. in. (3) Misture Cntent 6.6 % the tested variables, a brief statistical analysis in the frm f a factrial test matrix was made using the test results. Shwn in Table 4 is a sample matrix used in the determinatin f the results shwn in Table 5. These results indicate that the required increase in prductin capacity t 0 tns/hr (9 t/h) while maintaining the required material particle size f 95 percent less than in. (25 mm) can be met by using the Hell shredder with the discharge 75 percent pen in series with the Gruendler shredder using in. (25 mm) grate size. If maximum feed rate is maintained, a prductin capacity f 0 tns/hr (90 t/h) can be reached. Tables 6 thrugh 0 shw particle size distributin f light fractin material shred in the Gruendler shredder using grates with 4, 2,,, and in. (02, 5, 38, 25 3 mm) diameter hles. Table shws particle size distributin f light fractin material shred in the Hell shredder at varius feed rates with the shredder discharge full pen. As indicated in this table, while feed rate has an effect n particle reductin size, the Heil shredder is nt capable by itself f meeting the particle size requirement (95 percent less than in.) (25 mm) f this prgram. SUMMARY As a result f this prgram, it has been demnstrated that prductin f Refuse Derived Fuel frm slid waste can be enhanced by a series shredding system. As als demnstrated, energy requirements can be reduced by taking advantage f presize shredding t increase the thrughput capacity f an individual sluedder. The results f the experimental test prgram indicate that sequential (series) secndary shredding f the light fractin can increase prductin rate f the tertiary shredder while meeting the RDF particle size requirement. Operatin f the Gruendler 5640 shredder by itself, while able t meet particle size requirements, wuld nt meet prductin rate requirements.. Operatin f the Hell 42D shredder by itself, while able t meet prductin rate requirements f RDF, wuld nt meet required particle size requirements. Operatin f the Hell42D shredder in parallel with the Gruendler 5640 shredder enabled prductin rates t be met; hwever, the RDF particle size requirement was unable t be maintained. When perated in series t prduce the amunt and quality RDF required fr the cement burn prgram, the use f series shredding reduced the ttal energy requirements in hp/tn when cmpared t individual r parallel peratin. Althugh this test prgram has given sme basic infrmatin in the preparatin f Refuse Derived Fuel, additinal parameters which effect prcess design shuld cntinue t be investigated. 384

13 TABLE PARTICLE SIZE DISTRIBUTION OF SECONDARY SHRED RDF Heil 42D Vertical Shredder Discharge Full Open (27 x 2 inj (0.7 x 0.3m) Feed Rate, tns/hr (.4 t/h) Screen Si ze in. (mm) Weight % Retained Weight % Passing 3, (89) (76) (5) (25) 30 % (8) , 56.5 % (3) (3) Feed Rate 3 tns/hr (2.7 t/h ) Screen Size in. (mm) Weight % Retained Weight % Passi ng 3, (89) (76) (5 ) (25) % (8) % (3) % (3 ) Feed Rate 7.74 tns/hr (7.0 t/h ) Screen Size in. (mm) Weight % Retained Weight % Passing 4 (02) (5) (25) %(3) ,(3) Feed Rate 8.73 tns/hr (7.9 t/h) Screen Size in. (mm) Weight % Retained Weight % Passing 4 (02) (5) (25) 0.B 82.4, (3) ,(3)

14 Thse factrs which effect prcess design equipment selectin, capital and perating csts, and fuel requirements shuld cntinue t be researched in rder t design an ptimum RDF prcessing facility. While much infrmatin is available in basic shredder design, further study in the use f shredders fr RDF preparatin will prvide a much needed backgrund fr the design and use f shredders and pulverizers in the slid waste industry. ACKNOWLEDGMENTS Funding fr this prgram was prvided by the Office f Slid and Hazardus Waste Research, V.S. Envirnmental Prtectin Agency, Cincinnati, Ohi. Special acknwledgement is due Mr. Dnald A. Oberacker fr his effrts in btaining funding and directin fr this prject. The cperatin f the Maryland Envirnmental Service, particularly Mr. Thmas D. McKewen, Directr, and Dr. Cliff R. Willey, Chief, Technical Services, in prviding directin fr this prgram is gratefully acknwledged. The cperatin f the V.S. Army Cnstructin Engineering Research Labratry (CERL) Cl. James E. Hays, Cmmander and Directr, Champaign, lllinis, is gratefully acknwledged. We are particuhirly indebted t Mr. Bernard A. Dnahue, Envirnmental Engineering Team, fr his effrt in btaining the Heil42D surplus shredder withut which n test prgram culd have been cmpleted. Samples f test RDF were analyzed in the labratries f Baltimre Cunty Public Wrks Department with the cperatin f Mr. Jhn Beck, Chief, Test Labratries. Key Wrds Fuel Prduce Refuse Derived Fuel Research Rtary Kiln Shredding 386