Soma termik santral uçucu küllerinden nadir toprak elementlerinin (NTE) kazanımı
Recovery of rare earth elements (REEs) from Soma thermal power plant fly ash
- Tez No: 845455
- Danışmanlar: PROF. DR. GÜLAY BULUT
- Tez Türü: Yüksek Lisans
- Konular: Maden Mühendisliği ve Madencilik, Mining Engineering and Mining
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2024
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: Cevher Hazırlama Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Cevher Hazırlama Mühendisliği Bilim Dalı
- Sayfa Sayısı: 119
Özet
“Nadir toprak elementleri”(NTE) terimi, periyodik tabloda Lantanitler olarak sınıflandırılan lantan ve lutesyum elementlerinin yanı sıra itriyum ve skandiyum elementleri arasındaki 15 elementten oluşan bir grubu ifade eder. Bu elementler“nadir”olarak adlandırılmaktadır, çünkü zenginleştirme süreçleri yoluyla birbirlerinden seçici olarak ayırmak ve saf halde elde etmek zordur. NTE piyasasındaki yüksek arz talepleri ve artan fiyatlar nedeniyle birçok ülke yerel kaynaklardan faydalanmak için ikincil kaynaklara ve geri dönüşüme odaklanarak yeni kaynaklara yönelmiştir. Kömür ve kömür yan ürünlerinden NTE geri kazanımı potansiyel olarak umut verici bir kaynaktır. Bu tez çalışması kapsamında, Konya Şeker San. Tic. A.Ş. (Manisa/Soma) tarafından işletilen Soma Termik Santrali uçucu kül numunesinden nadir toprak elementlerinin kazanımı cevher zenginleştirme yöntemleri kullanılarak araştırılmıştır. Çalışmaların başında uçucu külün karakterizasyon çalışmaları yapılmıştır. Fiziksel zenginleştirme deneyleri kapsamında, özgül ağırlık farkına dayalı ayırma yapan Mozley masası ve santrifüjlü ayırıcılar (Multi Gravite Separatör (MGS) ve Knelson) kullanılmıştır. Fizikokimyasal zenginleştirme deneylerinde ise, Denver flotasyon cihazı kullanılarak karbon uzaklaştırma deneyleri gerçekleştirilmiştir. Kimyasal zenginleştirme deneyleri kapsamında ise, doğrudan asit liçi ve alkali ısıl işlem+asit liçi deneyleri yapılmıştır. Uçucu kül elek analizi deney sonuçlarına göre; malzemenin d80 boyutu 105 mikron olarak bulunmuştur. Temel oksit analizleri sonucu uçucu kül numunesinin başlıca SiO2, CaO, Al2O3 ve Fe2O3 bileşiklerinden oluştuğu tespit edilmiştir. Ayrıca, ICP-MS analizleri sonucunda uçucu kül numunesinin toplam NTE içeriği ASTM D6357 standartı ile yapılan külleme işlemine göre 197 g/t olarak elde edilmiştir. Fiziksel zenginleştirme deneyleri sonrasında fizikokimyasal zenginleştirme deneyleri gerçekleştirilmiştir. Flotasyon deneyleri kapsamında, karıştırma hızı 1000 dev/dk, PKO %10, doğal pH'sı olan 13,10 gibi parametreler sabit tutularak, Span80 ve Tween 20 ile hazırlanan emülsifiye kerosen 1500 g/t ve 2500 g/t miktarlarında kullanılarak deneyler yapılmıştır. Ayrıca, köpürtücü seçiminin flotasyon verimi üzerindeki etkisini incelemek için 250 g/t MIBC ve İzooktanol kullanılarak deneyler gerçekleştirilmiştir. Toplayıcı olarak Tween20 ile emülsifiye edilen kerosenin ve köpürtücü olarak MIBC'nin kullanıldığı flotasyon deneylerinde batan üründeki en yüksek NTE içeriğine (226 g/t) %89 NTE kazanma verimi ile ulaşılmıştır. Doğrudan asit liçi deneylerinde ise liç süresi 2 saat, katı:sıvı oranı 1:10, karıştırma hızı 400 dev/dk olarak seçilmiştir. Bu deneylerde kullanılan asitler HCl, H2SO4 ve HNO3 (0-3 mol/L konsantrasyonları arasında) olarak tercih edilirken, uygulanan liç sıcaklıkları 20, 50 ve 90°C'dir. Alkali ısıl işlem deneyi 400 °C'de, 2 saat boyunca, 1:1 oranda NaOH:uçucu kül kullanılarak gerçekleştirilmiştir. Alkali ısıl işlem ürünlerine uygulanan asit liçi deneylerinde liç süresi 2 saat, karıştırma hızı 400 dev/dk ve katı:sıvı oranı 1:10 olarak seçilirken, doğrudan asit liçinde kullanılan asitler benzer konsantrasyonlarda ve liç sıcaklıklarında kullanılmıştır. Alkali ısıl işlem sonrasında uçucu kül numunesine uygulanan asit liçi deneyleri sonucunda en yüksek ∑NTE çözündürme verimi olan %94,7'ye 3 mol/L HCl asit konsantrasyonu ve 20 ⁰C liç sıcaklığında ulaşılmıştır. Katı artıktaki NTE içeriği ise 114 g/t olarak tespit edilmiştir. Alkali ısıl işlem+asit liçi sonucundaki en uygun deney koşullarının tespitinden sonra liç süresinin belirlenmesine yönelik olan yapılan deneylerde 2 saat en uygun liç süresi olarak belirlenmiştir.
Özet (Çeviri)
The term“rare earth elements”(REE) refers to a group of 15 elements between the elements lanthanum and lutetium, as well as the elements yttrium and scandium, which are classified as Lanthanides in the periodic table. It is known that there are more than 250 minerals that contain REEs and that the average concentration of REEs in the Earth's crust is around 0.015%. These elements are referred to as“rare”because it is challenging to selectively separate them from one another through enrichment processes and acquire them in pure form. Due to the high supply demands and increasing prices in the REE market, many countries have focused on new resources by focusing on secondary resources and recycling to benefit from local resources. REE recovery from coal and coal by-products is a potentially promising resource. With the growing strategic importance of rare earth metals, the Chinese government designated these metals as“strategic commodities”in 2007. The fact that rare earths play a critical role in the defense industry is one of the main reasons why these metals are called strategic elements. They are also widely used in high-tech fields such as renewable energy, hybrid vehicles, permanent magnets and catalysts. Among alternative sources, coal and coal by-products, which are widely used especially in the energy sector, are considered as potential rare earth resources. Approximately 75% of the coal produced in Turkey is used in thermal power plants and this coal contributes around 30% to Turkey's electricity generation. The pulverized coal is sprayed into the combustion section of the boiler and burned at 1400 ⁰C. Pulverized coal ashes obtained from thermal power plants after coal combustion are used as cement additives in construction. Fly ash contains mainly Si, Al and Fe (both in crystalline and amorphous form) and has compositional characteristics similar to zeolites, which also contain minor elements such as Ca, Na, K and Ti. Fly ash is usually composed of hollow aluminosilicate microspheres (senosphere). These spherical particles are the result of solidification and cooling of gases during the combustion process under high temperature and pressure. Also, the content of some thermal power plant ashes can play an important role. Coal and coal by-products are reported to be significantly enriched with trace metals and have been proposed as a promising source of rare earth elements (REEs). NTE in lignite coals is known to be weakly correlated with the organic fraction of the coal. The recovery of valuable elements from these ash waste streams is well aligned with the“Waste to Value”concept and enhances the sustainability of current disposal practices. Coal resources and related wastes in our country offer an important opportunity when evaluated in terms of REE. Within the scope of this thesis, Konya Şeker San. (Manisa/Soma), the recovery of rare earth elements from Soma Thermal Power Plant fly ash sample was obtained by using ore beneficiation methods. In the study of physical beneficiation experiments, Mozzley table and centrifugal separators (MGS and Knelson) were used for separation based on specific gravity difference. In physicochemical beneficiation experiments, carbon removal experiments were carried out using Denver flotation cell. In chemical beneficiation experiments, direct acid leaching and alkaline heat treatment+acid leaching experiments were carried out. According to the fly ash sieve analysis test results, the d80 size was found to be 105 microns. Basic oxide analysis showed that fly ash sample was mainly composed of SiO2, CaO, Al2O3 and Fe2O3 compounds. In addition, ICP-MS analysis showed that the total REE content of the fly ash sample was 197 g/t according to the ashing process performed according to ASTM D6357 standard. As a result of the beneficiation experiment using Mozzley table, the highest ∑REE content was obtained in the light product with 238 g/t and 74.9% yield. From this result, it is understood that REE moves with light materials with low density. As a result of MGS experiments, it is seen that ∑REE is concentrated in the light product with a content of 242 g/t. As a result of the Knelson experiment, a 2.2 wt% heavy product was recovered with an REE recovery efficiency of 2.9% and REE content of 308 g/t. However, Mozzley table, MGS and Knelson beneficiation experiments showed that there was no effective separation due to the very low content and yields. After the physical enrichment experiments, physicochemical enrichment experiments were carried out. Within the scope of flotation experiments, experiments were carried out using emulsified kerosene 1500 g/t and 2500 g/t prepared with Span80 and Tween 20, keeping parameters such as mixing speed 1000 rpm, natural pH 13.10 constant. In addition, experiments were carried out using 250 g/t MIBC, ısooctanol to examine the effect of frother selection on flotation efficiency. In flotation experiments using kerosene emulsified with Tween20, the highest NTE content was obtained when MIBC was used as a frother with 89% REE recovery and 226 g/t REE content in the sink product. It is understood that the use of frother together with kerosene has a positive effect on flotation efficiency. The effect of acid type, concentration (1 mol/L, 2 mol/L and 3 mol/L) and temperature (20, 50, 90 ⁰C) parameters in direct acid leaching and alkaline pretreatment+acid leaching experiments were investigated. In direct acid leaching experiments, leaching time was selected as 2 hours, solid:liquid ratio as 1:10, and stirring speed as 400 rpm. The acid types to be used in the experiment were HCl, H2SO4 and HNO3, acid concentrations were 0 mol/L, 1 mol/L, 2 mol/L and 3 mol/L, different acid leaching temperatures (20°C, 50°C, 90°C) were tested. Alkaline heat treatment is applied to degrade the aluminosilicate structure to release the REE-containing phases. As a result of the NaOH heat treatment of the fly ash sample, it was observed that the Al203 and SiO2 phases reacted with the sodium structure and the formation of cancrinite occurred. When the XRD analyses of the products entering and leaving the alkali heat treatment were compared, it was seen that especially the glassy phase was disrupted and the expected form was formed as a result of alkali heat treatment, which is a pyrometallurgical process. The alkali heat treatment experiment was carried out at 400 °C for 2 hours using a 1:1 ratio of NaOH:fly ash. In acid leaching experiments applied to alkali heat treatment products, leaching time was 2 hours, stirring speed was 400 rpm and the solid:liquid ratio was 1:10, while the acids used in direct acid leaching were used at similar concentrations and leaching temperatures. As a result of acid leaching experiments applied to the fly ash sample after alkali heat treatment, the highest ∑NTE dissolution efficiency of 94.7% was achieved at 3 mol/L HCl acid concentration and 20 ⁰C leaching temperature. The NTE content in the solid residue was determined as 114 g/t. After the determination of the most suitable experimental conditions as a result of alkali heat treatment + acid leaching, 2 hours was determined as the most suitable leaching time in the experiments carried out to determine the leaching time. For the recovery of NTE from fly ash, a preliminary alkaline heat treatment followed by acid leaching can be recommended instead of direct acid leaching.
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