Patent Application
20100219106
Not Applicable
This specification is related to McAndrews, Held & Malloy attorney docket numbers:
The invention concerns processes for refining or otherwise treating oil sand ore, for example oil sand, tar sand, and oil shale, involving admixture of the ore with water to fluidize it during processing.
An oil sand deposit or ore principally contains bitumen, which is a very viscous variety of oil, combined with sand, clay, and water. In oil sand deposits, the bitumen encapsulates sand grains and captures a thin film of water between the grains and the bitumen. This water, known as connate water, is approximately 5% by weight of the ore and represents typical minimum inter granular water content. Additional water exists in the inter granular pore spaces of the ore, and may vary up to 20% by mass of the ore.
The oil sand ore can be processed by mining it from a deposit, combining the ore with water to form a slurry, and hydrotransporting the slurry to equipment for concentrating the bitumen and separating the bitumen from the tailings. “Hydrotransport” is defined as conveying solid/liquid mixtures such as slurries into or through process equipment. The bitumen is then further processed, for example by cracking and distilling, to produce petroleum products.
One known process for concentrating the bitumen, originally developed as the well-known Clarke process, is a froth flotation process in which the slurry is treated with lye (sodium hydroxide), and heated which causes the bitumen to separate from the sand grains and float to the top. The froth generated in the process is bitumen-rich and buoyant, and is removed from the top of the slurry, while the tailings (such as sand) sink to the bottom of the slurry and are removed. The slurry is heated to facilitate the froth flotation process.
Previously, a constant water flow has been added to a constant ore stream in preparation for hydrotransport.
An aspect of the invention concerns a process of regulating the water content of water-fluidized oil sand ore during processing of the ore.
In the process, a sample charge of comminuted oil sand ore having a bulk volume (Vt) and inter granular voids is placed in a container. The weight (mo) of the sample charge is determined. The intergranular voids of the sample charge are then filled with water. ρw is the density of the water. The weight (ma) of the intergranular water is then determined.
A target specific gravity value (SGmix) is selected for the fluidized oil sand ore. To consciously achieve the target specific gravity value, it is necessary to determine how much additional water to add. The volume of additional water, ΔV, to add to a sample charge of bulk volume Vt, to achieve the target specific gravity value (SGmix) is calculated by solving the following equation:
The determined volume ΔV of additional water, per bulk volume Vt of oil sand ore to be processed, is added to the oil sand ore. This produces water-fluidized oil sand ore. The water-fluidized oil sand ore is then processed to concentrate the bitumen.
Another aspect of the invention also concerns a process for regulating the water content of water-fluidized oil sand ore during processing of the ore. In this process, the mass fraction of inter granular and connate water in the oil sand ore is determined, as is the mass fraction of bitumen in the oil sand ore. A reference is consulted showing the mass fraction of water initially in the ore, versus the mass fraction of bitumen initially in the ore, versus the mass of water to be added per mass of ore. The mass of water indicated by the reference is added to the ore, producing water-fluidized oil sand ore. The water-fluidized oil sand ore is then processed to concentrate the bitumen.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which one or more embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are examples of the invention, which has the full scope indicated by the language of the claims. Like numbers refer to like elements throughout.
Referring first to
At the water addition station 20, water 22 is added to the ore 10 to facilitate hydrotreating or conveying the oil sand/water slurry to further processing equipment generally indicated at 24. The ore is combined with water and agitated to produce a sand/water slurry comprising bitumen carried on the sand. Additives such as lye (sodium hydroxide) are added to emulsify the water and the bitumen.
Referring now to
The slurry is introduced to the vessel 112 via the feed opening 124, adding to the body of material 114. In the vessel 112, the sand fraction 180 of the material 114 is heavier than the water medium. The sand fraction drops to the bottom of the vessel 112 to form a sand slurry 180 that is removed through the drain opening or sand trap 126. A slurry pump 182 is provided to positively remove the sand slurry 80.
The bitumen per se of the material 114 is heavier than the water medium, but attaches to air bubbles in the vessel 112 to form a bitumen-rich froth. The bitumen froth is floated off of the sand and rises to the top of the slurry. Agitation optionally can be provided in at least the upper portion of the vessel 112, forming bubbles that float the bitumen-rich fraction upward. The top fraction 128 is a froth comprising a bitumen-rich fraction dispersed in water, which in turn has air dispersed in it. The froth is richer in bitumen than the underlying material 114, which is the technical basis for separation.
The bitumen-rich froth 128 is forced upward by the entering material 114 until its surface 184 rises above the weir or lip 186 of the vessel 112. The weir 186 may encircle the entire vessel 112 or be confined to a portion of the circumference of the vessel 112. The froth 128 rising above the level of the weir 86 flows radially outward over the weir 186 and down into the launder 122, and is removed from the launder 122 through a froth drain 188 for further processing.
The specific gravity of the oil sand ore 10 as mined is typically given as 1.2 g/cm3, though specific deposits may have higher or lower specific gravity. Generally speaking, the specific gravity is inversely related to the proportion of water in the ore. Other characteristics of the deposit will also affect the specific gravity, such as the proportion of clay in the ore.
The hydrotransport equipment conveying the slurry from the water addition station 20 adds water to the ore to enable transport of the ore through a pipeline for processing. Previously, a constant water flow has been added to a constant ore stream in preparation for hydrotransport, without considering the amount of water in the ore.
The present inventors have determined that if the ore 10 contains more than the minimum amount of water, reflected by a lower specific gravity, adding a uniform additional quantity of water for hydrotreating introduces extra water that is not needed for hydrotreating (in view of the inter granular water), but must still be heated during subsequent processes that heat the ore slurry. For example, assume adding 600 kg of water per metric ton (1000 kg.) of ore with 5% inter granular water results in a mixture specific gravity (SG) of 1.2, and assume that a SG of 1.2 is low enough to hydrotransport the ore in particular equipment. If this same amount of water is added to ore with 20% inter granular water, the resulting slurry has 250 kg of excess water that is not needed to enable hydrotreating. Heating this excess water to the process temperature wastes energy. Additionally, more water than necessary is output from the process and requires waste treatment or other processing.
The inventors have determined that this problem they have identified can be addressed by metering the amount of hydrotreating water 22 added to the ore 10 according to one or more characteristics of the ore 10. Various characteristics of the ore 10 change in different samples of the oil sand ore 10, and may also change due to environmental factors in the mine (e.g., precipitation, humidity, or water table) or during transport, among other factors. Process conditions like the degree of packing may also affect the specific gravity of the ore.
To address these issues, the inventors have developed a process for regulating the water content of water-fluidized oil sand ore during processing of the ore.
A step 200 can be carried out by putting in a container a sample charge of comminuted oil sand ore having a bulk volume (Vt) and inter granular voids. A step 202 can be carried out by determining the weight (mo) of the sample charge. A step 204 can be carried out by filling the inter granular voids of the sample charge with inter granular water, where ρw is the density of the water. A step 206 can be carried out by determining the weight (ma) of the inter granular water. A step 208 can be carried out by selecting a target specific gravity value (SGmix) for the fluidized oil sand ore. A step 210 can be carried out by calculating the volume of additional water, ΔV, to add to a sample charge of bulk volume Vt, to achieve the target specific gravity value (SGmix) by solving the following equation:
A step 212 can be carried out by adding the volume ΔV of additional water per bulk volume Vt of oil sand ore to be processed, producing water-fluidized oil sand ore. A step 24 can be carried out by processing the water-fluidized oil sand ore to concentrate the bitumen.
Optionally, the process of
After a given calculation 210 has been done and an interval of time ΔT has elapsed, represented by the step 214, the process can be repeated. For example, the process can be repeated every minute, every 10 minutes, every hour, every time a new truckload of ore 10 is delivered to the hopper 14 (
Some other details of various embodiments follow.
The step 200 of putting a quantity Vt of the sample 220 in a container 222 is illustrated by
The step 202 of weighing the sample can be carried out in a variety of ways. For example, in a manual determination the container 222 can be weighed empty, then the sample 220 can be placed in the container, then the container 22 can be re-weighed with the sample 220 and tared by subtracting the weight of the empty container. Alternatively, the sample 220 can be weighed elsewhere, and then transferred to the container 222, reversing the order of the putting and weighing steps 200 and 202.
The step 204 of filling the voids or inter granular space 226 with water can be carried out as illustrated in
Optionally, during or after the filling step 204, the sample charge 220 can be vibrated to drive out inter granular gases. In an embodiment, vibrating can be carried out by subjecting the sample charge to ultrasonic energy, by agitating the sample charge, or by tapping the container. The container can be vibrated before the filling step 204 as well, for example to pack the sample uniformly before filling the interstices with water.
The weight of the inter granular water can be determined, as called for in step 206 of
Step 208 shown in
The desired total water content for the fluidized oil sand ore, including the connate and inter granular water in the ore as provided and the water added to the ore for processing, is a value in the range from about 4% to about 20% by weight, alternatively from about 4% to about 8% by weight, alternatively about 5% by weight.
The selecting step can be carried out at various times. For example, the specific gravity can be selected each time an ore sample is processed, based on process logs or other information regarding how well the process is running. Alternatively, the target specific gravity (SGmix) for the fluidized oil sand ore can be maintained at a constant level for multiple iterations of the process. Alternatively, the SGmix can be chosen at the time the processing equipment is designed, and never changed. Selection of the SGmix can be embodied in selection of the processing equipment that provides the SGmix. In another embodiment, the selecting step can be carried out by a machine operator or supervisor, based on observation of the process. For example, if an assessment is made that the process could be run with less water, the SGmix can be increased to provide a drier mix, and vice versa if the SGmix appears to be too high at the time.
The selecting step can be carried out in various ways. As one example, the target specific gravity (SGmix) can be selected for the fluidized oil sand ore by adopting a published value. As another example, the target specific gravity (SGmix) can be selected for the fluidized oil sand ore by analyzing an ore sample to determine how much water needs to be added to achieve the desired total water content, adding that amount of water to the ore sample, and determining the specific gravity of the ore sample with the added water. This can be done, for example, in trial runs of the machine in which the process is run with a set proportion of added water, the run is assessed, and the amount of water added is adjusted to achieve the desired result, such as the minimal energy input for successful processing. A sample of the slurry can then be taken and its specific gravity measured to select the SGmix for the process.
Step 210 shown in
The amount of additional water to be added per bulk volume Vt of oil sand ore can be expressed in terms of the volume or weight of the water to be added.
Step 212 is adding the quantity ΔV of water to the oil sand ore (which has not yet been watered to fill the voids; it is the oil sand ore as mined). The water can be added to the ore batchwise or continuously. An example of batchwise processing as the oil sand ore is provided to be processed is dumping a load 10 of ore from the dump truck 12 (
Another process of regulating the water content of water-fluidized oil sand ore during processing of the ore takes into account an additional factor: the mass fraction of bitumen in the oil sand ore. This method also can employ a different method of determining the amount of water to add to the ore. This process can be carried out as illustrated in
Referring to
The step 242 of determining the mass fraction of inter granular and connate water in the oil sand ore can be carried out gravimetrically, for example, by removing the water from a sample under conditions that do not substantially disturb the bitumen, as by gentle heating, and weighing the sample before and after heating to determine the amount of water driven off.
The step 240 of determining the mass fraction of bitumen in the oil sand ore is commonly carried out to assay the oil sand deposit and determine whether it is economically valuable to mine and process. Known methods can be used. An exemplary method is pulverizing an ore sample and extracting it with an organic solvent such as naphtha that dissolves the bitumen. The bitumen is then removed from the solvent, as by evaporating the solvent, and the amount of bitumen remaining can be determined gravimetrically by weighing the solvent containing bitumen, evaporating the solvent, and weighing the resulting bitumen.
The step 244 of consulting a reference to determine the amount of water to add to the oil sand ore, based on the mass fractions of bitumen and inter granular and connate water in the ore, can be carried out in various ways. “Reference” is used broadly here to indicate any source of information about the relation between the initial bitumen and water content of the sample and the desired total amount of water in the slurry for processing. The reference can be a plot, a numerical look-up table, a trial to determine the optimum water content of a particular sample of ore, a literature reference, or a record of the amount of water previously used successfully with ore having similar characteristics. Other references of any kind can also be used.
In
The reference of
The step 212 of adding an amount of water to the oil sand ore indicated by the reference, producing water-fluidized oil sand ore, can be carried out in the same way as the corresponding step of
The step 24 of processing the water-fluidized oil sand ore to concentrate the bitumen can be carried out in the same way as the corresponding step of
