Recycling processes

Modern secondary plants take in whole ULAB batteries and break them in a mechanical hammer-mill. The broken battery pieces are usually gravity separated in a series of water-filled tanks with slow-moving classifier belts to promote the capture of the battery paste. In this way, battery electrolyte is contained within the recycling process, and the acidic component can then be treated in one of the five ways [10]  

It is important to achieve maximum separation of the plastics from furnace materials, such as the oxides and grid metal, to minimize the risk of dioxin formation during the smelting process. 

Washed and dried polypropylene pieces are sent to a plastic recycler, where the chips are melted [12] and extruded to produce plastic pellets for use in the manufacture of battery cases and other plastic components. Great care must be taken to ensure that the mechanical breaker cleans the polypropylene chips free of any residual oxide, because subsequent handling of the chips by operating personnel, especially at the plastic recycling plant, can result in significant levels of lead exposure. Should the wash sprays on the breaker fail to remove all traces of battery paste, consideration should be given to further washing with a dilute sodium hydroxide solution. 

Another option for secondary smelters is to desulfurize the battery paste prior to smelting. Chemical desulfurization, however, is dependent on physical mixing conditions and temperature. Chemical desulfurization is achieved by adding a concentrated sodium carbonate solution to an agitated mix of battery paste sludge to convert the lead sulfates to lead carbonates. Complete conversion of lead sulfate to lead carbonate eliminates sulfur in the furnace feed material and sulfur dioxide in the exhaust gases. Complete desulfurization is, however, rarely achieved under normal industrial conditions. 

The basic desulfurization equation [14] for the conversion of lead sulfate to lead carbonate is  

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Polymer recycling process costs for various operations are summarized in Table 6. 

The stripper off-gas going to the high pressure carbamate condensers also contains the carbamate recovered in the medium and low pressure recirculation sections. Both of these systems ate similar to those shown in the total-recycle process. 

Other Processes. Flow sheets for typical partial-recycle process and typical once-through urea process are given in Figures 9 and 10, respectively. 

Because an excess of ammonia is fed to the reactor, and because the reactions ate reversible, ammonia and carbon dioxide exit the reactor along with the carbamate and urea. Several process variations have been developed to deal with the efficiency of the conversion and with serious corrosion problems. The three main types of ammonia handling ate once through, partial recycle, and total recycle. Urea plants having capacity up to 1800 t/d ate available. Most advances have dealt with reduction of energy requirements in the total recycle process. The economics of urea production ate most strongly influenced by the cost of the taw material ammonia. When the ammonia cost is representative of production cost in a new plant it can amount to more than 50% of urea cost. 

The environmental appHcations of infrared spectrometry are many and varied. Many appHcations at industrial sites are analogous to those for on-line process analysis waste streams and recycling processes can be monitored in the same way. Commercial infrared stack-gas monitors are based on either an extractive probe attached to a long-path gas ceU or an open-path (across stack) configuration (69). Stack plume and flare monitoring can be done externally... 

The surviving U.S. plants have embraced all types of waste treatment processes (see Wastes treatment, hazardous waste Wastes, industrial). The most desired poUution prevention processes are those which reduce the total amount of waste discharged. Treatment and disposal are less strongly emphasized options. Zero wastewater discharge faciHties and water recycling processes are becoming more common (55,56). 

The minerals processing industry has made contributions to all areas of technology, both in terms of products and processing. Technologies developed in the mineral industry are used extensively in the chemicals industry as well as in municipal and industrial waste treatment and recycling industry, eg, scrap recycling, processing of domestic refuse, automobiles, electronic scrap, battery scrap, and decontamination of soils. 

Lewis acids, such as the haUde salts of the alkaline-earth metals, Cu(I), Cu(II), 2inc, Fe(III), aluminum, etc, are effective catalysts for this reaction (63). The ammonolysis of polyamides obtained from post-consumer waste has been used to cleave the polymer chain as the first step in a recycle process in which mixtures of nylon-6,6 and nylon-6 can be reconverted to diamine (64). The advantage of this approach Hes in the fact that both the adipamide [628-94-4] and 6-aminohexanoamide can be converted to hexarnethylenediarnine via their respective nitriles in a conventional two-step process in the presence of the diamine formed in the original ammonolysis reaction, thus avoiding a difficult and cosdy separation process. In addition, the mixture of nylon-6,6 and nylon-6 appears to react faster than does either polyamide alone. 

Fig. 3. Used aluminum beverage cans (UBC) recycling process.

The hterature is hiU of detailed evaluations of recycled petroleum products (2,6,17,18,23,28) and investigations into the environmental ramifications of the recycling processes themselves (30). 

The initial use was as a blow moulded vessel for vegetable oil candles. However, because of its biodegradability it is of interest for applications where paper and plastics materials are used together and which can, after use, be sent into a standard paper recycling process. Instances include blister packaging (the compound is transparent up to 3 mm in thickness), envelopes with transparent windows and clothes point-of-sale packaging. 

Adhesives and resins are one of the most important raw materials in wood-based panels. Thus, each question concerning the life cycle assessment and the recycling of bonded wood panels does bring into question the adhesive resins used. This includes, for example, the impact of the resin on various environmental aspects such as waste water and effluents, emission of noxious volatile chemicals during production and from the finished boards, or the reuse for energy generation of wood panels. The type of resin has also a crucial influence on feasibility and efficiency for several material recycling processes. 

Urea Plant 6. Use total recycle processes in the synthesis process reduce microprill formation and carryover of fines in prilling towers. 

In the living cells of luminous bacteria, FMNH2 is produced by the reduction of FMN with NADH catalyzed by FMN-reductase. This process is, in effect, the recycling of FMN. In the cells, a long-chain aldehyde is produced by the reduction of the corresponding long-chain acid, which is also a recycling process. 

Plastics have many advantages. Included are the facts that they have the lowest energy consumption in the recycling processes of about 2 MJ/kg (2 to 2.5 MJ/I) and when incinerated the highest recovery energy content exists of about 42 MJ/kg. Some comparisons with other materials are provided. (1) Processing waste paper requires 6.7 MJ/kg and as a general rule about twice as much paper is needed compared to plastics for... 

Developments in the Hot-Gas-Recycle Process, Bureau of Mines Rep. Invest. (1965) 6609. 

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