Article pubs.acs.org/IECR
Ecofriendly Cold Ramming Paste for an Aluminum Electrolysis Cell with Furan Resin As a Binder Lin Tian,†,‡ Yang min Zhou,† Gang Xie,*,† Rong xing Li,† and Xiao hua Yu† †
Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, PR China Yunnan Metallurgical Group Co., LTD., Kunming 650224, PR China
‡
ABSTRACT: Cold ramming paste was synthesized with electro-calcined anthracite (ECA) and artificial graphite as an aggregate and furan resin as a binder. Properties of synthesized paste were investigated by Universal Testing Machine, thermogravimetry (TG) and gas chromatography (GC) mass spectrometry (MS). The results show that the synthesized paste is an ecofriendly material and that it has some superior physical properties such as low electrical resistivity, high compressive strength, appropriate sodium penetration, and thermal expansion, all of which can meet industry requirements. The TG curve of the paste can be divided into three stages and the lower heating rate should be used in the second stage. Moreover, the resin functional groups disappear more completely at higher carbonized temperature based on infrared (IR) spectrum analysis.
1. INTRODUCTION Cold ramming paste for aluminum electrolysis cell basically contains a mix of dry aggregate (mainlyelectro-calcined anthracite (ECA) and artificial graphite) and binder (mainly coal tar pitch), which can fill the gaps between and around the cathodic bottom blocks. The paste synthesized using coal tar pitch as a binder can release large amounts of polycyclic aromatic hydrocarbons (PAHs) during the tamping and starting up, some of which are very hazardous to the environment and workers. Highlighting environmental and health concerns, the aluminum industry is confronted with increasing pressure to change this process. So, it is urgent to synthesize a new paste, whose ramming temperature and PAHs, especially genotoxic PAHs, are low. Some scientists have realized this serious problem and have done some research work.1−6 For example, Kvam et al.1 studied coal tar pitch and resin as binders, respectively, to synthesize ramming paste and found that the amount of PAHs decreased obviously using resin as a binder. Paulus and Meseguer4 studied six binders such as coal tar pitch, petroleum pitch, and Novolak resin to synthesize the paste and found paste F (It is unknown what the F is) could offer superior environmental characteristics and good properties. Serge Lacroix5 reported that cold ramming paste was synthesized with coal tar pitch and resin as binders, respectively, and concluded that the toxicity of the paste using resin as a binder was very low. They pointed out a new approach1,4,5 that the paste can be synthesized using resin as a binder. But those synthesized pastes of ramming temperature (35−50 °C) could not have been tamped at room temperature (20 °C), which means that those pastes need to be preheated before ramming, so those pastes will increase energy consumption and affect the properties of tamped paste. Additionally, some properties were not measured such as sodium penetration. Allard et al.6 introduced a new paste called NeO2 and pointed out that the new paste had low hazardous PAHs and a wide temperature window, but some of its properties still need to be improved such as compressive strength during baking. © 2012 American Chemical Society
As is known, the paste is considered to be a key material in the cell with the increase in graphitization degree of carbon blocks,7−9 which is obviously a major concern for any cell. Inferior paste or improper ramming operation could cause shorter cell life or, even worse, early cell failure. So the appropriate properties of synthesized paste must be ensured, when an ecofriendly binder is used. The objective of this research is to synthesize an ecofriendly cold ramming paste of ramming temperature at room temperature with furan resin as a binder. Furthermore, the properties of synthesized paste can meet the industry standards.
2. EXPERIMENTAL SECTION 2.1. Materials. Cold ramming pastes were synthesized with ECA and artificial graphite as aggregate and furan resin as a binder. The typical size distribution of aggregate and basic physical properties of ECA are shown in Tables 1 and 2, respectively. The carbon content of artificial graphite is 98%. Table 1. Typical Particle Size Distribution of Aggregate particle size/mm mass ratio/%
5−3 20.87
3−1 31.49
1−0.074 33.90
