RO102382B1 - Methanol preparation process - Google Patents

Abstract

The invention relates to a process for obtaining a methanol, consisting of compressing gas Synthesis, methanol conversion of synthesis gas, in the presence of ternary catalysts of CuO-ZnO- -A1203, in a major synthesis reactor. Exploited in adiabatic, recirculation mode 4 ... 6 at a pressure of 50 ... 120 bar and temperature 24 ° C to 27 ° C, preceded by conversion of the fresh synthesis gas in the first reactor additional synthesis column type with movement radial flow of the fluid through the exploited catalyst bed in isothermal mode, without recirculation, mounted in series before the main reactor at temperatures and pressures equal to or greater than in the reactor main synthesis and followed by conversion unreacted gas from the reaction synthon main and purge gases extracted from the loop main synthesis, dioxide - enriched carbon so that the ratio H2 - CO / CO + CO2 is or 2 ... 2.3, in the second synthesis reactor additionally, column type with radial movement a fluid through the catalyst bed exploited in non-recirculated isothermal mode, mounted in series after the main reactor at temperatures as low as possible lower and at lower pressures of 2 ... 2,5 bar, with separation of crude methanol after each reactor; recirculation of purge gas to catalytic reforming sulfur / and combustion.

Description

The invention relates to a process for obtaining methanol, used as an intermediary in the chemical and petrochemical industry, as an additive to automobile fuel, as a fuel for gas-fired turbines and for the transport of methane gas from one continent to another.

Methods for obtaining methanol are known, based on the conversion reaction of the synthesis gas, on ternary CuO-ZnO-Al ₂ O ₂ catalysts, at pressures of 50 ... 120 bar and temperatures of 240 ... 270 ° C with the separation of the crude product, by cooling and condensation and the recirculation of the non-transformed gases, in the adiabatic synthesis reactor.

In order to maintain the concentration of inertes in the synthesis gas, below the permissible limit value, about 20 ... 40%, unreacted gases from the main synthesis loop, the fresh synthesis gas is extracted and recycled to catalytic reforming and / or combustion.

The recirculation of unreacted gases is necessary in the processes of industrial methanol production, because the conversion reaction to a single pass through the conversion reactors has a very low efficiency.

For the total conversion of the synthesis gas to a single passage, due to the reaction kinetics, the reactors become very large.

The degree of recirculation for the process of obtaining methanol under adiabatic regime is 7 ... 10 times, and for those under isothermal regime 3 ... 4 times higher than the quantity of freshly used synthetic gas. This recirculation is high energy consuming, consuming about 30% of the total compression energy. For this reason, in the last period several procedures have been developed with a low degree of recirculation.

A process for producing methanol, from the synthesis gas consisting of carbon dioxide CO, carbon dioxide CO ₂ and hydrogen H ₂ , is known, in which the conversion reaction to methanol takes place in two synthetic reactors, connected in series, in liquid phase, the reaction conditions being controlled in such a way that, in the first reactor, the conversion of carbon dioxide CO takes place mainly, and in the second reactor, introduced additionally, the methanol obtained, mainly the conversion of carbon dioxide ₂ , takes place. it is separated from the effluent of the two reactors by cooling and condensation, and the unreacted gases are introduced into the technological circuit.

The process has the disadvantage of large pressure losses in reactors.

Also known is a process for obtaining methanol from synthetic gas, consisting of carbon and hydrogen oxides, in which the conversion reaction to methanol takes place in two or three synthetic reactors, the latter being column-type reactors with radial circulation. of the fluid through the catalyst layer, connected in series for the purge gas extracted from the main loop, operated under isothermal regime, having the working pressure with 2 bars lower and the thermodynamic working point of 230 ° C.

The product has the disadvantage that it does not use the entire amount of hydrogen in the purge gas extracted from the main loop.

The object of the invention is to reduce energy and raw material consumption.

The technical problem to be solved by the invention is to establish the working conditions and the proportions of association of the components so that the reaction of conversion of the synthesis gas to methanol will take place with the reduction of the recirculation degree and with the increase of the production.

The process according to the invention removes the aforementioned disadvantages in that the conversion reaction of the synthesis gas to methanol takes place in the main synthesis reactor, operated in adiabatic regime, with the degree of recirculation 4 ... 6, being preceded by the conversion of the gas from synthesis, fresh, in the first additional synthesis reactor, column type, with the radial circulation of the fluid through the catalyst layer, operated in isothermal regime, without recirculation, mounted in series, before the main reactor, at working temperatures and pressures higher than this and being followed by the conversion of unreacted gases and purge gases extracted from the main synthesis loop, enriched with carbon dioxide so that the ratio H ₂ - CO / CO + CO ₂ is 2 ... 2,3, in that of second additional synthesis reactor, column type with radial flow of fluid through the catalyst layer, operated under isothermal regime, without recirculation ie, mounted in series after the main reactor, having working temperatures as low as possible and working pressure lower by 2 ... 2.5 bar.

The following is an example of an embodiment of the invention, in connection with the figure, which represents the technological scheme.

methane gas 23, steam 22 produced by cooling cracked and burned gases are introduced into the tubular reformer 1 in the recuperative boilers 2 supplied with water 21 and a part of CO ,, 25 from an external source 24, obtaining a mixture of oxides. of carbon and hydrogen 27 which is cooled in the heat recovery boilers 2 and by 28 it reaches a turbocharger 3 which compresses them up to the synthesis pressure, pressure which through 29 passes into the heat exchanger (gas-gas) 4, preheating. it is on account of the reacted gases, coming from the additional reactor 5, and through 30 are introduced, radially, in the synthesis catalyst, crossed by a system of concentric coils, through which the cooling medium circulates, so that the heat exchange is in cross-flow mode and isothermal. The cooling medium is pressurized water from the separator 6 through 31 and the pump 7 which flows the water through the coils, thus into the catalyst layer, after which through 32 the steam water emulsion is returned to the drum 6, where the saturated steam is extracted through 33 , and the evaporated water is filled by 34. The reacted gases leave the reactor 5 through 35, cool in 4 in counter current with the reaction mixture then through 36 enter the water cooled condenser 8, where the methanol produced condenses and through 37 it enters the separator 9 of which is extracted by 38, the separate methanol, and the unreacted gas 39 is mixed with the recirculated gas 40 from the recirculating synthesis loop and is compressed by the recirculator 10, up to the synthesis pressure. The gas thus compressed a cold part 42 is used as Quenche in the adiabatic reactor 11, and the other part 43, after preheating, in the gas-gas heat exchanger 13 passes through 44, at the top of the reactor circulating axially through the catalyst layer. The reacted gas exits the reactor through 45 passes through the same heat exchanger 12 counter-cooling, and then through 46 it enters the water condenser chiller 13, where it forms condensed methanol again, which through 47 together with the unreacted gases enters the separator.

14. The methanol is extracted by 49, and the unreacted gases leave by 48 from the separator, being divided into two streams, 40 gas recirculated in the synthesis loop and 50 purge gas to which carbon dioxide is added through 26, after which it passes through the gas-gas heat exchanger 15 preheating, through 51 radially penetrates, in the additional reactor 16 reacting again isothermal, the heat being taken up by the water stream 52 discharged by the pump 18 ee passes through the coils located in the catalyst and returns through 53 in drum 17, to release the formed steam extracting through 54, and the water is filled by 55.

The reacted gases exit the reactor 15 through 56, pass countercurrent through 15, then cool through 57, enter the condenser cooler 19 water-cooled, and the condensed methanol and waste gas pass through 58 into the separator 20, separating. Methanol is extracted through 60, and residual gas through 59, from where it is directed to combustion or other destinations. In a specific case of application, a synthesis gas consisting of 25.5 parts (CO + CO ₂ ) and 71.3 parts H ,, 3.2 inert parts having R = H ₂ -CO ₂ / CO + CO ₂ = 2,3 and COjCO = 1, enter through 30, into the isothermal reactor 5, in which 7.68 parts of methanol are produced, which is extracted through 38, and then into the synthetic loop, with recirculation, 14.27 parts continue to be produced. extra methanol and by 49 with only 553 parts reclaimed gas, and by adding 1 part CO, to the purge gas in column 16, another 1.34 parts methanol are formed, which is extracted by 60. So in total 23 , 39 parts methanol.

From the same fresh gas, without column 5 and 16, with an amount of 710 parts recirculated gas, only 19.8 parts methanol would have been obtained. The small CO ^ CO ratio favors increasing the amount of methanol produced in the reactor 5.

However, in order not to facilitate the overheating of the catalyst in reactor 5, the optimum ratio is about CO ₂ / CO = 0.4.

100,000 Nm ³ / h compressed at 52 bar is passed through a synthetic reactor, operated under isothermal regime, with radial flow of reactants, 235.67 to / day pure methanol is obtained after cooling and separation and 16.23 t / h 30 bar steam, temperature

For work being 255 ° C, the composition of the gas entrance in the column: CO = 15.48% CO, = 10.84% H, '= 70.11% ch ₄ = 2.91% N, = 0.28% H ₂ O = 0.38% After the separation of methanol remains 77014.41 Nm ³ / h waste gas with composites tion: CO = 10.94% CO, = 13.47% H, '= 70.89% ch ₄ = 3.78% N, = 0.36% H, 0 = 0.06%

CHjOH = 0.45%

This gas enters as a fresh gas in a recirculating synthesis loop and is converted, at a circulation rate of 5.2 at 270 ° C and a pressure of 51 bar in an adiabatic Quenche reactor at 459.88 t / methanol day remaining 27902.3 Nm ³ / h purge gas with the composition of:

CO = 7.885%

CO, = 10.445%

H, = 69.767%

CH ₄ = 10.443%

N, = 0.98%

H, 0 = 0.06%

CH, 0H = 0.451%

It is again passed through an additional synthesis reactor, operated in isothermal operating mode, at the pressure of P = 49 bar and the temperature of 230 ° C, obtaining 59.51 t / day crude methanol and a residual gas of 22 096, 7 Nm ³ / h having the composition:

CO = 3.83%

CO, = 11.23%

H ₂ = 69.95%

CH ₄ = 13.18%

N, = 1.24%

ΗΌ = 0.06%

CHjOH = 0.450% which can be used for combustion or in combination with CH ₄ and CO ₂ , to obtain fresh gas for synthesis.

Thus, a total production of 755.06 t / day pure methanol is obtained, obtained with a much lower degree of recirculation than in the classic version, when for this production it would have required a degree of recirculation of about 10 and without steam production.

The following advantages are obtained by applying the invention;

- increasing methanol production;

- increasing social productivity;

- reduction of production costs.

Claims (3)

Claim Process for obtaining methanol from synthesis gas, consisting of carbon dioxide CO, carbon dioxide CO ₂ and hydrogen H ₂ , obtained by catalytic reforming of natural gas and purge gas recycled with steam or steam and carbon dioxide CO ₂ , the synthesis gas compression, the conversion to methanol at 50 ... 120 bar pressure, and the temperature of 24O ... 27O ° C in synthetic reactors in the presence of ternary CuO-ZnO-AȚOj catalysts, with methanol separation and recirculation purge gas for catalytic reforming and / or combustion, characterized in that, for the purpose of reducing energy and raw materials consumption, the conversion reaction to methanol takes place in the synthesis reactor, mainly operated in Ad adiabatic regime, with the recirculation degree 4.,. 6, being preceded by the conversion of the fresh synthesis gas into the first additional synthesis reactor, column type, with the radial flow of the fluid through the catalyst layer, exploited in the isothermal regime, without recirculation, mounted in series, before the main reactor, at higher working temperatures and pressures than this and followed by the conversion of unreacted gases and purge gases extracted from the main synthesis loop, enriched with carbon dioxide, so as to encourage the ratio H ₂ - CO / CO + CO ₂ , 2,3, 2,3 in the second additional synthesis reactor, column type, 5 with the radial circulation of the fluid through the catalyst layer, exposed In isothermal regime, without recirculation, mounted in series, after the main reactor, having lower working temperatures and higher working pressures. 10 small with 2 ... 2.5 bar, with methanol separation after each reactor.