JP5063885B2 - Lead recovery apparatus and method - Google Patents

Description

  The present invention relates to a lead recovery apparatus and method, and more particularly to an apparatus and method for recovering lead from dust discharged from a cement kiln or chlorine bypass dust recovered by a chlorine bypass attached to the cement kiln.

  Conventionally, a part of combustion gas is extracted from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the bottom cyclone in order to remove chlorine and the like that cause problems such as blockage of the preheater in the cement manufacturing facility. Thus, a chlorine bypass for removing chlorine and the like is used. In this chlorine bypass, chlorine is unevenly distributed on the fine powder side of the dust generated by cooling the extracted exhaust gas, so the dust is separated into fine powder and coarse powder by a classifier, and the coarse powder is returned to the cement kiln system. The fine powder (chlorine bypass dust) containing the separated potassium chloride and the like was collected and added to the cement grinding mill system.

  However, in recent years, the recycling of waste as a raw material for cement or fuel has been promoted, and as the amount of waste processed increases, the amount of harmful lead brought into the cement kiln also increases, and the lead concentration in the cement is controlled. There is also a risk of exceeding the reference value. In addition to the chlorine bypass dust, the lead concentration in the dust discharged from the cement kiln and collected by the subsequent dust collector tends to increase, so a method for recovering lead from these dusts is required. It has been.

  Therefore, for example, in Patent Document 1, in order to effectively separate and remove the chlorine content and lead content in the waste, the waste water washing step, the filtered solid alkali elution step, and the filtrate A deleading step of precipitating and separating lead; a decalcification step of precipitating and separating calcium from the deleaded filtrate; and a salt recovery step of heating and filtering the filtrate to separate and recover chloride. A method for the treatment of wastes having is described.

  Further, in Patent Document 2, selenium and heavy metals contained in the dechlorination water washing solution of cement kiln extraction dust are treated to 0.1 mg / l or less below the wastewater standard value for the water pollution prevention method. A method for treating cement kiln bleed dust is described, in which water is added to form a slurry, followed by solid-liquid separation, and pH adjustment, a chelating agent for removing heavy metals, a polymer flocculant and the like are added.

  Furthermore, in Patent Document 3, in order to provide a treatment method excellent in the recovery effect of lead and the like contained in the waste, sulfuric acid, hydrochloric acid, nitric acid or carbon dioxide gas is added to the filtrate obtained by washing the waste containing heavy metal with water. In addition, heavy metals in the filtrate are precipitated as hydroxides, sulfates or carbonates, the precipitated sludge is alkali leached to elute heavy metals, the filtrate is neutralized or sulfided, and lead in the filtrate A method for precipitating and recovering heavy metals is disclosed.

JP 2003-1218 A JP 2005-103476 A JP 2002-11429 A

  However, the waste treatment method described in Patent Document 1 requires a filtration facility and a lead sulfide precipitation facility in order to deposit and filter lead sulfide through a water washing step of waste such as chlorine bypass dust. There was a problem that the equipment cost and the operating cost were high.

  In addition, the methods for precipitating and recovering heavy metals described in Patent Documents 2 and 3 have a problem that the operation cost increases because expensive chelating agents and chemicals are added.

  Therefore, the present invention has been made in view of the above-described problems in the prior art, and an apparatus that can keep equipment costs and operation costs low when recovering lead from cement kiln dust or chlorine bypass dust and It aims to provide a method.

To achieve the above object, the present invention provides a lead recovery device, cement kiln dust or chlorine bypass dust, and dissolution reaction vessel to be dissolved in water while reacting with the exhaust gas containing SOx, the lysis reactor The first vertical scrubber that reacts the slurry from the dissolution reaction tank and the exhaust gas containing the SOx in a cocurrent flow in the front stage, and the degassing of the degassing gas in the dissolution reaction tank in the rear stage of the dissolution reaction tank. And a second vertical scrubber that removes mist, and a flotation machine that recovers lead from the slurry discharged from the dissolution reaction tank.

  According to the present invention, in the dissolution reaction tank, calcium contained in cement kiln dust or chlorine bypass dust can be removed by reacting with SOx contained in the gas and recovered as gypsum. A high-concentration lead cake can be obtained when collecting lead in a selector. Accordingly, it is not necessary to use an expensive chemical such as sulfuric acid for removing calcium, and lead can be efficiently recovered from cement kiln dust or chlorine bypass dust while keeping facility costs and operation costs low.

  In the lead recovery apparatus, an SOx adsorption tower and an SOx desorption tower that supply a gas obtained by concentrating SOx from exhaust gas of a cement kiln, a chlorine bypass, a power generation boiler, or an incinerator as the exhaust gas containing the SOx to the dissolution reactor. Can be provided. Thereby, recovery of lead from cement kiln dust or the like and desulfurization of exhaust gas such as cement kiln can be performed simultaneously.

  Further, the first or / and second scissor scrubber can be a mixing scrubber. By using a high-efficiency scrubber such as a mixing-type scrubber, the reaction between cement kiln dust and the exhaust gas containing SOx can be promoted, the calcium removal efficiency can be improved, and lead sulfide recovery efficiency can be improved.

Furthermore, the present invention provides a lead recovery process, cement kiln dust or chlorine bypass dust, while reaction with exhaust gas containing SOx was dissolved in water, through the flotation operation from after dissolution the resulting slurry, said slurry separating the lead from or leaving gypsum to the slurry, and wherein the lead is separated gypsum from the slurry by performing either remain in the slurry. Thus, as described above, it is not necessary to use an expensive chemical such as sulfuric acid for removing calcium, and lead can be efficiently recovered from cement kiln dust or chlorine bypass dust while keeping operating costs low.

  In the lead recovery method, the amount of exhaust gas containing SOx can be controlled so that the pH of the slurry is 3 or more and 7 or less. By setting the pH of the slurry to 3 or more and 7 or less, scale troubles in the flow path of the slurry are prevented, and in the subsequent flotation operation, a flotation agent that does not function in an environment with high pH is also made to function reliably. be able to.

  In the lead recovery method, the exhaust gas containing SOx can be a gas obtained by concentrating SOx from exhaust gas from a cement kiln, a chlorine bypass, a power generation boiler, or an incinerator. Thereby, recovery of lead from cement kiln dust or the like and desulfurization of exhaust gas such as cement kiln can be performed simultaneously.

  As described above, according to the present invention, in recovering lead from cement kiln dust or chlorine bypass dust, it is possible to keep facility costs and operation costs low.

Figure 1 shows an embodiment of a lead recovery apparatus according to the present invention, the lead recovery device 1 is roughly, SOx to concentrate SOx from cement kiln exhaust gas (abbreviated as follows "exhaust gas") An adsorption tower 2 and a SOx desorption tower 3; a dissolution reaction tank 7 for dissolving cement kiln dust or chlorine bypass dust (hereinafter referred to as “dust”) stored in a dust tank 9 in water while reacting with SOx gas; From the slurry, the aging tank 12 for enlarging the gypsum particles generated by the reaction in the dissolution reaction tank 7, the chemical reaction tank 15 for reacting the slurry cooled by the cooler 14 with the sulfiding agent and the flotation agent, and A flotation machine 19 for collecting lead and gypsum, a filter press 20 for collecting the lead cake from the floss of the flotation machine 19, and a solid-liquid separation of the tail of the flotation machine 19 into gypsum cake and salt water It consists of a liquid separator 21 and the like.

  The SOx adsorption tower 2 and the SOx desorption tower 3 are provided for concentrating SOx from exhaust gas using an adsorbent such as activated carbon. Further, in order to supply the concentrated SOx to the scrubber 6, a roots blower 4 is disposed at the rear stage of the SOx desorption tower 3.

  The dissolution reaction tank 7 is provided with a stirring blade in a cylindrical main body, two vertical scrubbers 6 and 8 are disposed on the ceiling, and the slurry is circulated between the dissolution reaction tank 7 and the scrubber 6. For this purpose, a pump 5 is provided. The scrubber 6 is disposed in front of the dissolution reaction tank 7 and reacts the slurry from the dissolution reaction tank 7 and the SOx supplied by the roots blower 4 in parallel flow. Further, the scrubber 8 is disposed at the subsequent stage of the dissolution reaction tank 7 and performs dedusting of degassing gas and removal of mist from the dissolution reaction tank 7. A pump 11 for sending the slurry discharged from the dissolution reaction tank 7 to the aging tank 12 is disposed downstream of the dissolution reaction tank 7. A dust tank 9 is disposed to temporarily store the dust supplied to the dissolution reaction tank 7, and an exhaust fan 10 is disposed to discharge the exhaust from the scrubber 8 to the atmosphere.

  For the scrubbers 6 and 8, for example, a mixing type scrubber (such as a muscrubber manufactured by Mu Company Limited) can be used. The mixing type scrubber is characterized in that a plurality of guide vanes that give swirl to this flow are arranged in the cylinder in the process of gas and liquid moving countercurrent or in parallel flow in the cylinder, It is a device that brings gas and liquid into contact to perform reaction, dust collection, and the like. Preferably, the gas and the liquid are co-currentd, and guide vanes that give a right turn to the flow and guide vanes that give a left turn are alternately arranged.

The aging tank 12 is provided with a stirring blade in a cylindrical main body, in order to increase the diameter of gypsum particles generated by the reaction between dust and SOx in the dissolution reaction tank 7 and to increase the separation efficiency in the subsequent flotation machine 19. Is provided. The subsequent aging tank 12, a pump 13 for feeding the slurry discharged from ripe Naruso 12 to the cooler 14 is disposed. The cooler 14 is provided to cool the slurry from the aging tank 12 and cools the slurry to 50 ° C. or less suitable for flotation.

  The chemical reaction tank 15 includes stirring blades in a plurality of cylindrical main bodies, and is provided for adding and reacting a sulfiding agent and a flotation agent to the slurry from the cooler 14.

  The flotation machine 19 is provided to separate the slurry from the chemical reaction tank 15 into a floss containing lead and a tail-side slurry containing gypsum. The solid-liquid separation for solid-liquid separation of the slurry from the flotation machine 19 to obtain a gypsum cake and salt water by solid-liquid separation of the lead-containing floss to obtain a lead-sulfide cake. A vessel 21 is provided.

  Next, the operation of the lead recovery apparatus 1 having the above configuration will be described with reference to FIG.

  The exhaust gas is introduced into the SOx adsorption tower 2, and after SOx is adsorbed by the adsorbent, the SOx is desorbed in the SOx desorption tower 3, and the concentrated SOx gas is introduced into the scrubber 6 through the roots blower 4.

On the other hand, dust is supplied from the dust tank 9 to the dissolution reaction tank 7, dissolved in water in the dissolution reaction tank 7, becomes slurry, and is introduced into the scrubber 6 through the pump 5, and the scrubber 6 and the dissolution reaction tank 7 Circulate between them. In the scrubber 6, the slurry reacts with SOx gas, and SO ₂ reacts with Ca (OH) ₂ generated by the reaction of CaO in the dust with water,
CaO + H ₂ O → Ca (OH) ₂
SO ₂ + Ca (OH) ₂ → CaSO ₃ · 1 / 2H ₂ O + 1 / 2H ₂ O
CaSO ₃ · 1 / 2H ₂ O + 1 / 2O ₂ + 3 / 2H ₂ O → CaSO ₄ · 2H ₂ O
Produces gypsum.

  Here, the pH of the circulating liquid in the dissolution reaction tank 7 is controlled to 3 or more and 7 or less in order to prevent scale troubles in the flow path of the circulating slurry such as the scrubber 6 and the dissolution reaction tank 7.

  The exhaust gas in the dissolution reaction tank 7 is dedusted by the scrubber 8, and after the mist contained in the exhaust gas is removed, it is released to the atmosphere by the exhaust fan 10.

  The slurry from the dissolution reaction tank 7 is supplied to the maturation tank 12 via the pump 11, and after the gypsum particles generated by the above reaction are enlarged, the slurry is sent to the cooler 14 via the pump 13 and floated. It is cooled to 50 ° C. or lower suitable for selection.

  The slurry from the cooler 14 is supplied to the chemical reaction tank 15. In addition, sodium hydrosulfide (NaSH) is added to the chemical reaction tank 15 through a pump 16. The reason for adding sodium hydrosulfide is to sulfidize lead chloride and the like contained in the slurry and precipitate them as sulfides. This sulfuration produces lead sulfide (PbS). Here, as described above, the pH of the circulating liquid in the dissolution reaction tank 7 is 3 or more and 7 or less in order to prevent decomposition of NaSH that is easily decomposed at a low pH and to maintain the performance of the flotation agent described later. It is necessary to control the range.

Further, a flotation agent is added to the drug reaction tank 15 through a pump 17. For the flotation agent, an organic compound heavy metal scavenger having a xanthate group (R—O—Ca ₂ Na), a dicarbamic acid group (R—NH—CS ₂ Na), a thiol group (—SH), etc. Can be used. In this case, although the treatment effect of the scavenger deteriorates in the alkaline region, in the present invention, there is no problem because the pH of the circulating liquid tank is maintained at 3 or more and 7 or less as described above.

  The slurry from the chemical reaction tank 15 is supplied to the flotation machine 19. A flotation agent is supplied to the flotation machine 19 via a pump 18. MIBC (Methyl Isobutyl Carbinol) etc. can be used for a foaming agent. Air is further supplied to the flotation machine 19, and the slurry is separated into a floss containing lead and a tail-side slurry containing gypsum by a flotation operation.

The floss containing lead is supplied to the filter press 20 and separated into a cake containing lead sulfide and water. The cake containing lead sulfide is reused, for example, by being reduced to the mountain, and the separated water can be returned to the chemical reaction tank 15 and reused in the flotation process.

  On the other hand, the tail side slurry containing gypsum from the flotation machine 19 is solid-liquid separated in the solid-liquid separator 21, and the separated salt water can be added to the cement pulverization step. The separated salt water may be discharged into sewage or the ocean after water treatment, or after desalting in the salt recovery step, the obtained water may be returned to the dissolution reaction tank 7 or the like.

In the above embodiment, the case where sodium hydrosulfide is used as the lead sulfiding agent has been described. However, sodium sulfide (Na ₂ S) may be used instead of sodium hydrosulfide.

  In the above embodiment, the slurry discharged from the chemical reaction tank 15 is separated into the floss containing lead and the tail-side slurry containing gypsum by the flotation operation. It is also possible to float the plaster as a floss using a selection agent. However, in that case, since the foaming agent enters the gypsum side, a larger amount of foaming agent is required, and when adding gypsum to the cement mill, the foaming agent has an adverse effect on cement hardening. Since there is concern about giving, the method shown in the above embodiment is more preferable.

  Furthermore, although the case where the gas which concentrated SOx from the cement kiln exhaust gas is used as the exhaust gas containing SOx has been described in the above embodiment, SOx may be concentrated from the exhaust gas of a chlorine bypass, a power generation boiler or an incinerator.

It is a flowchart which shows one Embodiment of the lead collection | recovery apparatus concerning this invention.

Explanation of symbols

1 Lead recovery device 2 SOx adsorption tower 3 SOx desorption tower 4 Roots blower 5 Pump 6 Scrubber 7 Dissolution reaction tank 8 Scrubber 9 Dust tank 10 Exhaust fan 11 Pump 12 Aging tank 13 Pump 14 Cooler 15 Drug reaction tank 16 Pump 17 Pump 18 Pump 19 Flotation machine 20 Filter press 21 Solid-liquid separator

Claims (6)

A dissolution reaction tank for dissolving cement kiln dust or chlorine bypass dust in water while reacting with exhaust gas containing SOx;
A first vertical scrubber that reacts the slurry from the dissolution reaction tank and the exhaust gas containing the SOx in a parallel flow before the dissolution reaction tank;
A second vertical scrubber for removing dust and mist from the degassing gas in the dissolution reaction tank after the dissolution reaction tank;
Lead recovery apparatus characterized by comprising a flotation machine for recovering lead from the slurry discharged from the dissolution reactor.   The exhaust gas containing SOx includes a SOx adsorption tower and a SOx desorption tower for supplying a gas obtained by concentrating SOx from exhaust gas of a cement kiln, chlorine bypass, power generation boiler or incinerator to the dissolution reaction tank. The lead recovery apparatus according to claim 1. The lead recovery apparatus according to claim 1 or 2 , wherein the first or / and second scissor scrubber is a mixing scrubber. Cement kiln dust or chlorine bypass dust is dissolved in water while reacting with exhaust gas containing SOx,
Either by separating the lead from the slurry and leaving the gypsum in the slurry through a flotation operation, or by separating the gypsum from the slurry and leaving the lead in the slurry through a flotation operation after the dissolution A method for recovering lead. The lead recovery method according to claim 4 , wherein the amount of exhaust gas containing the SOx is controlled so that the pH of the slurry is 3 or more and 7 or less. The lead recovery method according to claim 4 or 5 , wherein the exhaust gas containing SOx is a gas obtained by concentrating SOx from exhaust gas from a cement kiln, a chlorine bypass, a power generation boiler, or an incinerator.

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