RU2533713C1 - Reactor for ammoniation of acids - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: reactor consists of a body, a reaction pipe entering it, acid feeding branch pipes, an ammonia feeding branch pipe set on the body, and a product withdrawing branch pipe. The ratio of free areas of the body and of the reaction pipe accounts for 1:1-0.5. The reaction pipe is of split type with telescopic joint of the parts fixed at the flanges which are set at the body end faces. The thickness of reaction pipe walls is by 8-10 times less than the thickness of the body walls. Nozzles for ammonia entering the reaction pipe are provided in the zone of acid feeding branch pipes on the reaction pipe wall. The diameter of the product withdrawing branch pipe accounts for 0.5-0.8 of the reaction pipe diameter.

EFFECT: simplified design and reduced metal consumption of a reactor, improved operating conditions.

3 cl, 1 dwg

Description

The invention relates to equipment used in the production of phosphorus-containing fertilizers. The main production stage is the acid ammonization stage, where pulp formation of phosphates and / or ammonium sulfates takes place.

In modern technologies for the production of phosphates and / or ammonium sulfates, various reactor designs are used without mechanical mixing of the components. The most common are tubular reactors in which the reactants are mixed and reacted to form a pulp of phosphates and / or ammonium sulfates, an intermediate product for the production of mineral fertilizers.

Thus, a tubular reactor is known, which is a horizontal or vertical pipe with nozzles for introducing acids and ammonia, moreover, to ensure an intensive hydrodynamic regime, the length of the reaction zone of the tubular reactor, starting from the ammonia injection site, for reliable implementation of the ammonization reaction taking into account possible fluctuations in flow rates and concentrations reagents should be 20-30 diameters. This is confirmed by the experience of its operation (Chemical and oil and gas engineering №11 / 2008, p.11).

In the author's certificate of the USSR No. 1084054, cl. B01F 3/04, publ. in 1984, a reactor was described that contains a housing with a nozzle coaxially located in it; nozzles for input and output of components; a washer is installed in the housing perpendicular to the axis with the intake nozzles fixed on it, on the one hand, 0.3–1 mm in length at a distance 0.2-0.3 diameters from its axis, their free ends are directed towards the nozzle, and on the other hand, a multi-helical spiral blade device. In this design, significant sticking of the pulp to the nozzle is possible, therefore, it is effective only for solutions.

A TP-200 tubular reactor with an inner diameter of 200 mm in diameter, tangentially located with an acid inlet and coaxial to the body with an ammonia nozzle ending in a perforated distributor (200 radial openings with a diameter of 200 mm) has been in operation for a long time. Inside the distributor there is a double-entry paddle auger designed for intensive spinning of ammonia jets. The effect of intensification of the mixing of ammonia and EPA increases with increasing load. The complexity of manufacturing, the relatively low productivity and a significant breakthrough of ammonia do not allow us to recommend this reactor for new industries (Chemical and oil and gas engineering No. 11/2008, p.12).

Also known is a tubular reactor for producing a pulp of ammonium phosphates, including a housing with a coaxially arranged device for supplying ammonia, a pipe for supplying acid, and a nozzle for leaving the pulp located at the end of the body, in which the device for feeding ammonia is made in the form of a pipe with installed at the end of the dispenser. Part of the distributor is provided with an external thread and connected to the ammonia supply pipe, and the part not included in the pipe is perforated with holes whose length is at least two hole diameters, and the angle of inclination of the axes of the holes to the axis of the reactor is 45-90 ° towards the pulp exit nozzle from the housing (RF patent No. 2360729, class B01F 3/04, publ. 07/10/2009).

All of the described reactors have one common drawback. Due to the fact that the reaction zone is in the housing, a corrosion-resistant material is required for the manufacture of the entire structure. Given the high pressure, the metal consumption of this design is very significant.

In this regard, as a prototype, we chose the reactor described in US patent No. 3954942, C05B 7/00, publ. 05/04/1976 This patent was granted for a method for the production of fertilizers from phosphoric and sulfuric acids, liquid or gaseous ammonia, but it contains a reactor in which they interact.

The acid ammonization reactor includes a cylindrical case made of black steel, inside which a reaction tube made of high alloy steel is installed. The annular cavity of the body from the ends is closed with plugs welded to the body and the reaction tube. The casing has ammonia inlet and outlet pipes, and the casing outlet pipe is connected to the inlet pipe of the reaction pipe and is located outside the casing. Acid feed pipes are also located on the reaction tube.

The advantage of this design is that ammonia, passing inside the case along the reaction tube, is heated and partially evaporated, which allows it to react with acids immediately after contact with them, thereby reducing the breakdown of unreacted ammonia from the reactor.

The disadvantage of this design is that the reaction tube is made whole, and since its end sections extending beyond the body are subject only to internal pressure, this tube should be thick-walled, i.e. metal consumption of this design in comparison with the known does not decrease. In addition, the construction is cumbersome (the presence of an external pipe for the flow of ammonia from the body into the central pipe) and is non-separable, i.e. non-repairable, which complicates its operation.

The objective of the invention was to simplify the design by reducing the metal consumption of the reactor and improving its operating conditions.

For this purpose, a reactor design is proposed, including a thick-walled case made of unalloyed steel, inside of which there is a thin-walled reaction tube that does not extend beyond the reactor body and is made of high-alloy steel. The body has only a nozzle for introducing ammonia, which enters the reaction tube through calibrated dies located on its wall. The housing at the ends is closed with removable flanges. The reaction tube consists of two parts telescopically connected to each other, which compensates for the uneven elongation of the body and the reaction pipe made of various materials. On one of the flanges, a pipe for introducing acids and a part of the reaction tube with dies are welded, on the other, a second part of the reaction tube and a thick-walled pipe for the exit of reaction products, and the weld between this pipe and the second part of the reaction pipe is located inside the body.

The pressure inside and outside the reaction tube is the same, which allows you to transfer the force from the reaction pressure to a thick-walled case made of cheaper material, i.e. make the reaction tube of high alloy steel and make the reactor less metal-intensive. The design of the reactor allows to reduce its cost and increase reliability due to the possibility of monitoring the condition and repair of a collapsible structure.

Figure 1 shows a longitudinal section of the proposed reactor.

The reactor includes the following elements: 1 - pipe for introducing acid into the reaction tube; 2 - flanges with gaskets sealing the reactor vessel; 3 - thick-walled housing made of a material resistant to corrosion; 4 - a pipe for introducing ammonia into the reactor vessel; 5 - pipe outlet of the product from the reactor; 6 - thin-walled reaction tube made of highly alloyed corrosion-resistant steel; 7 - nozzles of ammonia.

The reactor operates as follows: in the reactor vessel (3), equipped with flanges with gaskets (2), ammonia enters through the pipe (4), which is distributed over the annular section and through the nozzles (7) enters the reaction pipe (6), where through the pipe (1) acid is supplied. The reaction products are removed from the reactor through the pipe (5).

Parts of the reaction tube are connected telescopically. This design allows you to make the reactor collapsible, i.e. maintainable. In the proposed reactor, nozzles for introducing ammonia into the reaction tube are located near the junction of its two parts.

To exclude the possibility of reaction products entering the reactor vessel, the cross section of these nozzles should be less than the cross section of the annular zone between the vessel and the reaction tube. The cross section of the gap between the two parts of the reaction tube should be 10-15 times less than the nozzle section. If this ratio is less than 10, then the reaction products can enter through the gap into the reactor vessel and come into contact with its wall, which will lead to corrosion and loss of operability of the reactor. When the ratio of the cross sections is more than 15, the assembly of the reactor is complicated.

The ratio of free sections of the body and the reaction tube is 1: 1 ÷ 0.5. With a decrease in the cross section of the casing relative to the cross section of the reaction tube, the resistance increases, which leads to an increase in pressure in the reactor, i.e. it is not energetically profitable, with an increase in the free cross section of the vessel, the dimensions of the reactor increase, which, given the thickness of the vessel (4.5–9 mm), increases its material consumption. In the prototype, for example, this ratio is 4.6: 1.

The ratio of the diameters of the reaction tube and the outlet pipe of the product is 1: 0.8 ÷ 0.5. With an increase in the diameter of the nozzle over the specified ratio, mixing in the reactor deteriorates, which leads to a breakthrough of unreacted ammonia, and when it decreases below the specified limit, the pressure increases, i.e. it is not energetically beneficial. In the prototype, this ratio is 1: 1.

The length of the part of the reaction tube with nozzles is selected constructively and is 1.5–2 times the length of the part of the acid inlet pipe entering the inside of the reaction tube. With a decrease in the length of this part of the reaction tube, the zone of effective mixing of the reagents decreases, which leads to an overflow of ammonia; with an increase in the length of this part of the reaction tube, the length of the reactor increases.

Since the pressure in the reactor is the same on both sides of the reaction pipe, it is made with a wall thickness that is 8-10 times less than the wall thickness of the vessel, which allows using alloy steel (for example, EI 460) to reduce the cost of the reaction pipe, and therefore the entire reactor 2 - 2.5 times without reducing the time between overhauls. In the prototype, the thickness of the body and the reaction tube are the same, because both are under internal pressure.

Claims (3)

1. The reactor for the ammonization of acids, consisting of a body, a reaction pipe entering it, acid supply pipes, an ammonia input pipe installed on the body, and a product output pipe, characterized in that the ratio of free sections of the body and the reaction pipe is 1: 1 ÷ 0.5, the reaction tube is detachable with telescopic connection of the parts mounted on flanges mounted at the ends of the body, the wall thickness of the reaction pipe being 8-10 times less than the wall thickness of the body, in the area of the acid inlet pipe on the wall p promotional tubes are arranged nozzles for the passage of ammonia to the reaction tube, and the product exit tube diameter is 0.5-0.8 reaction tube diameter. 2. The reactor according to claim 1, characterized in that the cross section of the gap of the connection of the parts of the reaction tube is 10-15 times smaller than the nozzle section. 3. The reactor according to claim 1, characterized in that the length of the portion of the reaction tube with nozzles is 1.5-2 the length of the portion of the acid feed pipe entering the inside of the reaction tube.

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