CN1063775C - Method and device for making gasoline and diesel oil using waste plastics - Google Patents

Abstract

The present invention provides a method for preparing gasoline and diesel oil by using waste plastic. The method adopts a multi-tube reactor, waste plastic which is inputted into the reactor is decomposed into small molecule compounds whose carbon number is less than 100, distillates whose temperature is less than 360 DEG C are outputted for catalytic reforming reaction, and through fractionation or direct fractionation, gasoline and diesel oil are obtained. The method of the present invention and the multi-tube recirculation reactor which is especially made can effectively shorten time for leading the cracking temperature of the waste plastic to be reached, can enhance the cracking reaction speed of raw material, and can increase the yield of purpose products. No waste water, no waste gas and no waste slag are generated by the method, or little waste water, little waste gas and little waste slag are generated by the method. Through preliminary estimate, each ton of waste plastic can be used for preparing 700kg of gasoline and diesel oil, 100kg of gas and 200kg of slag. Therefore, the benefit of preapring gasoline and diesel oil by the waste plastic is obvious.

Description

Method and device for producing gasoline and diesel from waste plastics

The invention relates to a method and a device for preparing fuel oil from waste plastics.

With the development of social economy, human demand for plastic products is increasing. At the same time, a large amount of waste plastics are discharged every year, which not only causes new pollution and damage to the social ecological environment, but also is a waste of energy. . Utilizing waste plastics to produce gasoline and diesel oil (or liquid fuel) is generally considered to be the most reasonable and effective method among many waste plastics methods, and there are similar reports in the United States, Japan, Germany, Britain and my country. According to the existing methods, gasoline and diesel are generally obtained by pyrolysis, catalytic reforming and fractionation of waste materials, and gasoline and diesel are obtained directly without catalysis. The above reaction is to add waste plastics directly or through a screw propeller into the reaction kettle in a cold state or at a low temperature, and heat the bottom of the kettle to melt and crack the waste plastics at high temperature. This heating cracking method, on the one hand, due to the poor heat transfer performance of plastics, it takes a long time to heat the cracking temperature of waste plastics, thereby reducing the processing capacity of the process. On the other hand, since it is only limited to the heating at the bottom of the pot, and the high temperature, it will definitely cause local overheating, so that the wall of the vessel will be coked and ash, making it difficult to discharge slag, the process cannot be continuous, and the production capacity is low. U.S. Patents USP 4108730, 4175217 and 4118281 all use heavy circulating oil to dissolve waste plastics, and then carry out catalytic cracking. Although this process improves the dissolution rate of plastics, it requires a large amount of high boiling point heavy oil as thermal circulating oil. Not only increases the complexity of the process, but also increases the energy consumption. The method proposed by U.S. Patent USP 4851601 is to crush waste plastics, heat and melt them and then enter the pyrolysis reaction chamber for cracking. Japanese Patent JP 038690 also mentions that waste plastics are first melted and then cracked in a cracking kettle until catalytic separation. The above-mentioned two patents are characterized in that they all follow the process of melting first, then thermal cracking and then catalytic cracking in the pretreatment, the equipment is complex, and the process flow is long.

The purpose of the present invention is to overcome the disadvantages of the above method, to provide a continuous method of producing gasoline and diesel from waste plastics in which melting, cracking and separation are carried out in one step, and to provide a reactor specially designed for the method.

The method of waste plastics gasoline and diesel oil of the present invention is carried out as follows:

(1) The raw materials are broken to 2-3 cm after sorting, purification and dust removal,

(2) After the temperature of the reactor is raised to 200-300°C under normal pressure (heat transfer oil is added to the reactor at the initial stage of the reaction), the materials are transported to the multi-tube circulation reactor,

(3) When the reaction temperature rises to 350-500°C, waste plastics are decomposed into small molecular compounds with a carbon number less than 100. At this time, the fraction ≥360°C returns to the reactor through the overflow pipe, and the fraction <360°C The output from the reactor enters the catalytic reforming reactor through the draft tube, and then enters the fractionation tower, and the coke residue is discharged from the bottom of the reactor after settling.

(4) The gas entering the fractionation tower is fractionated to obtain gasoline, diesel oil and a small amount of heavy oil (or wax).

In the above method, the process of catalytic reforming can be selected according to needs, and the fraction <360°C output from the reactor can also directly enter the fractionation tower for fractionation without catalytic reforming. Both catalytic reforming and fractionation can be achieved using existing technologies in petroleum refining.

In the method of the present invention, since the three processes of material melting, cracking and separation must be realized in one reactor, a special reactor needs to be designed to achieve the above-mentioned purpose.

The multi-pipe circulating reactor designed for the above method of the present invention comprises a main circulation pipe 7, a waste plastics flow feed pipe 8 and an overflow pipe 9 are installed in the main circulation pipe 7, and a tray 10 is arranged on the top of the main circulation pipe, and the tray Install steam outlet pipe 12 and bubble cap 11 covered on the pipe 12, coil cooler 13 and demister 14 are arranged on the upper end of the tray, flow outlet 16 is arranged on the top, and upper and lower outlets are arranged on the bottom of the main circulation pipe. Two slag discharge isolation valves 3 and 1, between the two valves is the slag receiving cylinder 2, the upper circulation pipe 25 and the lower circulation pipe 4 connected with it are arranged on the periphery of the pipe 7, and the high temperature cracking pipe is set between 4 and 25 5. The upper circulation pipe is also connected to a heat transfer oil buffer cylinder 24, and the heat transfer oil feeding port 23, the purger inlet 21 and the vent port 22 are arranged on the cylinder.

Compared with the prior art, the method for producing gasoline and diesel from waste plastics of the present invention has the following advantages: 1. It overcomes the poor thermal conductivity of plastics and effectively shortens the time for waste plastics to reach the cracking temperature. Under the same temperature conditions, heating with hot melt can shorten the time by one time compared with dry heating; 2. The heat and mass transfer process is improved by adopting a multi-tube self-circulating reactor, and the raw material cracking reaction speed is increased. Increased processing capacity of the process; 3. The structure of the multi-tube self-circulation reactor can speed up the movement of the flow, and the scour effect of the fast flow makes the coke slag generated by the reaction have no chance to stay on the wall of the reactor, but enters the circulation pipe with the flow, from top to bottom, heavier The stream sinks to the bottom of the reactor and is regularly discharged through the slag discharger, thereby effectively realizing the purpose of continuous long-term operation of the process; 4. 4. Using liquid slag method to heat melt materials, saving energy consumption; 5. The process of controlling the fraction above 360°C to automatically return to the reactor and react again increases the yield of the target product; 6. The tower top demister is used to avoid the blockage of the system pipeline and ensure the smooth flow of the process; 7. Due to this The process adopts the idea of making full use of gas slag, so that there is no or less three wastes in this process.

The method and reactor of the present invention will be described in detail below with reference to the accompanying drawings and examples.

Fig. 1 shows that according to the method of the present invention and specially designed multi-tubular reactor structure schematic diagram.

FIG. 2 is a top view of FIG. 1 .

As shown in the figure, the reactor includes a main circulation pipe 7, a waste plastics flow feed pipe 8 and an overflow pipe 9 are installed in the pipe 7, and a tray 10 is arranged on the top of the pipe 7, and a vapor flow outlet pipe is installed on the tray 12 and the bubble cap 11 covered on the pipe 12, the upper end of the tray is provided with a coil cooler 13 and a demister 14, and the above parts are connected with the main circulation pipe through flanges 20 and 19, and a safety valve 15, a logistics Outlet 16, pressure gauge 17 and thermocouple tube 18. The periphery of the main circulation pipe 7 is provided with an upper circulation pipe 25 and a lower circulation pipe 4 communicating with it, a high-temperature cracking pipe 5 is set between 4 and 25, and a liquid level measurement sensor 6 is installed on the fork of the pipe 5 . The upper circulation pipe 25 is also connected to the heat transfer oil buffer cylinder 24, which is provided with a purge gas inlet 21, a vent port 22 and a heat transfer oil feed port 23. 26 is a pressure gauge, and 27 is a thermocouple. The lower part of the main circulation pipe 7 is the slag discharge part, and the upper and lower slag discharge isolation valves 3 and 1 are set respectively, and the slag receiving cylinder 2 is located between the two valves. Such a slag discharge design can ensure that the heat will not leak out to maintain the process Serialization. When using the above-mentioned reactor, heat conduction oil should be added at the initial stage of the reaction. The heat conduction oil is added from the feed port 23, enters the main circulation pipe 7 and the cracking pipe 5 through the buffer cylinder 24, the upper and lower circulation pipes 25, 4, and is controlled by the liquid level measuring instrument 6. The liquid level reaches 2/3 of the cracking tube, and then purged with an inert gas. The inert gas may be nitrogen, water vapor, flue gas, etc. The purge gas enters through the purge gas inlet 21 to purge the entire reactor, and the purge gas is discharged from the conduit 16 and then enters the atmosphere through the second-stage catalytic reactor connected behind. When the oxygen content of the tail gas is measured <1% , turn off the purge gas. After the purging is completed, start to heat up, the final temperature of the cracking tube is 500°C, and the final temperature of the main circulation tube is 450°C. When the temperature rises to 200-3000°C, the material enters the circulation pipe 7 through the feed pipe 8, where the fresh material and the high-boiling heat stream (<360°C) from the tower top overflow pipe 9 in the fresh material and the main circulation pipe pass through the cracking pipe 5 , the high-temperature liquid flow (<400°C) along the upper circulation pipe 25 directly contacts and melts, and makes the temperature in the main circulation pipe drop, and the material moves from top to bottom to 4 places in the lower circulation pipe. Since the temperature at the lower circulation pipe is higher than The temperature in the main circulation pipe, so the temperature of the material rises and gradually moves upward along the lower circulation pipe 4 until the high temperature cracking pipe 5 (the temperature is 460 ° C), where the material is rapidly cracked, due to the gap between the main circulation pipe 7 and the cracking pipe 5 The temperature difference between them causes the density difference in different pressure zones, thus causing the self-circulation of materials. The material cracked by the cracking pipe 5 goes to the main circulation pipe 7 along the upper circulation pipe 25, and the material speed suddenly slows down. After gas-liquid separation, the liquid phase part returns to the main circulation pipe 7, and the gas phase part passes through the tray 10 and passes through the bubble cap along the conduit 12. 11 Vapor-liquid mass transfer and heat exchange, and then through the cooler 13 to finally control the flow temperature ≤ 360 ° C, the material ≥ 360 ° C is cooled in the bubble cap 11 and returned to the main circulation pipe 7 through the overflow pipe 9, the distillation of < 360 ° C The part then enters the second-stage catalytic reforming reactor through the demister 14 along the conduit 16, or directly enters the fractionation tower.

The liquid-solid two-phase in the reactor settles and separates in the main circulation pipe 7, and the coke slag enters the slag receiving cylinder 2 through the slag isolation valve 3 at the bottom, and finally discharges from the valve 1. The molten liquid material then returns to the main circulation pipe 7 for further reaction. In the above reaction, after the materials are continuously added to the reactor, the gas, liquid and solid substances produced are separated through the reactor and discharged separately, forming a continuous reaction process.

In the above-mentioned multi-tubular circulation reactor, the design of the main circulation pipe 7 and the upper and lower circulation pipes 25 and 4 and the cracking pipe 5 can have multiple forms. What are drawn in the accompanying drawing is that the upper and lower circulation pipes and the cracking pipe are based on the main circulation pipe. A form in which the centers are arranged radially.

Example 1

Crush waste plastics to 2-3cm, sieve and remove dust for later use. When the temperature of the reactor rises to 250-300°C, the crushed waste plastics will enter the main circulation pipe, upper and lower circulation pipes and cracking pipes of the multi-tube reactor through the hopper through the screw propeller (screw insulation 230°C) from the feed pipe. The temperature of the main circulation pipe is raised to 400°C, and the reaction starts at 460°C in the cracking pipe, producing a gas-liquid-solid three-phase fluid, and the gas phase passes through the tray 10 along the conduit 12 bubble cap 11 to exchange heat and mass with the accumulated liquid on the tray , and then through the cooler 13 to finally check and control the tower top temperature to 360°C. The stream >360°C (boiling point) is cooled in the bubble cap 11, and returns to the main circulation pipe 7 through the overflow pipe 9, and the fraction ≤360°C enters the catalytic reforming reactor along the conduit 16 through the demister 14 for catalytic reforming . Catalytic reforming uses ZSM-5 molecular sieve as the catalyst, the reaction temperature is 280-380°C and normal pressure. The products after catalytic reforming enter the fractionation tower for fractionation. The temperature of the bottom of the fractionation tower is 400°C and the top of the tower is 195°C. The slag generated in the multi-tube reactor settles through the main circulation pipe 7, and enters the slag receiver 2 through the isolation valve 3 at the bottom of the reactor without stopping the machine, and then is discharged through the valve 1. The non-condensable gas and a small amount of heavy oil liquid phase slag produced in the above process can be recycled and used as heating fuel in this process, and a small amount of heavy oil can also be returned to the furnace for cracking through the heavy oil feeding pipe. Above-mentioned reaction generates product yield (in weight percentage) as follows:

Gasoline 42.82 Gas 9.74

Diesel 29.55 Residue 17.89

Example 2

Reaction process is with embodiment 1. The difference is that the fraction ≤ 360 ° C is discharged from the multi-tube reactor and directly enters the fractionation tower for fractionation without passing through the catalytic cracking reactor. The resulting product yield (in weight percent) is as follows:

Gasoline 22.6 Gas 5.63

Diesel 48.8 Residue 22.97

Claims (3)

1. A method for producing gasoline and diesel from waste plastics is characterized in that it proceeds in the following steps: (1) Sorting waste plastics. After purification and dust removal, it is broken to 2-3 cm. (2) Heat transfer oil is added to the multi-tube circulating reactor at the initial stage of the reaction, and the temperature is raised to 200-300°C under normal pressure conditions After that, the material is transported to the multi-tubular circulation reactor; (3) When the reaction temperature rises to 350-500°C, waste plastics are decomposed into small molecules with a carbon number less than 100 Compound, at this time, the fraction ≥360°C returns to the multi-tube circulation reactor through the overflow pipe, <360°C The fraction enters the reactor equipped with ZSM-5 catalyst from the multi-tubular circulation reactor through the draft tube, and the reaction The temperature is 280-380 ℃, normal pressure, the product after the reaction enters the fractionation tower; Discharge from the bottom of the circulating reactor; (4) The gas entering the fractionation tower is fractionated to obtain gasoline, diesel oil and a small amount of heavy oil (or wax), The gas released from the top of the tower is collected. 2. The method according to claim 1, characterized in that the <360°C distillate output from the multi-tubular circulation reactor Parts can directly enter the fractionation tower for fractionation. 3. A kind of multi-pipe circulation used in the method for producing gasoline and diesel from waste plastics according to claim 1 or 2 The reactor is characterized in that it comprises a main circulation pipe (7), and a waste plastic flow feed pipe is installed in the main circulation pipe (7) (8), the overflow pipe (9), the upper part of the main circulation pipe is provided with a tray (10), and the vapor flow outlet pipe (12) is installed on the tray And cover the bubble cap (11) on the pipe (12), the upper end of the tray is also provided with a coil cooler (13) and a demister (14), the top is provided with a flow outlet (16), and the bottom of the main circulation pipe is provided with two slag discharge isolation valves up and down (3) and (1), between the two valves is a slag receiving cylinder (2), and the periphery of the pipe (7) is provided with an upper circulation cylinder connected to it. Ring pipe (25) and lower circulation pipe (4), high temperature cracking pipe (5) is set between (4) and (25), upper circulation pipe Also connect a thermal oil buffer cylinder (24).

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