JP2000282155A - Lead separating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make usable wastes as a raw material of cement with reduced residual ratio of the lead contained therein by baking wastes, etc., to be treated at a temperature above the boiling point of lead chloride in the presence of chlorine of a quantity balanced with the total content of the lead compound and the alkaline metal compound. SOLUTION: Material to be treated containing lead compound such as residential and industrial wastes are baked at a temperature above the boiling point of lead chloride (about 950 deg.C) in the presence of chlorine, and the lead compound is vaporized and separated as lead chloride to reduce the lead content. The quantity of chlorine is balanced with the total content of the lead compound and the alkaline metal compound in the material to be treated. For example, the baking temperature of 950-1500 deg.C is preferable when the chlorine equivalent ratio A=(Cl-R)/Pb (Cl, R and Pb denote the chemical equivalent of chlorine, alkaline metal and lead, respectively) is >=-10, and further, the temperature is preferably 1,400-1,500 deg.C when A is between -10 and -5, and >=950 deg.C when A is >=-5. The residual ratio of lead contained in the wastes is <= about 20 wt.%, preferably <= about 3%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently separating lead from wastes and the like to greatly reduce the residual ratio of lead. More specifically, the present invention relates to a method for separating lead in which the residual ratio of lead contained in domestic and industrial wastes is reduced to 20% by weight or less, preferably 10% by weight or less, so that the lead can be used as a raw material for cement.

[0002]

2. Description of the Related Art In recent years, the amount of waste such as incinerated ash from municipal waste, incinerated ash from sewage sludge, its molten slag, and fly ash has been remarkably increased. As a disposal measure of these wastes, attempts have been made to recover contained metal compounds and use the incinerated materials as cement raw materials. This incinerated material contains a considerable amount of lead compounds derived from wastes, and it is necessary to separate this efficiently.

[0003]

The lead contained in the waste can be converted into lead chloride and volatilized by firing in the presence of chlorine. However, when an alkali metal coexists, there is a problem in that volatilization due to chlorination of lead is suppressed and lead cannot be separated sufficiently. Comparing the vapor pressures of alkali metal chloride and lead chloride, the vapor pressure of lead chloride is low, so it has been generally thought that the presence of alkali metal does not affect the volatilization of lead. Since lead is more likely to be chloride than lead, when lead and an alkali metal coexist, part of the lead chloride is converted to lead oxide by the alkali metal, and volatilization of lead is suppressed. Therefore, it is difficult to reduce the residual ratio of lead to 20 wt% or less when the boiling point of lead oxide (1470 ° C.) or lower.

The present invention solves the above-mentioned conventional problems in a method of separating lead from wastes and the like, and has a lead content of 20% by weight or less contained in household and industrial wastes.
It is an object of the present invention to provide a method for separating lead, which is preferably separated to 10% by weight or less and used as a cement raw material.

[0005]

That is, the present invention relates to an object of the present invention is to calcine an object to be treated containing a lead compound in the presence of chlorine to a temperature higher than the boiling point of lead chloride, convert the lead compound into lead chloride and volatilize. The present invention relates to a method for separating lead, characterized by firing in the presence of chlorine in an amount corresponding to the total amount of the lead compound content and the alkali metal compound content.

In the lead separation method of the present invention, the ratio of chlorine to the chemical equivalent of lead obtained by subtracting the chemical equivalent of alkali metal from the chemical equivalent of chlorine (chlorine equivalent ratio) is preferably -10 or more. The method includes a method of volatilizing and separating lead by controlling the amount and firing at a temperature of 950 to 1500 ° C.

More specifically, the lead separation method of the present invention comprises:
In the range of chlorine equivalent ratio -10 to -5, 1400 to 15
The method includes firing at a temperature of 00 ° C. and firing at a temperature of 950 ° C. or more in a range of chlorine equivalent ratio of −5 or more to reduce the lead residual ratio to 20 wt% or less, and more preferably a chlorine equivalent ratio of 8 or more. And reducing the residual ratio of lead to 3 wt% or less by firing at a temperature of 950.degree.

Further, the lead separation method of the present invention includes an embodiment in which the chlorine amount is the total amount of chloride added and the chloride content of the material to be treated, and the material to be treated is a cement raw material, a cement raw material. The present invention includes an embodiment in which all or a part of the object to be treated is domestic / industrial waste.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments. The lead separation method of the present invention is a method for subjecting an object to be treated containing a lead compound to baking in the presence of chlorine to a temperature equal to or higher than the boiling point of lead chloride, converting the lead compound to lead chloride, and volatilizing and separating the lead compound. It is characterized by firing in the presence of chlorine in an amount corresponding to the total amount of the alkali metal compound and the alkali metal compound content.

In the present invention, all or a part of the object to be treated is incinerated ash from municipal waste, incinerated ash from sewage sludge, domestic waste such as molten slag or fly ash thereof, or industrial waste such as shredder dust. . These incinerated ash and the like usually contain a lead compound in an amount of 0.1 to 0.5 wt%, and in most cases, about 1.5 wt%. Further, usually, 1 to 10% by weight of an alkali metal compound is contained together with lead. In addition,
In general, copper and zinc are contained at several wt% together with a lead compound and an alkali metal compound.

In the method of the present invention, the object to be treated is fired in the presence of chlorine in an amount corresponding to the total amount of the lead compound and the alkali metal compound. When a material containing both a lead compound and an alkali metal compound is fired in the presence of chlorine, the lead compound turns into lead chloride and volatilizes. Due to the formation of lead chloride, as shown in FIG. 1, the boiling point of lead chloride (PbCl ₂ ) (about 950 ° C.)
The reaction amount of chlorine reaches a peak in the vicinity, but above the melting point of alkali metal chloride (about 800 ° C), alkali metal has a greater tendency to generate chloride than lead, so that the alkali metal compound becomes lead chloride. From chlorine to chloride, and part of lead chloride turns into lead oxide. Since the vapor pressure of this lead oxide (PbO) is lower than the vapor pressure of lead chloride, the volatilization of lead is suppressed, and the reaction amount of chlorine by lead gradually decreases. On the other hand, as the firing temperature increases, the consumption of chlorine increases due to the generation of alkali metal chloride, and the chlorine consumption by the alkali metal reaches a peak near its boiling point. Therefore, lead cannot be sufficiently volatilized and separated with a chlorine amount corresponding to the content of the lead compound excluding the alkali metal content.

As described above, in order to volatilize and separate lead by calcining a compound containing both a lead compound and an alkali metal compound in the presence of chlorine, the amount of chlorine consumed when the lead compound is converted into lead chloride is determined. An amount of chlorine is necessary which is equal to the total amount of (ie. The amount of chlorine relative to the content of the lead compound) and the amount of chlorine consumed by the alkali metal compound (ie. The amount of chlorine relative to the alkali metal compound).

As a specific example, A = (Cl-R) / Pb (Cl
Is the chemical equivalent of chlorine, R is the chemical equivalent of the alkali metal, and Pb is the chemical equivalent of lead.) As shown in the equation, the ratio A of the equivalent of lead minus the equivalent of the alkali metal is subtracted from the equivalent of chlorine to the equivalent of lead.
(Abbreviated as chlorine equivalent ratio) within a predetermined range.

The residual ratio of lead varies greatly depending on the range of the chlorine equivalent ratio and the firing temperature. This relationship is shown in FIG. As shown in the figure, when the chlorine equivalent ratio is less than -10, when the firing temperature is 1400 ° C. or lower, the residual ratio of lead is 20 wt%.
As mentioned above, to reduce the lead residual ratio to 20 wt% or less, 1
It is necessary to fire at a temperature of 400 ° C. or higher. When the chlorine equivalent ratio is in the range of −10 or more, the firing rate is controlled at 950 to 1500 ° C. in accordance with the range of the chlorine equivalent ratio, so that the residual ratio of lead is reduced to 20% by weight or less, preferably 10% by weight or less. be able to.

Specifically, when the chlorine equivalent ratio is in the range of -10 to -5, the residual ratio of lead is generally 10 to 20% at the firing temperature of 1400 to 1500 ° C., and as the chlorine equivalent ratio approaches -5, the lead content becomes lower. The residual ratio of lead gradually decreases, and the residual ratio of lead is reduced to about 10 to 20% even at a temperature of about 1350 ° C. where the firing temperature is slightly lower. The tendency that the residual ratio of lead decreases as the chlorine equivalent ratio increases is the same even when the chlorine equivalent ratio is in the range of -5 or more, and in the range of the chlorine equivalent ratio of -5 to 8,
The residual ratio of lead is 10 to 20 at a firing temperature of 950 to 1350 ° C.
wt%, firing temperature is slightly higher than 1350 ~
At 1450 ° C., the residual ratio of lead is further reduced to about 10% or less. When the chlorine equivalent ratio is in the range of 8 or more, 950 ° C.
At the above firing temperature, preferably around 1350 ° C., the residual ratio of lead can be reduced to 3 wt% or less.

The amount of chlorine can be determined as the total amount of chloride contained in the waste and the amount of chloride (chlorine source) to be added. The waste having a high chlorine content relative to the lead content is heated at a firing temperature corresponding to the chlorine equivalent ratio A. For waste having a low chlorine content, a chlorine source is added, and the amount of the chlorine source added is adjusted so that the chlorine content equivalent A is in an appropriate range of -10 or more in consideration of the firing temperature, and firing is performed. As a chlorine source, calcium chloride or the like is suitable.

The waste treated by the method of the present invention has a low lead content and is suitable as a raw material for cement. Therefore, it can be used as a raw material for cement produced from incinerated municipal ash or sewage sludge ash or their molten slag or fly ash. Further, it can be used as a material for a cement raw material or a material for concrete.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples. Note that the present invention is not limited to these examples.

[0019] waste incineration ash having the composition shown in Examples and Comparative Example Table 1, limestone, calcium chloride was added (ash 35 wt%, limestone 64 wt%, calcium chloride 0~1.5wt%), ground and mixed with this Then, a sample having the composition shown in Table 2 was prepared. This sample was fired at the temperature shown in Table 3 and the lead residual ratio was examined. The results are summarized in Table 3. As shown in these results, by adjusting the chlorine equivalent ratio and the firing temperature, the lead residual ratio can be reduced to a desired level.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[Brief description of the drawings]

FIG. 1 is a graph showing the amount of reaction between lead and chlorine of an alkali metal (Na).

FIG. 2 is a graph showing the ratio of lead equivalent to chlorine equivalent ratio A [(Cl-R) / Pb] and firing temperature.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Taku Nakano 2-4-2 Daisaku, Sakura City, Chiba Pref.

Claims (7)

[Claims] 1. A method for baking an object to be treated containing a lead compound in the presence of chlorine to a temperature equal to or higher than the boiling point of lead chloride, converting the lead compound into lead chloride, and volatilizing and separating the lead compound. A method for separating lead, comprising calcination in the presence of chlorine in an amount commensurate with the total content of metal compounds. 2. The amount of chlorine is controlled within a range where the ratio of the chemical equivalent of lead to the chemical equivalent of lead obtained by subtracting the chemical equivalent of alkali metal from the chemical equivalent of chlorine (abbreviated as chlorine equivalent ratio) is -10 or more. The lead separation method according to claim 1, wherein the lead is volatilized and separated by firing at a temperature of 1500 ° C. 3. Firing at a temperature of 1400 to 1500 ° C. in a chlorine equivalent ratio of -10 to -5, and a chlorine equivalent ratio of -5.
3. The method of separating lead according to claim 1, wherein the residual ratio of lead is reduced to 20 wt% or less by firing at a temperature of 950 ° C. or higher in the above range. 4. The method for separating lead according to claim 1, wherein the residual ratio of lead is reduced to 3% by weight or less by baking at a temperature of 950 ° C. or more in a chlorine equivalent ratio of 8 or more. 5. The method for separating lead according to claim 1, wherein the amount of chlorine is a total amount of chloride added and chloride content of the material to be treated. 6. The lead separation method according to claim 1, wherein the object to be treated is a cement raw material, a cement raw material, or a concrete material. 7. The method for separating lead according to claim 1, wherein all or a part of the object to be treated is domestic / industrial waste.