PAPER MILL DEPOSIT CONTROL

Transcription

1 PAPER MILL DEPOSIT CONTROL INORGANIC DEPOSITS

2 INORGANIC DEPOSITS Scope of Problem Sources Problem Areas in Mill Analytical Methods Water Chemistry Scale Formation Treatment Options

3 SCOPE OF PROBLEM Loss in Productivity

4 PRODUCTIVITY LOSSES Downtime Machine Breaks Reduced Machine Speed Formation Problems Reduced Efficiency

5 COST OF DOWNTIME Loss of Profits on tons not produced Example: $300/ton x 20 ton/hr = $6,000/hr

6 SECONDARY EFFECTS Decreased Equipment Life Corrosion Lower Quality Product Increased Cost

7 INORGANIC DEPOSITS Sources of Components

8 SOURCES OF INORGANIC DEPOSITS Wood Water System Additives Secondary Fiber Byproducts of Pulping & Bleaching

9 WOOD COMPONENTS Calcium Magnesium Manganese Iron Barium Silica

10 VARIABILITY OF WOOD Bark Wood Species Lignin & Tannin Complexes with Fiber Location Sand & Dirt 10 x minerals in wood HW > SW Bleaching "Ion Exchange" Local Minerals Washing

11 WATER Calcium Magnesium Bicarbonate/Carbonate Iron Manganese Silicate

12 SYSTEM ADDITIVES Fillers CaCO3 Kaolin TiO2 Structured Pigments

13 SYSTEM ADDITIVES Aluminum compounds Alum Sodium Aluminate Polyaluminum Chloride

14 SYSTEM ADDITIVES Calcium Deinking Make-up Lime White Liquor Carryover CaCO3 Filler Water

15 SYSTEM ADDITIVES Silicate, Silica Bleaching Defoamer Dirt Sand Fillers

16 BYPRODUCTS OF PROCESS Oxalate Breakdown of cellulose Most likely in bleaching Lignin Modifications Vary ability to bind metals Oxidation releases metals Soft scale

17 INORGANIC DEPOSITS Problem Areas in Mills

18 KRAFT PULP MILL PROBLEM AREAS Scale Digesters Evaporators Hard Scale Soft Scale Liquor Lines Washers (w or w/o pitch) Sewer Lines Pumps

19 KRAFT MILL DEPOSIT TYPES Calcium Carbonate Pitch/Calcium Carbonate Silica Silicates (calcium or magnesium) Calcium Sulfate Barium Sulfate

20 MECHANICAL PULPING PROBLEM AREAS Trouble Spots Refiners Grinders Chests Screens Lines Pumps Combined with Fiber or Pitch

21 MECHANICAL PULP MILL DEPOSITS TYPES Alumina Barium Sulfate Silicates Manganese Dioxide Calcium Oxalate

22 BLEACH PLANT PROBLEM AREAS Scale Washers Liquor Lines Tower Chests Pumps

23 BLEACH PLANT DEPOSIT TYPES Calcium Carbonate Calcium Oxalate Silicates Barium Sulfate Manganese Dioxide Iron Oxide

24 DEINK PLANT DEPOSITS Calcium Carbonate Calcium soaps Silicates Fillers

25 PAPER MILL PROBLEMS Scale Chests Lines Cleaners Headbox Machine Frame Pumps

26 PAPER MACHINE PROBLEMS Fillers Deposits Headbox Machine Frame Chests Savealls

27 PAPER MILL DEPOSIT TYPES Fillers Alumina Iron Oxide Barium Sulfate Calcium Carbonate Calcium Oxalate

28 FELT FILLING Alumina Pitch Size Fillers CaCO 3

29 ANALYTICAL METHODS Inorganic Deposits

30 ANALYTICAL METHODS Atomic Absorption X-ray Fluorescence Microscopic Examination Wet Chemistry Speck & Spot Analyses

31 ATOMIC ABSORPTION Best Suited for Soluble Water Components Deposits must be Digested Extremely Accurate Laboratory Procedure Only

32 X-RAY FLUORESCENCE Sample must be Dried Small Sample Size Mapping Capabilities Laboratory Technique Only

33 MICROSCOPIC EXAMINATION Morphology of Particles Other Gross Contaminants Extent of Fiber & Fines Done at the Mill

34 WET CHEMISTRY Best Suited for Water Components Deposit Samples must be Digested Traditional High Accuracy Laboratory Method

35 SPECK & SPOT ANALYSIS Rapid Tests Semi-quantitative Identify Organic Components Mill Determination Good Problem Solving Tool

36 WATER CHEMISTRY IN PAPER MAKING Solubility, Precipitation, and Scale Formation

37 SOLUBILITY OF SALTS IN WATER Cl- HCO3- OH- NO3- CO3--- SO4-- PO4--- Na, K, NH4 S S S S S S S H+ S CO2 H2O S CO2 S S Ca++ S SS VSS S I VSS I Mg++ S S I S VSS S I Ba++ S VSS S S VSS I I Sr++ S VSS SS S I VSS I Fe++ S SS VSS S VSS S I Fe+++ S I I S I S I Al+++ S NP I S NP S I Cu++ S I I S I S I S > 5000 ppm SS ppm VSS ppm I < 20 ppm

38 SOLUBILITY PRODUCT CONSTANT CA + - C + A Ksp = [ C + - ] [ A ] [ CA ] + - Ksp = [ C ][ A ] (Slightly Soluble) (Very Low Solubility) * Concentration Expressed in Moles/Liter

39 SOLUBILITY PRODUCT CONSTANTS COMMON SCALE TYPES BaSO4 1.1 x10-10 BaCO3 2.6 x10-9 CaCO3 5.0 x10-9 Ca(OH)2 7.9 x10-6 CaOxalate 2.0 x10-8 Ca3(PO4)2 2.0 x10-33 CaSO4 3.7 x10-5 Fe(OH)2 1 x10-14 Fe(OH)3 2 x10-39 Al(OH)3 1 x10-9 Mg(OH)2 5.7 x10-12

40 CARBON DIOXIDE CHEMISTRY CO2 + H2O H2CO3 H2CO3 + NaOH NaHCO3 + H2O NaHCO3 + NaOH NaCO3 + H2O

41 CALCIUM CARBONATE CHEMISTRY CaCO3 + H2CO Ca + CO3 ++ Ca + 2HCO3 CaCO Ca + HCO3 + OH CaCO3 - + H2O ++ Ca + 2HCO3 - CaCO3 + CO2

42 CARBON DIOXIDE SPECIES vs. ph Fraction of Total Carbon Dioxide CO3 or bound CO HCO3 of half bound CO H2CO3 or CO2 gas ph

43 CALCIUM CARBONATE SCALE Heating 2 HCO 3 - CO CO 2 OH - + HCO 3 - CO H 2 O CaCO 3 has Inverse Solubility with Temperature

44 ALKALINITY TITRATION ppm H2SO4 added P Endpoint M Endpoint Na 2CO3 NaOH ph Value

45 SCALE FORMATION Precipitation of insoluble compounds from water, which adheres to a surface.

46 SCALE FORMATION PROCESS Dissolution Transportation Pr oblems? Deposition

47 REQUIREMENTS FOR SCALE FORMATION Supersaturation Nucleation Contact Time

48 SCALE DEPOSITION SCHEMATIC Suspended Solids Water Super satur ation Dissolved Minerals Nucleation Crystal Growth SCALE

49 NEGATIVE EFFECTS OF SCALE Heat Transfer Loss Flow Restriction Washing Problems Inaccurate Flow Measurements Formation Problems Stock Lumps Picking

50 MINERAL SCALE % Reduction in Heat Transfer Coefficient Al2O3 CaCO3 CaSO4 Clay SiO Scale Thickness (in.) Uniform Layer of Scale

51 HANDLING DEPOSIT PROBLEMS Treatment Options

52 TREATMENT OPTIONS Pretreatment to remove dissolved & suspended solids Softening Ion exchange Filtration Coagulation Reverse osmosis

53 WATER PRETREATMENT Sedimentation Clarification Chlorination Raw Water Lime Softening Filtration Adsorption Screens Aeration Ultrafiltration Reverse Ion Electro- Osmosis Exchange dialysis Pure Water

54 TREATMENT OPTIONS Leave solids in and treat to prevent deposition Scale Inhibitors Antifoulants Sludge conditioners Flocculants Coagulants Dispersants

55 TREATMENT OPTIONS Leave solids in and allow deposits to form - then remove periodically Chemical removal - boilouts Mechanical removal - hydroblasting Combination programs

56 DEPOSIT CONTROL ALTERNATIVES Inorganic Materials

57 CALCIUM CARBONATE PULP MILL Liquor Clarification ph Control Condensate for Pulp Washing Higher Flow Rates Acid cleaning Water Softening "Dispersants"

58 CALCIUM CARBONATE PAPER MILL ph Control Water Softening Improve Retention Dispersants Boilouts

59 BARIUM SULFATE PULP MILL Reduce H2SO4 Reduce Alum Reduce soda loss Boilouts Dispersants PAPER MACHINE Reduce Alum Reduce soda loss Dispersants Boilouts

60 MANGANESE DIOXIDE Water Softening Chlorination of Mill Water Chelating Agents Boilouts

61 IRON OXIDES Water Softening Chlorination of Mill Water Corrosion Inhibitors in Mill Water Low Iron Alum Chelating Agents Boilouts

62 SILICA & SILICATES Silicate Reduction (Bleaching) Water Softening Improved Chip Washing Switch Defoamers Improved Retention

63 FILLER DEPOSITS Wet End Chemistry Improve Retention Aluminum Chemistry ph Control Dispersants Boilouts

64 WET END CHEMISTRY Fiber source & properties Machine design Fillers ph Water chemistry Coagulants Flocculants System charge

65 ALUMINUM SPECIES vs. ph Fraction of Aluminum Al+3 Al+2 Al8(OH)20+4 Al(OH)3 Al(OH) ph

66 ALUMINA DEPOSITS Avoid ph shock Check for overuse Clarified White Water vs. Fresh Water Change feed points

67 SCALE INHIBITION Mechanisms for Control

68 HISTORICAL PERSPECTIVE Potato starch reported effective for boiler scale First scale control patent

69 LANGUAGE OF SCALE CONTROL Chelation Sequestration Complexation Antiprecipitation Threshold treatment Dispersant Deflocculant Antinucleation agent Modification Surface Modification Crystal modification Peptization

70 CHELATION Co-ordinate bonds with cations Interfere with the thermodynamics of crystal formation

71 CHELANTS & SEQUESTERANTS EDTA DTPA NTA Citrate Gluconate Tartrate Hexametaphosphate Polyphosphate Phosphonates Phosphate esters Lignosulfonate Tannin

72 CRYSTAL MODIFIERS Adsorb at surface of crystals Distort scale crystals as they grow Interfere with kinetics of crystal formation

73 THRESHOLD INHIBITORS Hexametaphosphate Polyphosphate Phosphonates Phosphate esters Lignosulfonate Tannin Polyacrylates Polymethacrylates Polymaleates Polyphosphonate CMC Alginates

74 DISPERSANTS Anionic Charge (increase repulsion) Lignosulfonate Tannin Polyphosphates Acrylic polymers Sulfonate polymers Copolymers & terpolymers

75 INORGANIC DEPOSITS CONTROL Know the entire process Understand your options Evaluate the economics of treatment ACTION Plan

76 INORGANIC DEPOSIT CONTROL The key to improved runnability.