RU45137U1 - TUBULAR FURNACE FURNACE - Google Patents

Abstract

The invention relates to tube furnaces used in the refining and petrochemical industries for heating and thermal decomposition of hydrocarbons and other products. The aim of the present invention is the intensification of heat transfer in a flameless combustion furnace, which is achieved by the fact that the surfaces of the radiating walls and coils are coated with compositions with a high degree of blackness at operating temperatures. Special coatings based on aluminosilicates and metal oxides with a degree of blackness of 0.9-0.95 have been developed.

Description

The invention relates to the refining and petrochemical industries, and more particularly to tube furnaces for heating and thermal decomposition of hydrocarbons and other products.

In the oil refining and petrochemical industries, tube furnaces are widely used for heating and chemical transformations of various raw materials [1, 2]. The most effective of them are flameless combustion furnaces with heat transfer from red-hot walls to a food coil [1, 2, 3]. The side walls of such furnaces are assembled from several rows of flameless burners of various types [1-3]. Due to the large surface of the radiating walls, satisfactory levels of radiation heat transfer and acceptable dimensions of the furnaces were achieved.

According to the Stefan-Boltzmann law, the intensity of radiant heat transfer between radiating and absorbing surfaces is proportional to the difference of the fourth degrees of temperature and the degree of blackness of these surfaces. Thus, the intensity of radiant heat transfer can be changed by artificially increasing or decreasing the degree of blackness of the heat exchange surfaces.

The aim of the present invention is to intensify heat transfer in a flameless combustion furnace by changing the degree of blackness of both the radiating walls and the product coil.

Special studies found that with increasing temperature, the blackness of all refractory materials decreases and in the temperature range 800-1000 ° C it is 0.5-0.7 (ε = 0.5-0.7). Approximately the same ε value is also observed for metal pipes, which are coated with a thin layer of metal oxides during operation. In the same time

the blackness of some materials based on metal oxides increases with increasing temperature and reaches ε = 0.9-0.95.

Using these scientific premises, a high-temperature tube furnace with an artificial increase in the degree of blackness of radiating walls and tubular coils is proposed. Special coatings based on aluminosilicates modified with metal oxides have been developed.

The goal (intensification of heat transfer in the radiation chamber of the furnace) is achieved by the fact that the surfaces of the radiating walls and coils are coated with compositions with a high degree of blackness at operating temperatures.

The flameless tube furnace consists of a convection zone 1 and a radiation chamber 2, the side walls of which are made of several rows of radiation burners 3. The surface of the ceramic blocks of the burners forming the radiation chamber is covered with a layer of material 4 with a high degree of blackness. Fuel combustion occurs on this blackened surface. Ceramics are heated depending on the operating mode of the furnace up to 800-1100 ° С. Heat, mainly radiation, is transferred to the food coil 5, which is also coated with a special composition with a high degree of blackness. Blackening of radiating walls and coils can be carried out in furnaces for various purposes.

The heated product is fed into the coil of the convection zone, where it is preheated and enters the radiation coil. As indicated, heat is transferred to it from the radiating walls. The fuel is hydrocarbon gas of any composition. In a radiation coil, the product is heated to the required temperature. For example, if it is a furnace for pyrolysis of hydrocarbons into olefins, then the temperature of the outgoing pyrogas is 800-870 ° C.

An artificial increase in the degree of blackness intensifies heat transfer, which leads to an increase in the efficiency of the furnace and fuel economy. The experiments showed that fuel economy reaches 10%. In addition, the developed coatings have high mechanical strength, and applying them to ceramic surfaces significantly increases the service life of the latter.

Coatings of refractory metals applied to the surface of the coil form a thermally and mechanically strong film chemically bonded to the metal, which significantly reduces the corrosion of the metal. The service life of the coil increases by 1.5-2.5 times.

Thus, the use in furnaces of mechanically and thermally durable coatings with a high degree of blackness gives a large economic effect.

LIST OF LINKS

1. Bakhshiyan Ts.A. Tubular furnaces with radiating furnace walls. - M .: GOSINTI, 1960 .-- 192 p.

2. Mukhina T.N., Drum N.L. et al. Pyrolysis of hydrocarbons. - M.: Chemistry, 1987 .-- 240 p.

3. Sulzhik N.I., Stepanov A.V. Resource conservation in petrochemical industries. - Kiev: Nora-print, 2000 .-- 340 p.

Claims (1)

A flameless tube furnace, which contains a convection zone and a radiation chamber, has a food coil installed inside the latter, which differs in that the radiating walls and the surface of the food coil are coated with substances based on aluminosilicates modified with metal oxides with a high degree of blackness at operating temperatures.