JPS6230601A - Method of supplying methanol cracking device with heat - Google Patents

Abstract

PURPOSE:To obtain a cracked gas easily at low cost without requiring a heater for raw material, etc., at starting, by supplying a necessary heat with a latent heat of a heating medium at starting, preheating methanol by the use of a sensible heat of the heating medium during normal operation and cracking it by a reactor. CONSTITUTION:A flow rate of methanol and water is adjusted to a given ratio and methanol and water are fed from the methanol supply line 1 and the pure water supply line 2 to a system. In starting, since there is no or an extremely small amount of a gas at the outlet gas line 8 of the reactor 7 and there is no heat source for the preheater 3 for raw material, steam having heated and evaporated a heating medium by the heater 6 for heating medium is sent from the heating medium feed supply line 5 to the evaporation superheater 4, provides methanol with heat, is condensed into liquid, returned to the heating medium heater, these operations are repeated and high heat load is supplied with the latent heat by phase change to evaporate methanol. On the other hand, during normal operation, the raw material is preheated with a gas of the outlet gas line 8 by the preheater 3, the temperature of the raw material is raised by the use of by sensible heat of the heating medium by the evaporation superheater 4, evaporated methanol is fed to the reactor 7 with a tube packed with a catalyst and methanol is cracked under heating to give a H2 gas or a mixed gas of H2 and CO.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for supplying heat to a methanol decomposition apparatus that decomposes methanol under a catalyst to produce hydrogen gas or a mixed gas of hydrogen and carbon monoxide. .

(Conventional technology) There is no need to overstate the importance of hydrogen in modern industry. Namely, ammonia synthesis, methano-μ synthesis, petroleum 1! From low-concentration, large-volume consumption types such as the LV manufacturing industry to high-concentration, low-volume consumption types such as the semiconductor industry and the space industry, it is used in a wide range of fields such as organic and inorganic chemical industries, food, metallurgy, electricity, and atomic energy. Hydrogen is indispensable, and the need for an inexpensive method to produce hydrogen has been voiced for a long time.

However, it is not easy to develop new techniques for producing hydrogen at low cost, and hydrogen is produced in small quantities by electrolysis of water, and in large quantities by catalytic reforming of hydrocarbons such as butane and naphtha.

On the other hand, -carbon oxide is used in the carbodimu reaction and oxo reaction in the organic chemical industry, and in the production of acetic acid and ethylene glyco-mu, and has recently attracted particular attention as a raw material for carbon engineering chemistry.

However, it is difficult to produce this carbon oxide at low cost.
It is produced by a partial oxidation reaction of hydrocarbons such as butane or heavy oil, or by recovery from gases containing carbon monoxide such as steel mill waste gas, but because the process is complicated, it is more expensive than hydrogen. It is gas.

Furthermore, mixed gases of hydrogen and carbon monoxide are often required at door-to-door ratios, but these are also produced by partial oxidation of heavy oil, coal, etc., which is also expensive. .

As an alternative to such conventional methods for producing hydrogen, carbon oxide, or a mixed gas thereof, methods that utilize methanol reforming or decomposition reactions have been attracting attention.

The reaction steps are as follows.

That is, when obtaining hydrogen as a product, methanol-p
The following equation progresses due to the steam reforming reaction.

CH30E + I (2”→3H, +CO,...
-(1) Furthermore, when obtaining a mixed gas of hydrogen and carbon monoxide as a product, the following equation proceeds in the decomposition reaction of methanol-μ.

CH, OH → 2H, + Co... (2) All of these reactions are reactions under a catalyst, and the reaction temperature is 300 to 4
It is an endothermic reaction at 00℃, and in equation (1), 1t s k
ca11 mol methanol, 21.4 kc in formula (2)
Requires reaction heat of ~al/7μ methanol.

This conventional technique is shown in FIG. 2, and its contents will be briefly explained.

Methanol and water adjusted to a predetermined flow rate ratio are
Supplied from μ supply line 1 and pure water supply fin 2,
After exchanging heat with the outlet gas from the reactor 7 in the raw material preheater 5, it is externally heated to the reactor inlet temperature in the evaporative heater 4,
Supplied to reactor 7. Reaction 'a7' is generally of the tubular type, in which methanol is passed through a bed filled with catalyst in the reaction tube.

A heating medium heated by burning fuel from the fuel supply fins 20 is passed through the heating medium heating furnace 16 to heat the reaction tube from the outside to supply the heat necessary for methano-p decomposition. A part of the heating medium from the heating medium heating furnace 16 is also supplied to the evaporative heater 4, and after cooling down, it is returned to the heating medium heating furnace 16 via the heating medium return fin 19 by the heating medium circulation pump 18. In the reactor 7, methanol is decomposed and hydrogen gas or a mixed gas of hydrogen and carbon monoxide is generated.This high-temperature gas is heated to the raw material in the raw material preheater 5, and then cooled to around room temperature in the cooler 9. After further cooling, the condensate containing unreacted methanol is separated in the gas-liquid separator 10, and this condensate is returned through the undecomposed methanol circulation fin 12, and only the gas component is transferred from the gas fin 11 to the gas vI11! Supply to unit 13. In the gas purification unit 15, after removing impurities or adjusting the hydrogen/-carbon monoxide gas ratio, the product gas is taken out from the product gas take-out line 14.

The condensed components in the gas-liquid separator 10 are returned to the pure water supply fins 2 through the circulation fins 12. Note that 15 is a starting material preheater.

(Problem to be solved by the invention) The problem with the conventional method shown in FIG. 2 is the raw material preheater 3.

That is, after normal operation is reached, high-temperature gas is obtained from the reactor 7, so the raw material preheater 3 can perform its function, but when the device is started, the heat source for preheating is not obtained from the process.

In this case, the general method is to supply a very small amount of raw material at startup, heat the heating medium for 100 degrees, and gradually increase the temperature of the entire system while increasing the load. This method takes a long time to start up and does not meet the requirement for short startup times. Therefore, we had no choice but to install a starting material preheater 15 as shown in Figure 2.
Take the method of preheating the raw materials.

As a heat source for this preheater, steam, electricity, or a part of a heating medium is used, but during normal operation, this preheater 15 is not bypassed, and there is a device that is used only during startup. Become.

Alternatively, it is possible to make the evaporative superheater 4 have a high heat load at startup, but since the heat load decreases during normal operation, this heat exchanger is over-designed.

The present invention seeks to provide a method for supplying heat to a methanol decomposition unit that can overcome the above-mentioned drawbacks of the conventional methods.

(Another Means to Solve the Problems) That is, the present invention provides an apparatus for decomposing methanol under a catalyst to produce hydrogen gas or a mixed gas of hydrogen and carbon monoxide, in which the heating medium is decomposed during a high heat load at the time of starting the apparatus. This is a heat supply method for a methanol decomposition apparatus characterized by supplying necessary heat by latent heat, and supplying necessary heat by sensible heat of a heating medium during low heat load during normal operation.

As mentioned above, in a methanol decomposition device that requires a large amount of heat at startup and a reduced heat load during normal operation, the present invention uses equipment designed with specifications for normal operation and changes only the operating conditions of the heating medium. This effectively copes with heat load fluctuations.

The heat transfer coefficient of a heat exchanger is greater than that without phase change.
It is a well-known fact that the value becomes larger when phase changes such as evaporation and condensation are involved.

Generally, the heat medium system shown in Fig. 2 is operated in the liquid phase, so the heat medium side of the evaporative superheater 4 is always in the liquid phase, and the heat transfer coefficient of this heat exchanger is 200 to 400 kcal/-・Hr・℃. be. On the other hand, when heat is supplied by condensing the heating medium in an evaporative superheater, the heat transfer coefficient on the heating medium side increases significantly, and therefore the overall heat transfer coefficient is 800 to 1000 kca]/rr.
It becomes possible to take the values of L2・Hr・℃. The aim of the present invention is to take advantage of this phenomenon and enable high heat load operation at startup using equipment designed with specifications for low heat load during normal operation.

One embodiment of the present invention will be described in detail with reference to FIG.

After adjusting the flow of methanol and water to a predetermined ratio,
The water is supplied to the μ supply fin 1 and the pure water supply fin 2 system, heated to the reactor inlet temperature by a preheater 3 and an evaporator superheater 4, and then supplied to a reactor 7 whose tube is filled with a catalyst. Heat necessary for the reaction to proceed is supplied to the reactor 7 by a high-temperature heating medium or electric heating (not shown), and methanol is decomposed to produce hydrogen gas or a mixed gas of hydrogen and carbon monoxide. During normal operation, this high-temperature gas is cooled in the raw material preheater 5, and further cooled to room temperature in the cooler 9, after which undecomposed methanol for recirculation is separated in the gas-liquid separator 10, and this is unseparated. It is returned to the system inlet through the decomposed methanol μ circulation line 12, and only the gas component passes through the gas purification unit 13 and is taken out as product gas from the product gas take-out line.

In this device, at startup, the reactor outlet gas fin 8
There is no gas in the
There is no heat source. Therefore, during normal operation, the total heat load of the raw material preheater 3 and the evaporative superheater 4 is
It has to be covered.

In this method, heat is supplied by circulating the heat medium heated by the heat medium heater 6. First, during a high heat load at startup, the heat medium evaporates in the heat medium heater 6 and becomes steam. The heat medium is then sent from the heat medium supply line 5 to the evaporative superheater 4. In this evaporative superheater 4, heat is given to methanol and the heating medium is condensed.
It becomes a liquid and is returned to the heat medium heater 6.

In this way, the heat medium repeatedly undergoes evaporation in the heat medium heater 6 and condensation in the evaporator superheater 4, thereby covering a high heat load with the latent heat generated by the phase change.

On the other hand, when normal operation starts and the preheater 3 starts to preheat the raw material using the outlet gas of the reactor, the evaporative superheater 4
The heat load will be reduced. In this case, the heating medium does not undergo a phase change and always circulates between the evaporative superheater 4 and the heating medium heater 60 in a liquid state, and the sensible heat of the heating medium provides the heat necessary for heating the methanol.

In such an operation, the evaporative superheater 4, the heat medium heater 6
The specifications and heat medium circulation site may be the same in either case, and what is changed is the #AIJX operating pressure and the amount of heat supplied from the heat medium heater 6. That is, during high heat load, the operating pressure of the heating medium is slightly lowered compared to during normal operation to cause a phase change, and the amount of heat supplied by the heating medium heater 6 is increased. Note that the heat supply method in the heat medium heater 6 may be an electric type, a fuel-fired type, or the like, and is not particularly limited.

(Example) Example 1 Methanol/1/938 mo/L//hour, water 94 mo/L//
The raw material at 20°C is supplied to start the equipment, and the raw material at 20°C is sent to the evaporation superheater, and the heat medium Therm-S 300 from Nippon Steel Chemical Industry is heated in the heat medium heater to produce a gaseous state at 380 to 400°C. It was circulated as a heating medium at a rate of about 6 kg/a112·G, and the methanol-μ was heated by condensation of this heating medium. The gaseous heating medium that heated methanol became a liquid heating medium at 200 to 600°C, returned to the heating medium heater, became a gaseous heating medium at the above temperature again, and was circulated to the evaporation superheater. As a result, methano-p
was heated to 350° C., and the heat load on the evaporative heater at this time was 14,500 kcal/hour.

The resulting evaporated methanol is supplied to the reactor and decomposed, producing 15767 μm of hydrogen, 694 μμ of carbon oxide, 947 μm of carbon dioxide, 94 moles of methane, and unreacted methanol per hour.
'56 moles of gas were obtained.

Example 2 During normal operation under the same conditions as Example 1, methanol was heated from 20°C to 170°C in the feedstock heater, while gas was heated at 3°C.
The temperature drops from 50℃ to 110℃, and the heat load is a a o o
It was kcal/hour.

In the evaporative heater, methanol is heated at a rate of about 9 yu/ls”
The liquid THERM-S 300 operated by the heating system 3
It is heated to 50℃, and the heat load at this time is t 700 kc.
al/hour. Furthermore, the properties of the gas produced by decomposing methanol in the reactor were the same as in Example 1.

Example 3 Methanol A/687 mo/L//hour, water 687 mo/L//
The raw material at 20°C is supplied to start the device, and the raw material at 20°C is sent to the evaporation superheater, and the heat medium THERM-S 50G from Nippon Steel Chemical Industry is heated in the heat medium heater to produce a gaseous state at 380-400°C. It was circulated as a heating medium at a rate of about 6 Y/12.G, and the methanol-μ was heated by condensation of the heating medium. As a result, methanol
It was heated to 350° C., and the heat load on the evaporative heater at this time was 18,600 kcal/hour.

The evaporated methanol is fed into the reactor and decomposed, producing 1154 moles of hydrogen, -508 moles of carbon oxide, and 6 moles of carbon dioxide per hour.
9 moles, 69 moles of methane, unreacted methano-A/41 mop
of gas was obtained.

Example 4 During normal operation under the same conditions as Example 3, methanol was heated from 20°C to 180°C in the feedstock heater, while gas was heated at 5°C.
Temperature decreased from 50℃ to 160℃, heat load was 5700kc
al/hour.

Methanol is heated at approximately qkg/aN2 in the evaporative heater.
It is heated to 350°C by liquid THERM-S 300 operated by G, and the heat load at this time is 12900 k
It was cal/hour. Furthermore, the properties of the gas produced by decomposing methanol in the reactor were the same as in Example 3.

Example 5 Using the same equipment as in the previous example, methanol/l/400 m/l
// hour, 600 moA//hour of water was supplied, and after being heated and evaporated, it was fed to the reactor. As a result, 1080 moμ of hydrogen, 3607 p of carbon dioxide, 21 mole of carbon oxide, and 15 mole of methane were produced per hour.
mol and some unreacted methanol were obtained. The heating medium heating operation during start-up operation and normal operation was the same as in the previous example.

(Effects of the Invention) As described above, there is no need for a raw material heater especially for startup and for heat medium piping thereto, which reduces the number of devices and contributes to reducing the cost of the device.

Additionally, it is easy to operate, leading to lower operating costs.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating one embodiment of the present invention, and FIG. 2 is a diagram illustrating a conventional method of supplying heat to a methanol decomposition apparatus. In the figure, 1: methanol supply line, 2:
Pure water supply line, 5: Raw material preheater, 4: Methanol evaporation superheater, 5: Heat medium circulation fin, 6: Heat medium heater, 7: Reactor, 8: Reactor outlet gas line, 9: Cooler, 10:
Gas-liquid separator, 11: Gas-liquid separator gas line, 12: Undecomposed methanol) V circulation line, 13: Gas loading unit,
14: 1ψ product gas extraction line, 15: Start? +1 Raw material preheater, 16: Heat medium heater, 17: Heat medium supply line, 1
8: Heat medium circulation pump, 19: Heat medium return line, 2
0: Fuel supply line sub-agent 1) Meifuku agent Ryo Hagiwara - Sub-agent Atsuo Anzai Ward 11+, -; continued on page 1) Inventor Yoshio Miyairi Marunouchi, Chiyoda-ku, Tokyo Inside the company

Claims (1)

[Claims] In equipment that produces hydrogen gas or a mixed gas of hydrogen and carbon monoxide by decomposing methanol under a catalyst, the required heat is supplied by the latent heat of the heating medium during the high heat load at startup, and the low heat during normal operation is supplied. A method for supplying heat to a methanol decomposition apparatus, characterized in that during load, necessary heat is supplied by sensible heat of a heating medium.