CA2180633A1 - Prevention of formation and destruction of organohalogen compounds in incineration of waste materials - Google Patents
Prevention of formation and destruction of organohalogen compounds in incineration of waste materialsInfo
- Publication number
- CA2180633A1 CA2180633A1 CA 2180633 CA2180633A CA2180633A1 CA 2180633 A1 CA2180633 A1 CA 2180633A1 CA 2180633 CA2180633 CA 2180633 CA 2180633 A CA2180633 A CA 2180633A CA 2180633 A1 CA2180633 A1 CA 2180633A1
- Authority
- CA
- Canada
- Prior art keywords
- incineration
- destroyer
- flyash
- gaseous
- dioxins
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
- A62D3/30—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents
- A62D3/38—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by oxidation; by combustion
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/68—Halogens or halogen compounds
- B01D53/70—Organic halogen compounds
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
- A62D2101/08—Toxic combustion residues, e.g. toxic substances contained in fly ash from waste incineration
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
- A62D2101/20—Organic substances
- A62D2101/22—Organic substances containing halogen
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
- A62D2101/20—Organic substances
- A62D2101/28—Organic substances containing oxygen, sulfur, selenium or tellurium, i.e. chalcogen
Abstract
Organohalogen compounds (OHC), including dioxins and furans, produced in waste incinerators are destroyed by introducing inorganic bases, either alone or in combination with aliphatic hydroxy compounds, into an incineration post combustion zone that contains gaseous incineration products. The destroyer compounds may also serve to inhibit the formation of OHC by catalysis at active sites on flyash produced in the incineration and also to remove acid gases from the gaseous incineration products. In this way, the concentration of OHC on flyash precipitated from the product gas stream is decreased as dioxins and acid gas concentrations in stack emissions from the incineration process also decreases.
Description
Wo 95118667 PCT/CA95/00012
2 1 80633 TITLE OF INVENTIQN
rKrV~ . lUr~l OF r~ ' AND V--;Lr~U~ OF
clDr-~ ~T.OnF~ ~Ur~L~S IN l~ OF
Wllq~ TFDTl~T.Q
FTr~r~n OF INVENTION
The present invention relates to the prevention of formation and destruction of organohalogen compounds including dioxins and furans in incineration of waste materials .
R~rRr7R~uND TO T~ J~ TIoN
The formation of organohalogen ~ ol~n~ (OHC), including polychlorinated dibenzo-p-dioxins ~PCDD) and dibenzo furans (PCDF), OCCUrB in all combustion processes which provides the n~r~a~ry favourable conditions and ingredients, such as c~rh~nPous, organohalogenated and 20 metallic materials. Municipal, medical and industrial waste incinerators are large contributors to the release of O~IC to the environment. Municipal solid waste incinerators are called "Resource Recoveryl1 plants, promising to provide steam and electricity while 25 simult~n~n1~1 y reducing trash volume by 90 percent .
Reduction in trash volume results in less transportation costs and land fill space. Due to these benefits, incineration is a viable alternative to landfill.
Ilundreds of such incinerators are in operation around the
rKrV~ . lUr~l OF r~ ' AND V--;Lr~U~ OF
clDr-~ ~T.OnF~ ~Ur~L~S IN l~ OF
Wllq~ TFDTl~T.Q
FTr~r~n OF INVENTION
The present invention relates to the prevention of formation and destruction of organohalogen compounds including dioxins and furans in incineration of waste materials .
R~rRr7R~uND TO T~ J~ TIoN
The formation of organohalogen ~ ol~n~ (OHC), including polychlorinated dibenzo-p-dioxins ~PCDD) and dibenzo furans (PCDF), OCCUrB in all combustion processes which provides the n~r~a~ry favourable conditions and ingredients, such as c~rh~nPous, organohalogenated and 20 metallic materials. Municipal, medical and industrial waste incinerators are large contributors to the release of O~IC to the environment. Municipal solid waste incinerators are called "Resource Recoveryl1 plants, promising to provide steam and electricity while 25 simult~n~n1~1 y reducing trash volume by 90 percent .
Reduction in trash volume results in less transportation costs and land fill space. Due to these benefits, incineration is a viable alternative to landfill.
Ilundreds of such incinerators are in operation around the
3 0 world .
One of the significant drawbacks to the incineration procedure is that several hundred stable and toxic compounds, including polychlorinated dibenzo-p-dioxins (abbreviated herein as PC3D and collectively commonly 35 termed "dioxins") and polychlorinated dibenzo~urans (abbreviated herein as PCDF and collectively commonly termed "furans"), are formed and are present in parts-per-million ~-nrr~ntrations both in the flyash formed dur~ng c~mbustion and in the stack emissions. The ~ WO95JI8667 2 1 8 0 6 3 3 PCT/CA95100012 formation of OHC, including PCDD and PCDF, in the process of combustion and pyrolysis of organic compounds in presence of inorganic halogenated compounds has been known for some time. The major sources of release of OHC, including dioxins and furans, are various incineration processes involving combustion of municipal waste, municipal 51udge, medical waste, polyvinyl chloride and other ha1Ogen-cnnt~;nin~ plastics.
Our research work shows that the formation of OHC, including dioxins and furans, occurs in municipal solid waste ;nr;n~ tr,rS (MSWI) around the world. It has been shown in our laboratories that combustion of PVC resulted in the formation of dioxins. Increased levels o~ dioxins and furan3 have been observed in stack emissions and in flyash when PVC was incinerated. One of the r -h~ni mq proposed for the formation of PCDD and PCDF is by reactions of molecular precursor species that are present during incineration, resulting in surface catalyzed synthesis of PCDD/PCDF on the flyash via recL~ J
free radical condensation, dechlorination, dehydL~ ation, t,rans-chlorination, isomeri2ation and other similar molecular r~rt;onq. From the fact that uncontrolled rf~isrt j on~ occur during the lncineration process, it can be presumed that all above m~nt i onF~d reactions can proceed due to the presence of different kinds of metal~metal-oxides, inorganic halides, organic materials and gaseous compounds, such as CH2-CH" CH=CE~, HzO, CO2 and HCl in the flue gas stream. Inorganic halides and acid gases can form in the incineration process at high temperatures from halogen-cnn~ininr plastics, moisture and small amounts of metals present in waste materials. These compounds constitute catalytic sites on the sur~ace on the f lyash produced during incineration to enhance the formation of PCDD/PCDF.
We have studied flyash samples from different ' incinerators around the world. The dioxins and furans have been detected in all incinerators studied. More than 600 compounds were detected in flyash samples that includes a large number of OHC.
Release of OHC, including dioxins and furans, by 5 MSWI through the stack emissions and flyash is of significant public concern. MSwI flyash containing high levels of dioxins and furans when dumped in landfill sites can leach dioxins in water system. Hence, there is a need for a technology which can provide safe 10 incineration of waste materials. The present invention relates to a method of reducing the OHC in the stack emissions and in flyash of the MSWI. There has been previously described in our U. S . Patents Nos . 4, 793, 270 and 5 ,113, 772, the provision of material acting as a 15 catalyst inhibitor in association with the f lyash so as to inhibit the catalytic activity of the f lyash towards the formation of chlorinated compounds, including dioxins and f urans .
US-A-5113772 descri~es the inhibition in an 20 incinerator of the ~ormation of dioxins and furans categorized by flyash from precursors using certain organic a ~ kA 1 i n~ and inorganic ~ l k~ 1 i n~ materials US-A-5021229 defines the addition of calcium-based sorbents, including calcium oxide, calcium hydroxide and 25 calcium carbonate in dry or slurry form to a flue gas stream from an incinerator to react with HCl in the f lue gas, by i n j ection at t emp eratures o f 4 0 0 o to 9 0 0 C .
WO-A-8800672 describes the formation of dioxins in the incineration of wastes using sodium carbonate or 30 sodium bicarbonate in solid form added to the waste.
DE-A--3527615 describes an incineration process in which HCl gas is reacted with a basic powdery material.
DE-A-3628043 describes a filter iL, ~l~Lu~ for purifying inhaled air comprising a plurality of layers of 35 absorption material including a calcium ammonium silicate material impregnated with glycol.
GEANDERTES BLATT
-2~80633 DE-A-3632366 describes a procedure for ~icp~c~l of halogenated cu~ uuu-,ds by bringing the halogenated materials into contact with a nucleophilic reaction partner at high temperature.
SI~MMARY t~F JNVRNTION ~ ~c It has now been found that inorganic bases, either alone or in combination with aliphatic hydroxy or polyllydLu~y compounds (such materials being herein termed de-LLUy~L:~ and inhibitor/de~LLuy~ ,,), are very effective in destroying OHC, including dioxlns and furans, on ~SWI
flyash. It i5 believed that the destroyers, when heated with flyash, react with the OHC and extract halogen to f orm neutral stable inorganic salts and organohydroxy ~ lllp-.:UII-15, which then react with more destroyer and metallic constituents in flyash at higher temperatures, resulting in their decomposition. Formation of dioxins and furans by the catalytic activity of f lyash and precursors in f lue gases at temperature between about 250 and about 400~C has been reported in our previous U.s. Patents Nos. 4,793,270 and 5,133,772. Inorganic bases have been used traditionally for conversion of OHC
into organohydroxy compounds under strictly controlled conditLons . The use of destroyers under drastic conditions, such as high temperatures and presence of air and steam, as provided herein, results in the reaction of OHC in the f lue gases and on f lyash particles with the destroyer to f orm the organohydroxy compounds, which ultimately decompose due to ~urther reactions with de~LLuy~ at higher temperatures. Hence, according to one aspect, the present investigation is directed towards the destruction of OHC on f lyash and in f lue gases produced during MSWI by the utilization of the destroyers in ~he manner described herein.
In another aspect, the present invention is directed towards the deac~ivation of the flyash and thus the prevention of the f ormation of OHC, including dioxins and GEANDER~Es ELA~
2 ~ ~0633 f urans . Research in our laboratories and a study of the correlation of operational conditions with levels of dioxins and furans detected in the stack emissions and in the flyash show that up to about 15% OHC compounds is s formed in the combustion process and the rr~-;n;n~ about 85% is formed by catalytic activity o~ flyash and small molecules, such as C~=CH~, CH=CH, H O, CO2 and HCl, present in f lue gas stream .
Thus, based on previous U.S. Patents Nos. 4,793,270 and 5 ,113, 772, inhibition of the formation of about 85%
of the OHC compounds, including dioxins and furans, was possible by the Introduction of inhibitors in the postcombustion zone of the incinerators at about 400C.
Since it is possible to introduce the presently-15 investigated destroyer compounds at a wide range of temperatures, from about 300 about 1100C, the present invention enables a higher destruction effLciency to be achieved. In laboratory experiments, complete destruction of all OHC on flyash has been found when 20 flyash was heated with inorganic bases at 400C.
Mixtures of inorganic bases and aliphatic hydroxy compounds (AHC) are highly effective when they were used in smaller amounts and even at lower temperatures (about 300O to about 500C) and the specific utilization of such 25 organic-inorganic complexes in decreasing PCDD/PCDF on flyash and stack emissions forms an aspect of the invention. Destroyer compounds also act as inhibitors and deactivate flyash sites responsible for the formation of the OHC . The ef f ect of temperature on the OHC on the 3 0 f lyash shows that the amount of dioxins and furans increases with temperature up to about 400OC When f lyash containing OHC was covered with destroyer compounds and heated, then destruction of OHC started at about 300OC and complete destruction of OHC had occurred 35 by the time the temperature reached about 400OC. Various destroyers have shown different destruction efficiency l~or OHC. An increase in the amount of destroyer (when only inorganic bases were used) increases its efficiency for destruction of OHC compounds. EIowever, the mixture of inorganic bases and AHC at 2 . 59~ (by Wt) of flyash shows optimum destruction efficiency for OHC. The destruction ef f iciency does not improve signif icantly by increasing the amount of inhibitor mixture. The technique described here is useful for the destruction of OHC, including dioxins and furans, at the source, i.e.
in the post combustion zone of ~SWI, using destroyers in the postcombustion zone.
Accordingly, in one aspect of the present invention, there i5 provided a method for incinerating waste materials h~herein dioxins and furans formed in the incineration are destroyed, which comprises incinerating waste materials selected from municipal solid waste, medical waste, municipal sludge, industrial waste and other materials, to form fly ash and gaseous products of incineration, comprising dioxins and furans; and passing the gaseous products of incineration to a precipitation step, wherein the fly ash is precipitated from the gaseous products of the inciner~tion; characterized by:
introducing at least one destroyer compound directly into the gaseous products of incineration during the passage of the gaseous products of incineration to the precipitation step to react with and destroy dioxins and furans present in the gaseous products of incineration prior to destroyer compound introduction to decrease dioxin and furan concentrations in stack emissions from the precipitation step.
In another aspect of this invention, any material, such as flyash, soil, sediment or sludge, containing high levels of OHC can be detoxicated by mixing the material with a suitable destroyer and heating the resulting mixture at about 300 to about 900C or, preferably, by incinerating such material in the existing incinerators Dtn~
~ 2180633 alony with other waste material~, and using destroyers in a postcombustion zone as described above. Accordingly, materials containing high levels o~ organohalogen compounds, including dioxins and furans, including soil, 5 sediment, sludge or flyash formed in an incineration operation, may be mixed with the waste materials to be incinerated according to the procedure provided herein to ef f ect destruction of the OHC in such materials .
,,C~s~ TFS ~
~ Wo 9S/18667 2 t 8 0 6 3 3 PcT~cAgsl0ool2 In another aspect of the invention, certain materials are used to effect inhibition/destruction of PCDD and PCDF which are mixtures of certain alkali metal hydroxides and certain ~l;rh~t;c hydroxy or polyhydroxy 5 c~ ...~,u1-d~. Such alkali metal hydroxide . ~s~u~ds may comprise ~zodium hydroxide or potassium hydroxide, particularly potassium hydroxide, while such a1 ;rh~t j c hydroxy or polyhydroxy compounds may comprise ethylene glycol or polytetrahydrofuran. A particularly preferred lO mixture of materials is a mixture of potassium hydroxide, ethylene glycol and silica gel.
Such materials may be effectively employed by direct injection as an aqueous solution into a post-combustion zone of an incinerator at a temperature of about 300 to about 500-C, preferably about 350 to about 450 C, more particularly around 400'C.
Accordingly, in this aspect of the invention, there is provided a method of decreasing the rnnnpntration Of organohalogen compounds in flyash and vent gas stream 20 formed in the incineration of combustible r~tP~; ;~
which comprises effecting combustion of combustible materials in a combustion zone to form gaseous combustion products nnnt~;nin~ e~trained flyash; conveying the gaseous combustion products from the combustion zone to 25 a precipitation zone; precipitating flyash from the gaseous combustion products in the precipitation zone;
venting the gaseous combustion products from the precipitation zone to provide the vent gas stream; and introducing to the gaseous combustion products during the 3 0 conveying step an aqueous solution of at least one mixture o~ alkali metal hydroxide and aliphatic hydroxy or polyhydroxy compounds at a temperature of the gaseous combustion products of about 300 to about 500 C.
The introduction of such organic-inorganic nnrrl P~Pq 35 to the combustion gas stream also may be c ' inP~ with introduction of an alkali metal hydroxide, in the form of .
-Wo 95/186~7 2 t 8 0 6 3 3 PCT/C~95100012 an ar~ueous solution thereof, particularly sodium hydroxide or potassium hydroxide, directly into the combustion gas stream, at a higher temperature above about 500'C, which may include multiple introductions at dif ferent higher t 1 ~ aLu~e levels of approximately 500 C, 600-C and 700 C.
R~7T~ DESt~TPTION OF DR~WINGS
Figure l is a 8- ~;r diagram of the experimental set-up used for the studies of the destruction, the inhibition of formation and catalytic formation of OHC on flyash;
Figure 2 is a graphical repr~C~.nt~t;nn of the native PCDD and PCDF present on MSWI flyash prior to ~no heat~
and after heat treatment of the flyash at various temperatures;
Figure 3 rn7~t~;nc a graphical repres~nt~tinn of the amounts of native PCDD (A) and PCDF ~B) on MSWI flyash heated without and with typical destroyers at various temperatures;
20 Figure 4 rnnt~;nc chromatograms showing the response of electron captor ~l~t~rtor for the O~C. Samples analyzed were l) MSWI flyash, no treatment, 2) MSWI
~lyash heated to 400 C without destroyer, 3) MSWI flyash heated at 400 C with destroyer (NaOH 5~ by wt . );
Figure 5 is a graphical repres~nt~t;nn of the amount of 13C PCDD produced on the flyash prior to (BG) and after destroyer tr~ tq of the flyash at 300-C;
Figure 6 is a graphical repres~nt~tinn of the effect of temperature on formation of dioxins from ''3C
p~ntarhlorophenol precursor on flyash coated by different destroyers (2~) at various t~ ~ aLuLes; and Figure 7 rnnt~inc graphical representation of the ~
decomposition of native dioxins and furans at various temperatures using ~rious destroyers.
-~ WO 95118667 2 1 8 0 6 3 3 PCT~C~35/00012 ,. g r.T~NT'T~T, DESrT~TPTI~ OF INVENTION
In the present invention, inorganic bases, either alone or in A~m; ~t~re with aliphatic hydroxy or polyhydroxy 'q (here termed destroyers) are 5 employed and their effect on organohalogen ~ uul,ds lOHC), including dioxins and furans, on flyash was investigated. It has been found that the destroyer U ~ lc, when coated on the flyash, effectively destroy OHC on the flyash at temperatures above about 300 C. The l0 destroyer compounds may be selected from inorganic bases which are hydroxides, oxides, ~rh~n~t~q, 1~yd- uue~
on:~t~q and silicates of one or more alkali metals or ~qlkPllinF~ earth metals. The destroyer compounds that have been found to be particularly effective are sodium 15 hydroxide ~NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca (OH) 2) ~ calcium oxide (CaO), magnesium oxide (MgO), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), calcium carbonate (CaCO3), sodium orthosilicate (NacSiOi), sodium metasilicate (Na2SiO3) and either used 20 alone or in ~ ;Ytllres with aliphatic hydroxy or polyhydroxy compounds (AHC). Such aliphatic hydroxy or polyhydroxy compounds may include ethylene glycol, l, 2-propanediol, l,4-b~t~ne~;ol, polytetrahydrofuran or mixtures of these ~u- ,~uul-ds . These destroyer compounds 25 can be used to effectively destroy OHC on the flyash and in the flue gases of solid waste incineration by introduction to the combustion gas stream at suitable temperature. In the laboratory tests, it has been found that the flyash coated with NaOX and XOH (2 to 43~) 30 destroys the formation of PCDD up to 99~ compared to the formation of pr-DD on untreated flyash. A similar effect was observed using an even smaller percentage of mixtures of NaOH or KOH in conjunction with aliphatic hydroxy compounds .
3~ Several experiments were conducted using the laboratory experimental set-up shown in Figure l. A MSWI
Wo 95/l8667 2 t 8 0 6 3 3 PCT/C~95/00012 , ~ 10 flyash (with native dioxins a~d furans produced in the inci~eration proce66 on it) was heated at temperatures 200- to 500 C in air under d~ _~' -ric pressure. It was found that the amount of native dioxins and furans 5 increased up to 350 C, probably due to presence of precursors on the flyash, which by catalytic activity of the 1yash, were converted into PCDD/PCDF. Above 350-C, the amount of PCDD/PCDF on the flyash decreased, probably due to a decreasing rate of forr~t;nn against the rate of 10 ~ ition of PCDD/PCDF. The flyash heated at 400 C
to 500 C showed very little amount of both PCDD/PCDF.
After the heat treatment at various temperatures, flyash samples were dried by heating at 150 C to remove toluene used for extraction. A catalytic activity test of the 15 flyash samples next was conducted at 300-C. The procedures for catalytic activity tests were similar to that reported in our previous U.S. Patents Nos. 4,793,270 and 5,113,772. It was found that flyash heated up to 500 C retained its catalytic activity to produce PCDD
20 from precursors, such as PCP, at lower temperatures such as 250- to 400 C.
In another set of laboratory experiments, heat treatment of 1yash coated by 2 to 5~ destroyer compounds shows that destruction of PCDD/PCDF started at 300 C and 25 was completed by the time the temperature reached 400-C.
~ence, the addition of destroyers makes the flyash complex destructive for organic compounds, even at 300-C, otherwise flyash promotes the formation of dioxins and furans (see Figures 2 and 3). The effectiveness of 30 destruction depends upon the amount of destroyer used and the temperature employed for the destruction. About 6 wt9~ destroyer at 300-C has the same effect as about 1 wt~i destroyer at 400 C. This result indicates that very little destroyer is required to achieve complete 35 destruction of the O~C, if destroyer can be introduced at temperatures ~etween 400 and 900 C, or up to llOO C, in WO 95118667 2 ~ 8 0 6 3 3 PCr1C~95100012 the postcombustion zone of the incinerator, ~erf~n~in~
upon the type of the destroyer used. Destruction efficiency also depends upon the melting point of the destroyer used. NaOH and ICOH are highly effective when used above about 390 C, Na2CO3 above about 800-C, and sodium meta- and ortho-silicates above about 900 C.
In general, destroyer compounds are used in any amount within a range of from about 0.5 to about 6 wt~ of the flyash produced in the incineration step. This quantity generally corresponds to about 0 . 025 to about 0.3 wt9~ of- the waste material incinerated.
The destroyer may be introduced to the post-combustion zone of the incinerator in any convenient form, for example, granular form, powder form or, preferably, as an aqueous solution.
Depending on the destroyer compound or compounds used, the destroyer compound may be introduced between the combustion chamber and precipitation zone of the incinerator at a suitable temperature of from about 300-to about ll00-C, preferably from about 300 to about 800 C
and particularly from about 300 to about 600 C.
The destroyer effect achieved herein also may be combined with the inhibition of formation of OHCs by flyash catalysis, as described in USPs 4,793,270 and 5, 113, 772, by introduction of a suitable inhibitor material as described therein, to the incinerator gas stream between the combustion zone and the precipitation zone, generally at a temperature o~ from about 300- to about 500 C. The present invention employs, in one emho~;m~nt, mixtures of materials as inhibitor~destroyers not contemplated in our earlier patents.
As will be apparent from the disclosure of USP
5 ,113, 772, some of the rnmrm-nrlq which were used as inhibitors of OHC formation in that patent are used herein as destroyers of OE~C. It is preferred herein to employ the same compounds for destruction and inhibition.
Wo 9S118667 2 1 8 0 6 3 3 PCT1CA95100012 In general, higher temperatures are required to effect destruction of OHC tqith such , 'R than inhibition of OHC formation. The destroyer and inhibitor compounds, therefore, may be added at different lor~t;nnq, and 5 accordingly, different temperatures, between the incinerator and the precipitator. The present invention employs, in one ~nhn~;r^nt, mixtures of ~-t~ as inhibitor/destroyers not cnnt~ _ 1 ^ted in our earlier patents .
Several mixtures of the above described inorganic bases and - their combination with AHCs were tested in laboratory experiments. A coating of 5 wt% NaOH on flyash completely destroyed all the OHC, including PCDD/PCDF, on the flyash at 400 C. In addition, the 15 flyash was F~rr~n~ntly deactivated for the formation of PCDD/PCDF. Deactivation of flyash is very important because it provides the means to introduce destroyers at any temperatures above 400 C for higher efficiency with a lower amount of destroyer. In this way, destroyers 20 effectively destroy an estimated l0 to lS~ OHC compounds produced in the furnace when introduced at about 400 to ll00-C in the post combustion zone of the incinerator.
The procedure also deactivates the flyash to prevent further formation of PCDD/PCDF (about 35 to go~) by 25 catalytic activity of the flyash in the cooler parts of the incinerator.
Acid ga6es which may be present in the incinerator gas stream, such as HCl, SO2 and M2~ also may react with the ~ inQ destroyer compounds, so that such acid gases 30 are removed from the gas stream, whereby their con^^n~tinn in the stack emissions decreases.
The dioxins and the furans exhibit varying degrees of toxicity, rl~renrlinj on the number of chlorine atoms present and the position of the chlorine substitution.
35 Usually toxicity of a particular sample is estimated ` based on amount of tetra- to octa- chlorinated dioxins Wo 95/18667 2 1 8 0 6 3 3 PCT/CJ~95/00012 and furans present. The formation of PCDD and PCDF for precursor m~q, such as chlornhen7~nrq~
chlorophf~nnl R and chlorodiphenyl ethers on flyash is illustrated by the following equation:
_ _ a ~ .~o ~ 7 + ~T + >~ 1 ~Y AS~ ~ P~::DF
10 m= I _ 6 n-- I - 5 ~) rT~ r)~ ~H~ ~Lu~ur~ul5 ~ 8 Cl, P~DD
~lrZ~MpT.~.':
15 Exam~le l:
This Example shows the effect of heat on the amount of native dioxins and furans present on MSWI flyash.
An experimental apparatus shown in the Figure l was used to test the effect of heat treatment and catalytic 20 activity of flyash samples. The apparatus comprised a glass tube (25 X l cm I .D. ) passing through the oven.
Part of the ~low tube was a re6ervoir where f lyash to be tested was packed. A flyash sample rom MSWI with all compounds produced in the process of the incineration on 25 it was heated at various temperatures to examine the effect of heat. In each experiment, 1.5 g of the flyash was placed in the glass tube. The section of the tube rnntAininrJ flyash was heated at various temperatures for 60 minutes using 3 ml/minute flow of air through the 30 tube. After completing the experiment, the flyash was spiked with an int~rnAl standard for recovery estimates.
Orga~ic rnmro~n~lc present on the flyash were extracted by eluting with 220 ml toluene. Extracts were cnnr~nt~ated by rotary evaporation to a few ml and final rnnr~nt~ation 35 in a sample vial to 500 ~Ll under a gentle stream o~ N2.
~ WO95118C67 2 1 8 0 6 3 3 PCTICA95100012 Figure 2 shows a graph of the amount o~ native dioxins and furans present on ~SWI flyash prior to ~no heat) and after heat tL~ ~`. t of the flyash at various temperatures. The results of these experiments reveal 5 that the flyash produced in the incineration process rnntRinc high levels of dioxins/furans (no heat plot) and precursors. The MSWI flya3h is highly catalytically active, which produces more dioxins/furans, probably from native precursors present on the flyash, when heated from 200- to 400'C.
After the heat treatment at various temperatures, flyash samples were dried by heating at l50 C to remove toluene used f or extraction . Then a catalytic activity test of these flyash samples was conducted at 300 C. In 15 the catalytic activity test, a volume of 50 /ll of 5 ~g/~Ll 13C_pCp solution in tl~;lnnl wag deposited on the gl~ss beads on top of the flyash and the solvent was allowed to evaporate. The section of the tube ~nnt~ ;ng flyash and 13C-PCP was heated at 300'C for 60 minutes using 3 20 ml/minute flow of air. After completing the experiment, the flyash was spiked with an internal standard for recovery estimates and extracted as - ;~nn~d above.
Analysis of extracts shows the f ormation of 33C PCDD .
This result indicates that merely heating the flyash does 25 not affect its catalytic activity.
mnle 2:
This Example shows the effect of 5~ destroyers on native PCDD/PCDF on the flyash.
In these experiments, fresh flyash (l0 g) rnnt~ining 30 native PCDD/PCDF was coated with a 5~ destroyer solution in water. A l . 5 g portion of destroyer coated and dried flyash was used in the heat treatment described in Example l. The amount of PCDD/PCDF detected in flyash coated by typical destroyers, namely NaOH and PSEGC (a 35 polysilicate-ethylene glycol complex formed from KOH:ethylene glycol:silicagel in respective weight ratios ~ WO 95/18667 2 1 8 0 6 3 3 PCTtCA9~100012 17: 60: 23 ) and heated at various temperature6 is shown in Figure 3 . Comparing the amounts of PCDD/PCDF on f lyash heated at various temperatures without (Figure 2) and with NaOX, PSEGC and SMSEG (a sodium metasilicate-5 ethylene glycol complex formed from sodium--t:~c;l;r~te:ethylene glycol in a weight ratio of 15:85) destroyers (Figure 3 ), it can be seen that no PCDD/PCDF
was produced between 300 C and 500 C on destroyer-coated flyash. In fact, the native PCDD/PCDF content of 10 destroyer-coated flyash was reduced at 300 C and completely eliminated at 400 C. The experiment at 500 C
also did not reveal any residual native PCDD/PCDF.
Similar results were obtained f or KPTHF, a mixture of KOH:PTHF (KOH:polytetrahydrofuran:: 25 :75) and other 15 destroyers with vary little variation in the destruction ef f iciency .
Figure 4 shows the plot of gas chromatography/
electron capture detector response f or various chlorinated rn7nroun~q on flyash from MSWI, the flyash 20 heated at 400-C, and the flyash coated by 5 wt~ NaOH and heated at 400-C. It is clear from Figure 4 that a large number of organohalogen ~ -c, including PCDD/PCDF, are present on flyash from MSWI (bottom tracing) . Merely heating the flyash at 400-C does not destroy the OHC on 25 the flyash (middle tracing) . However, 5 wt~ destroyer on the ~lyash effectively destroys all the OHC, including PCDD/PCDF, on the flyash ~top tracing) .
Af ter the heat treatment at various temperatures of the flyash samples coated by various destroyers, they 30 were extracted using toluene, after that they were dried by heating at 150 C to remove toluene used for extraction. A catalytic activity test of these flyash samples then was conducted using 13C PCP at 300 C, as described in the Example 1. Only traces of 13C labelled 35 PCDD were produced on these flyash samples from l3C-PCP
Wo 95118667 2 1 8 0 6 3 3 PCT1C~95100012 This result indicates that the catalytically active sites on the f lyash were removed by the destroyer .
Exam~le 3:
This Example shows the effect o~ amount and type of S destroyer used for coating the flyash in the forT~~t;nn of C PCDD f rom 13C PCP .
In these experiments, nine f lyash samples ( l . 5 y each) were coated by three different de~LL~,y~ namely Na,CO3, KOH and NaOH (l wt%, 2 wtg~ and 6 wt~) separately.
Catalytic activity tests were conducted on each coated sample at 300 C, as described in Example l. The analyses of the f lyash extracts are shown in Figure 5 .
Background(BG) represents the amount of 13C PCDD produced from 13C PCP on the flyash with no destroyer at 300 C.
From the plots, it can be seen that, as the amount of destroyer (wt~) increases, the formation of PCDD
decreases. The effect is consistent for all three destroyers used. There was a slight difference i~
activity of the destroyers to prevent the formation of 2 0 PCDD .
mn l e 4:
This Example shows the effect of temperature on the formation of 13C PCDD from 13C PCP on the flyash coated by variou6 destroyers.
In these experiments, three different destroyers, namely Na2CO3, KOH and ~aOH were coated ~2 wt~) separately on flyash samples. Catalytic activity tests were conducted on each coated sample at 300, 350 and 400 C, as described in Example l. The analyses of the flyash extracts are shown in Figure 6. Background(BG) represents the amount of 13C PCDD produced rom ~3C PCP on the flyash with no destroyer at 300-C. From the plots, it can be seen that the effectiveness of the destroyer increased with the temperature increases.
3 5 Figure 7 shows the percentage reduction or destruction of native dioxins and furans using various Wo 95/l8667 2 1 8 0 6 3 3 PCT/CA95/000l2 inhibitor/destroyers. The inhibitor/destroyers used were in these experiment6, namely:
i) KPTHF, a mixture of KOH:polytetrahydrofuran (25 : 75), 5% ~by wt) ii) SMSEG, sodium metasilicate:ethylene glycol ~15:85, 5% (by wt) iii) NaOH, 5~ (by wt) iv) PSEGC, potassium hydroxide:ethylene glycol:silica gel:: :17:60:23, 5~ ~by wt) The results seen in Figure 7 are compared with those f ound earlier .
From the results of Examples 3 and 4, it can be seen that the catalytic activity of flyash for the formation of PCDD from precursors was effectively reduced, either by using smaller amounts of destroyers at higher temperatures or by using larger amounts of destroyers at lower temperatures.
Exam~le 5:
This Example illustrates a commercial scale plant test.
A waste incinerator plant had three i n~ep~nr~nt incineration lines comprising an incineration grate for municipal waste, a waste to heat boiler (100 ton per day) and a multi-stage flue gas purification plant. From a refuse bunker, the waste is supplied to the incineration grate where it is burned at lD00-C. Flue gases flc>w through the boiler at a velocity of 6 to 12 M/second.
The inhibitor/destroyer mixtures were injected into the waste flue gas stream. KOH or NaOH as the de~L.~y~La were injected in a temperature window of 590 + 50 C and PSEGC or SMSGC (see Fxample 4) as the inhibitor/destroyers were inj ected in a temperature window of 375- + 50 C. The amount ~f each inhibitor and destroyer injection was 7 to 10~ by weight of the flyash produced. An injection nozzle unit was employed containing a pressure atomizer with a mixing chamber in wo 95rl866~r 2 ~ 8 0 6 3 3 PCT/CA95100012 which the destroyer or inhibitor was mixed with 13 times the amount of water by volume. The nozzles had a outside diameter of 12 mm and an opening of l, 6 mm and were operated with water at an inj ection pressure of 6 to 8 5 bar to distribute the destroyer/inhibitor uniformly thLUu~lluuL the flue gas.
Plant test I was conducted using combination I
consisting of KOH as destroyer and l?SEGC as inhibitor/destroyer, plant test II was conducted using 10 combination II consisting of ~NaO}l as destroyer and SMSGC
as inhibitor/destroyer and plant test III was conducted using ~ ' in~t;on I and activated carbon. On the fourth day of each test, the flue gas samples were collected for PCDD/PCDF measurements. Several flyash samples were l~ collected from the electrostatic -precipitator on the third and fourth day of each test. Sampling and analysis of the flue gas for PCDD/PCDF t~f~n~ n~ration were done with standard techniques.
The amount of PCDD/PCD~ detected on the f lyash 20 samples during the three tests is shown i~ the ollowing Table I:
WO 95/18667 2 ~ 8 0 6 3 3 PCT/CA9~100012 a , o ~D N ~ N ~D
~, ~: a O ~J
P~
.. ~
~ u7 r N Lt~ N
-. .
N ~ N H 0~ D
~ m .~ o~
A
~' O ~ O r~
ZJl 1~ N N N H . ~D
H
Jq O
a ~ ~ H ~ N H N .-1 N
f-l ~ r .
o ~
~ ~ f ~
E~ Z
C~ ~ N f'~
m E~ d Wo 95/18667 2 1 8 0 6 3 3 PCTIC~95/00012 AB may be seen from these results, with all other conditionB ,~ ;nin~ the same, injecting the de~L.uye-and inhibitors into the post combustion zone att -- aLuLes of 550 C and 350 C respectively, caused a 5 marked re~llrt;~n in the amount of PCDD/PCDF on the flyash samples from the electrostatic precipitator A
comparison between the individual tests shows that the best re~ ti~n of PCDD/PCDF of 999~ was achieved in Test III An overall reduction in PCDF of about 80 to 94~ was lO achieved in Tests I to III
The amount of total PCDD/PCDF detected in flue gases in background samples and samples collected during Tests I to III are shown in the following Table II
WO9!i/18667 2 1 8 0 6 33 PCT/CA9S1000~2 ~ .
E~
~C\ N ~ CO L~l Ul O
~ ~ E ~ ~ ~ N
E~ -'t~) C~ o 1'~ N :1 0 1''1 0~ N _I
~0 E~ r ~ ~ r ~D ~ N r 1`'1 S~ _ o D~ ' c4 E o rl ~ N Ir) ~ ~ r~ L~ ~ .1' N ~' ~`7 N ~I' ~ ~') ~ t~
C) Cq H
~n ~ ~ a E N N ~D ~D N ~ t~ Ll) t` r~
O H N N ~D N ~ I`') ~ ~ ~I N
U~
H
H
H H
_ ~ ~ H
Cl ~ V 3 a) 3 Il~
S~ H H H H C~ 3 3 c) s~
O -- H H H H H H 3 ~ ~t Il~
O ~ IJ CJ O a) H H H H H
O O O O O O G) C) C) ~q O -LLIl~i ~I W tlJ ~ E-' E- E-' ~U
C~ ~-l ., .. .. . ., H C~ ~ .-- .. . ..
W ~ _ L . L L
~1 ~ ~ ' , t I t Wo 95/18667 2 i 8 0 6 3 3 PCIIC~95/00012 As may be seen from the result3 of Table II, the PCDD/PCDF cono~ntration related to the toxic e~auivalent (TE) of USEPA was reduced in Te9ts I to III up to gl9~ in raw gas and up to 95% in pure gas.
The results crntAinpd in this Example demonstrate that the formation of ~CDD/PCDF during the incineration of waste can be PRs~nt;A~ly suppressed both the flyash from the electrostatic precipitator and in the flue gas by injection of desL~ uyc:~ ~ and inhibitors into the flue gas from the i~cinerators.
- SVMM~RY OF DISCL~)SURE
In the summary of thi6 disclosure, the present invention provides a method for destruction of organohalogen compounds (ûHC), including dioxins and furans, and for the prevention of formation of the O~C
and the acid gases in the combustion gas stream from waste inr;n~rA~rrs by employing certain inorganic bases, alone or their combination with aliphatic hydroxy rrrnrollnrlq (collectively called herein destroyers). The destroyers, such as alkali metal/AlkAl;n~ earth metal oxides, hydroxides, carbonates, bicarbonates and silicates and mixtures of alkali metal/~lkAl inP earth metals oxides, hydroxides, carbonates, bicArhr~n~tes, silicates and their mixtures with AliphAt;c hydroxy and/or polyhydroxy ~ o~n~lq, proved to be highly effective in the destruction and the prevention of formation of the O~C, including toxic dioxins and furans, in the post combustion zone of incinerators.
Modif ications are possible withi~ the scope of this 3 0 invention .
One of the significant drawbacks to the incineration procedure is that several hundred stable and toxic compounds, including polychlorinated dibenzo-p-dioxins (abbreviated herein as PC3D and collectively commonly 35 termed "dioxins") and polychlorinated dibenzo~urans (abbreviated herein as PCDF and collectively commonly termed "furans"), are formed and are present in parts-per-million ~-nrr~ntrations both in the flyash formed dur~ng c~mbustion and in the stack emissions. The ~ WO95JI8667 2 1 8 0 6 3 3 PCT/CA95100012 formation of OHC, including PCDD and PCDF, in the process of combustion and pyrolysis of organic compounds in presence of inorganic halogenated compounds has been known for some time. The major sources of release of OHC, including dioxins and furans, are various incineration processes involving combustion of municipal waste, municipal 51udge, medical waste, polyvinyl chloride and other ha1Ogen-cnnt~;nin~ plastics.
Our research work shows that the formation of OHC, including dioxins and furans, occurs in municipal solid waste ;nr;n~ tr,rS (MSWI) around the world. It has been shown in our laboratories that combustion of PVC resulted in the formation of dioxins. Increased levels o~ dioxins and furan3 have been observed in stack emissions and in flyash when PVC was incinerated. One of the r -h~ni mq proposed for the formation of PCDD and PCDF is by reactions of molecular precursor species that are present during incineration, resulting in surface catalyzed synthesis of PCDD/PCDF on the flyash via recL~ J
free radical condensation, dechlorination, dehydL~ ation, t,rans-chlorination, isomeri2ation and other similar molecular r~rt;onq. From the fact that uncontrolled rf~isrt j on~ occur during the lncineration process, it can be presumed that all above m~nt i onF~d reactions can proceed due to the presence of different kinds of metal~metal-oxides, inorganic halides, organic materials and gaseous compounds, such as CH2-CH" CH=CE~, HzO, CO2 and HCl in the flue gas stream. Inorganic halides and acid gases can form in the incineration process at high temperatures from halogen-cnn~ininr plastics, moisture and small amounts of metals present in waste materials. These compounds constitute catalytic sites on the sur~ace on the f lyash produced during incineration to enhance the formation of PCDD/PCDF.
We have studied flyash samples from different ' incinerators around the world. The dioxins and furans have been detected in all incinerators studied. More than 600 compounds were detected in flyash samples that includes a large number of OHC.
Release of OHC, including dioxins and furans, by 5 MSWI through the stack emissions and flyash is of significant public concern. MSwI flyash containing high levels of dioxins and furans when dumped in landfill sites can leach dioxins in water system. Hence, there is a need for a technology which can provide safe 10 incineration of waste materials. The present invention relates to a method of reducing the OHC in the stack emissions and in flyash of the MSWI. There has been previously described in our U. S . Patents Nos . 4, 793, 270 and 5 ,113, 772, the provision of material acting as a 15 catalyst inhibitor in association with the f lyash so as to inhibit the catalytic activity of the f lyash towards the formation of chlorinated compounds, including dioxins and f urans .
US-A-5113772 descri~es the inhibition in an 20 incinerator of the ~ormation of dioxins and furans categorized by flyash from precursors using certain organic a ~ kA 1 i n~ and inorganic ~ l k~ 1 i n~ materials US-A-5021229 defines the addition of calcium-based sorbents, including calcium oxide, calcium hydroxide and 25 calcium carbonate in dry or slurry form to a flue gas stream from an incinerator to react with HCl in the f lue gas, by i n j ection at t emp eratures o f 4 0 0 o to 9 0 0 C .
WO-A-8800672 describes the formation of dioxins in the incineration of wastes using sodium carbonate or 30 sodium bicarbonate in solid form added to the waste.
DE-A--3527615 describes an incineration process in which HCl gas is reacted with a basic powdery material.
DE-A-3628043 describes a filter iL, ~l~Lu~ for purifying inhaled air comprising a plurality of layers of 35 absorption material including a calcium ammonium silicate material impregnated with glycol.
GEANDERTES BLATT
-2~80633 DE-A-3632366 describes a procedure for ~icp~c~l of halogenated cu~ uuu-,ds by bringing the halogenated materials into contact with a nucleophilic reaction partner at high temperature.
SI~MMARY t~F JNVRNTION ~ ~c It has now been found that inorganic bases, either alone or in combination with aliphatic hydroxy or polyllydLu~y compounds (such materials being herein termed de-LLUy~L:~ and inhibitor/de~LLuy~ ,,), are very effective in destroying OHC, including dioxlns and furans, on ~SWI
flyash. It i5 believed that the destroyers, when heated with flyash, react with the OHC and extract halogen to f orm neutral stable inorganic salts and organohydroxy ~ lllp-.:UII-15, which then react with more destroyer and metallic constituents in flyash at higher temperatures, resulting in their decomposition. Formation of dioxins and furans by the catalytic activity of f lyash and precursors in f lue gases at temperature between about 250 and about 400~C has been reported in our previous U.s. Patents Nos. 4,793,270 and 5,133,772. Inorganic bases have been used traditionally for conversion of OHC
into organohydroxy compounds under strictly controlled conditLons . The use of destroyers under drastic conditions, such as high temperatures and presence of air and steam, as provided herein, results in the reaction of OHC in the f lue gases and on f lyash particles with the destroyer to f orm the organohydroxy compounds, which ultimately decompose due to ~urther reactions with de~LLuy~ at higher temperatures. Hence, according to one aspect, the present investigation is directed towards the destruction of OHC on f lyash and in f lue gases produced during MSWI by the utilization of the destroyers in ~he manner described herein.
In another aspect, the present invention is directed towards the deac~ivation of the flyash and thus the prevention of the f ormation of OHC, including dioxins and GEANDER~Es ELA~
2 ~ ~0633 f urans . Research in our laboratories and a study of the correlation of operational conditions with levels of dioxins and furans detected in the stack emissions and in the flyash show that up to about 15% OHC compounds is s formed in the combustion process and the rr~-;n;n~ about 85% is formed by catalytic activity o~ flyash and small molecules, such as C~=CH~, CH=CH, H O, CO2 and HCl, present in f lue gas stream .
Thus, based on previous U.S. Patents Nos. 4,793,270 and 5 ,113, 772, inhibition of the formation of about 85%
of the OHC compounds, including dioxins and furans, was possible by the Introduction of inhibitors in the postcombustion zone of the incinerators at about 400C.
Since it is possible to introduce the presently-15 investigated destroyer compounds at a wide range of temperatures, from about 300 about 1100C, the present invention enables a higher destruction effLciency to be achieved. In laboratory experiments, complete destruction of all OHC on flyash has been found when 20 flyash was heated with inorganic bases at 400C.
Mixtures of inorganic bases and aliphatic hydroxy compounds (AHC) are highly effective when they were used in smaller amounts and even at lower temperatures (about 300O to about 500C) and the specific utilization of such 25 organic-inorganic complexes in decreasing PCDD/PCDF on flyash and stack emissions forms an aspect of the invention. Destroyer compounds also act as inhibitors and deactivate flyash sites responsible for the formation of the OHC . The ef f ect of temperature on the OHC on the 3 0 f lyash shows that the amount of dioxins and furans increases with temperature up to about 400OC When f lyash containing OHC was covered with destroyer compounds and heated, then destruction of OHC started at about 300OC and complete destruction of OHC had occurred 35 by the time the temperature reached about 400OC. Various destroyers have shown different destruction efficiency l~or OHC. An increase in the amount of destroyer (when only inorganic bases were used) increases its efficiency for destruction of OHC compounds. EIowever, the mixture of inorganic bases and AHC at 2 . 59~ (by Wt) of flyash shows optimum destruction efficiency for OHC. The destruction ef f iciency does not improve signif icantly by increasing the amount of inhibitor mixture. The technique described here is useful for the destruction of OHC, including dioxins and furans, at the source, i.e.
in the post combustion zone of ~SWI, using destroyers in the postcombustion zone.
Accordingly, in one aspect of the present invention, there i5 provided a method for incinerating waste materials h~herein dioxins and furans formed in the incineration are destroyed, which comprises incinerating waste materials selected from municipal solid waste, medical waste, municipal sludge, industrial waste and other materials, to form fly ash and gaseous products of incineration, comprising dioxins and furans; and passing the gaseous products of incineration to a precipitation step, wherein the fly ash is precipitated from the gaseous products of the inciner~tion; characterized by:
introducing at least one destroyer compound directly into the gaseous products of incineration during the passage of the gaseous products of incineration to the precipitation step to react with and destroy dioxins and furans present in the gaseous products of incineration prior to destroyer compound introduction to decrease dioxin and furan concentrations in stack emissions from the precipitation step.
In another aspect of this invention, any material, such as flyash, soil, sediment or sludge, containing high levels of OHC can be detoxicated by mixing the material with a suitable destroyer and heating the resulting mixture at about 300 to about 900C or, preferably, by incinerating such material in the existing incinerators Dtn~
~ 2180633 alony with other waste material~, and using destroyers in a postcombustion zone as described above. Accordingly, materials containing high levels o~ organohalogen compounds, including dioxins and furans, including soil, 5 sediment, sludge or flyash formed in an incineration operation, may be mixed with the waste materials to be incinerated according to the procedure provided herein to ef f ect destruction of the OHC in such materials .
,,C~s~ TFS ~
~ Wo 9S/18667 2 t 8 0 6 3 3 PcT~cAgsl0ool2 In another aspect of the invention, certain materials are used to effect inhibition/destruction of PCDD and PCDF which are mixtures of certain alkali metal hydroxides and certain ~l;rh~t;c hydroxy or polyhydroxy 5 c~ ...~,u1-d~. Such alkali metal hydroxide . ~s~u~ds may comprise ~zodium hydroxide or potassium hydroxide, particularly potassium hydroxide, while such a1 ;rh~t j c hydroxy or polyhydroxy compounds may comprise ethylene glycol or polytetrahydrofuran. A particularly preferred lO mixture of materials is a mixture of potassium hydroxide, ethylene glycol and silica gel.
Such materials may be effectively employed by direct injection as an aqueous solution into a post-combustion zone of an incinerator at a temperature of about 300 to about 500-C, preferably about 350 to about 450 C, more particularly around 400'C.
Accordingly, in this aspect of the invention, there is provided a method of decreasing the rnnnpntration Of organohalogen compounds in flyash and vent gas stream 20 formed in the incineration of combustible r~tP~; ;~
which comprises effecting combustion of combustible materials in a combustion zone to form gaseous combustion products nnnt~;nin~ e~trained flyash; conveying the gaseous combustion products from the combustion zone to 25 a precipitation zone; precipitating flyash from the gaseous combustion products in the precipitation zone;
venting the gaseous combustion products from the precipitation zone to provide the vent gas stream; and introducing to the gaseous combustion products during the 3 0 conveying step an aqueous solution of at least one mixture o~ alkali metal hydroxide and aliphatic hydroxy or polyhydroxy compounds at a temperature of the gaseous combustion products of about 300 to about 500 C.
The introduction of such organic-inorganic nnrrl P~Pq 35 to the combustion gas stream also may be c ' inP~ with introduction of an alkali metal hydroxide, in the form of .
-Wo 95/186~7 2 t 8 0 6 3 3 PCT/C~95100012 an ar~ueous solution thereof, particularly sodium hydroxide or potassium hydroxide, directly into the combustion gas stream, at a higher temperature above about 500'C, which may include multiple introductions at dif ferent higher t 1 ~ aLu~e levels of approximately 500 C, 600-C and 700 C.
R~7T~ DESt~TPTION OF DR~WINGS
Figure l is a 8- ~;r diagram of the experimental set-up used for the studies of the destruction, the inhibition of formation and catalytic formation of OHC on flyash;
Figure 2 is a graphical repr~C~.nt~t;nn of the native PCDD and PCDF present on MSWI flyash prior to ~no heat~
and after heat treatment of the flyash at various temperatures;
Figure 3 rn7~t~;nc a graphical repres~nt~tinn of the amounts of native PCDD (A) and PCDF ~B) on MSWI flyash heated without and with typical destroyers at various temperatures;
20 Figure 4 rnnt~;nc chromatograms showing the response of electron captor ~l~t~rtor for the O~C. Samples analyzed were l) MSWI flyash, no treatment, 2) MSWI
~lyash heated to 400 C without destroyer, 3) MSWI flyash heated at 400 C with destroyer (NaOH 5~ by wt . );
Figure 5 is a graphical repres~nt~t;nn of the amount of 13C PCDD produced on the flyash prior to (BG) and after destroyer tr~ tq of the flyash at 300-C;
Figure 6 is a graphical repres~nt~tinn of the effect of temperature on formation of dioxins from ''3C
p~ntarhlorophenol precursor on flyash coated by different destroyers (2~) at various t~ ~ aLuLes; and Figure 7 rnnt~inc graphical representation of the ~
decomposition of native dioxins and furans at various temperatures using ~rious destroyers.
-~ WO 95118667 2 1 8 0 6 3 3 PCT~C~35/00012 ,. g r.T~NT'T~T, DESrT~TPTI~ OF INVENTION
In the present invention, inorganic bases, either alone or in A~m; ~t~re with aliphatic hydroxy or polyhydroxy 'q (here termed destroyers) are 5 employed and their effect on organohalogen ~ uul,ds lOHC), including dioxins and furans, on flyash was investigated. It has been found that the destroyer U ~ lc, when coated on the flyash, effectively destroy OHC on the flyash at temperatures above about 300 C. The l0 destroyer compounds may be selected from inorganic bases which are hydroxides, oxides, ~rh~n~t~q, 1~yd- uue~
on:~t~q and silicates of one or more alkali metals or ~qlkPllinF~ earth metals. The destroyer compounds that have been found to be particularly effective are sodium 15 hydroxide ~NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca (OH) 2) ~ calcium oxide (CaO), magnesium oxide (MgO), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), calcium carbonate (CaCO3), sodium orthosilicate (NacSiOi), sodium metasilicate (Na2SiO3) and either used 20 alone or in ~ ;Ytllres with aliphatic hydroxy or polyhydroxy compounds (AHC). Such aliphatic hydroxy or polyhydroxy compounds may include ethylene glycol, l, 2-propanediol, l,4-b~t~ne~;ol, polytetrahydrofuran or mixtures of these ~u- ,~uul-ds . These destroyer compounds 25 can be used to effectively destroy OHC on the flyash and in the flue gases of solid waste incineration by introduction to the combustion gas stream at suitable temperature. In the laboratory tests, it has been found that the flyash coated with NaOX and XOH (2 to 43~) 30 destroys the formation of PCDD up to 99~ compared to the formation of pr-DD on untreated flyash. A similar effect was observed using an even smaller percentage of mixtures of NaOH or KOH in conjunction with aliphatic hydroxy compounds .
3~ Several experiments were conducted using the laboratory experimental set-up shown in Figure l. A MSWI
Wo 95/l8667 2 t 8 0 6 3 3 PCT/C~95/00012 , ~ 10 flyash (with native dioxins a~d furans produced in the inci~eration proce66 on it) was heated at temperatures 200- to 500 C in air under d~ _~' -ric pressure. It was found that the amount of native dioxins and furans 5 increased up to 350 C, probably due to presence of precursors on the flyash, which by catalytic activity of the 1yash, were converted into PCDD/PCDF. Above 350-C, the amount of PCDD/PCDF on the flyash decreased, probably due to a decreasing rate of forr~t;nn against the rate of 10 ~ ition of PCDD/PCDF. The flyash heated at 400 C
to 500 C showed very little amount of both PCDD/PCDF.
After the heat treatment at various temperatures, flyash samples were dried by heating at 150 C to remove toluene used for extraction. A catalytic activity test of the 15 flyash samples next was conducted at 300-C. The procedures for catalytic activity tests were similar to that reported in our previous U.S. Patents Nos. 4,793,270 and 5,113,772. It was found that flyash heated up to 500 C retained its catalytic activity to produce PCDD
20 from precursors, such as PCP, at lower temperatures such as 250- to 400 C.
In another set of laboratory experiments, heat treatment of 1yash coated by 2 to 5~ destroyer compounds shows that destruction of PCDD/PCDF started at 300 C and 25 was completed by the time the temperature reached 400-C.
~ence, the addition of destroyers makes the flyash complex destructive for organic compounds, even at 300-C, otherwise flyash promotes the formation of dioxins and furans (see Figures 2 and 3). The effectiveness of 30 destruction depends upon the amount of destroyer used and the temperature employed for the destruction. About 6 wt9~ destroyer at 300-C has the same effect as about 1 wt~i destroyer at 400 C. This result indicates that very little destroyer is required to achieve complete 35 destruction of the O~C, if destroyer can be introduced at temperatures ~etween 400 and 900 C, or up to llOO C, in WO 95118667 2 ~ 8 0 6 3 3 PCr1C~95100012 the postcombustion zone of the incinerator, ~erf~n~in~
upon the type of the destroyer used. Destruction efficiency also depends upon the melting point of the destroyer used. NaOH and ICOH are highly effective when used above about 390 C, Na2CO3 above about 800-C, and sodium meta- and ortho-silicates above about 900 C.
In general, destroyer compounds are used in any amount within a range of from about 0.5 to about 6 wt~ of the flyash produced in the incineration step. This quantity generally corresponds to about 0 . 025 to about 0.3 wt9~ of- the waste material incinerated.
The destroyer may be introduced to the post-combustion zone of the incinerator in any convenient form, for example, granular form, powder form or, preferably, as an aqueous solution.
Depending on the destroyer compound or compounds used, the destroyer compound may be introduced between the combustion chamber and precipitation zone of the incinerator at a suitable temperature of from about 300-to about ll00-C, preferably from about 300 to about 800 C
and particularly from about 300 to about 600 C.
The destroyer effect achieved herein also may be combined with the inhibition of formation of OHCs by flyash catalysis, as described in USPs 4,793,270 and 5, 113, 772, by introduction of a suitable inhibitor material as described therein, to the incinerator gas stream between the combustion zone and the precipitation zone, generally at a temperature o~ from about 300- to about 500 C. The present invention employs, in one emho~;m~nt, mixtures of materials as inhibitor~destroyers not contemplated in our earlier patents.
As will be apparent from the disclosure of USP
5 ,113, 772, some of the rnmrm-nrlq which were used as inhibitors of OHC formation in that patent are used herein as destroyers of OE~C. It is preferred herein to employ the same compounds for destruction and inhibition.
Wo 9S118667 2 1 8 0 6 3 3 PCT1CA95100012 In general, higher temperatures are required to effect destruction of OHC tqith such , 'R than inhibition of OHC formation. The destroyer and inhibitor compounds, therefore, may be added at different lor~t;nnq, and 5 accordingly, different temperatures, between the incinerator and the precipitator. The present invention employs, in one ~nhn~;r^nt, mixtures of ~-t~ as inhibitor/destroyers not cnnt~ _ 1 ^ted in our earlier patents .
Several mixtures of the above described inorganic bases and - their combination with AHCs were tested in laboratory experiments. A coating of 5 wt% NaOH on flyash completely destroyed all the OHC, including PCDD/PCDF, on the flyash at 400 C. In addition, the 15 flyash was F~rr~n~ntly deactivated for the formation of PCDD/PCDF. Deactivation of flyash is very important because it provides the means to introduce destroyers at any temperatures above 400 C for higher efficiency with a lower amount of destroyer. In this way, destroyers 20 effectively destroy an estimated l0 to lS~ OHC compounds produced in the furnace when introduced at about 400 to ll00-C in the post combustion zone of the incinerator.
The procedure also deactivates the flyash to prevent further formation of PCDD/PCDF (about 35 to go~) by 25 catalytic activity of the flyash in the cooler parts of the incinerator.
Acid ga6es which may be present in the incinerator gas stream, such as HCl, SO2 and M2~ also may react with the ~ inQ destroyer compounds, so that such acid gases 30 are removed from the gas stream, whereby their con^^n~tinn in the stack emissions decreases.
The dioxins and the furans exhibit varying degrees of toxicity, rl~renrlinj on the number of chlorine atoms present and the position of the chlorine substitution.
35 Usually toxicity of a particular sample is estimated ` based on amount of tetra- to octa- chlorinated dioxins Wo 95/18667 2 1 8 0 6 3 3 PCT/CJ~95/00012 and furans present. The formation of PCDD and PCDF for precursor m~q, such as chlornhen7~nrq~
chlorophf~nnl R and chlorodiphenyl ethers on flyash is illustrated by the following equation:
_ _ a ~ .~o ~ 7 + ~T + >~ 1 ~Y AS~ ~ P~::DF
10 m= I _ 6 n-- I - 5 ~) rT~ r)~ ~H~ ~Lu~ur~ul5 ~ 8 Cl, P~DD
~lrZ~MpT.~.':
15 Exam~le l:
This Example shows the effect of heat on the amount of native dioxins and furans present on MSWI flyash.
An experimental apparatus shown in the Figure l was used to test the effect of heat treatment and catalytic 20 activity of flyash samples. The apparatus comprised a glass tube (25 X l cm I .D. ) passing through the oven.
Part of the ~low tube was a re6ervoir where f lyash to be tested was packed. A flyash sample rom MSWI with all compounds produced in the process of the incineration on 25 it was heated at various temperatures to examine the effect of heat. In each experiment, 1.5 g of the flyash was placed in the glass tube. The section of the tube rnntAininrJ flyash was heated at various temperatures for 60 minutes using 3 ml/minute flow of air through the 30 tube. After completing the experiment, the flyash was spiked with an int~rnAl standard for recovery estimates.
Orga~ic rnmro~n~lc present on the flyash were extracted by eluting with 220 ml toluene. Extracts were cnnr~nt~ated by rotary evaporation to a few ml and final rnnr~nt~ation 35 in a sample vial to 500 ~Ll under a gentle stream o~ N2.
~ WO95118C67 2 1 8 0 6 3 3 PCTICA95100012 Figure 2 shows a graph of the amount o~ native dioxins and furans present on ~SWI flyash prior to ~no heat) and after heat tL~ ~`. t of the flyash at various temperatures. The results of these experiments reveal 5 that the flyash produced in the incineration process rnntRinc high levels of dioxins/furans (no heat plot) and precursors. The MSWI flya3h is highly catalytically active, which produces more dioxins/furans, probably from native precursors present on the flyash, when heated from 200- to 400'C.
After the heat treatment at various temperatures, flyash samples were dried by heating at l50 C to remove toluene used f or extraction . Then a catalytic activity test of these flyash samples was conducted at 300 C. In 15 the catalytic activity test, a volume of 50 /ll of 5 ~g/~Ll 13C_pCp solution in tl~;lnnl wag deposited on the gl~ss beads on top of the flyash and the solvent was allowed to evaporate. The section of the tube ~nnt~ ;ng flyash and 13C-PCP was heated at 300'C for 60 minutes using 3 20 ml/minute flow of air. After completing the experiment, the flyash was spiked with an internal standard for recovery estimates and extracted as - ;~nn~d above.
Analysis of extracts shows the f ormation of 33C PCDD .
This result indicates that merely heating the flyash does 25 not affect its catalytic activity.
mnle 2:
This Example shows the effect of 5~ destroyers on native PCDD/PCDF on the flyash.
In these experiments, fresh flyash (l0 g) rnnt~ining 30 native PCDD/PCDF was coated with a 5~ destroyer solution in water. A l . 5 g portion of destroyer coated and dried flyash was used in the heat treatment described in Example l. The amount of PCDD/PCDF detected in flyash coated by typical destroyers, namely NaOH and PSEGC (a 35 polysilicate-ethylene glycol complex formed from KOH:ethylene glycol:silicagel in respective weight ratios ~ WO 95/18667 2 1 8 0 6 3 3 PCTtCA9~100012 17: 60: 23 ) and heated at various temperature6 is shown in Figure 3 . Comparing the amounts of PCDD/PCDF on f lyash heated at various temperatures without (Figure 2) and with NaOX, PSEGC and SMSEG (a sodium metasilicate-5 ethylene glycol complex formed from sodium--t:~c;l;r~te:ethylene glycol in a weight ratio of 15:85) destroyers (Figure 3 ), it can be seen that no PCDD/PCDF
was produced between 300 C and 500 C on destroyer-coated flyash. In fact, the native PCDD/PCDF content of 10 destroyer-coated flyash was reduced at 300 C and completely eliminated at 400 C. The experiment at 500 C
also did not reveal any residual native PCDD/PCDF.
Similar results were obtained f or KPTHF, a mixture of KOH:PTHF (KOH:polytetrahydrofuran:: 25 :75) and other 15 destroyers with vary little variation in the destruction ef f iciency .
Figure 4 shows the plot of gas chromatography/
electron capture detector response f or various chlorinated rn7nroun~q on flyash from MSWI, the flyash 20 heated at 400-C, and the flyash coated by 5 wt~ NaOH and heated at 400-C. It is clear from Figure 4 that a large number of organohalogen ~ -c, including PCDD/PCDF, are present on flyash from MSWI (bottom tracing) . Merely heating the flyash at 400-C does not destroy the OHC on 25 the flyash (middle tracing) . However, 5 wt~ destroyer on the ~lyash effectively destroys all the OHC, including PCDD/PCDF, on the flyash ~top tracing) .
Af ter the heat treatment at various temperatures of the flyash samples coated by various destroyers, they 30 were extracted using toluene, after that they were dried by heating at 150 C to remove toluene used for extraction. A catalytic activity test of these flyash samples then was conducted using 13C PCP at 300 C, as described in the Example 1. Only traces of 13C labelled 35 PCDD were produced on these flyash samples from l3C-PCP
Wo 95118667 2 1 8 0 6 3 3 PCT1C~95100012 This result indicates that the catalytically active sites on the f lyash were removed by the destroyer .
Exam~le 3:
This Example shows the effect o~ amount and type of S destroyer used for coating the flyash in the forT~~t;nn of C PCDD f rom 13C PCP .
In these experiments, nine f lyash samples ( l . 5 y each) were coated by three different de~LL~,y~ namely Na,CO3, KOH and NaOH (l wt%, 2 wtg~ and 6 wt~) separately.
Catalytic activity tests were conducted on each coated sample at 300 C, as described in Example l. The analyses of the f lyash extracts are shown in Figure 5 .
Background(BG) represents the amount of 13C PCDD produced from 13C PCP on the flyash with no destroyer at 300 C.
From the plots, it can be seen that, as the amount of destroyer (wt~) increases, the formation of PCDD
decreases. The effect is consistent for all three destroyers used. There was a slight difference i~
activity of the destroyers to prevent the formation of 2 0 PCDD .
mn l e 4:
This Example shows the effect of temperature on the formation of 13C PCDD from 13C PCP on the flyash coated by variou6 destroyers.
In these experiments, three different destroyers, namely Na2CO3, KOH and ~aOH were coated ~2 wt~) separately on flyash samples. Catalytic activity tests were conducted on each coated sample at 300, 350 and 400 C, as described in Example l. The analyses of the flyash extracts are shown in Figure 6. Background(BG) represents the amount of 13C PCDD produced rom ~3C PCP on the flyash with no destroyer at 300-C. From the plots, it can be seen that the effectiveness of the destroyer increased with the temperature increases.
3 5 Figure 7 shows the percentage reduction or destruction of native dioxins and furans using various Wo 95/l8667 2 1 8 0 6 3 3 PCT/CA95/000l2 inhibitor/destroyers. The inhibitor/destroyers used were in these experiment6, namely:
i) KPTHF, a mixture of KOH:polytetrahydrofuran (25 : 75), 5% ~by wt) ii) SMSEG, sodium metasilicate:ethylene glycol ~15:85, 5% (by wt) iii) NaOH, 5~ (by wt) iv) PSEGC, potassium hydroxide:ethylene glycol:silica gel:: :17:60:23, 5~ ~by wt) The results seen in Figure 7 are compared with those f ound earlier .
From the results of Examples 3 and 4, it can be seen that the catalytic activity of flyash for the formation of PCDD from precursors was effectively reduced, either by using smaller amounts of destroyers at higher temperatures or by using larger amounts of destroyers at lower temperatures.
Exam~le 5:
This Example illustrates a commercial scale plant test.
A waste incinerator plant had three i n~ep~nr~nt incineration lines comprising an incineration grate for municipal waste, a waste to heat boiler (100 ton per day) and a multi-stage flue gas purification plant. From a refuse bunker, the waste is supplied to the incineration grate where it is burned at lD00-C. Flue gases flc>w through the boiler at a velocity of 6 to 12 M/second.
The inhibitor/destroyer mixtures were injected into the waste flue gas stream. KOH or NaOH as the de~L.~y~La were injected in a temperature window of 590 + 50 C and PSEGC or SMSGC (see Fxample 4) as the inhibitor/destroyers were inj ected in a temperature window of 375- + 50 C. The amount ~f each inhibitor and destroyer injection was 7 to 10~ by weight of the flyash produced. An injection nozzle unit was employed containing a pressure atomizer with a mixing chamber in wo 95rl866~r 2 ~ 8 0 6 3 3 PCT/CA95100012 which the destroyer or inhibitor was mixed with 13 times the amount of water by volume. The nozzles had a outside diameter of 12 mm and an opening of l, 6 mm and were operated with water at an inj ection pressure of 6 to 8 5 bar to distribute the destroyer/inhibitor uniformly thLUu~lluuL the flue gas.
Plant test I was conducted using combination I
consisting of KOH as destroyer and l?SEGC as inhibitor/destroyer, plant test II was conducted using 10 combination II consisting of ~NaO}l as destroyer and SMSGC
as inhibitor/destroyer and plant test III was conducted using ~ ' in~t;on I and activated carbon. On the fourth day of each test, the flue gas samples were collected for PCDD/PCDF measurements. Several flyash samples were l~ collected from the electrostatic -precipitator on the third and fourth day of each test. Sampling and analysis of the flue gas for PCDD/PCDF t~f~n~ n~ration were done with standard techniques.
The amount of PCDD/PCD~ detected on the f lyash 20 samples during the three tests is shown i~ the ollowing Table I:
WO 95/18667 2 ~ 8 0 6 3 3 PCT/CA9~100012 a , o ~D N ~ N ~D
~, ~: a O ~J
P~
.. ~
~ u7 r N Lt~ N
-. .
N ~ N H 0~ D
~ m .~ o~
A
~' O ~ O r~
ZJl 1~ N N N H . ~D
H
Jq O
a ~ ~ H ~ N H N .-1 N
f-l ~ r .
o ~
~ ~ f ~
E~ Z
C~ ~ N f'~
m E~ d Wo 95/18667 2 1 8 0 6 3 3 PCTIC~95/00012 AB may be seen from these results, with all other conditionB ,~ ;nin~ the same, injecting the de~L.uye-and inhibitors into the post combustion zone att -- aLuLes of 550 C and 350 C respectively, caused a 5 marked re~llrt;~n in the amount of PCDD/PCDF on the flyash samples from the electrostatic precipitator A
comparison between the individual tests shows that the best re~ ti~n of PCDD/PCDF of 999~ was achieved in Test III An overall reduction in PCDF of about 80 to 94~ was lO achieved in Tests I to III
The amount of total PCDD/PCDF detected in flue gases in background samples and samples collected during Tests I to III are shown in the following Table II
WO9!i/18667 2 1 8 0 6 33 PCT/CA9S1000~2 ~ .
E~
~C\ N ~ CO L~l Ul O
~ ~ E ~ ~ ~ N
E~ -'t~) C~ o 1'~ N :1 0 1''1 0~ N _I
~0 E~ r ~ ~ r ~D ~ N r 1`'1 S~ _ o D~ ' c4 E o rl ~ N Ir) ~ ~ r~ L~ ~ .1' N ~' ~`7 N ~I' ~ ~') ~ t~
C) Cq H
~n ~ ~ a E N N ~D ~D N ~ t~ Ll) t` r~
O H N N ~D N ~ I`') ~ ~ ~I N
U~
H
H
H H
_ ~ ~ H
Cl ~ V 3 a) 3 Il~
S~ H H H H C~ 3 3 c) s~
O -- H H H H H H 3 ~ ~t Il~
O ~ IJ CJ O a) H H H H H
O O O O O O G) C) C) ~q O -LLIl~i ~I W tlJ ~ E-' E- E-' ~U
C~ ~-l ., .. .. . ., H C~ ~ .-- .. . ..
W ~ _ L . L L
~1 ~ ~ ' , t I t Wo 95/18667 2 i 8 0 6 3 3 PCIIC~95/00012 As may be seen from the result3 of Table II, the PCDD/PCDF cono~ntration related to the toxic e~auivalent (TE) of USEPA was reduced in Te9ts I to III up to gl9~ in raw gas and up to 95% in pure gas.
The results crntAinpd in this Example demonstrate that the formation of ~CDD/PCDF during the incineration of waste can be PRs~nt;A~ly suppressed both the flyash from the electrostatic precipitator and in the flue gas by injection of desL~ uyc:~ ~ and inhibitors into the flue gas from the i~cinerators.
- SVMM~RY OF DISCL~)SURE
In the summary of thi6 disclosure, the present invention provides a method for destruction of organohalogen compounds (ûHC), including dioxins and furans, and for the prevention of formation of the O~C
and the acid gases in the combustion gas stream from waste inr;n~rA~rrs by employing certain inorganic bases, alone or their combination with aliphatic hydroxy rrrnrollnrlq (collectively called herein destroyers). The destroyers, such as alkali metal/AlkAl;n~ earth metal oxides, hydroxides, carbonates, bicarbonates and silicates and mixtures of alkali metal/~lkAl inP earth metals oxides, hydroxides, carbonates, bicArhr~n~tes, silicates and their mixtures with AliphAt;c hydroxy and/or polyhydroxy ~ o~n~lq, proved to be highly effective in the destruction and the prevention of formation of the O~C, including toxic dioxins and furans, in the post combustion zone of incinerators.
Modif ications are possible withi~ the scope of this 3 0 invention .
Claims (25)
1. A method for incinerating waste materials wherein dioxins and furans formed in the incineration are destroyed, which comprises:
incinerating waste materials selected from municipal solid waste, medical waste, municipal sludge, industrial waste and other materials, to form fly ash and gaseous products of incineration, comprising dioxins and furans;
and passing said gaseous products of incineration to a precipitation step, wherein said fly ash is precipitated from the gaseous products of the incineration;
characterized by:
introducing at least one destroyer compound directly into said gaseous products of incineration during said passage of said gaseous products of incineration to said precipitation step to react with and destroy dioxins and furans present in the gaseous products of incineration prior to destroyer compound introduction to decrease dioxin and furan concentrations in stack emissions from the precipitation step.
incinerating waste materials selected from municipal solid waste, medical waste, municipal sludge, industrial waste and other materials, to form fly ash and gaseous products of incineration, comprising dioxins and furans;
and passing said gaseous products of incineration to a precipitation step, wherein said fly ash is precipitated from the gaseous products of the incineration;
characterized by:
introducing at least one destroyer compound directly into said gaseous products of incineration during said passage of said gaseous products of incineration to said precipitation step to react with and destroy dioxins and furans present in the gaseous products of incineration prior to destroyer compound introduction to decrease dioxin and furan concentrations in stack emissions from the precipitation step.
2. The method of claim 1 wherein waste materials containing high levels of dioxins and furans, including soil, sediments, sludge or flyash from other incinerations, are added to and mixed with the waste materials prior to incineration thereof.
3. The method of any one of claims 1 or 2 wherein the at least one destroyer compound is at least one hydroxide, oxide, carbonate, hydrogen carbonate or silicates of an alkali metal or alkaline earth metal
4. The method or claim 3 wherein said at least one destroyer compound is selected from NaOH, KOH, Ca(OH)2, MgO, CaO, Na2CO3, K2CO3, CaCO3, NaHCO3, KHCO3, Ca(HCO3)z, Na2SIO3 and Na4SiO4.
5. The method of any one of claims 1 to 4 wherein the destroyer compound is a mixture of one or more of the destroyer compounds identified in claim 3 or 4 with at least one aliphatic hydroxy or polyhydroxy compound.
6. The method of claim 5 wherein said aliphatic hydroxy or polyhydroxy compound is selected from ethylene glycol, 1,2-propanediol, 1,4-butanediol, polytetrahydrofuran and mixtures of these compounds.
7. The method of claim 6 wherein the destroyer compound is a mixture of potassium hydroxide, ethylene glycol and silica gel.
8. The method of any one of claims 1 to 7 wherein destroyer compounds are introduced directly into the gaseous products of incineration at a temperature of about 1100° to about 300°C.
9. The method of claim 8 wherein said temperature is about 800° to about 300°C, especially about 600° to about 300°C.
10. The method of any one of claims 1 to 9 wherein said at least one destroyer compound is introduced in an amount of from about 0.5 to about 6 wt% of the flyash produced.
11. The method of claim 10 wherein said at least one destroyer compound is introduced in an amount which corresponds to about 0.025 to about 0.3% of the waste materials incinerated
12. The method of any one of claims 1 to 11 wherein said at least one destroyer compound is introduced in granular form, in powder form, as an aqueous solution that is sprayed into the postcombustion zone or combinations thereof.
13. A method for incinerating waste materials wherein dioxins and furans formed in the incineration are destroyed, which comprises:
incinerating waste materials selected from municipal solid waste, medical waste, municipal waste, municipal sludge, industrial waste and other materials, to form fly ash and gaseous products of incineration, comprising dioxins and furans; and passing said gaseous products of incineration to a precipitation step, wherein said fly ash is precipitated from the gaseous products of incineration, characterized by:
introducing at least one destroyer compound directly into a post-combustion zone of the waste incinerator:
(a) in the form of an organic-inorganic complex at a temperature of about 300° to about 500°C, and (b) in the form of an alkali metal hydroxide at a temperature of above about 500°C, to react with and destroy dioxins and furans present in the gaseous products of incineration prior to said at least one destroyer compound introduction to decrease dioxin and furan concentrations in stack emissions from the precipitation step.
incinerating waste materials selected from municipal solid waste, medical waste, municipal waste, municipal sludge, industrial waste and other materials, to form fly ash and gaseous products of incineration, comprising dioxins and furans; and passing said gaseous products of incineration to a precipitation step, wherein said fly ash is precipitated from the gaseous products of incineration, characterized by:
introducing at least one destroyer compound directly into a post-combustion zone of the waste incinerator:
(a) in the form of an organic-inorganic complex at a temperature of about 300° to about 500°C, and (b) in the form of an alkali metal hydroxide at a temperature of above about 500°C, to react with and destroy dioxins and furans present in the gaseous products of incineration prior to said at least one destroyer compound introduction to decrease dioxin and furan concentrations in stack emissions from the precipitation step.
14. The method of claim 13 wherein said organic-inorganic complex is a mixture of an alkali metal hydroxide and an aliphatic hydroxy or polyhydroxy compound.
15. The method of claim 14 wherein said alkali metal hydroxide is potassium hydroxide or sodium hydroxide.
16. The method of claim 15 wherein said organic-inorganic complex is a mixture of potassium hydroxide with ethylene glycol and silica gel.
17. The method of any one of claim 13 to 16 wherein said organic-inorganic complex is introduced at a temperature of about 350° to about 450°C.
18. A method of decreasing the concentration of organohalogen compounds in flyash and vent gas stream formed in the incineration of combustible materials, which comprises:
effecting combustion of combustible materials in a combustion zone to form gaseous combustion products containing entrained flyash, conveying said gaseous combustion products from said combustion zone to a precipitation zone, precipitating flyash from said gaseous combustion products in said precipitation zone, and venting said gaseous combustion products from said precipitation zone to provide said vent gas stream, characterized by:
introducing to said gaseous combustion products during said conveying step an aqueous solution of at least one mixture of alkali metal hydroxide and aliphatic hydroxy or polyhydroxy compounds at a temperature of said gaseous combustion products of about 300° to about 500°C.
effecting combustion of combustible materials in a combustion zone to form gaseous combustion products containing entrained flyash, conveying said gaseous combustion products from said combustion zone to a precipitation zone, precipitating flyash from said gaseous combustion products in said precipitation zone, and venting said gaseous combustion products from said precipitation zone to provide said vent gas stream, characterized by:
introducing to said gaseous combustion products during said conveying step an aqueous solution of at least one mixture of alkali metal hydroxide and aliphatic hydroxy or polyhydroxy compounds at a temperature of said gaseous combustion products of about 300° to about 500°C.
19. The method of claim 18 wherein said aqueous solution is introduced at a gaseous combustion products temperature of said gaseous combustion products is from about 350° to about 450°C.
20. The method of claim 19 wherein said alkali metal hydroxide is sodium hydroxide or potassium hydroxide.
21. The method of claim 20 wherein said aliphatic hydroxy or polyhydroxy compound is ethylene glycol or polytetrahydrofuran.
22. The method of claim 18 wherein said aqueous solution is an aqueous solution of a mixture of potassium hydroxide, ethylene glycol and silica gel.
23. The method of claim 19 including introducing to said gaseous combustion products during said conveying step and aqueous solution of an alkali metal hydroxide at a temperature of said gaseous combustion product of at least about 500°C.
24. The method of claim 23 wherein said introduction of said gaseous solution of alkali metal hydroxide is effected at multiple different temperatures of said gaseous combustion products above about 500°C.
25. The method of claim 23 wherein said alkali metal hydroxide is sodium hydroxide or potassium hydroxide.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9400121A GB9400121D0 (en) | 1994-01-06 | 1994-01-06 | Prevention of formation and destruction of organohalogen compounds in incineration of waste materials |
| GB9400121.1 | 1994-01-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2180633A1 true CA2180633A1 (en) | 1995-07-13 |
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ID=10748427
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|---|---|---|---|
| CA 2180633 Abandoned CA2180633A1 (en) | 1994-01-06 | 1995-01-06 | Prevention of formation and destruction of organohalogen compounds in incineration of waste materials |
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| Country | Link |
|---|---|
| AU (1) | AU1410095A (en) |
| CA (1) | CA2180633A1 (en) |
| GB (1) | GB9400121D0 (en) |
| WO (1) | WO1995018667A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI945402A (en) * | 1994-11-16 | 1996-05-17 | Ahlstroem Oy | A process for treating process or flue gases containing halogen compounds |
| IT1280925B1 (en) * | 1995-08-25 | 1998-02-11 | Sea Marconi Technologies Sas | PROCEDURE FOR DECONTAMINATION AND OXIDANT COUNTERFLOW TREATMENT OF A LIQUID, GASEOUS OR SOLID MATRIX. |
| US5968467A (en) * | 1995-09-22 | 1999-10-19 | Kurita Water Industries, Co., Ltd. | Dioxin formation preventative in incinerators and method for preventing the formation of dioxins |
| WO1998009716A1 (en) * | 1996-09-06 | 1998-03-12 | The Dow Chemical Company | Process for reducing dioxin and furan emissions in the stack gas from an incinerator |
| US20140263058A1 (en) * | 2013-03-12 | 2014-09-18 | Richard H. Fagher | Methods of filtration and chemical treatment of waste water |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4130629A (en) * | 1977-12-16 | 1978-12-19 | Fmc Corporation | Control of halomethyl ether emissions |
| DE3527615A1 (en) * | 1985-08-01 | 1987-02-05 | Kloeckner Humboldt Deutz Ag | Process and plant for disposing of chlorine-containing wastes, in particular domestic and municipal refuse |
| DE3628403A1 (en) * | 1986-06-20 | 1988-02-25 | Hoelter Heinz | Separating off, by chemical absorption, highly toxic pollutants, such as dioxins, furans, formaldehydes, PAH's (polyaromatic hydrocarbons) and other toxic substances |
| US4681045A (en) * | 1986-07-21 | 1987-07-21 | William F. Cosulich Associates, P.C. | Treatment of flue gas containing noxious gases |
| DE3632366C2 (en) * | 1986-09-24 | 1997-12-18 | Boelsing Friedrich | Process for the removal of halogenated hydrocarbons from the gas phase |
| US5021229A (en) * | 1988-12-21 | 1991-06-04 | The United States Of America As Represented By The Environmental Protection Agency | Reduction of chlorinated organics in the incineration of wastes |
| US5113772A (en) * | 1990-07-16 | 1992-05-19 | University Of Water Of Waterloo | Suppression of dioxin production in the incineration of waste material |
| WO1992009528A1 (en) * | 1990-11-21 | 1992-06-11 | Lhoist Recherche Et Developpement S.A. | Method for preparing calcium and/or magnesium hydroxide, and use thereof |
-
1994
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1995
- 1995-01-06 WO PCT/CA1995/000012 patent/WO1995018667A1/en active Application Filing
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| WO1995018667A1 (en) | 1995-07-13 |
| GB9400121D0 (en) | 1994-03-02 |
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