Abstract
Deep rock is always under high-temperature conditions. However, traditional coring methods generally have no thermal insulation design, which introduces large deviations in the guidance required for resource mining. Thus, a thermal insulation design that utilizes active and passive thermal insulation was proposed for deep rock corers. The rationale behind the active thermal insulation scheme was to maintain the in situ core temperature through electric heating that was controlled by using a proportional-integral-derivative (PID) chip. Graphene heating material could be used as a heating material for active thermal insulation through testing. In regard to the passive thermal insulation scheme, we conducted insulation and microscopic and insulation effectiveness tests for hollow glass microsphere (HGM) composites and SiO2 aerogels. Results showed that the #1 HGM composite (C1) had an excellent thermal insulation performance (3 mm thick C1 can insulate to 82.6°C), high reflectivity (90.02%), and wide applicability. Therefore, C1 could be used as a passive insulation material in deep rock corers. Moreover, a heat transfer model that considered multiple heat dissipation surfaces was established, which can provide theoretical guidance for engineering applications. Finally, a verification test of the integrated active and passive thermal insulation system (graphene heating material and C1) was carried out. Results showed that the insulating effect could be increased by 13.3%; thus, the feasibility of the integrated thermal insulation system was verified. The abovementioned design scheme and test results provide research basis and guidance for the development of thermally insulated deep rock coring equipment.
Highlights
Deep mining has become more common owing to the exhaustion of shallow mineral resources [1], and many disasters have occurred in deep engineering [2]
Coal mining that gradually develops deeper is affected by temperature. erefore, many scholars have conducted research on the mechanical characteristics of coal, the gas adsorption/desorption behavior, and the seepage laws influenced by temperature
A deep rock corer that retains the insitu temperature of the core consists of active and passive thermal insulation
Summary
Deep mining has become more common owing to the exhaustion of shallow mineral resources [1], and many disasters have occurred in deep engineering [2]. Erefore, as the temperature increases, the mechanical characteristics of coal, the gas adsorption/ desorption behavior, and the seepage laws will change. Taking these properties of rock at a normal temperature as the properties of deep rock will introduce large deviations to the deep engineering. The insulation measures of the abovementioned corers are passive thermal insulation (reducing the heat dissipation of the core), and no active thermal insulation measures are taken (retaining the in situ temperature), thereby resulting in the core temperature still decreasing It is very different from thermal insulation measures of seafloor sediments, where deep rock is always under high-temperature conditions. A verification test was carried out on the combination of the graphene heating material and C1, as an integrated active and passive thermal insulation system. us, the feasibility and superiority of the thermal insulation scheme for coring technology were verified
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