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