Search

High sulfur petroleum cokes were calcined in a high temperature furnace to reduce the sulfur content 9 during the prebaked anode production, and that can be good for reducing environment pollution. The preparation test and performance analysis of anodes were carried out. The ways of injecting the desulfurized coke and its influence on quality of the anode are discussed. The results show that although the high temperature treatment greatly reduces the sulfur content of the high-sulfur petroleum coke, it has a negative effect on the microstructure and properties of the anode, and the desulfurized coke cannot be used to product anode in large quantities. A certain proportion of the desulfurized coke can be used with little effect on the anode properties. The present work can provide a reference for the application of high temperature desulfurized petroleum coke in anode production.

Effects of coke calcination levels on pore structure of carbon anodes have been investigated. Bench anodes were prepared by 3 types of cokes with 4 calcination temperatures (800°C, 900°C, 1000°C and 1100°C). The cokes and anodes were characterized using hydrostatic method, air permeability determination, mercury porosimetry, image analysis and confocal microscopy (CSLM). The cokes with different calcination levels are almost the same in LC values (19–20 A) and real density (1.967–1.985 g/cm3), while the anode containing coke calcined at 900°C has the lowest open porosity and air permeability. Pore size distribution (represented by Anode H sample) can be roughly divided into two ranges: small and medium pores in diameter of 10–400 μm and large pores of 400–580 μm. For the anode containing coke calcined at 800°C, a number of long, narrow pores in the pore size range of 400–580 μm are presented among cokes particles. Formation of these elongated pores may be attributed to coke shrinkages during the anode baking process, which may develop cracking in the anode under cell operations. More small or medium rounded pores with pore size range of 10–400 μm emerge in the anodes with coke calcination temperatures of 900°C, 1000°C and 1100°C, which may be generated due to release of volatiles from the carbon anode during baking. For the anode containing coke calcined at 1100°C, it is found that many rounded pores often closely surround large coke particles, which have potential to form elongated, narrow pores.

Petroleum cokes with different sulfur contents were calcined in a graphitization furnace, and the properties of the calcined cokes, such as real density, sulfur content, carbon lattice and so on, were analyzed. The results show that above 1200 °C, with the increase of calcination temperature, the main factors influencing the desulfurization mechanism, sulfur completely discharge temperature, porosity and the growth rate of the carbon lattice are the thiophene sulfur content and the sulfur side chain hydrocarbon bond proportion difference in petroleum cokes. The higher the sulfur content and the less the thiophene content, the lower the sulfur completely discharging temperature and the slower the growth of the coke lattice.

Three different types of petroleum cokes were studied in the temperature range between 700 and 1100 °C in a laboratory calciner. The properties of the calcined cokes, such as the real density, powder resistivity, Lc value, porosity and so on, were analyzed by SEM, TG, DTG and so on. It was found that the TG and DTG curves of low sulfur, medium sulfur and high sulfur petroleum cokes are quite different. The performance of the calcined coke, the desulfurization rate, the growth of carbon crystal and the porosity have obvious difference with the increase of calcining temperature. These findings can be used as the guidelines for the prebake anode production using these types of petroleum cokes.

The anode with under-calcined cokes have better component homogeneity and smaller carbon consumption in aluminum electrolysis. In this study, three types of petroleum cokes were calcined at 800, 900, 1000 and 1100 °C, respectively. The content of S and volatiles of cokes were measured against the calcining temperature. The air/CO2 reactivity, electrical conductivity, density, porosity, compressive/shear strength of the bench-scale anode sample made by these cokes were optimized as a function of calcining temperatures. In addition, the LC value and real density of cokes were tested to show calcining level of the cokes. Based on the results above, the optimum calcining level of cokes for the prebaked anodes was obtained.

The utilization of coal tar pitch coke as a substitute for petroleum coke in anodes was tested in the lab. The study was conducted in order to (1) find an alternative material to petroleum coke due to its high cost and deteriorating properties, and (2) determine the feasibility of using a current Chinese source of coal tar pitch coke for producing aluminum industry anodes.

Anode forming is one of the most important processes in pre-baked anode production, and most modern plants now use vibro-compactors to produce their green anodes. With a vibro-compactor both vibrating time and vibrating frequency can affect anode quality. Sunstone, the largest anode exporter in China, produces many different sizes of anodes, and therefore has to optimize forming parameters for each anode size produced. In this paper, results are given regarding a technique to optimize vibrating time for green anodes. This method can serve as a guide for any anode plant to determine the proper vibrating time for their anodes and therefore to improve their anode quality.

Shaft calcining technology is widely used in China for the calcination of green petroleum coke. It has the advantages of lower energy consumption and lower carbon burning loss compared to the rotary kilns. In this paper, a method of further reducing carbon burning loss using integrated technology is discussed.