Atık alkali pillerden pirometalurjik yöntem ile ferromangan ve çinko üretimi
Ferromanganese and zinc production with pyrometallurgical method from spent alkaline batteries
Yazar: SELÇUK YEŞİLTEPE
Danışman: PROF. DR. MUSTAFA KELAMİ ŞEŞEN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı / Üretim Metalurjisi ve Teknolojileri Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2015
Konu: Metalurji Mühendisliği = Metallurgical Engineering
Dizin: Tehlikeli atıklar = Hazardous wastes

Özet:
Elektrikli aletlerin kullanılmaya başlaması ve yaygınlaşması ile birlikte enerji ihtiyacı da artmıştır. Kullanımda olan elektrikli aletlerin taşınabilir olması ve sabit bir elektrik kaynağından bağımsız olarak çalışabilmesi düşüncesi ile piller günlük kullanıma girmiştir. Zamanla birlikte piller endüstrileşmiş, elektrikli alet kullanımı artmış ve değişik boyut ve kimyada piller üretilmeye başlanmıştır. Üretilen pillerin büyük çoğunluğunu yeniden kullanılamayan piller (primer) piller oluşturmuş ve atık pil sorunu ortaya çıkmıştır. Günümüzde ise atık pil miktarı dünya çapında milyon tonlar mertebesine ulaşmıştır. Atık pil miktarlarının yüksekliği, atık pillerin içerdiği zararlı materyaller ve atık pillerde bulunan değerlendirilebilir metal miktarı atık pillerin geri dönüştürülmesini zorunluluk haline getirmiştir.
Atık piller ile ilgili olarak ülkeler düzenlemeler getirmiş, atık pillerin toplanması ve geri dönüştürülmesi veya imha edilmesi üzerine belirli düzenlemeler getirilmiştir. Avrupa Birliği bu konuda 91/157/EEC adlı düzenlemeyi yürürlüğe sokmuş sonrasında ise yeni düzenlemeler ile birlikte 2006/66/EC direktifini yürürlüğe almıştır. Bu direktifte atık pillerin toplanması, atık pil toplama hedeflerinin belirlenmesi, geri dönüşüm prosesleri, pillerin içerebileceği ağır metal miktarları bulunmaktadır. Ülkemizde de Atık Pil ve Akümülatörlerin Kontrolü Yönetmeliği yayınlanmıştır.
Kullanımı gittikçe artan alkali pillerin geri dönüştürülmesi ve geri dönüşüm prosesinin bilimsel olarak incelenmesi için bu çalışma yürütülmüştür. Yapılan çalışmada pillerin içerdiği metallerin geri kazanımı, geri kazanım şartları incelenmiştir. Bu çalışma doğrultusunda atık alkali pillerin değerlendirilmesi için bir proses önerilmiştir.
Proseste ilk olarak mekanik yollarla pillerin parçalanması ve dış kısımdaki çelik kısım ile iç kısımda bulunan, kimyasal reaksiyonların gerçekleştiği pil pastası ayrılmıştır. Daha sonrasında pil pastası suda bekletilip süzülerek içerdiği potasyum hidroksit (KOH) ayrılmış ve toz haldeki pil pastası süzülmüştür. Sonraki aşamada tasarlanan reaksiyon kabı içerisinde pil pastasında bulunan çinko uçurulmuş ve toz toplama sistemi ile tutularak çinko eldesi yapılmıştır. Son aşama olarak ilk aşamada ayrıştırılan çelik kısım ile pil pastasında kalmış olan mangan oksit redükleyici ergitme yöntemi ile ergitilerek ferromangan alaşımı elde edilmiştir.

Abstract:
Battery is a device which turns chemical energy directly to electrical energy. First battery is made from Alessandro Volta and Luigi Galvani. Industrial battery use became available with Michael Faraday. Battery use became more common with increasing electrical device usage. Batteries made most of the electrical devices mobile. Mobile energy storage advantage made batteries very popular. Since battery usage increased battery waste is also increased. Rechargeable batteries, secondary batteries, could be reusable again with charging but single use batteries, primary batteries, are waste batteries after use. In today‟s world, battery industry, reached over millions of metric tonnes of battery production. Waste battery levels are parallel with increasing battery production and use. In 2012, European waste battery amount was about 250.000 metric tonnes.
Waste batteries are not ordinary waste and should be taken care with specially. In European Union 2006/66/EC directive is published and taken into action by European Parliament. Control of Waste Batteries and Accumulators Directive taken into action in 2015, in Turkey. These directives regulated batteries, heavy metal contents of batteries, battery waste and recycling techniques. These regulations made battery collection and recycling mandatory for producers and encouraged private sector for recycling plants. Waste batteries are hazardous to environment with their metal content and basic or acidic electrolyte. These compounds can be hazardous to soil and under water supplies. Furthermore waste batteries are containing valuable metals inside and these metals should be recovered. Waste battery recycling is both economically and environmentally mandatory.
In this study, alkaline spent batteries are researched. Alkaline batteries are containing potassium hydroxide as electrolyte, gelled zinc powder as anode and manganese dioxide as cathode materials. At first existing recycling technologies for primary batteries are researched. Pyrometallurgical processes are dominant in primary battery recycling. Basically in primer batteries recycling with pyrometallurgical method high vapour pressure metals are vaporized and metal is collected as condensed or oxidized powder henceforth left over metals are smelted and mostly ferroalloys produced to be sold to
xviii
steel producers. Hydrometallugical techniques are not in use industrially for primary batteries.
As the second step chemical analysis, XRD analysis and thermodynamic researches are conducted. Determining elements and phases of spent alkaline batteries is the first step of research. After determining phases and elements in spent alkaline batteries thermodynamic research is done. Process and reactions to produce metals are designed according to compounds and thermodynamic data of compounds. Production and recovery steps of potassium hydroxide, zinc, manganese and steel are defined. A flow sheet of process is proposed.
According to process planning spent alkaline batteries firstly mechanically crushed grinded and sieved. Battery paste and steel cover is separated. Battery paste is washed with water in order to eliminate potassium hydroxide. After that step battery powder is filtered and dried. Battery paste is prepared for further processing to recover zinc from it. For zinc recovery, a stainless steel reaction vessel is used. Vessel is designed and produced for zinc recovery specially. Potassium hydroxide recovered battery paste is mixed with coke coal and placed into the reaction vessel then placed in to furnace. Experiments for zinc recovery are performed with Argon gas at various temperatures and different experiment times. Reaction gas is passed through a gas cleaning system and gas contains zinc vapour is washed down. The water used in gas cleaning then used to prepare a solution of sulphuric acid to solve zinc in acid. Zinc recovery is researched under given conditions. Manganese dioxide and steel is smelted under slag in reductive conditions in order to produce ferromanganese alloy. Smelting is performed in an electric resistance furnace with addition of flux agents. Ferromanganese alloy then examined with optical microscope, scanning electron microscope, micro hardness testing machine. Results are discussed for the offered process conditions.
As a result potassium hydroxide is recovered to some extent. Recovery conditions of potassium hydroxide were not suitable for recovery of all potassium hydroxide in spent alkaline batteries. Possible improving conditions are offered for further researches.
Zinc recovery is examined in two steps. First step of process is reductive conditions for zinc and separating zinc from battery paste. At this point study was very promising and results showed that zinc oxide can be reduced to the zinc metal and vaporized. Chemical analysis of samples showed zinc could be separated almost completely under certain conditions. On the other hand zinc recovery rate was not coherent to zinc evaporation rate. Possible conditions caused to that incoherency between zinc evaporation step and recovery step is explained in this study.
For the last step of recycling process battery paste is mixed with steel cover and coke, lime stone, fluspar and silica added to graphite crucible. Crucible is placed in to furnace and heated to decided smelting temperature. After smelting is done crucible is cooled down in furnace and then metal and slag is taken out of crucible. Ferromanganese alloy is examined for micro structure, chemical analysis and micro hardness. Results showed that produced alloy is not commercial ferromanganese but a promising master alloy which can be used in ferromanganese production or can be improved to commercial grade ferromanganese.
As a result, this study showed that spent alkaline batteries can be used in potassium hydroxide, zinc and ferromanganese production. Improvements suggested can be useful for other researchers who are considering further research on this topic. Recycling of spent alkaline batteries with pyrometallurgical method is possible. If economic conditions are adjusted feasibly production of zinc and ferromanganese from spent alkaline batteries with pyrometallurgical method could be a environmentally friendly technology.