1000
Average
High
Low
800
600
400
200
0
2004
2006
2008
2010
2012
2014
2016
2018
2020
2022
Year
Figure 4 Historical pricing of anhydrous NH 3
Technology enhancements for Capex/Opex savings Bechtel continues to develop enhancements to the basic technology to help reduce the Capex and Opex of the facility and, therefore, the cost to produce the NH 3 . One of the lat- est patented enhancements is the addition of the ‘Bolt-On Absorber’ concept. The Bolt-On concept (see Figure 3 ) is used where a client has an existing sour water stripper producing a good-quality sour water stripper acid gas. By adding a water wash column in the sour water stripper acid gas line from the SWS or on a common feed line to the SRU, the NH 3 and some of the H 2 S are removed, leaving a high-quality H 2 S stream. The concentrated sour water stream from the bottom of the Bolt-On absorber is used as the feed for a smaller SWSPlus unit. The high-quality H 2 S stream from the Bolt-On Absorber is mixed with the H 2 S stream from the SWSPlus unit. They become the new feed to the existing
Claus sulphur recovery unit or sulphuric acid plant. This approach has the operational advantage of easily return- ing to normal operation (SWSAG to SRU by turning three diverter valves) if the SWSPlus is out of service for some reason. NH 3 market and historical use of SWSPlus Typical specifications for anhydrous ammonia and aqueous ammonia are below. Commercial-grade anhydrous NH 3 • 99.5 wt% NH 3 minimum • <0.5 wt% H 2 O maximum • 0.58 specific gravity at 100ºF • 5-10 ppmw oil maximum • Vapour pressure is approximately 200 psig at 100ºF (13.6 bar at 38ºC)
Path forward options : Another 500 MTPD SRU train (status quo) Stack emission
Sweet gas
Today : A facility has 1000 US gpm (227 tonnes/hr) of sour water and 700 MPTD sulphur
AAG
ARU
Stack emission
Sweet gas
Sour gas
Tail gas
Vent gas
AAG
ARU
SRU
TGTU
TOU
Sour gas
Tail gas
Vent gas
Sour water
SRU
TGTU
TOU
Stack emission
SWS
SWSAG
Sour water
Stripped water
SWS
Tail gas
Vent gas
SWSAG
Stripped water
SRU
TGTU
TOU
SWSPlus and a B olt- O n Absorber: Keeps the existing SWS and uses a smaller SWSPlus
Stack emission
Sweet gas
AAG
ARU
SWSPlus : Idle the existing SWS and no new SRU train
Stack emission
Sour gas
Sweet gas
Tail gas
Vent gas
AAG
ARU
SRU
TGTU
TOU
Sour gas
Tail gas
Vent gas
Sour water
SWS
SRU
TGTU
TOU
SWS
Stripped water
SWSAG
H S
Stack emission
Sour water
H S
SWSPlus Bolt- O n
H S
NH for sale
Tail gas
Vent gas
Stack emission
Concentrated sour water
Recycled water
SWSPlus
SRU
TGTU
TOU
Tail gas
Vent gas
H S
Smaller SWSPlus
Stripped water
SRU
TGTU
TOU
NH for sale
Figure 5 Case study comparing pre- and post-expansion
100
PTQ Q1 2023
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