Method and device for preparing biomass fuel oil by taking illegal cooking oil as raw material

Abstract

The invention discloses a method and a device for preparing biomass fuel oil by taking illegal cooking oil as a raw material, and belongs to the technical field of biomass energy. The method comprises the following steps: sequentially carrying out magnetic separation, hot water washing and composite adsorption gradient pretreatment on illegal cooking oil to obtain purified oil; purified oil is preheated and then enters a cascade reaction system, and catalytic cracking and hydrodeoxygenation are carried out without cooling; and the hydrogenation product is subjected to three-stage fractionation to extract main body biological fuel oil, and heavy components are recycled. The special device is composed of a pretreatment unit, a reaction unit and a fractionation unit which are sequentially connected, the reaction unit adopts a design that a fluidized bed cracking reactor is directly connected with a fixed bed hydrogenation reactor integrated with an ultrasonic transducer, and the fractionation unit is provided with a high-precision float valve tray system. According to the invention, the bottleneck of the conversion technology of high-impurity illegal cooking oil is broken through, the low-temperature fluidity and cleanliness of the product are obviously improved, the operation cycle of the device is long, the production cost and pollutant emission are greatly reduced, and an efficient and reliable solution is provided for recycling of kitchen waste oil.

Description

Technical Field

[0001] The present invention relates to the field of biomass energy technology, and more particularly to a method and a dedicated device for preparing high-calorific-value biomass fuel oil using waste cooking oil (gutter oil) as raw material through catalytic cracking and hydrogenation upgrading. The present invention particularly relates to a method and a device for preparing biomass fuel oil using gutter oil as raw material. Background Art

[0002] Waste cooking oil (commonly known as "gutter oil") is an important component of urban waste, with an annual global production of more than 60 million tons. This type of waste oil is mainly composed of triglycerides (accounting for 70-90%), mixed with free fatty acids (5-25%), colloids, phospholipids, metal ions (such as Fe 2+ , Ca 2+ Traditional landfill or incineration disposal methods not only result in a huge waste of renewable resources, but also lead to serious environmental risks such as heavy metal pollution in the soil and dioxin emissions.

[0003] Currently, the industry generally uses base-catalyzed transesterification (such as NaOH / KOH catalysis) to convert waste cooking oil into fatty acid methyl esters (biodiesel). However, this technology has significant shortcomings: when the free fatty acid content in the feedstock is high (acid value > 2 mgKOH / g), the fatty acids undergo a saponification reaction with the base catalyst (RCOOH + NaOH → RCOONa + H2O), which covers and deactivates the catalyst's active sites. Furthermore, the product becomes severely emulsified and difficult to separate, causing the conversion rate to plummet below 60%. To overcome these shortcomings, existing processes must include advanced pretreatment steps such as esterification pre-deacidification or molecular distillation, resulting in a significant proportion of pretreatment costs to the total production cost. More importantly, the resulting biodiesel generally has an oxygen content above 11 wt%, resulting in a low calorific value (approximately 37 MJ / kg) and poor low-temperature fluidity (cold filter plugging point > 5°C), failing to meet the national standard for 0# automotive diesel (GB 19147-2016).

[0004] Although the direct hydrodeoxygenation (HDO) process can produce high calorific value alkanes (>42MJ / kg), its practical application faces multiple obstacles: the sulfur, nitrogen compounds and metal ions (especially Ca2+) contained in waste cooking oil. 2+ The reaction process must be carried out at temperatures exceeding 300°C and a high pressure of 10 MPa, significantly increasing equipment investment costs. The high-temperature cracking of triglycerides generates reactive intermediates such as acrolein, which causes severe coking in the reactor (carbon deposition rate > 8 wt%), resulting in a shorter continuous operation cycle of the device.

[0005] Based on the current state of technology, the resource utilization of waste cooking oil faces three core contradictions: at the economic level, deep pretreatment and frequent catalyst replacement keep production costs high; at the product quality level, the cetane number of biodiesel is generally lower than 49 and the freezing point is higher than 0°C, making it difficult to meet the standards of high-grade fuel oil; at the environmental level, traditional processes produce 15wt% soap stock solid waste (classified as HW08 hazardous waste) and acidic wastewater with a COD value exceeding 5000mg / L for every ton of raw materials processed.

[0006] Therefore, the industry urgently needs to develop an integrated process that can adapt to complex feedstocks, reduce operating costs, and simultaneously produce qualified fuel oil. The synergistic catalytic cracking-hydrogenation upgrading technology proposed in this invention is an innovative solution designed to address this systemic challenge. Summary of the Invention

[0007] The purpose of the present invention is to solve the technical bottlenecks of poor raw material adaptability, low product quality and serious coking of the device during the conversion of high-impurity waste cooking oil, and to provide a high-efficiency and low-cost biomass fuel oil preparation method and device.

[0008] To achieve the above object, the present invention provides a method for preparing biomass fuel oil using waste cooking oil as raw material, comprising the following steps: Step 1: Gradient pretreatment: The waste cooking oil raw material is subjected to magnetic separation by a permanent magnetic drum with a magnetic field strength of ≥0.8T to remove iron impurities, then mixed with hot water for washing, and centrifuged to obtain an oil phase. The oil phase is passed through a fixed bed filled with a composite adsorbent to remove impurities and obtain purified oil. The obtained purified oil has a moisture content of ≤0.5wt% and an acid value of ≤1mgKOH / g. Step 2: Cracking-hydrogenation integrated reaction: After preheating, the purified oil enters the series reaction system and undergoes cracking reaction under the action of a cracking catalyst. The cracking products are directly introduced into the hydrogenation reactor for hydrodeoxygenation under the action of a hydrogenation catalyst, and the ultrasonic auxiliary system is simultaneously turned on; Step 3, fractionation, refining and circulation: The hydrogenated product enters a three-stage fractionation system after heat recovery through heat exchange. The operating temperature of the primary distillation tower is 120-180°C, and the operating temperature of the main distillation tower is 180-360°C. The main distillation tower produces biofuel oil, and the heavy components separated by the vacuum tower are returned to the cracking reactor.

[0009] Preferably, the hot water washing temperature in step 1 is 80±5°C, and the oil-water volume ratio is 1:1.5-2.5; Preferably, the composite adsorbent in step 1 is a mixture of ZSM-5 molecular sieve and activated clay in a mass ratio of 1:1.8-2.2.

[0010] Preferably, the cracking catalyst in step 2 is Ni-Mo / γ-Al2O3, wherein the NiO content is 4.5-5.5wt%, and the MoO3 content is 14.5-15.5wt%; and the specific surface area of the γ-Al2O3 carrier is ≥250 m² / g.

[0011] Preferably, the cracking operation conditions in step 2 are 380-420°C / 0.5-0.8 MPa / space velocity 0.8-1.2 h -1 .

[0012] Preferably, the hydrogenation catalyst in step 2 is Pt-SAPO-11 molecular sieve, with a Pt loading of 0.8-1.2 wt %; the SiO 2 / Al 2 O 3 molar ratio of the SAPO-11 molecular sieve is 0.1-0.3.

[0013] Preferably, the ultrasonic frequency in step 2 is 20-50 kHz, and the power density is 50-100 W / L.

[0014] Preferably, the recycling amount of the heavy component in step 3 is ≤ 15 wt % of the total amount of raw materials.

[0015] Another technical object of the present invention is to provide a waste cooking oil-based biofuel oil preparation device, comprising a pretreatment unit, a reaction unit and a fractionation unit connected in sequence; the pretreatment unit comprises a permanent magnet drum, a steam-jacketed washing tank, a three-phase horizontal screw centrifuge and an adsorption tower connected in sequence; the reaction unit comprises a tubular heat exchanger connected in series with the adsorption tower outlet, a fluidized bed cracking reactor equipped with a catalyst online regeneration unit, and a fixed bed hydrogenation reactor with an integrated ultrasonic transducer array, wherein the axial spacing of the transducers is ≤15 cm; the fractionation unit comprises a primary distillation tower, a main distillation tower equipped with 50 layers of floating valve trays and a reflux ratio controller, and a pressure reducing tower connected in sequence.

[0016] As a further embodiment of the present invention, the magnetic field strength of the permanent magnet drum is ≥ 0.8 T; the steam-jacketed washing tank is equipped with a temperature sensor and a steam flow control valve; the adsorption tower is filled with a ZSM-5 / activated clay composite adsorbent; the operating frequency of the ultrasonic transducer array is 20-50 kHz; the adjustment range of the reflux ratio controller is 1:1.5-2.0; and the outlet of the fluidized bed cracking reactor is directly connected to the inlet of the fixed bed hydrogenation reactor via an insulated pipeline, with no cooling device between the two reactors.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention's method for preparing biomass fuel oil from waste cooking oil utilizes a triple synergistic pretreatment system of intense magnetic separation, gradient water washing, and composite adsorption to efficiently remove heavy metal ions and acidic substances, thoroughly resolving the industry's challenge of traditional processes being unable to process high-acidity, high-impurity raw materials. Combined with a direct-connected cracking-hydrogenation integrated process, deep deoxygenation conversion is achieved under low-pressure conditions to produce high-purity biofuel oil.

[0018] 2. This method for producing biomass fuel oil from waste cooking oil utilizes a seamless, direct-connected dual-reactor design: fluidized-bed pyrolysis and ultrasonically enhanced hydrogenation. Combined with a high-precision fractionation system (multi-layered float valve trays and intelligent reflux control), this method achieves precise separation of key fractions and stable control of product quality, extending the device's continuous operation cycle. Wastewater recycling and a near-zero solid waste emission system address pollution issues, providing a sustainable development path for the industrialization of biomass energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic flow diagram of the device for preparing waste cooking oil-based biofuel oil according to the present invention; DETAILED DESCRIPTION

[0020] 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] 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. Example

[0022] See also Figure 1 In an embodiment of the present invention, a method for preparing biomass fuel oil using waste cooking oil as raw material comprises the following specific steps: Step 1: Gradient pretreatment: Use a dedicated device to pretreat the unit: catering waste oil (acid value 28 mgKOH / g, Ca 2+ The purified oil was then centrifuged and centrifuged at 3500 rpm for 24 h. The purified oil was then centrifuged at 70°C for 24 h. The purified oil was then centrifuged at 3500 rpm ...

[0023] Step 2: Integrated Cracking-Hydrogenation Reaction: The purified oil is preheated to 290°C in a tubular heat exchanger before entering a fluidized-bed cracking reactor, where it undergoes cracking over a Ni-Mo / γ-Al2O3 catalyst (NiO 5.0wt%, MoO3 15.0wt%) at 400°C / 0.7MPa. The cracking products are then passed directly to a fixed-bed hydrogenation reactor (with an integrated ultrasonic transducer array, 12cm axial spacing) for hydrodeoxygenation at 270°C / 3.2MPa over a Pt-SAPO-11 catalyst (Pt 1.0wt%) and ultrasonic waves (45kHz / 80W / L). The cracking products are introduced into the hydrogenation reactor via an insulated pipeline within 3 seconds, with a temperature drop rate of ≤50°C / s to prevent condensation and coking of heavy components.

[0024] Step 3: Fractional distillation, refining and circulation: The hydrogenated product is heat exchanged with the feed oil in a tubular heat exchanger to 150°C and then enters the fractionation tower. The primary distillation tower (120-180°C fraction cut) produces light hydrocarbons; the main distillation tower (50 layers of float valve trays, reflux ratio controller set to 1:1.8) produces 180-360°C biofuel oil; then the vacuum tower separates the heavy components >360°C (12wt%) and returns them to the cracking reactor through the circulation pump.

[0025] In this embodiment, the waste cooking oil-based biofuel production device includes a pretreatment unit, a reaction unit, and a fractionation unit connected in sequence. The pretreatment unit includes a permanent magnet drum, a steam-jacketed washing tank, a three-phase decanter centrifuge, and an adsorption tower connected in sequence. The reaction unit includes a tubular heat exchanger connected in series with the adsorption tower outlet, a fluidized bed cracking reactor equipped with an online catalyst regeneration unit, and a fixed-bed hydrogenation reactor integrated with an ultrasonic transducer array, wherein the transducers have an axial spacing of ≤15 cm. The fractionation unit includes a primary distillation tower, a main distillation tower equipped with 50 layers of float valve trays and a reflux ratio controller, and a vacuum tower connected in sequence. The magnetic field strength of the permanent magnet drum is ≥0.8 T. The steam-jacketed washing tank is equipped with a temperature sensor and a steam flow control valve. The adsorption tower is filled with a ZSM-5 / activated clay composite adsorbent. The operating frequency of the ultrasonic transducer array is 20-50 kHz. The adjustment range of the reflux ratio controller is 1:1.5-2.0. The outlet of the fluidized bed cracking reactor is directly connected to the inlet of the fixed bed hydrogenation reactor through an insulation pipeline, and there is no cooling device between the two reactors. Example

[0026] Step 1: Treatment of Fe 2+ 120 ppm waste oil, the adsorption tower is changed to ZSM-5 / activated clay = 1:1.8 (the rest of the equipment is the same as Example 1), the oil Fe 2+ Residual <1 ppm.

[0027] Step 2: Adjust the ultrasonic transducer to 50kHz / 100W / L (frequency within the range of 20-50kHz), and the deoxidation rate is 99.2%.

[0028] Step 3: The recycle amount of heavy components is 8wt% (≤15wt%), and the cetane number of the product is 61. Example

[0029] Step 1: Same as Example 1, the adsorbent was regenerated and reused 10 times in each batch.

[0030] Step 2: The cracking catalyst was automatically regenerated by burning at 450°C every 48 hours in an online regeneration unit with ultrasonic waves continuously activated. After 500 hours of operation, the cracking conversion rate remained at 90.2%. Nitrogen containing 2% oxygen by volume was introduced into the online regeneration unit and burned at 450°C for 4 hours, restoring the catalyst activity to 98.5%.

[0031] Step 3: The reflux ratio controller is maintained at 1:1.8, the heavy component circulation volume is 14wt%, and the distillation system continues to operate stably.

[0032] Comparative Example 1 Traditional transesterification process Step 1: Waste cooking oil (acid value 4.8 mgKOH / g) is esterified with sulfuric acid and then molecularly distilled (without dedicated pretreatment equipment).

[0033] Step 2: NaOH-catalyzed transesterification (without cracking-hydrogenation integrated device), the product is severely emulsified.

[0034] Step 3: Distill to obtain biodiesel (no fractionator for precise cutting), with a freezing point of +4°C.

[0035] Comparative Example 2: No ultrasonic assistance Step 1: Same as Example 1.

[0036] Step 2: The ultrasonic transducer array was turned off (violating the 20-50 kHz requirement), and the hydrogenation pressure was increased to 8.0 MPa; after 190 hours, the reactor pressure difference increased by 300%.

[0037] Step 3: Same as Example 1, except that the sulfur content of the product is increased to 35 ppm.

[0038] Comparative Example 3 Heavy Component Excessive Circulation Step 1 / 2: Same as Example 1.

[0039] Step 3: The heavy component circulation rate was 22 wt% (>15 wt% critical value). After 150 hours, the pipeline from the vacuum tower to the cracking reactor was blocked and the system was shut down.

[0040] Comparison table of biomass fuel oil data prepared in Examples and Comparative Examples

[0041] In summary, when Examples 1-3 directly treat high-acid value waste cooking oil (28-35 mgKOH / g), the product yield (90.5%-92.1%) is much higher than that of Comparative Example 1 (68%) for treating low-acid value oil, the sulfur content (7-9 ppm) is significantly lower than that of Comparative Example 1 (120 ppm) and Comparative Example 2 (35 ppm), the pour point (-16 to -15°C) is more than 20°C lower than that of Comparative Example 1 (+4°C) and is better than that of Comparative Example 2 (-10°C), and the operating cycle (500+ hours) is more than twice that of Comparative Example 2 (190h) and Comparative Example 3 (150h). This comprehensively proves that the present invention has comprehensive improvements in adaptability to high-acid value raw materials, product yield, cleanliness (low sulfur), low-temperature fluidity and long-term stability of the device.

[0042] 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 preparing biomass fuel oil using waste cooking oil as raw material, characterized in that The following steps are involved: Step 1: Gradient pretreatment: The waste cooking oil raw material is subjected to magnetic separation by a permanent magnetic drum with a magnetic field strength of ≥0.8T to remove iron impurities, then mixed with hot water for washing, and centrifuged to obtain an oil phase. The oil phase is passed through a fixed bed filled with a composite adsorbent to remove impurities and obtain purified oil. The obtained purified oil has a moisture content of ≤0.5wt% and an acid value of ≤1mgKOH / g. Step 2: Cracking-hydrogenation integrated reaction: After preheating, the purified oil enters the series reaction system and undergoes cracking reaction under the action of a cracking catalyst. The cracking products are directly introduced into the hydrogenation reactor for hydrodeoxygenation under the action of a hydrogenation catalyst, and the ultrasonic auxiliary system is simultaneously turned on; Step 3, fractionation, refining and circulation: The hydrogenated product enters a three-stage fractionation system after heat recovery through heat exchange. The operating temperature of the primary distillation tower is 120-180°C, and the operating temperature of the main distillation tower is 180-360°C. The main distillation tower produces biofuel oil, and the heavy components separated by the vacuum tower are returned to the cracking reactor.

2. A method for preparing biomass fuel oil using waste cooking oil as raw material according to claim 1, characterized in that: The hot water washing temperature in step 1 is 80±5°C, and the oil-water volume ratio is 1:1.5-2.

5.

3. A method for preparing biomass fuel oil using waste cooking oil as raw material according to claim 1, characterized in that: The composite adsorbent in step 1 is prepared by compounding ZSM-5 molecular sieve and activated clay in a mass ratio of 1:1.8-2.

2.

4. A method for preparing biomass fuel oil using waste cooking oil as raw material according to claim 1, characterized in that: In step 2, the cracking catalyst is Ni-Mo / γ-Al2O3, wherein the NiO content is 4.5-5.5wt% and the MoO3 content is 14.5-15.5wt%; the specific surface area of the γ-Al2O3 carrier is ≥250 m² / g.

5. A method for preparing biomass fuel oil using waste cooking oil as raw material according to claim 1, characterized in that: The cracking operation conditions in step 2 are 380-420℃ / 0.5-0.8MPa / space velocity 0.8-1.2h -1 .

6. A method for preparing biomass fuel oil using waste cooking oil as raw material according to claim 1, characterized in that: In step 2, the hydrogenation catalyst is Pt-SAPO-11 molecular sieve, with a Pt loading of 0.8-1.2 wt %; the SiO2 / Al2O3 molar ratio of the SAPO-11 molecular sieve is 0.1-0.

3.

7. A method for preparing biomass fuel oil using waste cooking oil as raw material according to claim 1, characterized in that: The ultrasonic frequency in step 2 is 20-50kHz, and the power density is 50-100W / L.

8. A method for preparing biomass fuel oil using waste cooking oil as raw material according to claim 1, characterized in that: The recycling amount of the heavy component in step 3 is ≤ 15wt% of the total amount of raw materials.

9. A biomass fuel oil preparation device using waste cooking oil as raw material for implementing the method according to any one of claims 1 to 8, characterized in that The invention comprises a pretreatment unit, a reaction unit and a fractionation unit connected in sequence; the pretreatment unit comprises a permanent magnet drum, a steam jacketed washing tank, a three-phase horizontal screw centrifuge and an adsorption tower connected in sequence; the reaction unit comprises a tubular heat exchanger connected in series with the outlet of the adsorption tower, a fluidized bed cracking reactor equipped with an online catalyst regeneration unit, and a fixed bed hydrogenation reactor integrated with an ultrasonic transducer array, wherein the axial spacing of the transducers is ≤15 cm; the fractionation unit comprises a primary distillation tower, a main distillation tower equipped with 50 layers of floating valve trays and a reflux ratio controller, and a vacuum tower connected in sequence.

10. The device for producing waste cooking oil-based biofuel oil according to claim 9, characterized in that: The magnetic field strength of the permanent magnet drum is ≥0.8T; the steam-jacketed washing tank is equipped with a temperature sensor and a steam flow regulating valve; the adsorption tower is filled with a ZSM-5 / activated clay composite adsorbent; the operating frequency of the ultrasonic transducer array is 20-50kHz; the adjustment range of the reflux ratio controller is 1:1.5-2.0; the outlet of the fluidized bed cracking reactor is directly connected to the inlet of the fixed bed hydrogenation reactor through an insulated pipeline, and there is no cooling device between the two reactors.

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