JP6327943B2 - Method for recovering valuable metals in waste - Google Patents

Description

  The present invention relates to a method for recovering valuable metals in waste, and more particularly, to a method for recovering valuable metals contained in waste such as municipal waste incineration ash and sludge.

  Conventionally, electronic substrates used in home appliances are recycled to collect valuable metals such as gold, silver, copper, tin, and nickel. Mercury is also collected through recycling of mercury lamps and fluorescent lamps.

  Patent Document 1 discloses that waste such as municipal waste is crushed with a crusher, moisture is removed with a dryer as necessary, and pyrolysis is performed in a pyrolysis furnace to produce a pyrolysis residue. After sorting char from the decomposition residue with a sorting device, it can be pulverized with a pulverizing device, the pulverized char can be transferred with a transfer means, and burned as fuel in another facility, so that valuable valuable metals and glass can be recovered. Waste fuel utilization methods have been proposed.

  Further, in Patent Document 2, fly ash is dechlorinated and washed, and the dechlorinated and washed fly ash, zinc-containing raw material, flux and coal are mixed, dried and pulverized, and then formed into briquette. A method for recovering valuable metals by smelting reduction is described.

JP 2000-283430 A JP 2007-186761 A

  However, in the above conventional technique, a large amount of energy is consumed for dry pulverization of wastes, heat treatment, etc., so that the operation cost increases. On the other hand, in the case of using a collection device such as a small batch type, there is a problem that it is difficult to realize from the profit side.

  Then, this invention is made | formed in view of the said problem, Comprising: It aims at collect | recovering the valuable metals contained in wastes, such as municipal waste incineration ash and sludge, at low cost.

In order to achieve the above object, the present invention is a method for recovering valuable metals from a cement manufacturing process having a cooling tower for cooling the entire amount of combustion gas discharged from a cement firing furnace, wherein the recovered gold or / and In order to increase the concentration of silver, a raw material containing chlorine bypass dust is supplied to the cement firing furnace, the dust contained in the exhaust gas of the cooling tower is collected, and the collected dust is washed with water to contain gold or / and silver. It is characterized by collecting dust.

  According to the present invention, a raw material containing chlorine bypass dust containing gold and / or silver recovered from a cement manufacturing process is heat-treated in the cement manufacturing process to recover gold or / and silver-enriched dust. Dust containing valuable metals can be recovered at low cost without the need for energy such as separate heat treatment.

  In the method for recovering valuable metals in the waste, the chlorine bypass dust is cooled while cooling a part of the combustion gas from the kiln exhaust gas passage from the bottom of the cement kiln having the preheater cyclone to the bottom cyclone. It can be recovered from the extracted gas extracted.

Further, after the chlorine bypass dust washed with water, acid washing or floating election Kosho sense, the can be supplied to the cement burning furnace, using a material with increased concentrations of valuable metals by washing with water or the like, it is recovered The valuable metal concentration of dust can be increased.

  Furthermore, the cement firing furnace can be an eco cement kiln for firing eco cement, and dust containing valuable metals can be recovered from the eco cement manufacturing process at low cost.

  The dust recovered from the exhaust gas of the cooling tower and washed with water is subjected to an acid leaching step and an alkali leaching step to collect dust containing gold and / or silver, thereby collecting dust having a higher valuable metal concentration. it can.

  Further, a part of the dust recovered from the exhaust gas of the cooling tower and washed with water, or a part of the dust subjected to the water washed dust in the acid leaching step and the alkali leaching step is recovered as dust containing gold or / and silver. The remainder can be returned to the cement firing furnace, and the concentration of valuable metals in the recovered dust can be further increased by circulating the dust.

  As described above, according to the present invention, valuable metals contained in waste such as municipal waste incineration ash and sludge can be recovered at low cost.

It is a whole block diagram which shows the cement baking apparatus to which the valuable metal recovery method in the waste which concerns on this invention is applied. It is a flowchart for demonstrating the HMX process process in the cement baking apparatus of FIG.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the following description, the method for recovering valuable metals in waste according to the present invention is applied to a cement manufacturing apparatus having a preheater cyclone and an ecocement firing apparatus having a cooling tower for cooling the entire amount of combustion gas. Will be described as an example.

  FIG. 1 shows a chlorine bypass facility 1 attached to a cement production apparatus having a preheater cyclone and an exhaust gas treatment facility 2 of an ecocement firing apparatus.

  The chlorine bypass facility 1 includes a probe 12 for extracting air while cooling a part G of combustion gas from a kiln exhaust gas passage from a kiln bottom of a cement kiln 11 to a lowermost cyclone (not shown), From the cyclone 13 as a classifier for separating the coarse dust D1 contained in the extracted gas G1, the heat exchanger 14 for cooling the extracted gas G2 containing the fine powder D2 discharged from the cyclone 13, and the heat exchanger 14 Filter 15 that collects the extracted gas G3, a dust tank 16 that stores the dust (D3 + D4) discharged from the heat exchanger 14 and the bag filter 15, and an exhaust gas that releases the exhaust gas G4 from the bag filter 15 to the atmosphere. It is composed of a fan 17 and the like.

  Each device in the chlorine bypass facility 1 is installed in a general chlorine bypass facility and will not be described in detail.

  The exhaust gas treatment facility 2 of the eco-cement firing apparatus includes a cooling tower 22 that cools the entire amount of combustion exhaust gas from the cement kiln 21, and a cyclone 23 that serves as a classification device for separating coarse powder from the exhaust gas G5 from the cooling tower 22. A first bag filter 24 that collects fine powder contained in the exhaust gas G6 from the cyclone 23, and a second bag that collects dust after adding an acid gas treatment agent GT such as slaked lime powder to the exhaust gas G7 from the first bag filter 24. A bag filter 25, a desulfurization tower 26 and a denitration tower 27 for desulfurizing and denitrating the exhaust gas G8 of the second bag filter 25, a regeneration tower 29 for heating and regenerating the activated coke AC discharged from the desulfurization tower 26, and a regeneration tower 29 Contains exhaust gas cleaning step 30 for cleaning exhaust gas G11, mercury recovery step 31 for recovering mercury from the exhaust gas after cleaning, and high-concentration chloride. HMX treatment process 32 for treating strikes D6 to D8 based on the zero emission concept, final waste water treatment process 33, and recovery device 34 for fractionating calcium starch CA containing valuable metals separated in HMX treatment process 32, Consists of.

  The cyclone 23 is provided for recovering coarse powder contained in the exhaust gas G5, and the recovered dust D6 is sent to the HMX processing step 32.

  The first bag filter 24 is provided to collect fine powder contained in the exhaust gas G6 from the cyclone 23, and the collected dust D7 is sent to the HMX processing step 32.

  The second bag filter 25 is provided to recover the dust D8 contained in the exhaust gas G7 after adding an acid gas treatment agent GT such as slaked lime powder as a desulfurizing agent to the exhaust gas G7. It is sent to the HMX processing step 32.

  The desulfurization tower 26 is provided to bring the exhaust gas G8 into contact with the activated coke AC, and to remove SOx contained in the exhaust gas G8 by adsorbing the activated coke AC. SOx in the exhaust gas is adsorbed and removed by activated coke AC as sulfuric acid.

The denitration tower 27 injects ammonia gas (NH ₃ ) into the exhaust gas G9 from the desulfurization tower 26, then contacts the exhaust gas G9 with the activated coke AC, reduces NOx to nitrogen by NH ₃ and renders it harmless. The NOx remaining in G9 is provided to be adsorbed and removed by the activated coke AC.

  The regeneration tower 29 is provided to regenerate the activated coke AC having a lowered activity, and the adsorbed material such as sulfuric acid and ammonium salt is heated and desorbed with hot air to restore the activity. During heat regeneration, nitrogen gas is supplied to purge the desorbed material from the activated coke AC.

  The exhaust gas cleaning step 30 is provided for cleaning the exhaust gas G11 from the regeneration tower 29, and is separated into a waste liquid W2 containing a large amount of mercury and a waste liquid W3 containing other components.

  The mercury recovery process 31 is provided for recovering mercury contained in the waste liquid W2 from the exhaust gas cleaning process 30, and separates the waste liquid W2 from the exhaust gas cleaning process 30 into sludge S containing mercury and the waste liquid W4.

  The HMX treatment step 32 is provided for recovering valuable materials from dusts D6 to D8 containing a high concentration of chloride. As shown in FIG. 2, water and caustic soda or acid are added to the dusts D6 to D8. An acid that removes the alkali salt with water at pH 9 to 11 (step S1), introduces the waste liquid W1 containing chlorine generated by the water washing into the final waste water treatment process 33, and leaches the solid content after the water washing with water and sulfuric acid. It supplies to a leaching process (step S2).

  From the acid leaching process (step S2), it is supplied to two processes. The leaching residue is supplied to the alkali leaching step (step S3). The leachate is supplied to the copper recovery step (step S4) after adding zinc powder. In the alkaline leaching step (step S3), caustic soda is added to make the state alkaline, and the leaching residue is converted to calcium starch CA, while the leachate is supplied to the zinc / lead recovery step (step S5).

  In the copper recovery process (step S4), due to the effect of the zinc powder added earlier, the copper artificial mineral is precipitated and recovered using the difference in ionization tendency, and the remaining liquid after the precipitation is recovered in the zinc / lead recovery process. (Step S5).

  In the zinc / lead recovery process (step S5), the supply of the leachate from the alkali leaching process (step S3) and the residual liquid from the copper recovery process (step S4) is received, and the pH is adjusted to 10-12 with caustic soda or sulfuric acid. The zinc / lead compound is precipitated and collected, and the remaining liquid after the precipitation is introduced into the final waste water treatment step 33. The recovered zinc / lead compound and copper artificial mineral are recovered as a non-ferrous metal refining raw material NI.

  Returning to FIG. 1, the final waste water treatment process 33 is provided for draining and discharging the waste liquids W3, W4, W1 from the exhaust gas cleaning process 30, the mercury recovery process 31 and the HMX treatment process 32, respectively. The iron starch I derived from the eco-cement raw material contained in the waste liquids W3, W4, W1 is recovered.

  The recovery device 34 is provided for separating the calcium starch CA separated in the HMX processing step 32, and the collected calcium starch CA is recovered as dust ME containing gold and silver.

  Next, a method for recovering valuable metals in waste according to the present invention using the cement baking apparatus will be described with reference to FIGS.

  In FIG. 1, a cement raw material supplied to a preheater (not shown) attached to the cement kiln 11 is preheated by a preheater, calcined in a calcining furnace (not shown), and then fired in the cement kiln 11. Is done.

  In addition to general-purpose raw materials (limestone, clay, iron slag, etc.), various wastes such as incinerated main ash, incinerated fly ash, sludge, and shredder dust are used as cement raw materials. For example, incineration main ash and incineration fly ash have been confirmed to contain 0.1 to 4 ppm of gold and 5 to 50 ppm of silver. The amount of incinerated main ash and incinerated fly ash used is preferably 10 kg or more, more preferably 20 kg or more per ton of clinker. By using 10 kg or more, the concentration of gold and silver in the chlorine bypass dust increases, and the dust ME that is finally recovered also increases in the concentration of gold and silver, so that it becomes more useful as a raw material for refining.

  In FIG. 1, when a part of the combustion gas G of the cement kiln 11 is extracted while being cooled by the probe 12, fine crystals of the volatile components in the combustion gas G are generated and valuable on the fine powder side of the dust contained in the extraction gas G1. Since the metal is unevenly distributed, the coarse powder D1 classified by the cyclone 13 is returned to the cement kiln system. On the other hand, the extraction gas G2 containing the fine powder D2 separated by the cyclone 13 is introduced into the heat exchanger 14 to exchange heat between the extraction gas G2 and the medium. The extraction gas G3 cooled by heat exchange is introduced into the bag filter 15, and the bag filter 15 collects the dust D4 contained in the extraction gas G3. The dust D4 collected by the bag filter 15 is once stored in the dust tank 16 together with the dust D3 discharged from the heat exchanger 14, and then used as a part of the mixed raw material RM for ecocement firing as chlorine bypass dust D5. The

  The obtained chlorine bypass dust D5 (D3 + D4) contains gold and silver precious metals derived from various wastes such as incinerated main ash together with chlorine. The concentration of these gold and silver is 2 to 10 times that of municipal waste incineration ash, although it depends on the operating conditions. Accordingly, gold and silver can be recovered more efficiently than when only municipal waste incineration ash is used as the raw material RM for the subsequent ecocement manufacturing process. Here, the chlorine bypass dust D5 can raise the density | concentration of gold | metal | money and silver by making chlorine concentration into a standard, Preferably it is 10 mass% or more, More preferably, it is 15% or more.

  As the chlorine bypass dust D5 increases in the passage of 10 μm, the coarse powder D1 containing calcium and silica is removed and the concentration of gold and silver increases. Therefore, the classification point of the cyclone 23 is adjusted to adjust the chlorine bypass dust D5. The 10 μm passage is preferably 80% by mass or more.

  Further, the amount of the extraction gas G1 (extraction amount) in the chlorine bypass facility 1 is preferably 0.1 to 20% of the combustion gas flowing through the kiln exhaust gas passage. The reason why the upper limit value of the amount of extraction is set to 20% is that heat loss is large, an economical stable operation of the kiln cannot be secured, and the concentrations of gold and silver are lowered. On the other hand, the reason why the lower limit value of the extraction amount is set to 0.1% is that gold and silver are recovered more without being discharged to the cement clinker.

  Eco-cement is manufactured by mixing the chlorine bypass dust D5 to create a blended raw material RM and firing the blended raw material RM in the cement kiln 21. After the combustion exhaust gas at 600 to 900 ° C. discharged from the cement kiln 21 is cooled by the cooling tower 22 to 150 to 200 ° C., dust (coarse powder) D6 contained in the exhaust gas G5 is recovered by the cyclone 23, and the first The bag filter 24 collects dust (fine powder) D7 contained in the exhaust gas G6 from the cyclone 23.

  Next, an acid gas treatment agent GT such as slaked lime powder is added as a desulfurizing agent to the exhaust gas G7 from the first bag filter 24 to lower the SOx concentration in the exhaust gas G7, and the second bag filter 25 contains the exhaust gas G7. Dust D8 is collected.

  The recovered dusts D6 to D8 are supplied to the HMX processing step 32. In the HMX processing step 32, as described above, copper, lead and zinc are recovered as the non-ferrous metal refining raw material NI, and the main component is calcium. Calcium starch CA is recovered. Here, since the concentrations of gold and silver in the dusts D6 and D8 are lower than those in the dust D7, preferably only the dust D7 is supplied to the HMX treatment step 32, and the dusts D6 and D8 are subjected to dealkalizing salt by washing with water. The concentration of gold and silver in the dust ME can be further increased by returning gold and silver to the mixed raw material RM and circulating gold and silver. The waste liquid W1 generated in the HMX treatment process 32 is sent to the final wastewater treatment process 33.

  The concentration of gold and silver in the calcium starch CA recovered in the HMX treatment step 32 is 10 to 100 times the concentration of gold and silver ore produced in the mine.

  Therefore, the calcium starch CA is entirely or partially taken by the recovery device 34 and recovered as dust ME containing valuable metals. The remainder of the calcium starch CA that has not been separated is returned to the cement kiln 21 as part R of the blended raw material together with the iron starch I from the final waste water treatment step 33. As a method of taking a part, the calcium starch CA that is always discharged may be collected at a constant rate, or may be collected and returned to the cement kiln intermittently.

On the other hand, in the desulfurization tower 26, the exhaust gas G8 from the second bag filter 25 is brought into contact with the active coke AC, and SOx contained in the exhaust gas G8 is adsorbed and removed as sulfuric acid on the active coke AC. Further, ammonia gas (NH ₃ ) is injected into the exhaust gas G9 from the desulfurization tower 26, and NOx is reduced to nitrogen by NH ₃ to make it harmless, and the exhaust gas G9 is brought into contact with the activated coke AC and remains in the exhaust gas G9. NOx is adsorbed and removed by the activated coke AC. At this time, mercury contained in the exhaust gas G8 is also adsorbed to the active coke AC. The cleaned exhaust gas G10 is discharged from the chimney 28 to the atmosphere.

  Next, hot air is introduced into the regeneration tower 29, and the activated coke AC discharged from the desulfurization tower 26 is heated and regenerated. As a result, sulfuric acid, mercury, ammonium salt and the like are desorbed from the activated coke AC.

  Next, exhaust gas G11 containing sulfuric acid, mercury, ammonium salt, etc. is introduced into the exhaust gas cleaning step 30 from the regeneration tower 29, and the activated coke AC dust contained in the exhaust gas G11 and mercury separated from the active coke are recovered. The exhaust gas after the dust of the active coke AC is recovered is washed again to neutralize sulfuric acid or sulfurous acid contained in the exhaust gas, and the waste liquid W3 generated by this washing is sent to the final waste water treatment step 33.

  Next, the waste liquid W2 discharged from the exhaust gas cleaning step 30 is recovered as a concentrated sludge S containing mercury in a mercury recovery step 31. The waste liquid W4 generated in the mercury recovery process 31 is sent to the final waste water treatment process 33.

  After recovering the iron starch I derived from the ecocement raw material from the waste liquids W1, W3, W4 sent to the final waste water treatment step 33, the residue is discharged.

  As described above, in the present embodiment, it is possible to collect dust containing gold and silver precious metals derived from eco-cement raw materials mainly composed of various wastes such as incineration ash and sludge.

  In the above embodiment, valuable metals are unevenly distributed in the fine powder D2 separated by the cyclone 13, that is, the chlorine bypass dust D5 composed of the dust D3 discharged from the heat exchanger 14 and the dust D4 recovered by the bag filter 15. Therefore, this chlorine bypass dust D5 was used as a part of the raw material RM for eco-cement firing, but without installing the cyclone 13, the total amount of dust contained in the extraction gas G1 by the probe 12 was recovered. It can also be used as part of a blended raw material RM for ecocement firing.

  Further, without supplying the chlorine bypass dust D5 as it is as a part of the preparation raw material RM to the cement kiln 21, water washing, acid washing, flotation or HMX treatment (treatment similar to the HMX treatment step 32) is performed, By supplying the cement kiln 21 after increasing the concentration, the concentration of gold and silver in the recovered dust ME can be increased. In addition, the amount of energy and water required for treating salt in the subsequent ecocement manufacturing process, and corrosion due to salt can be reduced, and the chlorine bypass dust that can be used can be increased. Dust ME having a high silver concentration can be obtained.

  The acid cleaning of the chlorine bypass dust D5 is to add hydrochloric acid or the like to the water washing solution when the chlorine bypass dust D5 is washed with water, thereby reducing the concentration of calcium or alkali salt contained in the chlorine bypass dust D5. It is possible to reduce the concentration of valuable metals in the recovered dust ME. Moreover, the washing efficiency can be improved by adding hydrochloric acid while preventing the formation of gypsum.

  In addition, the above-mentioned flotation of the chlorine bypass dust D5 means adding water and a sulfiding agent to the chlorine bypass dust D5, adding a collecting agent to the resulting slurry, and flotating the slurry to which the collecting agent has been added. The floss obtained by the beneficiation is solid-liquid separated, the solid is recovered by solid-liquid separation and used as a part of the blended raw material RM, thereby increasing the silver concentration of the blended raw material RM, and the silver concentration High dust ME can be recovered.

  Furthermore, if it is a cement manufacturing process which has a cooling tower which cools the whole quantity of the combustion gas discharged | emitted from the cement baking furnace, cement baking furnaces other than the eco-cement kiln which burns eco-cement can also be used.

  At the A cement factory, 20 kg of municipal waste incineration ash was used per ton of clinker, and other waste and limestone were also used to produce ordinary Portland cement. As a result, in the chlorine bypass facility 1 shown in FIG. 1, chlorine bypass dust D5 with Au: 2 mg / kg, Ag: 150 mg / kg, CaO: 41 mass%, Cl: 18 mass% was obtained.

  Next, a mixed raw material RM for ecocement (see FIG. 1) was prepared using chlorine bypass dust D5 obtained at the A cement factory and incinerated ash and limestone as other raw materials. Eco-cement is manufactured with this blended raw material RM, and dust D7 contained in the exhaust gas of the eco-cement baking apparatus is HMX-treated with the exhaust gas treatment facility 2 shown in FIG. Was able to obtain a calcium starch CA of 300 times the formulation raw material RM and an Ag concentration of 400 times that of the formulation raw material RM.

  At Port B Cement Factory, 40 kg of municipal waste incineration ash was used per ton of clinker and other waste and limestone were used to produce ordinary Portland cement. As a result, in the chlorine bypass facility 1 shown in FIG. 1, chlorine bypass dust D5 with Au: 6 mg / kg, Ag: 380 mg / kg, CaO: 14 mass%, Cl: 30 mass% was obtained.

  Next, a mixed raw material RM for ecocement (see FIG. 1) was prepared using chlorine bypass dust D5 obtained at the B cement factory and incinerated ash and limestone as other raw materials. Eco-cement is manufactured with this preparation raw material RM, dust D7 contained in the exhaust gas of the eco-cement baking apparatus is HMX-treated with the exhaust gas treatment facility 2 shown in FIG. 1, and calcium starch CA is obtained for 6 hours per day. Sampling (the rest was used as a raw material) continued for 1 month. As a result, a calcium starch CA having an Au concentration of 500 times that of the prepared raw material RM and an Ag concentration of 550 times that of the prepared raw material RM could be obtained.

  Thus, the obtained calcium starch CA has a concentration of gold and silver that is 20 times or more that of incinerated ash, and 50 or more times that of general natural ore.

DESCRIPTION OF SYMBOLS 1 Chlorine bypass equipment 2 Exhaust gas treatment equipment 11 (of eco-cement baking equipment) Cement kiln 12 Probe 13 Cyclone 14 Heat exchanger 15 Bag filter 16 Dust tank 17 Exhaust fan 21 Cement kiln 22 Cooling tower 23 Cyclone 24 First bag filter 25 1st 2 Bug filter 26 Desulfurization tower 27 Denitration tower 28 Chimney 29 Regeneration tower 30 Exhaust gas cleaning process 31 Mercury recovery process 32 HMX treatment process 33 Final wastewater treatment process 34 Recovery device AC Active coke CA Calcium starch D1 Coarse powder D2 Fine powder D3, D4 Dust D5 Chlorine bypass dust D6 to D8 Dust G Combustion gas G1 to G3 Extraction gas G4 to G7 Exhaust gas GT Acid gas treatment agent I Iron starch ME Dust containing valuable metals NI Nonferrous metal refining raw material S Sludge W1 to W4 Waste liquid RM Compounding raw material

Claims (6)

A method for recovering valuable metals from a cement manufacturing process having a cooling tower for cooling the entire amount of combustion gas discharged from a cement firing furnace,
In order to increase the concentration of recovered gold or / and silver, raw materials containing chlorine bypass dust are supplied to the cement firing furnace,
Collecting dust contained in the exhaust gas of the cooling tower;
A method for recovering valuable metals in waste, wherein the recovered dust is washed with water to recover dust containing gold and / or silver.   The chlorine bypass dust is recovered from the extracted gas extracted while cooling a part of the combustion gas from the kiln exhaust gas flow path from the bottom of the cement kiln having the preheater cyclone to the lowermost cyclone. The method for recovering valuable metals in waste according to claim 1. The washing chlorine bypass dust, after acid washing or floating election Kosho sense, valuable metal recovery method of the waste according to claim 2, wherein the feeding to the cement kilns.   4. The method for recovering valuable metals in waste according to claim 1, wherein the cement baking furnace is an eco cement kiln for baking eco cement.   5. The dust collected from the exhaust gas of the cooling tower and washed with water is subjected to an acid leaching step and an alkali leaching step to collect dust containing gold and / or silver. Method for recovering valuable metals in waste.   A part of the dust recovered from the exhaust gas of the cooling tower and washed with water, or a part of the dust subjected to the water-washed dust in the acid leaching step and the alkali leaching step is recovered as dust containing gold or / and silver, and the rest The method for recovering valuable metals in waste according to any one of claims 1 to 5, wherein the metal is returned to the cement firing furnace.

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