NANO-POROUS MEMBANES IN GAS PROCESSING

By Chris HeflinRachael HoukMike Jones

A theoretical analysis of non-chemical separation of hydrogen sulfide from methane by nano-porous membranes using capillary condensations from Chemical Engineering and Processing

INTRODUCTION

Natural Gas as it comes out of ground needs to have H2S removed before further processing Starting levels can be high (>5%) For US pipelines, limit is 4 ppm

Traditionally done through chemical means

One alternative is to use a nano-porous membrane to achieve a physical separation

Image Source: http://chemistry.about.com/od/factsstructures/ig/Chemical-Structures---H/Hydrogen-Sulfide.htm

CONVENTIONAL H2S SEPARATION

Traditional methods Wash with MEA, DEA, or other amines Use an oxide adsorbent

Disadvantages Consumes these chemicals Added hazards due to additional chemical

at site

AMINE WASH SEPARATION

Removes H2S, CO2, and mercaptans

Need a lot of equipment

Need both heating and cooling utilities

Image from http://en.wikipedia.org/wiki/Amine_gas_treating

OXIDE ADSORBENT

Excellent separation achieved Can have significant pressure drop Need high temperatures Use iron oxide or zinc oxide

Image from http://www.cwaller.de/sorbents.htm

CRITERIA FOR A GOOD MEMBRANE

Good selectivity in allowing H2S through and not CH4, only a small amount of CH4 dissolved in liquid H2S phase

Minimal pressure drop in bulk phase

MECHANISM

Bulk PhasePermeateH2S

H2S

H2S

H2S

CH4

CH4

CH4

CH4

CH4

CH4

FLOW

Nano-porous membrane

Not to scale

NANO-POROUOS MEMBRANES

Images from www.mdpi.com/1996-1944/3/1/165/ag sites.google.com/.../home/MAIN_NANO_2.jpgwww3.interscience.wiley.com/.../ncontent

TEMPERATURE VS PERMEABILITY

SEPARATION FACTOR

Where

x = mole fraction in the pore

y = mole fraction in the bulk

TEMPERATURE VS SEPARATION

So, How Are Nanoporous

Membranes Made?

SELF-ORDERING ELECTROCHEMICAL PROCESS A schematic diagram

showing pore formation by electrochemical self-ordering

A. Scheme of electrochemical cell for anodization and corresponding electrochemical reactions.

B. Scheme of pore formation, which includes several steps:

(I) the formation of oxide layer on metal surface;

(II) local field distributions caused by surface fluctuations;

(III) the initiation of pore growth by field-enhanced dissolution; and

(IV) the pore growth in steady-state condition

C. Typical current density curve obtained with anodization showing these stages

CYCLIC ANODIZATION

New development by Dr. Ducas Losic of the University of South Australia

A series of fabrication protocols to precisely control their most critical parameters, including pore diameters, pore geometry and surface chemistry

CONCLUSION

H2S separation is necessary: traditional methods are ok, but nano-porous membranes could do better

The H2S condenses and flows through the membrane to separate; this depends on temperature and pressure

Membranes can be made through self-ordering electrochemical process and cyclic anodazition

FURTHER RESEARCH

Gas mixtures of more than just methane and hydrogen sulfide, like actual natural gas

Optimized temperature and pressure Better manufacturing techniques,

particularly for large scale production Try a pilot plant scale testing

REFERENCES

http://en.wikipedia.org/wiki/Amine_gas_treating http://www.chem.tamu.edu/class/majors/chem470/Synthesis

_Gas.html http://www.thefuelman.com/Documents/H2S_removal.pdf http://en.wikipedia.org/wiki/Hydrogen_sulfide “Engineering of Nanomembranes for Emerging Applications”

by Dr. Ducas Losic http://www.azonano.com/details.asp?ArticleId=2445

“Simple and reliable technology for manufacturing metal-composite nanomembranes with giant aspect ratio” by Jovan Matovića and Zoran Jakšić http://www.sciencedirect.com

“Self-ordered nanopore and nanotube platforms for drug delivery applications” by Dusan Losic & Spomenka Simovic http://informahealthcare.com/doi/pdf/10.1517/17425240903300857?cookieSet=1

Group S2 rebuttal

Chris HeflinRachael Houk

Mike Jones

• Data used showed amine needed to be replaced slowly with a fresh stream because some of it leaves in the tail gas stream

• No info available on the cost of the nano-porous membrane to compare with traditional methods

• The presentation was right after Dr. Seminario did a harsh critique of a previous presentation, so there was reason to be nervous, but we should have rehearsed more.

• Thanks for the feedback on the animation and introduction. We’ll try to continue this practice in our future presentations.

Group S1

Group S1Review of Nano Membranes for Gas

Separation

Notes on Presentation

Positive Notes• Good at answering

questions• Separation animation was

helpful• Summary of chemical

method was thorough and educational

• Good analysis of research and future development needs

Opportunities for Improvement

• Presentation was very short– Could have included more

information and spent more time on use and applications

– Lasted less than 15 minutes

• More eye contact during presentation

• Cite sources on slides– Could not have known due to

guidelines being presented right before

Group S1

Grade

• Slides (20/20)– Informative, well designed

• Oral presentation (19/20)– Good skills but needed more eye contact

• Graphics (18/20)– Needed a few more pictures and diagrams

• Educational Value (20/20)– Topic was well explained

• Group Analysis of Research (19/20)– Needed a little more research on topic for thoroughness

• Overall (96/100)

Group S1

GROUP S3Review: nanoporous

membranesGroup S3:

Michael KoettingBradford Lamb

James Kancewick

Review

The presentation was informative and the slides were generally well done.

Student questions were answered confidently and in detail.

Presentation was not too detailed to be understandable by the audience, yet still detailed.

Review

Speaking could have been more polished, with more eye contact from some of the speakers and less reading from slides/notes.

Some figures in the slideshow were not explained, so they added very little to the presentation.

Despite this, however, the presentation was very good on the whole.

Scott MarwilDanielle MillerJoshua Moreno

Group S4

Group S4Review of Nano Membranes

for Gas Separation

Things Done Well

Very good job with the illustrations and the animations The group did a good job of answering the classes

questions in a full and in-depth manner The group members presenting knew the material and

did an good job relaying that knowledge onto the rest of the class

The Group was very well spoken They made good use of animations and pictures to

illustrate points Their introduction was very thorough and well written The material was presented in an interesting and

exciting way

Group S4

Things That Need Improvement The overall presentation was a little on the short

side. The group needs to develop a better introduction

to introduce the topic and background to the class instead of just jumping to the heart of the material so quickly

Sometimes the slides contained a bit too much information. They should try limit the amount of information on the slides so they can draw attention to the speaker.

The Not-So-Good

Group S4

Pradip RijalJason SavatskyTrevor SeidelLaura Young

Group S5

Group S5Review of Nano Membranes for Gas

Separation

Presentation Review

• The groups power presentation and visuals were very well done.

• They probably should have practiced the presentation a little more. The oral presentation was weak and unfocused.

• Their attire was appropriate for the occasion.

Group S5

John BaumhardtDaniel Arnold

Michael TrevathanMichael Tran

Group S6Review of Nano Membranes for Gas

Separation

Review

• Slide layout was agreeable and pleasant to look at.• The presentation was detailed and well thought out.• The further research section is a little weak (the

natural gas composition could have included a sample composition of “actual natural gas”

• The presentation overall was quite good, but the presenters seemed a little nervous, and were reading off of the slides.

Review of Information• From a natural gas background, the disadvantages listed are

not valid. In an amine system, there are no chemicals stored on site because there are very few reasons to change the amine. Apart from wanting to try a more efficient amine, standard amine reclamation (cleaning) can be performed to regenerate the existing amine.

• Even without regeneration, amine lasts years in plants without replacement.

• We would have liked a cost comparison of the nano-porous membranes vs the traditional amine, to determine the commercial viability of the membranes in gas plants.