WO2017030469A1

WO2017030469A1 - Reactor for dehydrogenation of c3-c5 paraffins

Info

Publication number: WO2017030469A1
Application number: PCT/RU2016/000551
Authority: WO
Inventors: Станислав Михайлович КОМАРОВ; Александр Алексеевич ДУШИН; Алексей Александрович КРЕЙКЕР
Original assignee: Акционерное общество "Специальное конструкторско-технологическое бюро "Катализатор"
Priority date: 2015-08-20
Filing date: 2016-08-16
Publication date: 2017-02-23
Also published as: RU2601002C1; CN107847894A

Abstract

The invention relates to the field of petrochemistry, and specifically to paraffin dehydrogenation reactors. A reactor for the dehydrogenation of C3-C5 paraffins with a boiling layer of fine-grained catalyst, including: a vertical cylindrical housing; a raw material vapor inlet fitting connected to a raw material distributor in the lower portion of the reactor housing; contact gas supply fittings; means for inputting and outputting a circulating catalyst; partitioning grates which have a free cross-section which increases with the height of the reactor and which separate the boiling layer of catalyst into sections; in which a calming grate is installed between a lower partitioning grate and the raw material distributor, said calming grate having a free cross-section which is larger than the free cross-section of the lower partitioning grate and which comprises more than 25% and less than 90% of the cross-section of the housing, and wherein the distance from said grate to the lower partitioning grate is 0.5-2.0 times the height of the section above the lower partitioning grate. The lower partitioning grate may have a free cross-section comprising 10-30% of the cross-section of the housing, while that of an upper partitioning grate may comprise 20-60% of same. The technical result of the claimed invention consists in increasing reactor output and improving dehydrogenation indicators.

Description

Reactor for paraffin dehydrogenation

HYDROCARBONS WITH ₃ - WITH ₅

Technical field

The invention relates to the field of petrochemistry, in particular to reactors for the dehydrogenation of C3-C5 paraffin hydrocarbons into the corresponding olefinic hydrocarbons used to produce the main monomers of synthetic rubber, as well as in the production of polypropylene, methyl tertiary butyl ether and others.

State of the art

Known reactor for the dehydrogenation of paraffin hydrocarbons with a fluidized bed of a fine-grained catalyst, containing a vertical cylindrical body and sectional gratings installed along the height of the fluidized bed at the same distance from each other. The catalyst circulates in the reactor-regenerator system and passes the reactor from top to bottom in contrast to the flow of raw material vapor rising from the bottom up (Synthetic Rubber Industry, Moscow, TsNIITENeftekhim, 1968, N ° 2, p. 8, R.K. Mikhailov, A.N. Bushin “Joint dehydrogenation of butane and isopentane in a fluidized bed of a fine-grained catalyst”).

However, in this reactor, the sectional gratings have the same free cross-section, which determines the uneven distribution of the catalyst over the sections of the reactor and low dehydrogenation rates — the olefin yields on the passed and decomposed raw materials.

The closest in technical essence is a reactor for the dehydrogenation of paraffin hydrocarbons Сз - С ₅ with a fluidized bed of a fine-grained catalyst, containing a vertical cylindrical body, sectional gratings with a free section increasing in height of the reactor, separating the catalyst layer into sections, a pipe for introducing raw material vapor connected to a distributor raw materials located in the lower part of the reactor vessel and nozzles for contact gas outlet, inlet and outlet of a circulating catalyst (patent RU 2156161, IPC B01 J8 / 04, C07C5 / 333 Op. 20.09.2000). In the specified reactor, the lower lattice has a free cross section of 10-30% of the cross section of the vessel, and the upper one is 20-60%.

The sectional gratings used in the reactor with the indicated free cross-section operate in an efficient mode close to the “flooding” mode with countercurrent movement of the catalyst and gas circulating through the reactor (feed vapor). In addition, to improve the operation of the lower part of the fluidized catalyst bed, in the space between the lower grate and the stripping section of the reactor, it is proposed:

use as a distributor of raw materials a tubular distributor equipped with nozzles directed downward and having a free section in the center of 0.25-4.00 section of the stripping section. Install such a distributor at a distance from the stripping section, comprising 0.5-3.0 of the height of the lower section of the fluidized catalyst bed.

- or install an additional tubular distributor of raw materials at a distance of 0.5-2.0 of the height of the lower section from the main distributor. The use for this of a distributor equipped with downward-directed nozzles and overlapping all sections of the reactor vessel.

As a result of the use of the last two constructive solutions, the stagnant zones in the distributor area are reduced, the stripping section is improved, and the gas distribution over the reactor cross section is improved.

The design of the known reactor eliminates the disadvantages of the above analogue, however, in turn, it is characterized by relatively low productivity, low dehydrogenation rates and low overhaul runs, largely related to the inefficient operation of the upper and lower sectional gratings and coking of the lower part of the reactor (gradual filling of the lower part of the reactor with a monolithic coke).

A reactor is known (patent RU 2301107, IPC B01J8 / 04, С07С5 / 333, op. 20.06.2007), in which the free section of the sectional gratings increases along the height of the reactor to the free cross section of the upper grate 60-90%, while the reactor contains input pipes circulating catalyst and riser risers, the ends of which are equipped with dust exhaust valves, located in the upper part of the fluidized bed in the space between the upper sectional grating and the level of the fluidized bed.

However, the possibilities arising from this increase in reactor productivity do not justify a significant decrease in dehydrogenation (olefin yields) due to the fact that it is impossible to implement an effective “flooding” mode on the upper sectional gratings of this reactor.

Disclosure of invention

The objective of the present invention is to increase the productivity of the reactor and indicators of dehydrogenation.

To solve this problem, a reactor is proposed for the dehydrogenation of paraffin hydrocarbons C ₃ - C ₅ with a fluidized bed of a fine-grained catalyst, containing a vertical cylindrical body, a pipe for introducing raw material vapor, connected to a raw material distributor in the lower part of the reactor vessel, nozzles for contact gas outlet, circulating inlet and outlet catalyst, sectional gratings with a free cross-section increasing along the height of the reactor, dividing the fluidized catalyst bed into sections, in which between the lower sectioning grating d and the raw material distributor installed a soothing grate, which has a free cross section greater than the free cross section of the lower section grating and comprising more than 25 and less than 90% of the cross section of the casing, while the distance from this grate to the lower section grating is 0.5–2, 0 section heights above the bottom sectional grill.

In addition, the sectional gratings in the reactor can be installed in groups of 2-6 gratings, while the gratings in each group have the same free section, which increases from group to group along the height of the reactor.

At the same time, a soothing grate can be installed above the upper sectioning grate, which has a free section greater than the free section of the upper sectioning grate and comprising more than 35 and less than 90% of the casing section, while the distance from this grate to the upper sectioning grate is 1.0-3 , 0 section heights under the upper sectional grill. A feature of the known reactors with a fluidized bed of fine-grained catalyst, divided by sectional gratings into sections, is the presence of three zones in the fluidized bed: the main reaction zone in the middle of the layer with sectioning gratings, the zone between the gas distributor (feed vapor) and the lower sectioning grating, and the zone between the upper sectional grating and fluidized bed surface in the reactor. The height of the zone between the raw material distributor and the lower sectioning grate is determined by the need to place support devices in it for securing the sectioning gratings and providing the possibility of installation and repair work in the lower part of the reactor in the zone where the raw material distributor is located (access through the hatch, etc.). The height of this space increases significantly with increasing power (diameter) of the reactors and reaches a large unit capacity of several meters in the reactors.

The upper zone (above the upper sectional grate to the surface of the fluidized bed of the reactor) also has a high height and contains a significant amount of catalyst due to the need to place the cyclone dust riser valves and the “hot” circulating catalyst inlet pipes in it.

Thus, most of the catalyst in known reactors is located in inefficient zones with a free disordered fluidized bed. The zone with intense heat and mass transfer, in which the fluidized bed is organized by sectioning gratings, contains only 50-60% of the total catalyst in the reactor (in space from the feed distributor to the surface of the fluidized bed).

With a free cross section of the lower sectioning grate in the known reactor of 10-30%, operating in a mode close to the "flooding" mode with a counterflow of solid and gas phases, a gas cushion of significant dimensions is formed under this grating. Moreover, in the lower part of the reactor, in the space between the distributor and the lower grate, an unorganized fluidized bed with a free surface is formed. A fluidized bed ruptures.

A large, free, unorganized fluidized bed is characterized by inhomogeneous boiling of a finely dispersed catalyst with the formation of large bubbles and channel breakthroughs of the gas phase. As a result, this leads to the occurrence of stagnant sections in the volume of the fluidized bed of catalyst and gas, significant pressure pulsations in the layer, local fluctuations in the level of the fluidized bed in the cross section of the apparatus and the release of large amounts of catalyst into the superlayer space.

With regard to the operating conditions of the known dehydrogenation reactor, the indicated features of the unorganized fluidized bed in the lower part of the reactor cause low heat and mass transfer and stagnation in this part of the fluidized bed, as well as disruption of the lower lattices of the reactor due to the emission of large amounts of catalyst from the free fluidized bed of the lower part reactor into the gas cushion volume of the lower sectional grate. All this reduces the level of dehydrogenation indicators, leads to coking of the lower part of the reactor and, as a result, reduces the period of overhaul of the installation (by increasing the duration of major repairs and unscheduled shutdowns), reducing its productivity.

The disorganized fluidized bed above the upper sectional grating, containing a large amount of catalyst, has low heat and mass transfer and, with significant level fluctuations, disrupts the stable operation of the upper sectional gratings of the reactor, which also reduces dehydrogenation.

In the proposed reactor, the installation under the lower sectioning grate of a stilling grate with an increased free cross-section (larger than the free section of the lower sectioning grating) in combination with the indicated distance from this grating to the lower parting grating allows reducing pressure pulsations in the lower part of the fluidized bed, stabilizing the operation of the raw material distributor and the upstream sectional gratings in the reactor. This increases the uniformity of the distribution of catalyst and gas in the cross section of the reactor during their countercurrent movement along the axis of the apparatus, improves heat and mass transfer, reduces stagnation, thermal and concentration irregularities in the fluidized bed. As a result, the dehydrogenation indices increase (the olefin yield on the passed and decomposed raw materials), the ablation of the catalyst from the fluidized bed decreases, and the loss of catalyst in production due to a more uniform fluidized bed in The proposed reactor reduces coke formation in the lower part of the reactor, decreases the formation of coke monolithic deposits in the reactor, deforming the internal devices of the reactor until they are completely destroyed (gratings, gas flow distributors, supporting structures, etc.) and violating the hydrodynamic regime of the reactor. At the same time, the overhaul run of the reactor and its productivity increase accordingly.

The operation of the stilling lattice in the indicated range of the free section is most effective due to the stable operation of the sectional lattices. The specified lattice allows you to get as close as possible to the most effective mode of choking sectional gratings. When the free section of the stilling grate is equal to or less than the free section of the lower sectioning grate, the mode of operation of the stilling grate goes into the flooding mode, while the height of the gas cushion increases sharply, and the catalyst “hangs”, stopping circulation. With a free cross section of the stilling lattice above 90%, its effect on the process becomes hardly noticeable.

The installation of sectional gratings in groups with the same free cross-section of the gratings in the groups and with increasing the specified section from group to group along the height of the reactor greatly simplifies the design of the reactor.

The installation of a stilling grate over the upper sectional grating with the indicated free cross-section and the distance to the upper sectioning grating also improves dehydrogenation by stabilizing and increasing the efficiency of the upper sectioning gratings. This soothing grid significantly reduces fluidization of the fluidized bed level, pressure pulsation, thermal and concentration irregularities in the upper part of the reactor.

The effectiveness of the lower and upper soothing grids is most significantly manifested in the indicated range of distances to the sectioning grids (the heights of the location of the soothing grids). Brief Description of the Drawings

Figure 1 shows a diagram of the proposed reactor. The reactor has a housing 1, pipelines and nozzles for input 2 and output 3 of the circulating catalyst, input of raw materials 4 and output of contact gas 5. The reactor also contains a distributor of raw materials 6. The fluidized bed of the catalyst in the reactor with level 7 is divided into sections by sectional gratings (lower grate - 9 and top - 10). At the same time, the lower sectional grating can have a free section, which is 10-30% of the cross section of the casing, and the upper one is 20-60%. Between the raw material distributor 6 and the lower sectioning grate 9, a soothing grate 11 with a free section of 25-90% is installed), while the distance “A” from the stilling grate to the lower sectioning grating 9 is 0.5-2.0 of the height of the lower section “B” . A soothing grid 12 with a free section of 35-90% is installed above the upper sectional grill 10. In this case, the distance from the upper sectional grate to the soothing “C” is 1.0-3.0 of the height of the upper section “D”. The sections contain fluidized-bed zones 8 and gas cushions 13. The reactor has a stripping section 14 with an inert gas supply pipe 15, a separation zone (superlayer space of the reactor) 16, in which cyclones for cleaning the contact gas are located before it leaves the reactor through the pipe 5 . In the space between the distributor of raw materials 6 and the lower stilling grid 11 is a mounting hatch 17.

The reactor operates as follows.

Evaporated paraffin hydrocarbons (raw materials) are fed into the reactor through a pipe and pipe 4 through a distributor 6. Inert section 14 is fed with inert gas to the stripping section 14 for stripping from the hydrocarbons of the catalyst leaving the reactor. In the lower part of the reactor (between the distributor 6 and the stilling grate 11), the raw material vapors are mixed with the stripping gases rising from the stripping section and then rise along the fluidized bed of the catalyst, pass through the lower stilling grate 11, the sectional gratings and the upper stilling grate 12, then fall into the separation zone 16.

Heat is supplied to provide an endothermic dehydrogenation reaction by a catalyst circulating through a regenerator. The regenerated and heated catalyst enters from the regenerator through pipeline 2 into the fluidized bed above the upper stilling grid 12 and then passes the reactor sections with the fluidized catalyst bed to counterflowing feed vapors, gradually cooling during the endothermic dehydrogenation reaction and through the stripping section 14 through the pipeline and pipe 3 in coked, reduced and cooled form it is returned to the regenerator for coke burning, oxidation and heating. In this case, the temperature profile of the reactor is formed with an increase in temperature from the zone of the fluidized bed of the reactor located between the distributor and the lower stilling grid to the zone of the fluidized bed above the upper stilling lattice.

The dehydrogenation contact gas after dedusting in the cyclones of the separation zone 16 is sent via pipeline 5 to the cooling and recovery of the obtained olefinic hydrocarbons.

The technical result of the claimed invention is to increase the productivity of the reactor and improve dehydrogenation (increase in the yield of olefins on the passed and decomposed raw materials), reduce the entrainment of the catalyst from the fluidized bed and reduce catalyst losses in production due to a more uniform fluidized bed in the proposed reactor, reducing coke formation in the lower part reactor, reducing the formation of coke monolithic deposits in the reactor, deforming the internal devices of the reactor up to their complete destruction (gratings, gas flow distributors, supporting structures, etc.) and violating the hydrodynamic regime of the reactor. At the same time, the overhaul run of the reactor and its productivity increase accordingly.

BEST MODE FOR CARRYING OUT THE INVENTION The invention is illustrated by the following examples when carrying out a process for the dehydrogenation of paraffin hydrocarbons.

Examples 1-5.

The dehydrogenation of isobutane to isobutylene is carried out on an AOK-73-24 aluminum-chromium catalyst obtained by impregnation of microspherical alumina containing Cr ₂ 0 ₃ - 15 wt.%. The tests were carried out at the factory, the diameter of the reactor is 4.6 m, the diameter of the regenerator is 5.0 m. The height of the reactor is 28 m. The number of sectional gratings in the reaction zone of the reactor is 12 pcs. The free section of the lower sectional grating is 23%. The free section of the upper sectional grating is 40%.

The volumetric feed rate is 165 hours ^"1 , the temperature above the upper grate is 575 ° C.

Examples 6-7.

The dehydrogenation of isopentane to isoamylenes is carried out on an AOK-73-24 aluminum-chromium catalyst obtained by impregnation of microspherical alumina containing Cr ₂ 0 ₃ - 15 wt.%.

The tests were carried out at the factory. The diameter of the reactor is 5.1 m. The diameter of the regenerator is 5.1 m. The height of the reactor is 22 m. The number of sectional gratings in the reaction zone of the reactor is 12 pcs. The free section of the lower sectional grating is 20%. The free section of the upper sectional grating is 30%.

The volumetric feed rate is 120 hours ^"1 , the temperature above the upper grate is 550 ° C.

The results of the proposed reactor are presented in table 1.

As can be seen from the data in the table, the use of soothing grids with the claimed parameters allows (examples N ° N ° 1-3 and 6) to significantly increase the dehydrogenation of paraffin hydrocarbons - the olefin yields on the passed and decomposed raw materials and the reactor productivity - compared with the indicators achievable in the prototype (example 7), as well as when using soothing gratings with parameters different from those stated (examples 4 and 5).

The increase in reactor productivity (the amount of olefins produced) occurs due to an increase in the yield of olefins, as well as a decrease in the amount of coke formed in the reactor, a decrease in the scale of destruction in the reactor due to coke deposits and, accordingly, a decrease in the duration of the overhaul of the reactor and the elimination of unscheduled shutdowns. Industrial applicability

The proposed reactor can be used to carry out processes for the production of propylene, n-butylenes, isobugylene and isoamylenes by dehydrogenation of the corresponding paraffinic hydrocarbons: propane, n-butane, isobutane and isopentane.

Table A 1.

Claims

CLAIM

1. A reactor for the dehydrogenation of C ₃ - C ₅ paraffin hydrocarbons with a fluidized bed of a fine-grained catalyst, including a vertical cylindrical body (1), a feed vapor input pipe (4) connected to a raw material distributor (6) in the lower part of the reactor casing (1), nozzles for the contact gas outlet (5), the inlet (2) and the outlet (3) of the circulating catalyst, sectional gratings with a free cross section increasing in height of the reactor, dividing the fluidized catalyst bed into sections, characterized in that between the lower sectioning grating (9) and a raw material limiter (6) has a soothing grate (11), which has a free cross section greater than the free cross section of the lower sectioning grating (9) and comprising more than 25 and less than 90% of the cross section of the casing (1), while the distance from this grate to the lower sectional lattice (9) is 0.5-2.0 the height of the section above the lower sectional lattice (9).

2. The reactor according to claim 1, characterized in that the sectional gratings in the reactor are installed in groups of 2-6 gratings, while the gratings in each group have the same free cross section, which increases from group to group along the height of the reactor.

3. The reactor according to any one of claims 1 to 2, characterized in that a soothing grate (12) is installed above the upper sectioning grate (10), which has a free section greater than the free section of the upper sectioning grate (10) and is more than 35 and less than 90% of the cross section of the casing (1), while the distance from this grate to the upper sectional grating (10) is 1.0-3.0 the height of the section under the upper sectioning grating (10).