US3502566A - Bacterial treatment of hot water process effluent discharge - Google Patents

Description

March 24, 1970 WATER TAR SANDS WATER R. I.. RAYMOND ETAL BACTERIAL TREATMENT OF HOT WATER PROCESS EFFLUENT DISCHARGE Filed May 29, 1968 DILUENT COMBINED FROTH 23 FROTH CENTRIFIJGE ZONE 24 BITUMEN PRODUCT SETTLED SCAVENGER POND ZONE I8 PRIMARY FRO-[H FROTH SETTLER CONDITIONING DRUM SCAVENGER SCREEN FROTH OVERSIZE SEPARATION SUMP ZONE 8 -AIR "k FLOTATION SCAVENGER MIDDLINGS ZONE TREATMENT CELL E /ZONE NUTRIENTS EggE E G a- '0 7 2 INVENTORS RICHARD L RAYMOND JAMES 0. HUDSON VIRGINIA -W. JAMISON United States Patent US. Cl. 208--11 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process for treating the water efiluent from a hot water process for treating tar sands. By this invention the settling of clay is facilitated by incorporating viable microorganisms into the water, such microorganisms being capable of sorbing bitumen. Upon settling, the treated water separates into a clean supernatant and a sludge of about ten percent solids.

The present invention relates to a process for treating water efiluents of specific composition. More Specifically, the invention relates to a process for clarifying the efiluent discharge from a hot water process for treating tar sands.

Numerous deposits of bituminous tar sands exist throughout the world. The most extensive deposits are found in northern Alberta, Canada. The sands are composed of a siliceous material, generally having a size greater than that passing a 325 mesh screen, saturated with a relatively heavy, viscous bitumen in quantities of from 5 to 21 weight percent of the total composition. More typically, the bitumen content of the sands is between about 8 to percent. This bitumen is quite viscous and contains typically 4.5 percent sulfur and 38 percent aromatics. Its specific gravity at 60 F. ranges typically from about 1.00 to about 1.06. The tar sands also contain clay and silt. Silt is defined as material which will pass a 325 mesh screen but which is larger than 2 microns. Clay is material smaller than 2 microns including some siliceous material of that size.

There are several well-known processes for effecting separation of bitumen from the tar sands. In the hot water method, the bituminous sands are jetted with steam and mulled with a minor amount of hot water at temperatures in the;.range of 140 to 210 F. The resulting pulp is dropped into a stream of circulating hot water and carried to a separation cell maintained at a temperature of about 150 to 200 F. In the separation cell, sand settles to the bottom as tailings and bitumen rises to the top in the form of an oil froth. An aqueous middlings layer containing some mineral and bitumen is formed between these layers. A scavenger step may be conducted on the middlings layer from the primary separation step to recover additional amounts of bitumen therefrom. This step usually comprises aerating the middlings as taught by K. A. Clark, The Hot Water Washing Method, Canadian Oil and Gas Industries 3, 46 (1950). Both froths can be combined, diluted with naphtha and centrifuged to remove more water and residual mineral. The naphtha is then distilled OE and the bitumen is coked to a high quality crude suitable for further processing. The hot water process is described in detail by Floyd et al. in United States application Ser. No. 509,589 now US. Patent No. 3,401,110 issued Sept. 9, 1968. The water which is used in the process is discharged from the system as an efiluent which comprises middlings material and sand tailings.

. The water portion of the efiluent must be stored, disposed of, or recycled back into the process. This portion con- 3,502,566 Patented Mar. 24, 1970 ice tains virtually all of the clay material which was present in the feed. Typically the amount is 2 to 10 weight percent of the feed. The material is smaller than 2 microns and exhibits extremely poor settling characteristics.

Because the water portion contains bitumen emulsions, finely dispersed clay with poor settling characteristics and other contaminants, water pollution considerations prohibit discarding the water into rivers, lakes or other natural bodies of water. The disposal of hot water process efiluent discharge has therefore presented a problem. It has been proposed that the water from the efiluent be stored in evaporation ponds but this proposal would involve large space requirements and the construction of expensive enclosure dikes. It has also been suggested that the water be recycled back into the process as an economic measure to conserve both heat and water. However, the dispersed silt and clay content of the recycled water can reduce primary froth yield by increasing the viscosity of the middlings layer and retarding the upward settling of bitumen flecks in the separation zone. If this retarding occurs, the smaller bitumen flecks and those that are more heavily laden with mineral matter stay suspended in the water of the cell and are removed with the middlings layer.

The present invention relates to a method for treating the water portion of the effluent discharge from the hot water process to make the water suitable for discard or recycle back into the process. In this specification the term pond water will be used to describe the water portion of the efiluent discharge. This pond water roughly has the same composition as the bitumen-lean middlings discharged fromthe process. It has been surprisingly observed that viable microorganisms capable of sorbing bitumen can be used to facilitate settling of pond water. It has further been found that the etfectivenes of microorganisms in facilitating the settling of pond water can be appreciably increased by optimizing the conditions for microbial development. The most surprising aspect of the present invention is that not only is the bitumen content of the water reduced but additionally changes in the settling properties of the water are produced. Clay can be caused to settle from the pond water to give a clear supernatant liquid substantially reduced in both clay and bitumen content.

It is not known with assurance why treatment of the pond water with microorganisms reduces bitumen content and changes the settling properties of the water. As to the bitumen reduction, it may be that the bacteria oxidize the hydrocarbons in the bitumen to less viscous, shorter chain length compounds. Hydrocarbons are one class of organics that natural bacteria oxidize and this process includes dehydrogenation of the hydrocarbons and reduction of other compounds. Numerous bacteria are useful in the present invention. The operable bacteria are those capable of growing and oxidizing hydrocarbons as well as other assimilable carbon compounds. Genera in which such hydrocarbon-consuming microorganisms fall include Micrococcus, Corynebacterium, Nocardia, Pseudomonas, Mycobacterium, Streptomyces, Aspergillus, Acetobacter and Achromobacteria.

In one embodiment of the present invention the conditions conducive to microbial growth are optimized by the addition of nutrients. Preferably the nutrients are a combination of one or more components from each of the following three classes: sources of assimilable carbon, sources of nitrogen and phosphates. Examples of assimilable carbon are naphthas, kerosene fuel oil, jet fuel and gas oil petroleum fractions and saturated hydrocarbons. Examples of nitrogen sources include urea, NH4NO3, NH4C1, (NH4)2SO4, NaNO and and of phosphates, K HPO Na HPO and KH PO The pre- 3 ferred nutrient combination comprises NH NO a mixture of Na HPO and KH PO and n hexadecane. The proportions of nutrients added to. promote microbial growth can vary within the teachings of the art. In one aspect the present invention can be described as an improvement to the hot water process for separating bitument from tar sands in which the hot water precess cornpri's'es forming a mixture of tar sands and water, passing the mixture into a separation zone to form an upper bitumen froth layer, a middlings layer comprising Water, mineral and bitumen, and a sand tailings layer and separately recovering said bitumen froth layer; from said separation zone. In this process, the improvement can be described as a process for facilitating the settling of rnineral from the'middlings layer which comprises removing at least a portion of the middlings from said separation zone, incorporating into the portion viabie microbial cells capable of sorbing bitumen, and settling the portion to produce a sludge layer characterized as; more rich in bitumen and mineral than the portion and a supernatant layer characterized as less rich in bitumen and mineral than the portion. In the process the conditions in the water can be controlled to giveioptimized microbial development by adding microbial growth nutrientssuch as nitrogens, phosphates and/or a readily assimilable carbon. The imgention can be practiced on any water-containing fraction discharged from the hot water process including the water of the efiluent discharge, bitumen-lean middlings and pond water. W

For the purpose of this invention, pond water is efiiuent discharge from a hot water process which efilue nt has been settled to give a composition comprising water containing up to about percent solids, between 80 percent and 100 percent of which is fine clay of a size smaller than 2 microns. The efiluentdischarge from a hot water process comprises middlings material of depleted bitumen content which has undergone final treatment, the sand tailings layer from the process and other discharged water-containing fractions which are not the primary 'products of the hot water process. The discharge is removed from the process 'area as a slurry of about to 55, typically 45, percent solids by weight. The efiluent contains virtually all of the clay material which was present in the feed. This material is smaller than 2 microns and has extremely poonsettling characteristics.

The figure a schematic flow diagram illustrating the process of the present invention. The invention is described in detail with reference to this drawing which shows a preferred embodiment of the present invention.

In the figure, bituminous tar sands are fed into the system through line 1 where they first pass to a conditioning drum or muller 2. Water and steam are introduced from 3 and mixed with the sands, The total water so introduced is a minor amount based on the weight of the taf sands processed and generally is in the range of '10 to percent by weight of the total mixture. Enopgh steam is introduced to raise the temperaturein the conditioning drum to within the range of 130 F. to 210 F. and preferably to above 176 F. Monovalent alkaline reagent can also be added to the conditioning drum usually in amount of from 0.1 to 3.0 pounds per ton of tar sand.

The amount ofsuch alkaline reagent preferably is regu- "lated to maintain the pH' of the middlings layer in separator zone 12 within the range of 7.5 to 9.0. Best results seem to be obtained at a pH value of 8.0 to 8.5. The amount of the alkaline reagent that needs to be added to maintain a pH value in the range of 7.5 to 9.0 may vary from time to time as the composition of the tar sands as obtained from the mine site varies. The best alkaline reagents to use for this purpose are caustic soda, sodium carbonate or sodium siiicate, although any of the other monovalent alkaline reagents can be used if desired.

Mulling of the tar sands produces a pulp which then passes from the conditioning drum as indicated by line 4 to a screen indicated at 5. The purpose of screen 5 is to remove from the tar sand pulp any debris, rocks, or oversizedilumps as indicated generally at 6. The pump then passes from screen 5 as indicated by 7 to a sump 8 where it is diluted' with additional water from 9 and a middlings recycle stream 10. Recycling of the, middlings is not essential in all cases, particuiarly when the clay content of the tar sands is high. In this event a relatively high rate of fresh feed water introduction through 9 can be employed to compensate for the high clay content while a correspondingly high rate of transfer of middlings layer through line 15 as hereinafter described can be maintained. Under these circumstances recycling of the other stream of middlings through line 10 to the sump is :not required.

Modifications that may be made in the process as above described include sending a minor portion of the middlings recycle stream from line 10 through a suitable line (not shown) to the conditioning drum 2 to supply all or a part of the water needed therein other than that suppliedthrough condensation of the steam which is consumed. Also, if desired, a stream of the middlings recycle can be introduced into the screen 5 to flush the pulp there'through and into the sump. As a, general 'rule the total amount of water added to the natural bituminous sands as liquid water and as steam prior to the separation step should be in the range of 0.2 to 3.0 tons per ton of the bituminous sands". The amount of water needed within this range increases as the silt and clay content of the bituminous sand in -creases. For example, when 15 percent by weight of the mineral matter of the tar sands has a particle size below 44 microns, the fresh water added generally can be about 0.3 to 0.5 ton'per ton of tar sands. On the other hand, when 30 percent of the mineral matter of water'should be used per ton of tar sandICorresp-ond- "ingly the amount of oil-rich middiings removed through line 11 will vary depending upon the rate of fresh water addition. As a general rule the rate of withdrawal of oilrich middlings to scavenger zone 16 will be 10 to gallons per mar tar sands processed when 15 percent by weight of the mineral matter is below 44 microns and to 250 gailons per'ton when from 25 to 30 percent of the mineral is of this fine particle size.

Further following the process, the pulped and diluted tar sands are pumped from the sump if through line 11 into the separation zone 12. The cell contains a relatively quiescent body of hot water which allows for the formation of a bitumen froth which rises to the celi top and is withdrawn via line 13, and a sand tailings layer which settles to the bottom to be withdrawn through line 14. An aqueous middlings layer between the froth and tailings layer contains silt and clay and some bitumen which failed to form forth. In order to prevent the buildup of clay in the system it is necessary to continually remove some of the middlings layer and supply enough water in the conditioning operations to compensate for that so removed. The rate at which the middlings need to be removed from .the system depends upon the content of clay and silt 'present in the tar sands feed and this will vary from time to time as the content of these fines varies. If the clay and silt content is allowed to build up in the system, both the density and the viscosity of the middlings layer will increase. Concurrently with such increase, an increase in the proportions of both the bitumen and the sand retained by the middlings will occur. If the clay and silt content is allowed to build up too high in the system effective separation no longer will occur and the process will become inoperative. This may be avoided by regulating the recycling and withdrawal of middlings and input of fresh water per the invention disclosed and claimed in the Floyd et al. United States Ser. No. 509,589, filed Nov. 24, 1965. However, even when the separation step is operating properly, the middlings layer withdrawn through line 15 is, for purpose of description, herein referred to as oil-rich middlings or bitumen-rich middlings.

The oil-rich middlings stream withdrawn from separator 12 through line 15 is sent to a scavenger zone 16 wherein an air flotation operation is conducted to cause the formation of additional bitumen froth which passes from the scavenger zone 16 through line 17 to a froth settler zone 18. An oil-lean middlings stream is removed from the bottom of the scavenger zone 16 via line 19.

In the settler zone 18, the scavenger froth forms into a lower layer of settler tailings which is withdrawn and recycled via line 20 to be mixed with oil-rich middlings for feed to the scavenger zone 16 via line 15. In the settler zone an upper layer of upgraded bitumen froth forms above the tailings and is withdrawn through line 21 and mixed with primary froth from line 13. The combined froths are at a temperature of about 160. They are heated with stream and diluted with sufficient naphtha or other diluent from 22 to reduce the viscosity of the bitumen for centrifuging in zone 23 to produce a bitumen product 24 suitable for further processing.

By the process of the present invention, the oil-lean middlings are fed via line 19 to treatment zone 25. Cells for the middlings treatment are prepared in cell propagation zone 26. The vat in zone 26 can be of the Waldhof- Mannheim design which is well known to the fermentation industry. Optimum conditions for obtaining suspended solids concentrations of LOGO-5,000 mg. per liter are as follows (parts used per 1000 parts of water): ammonium nitrate (1.0), disodium hydrogen phosphate (3.0) and potassium dihydrogen phosphate (2.0). Other inorganic nutrients, such as magnesium, manganese and ferrous ions can be added if necessary or desired in sufficient concentrations, although this supplementation is usually not required. All of the necessary nutrient salts are metered in as concentrated solutions via line 27 as analyses indicate a need.

After obtaining the proper nutrient mineral concentration, the propagator temperature is maintained at temperatures between 20 and 65 C. with the preferred condition at 28 to 32 C. The nutrient solution is vigorously agitated and aerated with a sparger (not shown). After inoculation with an enriched hydrocarbon oxidizing microorganism an alkane mixture (C to C is metered in as required via line 28. Aftena suitable initial growth period of 24 to 48 hours in which the suspended solids concentration reaches 5000 mg per liter, the operation is switched from a batch operation to continuous by introducing cells into the tailings treatment zone 25 via line 29 and recycling a portion of the middlings in zone 25 via line 30 back into zone 26. Once recycling has begun it isno longer feasible to determine and use suspended solids as a measurement of cell concentration due to the variation in solids concentration of the tailings. It is therefore necessary to maintain a concentration of assimilable hydrocarbon in the cell propagation zone 26 of 0.05 to 0.5 percent by volume to assure an adequate cell concentration for the tailings treatment area 25. Under normal operating conditions this hydrocarbon substrate will be supplied from recovered water from centrifuge zone 23 which contains naphtha that has been added as a diluent. After the proper hold-up time in zone 25 the treated middlings are discharged to settling zone 32 via line 31.

The improvement of the present invention has been described in reference to treatment of the oil-lean middlings from the flotation scavenger zone 16. This process is the preferred embodiment and takes advantage of the heat content of the middlings as they are discharged from the scavenger zone 19. However it should be noted that the process can be practiced on any water-containing fraction discharged from the hot water process.

The water treated in the process can be discharged into the settling pond 32 wherein improved settling of contaminents takes place. After settling the clarified water can be recycled back into the process. The drawing shows withdrawal of clarified pond water via line 33 back to line 9 where it is utilized to dilute the tar sands pulp in the sump 8.

The following examples illustrate the preferred em- 5 bodiment of the invention. A 100 ml. quantity of tailings pond water contained in a 500 ml. Bellco Flask was inoculated with a microorganism-genera, Nocardia. Nitrogen, as 0.2 percent NH NO phosphates, as a mixture of Na HPO and KH PO and a source of readily assimilable carbon, as n-hexadecane, were then added to the flasks in quantities as indicated by system 1 of Table I. Three other systems were similarly prepared as control mediums. The compositions of these systems are shown as systems 2, 3, and 4 of Table I.

TABLE I. PHYSICAL CONDITIONS FOR MIOROBIAL STUDIES IN POND WATER System Nitrogen Phosphates 1 n-Hexadecane 2 1.- 0.2% NH. N0 0.5 7 440 mg. 2.- 0 0.... 440 mg.

3 0.....3 0.". 0. 4 0.2% NH4NO 0.5% 0.

l Mixture of Na2HPO4 and K112 P04 to give pH 7.0. 2 Added incrementally.

TABLE IL-PERCENI BITUMEN IN SYSTEMS Days 1 2 3 4 1 .91 1.00 1.01 .93 2 .ss .95 .94 .92 40 3 .87 .98 .91 .88 c .80 .96 1. 09 .93

After shaking was discontinued, sample I settled to a clear supernatant and to a sludge of about ten percent solids. Some settling took place in samples 2 and 4 but little appreciable settling took place in system 3.

The data of Table II show that a bitumen decrease has been effected in system 1 where conditions for microbial development were optimized. Additionally, a visual inspection indicated that increased clay settling had occurred in systems 1, 2 and 4 over system 3 with system 1 exhibiting the most improved settling rate.

What is claimed is:

1. In the hot water process for treating bituminous tar sands which comprises; forming a mixture of tar sands and water, passing said mixture into a separation zone to form an upper bitumen froth layer, a middlings layer comprising water, mineral and bitumen and a sand tailings layer, and passing at least a portion of the middlings and tailings layer as a bitumen-lean water effluent from the separation zone to a settling zone, the improvement for facilitating settling of clay from at least a portion of the Water efiluent which comprises:

(a) establishing microbial growth conditions in said portion;

(b) incorporating in the said portion microbial cells capable of sorbing bitumen; and

(c) settling the portion to produce a supernatant layer characterized as less rich in bitumen and clay than said portion and a sludge layer characterized as more rich in bitumen and clay than said portion.

2. The process of claim 1 in which microbial growth conditions are enhanced by the incorporation of micro- 75 bial growth nutrients in step (a).

3. The process of claim 2 in which said nutrients are selected from the group consisting of nitrogens, phosphates, readily assimilable carbon and combinations thereof.

4. The process of claim 3 in which said nutrients comprise NH NO a mixture of Na HPO and KH P0 and n-hexadecane.

5. The process of claim 1 in which said supernatant layer is recycled as at least a portion of said water used to form said mixture of tar sands and water.

8 References Cited UNITED STATES PATENTS 10/1964 Davis et al. 2l0ll 7/1968 Baillie 208l1 X MICHAEL E. ROGERS, Primary Examiner 0.5. Ci. X.R.

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