Gas: heating and illuminating – Processes – Fuel mixtures
Reexamination Certificate
1999-07-15
2001-07-31
Tran, Hien (Department: 1764)
Gas: heating and illuminating
Processes
Fuel mixtures
C073S199000, C422S105000, C422S107000, C422S108000, C422S110000, C422S112000, C422S116000, C429S010000, C429S010000, C429S006000, C429S006000
Reexamination Certificate
active
06267792
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an apparatus and a method for controlling a reaction which occurs in a reformer for reforming hydrocarbon and reformate fuel into a desired type of fuel with a high concentration of hydrogen.
2. Description of Related Art
A reformer designed to reform a vapor mixture of methanol and water into reformate gas mainly composed of hydrogen is known. In principle, according to a reforming reaction occurring in the reformer, methanol reacts with water vapor so as to produce hydrogen gas. In other words, a water vapor reforming reaction occurs in the reformer. This is an endothermic reaction, as can be understood from equation (1) shown below.
CH
3
OH+H
2
O→3H
2
+CO
2
−49.5 kJ/mol (1)
Further, the activation temperature of a reforming catalyst is relatively high (about 300° C.). Therefore, in order to continue the above-mentioned reforming reaction, it is necessary to supply a corresponding amount of reaction heat.
On the other hand, as an example of a reforming reaction of methanol, there is a partial oxidation reforming reaction wherein hydrogen is produced through an oxidation reaction. This is an exothermic reaction, as can be understood from the equation (2) shown below.
CH
3
OH+½O
2
→2H
2
+CO
2
+189.6 kJ/mol (2)
The reactions represented by the aforementioned formulas (1) and (2) can be caused to proceed simultaneously. For example, there is known a fuel cell system of a type compatible with partial oxidation, wherein the heat generated in the partial oxidation reaction compensates for the heat absorbed in the water vapor reforming reaction (Japanese Patent Publication No. HEI 7-57756).
As is apparent from the equations (1) and (2), the amount of heat absorbed in the water vapor reforming reaction is greatly different from the amount of heat generated in the partial oxidation reaction. Thus, provided that these reactions occur simultaneously for methanol of 1 mol, a large amount of heat is generated and the catalyst reaches an excessively high temperature, so that the catalyst may deteriorate in activity or durability. Conversely, if the partial oxidation reforming reaction (equation (2)) is at a low ebb, the reforming catalyst falls in temperature, so that an undesirably large amount of methanol remains and an undesirably large amount of carbon monoxide gas is produced.
That is, even in the case where the water vapor reforming reaction is caused to proceed simultaneously with the partial oxidation reforming reaction, the proceeding of the water vapor reforming reaction may be adversely affected depending on a degree of the proceeding of the partial oxidation reforming reaction. For this reason, the reformer of a type compatible with partial oxidation needs to suitably control the partial oxidation reaction. However, the above-described known apparatus do not control the partial oxidation reaction. Therefore, the known apparatus have trouble in constantly maintaining the reforming portion at a temperature required for the reforming reaction. In particular, in the case where the amount of reformate fuel fluctuates in response to load fluctuations in an energy converter such as a fuel cell which consumes reformate fuel, the temperature of the reforming portion such as the reforming catalyst may become unstable. As a result, the reformate gas may deteriorate in quality.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the aforementioned disadvantages of known apparatus and methods. It is an object of the present invention to provide an apparatus and a method capable of constantly maintaining a reformer, that utilizes both a reforming reaction and a partial oxidation reforming reaction, at a temperature required for the reforming reaction.
In order to achieve the above-stated object, the present invention has focused attention on the fact that the oxygen supplied to the reforming portion undergoes the partial oxidation reaction. The amount of oxygen to be supplied can be determined based on either a required amount of reformate fuel contributing to the exothermic reforming reaction (the water vapor reforming reaction), or a required amount of reformate fuel contributing to the partial oxidation reaction. In the present invention, the amount of oxygen to be supplied is determined based on an amount of reformate fuel contributing to the partial oxidation reaction, which amount is determined based on a ratio between a theoretical endothermic value in the endothermic reforming reaction and a theoretical exothermic value in the partial oxidation reaction.
That is, according to one aspect of the present invention, a control apparatus for a reformer includes a controller for controlling the introduction of raw material and oxygen into the reformer and promoting an endothermic reforming reaction and an exothermic partial oxidation reaction, and for determining an amount of oxygen supplied for the partial oxidation reaction based on an amount of the raw material and on theoretical exothermic values in the reforming reaction and the partial oxidation reaction.
In the above aspect, the endothermic value and the exothermic value are balanced with each other in the reforming reaction, so that the portion of the reformer where the reforming reaction occurs can be maintained at a predetermined temperature. Consequently, the reforming reaction proceeds favorably, and high-quality fuel can be obtained.
In addition to the features of the above aspect, the controller determines an amount of time from supply of the raw material to occurrence of the reforming reaction and the partial oxidation reaction, and adjusts the determined amount of supply of oxygen based on that amount of time.
Thus, even if there is a fluctuation in the amount of supply of the raw material, the amount of supply of oxygen is corrected in accordance with a temporal delay of a fluctuation in the reforming reaction resulting from the fluctuation in amount of supply of the raw material. Therefore, the portion of the reformer where the reforming reaction occurs can be maintained at the predetermined temperature with higher precision.
Further, in addition to the features of the above aspect, the control apparatus can include a temperature detector for detecting a temperature of a portion of the reformer where the reforming reaction and the partial oxidation reaction occur, and the controller can adjust the determined amount of supply of oxygen based on the detected temperature. In this manner, the portion of the reformer where the reforming reaction occurs can be maintained at the predetermined temperature with still higher precision. As a result, the reforming reaction is stabilized and high-quality fuel can be obtained.
Further, in addition to the features of the above aspect, the controller can estimate a state quantity of oxygen supplied for the partial oxidation reaction, and adjust the determined amount of supply of oxygen based on the estimated state quantity of oxygen.
According to the above embodiment, the state quantity such as a feed pressure of oxygen is estimated in supplying oxygen, and the amount of supply of oxygen is corrected based on the estimated state quantity. Thus, the amount of supply of oxygen can be controlled precisely. As a result, the reforming reaction is stabilized and high-quality fuel can be obtained.
REFERENCES:
patent: 4125091 (1978-11-01), Hori et al.
patent: 4822521 (1989-04-01), Fuderer
patent: 4984456 (1991-01-01), Takahashi
patent: 5366821 (1994-11-01), Merritt et al.
patent: 0 743 694 A1 (1996-11-01), None
patent: 0 798 798 A2 (1997-10-01), None
patent: 0 834 948 A2 (1998-04-01), None
patent: 7-57756 (1995-03-01), None
Motozono Yoshikazu
Nagamiya Kiyomi
Yamaoka Masaaki
Yamashita Masashi
Oliff & Berridg,e PLC
Ridley Basia
Toyota Jidosha & Kabushiki Kaisha
Tran Hien
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