CA2670993A1 - System and method for economic transportation of sulfur - Google Patents

Abstract

This application relates to system and method for transporting elemental sulfur in an economically advantageous manner. Specifically, the method includes converting existing ocean and lake ships or building new ocean and lake ships to allow for the loading and transportation of a cargo of elemental sulfur in the bottom hold of the ship while the upper decks of the ship are used to carry a second cargo of containers. The invention enables elemental sulfur to be efficiently transported in a sulfur-slurry, pellet or molten sulfur form.

Description

SYSTEM AND METHOD FOR ECONOMIC TRANSPORTATION OF SULFUR
FIELD OF THE INVENTION

[0001] This application relates to system and method for transporting elemental sulfur in an economically advantageous manner. Specifically, the method includes converting existing ocean and lake ships or building new ocean and lake ships to allow for the loading and transportation of one cargo of elemental sulfur in the bottom hold of the ship while the upper decks of the ship are used to carry a second cargo of containers. The invention enables elemental sulfur to be efficiently transported in a sulfur-slurry or molten sulfur form.

BACKGROUND OF THE INVENTION

[0002] Sulfur is a well-known by-product of gas processing and is an essential ingredient for various industrial applications, including the production of sulfuric acid for use in the manufacture of phosphate fertilizers, with lesser amounts being used for the manufacture of pharmaceuticals, plastics and rubber. Elemental sulfur is routinely transported by ship, rail and truck in containment systems from the raw material source location to the buyer's location. As sulfur is a low value product, the cost of transportation from the point of production to the consumer plant is often a major factor in determining the price of sulfur to the buyer.

[0003] Elemental sulfur can be transported in a variety of forms, including solid sulfur cakes or pellets and molten sulfur in the liquid phase at 112.8 C (235 F) or higher.
Molten sulfur is typically moved through North America and Europe in insulated rail tank cars that carry about 80 tonnes per car. The cars are filled with molten sulfur and fitted with tracer lines such that the car can be heated with steam on arrival in order to return all of the sulfur to a molten state for complete unloading.

[0004] Transportation of molten sulfur across oceans is generally done in small specialty tankers of less than 20,000 tonnes and is usually confined to short distances of under 1000 kms. Molten sulfur shipments in tankers are generally restricted to transfers within Europe or between China and ports in Japan or Korea, due to the high cost of transporting molten sulfur by ship. Importantly, one of the contributing costs to the overall cost of transporting molten sulfur by ship is that the ship returns to the originating port empty.

[0005] For example, solid sulfur from Canada is typically moved to China or other markets in small pellet form in large bulk carriers of 50,000 tonnes capacity or larger.
Similar dry sulfur transfers occur between Middle East sulfur suppliers and their customers. In this case, the solid sulfur pellets are produced at a source plant usually by pouring molten sulfur droplets into a partially water-filled tower where they form a hardened pellet when they hit water at the bottom of the tower. Alternatively, another common method at sulfur production plants today is to produce hard pellets by pelletizing machines that create dustless sulfur which is generally considered easier to handle. Further still, a few sulfur plants in some countries still produce "broken" or "slab"
sulfur that consists of sulfur that has hardened and been broken into smaller pieces.
This is a very dusty product because the sulfur is friable and breaks apart during transportation. The dust can be dangerous and the shipment is frequently labeled as such. In this form, the broken sulfur is often shipped in large bags inside containers, but this adds to the cost of transporting sulfur.

[0006] Generally, an improved system and method for transporting sulfur in a safe and economically advantageous manner from its point of production to point of consumption is needed.

[0007] Recently, a process to convert elemental sulfur into a sulfur-slurry has been developed by the Alberta Research Council as described in U.S. Patent No.
5,788,896 and Canadian Patent No. 2,199,341. A sulfur-slurry is distinct from molten or solid sulfur as being comprised of a fine sulfur powder mixed with a liquid component (water or a hydrocarbon) that is able to "flow" as a result of turbulence within the slurry that keeps the sulfur powder in suspension.

[0008] Based on the foregoing, there continues to be a need to enhance the transportation efficiency of sulfur around the world. Specifically, there has been a need for a low-cost transportation system to efficiently transport sulfur in slurry form over long distances (i.e. overseas) in conjunction with other cargoes.

[0009] A review of the prior art indicates that various patents describe approaches for carrying different cargoes in the same ship at the same time or at different times depending on the return journey. Past patents also outline that a ship design can be modified to achieve different applications from the one hull to achieve more than one specialty purpose.

[0010] For example, U.S. Patent No. 2,357,477 describes a convoy of towed ocean-going cargo vessels and methods for shipping more than one cargo across the ocean at one time; U.S. Patent No. 2,107,590 describes a method for changing the characteristics of a ship and hull form of an icebreaking ship in order to create a ship that can be used for two purposes at the same time; U.S. Patent No. 1,106,193 describes a self-propelled dynamically positioned reel pipe laying ship that can handle different sizes of pipe on different legs of the voyage; U.S. Patent No. 2,198,358 describes a ship-based system for compressed natural gas transport that uses multiple high pressure cylinders to transport compressed natural gas within the hold of the ship; U.S. Patent No.
2,163,726 describes a method and system for fluid transport between two ships that uses an approach similar to designs used during World War II between corvettes and tankers in World War II in which two ships are drifting rather than under way; U.S.
Patent No.
1,052,723 describes a system for handling container cargo and a novel lifting device that uses hatchways to create a roadway within the hull for more efficient ways to move cargo within the ship; U.S. Patent No. 1,014,015 describes a ship-based system for handling two flowable cargoes of different densities on the same ship during the same voyage by a system of gates; and U.S. Patent No. 1,014,015 describes a ship cargo compartment for carrying and ventilating different types of cargo within the same ship at the same time.

SUMMARY OF THE INVENTION

[0011] In accordance with the invention, there is provided a method and apparatus for transporting elemental sulfur in an economically advantageous manner.

[0012] More specifically, there is provided a method for transporting elemental sulfur from a source location to a delivery location comprising the steps of:

a) transporting elemental sulfur from the source location to a first port via a first transportation apparatus; transferring the elemental sulfur from the first transportation apparatus to a hybrid ship wherein the hybrid ship includes a sulfur storage system and an on-deck container storage system;

b) transferring the ship from the first port to a second port;

c) transferring the elemental sulfur from the hybrid ship to a second transportation apparatus; and d) loading the on-deck container system with new containers and returning to the first port.

[0013] In one embodiment of the invention, the elemental sulfur is a sulfur-slurry in any or all of steps a), b), c) and d). In a further embodiment, the elemental sulfur is molten sulfur in any or all of steps a), b), c) and d).

[0014] In one embodiment, the hybrid ship includes a below-deck hold for containing a sulfur-slurry.

[0015] In another embodiment of the invention, the first transportation apparatus is a sulfur-slurry pipeline. In a further embodiment, the first transportation apparatus is a sulfur-slurry train car. In yet another embodiment, the first transportation apparatus is a molten sulfur train car.

[0016] In one embodiment, the sulfur-slurry comprises 85-99% (by volume) elemental sulfur; and 1-14% (by volume) liquid component, wherein the liquid component of the sulfur-slurry is selected from water or a liquid hydrocarbon.

[0017] In yet another embodiment, the method for transporting elemental sulfur further comprises the step of transporting a portion of the water or liquid hydrocarbon from the hybrid ship back to the source location.

[0018] In another aspect of the invention, the hybrid ship for simultaneously transporting sulfur and shipping containers comprises a below-deck sulfur storage system and an on-deck container storage system.

[0019] In one embodiment, the below deck sulfur storage system of the hybrid ship is a sulfur-slurry storage system or a molten sulfur storage system.

[0020] In a further embodiment, the sulfur storage system of the hybrid ship includes a compressor system for circulating compressed air through the sulfur-slurry storage system to maintain elemental sulfur in a slurry form.

[0021] In another embodiment, the sulfur storage system of the hybrid ship has a capacity of greater than 60,000 tonnes of elemental sulfur including up to 12 individual sulfur storage tanks.

[0022] In a further embodiment, the on-deck container storage system of the hybrid ship has a capacity of greater than 25,000 tonnes of shipping containers.

[0023] In one embodiment, the hybrid ship is a converted single-hull oil tanker.
BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention is described with reference to the accompanying figures in which:
Figure 1 is a sketch of a transportation process for a sulfur-slurry in accordance with one embodiment of the invention;

Figure 2 is front cross-sectional view of a hybrid ship in accordance with one embodiment of the invention;

Figure 3 is a side view of a unit train in accordance with one embodiment of the invention; and Figure 4 is a side view of a tank car in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
Overview [0025] In accordance with the invention and with reference to the figures, a system and method for the transportation of sulfur is described.

[0026] Figure 1 describes an apparatus and generalized steps within a transportation system 10 for transporting elemental sulfur (such as a sulfur-slurry) from a sulfur production site 12 to a sulfur destination site 26. While elemental sulfur can be transported in different forms in accordance with the invention, the following description primarily refers to a sulfur-slurry.

[0027] Generally, the transportation system includes a first transportation system such as a pipeline 16 to transport the sulfur-slurry from the sulfur production site to a first transportation system such as a unit train 18 with railway siding 16. The unit train transports the sulfur-slurry to an originating port 20 where the slurry is loaded onto a hybrid ship 22, whereupon the hybrid ship, also loaded with shipping containers, sails to a destination port 24. At the destination port the sulfur-slurry is offloaded onto a secondary means of transportation (i.e. train, trucks, or pipeline) to deliver the slurry to the sulfur destination site 26. Alternatively, the slurry may be converted into pellets or fertilizer directly at the destination port as may be desired. In addition, at the destination port, or another port, the containers are offloaded from the hybrid ship and new containers are loaded onto the hybrid ship for the journey back to the originating port.

[0028] Sulfur Production Site [0029] The first step in the sulfur-slurry transportation system 10 is to create a sulfur-slurry that can be transported in a fluid state. The sulfur-slurry is created at the sulfur production site 12. In accordance with sulfur-slurry technology, a sulfur-slurry consists of fine grain pulverized or micronized sulfur particles generally ranging in size from 20 to 200 microns in a solution of water, a petroleum solvent or a liquid gas such as carbon dioxide. Generally, the sulfur concentration within the slurry can range upward of 85%
during transportation of the slurry in a pipeline, and as high as 99% if the sulfur is allowed to settle during storage. In addition, the slurry can be diluted to have a lower concentration of sulfur if desired. A settled slurry can generally be restored by increasing circulation rates and/or dilution within the slurrying solution.

[0030] Pipeline [0031] A pipeline 14 is a relatively easy and low cost method of moving the sulfur-slurry from the production site 12 to another location. A pipeline can also be used to transport the sulfur-slurry from the destination port 24 to the sulfur destination site 26.

Transporting a sulfur-slurry by pipeline requires sufficient flow rates for a given sulfur concentration to ensure that the sulfur does not settle in the pipeline.

[0032] Train Transportation [0033] At an appropriate railway siding 16, sulfur-slurry is transferred from the pipeline into the unit train 18, as shown in Figure 3 and Figure 4. The unit train consists of a locomotive car 18b for powering the train and a plurality of custom built tank cars 18a (may be upwards of 50 or more tank cars) that are specifically adapted for carrying a sulfur-slurry or molten sulfur. The tank cars are connected by inter-car piping that includes a fill line 18c and flexible couplings 18d. The fill line goes through each tank car and runs from a fill point 18e in the locomotive car to the rear tank car, where it is connected to a return coupling 18f. The flexible couplings 18d connect each tank car to the adjacent tank car. The inter-car piping serves two purposes; to circulate the sulfur slurry while in transit to prevent settling of the slurry and to enable the efficient filling of all the tank cars through the one fill point. In a further embodiment when molten sulfur is being transported, the inter-car piping enables heating of the molten sulfur to maintain its fluidity.

[0034] When loading the unit train, the sulfur slurry or molten sulfur is preferably pumped into the fill line 18c through the fill point 18e. The sulfur travels through the fill line to the return coupling 18e where it enters the rear tank car. When the rear tank car reaches its capacity of sulfur slurry or molten sulfur, the sulfur flows through the flexible coupling 18d into the adjacent tank car. This process continues until all the tank cars are full of sulfur. In another embodiment, several tank cars can be filled simultaneously through a fill point located on each tank car.

[0035] Preferably, a drain 18g is located on the underside of each tank car to unload the sulfur from several tank cars simultaneously. Figure 3 shows multiple unloading facilities 18h that may be present at the railway siding.

[0036] The fill point in the locomotive car includes an appropriate system of circulating pumps with or without heaters (not shown) to ensure effective circulation of the sulfur slurry composition or molten sulfur. In one embodiment, the sulfur-slurry is kept in a slurry form by means of air being pumped through the fill line to keep the slurry mixed.

[0037] The unit train is generally an economical method for transporting the slurry to the originating port 20 where the slurry is offloaded from the train and onto the hybrid ship 22. The empty tank cars may be reloaded with some or substantially all of slurry liquid (water, petroleum solvent of liquid gas) to be transported back to the sulfur production site for use in creating the sulfur-slurry or in the production of sulfur.
That is, in the event that the slurry composition is adjusted as it loaded onto the hybrid ship, the remaining or removed slurrying liquid that is contaminated with sulfur may be transported back to the sulfur production site. For example, the sulfur-slurry composition in a rail car may be formulated with a higher liquid content whereas a sulfur-slurry container on the hybrid ship may utilize a lower liquid content. As a result, the excess liquid from the sulfur-slurry composition in the rail car may be transported back to the sulfur production site to avoid the need for disposal of the contaminated liquid and allowing for re-use of the contaminated liquid.

[0038] Hybrid Ship [0039] As shown in Figure 2, the hybrid ship and associated loading system generally includes a lower hold 40, a plurality of shipping containers 42, an upper deck 44, a plurality of sulfur storage tanks 46, a manifold 48, transportation pipes 50, a compressor unit 52, compressor pipes 54, and a container boom 56.

[0040] The hybrid ship 22 is generally designed to enable simultaneous transportation of both a fluid or semi-fluid cargo (i.e. a sulfur-slurry) and containers between the originating port and the destination port. On the return trip after the sulfur-slurry has been offloaded, different shipping containers can be transported back to the originating port on the upper deck of the ship. As a result, revenue from the transport of the shipping containers can help offset the costs of the ship returning to the originating port without sulfur in the lower hold, and the revenue from shipping both the containers and the slurry to the destination port can lower the cost of transporting the sulfur-slurry.

[0041 ] The size of the hybrid ship is generally larger than other vessels typically used to transport sulfur. In particular, the present invention contemplates ships enabling the transportation of approximately 60,000 tonnes of sulfur in up to 12 individual storage tanks 46 and 40,000 tonnes of shipping containers (approximately 2,000 units) on the deck 44. The preferred ship size is 100,000 tonnes, but the size can be increased as needed.

[0042] In addition, in one aspect of the invention, single hull oil tankers can be converted into hybrid ships as a sulfur-slurry is generally not considered to have major environmental consequences if spilled. This further reduces the cost of shipping sulfur as the capital costs of ship conversion compared to new construction are substantially lower.

[0043] As noted above, the hybrid ship is generally designed such that the fluid cargo is transported in the storage tanks 46 in the lower hold 40 of the ship while the shipping containers 42 are secured to the upper deck 44 of the ship. The manifold 48 is operatively configured to the upper deck and is used for loading and unloading the fluid cargo into and out of the storage tanks by means of the transportation pipes 50 and pumps (not shown) that connect the manifold to the storage tanks and the storage tanks to one another. Flexible pipes can connect to the manifold in port to fill or empty the storage tanks. The upper deck is open such that the shipping containers can be stacked and secured on the upper deck by means of the container boom 56 from above, which is commonly found in container ports.

[0044] In one embodiment, the sulfur-slurry is kept in a slurry form on the shipping voyage by the compressor unit 52 which pumps air through the compressor pipes 54 to keep the slurry mixed. In another embodiment, the sulfur-slurry is kept mixed by impellers in the storage tanks run by electric motors (not shown). Individual controllers are present on each storage tank to control the amount of agitation in the tank.
Appropriate sensors may be configured to the tanks to monitor the degree of agitation to prevent unwanted settling and potential solidification at the bottom of each tank 46.

[0045] Certain ports may be equipped with equipment for loading/unloading both sulfur and shipping containers. If not, it may be necessary to sail to two originating ports to separately load the sulfur-slurry and the containers, and to sail to two separate destination ports to unload the sulfur-slurry and unload the containers. At the destination port, the empty shipping containers and fluid cargo are generally offloaded by the same means as they were loaded. A new load of full shipping containers are loaded and stacked onto the upper deck of the ship and the ship can return to the originating port.

[0046] Once the sulfur-slurry is offloaded, it can be transported to the sulfur destination site as a slurry via railcar, trucks, or pipeline, or it can be turned into pellet form or fertilizer directly at the destination port and transported to the sulfur destination site.
[0047] In another embodiment, the sulfur may be transported in a molten form.
In this embodiment, the transportation equipment is modified to enable the handling of molten sulfur.

[0048] In particular, the hybrid ship would include sulfur containers and the appropriate heating system to ensure that the sulfur remains in the molten form for the duration of the voyage.

[0049] The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.

Claims (23)

1. A method for transporting elemental sulfur from a source location to a delivery location comprising the steps of:

a) transporting elemental sulfur from the source location to a first port via a first transportation apparatus;

b) transferring the elemental sulfur from the first transportation apparatus to a hybrid ship wherein the hybrid ship includes a sulfur storage system and an on-deck container storage system;

c) transferring the ship from the first port to a second port;

d) transferring the elemental sulfur from the hybrid ship to a second transportation apparatus; and e) loading the on-deck container system with new containers and returning to the first port.

2. A method as in claim 1 wherein the elemental sulfur is a sulfur-slurry in step a).

3. A method as in any one of claims 1-2 wherein the elemental sulfur is a sulfur-slurry in step b).

4. A method as in any one of claims 1-3 wherein the elemental sulfur is a sulfur-slurry in step c).

5. A method as in any one of claims 1-4 wherein the elemental sulfur is a sulfur-slurry in step d).

6. A method as in any one of claims 1-5 wherein the first transportation apparatus is a sulfur-slurry pipeline.

7. A method as in any one of claims 1-6 wherein the first transportation apparatus is a sulfur-slurry train car.

8. A method as in any one of claims 1-7 wherein the hybrid ship includes a below-deck hold for containing a sulfur-slurry.

9. A method as in claim 1 wherein the elemental sulfur is molten sulfur in step a).

10. A method as in claim 9 wherein the elemental sulfur is molten sulfur in step b).

11. A method as in claim 10 wherein the elemental sulfur is molten sulfur in step c).

12. A method as in claim 11 wherein the elemental sulfur is molten sulfur in step d).

13. A method as in any one of claims 9-12 wherein the first transportation apparatus is a molten sulfur train car.

14. A method as in any one of claims 2-8 wherein the sulfur-slurry comprises:
a) 85-99% (by volume) elemental sulfur; and, b) 1-14% (by volume) liquid component.

15. A method as in claim 14 wherein the liquid component is selected from water or a liquid hydrocarbon.

16. A method as in claim 15 further comprising the step of transporting a portion of the water or liquid hydrocarbon from the hybrid ship back to the source location.

17. A hybrid ship for simultaneously transporting sulfur and shipping containers comprising:

a) a below-deck sulfur storage system; and b) an on-deck container storage system.

18. A hybrid ship as in claim 17 wherein the below deck sulfur storage system is a sulfur-slurry storage system or a molten sulfur storage system.

19. A hybrid ship as in claim 18 wherein the sulfur storage system is a sulfur-slurry storage system and sulfur-slurry storage system includes a compressor system for circulating compressed air through the sulfur-slurry storage system to maintain elemental sulfur in a slurry form.

20. A hybrid ship as in any one of claims 17-19 wherein the sulfur storage system has a capacity of greater than 60,000 tonnes of elemental sulfur.

21. A hybrid ship as in claim 20 wherein the sulfur storage system includes up to 12 individual sulfur storage tanks.

22. A hybrid ship as in any one of claims 17-21 wherein the on-deck container storage system has a capacity of greater than 25,000 tonnes of shipping containers.

23. A hybrid ship as in any one of claims 17-22 wherein the hybrid ship is a converted single-hull oil tanker.