RU2796425C1 - Synthesis gas reactor and method for producing synthesis gas in synthesis gas reactor - Google Patents

Abstract

FIELD: synthesis gas reactors.

SUBSTANCE: present invention relates to a reactor for producing synthesis gas, as well as to a method for producing synthesis gas using this reactor. The proposed reactor contains a reactor chamber and systems for supplying the reaction mixture, supplying a heating agent, collecting synthesis gas, and removing products of combustion of the heating agent. In this case, the reactor chamber is a hollow cylinder of rotation, in the lower base of which there are inlets of the reactor channels uniformly spaced along the circumference, concentric guide, and the inlet of the heating system located in the center, and in the upper base there are outlets uniformly spaced around the circumference, concentric guide, openings of the reactor channels. Reactor channels are installed inside the reactor chamber with a diameter that ensures the characteristic thermal time of the catalyst is less than or equal to the residence time of the reaction mixture in the reactor channel, filled with catalyst with a bed porosity in the range from 0.2 to 0.4, located parallel to its longitudinal axis of symmetry and fixed on bases coaxially with the inlet and outlet holes, as well as a heating system, which is a pipe coaxially placed in the reactor chamber, in the wall of which holes are made in a given order to output thermal energy into the reactor chamber, fixed on the lower base coaxially with the inlet hole.

EFFECT: uniform heating of the catalyst layer, elimination of local overheating, sintering and deactivation of the catalyst, complete heating of the reaction gas mixture flow, which ensures a conversion rate of at least 92% at a mass flow rate of the reaction mixture of more than 10,000 h^-1.

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Description

The invention relates to reforming reactors for producing synthesis gas from natural gas.

During reforming, a mixture of natural gas, steam and/or oxygen is supplied to the reactor, while one part of the hydrocarbons is oxidized by oxygen and provides the high temperature necessary for reforming. The process of obtaining synthesis gas from natural gas containing mainly methane is a combination of partial oxidation, steam and carbon dioxide reforming. The reactions occurring during the catalytic reforming of methane can be represented as the following equations:

CH4+2O2 → 2H2O+CO2+ΔH01;

CH4+H2O → CO+3H2+ΔH02;

CH4+CO2 → 2CO+2H2+ΔH03;

where ΔH0i (i=1; 2; 3) are the standard thermal effects of chemical reactions at P=1 atm.t, T0=298 K.

For processing natural gas into synthesis gas by catalytic reforming, tubular reactors with a stationary catalyst bed are used. As catalysts for the conversion of hydrocarbons to produce synthesis gas, metals of group VIII of the periodic system of elements deposited on porous ceramic carriers are used.

The reforming of natural gas is carried out in the presence of a nickel-containing catalyst in the form of granules of various sizes and shapes, which are filled into the reactor tubes. In contact reformers, the heat necessary for the chemical process to proceed is transferred from the fuel combustion zone by means of its convective and radiative transfer to the outer surfaces of the reaction tubes. Due to the high thermal conductivity of the pipe metal, heat is accumulated by the gas phase and catalyst granules, the temperature of which is 100 ° C lower (especially in the central part of the catalyst layer) than the temperature of the inner wall of the pipe (Azotchik's Handbook. M .: Chemistry, 1986, p. 83; patent RU No. 2234458, С01С 1/04, published on August 20, 2004).

A known method for producing synthesis gas from a hydrogen-containing feedstock in a reversible flow reactor and a reactor for its implementation (see patent RU No. 2574464, IPC B01J 7/00, published on February 10, 2016).

The method for producing synthesis gas includes:

- heating to high temperature at least part of the chamber of the tubular reactor filled with a solid porous material;

- supply to the tubular reactor of two reagents - combustible and oxygen-containing gas in an amount not sufficient for complete oxidation of the fuel;

- carrying out the reaction of combustible and oxygen-containing gas in a layer of solid porous material;

- establishing a gas flow in the tubular reactor from one end of the reactor to the other end by supplying a gaseous reactant from one end of the reactor and withdrawing gaseous reaction products in the form of synthesis gas from the opposite end;

- temperature measurement in the reactor;

- periodic change in the direction of the gas flow in the reactor;

In this case, the reagents are fed into the reactor separately: one of the reagents, the gaseous reagent -A-, is fed from one end of the reactor, and the second reagent -B- is fed into the middle part of the reactor and the reagent B is mixed with the gaseous reagent A heated in the middle part of the reactor. due to heat exchange with a solid porous material.

The reactor for implementing the described method for producing synthesis gas includes a tubular gas-tight body and a reactor chamber, including the first and second ends, and the reactor chamber in the predominant part of its volume is filled with a solid porous material; the reactor is equipped with a system of gas pipelines connected to the first and second ends of the reactor chamber and shut-off valves that allow gas to be supplied to the first end and gas to be taken from the second end at the same time, or gas to be supplied to the second end and gas to be taken from the first at the same time, while the reactor additionally includes a pipeline attached to the middle part of the reactor chamber, allowing gas and/or liquid and/or finely dispersed solid material to be supplied to the reactor chamber.

The advantage of the reactor according to this invention lies in the separate supply of reactants: the gaseous mixture of hydrocarbons enters the beginning of the reactor, and steam is fed into the middle part of the reactor, where the reactants are mixed.

The disadvantages of this invention are the bulkiness and high metal consumption of the structure, the need to install several lines for supplying components of the feed stream to different parts of the reactor, the need to implement two parallel devices.

A known method for producing synthesis gas of a given composition of the main components of H ₂ and CO in the range of changing the ratio from 1:1 to 2:1 for the production of methanol, dimethyl ether or for Fischer-Tropsch syntheses (see patent RU No. 2228901, IPC S01V 3/ 38, published on July 27, 2003), which includes two stages: stage A) of partial oxidation and stage B) of residual methane conversion with products of stage A) on a catalyst, characterized in that stage A) of partial oxidation is carried out in two stages: a) non-catalytic partial oxidation of natural gas with oxygen to obtain a non-equilibrium content of H ₂ O and CH ₄ in the reaction products at a molar ratio of oxygen and methane approximately equal to 0.76-0.84, b) conversion of reaction products of stage (a) with corrective additions of CO ₂ and H ₂ O or H ₂ O and CH ₄ to form a gas mixture which undergoes steam conversion of the residual methane over a catalyst.

The disadvantages of this methane conversion reactor are functional and technological limitations associated with the need to supply high oxygen consumption (exceeding the mass consumption of convertible natural gas), the production of which requires large energy (up to 1000 kWh/t) and capital costs (up to 1500 USD). USA/kg⋅h ^-1 ). Soot formation, which sharply reduces the activity and service life of catalysts, is also a serious problem.

Also known is a radial-type catalytic reactor for producing synthesis gas (patent RU No. 2208475, IPC B01J 8/04, С01В 3/00, published on 07/20/2003), containing a gas distribution tube with a catalyst layer, which is made in the form of gas-permeable flat and corrugated reinforced tapes wound and sintered with a gas distribution tube with gaps between the turns to form gas-air channels between the tapes. The reactor has a heating device for putting it into operation. The gas distribution tube has perforations with a diameter smaller than the critical diameter to prevent flame penetration into the gas distribution tube. As a catalyst, a reinforced porous material is used containing active components: rhodium, nickel, platinum, palladium, iron, cobalt, rhenium, ruthenium, or mixtures thereof.

The disadvantage of this design of the reactor is the lack of serial technologies for the manufacture of reinforced porous materials mastered by the industry, high labor intensity and a decrease in the overall catalytic activity due to the use of reinforcing materials.

The closest analogue to the proposed invention is a compact reactor for producing synthesis gas from natural/associated gas in the process of autothermal reforming (see patent RU No. including reactor channels partially filled with catalyst and located parallel to the longitudinal axis of the reactor, a side product outlet pipe, provided with an air supply channel with a flow distributor, the outlet of which is located opposite the outlet of the reactor channels, while part of the catalyst is placed at the outlet of the reactor channels, between the reactor channels and reactor vessel, wherein the lower catalyst level is located between the outlets of the reactor channels and the air supply channel, while the internal cross-sectional area of the reactor vessel is 2.5-4 times greater than the total internal cross-sectional area of the reactor channels.

The disadvantage of this reactor is the low degree of conversion of natural gas into synthesis gas, limited by the intensity of heat transfer in the reactor channels. The speed and completeness of the catalytic chemical reactions of reforming is determined by temperature. Due to the low thermal conductivity of the ceramic catalyst carrier (1.6⋅10-6 m/s ² ) and high gas flow rates (more than 100,000 h ^-1 ), in reactors with large diameters and high space velocities, the reaction gas mixture is not fully heated . In addition, a significant disadvantage of catalysts based on granular oxide (ceramic) carriers is the high gas-dynamic resistance to the gas flow, which limits the volumetric feed rate and, as a consequence, the productivity of the reforming reactor in terms of synthesis gas.

The task to be solved by the claimed invention is the creation of a compact industrial synthesis gas reactor with a high degree of conversion conversion.

The technical results of the invention consist in uniform heating of the catalyst bed, elimination of local overheating, sintering and deactivation of the catalyst, complete heating of the reaction gas mixture flow, which ensures a conversion rate of at least 92% at a mass flow rate of the reaction mixture of more than 10,000 h ^-1 .

Technical results are achieved by the fact that in the reactor for producing synthesis gas, containing a reactor chamber and systems for supplying the reaction mixture, supplying a heating agent, collecting synthesis gas, removing combustion products of the heating agent, the reactor chamber is a hollow cylinder of rotation, in the lower base of which the inlets of the reactor channels and the inlet of the heating system located in the center are evenly spaced around the circumference, concentric guide, and the outlet holes of the reactor channels are uniformly spaced around the circumference, concentric guide, in the upper base, inside the reactor chamber there are reactor channels with a diameter that provides a characteristic the thermal time of the catalyst is less than or equal to the residence time of the reaction mixture in the reactor channel, filled with a catalyst with a bed porosity in the range from 0.2 to 0.4, located parallel to its longitudinal axis of symmetry and fixed on the bases coaxially with the inlet and outlet holes, as well as a heating system , which is a pipe coaxially placed in the reactor chamber, in the wall of which holes are made in a given order for the output of thermal energy into the reactor chamber, fixed on the lower base coaxially with the inlet.

The technical results are also achieved by the fact that the method for producing synthesis gas includes heating the internal volume of the reactor chamber by burning the heating agent supplied through the inlet to the heating system and supplying the reaction mixture through the inlets to the reactor channels, while the heating intensity is controlled by changing its volumetric flow rate, maintaining the isothermal regime along the entire length of the reactor channels.

The claimed technical solution is illustrated by drawings, in which Fig. 1 is a schematic longitudinal central section of the reactor chamber, FIG. 2 is a graph of the effect of catalyst bed porosity on the hydrogen to carbon monoxide molar ratio in methane reforming, FIG. 3 is a graph of the effect of catalyst bed porosity on methane reforming conversion, FIG. 4 are graphs of the performance of an isothermal methane reformer as a function of temperature.

The syngas production reactor contains a reactor chamber 1 with a lower base 2, in which the inlets 3 of the reactor channels and an inlet 4 of the heating system are made, the upper base 5, in which the outlets 6 of the reactor channels are made. Inside the reactor chamber there are reactor channels 7 filled with catalyst 8 and a heating system 9 with holes 10 for outputting thermal energy.

Systems 11, 12, 13, 14 are connected to the reactor chamber: supply of the reaction mixture, supply of the heating agent, collection of synthesis gas, removal of combustion products of the heating agent, respectively.

To ensure uniform heating of the catalyst layer and complete heating of the reaction mixture, the diameter of the reactor channels 7 filled with catalyst 8 is determined from the condition that the characteristic thermal time of the catalyst 8 is less than or equal to the residence time of the reaction mixture in the reactor channel 7.

For complete radial heating of the cylindrical reactor channel 7, the characteristic thermal time is:

Where: d _r is the inner diameter of the reactor channel 7, λ _r is the thermal diffusivity of the ceramic carrier of the catalyst 8.

The contact time of the reaction mixture in the reactor channel 7 is:

Where: L is the length of the reactor channel 7, u is the flow rate of the reaction mixture.

From the condition of complete heating of the inner layers of the catalyst 8, the characteristic thermal time should be less than the characteristic contact time in the reactor, and the maximum diameter of the reactor can be determined as:

To reduce the gas-dynamic resistance to the gas flow of the catalyst layer 8 based on granular oxide carriers, to increase the space velocity of the feedstock, and as a result of the performance of the reactor for producing synthesis gas, the fractional composition of the catalyst layer is selected from the condition of ensuring optimal porosity from the range of 0.2 ÷ 0, 4. The effect of the porosity of the catalyst bed 8 on the reforming efficiency is shown in FIG. 2, 3.

The key parameter of the reactor operation, which determines its efficiency (share composition of the conversion products), as well as its performance, is the thermal regime of the catalyst bed 8. The conversion of natural gas takes place with the absorption of heat, so the initial part of the reactor channels 7 requires active heating to maintain the occurrence of reversible chemical reactions in forward direction. The temperature in this case is limited by the requirements of the strength of the material of the walls of the reactor channels 7. Another limitation is associated with a drop in productivity with an increase in the temperature of the reforming products due to a decrease in their density.

Two limiting modes of operation can be distinguished: ideal isothermal - maintaining a constant temperature as a result of some complex heating; adiabatic - the walls of the channels are thermally insulated, the only source of heat is the heated gases at the inlet.

The isothermal mode provides the highest synthesis gas yield, while the adiabatic mode shows the worst-case reaction scenario. At the same time, the isothermal reactor reaches its maximum efficiency at temperatures above +1100°C, which is technically difficult due to the limitations imposed by the heat resistance of the material of the walls of the reactor channels 7 (see Fig. 4).

The results of calculations of the efficiency indicators of the reactor channel 7 for various operating modes are presented in the table:

It can be seen from the table that the efficiency of natural gas reforming in a tubular catalytic reactor is the higher, the closer the thermal mode of operation of the reactor channel is to the isothermal mode.

The implementation of the proposed method for producing synthesis gas in the described reactor is carried out as follows.

Through the supply system 12 and the inlet 4 in the base 2, the heating agent is supplied to the heating system 9 and ignited. The combustion of the heating agent provides heating of the internal volume of the reactor chamber 1 and reactor channels 7 with catalyst 8. By adjusting the volumetric flow rate of the heating agent supplied to the system 9, the operating temperature in the area of the reactor channels 7 is reached. In this case, the temperature is calculated according to the formula T( r)=A*G ⁰⁴ , where r is the distance from the central axis of the reactor chamber 1 to the central axis of the reactor channel 7, A is a numerical coefficient determined by the geometric dimensions of the reactor chamber 1 and the heating system 9, G is the volumetric flow rate of the heating agent. Due to the fact that the convection component of heating (due to the heat transfer of the gaseous medium inside the reactor chamber 1) is insignificant (less than 1%), compared with the radiation component, its value can be neglected. Then the temperature distribution along the length of the reactor channels 7 will depend only on the distribution of the cross-sectional area of the holes 10 along the length of the heating system 9 and is defined as T(l)=F(Sdl), where l is the distance from the lower base, F(Sdl) is the distribution function of the total cross-sectional areas at each height l.

After the reactor chamber 1 reaches the operating temperature regime in the zone of the reactor channels 7, the reaction mixture is fed into them through the system 11 and inlets 3, which, passing through the reactor channels 7 through the catalyst 8, undergoes reforming. The obtained reforming products through the outlet holes 6 in the upper base 5 and the synthesis gas collection system 13 go beyond the reactor chamber 1, after which they are separated.

The combustion products of the heating agent are removed from the reactor chamber 1 through the exhaust system 14 .

The table below shows the temperature values along the length of the reactor channels obtained during testing of the proposed technical solution (gas flow rate 12,500 h-1, pipe inner diameter 30 mm, Ni catalyst on a ceramic carrier with an average grain diameter of 4 mm). The average temperature value is given for the steady state gas flow through the tube with the catalyst based on the results of three measurements:

The same indicators of the set temperature along the entire length of each of the reactor channels, provided by the design of the proposed reactor and the implementation of the proposed method, make it possible to obtain a high degree of conversion in the production of synthesis gas on an industrial scale.

Claims (2)

1. A reactor for producing synthesis gas, containing a reactor chamber and systems for supplying the reaction mixture, supplying a heating agent, collecting synthesis gas, removing combustion products of the heating agent, characterized in that the reactor chamber is a hollow cylinder of rotation, in the lower base of which are made uniformly the inlets of the reactor channels and the inlet of the heating system located in the center, and in the upper base, the outlets of the reactor channels are evenly spaced around the circumference, concentric guide, inside the reactor chamber there are reactor channels with a diameter that provides a characteristic thermal the catalyst time is less than or equal to the residence time of the reaction mixture in the reactor channel, filled with a catalyst with a bed porosity in the range from 0.2 to 0.4, located parallel to its longitudinal axis of symmetry and fixed on the bases coaxially with the inlet and outlet holes, as well as the heating system, which is a pipe coaxially placed in the reactor chamber, in the wall of which holes are made in a given order for the output of thermal energy into the reactor chamber, fixed on the lower base coaxially with the inlet. 2. The method for producing synthesis gas in the reactor according to claim 1, including heating the internal volume of the reactor chamber of the reactor by burning the heating agent supplied through the inlet to the heating system and supplying the reaction mixture through the inlets to the reactor channels, while the heating intensity is controlled by changing the volume flow heating agent, ensuring that the isothermal regime is maintained along the entire length of the reactor channels.

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