RU2266779C2 - Catalytic reactor wit a vertical shelf-type head for the high-heat processes of the chemical synthesis - Google Patents

Abstract

FIELD: chemical industry; devices used in the high-heat processes of the chemical synthesis.

SUBSTANCE: the invention is pertaining to the field of chemical industry, in particular, to the devices used in the high-heat processes of the chemical synthesis. The catalytic reactor contains a high-pressure body, a support plate, a cover, elements of binding, a vertical shelf-type head with fire-grates, which are filled with the solid catalytic agent, and after each grate along the run of the reactionary gases inside the self-type head place a heat exchanger working on the different heat transfer medium. According to the first version in the capacity of the heat exchanger use a module-type heat exchange device consisting of three shells - an external shell, an internal shell and a separating shell in series inserted in each other with a backlash and hermetically fixed to the support plate of the section and the cover. The internal and external shells are hermetically fixed to the cover. The internal shell has an inserted rod acting as a mount of the shelf and simultaneously as an intensifier of a heat exchanging process. At that on the side surface of the rod there is an artificial macro-roughness. According to the second version in the capacity of heat exchangers they use several single type module heat exchange devices with individual elements of settings. The given engineering solution allows to improve characteristics of the heat-exchange.

EFFECT: the invention allows to improve characteristics of the heat-exchange process of the chemical synthesis.

4 cl, 5 dwg

Description

The invention relates to the field of chemical engineering, and specifically to reactors (columns) of catalytic synthesis. It is recommended to use it when creating new or upgrading existing reactors with a vertical shelf nozzle to produce various hydrocarbons, alcohols, ethers, ammonia and other substances from synthesis gas at pressures up to 35.0 MPa and temperatures up to 450 ° С. The preferred use of the invention is reactors with high heat and high synthesis temperatures. These include, for example, reactors:

- single-stage synthesis of dimethyl ether (DME) at pressures from 5.0 to 12.0 MPa and temperatures from 250 to 300 ° C;

- synthesis of gasoline from gas-vapor mixtures containing DME at pressures from 3.0 to 10.0 MPa and temperatures from 320 to 400 ° C.

For the indicated region of synthesis parameters, gas-phase multiband reactors of a vertical (column) and horizontal type with a fixed catalyst are most suitable. The catalyst is loaded in the form of a sprinkling of grains, granules, tablets on shelves or in boxes. Reaction gases (unreacted synthesis gas together with gas-phase synthesis products) are cooled between the shelves in the heat exchangers. Cold synthesis gas, extraneous gas, but mainly water (distillate) or high-temperature coolants can be used as the primary heat carrier in these heat exchangers. The primary heat carrier usually circulates in a closed circuit, transferring the heat received to the secondary heat carrier in external heat exchange devices (boilers - heat recovery units, etc.).

A typical circuit design of a vertical synthesis column with water heat exchangers built between the shelves is presented, in particular, in the book: MM Karaev et al. Synthetic methanol technology, Moscow, Chemistry, 1984, p.118.

The disadvantages of this reactor are significantly lower heat transfer coefficients from the reaction gases to the heat exchanger wall than the heat transfer coefficients from the wall of the heat exchanger to the heat carrier, which causes problems in regulating the heat transfer mode, in development and commissioning, etc.

Closest to the proposed catalytic reactor is a catalytic reactor with a vertical shelf nozzle for heat-intensive chemical synthesis processes, comprising a high-pressure housing, a base plate, a cover, strapping elements, on which the solid catalyst is poured onto the grate of the shelf nozzle, and after each grate along the reaction gases they have a heat exchanger operating on a foreign coolant and placed inside the shelf nozzle (SU 662134 A1, 05/15/1971).

The disadvantages of this reactor include low heat transfer characteristics, as well as difficulties encountered during assembly and disassembly of the device.

The technical result achieved by the implementation of the claimed invention is to improve the heat transfer characteristics, to provide the possibility of its regulation due to the presence of a removable pin and a change in the flow of extraneous coolant, as well as to simplify the assembly and dismantling of the reactor.

The specified technical result is achieved by the fact that in a catalytic reactor with a vertical shelf nozzle for heat-intensive chemical synthesis processes containing a high-pressure housing, a base plate, a cover, strapping elements, a solid catalyst is poured onto the grate of the shelf nozzle, and after each grate along the reaction gases have a heat exchanger operating on an extraneous coolant and placed inside the shelf nozzle, according to the invention the shelf nozzle is made of the same type sections, tightly fastened to each other and including a base plate, housing, shelf, consisting of a grate and a glass with a lid, while a heat exchanger uses a modular heat exchanger consisting of three shells - external, internal and separation, with the gap of the sections sequentially inserted into each other and tightly fastened to the base plate, and the cover, with which the inner and outer shells are hermetically fastened, and a pin acting as an element is inserted into the inner shell repleniya shelves intensifier and simultaneously the heat exchange process, while on the side surface of the pin is formed PU macroroughness.

Preferably, the shelf nozzle is mounted on a reactor support plate, through which all inlets and outlets are carried out, except for supplying the main flow of synthesis gas made in the reactor lid.

The specified technical result is also achieved by the fact that in a catalytic reactor with a vertical shelf nozzle for heat-intensive chemical synthesis processes containing a high-pressure housing, a base plate, a cover, strapping elements, a solid catalyst is poured onto the grate of the shelf nozzle, and after each grate along the way reaction gases have several heat exchangers operating on an external coolant and placed inside the shelf nozzle, according to the invention, the shelf nozzle it is made up of the same type of sections, hermetically fastened to each other and including a base plate, a housing, a shelf consisting of a grate and a glass with a lid, while the same type of heat exchangers use the same type of modular heat exchangers with individual settings, consisting of internal and separation shells, with a gap of sequentially inserted into each other and tightly fastened sections with a base plate, a pin is inserted into the inner shell, which acts as a fastening element for the shelf and at the same time an intensifier of the heat transfer process, and on the lateral surface of the pin an artificial macro-roughness is made, while the heat exchangers have a common outer shell and a cover.

Preferably, the shelf nozzle is mounted on a reactor support plate, through which all inlets and outlets are carried out, except for supplying the main flow of synthesis gas made in the reactor lid.

The invention is illustrated by drawings, where figure 1 shows the main view of the reactor with one MTU in the section; figure 2 is a main view of a typical section of the shelf nozzle; figure 3 - remote element A fragment of a typical section; figure 4 - remote element B of a fragment of a typical section; figure 5 is a variant of a section of a large-capacity reactor with several MTU.

The catalytic reactor (Fig. 1) consists of a high-pressure vessel 1, hermetically fastened to a base plate 2 and a cover 3. The internal volume of the vessel is occupied by a nozzle consisting of sections of the same type 4, which are sequentially and hermetically joined to each other. The lower section is mounted on the plate 2, for which a prefix adapter 5 is welded to the plate. A cover 6 is docked to the upper section, on which a removable glass 7 is fixed, with which it is docked with the cover 3.

In plate 2, through holes are made coaxially with which fittings, pipelines, pipes for supplying and discharging a heat carrier to each section, supplying cold synthesis gas, removing synthesis products, outputting various cables and pipelines from control system sensors, etc. are welded to it.

The cover 3 has a through central hole, coaxially with which a synthesis gas supply pipe and a docking cup 8 are welded to it.

The assembly sequence of the reactor is as follows:

(1) to the plate 2 through the spacer adapter 5 hermetically dock the lower section using a flange connector;

(2) next sections are sequentially docked to the lower section, the corresponding piping is mounted, namely, the coolant inlet and outlet pipelines, the cables of the measuring sensors, the sensors themselves, etc. (the number of sections can reach 10 pcs. or more);

(3) the cover 6 is docked to the uppermost section;

(4) on the plate 2 install the housing 1 and tightly fasten with it;

(5) using a special device, the glass 7 is aligned with the housing 1 and mounted on the lid 6;

(6) the lid 3 is hermetically docked to the body 1, while the glass 8 with a guaranteed clearance enters the glass 7.

Sealing of detachable joints is carried out using seals. Dismantling is carried out in the reverse order. For reliable operation, all pipelines located inside the housing 1 are mounted by welding. When disassembling, cutting is used, and when reassembling, mounting adapter sleeves are used.

Each section of the shelf nozzle 4 consists (see FIG. 2) of the base plate 9, to which the housing 10, MTU, the shelf, the catalyst bed 11, the perforated top cover 12, and the shelf fastening elements are welded. MTU consists of three cylindrical shells - external 13, internal 14, separation 15, inserted with a gap into each other. The gap can be maintained using noodles, wire, fins, etc. Inside the shell 14, a fixing pin 16 is inserted, which is part of the section assembly, and functionally also in the MTU, which acts as a filler and a gas flow turbulizer and forms an intense heat exchange zone. The shells 13, 14 and 15 are welded to the plate 9, in addition, the cover 17 is welded to the shells 13 and 14.

The shelf consists of a grate 18, a mesh 19, a glass 20 with a bottom 21. The grid 18 and a bottom 21 are welded to the glass 20, and the mesh 19 is supported on the grid 18 and tacked to it by spot welding or soldering. The housing 10 has an external thermal insulation 22, closed by a cover 23.

The shelf fastening elements are pin 16, nut 24, lock nut 25, cap 26, which acts as a gas distribution grill and compensator. A mesh 19 is installed between the perforated cover 12 and the catalyst bed 11. The cover 12 and the mesh 19 prevent the precipitation of the catalyst (especially small) during transportation and installation of the section. In some cases, these details in the design may not be used.

In the plate 9, the channels for supplying and discharging the coolant are made, together with the MTU parts, the elements of the plate 9 form the collectors for collecting and distributing the coolant. Coaxial with the bypass channels to the plate through the elbows are welded pipelines necessary for the installation of MTU strapping. Plate 9 is also used for mounting various sensors of the reactor monitoring and control system (thermocouples, pressure sensors, etc.).

During the operation of the reactor, the main flow of synthesis gas enters into it through a pipe in the cover 3.

A small part of the consumption of synthesis gas (up to 10%), previously cooled outside the reactor to 50 ... 100 ° C, enters the reactor through a fitting in the plate 2. Cold synthesis gas fills the gap between the nozzle and the high-pressure housing 1, providing it cooling and pressurizing the internal cavity of the reactor to operating pressure, incl. and for the purpose of unloading the shelf structure from a large differential pressure. Subsequently, through the gap between beakers 7 and 8, this stream of cold synthesis gas is mixed with the main flow of synthesis gas (hot), which, through the holes in the beaker 7, cover 6, and cap 26, enters with it the entrance to the upper section of the reactor. The synthesis gas sequentially passes through all sections from the upper to the lower and through the pipe in the plate 2 the synthesis products are removed from the reactor. The reaction gases of the previous section are the synthesis gas of the subsequent. The shelf nozzle has a higher temperature than the case. In order to exclude the possibility of the appearance of large thermal stresses in the reactor structural elements, the casing and the nozzle are fastened together only at one end, through the base plate. The pipelines of the inlet and outlet of the coolant of each section are made with expansion joints. Thus, during operation, the shelf attachment can expand freely.

Within each section, the gas sequentially passes a perforated cover 12, a grid 19, a catalyst bed 11, in which it is heated to within acceptable limits (by 30 ... 60 ° C). The reaction gases through the grid 19 and the grate 18 enter the manifold 27. Before feeding the reaction gases to the next section, they must be cooled to the same initial temperature or slightly higher. Gas cooling is carried out in MTU.

From the collector 27, through the openings in the shell 13, the synthesis gas enters the gap between it and the glass 20 (see FIGS. 3 and 4), passes upward along it, turns around and returns downward along the gap between the shell 14 and the pin 16, getting first into the manifold 28, and then through the holes in the cap 26 to the entrance to the next section. The coolant passes through the supply channel in the plate 9 into the distributing manifold 29, and then into the gap between the inner shell 14 and the separation shell 15. The coolant passes up the gap, unfolds under the lid, and returns along the gap between the separation shell 15 and the outer shell 13 to the prefabricated collector 30. From the collector 30, the coolant is discharged from the section through the drain channel in the plate 9. The heat transfer process occurs mainly during the movement of reaction gases in the gap between the pin 16 and the shell 14, and the coolant in the gap between the shells 14 and 15. The main heat flow passes through the wall of the shell 14 in section B. The heat flow through the wall of the shell 13 is significantly less than -for its greater thickness and significantly lower speeds of the reaction gases and coolant washing it.

The principle of movement of the coolant and reaction gases implemented in the heat exchanger, the so-called counterflow, very effective. It provides an approximate constancy of the heat flux along the length of the inner shell due to a slight change in the temperature difference between the reaction gases and the coolant.

If necessary, it is possible to implement another scheme of movement - forward flow. In this case, you need to swap the input and output of the coolant. As already noted, the pin 16 is at the same time a fastening element of the catalyst shelf and a gas flow turbulator. It allows you to significantly increase the efficiency of heat transfer by increasing the heat transfer coefficient α _g , which depends on the flow rate and artificial macro roughness of the pin - turbulizer. It should be noted that both of these parameters affect the pressure loss along the path, their growth is not unlimited. In section B (see FIG. 2), a necessary gap is formed between the pin 16 and the sheath 14, in which, due to the material of the pin, macro-roughness elements are made that turbulent the flow. Such elements may be;

(1) screw protrusions of single or multiple threads, the outer diameter of which is less than the inner diameter of the shell 14;

(2) fragments obtained by sequentially performing on the pin 16 of the left and right threads, the so-called "Needles", while the remaining thread parameters are the same, and their outer diameter is less than the inner diameter of the shell 14;

(3) longitudinal ribs whose height does not exceed the gap between the pin 16 and the sheath 14;

(4) annular protrusions, the height of which does not exceed half the gap between the pin 16 and the sheath 14;

(5) a combination of decisions under (3) and (4) and the like.

It is recommended that the maximum gas flow rate be limited to 50 m / s.

It is possible to use turbulizing elements on the outer surfaces of the shell 14, especially in the case of using gaseous coolant.

A distinctive feature of the proposed reactor is the use of an efficient, compact modular-type heat exchanger, which is placed inside the cup of the catalyst shelf, excluding its contact with the catalyst. This technical solution allows, in comparison with the prototype, to reduce the height of the reactor. The synthesis gas sequentially passes bulk and MTU. Turbulization of the gas flow, with a reasonable increase in pressure drop, increases α _g , bringing it closer to α _t . This circumstance allows, in addition to increasing the heat transfer intensity, to expand the range of regulation of gas temperature. Regulation is usually carried out by changing the flow rate of the coolant. The heat dissipation in each of the sections of the reactor is different. Typically, the upper sections operate with greater heat generation in the catalyst bed than the lower ones. To optimize heat transfer in the lower sections, it is possible to install pin 16 with a smaller size B (see figure 2), which determines the effective heat transfer area.

When converting the reactor to a different type of synthesis having different operating parameters, it is possible to use pin 16 with other turbulizing elements or size B.

To ensure reliable operation of the proposed reactor design, the pressure in the liquid-phase coolant (water) circuit is recommended at all operating modes to be set and provided with automation slightly lower than the synthesis gas pressure.

MTU can be tested at a pilot plant. When switching to commercial reactors of large sizes and power, the amount of MTU necessary to ensure a given heat removal can be increased to the desired one according to the results of design calculations. It can reach several tens, but their optimal number is from 3 to 37.

The use of MTU reduces the amount of refinement and commissioning of new reactors. An embodiment of a reactor section with several MTUs is shown in FIG. 5. Here, the shelf nozzle is also made of the same sections, hermetically fastened to each other and including a base plate, a housing, a shelf consisting of a grate and a glass with a lid. As heat exchangers, several similar modular heat exchangers of the same type are used with individual setting elements, consisting of an inner and a separation shell, with a gap of sequentially inserted into each other and hermetically fastened sections with a base plate. A pin is inserted into the inner shell of each MTU, which acts as an element for fastening the shelf and at the same time as an intensifier of the heat transfer process. An artificial macro roughness is made on the lateral surface of the pin. Moreover, several of the same type, spent MTU have a common outer shell 31 and a cover 32.

Claims (4)

1. A catalytic reactor with a vertical shelf nozzle for heat-intensive processes of chemical synthesis, comprising a high-pressure casing, a base plate, a lid, strapping elements, on which the solid catalyst is poured onto the grate grates of the shelf nozzle, and after each grate, a heat exchanger operating along the reaction gases external heat carrier and placed inside the shelf nozzle, characterized in that the shelf nozzle is made of the same sections, hermetically fastened to each other and on containing a base plate, a housing, a shelf, consisting of a grate and a glass with a lid, while a heat exchanger uses a modular heat exchanger, consisting of three shells - external, internal and separation, with a gap sequentially inserted into each other and hermetically fastened with the base plate of the section, and the cover, with which the inner and outer shells are hermetically fastened, and a pin is inserted into the inner shell, which acts as a fastening element for the shelf and at the same time as a process intensifier and heat exchange, thus on the side surface of the pin is formed PU macroroughness. 2. The reactor according to claim 1, characterized in that the shelf nozzle is installed on the base plate of the reactor through which all inlets and outlets are carried out, except for supplying the main flow of synthesis gas made in the reactor lid. 3. A catalytic reactor with a vertical shelf nozzle for heat-intensive processes of chemical synthesis, comprising a high-pressure casing, a base plate, a lid, strapping elements, on which the solid catalyst is poured onto the grate of the shelf nozzle, and after each grate, several heat exchangers operating along the reaction gases on an external coolant and placed inside the shelf nozzle, characterized in that the shelf nozzle is made of the same sections, hermetically fastened to each other and including a base plate, a housing, a shelf, consisting of a grate and a glass with a lid, the heat exchangers using the same type of modular heat exchangers with individual settings, consisting of an inner and a separation shell, with a gap sequentially inserted into each other and tightly fastened to the base plate of the section, a pin is inserted into the inner shell, which acts as an element for fastening the shelf and at the same time as an intensifier of the heat transfer process, On the new surface of the pin, an artificial macro-roughness is made, while the heat exchangers have a common outer shell and a cover. 4. The reactor according to claim 3, characterized in that the shelf nozzle is installed on the base plate of the reactor through which all inlets and outlets are carried out, except for supplying the main flow of synthesis gas made in the reactor lid.

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