NL1026346C2 - Binding heavy metals in waste incinerator ash, by mixing with acidic iron oxide or iron hydroxide - Google Patents

Abstract

The ash is mixed with iron hydroxide or iron oxide having an acidified surface. A method for binding heavy metals and/or heavy metal compounds (especially copper, antimony and molybdenum) present in ash from the floor of a waste incinerator comprises slaking the ash by passing it through a water bath and then ageing the wet ash by treating it with a carbon dioxide-rich gas. The optionally aged ash is mixed with a material which comprises iron (hydr)oxide and has an acidified surface. Independent claims are also included for the following: (1) Use of an iron ore concentrate with an acidified surface (e.g. fine iron ore) for binding heavy metals and/or heavy metal compounds present in ash from the floor of a waste incinerator which has been slaked with water in a liquid/solid (L/S) ratio of 0.17-4 (0.8) l/kg in order to produce ash which has a reduced leachable content; and (2) Aggregate, especially suitable for use as a building material, obtained by mixing optionally washed and aged ash from the floor of a waste incinerator with an iron (hydr)oxide-comprising material having an acidified surface.

Description

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Title: Method for binding heavy metals and / or heavy metal compounds in bottom ash

The invention relates to a method for binding heavy metals and / or heavy metal compounds, in particular copper, antimony and molybdenum, in the bottom ash formed by the incineration of waste.

Such a method is known from the European patent EP-B-0.669.900, and comprises treating the combustion residues, or slags, with CO2 gas at a temperature of room temperature to 200 ° C, under a pressure of atmospheric pressure up to 10 bar excess pressure. The reaction of CO2 with the (basic) slag produces carbonates, which is important for the fixation of heavy metals. In addition, a change in the pH of the material takes place through the formation of carbonates, that is to say a reduction to a neutral value, which has the consequence that the solubility of the harmful components is minimized.

However, as appears from Example 4 of EP-B-0 669 900, the leaching of copper decreases as a result of the aging treatment with CO2, but the leaching of antimony and molybdenum increases.

Due to this increase in the leaching values of antimony and molybdenum, the bottom ash does not comply with category 2 (not designed) of the Building Materials Decree and cannot be applied upon abolition of the Special Category.

As soon as the Special Category of the Building Materials Decree is abolished, the regulations with regard to the use of bottom-up ash are considerably tightened, in particular with regard to copper, molybdenum and antimony. In connection with this, a quality improvement of the bottom ash, such that the requirements of at least category 2 (and possibly category 1) of the Building Materials Decree are met, is highly desirable because the material then 1026346 "

Η I

I 2 I can be used as a loose aggregate (not designed) as a building material

I are applied. I

A method for treating bottom ash has now been found, which makes it possible for the leaching of both copper and antimony and molybdenum to become smaller, and therefore converts the bottom ash as a more valuable product that can and may be used in a building material.

The invention therefore relates to a method I as indicated above, which is characterized in that bottom ash, whether or not aged, is mixed with a

I (hydr) oxide-containing material containing an acidified I

surface. I

It is noted that from J.A. Meiroa, R.N.J. Comans, I

Journal of Geochemical Exploration 62 (1998) 299-304, known I

I 15 is for the leaching of antimony from bottom ash of an I

Reduce waste incineration plant by using bottom ash I

Mixing with an absorbent material that I

I contains iron / aluminum (hydr) oxides. In this publication I

I also mentioned that the addition of Fe (III) - or I

20 Al (III) salts to bottom ash, the leaching of both copper and I

I greatly reduces molybdenum. When the pH of the bottom ash I

However, if I is higher than 7.5, then the adsorption of antimony to I

The adsorbent material is too low. The pH of the I

I mixture was incidentally in the I published in this reference

Investigation set to a value of 7.5, 8.5 and 10.3 by I

nitric acid or caustic soda; some suggestion for an I

To provide a practicable process in which an I

however, such a pH adjustment is unnecessary. I

Surprisingly, in the process according to I

The invention has proved to be possible to prevent the leaching of copper, I

reduce antimony and molybdenum to acceptable levels, I

without the need to lower the bottom ash pH by I

Addition of acid by adding an iron-containing material

I have an acidified surface. I

The acidified surface of the ferrous material

I preferably has a pH of 4-6, in particular 4.8-5.1. I

The iron content, calculated as Fe 2 C> 3, of the material to be used in the invention is expediently from 50-80% 1026346 to 3% by weight, preferably from 56-73% by weight, in particular from 65-69 % by weight.

According to an attractive preferred embodiment of the method according to the invention, the iron (hydr) oxide-containing material consists of fine ore. Fine ore is an iron-containing residual material that arises from titanium oxide preparation as an iron ore concentrate from a sulfuric acid solution. Inherent to this preparation process is that the surface of the fine ore is acidic, so that upon addition of the fine ore to the aged bottom ash, according to the invention, the formed mixture need not be acidified. Moreover, the method according to the invention has the consequence that when using fine ore, which is a residual product, another residual product, namely bottom ash from the incineration, can be made more valuable, that is to say that the material obtained meets at least the requirements that are met set for category 2 (not designed) of the Building Materials Decree. As fine ore, for example, the SachtoFer® Feinerz marketed by the company Sachtleben Chemie GmbH, Duisburg, Germany.

According to an advantageous embodiment of the method according to the invention, the incandescent hot bottom ash is demineralized with water in an L / S ratio of 0.17-4, preferably 0.5-2 1 / kg, in particular about 0.8 1 / kg. It is noted in this connection that an L / S ratio of about 0.17 is common. Use of a higher L / S ratio appears to have a favorable effect on reducing the leaching of the heavy metals in the material treated according to the method according to the invention.

In addition to, or instead of, applying a higher L / S ratio during the sagging of the bottom ash formed, which takes place in the so-called sagging agent, the bottom ash can be subjected to a washing treatment with fresh water, which is applied to the bottom ash sprayed when leaving the 35 detox. This treatment takes place at normal temperature and pressure, and results in the adhering impurities being removed, so that the entire process can be carried out more efficiently.

1026346

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I 4 I

The invention further relates to the application I

I of an iron ore concentrate with acidified surface such as I

I fine ore, from bottom ash that has been sagged with fresh water in an I

I L / S ratio of 0.17-4 1 / kg, preferably 0.5-2 1 / kg, in I

In particular 0.8 l / kg, to obtain a bottom ash that is in I

I leach to a lesser extent. The invention also relates to I

on an aggregate as defined in claims 8 and 9 .. I

The invention is further elucidated with reference to the I

The following non-limiting examples. I

I 10 I

EXAMPLE 1 I

Bottom ash formed in a waste incineration plant was I

I in a manner customary in itself, in piping hot I

I condition deteriorated by the bottom ash on a conveyor belt I

I pass through a water-filled detacher. In the I

I de-snailer an L / S ratio of about 0.8 I was used

I 1 / kg. I

Subsequently, the bottom ash I had become slugged in this way

I accelerated outdated, also called composting, by using an I

Perforated floor of the composting plant a mixture I

I of air with approx. 8% CO2 blown through the bottom ash. I

I From the bottom ash, the I

I leaching of antimony, copper and molybdenum measured, I

I according to NEN7343. The results are shown I

I 25 in table 1. The I-category 7 according to BRL 2307

I limit value is also given in table 1. I

I _Table 1 I

Component__Sb (mg / kg) _ Cu (mg / kg) _ Mo (mg / kg) _ I

I untreated 0.92 7.07 1.05 I

bottom ash____I

I aged 0.7 1.7 0.37 I

I bottom ash____I

I requirement according to 0.41 3.3 0.85 I

I BRL 2307, I

I category 2 I

As the data in Table 1 shows, I

I aging of the bottom ash has a positive influence on the I

I 1026346

* I

5 (decrease) of the antimony, copper and molybdenum leaching. For antimony, however, this is not sufficient to meet the requirements for category 2 of the Building Decree.

EXAMPLE 2

Bottom ash from a waste incineration plant was aged in the same manner as in Example 1 and then mixed with an amount of fine ore, i.e. SachtoFer® Feinerz from Sachtleben Chemie GmbH, Germany. Of the mixture thus formed, the leaching of antimony, copper and molybdenum was determined in the same way. The results are shown in Table 2.

_Table 2 ___

Component__Sb (mg / kg) __ Cu (mg / kg) __ Mo (mg / kg) _ obsolete 0.73 1 0.64 (reference) ____ 7% fine ore__0.42__0.8__0.67_ 10% fine ore 0.48__0.85__0.71_ 20% fine ore 0.31__0.53__0.45_ requirement BRL 2307 0.41 3.3 0.85 category 2____ 15

In addition, the bottom ash was demolished with fresh water and then mixed with the SachtoFer® iron ore concentrate.

The leaching values of antimony, copper and molybdenum of the material thus obtained were determined in the same manner as above. The results are shown in Table 3.

_Table 3 ___

Component__Sb (mg / kg) __ Cu (mg / kg) __ Mo (mg / kg) _ blank__0.2__8.5__0.46_ 7% fine ore__0.13__4 ^ 3__0 ^ 5_ 14% fine ore 0.06__2.6__0.55_ requirement BRL 2307 0, 41 3.3 0.85 category 2____

On the basis of these results, the following can be concluded: 1026346 Η I 6 I - Washing the bottom ash will reduce the leaching of antimony and molybdenum in particular.

I - Aging of the bottom ash reduces the leaching of I copper; however, the leaching of antimony will increase.

The addition of an additive such as fine ore further reduces the leaching of copper and antimony of obsolete and / or "washed" bottom ash.

I EXAMPLE 3 10 Bottom ash samples from a number of waste incineration plants

I plants were washed after washing and / or aging, as in I

Example 1 is indicated, mixed with 7% or 20% fine ore.

From the material thus obtained and from the starting material

The material became the leaching values of antimony and copper I.

I determined. The results thereof are shown in Figures 1 and I

Figure 2, where I

I a: washed, non-aged bottom ash, I

b, c, f: unwashed, obsolete bottom ash, I

I 20 d, e: washed, aged bottom ash. I

I In both figures, the percentage leaching out compared to the I

I reference (100%) displayed. From the I shown in Figure 1

results show that there is a reduction to 41-71% of the I

I reference value for the leaching of antimony becomes I

I obtained by adding fine ore to the bottom ash. I

The results shown in Figure 2 show that the I

I addition of fine ore, the copper leaching lowers, even I

when due to a prior aging there is already a copper I

I reduction has taken place. In the worst case, an I found

Reduction to 76% of the reference value, and in the I

I most favorable case up to 14% of the reference value. I

I Incidentally, there were no significant differences

I observed between the applied doses of fine ore of I

7% and 20%. I

I 1026346 "

Claims (8)

1. A method for bonding heavy metals and / or heavy metal compounds, in particular copper, antimony and molybdenum, into the bottom ash formed by the incineration of waste, wherein the bottom ash formed during incineration is deflated by passing it through. a water bath, and then the moist bottom ash if desired aging by treatment with a gas rich in carbon dioxide, characterized in that the bottom ash, whether or not aged, is mixed with an iron (hydr) oxide-containing material which has an acidified surface. 10 Method according to claim 1, wherein the iron (hydr) oxide-containing material has an acidified surface with a pH of 4-6, preferably 4.8-5.1. Method according to claim 1 or 2, wherein the iron (hydr) oxide-containing material has an iron content, calculated as Fe 2 O 3, of 50-80% by weight, preferably 56-73% by weight. 4. Method according to one or more of claims 1 to 3, wherein the iron (hydr) oxide-containing material consists of fine ore. 5. Method according to one or more of claims 1 to 4, wherein the iron (hydr) oxide-containing material is used in an amount of 5-30% by weight, preferably 5-20% by weight, in particular 7% by weight. .% based on the weight of the bottom ash. 6. Method according to one or more of claims 1 to 5, wherein the bottom ash is demineralized with water in an L / S ratio of 0.17 to 4, preferably 0.5-2 1 / kg, in particular 0 , 8 l / kg 7. Use of an iron ore concentrate with an acidified surface, such as fine ore, as a material for binding heavy metals and / or heavy metal compounds in bottom ash formed during the incineration of waste, which has been demolished with 1026346 Η I 8 I water in an L / S ratio of 0.17-4 l / kg, preferably 0.5-1 2 l / kg, in particular 0.8 l / kg, to obtain a bottom ash that leaches out to a lesser extent. 58. Aggregate, in particular intended for use as building material, obtained by mixing washed ash, washed or not, and containing an iron (hydr) oxide material containing an acidified surface. 9. The aggregate according to claim 8, wherein the iron-containing (hydr) oxide-containing material that has an acidified surface I consists of fine ore. I 1026346