JPH03179090A - Reformer for manufacturing town gas - Google Patents

Abstract

PURPOSE:To obtain the title reformer of low-pressure cyclic type which can reduce the concentration of oxygen in the final supply gas by forming a constitution wherein a supplementary combustion chamber separate from a reformer body is connected to the body with a pipeline through a valve and is provided with air, fuel, and steam inlets and a pilot burner. CONSTITUTION:A reformer of low-pressure cyclic type in equipment for manufacturing town gas, which has a supplementary combustion chamber 5 separate from a reformer body 1, connected to the body 1 with a pipeline 6 through a valve 7, and provided with a burner 8 having such a constitution that air and gas are mixed at the base, a pilot burner 9 in such a position that the flames of the burner 8 and burner 9 cross each other and thereby the burner 8 can be ignited, and a steam introducing nozzle. When the above-mentioned reformer is used, the produced gas going out of a reactor has such a quality of low calorific value that dilution usually performed for adjusting the calorific value has already been done: that is, dilution is accomplished with an oxygen- free gas, so that the amount of air to be incorporated for adjusting the calorific value can be reduced and therefore the concentration of oxygen in the final supply gas can be lowered.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a reforming furnace for producing city gas.

[Prior art] City gas, especially those that use petroleum hydrocarbons as raw materials and steam-reformed gas (carbon oxide transformation, heating, etc., are also performed as necessary) are as follows. Dilution with air is used for several reasons.

The first reason is that the produced gas from the reformer has a low calorie, so it is necessary to adjust the calorie (calorific value) to that of the supplied gas. If you simply increase the heat with butane, etc., the gasification efficiency (total calories of supplied gas / total calories of raw materials and fuel) will be low, so butane, etc., which does not require the heat of reforming (that is, does not need to be decomposed), will be low. This is to improve gasification efficiency by introducing a large amount and diluting it again.

Furthermore, the calorie content of city gas must be kept constant in order to ensure the safety of combustion in gas appliances, calculation of gas charges, etc. As a way to keep the calorie constant, it is easier to control and raise the calorie to a higher value than the specified value and then dilute it with air, rather than using a substance such as butane whose calorie value fluctuates greatly when added in a small amount. It is.

For these reasons, gas plants that use gas obtained by steam reforming petroleum hydrocarbons always dilute the gas with air.

[Problem B to be Solved by the Invention] As described above, when the production gas is diluted with air, oxygen will inevitably be mixed in. Regarding this, there are the following problems.

Compressing flammable gas containing oxygen is dangerous, so according to the High Pressure Gas Control Law, which applies to gases of 10 kg/CIA or more, combustible gases containing 4% or more of oxygen must not be compressed. It is said that this should not happen. Therefore, when supplying city gas at high pressure (necessarily increasing the pressure due to equipment capacity issues as demand increases), the oxygen concentration of the final supplied gas must be less than 4%. Also, even if the pressure is medium pressure (1 kg/- or more and less than 10 + r/cd),
Needless to say, from safety concerns, it is desirable that the oxygen concentration be 4% or less.

Furthermore, there is no doubt that the danger increases even when oxygen is mixed with flammable gas and is not compressed. Of course, it is not within the explosive limit, but if such a gas were to leak, there is no doubt that it would mix with the atmosphere and quickly reach the explosive limit.

In other words, it is desirable to avoid mixing oxygen into the flammable gas as much as possible in order to avoid danger.

Furthermore, workpieces such as conduits and gas holders through which oxygen-containing gas passes are susceptible to corrosion depending on the oxygen concentration.

However, as described above, gas dilution is essential from the viewpoint of gas fee issues (cost reduction due to improved gasification efficiency) and ease of control (that is, consistency of quality).

Further, in order to improve the gasification efficiency, it is preferable to introduce as much as possible of the above-mentioned butane for adjusting the amount of heat. However, city gas is dangerous if its properties do not match those of the combustion equipment. Therefore, gas utilities must comply with the flammability range (13A, 5
In other words, as long as it is within this combustion range, it is sufficient to introduce as much butane, etc. as possible. However, even though it is still possible to introduce it from the viewpoint of the flammability range, it may not be possible from the viewpoint of oxygen concentration.

Therefore, the present inventors have devised a method of using a make burner that burns during the meter period, and have also applied for a patent.

In this method, since the production gas has already been diluted by the flue gas in the furnace, the degree of air dilution in subsequent steps is reduced, thereby reducing the oxygen concentration in the final feed gas.

However, when burned at high temperatures in a furnace, there is a problem in that nitrogen oxides (NOx) are generated.

[Means for Solving the Problems] In view of the above-mentioned current situation, the inventors of the present invention have completed the present invention as a result of intensive research, and its characteristics are as follows: In a reformer in a gas production facility, which has a sub-combustion chamber separate from the main body, the sub-combustion chamber is connected to the main body through a valve through piping, and is used for introducing air, fuel, and steam. It is equipped with a mouth and a viroft burner.

The low-pressure cyclic city gas production method is a production method in which a gas production process and a heating process for providing heat for the production reaction are performed alternately (cyclically).

Steam reforming of petroleum hydrocarbons produces hydrogen, carbon oxide,
When producing city gas containing carbon dioxide, etc., the steam reforming reaction is an endothermic reaction, so it is necessary to provide the necessary amount of heat. This is allowed to undergo a reforming reaction for a certain period of time, and when the catalyst layer in the reactor reaches a temperature below a certain level, production is stopped and fuel and air are introduced into the furnace to cause a combustion reaction, and the catalyst layer rises above a certain level. Raise the temperature to . Then, combustion is stopped, raw materials and steam are introduced again, and production begins.

This is the principle of the cyclic method.

Low-pressure type refers to one in which the reaction process is carried out at low pressure.
The entire production system is less than Ikg/edG.

A reformer is a reactor, and is a device in which a steam reforming reaction occurs.

The auxiliary combustion chamber is a container for burning fuel, and may be a normal combustion furnace in terms of structure. Further, this is provided separately from the reforming furnace, and is connected to the reforming furnace through piping or ducts so that the combustion exhaust gas from the sub-combustion chamber is introduced into the reforming furnace. Heat-resistant bricks or the like may be constructed on the inner walls. This piping or duct is provided with a valve, which adjusts the flow rate of exhaust gas and also serves as an emergency shutoff valve that is closed in an emergency. Of course, the flow rate adjustment and the emergency stop may be performed using separate valves.

This sub-combustion chamber is provided with inlets for air, fuel, and steam. The air and fuel inlets may have the structure of a normal burner. Further, the steam introduction port may be a normal nozzle or the like. This steam is used to adjust the combustion temperature and suppress the generation of nitrogen oxides (NOx) due to high-temperature combustion.

A viroft burner is for ignition and is constantly burning. The capacity is sufficient as long as it can ignite, and is preferably as small as possible.

It is also preferable to fill this sub-combustion chamber with an oxidation catalyst (platinum, iron-based, etc.) to enable combustion at as low a temperature as possible in order to suppress the generation of nitrogen oxides.

The piping that introduces fuel, air, etc. to the l111 combustion chamber is equipped with a regulating valve, so combustion can be performed at any time by controlling the valve regardless of the make period or heat period of the reforming furnace. Exhaust gas can be introduced.

This sub-combustion chamber can also be used as a heat source when the temperature is raised again after the reformer is stopped.

Next, the operation of this reforming furnace will be explained.

The reformer starts to operate cyclically, and combustion in the sub-combustion chamber stops during the heat period, and combustion occurs in the sub-combustion chamber only during the meter period. Combustion exhaust gas having a temperature close to the temperature inside the reactor is introduced into the reactor from the sub-combustion chamber. This is because if the temperature is too low, the temperature inside the reactor will drop, and if it is too high, the amount of nitrogen oxides generated will increase.

Usually, the combustion temperature in the sub-combustion chamber is preferably 600°C to 700°C.

The combustion exhaust gas from the auxiliary combustion chamber will be mixed with the production gas, and the gas will already be diluted in the reformer.

The steps after this reforming furnace are exactly the same as normal gas production steps. However, since it has already been diluted to some extent, the amount of air for normal air dilution will be reduced. This allows r! in the final feed gas! The I element concentration decreases.

Alternatively, the amount of combustion during the normal heat period may be reduced, and the combustion in the sub-combustion chamber may be performed continuously instead of cyclically.

The fuel for the auxiliary combustion chamber may be the same as that for normal heating, but considering that it will be mixed with the product gas, product city gas or the like may also be used.

Although the location of the sub-combustion chamber is not particularly limited, it is preferable to install it close to the reactor from the viewpoint of loss of =ti. Although there may be one sub-combustion chamber itself, there may be a plurality of sub-combustion chambers, and there may also be a plurality of connection lines with the reactor.

The amount of combustion in this auxiliary combustion chamber (that is, the capacity of the burner) is not particularly limited, and is determined by the amount of combustion exhaust gas to be mixed in, but is usually 5% of the heat burner.
~40% is good. This is because if it is less than 5%, there is almost no effect, and if it is more than 40%, the specific gravity of the produced gas becomes too large.

Further, the ratio of the raw material (metal butane, etc.) to the fuel for the make burner is approximately 20 to 20.

[Example] Next, the present invention will be described in more detail based on an example shown in the drawings.

FIG. 1 is a schematic sectional view showing an example of the reforming furnace 1 of the present invention. Catalyst Fit2, pilot burner 3, heat burner 4, etc. are provided in the same way as in a normal reforming furnace. A sub-combustion chamber 5 is provided separately from the reformer main body, and is connected to the reformer main body by a pipe 6.

Further, this piping 6 is provided with an emergency shutoff 7.

A burner 8 is attached to the sub-combustion chamber 5, and the burner 8 has a structure in which air and gas are mixed at the base. A pilot burner 9 is provided so that the position of the flame intersects with this burner 8, and the burner 8 is ignited by this. Furthermore, a steam introduction nozzle 10 is provided.

A predetermined fluid is sent to the nozzles provided in these sub-combustion chambers 5 in a normal manner. For example, by pump, blower, or autopressure.

Next, the properties of each part when producing gas using this reactor will be explained.

The source gas in Table 1 is the composition of the reformed gas when the burner in the auxiliary combustion chamber is not used, and is a production gas of a normal cyclic system. The manufacturing conditions are the same as the normal cyclic method, but the raw material is butane (same as the butane used to adjust the amount of heat).

These are not special conditions, but rather normal driving conditions.

The numbers in the table are volume % (dry basis) of the component gases.

It is assumed that the exhaust gas is the combustion exhaust gas of the burner in the sub-combustion chamber and has been completely combusted.

The gases of Examples 1 to 4 are the gases on the exit side of the reactor when they are respectively combusted by the burner in the sub-combustion chamber during the meter period. In order from Example-1, the fuel butane for the auxiliary combustion chamber is 0.05.0, 10.0.15.0 per liter of raw material butane.
．． It was introduced at a rate of 20%.

Table 2 shows the composition of the gas obtained by converting each of the above gases to CO at a conversion rate of 60%. Example-11 is Example-1, Example-21
corresponds to Example-2, Example-31 to Example-3, and Example-41 to Example-4, respectively. Moreover, the comparative example is a gas obtained by converting the original gas.

Table 3 shows the composition when the calorific value of the gas after metamorphosis is adjusted at a heating ratio of 65%. Adjusted calories are 5000Kca
l/Ns 3, and the combustion range is in the 6C range. The final dilution was done with air, and the composition of the butane for heating was 2.9% propane and 97% butane.
1% was used. Also, the composition of air is oxygen 21
%, calculated as 79% nitrogen.

As can be seen from Table 3, even with the same heating ratio as the comparative example, the oxygen concentration is low. This eliminates the above-mentioned disadvantages such as danger. In particular, in Examples 3 and 4, it is 3% or less, making it possible to compress to high pressures.

Moreover, on the contrary, the heating ratio can be increased as much as the combustibility and oxygen concentration allow, and the gasification efficiency can be improved.

[Effects of the Invention] When the reforming furnace of the present invention is used, the produced gas on the exit side of the reactor has a low calorie property, as if it had already been diluted during thermal fiffi adjustment. This means that the gas is diluted with a gas that does not contain oxygen, which reduces the amount of air mixed in when adjusting the amount of heat, and reduces the oxygen concentration of the final supplied gas.

In addition, compared to the method of diluting with combustion exhaust gas instead of air in the downstream heat adjustment process rather than inside the reactor,
There is almost no loss of heat.

Furthermore, various combustible gases can be produced using a cyclic production device. That is, by increasing the amount of exhaust gas in the furnace, the specific gravity of the manufactured gas increases, and in terms of combustibility, it approaches that of B gas.

Additionally, because combustion is not performed in a reforming furnace, but rather in a separate combustion chamber at a relatively low temperature, the generation of nitrogen oxides is extremely low.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an example of the device of the present invention. ...reactor ...Catalyst layer ...Viloft burner ...Heat burner ...Sub-combustion chamber

Claims (1)

[Claims] 1. In a reformer in a low-pressure cyclic city gas production facility, which has a sub-combustion chamber separate from the main body, the sub-combustion chamber is connected to the main body by piping via a valve, A reforming furnace for producing city gas, characterized by being provided with air, fuel, and steam inlets, and a pilot burner.