Study of synthesis processes of heat-insulating silicate materials for external protection of steel oil pipelines

Thermal insulation of steel oil pipelines allows to extend their service life and provide optimal characteristics of the petroleum products transportation. Currently used heat-insulating materials do not meet the requirements of durability and fire safety. Their most promising replacement is porous silicate materials, and one of their main advantages is the possibility to use various types of local raw materials. On the basis of the diatomite of the Chernoyarskoe deposit, the initial batch compositions were developed, their synthesis was carried out by the hydrate foaming mechanism, after which the density of the synthesized samples was determined and their internal structure was studied. The effect of each of the batch components on the intensity of melting and foaming of the initial diatomite was established. It was shown that the introduction of sodium hydroxide lowers the melting point, and the removal of chemically bound water during heating allows to obtain a porous structure. Sodium fluoride, which was introduced as flux, significantly reduces the viscosity of diatomite and, accordingly, the melting point. Using the differential thermal analysis, the physicochemical processes occurring during the thermal treatment of samples were investigated. It was found that mass loss is ensured by the removal of physically and chemically bound water at temperatures of 66.8–75.2 °C and 119.5–124.8 °C, respectively. Moreover, for compositions with the addition of sodium hydroxide, the total amount of bound water reaches 22.99–24.25 % due to the dehydration of sodium hydrosilicates. When processing the batches, observed endothermic effects were corresponded to the evaporation of physically and chemically bound water, and the polymorphic β-quartz → α-quartz transformation at 575 °C. The revealed regularities of the mechanism of diatomaceous raw materials foaming of make it possible to optimize the developed compositions and to obtain high-quality heat-insulating material for pipeline protection. The work was supported by the Russian Science Foundation, Project # 18-19-00455 “Development of integrated protection technology for oil and gas pipelines, operated in the Far East of Russia” within the framework of the 2018 competition “Conducting fundamental scientific research and exploratory scientific research by individual scientific groups”.