Numerical Study of CH4 Generation and Transport in XLPE-Insulated Cables in Continuous Vulcanization

Abstract

In this work, we apply a computational diffusion model based on Fick’s laws to study the generation and transport of methane (CH 4 ) during the production of a cross-linked polyethylene (XLPE) insulated cable. The model takes into account the heating process in a curing tube where most of the cross-linking reaction occurs and the subsequent two-stage cooling process, with water and air as the cooling media. For the calculation of CH 4 generation, the model considers the effect of temperature on the cross-linking reaction selectivity. The cross-linking reaction selectivity is a measure of the preference of cumyloxy to proceed either with a hydrogen abstraction reaction, which produces cumyl alcohol, or with a β -scission reaction, which produces acetophenone and CH 4 . The simulation results show that, during cable production, a significant amount of CH 4 is generated in the XLPE layer, which diffuses out of the cable and into the conductor part of the cable. Therefore, the diffusion pattern becomes a non-uniform radial distribution of CH 4 at the cable take-up point, which corresponds well with existing experimental data. Using the model, we perform a series of parametric studies to determine the effect of the cable production conditions, such as the curing temperature, line speed, and cooling water flow rate, on CH 4 generation and transport during cable production. The results show that the curing temperature has the largest impact on the amount of CH 4 generated and its distribution within the cable. We found that under similar curing and cooling conditions, varying the line speed induces a notable effect on the CH 4 transport within the cable, while the cooling water flow rate had no significant impact.