Recovered Paper Yield Estimate Using Laboratory + Mill Accounting Data

Transcription

1 Recovered Paper Yield Estimate Using Laboratory + Mill Accounting Data By: Robert de Jong 2 Fiber Consulting

2 Objective To get maximum quantity of RP to the PM headbox without affecting product quality Remove contaminants: Metal, plastic, wet strength, stickies Remove undesirable components: Such as ash, RP fines, solubles Minimize losses of good fibers from process, which will increase residue disposal costs Track RP yield to control process economics 2

3 Introduction Yield = (output tons / input tons) % As is or bone dry (BD) basis Accounting data subject to errors: Incorrect scale weights Inventory differences Broke accounting discrepancies Yield per RP Grade not identified 3

4 Hypothetical Mill Example Produces 21,000 as is tons / month Furnish = 30,000 as is tons / month SWL = 20% CBK = 20% ONP = 20% Wetlap Pulp Broke = 20% at PM = 20% at PM Numbers in Blue are Spreadsheet Variables 4

5 Assumed Moisture Content 60% % MOISTURE 50% 40% 30% 20% 50% Moisture content 10% 6% 6% 9% 7% 7% 0% SWL CBK ONP Wetlap Broke Product The 50% moisture content of Wetlap lowers yield 5

6 As is Furnish Comp. As is Yield Tons/mo. Moist. As is Cont. Input DP = 20% SWL 6,000 6% 20% CBK 6,000 6% 20% ONP 6,000 9% Input PM= 20% Wetlap 6,000 50% 20% Broke 6,000 7% TOTAL INPUT = 30,000 OUTPUT = 21,000 7% LOSSES = 9,000 YIELD = 21,000/30,000 = 70% 6

7 Recalculated on BD Basis BD Furnish Comp. Tons/mo. BD Input DP = 22.3% SWL 5, % CBK 5, % ONP 5,460 Input PM= 11.8% Wetlap 3, % Broke 5,580 TOTAL INPUT = 25,320 OUTPUT = 19,530 LOSSES = 5,790 YIELD = 19,530 / 25,320 = 77.1% 7

8 Typical Average Laboratory Data RP Grade 6 Cut Rej. Solubles BJ F&A SWL 0.2 % 4 % 26 % CBK 0.4 % 6 % 33 % ONP 1.4 % 1 % 27 % Wetlap Pulp 0 % 2.5 % 20 % Broke 0.1 % 1 % 11 % Fin. Product 0 % 1 % 11 % Numbers in Blue are Spreadsheet Variables 8

9 Allocating Coarse Rejects Coarse Rejects to landfill = 180 BD tons / mo (according to accounting data) Good fiber content = 30% (according to Lab) Allocate Coarse Rejects Input (% 6 cut rejects x BD RP tons + 30%) Compare with accounting data Distribute unaccounted tons Numbers in Blue are Spreadsheet Variables 9

10 6 Cut Rejects in Furnish + Product RP Grade SWL CBK ONP Wetlap Broke Total Product Lab Calc (BD tons/mo) 30% Fiber Unacc. 3 = 6 = 19 = 1 = 29 = Losses % good fiber per lab, 180 tons per accounting 10 9

11 Allocating Solubles Calculate input solubles (% solubles x BD RP tons ) Calculate solubles in Product (% solubles x BD Product tons ) Allocate output solubles (according to BD furnish composition) Input output tons = solubles per furnish component 11

12 RP Grade SWL CBK ONP Wetlap Broke Product Solubles in Furnish + Product Lab Calc (BD tons/mo) Tons In Prod = = = = = Losses

13 Calculate BJ Fines & Ash in PM Furnish and DIP Assume: Wetlap + Broke F & A retained 90% (determine when deink plant is down) Calculate F & A in Product Calculate F & A in Product Calculate F & A from wetlap + broke Difference is from DIP Allocate DIP F & A (according to DIP BD furnish) 13

14 BJ F & A in PM Furnish + Product RP Grade DIP Wetlap Broke Product Lab Calc ,148 (BD tons/mo) Tons in Product 540* = 552* = 1,056 1,092 2,148 BJ Losses *=90% PM fines & ash retained; rest is removed 14

15 RP Grade SWL CBK ONP Wetlap Broke Lab Calc. 1,466-1,861-1, BJ F & A in DIP (BD tons/mo) Tons in Product 356 = 356 = 344 = 540 = 552 = Sub- Total 1,056* 1,092 BJ Losses 1,111 1,505 1, , = 1056 in DIP 15

16 Calculate Residue Losses Assume: Residue contains 20% good fiber (according to lab samples) Accounting reports 4,900 tons BD residue (according to truck weights x average dry solids content of residue) Add BJ losses + 20% fiber losses Compare with accounting BD residue losses Distribute unaccounted losses 16

17 RP Grade SWL CBK ONP Wetlap Broke BJ Losses 1, , , ,758 + Residue Losses (BD tons/mo) 20% Fiber Unacc. 74 = 101 = 76 = 4 = 4 = 390 = Residue Losses 1,407 1,907 1, ,900 20% Fiber in residue per Lab, 4,900 tons per acc. 17

18 Calculate Total Losses Add losses per grade and per category Coarse rejects + good fiber Solubles Fines & ash + good fiber Compare with accounting BD losses BD accounting losses calculated losses = unaccounted losses Distribute unaccounted losses proportionally 18

19 RP Grade SWL CBK ONP Wetlap Broke Summary of Losses per Grade Coarse Rejects (BD Tons/mo) Soluble F&A 1, , , ,900 + Unacc. 44 = 62 = 43 = 4 = 3 = 156 = Total Losses 1,651 2,299 1, ,790* 25,320 BD tons input - 19,530 output = 5,790 tons 19

20 Calculate Yield Subtract BD losses per grade from BD input per grade = BD output per grade BD yield per grade = (BD output / BD input )% As is yield per grade = ( as is output / as is input )% 20

21 21 21 BD Yield Calculation BD Yield Calculation 19,530 19,530 Product Product 77.1% 77.1% 19,530 19,530 5,790 5,790 25,320 25, % 98.2% 5,478 5, ,580 5,580 Broke Broke 95.6% 95.6% 2,869 2, ,000 3,000 Wetlap Wetlap 70.6% 70.6% 3,854 3,854 1,606 1,606 5,460 5,460 ONP ONP 59.2% 59.2% 3,341 3,341 2,299 2,299 5,640 5,640 CBK CBK 70.7% 70.7% 3,989 3,989 1,651 1,651 5,640 5,640 SWL SWL Yield Yield BD BD Output Output Losses Losses BD BD Input Input RP RP Grade Grade

22 As is Yield Calculation RP As is BD As is Grade Input Losses Output Yield SWL 6,000 1,651 4, % CBK 6,000 2,299 3, % ONP 6,000 1,606 4, % Wetlap 6, , % Broke 6, , % 30,000 5,790 21, % Product 21,000 22

23 Yield per RP Grade 100% 90% BD As is 95.6% 98.2% YIELD. 80% 70% 60% 70.7% 59.2% 70.6% 77.1% 50% 40% 71.5% 59.9% 69.1% 51.4% 98.2% 70.0% SWL CBK ONP Wetlap Broke Process 23

24 Calculate Furnish Cost to Headbox As is yield can be used to calculate yielded cost to the headbox (if that RP grade was used 100%) Add RP cost + Freight + Mill storage & handling Divide by as is yield = furnish cost / as is ton Furnish cost RP cost = shrink cost per ton Example for SWL (per (per as is ton): $270 + $20 freight + $10 S&H = $300 Furnish cost = $300 / 71.5% = $416 Shrink = $416 $300 = $116 24

25 Allocate Residue Costs Monthly residue disposal costs can be allocated per RP grade: Determine residue disposal cost per BD ton (incl. polymer costs, transport + disposal fee) Add BD residue losses per grade Divide losses by as is PM tons for each grade Example for CBK (using hypothetical numbers) (using hypothetical numbers): Disposal cost = $5,080,000 / (4, ) = $100 Residue losses = (1, ) / 3,592 = 0.54 $100 x 0.54 BD tons residue / PM ton = $54 25

26 Allocate Bleach Costs Determine bleach cost per brightness ton Say monthly bleach costs = $360,000 21,000 PM tons x brightness increase = 120,000 $360,000 / 120,000 brightness tons = $3 Example for ONP: 4,144 PM tons x brightness increase = 100, ,000 brightness tons x $3 = $300,000 $300,000 / 4,144 PM tons = $72 26

27 Allocated Grade Cost to the Headbox $ US$ / As is ton. $400 $300 $200 $ % % Allocated Costs Bleach Reject Disposal Yield Loss RP+Frt+S&H $0 SWL CBK ONP 113% 27

28 Conclusion By combining average lab data for each furnish component + monthly mill accounting data in a spreadsheet, you can calculate yield to the headbox for each RP grade. Convert the data to a BD basis. Allocate furnish losses to appropriate RP grade. Calculate BD yield per RP grade Use this information to calculate the actual grade cost to the headbox. 28

29 Acknowledgment The help of M. Doshi of Progress in Paper Recycling in reviewing the abstract + paper is greatly appreciated. Questions? 29