JPS6246902A - Evaporator for methanol reformer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an evaporator that is a component of a methanol reformer.

Generally, a methanol reformer consists of an evaporator heated by a burner, a superheater, and a reforming catalyst bed. First, the methanol aqueous solution is gradually evaporated while flowing through the evaporator, and then heated to about 300℃ in the superheater. It is supplied as steam to the reforming catalyst bed, where it is converted into hydrogen-rich gas. This hydrogen-rich gas is supplied to the fuel electrode as the fuel gas of the fuel cell, and a cell reaction occurs between it and the air that can be supplied to the air electrode as an oxidizing agent to generate hydrogen.

The conventional evaporator has a coiled tube (main part) as shown in Figure 3.
It consisted of a), an inlet pipe (b) and an outlet pipe (c) before and after it, all of which had the same diameter. However, since the burner heat is sent downward rather than upward, the amount of evaporation in the upper coil section is large, and the volume of gas and liquid increases significantly as it moves downward. Therefore, with coils of the same diameter, the flow velocity increases,
There was a risk that steam would condense due to insufficient heat received at the bottom of the coil.

This occurs especially when the amount of liquid to be supplied is increased by using a coil with a small number of turns due to the requirements of the /h type, and if the methanol aqueous solution cannot be sent to the superheater in a completely evaporated state, There was a problem that the steam temperature necessary for reforming could not be obtained.

The present invention solves the above problems and provides an evaporator that can completely vaporize an aqueous methanol solution even if the amount of the aqueous methanol solution supplied is increased.

In this invention, the diameter of the coiled tube of the evaporator is gradually increased from the upper part near the burner to the lower part, and the inlet tube leading to the coiled tube for the methanol aqueous solution and the outlet tube leading to the superheater for the evaporated gas. The diameter of the valley is made to match the diameter of the upper and lower valleys of the coiled tube, respectively.

According to this invention, even if the volume of gas and liquid increases due to evaporation in the upper part of the coiled tube, this is absorbed in the lower part of the coiled tube, which is gradually expanding in diameter, so that the flow velocity does not increase significantly. Since the amount of heat received does not decrease even in the lower part, the gas phase does not condense as in the conventional case, and even if the amount of methanol aqueous solution supplied increases, it is possible to smoothly evaporate it despite the small size.

Embodiments of the invention are described below with reference to the figures.

The methanol reformer has a burner (2) at the top of a heat-insulating outer can (1), and inside the outer can (1) is an annular chamber (3) filled with a reforming catalyst inside and outside double walls. A superheater (4) and an evaporator (5) are arranged concentrically with this annular chamber.

As shown in Fig. 2, the evaporator (5) has a coiled tube (6) whose diameter gradually increases downward from the top near the burner (2). ) is divided into three sections, the diameter of which is the same as that of the liquid introduction tube (7) in the L part coil (61) (this is taken as 1), and 1.5 in the middle coil (62).
The lower coil (63) is twice as large, and the tube cross-sectional area has a ratio of 1 for the upper coil, 2.25 for the middle coil, and 4 for the lower coil. The steam outlet pipe (8) leading to the superheater (4) has the same diameter as the lower coil (63).

The coils (61) (62) <63) having different diameters are connected using appropriate connectors.

Methanol aqueous solution supplied to the evaporator 5 from a mixed species (not shown)? & (methanol: water - 1 mol% = 1.3
mole%) is introduced from above through the introduction pipe (7) into the coiled pipe (6).
) It evaporates without flowing down inside. In this case, the amount of evaporation is large in the upper coil (61) near the burner (2), and the gas-liquid volume increases significantly, but this is absorbed by the intermediate coil (62), which has a sequentially larger diameter, and then by the lower coil (63). Since the flow rate does not increase significantly, the amount of heat received by the lower coil (63) remote from the burner does not decrease, and therefore the gas phase does not return to the liquid phase.

This steam is sent to the superheater (4) via the outlet pipe (8),
There, it becomes superheated steam at about 300°C and enters the annular chamber (3) via the conduit (9). In this chamber (3), due to the action of the reforming catalyst, hydrogen 11/thigas (H2: CO2 - 80:20
) and supplied as fuel gas for the fuel cell through the delivery pipe (10). The blower (11) provides fuel air to the burner (2) and sends its heat downward.

An example of the design of a methanol reformer is an external height of 400 m in ψ height, a diameter of 200 m, and an evaporator coil (
The taste of 6) is 100-150m. This capacity glue homer can be used as a fuel gas source to supply one small fuel tank with an output of about 3 to 5 kW.

As described above, according to the present invention, the diameter of the coil portion of the evaporator gradually increases from the upper part near the burner toward the lower part, so that the increase in volume of the gas-liquid phase due to evaporation of the methanol aqueous solution can be absorbed. Suppressing the flow velocity and receiving p8ji in the lower coil
Since i does not decrease, the gas phase does not condense, and even if the amount of methanol aqueous solution supplied increases, it can be smoothly evaporated.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a methanol reformer equipped with an evaporator of the present invention, FIG. 2 is a front view of the evaporator of the present invention, and FIG. 3 is a conventional evaporator. 2: burner, 3: annular chamber, 42 superheater, 5: evaporator,
61.62.63: Coils with different diameters, 7: Introduction tube,
8: Leading pipe.

Claims (1)

[Claims] (1) The diameter of the coiled tube is gradually increased from the upper part near the burner to the lower part, and each diameter of the inlet pipe leading to the coiled pipe for methanol aqueous solution and the outlet pipe leading to the superheater for evaporated gas. The evaporator for a methanol reformer is characterized in that the diameters of the upper and lower portions of the coiled tube correspond to the respective diameters of the coiled tube.