JPS623761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steam reforming method for methanol, and more specifically, when hydrogen is obtained from methanol using two reactors, a main reactor and a side reactor, the temperature of the side reactor is controlled. This article relates to a steam reforming method for methanol. Conventionally, the method of steam reforming methanol as a raw material to obtain a gas whose main component is hydrogen is as follows:
Two methods are known: a method using an adiabatic reactor and a method using an externally heated reactor. Compared to externally heated reactors, adiabatic reactors have
While the structure is simple, the cost of the equipment is low, and the loading and unloading of the catalyst is easy, steam reforming of methanol is a highly endothermic reaction, so the heat required for the reaction is small. The energy must be provided by the energy brought in by the reactants, and as a result the raw materials must be heated to high temperatures, which poses a great risk of thermally deteriorating the catalyst. In order to avoid deterioration of the catalyst, the steam ratio may be increased, but this increases the amount of steam used and is uneconomical. A method using a multi-stage insulation type has also been proposed,
Since this reaction has a large endothermic effect, the reaction rate decreases as the temperature of the reactants decreases, and external heating may have to be used. Therefore, there is a need for a method that avoids the above-mentioned drawbacks while employing an external heating type. For this purpose,
It is conceivable to install two stages of external heating types. Two small-scale reactors are installed in series without increasing the scale of expensive reactors, and unreacted methanol flowing out from the first stage reactor is reformed in the second stage reactor. Even if the catalyst in the first stage reactor deteriorates and unreacted methanol increases, there is still room for reforming in the second stage reactor. When catalyst deterioration in the first stage reactor progresses, replace the catalyst only in the first stage reactor and use the second stage reactor upstream and the first stage reactor downstream to use the catalyst effectively. The idea is to do so. However, in this case, since only a small amount of heat is required to be supplied to the subsequent reactor, an adiabatic type is sufficient without the need for an expensive external heating type. The present invention provides a method in which an external heating type is used as the main reactor and an adiabatic type is used as the finishing side reactor. However, this method also has the following drawbacks. (1) If the adiabatic reactor inlet temperature is not restricted, the temperature may drop too much depending on the amount of unreacted from the first stage.
Unreacted substances will flow out. (2) If the inlet temperature is raised even though there are no unreacted substances, carbon monoxide will increase. (3) If the amount of unreacted substances increases, thermal deterioration may occur, requiring a higher temperature. The inventors of the present invention have conducted intensive research on the above points and have completed the present invention. That is, the present invention provides a method for steam reforming methanol using an externally heated main reactor and an adiabatic side reactor, in which a heating furnace for the main reactor and a preheater for the side reactor are shared, and the main reaction This is a method of controlling the temperature of the side reactor by injecting boiler feed water or steam into the outlet gas line of the reactor near the inlet or outlet of the heating furnace. When controlling the reactor temperature, priority is given to controlling the temperature of the externally heated reactor, which is the main reactor, so it is difficult to control the inlet temperature of the adiabatic reactor, which is the side reactor, and the inlet temperature becomes high. I end up. If the side reactor is operated in a situation where the side reactor inlet temperature is higher than the main reactor outlet temperature, a reverse shift reaction will occur in the side reactor when there is no or little unreacted methanol, resulting in a decrease in the purity of the product. This is undesirable because it causes a decrease in yield, and furthermore, if the temperature exceeds the allowable temperature limit of the catalyst, the activity decreases. One way to solve this problem is to install a bypass between the main reactor and the side reactor without using a heating furnace, but in order to suppress the temperature rise at the inlet of the side reactor, increasing the bypass may cause the There is a risk that the temperature of the process gas inside the pipe will rise too much.
To counter this, for example, high-quality materials are required for the heating tube. It is possible to bypass the combustion gas side of the heating furnace, but this is not practical because it complicates the structure of the heating furnace and increases construction costs. It is also possible to set an appropriate inlet temperature of the side reactor depending on the concentration of methanol at the outlet of the main reactor, but in this case, unreacted methanol must be analyzed, so this is not suitable for actual operation. Difficulties arise. As described above, in order to suitably obtain a gas containing hydrogen as a main component from methanol using the main reactor and the side reactor, there remains the problem of controlling the temperature of the side reactor. A preferred embodiment of the invention includes injection of boiler feed water or steam into the feed gas of the side reactor near the furnace inlet or outlet;
This is carried out by controlling the temperature of the side reactor. The present invention will be explained below with reference to the drawings. FIG. 1 is a process sheet showing a preferred embodiment of the present invention. In the steam reforming reaction of methanol, methanol is supplied from methanol supply line 1, while steam is supplied from steam supply line 2 and mixed. The mixing ratio of methanol and steam at this time is 0.5 mol H ₂ O / mol methanol ~
A range of 7.0 mol H ₂ O/mol methanol is suitable, especially 1.0 mol H ₂ O/mol methanol to 5.0 mol H 2 O/mol methanol.
A range of mol H ₂ O/mol methanol is preferred.
This mixed fluid consisting of methanol and steam is heated to an externally heated reactor (main reactor) 3 at a predetermined temperature.
The methanol reforming reaction takes place.
A heat medium circulation line 6 is provided between the external heating type reactor 3 and the heating furnace 4 via a pump 5, so that the inside of the external heating type reactor 3 is kept at a constant temperature. The methanol reforming reaction in the externally heated reactor 3 is carried out at a temperature of 180 to 500°C, preferably 180°C.
The reaction is carried out in the presence of a copper-based catalyst under the reaction conditions of ~350°C and a pressure of 0~50 kg/ ^cm2 . The gas thus obtained is introduced into the adiabatic reactor (side reactor) 8 through the main reactor outlet gas line 7 and the heating tube of the heating furnace 4 . At this time, a valve 9 or 10 is installed in the main reactor outlet gas line 7 near the inlet or outlet of the heating furnace 4.
Injection of boiler feed water or steam is performed from a boiler feed water or steam injection line 11 having a boiler feed water or steam injection line 11, and the temperature of the side reactor 8 is controlled. The reaction gas in the adiabatic reactor 8 has a temperature of 180 to 500°C, preferably 180 to 350°C,
Under reaction conditions of a pressure of 0 to 50 kg/cm ² and in the presence of a copper-based catalyst, unreacted methanol is further reformed, and a gas containing hydrogen as a main component is obtained from the product gas line 12. In addition, in the present invention, it is also possible to provide a valve in each of the methanol supply line 1 and the steam supply line 2 to adjust the amount of methanol and the amount of steam. Further, it is desirable to provide temperature detectors in the heat medium circulation line 6 and the main reactor outlet gas line 7 to control the temperatures of the main reactor 3 and the side reactor 8. The present invention as described above has the following effects. (1) By increasing the amount of steam entering the side reactor through boiler feed water or steam injection, methanol decomposition progresses in an equilibrium manner, improving the yield and further increasing the hydrogen concentration. (2) The temperature at the inlet of the side reactor can be appropriately controlled, extending the life of the catalyst. (3) Temperature control has quick response. (4) Equipment costs are low because high-grade materials are not used for the heating tubes and there is no need to install a combustion exhaust gas bypass in the heating furnace itself. The present invention will be specifically described below based on comparative examples and examples. Comparative example 1 H ₂ O 16.8Kg/HR for methanol 20Kg/HR
mixed and sent to external heating type reactor 3, 325
The reaction was carried out while maintaining the temperature at 11 Kg/cm ² ·G. Since undecomposed methanol flows out of the externally heated reactor outlet gas (analytical value: approximately 20%), this outlet gas is preheated to 425°C and then fed into the adiabatic reactor 8 for reaction. , the temperature at the adiabatic reactor outlet became 325℃. This gas was cooled to remove water vapor, and 2.4 m ³ /HR of gas having the composition shown in Table 1 was obtained. Comparative example 2 H ₂ O 16.8Kg/HR for methanol 20Kg/HR
mixed and sent to external heating type reactor 3, 325
The reaction was carried out while maintaining the temperature at 11 Kg/cm ² ·G. Since undecomposed methanol flows out of the externally heated reactor outlet gas (analytical value: approximately 20%), this outlet gas is preheated to 470°C and then fed into the adiabatic reactor 8 for reaction. , the temperature at the adiabatic reactor outlet was 360℃. This gas was cooled to remove water vapor to obtain a gas having the composition shown in Table 1. 【table】

[Brief explanation of the drawing]

FIG. 1 is a process sheet showing one embodiment of the present invention. 1... Methanol supply line, 2... Steam supply line, 3... Main reactor (external heating type reactor), 4
... Heating furnace, 5... Pump, 6... Heat medium circulation line,
7... Main reactor outlet gas line, 8... Side reactor (adiabatic reactor), 9, 10... Valve, 11... Boiler feed water or steam injection line,
12...Produced gas line.

Claims (1)

[Claims] 1 In a method of steam reforming methanol using an externally heated main reactor and an adiabatic side reactor, the heating furnace for the main reactor and the preheater for the side reactor are shared, and the outlet gas of the main reactor is A steam reforming method for methanol characterized by controlling the temperature of a side reactor by injecting boiler feed water or steam near the inlet or outlet of a heating furnace in a line.