JP4135871B2 - Apparatus and method for reforming kerosene or light oil using exhaust heat as a heat source - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a device and method for reforming kerosene or light oil, and is mainly used in the fields of energy conversion devices, chemical plants and the like that use reformed gas or methane-rich gas as fuel or raw material.
[Prior art]
Conventionally, a practical process for reforming kerosene or light oil or directly producing methane-rich gas is not generally known. Therefore, FIG. 4 shows a conventional naphtha reforming apparatus as a similar technique. FIG. 5 shows a conventional naphtha evaporator. Further, FIG. 6 shows a methane rich gas production process by coal gasification. The point of the present invention is clarified by comparison with these.
First, in the naphtha reformer, naphtha A is vaporized by the naphtha evaporator 1, mixed with reformed gas containing hydrogen, and desulfurized by the desulfurizer 2. In the desulfurizer, first, organic sulfur in naphtha and hydrogen in the reformed gas react with each other in the presence of a catalyst to form hydrogen sulfide (H ₂ S), and then zinc oxide (H ₂ S) filled in the desulfurizer ( It reacts with ZnO) and is desulfurized.
The desulfurized naphtha is mixed with the steam generated in the exhaust heat boiler 3 and sent to the reformer 4. In the reformer, while being heated by a heating source such as combustion gas, naphtha and water vapor react with each other in the catalyst, and methane (CH ₄₎ , hydrogen (H ₂₎ , carbon monoxide (CO), carbon dioxide ( It is converted into a reformed gas containing CO ₂₎ and water vapor (H ₂ O). A part of the reformed gas containing hydrogen is pressurized by the compressor 5 and then mixed with naphtha before the desulfurizer as a hydrogen source required for naphtha desulfurization.
In this case, a naphtha evaporator as shown in FIG. 5 was used. That is, the liquid naphtha A is supplied to the gas-liquid separation drum 6 that separates the naphtha gas and the liquid, and the liquid naphtha is supplied to the bottom of the naphtha evaporator 1 through the gas-liquid separation drum. The liquid naphtha is heated from the surroundings by the hot gas in the process of rising in the tube of the evaporator, and evaporates.
FIG. 6 shows a simplified process for producing methane-rich gas from coal. Coal is gasified in the gasification furnace 7 by reacting with water vapor and oxygen. The composition of the generated gas varies depending on the process to be used, but generally contains H ₂ , CO, CO ₂ , and H ₂ O as main components and also contains some hydrocarbon gas such as CH ₄ . The coal gasification gas is converted into methane-rich gas by the methanation reactor 8 in the presence of a nickel catalyst. In this case, since the methanation reaction is an exothermic reaction, cooling is required.
[0002]
[Problems to be solved by the invention]
(1) Naphtha is the same, but kerosene or light oil is composed of multi-component systems with different boiling points, so when the liquid is flowed upward from the bottom, the high-boiling fraction is concentrated in the liquid depending on the state, It becomes difficult to evaporate all the components uniformly. Further, since the heat receiving area of the liquid, that is, the heat receiving area for evaporation is determined depending on the position of the liquid level in the pipe, it is difficult to control the evaporation amount in combination with the fluctuation of the boiling point. In a chemical plant that always handles a certain amount, it may be possible to solve the above problem by searching for one optimum operating condition, but the load, that is, the supply amount of liquid is always different as in the case of power generation equipment. Under conditions, it is difficult to obtain stable evaporation. Furthermore, since the concentration of the high boiling fraction requires a higher heat source temperature, it may lead to thermal decomposition and carbon deposition, which is very dangerous. In particular, when handling kerosene or light oil, the molecular weight is larger than that of naphtha, so concentration of heavy components leads to carbon deposition.
(2) In order to remove organic sulfur contained in kerosene or light oil, it is reacted with hydrogen using a cobalt molybdenum (CoMo) or nickel molybdenum (NiMo) based catalyst to convert organic sulfur into H ₂ S. After conversion, it must be removed with ZnO in the form of zinc sulfide (ZnS). For this reason, it is necessary to supply hydrogen to the desulfurization apparatus. As a method for supplying this hydrogen, in the conventional naphtha reforming process, since the reformed gas contains hydrogen, a part of the product gas is recirculated and used. However, since the pressure of the product gas is always lower than the pressure of the naphtha to be supplied, a compressor is required to supply hydrogen upstream. However, since hydrogen is a gas that is very easily leaked and it is necessary to supply hydrogen at a high pressure, the compressor is difficult to seal, expensive, and highly dangerous. In addition to this, there is a method of supplying hydrogen by electrolysis of water, but it is very expensive, consumes a large amount of power, and has a problem in practical use.
(3) Further, in the conventional process for producing synthetic natural gas from coal, the gas generated by gasification is methanated with a Ni-based catalyst in a methanation reactor. This methanation reaction is a large exothermic reaction, and unless it is properly cooled, there is a concern that the reaction may run out of control or the temperature may rise too much, causing the catalyst to deteriorate, and the reactor design is very difficult.
[0003]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is a method for reforming kerosene or light oil by heating a raw material gas heater, an evaporator for kerosene or light oil, and an exhaust heat recovery boiler with an exhaust heat source. After mixing the vaporized gas of kerosene or light oil produced with water vapor, this mixed gas is introduced into the raw material gas heater and heated, and then the heated mixed gas is introduced into the reactor filled with the nickel catalyst. In addition, the reforming reaction of kerosene or light oil and the methanation reaction are performed in parallel under heat insulation.
Further, the kerosene or light oil reforming apparatus of the present invention includes an evaporator for evaporating kerosene or light oil by a heat source, an exhaust heat recovery boiler heated by an exhaust heat source, and vaporization of kerosene or light oil vaporized by the evaporator. Means for mixing the gas with water vapor from the exhaust heat recovery boiler, a raw material gas heater for introducing the mixed gas and heating the mixed gas, and a nickel catalyst, and heating with the raw material gas heater And a reactor for introducing a reforming reaction of kerosene or light oil and a methanation reaction in parallel under heat insulation.
(1) In order to always uniformly evaporate each component of a multicomponent liquid such as kerosene or light oil, even if a component having a low boiling point is vaporized first by flowing the liquid from top to bottom, The remaining high-boiling fraction is further heated while descending in the pipe and is sequentially evaporated, so that the high-boiling fraction is not concentrated as a liquid. During this time, since the time for heating the high-boiling fraction is required, it is necessary to have a structure that allows sufficient passage time of the liquid in the tube, and the heat transfer tube is bent for this purpose. In addition, even when the supply amount is very small, it is preferable that the supply of liquid from the header to each heat transfer tube is due to overflow so that the liquid is uniformly distributed to each heat transfer tube. Furthermore, in order to prevent carbon deposition, it is necessary to control the temperature on the heat source side because the heat source temperature needs to be kept to the minimum necessary for evaporation and some overheating.
(2) Hydrogen supply for the desulfurizer is required to be a hydrogen gas supply facility that has a risk of hydrogen leakage, that is, eliminates a seal portion that easily leaks, consumes less energy, and has low equipment costs. Is done. Therefore, a part of the kerosene or light oil that has been pressurized by the pump and supplied to the vaporizer is branched, reformed using the same heat source in a high-pressure state, and the high-pressure reformed gas is vaporized Or by mixing with light oil, hydrogen can be supplied without using a compressor and without using extra power.
(3) The methanation reaction that generates methane from gas such as H ₂ , CO, CO ₂ , H ₂ O is a remarkably exothermic reaction, but the reforming reaction that reacts kerosene or light oil with steam is an endothermic reaction. Therefore, when only the reforming reaction is performed, the reactor needs to be heated from the outside, and when only the methanation reaction is performed, the reactor needs to be cooled. However, if the vaporized kerosene or gas oil / water vapor mixed gas is supplied to one reactor and the reforming reaction and methanation reaction occur simultaneously, the temperature change in the reactor is offset and the temperature rises significantly. Does not happen. However, if S / C (steam / carbon ratio), which is one factor that governs this reaction, is increased, the reforming reaction is likely to occur, but the methanation reaction is difficult to proceed, and if it is decreased, the reforming reaction occurs. It becomes difficult and carbon deposition is likely to occur. In addition, the operating temperature is an important factor governing the reaction, and at the same time, the temperature is governed by the reaction. Therefore, it is absolutely important to control the reaction conditions well in order to cause two reactions simultaneously in one reactor.
[0004]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, although this invention aims at reforming kerosene or light oil, or producing | generating methane rich gas, in the following description, in order to simplify description, all raw materials are demonstrated as kerosene. Accordingly, the titles of FIGS. 1 and 2 are also kerosene. FIG. 1 shows a system flow diagram for generating kerosene reformed gas or methane-rich gas. Both the reformed gas and methane rich gas are composed of H ₂ , CO, CO ₂ , H ₂ O, and CH ₄ and are called methane rich gas when the methane concentration is high. Called methane rich gas. FIG. 1 shows that the generated methane-rich gas is supplied to the anode of an internal reforming type molten carbonate fuel cell (MCFC), and the exhaust of the cathode is used as a heat source for a raw material gas heater, a kerosene evaporator, and an exhaust heat recovery boiler. In this case, an application example of the present invention is shown. However, since the portion other than the MCFC can be used for other purposes, and the cathode exhaust is a combustion gas and is not special, the description of the MCFC portion Is basically omitted, and a method and apparatus for reforming kerosene and generating methane-rich gas will be described below. The kerosene G stored in the kerosene tank 10 is boosted by the kerosene pump 11, the flow rate is controlled by the flow rate control valve 12, and then supplied to the kerosene evaporator 16 through the restriction orifice 15. Further, a small amount of another kerosene whose flow rate is controlled by another flow rate adjusting valve 13 is sent to the hydrogen gas generator 17 from the pump discharge side. The discharge amount of the pump is always larger than the sum of the flow rates flowing through the flow rate control valves 12 and 13, and excess kerosene is returned to the kerosene tank 10 via the pressure control valve 14. In the kerosene evaporator, kerosene is vaporized using the MCFC cathode exhaust as a heat source. In the hydrogen gas supply device, a small amount of kerosene is reformed using the cathode exhaust as a heat source and mixed with vaporized kerosene. Details of the hydrogen supply device by reforming the kerosene will be described later. The vaporized kerosene and reformed gas mixture is supplied to the desulfurizer 18. In the desulfurizer, first, organic sulfur and hydrogen in kerosene are reacted with a CoMo-based catalyst to convert organic sulfur into H ₂ S, and then the sulfur content is removed as ZnS by ZnO filled in the desulfurizer. To do. Dust is removed from the desulfurized kerosene gas by the filter 19, and then the pressure is reduced by the pressure control valve 20, and then mixed with water vapor. The water vapor is generated by the exhaust heat recovery boiler 25 using the cathode exhaust as a heat source, and is supplied by the flow rate control valve 29 so as to have a preset S / C. The mixed gas of kerosene gas and water vapor is heated to the reaction temperature by the source gas heater 30 using the cathode exhaust as a heat source, and is supplied to the reactor 31. Here, the supplied gas causes a reforming reaction and a methanation reaction simultaneously in the reactor by the nickel-based catalyst, and methane-rich gas is generated. In order to control the temperature of the gas supplied to the reactor 31, bypass control systems 55a and 55b for cathode exhaust are installed, thereby simultaneously preventing overheating of the kerosene evaporator. The generated methane-rich gas, after removing dust by the filter 32, is depressurized by the pressure control valve 33 and supplied to the anode of the MCFC 34. Note that about 75% of the fuel is used for the power generation reaction at the anode, and the rest is sent to the catalytic combustor 36 where it is burned by the air supplied by the air blower 35 and supplied to the cathode of the MCFC 34. Part of CO2 and oxygen is consumed at the cathode, and the remainder is sent to the fuel heater (raw material gas heater) 30 at about 650 ° C. as cathode exhaust, and is subsequently used as a heat source for the kerosene evaporator and exhaust heat recovery boiler. . FIG. 2 shows the detailed structure of the kerosene evaporator. Cathode exhaust enters from the lower N2 and exits from the upper N1. On the other hand, kerosene is supplied to the supply header (upper header) N3 and supplied to the heat transfer tube connected to the upper portion of the header by overflow. Kerosene flows downward in the bent heat transfer tube, and in the middle, each component is sequentially vaporized and exits from the evaporator outlet (lower header) N4. FIG. 3 shows a flowchart of the hydrogen supply apparatus. The kerosene necessary for supplying the necessary hydrogen is supplied by the flow rate control valve 13 and sent to the kerosene vaporizer 39 via the check valve 37 and the block valve 38. Therefore, kerosene is vaporized using the cathode exhaust as a heat source. On the other hand, the hydrogen gas K from the hydrogen cylinder 40 is mixed with the vaporized kerosene G ′ and hydrogen through the pressure reducing valve 41, the flow rate adjusting valve 42, and the check valve 43. This gas is supplied to the desulfurizer 45 via the block valve 44. In the desulfurizer 45, first, organic sulfur and hydrogen in kerosene are reacted by a CoMo-based catalyst, converted to H ₂ S, removed in the form of ZnS by the filled ZnO, and passed through the block valve 46, The steam is mixed with the steam B ″. The steam is steam from the dedicated high-pressure steam generator 52 and is mixed with the kerosene gas G ′ / K through the flow rate control valve 47 and the check valve 48, and the block valves 49 a and 49 b are connected. In the reformer, the reformer is reformed by the Ni-based catalyst and mixed with the vaporized kerosene G ′ from the kerosene evaporator 16 through the block valves 51a and 51b. ,. desulfurizer showing the preferred operating conditions of the system for producing methane-rich gas from kerosene 7 operating pressure 1～2MPa (first pressure), and the operating temperature 300 to 400 ° C. Increasing the pressure suppresses hydrocracking of hydrocarbons, increases the selectivity of the reaction between hydrogen and organic sulfur, stabilizes the reaction, and at the same time reduces hydrogen consumption. The operating conditions are a pressure of 300 to 600 kPa (second pressure) , a temperature of 400 to 550 ° C., and a steam / carbon ratio of 2 to 2.5, in which the reforming reaction is performed in one reactor. On the other hand, the operating condition of the exhaust heat recovery boiler is that the operating pressure is 0.5 to 1 MPa and superheated steam at 200 to 350 ° C. is generated.
[0005]
【The invention's effect】
The system for producing methane-rich gas from the kerosene or light oil of the present invention described above has the following characteristics.
(1) Conventionally, a practical system for generating reformed gas or methane-rich gas from kerosene or light oil has not been known. On the other hand, in the case of clean distributed power sources such as fuel cell power generation facilities, many are designed using natural gas as fuel. However, there are many areas where the supply of natural gas cannot be obtained, which has been an obstacle to popularization. According to the present invention, a clean distributed power source can be installed even in an area where supply of natural gas cannot be obtained. Furthermore, kerosene and light oil are easy to obtain, are generally cheaper than natural gas, and can be stored. Therefore, it is possible to cope with an emergency such as a disaster. As a result, if clean distributed power sources become widespread, the environmental improvement effect will be great.
(2) Conventionally, a reforming reaction and a methanation reaction have been performed separately for heavy components of naphtha or higher. Although this can achieve the purpose more reliably, the number of reactors becomes two, the reforming reaction is an endothermic reaction, and heating from the outside is required. On the other hand, methanation is an exothermic reaction and requires cooling, which makes the reactor very expensive as a whole. In the present invention, since the reforming reaction and methanation reaction are simultaneously performed in one reactor, the number of reactors becomes one, and heating and cooling facilities are not required, so that the facilities are not only inexpensive. By offsetting heat absorption and heat generation, the apparatus can be operated safely without an abnormal increase in temperature despite a large amount of methanation. For this implementation, it is necessary to satisfy the two reaction conditions at the same time, and therefore it is necessary to carry out the reaction under limited operating conditions.
(3) In the present invention, a large pressure difference is provided between the desulfurizer and the reactor. That is, the desulfurizer is operated at a high pressure and the reactor is operated at a low pressure. As a result, while the reactor can achieve its purpose, in the desulfurizer, consideration is given to reducing the hydrogen consumption and at the same time suppressing the hydrocracking reaction of hydrocarbons to enable a stable desulfurization reaction.
(4) In this type of conventional system, the most common method for supplying hydrogen required for desulfurization is to supply the product gas with a compressor. This method is not preferable from the viewpoints of gas leakage from the compressor, power consumption, facility costs, and the like. There is also a method of supplying hydrogen by electrolysis of water, but this is also not preferable from the viewpoint of power consumption and equipment cost. The present invention makes use of the fact that kerosene or light oil is a liquid, boosts the pressure with a pump with low power consumption, operates the reformer for supplying hydrogen at a higher pressure, and sets the desulfurizer side to a lower pressure. By operating at, hydrogen can be supplied to the desulfurizer at low cost without using a compressor.
(5) Furthermore, conventionally, there is no known evaporator that can stably vaporize kerosene or light oil composed of multiple components without concentrating heavy components. If concentration of heavy components occurs, the heating temperature also increases, and carbon deposition due to thermal decomposition tends to occur. In the kerosene evaporator of the present invention, the heat transfer tube is bent so that the liquid flows from the top to the bottom so as not to cause the concentration of heavy components, and the residence time in the tube can be sufficiently obtained. Further, a system is used in which the liquid is supplied by overflow so that the liquid is evenly distributed to the heat transfer tubes even when the flow rate at the time of low load is small. Thereby, kerosene can be vaporized without causing the above problem.
[Brief description of the drawings]
FIG. 1 is a flow diagram of a system for generating reformed gas or methane rich gas from kerosene according to the present invention. FIG. 2 is a structural diagram of a kerosene evaporator according to the present invention. System flow diagram [Fig. 4] System flow diagram of conventional naphtha reformer [Fig. 5] Structural diagram of conventional naphtha evaporator [Fig. 6] Conceptual diagram of conventional methanation reactor [Fig. 7] The figure which shows the preferable operating conditions of the system which produces | generates methane rich gas from kerosene of invention.
DESCRIPTION OF SYMBOLS 1 Naphtha evaporator 2 Naphtha desulfurizer 3 Waste heat recovery boiler 4 Reformer 5 Reformed gas compressor 6 Gas-liquid separation drum 7 Coal gasifier 8 Methanation reactor 10 Kerosene tank 11 Kerosene pump 12 Flow control valve 13 Flow rate Control valve 14 Pressure control valve 15 Restriction orifice 16 Kerosene evaporator 17 Hydrogen gas supply device 18 Kerosene desulfurizer 19 Filter 20 Pressure control valve 21 Water treatment device 22 Treated water tank 23 Feed water pump 24 Restriction orifice 25 Waste heat recovery Boiler 26 Steam separator drum 27 Water level control valve 28 Pressure control valve 29 Flow control valve 30 Fuel heater 31 Reactor 32 Filter 33 Pressure control valve 34 Molten carbonate fuel cell (MCFC)
35 Air blower 36 Catalytic combustor 37 Check valve 38 Block valve 39 Kerosene vaporizer 40 Hydrogen cylinder 41 Self-acting pressure control valve 42 Flow control valve 43 Check valve 44 Block valve 45 Desulfurizer 46 Block valve 47 Flow control valve 48 Reverse Stop valve 49a Block valve 49b Block valve 50a Reformer 50b Reformer 51a Block valve 51b Block valve 52 High pressure steam generator 55a Temperature control valve 55b Temperature control valve A Naphtha (liquid)
A 'Naphtha (gas)
B Supply water B 'Treated water B "Steam C Reformed gas D Coal gasifier raw material E Coal gasification gas F Methane rich gas G Kerosene (liquid)
G 'Kerosene (gas)
H Air I Cathode inlet gas J Cathode outlet gas N1 Cathode outlet N2 Cathode outlet N3 Kerosene inlet N4 Kerosene outlet TW1 Thermocouple inlet TW2 Thermocouple inlet Ni Nickel catalyst CoMo Cobalt molybdenum catalyst ZnO Zinc oxide desulfurizer CW Cooling water MCFC Molten carbonate fuel cell

Claims (6)

A method of reforming kerosene or light oil by heating a raw material gas heater, an evaporator of kerosene or light oil, and an exhaust heat recovery boiler with an exhaust heat source,
After mixing the vaporized gas of kerosene or light oil produced and water vapor, this mixed gas is introduced into the raw material gas heater and heated, and then the heated mixed gas is introduced into the reactor filled with the nickel catalyst. A method for reforming kerosene or light oil, wherein the reforming reaction and methanation reaction of kerosene or light oil are performed in parallel under heat insulation.   A part of kerosene or light oil supplied to the evaporator is branched, reformed to a gas containing hydrogen, mixed with vaporized kerosene or light oil, guided to a desulfurizer, desulfurized, and then feed gas The method for reforming kerosene or light oil according to claim 1, wherein the method is introduced into a heater.   The operating conditions of the reactor are as follows: the pressure is 300 to 600 kPa, the temperature is 400 to 550 ° C., the water vapor / carbon ratio is 2 to 2.5 in molar ratio, and the reforming reaction and methanation reaction of kerosene or light oil are conducted under heat insulation. The method for reforming kerosene or light oil according to claim 1, wherein the methane-rich gas is directly generated from kerosene or light oil by performing in parallel. Kerosene or light oil is vaporized under a first pressure, desulfurized and then depressurized , mixed with water vapor, heated with a source gas , and then reacted with a source gas under a second pressure. The method for reforming kerosene or light oil according to claim 1. An evaporator that evaporates kerosene or light oil by a waste heat source;
An exhaust heat recovery boiler heated by an exhaust heat source;
Means for mixing kerosene or gas oil vaporized by the evaporator and water vapor from the exhaust heat recovery boiler;
A raw material gas heater that heats the mixed gas when the mixed gas is introduced;
A reactor filled with a nickel catalyst, introduced with a mixed gas heated by the raw material gas heater, and performing a kerosene or light oil reforming reaction and a methanation reaction in parallel under heat insulation. A kerosene or light oil reforming device. Means for branching a part of kerosene or light oil supplied to the evaporator and supplying it to a hydrogen gas supply device;
A hydrogen gas supply device that reforms the branched kerosene or light oil into a gas containing hydrogen;
Means for mixing the gas from the hydrogen gas supply device with the vaporized gas of kerosene or light oil;
A desulfurizer for desulfurizing the mixed gas,
The kerosene or light oil reforming device according to claim 5, wherein the vaporized gas of kerosene or light oil desulfurized by the desulfurizer is mixed with water vapor from the exhaust heat recovery boiler and introduced into the raw material gas heater.

Images