CN105753203B - A kind of oil sand washing water treatment method - Google Patents

Abstract

An oil sand washing water treatment method, comprising the following steps: 1) mixing the wastewater separated after washing the oil sand with acid or alkali through a first-stage Venturi mixer, and adjusting the pH value of the wastewater to 7.6-8.6; 2) the treated wastewater is mixed with a demulsifier through a second-stage Venturi mixer again; 3) discharging the wastewater treated in the step 2) into an oil removal sedimentation tank, and removing suspended oil and sandy soil; 4) performing cyclone separation on the wastewater after oil removal sedimentation to remove particles with the particle size of more than 50 microns in the water; 5) enabling the wastewater after cyclone separation to enter a coagulation air flotation device, and further removing suspended matters and petroleum substances in a suspended and dissolved state in the wastewater; 6) filtering the wastewater treated in the step 5) to obtain oil sand washing water. The technical method has short flow and low energy consumption in the treatment process, and can remove sand particles, clay and oil sand asphalt in the oil sand washing wastewater more thoroughly.

Description

A kind of oil sand washing water treatment method

technical field

The invention relates to a treatment method for oil sand washing water. After the oil sand washing water is treated, various substances such as sand grains, clay, oil sand asphalt and chemical agents are removed, and the oil sand washing water is recycled as the oil sand washing water.

Background technique

As an unconventional petroleum resource, oil sand contains 5-20% bitumen, 80-85% sand and clay, and 3-5% water content. Its resources account for about 30% of the world's oil reserves. If all of them are exploited and utilized, according to the current world energy demand level, they can be consumed by the world for hundreds of years. The development and utilization of oil sands has become a new economic growth point. According to the statistics of major oil sand resource countries, the world's proven oil sand resources are about 3.8 trillion barrels. Mainly distributed in Canada, Venezuela and the United States, most of the oil sand resources in the world are concentrated in the Athabasca River Basin in northern Alberta, Canada, Peace Lake and the Cold Lake area at the junction of Alberta and Saskatchewan. The development of oil sands has made Canada's oil reserves second only to Saudi Arabia, ranking second in the world, making the international community more aware of the value of oil sands. A large number of oil sand resources have also been discovered in my country, with reserves of about 100 billion tons, ranking fifth in the world, mainly concentrated in 24 basins including Junggar, Qaidam, Ordos and Songliao. In the national survey of oil and gas resources in my country, oil sand resources were included in the evaluation system for the first time. After evaluation, the oil content of oil sand in my country is 5% to 20%, which has good economic development value and prospects.

At present, the mining and separation of oil sands in the world is still in its infancy. Oil sands have high viscosity, high density, and separated heavy oil contains a large number of tiny sand particles and minerals. In the separation, processing and tailings treatment of oil sand bitumen There are still many technical problems, and the application of oil sands mining has been restricted. Huge toxic tailing ponds are produced during the oil sand mining process, causing great harm to the environment. Seven of the largest oil sands companies (Canadian Natural Resources, Imperial Oil, ShellCanada, Suncor Energy, Syncrude Canada Ltd., Teck Resources and Total E&PCanada) formed an alliance in December 2010 to address one of the industry's toughest challenges: Clean up their giant toxic tailings ponds. This means that oil sands companies will work together as a unified force to promote tailings management and exchange know-how, rather than trying to sell or license their intellectual property.

At present, oil sand open-pit mining mainly uses water washing and separation technology, using hot alkaline water to heat and stir to separate oil and sand. The waste generated during the separation process is mainly water, oil sand bitumen, suspended matter, clay, sand, and chemicals. mixture. Since the asphalt is mixed with water and clay very uniformly, it is very difficult to settle and separate. At present, there are more than 800 million cubic meters of tailings stored in 142 square kilometers of tailings ponds in the oil sands mining area of Alberta, Canada, and the tailings inventory continues to increase. Based on centrifuge simulation research, it takes more than 130 years for the aged fine soil tailings in the tailings pond to settle and separate freely. It not only stores a large amount of water but also occupies a vast area of land. The tailings pond wastewater produced after oil sand washing The treatment and utilization of oil sands is one of the great challenges faced by oil sands treatment companies.

CN101855177A proposes a membrane separation method to treat oil sand washing tailings pond water. The waste water contains a large amount of clay, oil sand asphalt and chemical agents, and the membrane is easy to be blocked during the treatment process, which consumes a lot of energy.

CN103359861A proposes a treatment method for oil sand washing wastewater, including the following steps: homogenize the oil sand mining sewage in a homogenizing tank, and then enter the homogenized sewage into an air flotation degreasing device for air flotation degreasing Treatment, removal of part of suspended oil and a small amount of emulsified oil; the sewage after air flotation enters the flocculation and air flotation device to separate flocs; the flocculation and air flotation sewage is centrifuged to obtain water for reinjection of oil sand formations. In the process of air flotation degreasing and flocculation air flotation, the sewage contains a lot of clay and sand, which is easy to block pipelines and equipment, and affects the long-term operation of the device.

CN103351072A provides a method for treating oil sand mining waste water, homogenizing the sewage separated by oil sand washing, then carrying out air flotation to remove oil, removing most of the suspended oil and a small amount of emulsified oil, and then carrying out flocculation treatment, the flocculated The waste water is clarified, filtered, softened and centrifuged to obtain boiler refill water. This process method has a long process flow and high energy consumption, and in the pretreatment process, a large amount of sand contained in the washing water has not been deeply removed and separated, which will bring great difficulties to the subsequent treatment of wastewater.

CN102676199A The invention discloses a treatment system for oil sand tailings or oil sand pulp, which can recover residual bitumen from oil sand tailings or oil sand pulp, and can solidify the oil sand tailings, so that the oil sand tailings can be easily processed with economical and Dispose of in an environmentally friendly manner.

To sum up, although the current oil sand washing water treatment technology can achieve certain treatment and reuse effects, there are still shortcomings, which affect the reuse of oil sand washing water and form a large number of tailing ponds , causing waste of water resources and serious environmental pollution, which needs to be dealt with urgently.

Contents of the invention

The purpose of the present invention is to provide a method for treating oil sand washing water, so as to overcome the defects in the prior art that easily cause waste of water resources and serious environmental pollution.

To achieve the above object, the invention provides a method for treating oil sand washing water, comprising the following steps:

Step 1: The waste water separated from the oil sand washing is mixed with acid or alkali through the first-stage Venturi mixer, and the pH value of the waste water is adjusted to be between 7.6 and 8.6;

Step 2 The wastewater treated in Step 1 is mixed with the demulsifier again through the second-stage Venturi mixer, and the dosage of the demulsifier is controlled to be 30-300mg/L;

Step 3: Discharge the wastewater treated in Step 2 into the oil separation sedimentation tank, keep the residence time of the wastewater at 0.5-3.0h, and remove suspended oil and sand;

Step 4 Separating the waste water after oil separation and sedimentation by cyclone to remove particles with a particle size of 50 μm or more in the water;

Step 5: Enter the coagulation and air flotation device with the cyclone-separated wastewater to further remove suspended solids and suspended and dissolved petroleum substances in the wastewater;

Step 6: Filter the wastewater treated in Step 5 to obtain oil sand washing water.

Wherein, the acid described in the step one is selected from hydrochloric acid, sulfuric acid or nitric acid.

Wherein, the acid described in the step one is concentrated sulfuric acid.

Wherein, the acid described in the step one is a weak acid.

Wherein, the alkali described in the step one is selected from sodium hydroxide or potassium hydroxide.

Wherein, the base described in the step 1 is a weak base.

Wherein, the alkali described in the step one is selected from sodium hydroxide or potassium hydroxide.

Wherein, the pH value in the first step is 7.6-8.2.

Wherein, the dosage of the demulsifier in the second step is 50-150 mg/L.

Wherein, the residence time of the wastewater in the step 3 is 1 to 2.5 hours.

Wherein, in the fifth step, a flocculant is added to the coagulation air flotation device.

Wherein, the flocculant is an inorganic polymer flocculant or an organic polymer flocculant.

Wherein, the inorganic polymer flocculant is polyaluminum chloride or polyaluminum silicate.

Wherein, the organic polymer flocculant is cationic polyacrylamide.

Wherein, the cationic polyacrylamide has a molecular weight of 7 million to 10 million.

Wherein, the dosage of the inorganic polymer flocculant is 40-100 mg/L.

Wherein, the dosage of the organic polymer flocculant is 2-50 mg/L.

Wherein, the material of the filter element used for filtering in the step 6 is quartz sand, activated carbon or chemical fiber.

Wherein, the demulsifier in the second step is an ether demulsifier, an aldehyde demulsifier or a lipid demulsifier.

The beneficial effects of the present invention are:

The present invention adopts a combined treatment method of "oil separation sedimentation-cyclone separation-coagulation air flotation-filtration". Its advantages are as follows: ① For a large amount of sand contained in oil sand washing wastewater, according to the difference in particle size and settling time, multi-level classification treatment is carried out, and the sand is settled more thoroughly; ② According to the asphalt-based oil in the wastewater Petroleum substances exist in different states in the wastewater, and the particle size of the oil droplets is different, and the separation and removal of petroleum substances is more thorough; Waste water can be recycled as oil sand washing water; ④Two-stage Venturi mixers are used in series to ensure fast material flow and prevent large-diameter sand particles from depositing inside equipment or pipelines, causing blockage; The device is used, the method flow is short, the energy consumption is low, and the treatment effect is good.

Description of drawings

Fig. 1 is the schematic flow chart of the method of embodiment 1.

In Fig. 1, 1-Venturi mixer; 2-Venturi mixer; 3-oil separation settling tank; 4-cyclone; 5-coagulation air flotation device; 6-filter.

Detailed ways

In the present invention, firstly, the oil sand washing wastewater is neutralized and mixed with a demulsifier through a Venturi mixer, and then discharged into the oil separation settling tank, and the effluent of the oil sand tank is subjected to the treatment of cyclone separation, air flotation and filtration, and the oil sand is washed The waste water generated after treatment is recycled. Specifically include the following steps:

Step 1: The waste water separated from oil sand washing is mixed with strong acid (or alkali) through the first-stage Venturi mixer, and the pH value of the waste water is adjusted to be between 7.6 and 8.6;

Step 2 The waste water treated in Step 1 is mixed with the demulsifier through the second-stage Venturi mixer again, and the dosage of the demulsifier is controlled to be 30-300mg/L;

Step 3: Discharge the wastewater treated in Step 2 into the oil-separating sedimentation tank, keep the residence time of the wastewater at 0.5-3.0 hours, and remove most of the suspended oil in the water and a large amount of sand in the wastewater;

Step 4 Separating the waste water after oil separation and sedimentation by cyclone to remove particles with a particle size of 50 μm or more in the water;

Step 5: Enter the coagulation and air flotation device with the cyclone-separated wastewater to deeply remove suspended solids, suspended and dissolved petroleum substances in the wastewater;

Step 6: Filter the wastewater treated in Step 5. The turbidity of filtered water is ≤5 NTU, the content of petroleum is ≤25 mg/L, and the content of suspended solids is ≤25 mg/L to obtain oil sand washing water.

The preferred processing conditions of the present invention are as follows:

The acid added in the Venturi mixing is selected from hydrochloric acid, sulfuric acid, nitric acid, etc., preferably concentrated sulfuric acid, and other weak acids can also be selected. The base is selected from sodium hydroxide, potassium hydroxide, and other weak bases can also be selected.

The pH value is preferably 7.6-8.2; the dosage of demulsifier is preferably 50-150 mg/L, and the residence time of wastewater in the sedimentation tank is preferably 1-2.5 h.

Coagulation and air flotation treatment requires flocculants, and the flocculants are inorganic polymer flocculants and organic polymer flocculants; inorganic polymer flocculants are preferably polyaluminum chloride and polyaluminum silicate, and the dosage is preferably 40-100mg/ L; The organic polymer flocculant is preferably cationic polyacrylamide, the molecular weight is preferably 7 million to 10 million, and the dosage is preferably 2 to 50 mg/L.

The material of the filter element can be selected from quartz sand, activated carbon and chemical fiber, etc., and the material of chemical fiber and quartz sand is preferred.

The demulsifier can choose ether demulsifier, aldehyde demulsifier or lipid demulsifier.

In the present invention, the oil sand washing wastewater is added with concentrated sulfuric acid during the mixing period of the first Venturi, and after adjusting the pH of the wastewater, it enters the second Venturi mixer. In the oil settling tank, the oil droplets in the emulsified state are aggregated, floated up and removed, and a large amount of sand and soil in the wastewater are settled and removed; the effluent from the settling tank enters the cyclone separator, and the different centrifugal forces generated by the density difference further remove the particle size of about The sand above 50μm; the wastewater treated by the cyclone enters the coagulation air flotation device, and the stable state of the colloid in the water is destroyed by adding high-priced electrolytes, so that the suspended matter is destabilized, condensed and removed. During the air flotation process, a large amount of The microbubbles adhere to the surface of the oil droplets, which help to float and remove the fine oil droplets in suspension; a large number of alum flowers are generated during the coagulation process, and the wastewater is deeply removed by using the adsorption and "netting" effect of the alum flowers Petroleum substances in an emulsified state. Wastewater after coagulation and air flotation treatment enters the filter. After filtration, the water turbidity is ≤5NTU, the petroleum content is ≤25mg/L, and the suspended solid content is ≤25mg/L. The wastewater can be used as oil sand washing water for recycling. .

The main feature of the present invention is that the sand content in the waste water separated by oil sand washing is high, and there are not only sand particles but also a large amount of clay in the waste water, which is easy to block pipelines and equipment, and is difficult to settle and separate; the petroleum substances in the waste water are asphalt The density of asphalt-based crude oil is closer to that of water, and the asphalt-based crude oil is well mixed with sand and clay, making it difficult to separate. The two-stage Venturi mixer is selected to be used in series because the material flow velocity in the Venturi mixer is high, which prevents a large amount of sand contained in the waste water from settling and blocking equipment and pipelines.

The invention uses an oil-separating settling tank, and the waste water can settle into the sandy soil with a large particle size in the equipment, and at the same time, part of the suspended petroleum in the waste water is floated and separated.

The invention uses a cyclone to separate a large amount of sand and soil contained in waste water, relies on the centrifugal force generated during the high-speed fluid flow and rotation process to separate the sand and soil in the waste water, and has high separation efficiency and fast separation speed.

The present invention uses coagulation air flotation to treat suspended solids and oils in wastewater. The main reason is that by adding high-priced electrolytes, the stable state of colloids in water is destroyed, and suspended solids are destabilized, condensed and removed. During the process of air flotation, a large amount of The microbubbles adhere to the surface of the oil droplets, which help to float and remove the fine oil droplets in the suspended state; a large number of alum flowers are generated during the coagulation process, and the adsorption and "net capture" of the alum flowers are used to deeply remove the waste water. Petroleum substances in an emulsified state.

The present invention uses the filter as the final treatment process before the oil sand washing wastewater is reused. The main reason is to increase the level of security and safety for the reused water, and can filter suspended solids and petroleum substances in the wastewater.

Example 1:

The pH value of the oil sand washing wastewater is 10.2, the sand content is 5600mg/L, and the oil content is 1200mg/L. After mixing with concentrated sulfuric acid through a Venturi mixer, the pH value of the wastewater is adjusted to 7.6, and then 100mg of polyether is added to break the emulsion. /L, mixed by a Venturi mixer, the wastewater enters the oil separation settling tank, the settling time is 1.6h, the sand content in the effluent of the settling tank is 1100mg/L, and the oil content is 100mg/L. The wastewater treated in the settling tank is sent to the cyclone, and the sand content after cyclone separation is 160mg/L, and then the coagulation air flotation and filtration device is carried out. The dosage of polysilicate aluminum is 50mg/L, and the cationic poly The amount of acrylamide added is 2 mg/L, and the filter is filled with coconut shell activated carbon. The turbidity of the filter effluent is 4.6NTU, the petroleum content is 6.0mg/L, and the suspended solid content is 23mg/L. The wastewater can be used as oil sand washing water for recycling.

Comparative example 1:

The oil sand washing wastewater has a pH value of 10.2, a sand content of 5600 mg/L, and an oil content of 1200 mg/L. It is homogenized in a homogenizing tank, and the pH value of the wastewater is adjusted to 7.6. For the air flotation device, the dosage of polyaluminum silicate is 50mg/L, and the dosage of cationic polyacrylamide is 2mg/L. Sent to the garbage disposal site for centralized treatment. Analysis of the effluent from the air flotation device showed that the turbidity of the effluent was 36.7NTU, the content of petroleum was 52mg/L, and the content of suspended solids was 87mg/L. Further treatment is needed; the more serious problem is that there is a large amount of sand and soil deposits in the neutralization adjustment tank, air flotation tank and the inlet and outlet pipelines of the equipment, which need to be cleaned continuously to maintain the operation of the device.

Example 2:

The pH value of the oil sand washing wastewater is 9.8, the sand content is 3300mg/L, and the oil content is 1400mg/L. After mixing with concentrated sulfuric acid through a Venturi mixer, the pH value of the wastewater is adjusted to 7.9, and then 100mg of polyether is added to break the emulsion. /L, mixed by a Venturi mixer, the wastewater enters the oil separation settling tank, the settling time is 3h, the sand content in the effluent of the settling tank is 1000mg/L, and the oil content is 110mg/L. The wastewater treated in the settling tank is sent to the cyclone, and the sand content after cyclone separation is 120mg/L, and then the coagulation air flotation and filtration device is carried out. The dosage of polysilicate aluminum is 80mg/L, and the cationic poly The amount of acrylamide added is 30 mg/L, and the filter is filled with quartz sand. The turbidity of the filter water is 5.0NTU, the petroleum content is 24mg/L, and the suspended solid content is 25mg/L. The wastewater can be used as oil sand washing water for recycling.

Example 3:

The pH value of the oil sand washing wastewater is 9.0, the sand content is 6000mg/L, and the oil content is 1500mg/L. After mixing with concentrated sulfuric acid through a Venturi mixer, the pH value of the wastewater is adjusted to 8.2, and then 220mg of polyether is added to break the emulsion. /L, mixed by a Venturi mixer, the wastewater enters the oil separation settling tank, the settling time is 3h, the sand content in the effluent of the settling tank is 1800mg/L, and the oil content is 150mg/L. The wastewater treated in the settling tank is sent to the cyclone, and the content of sand and soil after cyclone separation is 170mg/L, and then the coagulation air flotation and filtration device is carried out. The dosage of polysilicate aluminum is 100mg/L, and the cationic poly The amount of acrylamide added is 50mg/L, and the filter is filled with chemical fiber filler. The turbidity of the filter water is 3.0NTU, the petroleum content is 16mg/L, and the suspended solid content is 20mg/L. The wastewater can be used as oil sand washing water for recycling.

Example 4:

The pH value of the oil sand washing wastewater is 12.0, the sand content is 1200mg/L, and the oil content is 900mg/L. After mixing with concentrated sulfuric acid through a Venturi mixer, the pH value of the wastewater is adjusted to 8.6, and then 30mg of polyether is added to break the emulsion. /L, mixed by a Venturi mixer, the wastewater enters the oil separation settling tank, the settling time is 1.0h, the sand content in the effluent of the settling tank is 400mg/L, and the oil content is 90mg/L. The wastewater treated in the settling tank is sent to the cyclone, and the content of sand and soil after cyclone separation is 80mg/L, and then the coagulation air flotation and filtration device is carried out. The dosage of polysilicate aluminum is 60mg/L, and the cationic poly The amount of acrylamide added is 50 mg/L, and the filter is filled with quartz sand. The turbidity of the filter effluent is 4.6NTU, the petroleum content is 20mg/L, and the suspended solid content is 18mg/L. The wastewater can be used as oil sand washing water for recycling.

The present invention adopts a combined treatment method of "oil separation sedimentation-cyclone separation-coagulation air flotation-filtration". Its advantages are as follows: ① For a large amount of sand contained in oil sand washing wastewater, according to the difference in particle size and settling time, multi-level classification treatment is carried out, and the sand is settled more thoroughly; ② According to the asphalt-based oil in the wastewater Petroleum substances exist in different states in the wastewater, and the particle size of the oil droplets is different, and the separation and removal of petroleum substances is more thorough; Waste water can be recycled as oil sand washing water; ④Two-stage Venturi mixers are used in series to ensure fast material flow and prevent large-diameter sand particles from depositing inside equipment or pipelines, causing blockage; The device is used, the method flow is short, the energy consumption is low, and the treatment effect is good.

Certainly, the present invention also can have other various embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes All changes and modifications should belong to the protection scope of the claims of the present invention.

Claims (18)

1. A method for treating oil sand washing water, comprising the following steps: Step 1: The waste water separated from oil sand washing is mixed with acid or alkali through the first-stage Venturi mixer, and the pH value of the waste water is adjusted to be between 7.6 and 8.6; Step 2: The wastewater treated in Step 1 is mixed with the demulsifier again through the second-stage Venturi mixer, and the dosage of the demulsifier is controlled to be 30-300mg/L; Step 3: discharge the waste water treated in step 2 into the oil-separating settling tank, keep the residence time of the waste water at 0.5-3.0 h, and remove suspended oil and sand; Step 4: performing cyclone separation on the waste water after the oil separation and sedimentation, and removing particles with a particle size of 50 μm or more in the water; Step 5: Put the wastewater separated by cyclone into the coagulation air flotation device to further remove the suspended solids in the wastewater and the suspended and dissolved petroleum substances; Step 6: Filter the wastewater treated in Step 5 to obtain oil sand washing water. 2. The oil sand washing water treatment method according to claim 1, characterized in that, the acid described in step 1 is selected from hydrochloric acid, sulfuric acid or nitric acid. 3. The oil sand washing water treatment method according to claim 1, characterized in that, the acid described in the step 1 is concentrated sulfuric acid. 4. The oil sand washing water treatment method according to claim 1, characterized in that, the acid described in step 1 is a weak acid. 5. The method for treating oil sand washing water according to claim 1, characterized in that the alkali in the step 1 is selected from sodium hydroxide or potassium hydroxide. 6. The method for treating oil sand washing water according to claim 1, characterized in that the alkali described in the step 1 is a weak alkali. 7. The method for treating oil sand washing water according to claim 1, characterized in that the pH value in the first step is 7.6-8.2. 8. The method for treating oil sand washing water according to claim 1, characterized in that the dosage of the demulsifier in the second step is 50-150 mg/L. 9. The method for treating oil sand washing water according to claim 1, characterized in that the residence time of the wastewater in the step 3 is 1-2.5 hours. 10. The method for treating oil sand washing water according to claim 1, characterized in that, in the fifth step, a flocculant is added to the coagulation and air flotation device. 11. The method for treating oil sand washing water according to claim 10, characterized in that the flocculant is an inorganic polymer flocculant or an organic polymer flocculant. 12 . The method for treating oil sand washing water according to claim 11 , wherein the inorganic polymer flocculant is polyaluminum chloride or polyaluminum silicate. 13 . 13. The method for treating oil sand washing water according to claim 11, characterized in that the organic polymer flocculant is cationic polyacrylamide. 14. The method for treating oil sand washing water according to claim 13, characterized in that the cationic polyacrylamide has a molecular weight of 7 million to 10 million. 15. The method for treating oil sand washing water according to claim 11, characterized in that the dosage of the inorganic polymer flocculant is 40-100 mg/L. 16. The method for treating oil sand washing water according to claim 11, characterized in that the dosage of the organic polymer flocculant is 2-50 mg/L. 17. The method for treating oil sand washing water according to claim 1, wherein the material of the filter element used for filtering in the step 6 is quartz sand, activated carbon or chemical fiber. 18. The method for treating oil sand washing water according to claim 1, wherein the demulsifier in the second step is an ether demulsifier, an aldehyde demulsifier or a lipid demulsifier.