CN117185593A - Method for stripping treatment of oily sludge based on supercritical carbon dioxide - Google Patents
Method for stripping treatment of oily sludge based on supercritical carbon dioxide Download PDFInfo
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- 239000010802 sludge Substances 0.000 title claims abstract description 220
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 110
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 55
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 55
- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000000926 separation method Methods 0.000 claims abstract description 56
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims abstract description 17
- 238000005496 tempering Methods 0.000 claims abstract description 13
- 230000003750 conditioning effect Effects 0.000 claims description 38
- 238000003860 storage Methods 0.000 claims description 29
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- 125000002091 cationic group Chemical group 0.000 claims description 19
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- 238000000194 supercritical-fluid extraction Methods 0.000 claims description 19
- 230000008961 swelling Effects 0.000 claims description 16
- 238000006243 chemical reaction Methods 0.000 claims description 15
- 238000004064 recycling Methods 0.000 claims description 12
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims description 10
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 9
- 238000007906 compression Methods 0.000 claims description 9
- 239000012065 filter cake Substances 0.000 claims description 8
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 7
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims description 5
- 235000017557 sodium bicarbonate Nutrition 0.000 claims description 5
- BJEPYKJPYRNKOW-REOHCLBHSA-N (S)-malic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O BJEPYKJPYRNKOW-REOHCLBHSA-N 0.000 claims description 3
- BJEPYKJPYRNKOW-UHFFFAOYSA-N alpha-hydroxysuccinic acid Natural products OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 claims description 3
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 239000002535 acidifier Substances 0.000 description 8
- 208000005156 Dehydration Diseases 0.000 description 7
- 230000018044 dehydration Effects 0.000 description 7
- 238000006297 dehydration reaction Methods 0.000 description 7
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 125000000218 acetic acid group Chemical group C(C)(=O)* 0.000 description 2
- 150000001555 benzenes Chemical class 0.000 description 2
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- Treatment Of Sludge (AREA)
- Extraction Or Liquid Replacement (AREA)
Abstract
The invention belongs to the technical field of oily sludge treatment, and particularly discloses a method for stripping and treating oily sludge based on supercritical carbon dioxide, which comprises the steps of firstly carrying out tempering treatment on the oily sludge by using anhydrous sodium carbonate, secondly acidizing the oily sludge in a supercritical carbon dioxide state to enable the sludge to be in a porous structure, fully extracting oil on the surface of the oily sludge, and then changing external conditions to enable CO in the supercritical state after extraction 2 The oil is converted into a gaseous state, and the separation from the oil phase is completed, so that the purpose of efficiently stripping the oil from the oil-containing sludge is achieved. The invention is green and environment-friendly, has no secondary pollution, has good treatment effect and high treatment efficiency, and the oil content of the treated oil-containing sludge can reach within 2 percent, thereby meeting the requirements of containingThe oil sludge discharge standard requirement realizes innocent treatment and resource utilization of the oil sludge, provides technical guarantee for high-efficiency utilization of the oil sludge resource by the oil sludge, has obvious economic and environmental protection comprehensive benefits, and has higher industrial application value.
Description
Technical Field
The invention belongs to the technical field of oily sludge treatment, and particularly relates to a method for treating oily sludge based on supercritical carbon dioxide stripping.
Background
The oil sludge is mainly oil-containing sludge formed by mixing crude oil or other oil products and solid phase in the oilfield production process, and is solid waste rich in mineral oil, and the main components of the oil sludge are crude oil, sludge and water. The solid particle size is mostly between 1 and 100 μm, the composition of the oil depends on the crude oil type, different processes and operating conditions of the refinery, while the composition of the sludge may vary over time. The sludge usually contains a certain amount of crude oil (with the concentration of 5-80%), heavy metal ions (such as iron, copper, shackles and the like) and inorganic salt compounds (with the concentration of 5-20%), and the like. The oil phase in the oil sludge generally contains substances such as benzene series, phenols and the like, and is accompanied with malodor and toxicity, if the oil sludge is directly contacted with natural environment, the soil is poisoned, acidified or alkalized, the soil and soil texture structure is changed, the plant root system is prevented from growing, the water body and vegetation are polluted greatly, and meanwhile, the waste of petroleum resources is also caused.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a method for stripping treatment of oily sludge based on supercritical carbon dioxide, so as to solve the problems that substances such as benzene series, classification and the like in the oily sludge cause great pollution to water bodies and vegetation and simultaneously cause petroleum resource waste.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
the invention provides a method for treating oily sludge based on supercritical carbon dioxide stripping, which comprises the following steps:
step 1: oil-containing sludge tempering and centrifuging
Injecting the oily sludge into an oily sludge conditioning tank, adding a conditioning agent into the oily sludge conditioning tank to condition, centrifugally dewatering, and acidizing the oily sludge in the oily sludge conditioning tank by an acidifier; the sewage enters a plate-and-frame filter press for filter pressing, the sewage after filter pressing is sent to a sewage combination station for treatment, and the filter cake is mixed with an oil sludge cake to be used as the oil sludge to be treated;
step 2: supercritical stripping
The sludge to be treated is sent into a sectional supercritical fluid extraction device by a screw conveyor, and low-pressure carbon dioxide in a gas storage tank is compressed into supercritical CO by a compressor 2 Heat exchange is carried out through a heat exchanger to carry out supercritical CO 2 As stripping agent, performing supercritical fluid stripping on oil phase of the oil sludge to be treated to obtain stripped sludge and stripped CO 2 And a stripped oil phase mixture; the stripped sludge falls into an oil sludge storage tank at the bottom of the segmented supercritical fluid extraction device;
step 3: CO 2 Is separated and recycled
Stripped CO 2 The oil phase mixture after stripping is firstly separated by a first separating device and then enters a second separating device for deep separation, and the stripped CO is separated 2 The gas converted from the supercritical state is discharged from the top of the first separation device and the second separation device,enters an air storage tank for recycling and simultaneously produces CO removal 2 Oil phase, CO removal 2 The oil phase is discharged from the bottoms of the first separation device and the second separation device.
Further, the modifier in the step 1 is anhydrous sodium carbonate or anhydrous sodium bicarbonate and cationic polyacrylamide flocculant, and the total added amount of the modifier is 0.1-0.5% of the mass of the oily sludge.
Further, the mass ratio of the anhydrous sodium carbonate or anhydrous sodium bicarbonate to the cationic polyacrylamide flocculant is 1 (1.2-1.8).
Further, the cationic polyacrylamide flocculant is cationic polyacrylamide with a weight average molecular weight of 8000-120000 daltons.
Further, in the step 2, the acidulant is acetic acid, citric acid, malic acid or other biodegradable organic acid, and the pH is adjusted to 3-4 by the acidulation treatment.
Further, the low-pressure carbon dioxide in the air storage tank is compressed into supercritical CO through the compressor in the step 2 2 And exchanges heat through a heat exchanger, specifically: compressing low-pressure carbon dioxide with the pressure lower than 5MPa in a gas storage tank to 30MPa by a compressor, and compressing the low-pressure carbon dioxide to supercritical CO 2 The temperature of the carbon dioxide is increased to 70-80 ℃ in the compression process, and heat exchange is carried out by a heat exchanger to carry out supercritical CO 2 The temperature of (2) was reduced to 60 ℃.
Further, the volume ratio of the stripping agent to the sludge to be treated in the step 2 is 1 (1-6).
Further, the reaction temperature in the step 2 is 60 ℃ when the supercritical fluid stripping is carried out on the oil phase of the oil sludge to be treated, the supercritical swelling pressure is 18-30 MPa, and the swelling time is 2.5-3 h.
Further, the oil content of the sludge after stripping in the step 2 is 0.8-2%.
Further, the stripped CO in step 3 2 After the stripped oil phase mixture enters the first separation device and the second separation device, the pressure of the first separation device is reduced to 5MPa, and the pressure of the second separation device is reducedDown to atmospheric pressure.
The invention has at least the following beneficial effects:
the invention firstly utilizes anhydrous sodium carbonate to carry out tempering treatment on the oily sludge, secondly acidizes the oily sludge in a supercritical state of carbon dioxide to enable the sludge to be in a porous structure, fully extracts oil on the surface of the oily sludge, and then changes external conditions to enable CO in the supercritical state after extraction 2 The oil is converted into a gaseous state, and the separation from the oil phase is completed, so that the purpose of efficiently stripping the oil from the oil-containing sludge is achieved. The method is environment-friendly, has no secondary pollution, has good treatment effect and high treatment efficiency, ensures that the oil content of the treated oil-containing sludge can reach within 2%, meets the emission standard requirement of the oil-containing sludge, realizes harmless treatment and resource utilization of the oil-containing sludge, provides technical guarantee for the efficient utilization of the oil sludge resource by the oil-containing sludge, has remarkable economic and environment-friendly comprehensive benefits, and has higher industrial application value.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
In the drawings:
FIG. 1 is a supercritical CO of the present invention 2 And (3) a process flow diagram of stripping treatment of oily sludge.
Reference numerals: 1. an oil sludge tempering tank; 2. a plate and frame filter press; 3. a screw conveyor; 4. a segmented supercritical fluid extraction device; 5. a first separation device; 6. a second separation device; 7. a gas storage tank; 8. a compressor; 9. a heat exchanger.
Detailed Description
The invention will be described in detail below with reference to the drawings in connection with embodiments. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The following detailed description is exemplary and is intended to provide further details of the invention. Unless defined otherwise, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the invention.
Supercritical Fluid Extraction (SFE) is a new green separation technology which is rapidly developed. Supercritical fluid refers to a fluid having a temperature and pressure above a critical temperature and pressure. Supercritical fluids are special fluids between gases and liquids, which have both gas and liquid properties, with densities close to those of liquids, with capacities for dissolving liquids and solids close to common liquid solvents, and viscosities and diffusion rates close to those of common gases. Therefore, the supercritical fluid has better permeability and stronger dissolution capacity, and has higher mass transfer rate and capability of quickly reaching extraction equilibrium, and the supercritical CO is utilized 2 The method for extracting the oil-containing sludge in the oil field is an efficient and environment-friendly treatment method. Supercritical extraction is to extract and separate substances by utilizing the characteristic of supercritical fluid, and then change the supercritical fluid into common gas by means of isothermal depressurization or isobaric heating, so as to separate the extractant from the substances to be separated. Carbon dioxide was selected as the supercritical extractant in the present invention, and the critical data are shown in table 1.
TABLE 1 critical parameters of supercritical fluid extractants
Supercritical CO 2 The extraction is carried out by adopting CO 2 CO in supercritical state as solvent 2 The fluid has larger density and dielectric constant, has strong dissolving power on a plurality of substances, has a separation rate which is far faster than that of liquid extraction and is changed sharply along with the change of pressure and temperature, thus not only having selectivity on the solubility of certain substances, but also being easy to separate solvent and extract. Compared with the conventional separation method, the method has the characteristics of low extraction temperature, strong selectivity, high efficiency, low energy consumption, no pollution and the like, and is particularly suitable for extracting fat-soluble, high-boiling point and thermosensitive substances, and simultaneouslyAnd is also suitable for fine separation of different components. Aiming at the property of the oil sludge, the extraction pressure is 5-20 MPa.
As can be seen from table 2, the fluid has the dual characteristics of gas-liquid two phases in the supercritical state, and has high diffusion coefficient and low viscosity equivalent to those of gas, density similar to that of liquid and good dissolution capability. Carbon dioxide is used as a supercritical fluid, the critical temperature is 31.1 ℃, the critical pressure is 7.39MPa, and the operation temperature and the operation pressure are relatively easy to realize. CO 2 The dissolution capacity of (2) is completely dependent on temperature and pressure, and has the characteristics of supercritical fluid such as density close to liquid, viscosity close to gas and diffusion speed, and the like, and CO 2 The mass transfer rate is far greater than the solvent extraction rate in the liquid state, and the equilibrium can be obtained quickly. Aiming at the property of the oil sludge, the lower extraction temperature is 30-80 ℃.
TABLE 2 comparison of supercritical fluid to gas and liquid Properties
The invention provides a method for stripping treatment of oily sludge based on supercritical carbon dioxide, which comprises the steps of firstly carrying out quenching and tempering treatment on the oily sludge by using a special quenching and tempering agent, secondly acidizing treatment under a supercritical carbon dioxide state to enable the sludge to be in a porous structure, fully extracting oil on the surface of the oily sludge, and then changing external conditions to enable CO in the supercritical state after extraction 2 The oil is converted into a gaseous state, and the separation from the oil phase is completed, so that the purpose of efficiently stripping the oil from the oil-containing sludge is achieved.
As shown in fig. 1, the method for treating the oily sludge based on supercritical carbon dioxide stripping of the invention comprises the following steps:
step 1: oil-containing sludge tempering and centrifuging
Injecting the oily sludge into an oily sludge conditioning tank 1 by a slurry pump, adding a conditioning agent into the oily sludge conditioning tank 1 for conditioning and centrifugal dehydration, wherein the conditioning agent is anhydrous sodium carbonate or anhydrous sodium bicarbonate with the mass ratio of 1 (1.2-1.8) and cationic polyacrylamide flocculant with the weight average molecular weight of 8000-120000 daltons for conditioning and dehydration treatment, and the total addition amount of the conditioning agent is 0.1-0.5% of the mass of the oily sludge; after standing for 6 hours, acidizing the oily sludge in the oil sludge conditioning tank 1 by using an acidifier, wherein the acidifier is acetic acid, citric acid, malic acid or other green and environment-friendly biodegradable organic acids, and acidizing the oily sludge to adjust the pH to 3-4; and (3) the wastewater enters a plate-and-frame filter press 2 for filter pressing, the sewage after filter pressing is sent to a sewage combination station for treatment, and the filter cake and the sludge cake are mixed and then used as sludge to be treated.
Step 2: supercritical stripping
Feeding the sludge to be treated into a segmented supercritical fluid extraction device 4 by using a screw conveyor 3; the low-pressure carbon dioxide with the pressure lower than 5MPa in the gas storage tank 7 is compressed to 30MPa by the compressor 8, and the low-pressure carbon dioxide is compressed to supercritical CO 2 The temperature of the carbon dioxide rises to 70-80 ℃ in the compression process, and the supercritical CO is subjected to heat exchange through a heat exchanger 9 2 Is cooled to 60 ℃ by supercritical CO 2 As a stripping agent, the oil sludge to be treated falls down by gravity from top to bottom, supercritical carbon dioxide flows from bottom to top and is reversely mixed with the oil sludge to be treated for reaction, then the supercritical fluid stripping is carried out on the oil phase of the oil sludge to be treated, the volume ratio of the stripping agent to the oil sludge to be treated is 1 (1-6), the reaction temperature is 60 ℃, the supercritical swelling pressure is 18-30 MPa, the swelling time is 2.5-3 h, and the stripped sludge and the stripped CO are obtained 2 And the oil phase mixture after stripping, the oil content of the sludge after stripping is 0.8-2%; the stripped sludge falls into an oil sludge storage tank at the bottom of the segmented supercritical fluid extraction device 4, and the oil content meets the requirement of a sludge discharge standard.
Step 3: CO 2 Recycling use
Stripped CO 2 The oil phase mixture after stripping is firstly separated from the first separating device 5, then enters the second separating device 6 for deep separation, the pressure of the first separating device 5 is reduced to 5MPa, the pressure of the second separating device 6 is reduced to the atmospheric pressure, and the stripped CO is reduced to the atmospheric pressure 2 The supercritical state is converted into the gaseous state, the gaseous state is discharged from the top parts of the first separation device 5 and the second separation device 6, enters the air storage tank 7 for recycling, and meanwhile, the stripped oil is generated,the oil after the stripping is discharged from the bottoms of the first and second separating devices 5 and 6.
Example 1
Taking the example of oily sludge produced in the sewage treatment section of a certain oil extraction plant in the northern part of Shaanxi, the initial water content of the oily sludge is 60%, the oily substances are 26%, the mud content is 14%, and the method for stripping and treating the oily sludge based on supercritical carbon dioxide comprises the following steps:
step 1: oil-containing sludge tempering and centrifuging
Injecting the oily sludge into an oily sludge conditioning tank 1 by a slurry pump, and respectively adding anhydrous sodium carbonate and cationic polyacrylamide with weight average molecular weight of 10000 daltons into the oily sludge conditioning tank 1 to carry out conditioning centrifugal dehydration, wherein the mass ratio of the anhydrous sodium carbonate to the cationic polyacrylamide is 1:1.2, and the total adding amount is 0.2% of the mass of the oily sludge; after standing for 6 hours, acidizing the oily sludge in the oil sludge conditioning tank 1 by an acidifier, and acidizing to adjust the pH value to 3; and (3) the wastewater enters a plate-and-frame filter press 2 for filter pressing, the water content of the obtained oil sludge cake is 27%, the oil content is 48%, the mud content is 25%, the sewage after filter pressing is sent to a sewage combination station for treatment, and the filter cake and the oil sludge cake are mixed to be used as the oil sludge to be treated.
Step 2: supercritical stripping
Feeding the sludge to be treated into a segmented supercritical fluid extraction device 4 by using a screw conveyor 3; the low-pressure carbon dioxide with the pressure lower than 5MPa in the air storage tank 7 is compressed to 30MPa by a compressor 8 to obtain supercritical CO 2 The temperature of the carbon dioxide rises to 70 ℃ in the compression process, and supercritical CO is sent through the heat exchanger 9 2 Is cooled to 60 ℃ by supercritical CO 2 As a stripping agent, the oil sludge to be treated falls down by gravity from top to bottom, supercritical carbon dioxide flows from bottom to top and is reversely mixed with the oil sludge to be treated for reaction, then supercritical fluid stripping is carried out on the oil phase of the oil sludge to be treated, the volume ratio of the stripping agent to the oil sludge to be treated is 1:3, the reaction temperature is 60 ℃, the supercritical swelling pressure is 20MPa, the swelling time is 2.5h, and the stripped sludge and the stripped CO are obtained 2 And the oil phase mixture after stripping, the water content of the sludge after stripping is 23%, the oil content is 2%, and the sludge content is 75%; after peeling offThe sludge falls into an oil sludge storage tank at the bottom of the segmented supercritical fluid extraction device 4, and the oil content meets the requirement of a sludge discharge standard.
Step 3: CO 2 Recycling use
Stripped CO 2 The oil phase mixture after stripping is firstly separated from the first separating device 5, then enters the second separating device 6 for deep separation, the pressure of the first separating device 5 is reduced to 5MPa, the pressure of the second separating device 6 is reduced to the atmospheric pressure, and the stripped CO is reduced to the atmospheric pressure 2 The oil is converted into gas from a supercritical state and is discharged from the tops of the first separation device 5 and the second separation device 6, enters the gas storage tank 7 for recycling, and meanwhile, stripped oil is generated and discharged from the bottoms of the first separation device 5 and the second separation device 6.
Example 2
Taking the example of oily sludge produced in the sewage treatment section of a certain oil extraction plant in the northern part of Shaanxi, the initial water content of the oily sludge is 60%, the oily substances are 26%, the mud content is 14%, and the method for stripping and treating the oily sludge based on supercritical carbon dioxide comprises the following steps:
step 1: oil-containing sludge tempering and centrifuging
Injecting the oily sludge into an oily sludge conditioning tank 1 by a slurry pump, and respectively adding anhydrous sodium carbonate and cationic polyacrylamide with weight average molecular weight of 10000 daltons into the oily sludge conditioning tank 1 to carry out conditioning centrifugal dehydration, wherein the mass ratio of the anhydrous sodium carbonate to the cationic polyacrylamide is 1:1.2, and the total adding amount is 0.2% of the mass of the oily sludge; after standing for 6 hours, acidizing the oily sludge in the oil sludge conditioning tank 1 by an acidifier, and acidizing to adjust the pH value to 3; and (3) the wastewater enters a plate-and-frame filter press 2 for filter pressing, the water content of the obtained oil sludge cake is 27%, the oil content is 48%, the mud content is 25%, the sewage after filter pressing is sent to a sewage combination station for treatment, and the filter cake and the oil sludge cake are mixed to be used as the oil sludge to be treated.
Step 2: supercritical stripping
The sludge to be treated is sent into a segmented supercritical fluid extraction device 4 by a screw conveyor 3, and low-pressure carbon dioxide with the pressure lower than 5MPa in a gas storage tank 7 is compressed to 30MPa by a compressor 8, so as to obtain supercritical CO 2 The temperature of the carbon dioxide rises to 70 ℃ in the compression process, and supercritical CO is sent through the heat exchanger 9 2 Is cooled to 60 ℃ by supercritical CO 2 As a stripping agent, the oil sludge to be treated falls down by gravity from top to bottom, supercritical carbon dioxide flows from bottom to top and is reversely mixed with the oil sludge to be treated for reaction, then supercritical fluid stripping is carried out on the oil phase of the oil sludge to be treated, the volume ratio of the stripping agent to the oil sludge to be treated is 1:1, the reaction temperature is 60 ℃, the supercritical swelling pressure is 20MPa, the swelling time is 2.5h, and the stripped sludge and the stripped CO are obtained 2 And the oil phase mixture after stripping, the oil content of the sludge after stripping is 1.1%; the stripped sludge falls into an oil sludge storage tank at the bottom of the segmented supercritical fluid extraction device 4, and the oil content meets the requirement of a sludge discharge standard.
Step 3: CO 2 Recycling use
Stripped CO 2 The oil phase mixture after stripping is firstly separated from the first separating device 5, then enters the second separating device 6 for deep separation, the pressure of the first separating device 5 is reduced to 5MPa, the pressure of the second separating device 6 is reduced to the atmospheric pressure, and the stripped CO is reduced to the atmospheric pressure 2 The oil is converted into gas from a supercritical state and is discharged from the tops of the first separation device 5 and the second separation device 6, enters the gas storage tank 7 for recycling, and meanwhile, stripped oil is generated and discharged from the bottoms of the first separation device 5 and the second separation device 6.
Example 3
Taking the example of oily sludge produced in the sewage treatment section of a certain oil extraction plant in the northern part of Shaanxi, the initial water content of the oily sludge is 60%, the oily substances are 26%, the mud content is 14%, and the method for stripping and treating the oily sludge based on supercritical carbon dioxide comprises the following steps:
step 1: oil-containing sludge tempering and centrifuging
Injecting the oily sludge into an oily sludge conditioning tank 1 by a slurry pump, and respectively adding anhydrous sodium carbonate and cationic polyacrylamide with weight average molecular weight of 10000 daltons into the oily sludge conditioning tank 1 to carry out conditioning centrifugal dehydration, wherein the mass ratio of the anhydrous sodium carbonate to the cationic polyacrylamide is 1:1.2, and the total adding amount is 0.2% of the mass of the oily sludge; after standing for 6 hours, acidizing the oily sludge in the oil sludge conditioning tank 1 by an acidifier, and acidizing to adjust the pH value to 3; and (3) the wastewater enters a plate-and-frame filter press 2 for filter pressing, the water content of the obtained oil sludge cake is 27%, the oil content is 48%, the mud content is 25%, the sewage after filter pressing is sent to a sewage combination station for treatment, and the filter cake and the oil sludge cake are mixed to be used as the oil sludge to be treated.
Step 2: supercritical stripping
The sludge to be treated is sent into a segmented supercritical fluid extraction device 4 by a screw conveyor 3, and low-pressure carbon dioxide with the pressure lower than 5MPa in a gas storage tank 7 is compressed to 30MPa by a compressor 8, so as to obtain supercritical CO 2 The temperature of the carbon dioxide rises to 70 ℃ in the compression process, and supercritical CO is sent through the heat exchanger 9 2 Is cooled to 60 ℃ by supercritical CO 2 As a stripping agent, the oil sludge to be treated falls down by gravity from top to bottom, supercritical carbon dioxide flows from bottom to top and is reversely mixed with the oil sludge to be treated for reaction, then supercritical fluid stripping is carried out on the oil phase of the oil sludge to be treated, the volume ratio of the stripping agent to the oil sludge to be treated is 1:1, the reaction temperature is 60 ℃, the supercritical swelling pressure is 18MPa, the swelling time is 3h, and the stripped sludge and the stripped CO are obtained 2 And the oil phase mixture after stripping, the oil content of the sludge after stripping is 0.8%; the stripped sludge falls into an oil sludge storage tank at the bottom of the segmented supercritical fluid extraction device 4, and the oil content meets the requirement of a sludge discharge standard.
Step 3: CO 2 Recycling use
Stripped CO 2 The oil phase mixture after stripping is firstly separated from the first separating device 5, then enters the second separating device 6 for deep separation, the pressure of the first separating device 5 is reduced to 5MPa, the pressure of the second separating device 6 is reduced to the atmospheric pressure, and the stripped CO is reduced to the atmospheric pressure 2 The supercritical state is converted into the gas state and is discharged from the tops of the first separation device 5 and the second separation device 6, the gas is recycled in the gas storage tank 7, meanwhile, the stripped oil is generated, and the bottoms of the first separation device 5 and the second separation device 6 are discharged.
Example 4
Step 1: oil-containing sludge tempering and centrifuging
Injecting the oily sludge into an oily sludge conditioning tank 1 by a slurry pump, and respectively adding anhydrous sodium carbonate and cationic polyacrylamide with the weight average molecular weight of 8000 daltons into the oily sludge conditioning tank 1 to carry out conditioning centrifugal dehydration, wherein the mass ratio of the anhydrous sodium carbonate to the cationic polyacrylamide is 1:1.2, and the total adding amount is 0.1% of the mass of the oily sludge; after standing for 6 hours, acidizing the oily sludge in the oil sludge conditioning tank 1 by an acidifier, and acidizing to adjust the pH value to 3; and (3) the wastewater enters a plate-and-frame filter press 2 for filter pressing, the sewage after filter pressing is sent to a sewage combination station for treatment, and the filter cake and the sludge cake are mixed and then used as sludge to be treated.
Step 2: supercritical stripping
The sludge to be treated is sent into a segmented supercritical fluid extraction device 4 by a screw conveyor 3, and low-pressure carbon dioxide with the pressure lower than 5MPa in a gas storage tank 7 is compressed to 30MPa by a compressor 8, so as to obtain supercritical CO 2 The temperature of the carbon dioxide rises to 70 ℃ in the compression process, and supercritical CO is sent through the heat exchanger 9 2 Is cooled to 60 ℃ by supercritical CO 2 As a stripping agent, the oil sludge to be treated falls down by gravity from top to bottom, supercritical carbon dioxide flows from bottom to top and is reversely mixed with the oil sludge to be treated for reaction, then supercritical fluid stripping is carried out on the oil phase of the oil sludge to be treated, the volume ratio of the stripping agent to the oil sludge to be treated is 1:1, the reaction temperature is 60 ℃, the supercritical swelling pressure is 18MPa, the swelling time is 2.5h, and the stripped sludge and the stripped CO are obtained 2 And the oil phase mixture after stripping, the oil content of the sludge after stripping is 0.8%; the stripped sludge falls into an oil sludge storage tank at the bottom of the segmented supercritical fluid extraction device 4, and the oil content meets the requirement of a sludge discharge standard.
Step 3: CO 2 Recycling use
Stripped CO 2 The oil phase mixture after stripping is firstly separated from the first separating device 5, then enters the second separating device 6 for deep separation, the pressure of the first separating device 5 is reduced to 5MPa, the pressure of the second separating device 6 is reduced to the atmospheric pressure, and the stripped CO is reduced to the atmospheric pressure 2 Conversion from supercritical state to gaseous state is discharged from top of the first and second separation devices 5 and 6And the oil enters the air storage tank 7 for recycling, meanwhile, stripped oil is generated, and the bottoms of the stripped oil first separation device 5 and the stripped oil second separation device 6 are discharged.
Example 5
Step 1: oil-containing sludge tempering and centrifuging
Injecting the oily sludge into an oily sludge conditioning tank 1 by a slurry pump, and respectively adding anhydrous sodium carbonate and cationic polyacrylamide with the weight average molecular weight of 120000 daltons into the oily sludge conditioning tank 1 to carry out conditioning centrifugal dehydration, wherein the mass ratio of the anhydrous sodium carbonate to the cationic polyacrylamide is 1:1.8, and the total adding amount is 0.5% of the mass of the oily sludge; after standing for 6 hours, acidizing the oily sludge in the oil sludge conditioning tank 1 by an acidifier, and acidizing to adjust the pH value to 4; and (3) the wastewater enters a plate-and-frame filter press 2 for filter pressing, the sewage after filter pressing is sent to a sewage combination station for treatment, and the filter cake and the sludge cake are mixed and then used as sludge to be treated.
Step 2: supercritical stripping
Feeding the sludge to be treated into a segmented supercritical fluid extraction device 4 by using a screw conveyor 3; the low-pressure carbon dioxide with the pressure lower than 5MPa in the air storage tank 7 is compressed to 30MPa by a compressor 8 to obtain supercritical CO 2 The temperature of the carbon dioxide rises to 80 ℃ in the compression process, and supercritical CO is sent through the heat exchanger 9 2 Is cooled to 60 ℃ by supercritical CO 2 As a stripping agent, the oil sludge to be treated falls down by gravity from top to bottom, supercritical carbon dioxide flows from bottom to top and is reversely mixed with the oil sludge to be treated for reaction, then supercritical fluid stripping is carried out on the oil phase of the oil sludge to be treated, the volume ratio of the stripping agent to the oil sludge to be treated is 1:6, the reaction temperature is 60 ℃, the supercritical swelling pressure is 30MPa, the swelling time is 3h, and the stripped sludge and the stripped CO are obtained 2 And the oil phase mixture after stripping, the oil content of the sludge after stripping is 2%; the stripped sludge falls into an oil sludge storage tank at the bottom of the segmented supercritical fluid extraction device 4, and the oil content meets the requirement of a sludge discharge standard.
Step 3: CO 2 Recycling use
Stripped CO 2 The oil phase mixture after being stripped is firstly separated into a first separation device 5Preliminary separation, deep separation in the second separator 6, pressure reduction in the first separator 5 to 5MPa, pressure reduction in the second separator 6 to atmospheric pressure, and stripping of CO 2 The supercritical state is converted into the gas state and is discharged from the tops of the first separation device 5 and the second separation device 6, the gas is recycled in the gas storage tank 7, meanwhile, the stripped oil is generated, and the bottoms of the first separation device 5 and the second separation device 6 are discharged.
It will be appreciated by those skilled in the art that the present invention can be carried out in other embodiments without departing from the spirit or essential characteristics thereof. Accordingly, the above disclosed embodiments are illustrative in all respects, and not exclusive. All changes that come within the scope of the invention or equivalents thereto are intended to be embraced therein.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.
Claims (10)
1. A method for treating oily sludge based on supercritical carbon dioxide stripping, which is characterized by comprising the following steps:
step 1: oil-containing sludge tempering and centrifuging
Injecting the oily sludge into an oily sludge conditioning tank (1), adding a conditioning agent into the oily sludge conditioning tank (1) to condition, centrifugally dewatering, and acidizing the oily sludge in the oily sludge conditioning tank (1) by an acidizing agent; press-filtering in a plate-and-frame filter press (2), and delivering the press-filtered sewage to a sewage joint station for treatment, wherein the filter cake and an oil sludge cake are mixed to be used as oil sludge to be treated;
step 2: supercritical stripping
The sludge to be treated is sent into a sectional supercritical fluid extraction device (4) by a screw conveyor (3), and gas storage is carried out by a compressor (8)Compression of low pressure carbon dioxide in tank (7) to supercritical CO 2 And exchange heat by a heat exchanger (9) to supercritical CO 2 As stripping agent, performing supercritical fluid stripping on oil phase of the oil sludge to be treated to obtain stripped sludge and stripped CO 2 And a stripped oil phase mixture; the stripped sludge falls into an oil sludge storage tank at the bottom of the segmented supercritical fluid extraction device (4);
step 3: CO 2 Is separated and recycled
Stripped CO 2 The oil phase mixture after stripping enters a first separating device (5) for preliminary separation, then enters a second separating device (6) for deep separation, and the CO after stripping 2 The supercritical state is converted into the gaseous state and is discharged from the tops of the first separation device (5) and the second separation device (6), and enters the gas storage tank (7) for recycling, and CO removal is generated at the same time 2 Oil phase, CO removal 2 The oil phase is discharged from the bottoms of the first separation device (5) and the second separation device (6).
2. The method for stripping treatment of oily sludge based on supercritical carbon dioxide as claimed in claim 1, wherein the conditioning agent in the step 1 is anhydrous sodium carbonate or anhydrous sodium bicarbonate and cationic polyacrylamide flocculant, and the total addition amount of the conditioning agent is 0.1-0.5% of the mass of the oily sludge.
3. The method for treating the oily sludge based on supercritical carbon dioxide stripping according to claim 2, wherein the mass ratio of the anhydrous sodium carbonate or the anhydrous sodium bicarbonate to the cationic polyacrylamide flocculant is 1 (1.2-1.8).
4. The method for treating oily sludge based on supercritical carbon dioxide stripping according to claim 2, wherein the cationic polyacrylamide flocculant is cationic polyacrylamide with a weight average molecular weight of 8000-120000 daltons.
5. The method for treating oily sludge based on supercritical carbon dioxide stripping according to claim 1, wherein the acidulant in step 2 is acetic acid, citric acid, malic acid or other biodegradable organic acid, and the acidulant is used for regulating pH to 3-4.
6. The method for treating oily sludge based on supercritical carbon dioxide stripping according to claim 1, wherein the low-pressure carbon dioxide in the air storage tank (7) is compressed into supercritical CO by the compressor (8) in the step 2 2 And exchanges heat through a heat exchanger (9), specifically: the low-pressure carbon dioxide with the pressure lower than 5MPa in the gas storage tank (7) is compressed to 30MPa by the compressor (8), and the low-pressure carbon dioxide is compressed to supercritical CO 2 The temperature of the carbon dioxide is increased to 70-80 ℃ in the compression process, and the supercritical CO is subjected to heat exchange through a heat exchanger (9) 2 The temperature of (2) was reduced to 60 ℃.
7. The method for stripping treatment of oily sludge based on supercritical carbon dioxide according to claim 1, wherein the volume ratio of the stripping agent to the oily sludge to be treated in the step 2 is 1 (1-6).
8. The method for treating the oily sludge based on supercritical carbon dioxide stripping according to claim 1, wherein the reaction temperature in the supercritical fluid stripping of the oil phase of the oily sludge to be treated in the step 2 is 60 ℃, the supercritical swelling pressure is 18-30 MPa, and the swelling time is 2.5-3 h.
9. The method for stripping treatment of oily sludge based on supercritical carbon dioxide as claimed in claim 1, wherein the oil content of the stripped sludge in the step 2 is 0.8-2%.
10. The method for treating oily sludge by supercritical carbon dioxide stripping according to claim 1, wherein the stripped CO in step 3 2 From the oil phase mixture after stripping into the first separating device(5) And after the second separation device (6), the pressure of the first separation device (5) is reduced to 5MPa, and the pressure of the second separation device (6) is reduced to atmospheric pressure.
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