JP2004244274A - Hydrogen-containing gas producer and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To meet a demand for a hydrogen-containing gas producer in which the reforming catalyst undergoes less deactivation and can therefore be continuously used even when an easily storable and transportable feedstock such as naphtha or kerosene is used and can do without the stock of a hydrogen gas or an inert gas for the start or stop of operation. <P>SOLUTION: The hydrogen-containing gas producer uses a hydrocarbon (e.g. naphtha or kerosene) as a feedstock and produces the hydrogen-containing gas by steam reforming. Its steam reforming process is divided into a low-temperature steam cracking zone and a high-temperature steam cracking zone. Reactors having a structure capable of being externally heated and cooled are used as the low-temperature steam reforming reactor and a CO converter to effect two-stage reforming including low-temperature steam reforming and high-temperature steam reforming. This can solve the problem wherein the hydrocarbon feedstock undergoes heat decomposition and carbon deposition upon being heated in the high-temperature steam reforming zone. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for producing a hydrogen-containing gas by steam-reforming hydrocarbons such as naphtha and kerosene, and an operation method thereof.
Specifically, in a hydrogen-containing gas producing apparatus, even if raw materials such as naphtha and kerosene that are easy to store / transport are used, the activity of the reforming catalyst can be continuously used with little reduction, and hydrogen gas or gas for starting and stopping operation can be used. It is desired that inert gas is not always required.
In particular, in the case of a device for supplying a hydrogen-containing gas to a small fuel cell power generation system, the demand is strong. The present invention meets that need.
[0002]
[Prior art]
A conventional hydrogen-containing gas production apparatus employs a method in which a raw material carbon-containing compound is steam-reformed to obtain a hydrogen-containing gas and CO is converted into CO.
[0003]
When the raw material hydrocarbon becomes heavier, carbonaceous material adheres to the reforming catalyst and causes a decrease in activity.In severe cases, the catalyst collapses, the gas flow deteriorates, and the high-temperature steam reforming reaction tube is overheated and damaged. It can be trouble.
Raw materials that can be stably treated with less such troubles are natural gas and city gas LPG, and a special catalyst is required to reform naphtha.
[0004]
When the reforming process is divided into low temperature and high temperature, and the hydrocarbon is converted into CH4, H2, CO, and CO2 in the low temperature steam reforming process, and then subjected to the high temperature steam reforming process, the two-stage reforming method is adopted. Trouble in carbon deposition in the reforming step is significantly reduced.
[0005]
The low-temperature steam reforming step is performed in an adiabatic reactor, and the reaction pressure is 10 to 20 kg / cm 2 -G, the inlet temperature of the reactor and the steam ratio are 350 to 450 ° C. for the LPG raw material S / C = 1.5 to 2.0 moles / C-atom The naphtha raw material is used at 450 to 500 ° C. and S / C = 1.7 to 2.0.
[0006]
Steam is added to the low-temperature steam-reformed gas to adjust the total steam ratio to about S / C = 3 to 4 moles / C-atom, and the high-temperature steam is reformed at an inlet temperature of about 350 to 450 ° C and an outlet temperature of about 750 to 800 ° C. Quality.
[0007]
At the start of the operation of the conventional apparatus, hydrogen gas is flowed, the temperature of the catalyst layer is raised by the heat of the circulating gas, and the catalyst is reduced / activated. Enter manufacturing operation.
[0008]
When the operation is stopped, the supply of hydrocarbons is stopped, hydrogen or inert gas is supplied and circulated, the temperature is lowered, and the supply of steam is stopped at a temperature equal to or higher than the temperature at which steam condenses. The method of saying is taken. (For example, refer to Patent Document 1.)
[0009]
[Patent Document 1]
JP 2001-143731 A
[Problems to be solved by the invention]
Hydrogen energy supply, especially hydrogen-containing gas production equipment for fuel cell power generation systems, is easy to transport and store raw materials, safe, easy to handle, low-pressure so as not to be subject to the high-pressure gas control law, and has a permanent supply of hydrogen and inert gas. It is required that they do not have to do it. Looking at the prior art from such a viewpoint, there are the following problems.
[0011]
We want to use naphtha or kerosene as a raw material because it is easy to transport and store, but we need to develop a practical catalyst because carbonaceous materials adhere to the steam reforming catalyst and cause deterioration in activity. .
Even if it is attempted to reform with a conventional catalyst using a combination of low-temperature steam reforming and high-temperature steam reforming, if hydrocarbons are reformed at a low pressure in an adiabatic reactor, the balance between the reforming reaction and methanation reaction rates will be lost. It has been found that there is a portion where the temperature becomes lower than the inlet temperature, and the activity decrease due to carbonaceous adhesion is increased.
Increasing the water vapor ratio is a direction that can be prevented by increasing the water vapor ratio, but in fact increasing the water vapor ratio increases the endothermic reaction and lowers the reaction temperature. It turned out not to be solved.
Because of the limitations of Ni-based reforming catalysts that have been put into practical use and that have a long track record, there is a possibility of using Ru-based catalysts, but this may be expensive, and handling of only the reforming process becomes easier. However, other processes become a bottleneck.
Hydrogen and inert gas are required when starting and stopping operation.
It takes time to start / stop operation.
[0012]
The present invention provides an apparatus and an operation method for solving the above-mentioned problems when the conventional hydrocarbon reforming technology is applied to the production of a small and simple hydrogen-containing gas for a fuel cell power generation system, for example. Is what you do.
[0013]
[Means to solve the problem]
The present inventors have found that a liquid hydrocarbon such as naphtha or kerosene is used as a raw material to suppress a decrease in activity due to carbonaceous deposition, to shorten the operation start / stop time, and to use a hydrogen-containing gas without a hydrogen gas inert gas. The subject was solved by conducting intensive research on an apparatus and an operating method for manufacturing the same and combining the following technologies.
[0014]
When steam reforming hydrocarbons such as naphtha and kerosene, the catalytic activity decreases and collapses due to carbonaceous deposition / adhesion. In other cases, the reforming reaction does not proceed while being adsorbed on the catalyst due to the low reaction temperature, resulting in decomposition / polymerization.
[0015]
By performing the two-stage reforming of low-temperature steam reforming and high-temperature steam, the problem of pyrolysis / carbon deposition is solved because the raw hydrocarbon is heated to a high temperature in the high-temperature steam reforming section.
[0016]
However, the problem is low temperature steam reforming. It is often said that the reaction rate increases exponentially with an increase in temperature, but conversely, the reaction rate decreases exponentially with a decrease in temperature.
Performing the reforming reaction at a low pressure and a high steam ratio means that the reaction has a good endotherm, and if a low-temperature steam reforming reaction is performed in an adiabatic reactor as in the prior art, the temperature of the catalyst layer drops below the inlet temperature as the reaction progresses. The reaction rate decreases, and the hydrocarbon adsorbed on the catalyst does not proceed to gasification (reforming), but rather covers the active site and causes a decrease in activity.
[0017]
The present inventors have successfully proposed the following two points to solve this problem.
First, a low-temperature steam reforming reactor having a structure capable of being heated from the outside was adopted, and a decrease in the temperature of the catalyst layer accompanying the progress of the reaction was suppressed by supplying heat from the outside.
At this time, if the temperature is raised locally even by using a heating source that is too high, the thermal decomposition of the raw material hydrocarbon occurs, which causes a trouble of carbonaceous deposition. Therefore, the temperature of the heating source is preferably 650 ° C. or less, It is important that the temperature be 600 ° C. or lower.
[0018]
Second, if the carbonaceous matter deposited on the catalyst by the low-temperature reaction is left for a long time and the operation is continued as it is, decomposition / polymerization proceeds and gasification (reforming) becomes difficult, but it is difficult to remove it. It has been found that if the regenerating treatment is performed, the catalyst can be removed from the catalyst to recover the activity.
[0019]
The following method was found to be effective for regenerating a catalyst to which carbonaceous substances had adhered due to a low-temperature reaction.
By increasing the heating temperature of the low-temperature steam reforming reactor, gasification of the attached carbonaceous material is promoted.
At this time, it is more effective to increase the temperature of the catalyst layer to which the carbonaceous material is attached (the lowest temperature during normal operation) by reducing the supply of the raw material or increasing the steam ratio. is there.
[0020]
When a Ru-based catalyst is used as the low-temperature steam reforming catalyst, it is possible to completely stop the supply of the raw material hydrocarbons and gasify the adhering carbonaceous material using only steam.
[0021]
When a circulating compressor or blower capable of circulating gas in the system is available, a regeneration operation for recycling the reformed gas to the low-temperature steam reforming reactor can be performed.
Recycling part of the generated hydrogen-containing gas to the low-temperature steam reforming reactor while continuing the reforming operation can raise the temperature of the low-temperature steam reforming catalyst layer by not only external heating but also methanation reaction. It is also advantageous because gasification of carbonaceous material by hydrogen gas occurs.
[0022]
When the hydrogen-containing gas producing apparatus of the present invention is combined with a fuel cell power generation system, an air blower necessarily provided on the fuel cell power generation side is used for gas circulation.
By stopping the power generation reaction by the fuel cell during the regeneration operation of the reforming catalyst, the air blower can be diverted to gas recycling, and thus it is a proposal to omit the provision of a new auxiliary device for recycling.
[0023]
Calculation example-1
Raw material hexane, steam ratio = 1.5 moles / C-atom, reaction pressure = 15 kg / cm2-G, reaction pressure = 0.5 kg / cm2-G, and steam ratio = 3.0 moles / C-atom reaction pressure = 0. The relationship between the inlet temperature and the outlet temperature when the reaction is performed in an adiabatic reactor at 5 kg / cm2-G can be calculated and obtained.
[0024]
Kerosene desulfurized to 0.05 ppm or less was stored in a container, and this was fed at a predetermined flow rate using a liquid sending means. Kerosene that reaches the evaporator, which has been previously controlled to be constant at 300 ° C., evaporates and reaches the preheater in a gaseous state.
At the same time, liquid was sent at a predetermined flow rate from a pure water container storing pure water using a liquid sending means. Also in this case, the pure water which reaches the evaporator, which is controlled to be constant at 120 ° C. in advance, evaporates and reaches the preheater in a gaseous state.
The raw fuel mixed in the preheater in the gas state is further heated by the preheater based on the information of the inlet gas temperature detecting means so as to be input to the reactor at a predetermined temperature, and then reaches the reactor.
When external heat supply was necessary, the reactor was heated by an electric heater.
After the reaction of the gas reacted in the reactor, the temperature of the produced gas is detected by the outlet gas temperature detection means, and the unreacted liquid of the post-reaction gas cooled and condensed by the condenser is stored in the condensed liquid container. The state of the unreacted liquid was extracted from the condensed liquid sampling port as necessary and confirmed.
The post-reaction gas from which the condensed liquid has been separated is discharged from the post-reaction gas outlet after confirming the gas flow rate by gas flow rate detection means. If necessary, in order to know the composition of the gas after the reaction, a gas was sampled from the generated gas sampling port and subjected to gas analysis. During operation of the present apparatus, the reaction pressure is detected by the pressure detecting means, and the reaction pressure is adjusted to a predetermined pressure by the reaction pressure control valve.
By the way, at the time of the above operation, the valve is closed, but in the embodiment assuming the reformed gas recycling, this valve is opened, each gas is used, and each gas is set to a predetermined flow rate by the mass flow controller, and the static flow is performed. It differs from the flow of the kerosene / pure water system only in that it is mixed with a mixer, sent to a pure water evaporator and sent to a preheater in a state of being mixed with pure water vapor.
[0025]
Example 2
Kerosene (desulfurized kerosene desulfurized to 0.05 ppm or less) was used, and kerosene was supplied at a ratio of 0.33 [L / Hr] to water = 0.93 [L / Hr]. The gas was heated by a preheater so that the gas temperature obtained by the temperature detecting means became 480 ° C., and reacted by an adiabatic reactor (heating to compensate for heat loss). The outlet temperature obtained by the outlet gas temperature detecting means was 410 ° C. The gas was cooled and the water vapor was condensed to analyze the gas composition. No oil was found on the liquid sampled from the condensed liquid sampling port. Five hours after the start of the reaction, the generated gas flow rate that could be confirmed by the gas flow rate detecting means decreased, and oil was observed on the liquid sampled from the condensed liquid sampling port.
[0026]
Example 3
The heat was supplied to the reactor with an electric heater so that the gas temperature obtained by the outlet gas temperature detecting means became 480 ° C., the same temperature as the gas temperature obtained by the inlet gas temperature detecting means, and the experiment was carried out in the same manner as in Example 1. Did. After cooling this gas and condensing the unreacted liquid, the composition on the outlet gas side was analyzed. No oil was found on the liquid sampled from the condensed liquid sampling port. Even after 10 hours from the start of the reaction, there was no change in the generated gas flow rate confirmed by the gas flow rate detecting means, and no oil was found on the liquid sampled from the condensed liquid sampling port.
[0027]
Example 4
As a result of Example 1, the oil content was confirmed on the condensed water in about 5 hours. Therefore, the supply amount of kerosene was reduced to 1/2, the heating to the reactor was strengthened by the electric heater, and the gas obtained by the outlet gas temperature detecting means was obtained. Heating was performed so that the temperature became 480 ° C., the same temperature as the gas temperature obtained from the inlet gas temperature detecting means, and the temperature was maintained for 2 hours. Thereafter, the kerosene supply amount was returned to the original value, and the heating conditions of the electric heater were also returned to the original state, and the state was substantially adiabatic.The generated gas flow rate confirmed by the gas flow rate detecting means returned to the initial state, and the condensed liquid was returned. No oil was found on the liquid sampled from the sampling port. However, after operating for 5 hours under these conditions, the generated gas flow rate that could be confirmed by the gas flow rate detection means decreased, and oil came to be recognized on the liquid sampled from the condensed liquid sampling port.
[0028]
Example 5
As a result of Example 1, oil was found on the condensed water in about 5 hours. Therefore, the supply amounts of kerosene and water were reduced to half, and the circulation of the gas at the outlet of the steam reformer was assumed. As a gas, H2 gas, CO2 gas, and CH4 gas were respectively sent using a mass flow controller, and H2 = 30 vol%, CO2 = 23 vol%, CH4 = 47 vol%, and a total of 0.59 Nm3 / Hr was sent. It was preheated so that the gas temperature obtained by the inlet gas temperature detecting means became 480 ° C., and then supplied to the reactor. The gas temperature obtained by the outlet gas temperature detecting means was 452 ° C. After maintaining under these conditions for 2 hours, the simulated reformed gas was stopped, the supply amounts of kerosene and pure water were restored, and the heating conditions with the electric heater were also restored to the original state. The flow rate of the generated gas confirmed by the detection means also returned to the initial flow rate, and no oil was found on the liquid sampled from the condensed liquid sampling port. However, after operating for 5 hours under these conditions, the generated gas flow rate that could be confirmed by the gas flow rate detection means decreased, and oil came to be recognized on the liquid sampled from the condensed liquid sampling port.
[0029]
From the calculation example 1, it is understood that when the steam ratio is low and the steam ratio is high, the reaction is not performed under adiabatic conditions in a temperature range of about 450 to 500 ° C. in which the low-temperature steam reforming catalyst works effectively.
[0030]
From Example 1, it was shown that when a low-temperature steam reforming reaction was carried out in an adiabatic reactor as in the prior art under the conditions of low pressure and high steam ratio, the activity was reduced in a short time.
[0031]
In Example 2, it was shown that the activity reduction was small when steam reforming was performed by the method of the present invention.
[0032]
In Examples 3 and 4, it was shown that the catalyst degraded in the low-temperature region can be raised in temperature, raised in S / C, or recovered in activity by reformed gas, that is, can be regenerated.
[0033]
The elimination of the need for hydrogen gas and inert gas at the start / stop of the operation means that the deterioration due to oxidation by water vapor or air can be regenerated by the reaction gas as well as the deterioration due to the low-temperature steam reaction.
[0034]
If it is oxidized at high temperature, even if it is reduced, it is not possible to regenerate the sintering portion, but if it is oxidized at 200 ° C or less, preferably 120 ° C or less without generating heat, the catalyst becomes mild. It is the same as the stabilization treatment that can be oxidized and handled in the air, and can be easily reduced / activated at a low temperature.
[0035]
In the present invention, since the reactor is provided with an external heating type, it can be heated to a temperature at which water vapor does not condense without circulating the gas. In a short time, steam and raw hydrocarbons are flown, air and combustion gas are stopped, and the catalyst oxidized temporarily at a low temperature can be reduced (regenerated) for operation.
In particular, the operation of recycling the reformed gas is a preferable operation because the catalyst layer can be heated by the reaction and the catalyst can be reduced by the reformed gas.
In the vaporization method of petroleum-based liquid fuel such as kerosene or other water-insoluble liquid fuel, liquid fuel and water are alternately arranged at appropriate small intervals in a liquid feed pipe, and then guided to a vaporizer to be heated. A method for vaporizing a water-insoluble liquid fuel used in a fuel cell system, which comprises evaporating and vaporizing.

Claims (8)

A device that produces hydrogen-containing gas by steam reforming using hydrocarbons such as naphtha and kerosene as raw materials. The steam reforming process is divided into a low-temperature steam reforming region and a high-temperature steam reforming region. An apparatus for producing a hydrogen-containing gas, wherein a reactor having a structure capable of externally heating / cooling is used as a reactor and a CO conversion reactor. Using naphtha, kerosene, etc. as raw materials, low-temperature steam reforming at a reaction pressure of 9.8 kg / cm2-G or less and a steam ratio of S / C = 2.0 to 5.0 moles / atom, followed by high-temperature steam reforming. The hydrogen-containing gas producing apparatus according to claim 1, wherein: When the reforming catalyst and the shift catalyst are heated from the outside and reach a temperature at which water vapor is not condensed, the raw material hydrocarbon is supplied at 200 ° C. or lower, preferably 120 ° C. or lower, and then the temperature is raised to a predetermined reaction temperature. 2. The hydrogen-containing gas producing apparatus according to 1. If it is necessary to circulate and supply air and combustion gas into the system at the start / stop of the operation, the catalyst layer must be kept at 200 ° C or lower, preferably 120 ° C, in order to minimize oxidation of the catalyst. The method for operating a hydrogen-containing gas producing apparatus according to claim 1, wherein: The method for operating a hydrogen-containing gas producing apparatus according to claim 1, wherein a reformed gas (hydrogen-containing gas) is circulated in the system at the start / stop of the operation to activate or prevent oxidation of the catalyst. When power generation / heat supply is performed in combination with the reformer of the present invention and a fuel cell, the structure is such that the air supply blower of the fuel cell is used for gas supply / circulation during operation start / stop. The hydrogen-containing gas producing apparatus according to claim 1. When the activity of the low-temperature steam reforming catalyst is lowered due to carbonaceous adhesion, oxidation, etc., the supply amount of the raw material hydrocarbon is reduced, only the steam is supplied, or the supply of the reformed gas is circulated to remove the carbonaceous material. The method for operating a hydrogen-containing gas producing apparatus according to claim 1, wherein the catalyst is reduced. 2. The hydrogen-containing gas producing apparatus according to claim 1, wherein the low-temperature steam reforming step uses a catalyst (Ru-based catalyst) that does not require reduction and can be subjected to steam processing, and the high-temperature steam reforming catalyst uses a Ni-based catalyst.