JP5047202B2 - Acid gas neutralization method - Google Patents

Description

The present invention neutralizes acid gases for neutralizing and detoxifying various acid gases such as acid gases generated when decomposing halogen compounds such as chlorofluorocarbons and acid gases discharged from a garbage incinerator. It is about the method .

  Fluorocarbons such as chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), and hydrofluorocarbon (HFC) are environmental pollutants. Therefore, from the viewpoint of protecting the global environment, regulations and reduction of use by the Freon Recovery and Destruction Law are required. ing. Therefore, various decomposition treatment methods are provided for chlorofluorocarbons, and the applicant also provides various superheated steam reaction methods as effective decomposition treatment methods (Patent Documents 1 and 2).

According to these superheated steam reaction methods, chlorofluorocarbons can be effectively decomposed at normal pressure using superheated steam, but acid gas containing HCl and HF is generated by the decomposition process. In order to render this acidic gas harmless, it is necessary to neutralize it. Conventionally, a means for neutralizing by showering a mixed solution of calcium hydroxide (CaH ₂ O ₂ ) in an acid gas is known. The neutralization reaction is as follows.
Ca (OH) ₂ + 2HCl → CaCl ₂ + 2H ₂ O
Ca (OH) ₂ + 2HF → CaF ₂ + 2H ₂ O

  FIG. 3 is a system diagram schematically showing a conventional neutralization treatment method using a mixed solution of calcium hydroxide, and piping of an acidic gas 41 generated by decomposing CFCs using superheated steam or the like. It is supplied to the first cleaning tower 43 via 42 and further supplied to the second cleaning tower 45 via the pipe 44. The first cleaning tower 43 and the second cleaning tower 45 are immersed in a neutralization tank 47 that stores a neutralization solution 46 made of a mixed solution of calcium hydroxide having a predetermined concentration. The neutralization liquid 46 in the neutralization tank 47 is showered from above the first washing tower 43 and the second washing tower 45 through the pipe 49 using the neutralization liquid transfer pump 48, and the first After passing through the washing tower 43 and the second washing tower 45, it returns to the neutralization tank 47 again, and this operation is performed by circulation. And in the 1st washing tower 43 and the 2nd washing tower 45, when neutralization liquid 46 contacts acid gas 41, acid gas 41 is neutralized and detoxified.

  Since the temperature of the neutralizing solution 46 increases when it comes into contact with the acidic gas 41, the temperature of the neutralizing solution 46 is maintained at a predetermined temperature by passing through the cooling tower 50 and cooling with cooling water in the middle of the pipe 49. 51 is a cooling water supply pipe to the cooling tower 50, and 52 is a cooling water discharge pipe from the cooling tower 50. After the acid gas 41 is neutralized and rendered harmless in this manner, the acid gas 41 is sucked into the blower 53 from the second cleaning tower 45 and released to the atmosphere via the pipe 54. In the illustrated example, two washing towers, the first washing tower 43 and the second washing tower 45, are used. However, the number of washing towers is arbitrarily determined, such as using a third washing tower from the viewpoint of fuel safety. Can be set.

The neutralization liquid 46 in the neutralization tank 47 repeats the showering to the first washing tower 43 and the second washing tower 45 to come into contact with the acid gas 41 and repeats the neutralization treatment, whereby calcium chloride (CaCl ₂ ) and calcium fluoride (CaF ₂ ) are produced and become a slurry to gradually lose the neutralizing ability of the acid gas 41. Therefore, the pH in the neutralization tank 47 is measured with a pH meter (not shown), and when the pH is around 7, the entire neutralization solution 46 is replaced to fill the neutralization solution 46 made of a new mixed solution of calcium hydroxide. To use.

  Since the used neutralization liquid 46 is in the form of a slurry, it is discharged from the neutralization tank 47 to the aggregation tank 57 via the pipe 56 using the slurry transfer pump 55. Then, an appropriate flocculant 58 is added to the flocculation tank 57 and mixed to flocculate the used neutralized liquid 46 in a slurry form so as to form a floc of a predetermined size. Next, the residue transfer pump 59 is used to supply the dehydrator 61 from the flocculation tank 57 through the pipe 60 to dehydrate to a predetermined moisture content, and the dehydrated residue 62 and the dehydrated liquid 63 are separated. The dehydrated liquid 63 is discarded while being treated as waste.

  In general, a means for incineration using an incinerator is used for the final treatment and volume reduction of various kinds of garbage discharged in daily life, social life, and production activities of various factories. Such waste incineration is an excellent treatment method in terms of hygiene, but substances that cause environmental pollution such as acid gas and dioxins are also generated in the process of incineration of waste. Therefore, processing for detoxifying acid gas generated by incineration of garbage is also required. Conventionally, means for spraying calcium hydroxide to acid gas discharged from an incinerator (dry method), means for showering a mixed solution of calcium hydroxide (wet method), slurry of calcium hydroxide and water-absorbing polymer particles There is provided means (semi-dry method) for bringing the water in the slurry into volatilization by the heat of the acid gas as well as contacting with the acid gas in the form (Patent Document 3).

Japanese Patent No. 3607624 Japanese Patent No. 3669881 JP-A-9-192449

  The neutralization method using a conventional calcium hydroxide mixed solution in which powdered calcium hydroxide as shown in FIG. 3 is mixed with water as a neutralizing solution is a mixed solution in which 10 to 15% by weight of calcium hydroxide is mixed. It is necessary to produce equipment for circulating as a neutralizing liquid. For this reason, failure of the circulating pump of the mixed solution and clogging of the piping are likely to occur. Further, since a flocculant is added to the neutralized liquid after use to cause aggregation, and then a dehydrating facility and a drainage facility are required for solid-liquid separation, the neutralizing apparatus is greatly complicated. Furthermore, since the residue after dehydration has a water content of about 50%, the amount of treatment increases and cannot be reused. Furthermore, this process is a batch process and cannot be processed continuously. The mixed solution of calcium hydroxide is used only for neutralization.

And since calcium hydroxide (CaH ₂ O ₂ ) reacts with carbon dioxide (CO ₂ ) in the acidic gas to produce calcium carbonate (CaCO ₃ ), the amount of acid treatment is relatively reduced accordingly. Therefore, the usage efficiency is poor and only about 70% can be used. Furthermore, since calcium hydroxide (CaH ₂ O ₂ ) is a powder, a secondary disaster such as powder scattering occurs when it is put into the neutralization tank.

Therefore, instead of the conventional neutralization method using a mixed solution or powder of calcium hydroxide, the inventors neutralize various acid gases in a compact manner and make them harmless by a simpler method. An object of the present invention is to provide a method for neutralizing acid gas.

In order to achieve the object of the present invention, a certain amount of calcium carbonate having a diameter of 10 mm to 30 mm is filled in a neutralization tower, and 500 ° C. is brought into contact with the calcium carbonate filled in the neutralization tower. By supplying and passing a certain amount of acid gas cooled to the neutralization tower, the acid gas is neutralized, and cooling air is supplied into the neutralization tower to reduce the heat of neutralization. While maintaining the temperature in the neutralization tower at 400 ° C. to 500 ° C., the neutralized tower is discharged from the neutralized tower, and the neutralized product is discharged on the surface. Provided is a method for neutralizing an acidic gas, in which the surface of calcium carbonate is exposed by peeling off and removing the sum product, and is supplied again into the neutralization tower to neutralize the acidic gas .

Further, granular calcium carbonate having a diameter of 10 mm to 30 mm was continuously supplied into the neutralization tower to fill a certain amount, and cooled to 500 ° C. so as to come into contact with the calcium carbonate supplied into the neutralization tower . By supplying and passing a certain amount of acid gas continuously into the neutralization tower, the acid gas is neutralized , and cooling air is supplied into the neutralization tower to reduce the heat of neutralization. While maintaining the temperature in the neutralization tower at 400 ° C. to 500 ° C., the calcium carbonate in which the neutralized product is generated on the surface is sequentially discharged from the neutralization tower after the neutralization treatment, and this is circulated. circulation to expose the surface of the calcium carbonate by removing by peeling the neutralized product in the course, was continuously fed into the neutralization tower again, among the acid gas neutralizing process continuously acidic gases A sum processing method is provided.

Then, the acid gas generated when the organic halogen compound such as CFC, HCFC, HFC, PFC, SF ₆ is decomposed or the acid gas discharged from the waste incinerator is neutralized as the acid gas .

According to the present invention as described above, or showering a mixture solution of a conventional calcium hydroxide, powder of calcium hydroxide as compared to means for spraying the acidic gases, diameter of acid gas was cooled to 500 ° C. Since it is only necessary to pass through a neutralization tower filled with a neutralizing agent made of calcium carbonate in a granular form of 10 mm to 30 mm , it is easy to handle without scattering and continuously various acid gases in a compact manner. Alternatively, it can be neutralized and neutralized by batch processing. Then, carbonate calcium or Ranaru neutralizing agent has a high supplement rate of acid gas, a high performance as a neutralizing agent. Moreover, unlike the conventional mixed solution of calcium hydroxide, the neutralized residue does not become a slurry, and no dehydration treatment is required, and disposal is easy. Furthermore, it can be reused as construction sub-materials such as roadbed materials.

  In particular, by supplying cooling air into the neutralization tower, the temperature in the neutralization tower can be maintained at approximately 400 ° C. to 500 ° C., and the chloride produced by neutralizing the acidic gas containing hydrogen chloride. It is possible to prevent calcium from dissolving and becoming liquid at a temperature around 770 ° C. For this reason, the liquefied calcium chloride covers the periphery of the neutralizing agent to prevent the neutralizing agent from being discharged and the neutralizing agent can be discharged smoothly. Furthermore, by using the neutralizing agent in a circulating state, the neutralized product can be removed by exposing the surface of the neutralizing agent during the circulation, and the neutralizing agent can be regenerated and used repeatedly.

Then, carbonate calcium or Ranaru neutralizing agent need only continuously or intermittently introduced into the neutralization tower from the neutralization agent tank, it is easy to handle. Further, since only respond with carbonate calcium or Ranaru neutralizing agent is an acid, the amount of processing is stable and also even if the undecomposed organic gas freon gas or the like, in the acid gas was present because it is decomposed by contacting the neutralization tower and granular diameter 10mm~30mm was a neutralizing agent consisting of calcium carbonate, it is highly safe and reliable.

1 is a system diagram schematically showing a first embodiment of the present invention. The system diagram which shows 2nd Embodiment of this invention roughly. The system diagram which shows the conventional neutralization processing method roughly.

The target of neutralization and detoxification by the present invention is, for example, hydrogen chloride (HCl) or fluorine generated when an organic halogen compound such as CFC, HCFC, HFC, PFC, or SF ₆ is decomposed using superheated steam. Various acid gases such as hydrogen chloride (HF), hydrogen chloride (HCl), sulfur dioxide (SO ₂ ), etc. discharged from a garbage incinerator. .

Embodiments of the neutralizing treatment method for acid gas according to the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram schematically showing a first embodiment of the present invention, in which the present invention is applied to neutralization of acid gas generated when decomposing CFCs using superheated steam.

  In the figure, reference numeral 1 denotes a chlorofluorocarbon gas to be decomposed and supplied from a predetermined tank to be decomposed. Reference numeral 2 denotes water for heating to obtain superheated steam, which is supplied from a predetermined water tank. Note that preheated superheated steam may be supplied instead of water. Reference numeral 3 denotes air, which is supplied from a predetermined air compressor. The Freon gas 1, water 2 and air 3 are mixed at an appropriate ratio via the pipe 4 and heated to a predetermined temperature by the preheater 5 and fed into the reactor 6. The reactor 6 is an apparatus for decomposing the chlorofluorocarbon gas 1 with superheated steam, and is heated to a predetermined temperature by a heater 7. The temperature of the superheated steam necessary for the decomposition treatment varies depending on the type and amount of the chlorofluorocarbon gas and whether or not air is supplied, but can be decomposed by controlling the temperature to about 850 ° C to 950 ° C. The air 3 is for accelerating the oxidation reaction with oxygen in the air and can be omitted.

  By passing the fluorocarbon gas 1 heated to a predetermined temperature through the reactor 6 together with the superheated steam for a certain period of time, the fluorocarbon gas 1 in the superheated steam is decomposed to produce hydrogen chloride (HCl) or hydrogen fluoride (HF). Acid gas is generated as a cracked gas containing. Since this acidic gas has a temperature of 900 ° C. to 1000 ° C., it is sent to the cooling jacket 9 of the next stage via the pipe 8 and cooled to around 500 ° C. This acidic gas of about 500 ° C. is the subject of neutralization of the present invention, and is supplied to the neutralization tower 11 via the pipe 10 as the acidic gas supply means. The supply of the acid gas to the neutralization tower 11 may be continuous or intermittent.

The neutralization tower 11 is a cylindrical body arranged in a bowl shape, and is filled with a neutralizing agent 12 inside. The neutralizing agent 12 is made of calcium carbonate (CaCO ₃ ) or calcium oxide (CaO) or a mixture of calcium carbonate and calcium oxide, and is suitably used in a state of being formed into granules having a diameter of about 10 mm to 30 mm. A lump of a predetermined size exceeding 30 mm may be used. In short, there is no particular limitation as long as the acidic gas supplied through the pipe 10 can efficiently contact the neutralizing agent 12 packed in the neutralizing tower 11 and pass between them. Therefore, if it is in powder form, the acid gas cannot pass between the neutralizing agents 12, and if it is too large in block form, the contact with the acid gas is not sufficient and is inappropriate. As described above, the neutralizing agent 12 according to the present invention is calcium carbonate or calcium oxide or calcium carbonate and oxidized with high efficiency as a neutralizing agent, which is easy to handle without scattering and has a high acid gas supplement rate. It is characterized by using a mixture of calcium in the form of lumps and granules.

  The neutralizing agent 12 is stored in the neutralizing agent tank 13, taken out from the lower part of the neutralizing agent tank 13, transported by a screw transfer machine 14 as neutralizing agent supply means, and continuously from the upper part of the neutralizing tower 11. Or intermittently. Then, the used neutralizing agent 12 is taken out from the lower part of the neutralizing tower 11 and is continuously or intermittently conveyed by a screw transfer machine 15 as a neutralizing agent discharging means, and discharged to the neutralization residue tank 16. Stored.

  The acidic gas supplied to the neutralization tower 11 is neutralized by contacting with the neutralizing agent 12 filled in the neutralization tower 11. The neutralization mechanism will be described below using hydrogen chloride (HCl) and hydrogen fluoride (HF) as examples.

[When using calcium carbonate (CaCO ₃ ) as the neutralizing agent 12]
CaCO ₃ + 2HF → CaF ₂ + H ₂ O + CO ₂
CaCO ₃ + 2HCl → CaCl ₂ + H ₂ O + CO ₂

[When using calcium oxide (CaO) as the neutralizing agent 12]
_{CaO + 2HF → CaF 2 + H} 2 O
CaO + 2HCl → CaCl ₂ + H ₂ O

When the acid gas contains hydrogen chloride (HCl), calcium chloride (CaCl ₂ ) is generated by neutralization. Calcium chloride is usually a solid, but dissolves and becomes liquid at around 770 ° C. This liquid calcium chloride coats the periphery of the neutralizing agent 12 in the neutralizing tower 11 and is cooled and solidified again in the discharge process from the neutralizing tower 11 to bind the neutralizing agent 12. It cannot be discharged from the lower part of the Japanese tower 11 by the clew transfer machine 15. Therefore, in order to prevent such liquefaction of calcium chloride, the neutralization tower 11 was supplied from a predetermined compressor so that the temperature in the neutralization tower 11 was not raised to about 700 ° C. or higher. The cooling air 17 is appropriately injected continuously or intermittently from a position having a high cooling effect through the pipe 18 so that the temperature in the neutralization tower 11 is approximately 400 ° C to 500 ° C.

  The neutralizing agent 12 generates calcium chloride and calcium fluoride by contacting with the acid gas, and the surface is covered with these products, so that the neutralizing ability is gradually lost. Therefore, an acid concentration meter (not shown) is installed in the pipe 19 for discharging the neutralized exhaust gas so that the acid concentration of the exhaust gas is constantly monitored and replaced before the neutralizing ability of the neutralizing agent 12 decreases. To do. For the replacement of the neutralizing agent 12, the supply of the acidic gas from the pipe 10 is stopped, and all the used neutralizing agent 12 in the neutralizing tower 11 is discharged to the neutralization residue tank 16 using the screw transfer machine 15. Then, the new neutralizing agent 12 can be carried out by a batch system in which the neutralizing agent tank 13 is supplied to the neutralizing tower 11 using the screw transfer machine 14. Further, continuous operation can be performed by discharging the used neutralizing agent 12 from the lower portion while introducing the neutralizing agent 12 from the other tank to the upper portion of the neutralizing tower 11.

  Alternatively, in consideration of the amount of acid gas supplied from the pipe 10 and the acid concentration, the speeds of the screw transfer device 14 and the screw transfer device 15 are synchronized, and the screw transfer device 14 causes a constant amount of water from the upper part of the neutralization tower 11. A continuous operation can be performed by discharging the same amount of the used neutralizing agent 12 from the lower part of the neutralizing tower 11 by the screw transfer machine 15 while continuously supplying the summing agent 12. Furthermore, it is possible to operate continuously by installing a level sensor in the neutralization tower 11 and driving the screw transfer machine 14 and the screw transfer machine 15 according to the set value of the level sensor. In other words, the neutralization tower 11 can always be operated in a state where a certain amount of new neutralizing agent 12 is stored.

  Further, the neutralizing tower 11 filled with the neutralizing agent 12 can be provided without providing the neutralizing agent 12 supply / discharge means such as the neutralizing agent tank 13, the screw transfer machines 14 and 15, and the neutralization residue tank 16. It can also be configured as a cartridge, and the used neutralizing agent 12 can be replaced with the neutralizing tower 11 for use. The used neutralizer 12 in which calcium chloride or calcium fluoride is generated is stored in the neutralization residue tank 16 and then transferred to the residue waste tank 28 for disposal as industrial waste, or the roadbed Reuse as materials.

  The neutralized exhaust gas is supplied from the upper part of the neutralization tower 11 to the dust removal tower 20 via the pipe 19, and the dust of the neutralizing agent 12 is removed by the showered water from the upper part of the dust removal tower 20. 21 is a pump for circulating water in the dust removal tower 20 and showering from above, 22 is a pipe for circulating cooling water to the dust removal tower 20, and 23 is a cooling jacket for cooling the circulating water. It is. The exhaust gas from which dust has been removed is supplied from the upper part of the dust removal tower 20 to the mist removal tower 25 through the pipe 24 and removed, and then sucked into the blower 26 and released from the pipe 27 to the atmosphere. The acid gas moves from the reactor 6 to the neutralization tower 11, the dust removal tower 20, and the mist removal tower 25 by the pressure gradient caused by the suction of the blower 26.

  Next, a second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. FIG. 2 is a system diagram schematically showing a second embodiment of the present invention, in which the neutralizing agent 12 after the neutralization treatment with a neutralized product formed on the surface is discharged from the neutralization tower 11 and then circulated. In the middle of circulation, the neutralizing agent 12 is brought into contact with each other to peel the neutralized product, so that the surface is exposed and regenerated as the neutralizing agent 12, and again as the neutralizing agent 12 in the neutralizing tower 11 To supply.

  The neutralization residue tank 16 is connected to the neutralizing agent tank 13 by a pipe 31, the neutralizing agent tank 13 is connected to a filter 33 by a pipe 32, and the filter 33 is connected to a vacuum pump 35 by a pipe 34. Therefore, when the vacuum pump 35 is driven, the air in the neutralizing agent tank 13 is sucked and removed through the pipe 34, the filter 33, and the pipe 32 to be negative pressure. Since the neutralizer tank 13 having a negative pressure is connected to the neutralization residue tank 16 by the pipe 31, the used neutralizer 12 in the neutralization residue tank 16 passes through the pipe 31 to the neutralizer tank. 13 is circulated by being moved by suction. Instead of the vacuum pump 35, other suction pumps can be used.

  Since the used neutralizing agent 12 collides with each other during the suction movement, the calcium chloride and calcium fluoride neutralized products formed on the surface of the used neutralizing agent 12 are peeled off and removed. Calcium carbonate and calcium oxide are again exposed on the surface of the neutralizing agent 12 and are regenerated as the neutralizing agent 12. Further, the neutralized product is also peeled off when the surface of the used neutralizing agent 12 rapidly shrinks during cooling by jetting the cooling air 17. The regenerated neutralizer 12 is sequentially supplied again from the neutralizer tank 13 into the neutralization tower 11 via the screw transfer machine 14. On the other hand, the neutralized product peeled off from the used neutralizing agent 12 is supplemented by the filter 33 from the neutralizing agent tank 13 by the pipe 32. Therefore, the filter 33 may be discarded as appropriate. As described above, according to the second embodiment, the neutralizing agent 12 can be repeatedly used by circulation and regeneration.

  When the neutralizing agent 12 is worn and reduced by repeated use a certain number of times, the used neutralizing agent 12 is transferred from the neutralization residue tank 16 to the residue waste tank 28 and discarded as industrial waste. Process or reuse as roadbed materials. When the neutralizing agent 12 is sucked from the neutralization residue tank 16 into the neutralizing agent tank 13, the screw transfer machine 14 and the supply of acid gas are stopped. Further, when the neutralizing agent 12 is supplied from the neutralizing agent tank 13 to the neutralizing tower 11 via the screw transfer device 14, it is possible to continuously supply the acidic gas to the neutralizing tower 11. .

The reactor 6, a chlorofluorocarbon CFC-22 of 2.6 m ³ / h, superheated steam 5.2 m ³ / h, and decomposed by supplying with air 7.8m ³ / h, 19.42m ³ / An acidic gas of h was obtained. HCl in acid gas 19.42m ³ / h is 2.59m ³ / h, HF is 5.18m ³ / h, the balance being superheated steam and CO ₂ and air. The acidic gas is continuously supplied to and passed through the neutralizing tower 11 filled with granular calcium carbonate having a particle diameter of 10 mm as the neutralizing agent 12, so that the acidic gas is neutralized and discharged from the pipe 19. The acid concentration of the exhaust gas after neutralization was measured. The neutralization tower 11 used had a diameter of 300 mm, and 150 kg of the neutralizing agent 12 was continuously supplied thereto at a flow rate of 120 kg / h. Therefore, 120 kg of the neutralizing agent 12 is always filled in the effective height of about 800 mm in the neutralizing tower 11, and the remaining 30 kg is peeled off the neutralized product formed on the surface while circulating outside the neutralizing tower 11. And is being played. In addition, the decomposition reaction formula of CFC-22 is as follows.
CHClF ₂ + H ₂ O + 0.5O ₂ → 2HF + HCl + CO ₂

  The acid gas of Example 1 was neutralized by continuously supplying and passing through the neutralization tower 11 filled with granular calcium oxide having a particle diameter of 10 mm as a neutralizing agent. The acid concentration of the exhaust gas after neutralization was measured.

The reactor 6, a chlorofluorocarbon CFC-134a of 2.2 m ³ / h, superheated steam 4.4 m ³ / h, and decomposed by supplying with air 19.8m ³ / h, 31.84m ³ / An acidic gas of h was obtained. HCl in acid gas 31.84m ³ / h is ^0m 3 / h, HF is 8.78m ³ / h, the balance being superheated steam and CO ₂ and air. The acidic gas is continuously supplied to and passed through the neutralization tower 11 filled with granular calcium carbonate having a particle diameter of 10 mm as a neutralizing agent, so that the acidic gas is neutralized and discharged from the pipe 19. The acid concentration of the exhaust gas after neutralization was measured. The decomposition reaction formula of CFC-134a is as follows.
_{C 2 H 2 F 4 + H} 2 O + 1.5O 2 → 4HF + 2CO 2

  The acidic gas of Example 3 was continuously supplied to and passed through the neutralization tower 11 filled with granular calcium oxide having a particle diameter of 10 mm as a neutralizing agent, so that the acidic gas was neutralized. The acid concentration of the exhaust gas after neutralization was measured.

In the reactor 6, 1.9 m ³ / h Freon CFC-R12 was supplied with superheated steam of 7.4 m ³ / h and decomposed to obtain 12.96 m ³ / h acid gas. HCl in acid gas 12.96m ³ / h is 3.7m ³ / h, HF is 3.7 m ³ / h, the balance being superheated steam and CO _2. The acidic gas is continuously supplied to and passed through the neutralization tower 11 filled with granular calcium carbonate having a particle diameter of 10 mm as a neutralizing agent, so that the acidic gas is neutralized and discharged from the pipe 19. The acid concentration of the exhaust gas after neutralization was measured. The decomposition reaction formula of CFC-R12 is as follows.
CCl ₂ F ₂ + 2H ₂ O → 2HF + 2FCl + CO ₂

  The acid gas of Example 5 was continuously supplied to and passed through the neutralization tower 11 filled with granular calcium oxide having a particle diameter of 10 mm as a neutralizing agent. The acid concentration of the exhaust gas after neutralization was measured.

[Comparative Examples 1-3]
The same acid gas as in Example 1 is supplied to the first washing tower 43 shown in FIG. 3, and the mixed solution in which 15% by weight of calcium hydroxide is mixed is neutralized by showering. The acid concentration of the exhaust gas after neutralization discharged from the reactor was measured as Comparative Example 1. Similarly, what measured the acid concentration of the exhaust gas neutralized with the same acidic gas as in Example 3 was used as Comparative Example 2, and what measured the acid concentration of the exhaust gas neutralized with the same acidic gas as in Example 5 It was set as Comparative Example 3.

[Comparative Examples 4 to 6]
The acid gas of Example 1 was supplied to a cylindrical body having a diameter of 250 mm and a height of 2000 mm, neutralized by spraying calcium hydroxide powder from above at a drop rate of 1 Kg / min, and the neutralized exhaust gas acid. The concentration was measured and used as Comparative Example 4. Similarly, the measurement of the acid concentration of the exhaust gas neutralized with the same acidic gas as in Example 3 is referred to as Comparative Example 5, and the measurement of the acid concentration of the exhaust gas neutralized with the same acidic gas as in Example 5 is performed. It was set as Comparative Example 6. Table 1 shows the acid concentration of the exhaust gas after neutralization in Examples 1 to 6 and Comparative Examples 1 to 6 described above.

  As shown in Table 1, the present invention using a neutralizing agent made of calcium carbonate or calcium oxide can neutralize HCl or HF to a concentration of <1 ppm or less. On the other hand, Comparative Examples 1, 2 and 3 in which the mixed solution of calcium hydroxide was showered with the conventional acid gas shown in FIG. 3 were used for the acid concentration of HCl or HF only by showering in the first washing tower. Is 50 to 100 ppm or 100 to 200 ppm and is not neutralized, and it is necessary to repeat showering of a mixed solution of calcium hydroxide. Further, in Comparative Examples 4, 5, and 6 in which calcium hydroxide powder is sprayed on an acidic gas, the acid concentration of HCl and HF is 780 ppm or more, and it is understood that neutralization is insufficient. In addition, the conventional calcium hydroxide mixed solution is aggregated by adding a flocculant after use, and even after dehydration and solid-liquid separation, the residue after dehydration has a water content of about 50%. In contrast to the increased amount of processing, the present invention has a small amount of residue, which reduces the cost for the processing and can be reused.

Further, in the present invention, as the neutralizing agent 12, calcium hydroxide in a predetermined lump shape or granular form having a diameter of about 10 mm to 30 mm can be used. The problem to be solved by the present invention is not the problem of neutralization ability of calcium hydroxide itself, but neutralization consisting of a conventional calcium hydroxide mixed solution in which powdered calcium hydroxide is mixed with water exclusively. This eliminates the drawbacks of the liquid. Therefore, even if calcium hydroxide is used as a raw material, if it is made into a predetermined lump or granular form having a diameter of about 10 mm to 30 mm, the disadvantage can be eliminated, so that it can be used as the neutralizing agent 12 of the present invention. The neutralization method and its apparatus can also use 1st Embodiment and 2nd Embodiment as they were, and have neutralization capability equivalent to Examples 1-6. In addition, the neutralization reaction with respect to HCl and HF is as follows and is the same as the conventional one.
Ca (OH) ₂ + 2HCl → CaCl ₂ + 2H ₂ O
Ca (OH) ₂ + 2HF → CaF ₂ + 2H ₂ O

  Note that calcium hydroxide in a predetermined lump or granular form having a diameter of about 10 mm to 30 mm needs to be granulated from powder, and calcium hydroxide itself is more expensive than calcium carbonate or calcium oxide as a raw material. As the neutralizing agent 12, it is more practical to use calcium carbonate or calcium oxide as a raw material.

According to neutralization treatment method of acid gases in accordance with the present invention, since it is only necessary to pass the neutralization tower filled with particulate neutralizing agent comprising an acid gas from the calcium carbonate, that the neutralizing agent is scattered It is easy to handle and compact, and various acid gases such as acid gas generated when halogen compounds such as chlorofluorocarbons are decomposed and acid gas discharged from garbage incinerators are continuously or batch processed. It can be harmed and harmed.

DESCRIPTION OF SYMBOLS 1 ... Freon gas 2 ... Water 3 ... Air 4, 8, 10, 18, 19, 22, 24, 27, 31, 32, 34 ... Piping 5 ... Pre-heater 6 ... Reactor 7 ... Heater 9, 23 ... Cooling Jacket 11 ... Neutralization tower 12 ... Neutralizing agent 13 ... Neutralizing agent tank 14, 15 ... Screw transfer device 16 ... Neutralization residue tank 17 ... Cooling air 20 ... Dust removal tower 21 ... Pump 25 ... Mist removal tower 26 ... Blower 33 ... Filter 35 ... Vacuum pump

Claims (4)

The neutralization tower is filled with a certain amount of granular calcium carbonate having a diameter of 10 mm to 30 mm, and a certain amount of acidic gas cooled to 500 ° C. is neutralized so as to come into contact with the calcium carbonate filled in the neutralization tower. The acidic gas is neutralized by supplying it through the tower and passing through it , and cooling air is supplied into the neutralizing tower to reduce the heat of neutralization. By keeping the temperature at ℃ and discharging the neutralized product from the neutralization tower after neutralization treatment, the calcium carbonate with the neutralized product formed on the surface is circulated, and the neutralized product is peeled off and removed in the middle of the circulation. A method for neutralizing an acidic gas, wherein the surface of calcium carbonate is exposed and supplied again into the neutralization tower to neutralize the acidic gas. Particulate calcium carbonate having a diameter of 10 mm to 30 mm is continuously supplied into the neutralization tower to fill a constant quantity, and then cooled to 500 ° C. so as to come into contact with the calcium carbonate supplied into the neutralization tower. The neutral gas is neutralized by supplying and passing the acid gas continuously through the neutralization tower, and the neutralization heat is reduced by supplying cooling air into the neutralization tower. While maintaining the temperature in the tower at 400 ° C. to 500 ° C., the calcium carbonate in which the neutralized product is generated on the surface is sequentially discharged from the neutralized tower after the neutralization treatment, and this is circulated and circulated. In which the neutralized product is peeled and removed to expose the surface of calcium carbonate , and continuously fed again into the neutralization tower, where the acidic gas is continuously neutralized. Gas neutralization method. The method for neutralizing an acidic gas according to claim 1 or 2 , wherein the acidic gas is an acidic gas generated when an organic halogen compound such as CFC, HCFC, HFC, PFC, or SF ₆ is decomposed. The acid gas neutralization method according to claim 1 or 2 , wherein the acid gas is an acid gas discharged from a garbage incinerator.

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