PLACID process

To conclude this section, reference may be drawn to what is called the Placid process for recycling lead from batteries. Placid denotes the leaching of lead in warm, slightly acidic, hydrochloric acid brine to form soluble lead chloride. Lead is won from the lead chloride on the cathode of an electro winning cell and is collected. Chloride anions are released simultaneously, but then react immediately with hydrogen ions that have been produced stoichio-metrically from electrolysis of water in the anolyte and passed into the catholyte through a membrane. The hydrochloric acid that is formed is returned as a make-up content to the leaching bath. 

PLACID/PLINT process [13,14], The PLACID process (see also Chapter 16) is based on the electrowinning of lead from a chloride solution in a cell where the cathode and anode are separated by a semipermeable membrane. Lead oxide and lead dioxide are converted to soluble lead chloride, whilst lead sulfate is converted in a hot brine circuit. The sulfate ion is removed as gypsum after the addition of lime. The FLINT process is an advanced adaptation of the PLACID process and operates in parallel with a pyrometallurgical route that smelts the metallic lead fractions from the battery. 

In the case of the PLACID process, hydrochloric acid is regenerated in the electrolytic cells, so lime is the only consumable. When the FLINT process is applied, make-up acid addition is necessary, and sulphuric acid can replace hydrochloric acid because of its lower cost. 

Figure 1 - PLACID Process, Conceptual Block Diagram...

The PLACID process could be perfectly integrated if it were employed in parallel with a pyrometallurgical smelter. In this way, any lead fumes, drosses and slags from Ae pyrometal-lurgical line can be passed to the leaching bath of the PLACID line and the cements from the purification stqi could be fed into the furnace. Important gains would be obtained fix)m the oiviromnental, process efficiency, product quality and economical points of view. 

The European organisations that have developed the PLACID Process into the Brite-Euram Programme wish to express their gratitude to the European Community for its encouragement, support and partial funding of the project. 

G. Diaz, C. Frias, L.M. Abrantes, A. Aldaz, K. van Deelen, and R. Couchinho, Lead-Acid Battery Recycling by the PLACID Process - A Global Approach , TMS Third International Symposium on the Recycling of Metals and Materials. Point Clear, Alabama, 1995, 843-856. 

Fig 9.4 - Aqueous chloride electrolysis tor lead (PLACID process). 

Although substantial work has been carried out on the recovery of lead from battery residues by electrolytic means, no system has been adopted for large-scale commercial operations. Companies such as Engitech Impianti in Italy and RSR in the USA have patents on electrolytic systems, whilst a European consortium, led by Tecnicas Reunidas in Spain, has developed the chloride-based PLACID and FLINT lead recovery processes. 

The PLACID hydrometallurgical process provides the benefit of minimal occupational lead exposure because there are no lead emissions or any lead dust from by-products or residues. 

Lead dissolution efBciency is very high. In a PLACID-/ o or PLINT-/ o combined process, the overall measured extraction rate was 99.5%, because the leaching process extracted the available lead from slags and other products already rejected by the furnace operation. 

Based on the above operating and investment costs, several DCF (discounted cash flow) calculations have been carried out. An IRR (internal rate of return) in the range of 16% to 28% has been worked out, which indicates that both the PLACID and FLINT processes are economically very attractive. 

When PLACID or FLINT hydrometalluigical processes were implemented in parallel with any existing pyrometallurgical battery recycling plant, the environmental, technical and economical aspects of the integrated plant could be substantially improved. The proposed new processes are simple, efficient, very flexible and profitable, which make them ideal for being adapted to the customer s needs and local requirements. 

The final evaluation study of both the PLACID and FLINT processes, applied to a selected base case producing 20,000 t/y of lead with a purity of 99.99% indicated very satisfactory results, which facilitate their industrial implementation in the short term. The... 

G. Diaz and D. Andrews, Placid - A Clean Process for Recycling Lead from Batteries , Journal of Metals. Vol. 48, 1996,29-31. 

Papa Rao, S.S., et al, August 9—12, 2009. Experimental studies of the interaction between ULK films, CMP slurries down-stream processes. In 14th International Symposium on Chemical Mechanical Planarization, Lake Placid. 

In 1988, Laursen made the observation that mussels inhabiting the turbulent oceanic environment secrete proteins with little variation from the consensus sequence whereas those found in placid inland lagoons show large variations. Presumably, sea mussels, through a process of natural selection have arrived at an ideal sequence of amino acids that produce the most effective glue. The relationship of the amino acid sequence of this protein to its efficient functioning as a glue is thus clearly demonstrated. ... 

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