JPH04131101A - Collection method for sublimable compounds - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for collecting sublimable compounds.

[Conventional technology]

When collecting sublimable compounds, a method is usually adopted in which the airflow containing them is cooled and collected, but when collecting them as a solid, they adhere to the cooling surface and cause problems such as blockage. , resulting in a decrease in cooling capacity.

If the melting point is relatively low, such as phthalic anhydride, a method is adopted in which crystals are actively deposited on the cooling surface, and once a certain amount of crystals have been deposited, the cooling surface is heated to melt the crystals and collect them as a liquid. has been done. In this method, it is necessary to prepare two or more coolers and operate them while switching between them. It is difficult to use this method for materials such as naphthalic anhydride and pyromellitic anhydride, which have high melting points. Publication No. 2-40.203, Japanese Unexamined Patent Publication No. 1983
3-10.790 (Japanese Patent Laid-Open No. 54-79.245), and a method in which an air flow containing the same is guided at a relatively low speed to the cooling surface of a cooler to cause precipitation (Japanese Patent Application Laid-Open No. 1987-79.245).

However, all of these methods have the problem that the apparatus becomes very large. In addition, JP-A-54-79.245 discloses that a hot reaction gas containing pyromellitic anhydride is brought into contact with a solid sphere carried by air, the sphere absorbs heat, and is covered with a sublimating compound. A method of collecting sublimable compounds in this manner has been introduced, but it is said that this method requires mechanically complex equipment.

[Problem to be solved by the invention]

An object of the present invention is to efficiently, continuously, and stably recover a sublimable compound from an air stream containing a sublimable compound gas using a relatively compact device.

[Means to solve the problem]

The present invention involves dispersing and entraining particles made of wear-resistant material in an air flow containing sublimable compound residue, and causing the particles to flow into a cooler, precipitating sublimable compound crystals on the cooling surface of the cooler, and , the particles are collided with the surface of the precipitation to exfoliate the crystals into powder, an air flow containing the particles and the exfoliated crystal powder flows out of the cooler, and is charged into a separator to separate the particles from the air flow. The separated particles are circulated as particles to be dispersed and entrained in the air stream containing the sublimable compound gas, and the air stream containing the crystal powder is charged into a collector to collect the sublimable compound crystals. This is a method for collecting sublimable compounds.

Examples of sublimating compounds include pyromellitic anhydride, phthalic anhydride, naphthalic anhydride, anthraquinone, benzoic acid, maleic anhydride, phenylmaleic anhydride, phenanthrenequinone, and nicotinic acid. There is no restriction as long as it contains these in gaseous form, but preferably it is a reaction product gas obtained by reacting a sublimable compound in a gas phase from a corresponding raw material. Examples of such gas streams include pyromellitic anhydride-containing product gas obtained by catalytic gas phase oxidation of tetraalkylbenzene with an oxygen-containing gas, and phthalic anhydride obtained by catalytic gas-phase oxidation of naphthalene or orthoxylene with an oxygen-containing gas. Examples include a naphthalic anhydride-containing product gas obtained by catalytic gas-phase oxidation of acenaphthene with an oxygen-containing gas, and an anthraquinone-containing product gas obtained by catalytic gas-phase oxidation of anthracene with an oxygen-containing gas. Such airflow is typically 1rrr
Each container contains 10 to 100 g of a sublimable compound, and its temperature is about 250 to 450°C. The speed of the airflow must be such that the particles described below are dispersed and entrained.

The particles dispersed and entrained in this airflow need to be made of wear-resistant material, but they also need to be of a size or mass that allows them to be entrained in the airflow, have a predetermined momentum, and be able to withstand impact. There is.

In this sense, suitable materials for the particles include ceramics such as alumina and aluminosilicate, metals, etc., and a suitable shape is a spherical shape without regular corners. The size of the particles varies depending on their density, but the size is 0.
It is 5 to 5 mm, preferably 1 to 3 mm. If the particles are small, it will be difficult to separate them from the crystal powder of the sublimable compound, and if the particles are large, the speed of the airflow required to disperse and entrain the particles in the airflow will increase, requiring a large amount of energy.

The amount of particles dispersed in the airflow is 0.0005 to lv.

IN, preferably 0. 001~0. A range of 5 volX is preferable; if it is too low, the effect of exfoliating the crystals will be insufficient, and if it is too high, a large amount of energy will be required.

Note that in the step of dispersing the particles in the air stream, the sublimable compound is not substantially precipitated.

The airflow with dispersed and entrained particles is charged into a cooler. The cooler may have a structure that uses a cooling surface to cool the airflow and deposit crystals on the cooling surface, but it is preferable that the cooler has a large cooling area in order to improve cooling efficiency. Further, in order to reduce pressure loss, it is preferable that the cooling surface be arranged substantially parallel to the air flow. As such a cooler, there is a vertical multi-tube heat exchanger in which the refrigerant flows through the shell side, and it is preferable that the air flow be introduced from the lower part of the cooler and flowed out from the upper part. In the cooler, the air stream is cooled until almost all of the sublimable compound is precipitated, and the sublimable compound is precipitated on the cooling surface. At the same time, some of it also precipitates in the airflow. Then, the entrained particles collide with the cooling surface on which the sublimable compound has precipitated, exfoliating the precipitated crystals into powder. The cooled air stream containing the particles and crystal powder exits the cooler.

The exiting air stream is charged to a separator to separate the particles. As this separator, a type such as a cyclone that separates materials based on differences in weight and size is suitable. The relatively light and small crystalline powder of the sublimable compound is entrained in the air stream and further charged into a collector where it is separated. As this collector, a filter type such as a bag filter is suitable. The air flowing out from the collector is cleaned as necessary and then discharged. The crystal powder collected by the collector is recovered as a product. Then, the particles separated by the separator are circulated as particles to be dispersed and entrained in the airflow containing the gas of the sublimable compound. Note that it is natural that the shape, arrangement, etc. of the device used in the collection method of the present invention may change.For example, a separation means may be attached to the top of the cooler,
Both separators may be integrated.

〔Example〕

Example 1 A sublimable compound was collected using the apparatus shown in FIG. In FIG. 1, 1 is a cooler, 2 is a separator, and 3 is a collector. A plurality of tubes 4 are arranged inside the cooler, around which the refrigerant flowing in from the tube 11 and flowing out from the tube 12 is cooled, and the airflow is provided at the bottom. It flows into the mixing part 9, passes through the pipe 4, and flows out from the upper part. The separator is of the cyclone type, and has a charging port communicating with the outlet of the cooler 1 at the top, a particle discharge port communicating with the mixing section 9 at the bottom, and a collector 3 at the top. It has an airflow outlet that communicates with the charging port. The collector is a bag filter and has a crystal powder outlet 6 and an airflow discharge lower.

The air stream 8 containing the sublimable compound gas flows into a mixing section 9 provided at the bottom of the cooler, where it is mixed with wear-resistant particles 5 and flows into the cooler 1 .

Here, the sublimable compound is deposited on the wall surface of the tube 4, peeled off into powder, flows out from the upper part along with the air flow, and is charged into the separator 2. Here, the particles 5 are separated, dropped to the bottom, and sequentially sent to the mixing section 9 for circulation use. Note that a perforated plate 10 through which the particles 5 do not pass is attached to the bottom of the mixing section. The air stream exiting from the top of the separator 2 is charged to a collector 3, where the crystal powder is collected.

A reaction product gas (40 g/n (containing) of naphthalic anhydride) obtained by catalytic gas phase oxidation of acenaphthene was collected as an air stream containing a sublimable compound gas.The conditions were as follows.

Wear-resistant particles Two spherical alumina ball diameter IM, mixing amount 0.2 volX Air flow temperature: Input: 250℃, Output: 150℃ Airflow flow rate:
680 Nrd/hr Cooler: Tube: 25.4mmφX 8.000 ll1
m x 50 shells: 300mmφX 10. C1
00+nm Example 2 A reaction product gas (containing 44 g/m of non-hopyromellitic acid) obtained by catalytic gas phase oxidation of Durene was collected as an air flow containing a gas of a sublimable compound. The conditions are as follows.

Wear-resistant particles Two spherical alumina balls with a diameter of 1 stroke, mixing amount 0.17 volN, air flow temperature for two people, 250°C, output: 150°C Airflow flow rate:
12.5 Nr+f/hr cooler: Tube: 25.4mm
φX5,000mmX 1 shell: 48.6mmφ
In both cases of X6,0OOn+m, the flow rate in the tube of the cooler was 10 to 20 m/sec, and there was no blockage and stable operation was performed. Also, the heat transfer coefficient of the cooling surface is 3
It was almost stable around 0Kcal/rd h °C.

〔Effect of the invention〕

According to the collection method of the present invention, not only can problems such as blockage be almost eliminated, but also a decrease in the heat transfer coefficient can be prevented, and therefore the device can be made smaller.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the apparatus used in the method of the present invention. Explanation of symbols (1)...Cooler, (2)...Separator, (
3)... Collector, (5)... Particles, (8)...
··air current. Patent applicant: Nippon Steel Chemical Co., Ltd.

Claims (3)

[Claims] (1) Particles made of wear-resistant material are dispersed and entrained in an air flow containing sublimable compound gas and flowed into the cooler, and crystals of the sublimable compound are precipitated on the cooling surface of the cooler, and The particles collide with this precipitation surface to exfoliate the crystals into powder, the air flow containing the particles and exfoliated crystal powder flows out of the cooler, and is charged into a separator to separate the particles from the air flow. The separated particles are circulated as particles to be dispersed and entrained in the air stream containing the sublimable compound gas, and the air stream containing the crystal powder is charged into a collector to capture the sublimable compound crystals. 1. A method for collecting sublimable compounds, characterized by collecting them. (2) The method for collecting a sublimable compound according to claim 1, wherein the sublimable compound is phthalic anhydride, naphthalic anhydride, or pyromellitic anhydride. (3) The sublimation property according to claim 1, wherein the air stream containing the gas of the sublimable compound is a reaction product gas obtained by catalytic gas phase oxidation of a raw material consisting of o-xylene, naphthalene, tetraalkylbenzene, acenaphthene, or anthracene. How to collect compounds.