JP3621597B2 - Waste gas treatment apparatus and treatment method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waste gas treatment apparatus and treatment method, and more particularly, waste containing oil, carbon and polymer solid powder, hydrogen chloride, and other combustible gases generated in the process of thermally decomposing waste plastic. The present invention relates to a gas processing apparatus and a processing method thereof.
[0002]
[Prior art]
The number of discarded plastics in industrial and general wastes is increasing, but the problem of environmental pollution associated with disposal such as incineration and landfilling is becoming more serious. In particular, the generation of dioxins in incineration is a major social problem.
[0003]
As one of the waste plastic treatments, recently, vinyl chloride-based materials have been separated and removed, or decomposed at a relatively low temperature of 300 to 400 ° C. and dechlorinated. A method of recovering and utilizing in a form has been studied and put into practical use. Among these, in the treatment method in which pyrolysis and solid fuel are produced, a high-temperature waste gas containing solid powders such as a large amount of gaseous high-boiling hydrocarbons, mist-like oil, carbon and polymer is generated together with hydrogen chloride. . This waste gas is usually supplied to a gas / solid-liquid separator such as a cyclone system, and after oil classification, carbon powder and the like contained in the waste gas are separated and removed, 50-60 in a water-cooled cooling tower. It is cooled to below ℃ and then treated by removing hydrogen chloride contained in a water-absorbing absorption tower.
[0004]
[Problems to be solved by the invention]
However, in conventional cyclone gas / solid-liquid separation treatment, the separation performance is not sufficient, and the waste gas contains a large amount of high-boiling gaseous and mist oils, and solids such as carbon and polymers. Since they contain a considerable amount of powder, they are mixed in the process of separating and accumulating in the equipment, and in the case of heat insulation that is usually applied, the temperature drops due to heat dissipation and the fluidity of the oil classification decreases, and these materials stick to each other. As a result of solidification, there have been situations in which the flow path is blocked or it is difficult to extract the separated oil classification. Further, in the piping lines before and after the separation device, the flow path is blocked due to accumulation of deposits such as oil due to the same phenomenon. For this reason, it is necessary to dismantle the separation device and the piping line frequently, and to remove and clean the accumulated and shielded deposits, resulting in problems such as long-term stable treatment operation.
[0005]
[Means for Solving the Problems]
As a result of earnestly examining a more continuous and efficient treatment method of waste gas, the present inventor has applied these methods to a problem that the waste gas generated from the thermal decomposition apparatus is applied with a cooling cleaning method that maintains a high temperature. As a result, the present invention has been completed.
[0006]
That is, the present invention is a treatment apparatus for waste gas generated when waste plastic is thermally decomposed by a thermal decomposition apparatus, and is a lower part for separating and removing the waste gas into oil and solid powder and hydrogen chloride. A cooling and washing tower having a spray-type cooling unit at the top, a cooling and washing tower having a leakage shelf type washing unit, a stirring device for mixing and homogenizing the separated oil and solid powder, and a jacket for heating and keeping the vessel body heated, And an absorption washing tower for removing hydrogen chloride in the residual gas.
[0007]
In addition, the present invention is a method in which high-temperature waste gas generated by thermal decomposition of waste plastic is rapidly cooled and condensed in a spray-type cooling unit at the bottom of the cooling and washing tower, and washed in an upper leaky shelf type washing unit to obtain oil and solids The powder is separated , and then the waste liquid containing the separated oil and solid powder is heated and kept warm in the washing liquid receiving tank, mixed and homogenized, separated and recovered, and hydrogen chloride in the remaining gas is removed by the absorption washing tower. The waste gas processing method characterized by the above is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The waste gas treatment apparatus of the present invention comprises a cooling washing tower (FIG. 1) for separating and removing the waste gas into oil and solid powder and hydrogen chloride, and an absorption washing tower (FIG. 1) for removing hydrogen chloride in the residual gas. 2), the structure and operation will be described below.
[0009]
In the waste gas treatment apparatus of the present invention, the waste plastic pyrolysis apparatus, for example, the cracked waste gas from the pyrolysis solid fuel conversion apparatus or the like has a spray type cooling unit 4 in the lower part and a leaky shelf type cleaning part 5 in the upper part. Directly supplied to the bottom of the cooling washing tower 2.
[0010]
Here, it is preferable that the piping line 25 from the thermal decomposition apparatus to the cooling and washing tower 2 is shortest and is heated and kept warm with a band heater or the like to keep the waste gas at a predetermined temperature. That is, it is preferable to maintain the waste gas temperature at 300 to 350 ° C., which is close to the decomposition temperature in the thermal decomposition apparatus, by external heating that compensates for heat dissipation. The waste gas includes a wide range of oil classifications having a boiling point of 150 to 500 ° C. and a carbon number of C _{8 to} C _40. By maintaining the waste gas temperature at 300 to 350 ° C., the viscosity and adhesion of mist oil At the same time, the aggregation of gaseous oil can be suppressed, and the mixing of these oils with solid powders such as carbon and polymer, condensation due to bonding, and the occurrence of adhesion can be prevented. Thereby, clogging of the flow path due to adhesion and accumulation of condensed matter such as oil in the piping line can be eliminated.
[0011]
Waste gas introduced into the bottom of the spray-type cooling unit 4 from the pyrolyzer comes into contact with several hundreds of microns of room temperature washing water sprayed and flowed down from the spray nozzle 36 while rising, and cooled to 60 to 100 ° C. Is done. This cooling condenses most of the oil having a carbon number of ₉ or more, and solid powder such as carbon and polymer is separated and removed in the waste water in addition to the oil due to the cleaning effect. In addition, the washing water used here can circulate and use the hydrochloric acid aqueous solution produced | generated in this waste gas processing process other than water.
[0012]
Next, the cooled waste gas rises and enters the leaky shelf type washing unit 5 at the top of the tower, and the washing water sprayed from the tower top spray nozzle 35 and the washing water flowing down through the leaky shelf having porosity. In each stage and further cooled, mainly the low-boiling point gaseous hydrocarbons having a carbon number of ₉ or less are condensed, and the fine mist-like oil that has not been separated and removed by the spray part is formed into solids such as carbon and polymer. It is washed away with the powder and separated and removed in the waste water. Here, the leakage shelves are preferably provided in a plurality of stages, for example, 3 to 5 stages. Further, the leak shelf is preferably about several millimeters, preferably 3 to 10 millimeters in diameter, from the viewpoint of contact efficiency between washing water and waste gas and prevention of clogging. In addition, the washing water used here can also circulate and use hydrochloric acid aqueous solution.
[0013]
Here, the cooling washing tower 2 is preferably a rigid cylindrical type. Also, the inner wall surface of the cooling and washing tower, particularly the spray-type cooling unit main body, increases in the viscosity of the oil classification in the waste liquid in contact with the inner wall due to a decrease in temperature under normal heat retention, and accumulates and accumulates. As a result of investigating the viscosity depending on the temperature of this kind of oil, it was experimentally confirmed that the sludge-like material at around 40 ° C. became a viscosity of about 2900 centipoise at 55 ° C. and the adhesion was also lowered. For this reason, the tower main body, particularly the spray-type cooling section, is provided with a heat insulation structure for preventing the oil from condensing and adhering to the outer wall, for example, a jacket 28, so that the fluidity of the oil can be ensured by heating medium heating to 60 ° C. or higher. It is preferable to be able to hold.
[0014]
The drained water after cooling and washing is accommodated in a washing liquid receiving tank 3 provided at the bottom of the tower, that is, at the bottom of the spray type cooling unit. And in the washing | cleaning-liquid receiving tank 3, it is set as the jacket structure 29 similarly to the main body of the cooling washing tower 2, and the waste liquid containing solid powders, such as an oil component, carbon, and a polymer, is heated and heated at 60 degreeC or more with a heat medium heating and stirring apparatus. And mixing and homogenizing is preferable. As a result, the oil classification can be prevented from sticking and accumulating on the inner surface and bottom surface of the main body of the receiving tank, and a stable continuous supply by the pump to the oil / water separation step can be performed. Further, the separated and recovered oil is appropriately stored and reused.
On the other hand, the residual gas obtained by removing and purifying most of the condensable oil, solid powder such as carbon and polymer in the cooling washing tower is discharged from the top of the tower and sent to the absorption washing tower to remove the contained hydrogen chloride.
[0015]
The absorption cleaning tower 6 is preferably of a filling type in which a ceramic packing 7 such as lath shilling is arranged. The waste gas supplied to the lower part of the tower comes into contact with the washing water flowing down from the tower upper spray nozzle 37 while rising in the filler, and the contained hydrogen chloride is absorbed and removed. The washing water used here can also circulate a hydrochloric acid solution.
[0016]
In addition, the remaining combustible components (carbon monoxide, hydrocarbons having a carbon number of ₄ or less, etc.), and the malodorous and harmful gases contained therein are supplied to a waste gas incinerator for incineration detoxification treatment and released into the atmosphere. .
[0017]
【Example】
Next, the waste gas treatment apparatus of the present invention will be described more specifically with reference to FIG.
[0018]
In the dechlorination extrusion fueling device 1 that processes about 250 kg / h of waste plastic (containing about 3.6% of vinyl chloride), the temperature is 350 ° C., high boiling point hydrocarbon and mist oil content is 3.8 kg / h, carbon and polymer-like About 25.2 kg / h of flammable waste gas containing 0.2 kg / h of solid powder and 3.7 kg / h of hydrogen chloride is generated. This waste gas generated from the vent of the fueling apparatus 1 is supplied to the cooling and washing tower 2 in a state of being maintained at a temperature of 300 to 350 ° C. through a pipe 25 having a heat insulation structure by a band heater.
[0019]
The waste gas supplied to the spray-type cooling unit 4 at the lower part of the cooling and washing tower 2 rises, and the concentration is about to be circulated and supplied through the water supply tank 19, the normal temperature supplementary water supplied by the pump 24, the pump 22, and the pipe 44. Combined with 6% hydrochloric acid aqueous solution at a temperature of about 37 ° C., contacted with about 206 kg / h of washing water sprayed through the pressure regulating valve 33 and the upper spray nozzle 36, and rapidly cooled to about 60 ° C. At the same time, most of the oil and solid powder such as carbon and polymer are washed away. Next to the spray type cooling unit 4, this gas is sent to the upper leaky shelf type cleaning unit 5. It has a structure consisting of three stages of perforated plates having a pore diameter of several millimeters. The waste gas is sprayed through the upper spray nozzle 35 as it rises and flows down at a temperature of about 85 kg / h, a temperature of 37 ° C., and a hydrochloric acid concentration of about 6%. It is brought into contact with each wash shelf and cooled to about 50 ° C., and the remaining condensed and mist-like oil, carbon and polymer solid powders are washed away. The main body of the cooling and washing tower 2 has a jacket structure 28, and is heated and kept at about 60 ° C. by passing a heat medium of about 100 ° C. supplied from the heat medium heating device 18 through the pump 23. Prevents adhesion and accumulation on the inner surface. Further, in this cooling washing tower 2, about 30% of the total amount of hydrogen chloride contained in the waste gas is simultaneously washed and removed.
[0020]
The residual gas treated in the cooling and washing tower 2 is sucked and exhausted from the upper part of the tower and supplied to the absorption and washing tower 6. The absorption washing tower 6 is a packed type using Raschig rings 7. The residual gas supplied to the lower part of the tower is brought into contact with cleaning water used for circulation of about 95 kg / h, hydrochloric acid concentration of 6% flowing down from the tower upper spray nozzle 37 while rising in the packing material, and containing hydrogen chloride. About 2.7 kg / h is absorbed and removed, resulting in an exhaust gas having a hydrogen chloride concentration of 50 ppm or less. Then combustible components (carbon monoxide, the number of C ₄ or less hydrocarbons such as carbon) which is supplied through an exhaust pump 8 to the exhaust gas incinerator 9 remaining, and malodor containing and harmful gas incineration, is detoxification atmosphere Released. At this time, since the exhaust gas has a calorific value of about 5000 kcal / Nm ³ , heat is recovered as steam.
[0021]
The cleaning effluent generated in the cooling cleaning tower 2 flows down and is stored in a cleaning liquid receiving tank 3 provided directly connected to the bottom of the tower. The cleaning liquid receiving tank 3 includes a stirring device 20, and the main body has a jacket structure 29. The tank body is heated and kept at about 60 ° C. by passing a heating medium of about 100 ° C. supplied from the heating medium heating device 18 through the jacket. The stored washing waste liquid is mixed and homogenized by the stirring device 20 and is dispersed so that solid powders such as oil, carbon and polymer are not separated or agglomerated. These operations prevent oil classification and heavy solid powder from adhering and accumulating on the inner wall of the tank body, and cleaning drainage without causing pipe blocking due to a lump solidified material. A predetermined amount is extracted stably and automatically through the pump 10. At this time, as a matter of course, the piping line is heated and maintained by a band heater or the like and maintained at about 60 ° C.
[0022]
Next, this washing drainage is sent to the oil / water separator 11 of the specific gravity difference separation type, and the oil classification of about 4.2 kg / h containing several percent of water in the upper part has a concentration of about 6.3% and 295 kg / h in the lower part. Are separated from each other. In addition, heavy oil classification and polymer-like solid powder contained in a very small amount are separated and removed from the bottom of the separator. The oil separated from the upper part is stored and used in the recovered oil tank 13 via the pipe 27. The oil separator 11, the pipe 27, and the recovered oil tank 13 in this processing operation are all heated and insulated so as to maintain 60 ° C. or higher in order to ensure the oil flow.
[0023]
On the other hand, the separated aqueous hydrochloric acid solution is cooled to about 37 ° C. by the cooler 15 and merged with the washing waste water from the absorption washing tower 6 to become about 392 kg / h and a hydrochloric acid concentration of about 6.9%. Sent. Here, this waste water is accommodated in the circulation tank 17 after the oil component contained in a trace amount is removed. Here, the waste water is discharged at the pump 21 as hydrochloric acid having a predetermined concentration of about 54 kg / h and reused, while a part is diluted with make-up water corresponding to the outflow, the pump 22, the pipes 39, 40. And then recycled as wash water for the cooling and washing tower 2 and the absorption washing tower 6.
[0024]
【The invention's effect】
According to the waste gas treatment device of the present invention, hydrogen chloride in the waste gas generated from the waste plastic thermal decomposition device can be efficiently removed, and solid powders such as oil, carbon, and polymer contained in the waste gas. Can be recovered without sticking and solidifying, enabling stable long-term operation of the system.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a cooling washing tower in a waste gas treatment apparatus of the present invention.
FIG. 2 is a configuration diagram showing an absorption cleaning tower in the waste gas treatment apparatus of the present invention.
FIG. 3 is a configuration diagram showing the entire waste gas treatment apparatus of the present invention.
[Explanation of symbols]
1: Dechlorination extrusion fueling device 2: Cooling washing tower 3: Cleaning liquid receiving tank 4: Spray type washing part 5: Leaky shelf type washing part 6: Absorption washing tower 7: Raschig ring 8: Exhaust pump 9: Exhaust gas incinerator 10: Exhaust Liquid pump 11: Oil / water separator 12: Drain pump 13: Recovery oil tank 14: Pump 15: Cooler 16: Waste water purification device 17: Circulation tank 18: Heat medium heating device 19: Water supply tank 20: Stirring devices 21-24 : Pumps 25 to 27: Heater heating pipes 28 to 31: Jackets 32 to 34: Pressure regulating valves 35 to 37: Spray nozzles 38 to 44: Pipe a: Purified waste gas b: Recovered oil c: Recovered hydrochloric acid d: Recovered solid e : Supply water f: Steam

Claims (4)

A treatment apparatus for waste gas generated when waste plastic is thermally decomposed by a thermal decomposition apparatus, and a spray-type cooling unit for separating and removing the waste gas into oil, solid powder, and hydrogen chloride. A cooling washing tower having a leaky shelf-type washing unit at the top, a stirring device for mixing and homogenizing the separated oil and solid powder, a washing liquid receiving tank having a jacket for heating and keeping the tank body, and chlorination in the residual gas A waste gas treatment apparatus comprising an absorption cleaning tower for removing hydrogen. The waste gas treatment apparatus according to claim 1, wherein the spray-type cooling section includes a heat and heat retaining structure for preventing condensation of oil on the outer wall. The waste gas processing apparatus of Claim 1 or 2 provided with the piping line heated at 300-350 degreeC from the thermal decomposition apparatus to the cooling washing tower. The high-temperature waste gas generated by the thermal decomposition of waste plastic is rapidly cooled and condensed in the spray-type cooling unit at the bottom of the cooling and washing tower, and washed in the leaky shelf-type washing unit at the top to separate oil and solid powder , Waste gas containing the separated oil and solid powder is heated and kept in a washing liquid receiving tank, mixed and homogenized, separated and recovered, and hydrogen chloride in the remaining gas is removed by an absorption washing tower. Processing method.

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