CN1702037A - Process for preparing CO and synthetic gas and methanol by steam conversion of hydrocarbons - Google Patents

Abstract

The invention relates to a method of hydrocarbon steam conversion to produce CO, synthetic gas and methanol. A heat-exchanger type first converter completes first steam conversion reaction of hydrocarbons. Second converter is fed with reformed gas from the first converters to complete part oxidation reaction of hydrocarbons and deep conversion reaction of CH4. Second reformed gas generated in second converter is processed in separation facility to separate part CO used as oxidation acetate of raw gas. Residue gas is sent to compound carbinol. Said invention not only makes the most use of higher calorific value of second reformed gas from said second converter to heat logistics to act chemical reaction in heat-exchanger type first converter tube, but also utilizes energy of system to basically realize self-thermal balance. The invention is adapted to not only new methanol-acetate associated enterprises but also technical innovation of old methanol factory to add new product of acetate.

Description

A method for preparing CO, synthesis gas and methanol by steam reforming of hydrocarbons

technical field

The invention relates to a method for preparing CO, synthesis gas and methanol by steam reforming of hydrocarbons.

Background technique

Using gaseous hydrocarbons as raw materials to prepare raw material gas for ammonia synthesis, the earliest industrialized process is partial oxidation at atmospheric pressure. With the development of metallurgical technology, the processing and production of high-temperature resistant alloy conversion tubes (such as HK-40, HP-Nb) has been obtained. Solved, the gaseous hydrocarbon pressurized steam reforming process has replaced the atmospheric partial oxidation process. So far, the conversion pressure has been increased from normal pressure to 3.0-4.3MPa, and the production scale is becoming larger and larger. The largest single-series synthetic ammonia in the world today is 1700MTPD, and the largest single-series methanol is above 2540MTPD. The traditional synthesis gas preparation process, whether it is atmospheric pressure partial oxidation or pressurized continuous conversion process, is to directly introduce high-temperature process gas into waste heat boiler to generate high-parameter steam, and the heat required for steam conversion of gaseous hydrocarbons has to be burned partly hydrocarbons to resolve.

The core of the energy-saving process is to reduce the consumption of hydrocarbons for combustion as much as possible, so as to realize the autothermal balance or semi-autothermal balance of the conversion process.

In order to realize the autothermal balance or semi-autothermal balance of the conversion process, since the 1980s, foreign countries have started to develop the heat exchange conversion gas production process. The earliest to achieve industrialization is the LCA process of the British ICI company, and its production scale is 300-450MTPD. This process uses a heat exchange reformer to replace the traditional externally heated primary reformer, and shifts part of the CH ₄ steam reforming load of the primary reformer to the secondary reformer, adding excess air to the secondary reformer to maintain the system Self-heating balance, while using the high-temperature process gas from the second-stage reformer to exchange heat between the outside of the heat-exchanging primary reformer tube and the reactants in the tube to provide the heat required for the steam reforming reaction of hydrocarbons in the tube. In order to meet the requirement of H ₂ /N ₂ in the feed gas for the ammonia synthesis reaction, a PSA device is installed to remove the excess nitrogen brought into the system along with the excess air, and also remove CO ₂ gas. The LCA process causes a certain amount of H ₂ loss in the process of removing excess N ₂ . In order to overcome this shortcoming, the Grodno Nitrogen Complex Enterprise in Belarus adopts a heat exchange type primary reformer followed by a series of oxygen-enriched air secondary Stage reforming process, so as to achieve the purpose of self-heating balance of the system, and there is no problem of H ₂ loss, but another set of PSA air separation (or air separation) device needs to be installed.

At the end of the last century, I.C.I successfully developed the LCM process for the production of methanol synthesis gas on the basis of the LCA process, that is, the excess air is replaced by adding pure oxygen in the secondary reformer. At the same time, in China, the heat exchange type oxygen-enriched air conversion ammonia synthesis raw material gas, the heat exchange parallel conversion and the heat exchange series conversion ammonia synthesis raw material gas, and the heat exchange pure oxygen two-stage conversion system have also been successfully developed. Methanol synthesis feed gas and heat exchange parallel conversion series pure oxygen two-stage conversion to methanol synthesis feed gas.

However, in the above-mentioned processes, natural gas resources are not fully utilized, methanol production cannot be combined with methanol carbonylation acetic acid production, a large amount of fuel gas is required to be burned, and the problem of hydrogen and carbon imbalance in synthesis gas cannot be fundamentally solved.

Contents of the invention

The main purpose of the present invention is to make full use of natural gas resources, to combine methanol production and methanol carbonylation acetic acid production, to realize resource recycling, reduce fuel gas consumption, save energy and reduce consumption, reduce investment and shorten construction period, and fundamentally solve the problem of The problem of hydrogen and carbon imbalance in syngas is solved.

In order to achieve the above object, the present invention provides a method for preparing CO and synthesis gas by steam reforming of hydrocarbons. The feed gas containing hydrocarbons used in this method is natural gas, liquefied petroleum gas or gas, and its technological process is as follows:

A. The raw material gas containing hydrocarbons is mixed with steam and then preheated by an inlet/outlet heat exchanger, and then enters a heat exchange type primary reformer, and the hydrocarbons are steam reformed in the heat exchange type primary reformer The heat required for the steam reforming reaction of hydrocarbons comes from the heat energy of the high-temperature second-stage reforming gas generated by the first-stage reformer. The first-stage reforming gas generated by the heat-exchanging primary reformer enters the second-stage reformer, and the partial oxidation reaction of hydrocarbons and the deep conversion reaction of _CH4 are carried out in the second-stage reformer , the heat required for this reaction is supplied by the combustion heat released by the combustion reaction of _H2 gas and _O2 gas in the second-stage reformer and the partial oxidation reaction of _CH4 and _O2 gas; _CO2 gas is added to the reformer for steam reforming reaction to adjust the _H2 /C ratio, or pure oxygen is added to the secondary reformer to maintain the thermal balance of the system and the lowest _N2 content in the secondary reforming gas, Or add feed gas containing hydrocarbons into the secondary reformer to increase the CO content in the secondary reforming gas and save energy;

B. The high-temperature secondary reforming gas generated by the secondary reformer first provides heat to the heat-exchanging primary reformer, enters the inlet/outlet heat exchanger after its own temperature is lowered, and then enters the gas after being cooled by water The CO separation device separates part of CO, and the remaining tail gas is used as synthesis gas.

The raw material gas containing hydrocarbons described in step A of the above preparation method is mixed with steam and then preheated to a temperature of 400-600° C. and a pressure of 0.4-4.0 MPa through the inlet/outlet heat exchanger, and then enters the The heat exchange type primary reformer; the temperature of the primary reformed gas at the outlet of the heat exchange type primary reformer is 500-750°C, and the molar ratio of _CH in it on a dry basis is 12% to 28%; the secondary reformer The temperature of the secondary reformed gas at the outlet is 800-1070°C.

The _CO described in step A of the above preparation method is preheated to a temperature of 100-200° C. through a heating furnace before being added to the second-stage reformer; The feed gas containing hydrocarbons is preheated to a temperature of 330-410° C. through the heating furnace before being added; the oxygen described in step A is preheated to a temperature of 330-410° C. The temperature is 250-350°C.

The gas composition of H ₂ , CO and CO ₂ in the synthesis gas prepared by the above preparation method can meet the following conditions and be used in the low-pressure methanol synthesis process:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; CO</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2.05</span>}<span\; class="notranslate">\; ~</span>\mathrm{<span\; class="notranslate">\; 2.15</span>}$

In the formula: f-ratio, yuan unit,

H ₂ - molar flow rate of hydrogen, kmol/h,

CO ₂ - molar flow rate of carbon dioxide, kmol/h,

CO-molar flow rate of carbon monoxide, kmol/h.

The CO prepared by the above preparation method can be used as raw material gas for methanol carbonylation of acetic acid, and the obtained synthesis gas can be used as raw material gas for methanol synthesis.

The present invention also provides a method for preparing methanol by using synthesis gas. The _H2 , _CO2 -enriched gas and tail gas obtained by separating the purge gas produced in the process of preparing methanol from the synthesis gas are returned to the synthesis gas preparation process, Realize resource recycling. The technological process of this method is as follows:

A. The feed gas containing hydrocarbons and the purge gas produced in the methanol synthesis process are separated and obtained _H2 is mixed with steam and then preheated by an inlet/outlet heat exchanger and enters a heat exchange type one-stage conversion The steam reforming reaction of hydrocarbons is carried out in the heat-exchanging primary reforming furnace. The heat required for the steam reforming of hydrocarbons comes from the heat energy of the high-temperature secondary reforming gas generated by the primary reforming furnace. Obtained by the indirect heat exchange between the high-temperature secondary reforming gas and the reactants in the tube of the heat-exchanging primary reforming furnace. The primary reforming gas generated by the heat-exchanging primary reforming furnace enters the secondary reforming furnace. The partial oxidation reaction of hydrocarbons and the deep conversion reaction of CH ₄ are carried out in the second-stage reformer, and the heat required for this reaction is generated by the combustion reaction of H ₂ gas and O ₂ gas in the second-stage reformer and CH ₄ and O ₂ The supply of combustion heat released by the partial oxidation reaction of gas; at the same time, adding the CO2 _- enriched gas obtained by separating the purge gas into the secondary reformer for steam reforming reaction to adjust the ratio of _H2 /C, or Add pure oxygen to the secondary reformer to maintain system heat balance and the lowest _N content in the secondary reforming gas, or add raw material gas containing hydrocarbons to the secondary reformer to increase the nitrogen content of the secondary reformer. The content of CO in the stage reforming gas and can save energy;

B. The high-temperature secondary reforming gas generated by the secondary reformer first provides heat to the heat-exchanging primary reformer, enters the inlet/outlet heat exchanger after its own temperature is lowered, and then enters the gas after being cooled by water The CO separation device separates part of CO, and the remaining tail gas is used as synthesis gas.

C. The _CO described in step A is preheated to a temperature of 100-200° C. through a heating furnace before being added to the second-stage reformer; The feed gas of hydrocarbons is preheated to a temperature of 330-410°C through the heating furnace before being added; the oxygen described in step A is preheated to a temperature of 250-350°C, part of the fuel gas of the heating furnace is the tail gas remaining after the purge gas is separated from H ₂ and CO ₂ -enriched gas.

The process condition of the above-mentioned method for utilizing syngas to prepare methanol is: the feed gas containing hydrocarbons described in step A, _H2 and the mixed gas of water vapor are preheated to a temperature of 400-600°C, the pressure is 0.4-4.0MPa, and then enters the heat-exchanging primary reformer; the temperature of the primary reforming gas at the outlet of the heat-exchanging primary reformer is 500-750°C, and the dry basis of CH ₄ in it is The molar ratio is 12-28%; the temperature of the secondary reformed gas at the outlet of the secondary reformer is 800-1070°C.

The devices (or methods) that can be used to separate CO from the cooled secondary reformed gas in this preparation method include PSA separation and adsorption devices, cryogenic separation of CO, or complex absorption separation of CO. PSA separation and adsorption is recommended. device.

The vapor conversion reaction of hydrocarbons such as methane in the tube of the heat exchange type primary reformer of the present invention is as follows:

In the second-stage reformer, since pure oxygen, CO ₂ and methane and other hydrocarbons are added to the second-stage reformer, the steam reforming reaction is as follows:

The synthesis gas obtained by the preparation method can be used as raw material gas in the joint production process of methanol and acetic acid, and can also be used to produce methanol alone. At the same time, it can provide high-purity CO product gas with a purity of 99.8% to other users. The present invention has the following characteristics:

1. This preparation method is superior to the traditional externally heated steam reforming process. It can use the high-level thermal energy of the outlet gas of the second-stage reformer to heat the reactants in the tube of the heat-exchanging first-stage reformer to provide the necessary heat for its steam reforming reaction. At the same time, the process waste heat of the second-stage reforming gas between the tubes of the heat-exchanging primary reformer is used to preheat the natural gas/process steam mixture to the inlet temperature of the heat-exchanging primary reformer; as raw material gaseous hydrocarbons and process oxygen and CO ₂ The preheated heating furnace has an extremely low heat load, and its fuel gas can be either a small amount of gaseous hydrocarbons, or the tail gas of methanol synthesis purge gas recovered by _H2 and _CO2 , or a mixture of the two, from In the production practice site, it is difficult to observe the flue gas emission from the heating furnace with the naked eye. Therefore, the fuel gas consumption of this process is very low, so the unit product consumption quota is low, the energy consumption is low, and the self-heating balance of the hydrocarbon steam reforming reaction process is basically realized.

2. This preparation method is to transfer a part of _CH4 steam reforming from the primary reformer to the secondary reformer. The thermal equipment is equivalent, about 94%, while the thermal efficiency of the secondary reformer is close to 100%.

3. Since the content of various gases added to the secondary reformer can be adjusted, and part of the secondary reformed gas can be directly mixed with the tail gas after CO separation as synthesis gas without going through the CO separation device, so the obtained gas can be adjusted. The ratio of hydrogen to carbon in the synthesis gas completely solves the problem of the imbalance between hydrogen and carbon in the synthesis gas.

4. It is proved from production practice experience that the heat exchange reformer can operate normally even when the load is as low as 20%, and the adjustment of various production control indicators is convenient and quick.

5. It can realize the joint production of methanol and acetic acid, and realize the recycling of resources, thereby greatly reducing various consumption indicators.

Description of drawings

Fig. 1 is the system and process flow diagram for preparing CO, syngas and methanol by the preparation method.

Detailed ways

Referring to Fig. 1, the feed gas containing hydrocarbons enters the heating furnace 7 to be preheated to 330-410°C through the pipeline 1 (or after being mixed with the H ₂ obtained from the separation of the purge gas from the methanol synthesis from the pipeline 3), and then passes through the pipeline 8 enters the hydrodesulfurization tank 28 to remove sulfur harmful to subsequent processes, and the reactor is equipped with a catalyst. The desulfurized gas flows out through the pipeline 9 and mixes with the process steam from the pipeline 5, which is preheated to 250-300°C through the heating furnace (the superheated steam pressure is 0.3-4.5MPa), which is the process raw material gas, which enters the inlet/outlet exchange The heater 19 is preheated to 400-600° C., and enters the reforming tube of the heat-exchanging primary reforming furnace 14 through the pipeline 10, and the reforming tube is equipped with a catalyst. In the tubes of the heat exchange primary reformer, with the help of the heat provided by the high-temperature process gas from the secondary reformer 17 between the tubes, the raw hydrocarbons and water vapor react chemically to generate CO and H ₂ . When the reforming reaction of the heat exchange type primary reformer 14 has been carried out to a certain extent, the temperature of the primary reformed gas at the outlet of the heat exchange type primary reformer is 500-750° C., and the molar ratio of _CH in it on a dry basis is 12-28%. The first-stage reforming gas enters the adiabatic second-stage reformer 17 through the outlet pipe 16, and the second-stage reformer is filled with catalyst. Process oxygen enters the heating furnace 7 through the pipe 2, preheats it to 250-350°C, and enters the top of the second-stage reformer 17 through the pipeline 12, where it is turbulently mixed with the first-stage reforming gas from the pipeline 16. The combustion reaction of hydrogen and oxygen occurs at the top, which provides the required heat for the subsequent methane deep conversion reaction. Part of the desulfurized raw material gas from the pipeline 29 enters the secondary reformer and performs a partial oxidation reaction in its non-catalytic reaction space. . The CO ₂ gas from the pipeline 4 enters the heating furnace 7 and is preheated to 100-200°C. After being mixed with the primary reforming gas from the pipeline 16 through the pipeline 13, it enters the secondary reforming furnace 17 for steam reforming of CH ₄ +CO ₂ reaction. When the conversion reaction in the second-stage reformer has progressed to a certain extent, that is, when the outlet temperature reaches 800-1070°C, the outlet gas of the second-stage reformer 17 enters the tube of the heat-exchanging first-stage reformer 14 through the pipeline 18, and the second-stage reformer gas The high-level process waste heat is transferred to the reactants in the pipe, and its own temperature drops to 500-750°C and enters the inlet/outlet heat exchanger 19 through the pipeline 15, preheats the raw material gas to 400-600°C, and then enters the reformed gas waste after its own temperature is lowered again. The boiler 20 further recovers the heat in the reformed gas in the form of by-product steam, and then enters the boiler feed water preheater 22 and water cooler 23 through the pipeline 21, and cools the reformed gas to about 40°C with water and enters the PSA transformer through the pipeline 24 The adsorption separation device 25 separates part of the CO in the reformed gas, and sends it to be used as the raw material gas for carbonylation of methanol to acetic acid. The tail gas 27 after separating CO contains a large amount of effective components such as H ₂ , CO ₂ and CO, and is sent to be used as the raw material gas for carbonylation of methanol to acetic acid. methanol synthesis gas. The output of methanol is controlled by adjusting the size of the PSA auxiliary line valve. The steam by-produced by the reforming gas waste boiler 20 is sent to the main pipe through the pipeline 28 after being separated from water by the steam drum.

The obtained syngas is in the process of synthesizing methanol, and the _H2 , _CO2- enriched gas and tail gas separated from the purge gas are returned to the pipeline 3, pipeline 4 and pipeline 13 respectively (the tail gas is used as fuel gas) parts to realize the recycling of resources.

Finally, it should be noted that the above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the present invention can still be modified and \or equivalent substitutions without departing from the spirit and scope of the invention.

Claims (9)

1, a kind of hydrocarbon steam conversion prepares the method for CO and synthetic gas, it is characterized in that:

A, the unstripped gas of hydrocarbon-containifirst material mixes with water vapor after enter a heat exchange type one-stage converter after the import/export interchanger preheating, in described heat exchange type one-stage converter, carry out the hydrocarbons steam reforming reaction, the heat energy of two sections reforming gas of high temperature that the required heat of described hydrocarbons steam reforming reaction generates from a secondary reformer, this heat obtains by the indirect heat exchange between two sections reforming gas of high temperature and the heat exchange type one-stage converter inner reaction tube thing, one section reforming gas that described heat exchange type one-stage converter generates enters described secondary reformer, carries out hydrocarbons partial oxidation reaction and CH in described secondary reformer ₄Degree of depth conversion reaction, the required heat of this reaction is by the H in the described secondary reformer ₂Gas and O ₂Gas generation combustion reactions and CH ₄With O ₂The combustion heat that gas generation partial oxidation reaction is emitted is supplied with; Simultaneously in described secondary reformer, add CO ₂Gas carries out steam reforming reaction, in order to regulate H ₂/ C ratio, or add pure oxygen to described secondary reformer is in order to keep minimum N in system's thermal equilibrium and the two sections reforming gas ₂Content, or add the unstripped gas contain hydrocarbons in described secondary reformer is in order to the content that increases CO in two sections reforming gas and can be energy-conservation;

Two sections reforming gas of high temperature that B, described secondary reformer generate, at first heat is offered described heat exchange type one-stage converter, self temperature enters described import/export interchanger after reducing, and enters the CO tripping device again after water cooling, cutting out partial CO, remaining tail gas is as synthetic gas.

2, hydrocarbon steam conversion according to claim 1 prepares the method for CO and synthetic gas, the unstripped gas that it is characterized in that the hydrocarbon-containifirst material described in the steps A mixes with water vapor after described outlet/inlet interchanger is preheating to temperature is 400～600 ℃, and pressure is to enter described heat exchange type one-stage converter behind 0.4～4.0MPa; One section reforming gas temperature of the outlet of described heat exchange type one-stage converter is 500～750 ℃, CH ₄Butt mol ratio therein is 12～28%; The temperature of two sections reforming gas of the outlet of described secondary reformer is 800～1070 ℃.

3, hydrocarbon steam conversion according to claim 1 prepares the method for CO and synthetic gas, it is characterized in that the CO described in the steps A ₂Being preheating to temperature through a process furnace before joining described secondary reformer is 100～200 ℃; The unstripped gas of the hydrocarbon-containifirst material that joins described secondary reformer described in the steps A was preheating to temperature through described process furnace before adding be 330～410 ℃; Oxygen described in the steps A was preheating to temperature through described process furnace before joining described secondary reformer be 250～350 ℃.

4, hydrocarbon steam conversion according to claim 1 and 2 prepares the method for CO and synthetic gas, it is characterized in that the H in the described synthetic gas ₂, CO and CO ₂Gas composition meets the following conditions, and is used for the low pressure methanol synthesis technique:

$f=\frac{H_2-{\mathrm{CO}}_2}{\mathrm{CO}+{\mathrm{CO}}_2}=2.05~2.15$

In the formula: f-ratio, first unit,

H ₂The molar flow of-hydrogen, kmol/h,

CO ₂The molar flow of-carbonic acid gas, kmol/h,

The molar flow of CO-carbon monoxide, kmol/h.

5, the CO of the described method preparation of a kind of claim 1 is as the methanol carbonyl synthesized acetic acid unstripped gas.

6, the synthetic gas of the described method preparation of a kind of claim 1 is as the methyl alcohol synthetic raw gas.

7, a kind of method of utilizing synthesis gas preparation methyl alcohol, the H that the off-gas that it is characterized in that producing in the synthesis gas preparation methanol process obtains through separation ₂, rich CO ₂Gas and tail gas turn back in the synthesis gas preparation process, realize resource circulation utilization.

8, the method for utilizing synthesis gas preparation methyl alcohol according to claim 7 is characterized in that the preparation method of described synthetic gas is as follows:

The off-gas that produces in the unstripped gas of A, hydrocarbon-containifirst material and the described methyl alcohol building-up process is through separating the H that obtains ₂Mix after enter a heat exchange type one-stage converter after the import/export interchanger preheating with water vapor, in described heat exchange type one-stage converter, carry out the hydrocarbons steam reforming reaction, the heat energy of two sections reforming gas of high temperature that the required heat of described hydrocarbons steam reforming reaction generates from a secondary reformer, this heat obtains by the indirect heat exchange between two sections reforming gas of high temperature and the heat exchange type one-stage converter inner reaction tube thing, one section reforming gas that described heat exchange type one-stage converter generates enters described secondary reformer, carries out hydrocarbons partial oxidation reaction and CH in described secondary reformer ₄Degree of depth conversion reaction, the required heat of this reaction is by the H in the described secondary reformer ₂Gas and O ₂Gas generation combustion reactions and CH ₄With O ₂The combustion heat that gas generation partial oxidation reaction is emitted is supplied with; In described secondary reformer, add the rich CO that described off-gas obtains through separation simultaneously ₂Gas carries out steam reforming reaction, in order to regulate H ₂/ C ratio, or add pure oxygen to described secondary reformer is in order to keep minimum N in system's thermal equilibrium and the two sections reforming gas ₂Content, or add the unstripped gas contain hydrocarbons in described secondary reformer is in order to the content that increases CO in two sections reforming gas and can be energy-conservation;

Two sections reforming gas of high temperature that B, described secondary reformer generate, at first heat is offered described heat exchange type one-stage converter, self temperature enters described import/export interchanger after reducing, and enters the CO tripping device again after water cooling, cutting out partial CO, remaining tail gas is as synthetic gas.

CO described in C, the steps A ₂Being preheating to temperature through a process furnace before joining described secondary reformer is 100～200 ℃; The unstripped gas of the hydrocarbon-containifirst material that joins described secondary reformer described in the steps A was preheating to temperature through described process furnace before adding be 330～410 ℃; Oxygen described in the steps A was preheating to temperature through described process furnace before joining described secondary reformer be 250～350 ℃, and the part of fuel gas of described process furnace is that described off-gas is through separating H ₂With rich CO ₂Remaining tail gas behind the gas.

9, the method for utilizing synthesis gas preparation methyl alcohol according to claim 8 is characterized in that unstripped gas, the H of the hydrocarbon-containifirst material described in the steps A ₂Being preheating to temperature with the gas mixture of water vapor through described outlet/inlet interchanger is 400～600 ℃, and pressure is to enter described heat exchange type one-stage converter behind 0.4～4.0MPa; One section reforming gas temperature of the outlet of described heat exchange type one-stage converter is 500～750 ℃, CH ₄Butt mol ratio therein is 12～28%; The temperature of two sections reforming gas of the outlet of described secondary reformer is 800～1070 ℃.