Preparation method and device for producing fraction type fuel oil from waste mineral oil

Abstract

The invention relates to the technical field of waste mineral oil recycling, and discloses a preparation method and device for producing fraction type fuel oil from waste mineral oil. According to the method, moisture, metal and impurities are deeply removed through three-stage synergistic pretreatment of sedimentation, centrifugation and adsorption, a light and heavy fraction distillation range is precisely cut through a tandem two-stage reduced pressure distillation system, and finally distillate oil, an antioxidant and a flow improver are compounded and blended under the protection of nitrogen, so that a fuel oil product with high flash point and excellent low-temperature fluidity is obtained. The matched device comprises a pretreatment unit, a double-tower reduced pressure distillation unit and a blending unit, wherein a reduced pressure distillation tower is provided with a special vacuum system to realize narrow distillation range control. The problems of equipment coking and low yield caused by insufficient pretreatment in the traditional process are solved in a breakthrough manner, the yield and quality of the fuel oil are essentially improved, meanwhile, the investment cost and energy consumption are remarkably reduced by simplifying the device structure, efficient conversion of the waste mineral oil is realized, and an industrial demonstration path is provided for hazardous waste recycling.

Description

Technical Field

[0001] The present invention relates to the technical field of waste mineral oil resource utilization, and relates to a method and simplified device for producing distillate fuel oil through efficient pretreatment-vacuum distillation-fraction blending technology, and specifically to a preparation method and device for producing distillate fuel oil from waste mineral oil. Background Art

[0002] Waste mineral oil, a typical hazardous waste generated during industrial production (hazardous waste category HW08), primarily includes waste lubricating oil, hydraulic oil, and transformer oil. This type of oil contains toxic and hazardous substances such as heavy metals (lead and chromium), polycyclic aromatic hydrocarbons (PAHs), and sulfides. If discharged without proper disposal, one liter of waste oil can contaminate one million liters of freshwater, leading to excessive accumulation of heavy metals in soil and irreversible ecological damage. More seriously, Class I carcinogens such as benzo[alpha]pyrene (BaP) in waste mineral oil can bioaccumulate through the food chain, posing a direct threat to human health. Consequently, global regulations mandate the recycling of waste mineral oil. For example, the EU Waste Framework Directive stipulates a recycling rate of at least 85%, and my country's Technical Specifications for Pollution Control in Waste Mineral Oil Recycling prioritize resource utilization. Against this backdrop, the development of green, low-carbon, and efficient recycling technologies has become an urgent industry need.

[0003] Existing waste mineral oil regeneration technologies primarily fall into three categories: physical refining, chemical treatment, and combined processes. Physical refining centers around distillation, exemplified by thin-film evaporation. This process separates different fractions by forming a liquid film of waste oil under vacuum and rapidly heating it. Despite its relatively simple equipment structure, this process faces severe coking issues in practice. When the oil temperature exceeds 260°C, colloids and asphaltenes in the waste oil rapidly carbonize on the heated surface, reducing heat transfer efficiency by over 30%. Chemical treatment relies on refining with strong acids (such as sulfuric acid) or solvents (such as propane). While sulfuric acid refining effectively removes impurities, it produces large amounts of hazardous acid slag. The treatment cost of acid slag is high, and the sulfur dioxide released during the neutralization process contributes to air pollution. While solvent refining offers slightly better environmental performance, the significant energy consumption associated with recovering solvents like propane undermines its economic viability.

[0004] To overcome the limitations of single technologies, the industry is gradually turning to combined process development. A common model is "vacuum distillation + hydrorefining." This approach first uses vacuum distillation to cut the distillate, then catalytically hydrodesulfurizes and denitrogenates the distillate. While this approach theoretically produces high-purity base oil, practical industrialization faces three major bottlenecks: First, incomplete pretreatment leads to low distillation efficiency. Emulsified water in waste oil (typically 5-10%) vaporizes and expands during distillation, causing equipment flooding and cross-contamination of the distillates. Unremoved trace metal particles (such as iron filings) become coking nuclei, accelerating carbide formation. Second, the distillate cutting accuracy is insufficient. Traditional single-stage distillation towers struggle to precisely control the distillation range, leading to significant mixing of light and heavy components. Simulations show that a ±5°C fluctuation in the tower top temperature can reduce the target distillate yield by 12 percentage points. Third, product post-processing is inadequate. Simply blending distillates without molecular structure optimization results in poor low-temperature fluidity and insufficient oxidative stability.

[0005] In summary, the current recycling of waste mineral oil resources urgently requires the development of a high-yield, low-cost, and easily scalable technology for producing distillate fuel oil from waste mineral oil. This technology should focus on: 1) developing an efficient fractionation pretreatment process to completely remove water, impurities, and metals; 2) establishing precise fraction cutting control methods; and 3) designing a compounding efficiency-enhancing solution tailored to the fuel oil's characteristics. By avoiding complex equipment modifications through process innovation, environmental regulations can be met while achieving economic feasibility, providing a new technological option for the efficient resource utilization of waste mineral oil. Summary of the Invention

[0006] The purpose of the present invention is to solve the technical bottlenecks of incomplete pretreatment, low fraction cutting accuracy and serious coking in the waste mineral oil regeneration process, and to provide a high-efficiency and low-cost distillate fuel oil preparation method and device.

[0007] To achieve the above object, the present invention provides a method for producing distillate fuel oil from waste mineral oil, comprising the following steps: Step 1: Tertiary pretreatment: The waste mineral oil is heated to 60-80°C and allowed to settle for 20-24 hours to separate the wastewater. The waste oil is then centrifuged at 2500-3500 rpm to remove metal particles. Finally, the waste oil is passed through an adsorption tower filled with activated clay to remove colloids and pigments, yielding purified oil (water content ≤ 0.5wt%, metal content ≤ 50ppm). Step 2, two-stage vacuum distillation: the purified oil enters the first vacuum distillation tower (vacuum degree -0.07~-0.09 MPa, temperature 230~260℃), cutting the light fraction at the distillation range of 180~350℃ (yield 60~65wt%); the heavy oil at the bottom of the tower enters the second vacuum distillation tower (vacuum degree -0.09~-0.10 MPa, temperature 270~310℃), cutting the heavy fraction at the distillation range of 350~450℃ (yield 25~30wt%); Step 3: Blending and enhancing the distillate fractions: light fractions and heavy fractions are mixed in a mass ratio of 6:4 to 7:3, 0.05 to 0.15 wt% of an antioxidant and 0.03 to 0.08 wt% of a flow improver are added, and the mixture is stirred for 30 minutes to obtain distillate fuel oil.

[0008] Preferably, the sedimentation dehydration in step 1 is carried out in a sedimentation tank with a steam coil, and the standing time is 22±0.5h; Preferably, the amount of activated clay in step 1 is 3-5 wt% of the mass of the purified oil, and the adsorption temperature is 80-100°C; Preferably, the first-stage vacuum distillation tower in step 2 uses structured packing, and the packing height is ≥4.5m; Preferably, the light fraction yield in step 2 is controlled to be 60-65wt%, and the heavy fraction yield is 25-30wt%; Preferably, the antioxidant in step 3 is butylated hydroxytoluene (BHT), and the flow improver is polyacrylate; Preferably, the blending process in step 3 is carried out under nitrogen protection, and the oxygen content is ≤50ppm.

[0009] Another object of the present invention is to provide an apparatus for producing distillate fuel oil from waste mineral oil, comprising a pretreatment unit, a distillation unit, and a blending unit connected in sequence. The pretreatment unit comprises a settling tank with a steam-heated coil, a horizontal centrifuge, and an adsorption tower filled with activated clay. The settling tank outlet is connected to the inlet of the horizontal centrifuge, and the oil phase outlet of the horizontal centrifuge is connected to the inlet of the adsorption tower. The distillation unit comprises a first-stage vacuum distillation tower and a second-stage vacuum distillation tower connected in series. The outlet of the adsorption tower is connected to the feed inlet of the first-stage vacuum distillation tower, the bottom oil outlet of the first-stage vacuum distillation tower is connected to the feed inlet of the second-stage vacuum distillation tower via a high-temperature oil pump, the light fraction outlet of the first-stage vacuum distillation tower is connected to a light fraction receiving tank, and the heavy fraction outlet of the second-stage vacuum distillation tower is connected to a heavy fraction receiving tank. The blending unit comprises a light fraction receiving tank, a heavy fraction receiving tank, and a blending tank. The outlets of the light fraction receiving tank and the heavy fraction receiving tank are both connected to the inlet of the blending tank, which is then connected to a finished product storage tank. The outlets of the light fraction receiving tank and the heavy fraction receiving tank are connected to the inlet of the blending tank via a metering pump, forming a fully enclosed continuous production system.

[0010] As a further solution of the present invention: a conical mud collecting hopper and a sewage valve are configured at the bottom of the sedimentation tank; the adsorption tower is equipped with a double-layer filter screen of 80 mesh and 120 mesh, and the height-to-diameter ratio of the activated white clay filling layer is greater than or equal to 3 to 1; a temperature sensor with a range of 0 to 300 degrees Celsius and a vacuum pressure gauge with a range of minus 0.1 to 0 MPa are installed on the top of the first-stage vacuum distillation tower and are connected to a vacuum pump P1, and the second-stage vacuum distillation tower is connected to a vacuum pump P2; the blending tank is equipped with an agitator with a speed of 50 to 100 revolutions per minute and a nitrogen injection pipe with a flow rate of 0.5 to 1.0 cubic meters per hour.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses a three-stage synergistic pretreatment system of sedimentation-centrifugation-adsorption to thoroughly remove moisture, metal particles and colloidal impurities from waste oil (moisture removal rate >98%, metal removal rate >95%), solving the problem of distillation coking at the source. The continuous operation cycle of the device exceeds 8,000 hours, which is more than three times longer than the cleaning cycle of traditional thin-film evaporation processes. The heat transfer efficiency only decreases by less than 5%, far lower than the industry's attenuation level of 30-40%.

[0012] 2. Based on the precise control of the narrow distillation range of two-stage vacuum distillation (180-350°C for the first tower and 350-450°C for the second tower), the total fuel oil yield is increased to over 85%, meeting the EU's mandatory recycling rate standards. The key product performance is significantly improved: the flash point reaches 82-86°C (better than the national standard ≥80°C), the cold filter point is reduced to -6-8°C (resolving the fluidity defect of >0°C in traditional processes), and the sulfur content is stably below 0.3wt%, exceeding the fuel oil quality requirements of GB 16663-1996.

[0013] 3. The entire device integrates only seven standard chemical units, such as settling tanks and centrifuges, which reduces more than five devices compared to traditional vacuum distillation hydrogenation systems, reduces investment costs by 40%, and controls energy consumption per ton of processing within 180 kW·h (less than 60% of the 300 kW·h of traditional processes). There is no acid slag, hazardous waste, or solvent pollution throughout the process, fully complying with the HJ 607-2011 pollution control standard, providing an economical and efficient industrial path for the resource utilization of waste mineral oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a process flow chart for preparing distillate fuel oil from waste mineral oil according to the present invention. DETAILED DESCRIPTION

[0015] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0016] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and should not be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, they can be fixedly connected, detachably connected, or connected in one piece; they can be mechanically connected or electrically connected; they can be directly connected, or indirectly connected through an intermediate medium, or they can be internal connections between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The following describes an embodiment of the present invention based on its overall structure.

[0017] Example 1 Preparation method of distillate fuel oil from waste mineral oil See also Figure 1 The method for producing distillate fuel oil from waste mineral oil comprises the following steps: Step 1: Three-level preprocessing: Waste mineral oil was heated to 60°C and allowed to settle for 24 hours to separate the wastewater. Metal particles were removed by a horizontal centrifuge (2500 r / min) and then passed through an adsorption tower (adsorption temperature 90°C) filled with activated clay (4 wt%) to remove colloids and pigments. Step 2, two-stage vacuum distillation: the purified oil enters the first vacuum distillation tower (vacuum degree -0.07 MPa, temperature 230°C), cutting the light fraction with a distillation range of 180-350°C; the heavy oil at the bottom of the tower enters the second vacuum distillation tower (vacuum degree -0.09 MPa, temperature 270°C), cutting the heavy fraction with a distillation range of 350-450°C; Step 3: Fraction blending and efficiency enhancement: light fraction and heavy fraction were mixed in a mass ratio of 6:4, 0.05 wt% butylated hydroxytoluene and 0.03 wt% polyacrylate were added, and stirred for 30 min.

[0018] This embodiment is implemented using a dedicated device: the pretreatment unit includes a settling tank with a steam-heated coil and a conical mud collecting hopper at the bottom, a horizontal centrifuge, and an adsorption tower with a built-in 80 / 120 mesh double-layer filter and an activated white clay filling layer with a height-to-diameter ratio of ≥3:1 (the settling tank → centrifuge → adsorption tower are connected in sequence); the distillation unit includes a first-stage vacuum distillation tower (equipped with a vacuum pump P1 and a temperature / vacuum instrument) and a second-stage vacuum distillation tower (equipped with a vacuum pump P2) connected in series, with the adsorption tower → first-stage tower → high-temperature oil pump → second-stage tower connected in sequence. The light fraction outlet of the first-stage tower is connected to a light fraction receiving tank, and the heavy fraction outlet of the second-stage tower is connected to a heavy fraction receiving tank. The blending unit merges the outlets of the two receiving tanks into a blending tank equipped with a stirrer with a speed of 50-100 r / min and a 0.5-1.0 m³ / h nitrogen injection pipe, and finally connects to the finished product storage tank to form a fully enclosed production system.

[0019] Example 2 Preparation Method of Distillate Fuel Oil from Waste Mineral Oil Step 1: Tertiary pretreatment: The waste mineral oil is heated to 80°C and allowed to settle for 20 hours to separate the wastewater. Metal particles are removed by a horizontal centrifuge (3500 rpm), and the oil is passed through an adsorption tower filled with activated clay to remove colloids and pigments. Step 2: Two-stage vacuum distillation: The purified oil enters the first vacuum distillation tower (vacuum degree -0.09 MPa, temperature 260°C), cutting the light fraction with a distillation range of 180-350°C; the heavy oil at the bottom of the tower enters the second vacuum distillation tower (vacuum degree -0.10 MPa, temperature 310°C), cutting the heavy fraction with a distillation range of 350-450°C; Step 3: Fraction blending and efficiency enhancement: light fraction and heavy fraction were mixed in a mass ratio of 7:3, 0.15 wt% butylated hydroxytoluene and 0.08 wt% polyacrylate were added, and stirred for 30 min.

[0020] The apparatus for producing distillate fuel oil from mineral oil in this embodiment is the same as that in Example 1 and will not be described in detail here.

[0021] Example 3 Preparation Method of Distillate Fuel Oil from Waste Mineral Oil Step 1: Tertiary pretreatment: The waste mineral oil is heated to 70°C and allowed to settle for 22 hours to separate the wastewater. Metal particles are removed by a horizontal centrifuge (3000 rpm), and the oil is passed through an adsorption tower filled with activated clay to remove colloids and pigments. Step 2: The purified oil enters a primary vacuum distillation tower (vacuum degree -0.08 MPa, temperature 245°C) to cut the light fraction in the distillation range of 180-350°C; the heavy oil at the bottom of the tower enters a secondary vacuum distillation tower (vacuum degree -0.095 MPa, temperature 290°C) to cut the heavy fraction in the distillation range of 350-450°C; Step 3. Fraction blending and efficiency enhancement: The light fraction and the heavy fraction were mixed in a mass ratio of 6.5:3.5, 0.10 wt% butylated hydroxytoluene and 0.05 wt% polyacrylate were added, and stirred for 30 min.

[0022] The apparatus for producing distillate fuel oil from mineral oil in this embodiment is the same as that in Example 1 and will not be described in detail here.

[0023] Comparative Example 1 The steps are the same as those in Example 1, but without the three-stage pretreatment, two-stage vacuum distillation is directly performed.

[0024] Comparative Example 2 The steps were the same as those in Example 2, except that the reduced pressure distillation was changed to single-stage distillation with a vacuum degree of -0.08 MPa and a temperature of 280°C.

[0025] Comparative Example 3 The steps are the same as those in Example 3, but no antioxidant or flow improver is added to the fraction blending.

[0026] Performance Testing The fuel oils prepared in Examples 1-3 and Comparative Examples 1-3 were tested for moisture removal rate, metal removal rate, total yield, flash point, cold filter plugging point, and sulfur content. The test methods are as follows: 1. Moisture removal rate: Determine the moisture content of raw materials and purified oil according to the distillation method in GB / T 260, and calculate (raw material moisture - purified oil moisture) / raw material moisture × 100%; 2. Metal removal rate: Determine the metal content of raw materials and purified oil according to ASTM D5185 ICP-AES method, and calculate (raw material metal content - purified oil metal content) / raw material metal content × 100%; 3. Total yield: finished fuel oil mass / raw material mass × 100%; 4. Flash point: Determined according to GB / T 261 closed cup method; 5. Cold filter plugging point: measured according to SH / T 0248 standard method; 6. Sulfur content: Determined according to GB / T 17040 energy dispersive X-ray fluorescence spectrometry.

[0027] The waste mineral oil raw material used in the test had an initial moisture content of 5-8 wt %, a metal content of 200-300 ppm, and a sulfur content of 1.2-1.8 wt %. The test results of the distillate fuel oils prepared in each embodiment and comparative example are shown in Table 1 below: Table 1 Comparison of the distillate fuel oil data prepared in the examples and comparative examples Test results:

[0028] Note: Comparative Example 1 was not pretreated, so the moisture / metal removal rate was not tested. In summary, the present invention has successfully overcome the industry's stubborn problems of equipment coking, low yield and substandard product performance in the waste mineral oil regeneration process through the three-stage coordinated pretreatment to completely remove moisture and metal impurities, two-stage vacuum distillation to accurately cut the narrow distillation range, and antioxidant-flow coordinated compounding efficiency enhancement. The total yield of fuel oil is stable ≥85% (meeting EU mandatory standards), flash point 82-86℃ (better than national standard ≥80℃), cold filter point ≤-6℃ (breaking the traditional process limit of >0℃). At the same time, the operation cycle of the device exceeds 8,000 hours and the energy consumption per ton of processing is reduced by more than 40%, providing an economical, efficient, green and low-carbon industrial conversion path for the resource utilization of waste mineral oil.

[0029] The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for producing distillate fuel oil from waste mineral oil, characterized in that The following steps are involved: Step 1, tertiary pretreatment: The waste mineral oil is heated to 60-80°C and allowed to settle for 20-24 hours to separate the wastewater. The waste oil is then passed through a horizontal centrifuge to remove metal particles. The waste oil is then passed through an adsorption tower filled with activated clay to remove colloids and pigments to obtain purified oil. Step 2, two-stage vacuum distillation: the purified oil enters the first vacuum distillation tower, where it is cut to obtain light fractions; the heavy oil at the bottom of the tower enters the second vacuum distillation tower, where it is cut to obtain heavy fractions; Step 3: Blending and enhancing the distillate fractions: light fractions and heavy fractions are mixed in a mass ratio of 6:4 to 7:3, 0.05 to 0.15 wt% of an antioxidant and 0.03 to 0.08 wt% of a flow improver are added, and the mixture is stirred for 30 minutes to obtain distillate fuel oil.

2. The method for producing distillate fuel oil from waste mineral oil according to claim 1, wherein: The sedimentation dehydration in step 1 is carried out in a sedimentation tank with a steam coil, and the standing time is 22±0.5h; the horizontal centrifuge removes metal particles at a centrifugal speed of 2500~3500 r / min.

3. The method for producing distillate fuel oil from waste mineral oil according to claim 1, wherein: The amount of activated clay used in step 1 is 3-5wt% of the mass of the purified oil, the adsorption temperature is 80-100°C, and the purified oil has a moisture content of ≤0.5wt% and a metal content of ≤50ppm.

4. The method for producing distillate fuel oil from waste mineral oil according to claim 1, wherein: The first-stage vacuum distillation tower in step 2 uses structured packing with a packing height of ≥4.5m; the distillation range of the light fraction is 180-350°C; the distillation range of the heavy fraction is 350-450°C.

5. The method for producing distillate fuel oil from waste mineral oil according to claim 1, wherein: The vacuum degree of the first-stage vacuum distillation tower in step 2 is -0.07 to -0.09 MPa, and the temperature is 230-260°C; the vacuum degree of the second-stage vacuum distillation tower is -0.09 to -0.10 MPa, and the temperature is 270-310°C.

6. The method for producing distillate fuel oil from waste mineral oil according to claim 1, wherein: In step 3, the antioxidant is butylated hydroxytoluene, and the flow improver is polyacrylate.

7. The method for producing distillate fuel oil from waste mineral oil according to claim 1, wherein: The blending process in step 3 is carried out under nitrogen protection, and the oxygen content is ≤50ppm.

8. A device for producing distillate fuel oil from waste mineral oil for implementing the method according to any one of claims 1 to 7, characterized in that: The device includes a pretreatment unit, a distillation unit and a blending unit connected in sequence; the pretreatment unit includes a sedimentation tank with a steam heating coil, a horizontal centrifuge and an adsorption tower filled with activated clay, the sedimentation tank outlet is connected to the horizontal centrifuge inlet, and the horizontal centrifuge oil phase outlet is connected to the adsorption tower inlet; the distillation unit includes a first-stage vacuum distillation tower and a second-stage vacuum distillation tower connected in series, the adsorption tower outlet is connected to the first-stage vacuum distillation tower feed inlet, the first-stage vacuum distillation tower bottom oil outlet is connected to the second-stage vacuum distillation tower feed inlet via a high-temperature oil pump, the first-stage vacuum distillation tower light fraction outlet is connected to a light fraction receiving tank, and the second-stage vacuum distillation tower heavy fraction outlet is connected to a heavy fraction receiving tank; the blending unit includes a light fraction receiving tank, a heavy fraction receiving tank and a blending tank, the light fraction receiving tank and the heavy fraction receiving tank outlets are both connected to the blending tank inlet, the blending tank outlet is connected to a finished product storage tank, and the light fraction receiving tank and the heavy fraction receiving tank outlets are connected to the blending tank inlet via a metering pump, forming a fully enclosed continuous production system.

9. The device for producing distillate fuel oil from waste mineral oil according to claim 8, characterized in that: The bottom of the settling tank is equipped with a conical mud collecting hopper and a sewage valve; the adsorption tower is equipped with a double-layer filter screen of 80 mesh and 120 mesh, and the height-to-diameter ratio of the activated white clay filling layer is ≥3:1; the top of the first-stage vacuum distillation tower is equipped with a temperature sensor with a range of 0-300°C and a vacuum pressure gauge with a range of -0.1-0 MPa and is connected to a vacuum pump P1, and the second-stage vacuum distillation tower is connected to a vacuum pump P2; the blending tank is equipped with an agitator with a speed of 50-100 r / min and a nitrogen injection pipe with a flow rate of 0.5-1.0 Nm³ / h.

10. The device for producing distillate fuel oil from waste mineral oil according to claim 8, characterized in that: A temperature sensor with a range of 0 to 300 degrees Celsius and a vacuum pressure gauge with a range of -0.1 to 0 MPa are installed on the top of the first-stage vacuum distillation tower and connected to a vacuum pump P1. The second-stage vacuum distillation tower is connected to a vacuum pump P2.

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