Method of crystallizing sublimating substances

The invention relates to chemical technology and can be used in the processes of purification and separation of naphthalene, anthroquinone, phenanthrene, benzoic and terephthalic acids, naphthols, resorcinol, phthalic anhydride, sulfur, and ₅and other sublimating substances of organic and inorganic synthesis, capable of condensing from the vapor phase to the solid state in the processes of gas purification from these products.

A known method of crystallization of sublimating substances from a vapor-gas stream by cooling the latter in a fluidized bed with a nozzle of inert solid particles of a round shape [1].

The disadvantage of this method is the low productivity, large distribution ¹⁵the course of the refrigerant, the complexity of the regeneration of particles, leading to the complexity of the process.

The purpose of the invention is to increase productivity, reduce refrigerant consumption and simplify the process. _m

This goal is achieved by the fact that according to the known method of crystallization of sublimated substances from a vapor-gas stream by cooling the latter in a fluidized bed with a nozzle of inert solid particles of a rounded shape, cooling is carried out by finely dispersing the refrigerant into the layer until it passes into a vapor state.

Moreover, the particle diameter of the nozzle should be equal to 1 X 10 '³—3 X 10 '³ m, density 6 X 10³ - 10x 10³ kg / m and the fluidization number is 1.5-6.

In addition, water is used as a refrigerant, the flow rate of which is controlled by the temperature of the vapor above the layer.

Example 1. Spend the crystallization of vapors of naphthalene from the vapor-gas stream. For this, air with a flow rate of 20 kg / h, with a concentration of naphthalene 30 X 10 '³ kg / kg air and a temperature of 81 ° C are fed into a fluidized bed condenser desublimator. The layer nozzle is a vapor-shaped fraction of nickel particles with a diameter of 1.8X 10³2.1 x 10³ m. The height of the nozzle layer 4 X 10²m fluidization number 2.2, condensation temperature 38.5 ° C. For cooling, spray water with a temperature of 20 ° C by a pneumatic nozzle. The water flow rate is manually controlled by changing the pressure in the vessel from which water is supplied to the nozzle. The temperature is recorded with a laboratory mercury thermometer located directly above the layer. Water consumption is 0.4 kg / h.⁵

96% of the naphthalene contained in the gas crystallizes in the form of small flakes and is carried into the filter by an air stream. The specific productivity is 12.5 X 10³kg / h of product from 1 m³ layer. ₁₀Particles of the aerosol layer are practically not exposed.

Example 2. In the same way carry out the crystallization of vapors of benzoic acid with a concentration of 80 X 10 '³ kg / kg of air. The temperature of the gas-vapor mixture is 150 ° C; the condensation temperature is 50 ° C. The water consumption is 1.08 kg / h. 98% of the benzoic acid entering the apparatus crystallizes. Specific Productivity 20.8 X 10³ kg / h of product from 1 m³ layer. ₂₀

Example 3. In the same way, crystallization of vapors of phthalic anhydride with a concentration of 30 X 10³ kg / kg air. The temperature of the gas-vapor stream is 145 ° С; the condensation temperature is 50 ° С. Water consumption 0.97 kg / h. Crystallizes 98 ° /₀ ft-25 of the left anhydride contained in the air.

Specific productivity is equal to

12.5 x 10³ kg / h of product from 1 m³ layer, whereas according to the known method it is equal to about 78-100 kg / h of product from 1 m³layer, i.e., more than 100 times less than by the proposed method. In all the examples cited, the particles were not aerosized.

Example 4. In order to show the insufficiency of just replacing the nozzle with a heavier and larger one, the steam-gas stream is cooled first by the known method and then by the proposed method.

For this, 20 kg / h of air containing naphthalene vapors with a concentration of 25 X 10 'are supplied^J kg / kg air and temperature ⁴⁰81 ° C, in a condenser-desublimator with a fluidized bed. Cooling is carried out by means of heat exchange elements with a specific surface area of ​​269 m²/ m³ layer nozzles. The refrigerant is water₄₅Torah is heated from 15 to 25 ° C. In order to provide cooling of the vapor-gas flow to 39 ° C, 20 sections with a fluidized bed with a total height of the nozzle layer of 0.8 m are required. The nozzle is a fraction of spherical nickel particles with a diameter of 1.8 X 10 '³-2.1 X 10 '³m

Water consumption 16 m³/ h During crystallization, 46% of the product settles on the particles, the rest of the crystalline product is taken out into the filter in the form of small cups. The total degree of condensation is 93%. The specific productivity is 723 kg / h with 1 m³ nozzle layer.

The proposed method serves 20 kg / h of air containing vapors of naphthalene with a concentration of 25 X 10 '³ kg / kg of air into a condenser-desublimator with a fluidized bed. The crystallization temperature is 39 ° C. Crystallization is carried out as in example 1. The flow rate of water is 0.4 kg / h, that is, 40 times less than according to the known method. The specific productivity in this case is 10.4X 10³ kg / h, which is 14 times more than in the well-known manual. Therefore, to achieve the objective of the invention, it is necessary to use the particles of the nozzle of the indicated parameters and spray water into the fluidized bed with its complete evaporation.

Thus, the use of the proposed method of crystallization from a gas-vapor stream increases the specific productivity of the packing layer by more than 10 times, reduces the refrigerant consumption by more than 10 times and simplifies the process.