JPS649358B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a fuel gas containing methane as a main component by reacting hydrocarbons and/or oxygen-containing hydrocarbon compounds with steam, and more specifically, a method that combines a catalytic combustion process and a steam reforming process. The present invention relates to a method for producing fuel gas. Conventionally, the calorific value is approximately 5000Kcal for city gas.
A cyclic catalytic cracking method is known as a method for producing fuel gas of about 100%. When hydrocarbons are used as feedstock, this method is simple in equipment and does not require any special additional equipment, so it is widely used in gas businesses, and is particularly popular in small and medium-sized gas businesses in rural areas.
The cyclic method is a method that utilizes the reforming of feedstock oil through an endothermic gasification reaction between the feedstock oil and steam, and is a method in which heating periods and production periods are alternately repeated. During the heating period, the feedstock oil and air are burned in a burner to heat the Chetsuka brick and the reforming nickel-based catalyst layer, and at the same time, the carbon deposited on the catalyst is incinerated, and the amount of heat stored therein is used to carry out the endothermic gasification reaction described above in the next production period. proceed. The reactor (reforming reactor) that is the main body of the reaction is generally a fireproof brick lined cylindrical container containing a nickel catalyst, and is usually equipped with feed oil and air supply means, a combustion burner,
Equipment such as an air preheater and steam preheater is attached. The temperature inside the reactor is raised to a reaction temperature of 800 to 900°C by partially burning raw material oil (heated oil) with air using a burner built into the furnace. Although there are various types of reactors, the reaction is carried out at low pressure due to the high reactor temperature and constraints on the reactor material and structure, and therefore pressurization is required to store the fuel in the gas tank. Particularly fundamental problems are that because the heating period and the manufacturing period are performed alternately, the distribution of the flow passing through the catalyst layer tends to be uneven, and due to burner combustion, the heating oil is completely combusted and local heating occurs.
This will cause an abnormality in the temperature distribution of the catalyst layer, leading to a decrease in gasification performance. Further, there are problems such as the composition of the fuel gas not being constant due to alternating repetition of the heating period and the manufacturing period and fluctuations in the temperature distribution of the catalyst layer. The present invention has been made in view of the above-mentioned current situation, and its purpose is to constantly produce fuel gas having a calorific value similar to that of the cyclic method by a combustion reaction and a steam reforming reaction at a low temperature under medium-high pressure. The purpose is to provide a method. The method for producing fuel gas of the present invention which achieves the above object is a method for producing a fuel gas containing methane as a main component by reacting a raw material oil consisting of hydrocarbons and/or an oxygen-containing hydrocarbon compound with steam. , raw oil in a catalytic combustion zone with a noble metal catalyst layer,
Feedstock oil and steam are heated by passing oxygen-containing gas, water vapor, and recycled gas from the reforming zone, and then passing the catalytic combustion zone treated gas to a reforming zone having a reforming catalyst layer. do. The present invention includes a catalytic combustion process and a steam reforming process,
Combining the recycled gas from the reforming zone by passing it through the catalytic combustion zone, this makes it possible to regularly carry out combustion reactions and steam reforming reactions at temperatures below 500°C under a pressure of 2 atmospheres or more. It is something. In other words, part of the combustion reaction is a reaction between hydrogen gas in the recycled gas and a supplied oxygen-containing gas, such as oxygen gas in the air. In addition, another combustion reaction, the combustion reaction between the feedstock oil and oxygen, preheats and raises the temperature of the feedstock oil and steam necessary for the steam reforming reaction, thereby stabilizing the catalytic combustion and steam reforming reactions. It will be done. This method allows the use of oxygen-containing hydrocarbon compounds such as alcohols, in addition to the hydrocarbons used in the cyclic method, as the feedstock oil. These feedstock oils are not particularly limited, but desirably have a boiling point of 250°C or lower, and petroleum fractions with a boiling point of 120°C or lower, such as liquefied petroleum gas (LPG) or light naphtha, are generally used. The present invention will be further described with reference to the accompanying drawings:
The attached drawings show a flowchart of a specific example of carrying out the present invention.
1 is an air supply system, 2 is a feedstock oil supply system, 3 is a water supply system, 4 is a catalytic combustion tower, 5 is a steam reforming tower, 6 is a heat exchanger, and 7 is a notch for removing steam. Out drum, 8 is generated gas holder, 9
1 is a fuel gas supply system, 10 is a recycled gas circulation system, 11 is a compressor, and 12 and 13 are steam supply systems. In order to produce fuel gas containing H ₂ , CO, CO ₂ , and CH ₄ , a part of the fuel gas from the generated gas holder 8 is used as recycled gas at startup, and the circulating system 10
The air is compressed by a compressor 11 and introduced into the catalytic combustion tower 4 along with air and steam preheated by a heat exchanger 6. The catalytic combustion tower 4 is filled with a catalyst in which a noble metal is supported on a heat-resistant oxide carrier such as alumina or silica. In the catalytic combustion tower 4, the temperature is increased mainly by the H2 _{- O2} reaction. The heated mixed gas of recycle gas and steam is then introduced into a steam reforming tower, where the temperature of the tower is raised. The steam reforming tower 5 may be filled with a nickel and/or cobalt catalyst as a reforming catalyst, and the catalyst may be reduced when the temperature is raised. The heated mixed gas from the steam reforming tower 5 is introduced into the heat exchanger 6 and the water supply system 3
generates steam by exchanging heat with water from the The mixed gas is then introduced into the knockout drum 7.
Water vapor is removed and stored in a product gas holder. In addition, since the generated gas cannot be recycled during initial startup, hydrogen-containing gas such as bottled gas is used instead of recycled gas. As mentioned above, the catalytic combustion tower 4 and the steam reforming tower 5
After the temperature has been raised, the feedstock oil is introduced into the catalytic combustion tower, heated, and then connected to the steam reforming tower 5, and steam is introduced from the steam supply system 13 to start the reaction in the steam reforming tower 5. Adjust the amount of water vapor to suit. In order to set the inlet temperature required for the reaction in the steam reforming tower 5, the catalytic combustion tower adjusts the amount of heat generated by the combustion reactions of the raw oil and air, and the hydrogen gas and oxygen in the recycled gas. Therefore,
In steady-state operation, the amount of air in the catalytic combustion tower is adjusted to allow a partial combustion reaction between part of the feedstock oil and air to take place, and the introduction of recycled gas can be restricted. In the steam reforming tower 5, a product gas containing CH ₄ as a main component and containing H ₂ , CO, CO ₂ and H ₂ O is obtained by the reaction of the raw material oil and steam, as shown in Examples below. The generated gas undergoes heat exchange through a heat exchanger 6, and then H ₂ O is removed in a knockout drum 7, and then stored in a generated gas holder as fuel gas, and a portion is circulated as recycled gas. . The noble metal catalyst used in the catalytic combustion zone may be any commonly used noble metal catalyst, such as alumina,
For example, 0.1
A low proportion of platinum group metal catalyst of ~0.5% by weight,
No reduction operation is required before use. On the other hand, the reforming catalyst used in the steam reforming zone is a normal nickel and/or cobalt catalyst.
Or the cobalt content is 40-80% by weight. Examples of this type of catalyst include Ni-Al ₂ O ₃ (Japanese Patent Publication No. 44-17737), Ni-MgO (Japanese Patent Application Laid-open No. 76902-1983), Ni-
La ₂ O ₃ -Al ₂ O ₃ (Japanese Unexamined Patent Publication No. 53-31590) is known. The appropriate temperature conditions for the catalytic combustion zone are 300°C to 500°C, and the pressure may be 2 to 100 atmospheres, but is not particularly limited. The supply speed of recycled gas and feedstock oil is
The SV (space velocity) is 5000 to 100000h ^-1 . The amount of air added to the recycled gas is 4 to 10% by volume in terms of the O ₂ concentration in the recycled gas, and is preferably equivalent to the H ₂ concentration in the recycled gas. The reaction temperature in the steam reforming zone is 350-500
It is ℃. According to the present invention, it is possible to obtain a fuel gas containing 40% by volume or more of CH ₄ , and there is no need to cycle between the heating period and the production period in a steady state, except for the heating period at startup. Because fuel gas can be produced in the same state, the equipment, including the fuel gas tank, can be made smaller. Next, the present invention will be explained with reference to examples, but the present invention is not limited thereto. Example In this example, the apparatus is of a high-pressure flow type, and the catalytic combustion zone is located in the center of the reaction tube with an inner diameter of 15 mm and a length of 400 mm.
A catalyst (reduced state) having a diameter of 3 mm and a length of 3 mm and carrying 0.3% by weight of PD was packed in alumina. The steam reforming zone is a reaction tube with an inner diameter of 4.6 mm and a length of 600 mm, and a NiO−La ₂ O ₃ −Al ₂ O ₃ catalyst produced by a three-stage precipitation method is crushed into 0.5 to 1.0 mm in the center of the zone. It was filled to a length of about 30 cm. (Catalyst amount: approx. 5 ml). The catalyst was reduced at 500° C. for 4 hours prior to use. A thermocouple is slid inside the thermocouple insertion tube installed in the center of the catalytic combustion reaction tube to measure the temperature inside the catalyst layer, and the TCD is used to observe changes in the gas composition before and after the reaction tube.
(Thermal Conductivity Detector) and FID
(Flame Ionization Detector) was installed. Similarly, the temperature distribution of the catalyst layer of the steam reforming reaction tube was measured, the reaction end point was determined from the temperature distribution, and the deterioration rate of the catalyst was determined from the time change. This experiment was conducted at a catalytic combustion zone pressure of 9.0 to 8.0 Kg/cm ² G,
The steam reforming was carried out under pressure at a zone pressure of 7.0 Kg/cm ² G. The measurement positions and measured values were as shown in the table below. The measurement positions were as follows, and the measured amounts were expressed in moles (relative amounts) and composition %. A Butane supply B Air supply C Water supply D Cycle gas supply E Catalytic combustion zone inlet F Catalytic combustion zone outlet G Steam reforming zone outlet

[Table] From the previous experiment, the combustion reaction was performed at a reaction initiation temperature of 25°C.
It reaches about 470℃ within 1 hour and progresses steadily.
The steam reforming reaction proceeded at 480°C, and the maximum deterioration rate was 0.78 mm/hr. As is clear from the above description, the present invention allows the reaction to be carried out constantly without alternating the heating period and the manufacturing period, and it is easy to adjust the operation according to the amount of fuel gas supplied.

[Brief explanation of drawings]

The accompanying drawings show a flow chart of one embodiment of the present invention. 1... Air supply system, 2... Raw material oil supply, 3... Water supply system, 4... Catalytic combustion tower, 5... Steam reforming tower, 7... Knockout drum, 8... Produced gas holder, 9...
Fuel gas supply system, 10...recycled gas circulation system,
12, 13...Steam supply system.

Claims (1)

[Claims] 1. In a method for producing a fuel gas containing methane as a main component by reacting a feedstock oil consisting of hydrocarbons and/or an oxygen-containing hydrocarbon compound with steam,
Feedstock oil, oxygen-containing gas, steam, and recycle gas from the reforming zone are passed through a catalytic combustion zone having a precious metal catalyst layer to raise the temperature of the feedstock oil and steam, and then the treated gas in the catalytic combustion zone is passed through the reforming catalyst layer. 1. A method for producing fuel gas, the method comprising: conducting the fuel gas through a reforming zone having a reforming zone.