Increasing Combined Heat and Power from Anaerobic Diges7on by Adding Fats, Oil, and Grease and High- Strength Wastes to Digesters

Transcription

1 Increasing Combined Heat and Power from Anaerobic Diges7on by Adding Fats, Oil, and Grease and High- Strength Wastes to Digesters Robert H. (Bob) Forbes, Jr., P.E. Residuals Technology Leader, Eastern U.S. 12 th Annual Spring Conference of the North Carolina AWWA- WEA Tuesday April 16,

2 Agenda Basic concepts and acronyms Project descripoons Results to date Lessons learned Conclusions and recommendaoons 2

3 Acronyms General to this pracoce: FOG = fats oil & grease HSW = high- strength wastes CHP = combined heat & power ICE = internal combusoon engine WRRF = water resource recovery facility Specific to this session: FWH- WRC = F. Wayne Hill Water Resources Center (GwinneY County, GA) MB- WRRF = Douglas L. Smith Middle Basin WRRF (Johnson County, KS) 3

4 Smith Middle Basin WRRF 35- mgd (132,000 m 3 /day) capacity WRRF FOG/HSW receiving facility to process 14,500 gal/day (55 m 3 /day) on average Cold winter & snow requires building enclosure & heated tanks MulOple day tanks, heaong and equalizaoon systems Two 1.06 megaway (MW) internal combusoon engines (ICE) Facili7es 4

5 Facili7es Middle Basin WRRF Johnson County, KS 5

6 Facili7es F. Wayne Hill WRC 60- mgd (227,000 m 3 /day design capacity) Receives combined sludge from Yellow River WRRF cfm ( m 3 / day) biogas producoon Less than half of biogas uolized prior to CHP 2.15 megaway (MW) GE- Jenbacher engine Up to 75,000 gal/day (280 m 3 /day FOG/HSW receiving capacity 6

7 FWH- WRC FOG/HSW/Cogen SchemaOc FWH- WRC FOG/HSW and CHP system GwinneI County, GA 7

8 Results to Date Middle Basin WRRF HSW is generally more desirable than FOG CharacterisOcs of HSW more predictable High FOG loads someomes associated with digester foaming Most HSW is of higher strength = more biogas Loads of HSW higher and more consistent Digester performance has improved and biogas producoon increased as a result of acclimaoon to both FOG and HSW 8

9 Results to Date - Middle Basin WRRF 9

10 Results to Date - Middle Basin WRRF 400, ,000 Digester 4 Start- up Foaming Loss of HSW 300,000 Start FOG AddiOon 250,000 Digester Gas Produced, cubic feet/day 200, , ,000 50,000-1/1/2009 3/1/2009 5/1/2009 7/1/2009 9/1/ /1/2009 1/1/2010 3/1/2010 5/1/2010 7/1/2010 9/1/ /1/2010 1/1/2011 3/1/2011 5/1/2011 7/1/2011 9/1/ /1/2011 1/1/2012 3/1/2012 5/1/2012 Total Digester Gas 7 per. Mov. Avg. (Total Digester Gas) 10

11 Lessons Learned Middle Basin WRRF Paying closer ayenoon to blend of FOG and HSW has improved digesoon performance and produced more biogas, reducing natural gas consumpoon SCADA system improvements will help synchronize ICE s with WRRF power demands Equipment parts in contact with FOG and HSW have been replaced with corrosion resistant parts, e.g.: Grinder cuhng blades changed to stainless steel Rotary lobe wear plates also changed to stainless steel Buna- N lining added to parts such as rotary lobes, gaskets, and check valve flappers. 11

12 Results to Date F. Wayne Hill WRC Primary Sludge Pumping More being produced and pumped Less thickening in primary clarifiers Digester HRT to 15 days WAS Thickening RDT Thickeners in OperaOon March 2012 Started receiving FOG February/March

13 Results to Date F. Wayne Hill WRC Sludge GeneraOon and Gas ProducOon PS:WAS = 0.71 PS:WAS =

14 Results to Date F. Wayne Hill WRC Generator Maintenance Typical shakedown issues (thermocouples, instrumentaoon, fine- tuning) Trained full- Ome maintenance mechanic in February 2012 Increased generator runome 258 hours/month (August 2011 to April 2012) = 18,020 kwh/mo 443 hours/month (May to June 2012) = 31,350 kwh/mo 14

15 Results to Date F. Wayne Hill WRC Biogas and Power ProducOon Generator Maintenance 15

16 Power Genera7on: Predicted vs Actual F. Wayne Hill WRC Business Case Evalua7on 1 August 2011 June May June Average Daily Gas Genera7on 323 scfm 291 scfm 320 scfm Average Daily Power Genera7on 28,579 kwh/d 20,447 kwh/d 31,356 kwh/d Average Daily Hours of Opera7on /2012 Average for a 1.9MW generator MW Generator 16

17 Average Cost of Energy at FWH- WRC June July

18 Impact of Real- 7me Power Pricing on CHP Opera7on to Maximize Savings 18

19 Energy Savings at FWH-WRC from Cogeneration System in 2011 and 2012 Year Power generated onsite (kwh) Total Power Used (kwh) % of power generated on- site kwh/mg treated Avg Power Cost Avoided Energy Cost 2011 average day % $ 25, total $ 204, average day % $ 21, total $ 260,511 19

20 Lessons Learned FWH- WRC OpOmizing sludge feed to digester increased biogas producoon FOG and HSW addioon have resulted in more biogas producoon, plus revenues of almost $300,000 in 2012 Hiring qualified maintenance staff for generator has boosted run Ome and electricity generaoon Natural gas glut has reduced electricity rates, reducing predicted savings OpOmizing power generaoon to shave peaks maximizes energy savings, especially with real- Ome pricing structure 20

21 Conclusions & Recommenda7ons Using digester gas to fuel CHP projects is a growing pracoce to reduce energy demand at WRRFs. Receiving FOG and HSW can create revenue by Opping fees and boost gas producoon, thereby making CHP more economically ayracove than digesong biosolids alone. The manner in which FOG and HSW are received at a WRRF and fed to digesters is criocal to avoid digesoon upsets. For example, heated storage tanks for blending and leveling FOG/HSW feed rates to digesters are required. 21

22 Conclusions & Recommenda7ons FOG and HSW facilioes with CHP can offer simple payback periods of 4 to 9 years, even with relaovely low power rates. Site- specific issues such as Opping fees and power- rate structure will affect lifecycle costs and payback period. The pracoce is growing sufficiently that standard procedures and best pracoces are being developed. For example, SOPs at the MB- WRRF and the FWH- WRC will contribute to industry standards. 22

23 Acknowledgements Management and Staff of Johnson County Wastewater Management and Staff of GwinneY County Department of Water Resources Project partners Crowder ConstrucOon and Hazen & Sawyer on GwinneY County projects Project partners Archer ConstrucOon and HDR on Johnson County project CH2M HILL project staff on both projects 23

24 Increasing Combined Heat and Power from Anaerobic Diges7on by Adding Fats, Oil, and Grease and High- Strength Wastes to Digesters QUESTIONS? m 24

25 AddiOonal Slides for Q & A 25

26 Typical Business Case Evalua7on for CHP Project Impact of Biogas Produc7on and Power Cost on Payback Period 26

27 Primary Sludge and Biogas Produc7on Before and Ajer Primary Clarifier Improvements 27

28 Power Savings: Predicted vs Actual F. Wayne Hill WRF Business Case Evalua7on 1 August 2011 June May June Average Daily Savings $2, $ $ Maximum Daily Savings N/A $ $ Average Cost of Electricity $ cents/kwh cents/ kwh /2012 Average for a 1.9MW generator MW Generator 28

29 FWH- WRC CHP and FOG Projects 2012 Costs and Revenues 29