WO2012091398A2 - Method for manufacturing synthetic natural gas - Google Patents

Abstract

The present invention relates to a method for manufacturing synthetic natural gas. In the method for manufacturing synthetic natural gas (SNG), a primary methane synthesis reaction process is performed on synthetic gas generated after fuel-gasification and dust-collection processes are performed, and then a water-gas shift reaction process is performed on only a portion of the gas, and the remaining gas is bypassed. Then, the gases are remixed to perform a secondary methane synthesis reaction process, thereby controlling the generation of methane synthesis reaction heat and improving the lifespan of a catalyst.

Description

Manufacturing method of synthetic natural gas

The present invention relates to a method and apparatus for producing a synthetic natural gas.

Synthetic Natural Gas (SNG notation) production process that has reached the commercialization level up to now has a clean synthesis gas desulfurized using a Ni-based catalyst (sulfur compound concentration such as H ₂ S, COS in the synthesis gas is 0.1 ppm). Until now, a process for synthesizing purified clean syngas has been developed. Currently commercial desulfurization process is operated at room temperature or below room temperature, clean syngas discharged from the desulfurization process at room temperature or below room temperature is methane synthesis by heating the synthesis gas to at least 250 ℃ through separate heat exchanger in SNG synthesis process. Fed to the reactor (because the catalyst is activated above 250 ° C. to proceed with methane synthesis).

A schematic diagram of the existing commercialized SNG synthesis process has been proposed in two processes, as shown in the accompanying drawings, FIGS. 1 and 2.

First, the process of FIG. 1 passes through the heat recovery and dust collection process of the synthesis gas obtained through coal gasification, and then adjust the H ₂ / CO molar ratio to about 3.0 through the water gas conversion process. At this time. The exhaust gas temperature should be lower than the synthesis gas temperature up to room temperature above 300 ℃, due to the nature of the desulfurization process operating at or below room temperature. After removing sulfur compounds (H ₂ S, COS) and CO ₂ contained in the synthesis gas at room temperature or below room temperature, it is supplied to the SNG synthesis process. In this case, the syngas supplied to the SNG synthesis process is preheated to 250 ° C. or more at room temperature through an appropriate heat exchange method, and then supplied to the methane synthesis reactor in the SNG synthesis process.

In addition, referring to Figure 2 showing a process of simultaneously performing methane synthesis and water gas conversion, the synthesis gas obtained through coal gasification is cooled to room temperature or below room temperature after cooling and dust collection through a heat exchanger is supplied to the desulfurization process. A clean synthesis gas discharged from the desulfurization process is supplied to the after preheating to more than 250 ℃ through a suitable heat exchanger, a catalyst to proceed with the methane synthesis reaction and the water gas shift reaction at the same time filling the reactor CH ₄ and CO ₂ is a main component of SNG Can be obtained. In this case, since CO ₂ is generated by the water gas shift reaction, a CO ₂ separation process is required at a later stage. In this case, a catalyst capable of simultaneously performing a methane synthesis reaction and a water gas shift reaction is used. That is, the water gas conversion process and the methane synthesis process should be configured separately, or the catalyst should be developed so that the water gas conversion reaction and the methane synthesis reaction can proceed simultaneously.

In addition, although it has not been commercialized yet, Korean Patent Publication No. 2010-116540 discloses that Ce-Mo catalysts are suitable as methane synthesis catalysts for syngas containing sulfur compounds. SNG manufacturing process that does not require overheating process is proposed. That is, as shown in FIG. 3, the high-temperature synthesis gas supplied from the gasifier is passed through the dust collecting and water gas conversion process, and then supplied to the methane synthesis process through the water gas conversion process at a temperature of 300 ° C. or higher to minimize unnecessary heat exchange processes. In addition, a method for separating desulfurization and CO ₂ at the end of the methane synthesis process is proposed. Even in this case, there is a disadvantage in that a catalyst suitable for sulfur-containing syngas is used.

Accordingly, the present inventors have made efforts to solve the above problems, and as a result, the present invention is completed by developing a method and apparatus for producing a synthetic natural gas that can control the generation of methane synthesis heat of reaction and extend the life of the catalyst. It became.

Therefore, in the present invention, after the first methane synthesis reaction proceeds to the synthesis gas generated after fuel gasification and dust collection, only a part of the gas undergoes a water gas conversion reaction, the remaining gas is bypassed, and the mixed gas is again methane synthesis. It is an object of the present invention to provide a method for producing a synthetic natural gas that can control the generation of methane synthesizing heat by extending the reaction and extend the life of the catalyst.

In addition, the present invention has another object to provide a manufacturing apparatus for the production of the synthetic natural gas.

The present invention as a means for solving the above problems,

A first step of performing a first methane synthesis reaction in a saturated state in which a synthesis gas produced after fuel gasification and dust collection is mixed with steam; And

Part of the syngas discharged from the first methane synthesis reaction proceeds with the water gas shift reaction, and the remaining gas is bypassed without performing the water gas shift reaction and then discharged from the water gas shift reaction. A second step of performing a secondary methane synthesis reaction by mixing the synthesized synthesis gas and the bypassed synthesis gas;

It provides a method for producing a synthetic natural gas (SNG) comprising a.

Moreover, this invention is another means for solving the said subject,

A saturation unit for mixing the syngas generated after fuel gasification and dust collection with steam;

A primary methane synthesis reaction unit for methanating the saturated gas generated in the saturation unit;

A water gas shift reaction unit for converting a portion of the syngas discharged from the primary methane synthesis reaction unit into a water gas shift reaction;

A bypass unit for bypassing the remainder of the syngas discharged from the first methane synthesis unit not passing through the water gas shift reaction unit; And

A secondary methane synthesis reaction unit for mixing the syngas discharged from the water gas conversion reaction unit with the synthesis gas of the bypass unit to perform secondary methanation reaction;

It provides a device for producing a synthetic natural gas (SNG) comprising a.

The SNG manufacturing method according to the present invention does not perform the water gas conversion reaction of the synthesis gas (H ₂ / CO ratio 0.5 to 1.0) discharged from the gasifier, and undergoes the methane synthesis reaction first to generate the heat generated by the methane synthesis reaction It is possible to extend the life of the catalyst by lowering the temperature of the catalyst layer to suppress a sudden temperature rise.

In addition, the present invention can be used for both the clean gas (sweet gas) and the sulfur-containing synthetic gas (sour gas) not subjected to the desulfurization process after the dust and desulfurization process.

In addition, the present invention does not require a synthesis gas recirculation system for temperature control is easy to operate and can significantly reduce the construction cost.

1 and 2 illustrate a SNG manufacturing process using clean gas after desulfurization.

Figure 3 shows the SNG production process from coal using a sour gas before desulfurization.

4 shows an SNG manufacturing process according to an embodiment of the present invention.

5 shows an SNG manufacturing process according to an embodiment of the present invention.

[Description of the code]

Saturator

2. Methanator 1

3. cooler 1

4. water gas shift reactor

5. By-pass valve

6. cooler 2

7. Methanator 2

8. cooler 3

9. Methanator 3

10. cooler 4

11.methanator 4

12. cooler 5

The present invention comprises a first step of performing a first methane synthesis reaction in a saturated state in which a synthesis gas produced after fuel gasification and dust collection is mixed with steam; And a portion of the syngas discharged from the first methane synthesis reaction proceeds with a water gas shift reaction, and the remaining gas bypasses the water gas shift without a water gas shift reaction. And a second step of performing the secondary methane synthesis reaction by mixing the discharged synthesis gas and the bypassed synthesis gas.

The fuel may be a hydrocarbon-based raw material, for example, coal, biomass, waste, heavy residue oil, but is not limited thereto.

The synthesis gas of the first step is a synthesis gas that is typically used in the natural gas manufacturing process, may be a sweet gas that has been further desulfurized through fuel gasification and dust collection, and has not undergone desulfurization. It may be a sour gas containing. In addition, the syngas preferably satisfies the condition of H ₂ / CO molar ratio of 0.5 to 1.0.

In addition, the SNG manufacturing method according to the present invention may be carried out in a single reactor, it is possible to perform one SNG manufacturing process in multiple reactors.

In addition, the SNG production method according to the present invention may further perform a methane synthesis reaction even after the secondary methane synthesis reaction.

Hereinafter, the present invention will be described in more detail.

The main reaction equations for the water gas shift reaction and the methane synthesis reaction to produce SNG are as follows.

Methane synthesis scheme: CO + 3 H ₂ → CH ₄ + H ₂ O (heat of reaction: 206 kJ / mol)

Water gas shift reaction formula: CO + H ₂ O → H ₂ + CO ₂ (heat of reaction: 41 kJ / mol)

Since the synthesis gas supplied to the first methane synthesis reaction has a H ₂ / CO molar ratio of 1.0 or less (preferably 0.5 to 1.0), there is less heat of reaction than when using a synthesis gas having a H ₂ / CO molar ratio of 3.0, Since the water in the synthesis gas is saturated, the temperature rise of the catalyst layer is low, which may solve the problem of sintering of the catalyst, which is problematic at 700 ° C or higher. As such, the synthesis gas obtained by the first methane synthesis reaction has a low CH ₄ concentration and unconverted CO and H ₂ are present, so that only a part of the gas discharged from the first methane synthesis reaction undergoes the water gas shift reaction. After advancing, the remaining gas is bypassed and mixed with the gas which has undergone the water gas shift reaction, and the H ₂ / CO molar ratio is adjusted to 2.7 to 3.3 (preferably 2.9 to 3.1). At this time, the synthesis gas discharged from the first methane synthesis reaction may further comprise the step of cooling to 300 to 350 ℃. Thus, water gas shift process and a water gas shift process, the by-pass gas by gas (secondary methane gas to be supplied to the synthesis reaction) mixing the CH ₄ component and, CO, H ₂ Component (H ₂ / CO molar ratio of 2.7 to 3.3) and CO ₂ produced by the water gas shift reaction, and H ₂ O. The gas having this composition causes the secondary methane synthesis reaction to proceed again. The secondary methane synthesis reaction may be repeated one or more methane synthesis reactions (when used as a single reactor, it is composed of a secondary methane synthesis catalyst layer, a tertiary methane synthesis catalyst layer, a quaternary methane synthesis catalyst layer, etc.) In case of using multiple reactors, it consists of secondary methane synthesis reactor, tertiary methane synthesis reactor, quaternary methane synthesis reactor, etc.).

In addition, the syngas discharged by the first methane synthesis reaction may further require cooling to 280 to 320 ℃ in order to prevent excessive temperature rise in the secondary methane synthesis reactor which is connected in a subsequent step before the water gas conversion reaction, By adjusting the gas supply amount of the gas shift reaction through a bypass valve, the H ₂ / CO molar ratio in the gas supplied to the secondary methane synthesis reaction is adjusted to be 2.7 to 3.3.

The present invention also provides

A saturation unit for mixing the syngas generated after fuel gasification and dust collection with steam;

A primary methane synthesis reaction unit for methanating the saturated gas generated in the saturation unit;

A water gas shift reaction unit for converting a portion of the syngas discharged from the primary methane synthesis reaction unit into a water gas shift reaction;

A bypass unit for bypassing the remainder of the syngas discharged from the first methane synthesis unit not passing through the water gas shift reaction unit; And

A secondary methane synthesis reaction unit for mixing the syngas discharged from the water gas conversion reaction unit with the synthesis gas of the bypass unit to perform secondary methanation reaction;

It relates to an apparatus for producing synthetic natural gas (SNG) comprising a.

The methane synthesis and water gas shift reaction units may be included in a single reactor, or each of the units may constitute a single reactor, and one process may be performed in multiple reactors.

A methane synthesizing unit may be continuously added to the rear end of the secondary methane synthesizing unit.

An example of the case of using the single reactor described above is shown schematically in FIG. 4.

Figure 4 shows the SNG production process consisting of a methane synthesis catalyst layer, a water gas shift reaction catalyst layer, and a plurality of methane synthesis catalyst layer in one reactor. That is, the synthesis gas discharged from the gasifier is cooled to a suitable temperature by heat recovery, and then collected by dust collection and desulfurization (yet H ₂ / CO molar ratio is still between 0.5 to 1.0) and supplied to a saturator that mixes steam and syngas. After the water is saturated in the synthesis gas in the saturator, it is preheated to 250 ° C or more, and then supplied to the methane synthesis catalyst layer. In this case, the temperature of the syngas discharged from the methane synthesis catalyst layer does not exceed 700 ° C. This is because the heat of methane synthesis reaction is not large because the water is saturated and H ₂ / CO = 0.5 to 1.0. The gas discharged from the first methane synthesis catalyst layer is cooled to between 300 and 350 ° C. in the water gas shift reaction, and then some gas is supplied to the water gas shift reaction catalyst layer, and the remaining gas is passed through the bypass pipe to the water gas shift reaction catalyst layer. Do not go through. Water gas shift reaction catalyst, the by-pass pipe are here equipped a mixture of a gas by-pass through the gas and the bypass conduit passes through the water gas shift catalyst layer through a bypass flow rate adjustment H ₂ / CO molar ratio of 2.7 to 3.3 ( Preferably 2.9 to 3.1). That is, the H ₂ / CO molar ratio in the gas mixed with the gas passed through the water gas shift reaction catalyst layer and the gas supplied through the bypass pipe is 2.7 to 3.3 (preferably 2.9 to 3.1). If the H ₂ / CO ratio in the syngas discharged from the first methane synthesis catalyst layer is out of the above range, the gas discharged from the first methane synthesis catalyst layer is bypassed to supply the gas to the aqueous gas conversion process. Since the water gas shift reaction is also an exothermic reaction, the exhaust gas is further cooled to 280 to 320 ° C., and then supplied to the secondary or tertiary methane synthesis catalyst layer to supply the required CH ₄ concentration (specifically, 96 to 99). %).

When methane synthesis using desulfurized sweet gas is carried out under a Ni-based catalyst, and when using a sour gas without desulfurization, it is preferably carried out under a Ce-Mo catalyst, but is not limited thereto. Do not.

In addition, the water gas shift reaction is preferably performed under a Co-Mo catalyst, but is not limited thereto.

In addition, an example of the case of performing in a multi-reactor is shown in FIG. The concept of the catalyst bed shown in FIG. 4 is configured for each independent reactor to facilitate cooling. After passing through the saturator (1), the synthesis gas passes through the first methane synthesis reactor (2), and after cooling to 300 to 350 ℃, some gas is passed through the gas to the water gas conversion reactor (4), the remaining gas Bypass the H ₂ / CO molar ratio in the gas when mixed with the gas passed through the water gas conversion reaction at the rear of the water gas conversion reactor to 2.7 to 3.3 (preferably 2.9 to 3.1). If the ratio of H ₂ / CO in the syngas discharged from the primary methane synthesis reactor is out of the above range, all gases discharged from the primary methane synthesis reactor are bypassed to supply gas to the aqueous gas conversion process. The gas discharged from the water gas shift reactor (4) is passed through the secondary and tertiary methane synthesis reactors so as to be SNG having the required CH ₄ concentration. In other words, the concentration of CH _{4 in the} SNG can be controlled by controlling the number of methane synthesis reactors.

This process is applied to the sweet gas that has passed through the dust collection and desulfurization process, but can also be applied to the sour gas that has passed only the dust. Instead, catalysts applicable to syngas containing sulfur must be used.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the invention, the content of the present invention is not limited by the following examples.

Example 1: SNG Preparation Using Multiple Reactors (Figure 5)

Table 1 shows the gas composition for each position of the multiple reactor (Fig. 5). First, the syngas flow rate is 1000 Nm ³ / h (H ₂ / CO supply ratio is 0.93) at 41 atm, steam flow rate is 512 Nm ³ / h. In particular, CO ₂ in the syngas supplied from the gasifier has the advantage that can be supplied to the primary methane synthesis reactor without separate separation. The concentration of CH ₄ at the rear end of the first methane synthesis reactor is about 15.7%, and the reaction temperature is 698 ° C. Only a portion (12%) of the gas generated at the outlet of the first methane reactor is fed to the water gas shift reactor (at which time the reactor is cooled to about 320 ° C.) and the remaining (88%) is bypassed to discharge the water gas shift reactor. The mixture was mixed with gas and supplied to a secondary methane synthesis reactor. At this time, the composition of the inlet of the secondary methane synthesis reactor confirmed that the H ₂ / CO ratio was 3.0. The mixed gas was fed to the secondary methane synthesis reactor to proceed with the secondary methane synthesis reaction, and the concentration of CH ₄ at the outlet of the secondary methane synthesis reactor was about 28.2%, and the reaction temperature was 533 ° C. At the outlet of the tertiary methane synthesis reactor, the concentration of CH ₄ was 34.4%, and when the CO ₂ removal was 99%, the SNG concentration finally obtained was about 97%.

Table 1 division Supply synthetic gas steam After the first methane synthesis reactor Secondary methane synthesis reactor inlet Secondary methane synthesis reactor outlet Tertiary methane synthesis reactor outlet Dry sng Temperature() 280 254 698.2 297.6 532.6 351.9 25 Pressure (bar) 40 43 40 - 40 40 40 Mole Flow (kmol / hr) 44.6 22.8 48.208 48.208 44.184 42.888 15.989 Volume Flow (Nm ³ / h) 1,000 512 1,080 1,080 990 961 358 mole% (dry) CO 37.5 - 10.9 9.7 1.7 0.0 0.1 H ₂ 35.0 - 28.2 29.0 11.3 1.8 0.2 CO ₂ 22.2 - 44.8 45.4 58.3 63.3 1.4 CH ₄ 4.9 - 15.7 15.5 28.2 34.4 96.9 H ₂ O - 100.0 - - - - - N ₂ 0.3 - 0.3 0.3 0.3 0.4 1.4 H ₂ / CO ratio 0.9 - 2.6 3.0 - - -

Claims (13)

A first step of performing a first methane synthesis reaction in a saturated state in which a synthesis gas produced after fuel gasification and dust collection is mixed with steam; And Part of the syngas discharged from the first methane synthesis reaction proceeds with the water gas shift reaction, and the remaining gas is bypassed without performing the water gas shift reaction and then discharged from the water gas shift reaction. A second step of performing a secondary methane synthesis reaction by mixing the synthesized synthesis gas and the bypassed synthesis gas; Method of producing a synthetic natural gas (SNG) comprising a. The method of claim 1, The fuel is a method for producing a synthetic natural gas (SNG), characterized in that the raw material of the hydrocarbon series. The method of claim 1, The synthesis gas of the first step is a method of producing a synthetic natural gas (SNG), characterized in that the H ₂ / CO molar ratio of 0.5 to 1.0. The method of claim 1, Method for producing a synthetic natural gas (SNG), characterized in that further comprising the step of performing a methane activation reaction after the secondary methane synthesis reaction. The method of claim 1, Method of producing a synthetic natural gas (SNG), characterized in that for further performing the desulfurization process after the dust collection. The method of claim 1, Method of producing a synthetic natural gas (SNG), characterized in that further comprising the step of cooling the synthesis gas discharged from the first methane synthesis reaction to 300 to 350 ℃. The method of claim 1, Method for producing a synthetic natural gas (SNG), characterized in that further comprising the step of cooling the synthesis gas discharged from the water gas conversion reaction to 280 to 320 ℃. The method of claim 1, Method of producing a synthetic natural gas (SNG), characterized in that by adjusting the molar ratio of H ₂ / CO in the mixed gas to 2.7 to 3.3 during the second methane synthesis reaction. The method of claim 1, Method of producing a synthetic natural gas (SNG), characterized in that carried out in one reactor or one process. A saturation unit for mixing the syngas generated after fuel gasification and dust collection with steam; A primary methane synthesis reaction unit for methanating the saturated gas generated in the saturation unit; A water gas shift reaction unit for converting a portion of the syngas discharged from the primary methane synthesis reaction unit into a water gas shift reaction; A bypass unit for bypassing the remainder of the syngas discharged from the first methane synthesis unit not passing through the water gas shift reaction unit; And A secondary methane synthesis reaction unit for mixing the syngas discharged from the water gas conversion reaction unit with the synthesis gas of the bypass unit to perform secondary methanation reaction; Apparatus for producing a synthetic natural gas (SNG) comprising a. The method of claim 10, Apparatus for producing a synthetic natural gas (SNG), characterized in that further comprising a cooling device at the rear end of the methane synthesis reaction unit. The method of claim 10, Apparatus for producing a synthetic natural gas (SNG), characterized in that further comprising a cooling device at the rear end of the water gas conversion reaction unit. The method of claim 10, Synthetic gas supplied to the saturation unit is a synthetic natural gas (SNG) manufacturing apparatus, characterized in that the synthesis gas after the desulfurization process.

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