# Presentation: 695319

## Acid Gas Removal Options for Minimizing Methane EmissionsLessons Learned from Natural Gas STAR

**Processors Technology Transfer Workshop**
** ****Pioneer Natural Resources, Inc., **
**Gas Processors Association and**
**EPA’s Natural Gas STAR Program**
**September 23, 2004**

## Acid Gas Removal: Agenda

- Methane Losses
- Methane Recovery
- Is Recovery Profitable?
- Industry Experience
- Discussion Questions

## Methane Losses from Acid Gas Removal

- There are 291 acid gas removal (AGR) units in gas processing plants1
**Emit 644 MMcf annually****1**
**6 Mcf/day emitted by average AGR unit****1**
**Most AGR units use diethanol amine (DEA) process or Selexol****TM**** process**

- 1Inventory of U.S. Greenhouse Gas Emissions and  Sinks 1990 - 2002

## What is the Problem?

- 1/3 of U.S. gas reserves contain CO2 and/or N21
- Wellhead natural gas may contain acid gases
**H****2****S, CO****2,**** corrosive to gathering/boosting, transmission lines and distribution equipment**
**Off-spec pipeline quality gas**
- Acid gas removal processes typically use DEA to absorb acid gas
- DEA regeneration strips acid gas (and absorbed methane)
**CO****2**** (with methane) is typically vented to the atmosphere**
**H****2****S is typically flared or sent to sulfur recovery**

- 1http://www.engelhard.com/documents/GPApaper2002.pdf

## Typical Amine Process

**Filter**

**Exchanger**

**Booster Pump**

**Flash Tank**

**Sour Gas**

**Sweet Gas**

**Contractor (Absorber)**

**Rich Amine**

**Lean Amine**

**Stripper (DEA)**

**Condenser**

**H****2****S to sulfur plant or flare**

**Reflux Pump**

**Reboiler**

**Heating Medium**

**CO****2**** to atmosphere**

**Notes:**
I think this process diagram is too much for our purposes...suggest removing pumps & exchangers.

## Methane Recovery - New Acid Gas Removal Technologies

- GTI & Uhde Morphysorb® Process
- Engelhard Molecular Gate® Process
- Primary driver is process economics, not methane emissions savings
- Reduce methane venting by 50 to 100%

## Morphysorb®  Process

**Absorber**

**Crude Gas**

**Flash 1**

**Flash 2**

**Clean Gas**

**Flash 3**

**Flash 4**

**Acid Gas**

**Compression**

**Compression**

**Pump**

## Morphysorb® Process

- Morphysorb® absorbs acid gas but also absorbs some methane
**Methane absorbed is 66% to 75% lower than competing solvents****1**
- Flash vessels 1 & 2 recycled to absorber inlet to minimize methane losses
- Flash vessels 3 & 4 at lower pressure to remove acid gas and regenerate Morphysorb®

- 1Oil and Gas Journal, July 12, 2004, p57

## Is Recovery Profitable?

- Morphysorb® can process streams with high (>10%) acid gas composition
- 30% to 40% Morphysorb® operating cost advantage over DEA or SelexolTM 2
**66% to 75% less methane absorbed than DEA or Selexol****TM**
**About 33% less THC absorbed****2**
**Lower solvent circulation volumes**
- At least 25% capital cost advantage from smaller contactor and recycles2
- Flash recycles 1 & 2 recover ~80% of methane that is absorbed1

- 1Oil and Gas Journal, July 12, 2004, p57, Fig. 7
- 2GTI

## Industry Experience - Duke Energy

- Kwoen plant does not produce pipeline-spec gas
**Separates acid gas and reinjects it in reservoir**
**Frees gathering and processing capacity further downstream**
- Morpysorb® used in process unit designed for other solvent
- Morphysorb® chosen for acid gas selectivity over methane
**Less recycle volumes; reduced compressor horsepower**

## Methane Recovery - Molecular Gate® CO2 Removal

**Methane Recovery - Molecular Gate****®**** CO****2 ****Removal**

- Adsorbs acid gas contaminants in fixed bed
- Molecular sieve application selectively adsorbs acid gas molecules of smaller diameter than methane
- Bed regenerated by depressuring
**5% to 10% of feed methane lost in “tail gas” depressuring**
**Route tail gas to fuel **

**CH****4**

**CO****2**

**C3+ adsorbed on binder**

## Molecular Gate® Applicability

- Lean gas
**Gas wells**
**Coal bed methane**
- Associated gas
**Tidelands Oil Production Co.**
- 1 MMcf/d
- 18% to 40% CO2
- Water saturated
**Design options for C****4****+ in tail gas stream**
- Heavy hydrocarbon recovery before Molecular Gate®
- Recover heavies from tail gas in absorber bed
- Use as fuel for process equipment

- Source: http://www.engelhard.com

## Molecular Gate® CO2 Removal

**Molecular Gate****®**** CO****2**** ****Removal**

**10 psi pressure drop**

**Product**
**95% of C****1**
**90% of C****2**
**50% of C****3**

**5 psia**

**Tail Gas**
**5% of C****1**
**10% of C****2**
**50% of C****3**
**C****4****+**
**CO****2**
**H****2****S**
**H****2****O**

**Enriched C1**** **
**30 psia**

**High Pressure Feed**
**  ****C****1**
**  ****C****2**
**  ****C****3**
**  ****C****4****+**
**  ****CO****2**
**  ****H****2****S**
**  ****H****2****O**

**Pressure Swing Adsorption**

**Vacuum**
**Compressor**

**C4+ Recovery**

**Dehydration**

## Industry Experience - Tidelands Molecular Gate® Unit

- http://www.Engelhard.com/documents/CO2%20Removal-1.pdf

- First commercial unit started on May 2002
- Process up to 10 MMcf/d
- Separate recycle compressor is required
- No glycol  system is required
- Heavy HC removed with CO2
- Tail gas used for fuel is a key optimization: No process venting
- 18% to 40% CO2 removed to pipeline specifications (2%)

## Is Recovery Profitable?

- Molecular Gate® costs are 20% less than amine process
**9 to 35 ****¢ / ****Mcf product depending on scale**
- Fixed-bed tail gas vent can be used as supplemental fuel
**Eliminates venting from acid gas removal**
- Other Benefits
**Allows wells with high acid gas content to produce (alternative is shut-in)**
**Can dehydrate and remove acid gas to pipeline specs in one step**
**Less operator attention**

## Comparison of AGR Alternatives

|  | Amine Process | Morphysorb®  Process | Molecular Gate® CO2
 |
| --- | --- | --- | --- |
| Absorbent or
Adsorbent | Water & Amine | Morpholine Derivatives | Titanium Silicate |
| 
Regeneration | Reduce Pressure & Heat | Reduce Pressure
 | Reduce Pressure to Vacuum
 |
| Primary Operating Costs | Amine & Steam | Electricity | Electricity |
| Capital Cost

Operating Cost | 100%

100% | 75%

60% – 70% | <100%

80% |

- 1http://www.gastechnology.org
- 2http://www.engelhard.com

## Discussion Questions

- Have you studied either of these technologies?
- What are the barriers (technological, economic, lack of information, regulatory, focus, manpower, etc.) that are preventing you from** **implementing either of these technologies?