PROJECT DESCRIPTION
BACKGROUND
In France, 30,000 tons of batteries are consumed every year. This represents 4,500 tons of zinc, 5,500 tons of manganese dioxide, and 5 to 10 tons of mercury. For the European Union, it means massive byproducts that include 30,000 tons of zinc, 36,000 tons of manganese dioxide and 30 to 40 tons of mercury every year. Landfilling or incinerating used batteries means discarding thousands of tons of valuable raw materials. A net loss of 100 million US $ every year in Europe. There is are also ecological and health costs. Most of the components of a battery are considered dangerous and classified as special industrial rejects. Some are among the most toxic materials known. Spent batteries pollute the soil and the aquifers and become a public health liability. One kilo of buried batteries pollutes 10 to 20 cubic meters of soil for 20 years. The only global solution to this various problems is recycling. There are several methods for recycling, but only 2 main groups: Pyrometallurgy: In this method, combustion is used to volatilize certain metals and produce ashes of the others. The ashes are filtered and washed to recover the metals. Hydrometallurgy: In this method, the batteries are first crushed and screened, the fines are leached to dissolve the metals that are then recovered with a specific treatment. Out of 3 hydrometallurgical processes, only one uses an alkaline solution and this is the Zimaval Process. The originality and innovation of the Zimaval process lies in the use of alkaline-based zinc hydrometallurgy. Zinc oxide and zinc metal are both dissolved in a solution of caustic soda and then zinc powder is deposited by electrolysis. What makes this approach outstanding is the selectivity of the media: only amphoteric metal oxides are significantly soluble in NaOH. The other metallic oxides like iron, cadmium, nickel, manganese, silicon, and mercury turn into insoluble hydroxides. Therefore, many complex zinc scraps can be treated, including light ashes from the incineration of common garbage, zamac or brass scraps, EAF dusts, catalysts, etc. The selectivity of the media leads to a short purification chain and produces high quality zinc metal powder. The process consists of: 1) simple sorting of collected batteries - rough screening of NiCd packs and lead accumulators-. The process is not very sensitive to impurities; 2) crushing and screening of the low value components - scrap, paper, plastics and non ferreous-; 3) hydrometallurgical and electrochemical zinc powder recovery in an alkaline medium; 4) hydrometallurgical and electrochemical manganese dioxide recovery in acid medium. The proposed quarter sized scale installation is dedicated to: 1. the transfer of the process to waste treatment and recycling and of the alkaline leaching technology to the zinc industry in order to allow for the marketing and development of this technology. 2. the manufacturing of high specific area zinc powder in order to prospect for new possible uses -anticorrosion, precious metal cementation, powders metallurgy- and to define the conditions of a low zinc content oxidized wastes recovery development.
OBJECTIVES
The main purpose of ZIMAVAL project was to prove that it is possible, at an industrial scale, to recuperate and recycle the main components of used batteries (zinc, manganese dioxide, mercury and stainless steel) and to produce high added value products - anticorrosion paints and/or batteries, colouring, etc.. That is to say: 1. to produce high grade raw materials (high specific area zinc powder and manganese dioxide) from waste; and, 2. to transfer the process to waste treatment and recycling industrialists.
RESULTS
The Zimaval Process recycles all categories of zinc containing batteries including: · Saline: containing zinc metal and manganese dioxide · Alkaline: containing zinc powder and manganese dioxide · Zinc /air: containing zinc powder and oxygen absorbed on carbon The trials of the pilot plant proved that lithium, nickel and cadmium do not interfere with the chemical process, providing that their quantities remain low. The process can accommodate 99% of all collectable batteries, but the sorting phase removes button batteries, lead-acid batteries and NiCd batteries. The process recycles and valorizes almost all the contents of primary batteries. It is important to note that: (i) the electrolyte contained in recycled primary batteries is 100% reused as it participates in the alkaline dissolution, and (ii) the sulfuric acid used in the acid process is recycled from used automotive lead-acid batteries. Papers and plastics along with the addition of carbon scraps are valorised as fuel. The only solid reject is the iron hydroxide precipitate - about 16 kg/ton- which is sent to landfill. The result is a recycling ratio in excess of 98 %. A part of the originality of the process is the possibility of marketing the resulting products to the primary battery industry thus creating a real recycling circuit with a significant added value. Zinc powder is easily marketed and a simple micronisation process leads to higher selling prices in the anti-corrosion paint industry. Manganese can be recycled as carbonate or sulfate for the pigments and chemical industry. Polypropylene from industrial batteries contains no impurities and can go straight back to battery casing manufacturers. Unfortunally, the ZIMAVAL company has gone bankrupt early 2003, leaving an important stock of batteries untreated.The Zimaval Process recycles all categories of zinc containing batteries including: · Saline: containing zinc metal and manganese dioxide · Alkaline: containing zinc powder and manganese dioxide · Zinc /air: containing zinc powder and oxygen absorbed on carbon The trials of the pilot plant proved that lithium, nickel and cadmium do not interfere with the chemical process, providing that their quantities remain low. The process can accommodate 99% of all collectable batteries, but the sorting phase removes button batteries, lead-acid batteries and NiCd batteries. The process recycles and valorizes almost all the contents of primary batteries. It is important to note that: (i) the electrolyte contained in recycled primary batteries is 100% reused as it participates in the alkaline dissolution, and (ii) the sulfuric acid used in the acid process is recycled from used automotive lead-acid batteries. Papers and plastics along with the addition of carbon scraps are valorised as fuel. The only solid reject is the iron hydroxide precipitate - about 16 kg/ton- which is sent to landfill. The result is a recycling ratio in excess of 98 %. A part of the originality of the process is the possibility of marketing the resulting products to the primary battery industry thus creating a real recycling circuit with a significant added value. Zinc powder is easily marketed and a simple micronisation process leads to higher selling prices in the anti-corrosion paint industry. Manganese can be recycled as carbonate or sulfate for the pigments and chemical industry. Polypropylene from industrial batteries contains no impurities and can go straight back to battery casing manufacturers. Unfortunally, the ZIMAVAL company has gone bankrupt early 2003, leaving an important stock of batteries untreated.
