Natural Gas Hydrate Transportation* David Mannel**, David Puckett**, and Miguel Bagajewicz

University of Oklahoma- Chemical Engineering

AbstractWe investigate the possible use of hydrates for natural gas transportation using shops. Natural gas hydrates were found to be economically less favorable than LNG for the transportation of natural gas. However, natural gas hydrates were found to be economically viable for small capacity peak-shaving plants and natural gas storage.

The ships have small refrigeration units to keep the blocks of hydrate frozen, since they are shipped at atmospheric pressure.For a shipping distance of 4,000 miles and 1.5 million tons of hydrate per annum, the fixed capital investment for shipping the natural gashydrates is $1,100,000,000.

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The natural gas hydrates are produced in a stirred tank reactor, and then they are frozen into blocks and loaded onto ships. The required fixedcapital investment is $23,000,000 with a production rate of 1.5 million tons per annum. All equipment prices are given for a production of1.5 million tons per annum.

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LNG has a lower TAC and a higher ROI.LNG is a proven and well developed technology.

LNG is a better option than NGH for the transport of natural gas.

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LNG

Natural Gas Hydrate Synthesis

Peak-Shaving

The TAC/ton, FCI/ton, and ROI is better for NGH with transportation distances of 0 miles.

NGH is a better option for peak-shaving the cost of natural gas.

References

The blocks of hydrates are decomposed in a pressurized vessel, and then leaves the vessel at pipeline pressure.The fixed capital investment for the regasification facility is $140,000,000 for a production rate of 1.5 million tons per annum.

Natural Gas Hydrate Transportation

Natural Gas Hydrate Regasification

Liquefied Natural Gas Natural Gas Hydrates

PC

FC

Low PressureSteam

Condensate

SolidIce-Hydrate

Natural Gas toWater Removal

PressureVessel

Heating KettleLiquid Water

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NGH TAC vs Capacity

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Increasing distance increases the TAC/ton. Adding ships causes a sharp increase in TAC/ton.

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LNG TAC per ton

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Increasing distance increases TAC/ton.

A positive ROI occurs with sales of $80/ton.

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A positive ROI occurs with sales of $100/ton for low production capacities.

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NGH ROI 4000 miles

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As distance increases the sales increases to $180/ton to maintain a positive ROI.

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LNG 4000 miles

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As distance increases the sales increases to slightly above $120/ton to maintain a positive ROI.

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NGH vs LNG Peak-Shaving

NGH FCI/ton

LNG FCI/ton

NGH TAC/ton

LNG TAC/ton

Natural gas hydrate peak-shaving has a lower TAC/ton and FCI/ton than LNG.

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NGH vs LNG Peak-Shaving

NGH ROI ($100/ton)

LNG ROI ($100/ton)

Natural gas hydrate peak-shaving has a higher ROI than LNG.

CSTR cost $1,760,000

Compressor Equipment Cost:

Recycle Compressor Cost: $2,200,000

Intake Compressor Cost: $870,000

Total Cost: $3,070,000

Pump cost:$690,000

Heat exchanger costInitial Cooling Heat Exchanger Cost: $235,000Post Cooling Heat Exchanger Cost: $113,000

44 pressure vessels:V = 294 m3

$5,400,000

776 storage vessels:V = 150 m3

$30,000,000 Heating Costs for the kettle

Found using the heat of dissociation of methane hydrates, the specific heats of hydrate and water, and the required gas flow rate.

Cost of 1 MM BTU assumed to be $7.33

Total heating cost$40,000,000

Shipping costs are contracted out at $65,000/day for 57,000 tons LNG. The total annualized cost for a LNG tanker is less than $23,000,000/year, or $63,000/day.Contracting out the shipping is the worse case scenario for LNG.

Capacity 145,000 metric tons

Capacity of 186,000 m3

Length 290mBeam 45mDraught 18mBase price $165,000,000

Atmospheric PressureTank Outer Diameter29.5 mTank Thickness3.65mmSteel Weight1300 tons

Ambient Temperature Tank Outer Diameter29.5 mTank Thickness0.31mSteel Weight113000 tons

358540 ton ice-hydrate blocks required

(*) This work was done as part of the capstone Chemical Engineering class at the University of Oklahoma(**) Capstone Undergraduate students  

Cost data for LNG was obtained at plant capacities

of 1 mtpa, 2 mtpa, and 3.5 mtpa.

Costs are taken as the average costs for a range of plant designs.

Economic Comparison

Ballard, A. L., & Sloan, E. D. (2001). Hydrate phase diagrams for methane + ethane + propane mixtures. Chemical Engineering Science (53), 6883-6895.

Englezos, Kalogerakis, Dholabhai, & Bishnoi. (1987, November). Kinetics of formation of methane and ethane gas hydrates. Chemical Engineering Science , 2647-2666.

Koh, C. A., & Sloan, E. D. (2007). Natural gas hydrates: Recent advances and challenges in energy and environmental applications. AIChE Journal , 53 (7), 1636-1643.

Perry, R., & Green, D. (1997). Perry's Chemical Engineers' Handbook (7th ed.). McGraw-Hill.

Pinnau, & Toy. (1996, January 10). Gas and vapor transport properties of amorphous perfluorinated copolymer membranes. Journal of Membrane Science , 125-133.

Rueff, R. M., Sloan, E. D., & Yesavage, V. F. (1988). Heat Capacity and Heat of Dissociation of Methane Hydrates. AIChE Journal , 1468-1476.

Sloan, E. D. (2003). Fundamental Principles and Applications of Natural Gas Hydrates. Nature , 426, 353-359.

Stopford, M. (1997). Maritime Economics (2nd ed.). Routledge.

UNCTAD, S. (2007). Review of Maritime Transport. New York and Geneva: United Nations.

HydratesNatural gas hydrates are a small molecule of gas (methane, ethane, propane) that become encapsulated in a cage of water at low temperatures and high pressures.