Confidential

Acid Plant Strong Acid Section

Garrett Palmquist

MECS Inc.

3 October 2010

Confidential

Topics for Discussion

Main Equipment and Its Purpose,

Operating Conditions, and Limits

Flow Schemes

Notable Failures

Confidential

Main Equipment and Its Purpose

Final Tower

Interpass Tower

Drying Tower

Pump TanksAcid Coolers

Confidential

Main Equipment and Its Purpose

DRYING

TOWER

INTERPASS

ABSORBING

TOWER

FINAL

ABSORBING

TOWER

Strong Acid Towers

PRODUCT

ACID

FINAL TOWER

MIST

ELIMINATORS

CWS CWS CWS CWRCWRCWR

DRYING TOWER

MESH PAD

DRYING

TOWER

INTERPASS

ABSORBING

TOWER

DT ACID COOLERIPAT

ACID COOLERPRODUCT

ACID COOLER

INTERPASS

TOWER MIST

ELIMINATORS

FINAL

ABSORBING

TOWER

DT PUMPTANKINTERPASS TOWER

PUMP TANK

CWSCWR

FAT

ACID COOLER

FINAL TOWER

PUMP TANK

WATER WATER

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

Confidential

Strong Acid Drying Tower

Purpose

Water vapor removed with strong sulfuric acid

Typically -40 °F gas dewpoint

Required to prevent acid condensation in downstream equipment in dry gas plants

Operating Conditions

93% - 98% H2SO4

120 – 180 °F (50 – 80 °C), colder at lower acid strength

Constant, uniform acid flow

Confidential

Strong Acid Absorbing Tower

Purpose

SO3 vapor absorbed and reacted with strong sulfuric acid

SO3 + H2O -> H2SO4 + Heat

Operating Conditions

98% - 99% H2SO4

170 – 180 °F (75 – 80 °C)

Constant, uniform acid flow

Materials

CS Brick-Lined

Alloy

Confidential

Strong Acid Tower Details- Distributors

Confidential

Strong Acid Tower Details- Packing and Supports

Confidential

Strong Acid Tower Details- Mist Eliminators

Mesh Pad

Mist Eliminator Tubesheet

Brownian

Diffusion

Impaction

Confidential

PUMP TANK

Main Equipment and Its Purpose

Strong Acid Pump Tanks

PRODUCT

ACID

FINAL TOWER

MIST

ELIMINATORS

CWS CWS CWS CWRCWRCWR

DRYING TOWER

MESH PAD

DRYING

TOWER

INTERPASS

ABSORBING

TOWER

DT ACID COOLERIPAT

ACID COOLERPRODUCT

ACID COOLER

INTERPASS

TOWER MIST

ELIMINATORS

FINAL

ABSORBING

TOWER

DT PUMPTANKINTERPASS TOWER

PUMP TANK

CWSCWR

FAT

ACID COOLER

FINAL TOWER

PUMP TANK

WATER WATER

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

Confidential

Strong Acid Pump Tanks

Purpose: Hold acid when plant is shutdown and provide enough acid during operation for circulating pumps

Operating Conditions: Same as the towersMaterials

CS Brick-lined

Alloy

Components

Pumps

Acid Returns

Dilution Water Addition

Analyzers and Sample Stations

Overflow and Vent

Baffles

Safety Showers

Confidential

Strong Acid Pump Tanks - Internals

Dilution water addition

near side acid return

Pair of acid pumps

Confidential

Main Equipment and Its Purpose

Strong Acid Coolers

CWS CWR

ACID COOLER

CWR

CWS

ACID COOLER

PRODUCT

ACID

FINAL TOWER

MIST

ELIMINATORS

CWS CWS CWS CWRCWRCWR

DRYING TOWER

MESH PAD

DRYING

TOWER

INTERPASS

ABSORBING

TOWER

DT ACID COOLERIPAT

ACID COOLERPRODUCT

ACID COOLER

INTERPASS

TOWER MIST

ELIMINATORS

FINAL

ABSORBING

TOWER

DT PUMPTANKINTERPASS TOWER

PUMP TANK

CWSCWR

FAT

ACID COOLER

FINAL TOWER

PUMP TANK

WATER WATER

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

Confidential

Strong Acid Coolers

Purpose: Remove heat from circulating acid using cooling water

or BFW

Operating Conditions:

93% - +99% acid

100 – 250 °F (40 – 120 °C), material dependent

Maximum acid velocity (corrosion)

Minimum water velocity (fouling)

Shell & Tube

Plate & Frame

Confidential

Strong Acid Coolers

Materials – Shell and Tube

316 / 304 SS anodically protected

Alloy (ZeCor, 310 SS, etc.)

Materials – Plate and Frame

Hastelloy C-276 (low temperature)

Hastelloy D-205 (high temperature, low chlorides)

Confidential

Strong Acid Piping

Alloy systems

310 SS (velocity sensitive)

ZeCor

Iron systems

MONDI

Other ductile iron

Other systems

Anodically-protected

Lined

Confidential

Common IPAT/FAT pump tank with crossflow stripperCommon IPAT/FAT pump tankSeparate pump tanks, SO2 stack / product limits

PRODUCT

ACID

FINAL TOWER

MIST

ELIMINATORS

CWS CWS CWS CWRCWRCWR

DRYING TOWER

MESH PAD

DRYING

TOWER

INTERPASS

ABSORBING

TOWER

DT ACID COOLERIPAT

ACID COOLERPRODUCT

ACID COOLER

INTERPASS

TOWER MIST

ELIMINATORS

FINAL

ABSORBING

TOWER

DT PUMPTANKINTERPASS TOWER

PUMP TANK

CWSCWR

FAT

ACID COOLER

FINAL TOWER

PUMP TANK

WATER WATER

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PRODUCT

ACID

FINAL TOWER

MIST

ELIMINATORS

CWS CWSCWRCWR

DRYING TOWER

MESH PAD

DRYING

TOWER

INTERPASS

ABSORBING

TOWER

DT ACID COOLERPRODUCT

ACID COOLER

INTERPASS

TOWER MIST

ELIMINATORS

FINAL

ABSORBING

TOWER

DT PUMPTANK

CWSCWR

COMMON

ACID COOLER

INTERPASS / FINAL TOWER

PUMP TANK

WATER

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PRODUCT

ACID

FINAL TOWER

MIST

ELIMINATORS

CWS CWSCWRCWR

DRYING TOWER

MESH PAD

DRYING

TOWER

INTERPASS

ABSORBING

TOWER

DT ACID COOLERPRODUCT

ACID COOLER

INTERPASS

TOWER MIST

ELIMINATORS

FINAL

ABSORBING

TOWER

DT PUMPTANK

CWSCWR

COMMON

ACID COOLER

INTERPASS / FINAL TOWER

PUMP TANK

WATER

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

CROSS-

FLOW

STRIPPER

AIR

Flow Schemes

PRODUCT

ACID

FINAL TOWER

MIST

ELIMINATORS

CWS CWS CWS CWRCWRCWR

DRYING TOWER

MESH PAD

DRYING

TOWER

INTERPASS

ABSORBING

TOWER

DT ACID COOLERIPAT

ACID COOLERPRODUCT

ACID COOLER

INTERPASS

TOWER MIST

ELIMINATORS

FINAL

ABSORBING

TOWER

DT PUMPTANKINTERPASS TOWER

PUMP TANK

CWSCWR

FAT

ACID COOLER

FINAL TOWER

PUMP TANK

WATER WATER

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

PROCESS

GAS

Separate pump tanks, lax SO2 stack / product limits

Confidential

STEAM

INJECTION

VESSEL

HEAT

RECOVERY

TOWER

LP

STEAM

IMPORT

HRS BOILER

HRS

HEATER

HRS

PREHEATER

HRS

DILUTER

HEAT

RECOVERY

TOWER MIST

ELIMINATORS

GAS OUT

GAS IN

STAGE 2

ACID IN

TO ACID

SYSTEM

TREATED

WATER

DEAERATOR

AND BFW PUMP

IP STEAM

BLOWDOWN

TO ACID

SYSTEM

HRS

DRAIN PUMPS

FROM ACID

SYSTEM

Heat Recovery System (HRS)

Replaces tower and

pump tank

Replaces acid cooler(s)

Replaces the interpass circuit

Operates at 400 – 440 F, >99%

H2SO4

Recovers excess heat as 150

psig steam

Special alloy materials

More expensive, but offset

by steam product (>0.4 t/t)

>1000 MTPD, >10% SO2

440 F

99.6% H2SO4

400 F

99% H2SO4

150 psig steam Teflon-lined

ZeCor-310M

ZeCor-310M

Confidential

Acid System Failures – Packing Collapse

Hot shutdown for a FAT cooler leak

Acid circulation was temporarily stopped

Thermal shock to Aludur beams collapsed packing

Packing blocked

tower acid outlet

Acid level covered

gas inlet

Blower surged and

wave of acid

knocked brick

arches over

Confidential

Acid System Failures – Cooler Leak

Leak in drying tower cooler goes undetected for several

hours

System cannot be drained for several days

H2 corrosion by-product collects in IPAT and explodes

Tower, tubesheet, and mist eliminators damaged

Confidential

Acid System Failures – Distribution and Mist

Elimination

Contributors:

Corroded distributors

Plugged seal cups

Acid on the tubesheet

Damaged mist eliminators

Confidential

Acid System Failures – Distribution and Mist

Elimination

Bad Stack

Plugged and

corroded heat

exchanger

Black catalyst

Confidential

Thank you.