Post on 24-Jul-2020
ACCESSING DISTRIBUTED NATURAL GAS: A SYSTEMS PERSPECTIVE Richard Pattison
The University of Texas at Austin – McKetta Department of Chemical Engineering
Background – Stranded and Associated Gas
“Thinking Small” – Proposed Gas-To-Liquids Concept
Stranded gas: Small, remote deposits
too difficult and/or expensive to extract
~7000 tcf worldwide
Associated gas: Found within oil wells –
often flared or reinjected
~4.5 trillion megajoules wasted in
2011
~$100 Billion oil equivalent
Challenges:
Logistical - transportation
• Pipeline
• Liquefaction
• Gas-to-liquids
Technological: Gas-To-Liquids
efficient scale down
Goal: Develop small, cheap, “intensified” Gas-To-Liquids (GTL) process with
higher efficiency, and lower capital costs
GTL uses Methane steam reforming (MSR) followed by Fischer Tropsch
synthesis (FT) to convert natural gas into synthetic crude.
Novel Control Approaches
Stranded gas feed pressure and
composition fluctuate over time affecting the
temperature profile in the reactors.
Temperature excursions can damage the
reactors and catalysts. We modelled the
reactors with Phase Change Material confined
within the reactor structure to prevent local
temperature excursions during disturbances.
Simulations showed excellent disturbance
rejection.
We segmented catalyst geometry to modulate
reactor temperatures.
Current and Future Work
Optimize the process under uncertain
operating conditions
Tmelt
z
Tsafe
Simulations show reactor temperatures reduced by
100OC without a reduction in performance.
Vision:
• 500 barrel/day modular GTL plant
• ~$6 Million investment
• ~10 tons
• 10 meters long x 2 meters wide x 3 meters tall
• Transportable by train/truck to production wells
[1] Pattison, R.C. and Baldea, M. A thermal-flywheel approach to distributed temperature control in microchannel reactors. AIChE Journal. 2013. [2] M. Baldea, R.C. Pattison, Energy storage-based temperature control in microchannel reactors, patent application pending [3] A Thermal-Flywheel Approach to Distributed Temperature Control in Microchannel Reactors, R.C. Pattison, M. Baldea, American Institute of Chemical Engineers Annual Meeting, Pittsburgh, PA, October 28 – November 2, 2012
Stranded deposits are geographically separated from consumers
Major deposits: Russia (Eastern), Middle East, South America
Major consumers: United Sates, Europe, Russia (Western), China
Source: BP
Channel thickness ~ 1 mm
Catalyst coatings ~ 10 μm
The intensified process concept utilizes CPRs for MSR and FT. Mass
and energy recycle streams make the process tightly integrated and
highly efficient:
Re
form
ing
Co
mb
ustio
n
Reforming catalyst
Blank section
Combustion catalyst
Wall plate
Catalytic Plate Reactors (CPRs) place exothermic and endothermic reaction
in close contact. Small length scales and large surface areas promote process
intensification by reducing sizes and capital costs by an order of magnitude.
Develop novel pseudo-transient method for
simulating and optimizing high dimensional
nonlinear systems
𝑓1 𝑥1, 𝑥2, … 𝑥𝑛 = 0 𝑓2 𝑥1, 𝑥2, … 𝑥𝑛 = 0 … 𝑓𝑛 𝑥1, 𝑥2, … 𝑥𝑛 = 0
𝜏1𝑑𝑥1𝑑𝑡
− 𝑓1 𝑥1, 𝑥2, … 𝑥𝑛 = 0
𝜏2𝑑𝑥2𝑑𝑡
− 𝑓2 𝑥1, 𝑥2, … 𝑥𝑛 = 0
…
𝜏𝑛𝑑𝑥𝑛𝑑𝑡
− 𝑓𝑛 𝑥1, 𝑥2, … 𝑥𝑛 = 0
Enhanced sensing techniques – measure electrical resistance along reactor
Use Principal Component Analysis (PCA) to detect temperature/composition disturbances
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
800
900
1000
1100
1200
1300
Tem
per
atu
re (
K)
Dimesionless axial coordinate ()
Base case
Segmented Catalyst
100OC
PCM
Steady State profile Disturbance
Stranded GasMSR FT
Synthetic Crude