4/12/2010

1

Conceptual Design of Thermal Hydrolysis Processes for Enhanced SolidsProcesses for Enhanced Solids Reduction from Anaerobic Digestion

Mohammad Abu-Orf, PhD

AECOM Water

North America Biosolids Practice Leader

Outline

1. Overview of Thermal Hydrolysis Pretreatment Processes

1-TH Overview

2. Cambi Process– Process components– Reactor design– Reactor sequencing/operation

3. BioThelys Process

2-Cambi

3-BioThelys– Process components– Reactor design– Reactor sequencing/operation

4. Future of Thermal Hydrolysis April 12, 2010 Page 2

4-Future of TH

4/12/2010

2

1. Overview of Thermal Hydrolysis Pretreatment ProcessesPretreatment Processes

Page 3

Thermal Hydrolysis Process (THP)Process• Treat dewatered sludge prior to

anaerobic digestion, under the following conditions:

Hi h f

Result• Decrease viscosity

– Allows sludge mixing at higher concentrationD di ti l

1-TH Overview

– High temperature of 150°C to 170°C

– Under pressure of 6 to 9 bars– Reaction time 20 to 30 min

• Dewatered sludge from 14 to17%

• Input to digestion 10 to 12%

– Decrease digestion volume

• Sterilized sludge (Class A)

• Improvement anaerobic digestion– Increase VS reduction– Improve biogas production– Reduce mass for further

processingInput to digestion 10 to 12% processing

Before TH After TH

4/12/2010

3

Thermal Hydrolysis for Anaerobic Digestion

7 Desired Parameters

for

1. Class A biosolids: sustainability and reuse cost2. Less digestion volume: water content of the feed3. High digestibility: more gas4. Good dewaterability: less hauling and cost 5 Minimize FC reactivation/regrowth potential and odors:

1-TH Overview

for Digestion

5. Minimize FC reactivation/regrowth potential and odors: sustainability for land application

6. High digester loading rate7. Good mixing efficiency

Thermal Hydrolysis Achieves All Above• Pasteurized solids, Class A• Digester is fed at 11-12% total solids (half), energy

Aberdeen

Digester is fed at 11 12% total solids (half), energy efficiency

• Volatile solids destruction is high 55- 65%• Dewatered cake is in low to mid 30%• Proven to not have problem with FC

reactivation/regrowth, better odor quality• 50% more solids loading compared to conventional • Power required to mix digester is less

Considerations for Thermal Hydrolysis

• Only achieve Class A if all sludges are treated by THP

• 10-12% into digestion if both primary and WAS are g p ytreated

• % solids to the digester is determined partly by % N

• THP WAS only plant goes into digester by a smaller percentage

THP d t t d h t t b i l• THP needs to capture and re-use heat to be economical

• Hydrolyzed sludge stinks, need tight sealing with potential for gas escape

April 12, 2010 Page 6

4/12/2010

4

Two Main Thermal Hydrolysis Processes

They are different processes in terms of operations and design

1-TH Overview

BioTHELYS CAMBIReactors in parallel Reactors in series

Flash steam

Reactor 2

Flash steam

Fresh steam Reactor 1

Fresh steam

Pulper Flash tankReactors

Thermal Hydrolysis References1-TH Overview

Cambi BioThelysFirst installation in 1996 First installation in 2006First installation in 1996 First installation in 200620 plants in operation 4 plants in operation5 plants ordered and under construction

All

All plants as of 2010 are outside North America

Plants are in France only

Treating ~ 417,600 dry tonnes/yr Treating ~ 6,200 dry tonnes/yr (1.5% of Cambi)

April 12, 2010 Page 8

of Cambi)Smallest plant is ~ 3.3 dtpd Smallest plant is 3 dtpdLargest plant is ~ 250 dtpd Largest is 5 dtpd

4/12/2010

5

2. Cambi Process

1-TH Overview

2-Cambi

Process

Typical Cambi™ Integration with WWTP2-Cambi

Typical Cambi

Typical WWTP

scope forthis area

4/12/2010

6

Cambi and Reactor Operation (90 minute cycle time)

Dewatered solids (14.7%)

Recycled Steam

2-Cambi

Fresh Steam

~11% to digestion

FLASHTANK

PULPER REACTOR

Dilution Water

HE

Step Action Time Description1 Fill 15 min Fill Reactor with 7.6 m3 of sludge (12 m3 reactor)

2 Steam injection 15 min Inject steam in the Reactor

3 React 30 min Hold Reactor at 165C and 90 psig

4 Steam out 15 min Release steam to Pulper

5 Empty 15 min Transfer sludge to Flash Tank by pressure release.

Reactor Sizing for Cambi

• Standard size Pulper and Flash tanks

• Standard size reactor is 12 m3 and expected to operate 70% (7.6 m3)

2-Cambi

• Assuming a 14.7% and 90 minute cycle time– Capacity of each reactor is 17.9 dry metric ton/day, use 95% up time

• For effective asset use, one train with one reactor can process sludge from a 15-20 MGD plant

• Use maximum month or maximum-15d to determine number of reactors, and number of Cambi trains

• At average day more Cambi capacity allowing some level of• At average day, more Cambi capacity, allowing some level of redundancy depending on plant size

• Can increase Cambi throughput through reducing reaction time and increase solids input concentration

• Uses 1 lb of fresh steam per dry ton of solids processed

4/12/2010

7

Cambi Reactors Sequencing (example 3 reactors)• Reactors are doing different

things at same point in timeChertsey, UK

2-Cambi

• Only valves opening and closing to direct sludge and steam

• Works best if runs continuously, no cooling down

z

down15 min 15 min 30 min 15 min 15 min

Reactor 1 Fill Steam In React Steam out EmptyReactor 2 Empty Fill Steam In React Steam outReactor 3 Steam out Empty Fill Steam In React

3. BioThelys ProcessIs it really a “copy cat” of Cambi?

1-TH Overview

2-Cambi

3-BioThelys

4/12/2010

8

G h ld

Cogeneration

Dewatering

Sludge Water kW

HeatLive steamBiogas

Fl h tF di G h ld

Cogeneration

Dewatering

Sludge Water kW

HeatLive steamBiogas

Fl h tF di

BioThelys in Saumur, France

15 %

3-BioThelys

Anaerobic digester

Gas holder

Buffertank

Heatexchanger

THELYS reactors

Boiler

Service water

Flash steam

Hydrolysed sludge

Feedingtank

Anaerobic digester

Gas holder

Buffertank

Heatexchanger

THELYS reactors

Boiler

Service water

Flash steam

Hydrolysed sludge

Feedingtank

Mesophilic anaerobic digestion

110°C

45°C

38°C 15 days

Dewatering

Dewaterd sludge

Return liquor

BioTHELYS®D Process

Digested sludge

Dewatering

Dewaterd sludge

Return liquor

BioTHELYS®D Process

Digested sludge

Storagecells

15 days

27-29%

8 monthsAgricultural valorisation

BioThelys Rector Operation (150 min cycle time)25 min  20 min   25 min 30 min  20 min  25 min   5 min

3-BioThelys

Raw sludge

0Live steam

1Raw sludge

2Flash steam

3Live steam

4Flash steam

65Raw sludge

7Live steam

BA BA

15°C

160°C

BA

160°C

BA

160°C

110°C

15°C

75°C

A

110°C

B

Hydrolysed sludge

75°C

160°C

BA

15°C

75°C

160°C

110°C

BA

160°C

Hydrolyse sludge

BA

75°C

160°C

110°C

4/12/2010

9

Reactor Specifications• Standard design uses 2 reactors, each reactor to be filled at 50%

• All reactors are same size and same function, no Pulper or Flash Tanks

• Kruger custom design the reactors to meet the process needs and

3-BioThelys

Kruger custom design the reactors to meet the process needs and application – Previous sizes include 3.1, 3.9, 4.6, 4.9 m3 thus expected to be more economical than Cambi

for smaller size plants

• Consider plant processing 4.5 dtpd, with two (2) 3.1 cubic meter reactors as a practical minimum size plant

• The operations of thermal hydrolysis and regulation around boiler operators may increase the practical minimum size due to staffingoperators may increase the practical minimum size due to staffing requirements

• Veolia can design/construct trains of 3 reactors (scale and economy)

• The total cycle time is 165 min for 3 reactors (compared to 150 min with 2 reactors). The flash steam goes from reactor 1 to 2 and 2 to 3 and 3 to 1

Page 17

BioThelys Reactor Sizing• Assuming a 15% solids feed and 150 minute cycle time, and 50%

active volume

• One cubic meter able to process 0.72 metric dtpd

3-BioThelys

• The flexible size of Biothelys allows more efficient sizing

Reactor size (m3)

Metric dtpd processed per

reactor

Plant sizedtpd

(2 reactors)3.1 2.25 4.54.9 3.5 7.012.5 9.0 18.0

• The flexible size of Biothelys allows more efficient sizing

• However, standardized Cambi reactor size increases quality control

• If one reactor is out, process is out

• No Flash tank to equalize the flow to digestion

4/12/2010

10

Issues to consider when adapting Thermal Hydrolysis • Maintenance of the process components can be a challenge

• Operators skill – require operators used to pressure and steam

• Regulations regarding frequency of pressure vessel inspection include in the

3-BioThelys

• Regulations regarding frequency of pressure vessel inspection – include in the design

• Ammonia in recycled stream can be a concern

• Two dewatering steps

• Require proper screening of sludge

• Delivery method in Europe mainly DB and DBO in one package with digestion and co-gen, guarantees usually in terms of electricity production per solids processed

• Processing FOG through digestion requires separate system of pasteurization after treatment to incorporate with digestion for Class A production

• Issues with rDON and recalcitrant COD

• If flash tank is inside needs to manage building environment (process gets hot)

April 12, 2010 Page 19

The Future of Thermal Hydrolysis

1-TH Overview

2-Cambi

Hydrolysis

3-BioThelys

4-Future of THTH

4/12/2010

11

Cambi Progress Increased plant size is a sign of credibility Took off since 2006, start of BioThelys

Cambi Plants Biosolids treated by Cambi

4-Future

Cambi Plants Biosolids treated by Cambi

10

15

20

25New Plants OnlineCumulative Plants

200,000

250,000

300,000

350,000

400,000

450,000New Capacity Online, DTPYCumulative Capacity, DTPY

April 12, 2010 Page 21

0

5

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

0

50,000

100,000

150,000

1996

1998

2000

2002

2004

2006

2008

2010

North America Update

Blue Plains• 4 Cambi trains, six reactors per train

Trinity River Authority• CDM/AECOM team

recommended thermal

4-Future

• 4 digesters

• New pre-dewatering facility: centrifuge

• New post-dewatering facility: (BFP)

• ~10-14 MW facility

recommended thermal hydrolysis as the best option to process residuals at CRWS – phased approach

Hamilton• AECOM/CH2MHILL team

d d th l

April 12, 2010 Page 22

recommended thermal hydrolysis of WAS to increase gas generation and energy revenues from cogeneration, and to avoid expanding digesters

4/12/2010

12

New Advancement from Veolia

• Veolia Water Systems is rolling a new thermal hydrolysis design (Exelys) during 2010 RBC in Savannah

4-Future

Savannah

• Claims:– Increase energy efficiency – Plug flow, continuous one reactor design– Compact, with lower footprint

April 12, 2010 Page 23

Thank you!

Mohammad Abu-Orf, PhDAECOM Water

North America Biosolids Practice LeaderMohamma.abu-orf@aecom.com