No abstract

A technology system of copper slag thermal energy recovery and direct reduction (TER-DR) was proposed in this paper. The effects of CaO addition and C/O on the reduction characteristics were discussed. CaO can improve the reduction reaction of 2FeO•SiO 2 in copper slag and decreases the Gibbs free energy significantly. Besides, CaO improves the reduction mass loss (RML) and reduction rate, and peaks of the DTG curves move to lower temperature. The temperature of the DTG peaks decreases by 54 K. CaO decreases the activation energy. When CaO/S is 0.3, copper slag has the highest RML and reduction rate and lowest activation energy. Furthermore, with an increase of the biochar addition ratio, values of RML and DTG peaks increased sharply. On the basis of Coats−Redfern method, reaction kinetics copper slag reduction is acquired: 960−1478 K, C and [O] diffusion in copper slag is the reaction rate-controlling step; 1478−1703 K, chemical reaction rate of C and CO with [O] in copper slag is the rate-controlling step. Mechanism function does not change with the variation of CaO/S and C/O in experiments. Without CaO addition, CO 2 is difficult to be produced; when CaO is added, reduction of the 2FeO• SiO 2 rate is improved. CaO•SiO 2 , CO 2 , and CO will be produced together.

Re-crosslinkable preformed particle gel (RPPG) is a newly developed conformance control agent that can reassemble as an integrity after swelling in water. However, the RPPG has the potential to plug the injection facilities or wellbore if a treatment is not properly designed. This study focuses on selecting and evaluating the oxidizing breakers that can effectively degrade the RPPG. Bottle tests were conducted by immersing the re-crosslinked RPPG in the breaker solutions. The RPPG weight change was measured with time to analyze the breaking process. Four types of oxidizing breakers, NaClO, Ca­(ClO)2, heat-activated Na2S2O8, and NaOH-activated Na2S2O8 were examined. The effect of factors, including breaker concentration, temperature, RPPG concentration on the gel breaking rate and completeness, was investigated. According to the results, three of the breakers were proven effective, excluding the Ca­(ClO)2, which impaired the breaking process by generating a compact cover on the surface of RPPG. The NaOH-activated Na2S2O8 was the most effective breaker benefitting from its wide practical temperature range and effectiveness at the conditions of low breaker concentration or high RPPG concentration. More generally, the RPPG breaking was faster and more complete with a higher breaker concentration or a higher temperature. However, the increment of the RPPG concentration significantly increased the breaking time and the percentage of residue weight to the RPPG original weight.

No abstract