CN104150441A - Method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas - Google Patents

Abstract

The invention relates to a method for converting a Fischer-Tropsch synthesis tail gas into a Fischer-Tropsch synthesis feed gas. The method comprises the following steps that: carrying out catalytic hydrogenation reaction on the Fischer-Tropsch synthesis tail gas in a hydrogenation reactor filled with a hydrogenation catalyst, so as to convert the Fischer-Tropsch synthesis tail gas into saturated hydrocarbon; then carrying out steam reforming and partial oxidation in a primary converter and a secondary converter, carrying out water gas shift reaction in an intermediate converter and finally carrying out gas-liquid separation, wherein a gas phase is the feed gas which meets the requirement for hydrogen carbon ratio required by Fischer-Tropsch synthesis. The method disclosed by the invention has the advantages of simple process and convenience for operation.

Description

A method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas

technical field

The invention relates to a method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas.

Background technique

Fischer-Tropsch synthesis tail gas refers to the gas produced during the conversion of synthesis gas (H ₂ and CO) into hydrocarbons through Fischer-Tropsch synthesis in the presence of a catalyst, mainly composed of H ₂ , CO, CO ₂ and low-carbon hydrocarbons. mixed composition. Among them, the low-carbon hydrocarbons are mainly CH ₄ , and its content is usually 20-60% (mol percent), and in addition, the low-carbon hydrocarbons also contain 1-10% (mol percent) of low-carbon olefins. In the currently disclosed prior art, there are mainly two ways to utilize Fischer-Tropsch synthesis tail gas, one is to obtain _H2 and methane gas, etc. through separation; the other is to convert hydrocarbons (mainly methane) in the tail gas It is synthesized gas, and then returned to the Fischer-Tropsch synthesis unit as raw material gas to further synthesize oil products, thereby improving raw material utilization and oil product yield.

Patent CN101273112B discloses a method for preparing and converting synthesis gas, which is to convert the raw material gas containing _CH in the shift stage to generate H _and CO synthesis gas, which is then used for Fischer-Tropsch synthesis reaction, Fischer-Tropsch synthesis The tail gas is converted by steam to CH ₄ in the tail gas, and CO ₂ is removed to produce hydrogen-rich gas.

Patent CN102614763A discloses a treatment method for Fischer-Tropsch synthesis tail gas, including decarburization, membrane separation, low-temperature oil washing, tail gas conversion and pressure swing adsorption steps. The treatment method needs to remove _CO in the Fischer-Tropsch synthesis tail gas through decarbonization Separate, and then through the membrane separation unit and the crude synthesis gas through the conversion and pressure swing adsorption unit to recover H ₂ for the whole plant, and the analysis gas is used as fuel gas.

Patent CN102614764B discloses a process for preparing high-purity hydrogen from Fischer-Tropsch synthesis tail gas. The process includes four steps of partial oxidation of light hydrocarbons, shifting, decarburization, and pressure swing adsorption, and can obtain hydrogen with a purity of more than 99%. Therefore, the main purpose of this process is to produce high-purity hydrogen.

Patent CN102703108A provides a process method for Fischer-Tropsch synthesis and tail gas utilization. The method uses pressure swing adsorption technology to extract hydrogen and methane from Fischer-Tropsch synthesis tail gas, and then mixes them with Fischer-Tropsch synthesis feed gas in a certain proportion, thereby realizing Recycling of Fischer-Tropsch synthesis tail gas. The main purpose of this method is to reduce the load of the conversion process in the Fischer-Tropsch synthesis unit, thereby improving the production efficiency and economical efficiency of the Fischer-Tropsch synthesis unit, but the method requires high purity control of _H2 and _CH4 .

Patent CN102730637A discloses a low-carbon exhaust Fischer-Tropsch synthesis tail gas comprehensive utilization process, which converts non-circulating tail gas after Fischer-Tropsch synthesis reaction into hydrogen-rich gas, and extracts high-purity hydrogen from the hydrogen-rich gas for utilization .

Fischer-Tropsch synthesis tail gas contains CO ₂ and some low-carbon hydrocarbons, and the hydrogen-to-carbon ratio in the tail gas cannot directly meet the requirements of Fischer-Tropsch synthesis. Converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis raw material gas can improve carbon utilization And the production capacity of the synthetic oil device, no report was found after searching.

Contents of the invention

The purpose of the present invention is to provide a method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas with simple process and convenient operation.

The invention is to obtain the _H2 /CO ratio suitable for the Fischer-Tropsch synthesis gas by performing catalytic hydrogenation, steam reforming, partial oxidation and water vapor shift process adjustment on the unsaturated low-carbon hydrocarbons in the Fischer-Tropsch synthesis tail gas. Raw gas.

The technical scheme adopted in the present invention is:

A method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis raw material gas, comprising four steps of catalytic hydrogenation, steam reforming and partial oxidation reaction, medium temperature water-vapor shift reaction, waste heat recovery and gas-liquid separation, characterized in that the The catalytic hydrogenation process is to convert the unsaturated hydrocarbons in the Fischer-Tropsch synthesis tail gas into saturated hydrocarbons through catalytic hydrogenation reaction in a hydrogenation reactor equipped with a hydrogenation catalyst; the steam reforming and partial oxidation The reaction process includes two reformers, a first-stage reformer and a second-stage reformer. The mixed gas composed of water vapor and the catalytically hydrogenated Fischer-Tropsch synthesis tail gas enters the first-stage reformer equipped with reforming catalyst A to complete the preliminary conversion. The gas from the first-stage reformer enters the second-stage reformer equipped with reforming catalyst B, and at the same time, the preheated pure oxygen is passed into the second-stage reformer to carry out a small amount of Fischer-Tropsch synthesis tail gas oxidation reaction to complete the deep conversion. The feed rate of steam and pure oxygen is used to adjust the water-to-carbon ratio of the mixed gas in the first-stage reformer and the oxygen-carbon ratio of the mixed gas in the second-stage reformer, as well as the operating temperature and pressure of the first-stage reformer and the second-stage reformer , and finally carry out the water vapor shift reaction in the intermediate transformer furnace equipped with a catalyst. The waste heat recovery and gas-liquid separation process is to recover the heat of the material obtained by the water vapor shift reaction, and then carry out gas-liquid separation. The gas phase is to meet the Fischer-Tropsch synthesis Raw material gas with the required ratio of hydrogen to carbon.

Further, a sleeve-type heat exchanger is arranged outside the first-stage reformer, and the high-temperature second-stage reforming gas from the second-stage reformer transfers part of the heat to the sleeve-type heat exchanger, and then the heat is transferred by the sleeve-type heat exchanger. The heat exchange between the heater and the reactants in the primary reformer provides a heat source for the reforming reaction in the primary reformer; the heat required for the reformation in the secondary reformer is passed through the Pure oxygen is provided by the combustion reaction of hydrogen, methane, carbon monoxide and pure oxygen in part of the first-stage reformed gas on the top of the second-stage reformer.

Further, the hydrogenation catalyst in the catalytic hydrogenation step is JT-202, the operating temperature is 220-250°C, the operating pressure is 2.0-3.0MPa, and the space velocity is 1000-2000h ^-1 .

Further, the reforming catalysts A used in the primary reformer are Z112-HA and Z112-HB, and the water-to-carbon molar ratio of the mixed gas in the primary reformer is 2.5-3.5 (number of water vapor molecules): 1 (carbon atoms number), the operating temperature is 650-850°C, the operating pressure is 2.0-3.0MPa, and the space velocity is 1000-2000h ^-1 .

The change and control of the amount of water vapor is calculated and measured by using the index of water-carbon ratio, which is defined as the ratio of the number of water vapor molecules converted into the furnace gas to the number of carbon atoms in the raw material hydrocarbon. The water-to-carbon ratio is a more accurate indicator. When calculating the ratio of raw materials, it is first required to calculate the total number of carbon atoms (usually written as ∑C) contained in each molecule of gas, and then compare it with the number of water vapor molecules.

∑C＝1×C1+2×C2+3×C3+……+n×Cn (1)

Wherein C1, C2, C3, ..., Cn are the carbon atoms in the feed gas with 1, 2, 3, ..., and n is the volume fraction of hydrocarbons. For example, the raw material Fischer-Tropsch synthesis tail gas contains not only methane, but also a small amount of ethane. When reacting with water vapor, one molecule of methane is counted as one carbon atom, one molecule of ethane is counted as two carbon atoms, and so on for other hydrocarbons.

Further, the water vapor is saturated water vapor with a temperature of 200-300°C and a pressure of 2.0-3.0 MPa.

Further, the weight ratio of Z112-HA to Z112-HB is (0.8-1.2):(0.8-1.2).

Further, the preheated oxygen enters the secondary reformer, and the oxygen-to-carbon molar ratio of the gas in the secondary reformer is 0.4-0.6.

The change and control of the partial oxidation reaction is calculated and measured by the oxygen-carbon ratio index, which is defined as the ratio of the molar amount of oxygen fed into the secondary furnace to the molar amount of alkane carbon atoms in the secondary reformed gas. In this definition, carbon The statistical method of atomic moles is the same as the statistical method of carbon atom moles in the above definition of water-to-carbon ratio.

Further, the reforming catalyst B in the secondary reformer is CZ-7, the operating temperature is 850-1300°C, the operating pressure is 2.0-3.0 MPa, and the space velocity is 1000-2000h ^-1 .

Further, the catalyst in the medium-change furnace is NB113, the operating temperature is 340-360°C, the operating pressure is 2.0-3.0MPa, and the space velocity is 1000-2000h ^-1 .

Further, the ratio of H ₂ /CO in the Fischer-Tropsch synthesis feed gas obtained according to the method of the present invention is 2.9-3.5.

Compared with the prior art, the present invention has the following significant advantages:

The method of the present invention adjusts the operations such as water-to-carbon ratio and oxygen-to-carbon ratio in steam reforming and partial oxidation reaction processes by controlling the feed rate of steam and pure oxygen, and can obtain hydrogen suitable for Fischer-Tropsch synthesis. The raw material gas with carbon ratio makes the raw materials of Fischer-Tropsch synthesis more fully utilized, the carbon utilization rate is improved, the process is simple, and the operation is convenient, thus overcoming the problem of hydrogen and gas in the Fischer-Tropsch synthesis tail gas treatment process in the prior art. It is a complex and difficult technical problem to separate and extract methane separately and then utilize it.

Description of drawings

Fig. 1 is a schematic diagram of the production process of the present invention.

In the figure, 1 is a heat exchanger; 2 is a hydrogenation reactor; 3 is a heating sleeve; 4 is a first-stage reformer; 5 is a second-stage reformer; 6 is a heat exchanger; Boiler; 9 is a gas-liquid separator.

Detailed ways

The technical solution of the present invention will be described in detail below in combination with the purpose and principle of the present invention.

The present invention uses Fischer-Tropsch synthesis tail gas as raw material, and converts it into Fischer-Tropsch synthesis raw material gas through a steam reforming process. , partial oxidation and other process adjustments, so as to obtain a feed gas suitable for the H ₂ /CO ratio required for Fischer-Tropsch synthesis gas.

In the method of the present invention, the change and control of the amount of water vapor is calculated and measured by using the index of water-carbon ratio, which is defined as the ratio of the number of water vapor molecules converted into the furnace gas to the number of carbon atoms in the raw material hydrocarbon. The water-to-carbon ratio is a more accurate indicator. When calculating the ratio of raw materials, it is first required to calculate the total number of carbon atoms (usually written as ∑C) contained in each molecule of gas, and then compare it with the number of water vapor molecules.

∑C＝1×C1+2×C2+3×C3+……+n×Cn (1)

Wherein C1, C2, C3, ..., Cn are the carbon atoms in the feed gas with 1, 2, 3, ..., and n is the volume fraction of hydrocarbons. For example, the raw material Fischer-Tropsch synthesis tail gas contains not only methane, but also a small amount of ethane. When reacting with water vapor, one molecule of methane is counted as one carbon atom, one molecule of ethane is counted as two carbon atoms, and so on for other hydrocarbons.

In the method of the present invention, the change and control of the partial oxidation reaction is calculated and measured by the oxygen-to-carbon ratio index, which is defined as the ratio of the amount of oxygen introduced into the second-stage furnace to the molar number of alkane carbon atoms in the second-stage reforming gas, The statistical method for the number of moles of carbon atoms in this definition is the same as the statistical method for the number of moles of carbon atoms in the above-mentioned definition of the water-to-carbon ratio.

Under the guidance of above-mentioned purpose and principle, the present invention proposes following Fischer-Tropsch synthesis tail gas conversion process:

The method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis raw material gas includes four steps of catalytic hydrogenation, steam reforming and partial oxidation reaction, medium temperature water vapor shift reaction, waste heat recovery and gas-liquid separation.

(1) Catalytic hydrogenation process

The unsaturated hydrocarbons in the Fischer-Tropsch synthesis tail gas are very prone to carbon deposition in the subsequent conversion process, which affects the subsequent conversion process, especially the normal operation of the first-stage reformer. Therefore, the main purpose of this process is to Catalytic hydrogenation reaction is carried out to convert the unsaturated hydrocarbons in the Fischer-Tropsch synthesis tail gas into saturated hydrocarbons by hydrogenation. The specific reaction is as follows:

This process uses a hydroconversion catalyst JT-202 that does not require special activation treatment, and the hydroconversion catalyst is purchased from Northwest Research Institute of Chemical Industry. The model, composition, properties and dosage of the hydroconversion catalyst are shown in Table 1.

Table 1

The saturated hydrocarbons (C2-C4) generated after the hydrogenation reaction in this process will also increase the possibility of carbon deposits, which can be controlled by adjusting the amount of steam in the subsequent steam reforming reaction and partial oxidation reaction process.

It can be seen from Figure 1 that the Fischer-Tropsch synthesis tail gas enters the hydrogenation reactor 2 after being preheated by the heat exchanger 1, and undergoes a hydrogenation reaction under the action of a catalyst. After the hydrogenation reaction, the mixed gas enters the first-stage reformer 4 for a reforming reaction.

(2) Steam reforming and partial oxidation reaction

This process includes a primary reformer 4 and a secondary reformer 5, the main purpose of which is to maximize the generation of _H2 and CO through steam reforming and partial oxidation reactions in the primary reformer 4 and secondary reformer 5.

The type, composition, properties and dosage of the catalysts used in the primary reformer 4 and the secondary reformer 5 of this process are shown in Table 2.

Table 2

It can be seen from Figure 1 that the mixed gas of saturated water vapor with a temperature of 200-300°C and a pressure of 2.0-3.0 MPa and the hydrogenated Fischer-Tropsch synthesis tail gas enters the first-stage reformer 4, where Z112-HA and Z112-HB catalysts In the presence of the same time, the steam reforming conversion reaction of gaseous alkanes is carried out. The first-stage reforming gas from the first-stage reformer 4 enters the second-stage reformer 5, and at the same time, the preheated pure oxygen is passed into the second-stage reformer 5 according to the oxygen-to-carbon ratio described in the embodiment of the present invention. The first-stage reformed synthesis gas and the pure oxygen are mixed in the second-stage reformer 5 to generate combustion reactions of H ₂ and a small amount of CH ₄ , CO and O ₂ . The remaining gas is deeply reformed in the secondary reformer 5 under the pressure of 2.0-3.0 MPa and the presence of a CZ-7 catalyst, and the residual CH ₄ content in the secondary reforming gas is reduced to 0.5% (dry basis, volume percentage) or less.

In this process, the steam reforming reaction and water vapor shift reaction equations are as follows:

CH ₄ +H ₂ O=CO+3H ₂ -ΔQ ₁ (3)

C _n H _2n+2 +nH ₂ O=nCO+(2n+1)H ₂ -ΔQ ₂ (4)

CO+H ₂ O=CO ₂ +H ₂ +ΔQ ₃ (5)

The equilibrium composition of the primary reformer 4 depends on reactions (3) and (5). This is because the increase of the water-to-carbon ratio, that is, the increase of water vapor is beneficial to the methane reforming reaction. However, when the water-to-carbon ratio reaches a certain value, the effect on increasing the conversion rate of methane is not significant, and an excessively large water-to-carbon ratio will easily lead to an increase in the pressure drop in the reformer, thereby increasing the consumption of water vapor. A lower water-to-carbon ratio will easily cause carbon deposition on the catalyst, so the water-to-carbon ratio should be strictly controlled. In the steam reforming conversion process, the control and adjustment of the water-to-carbon ratio in the first-stage reformer is one of the technical keys of the present invention. In the method of the present invention, the operating temperature in the first-stage reformer 4 is 650-850°C, the operating pressure is 2.0-3.0 MPa, and the water-to-carbon ratio of the mixed gas is 2.5-3.5.

In the above-mentioned steam reforming conversion process, the heat required for the first-stage reforming conversion reaction process comes from the heat released by the reaction in the second-stage reformer 5 . A sleeve-type heat exchanger 3 is arranged outside the first-stage reformer 4, and the high-temperature second-stage reformed gas from the second-stage reformer 5 transfers part of the heat to the sleeve-type heat exchanger 3, and then passes through the sleeve The tubular heat exchanger 3 transfers heat to the primary reformer 4 . The heat required for the further hydrocarbon conversion reaction of the first-stage reforming gas in the second-stage reformer 5 is to pass pure oxygen into the combustion chamber of the second-stage reformer 5, and then a partial oxidation reaction occurs in the combustion chamber. That is, it is provided by the combustion reaction of hydrogen, part of methane, carbon monoxide and oxygen. Concrete reaction equation is as follows:

CH ₄ +2O ₂ =CO ₂ +2H ₂ O+ΔQ ₅ (7)

Because the combustion reaction speed of hydrogen is very fast, in fact, the combustion reaction of hydrogen is mainly carried out in this part. The highest temperature of this part is between 1400-1600 ℃. Therefore, the control and adjustment of the oxygen-carbon ratio in the secondary reformer is another technical key of the present invention. In the method of the present invention, the oxygen-to-carbon ratio of the mixed gas in the second-stage reformer 5 is 0.4-0.6, and the oxygen in this process needs to be heated to 100-500° C. before being passed into the Fischer-Tropsch synthesis tail gas. By controlling and adjusting the oxygen-carbon ratio of the mixed gas in the second-stage reformer 5, the operating temperature in the second-stage reformer 5 can be controlled to be 850-1300° C., and the operating pressure is 2.0-3.0 MPa.

On the catalyst bed in the secondary reformer 5, the remaining methane further undergoes water-steam reforming reaction (3) and water-steam shift reaction (5). The composition of the secondary reformed gas depends on the shift reaction (5). Through the above-mentioned control and adjustment in the secondary reformer, the content of methane is finally reduced to below 0.5v% (dry basis, volume percentage).

(3) Water vapor shift reaction of medium transformer

The gas after the second-stage conversion enters the intermediate transformer after recovering waste heat for many times, and part of the CO in the intermediate transformer undergoes a water vapor shift reaction (5), so that the hydrogen-carbon ratio of the Fischer-Tropsch synthesis tail gas can be adjusted.

Since the reaction is a reversible exothermic reaction, lowering the temperature or increasing excess water vapor is conducive to the conversion reaction to the right. The conversion reaction can greatly accelerate its reaction speed by means of a catalyst. What is actually carried out in this device is CO Partial conversion of H ₂ /CO can be adjusted to 2.9 ~ 3.5, so as to meet the requirements of Fischer-Tropsch synthesis.

table 3

Catalyst model Catalyst composition Medium Transformer 7 NB113 Fe ₂ O ₃ ≥75%, Cr ₂ O ₃ ≥7.5%

(4) Waste heat recovery and gas-liquid separation

The main purpose of this process is to maximize heat recovery and obtain raw material synthesis gas that meets the hydrogen-carbon ratio required by Fischer-Tropsch synthesis.

After all the heat has been recovered, the reformed gas in the second stage is finally cooled by the gas-liquid separator 9 to separate free water, so that the raw material gas that meets the hydrogen-carbon ratio required by the Fischer-Tropsch synthesis can be obtained.

The waste heat recovery process is actually carried out for the heat released by the combustion reaction in the secondary reformer 5 . The heat carried by the second-stage reformed gas obtained through the combustion reaction is transferred to the sleeve heat exchanger 3 to provide a heat source for the reforming reaction in the first-stage reformer 4, and the gas after heat exchange through the sleeve heat exchanger 3 After entering the heat exchanger 6, part of the heat is used for the intermediate transformer furnace 7 to provide reaction heat, and the other part of the heat is recovered by the waste heat boiler 8 and enters the heat exchanger 1 for preheating the Fischer-Tropsch synthesis tail gas.

The present invention will be further described in detail below in conjunction with the accompanying drawings and preferred embodiments.

Example 1

(1) Fischer-Tropsch synthesis tail gas at 40°C, 2.4 MPa, and space velocity of 1500 h ^-1 (its main components are 16.4% CO, 40.3% H ₂ , 40.2% CH ₄ , 1.2% low-carbon hydrocarbons, 0.1% CO ₂ , 1.83% N ₂ ) is preheated to 200°C and enters the hydrogenation reactor 2, under the action of the catalyst JT-202, the hydrogenation reaction is carried out under the conditions of 230°C, 2.4 MPa, and a space velocity of 1500h ^-1 , C ₂ H ₄ and C ₃ H ₆ are all converted into C ₂ H ₆ and C ₃ H ₈ , the gas after hydrogenation is mixed with saturated steam at 230°C and 2.4MPa according to the water-to-carbon ratio of 3.0, then heated to 500°C and enters the primary reformer 4 middle;

(2) The mixed gas entering the primary reformer 4 is in the presence of catalysts Z112-HA and Z112-HB at a weight ratio of 1:1, the operating temperature is 720°C, the pressure is 2.4 MPa, and the space velocity is 1500 h ^-1 , and is produced by Part of the heat provided by the high-temperature reformed gas from the secondary reformer 5 to the heat exchange sleeve 3 is used as the heating heat source for the reaction to carry out the steam reforming conversion reaction of gaseous alkanes, and the _CH4 content in the outlet gas is reduced to 18.7%, and then enters In the second-stage reformer 5, the oxygen-to-carbon ratio is 0.45, and the _O2 is preheated to 200°C and then mixed with the first-stage reforming gas in the second-stage reformer 5 to generate H ₂ and part of CH ₄ , CO and O ₂ Combustion reaction, the reaction heat of which provides the necessary heat for the methane deep conversion reaction, and the rest of the gas is deep converted in the second-stage reformer 5 under the conditions of catalyst CZ-7, 1000 °C, 2.4 MPa, and a space velocity of 1500 h ^-1 , the residual _CH content in the secondary reformed gas is reduced to 0.50v% (dry basis);

(3) The second-stage reforming gas transfers part of the heat to the casing heat exchanger 3 to provide a heat source for the conversion reaction in the first-stage reforming furnace 4, and the heat exchanged through the casing heat exchanger 3 is passed into the heat exchanger After 6, part of the heat is used in the intermediate transformer furnace 7 to provide reaction heat, and the other part of the heat is recovered by the waste heat boiler 8 and enters the heat exchanger 1 for preheating the Fischer-Tropsch synthesis tail gas.

After all the heat recovery, the secondary reformed gas undergoes water-vapor shift reaction under the presence of NB113 as the catalyst in the intermediate transformer furnace 7, at an operating temperature of 360°C, at an operating pressure of 2.4 MPa, and at a space velocity of 1000 h ^-1 . The gas-liquid separator 9 cools and separates free water to obtain raw material gas that meets the ratio of hydrogen to carbon required by Fischer-Tropsch synthesis.

Example 2

(1) Fischer-Tropsch synthesis tail gas at 40°C, 2.5 MPa, and space velocity of 1200 h ^-1 (its main components are 16.4% CO, 40.3% H ₂ , 40.2% CH ₄ , 1.2% light hydrocarbons, 0.1% CO ₂ , 1.83% N ₂ ) is preheated to 220°C and enters the hydrogenation reactor 2, under the action of the catalyst JT-202, the hydrogenation reaction is carried out under the conditions of 220°C, 2.5 MPa, and a space velocity of 1100h ^-1 , C ₂ H ₄ and C ₃ H ₆ are all converted into C ₂ H ₆ and C ₃ H ₈ , the gas after hydrogenation is mixed with saturated steam at 230°C and 2.5 MPa according to the water-to-carbon ratio of 2.9, then heated to 500°C and enters the primary reformer 4 middle;

(2) The mixed gas entering the primary reformer 4 is in the presence of catalysts Z112-HA and Z112-HB at a weight ratio of 0.9:1.1, the operating temperature is 740°C, the pressure is 2.5 MPa, and the space velocity is 1100 h ^-1 , and is produced by Part of the heat provided by the high-temperature reformed gas from the secondary reformer 5 to the heat exchange sleeve 3 is used as a heating heat source for the reaction to carry out the steam reforming conversion reaction of gaseous alkanes, and the _CH4 content in the outlet gas is reduced to 19.5%, and then enters In the second-stage reformer 5, the oxygen-to-carbon ratio is 0.5, and the _O2 is preheated to 200°C and then mixed with the first-stage reforming gas in the second-stage reformer 5 to produce H ₂ and part of CH ₄ , CO and O ₂ Combustion reaction, the reaction heat of which provides the necessary heat for the methane deep conversion reaction, and the rest of the gas is deep converted in the second-stage reformer 5 under the conditions of catalyst CZ-7, 1100 ° C, 2.5 MPa, and a space velocity of 1100 h ^-1 , the residual _CH content in the secondary reformed gas is reduced to 0.49v% (dry basis);

(3) The catalyst in the intermediate transformer furnace 7 is NB113, the operating temperature is 350 ° C, the operating pressure is 2.5 MPa, and the water vapor shift reaction is carried out at a space velocity of 1200 h ^-1 , and other conditions are the same as (3) in Example 1.

Example 3

(1) Fischer-Tropsch synthesis tail gas at 40°C, 2.3 MPa, and space velocity of 1000 h ^-1 (its main components are 16.4% CO, 40.3% H ₂ , 40.2% CH ₄ , 1.2% low-carbon hydrocarbons, 0.1% CO ₂ , 1.83% N ₂ ) is preheated to 240°C and enters the hydrogenation reactor 2, under the action of the catalyst JT-202, the hydrogenation reaction is carried out at 230°C, 2.3 MPa, and a space velocity of 1200h ^-1 , C ₂ H ₄ and C ₃ H ₆ are all converted into C ₂ H ₆ and C ₃ H ₈ , the gas after hydrogenation is mixed with saturated steam at 230°C and 2.3 MPa according to the water-to-carbon ratio of 2.7, and then heated to 500°C to enter the primary reformer 4 middle;

(2) The mixed gas entering the primary reformer 4 is in the presence of the catalyst Z112-HA and Z112-HB at a weight ratio of 0.8:1, the operating temperature is 800°C, the operating pressure is 2.3 MPa, and the space velocity is 1200 h ^-1 , and Part of the heat provided by the high-temperature reformed gas from the secondary reformer 5 to the heat exchange sleeve 3 is used as the heating heat source for the reaction to carry out the steam reforming conversion reaction of gaseous alkanes, and _the CH content in the outlet gas is reduced to 20.5%, and then Enter the secondary reformer 5, with an oxygen-to-carbon ratio of 0.6, preheat the _O2 to 200°C and mix it with the primary reforming gas in the secondary reformer 5 to generate H ₂ and part of CH ₄ , CO and O ₂ The combustion reaction of methane, its reaction heat provides the necessary heat for the methane deep conversion reaction, and the rest of the gas is in the second-stage reformer 5, under the conditions of catalyst CZ-7, 1300 ° C, 2.3 MPa, and a space velocity of 1200 h ^-1 for deep conversion. Conversion, the _residual CH content in the secondary conversion gas is reduced to 0.5v% (dry basis);

(3) The catalyst in the intermediate transformer furnace 7 is NB113, the operating temperature is 360 ° C, the operating pressure is 2.3 MPa, and the water vapor shift reaction is carried out at a space velocity of 1200 h ^-1 , and other conditions are the same as (3) in Example 1.

The specific component molar composition and H ₂ /CO ratio of syngas are shown in Table 4.

Example 4

(1) Fischer-Tropsch synthesis tail gas at 40°C, 2.1 MPa, and space velocity of 1800 h ^-1 (its main components are 16.4% CO, 40.3% H ₂ , 40.2% CH ₄ , 1.2% low-carbon hydrocarbons, 0.1% CO ₂ , 1.83% N ₂ ) is preheated to 200°C and enters the hydrogenation reactor 2, under the action of the catalyst JT-202, the hydrogenation reaction is carried out under the conditions of 240°C, 2.1 MPa, and a space velocity of 1800h ^-1 , C ₂ H ₄ and C ₃ H ₆ are all converted into C ₂ H ₆ and C ₃ H ₈ , the gas after hydrogenation is mixed with saturated steam at 230°C and 2.1 MPa according to the water-to-carbon ratio of 3.0, then heated to 500°C and enters the primary reformer 4 middle;

(2) The mixed gas entering the primary reformer 4 is in the presence of catalysts Z112-HA and Z112-HB at a weight ratio of 1.1:0.9, the operating temperature is 720°C, the operating pressure is 2.1 MPa, and the space velocity is 1800 h ^-1 , and Part of the heat provided by the high-temperature reformed gas from the secondary reformer 5 to the heat exchange sleeve 3 is used as a heating heat source for the reaction to carry out the steam reforming conversion reaction of gaseous alkanes, and _the CH content in the outlet gas is reduced to 17.9%, and then Enter into the secondary reformer 5, the oxygen-to-carbon ratio is 0.42, preheat O ₂ to 200°C and mix with the primary reforming gas in the secondary reformer 5 to generate H ₂ and part of CH ₄ , CO and O ₂ The combustion reaction of methane, its reaction heat provides the necessary heat for the methane deep conversion reaction, and the rest of the gas is in the second-stage reformer 5, under the conditions of catalyst CZ-7, 1000 ° C, 2.1 MPa, and a space velocity of 1800 h ^-1 for deep conversion. Conversion, the residual _CH content in the secondary conversion gas is reduced to 0.45v% (dry basis);

(3) The catalyst in the intermediate transformer furnace 7 is NB113, the operating temperature is 360°C, the operating pressure is 2.1 MPa, and the water vapor shift reaction is carried out at a space velocity of 1800 h ^-1 , and other conditions are the same as (3) in Example 1.

Example 5

(1) Fischer-Tropsch synthesis tail gas at 40°C, 2.4 MPa, and space velocity of 1200 h ^-1 (the main components are 16.4% CO, 40.3% H ₂ , 40.2% CH ₄ , 1.2% light hydrocarbons, 0.1% CO ₂ , 1.83% N ₂ ) is preheated to 200°C and enters the hydrogenation reactor 2, under the action of the catalyst JT-202, the hydrogenation reaction is carried out at 230°C, 2.4 MPa, and a space velocity of 1000h ^-1 , C ₂ H ₄ and C ₃ H ₆ are all converted into C ₂ H ₆ and C ₃ H ₈ , the hydrogenated gas is mixed with saturated steam at 230°C and 2.4 MPa according to the water-to-carbon ratio of 3.1, and then heated to 500°C to enter the primary reformer 4 middle;

(2) The mixed gas entering the primary reformer 4 is in the presence of catalysts Z112-HA and Z112-HB at a weight ratio of 1:1, the operating temperature is 710°C, the operating pressure is 2.4 MPa, and the space velocity is 1000 h ^-1 , and Part of the heat provided by the high-temperature reformed gas from the secondary reformer 5 to the heat exchange sleeve 3 is used as the heating heat source for the reaction to carry out the steam reforming conversion reaction of gaseous alkanes, and _the CH content in the outlet gas is reduced to 16.2%, and then Enter the secondary reformer 5, with an oxygen-to-carbon ratio of 0.48, preheat the _O2 to 200°C and mix it with the primary reforming gas in the secondary reformer 5 to generate H ₂ and part of CH ₄ , CO and O ₂ The combustion reaction of methane, its reaction heat provides the necessary heat for the methane deep reforming reaction, and the rest of the gas is deep reformed in the secondary reformer 5 under the conditions of catalyst CZ-7, 1050°C, 2.4 MPa, and a space velocity of 1000 h ^-1 Conversion, the residual _CH content in the secondary conversion gas is reduced to 0.48v% (dry basis);

(3) The catalyst in the intermediate transformer furnace 7 is NB113, the operating temperature is 360°C, the operating pressure is 2.4 MPa, and the water vapor shift reaction is carried out at a space velocity of 1000 h ^-1 , and other conditions are the same as (3) in Example 1.

Example 6

(1) Fischer-Tropsch synthesis tail gas at 40°C, 2.8 MPa, and space velocity of 1200 h ^-1 (its main components are 16.4% CO, 40.3% H ₂ , 40.2% CH ₄ , 1.2% low-carbon hydrocarbons, 0.1% CO ₂ , 1.83% N ₂ ) is preheated to 200°C and enters the hydrogenation reactor 2, under the action of catalyst JT-202, the hydrogenation reaction is carried out under the conditions of 230°C, 2.8 MPa, and a space velocity of 1200h ^-1 , C ₂ H ₄ and C ₃ H ₆ are all converted into C ₂ H ₆ and C ₃ H ₈ , the gas after hydrogenation is mixed with saturated steam at 230°C and 2.8MPa according to the water-to-carbon ratio of 3.3, then heated to 500°C and enters the primary reformer 4 middle;

(2) The mixed gas entering the primary reformer 4 is in the presence of catalysts Z112-HA and Z112-HB at a weight ratio of 1:0.9, the operating temperature is 680°C, the operating pressure is 2.8MPa, and the space velocity is 1200 h ^-1 , and Part of the heat provided by the high-temperature reformed gas from the secondary reformer 5 to the heat exchange sleeve 3 is used as a heating heat source for the reaction to carry out the steam reforming conversion reaction of gaseous alkanes, and _the CH content in the outlet gas is reduced to 19.5%, and then Enter the secondary reformer 5, with an oxygen-to-carbon ratio of 0.5, preheat the _O2 to 200°C and mix it with the primary reforming gas in the secondary reformer 5 to generate H ₂ and part of CH ₄ , CO and O ₂ The combustion reaction of methane, its reaction heat provides the necessary heat for the deep conversion reaction of methane, and the rest of the gas is deep converted in the second-stage reformer 5 under the conditions of catalyst CZ-7, 900°C, 2.8MPa, and a space velocity of 1200h ^-1 , the residual _CH content in the secondary reformed gas is reduced to 0.40v% (dry basis);

(3) The catalyst in the intermediate transformer furnace 7 is NB113, the operating temperature is 350 ° C, the operating pressure is 2.8 MPa, and the water vapor shift reaction is carried out at a space velocity of 1500 h ^-1 , and other conditions are the same as (3) in Example 1.

In the best embodiments 1-6 of the present invention, the operating conditions of catalytic hydrogenation 2, the water-to-carbon ratio of the mixed gas in the first-stage reformer 4 and the oxygen-carbon ratio of the mixed gas in the second-stage reformer 5, the first-stage reformer 4 and the second-stage reformer 4 See Tables 4 and 5 for the operating conditions of the stage reformer 5 and the operating conditions of the intermediate converter. The specific component molar composition and H ₂ /CO ratio of the finally obtained synthesis gas are shown in Table 6.

Table 4 Operation conditions of catalytic hydrogenation and primary reformer

Table 5 Operating conditions of the secondary reformer and intermediate converter

Table 6 Composition of product syngas

In the prior art, the tail gas of Fischer-Tropsch synthesis oil is used as raw material to obtain synthesis gas through steam reforming, and the synthesis gas obtained by returning to the Fischer-Tropsch synthesis unit for reuse has high _H2 and low CO content in the steam-reformed gas. H ₂ /CO reaches above 4.22. It can be seen from Table 6 that the content of CH ₄ in the raw material gas obtained according to the method of the present invention is below 0.5, and the ratio of H ₂ /CO is 2.9-3.5. The synthesis gas obtained by the method of the present invention is directly passed into the raw material synthesis gas of Fischer-Tropsch synthesis oil, thereby turning the waste of Fischer-Tropsch synthesis tail gas into treasure, making the Fischer-Tropsch synthesis raw materials more fully utilized, and improving the Carbon utilization of Fischer-Tropsch synthesis gas.

The method of the present invention is particularly applicable to the process of Fischer-Tropsch products such as Fischer-Tropsch synthetic diesel oil and naphtha, and the improvement of existing processes, especially using the Fischer-Tropsch synthetic oil tail gas as a raw material to obtain synthesis gas through steam reforming, and to convert the Fischer-Tropsch synthetic oil The Tropsch synthesis gas is converted into feed gas and returned to the Fischer-Tropsch synthesis unit for reuse in the production process.

The above description is only the preferred mode of the embodiment of the present invention, and the present invention is not limited to the above embodiment. For those skilled in the art, the present invention can have various changes and replacements, such as adopting carbon dioxide reforming method or partial oxidation The recycling process of Fischer-Tropsch synthesis waste gas in the Fischer-Tropsch synthesis reaction of the method, and the process of using the method of the present invention in combination with other Fischer-Tropsch synthesis waste gas or promoting the reuse of Fischer-Tropsch synthesis waste gas. therefore. Any modification, equivalent replacement, improvement, etc. made under the principles and spirit of the embodiments described in the method of the present invention belong to the protection scope of the present invention.

Claims (15)

1. A method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas, comprising catalytic hydrogenation, steam reforming and partial oxidation reaction, medium temperature water-vapor shift reaction, waste heat recovery and gas-liquid separation four operations, characterized in that The catalytic hydrogenation process is to convert the unsaturated hydrocarbons in the Fischer-Tropsch synthesis tail gas into saturated hydrocarbons through the catalytic hydrogenation reaction in a hydrogenation reactor equipped with a hydrogenation catalyst; the steam reforming and partial The oxidation reaction process includes two reformers, a first-stage reformer and a second-stage reformer. The mixed gas composed of water vapor and the Fischer-Tropsch synthesis tail gas that has undergone catalytic hydrogenation enters the first-stage reformer equipped with reforming catalyst A to complete the preliminary conversion. The gas from the first-stage reformer enters the second-stage reformer equipped with reforming catalyst B, and at the same time, the preheated pure oxygen is passed into the second-stage reformer to carry out a small amount of Fischer-Tropsch synthesis tail gas oxidation reaction to complete deep reforming, and finally The water-vapor shift reaction is carried out in the intermediate transformer furnace equipped with a catalyst. The waste heat recovery and gas-liquid separation process is to recover the heat of the material obtained from the water-vapor shift reaction, and then perform gas-liquid separation. The gas phase is to meet the requirements of Fischer-Tropsch synthesis. raw material gas with a hydrogen-to-carbon ratio. 2. The method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas as claimed in claim 1, characterized in that the hydrogenation catalyst in the catalytic hydrogenation process is JT-202. 3. A method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas as claimed in claim 1, characterized in that the operating temperature in the catalytic hydrogenation process is 220-250°C, and the operating pressure is 2.0-3.0MPa , the air speed is 1000-2000h ^-1 . 4. The method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas as claimed in claim 1, characterized in that the reforming catalyst A used in the first-stage reformer is Z112-HA and Z112-HB. 5. a kind of Fischer-Tropsch synthesis tail gas as claimed in claim 4 is converted into the method for Fischer-Tropsch synthesis feed gas, it is characterized in that the weight ratio of described Z112-HA and Z112-HB is (0.8-1.2): (0.8- 1.2). 6. A method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas as claimed in claim 1, characterized in that the water-to-carbon molar ratio of the mixed gas in the primary reformer is 2.5-3.5:1. 7. A method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas as claimed in claim 1, characterized in that the operating temperature in the first-stage reformer is 650-850°C, the operating pressure is 2.0-3.0MPa, and the space velocity It is 1000-2000h ^-1 . 8. The method for converting a Fischer-Tropsch synthesis tail gas into a Fischer-Tropsch synthesis feed gas as claimed in claim 1, wherein the steam is saturated water with a temperature of 200 to 300°C and a pressure of 2.0 to 3.0 MPa steam. 9. a kind of Fischer-Tropsch synthesis tail gas as claimed in claim 1 is converted into the method for Fischer-Tropsch synthesis raw material gas, it is characterized in that described through preheated oxygen enters two-stage reformer, and the oxygen of gas in two-stage reformer The carbon molar ratio is 0.4-0.6. 10. The method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas as claimed in claim 1, characterized in that the reforming catalyst B in the second-stage reformer is CZ-7. 11. A method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas as claimed in claim 1, characterized in that the operating temperature in the second-stage reformer is 850-1300°C, and the operating pressure is 2.0-3.0 MPa, the air speed is 1000-2000h ^-1 . 12. The method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis feed gas as claimed in claim 1, characterized in that the catalyst in the intermediate converter is NB113. 13. A method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis raw material gas as claimed in claim 1, characterized in that the operating temperature in the medium transformer furnace is 340-360°C, and the operating pressure is 2.0-3.0MPa , the air speed is 1000-2000h ^-1 . 14. a kind of Fischer-Tropsch synthesis tail gas as claimed in claim 1 is converted into the method for Fischer-Tropsch synthesis raw material gas, it is characterized in that a jacketed heat exchanger is arranged outside the first-stage reformer, which comes from the second-stage conversion The high-temperature secondary reforming gas of the furnace transfers part of the heat to the sleeve-type heat exchanger, and then the heat exchange is performed between the sleeve-type heat exchanger and the reactants in the first-stage reformer, so that the reforming reaction in the first-stage reformer Provide heat source. 15. A method for converting Fischer-Tropsch synthesis tail gas into Fischer-Tropsch synthesis raw material gas according to any one of claims 1-14, characterized in that the obtained Fischer-Tropsch synthesis raw material gas has a _H2 /CO molar ratio of 2.9 -3.5.