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Maximizing Energy Savings in a Multiple Hearth Furnace

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Maximizing Energy Savings in a Multiple Hearth Furnace

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    1. Maximizing Energy Savings in a Multiple Hearth Furnace By Nick Shirodkar WSSC

    2. Solids Handling Building at WB Furnace Stacks

    3. HRAS Clarifier Clarified effluent is considered secondary effluent

    4. Heat Treatment Biosolids are heated to 380 degrees Fahrenheit for about 45 minutes, thus collapsing cell walls and releasing cell bound water.

    5. High Speed Centrifuge

    6. Incinerator Feed Pump

    7. Hearth-3 a Burning Hearth

    8. Hearth-5 Char Burning

    9. Days/Fiscal Year of Dual Incineration

    10. Western Branch Solids Currently undergoing Enhanced Nutrient Removal (ENR) upgrade

    11. Current Improvements FGR, Heat Exchanger, CSJ, Venturi Scrubber

    12. A 3-D Schematic of Furnace Improvements

    13. Convection Concept in CSJ

    14. Circle Slot Jet

    15. Solids handling scheme at the WB Each MHF processes 13 dtpd at 24% Current furnace upgrades will allow each MHF to process a minimum of 18 dtpd @24% (original capacity 25 dtpd @ 30%) Each MHF requires 6 weeks down time for maintenance Overall plan for 12 scheduled and 2 unscheduled = 14 wks Solids processing beyond MHF capacity is needed

    16. Four alternatives were considered following initial screening Electrodewatering (EDW) technology Belt dryer technology to process excess solids beyond MHF capacity and reduce hauling quantities Lime stabilization of excess solids to produce Class A or Class B biosolids for hauling and off-site disposal Replace DAF with centrifugal thickening, upgrade MHF and use lime for excess solids

    17. Solids Processing Scheme with Electrodewatering at WB

    18. Principle of Elcotech, Canada

    19. City of Valleyfield (Quebec) WWTP: 100% waste activated sludge After BFP dewatering CINETIK specifications: Two (2) units, Model CINETIK-600 Capacity: 900 kg/hour per unit Feed Sludge: 14% Outlet Cake Dryness: 25% Power consumption: average 100 kWh/Wet Ton Solids Recovery Rate: higher than 99%

    20. Two scenarios considered: Scenario I: representing MHF normal operating conditions (target dryness from 24 % to 30 %) Scenario II: representing truck hauling conditions when MHF is down (target dryness from 24 % to ~ 45 %) EDW conceptual design parameters for WB

    21. Objectives of the pilot scale testing Verify achieving desirable cake solids of 30-32% and 45-47% for the two scenarios Determine the corresponding cake throughputs in DT/day with the two operating scenarios Determine the electricity consumption in kw-h/DT with the anticipated two operating scenarios Test performance with Electrodewatering Agent (EDA) Measure the level of cake stabilization (fecal coliform colonies) in low throughput, high cake solids scenario when cake is expected to be hauled away Measure the filtrate characteristics (at least once) in both scenarios in terms of TS, TKN, TSS, TDS

    22. Cake sludge delivery to EDW unit

    23. Filtrate outlet

    24. Cake dryness with treatment time, NO EDA 32% goal was achieved with 5 min treatment time 33.5% during two-days trial using 7 min Varying results can be due to inefficient sludge distribution in the headbox (not a problem with the full scale) 6 min treatment time can achieve the goal

    25. Sizing linear EDA units A throughput of 11 dtpd of 25% inlet sludge may achieve final dryness of 30% at 4.8 minute treatment time, Need EDA to achieve dryness beyond 40% A throughput of 7 dtpd of 25% inlet sludge may achieve final dryness of 41% at 8.6 minute treatment time with EDA

    26. Summary knowledge on EDW Achieve 35-50% cake solids from >10% input Technology fills the technological and financial gap between mechanical dewatering and traditional thermal drying Ideal for plants requiring upgrade in their dewatering system Reduce volume by 50-65% No polymer or chemical is needed - electricity consumption depends on solids type, throughput, and desired dryness Achieve pathogen inactivation, can produce Class A (satisfy time, temperature relationship), need EPA approval Cake has little odor, odor during process (collect and treat)

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