JPS5817121B2 - Kangenseigusnoseizohou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of a reducing gas containing high concentrations of hydrogen and carbon monoxide from gaseous hydrocarbons or hydrocarbon oils.

Reducing gases are important as raw materials for the metallurgical industry or the organic synthetic chemical industry.

It is naturally desirable that the total concentration of hydrogen and carbon monoxide contained in the reducing gas be high, and at the same time, it is necessary that the relative ratio of the concentrations of these two components be in accordance with the purpose of use.

Steam reforming of light hydrocarbons is widely used to produce synthesis gas that contains hydrogen at a high concentration. As long as a sufficient amount of steam is supplied, stable continuous production is possible.

In the steam reforming method, it is desirable that the raw material hydrocarbon be as light as possible, and when using a commonly used nickel catalyst, desulfurized hydrocarbon oil with a final boiling point of about 350°C can be used as the hydrocarbon oil. is among the heaviest, and only after a sufficient amount of water vapor is added can hydrogen, for example 42.4 vol., be produced without carbon deposition on the catalyst surface. %
, carbon monoxide 9.5vo 10%, carbon dioxide 8.3vo
1. %, methane 3.2vol. %, water vapor 36.6vo
1. % of gas is produced continuously.

In this case, the ratio between the amount of water vapor added and the amount of carbon in the feedstock hydrocarbon needs to be at the minimum value in practice, at a H20/C molar ratio of about 3; if it is less than this, free carbon will be deposited on the catalyst surface. This occurs and the catalytic ability is rapidly impaired, making it impossible to continue the gasification reaction continuously.

In the conventional steam reforming method using a nickel catalyst, the use of heavy hydrocarbon oil with a final boiling point above the above limit as a raw material is difficult due to significant carbon precipitation even though the amount of steam increases. This makes it completely impossible for the reaction to continue.

The oxygen constituting the steam combines with carbon in the raw material hydrocarbon to produce carbon oxide, and the hydrogen constituting the steam is useful for increasing the hydrogen concentration in the product gas.

Currently, in the steam reforming method that is widely used, there are strict restrictions on the quality of hydrocarbons and the amount of steam supplied to the reaction zone in the nine ways described above, so the relative content ratio of each component gas in the product gas is approximately The range in which the ratio can be arbitrarily changed is extremely small.

In the conventional method, it is undesirable or impossible to arbitrarily change the ratio of the amount of each component gas, and it is the best way to prevent deterioration of catalyst performance due to impurities such as sulfur in the hydrogen as a raw material or to avoid carbon precipitation. We are in a situation where we have no choice but to focus on this.

The inventors have previously proposed a steam reforming method that can avoid these limitations of commonly used nickel catalysts, using a different type of catalyst that does not contain any nickel and is manufactured using a special preparation method. We have completed a method for continuous steam reforming of heavy hydrocarbons, which cannot be used as side bottom feedstock, using a nickel catalyst for a long period of time without any carbon precipitation.

In the inventors' method, the fired product of a binary system of high-purity calcium oxide and aluminum oxide does not produce carbon deposits on the surface of the fired product in the presence of water vapor, and the following reaction between carbon and water vapor is significantly promoted. It is based on the discovery of the phenomenon of

C+HO-pCO+H2 C+2H20→C02+2H2 What is extremely important in this phenomenon is that the two-component fired product needs to have high purity.

It is essential that silicon oxide, which is normally contained in strong, refractory fired products, is not present in more than a small tolerable amount in the fired product used as a catalyst in the process of this invention.

When the silicon oxide content exceeds a permissible value, this catalytic property disappears rapidly.

Regarding other impurity components other than silicon oxide, oxides of elements of Group I of the periodic table or heavy metal oxides are also harmful.

However, silicon oxide is most likely to be present in large amounts as an impurity in commonly available raw materials for calcium oxide and aluminum oxide.

The presence of oxides of other alkaline earth metals in the same family of calcium, such as beryllium, magnesium, and strontium, in the fired product as a third component other than calcium oxide and aluminum oxide may cause a decrease in catalytic performance. No.

In addition to high catalytic performance, it is practically extremely important that the catalyst has the strength to be used in the reaction system for a long time without being damaged.

In order to avoid the inclusion of silicon oxide, which is useful for producing strong calcined products, in the catalyst of the process of this invention, special preparation methods are required to produce a catalyst with the necessary strength.

First, refractory calcium aluminate powder is required as a raw material for catalyst production.

As calcium aluminate, CaO・6A1203.
Ca0・2. Al2O3, CaO-Al2O3゜12C
It is known that a0.7A1203 or 3CaO.Al2O3 exists, but what is referred to here as refractory calcium aluminate powder has a roasting temperature of approximately 1.6
It is a mixed fine powder of highly pure crystals having the above chemical composition, which has a fire resistance of 00° C. or higher and does not contain impurities such as silicon oxide.

As a refractory calcium aluminate powder, a blend of high purity aluminum oxide and calcium oxide is heated to 1,600°C.
A powder obtained by pulverizing the baked ingot after firing at the above high temperature may be used.

After manufacture, the refractory calcium aluminate powder must be stored in highly dry conditions.

High purity calcium oxide powder and aluminum oxide powder are required as other catalyst manufacturing raw materials.

Substances that convert into these two highly pure oxide powders upon heating can also be used.

High purity calcium oxide and/or aluminum oxide is added to the calcium aluminate powder prepared by high heat treatment to obtain the desired ratio of calcium oxide to aluminum oxide in the catalyst components of the catalyst. Add it, knead it in water and mold it at room temperature for at least 24 hours.
After being allowed to stand for a period of time to harden, it is dried and fired at 1,150°C or higher for 2 hours or more to achieve a compressive strength of 180.
The fired product is made of

When the desired catalyst component can be obtained by calcining only calcium aluminate powder, addition of calcium oxide and aluminum oxide is not essential.

In order to maintain the strength of the fired product and the catalytic ability, the calcium oxide content is kept within 10 wt.% or more and 60 wt.% or less.

As mentioned above, the most important requirement for these catalyst production raw materials is their purity.

Regarding silicon oxide, which is likely to be present in the highest amount as an impurity in these raw materials, the silicon oxide content in each raw material is adjusted so that the silicon oxide content in the manufactured catalyst is 1 wt.% or less. Regulated.

In the presence of the catalyst thus prepared, if the reaction temperature, space velocity, or water vapor to carbon molar ratio of the feed stream to the gasification reaction zone is maintained appropriately depending on the type of feedstock hydrocarbon, carbon deposition on the catalyst can be prevented. The gasification reaction is allowed to proceed continuously in a state where there is no gas.

In the steam reforming method using a nickel catalyst, it is possible to gasify a heavy hydrocarbon oil fraction, much less a heavy hydrocarbon oil containing distillation residue oil, but the method used in the method of the present invention According to the catalyst, the gasification reaction of heavy hydrocarbon oil containing distillation residue oil can proceed continuously without carbon deposition on the catalyst surface.

Although it is unclear why the catalyst of the method of this invention produces such an effect, it is believed that this catalyst has an extremely strong carbon repelling force.

It is easy to understand that it is theoretically possible to use carbon dioxide as an oxygen-containing substance instead of steam in steam reforming, and this has been widely known for a long time, but in practice This increases the total amount of carbon fed into the reaction zone, increasing the risk of carbon precipitation.Using carbon dioxide as an oxygen-containing substance is a common problem, since there is little possibility of using heavier hydrocarbon oils. In the steam reforming method, this is only theoretically possible, but not practical.

The calcium oxide/aluminum oxide catalyst used in the method of this invention is capable of continuously gasifying heavy hydrocarbons, which were considered to be unusable as raw materials for steam reforming. The inventors conducted experiments to determine whether or not it is useful not only as a carbon dioxide gas reforming catalyst but also as a carbon dioxide gas reforming catalyst.

A series of gasification experiments were conducted in which the amount of carbon dioxide gas supplied to the steam reforming reaction system was gradually increased, and the amount of steam supplied was correspondingly decreased.

Finally, the water vapor supply was reduced to zero and carbon dioxide was used as the oxygen source for the reforming reaction.

As a result of these series of experiments, high purity calcium oxide
It has been found that the carbon repulsion of the aluminum oxide two-component catalyst is the same as in the case of steam reforming, and the reforming reaction can be carried out continuously with a good carbon gasification rate.

From these experimental results, it was found that the ratio of hydrogen to carbon monoxide in the reducing gas produced by changing the combination of the type of hydrocarbon used as a raw material and the ratio of carbon dioxide gas and steam used as a reforming agent was determined. It has become clear that it can be varied within a relatively wide range.

That is, the molar ratio of hydrogen to carbon oxide in the reducing gas produced ranged between 0.5 and 4.42.

The method of this invention is a continuous gasification method suitable for obtaining a product gas with a H2/CO ratio of 3 or less, particularly 2 or less.

According to the present invention, since there is no carbon precipitation, within this ratio range, reducing gas of any ratio can be easily obtained by changing the composition of the feed stream to the gasification reaction zone and the gasification reaction conditions. be able to.

Since this is a carbon dioxide gas reforming method, it is possible to separate carbon dioxide, which is an unnecessary component from the produced reducing gas, and supply it again to the gasification reaction zone as a reforming agent.

Alternatively, it is also possible to circulate a portion of the reducing gas produced without separating carbon dioxide, which is an unnecessary component, to the gasification reaction zone.

The reducing gas used to reduce the ore in the metallurgical process and enriched with carbon dioxide is suitable for recycling to the gasification reaction zone.

Example A120379.27%, Ca118.57%tF
e2030.21%.

81020.12%, ignition loss 1.50%, fineness 88
54.5 parts of precipitated calcium carbonate powder is blended with 45.5 parts of high-grade electrofused alumina cement of 97% micron or less, fire resistance 1, 8oo'C, and further contains 3 parts of white kerosene, 1 part of methyl cellulose, and 27 parts of water. After adding 100% and thoroughly kneading,
It was molded into pellets with a diameter of 12.5 mm and a length of 13 mm.

This molded product was placed in a sealed container and cured at room temperature for 24 hours or more to harden while preventing moisture evaporation.

Through this curing, the compressive strength reached approximately 120.

After curing, the molded product was gradually dried. The molded product was filled in a fireproof container, such as an alumina sagger, which is difficult to fuse with the molded product, and sintered in a heavy oil-fired tunnel kiln.

In this sintering, the initial temperature was gradually increased, and after the dehydration of the molded product and the volatilization and combustion of the contained organic matter were almost completed, the temperature increase rate was set at a constant rate.

During this heating period, the components will be thermally decomposed to about 1,000℃.
The removal of bound water is completed, and solid-state reactions occur between calcium aluminate particles or between acid binder components such as calcium oxide and aluminum oxide.

This firing was accomplished by finally increasing the temperature to 1.300°C and maintaining this temperature for 2 hours.

The chemical composition of the fired product thus obtained was Ad20349.
04%, Ca050.13%, Mg0o, z5%, N
a2O0.30%, Fe2030.18%, S t0
It has an apparent porosity of 48.2%, an apparent specific gravity of 2.76, and a bulk specific gravity of 1.42, and does not disintegrate in boiling water, and the weight increase due to boiling is 17.8%. , the room temperature compressive strength was 415~.

This fired product catalyst has an inner diameter of 20 mm where the outer wall is heated by electric heat.
rIL7It20 in a vertical tubular reactor with a length of 280 mm
It was packed to form a bed of 0 mrn.

A mixture of raw material hydrocarbon and a modifier was continuously passed from the top to the bottom of this vertical tubular reactor for a predetermined gasification reaction time.

Thereafter, air was supplied to the catalyst bed in the vertical tubular reactor to convert the precipitated carbon on the catalyst surface into carbon dioxide, which was absorbed into soda asbestos to quantify the precipitated carbon.

Table 1 shows the results of experiments using naphtha as a raw material.

This naphtha had the following properties.

EBP 180°C Specific gravity 0.7413 Elemental analysis (wt, %) Carbon 8524 Hydrogen 14.74 Sulfur Trace Table 3 shows the experimental results when naphtha and Kuwaiti crude oil were gasified under pressure.

It is an essential condition that the catalyst used in the method of this invention has high purity, and in order to demonstrate this, a catalyst prepared by specifically containing silicon oxide as an impurity in the catalyst of this invention was used. The results of experiments using the method of this invention are shown in Table 4 as a comparative example.

As shown by the results of Experiment Nos. 19, 20, 22, and 23, as the silicon oxide content increases, the amount of carbon deposited on the catalyst bed increases significantly, and the precipitated carbon increases the flow resistance of the catalyst bed, resulting in an increase in the reaction rate. The pressure at the vessel inlet rose extremely, and it became impossible to continue the gasification reaction within a short time.

Claims (1)

[Claims] 1. In producing a reducing gas by reacting a gaseous or liquid hydrocarbon raw material with carbon dioxide or a mixture of carbon dioxide and water vapor under normal pressure or normal temperature and normal pressure, the gasification reaction temperature is set to 950 to 1,000 ℃. Within the range of 100°C, the ratio of the amount of oxygen in the carbon dioxide or the mixture to the amount of carbon in the hydrocarbon (in 002') (
The I/C atomic ratio or the atomic ratio of 8 in 002 + H20 is 2.59 or less, and the catalyst is made of only high-purity calcium oxide and high-purity aluminum oxide, and only refractory calcium aluminate powder or this A mixed powder of a powder and one or more powders selected from two types of powder: calcium oxide and aluminum oxide, or a refractory calcium aluminate powder and a powder that converts into calcium oxide upon heating, and aluminum oxide. The mixed powder with one or more powders selected from the two types of powders is kneaded and molded with water and cured, and then the precipitated carbon is removed in the presence of a substance fired at a high temperature of about 1,150°C or higher. i
A method for producing a reducing gas.