Water content in hydrate slurry is frozen to form hydrate-ice blocks at 241 K. Blocks are then depressurized to 1 atm and handled in solid form. 1 mtpa, 750 psia, 388 K 6.47 mtpa, 750 psia, 298K 19.41 mtpa, 750 psia, 273K 7.47 mtpa, 14.7 psia, 241K 750 psia, 273K
H YDRATE S YNTHESIS CSTR For 1.5 mtpa methane production: V total =(3,130 mol CH 4 /s)/(1.29 mol/m 3 * s) V total =2,430 m 3 32 reactors used V reactor = 76 m 3 Perry, R., & Green, D. (1997). Perry's Chemical Engineers' Handbook (7th ed.). McGraw-Hill.
H YDRATE S YNTHESIS CSTR Equipment Cost: $1,760,000 Perry, R., & Green, D. (1997). Perry's Chemical Engineers' Handbook (7th ed.). McGraw-Hill.
H YDRATE S YNTHESIS Compressors Compressors sized using PRO II Compressor Equipment Cost: Recycle Compressor Cost: $2,200,000 Intake Compressor Cost: $870,000 Total Cost: $3,070,000 Perry, R., & Green, D. (1997). Perry's Chemical Engineers' Handbook (7th ed.). McGraw-Hill.
H YDRATE S YNTHESIS Pumps Pumps sized using P = HQη/3960 H = 150ft n = 74% Q = 3,800 lb/s Pump cost: $690,000 Perry, R., & Green, D. (1997). Perry's Chemical Engineers' Handbook (7th ed.). McGraw-Hill.
H YDRATE S YNTHESIS Heat Exchangers Heat exchangers sized using: Q=UAT Heat exchanger cost based on area Initial Cooling Heat Exchanger Area: 35,000 ft 2 Initial Cooling Heat Exchanger Cost: $235,000 Post Cooling Heat Exchanger Area: 16,000 ft 2 Post Cooling Heat Exchanger Cost: $113,000 Perry, R., & Green, D. (1997). Perry's Chemical Engineers' Handbook (7th ed.). McGraw-Hill.
H YDRATE T RANSPORTATION Capacity 145,000 metric tons Capacity of 186,000 m 3 Length 290m Beam 45m Draught 18m Base price $165,000,000 UNCTAD, S. (2007). Review of Maritime Transport. New York and Geneva: United Nations.
H YDRATE T RANSPORTATION - S LURRY Slurry Transport Advantages Faster loading and unloading (8400 – 14000 tons per hour). Ease of handling hydrate as fluid. Slurry Transport Disadvantages Loss of ship capacity to anti- freezing agents (4% - 5% of cargo weight). Additional equipment required to remove anti-freezing agents from gas.
H YDRATE T RANSPORTATION - S OLID Solid Transport Advantages Simplified regasification facility. Slightly more capacity per ship than with slurry (4% - 5%). Solid Transport Disadvantages Slower loading and unloading (2000 – 4000 tons per hour). Additional solid handling equipment required.
H YDRATE T RANSPORTATION DistanceTransit Time (18kts) Total Trip Time (Slurry/Solid) Total Time Savings With Slurry 1000 mi4.6 days7.8 days/9.1 days14.3% 2000 mi9.3 days12.5 days/13.8 days 9.4% 3000 mi13.9 days17.1 days/18.4 days 7.1% 4000 mi18.5 days21.7 days/23 days5.7% 5000 mi23.1 days26.3 days/27.6 days 4.7% Slurry handling is the best option for shipping distances of 2500 miles or less. Solid handling is the best option for shipping distances of 3500 miles or more.
H YDRATE T RANSPORTATION Hydrate is stored in ship at equilibrium with either temperature or pressure. The two limiting conditions are 1 atm of pressure at 241 K or 85 atm of pressure at 285 K. Determinants of optimum pressure and temperature are cost and weight of steel required in hydrate storage vessel.
H YDRATE T RANSPORTATION Faupel formula used to determine minimum steel thickness necessary for hydrate storage vessel. Minimum Bursting Pressure = (2/3)*Yield Tensile Strength*ln(Ratio of Inner and Outer Diameters) 1020 carbon steel used. Yield tensile strength of 1020 carbon steel is 350 Mpa.
H YDRATE T RANSPORTATION Ambient Temperature Tank Outer Diameter 29.5 m Tank Thickness 0.31m Steel Weight (if full length of vessel) 113000 tons 0.31m 29.5m
H YDRATE T RANSPORTATION Atmospheric Pressure Tank Outer Diameter 29.5 m Tank Thickness 3.65mm Steel Weight (if full length of vessel) 1300 tons 3.65mm 29.5m
H YDRATE T RANSPORTATION Shipping cost for 1.5 mtpa and distance of 4000 miles. Shipping at ambient temperature (FCI): $2,050,000,000 Shipping at atmospheric pressure (FCI): $1,100,000,000
H YDRATE T RANSPORTATION Ballast Inner Hull Insulation Inner Membrane Outer Membrane
H YDRATE T RANSPORTATION 3585 40 ton ice-hydrate blocks required
H YDRATE T RANSPORTATION Refrigeration can be used to prevent hydrate dissociation. With 4 of polyurethane insulation and a well- sealed cargo hold, 1.5 tons of refrigeration are required. Cost of refrigeration $6,300
Pressure Vessel size based on required production level of natural gas. For 1.5 mtpa capacity. 44 pressure vessels: V = 294 m 3 $5,400,000 776 storage vessels: V = 150 m 3 $30,000,000 Perry, R., & Green, D. (1997). Perry's Chemical Engineers' Handbook (7th ed.). McGraw-Hill.
H YDRATE D ISSOCIATION 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 $40,000,000 Rueff, R. M., Sloan, E. D., & Yesavage, V. F. (1988). Heat Capacity and Heat of Dissociation of Methane Hydrates. AIChE Journal, 1468-1476.
P RODUCTION S UMMARY The natural gas hydrates are produced in a stirred tank reactor. The hydrates are frozen into blocks and loaded onto ships. The ships have small refrigeration units to keep the blocks frozen. The ships are at atmospheric pressure
P RODUCTION S UMMARY The blocks of hydrates are decomposed in a pressurized vessel. The hydrate leaves the vessel at pipeline pressure.
LNG C OST E STIMATION Cost data for LNG was obtained at plant capacities of 1 mtpa, 2 mtpa, and 3.5 mtpa.
LNG C OST E STIMATION Costs are taken as the average costs for a range of plant designs.
LNG C OST E STIMATION Operating Cost CapacityLiquification (2007$/ton)Regasification (2007$/ton) 100000071.2511.875 200000061.757.125 350000052.254.75
LNG C OST E STIMATION 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. UNCTAD, S. (2007). Review of Maritime Transport. New York and Geneva: United Nations.
E CONOMIC C OMPARISON The TAC per ton of methane produced is plotted against capacity in tons.
E CONOMIC C OMPARISON 0 miles shows the TAC per ton that comes from the production and regasification plants. Production Regasification
E CONOMIC C OMPARISON Distance from Algeria to Cove Point, Maryland is about 4000 miles. TAC per ton is shown for 1000 – 5000 miles.
Increasing distance increases the TAC/ton. Adding ships causes a sharp increase in TAC/ton.
LNG has a lower TAC/ton for transportation distances greater than 0 miles.
Increasing transportation distance increases the difference in the TAC/ton for LNG and NGH.
E CONOMIC C OMPARISON The cost of shipping LNG is less than the shipping cost for NGH. LNG has a higher energy density than NGH. 1 ton LNG = 1 ton natural gas 1 ton hydrate = 0.134 tons natural gas and 0.866 tons water. NGH requires 7 times the shipping weight of LNG.
E CONOMIC C OMPARISON For 1.5 mtpa transported 4000 miles
E CONOMIC C OMPARISON The FCI per ton of natural gas is plotted against the capacity in tons. 0 miles shows the FCI for the production and regasification plants.
FCI/ton increases with transportation distance. Adding ships produces a large increase in FCI/ton.
E CONOMIC C OMPARISON The ROI is found by dividing the profit by the TCI. The TCI is found by assuming that TCI=FCI+WC=FCI/0.85 The profit is taken as sales-cost-depreciation, or sales-TAC. Sales is varied between $0 and $200 per ton of methane
E CONOMIC C OMPARISON ROI is found by: ROI=((Sales-TAC)/TCI)*(ton/ton) ROI=(Sales/ton-TAC/ton)/(TCI/ton) ROI=((Sales/ton)/(TCI/ton))-((TAC/ton)/(TCI/ton)) (TCI/ton) and (TAC/ton) have already been calculated, therefore (Sales/ton) is only thing to vary.
As distance increases the sales increases to $180/ton to maintain a positive ROI.
As distance increases the sales increases to slightly above $120/ton to maintain a positive ROI.
Natural gas hydrate peak-shaving has a lower TAC/ton and FCI/ton than LNG.
Natural gas hydrate peak-shaving has a higher ROI than LNG.
C ONCLUSION 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. 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.