JPH034597B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing city gas using methanol as a raw material. (Technical background) Recently, gas has been used as a raw material for city gas mainly in metropolitan areas.
With the introduction of LNG (liquefied natural gas), city gas with a high calorific value is being collected, but in the case of LNG, it is necessary to transport and store it at an ultra-low temperature of minus 162 degrees Celsius, which is difficult for city gas companies in small and medium-sized cities. Reminder,
There are many technical and economic problems regarding storage, etc. For this reason, efforts are being made to develop means for producing city gas using methanol as a raw material, which is liquid at room temperature and easy to transport and store. In addition to the above-mentioned advantages in terms of transportation and storage, this methanol can be obtained constantly at low cost from overseas abundant resources such as coal and natural gas, and is also free from sulfur, nitrogen, and heavy metals. It has the advantages of not containing any impurities and requiring no desulfurization work, and is seen as a promising future city gas raw material. (Prior art and its problems) Conventionally, as a means for producing city gas using methanol as a raw material, the method described in, for example, Japanese Patent Publication No. 57-24835 is known. This conventional method involves catalytic cracking of a raw material mixture of methanol and water in the presence of a ruthenium (Ru) catalyst to produce hydrogen (H ₂ ), carbon monoxide (CO), and carbon dioxide (CO ₂ ). It generates gas and also methanizes hydrogen and carbon monoxide. Note that after this methanation, decarboxylation, dehydration, and calorific value adjustment are performed. According to such conventional means, since the gas produced by catalytic cracking is further subjected to a methanation operation, there are problems in that the manufacturing cost is increased, the manufacturing efficiency is lowered, and the device structure becomes complicated and large. (Problems to be Solved by the Invention) The problems to be solved by the present invention are that methane-containing gas is generated from a mixed raw material of methanol and water in only one reaction step, and that methanol is This eliminates the need to supply fuel for heating raw materials and water to be mixed with methanol. (Means for Solving the Problems) The technical means of the present invention to solve the above problems is to heat a mixture of methanol and water to a required temperature by heat exchange with a heat medium, and then reduce the content of sulfur compounds. Via a nickel-based catalyst supported on an alumina-based carrier with a reduced specific surface area.
A methane-containing gas is directly generated by the reaction under low-temperature reaction conditions of about 300℃ or less, and after separating water from the methane-containing gas, a high amount of heat is generated through the steps of removing carbon dioxide, dehydration, and increasing heat by adding butane. Town gas is regularly produced, and the water mixed with the methanol and the heat source for heating the heat medium are all separated from the methane-containing gas during the production process, except for being supplied from outside at startup. This is done using the reaction heat generated when gas containing water and methane is generated. (Specific Description of the Invention) Hereinafter, the method for producing high-calorific city gas as a methanol raw material of the present invention will be described in detail based on the process flow shown in FIG. The raw material methanol is mixed with water and sent to the reactor 1. At this time, the mixed raw material of methanol and water is heated and vaporized by recovering the heat of the reaction gas coming out of the reactor 1 and the heat of the methanation reaction caused by the gas phase contact reaction in the reactor 1, and then sent to the reactor 1. That is, the methanol/water mixed raw material sequentially passes through a preheater 2 in which a reaction gas flows through a heat exchanger, an evaporator 3 in which a heating medium heated by the heat of methanation reaction in the reactor 1 circulates and flows, and a superheater 4. Thereby, it is preheated in the preheater 2, vaporized in the evaporator 3, further heated in the superheater 4, and sent to the reactor 1. The reactor 1 performs a vapor phase contact reaction of the methanol/water mixed raw material heated and vaporized in the preheater 2, evaporator 3, and superheater 4 in the preheater 2, evaporator 3, and superheater 4 in the presence of a catalyst to generate a methane-containing mixed gas as a reaction gas. For example, it has a shell-and-tube structure. The catalyst packed in the tube of the reactor 1 is made by supporting a nickel-based catalyst on an alumina-based carrier with a reduced content of sulfur compounds and a _reduced specific surface area. ^-2 ) 1.2% by weight or less of finely powdered r-alumina or finely powdered alumina hydrate supported on a carrier of nickel (Ni) and/or a part of nickel or its reduced product, or
A reduced product of nickel is supported on a silica/alumina carrier having a specific surface area of 350 m ² /g or less. This catalyst has the characteristics of exhibiting high low-temperature activity and ^high methanation rate, and produces a methane-containing mixed gas (CH ₄ 72%, CO 25% and _H2 3%) can be produced in only one stage _of reaction. After water is separated from the generated methane-containing mixed gas, it is decarbonized and dehumidified, and further heated by mixing with butane to produce high calorific value city gas. Separation of water from the methane-containing mixed gas is carried out in the reaction gas separation tank 5 according to a conventional method. At step 2, the heat is recovered to the methanol/water mixed raw material, and at the same time, the heat is recovered to potassium carbonate vapor at the reboiler 6 in the decarbonation gas step, further cooled at the cooler 7, and then sent to the reaction gas separation tank 5. 1. The methanation reaction by gas phase catalytic reaction in the reactor 1 is an exothermic reaction, and the reaction heat generated here is sent to the evaporator 3 via the superheater 4 via a heating medium. Then, the heat is recovered to the methanol/water mixed raw material that is evaporated in evaporator 3, and then the heat is recovered in evaporator 3.
Then, the heat is recovered by the methanol/water mixed raw material that is preheated by the preheater 2 and sent. The above heat medium is a molten salt that melts at 142°C, and is circulated through the heat medium circulation path A via the heat medium storage tank 8, the reactor 1, the superheater 4, and the evaporator 3 by the operation of the pump 9, and is reacted. The reaction heat of the methanation reaction is absorbed in the reactor 1 during normal operation, and the heat is recovered into the methanol/water mixed raw material in superheater 4 and evaporator 3 during normal operation, and this methanol/water is recovered.
The water mixed feed is heated together with the methane-containing mixed gas exiting the reactor 1 to the required temperature, ie the activation temperature. That is, the heat of the methanation reaction and the heat of the methane-containing mixed gas generated by the reaction cover all of the amount of heat required to generate the methane-containing mixed gas. Incidentally, since the reaction heat is generated in an amount larger than necessary, the heat medium temperature controller 10 is used to cool and adjust the temperature. This heating medium temperature regulator 10 is provided between the heating medium storage tank 8 and the reactor 1. In addition, the separated water separated from the methane-containing mixed gas in the reaction gas separation tank 5 is used as water to mix with the raw material methanol supplied by the methanol feed pump 11 from an external methanol supply source to produce a methanol/water mixed raw material. It is recycled and used, but the remainder is discarded. That is, the entire amount of water required for producing the methanol-containing mixed gas is covered by this separated water. The water mentioned above is mixed with methanol in order to prevent carbon precipitation during the gas phase contact reaction in the reactor 1, and the molar ratio of water to methanol is preferably adjusted to 0.5. When the water/methanol molar ratio is set to 0.7 or more, the amount of heat required to heat the methanol/water mixed raw material to the required temperature increases, and all of that heat is used to heat and methanize the methane-containing mixed gas exiting reactor 1. In order to cover the heat from the reaction, it is difficult to provide sufficient heat insulation and heat retention, and the burden on the circulation system also increases, which is disadvantageous in terms of manufacturing costs. Furthermore, if the water/methanol molar ratio is set to 0.3% or less, carbon precipitation problems are bound to occur during long-term steady operation. Of course, at startup, there is no water separated from the methane-containing mixed gas, and no reaction heat is generated to heat the heating medium, so there is no need for external water supply or heat from an external heat source. Although it is necessary to heat the medium, after the transition to steady operation there is no need for this at all, and it is sufficient to just feed methanol. The startup will be described later. Next, the decarbonation gas step, dehumidification step, and butane heating step are performed by conventional methods. That is, the methane-containing mixed gas from which water has been separated in the reaction gas separation tank 5 is removed by absorbing carbon dioxide into potassium carbonate in the carbon dioxide absorption tower 12, and then passed through the coolers 13, 14, and 15 to the purified gas water separation tank. 1
6, where water is separated. The calorific value of the methane-containing mixed gas was reduced to 9200Kcal/ ^Nm3 by removing carbon dioxide gas in the decarbonation process described above.
It can be increased to a certain extent. Note that this decarbonation step can of course be performed by other methods such as a dry method (PSA method). Finally, a required amount of butane is mixed with the decarbonated gas and the dehumidified purified gas via the mixer 17, and the amount of heat is increased and adjusted to about 11000 Kcal/Nm ³ . At this time, butane is evaporated by recovering heat from the decarbonated methane-containing mixed gas that has left the carbon dioxide absorption tower 12 and has not passed through the first cooler 13. In this way, city gas with high calorific value can be constantly obtained at room temperature. The flowchart of the city gas production process is shown in Figure 2. Next, although not directly related to the gist of the present invention, some explanation will be given regarding the start-up when carrying out the method for producing high-calorific city gas as a raw material for methanol according to the present invention. At startup, water for mixing with methanol is supplied from outside by a water feed pump 18. Further, the temperature of the heating medium is raised by a heating medium heating furnace 19 provided between the reactor 1 and the superheater 4 in the heating medium circulation path A, and a heater 20 provided in the heating medium storage tank 8. The means and process of heating the heating medium described above are shown in Figures 3 to 7.
To explain based on the figure, as shown in FIG. 3, a bypass is appropriately provided in the heat medium circulation path A, and a first
circulation system a, heat medium storage tank 8 to heat medium temperature regulator 10;
The second circulation system b returns to the heat medium storage tank 8 via the heat medium heating furnace 19, and the heat medium is returned from the heat medium storage tank 8 to the heat medium temperature regulator 10, the heat medium heating furnace 19, the superheater 4, and the evaporator 3. The route B that forms the third circulation system c that returns to the storage tank 8 and connects the supply of raw materials to the extraction of city gas includes an ethanol/water mixture in the middle of the pipe leading from the reaction gas separation tank 5 to the carbon dioxide absorption tower 12. A bypass 22 equipped with a start-up blower 21 is provided by connecting the upstream side of the preheater 2 of the pipeline for supplying the raw material, and connects the start-up blower 21 to the preheater 2, the evaporator 3, the superheater 4, the reactor 1, A fourth circulation system d is formed which returns to the start-up blower 21 via the preheater 2, the reboiler 6, and the reaction gas separation tank 5. First, the heat medium in the heat medium storage tank 8 is heated by the heater 20, and the pump 9 is operated to circulate and flow the heat medium into the first circulation system a, so that the temperature of the heat medium is 170°C.
(Figure 4). Subsequently, the flow of the heating medium is switched to the second circulation system b, and fuel is supplied to the heating medium heating furnace 19 to be combusted and heated, and the temperature of the heating medium is raised to about 250°C (fifth
figure). Next, the flow of the heat medium is switched to the third circulation system c (Fig. 6). Thereafter, nitrogen (N ₂ ) is fed into the fourth circulation system d by the start-up blower 21 and circulated. Then, Chituso (N ₂ ) flowing through the fourth circulatory system d
The heat of the heat medium is recovered by the evaporator 3 and the superheater 4, and the temperature is raised to about 250°C, which is the heat medium temperature, and the reactor 1 is heated to obtain the activation temperature (Fig. 7). When the above reaction conditions are established, the flow of the heating medium is switched to the normal heating medium circulation path A, and the raw material prepared by adding field water to methanol is fed into the reactor 1. As a result, reaction heat is generated and water is separated from the reaction gas (methane-containing mixed gas).Then, this reaction heat and separated water are used to supply feed water and fuel to the heating furnace 19. is stopped and steady temperature rotation is performed. (Example) Regarding the method for producing high-calorific city gas as a methanol raw material according to the present invention, an example in which high-calorific city gas was actually manufactured based on the process flow shown in FIG. 1 will be shown below. Example 1 Water and methanol as raw materials, with a molar ratio of 0.5,
In the reactor 16, the reaction temperature is 305°C and the reaction pressure is 9.0.
When operated under the condition of Kg/cm ² G, a manufactured gas having the following properties was obtained. Calorific value 11000Kcal/Nm ³ Specific gravity 0.68 WI (Wotsupe index) 13340 CP (combustion velocity) 41.9cm/s Table 1 shows various numerical values for each stream number in the flowchart shown in Figure 2 for this example. . Example 2 Water and methanol as raw materials, with a molar ratio of 0.5,
In the reactor 16, the reaction temperature was 299°C and the reaction pressure was 8.9°C.
When operated under the condition of Kg/cm ² G, a manufactured gas having the following properties was obtained. Calorific value 11000Kcal/Nm ³ Specific gravity 0.68 WI (Wotsupe index) 13340 CP (combustion velocity) 41.6cm/s Table 2 shows various numerical values for each stream number in the flowchart shown in Figure 2 for this example. .

【table】

【table】

[Table] (Effects) Since the present invention has the above configuration, it has the following advantages. (1) Methanol is methanated by a gas phase catalytic reaction in the presence of a catalyst in a reactor, and a methane-containing mixed gas with a high methane yield can be obtained in one step using one reaction means. (2) The mixture of water and methanol can be made up entirely of water separated from the methane-containing gas mixture. (3) The reaction heat in the reactor and the heat of the methane-containing mixed gas discharged from the reactor can be recovered and used for heating the methanol/water mixed raw material. (4) Therefore, according to (2) and (3) above, it is possible to constantly obtain a methane-containing mixed gas by only intermittent supply of methanol and without any supply of heating energy or raw material water, which is economical. The effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a process flow schematically showing an example of the process of implementing the present invention, and FIG. 2 is a flowchart showing an embodiment of the present invention. Indicates the measurement position of the indicated specifications. FIGS. 3 to 7 are explanatory diagrams illustrating the start-up process.

Claims (1)

[Claims] 1. After heating a mixture of methanol and water to the required temperature by heat exchange with a heat medium, the mixture is heated to 300°C via a nickel-based catalyst supported on an alumina-based carrier with a reduced content of sulfur compounds and a reduced specific surface area.
A methane-containing gas is directly generated by the reaction under low-temperature reaction conditions, and after separating water from the methane-containing gas, it undergoes the steps of carbon dioxide removal, dehydration, and heating by adding butane to produce high-calorie city gas. The water to be mixed with the methanol and the heat for heating the heating medium are supplied from outside at the time of start-up. A method for producing high calorific city gas as a raw material for methanol, characterized in that the heat of reaction generated during generation of methane-containing gas is used.