Assessment of Industrial Modules to Design a GFMA Process for Cyanide Recovery Based on a Phenomenological Model

Abstract

Cyanide recovery in the gold-mining industry is a crucial step in terms of the cost of operation. Currently, a process such as AVR (acidification, volatilization and recycling), based on packed towers for stripping and absorption stages, addresses this issue with high levels of investment and operational costs. Gas-filled membrane absorption (GFMA) emerges then as an attractive alternative because the stripping and absorption stages can be performed in a single stage, reducing associated investment and operational costs. Despite the advantages of this technology, applications at industrial scale are still emerging. A possible reason is the lack of clear scaling-up methodologies where experimental data can be taken to select the optimum industrial hollow-fiber membrane contactor module (HFMC). The present study proposes a methodology to select adequately between available industrial Liqui-Cel TM modules to design a process under optimal operational conditions. The methodology is based on a phenomenological model developed for recovering cyanide by using the GFMA process. Simulation of the Liqui-Cel TM industrial membrane modules employed to recover cyanide in the GFMA process, both in a batch arrangement with a feed-flow rate, and in the range 10-125 m 3 /h, showed that in terms of cyanide recovery there are no differences between the modules tested when they work at the same feed-flow rate. The design criteria to scale-up was determined: to ensure performance at different scales, the length of the transfer unit (HTU) should be kept at different capacities of HFMC modules that comprise the equipment characteristics (mass-transfer area, stream velocities, and mass-transfer coefficient values). Additionally, the number of commercial modules Liqui-Cel TM required to treat 57 m 3 /h and 250 m 3 /h ensuring a cyanide recovery of 95% was also determined. Finally, the most profitable option (lower pressure drop and module cost) resulted in the use of the 14 × 40 Liqui-Cel TM module.

An Experimental Study of Membrane Contactor Modules for Recovering Cyanide through a Gas Membrane Process

“…Here, these steps are undertaken separately. These advantages have promoted the study of this technology for cyanide recovery in gold mining [8][9][10][11][12] as an alternative to the conventional method based on packed towers for both stripping and absorption stages, namely the AVR (acidification, volatilization and recycling) process [13]. In fact, the GFMA process has an additional advantage with respect to the AVR technology, related to safety management.…”

“…In the AVR process, there is a gas-flow of air containing HCN which forces the inclusion of a complex and redundant control system. By contrast, the GFMA process encloses the gaseous HCN inside the pores of the membrane, limiting the risks of HCN leaking [8,10,12].…”

“…This is because scaling-up results obtained from the laboratory scale towards an industrial case lack an experimental and theoretical methodology. Possible causes are: the high quantity of types of membrane contactor modules and their respective mass-transfer correlations [11], differences between the traditional industrial modules available and modules used at laboratory scale [12], and variability of the real solution characteristics. In a previous work, a methodology to scale-up the GFMA process, based on a phenomenological model, was developed [12].…”

“…Possible causes are: the high quantity of types of membrane contactor modules and their respective mass-transfer correlations [11], differences between the traditional industrial modules available and modules used at laboratory scale [12], and variability of the real solution characteristics. In a previous work, a methodology to scale-up the GFMA process, based on a phenomenological model, was developed [12]. This study proposed that the mass-transfer coefficient must be estimated to obtain the overall mass-transfer coefficient.…”

Special Issue on “Membrane Materials, Performance and Processes”

“…On the same application, Arias et al [4] used a nonlinear mathematical programming (NLP) to simulate and optimise membrane configuration and operation conditions. In another application, Estay et al [5] studied cyanide recovery from gold mining industries, an important environmental application, focusing on industrial hollow fiber membrane contactor module. All these reports considered the engineering economics, an important assessment for the deployment of membranes in industrial applications.…”