The present invention relates to a process in accordance with the preamble of claim 1 for processing fluorescent lamps and similar objects chiefly made from glass that contain hazardous materials so as to convert said contained hazardous materials into a nonhazardous form.

The invention also concerns an apparatus in accordance with the preamble of claim 1 suited for implementing said process.

A great variety of light sources such as fluorescent lamps and sodium vapor lamps contain toxic materials, thus turning such lamps into hazardous waste when dis¬ carded. The same problem pertains to mercury-containing thermometers, picture tubes, switches and other devices incorporating environmentally hazardous materials. If such a device is broken, the contained hazardous material is released into the environment, whereby for instance the mercury contained in fluorescent lamps can be carried over to the biological life cycles as it is easily converted by microbes into methyl mercury, which is toxic and readily accumulated in the nutrient enrichment pathway.

Multiple different processes have been developed for treating mercury-containing waste. In practice such processes are divided into two major categories: distillation processes and wet processes. In the dry distillation processes the mercury is evaporated and condensed, in other words, distilled. This process is capable of a reasonably high degree of mercury recovery, and the final product is relatively pure mercury suited for reuse. In wet processes the objects containing mercury or other hazardous material are broken submerged in a liquid, whereby the goal is to transfer the mercury into the washing liquid. Mercury contained in the liquid is subsequently precipitated as a metal salt precipitate, thus converting the mercury into a low- solubility form posing no further environmental risk.

In a prior-art approach the fluorescent lamps being processed are sorted and manually placed on a feed conveyor, after which the ends of the fluorescent lamps are cut off and the inner wall of the glass tube is cleaned by air blowing. The fluorescent phosphor material and the mercury adhering to the inner surface as a powdered layer are carried along with the blowing air into air-tight tanks where the blowing air is filtered by means of activated carbon filters prior to discharge into the atmosphere. The glass and metal parts of the lamps are then transferred to recycling. This process is handicapped by the highly manual steps of lamp sorting and placing, and the relatively inferior scrubbing result attainable by means of air blowing. The quality of the discharged blowing air must be continually monitored and the filters must be periodically replaced to avoid mercury release into the environment. The spent filters pose an environmental hazard, because the filtered substances in them are not bound into chemically nonhazardous compounds.

In dry distillation processes the waste batch being treated is placed in a distillation chamber, which is heated to 400 - 500 °C and brought to a partial vacuum by means of a vacuum pump. The mercury is evaporated and thus detached from the waste, after which it can be flushed away from the chamber along with the exiting air flow. Organic matter is removed from the air flow by incineration at approx. 800 °C and the flue gas is cooled to a relatively low temperature, whereby the mercury is condensed and thus separated from the air flow. The rest of the spent carrier gas must be cleaned by means of, e.g., active carbon filtering and then removed from the system with the help of the vacuum pump.

The dry distillation process is slow and highly energy-consuming, because the material being treated, as well as the vacuum chamber, must be heated to a high temperature for each batch and next, subsequent to distillation, again cooled, whereby energy losses occur. To improve the processing capacity, a sorting apparatus has been developed in which the glass tubes are crushed, the coarse glass particles and metal are separated from the fine-grain glass grit in a vibrating screen and only the fine-grain material is subjected to the distillation step. This is possible as the mercury is chiefly adhered to the fine-grain material and thus the coarse

material can be taken to recycling without further processing. The major drawback of this process is the batchwise operation and that mercury may be released in substantial amounts into the environment along with the coarse fraction of crushed material.

5

A wet process in use is based on placing the tubes being treated into a tank which is filled with a liquid so that the tubes remain below the liquid upper level. Next, the tubes are crushed by lowering a crushing plate, which during the loading step was elevated above the basin, toward the basin bottom, whereby the tubes are crushed. o The metals and the metallic vapors are bound into sulfides in the liquid. The crush¬ ing apparatus which is placed on a truck can be discharged into a special container and subsequently the container contents' are processed at a central waste treatment plant. The drawbacks of this apparatus include its batchwise operation and that the crushed material and spent liquid must be transported to further processing in a 5 special plant. Thus, the apparatus is suited for receiving small batches of fluorescent lamps in, e.g., suburbs, but not for continuous industrial-scale processing of objects containing hazardous substances. Obviously, the apparatus can be designed for fixed operation, whereby its batchwise function still remains its greatest drawback.

0 It is an object of the present invention to achieve a process and an apparatus suited for efficient and continuously operating treatment of fluorescent lamps and similar objects and simultaneously cleaning the glass and metal scrap thus obtained to a high degree of cleanliness.

5 It is a further object of the present invention to achieve a process and apparatus suited for treating objects of different types and shapes containing different kinds of hazardous substances.

The invention is based on feeding the objects being processed through a liquid spray 0 air lock into a crusher, where they are crushed and the obtained crushed material is washed with the help of high-pressure liquid jets, after which the glass and the

metals are separated from the liquid and the liquid is treated to neutralize and separate the hazardous substances.

More specifically, the process according to the invention is characterized by what is 5 stated in the characterizing part of claim 1.

Furthermore, the apparatus according to the invention is characterized by what is stated in the characterizing part of claim 7.

o The invention offers significant benefits.

The greatest economical advantage of the invention is its continuous function. Continuous operation offers the lowest possible energy and manpower need. The crushing and washing steps of the objects being processed are fully separated from 5 the environment, and the objects are fed intact to the crushing step. As the apparatus is free from releases of environmentally hazardous vapors and other substances of health risk, the process provides good occupational health safety. The duration of the cleaning step can be adjusted and the apparatus achieves extremely low residual contents. The mercury contents of processed glass and metal can be reduced at a 0 level of 6 to 2 mg/kg, thus rendering the final products well suited for reuse. Water spent in the process is also efficiently purified from mercury to a low level even permitting direct discharge to a communal sewer, while in practice the water is advantageously recycled for use in the water spray air lock and as washing water, whereby the amount of water escaping the process is minimal. This small quantity of 5 water leaves the system only as adhered to the crushed glass and metal plus the filtrated precipitate. The apparatus and process can be applied to objects and substances of various kinds without design changes. Obviously, the choice of the process chemicals is dictated by the materials contained in the objects to be processed. A further benefit of the invention is that it can have a modular construction, thus permitting easy transfer when necessary. This benefit is of . particular value in the erection of new installations as the equipment can be completely assembled and tested prior to its delivery to the user.

The invention is next examined in greater detail with the help of the annexed drawings in which

Figure 1 shows a block diagram of the process according to the invention.

Figure 2 shows a flow diagram of the process according to the invention.

Figure 3 shows a more detailed diagram of the entrance side equipment of the process.

With reference to the block diagram of Fig. 1, the flow scheme of the treatment pro¬ cess according to the invention is outlined. The intact fluorescent lamps are first fed to the crushing unit where their glass parts are crushed and the aluminum socket parts are flattened thereby separating from the glass. The lamps are fed to the crush- ing unit via a water spray air lock to prevent hazardous vapors possibly released from the lamps during their crushing from escaping into the environment. The crushed material exiting the crushing unit is washed by high-pressure water jets, the washed material is dewatered and the glass particles and aluminum socket parts are separated from each other and shipped to reuse at glass/glass wool plants and scrap retailers.

In the subsequent process steps the water used in the water spray air lock and washing steps is treated to remove mercury and fluorescent phosphors mixed with the water. The pH of the water is first adjusted to a proper level for the ensuing process step by adding a caustic, after which a precipitation agent is dosed in the water. The precipitation step may involve different kinds of auxiliary treatments, of which flocculation is indicated in Fig. 1. Following flocculation, the water is routed to a clarification basin and the overflow of the clarifier is recycled back to the start of the process for use in the water spray air lock or as washing water. The pH of the overflow is adjusted to a proper level by acid addition to the water. The underflow of the clarifier which contains the metal precipitate is taken to a filter, wherefrom the filtered water is recycled back to the water spray air lock and

washing steps, while the mercury containing precipitate is removed for transfer to a proper storage.

With reference to Fig. 2, a more detailed description of the process is given. 5

It must be understood that the apparatuses discussed in the following description exemplify in each process step only one alternative suited for use in the most advan¬ tageous embodiment of the invention illustrated in Figs. 2 and 3. Alternative embodiments of apparatuses suited for use in the different process steps are o discussed at the end of the description given below.

The processing of discarded fluorescent lamps in the apparatus starts by the loading of the lamps into a feeder hopper 29 of a conveyor 1. The feeder hopper 29 is a downward tapering tank having its bottom downward slanted toward the receiving 5 end of the conveyor and said slanted bottom is provided with hole through which the lamps can land on the receiving end of the conveyor 1. The belt of the conveyor 1 is made from rubber and has crosswise placed comb plates 30 at fixed spacings that pick one lamp at a time from the feeder hopper onto the conveyor 1. The conveyor 1 operates upward slanted and lifts the fluorescent lamps in a transverse position to 0 the upper part of a crusher feed cone 2 wherefrom they fall through a water spray air lock down along the feed cone 2 and into the throat of a two-roll crusher 3 located at the lower end of said feed cone. The conveyor 1 and the crusher feed cone 2 are encased in an entirely air-tight manner, whereby no harmful substances can escape from the housing into the environment. The housing roof of the crusher 5 feed cone 2 is provided with a hatch through which objects with a shape different from that of a fluorescent lamp can be tipped into the feed cone 2.

The upper end of the conveyor 1 has a curtain of plastic strips through which the fluorescent lamps pass. The purpose of the curtain is to prevent water and crushed 0 glass from splashing onto the conveyor 1. In the crusher feed cone 2 the lamps pass through water spray air locks formed by two nozzle manifolds 4. The nozzle mani¬ folds 4 are placed in a recess in the wall of the crusher feed cone 2, and each nozzle

ejects a sideways fanned jet. The fanned jets are aligned obliquely downward so as to overlap at their edges, whereby the water spray air lock formed at the wall of the crusher feed cone 2 is homogeneous thus preventing the access of rising vapors through the air lock. The nozzles 4 are located in two vertically displaced manifolds thus causing the lamps falling in the cone 2 to pass through two water spray air locks. The location of the lower water spray air lock is selected so as to permit a lamp of longest possible size to fit in a vertical position in the space between the crusher 3 and the lower water spray air lock, whereby all lamp sizes are subjected to crushing only after completely falling below the water spray air lock, thus prevent- ing any release of hazardous substances from the breaking lamps through the water spray air locks.

At the lower end of the crusher feed cone 2 the lamps e"ter the crusher 3 formed by two parallel, rotating rolls. The perimeter of the rolls is provided with longitudinal grooves which pull the objects entering the throat of the crusher to the gap between the rolls and crush them. The gap between the rolls is adjustable in the range 2 - 25 mm and the gap is preferably adjusted such that the rolls crush the lamps into particles of equal size and slightly flatten the aluminum socket parts adhering to the ends of the lamps. Obviously, further processing of crushed material with a homo- geneous particle size is easier than that of a wide particle size distribution.

After emerging from the crusher 3, the glass particles, aluminum parts and the water sprayed from the nozzles 4 are taken into a pipe 5 exiting at the lower end of a washing drum 6. The crushed material is transferred in the pipe 5 by means of high- pressure water jets. The washing drum 6 is placed in a slightly inclined position and its inclination can be adjusted to control the washing step. The lower end of the drum 6 has an opening and an exit nozzle 7 through which the washing water and the water carried over with the crushed material are removed from the drum 6. The opening to the exit nozzle 7 is provided with screen plate 31, which prevents the crushed material from exiting the drum 6 along with the removed water. Another function of the screen plate 31 is to determine the water level in the drum 6. For approx. 1/3 of the total length of the drum 6, the inner perimeter of the drum 6 is

provided at its lower end with lifting vanes 32 which during the rotation of the drum tend to elevate the crushed material that enters at the lower end of the drum 6 onto inner perimeter of the drum 6. Thus, during the washing step, a portion of the crushed material residing in the drum 6 is submerged in water on the drum bottom, 5 while another portion of the material is elevated by the lifting vanes 32 into a slanted layer along the inner perimeter of the drum.

The center axis of the washing drum 6 is formed by a pipe 8 having a row of wash¬ ing jet nozzles 33 aligned toward the layer of crushed material elevated above the o water level. The washing of the crushed material in the drum takes place so that the lifting vanes 32 elevate the crushed material from the bottom of the drum 6 and the high-pressure water jets ejected from the washing jet pipe 8 wash the crushed material against the inner perimeter of the drum. The washing effect is accentuated by the abrasion of the crushed particles against each other, whereby a good washing 5 result is obtained.

The inner perimeter of the washing drum 6 over the section not having the lifting vanes 32 is provided with a segmentally assembled lift auger 34, which transfers the washed material to the upper end of the washing drum 6. The central pipe 8 of the 0 washing jets extends essentially over the entire length of the lifting auger 34, and the washing of the particles is thus continued also in this section of the drum 6. Several design parameters can be varied to modify the retention of the particles in the drum and its different sections, and thereby, the desired washing function. The lifting vanes 32 at the lower end of the drum are inclined so as to effect a slight upward 5 transfer of the crushed material in the drum. As the angle of the vanes 32 is adjustable, this parameter can be varied to control the retention of the crushed material in the actual cleaning stage. A retention of approximately four minutes is desirable, which is achieved by a drum rotational speed of 8 r/min, whereby each particle is theoretically subjected 32 times both to a water jet and rotated through a 0 full mixing cycle in the washing section. Thus, a multistage washing action is achieved by means of a continuously operating drum. The entrance end of the lifting auger has a controllable vane segment whose angle control permits the adjustment of

the amount of crushed material lifted from the drum onto the auger 34 per revolution. This transfer rate is desirably controlled essentially equal to feed rate of untreated crushed material entering the drum 6. The retention of the crushed particles on the auger section 34 is approximately two minutes during which time they are further subjected 16 times to the washing action of the high-pressure water jets. The retention of the crushed material in the drum can be additionally controlled by altering the inclination angle of the washing drum 6. Appropriate positions for the control elements are easiest found by means of practical tests.

The crushed material transferred to the upper section of the washing drum 6 is re¬ moved from the drum 6 via a nozzle 9 landing next in a screen drum 10, where the crushed glass is separated from the aluminum socket parts of the fluorescent lamps. The screen drum 10 is an inclined drum with an envelope made from steel fabric of appropriate mesh. The crushed material enters the drum from its upper end and starts moving toward the lower end of said drum 10, whereby the crushed glass with a particle size smaller than that of the aluminum socket parts of the lamp can fall through the envelope mesh of the drum 10 onto a conveyor 11, wherefrom it is conveyed to a crushed glass container 12. Simultaneously, the aluminum parts travel to the lower end of the screen drum 10 and land on a conveyor 13 and further to a metal scrap container 14. The conveyors 11 and 13 can be of any conventional type of conveyor and standardized containers can be advantageously employed as storage containers. The separated materials can be then transported in the containers to reuse.

The water discharged from the washing drum 6 is treated in the following manner. The washing water is pumped to a precipitation tank 17 along a line 15 with the help of a pump 16. Prior to precipitation, the pH of the aqueous solution is adjusted to a proper level for precipitation. The pH adjustment is implemented by caustic addition (10 % caustic solution) by means of a dosing pump. The desired amount of caustic is added to the inlet side of the transfer pump 16, whereby good mixing of the caustic in the washing water flow is attained. In the precipitation tank 17 a precipitation agent is added to the aqueous solution, whereby the mercury and other

heavy metals react so as to form salts of extremely low solubility. The precipitation agent employed can be sodium sulfide, dithiocarbamate or trimercaptotriazine or any other suitable reagent. The last one of the listed agents is commercially known by the trade name TMT 15. The entering aqueous solution is stirred by a mixer 18 to 5 attain good mixing of the precipitation agent with the aqueous solution, and the detention of the mixed solution in the tank 17 is about 10 minutes.

The mixing of the required amount of precipitation agent takes places in the precipi¬ tation tank. The dosing pump for the precipitation agent can be controlled manually o or automatically according to the feed rate of the entering aqueous solution. The feed rate of the precipitation agent is set to correlate with the mercury concentration of the aqueous solution. In practice, the precipitation agent is overdosed to the precipitation process to ensure that all mercury is positively reacted with the precipitation agent. 5

From the precipitation tank the reacted aqueous solution is pumped to a rapid mixing compartment 19 and a coagulation agent is dosed into the inlet line of the aqueous solution to the rapid mixing compartment. The coagulation agent employed can be any conventional water treatment chemical such as ferrous sulfate, ferrous chloride 0 or lime. In this stage the mixture is agitated vigorously by means of a high- efficiency mixer 20 to attain complete mixing of the different chemicals in the aqueous solution. From the mixing compartment 19 the aqueous solution exits as overflow to a flocculation tank proper 21, a flocculation agent is added to the overflow aqueous solution and the mixture is further subjected to mild agitation by 5 means of a mixer 22. The flocculation agent employed can be any conventional water treatment chemical such as polyacrylamide.

From the flocculation tank 21 the aqueous solution flows to a clarifier 23 in which the precipitate settles onto the bottom of the clarifier 23. The overflow of the clarifi- cation stage is routed to a purified water tank 24, wherefrom it is further pumped back to the washing process and the water spray air lock along lines 25 and 26. The

purified water tank is provided with a liquid level switch which performs water replenishment to the system by controlling a magnetic valve.

The underflow from the clarifier is removed from the clarifier tank and routed to, e.g., a pressurized plate filter 27 in which the precipitate cake accumulates on the plate outer surface. From the vertical filter plate the precipitate is easily removed by compressed-air blowing or water jets. The precipitate is collected in a precipitate container 28 and the filtrate is recycled back to the purified water tank 24 of the clarifier 23.

According to the literature, the mercury content of intact fluorescent lamps is approx. 100 ppm, while variations about the quoted value do occur and a continual trend to lower concentrations exists.

The present process and its different stages have been subjected to extensive labora¬ tory tests. The tests have particularly been conducted on the attainable mercury con¬ tents. According to test analyses, the mercury contents of the final products from the washing process were as follows:

1. Crushed glass

The mercury content of the washed glass is below 6 mg/kg, and the glass can be shipped as such for reuse in, e.g. a glass wool plant.

2. Aluminum sockets of fluorescent lamps The mercury content of aluminum socket parts is below 4 mg/kg, and the aluminum can be reused and shipped as such to a scrap metal vendor or smelter.

3. Glass-dust-containing precipitate

This precipitate contains the mercury washed from the fluorescent lamps, as well as the fluorescent phosphor materials. The fluorescent phosphors are not environ¬ mentally hazardous compounds. The metals are contained in the precipitate as sulfides or TMT-bound mercury compounds or other compounds which have an

extremely low solubility in water and are nonreactive with other substances, thus being nonhazardous to the environment. According to the tests performed (EPA shaking test), the precipitate is compatible with threshold limits set for materials acceptable at dump sites.

5

Water is removed from the process only as carry-over with the above-mentioned final products, that is, in extremely minor amounts. The mercury content of clarified or filtered water is below 0.005 mg/1, whereby its release to the sewer (e.g., during maintenance operations) is also compatible with the wastewater recommendations o issued in Finland.

Obviously, the apparatus can be varied in multiple ways within the scope of the annexed claims. For instance, the conveyor feeding the objects to be processed into the crusher feed cone 2 can have varied forms of design and even omitted, whereby 5 the objects can be fed into the crusher feed cone 2 manually for instance. However, the feeding of fluorescent lamps through the water spray air lock 4 is advantageously implemented so that the objects pass through the air lock one by one at short inter¬ vals thus keeping the air lock as air-tight as possible. Satisfactory air-tightness is obtainable by a single water spray air lock alone, while the number of such air locks 0 is preferably two or possibly even more.

The shape and design of the crusher feed cone 2 can be varied by a wide latitude. The crusher 3 can have an alternative design of a single-roll crusher or a jaw crusher, while the continuous-function crushers of the roll crusher type are optimally 5 suited for implementing the desired continuous function of the apparatus according to the present invention. The washing drum 6 can be replaced by other arrangements capable of subjecting the crushed material to the effect of multiple sequentially working high-pressure water jets. An alternative embodiment is formed by a com¬ bination of a vibrating conveyor with multiple crosswise aligned water jets. 0 Obviously, the screen drum 10 can be replaced by different types of screens and other separating apparatuses, while the above-described separating equipment of the

screen drum type again is considered optimal owing to the easy implementation of the continuous separation it can provide.

The chemical treatment of the washing water as such is well recognized in the art and also a great number of different water treatment chemicals are in conventional use. A person skilled in the art has no difficulty in finding proper chemicals and dosing rates for each type of waste material being processed. The characterizing pro¬ perty of the present invention related to the above-discussed process stage is the re¬ cycling of the process water, whereby a low make-up water consumption is attained and release of spent water to the sewer can be avoided. If desired, addition of detergents or other chemicals to the water pumped to the water spray air lock and washing jets is possible though not mandatory owing to the substantially good wash¬ ing efficacy obtainable by virtue of the present invention even without such additional measures.

To implement the invention, not all elements discussed in the exemplifying embodi¬ ment described above are necessarily required, but rather, they can be readily combined in alternative practical realizations of the invention within the scope of the annexed claims.