(CHP) From Anaerobic Digestion By Adding Fats, Oil

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(CHP) From Anaerobic Digestion By Adding Fats, Oil

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, 2013

1


Agenda

• Basic concepts and

acronyms

• Project descripOons

• Results to date

• Lessons learned

• Conclusions and

recommendaOons

2


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


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


Facili7es

Middle Basin WRRF

Johnson County, KS

5


Facili7es

F. Wayne Hill WRC

• 60-­‐mgd (227,000 m 3 /day

design capacity)

• Receives combined sludge

from Yellow River WRRF

• 300-­‐400 cfm (8.5-­‐11.3 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


FWH-­‐WRC FOG/HSW/Cogen SchemaOc

FWH-­‐WRC FOG/HSW

and CHP system

GwinneI County, GA

7


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


Results to Date -­‐ Middle Basin WRRF

9


Results to Date -­‐ Middle Basin WRRF

400,000

350,000

Digester 4

Start-­‐up

Foaming

Loss of

HSW

300,000

Start FOG

AddiOon

250,000

Digester Gas Produced, cubic feet/day

200,000

150,000

100,000

50,000

-

1/1/2009

3/1/2009

5/1/2009

7/1/2009

9/1/2009

11/1/2009

1/1/2010

3/1/2010

5/1/2010

7/1/2010

9/1/2010

11/1/2010

1/1/2011

3/1/2011

5/1/2011

7/1/2011

9/1/2011

11/1/2011

1/1/2012

3/1/2012

5/1/2012

Total Digester Gas

7 per. Mov. Avg. (Total Digester Gas)

10


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


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 2012

12


Results to Date – F. Wayne Hill WRC

Sludge GeneraOon and Gas ProducOon

PS:WAS = 0.71 PS:WAS = 1.24

13


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


Results to Date – F. Wayne Hill WRC

Biogas and Power ProducOon

Generator

Maintenance

15


Power Genera7on: Predicted vs Actual

F. Wayne Hill WRC

Business Case

Evalua7on 1

August 2011 – June May – June 2012 2

2012 2

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

15.2 8.5 14.5

1

2011/2012 Average for a 1.9MW generator

2

2.18 MW Generator

16


Average Cost of Energy at FWH-­‐WRC

June 2011 -­‐ July 2012

17


Impact of Real-­‐7me Power Pricing on CHP Opera7on to

Maximize Savings

18


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 512211 4693677 11.25% 4953 0.0474 $ 25,607

2011 total 4097690 56324126 $ 204,859

2012

average day 593171 4430716 13.47% 5209 0.0360 $ 21,709

2012 total 7118051 53168594 $ 260,511

19


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


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


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


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


Increasing Combined Heat and Power from

Anaerobic Diges7on by Adding Fats, Oil, and

Grease and High-­‐Strength Wastes to Digesters

QUESTIONS

bob.forbes@ch2m.co

m

24


AddiOonal Slides for Q & A

25


Typical Business Case Evalua7on for

CHP Project

Impact of Biogas Produc7on and Power Cost on Payback Period

26


Primary Sludge and Biogas Produc7on Before

and Ajer Primary Clarifier Improvements

27


Power Savings: Predicted vs Actual

F. Wayne Hill WRF

Business Case

Evalua7on 1

August 2011 – June May – June 2012 2

2012 2

Average Daily

Savings

$2,000.63 $746.86 $931.74

Maximum Daily

Savings

N/A $9010.67 $1571.07

Average Cost of

Electricity

$0.07 3.684667 cents/kWh 3.289554 cents/

kWh

1

2011/2012 Average for a 1.9MW generator

2

2.18 MW Generator

28


FWH-­‐WRC CHP and FOG Projects

2012 Costs and Revenues

29

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