CA2110400A1

CA2110400A1 - Process for recycling solids, powders and sludges contaminated with mercury

Info

Publication number: CA2110400A1
Application number: CA002110400A
Authority: CA
Inventors: Jozef Hanulik; Jean-Francois Equey
Original assignee: Individual
Current assignee: Recytec SA
Priority date: 1992-04-01
Filing date: 1993-03-31
Publication date: 1993-10-14
Also published as: NO934344L; FI935368A; NO934344D0; AU3950293A; JPH07500380A; FI935368A0; EP0587867A1; WO1993020593A1; AU661395B2

Abstract

ABSTRACT OF THE DISCLOSURE

When a mixture of spent electric batteries is treated by pyrolysis, a pyrolysis slag is obtained having at least a residual mercury content between 50 and 1500 ppm, according to the battery type. It does not seem possible to eliminate this residual content by simply modifying the parameters of this pyrolysis process. The residual content may however be lowered below 10 ppm by a second thermal treatment between 500 °C and 700 °C. Preferably the material to be treated is crushed between the first pyrolysis and the second thermal treatment, and the second thermal treatment is carried out while air or nitrogen is blown through the material.

Description

~ ~f ~
W~> 93/20593 PCT/E~P93/00793 The present inve~tio~ relate~ to a proce6s for the decontamination by pyrolyE~i~ of mercury-contaminated ~o}id~, powders and ~ludges.
The present i~vention i8 u~ed in partiaular in a proces~ for the recycling of a mixture of exhausted equipment batteries of a~y chemical composition, in which, in a fir~t step~ the unsorted mixture i8 pyrolyzed a~d then the pyroly~is slag i~ further proce~sed.
EP-0-274 059 disclos~s a process for the recycling of such a mixture (and of a~sembled printed circuit boards and electronia components), in which according to the teaching of the patent a pyrolysis of the unsorted mixture i8 carried out at a temperature between 450C and 650C, then an electrolysis of the pyrolysi~ slag is carried out in a solutio~ o tetra-fluoroboric acid and salts thereof, and then a separation of the eleatrolysis products and removal of the product~
~roduced at the electrodes are carried out.
At ~hese pyrolysis temperatures, pla~tic, starch, pigments and other organic components are carbonized without complex degradatisn products (in particular PCBs, dioxins) already being formed. The pyrolysis iB prefer~
ably carried out in an inert or in a reducing atmssphere in order to avoid the risk of explosion and to prevent the metal oxidation. The ~olatile components are with~
drawn from the furnace or distilled off. The pyroly6i~
gas products and vapor products such as water, carbon dioxide, ca:rbon monoxide, h~drochloric acid, amonium chloride and, in particular, mercury are passed according to know~ technology through coolers, scrubbing column~
and gas filt:er plants, in particular the mercury being condensed and recovered. It has been shown that in the ca~e of conventional mercury concentrations in the starting material, from a few thousa~d to a few ten thousand ppm of by far the majority di~till, but the remaining mercury in the pyrolysi~ slag i8 present at a

2~

mean concentration of 50 to 500 ppm.
Supplementary to thi~ teaching according to the patent, it i~ po~ible to ~hred and wa~h the pyrolysis slag in order thus to reduce the content of salts, such as KCl, Z~Cl2, before the pyrolysia slag iB conducted to the electrolysis bath. It is eq~ually possible to separate the wa~hed or unwashed shreclded pyrolysis 61ag by a ~creen having a mesh width o~E approximately 2 mm into metallic coarse components and powder and equally to separate off the iron piece~ by an electromagnet accord-ing to known technology. The electrolysi~ can then be carried out separately for the powder component and for the coarse components: this i~ expedient, because the aoarse components contain a high proportion of metal and the electrolysis can be carried out simply and with a low energy consumption, while tha electrolysis of the powder proceeds lengthily, expensively and with a high energy consumption. In an indu~trial bat~ery recycling plant which uses this process, the capital costs and operating costs or the electroly~is o~ the powder are approxi-mately ~ive times as high as those for th~ electrolysis of the coar~e components. It would therefore be desirable for cost reduction to ~urther process the powder portion otherwise than by electroly~is.
Studies of the unwashed powder present after the pyrolysis show, for example, the following compo~ition:
approximately 25-40% NnOx, 15 to 25% graphite, approxi-mately 20-30% Zn and ZnO, approximately 5 to 10~ Fe and FeOx, approximately 5 to 7% water-soluble salts and finally approximately 50 to 500 ppm Hg and approximately 200 to 3000 ppm Cd or CdO, depending on origin. This high mercury contamination makes impossible a direct sale of the powder as a by-product to the major metal industries, because these generally o~ly accept MnO-Zn powder having mercury contamination below the 10 ppm limit.
On the other hand, in the above-described pro-cess, the residual content of mercury of the pyrolyRis slag is carried along during the scrubbing and screening process steps (and only separated out during the electroly iB), BO that these have to be carried out with special precautionary measures. It would therefore be de~irable in the above-described proce~ to reduce the mercury level beneath the generally accepted 10 ppm limit at the earliest po~sible stage.
EP-A-0-075 978 disc].ose~ a proceRs for the recovery of metals from scrap of nickel-cadmium atorage batteries, in which the organic constituents are removed by pyrolysis in an inert ga~/oxygen atmosphere, then at high te~perature the cadmium is distilled off and con-densed and a mixture of nickel and iron ~crap i~ obtained a~ a residue. The problem of mercury contamination when the mercury-containing batteries are pre~ent in the starting mixture is not recognized or covered by EP-A-0 075 978. It iB not obvious from this patent -whether the mercury distillR off with the cadmium or is retained in the Ni-Fe ~crap.
EP-A-0 158 627 describes a process for the recovery of ferromanganese from discharged zinc-carbon-20 manganese oxide batteries. According to this process, the `
battery scrap, together with carbon and iron i8 fused in ;~
a reduction vessel at approximately 1400C to 1600C, volatilized zinc being recondensed on the one hand, and mangane6e recovered as ferromanganese. In small bat- ;~
terie~, the mercury content can be up to 3% by weight.
For its removal, the batteries are comminuted a~d the scrap, before the reducing fusion, being heated to ;-temperatures around approximately 600, similarly to the pyroly~i~ process step described in EP-A-0 274 059. The ;~
,mercury residue, not specified in EP-A-0 158 627, in the pyrolysis slag after this first process ~tep ~hould therefore be in the same range of values.
It has been shown that the residual values of the ~-mercury contamination of the powder portion of the pyrolysi~ ~lag of battery mixtures of conventional type, as were on the market in earlier years, i~ on average around 150 ppm. In mixtures which are predominantly com~
po~ed of alkali batteries of the t~pes which are newly on -~
the mar~et, thi~ residual value iR Up to 1500 ppm Hg. ~-'". .:`,'''''-~:' .

7 a ~

It ha~ now been ~hown that it i~ not po~sible to reduce these re~idual value~ in a single pyroly~is, either by increasing the pyrolysis temperature within the industrially acceptable temperature range, by prolonging the pyrolysis time, by blowing through N2 gas for addi-tional entrainment of the mercury vapor~ or by other obviou~ measure~.
The object of the in~ention i8 therefore to improve the process me~tionecl at the outRet in such a manner that the residual content of the mercury after the thermal txeatment is less than 10 ppm.
A process having the eature~ of patent claim 1 achieved this object.
Preferred embodimentR of the process according to the invention result from the ~ubclaims.
The second thermal treatment according to the invention of the pyrolyzed and chopped material can be carried out either on the entire ~tarting material or else only on a part thereof, preferably the fine portion or powder obtained by screening.
It has surprisingly ensued that chopping (~hred-ding) the starting material and a subsequent single pyrolysis only seldom achieves a mercury residue below 100 ppm, whatever p~rolysis parameters are selected. If, in contraRt, after a first pyrolysis step the pyrolysis slag is subjected to a second thermal treatment, mercury residual values around 10 ppm are systematically achieved, usually beneath this. The pos~ibly coarRe or clumped pyrolysis slag can, as required, be appropriately Icomminuted and/or loosened, and by adjusting the proce~s parameter~ (time, temperature, stirring, gas faed etc) in each case according to composition and type of the material to be treated, those skilled in the art can usually reduce the mercury residue to 0.9 to 6 ppm by the second thermal treatment according to the in~ention.
Ac-cording to the invention, the following mate rials can be subjected to the second thermal treatment:
- all of the pyrolysis slag coarsely shredded, unwashed .. . .. . .. . . . . . . . .

, .- ; ... - ,.. -, , . . :~ .. . . ...... .. - . .

i :. ' . ' ', ' '. ' ' ! , . , ~ , . i . ...

2 ~
- all of the pyrolysis Rlag coarsely shredded, washed - all of the pyrolysis slag coar~ely shredded and then finer comminuted, unwashed - all of the pyrolysi~ slag coarsely shredded and then iner comminuted, washed. After coarse shredding and . ' screening, - the finer ~ortion u~washed, not milled - the finer portion washed, not milled (sludge) - the iner portion unwashed, milled - the finer portion wa~hed and milled ~sludge).
The coar6er portion can, after screening, be likewi~e thermally treated.
~owever, the application of the process according .
to the invention is not restricted to the above-listed mercury-contaminated solid~ powderR and sludges rom exhauated batteries, but it can also be applied to other mercury-containing industrial wastes, for example Hg-amalgam-containing raw materials and intermediate ;~
20 products which have a abrication defect. ~;
The second thermal treatment can be carried out either under a reducing atmosphere (N2) or under an oxidative (air/02) atmosphere.
I the second thermal treatment is carried out under an oxygen-containing atmosphere, the following advantageous aspects result~
a) the combination o heating and oxidation by air in the second thermal treatment oxidizes the combus-tible or oxidizable mixture components, such as graphite, , 130i ~Z~, Cd, amalgams and a binding with the mercury i8 prevented, as a result o which the mercury can more ~--easily be removed by suction.
b) the combustion of the graphite to give C02 effects an additional internal flushing of the material in the furnace and acilitates the transport away of the Hg.
c) the treated material i~ reed from graphite and carbon residue~
d) the oxidation reaction and combustion reaction ~.'' ' . .; .

f' are entirely exothermic, which co~tributes to the heating a~d reduceR the consumption of supplied energy.
If the material which i8 to be treated by the ~econd thermal process step contain~ a ~ignificant proportion of higher manganese oxide~ (MnO2, Mn304 or Mn203), oxidative conditions prevail in the treated mass, even without oxygen-containing gas supply. AB a re~ult, carbon residues and likewise Cd and Zn are at least partially oxidized. The CO2 formed contributes to the removal o~ the Hg and CdO iB much les~ volatile than metallic Cd ~o that lesR Cd distills over. Even without oxygen supply, local overtemperature~ with respect to the adjusted furnace setpoint have been detected in the treated mass, which i~ possibly due to non-homogeneous distributions of MnO2 and C and local exothermic reac-tions. Blowing through N2 gas instead of air can reduce such overtemperatures from approximately 100 to 150C to about 50C. Although these overtemperatures have no direct influence on the xemoval of mercury achieved in the inal result, they ~hould be avoided if it is undesirable that Cd distills of togethex with the mercury vapor and condenses in the cooler. If it is desired to avoid Cd distilling off, the temperatuxe of the treated mass should as far as possible not exceed or hardly exceed 700C. Since, on the other hand, all those substances which can lead to the PCB or dioxin formation have already been taken off in the first pyroly~is, the second pyrolysis can take place at higher temperatures than the first (which is conventionally carried out at ,500~C to 550C;. The second thermal treatment is prefer-ably carriecl out at temperature~ around or above 600C
~or optimal remo~al of mercury. Since, when a second thermal treatment is u~ed, it no longer matterR that in ..
the first pyrolysis the first removal of mercury be aB
complete as possible, this first pyrolysis can now be carried out at somewhat lower temperatures ~400C to 500C) instead of the otherwise used 500C to 550C.
If, in contrast, it is desired to distill off the cadmium, it is advisable to create reductive conditions ~ ~a~

in the treated mass and to distill off cadmium vapor~ at elevated temperature: this can, for example, be achieved by adding carbon to the material before the beginning of the ~econd thermal treatment (po~sibly even before the first pyrolysis), which carbon in a ~irst phase of the treatment in which the furnace temperature is held below 700C, which reacts the manganese oxides, after which the ~urnace t~mperature i8 increased above the boiling point (750C) of the cadmium, for the volatilization thereof.
The pre~ent inventio~ i8 now described in more detail with re~erence to a preferred embodiment and particular examples, drawings and refiults of mea~urement.
Figure la show~ a sch2matic course of a preferred proce6a according to the present invention.
Fisure lb shows the temperature-time cour~e in the furnace (O), and at various measurement points P in the maR~ of the treated powder (P1 ; P2 + ; P3 * ;
P4 3 ; P5 x) with progre3eive heating of the furnace and without gas supply.
The Figures 2a and 2b show the temperature-time course in the furnace (O) and at the measurement points P1-PS at a con~tant furnace temperature of 600C, in each case with air and nitrogen through-flow.
The Figures 3a and 3b show the temperature-time course in the furnace (O) and at the measurement points Pl-P5 at a constant furnace temperature of 500C, in each aase with air and nitrogen through-flow.
In Figure la, the box labeled with the designation nu~ber 1 symbolizes the pyroly~is furnace.
30 ~IThe battery ~ixture symbolized by 0 is placed into thi~
The first pyrolysis which takes place in the furnace 1 is preferably carried out at a temperature between 450C-700C. In this ca~e, there escape, inter alia, the organic sub~tances, water, oils and the majority of the mercury. In order to avoid explosive gas mixtures in the furnace, nitrogen is conventionally blown through the furnace. This nitrogen simultaneou~ly serves as a trans-port medium for the mercury vapor~. All of the sub~tance~
are removed by suction from the furnace and passed .,: ~ ,.:
, . ~ .

a~

through an exhaust ga~ filtration plant 3. The mercury removed by ~uction will be procluced hexe. The exhau~t gas filtration plant i8 described in more detail in EPA-0 274 059 which is herewith incorporated into the description. The pyrolysis slag 2 is removed from the furnace 1 and fed to a shredder 4. The commi~uted pyrolysis 81 g is then washed at 5. In this case, a majority of the water-soluble ~alts are washed out. The water-soluble 8alt8 6 can subse~uently be removed from the water by known processes/ ~or example crystalliz-ation. The shredded and washed pyrolysis slag is then separated at 7 by a screen into coarse components 8 and fine components or powder 10. The coarse components are compoaed essentially of Zn, Cu, Ni and graphite residues.
Iron portions, which can likewise be present, can be removed by a magnet 14. The reimaining coarse ciomponents are placed into an electrolysis bath and here separated electroIytically. The metals produced at the cathode are removed and æold to metal industry enterprises (arrow 13)~
The ine components 10 screened out are not fed to a powder electrolysis plant, but are fed to a second pyrolysis. This can take place either in the already-mentioned batch furnace 1 or in a second continuous furnace 11 having a conveyor screw. Since all organic substances have now been carbonized in the first pyroly-sis, the second pyrolysis can take place at higher temperature~, 600C to 700C. Depending on the starting material 10, either air L or nitrogen or no gas at all ,can be blown through the furnace (1, 11). The more vigorous the spontaneous gas development in the second -~
pyrolysis i~, the lower the amount of air which is required as a transport medium for the mercury transport is.
Depending on the starting material, the second thermal treatment can also be carried out in the temper-ature range 500-600C.
The volatile portions produced in the second pyrolysis are in turn fed to an exhaust gas filter plant, . :~ . - .. . . ~ . .

- ~ . i ~ .. . .
.. . . ~ . .
:: , . . : . ~ .: .
:.... . . ..

., 211 0 :1 lJ ,~ ' .

which is the same aR or similar to that of the exhaust gas filter plant 3. The mercury removed from the exhau~t gas purification Rystem 3 or 12 is supplied to reuse.
By way of example, the following resultR are gi~en in the second thermal treatment according to the inve~tion:
ExamPle A laboratory furnace is adjusted to a setpoint temperature (600C or 700C). Powder substance~ from a first pyroly~is are placed in a crucible (layer thickness 4 cm) and put into the furnace. The experiment proceeds ~tatically, that iR without stirring and without ga~
through-flow. Substances tested:
- powder from a mixed battery stock; Hg residual content: 150 ppm - powder from alkali batteries; Hg residual content~
1500 ppm - Hg-Zn amalgam granules in KOH-containing starch gel;
Hg resldual content: 14,0Q0 ppm.
In the statement o~ the residence times in the furnace, 45 minutea are allowed for the temperature adaptation of the samples. The results are reproduced in --Table 1. (W = washed; NW = not washed, M = milled;
NM = not milled). From this it can be seen that mercury 25 can easily be removed from already-pyrolyzed powder from ~;
a stock of mixed types of batteries, but that mercury can -~
only be removed from powder originating from alkali batteries at a higher temperature and residence time under ~tatic conditions.
IE~ample 2 Temperature variations in the treated mass. ~-The ~amples (1.7 kg) are placed into a laboratory cxucible and form a layer of 8 cm thickness. GaR
t5 literB per minute) can flow through the mas~ through a perforated tube. The temperature~ in the samples are measured locally at a plurality of positions by Ni-Cr probes.
Figure lb shows a temperature course without ga~
supply. The furnace i~ progresRively heated and reache~

2 ~

600C in the course of 5 hours. It iR seen that the powder temperature follows the furnace temperature until the latter reaches 400C. When the furnace temperature exceeds 400C, still higher temperatures are measured in the powder which vary locally and can only be generated by Qpontaneous exothermic reactio~s in the ma~s. Locally and for a ~hort time, a temperature in the mass can exceed the furnaca temperature by 120C.
The Figures 2a, 2b, 3a and 3b show temperature profiles of pyrolyzed alkali battery p~wder with air supply and nitrogen supply at constant furnace temperatures of 600C
and 500C respectively. The foll~wing can be seen fr~m the figures: if air is blown through powder treated at 600DC, temperatures are measured which can rise in the center of the sample up to 830C. In contrast, the supply of nitrogen reduces the occurrence of overtemperatures. m e t~mperature differences (overtem~eratures with respect to the furnace temperature) are smaller than without gas supply.
At a furnace temperature of 500C, a complex temper-ature profile is Gbtained with air ~upply and a temperature-regulating effect is obtained with nitrogen supply. In this last case, the temperature does not exceed 550C.
The mercury residues in the powders treated under gas supply were measured at at least two positions (P1 and P2), Table 2 displays the measurement results. From this it i3 see~ that at 600C furnace temperature, the removal of mercury under gas supply can be satisfactorily carried out both with air and with nitrogen, that in contrast at a furnace temperature of 500C less reproducible and unsatis-factory results are achieved, both under nitrogen as underoxygen ~upply, for a treatment duration of 3 hours.
Example 3 2 kg of pyrolyzed unwashed battery powder are placed into a quartz vessel, which is put into a laboratory urnace (Naber type). The second thermal treatment is carried out at 600C under nitrogen or air through-flow of one cubic meter per hour for various treatment times. The results are repro-duced in Table 3.

~, :. . , . - . .
: ' . : - ! ' ' ' : . ' ' ~ . ; ' ' :
, 21.~ 0 Example 4 Re ult~ in the pilot furnace containing a stirrer screw 100 kg of pyrolyzed battery powder are placed into a pilot furnace having an inter~al ~tirrer screw. ~ -The powder iB stirred by the rotation to and fro of the screw (speed of rotation 5 to 7 revolution~ per minute).
After each hour a sample is removed and analyzed. The entire trea~ment i8 carried out under a gas through-flow of 2 cubic meters per hour of nitrogen. Table 4 show~ the measurement results which were obtained with five dif-ferent lots o~ pyrolyzed powder from the production.
ExamPle 5 Results in the continuouQly fed pilot furnace containing a stirrer ~crew 100 kg of pyrolyzed battery powder are placed into a pilot urnace having an internal screw. The ~urnace is replenished during the thermal treatment, while the powder is conveyed by the screw. The results are reproduced in Table 5 (in the two last Qamples "*", the screw was rotated very slowly.
Exam~le 6 , Results in the industrial plant. `' `
The pyrolysi~ furnace of the industrial plant was used. Screened powder from the first pyrolysis was used from stocks of mixed batteries and from alkali batteries.
The mercury re~idues in these powders were 500 or 1000 ppm mercury. The charges were between 700 and 1300 kg. The batches were processed under a through-flow of 1 cubic meter per hour of nitrogen ~or 30 hours. Table ~-`
6 shows that at furnace temperatures of 700C, the mercury re~idue of all batches could be ~ati~factorily reduced to a few ppm.
Example 7 ~
1 kg of shredded pyrolyzed thermometers wa~ ;
placed into the laboratory pyrolysis furnace. The mi~ture actually composed of glass Qplinters, carbon, metal component~ and mercury contained a contamination of approximately 500 ppm mercury. The slag was kept for

3 hours at approximately 500C and 1 m3/h of air was -.. , -,, .......... . ~ . . . . ;.. .. ., . .: .- . .... - . . ~ . , pas~ed through~ The final weight of the ~lag was 940 g and had a mercury concentration of 9 ppm.
~xam~le 8 1 kg of amalgam-containing, already-pyrolyzed sludges having an ~g content of 8000 ppm from dental practices was placed into the laboratory pyroly~is furnace and kept for 3 hours at a temperature o~ 850C.
During thi~ time, in total 5 m3 o~ air were blown through the furnace. The final weight of the material removed was 970 g. A mercury concentration therein of 8 ppm was determined.
The flow diagram shown in process diagram 1 can obviously be ad~antageously changed in the aontext of the pre~ent invention. For example, the pyrolyzed and shred-ded material is screened and both the fine components andthe coarse components are subjected to the second thermal treatment, without pre~ioualy being washed: as a result, the energy for water evaporation of the washed and moist material i~ saved. The second pyrolysis of the coarse components (essentially Cu, Ni, Zn, Fr pieces) free~
these, before the further treatment, from toxic Hg residues, ~o that this ~urther treatment is facilitated.
The second thermal treatme~t of the coarse components iR
carried out essentially more rapidly and more easily than that of the powder.
Hitherto, the relatively high mercury portion in the powder had been considered to be unavoidable. The mercury contamination could not be reduced to the desired low contamination below 10 ppm e~en with formation of l~acuum in the furnace or with nitrogen flushings.; Only the apparently senseless repeated thermal treatment ~whether in ;the form of a secGnd pyrolysis or a calcination) of the already for the first time pyrolyzed material leads to the desired result.

2 ,l 1. 0 1 ~ O

TABL~ 1 .. _ .
MATERIAL, TEMPERATUR~ NW NW W W :~
g a ter TIME NM M NM M
pyroly~is . ~ .
Mixed 700C 1.4 ppm 1.4 1.5 1.6 batterie~ 1.5 hours 150 ppm 700C 1.4 1.5 1.8 1.7

4 hours .
600C 2.3 ~ 1.9 2.4 1.5 hours : :
. . "'~
Alcali 700C 21B 88 457 354 .
batterie~ l.S hour8 ~ :~
1500 ppm :

4 hour~ _ :
700C 5 13 150 139 .:-~
8 hours .
600~ 122 110 532 297 ::.
4 hours .~ ''.' Hg-Zn/ 700C 11.8 13.4 ~:~
/starch ge~ 1.5 hour~
14,000 ppm . . :.
700C 9.4 11.1 : : .
3.5 hours ~:

~ 14 - 2 :gi ~
TABL~ 2 TEMP~R~TURE GAS P1 P2 SUPPLY (ppm Hg) (ppm Hg) 600C Air 4.8 3.4 600C N~ 5.2 __ 4.6 500C Air 294 _ 161

5 o o ~ - N2 141 12 . 5 TABL~ 3 ... .........
Hg TEMP~RATURE TkEATM~NT TRANSPORT Hg INITIAL VALUE DURATION G~S FINAL V~LUE
(ppm) _ (HOURS) (ppm) .
1500 600C 4 .... N2 5 200 600C 3.5 N2 2~5 _ , __ 1500 600C 3 N~ 5 TAB~ 6 Hg BATCH Hg INITIAL VALUE kg FINAL VALUE
(ppm) (ppm) __ _ .
500 70~ 3 . 5 .

1000 1300 4.5 L O ;~
- 15 - :
TABLE: 4 :

_ . . '- '' ~:"
Hg FURNACE TREAl~ENT Hg INITIA:t VALUE TEMPERATURE DURATION FINAI. VALUE
(ppm) (HOIJRS ) (ppm) ~: :
.. _..... _ .

. 3 _ 6 . 6 __ ~:
4 3 ;::
._ _ ~ '.',~'`',"
22 700 C 1 4 . 3 .
:
2 2 9 .; ~

_ _. ...... ___ .~
77Q 600C 2 435-_ ::

3 3 . 7 . ____ :' . _ 3 .4 - .
. _ . _ , ~':: `, ' O SOO'C ~ '~

'';'~' '' ,,. ":i~,,, "., ,,. ,,., " .,; ,,, . ,' - 16 - 2 L 1~
~ r~
~ H ~ ~ ~ t`~ co ~

~! _. _ . .
J o ~ ~Z;N O L ~ h ~ ~;N

~ ~ ~3 "b "b ~i "b ~ ~ ~i ~ ~ U~ ~O ~
~ _ : , .

~I h O ~ In u~ ~`1 ~
~ ~ ~r~ ~ ~ rl ~1 ' In $~

~ E~ ~ o o o o o o ;
t) h m ~ c~ ~ ~ co c~
H ~ P -1 rl t`l ~ ~ ~ . ~:

H-- _ ___ _ ~ ~
~ _ ~ V C.) ~1 ~ ~,) ~,) ,".: '~
~2 o o o o o o : I ',.
, P~ o o U~ o o o ~ ~D ~D Il~ 1~ ~ ~

P _ _ . .
i~ o o o o ~
1 ~? ~ o o ,~
~¢ O ~`1 rl ~1 ~ ~'3 ', -1~ ~ r I rl rl rl ~1 ~ ,, .... ~,

Claims

PATENT CLAIMS

1. Process for the decontamination by pyrolysis of mercury-contaminated solids, powders and sludges, in which the contaminated material is subjected to a first pyrolysis in a heated furnace, characterized in that the already-pyrolyzed material is subjected to a second thermal treatment by heat, the Hg and/or the Hg compounds being evaporated out of the treatment furnace and being transported away out of the furnace by the gas stream produced in the treatment furnace or fed to the treatment furnace and to an exhaust gas purification system.

2. Process according to claim 1, characterised in that the second thermal treatment is carried out under through-flow of oxygen-containing gas, in particular air, through the furnace, preferably through the treated material.

3. Process according to claim 1, characterized in that the second thermal treatment is carried out under through-flow of reducing gas, in particular nitrogen, through the furnace, preferably through the treated material.

4. Process according to one of claims 1 to 3, characterized in that the pyrolysis slag is cooled and comminuted between the first pyrolysis and the second thermal treatment.

5. Process according to one of claims 1 to 3, characterized in that carbon, preferably in graphite form, is added to the material to be treated.

6. Process according to one of claims 1 to 3, characterized in that the first pyrolysis is carried out between 450°C and 700°C and the second thermal treatment is carried out between 500°C and 700°C.

7. Process according to one of claims 1 to 3, characterized in that the second thermal treatment is carried out in a continuous furnace to which the material to be treated is fed continuously and which mixes the said material during the treatment.

8. Process according to one of claims 1 to 3, characterized in that the material to be treated is composed of used equipment batteries.

9. Process according to claim 8, characterized in that the pyrolysis slag is shredded in the first step, after which the shredded pyrolysis slag is subjected to the second thermal treatment.

10. Process according to claim 8, characterized in that the unsorted batteries are pyrolyzed in a first step and then the pyrolysis slag is shredded, the coarse components are mechanically separated off from the fine components, after which the fine components are subjected to the second thermal treatment.

11. Process according to claim 8, characterized in that the unsorted batteries are pyrolyzed in a first process step and then the pyrolysis slag is shredded, washed and screened, whereupon the coarse components are separated off and subjected to an electrolysis and the screened out and washed fine material is subjected to the second thermal treatment.