A POSM device and a method for recycling waste oil generated by the device

Abstract

A method for recycling waste oil generated by a POSM device comprises the following steps: step 1. pretreatment of waste oil; step 2. washing and emulsification of waste oil; step 3. static precipitation of waste oil; step 4. centrifugal separation: the emulsion filtered to remove solid sediment is centrifuged by a centrifugal separation device, and the separated oil phase enters step 5, step 5. vacuum distillation: the oil phase separated by centrifugation is vacuum distilled, so that all components with a boiling point below 250°C are distilled and condensed and collected; components with a boiling point above 250°C enter step 6; step 6. polymer cracking: the hydrocarbon phase of the cracking gas after cooling is sent back to the MBA dehydration / SM refining unit; step 7. anaerobic calcination to obtain biochar. The present invention can simply, economically and efficiently treat the waste oil of the POSM device to make it resource-based and harmless, so that the high value-added resources contained in the waste oil of the POSM device can be reused, thereby greatly improving the economic and social benefits of the POSM device.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry and relates to the recovery of chemical products, and in particular to a POSM device and a method for recycling waste oil generated by the device. Background Art

[0002] With the adjustment of national energy policies and changes in the international crude oil market, large-scale oil refining companies will gradually move away from fuel oil and enter an era of comprehensive chemicalization in the future.

[0003] The propylene oxide / styrene (POSM) unit (hereinafter referred to as the "POSM unit") produces propylene oxide and styrene, which are basic petrochemical products and the future investment focus of oil refining companies. In the foreseeable future, domestic petrochemical companies will form an annual POSM production capacity of one million tons, and POSM projects will flourish in petrochemical companies.

[0004] However, the core technology of POSM units is in the hands of the world's three largest petrochemical giants, and technology transfer is strictly controlled. Since the waste oil produced by POSM units was usually used as waste fuel oil for direct combustion as boiler fuel, these world giants do not have special technology for disposing of waste oil produced by POSM units. According to the new version of the National List of Hazardous Wastes, POSM unit waste oil has been listed as HW11 "distillation residue" type toxic hazardous waste, waste code 261-161-11 (heavy fractions produced in the process of direct catalysis of benzene and ethylene, co-oxidation of ethylbenzene and propylene, and catalytic dehydrogenation of ethylbenzene to produce styrene), and must be treated as hazardous waste. At present, the treatment of waste oil produced by POSM units is also a difficult task for the above three largest petrochemical giants. For this high-viscosity copper-chromium waste oil, several domestic joint ventures have previously adopted incineration technology, which not only wastes precious resources, is costly and expensive, but also direct incineration is no longer allowed since the implementation of the new version of the National List of Hazardous Wastes; some manufacturers use this waste oil to produce hydrogen, but waste high-value-added solvents and styrene, and the conversion efficiency is low and the cost is high.

[0005] POSM waste oil is a mixture of heavy components produced by the process, mainly from MBA (methyl benzyl alcohol) dehydration / SM (styrene) refining unit and ACP (acetophenone) hydrogenation unit. A typical list of the main components of POSM waste oil is as follows: Figure 2 and Figure 3 As shown, various substances in the waste oil of POSM device have high added value, so it should be recycled as a resource. However, it has the characteristics of high density (1.03), high viscosity (kinematic viscosity is about 46mm2 / s), salt, heavy metals (Cr content 23ppm, Cu content 218ppm), high molecular polymer (content is more than 50%), etc., which makes the recycling of waste oil of POSM device an urgent problem to be solved by POSM devices at home and abroad. Summary of the invention

[0006] In order to overcome the defects of the prior art, the present invention discloses a POSM device and a method for recycling waste oil generated by the device.

[0007] The POSM device of the present invention comprises an MBA dehydration / SM refining unit and an ACP hydrogenation unit, and is characterized in that: it also comprises a waste oil recovery system, and the waste oil recovery system comprises a stirring tank, an ultrasonic emulsification tank, a static sedimentation tank, a centrifugal separation device, a vacuum distillation device, a cracking device and an anaerobic calcining device which are connected in sequence; the solvent oil outlet of the vacuum distillation device is connected to the inlet of the stirring tank, the liquid phase outlet of the static sedimentation tank is connected to the inlet of the centrifugal separation device, the oil phase outlet of the centrifugal separation device is connected to the vacuum distillation device, the gas phase outlet of the cracking device is connected to the MBA dehydration / SM refining unit through a cooling device, and the solid outlet is connected to the anaerobic calcining device.

[0008] Preferably, the ultrasonic emulsification tank comprises a water washing liquid tank, and the water phase outlet of the centrifugal separation device is connected to the water washing liquid tank.

[0009] Preferably, the vacuum distillation apparatus is a thin film evaporator.

[0010] The present invention also discloses a method for recycling waste oil generated by a POSM device, comprising the following steps:

[0011] Step 1. Pretreatment of waste oil: Add the waste oil to be treated and the solvent for dissolving the polymer in the waste oil into a stirring tank; introduce steam from the bottom of the stirring tank and stir evenly;

[0012] Step 2. Emulsification of waste oil by water washing: pump the waste oil after viscosity reduction into an ultrasonic emulsification tank, add NaCl solution, and adjust the pH value to 7-8 with hydrochloric acid and NaOH solution; add emulsifier into the ultrasonic emulsification tank for full emulsification.

[0013] Step 3. Let the waste oil settle: pump the emulsified waste oil after ultrasonic emulsification into a cone-bottom tank, let it settle, discharge the sediment, and leave the liquid in the tank;

[0014] Step 4. Centrifugal separation: The emulsion after filtering out the solid sediment is centrifuged using a centrifugal separation device, and the separated oil phase enters step 5, and the water phase is purified and returned to step 2 to produce a NaCl solution;

[0015] Step 5. Vacuum distillation: The oil phase separated by centrifugation is subjected to vacuum distillation to distill all components with a boiling point below 250°C and condense and collect;

[0016] At least part of the condensed oil obtained by distillation is returned to step (1) as a polymer solvent;

[0017] Components with a boiling point above 250°C enter step 6;

[0018] Step 6. Polymer cracking: The waste after vacuum distillation is sent to the cracking furnace by a screw machine for cracking; the hydrocarbon phase of the cracking gas is sent back to the "MBA dehydration / SM refining" unit of the POSM device after cooling to achieve resource recycling; the cracking non-condensable gas is burned for heat recovery or sent to the factory for centralized flare incineration;

[0019] Step 7. Anaerobic calcination: The cracking residue is anaerobic calcined in a calcining furnace to obtain biochar.

[0020] Preferably, in step 1, the temperature in the stirring tank is 80-90°C.

[0021] Preferably, in step 2, the concentration of the NaCl solution is 25wt%.

[0022] Preferably, in step 3, the conical bottom tank is kept warm during the precipitation process and allowed to settle for more than 4 hours.

[0023] Preferably, the reduced pressure distillation in step 5 adopts a thin film evaporator, the heating method is steam, the heating temperature is 180° C., and the pressure in the evaporator is about 226±6.6 kPa.

[0024] Preferably, the calcination temperature in step 7 is 700-750 degrees Celsius.

[0025] Preferably, the non-condensable gas that may remain in steps 5 to 7 is burned.

[0026] The POSM device and the method for recycling waste oil produced by the present invention can simply, economically and efficiently process the waste oil of the POSM device to make it resource-based and harmless, so that the high value-added resources contained in the waste oil of the POSM device can be recycled, thereby greatly improving the economic and social benefits of the POSM device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a specific implementation of the POSM device of the present invention;

[0028] Figure 2 The table below shows the physical properties and metal element content of waste oil discharged from a typical existing POSM unit. LHV is the net thermal efficiency.

[0029] Figure 3 for Figure 2 Table of main components of the waste oil. DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are described in further detail below.

[0031] The POSM device of the present invention comprises an MBA dehydration / SM refining unit and an ACP hydrogenation unit, and also comprises a waste oil recovery system, wherein the waste oil recovery system comprises a stirring tank, an ultrasonic emulsification tank, a static sedimentation tank, a centrifugal separation device, a vacuum distillation device, a cracking device and an anaerobic calcining device which are connected in sequence; the solvent oil outlet of the vacuum distillation device is connected to the inlet of the stirring tank, the liquid phase outlet of the static sedimentation tank is connected to the inlet of the centrifugal separation device, the oil phase outlet of the centrifugal separation device is connected to the vacuum distillation device, the liquid phase outlet of the cracking device is connected to the MBA dehydration / SM refining unit, and the solid outlet is connected to the anaerobic calcining device.

[0032] A typical value of the organic content table of waste oil produced by MBA (methyl benzyl alcohol) dehydration / SM (styrene) refining and ACP (acetophenone) hydrogenation unit is as follows Figure 3 As shown, it contains a large amount of organic components with recycling value. Based on the above POSM device, the method for recycling the waste oil produced therefrom comprises the following steps:

[0033] Step 1. Pretreatment of waste oil: Add the waste oil to be treated and the solvent for dissolving the polymer in the waste oil into a stirring tank; introduce steam from the bottom of the stirring tank and stir evenly;

[0034] This step reduces the viscosity of the waste oil and facilitates emulsification. Since the main components of POSM waste oil are various solvents, styrene polymers and other polymers, heavy metals are entrained therein. Adding solvents to dissolve these polymers can reduce the viscosity of the waste oil and is more conducive to the precipitation of heavy metals. Steam is introduced from the bottom of the stirring tank while maintaining the temperature in the stirring tank at 80-90°C to reduce the viscosity.

[0035] In this step, the solvent can be recovered from the condensed oil obtained in the subsequent step 5 as the solvent.

[0036] Step 2. Emulsification of waste oil by water washing: pump the waste oil after viscosity reduction into an ultrasonic emulsification tank, add NaCl solution, and adjust the pH value to 7-8 with hydrochloric acid and NaOH solution; add emulsifier into the ultrasonic emulsification tank for full emulsification.

[0037] Since the specific gravity of waste oil is about 1.03, in order to make the hydrocarbon and water phases separate better, the concentration of NaCl solution added in this step is about 25% to increase the specific gravity of the water phase;

[0038] Since heavy oil contains heavy metal ions such as Cr and Cu, the pH value of the washing water needs to be adjusted to 7-8 with hydrochloric acid and NaOH to meet the pH value for the best precipitation of heavy metal ions such as Cr and Cu;

[0039] Emulsifiers are added to the ultrasonic emulsification tank to convert the water-in-oil emulsion into an oil-in-water emulsion, so that the solid residue can be desorbed from the oil phase.

[0040] Step 3. Let the waste oil settle: pump the emulsified waste oil after ultrasonic emulsification into a cone-bottom tank, let it settle, discharge the sediment, and leave the liquid in the tank;

[0041] In this step, after the emulsion after ultrasonic emulsification is pumped into the conical bottom tank, the conical bottom tank should be insulated; it is left to settle for more than 4 hours, so multiple standing tanks should be set; the released precipitates are hydroxide precipitates such as Cr, Cu and other solid residues in the waste oil. Since the solid residues contain heavy metal elements, etc., they can be safely disposed of separately, which is not involved in the present invention.

[0042] Step 4. Centrifugal separation: The emulsion after filtering out the solid sediment is centrifuged using a centrifugal separation device, and the separated oil phase enters step 5, and the water phase is purified and returned to step 2 to produce a NaCl solution;

[0043] In this step, the NaCl solution is recycled, which not only reduces costs, but also because the waste oil contains more water-soluble components such as alcohols, etc., but the NaCl washing water is recycled to easily form a saturated solution of these soluble components, so it does not affect the washing effect.

[0044] Step 5. Vacuum distillation: The oil phase separated by centrifugation is subjected to vacuum distillation to distill all components with a boiling point below 250°C and condense and collect;

[0045] The condensed oil obtained by distillation can be directly returned to step (1) as a polymer solvent. Since the solvent required in step (1) is limited, usually only a part of it is used as a solvent, and the remaining condensed oil can be purified and refined and directly reused as special solvent oil and raw material oil in the corresponding production links;

[0046] Components with a boiling point above 250°C enter step 6;

[0047] The vacuum distillation device can use a thin film evaporator, the heating method is steam, the heating temperature is 180°C, and the pressure in the evaporator is about 200±50mmHg (26±6.6kPa), so that the monomer solvent with a boiling point below 250°C is distilled out, and a part of the distilled condensed oil is directly returned to step (1) as a solvent for waste oil, and the remaining condensed oil is purified and refined and reused as solvent oil and raw material oil in related production links; the distillation residue is in a molten state at this time and still has a certain fluidity, mainly styrene polymers and a small amount of high-boiling point heavy oil, which is sent to step 6 by a screw machine and cracked by a cracking furnace.

[0048] Step 6. Polymer cracking: The waste after vacuum distillation is sent to the cracking furnace by a screw machine for cracking; the hydrocarbon phase of the cracking gas is sent back to the MBA dehydration / SM refining unit of the POSM device after cooling to achieve resource recycling; the cracking non-condensable gas is burned for heat recovery or sent to the factory for centralized flare incineration;

[0049] According to the experimental verification of the inventors, the pyrolysis temperature range of polystyrene is 300-450℃, the peak temperature is 410℃, and the complete cracking temperature is about 480℃. In addition to the residual carbon, the cracking products of polystyrene include about 50% styrene monomer, about 30% polymers and repolymers, about 18% ethylbenzene and other single benzene ring compounds, and about 2% compounds without benzene rings. The cracking distillate is a mixture mainly composed of styrene monomer, which can be directly used for styrene recovery in the MBA dehydration / SM refining unit in the POSM device.

[0050] Step 7. Anaerobic calcination: The cracking residue is anaerobic calcined in a calcination furnace to obtain biochar. The calcination temperature is usually 700-750°C, the organic matter is completely distilled, and the final residue is biochar. Since the heavy metal elements have been removed before, the biochar no longer contains heavy metal elements and can be sold as fuel or other products. Specific embodiments

[0051] Step 1: Put the waste oil from the temporary waste oil storage tank into the mixing tank; add distilled oil as solvent from the top of the mixing tank; pass 180℃ steam from the bottom of the mixing tank; stir evenly. The amount of steam to be passed should be to keep the temperature in the tank at 80-90℃; add the amount of distilled oil so that the instant detection value of the kinematic viscosity of the waste liquid is about 180cst.

[0052] Step 2: Pump the waste oil after viscosity reduction into the ultrasonic emulsification tank, add 25% mass percentage concentration of NaCl solution, and adjust the pH value to 7-8 (real-time detection value) with 20% hydrochloric acid and 20% NaOH solution; add emulsifier to the ultrasonic emulsification tank; fully emulsify. During this process, the emulsification tank body should be insulated.

[0053] Step 3: Pump the emulsified liquid into a cone-bottom tank, let it settle for 4 hours, separate into layers, and release the sediment from the bottom. The sediment will be handed over to a qualified hazardous waste disposal unit for disposal. During this process, the static sedimentation tank should be insulated.

[0054] Step 4: The emulsion with the solid sediment removed is pumped into a centrifugal separation device for centrifugal separation, and the water phase is returned to step 1 for recycling after purification; the oil phase is put into a temporary storage tank for standby use.

[0055] Step 5: The waste oil after centrifugal separation is distilled under reduced pressure from the temporary storage tank through a thin film evaporator. The heating method of the thin film evaporator is 180°C pipeline steam, the heating temperature is 180°C, and the pressure in the evaporator is about 200±50mmHg (26±6.6kPa), so that all components with a boiling point below 250°C are distilled out, and the distillate oil is sent to the temporary storage tank for temporary storage, and a part of the distillate oil is returned to step 1 as a polymer solvent; the remaining distillate oil is purified and refined and directly reused as a special solvent oil in the corresponding production link. The non-condensable gas produced by the reduced pressure distillation is burned for heat recovery or sent to the factory for centralized flare incineration.

[0056] Step 6: The waste material after vacuum distillation in the thin film evaporator is sent to the cracking furnace by a screw machine for cracking. The heating temperature is 450-480℃ and the heating is electrically controlled. The hydrocarbon phase of the cracking gas is quickly cooled and sent back to the MBA dehydration / SM refining unit of the POSM device to achieve resource recycling. Inhibitors can be added during the cooling process to prevent repolymerization. The cracking non-condensable gas is burned for heat recovery or sent to the factory for centralized flare incineration.

[0057] Step 7: The pyrolysis residue is calcined in a calcining furnace at an oxygen-free temperature of 700-750°C, using electric control heating to generate biochar. The gas generated by the calcination is burned for heat recovery or sent to the factory for centralized torch incineration.

[0058] The present invention is verified by a small test experiment according to the above steps, and the results are as follows:

[0059] In step 1, the waste oil used for the experiment is taken from the waste oil in the large tank. The homogenization has been completed and the property is semi-fluid. The amount taken is 1000g; the amount of solvent oil is 500ml; the amount of 25% NaCl is 200ml; a small amount of 20% hydrochloric acid and 20% NaOH.

[0060] In step 4, the volume of the separated oil phase is 1486 ml.

[0061] In step 5, the volume of solvent oil obtained is 927 ml.

[0062] In step 6, 415 ml of cracking condensate oil is obtained.

[0063] In step 7, the weight of the biochar obtained was 97 g.

[0064] After testing, the biochar obtained in step 7 contained a total chromium content of 11 mg / kg and a total copper content of 32 mg / kg, and no other heavy metal factors were detected. The heavy metal content of the biochar product is lower than the "first-level natural background" standard in the "Soil Environmental Quality Standard" (GB15618-1995), and is also much lower than the "Agricultural Land Soil Pollution Risk Screening Value (Basic Item)" standard in the "Soil Environmental Quality-Agricultural Land Soil Pollution Risk Control Standard" (GB15618-2018), and can be sold as a product.

[0065] The present invention achieves recycling and standard discharge of the mixed waste oil of the POSM device. Among them, NaCl solution is not used as a consumable and can be recycled; since the chromium and copper content in the waste oil is small, the consumption of NaOH and hydrochloric acid is very small; water can be recycled in the process and is not discharged externally; solid waste only contains precipitated chromium hydroxide, copper hydroxide and sand and stone debris, and the amount of solid waste generated is greatly reduced compared with other treatment methods; waste gas and non-condensable gas can be disposed of by burner or centralized torch incineration, and since the raw materials do not contain organic chlorine and halogen, dioxins will not be generated during the incineration process, reducing air pollution.

[0066] The present invention aims at the characteristics of low carbonization degree of mixed waste oil of POSM device, in which the organic matter content is more than 98.5%. In particular, the regenerated solvent and styrene monomer are high value-added products. There is no special restriction on raw materials, and the resource recycling is emphasized, with obvious economic benefits.

[0067] The foregoing describes various preferred embodiments of the present invention. Unless the preferred implementation modes in various preferred embodiments are obviously self-contradictory or based on a certain preferred implementation mode, various preferred implementation modes can be arbitrarily superimposed and used in combination. The embodiments and specific parameters in the embodiments are only for clearly describing the invention verification process of the inventor, and are not used to limit the patent protection scope of the present invention. The patent protection scope of the present invention shall still be based on its claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recycling waste oil produced by a POSM device for producing propylene oxide and styrene, characterized in that: The following steps are involved: Step 1. Pretreatment of waste oil: Add the waste oil to be treated from the methylbenzyl alcohol dehydration / styrene refining unit and the acetophenone hydrogenation unit and the solvent for dissolving the polymer in the waste oil into a stirring tank; introduce steam from the bottom of the stirring tank and stir evenly; Step 2. Washing and emulsifying the waste oil: pump the waste oil after viscosity reduction into an ultrasonic emulsification tank, add NaCl solution, and adjust the pH value to 7-8 with hydrochloric acid and NaOH solution; add emulsifier to the ultrasonic emulsification tank for full emulsification; in step 2, the concentration of NaCl solution is 25wt%; Step 3. Let the waste oil settle: pump the emulsified waste oil after ultrasonic emulsification into a cone-bottom tank, let it settle, discharge the sediment, and leave the liquid in the tank; Step 4. Centrifugal separation: The emulsion after filtering out the solid sediment is centrifuged using a centrifugal separation device, and the separated oil phase enters step 5, and the water phase is purified and returned to step 2 to produce a NaCl solution; Step 5. Vacuum distillation: The oil phase separated by centrifugation is subjected to vacuum distillation to distill all components with a boiling point below 250°C and condense and collect; At least part of the condensed oil obtained by distillation is returned to step (1) as a polymer solvent; Components with a boiling point above 250°C enter step 6; Step 6. Polymer cracking: After vacuum distillation, the components with a boiling point above 250°C are sent to the cracking furnace by a screw compressor for cracking; the hydrocarbon phase of the cracking gas is sent back to the methyl benzyl alcohol dehydration / styrene refining unit of the POSM device after cooling to achieve resource recycling; the cracking non-condensable gas is burned for heat recovery or sent to the factory for centralized flare incineration; Step 7. Anaerobic calcination: The cracking residue is anaerobic calcined in a calcining furnace to obtain biochar.

2. The method for recycling waste oil produced by the POSM device as claimed in claim 1, characterized in that, In the step 1, the temperature in the stirring tank is 80-90°C.

3. The method for recycling waste oil produced by the POSM device as claimed in claim 1, characterized in that, In the step 3, the conical bottom tank is kept warm during the precipitation process and allowed to settle for more than 4 hours.

4. The method for recycling waste oil produced by the POSM device as claimed in claim 1, characterized in that: In the step 5, the reduced pressure distillation adopts a thin film evaporator, the heating method is steam, the heating temperature is 180° C., and the pressure in the evaporator is 226±6.6 kPa.

5. The method for recycling waste oil produced by the POSM device as claimed in claim 1, characterized in that: The calcination temperature in step 7 is 700-750 degrees Celsius.

6. The method for recycling waste oil produced by the POSM device as claimed in claim 1, characterized in that: The remaining non-condensable gas in steps 5 to 7 is burned.

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