THERMAL HYDROLYSIS: DESIGN, COMMISSIONING AND LESSONS LEARNED THROUGH A HISTORY OF INSTALLATIONS GREG KNIGHT

THERMAL HYDROLYSIS: DESIGN, COMMISSIONING AND LESSONS LEARNED THROUGH A HISTORY OF INSTALLATIONS GREG KNIGHT

OVERVIEW 1. BRIEF INTRODUCTION TO THP 2. DRIVERS FOR IMPLEMENTATION 3. DESIGN CONSIDERATIONS 4. COMMISSIONING 2

INTRODUCTION TO THERMAL HYDROLYSIS PROCESS 3

THERMAL HYDROLYSIS Complex Organics Simpler Carbohydrates 4 4

Steam) CAMBI (BATCH SYSTEM) REACTORS (2 TO 4) FLASH TANK PULPER DEPRESSURISE TO JUST ABOVE ATMOSPHERIC PRESSURE SLUDGE FEED (CONTINUOUS) 16.5% DS 320 o F 90 PSI HOLD FOR 20-30 MIN SLUDGE DISCHARGE (CONTINUOUS) 225 o F 14% DS 5

VEOLIA EXELYS (CONTINUOUS THP) HEAT RECOVERY TO STEAM BOILER HEAT RECOVERY PLUG FLOW REACTOR REACT @ 320 O F, 90 PSI SLUDGE 140 220 O F Steam DILUTION WATER SLUDGE FEED (CONTINUOUS) 22% DS 10-12% DS 70 dtpd facility in Lille currently being commissioned 6

DRIVERS 7

ADVANTAGES OF THP Less digester volume required for a given solids throughput Higher COD and VS conversion in digesters More biogas Higher electrical output if using CHP Less dry solids for disposal Better dewaterability Less volume of wet sludge for disposal Pathogen free product 8

DRIVERS Less digester volume required for a given solids throughput Higher COD and VS conversion in digesters More biogas Higher electrical output if using CHP Less dry solids for disposal Better dewaterability Less volume of wet sludge for disposal Pathogen free product Power Production Disposal Cost Footprint 9

DIFFERENCES BETWEEN DRIVERS BETWEEN EUROPEAN AND USA PROJECTS Power generation $0.07 / kwh USA, $0.22 / kwh in UK 100 dtpd facility, increased revenue with THP compared to conventional digestion: UK = $570k / year, $8.5m as a 20 year NPV USA = $180k / year, $2.7m as a 20 year NPV Difference of $5.8m NPV Power production is less of a driver for THP in the USA Sludge disposal savings + available digester volume are more important Need to assess projects on a case by case basis 10

DESIGN CONSIDERATIONS 11

EVOLUTION OF THP. 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Dublin Bay Cotton Valley Whitlingham Davyhulme Cotton Valley Dublin Bay Whitlingham Davyhulme 12

EVOLUTION OF THP. 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Dublin Bay Cotton Valley Whitlingham Davyhulme Early TH Teething Issues Screenings build up Grit abrasion Pipework blockages Reactor feed pumps failing Odor issues with thermal oxidizer & pressure release valves Solutions Good sludge screening Good grit removal Wear plates in flash tanks Minimize pipe runs Recirculate digested sludge Customized Seepex Pump Run continuously Fit bursting discs on PRVs New odor condensing rig But what else have we learned along the way.? 13

Viscosity [Pas] SLUDGE RHEOLOGY Dublin design: It behaves like sludge of half the dry solids Hydrolysed or hydrolysed + digested? BHR Group: member funded research program 1.00 0.10 5.02% Cambi Digested, Chertsey, 35C (31-09) 4.54% Cambi Digested, Cotton Valley, 35C (31-09) 7.0% CAMBI Digested Whitlingham 40C 7.27% DS CAMBI digested Cotton Valley 39C 5.6% Cambi Digested 35C (7-08) 5% SRDB Digested (35C) 5% SRDB Digested (35C) Upper 95% 5% SRDB Digested (35C) Lower 95% 3.7%DS Cambi Digested Dublin 50C 3.7%DS Cambi Digested Dublin 50C 6.2%DS Cambi Digested Dublin 50C Sludge rheology database 0.01 Shear rate [1/s] Lots of data on hydrolysed & hydrolysed + digested as well as conventional digested sludge Better pipework hydraulic calculations & confidence in CFD for mixing Before THP 4%TS With THP 6%TS Existing Mixers With THP 6%TS Improved Mixing Varma 2008 Varma 2008 Dawson 2009 14

TATTERSALL COMMISSIONING OF THE ADVANCED DIGESTION PLANT AT DAVYHULME DYNAMIC STEAM MODELLING DURING DESIGN 1/28/2015 Original Valve Open Position Variable Steam Demand Modified Valve Open Position Smoother Steam Demand Drop in steam demand between reactor steam fill cycles is removed by modification of the steam inlet valve opening position

GAS HOLD UP WITH THP 30 % more gas production per unit solids Double the feed solids concentration 2.6 times as much gas per unit volume Higher viscosity due to higher solids content (bubbles escape more slowly) Fresh Sample After 30 minutes Has caused overflow of digesters in the UK Need to onsider impacts during hydraulic design. 16

FIN / FAN ADIABATIC COOLER POTABLE WATER Typical design used in Northern Europe Limited cooling in hot / humid climates Alternatives: Plant effluent HX Cooling tower Chiller GLYCOL/W ATER SLUDGE IN 50 o C 122 F SLUDGE OUT 40 o C 104 F 17

GAS UTILIZATION SYSTEM REQUIREMENTS FOR THP GAS STORAGE Variable STEAM PLANT STEAM Fairly constant BIOGAS GAS UTILIZATION SYSTEM (E.G. CHP) How variable? MARKETABLE OUTPUT 18

SIDESTREAM TREATMENT CONSIDERATIONS Primary Treatment Secondary Treatment Available capacity Operational cost of treating sidestream loads Pre-Dewatering THP & Digestion Dewatering Consider rdon impacts on total nitrogen consents Consider options for phosphorus reduction or recovery Note increased struvite precipitation potential with THP [Mg 2+ ] [NH 4+ ] [PO 4 3- ] > K sp Sidestream Treatment Up front capital cost Operational cost savings Life cycle cost compared to mainstream treatment What is the payback period on investment? 19

SPECIFIC STEAM DEMAND AS A FUNCTION OF FEED SOLIDS AND HEAT RECOVERY EFFICIENCY (FEED TEMPERATURE 59F) 20

DESIGNING FOR SUCCESSFUL START UP AND COMMISSIONING 21

WHAT DO WE NEED FOR DIGESTER START-UP? THP processed sludge is sterile. You need a source of anaerobic bacteria Or you will be waiting a very long time... Can t I just fill the digester with THP output and Wait? Heat Alkalinity 22

SO WHAT ARE THE OPTIONS? Use raw sludge Convert existing digesters Import conventional liquid sludge Import liquid THP digested sludge Import cake THP sludge and dilute 23

COMMISSIONING A RECENT EXAMPLE Digesters 1 & 2 cleaned out, new gas mixing system Digesters 3 to 8 not cleaned out, change over from mesophilic digestion 24

PLANNING FOR DIGESTER START UP 25

STREAMS 2, 3 & 4 CONVERTING CONVENTIONAL DIGESTERS Intended approach Switch feed from non TH to TH sludge at low organic loading Gradually ramp up TH feed over several weeks 26

STREAM 2 RAMP UP Digester stability problems 27

STREAM 2 RAMP UP Sludge transferred from digesters 1&2 Highlights importance of TH acclimatized bacterial population 28

STREAM 2 METHANE CONTENT, VFA/ALK AND PH Decrease in gas methane content was evident significantly in advance of increased VFA/alk ratio 29

STREAM 4 Acclimatized sludge transferred prior to ramp up Ramp up beat schedule at ~25 days 30

Percentage BIOGAS UTILIZATION 100 90 80 70 60 A significant part of this improvement was driven by the steam demand modelling 50 40 Mar 14 Feb 14 Jan 14 Dec 13 Nov 13 Oct 13 Sep 13 Aug 13 Jul 13 Jun 13 Percentage biogas usage on CHP engines Biogas usage on VAB Percentage biogas usage on flare Percentage biogas usage on boilers 31

Total power generated (kw) Specific power output (Kw/tds) ELECTRICAL GENERATION 9000 1000 8000 900 7000 800 6000 700 5000 600 4000 500 3000 400 Mar 14 Feb 14 Jan 14 Dec 13 Nov 13 Oct 13 Sep 13 Aug 13 Jul 13 Jun 13 Total power output Specific power output 32

MONITORING AND PREVENTATIVE MAINTENANCE Blow down the pulper level transmitter (daily) Grease all valves Walk down all pumps for visual / audio check (2 x day) Monitor trends for reactor fill & pressure Reactor pump wear Steam / blow down valves sticking Log seepex pump VSD speed & pressure for wear Measure sludge dry solids (2 x day) Annual shutdown for inspection 33

SUMMARY Energy production is less of a driver for THP projects in the USA compared to EU. Careful case by case assessment is required, sensitivity to disposal cost savings is particularly important Early teething problems with TH facilities have been overcome as the technology has developed. A number of integration issues need careful consideration during design, commissioning and operation Courtesy: Veolia 34

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Steam Heat CONFIGURATIONS - SINGLE DIGESTION CHP Typical configuration used on most TH facilities to date. Boiler Solids Dewatering Thermal Hydrolysis Digestion Dewatering 36

Steam Heat CONFIGURATIONS - DOUBLE DIGESTION Biogas CHP Boiler Solids Thickening Digestion Dewatering Thermal Hydrolysis Digestion Dewatering Increased VS destruction Increased gas production / better energy balance Smaller THP capacity required Existing sites with lots of digester capacity 37

RAPID VOLUME EXPANSION Normal Operation 38

RAPID VOLUME EXPANSION Stop Feeding 39

RAPID VOLUME EXPANSION Start Feeding 40