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

1. Natural Gas Hydrate Transportation* David Mannel**, David Puckett**, and Miguel Bagajewicz University of Oklahoma- Chemical Engineering (*) This work was done as part of the capstone Chemical Engineering class at the University of Oklahoma (**) Capstone Undergraduate students   Economic Comparison • Natural Gas Hydrate Synthesis • Abstract We 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. • Natural Gas Hydrates • Liquefied Natural Gas • CSTR cost $1,760,000 • Compressor Equipment Cost: • Recycle Compressor Cost: $2,200,000 • Intake Compressor Cost: $870,000 • Total Cost: $3,070,000 Increasing distance increases the TAC/ton. Adding ships causes a sharp increase in TAC/ton. Increasing distance increases TAC/ton. - - Natural 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. • Heat exchanger cost • Initial Cooling Heat Exchanger Cost: $235,000 • Post Cooling Heat Exchanger Cost: $113,000 Hydrates • Pump cost: • $690,000 The natural gas hydrates are produced in a stirred tank reactor, and then they are frozen into blocks and loaded onto ships. The required fixed capital investment is $23,000,000 with a production rate of 1.5 million tons per annum. All equipment prices are given for a production of 1.5 million tons per annum. • Peak-Shaving A positive ROI occurs with sales of $100/ton for low production capacities. Natural gas hydrate peak-shaving has a lower TAC/ton and FCI/ton than LNG. A positive ROI occurs with sales of $80/ton. - • Natural Gas Hydrate Transportation Ambient Temperature Tank Outer Diameter 29.5 m Tank Thickness 0.31m Steel Weight 113000 tons Atmospheric Pressure Tank Outer Diameter 29.5 m Tank Thickness 3.65mm Steel Weight 1300 tons • Capacity 145,000 metric tons • Capacity of 186,000 m3 • Length 290m • Beam 45m • Draught 18m • Base price $165,000,000 3585 40 ton ice-hydrate blocks required Natural gas hydrate peak-shaving has a higher ROI than LNG. As distance increases the sales increases to slightly above $120/ton to maintain a positive ROI. As distance increases the sales increases to $180/ton to maintain a positive ROI. • 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. 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 gas hydrates is $1,100,000,000. • LNG • Natural Gas Hydrate Regasification • 44 pressure vessels: • V = 294 m3 • $5,400,000 • 776 storage vessels: • V = 150 m3 • $30,000,000 • Costs are taken as the average costs for a range of plant designs. • 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. • 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 • Cost data for LNG was obtained at plant capacities • of 1 mtpa, 2 mtpa, and 3.5 mtpa. • References • Pinnau, & Toy. (1996, January 10). Gas and vapor transport properties of amorphous perfluorinated copolymer membranes. 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Perry's Chemical Engineers' Handbook (7th ed.). McGraw-Hill. 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. 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.