AU624414B2

AU624414B2 - A process and apparatus for the conversion of solid waste into glass

Info

Publication number: AU624414B2
Application number: AU41060/89A
Authority: AU
Inventors: Heinz Merlet; Helmut Pieper; Helmut Sorg; Hartmut Zschocher
Original assignee: Beteiligungen Sorg GmbH and Co KG
Current assignee: Beteiligungen Sorg GmbH and Co KG; GEA Group AG
Priority date: 1988-09-10
Filing date: 1989-09-04
Publication date: 1992-06-11
Anticipated expiration: 2009-09-04
Also published as: EP0359003A2; JPH07102977B2; AU4106089A; DE58906363D1; DK169057B1; EP0359003A3; EP0359003B1; DK441489A; JPH02175620A; ES2047074T3; DK441489D0

Description

:Crr~ 41 4 COMPLETE SPECIFICATION FOR OFFICE USE Application Number: Lodged: Complete Specification Priority: Class Int. Class Lodged: Accepted: Published: Related Art: o po 9 p 0 *000 0 TO BE COMPLETED BY APPLICANT 1QL Name of Applicant: A SORG GmbH Co. KG. and METALLGESELLSCHAFT AG.

Address of Applicant: Im Aller 23, D-8770 Lohr/Main, Federal Republic of Germany and Reuterweg 14, D-6000 Frankfurt 1, Federal Republic of Germany respectively.

p 0 0 0 0 Actual Inventors: Address for Service: Helmut SORG, Helmut PIEPER, Hartmut ZSCHOCHER and Heinz MERLET SMITH SHELSTON BEADLE 207 Riversdale Road Box 410) Hawthorn, Victoria, Australia Complete Specification for the invention entitled: o*0 A PROCESS AND APPARATUS FOR WASTE INTO GLASS THE CONVERSION OF SOLID of this invention, including The following statement is a full description the best method of performing it known to us: Page 1 Our Ref: #4016 JC:WB 24sor 1 u i The invention relates to a process for the conversion of solid, mostly dehydrated waste substances into glass, wherein the waste substances are mixed with one or several additives to form a batch to be melted. A major portion of the batch is melted into a glass melt by supplying heat and a minor portion is exhausted from the melting batch as an exhaust gas. Solid vitreous bodies are formed from the «glass melt by means of casting and cooling. Furthermore, r r the invention relates to an apparatus for the working of *0 this process.

It has long been known, to convert toxic and radioactive waste substances in the form of slurries or suspensions into glass by means of melting after adding o 0. additives and mixing it into a batch. The formerly loose waste substances are now tightly incorporated in the glass.

o Glass possesses the advantages property that it is difficult to leach out, thus permitting the release of heavy metal and other substances contained in the glass only to such a small extent that the storage or the use of bodies made of such 0O glass does not cause any problems. One difficulty regarding the vitrification of waste substances is their generally high percentage of chlorides -2ll i i| t;S_ :~lj: r r

-I,

t "600 and calcium sulfate. Thc',cra integrated into the glass melt only to a very small extent during the melting process even if the chloride and sulphur capacity of the glass melt is completely saturated, which is due to the large amount of these substances present. Hence, large amounts of exhaust gas containing gases of chlorides and sulfate, especially Cl, HC1, SO 2 and SO, are a disadvantageous result.

Contrary to that, it is a matter of fact that a sufficient amount of heavy metal and additional alkali escaping from F the glass melt by means of vaporization. The most S aggravating disadvantage of the known process, especially 0 with regard to its environmental effects, is the formation or possible formation of dioxin and/or furan when the batch is heated during the melting process. This occurs when the 15 waste substances to be converted still contain organic components, from which these harmful substances are formed 0 under temperatures occurring during the melting of the batch.

.rJI 6 0 ao 046 0 0 o« 0 4l SUMMARY OF THE INVENTION Hence, it is the object of the invention to provide a process which is less harmful to the environment and excludes especially the emission of dioxin and/or furan even -3r I~ ii; i i ;d ii b

I~

-4if heterogeneous, organic components as well as heavy metal are employed. Furthermore, it is the object of the invention to provide an apparatus for the working of this process.

Accordingly, the invention provides a process for converting solid, dehydrated waste substance into glass, comprising mixing the waste substances with at least one additive to form a mixed batch, generating a gall layer of alkali salt or alkaline earth salt on the surface of a glass melt heated solely by electrodes, and introducing the mixed batch onto said glass melt surface so that a major portion is melted into the melt and a minor portion produces an exhaust gas emerging O" from the melt, said gall layer serving as a melt 0 accelerator, introducing the exhaust gas into the batch to be melted, thereby cooling said gas and producing condensation products in the batch, and reintroducing said condensation products into the melt with the batch. I The first part of the object is achieved in a process where the waste substance is incineration ash, i and hot exhaust gas is withdrawn under exclusion of surrounding air and reintroduced into the batch to be melted where it is cooled down to 20 to 50 C.

Condensation products resulting from the cooling process bc/13/4016.res 92 3 17

'I

i f are melted with the batch, and the cold exhaust gas emerging from the batch to be melted is purified.

The new process permits the conversion of a so far very problematic waste substance, i.e. incineration ash, into glass in an ecologically beneficial way despite the fact that such ash products are heterogeneous and consist of high and unstable percentages especially of carbon, mercury, lead, tin, zinc, calcium, chlorides, and halides. A major portion of these harmful substances is directly integrated into the glass melt, hence, they are tightly incorporated. Harmful substances escaping as gases are mostly condensed by cooling within the batch to be molten and then reintroduced into the melting mass. The remaining, relatively small amount of cold exhaust gases are neutralized in a subsequent purification process.

0'

AW

c, 9 3

L

C 1 4.-

I';

r: if A further development of the process provides a reheating of the hot exhaust gas which escapes from the batch to be molten to at least 1200 0 C for a residence time of at least 1.5 second. The gas is then pre-cooled under partial condensation to 200 to 300 0 C and subsequently reintroduced into the batch to be molten where it is cooled down to 20 to 50 0 C; the condensation products resulting from the pre-cooling are reintroduced into the batch to be l molten and/or exhausted. Reheating the exhaust gas to definitely eliminates a possible presence of dioxin and 0 furan. Hence, the average temperature and residence time must be selected to ensure the elimination desired. The subsequently exhausted gas basically contains only chlorides, sulfates, carbon dioxide, and alkali and heavy 15 metal vapor. Through a following pre-cooling to 200-300°C a0o o the hot exhaust gas is partially condensed, hence reduced in its quantity as well as in its number of components. The o return pipes provided for the reintroduction of the condensation products into the batch to be molten keep these 20 products in a closed circuit; they are gradually converted into glass. After an initial phase a balanced condition is reached causing the amount of condensation products to remain constant. Passing the pre-cooled exhaust gas through the batch to be molten causes vapors which condense only at i: q :i: ib l f:' i I i ~3 i

I

ie: low temperatuares, like heavy-metal vapor and especially mercury vapor, to be deposited on batch particles, thus being reintroduced to the melting process. Due to the strong cooling while passing through the batch, the chlorides and sulfates are practically completely condensed.

If more chlorides and sulfates are vaporized than can be dissolved in the glass melt after the reintroduction of the condensed products, these substances are enriched in the rc r batch. To avoid this, the surplus condensation product 0 resulting from the pre-cooling is advantageously removed.

0 These condensation products are for the most part solid.

S: The remaining cold exhaust gas then contains almost exclusively hydrogen chloride (HC1) and sulfur dioxide (SO 2 in high concentration. The volume of the remaining exhaust gas is relatively small, compared to the throughput of 8 incineration ash. Moreover, the relatively high concentration and the simple composition of the cold exhaust gas is advantageous to the subsequent final gas purification. The gas purification requires only a 2z0 relatively small capacity and provides comparatively pure i separation products, especially sodium chloride and sodium sulfate, which can be used, for example, for the manufacture of soda. The heat energy required for the melting process is electrically generated, thus avoiding the addition of i -6-

"I

I y combustion gas of a fossil-fuel-operated heating device to the exhaust gas resulting from the melting batch, a fact which would complicate the exhaust gas treatment.

The new process is ecologically very beneficial as well as economical. On the one hand, the exhaust gas emission is largely reduced and on the other hand the process provides raw material for other purposes; for example vitreous bodies which are employed as construction materials and the already mentioned sodium chloride and sodium sulfate. The new process excludes any emission of dioxin and/or furan.

o &o Furthermore, the new process permits a reheating of the hot exhaust gas in a separate after-burner. This variant of *4 the process is not as economical with regard to the energy consumption, however, it does not require a complicated oe: 15 melting device. Furthermore, it is advantageous that the o' entire glass bath can be covered by the batch, permitting a major portion of the alkali and heavy metal vapor to be i 0 4 condensed under the batch cover in the furnace. An alternative and particularly energy saving embodiment of the .o process suggests that a part of the glass melt surface be free of batch; the hot exhaust gas escaping from the melting batch be then passed over the batch-free part of the glass melt surface and thus reheated by heat absorption from the glass melt.

-L i i. ii 4" J Another alternative suggests that the cold exhaust gas emerging from the batch to be molten be reheated up to a temperature of at least 1200°C for a period of at least 1.6 seconds and then be subject to purification. The exhaust gas reheating eliminates dioxin and/or furan, thus ensuring that there is no escape of these harmful substances.

As a last alternative regarding the reheating of the exhaust gas, the process suggests that the exhaust gas emerging from the purification process be reheated to a temperature of at least 1200 0 C for a period of at least seconds. This also ensures an elimination of dioxin and/or furan. The selection of an appropriate variant is up to the o g.o expert and depends on the requirements and conditions of the individual case.

0 :'i6 With regard to the additives, the process suggests the use of substances containing SiO 2 especially sand and/or phonolite. These additives are easy to handle and inexpensive. Alternatively and/or supplementary, cullet can o0 be employed as an additive containing SiO 2 The process oc 0 00 0 o a4 also suggests that the gas escaping from the melting batch as well as the hot exhaust gas be exhausted under subatmospheric pressure and pre-cooled and that the pre-cooled exhaust gas be then put under super atmospheric pressure. The exhaust gas can then be passed through the -8-

I

B

1 j i iB: i~f

P.

i81_ batch to be molten in a counterflow and the pressure of the cold exhaust gas escaping from the batch to be molten can be controlled so that it be basically identical with the pressure of the surrounding air. On the one hand this ensures that no exhaust gas resulting from the melting batch escapes into the environment; on the other hand there is a sufficient throughput of pre-cooled exhaust gas through the batch to be molten. Finally, it is also achieved that there is no major escape of exhaust gas into the environment during the formation of the batch and that no additional air infiltrates the exhaust gas.

o Apparatus for practicing the process includes a batch o mixer and a closed glass melting furnace. The batch mixer has an inlet for incineration ash and additives, and an outlet for the mixed batch, as well as gas inlet and a gas 0 outlet for passing exhaust gas from the furnace through the batch. A batch outlet provides charge to one end of the furnace, which has a molten glass outlet at the opposite end.

o 0 one 00~u" p..s 0 pose 0.4i 0 0 0'4 00 0 o o 0 This apparatus permits a safe, continuous, and ecologically beneficial working of the above described process.

o0 *00: i t t i

P

ii -9- 1 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 Figures 2 Figure 5 Figure 6 Figure 7 is a diagrammatical cross section view of the first embodiment, to 4 show the apparatus in its respective second, third, and fourth embodiments, is a schematic of a first embodiment of gas purification device, is a schematic of a second embodiment of gas purification device, is a flow diagram of a system of removing dust and filtrate slurry from the exhaust gas.

a at 0 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS a .Figure 1 shows supply vessels 2, batch mixer 3, a glass S melting furnace 4, a glass working machine, an exhaust gas o cooler 6, and a gas purification device 7.

The supply vessels 2 serve to hold and store incineration ash 80 and additives 81. The bottom end of each supply vessel 2 is provided with a dosing sluice S* for example a cellular wheel sluice. These dosing sluices Slod" end in a common conveyor device 21, in this case a screw conveyor, which leads to the top of the batch mixer 3. The batch mixer 3 consists of a funnel-like housing 30 and a mixing screw 31 disposed in housing 30. The mixing screw 31 i iI i; runs parallel to the inner side of the lateral wall of housing 30; it can be rotated around its own axis as well as around an axis running vertically through the center of the housing 30 of the batch mixer. The upper part of housing 30 is provided with a solid substance inlet which is connected with the above mentioned conveyor device 21. The bottom end of housing 30 of the batch mixer 3 is provided with a solid substance outlet leading to a batch conveyor 46. The batch conveyor 46 is already part of the glass tO melting furnace 4. The glass melting furnace 4 includes a tank 41 of fire-proof material covered by a superstructure 42, also made of fire-proof material. The tank 41 and the o 0 superstructure 42 rest on a support configured as steel girders. The external surface of the superstructure 42 of oro o 5 the glass melting furnace 4 has a gastight cover 42' o o S consisting of sheet steel. The cover 42' reaches up to the top rim of tank 41 to which it is joined in a sealed connection. From the top downward, heating electrodes 43 0o0e o pass through the superstructure 42 and the cover 42' into O ,o the interior of the glass melting furnace 4. The interior of the glass melting furnace is subdivided into two o0 different areas: a melting area, which is represented on the right side of Figure i. A suspended and straight arch 0 4esus 44 subdivides the glass melting furnace into said areas.

-11- L1L It j A I This arch 44 protrudes downwardly and is configured as a part of the superstructure 42 from which it is suspended.

During operation of the glass melting furnace 4 this arch 44 is close to the surface 84' of a glass melt 84 contained in the furnace 4, and serves as a perpendicular dividing wall to form the gas area of furnace 4. Furthermore, under arch 44 there is a coolant tube 45 which runs parallel to this arch across the glass melting furnace 4. The coolant tube passes exactly at the same level with the surface 84' of the glass melt 84 and causes the glass melt 84 to solidify in the area surrounding the tube 45. The right end of the glass melting furnace is provided with a glass melt outlet ooc ~o 0 09 48 where a diagrammatically represented glass working eoso 9o°" machine 5 is added. Finally, the right end of the glass oooo C5 melting furnace 4 is also provided with an upward exhaust 0:o gas outlet 47 passing through the superstructure 42.

A heat insulated gas pipe 60 from the exhaust gas outlet 47 of the glass melting furnace 4 to the gas inlet 61 *oMVr oo of the exhaust gas cooler. In addition to the gas inlet 61, oY the exhaust gas cooler 6 is also provided with a gas outlet 62 and an outlet 63 for condensation products. Both outlets ec are disposed on the bottom end of exhaust gas cooler 6.

o Furthermore, the exhaust gas cooler 6 is furnished with a o 00device 65 for the feeding as well as the supply and the06 device 65 for the feeding as well as the supply and the -12- 1' 2' 4 f *0 discharge of a coolant, cooling water or cooling air.

On top of the exhaust cooler 6, a mechanical cleaning device 66 is indicated by means of which the gas containing parts of the exhaust gas cooler 6 are continuously or periodically Scleansed of the condensation products which result from exhaust gas cooling. The condensation product outlet 63 of the exhaust gas cooler 6 is connected to the feeding side of the batch mixer 3, i.e. to the upper part of its interior, via another conveyor device 64, in this case also a screw conveyor. For this purpose, the upper part of the housing of the batch mixer 3 is provided with a condensation product inlet 36. If required, the condensation products can be discharged either partially or completely via a switch 69 which is disposed on the upper end of the conveyor device 64.

A first suction fan 67, whose end is joined to a connecting pipe 68, is disposed downstream of the gas outlet 62 of the exhaust gas cooler 6. The connecting pipe 68 leads to a gas inlet 34 of the batch mixer 3. The gas inlet :7C 34 in disposed in the bottom part of the housing 30, and is configured to permit the gas to enter the interior of the houiing 30, but to prevent any batch discharge from the interior of housing 30 into pipe 38.

-13- 5I .0 1, e I i i;

I

4 i ;j iiii

;-I

?t:f ii! ii :3 1- 4 4

I

A gas outlet J3, followed by a second downstream suction fan 70, is disposed on the opposite end of gas inlet 34, i.e. on the upper end of batch mixer 3. The power of the first suction fan 67 and of the second suction fan can be controlled, preferably by a common control device. A gas pipe 71 leads from the outlet of the second suction fan to a gas purification device 7 whose components are generally known and are therefore not listed in detail.

t Finally, a chimney 79 is disposed downstream of the outlet t t0 of the gas purification device 7.

The embodiment represented in Figure !2 has a slightly :S different configuration than the embodiment as described in Figure 1. The arch 44 of Figure 1 is omitted in the glass melting furnace 4 of Figure 2; the superstructure 42 of the glass melting furnace 4 is configured as one single o o0 continuous component with the furnace interior forming one single area. Furthermore, the coolant tube 45 of the glass o* melting furnace according to Figure 1 is moved towards the li i discharge end of the glass melting furnace 4, i.e. to the right side. This permits the batch 83, which floats on the glass melt 84, to cover almost the entire surface 84' of the glass melt 84. This causes a major part of the gases and vapor escaping from the glass melt 84 to condense on the batch resting thereon. Thus, the amount of exhaust gas is -14- 7 k-a reduced. At the same timc, the temperature of the gas i emerging from the glass melting furnace 4 through outlet 47 is reduced. At this point, the temperature is between 300 and 500 0 C. In order to ensure a complete elimination of dioxin and/or furan in the exhaust gas, a separate gas heater 91 is employed in the gas pipe 60 disposed downstream of the gas exhaust outlet 47. This gas heater 91 is only diagrammatically indicated and can be of conventional design. The incoming gas is heated to a temperature of at least 1200 0 C for a period of at least 1.5 seconds.

Itt do Other details of the apparatus of Figure 2 correspond to the apparatus of Figure 1, with same parts of the apparatus being characterized by the same numbers.

In a third embodiment of the apparatus, shown in Figure 3, the exhaust gas cooler 6 inclusive of the mating gas pipe 60 is omitted. The glass melting furnace 4 corresponds in its essential parts to the glass melting furnace as a represented in Figure 2. It differs from the latter inasmuch that the gas exhaust outlet 47' is disposed at the furnace 4. This exhaust gas outlet 47' is connected to the intake of the first suction fan 67 via a short gas pipe From this point, an already described connection pipe 68 leads to the batch mixer 3.

L- 71:. Ii. i. iIi Since there are no condensatic.oducts fed to the exhaust gas cooler, the batch is, in its upper part, configured without the charging inlet 36 as described in the embodiments of Figures 1 and 2.

The heat necessary for the definite elimination of dioxin and/or furan is generated by a separate gas heater 91. In the apparatus according to Figure 3 this gas heater 91 is connected to the exhaust gas pipe 71 leading from the second suction fan 70 to the gas purification device 7.

The embodiment of Figure 4 corresponds mostly to the embodiment of Figure 3. It differs from the latter in that the separate gas heater 91 for the heating of the gas and the elimination of possible dioxin and/or furan is disposed downstream of the gas purification device 7 and is incorporated in the gas pipe leading to chimney 79. This embodiment offers the particular advantage that the amount of gas to be heated after passing the gas purification S( t4t device amounts only to about 50% of the original amount of gas which means saving heating energy.

The following is a description of how the process works, based on the apparatus described in Figure i.

Incineration ash 80 from a refuse incinerator or a garbage disposal plant is fed to the first supply vessel 2.

The remaining supply vessels 2 are charged with the S-16ii Condensation products resulting from the cooling process 'wJ 92 3 17 S Sbc/13/4016.res 9 3 17 if required, cullet, By means of the dosing sluices r i! necessary additives 81, especially sand and ,..onolite and, if required, cullet, By means of the dosing sluices premeasured amounts of incineration ash 80 and additives 81 are taken from the supply vessels 2 and fed via conveyor device 21 to vessel 30 of batch mixer 3, where the individual components are mixed by a mixer screw 31 in order to form a homogenous batch 82 which can be molten. The 00 prepared batch 82 is fed through the solid substance outlet 0000 ooo 33 of the batch mixer to the interior of the glass melting 000e furnace 4 by means of the batch charging device 46. During 8000 operation, the glass melting furnace 4 is filled with glass melt 84 up to a certain level. The surface 84' of the glass melt 84 is exactly at the same level with the coolant tube and just below the arch 44.

000 00oo6 The batch which is supplied by the batch charging 0 3 "00 device floats as a melting batch 83 on the glass melt 84 and is distributed on the surface 84' of the latter in the melting area (left part) of the glass melting furnace 4. A solidification of the glass melt 84 in the area surrounding *000 2O the coolant tube caused by a coolant passing through the latter prevents the melting batch 83 from passing beyond the arch 44 and the coolant tube 45. The heat energy required for the melting of the batch 83 is generated as joulean heat by heating electrodes 43, whose bottom ends protrude into -17- I l 1 the glass melt 84 which, in turn, assumes the function of an Fi ohmic resistor.

During the melting process, gases escape from the batch 83 with an exhaust gas temperature between 100°C and 1000 0

C.

Basically, this exhaust gas can contain SO 2 HC1, chloride, sulfates, carbon dioxide, alkali and heavy metal vapor, and dioxin and/or furan.

This exhaust gas 85 enters the right side of the interior of the glass melting furnace 4 through a crack between the bottom of arch 44 and the coolant tube 45. The surface 84' of the glass melt 84 in this part of the glass melting furnace 4 is free of batch. The glass melt 84 contained in this part of the glass melting furnace 4 has a temperature of approximately 1400 0 C. Hence, the temperature 1:5 in the upper part of the glass melting furnace 4 above the melt 84 amounts to at least 1300-1350 0 C. To achieve the S< highest possible temperature it is advantageous to provide the superstructure 42 of the glass melting furnace 4 with a Litt best possible insulation. The gas entering this area of the o glass melting furnace 4 is reheated by absorbing heat from the glass melt. An appropriate adjusting of the flow rate I and a corresponding selection of the dimensions of glass melting furnace causes the temperature of the hot exhaust gas to amount to at least 1200°C for a period of at least 1 -ie-.

i l 1

II.

i 1i i, I i 1 7i2% seconds. Thus, the dioxin and/or furan which is possibly contained in the exhaust gas is definitely eliminated; consequently the hot exhaust gas contains only the chlorides, sulfates, carbon dioxide and the alkali and heavy metal vapors.

This hot exhaust gas is exhausted through the heat insulated pipe 60. Basically, the insulation serves to prevent a cooling and thus a subsequent condensation of the 4 of hot exhaust gas 86 within the pipe 60. The hot exhaust 0a0 10O gas is fed through gas inlet 61 to exhaust gas cooler 6, where it is cooled down to a temperature between 300 and 500 0 C, a process whereby a part of the exhaust gas is condensed and deposited within the c-haust gas cooler 6.

The resulting condensation products 88 are removed

D

S

A

0re continuously or periodically by means of a cleaning device 66 and fed to condensation product outlet 63 which is below '0 the exhaust gas cooler 6. The condensation products 88 are fed via conveyor device 64 through condensation product inlet 36 to the interior of the batch mixer 3 and thus reintroduced into the batch to be molten. If necessary, the condensation products cna be removed completely or partially via outlet 69.

I;

*1.

LI)

-19- 1 i The pre-cooled exhaust gas 87 exits the exhaust gas cooler via gas outlet 62 and reaches the first suction fan 67, which generates at its intake, within the exhaust gas cooler 6, in the pipe 60 and in the glass melting furnace 4, a pressure less than the pressure of the surrounding air. On the side facing towards the conveyor, the pre-cooled exhaust gas passes through the connecting pipe 68 towards the batch mixer 3 at a pressure higher than the pressure of the surrounding air. This pre-cooled 'tCIO exhaust gas 87, being under a superatmospheric pressure, is ft t t fed into the batch 82 contained in the interior of the batch mixer 3 via gas inlet 34. While the exhaust gas 87 is passing through, it condenses and thereby is cooled down to approximately 20-50 0 C. It emerges from the surface of the t ti15 batch 82 as a cold exhaust gas. In addition to the mixing of the individual batch components, the mixer screw 31 keeps the batch loose and permeable to gas. Due to the intense t cooling, even low condensing vapor e.g. heavy metal vapor condenses within the batch 82 to be molten. The cold S o10 exhaust gas 89 escaping through gas outlet 35 of the batch mixer 3 contains basically only HCl and SO 2 Interacting with a corresponding control unit and a pressure sensor, it is the purpose of the second suction fan I which is disposed downstream of the gas outlet 35, to -7maintain the pressure of the cold exhaust gas 89 in the upper part of the batch mixer at approximately the same level with the pressure of the surrounding air. This prevents the intrusion of exhaust gas and additional air 6 into the system.

The cold exhaust gas 89 which is basically a concentrated gas consisting of chlorides, SO 2 and SO 3 is fed to the gas purification device 7 via pipe 71 where it is subject to purification. The remaining exhaust gases 0especially N 2

CO

2 and small amounts of oxygen, which escape from the gas purification device are finally exhausted into the environment through chimney 79. The relatively harmless components of the remaining exhaust gas 90 are not hazardous or pollutant to the environment.

level wAccording to the ssupr of esentative embodiments, the apparatus 1 provides, in addition to the remaining exhaust Thegas, a vitreous body 9 which can be reused as a raw material for further industrial purposes. These vitreous bodies 9it is are manufactured continuously from the discharged glass Sespec84''iall by means of a glass working machine 5. These vitreouscape frbodies can be used, for example, as ballast or concreted into additivesording to the representative embodiments, the -21- V *i 1 -8-

I

The size of the glass melting furnace 4 and hence the volume of the glass melt 84 contained therein are advantageously selected to be large enough so that deviations in the composition of the incineration ash, which might occur, do not suddenly change the entire chemistry of the molten glass. Changes of the glass melt composition 84 can be determined very quickly, e.g. by changes in the electrical resistance of the glass melt 84 between the electrodes. These measured values can be used to control 01 10 the mixture of the incineration ash 80 and the individual o 00 additives, especially additives with a certain alkali 01-g percentage, e.g. phonolite.

Another possibility for monitoring the composition of 006 the glass melt 84 is to examine the crystallization of the final glass product. Glass compositions within certain e4 e 0 limits form certain crystals which can be easily recognized in the final glass. They indicate if and how the °0 o composition of the glass has been modified. The amount of the incineration ash 80 and the additives to be added can P o0 then be correspondingly adapted. Figures 5 and 6 show two embodiments of the gas purification device 7. Figure 5 represents a wet cleaning device 7, and Figure 6 a dry or semi-dry cleaning device 7.

-22- V idiivs eseilyadtvswihacranak k -9- According to Figure 5, the cold exhaust gas 89 is fed through pipe 71 to a first purification stage 72. This first purification stage serves to wash out especially HC1 gas from the exhaust gas. In a second purification stage 72' SO 2 is washed out. A subsequent drop separator 73 separates the water drops which were dragged along. In a gas reheating stage 74, the gas is reheated to an appropriate temperature between 30 and 90 0 C and subsequently fed through an activated carbon filter stage 78. After i0 passing this stage the remaining exhaust gas 90 consists C C basically of N 2 C0 2 and small amounts of oxygen which are rt exhausted into the environment via chimney 79.

For the HC1 separation in the first purification state 72, an acid, preferably of pH less than 1, has to be selected. For the separation of SO 2 in the second purification stage 72', however, a pH of 6-7.5 is preferred.

4 it Preferably, both purification stages 72 and 72' operate on reversed current, however, direct current is also possible.

Mercury which is possibly present in the exhaust gas 89 is 1* O separated in the activated charcoal filtering stage. The amount of waste water and slurry resulting from the purification stages 72 and 72' and from the drop separator are fed advantageously to a waste-water purifying plant.

-23i The seco.d embodiment of the gas purification device 7, shown in Figure 7 has as a first component a saturator 75 to which the cold exhaust gas 89 is fed, also via pipe 71.

Once the exhaust gas is saturated with water in the saturator 75, it is introduced to a fluidized bed or a spray adsorber 76. Preferably, NaOH or Ca(OH) in watery solution are admitted to the spray adsorber. In a gas temperature regulating stage 77 the escaping gas is brought to an optimum temperature for the subsequent activated charcoal filtering stage 78. The finally remaining exhaust gas which escaped is exhausted into the environment through chimney o 79.

:The waste waters and the solid substances resulting 0 from this process are subject to further purification, e.g.

in a waste-water purification plant or are dumped or reused.

Due to the relatively simple, defined composition of 0 00 a the exhaust gas 89, the gas purification devices serve to recover sodium chloride and sodium sulfate in a relatively °p pure form. These raw substances, in turn, can be used for o0 the manufacture of soda.

1-i -24-i i S iti i.

L

.1:

J;

Apart from glass, products resulting from the inventive process are glass gall, dust, and/or slurry which have to be deposited or further processed if they are not used as a construction material like the glass.

It is thus a further object of the invention, to solve the problem of substances resulting from the melting of incineration ash in glass, which substances have not been deposited at all, or only to a small extent. The process should operate inexpensively, by means of conventional industrial apparatus, and should be safe So and troublefree.

r o This further object is achieved, by adding dust resulting from D gas purification into the batch, which dust may be a filtrate o slurry.

In order to have an absolutely harmless pure gas, the exhaust 1 5 gas is fed through an activated charcoal filter after purification.

In order to concentrate the exhaust gas, it is advantageous to cool it before and after purification.

o The total amount of harmful substances discharged from the process is reduced by those substances resulting from the gas purification and the heavy metals contained in the melt. Since the solubility for the heavy metals contained in the glass melt, and in a broader sense for all metals contained therein, is no exceeded during the process, all heavy metals are incorporated in i the glass, where they cannot be leached out, by reintroduction into the glass melt.

It is further surprising that the glass gall residue is relatively clean. This is due to the fact that a larger amount of gall, as compared to the process, permits a more exact separation and the gall thus reaches also a higher degreee of purity. It is possible to use this glass gall as a raw material for chemical pruposes. The glass gall percentage amounts to approximately of the incineration ash employed.

The claims form part of the disclosure of this specification.

00oo00 0 0 0000 0000 o a 0 J 0 0000 0000 o0 00 o*oo 0000 00 o 0 0 0 0 G0o 000 00 0 000 26

Claims

1. Process for converting solid, dehydrated waste substance into glass, comprising mixing the waste substances with at least one additive to form a mixed batch, generating a gall layer of alkali salt or alkaline earth salt on the surface of a glass melt heated solely by electrodes, and introducing the mixed batch onto said glass melt surface so that a major portion is melted into the melt and a minor portion produces an exhaust gas emerging from the melt, said gall layer serving as a melt accelerator, introducing the exhaust gas into the batch to be melted, thereby cooling said gas and producing condensation products in the batch, and reintroducing said condensation products into the melt with the batch.

2. Process as in claim 1 wherein part of said gall layer is periodically removed to maintain a thickness between 2 and 5 cm.

3. Process as in claim 1 wherein said exhaust gas and the resulting condensation products contain alkali therein, said gall layer comprising one or more alkali salts from the group consisting of Na 2 SO,, K 2 SO 4 Li,SO,, and LiCI, said gall layer being generated during the melting process by adding one or more alkaline earth f 7* salts from the group consisting of CaSO,, CaCl,, MgSO,, 4 bc/13/4016.re 92 3 17 4 I 4 28 and Mgcl,, said alkaline earth salts reacting with said alkali to produce said alkali salts.

4. Process as in claim 3 wherein said alkaline earth salts are added to the melt with the batch.

Process as in claim 3 wherein said alkaline earth salts are added to the melt separately from the batch.

6. Process as in claim 1 wherein said gall layer comprises one or more alkaline earth salts from the group consisting of CaSO, and MgSO,.

7. Process as in claim 6 wherein said exhaust gas and the resulting condensation products contain little or no alkali.

8. Process as in claim 1 wherein said solid, dehydrated waste substance in incineration ash.

9. Process as in claim 1 further comprising purifying the exhaust gas emerging from the batch to be melted, said purifying comprising removing dust from said exhaust gas and reintroducing said dust into the batch to be melted. A process for the conversion of solid, dehydrated waste substances into g.ass substantially as hereinbefore described with reference to the accompanying drawings. DATED this 17 March 1992 CARTER SMITH BEADLE Fellows Institute of Patent Attorneys of Australia Patent Attorneys for the Applicant: BETREILIGUNGEN SORG GMBH CO. KG and METALLGESELLSCHAFT A.G. 6 btc/13/016.res 92 3 17 it I 1 i