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Diatomite components are used in the design of the thermal insulation for a high-temperature furnace. It is shown that the proposed construction for the heat insulation has an advantage over existing ones.Keywords: thermal insulation, high-temperature furnace, diatomite, foam diatomite brick, thermal conductivity, refractory layer, high-temperature and low-temperature insulation layers, Diatom Corporation.Increasing prices of all forms of energy resource make it particularly important to have energy saving in industrial furnaces. Effective methods of energy saving involve improved thermal insulation (TI), which should be realized also in large heating plants in metallurgy, as well as on lower-power but more numerous flame and electrical furnaces as used in engineering and mechanical repairing undertakings in Russia.The high-temperature furnaces used in engineering processes operate at medium temperatures in the working chamber between 700 and 1000°C, so the TI must have a certain specific aspect. The basic load-bearing wall in a traditional TI is provided by the lining made of firebrick, as most readily available and relatively cheap. The thermal insulation is used as an additional layer between the lining and the sealed body of the furnace to reduce the loss of heat to the environment. The furnace then has a low efficiency (from 15 to 25%), and it takes a long time to reach the working condition (not less than 2 h), with high losses of the heat through the TI into the environment (up to 10% of the thermal power). Periodic repairs (once in 1 -2 years) are laborious and involve considerable expense for refractory and thermal insulation materials.Proposals have been made [1] to optimize the TI parameters in industrial furnaces, which consider the heat transfer through the TI into the environment by thermal conduction in the refractory and insulating layers, together with the heat losses on heating up the TI and the expense in acquiring refractory and thermal insulation materials. No allowance is made for the no less important parameters of the TI materials: mechanical strength and prolonged use at elevated temperatures [2].We consider an example for quantitative evaluation of performance for these proposals in a gas-heated impeller furnace of power 800 kW, which is used in the forging shop at Ul=yanovsk automobile plant for a heat treatment of forgings and castings. The furnace is fitted with a two-layer TI, in which the internal refractory layer on the roof and walls is of thickness 230 mm and made from ShL-1.3 No. 5 insulating firebrick and represents the basic load-bearing structure in the TI, while the heat insulating layer of thickness 114 mm is made of KPD-500 foam diatomite brick. The measured temperature distribution in the TI walls (Fig. 1a ) shows that the main thermal resistance in the TI (not less than 70%) provides the thermal insulation layer, while the temperature level (Fig. 1a ) for its foam diatomite brick has a considerable margin (up to 900°C).The thermal resistance R of the TI in industrial fur...