Primary reformer with secondary inlet channels supplying the burner

[0001] The invention relates to a reactor for the catalytic reforming of hydrocarbons by steam under elevated pressure, by means of which synthesis gas is produced.

Such synthesis gas is used, for example, to produce ammonia, hydrogen and methanol.

[0002] Reactors for catalytic steam reforming of hydrocarbons have been known for a long time and in many embodiments. For large installations, a design has been adopted that uses a vaulted box furnace with vertical reaction tubes or cavity tubes. The reaction tubes are arranged in rows. Process gas, which is process gas, flows through the pipes from top to bottom. The process gas is subjected to a so-called split process.

[0003] Gas exit temperatures are usually 850 ° C and above. The process gas collects in the lower part - inside or outside the furnace - in so-called output collectors. In the "streets" located between the rows of pipes there are vertically placed burners, burning down. This area is referred to as the furnace chamber. The flue gas produced flows through the furnace from top to bottom and is drawn off through so-called flue gas tunnels located at the bottom. Temperatures in the oven chamber are on average around

1000 up to 1250 ° C. For thermal insulation and protection against high temperatures, the furnace walls are lined with a fireproof protective layer.

[0004] In a furnace heated reaction space, there is usually a series of gas-tight closed vertical pipes arranged in rows and suitable for filling with catalyst. They are used to carry out the process and have devices for feeding the reformed hydrocarbon and steam heated to 650 ° C to the reaction space, and devices for removing the synthesis gas from the reaction space.

[0005] The furnace space in which the furnace devices are arranged has in the lower part a chamber for collecting flue gas and a plurality of essentially horizontally arranged, running parallel to each other and perpendicular to the pipes of vertical flue gas tunnels. These masonry tunnels have holes on the sides to allow exhaust gases to be drawn off the furnace space. Tunnels are usually made of wall materials.

[0006] WO2005 / 018793 A1 describes a typical furnace system and a method of catalytic reforming hydrocarbons with steam into synthesis gas under increased pressure. For a more even flow of flue gas and a more even distribution of the tanning temperature, a special shape of the outer walls of the tunnels is used. WO2006 / 119812 A1 describes a typical furnace arrangement and method for catalytic steam reforming hydrocarbons into synthesis gas with oxygen supply to adjust stoichiometry and a special additionally activated porous burner to avoid soot formation.

[0007] For all the reforming systems described, it is common that the tanning apparatus, consisting of a plurality of spaced interchangeable reaction tubes of the burners, heats the furnace space through the reforming tubes through it. The burners used for tanning the furnace space are usually supplied with fuel gas and air through separate channels. In this case, fuel gas is supplied to the burner space separately from the air supply. The passage of gas inlets to the burner space takes place either through the refractory lining of the furnace or directly in front of it. In the constructions used so far, the ratio of fuel gas and air for burners is controlled by a throttle or a similar device for setting the gas flow when supplying air. With such a device you can control the firing by burners and thus the oven temperature. This design is effective, but it has the disadvantage that it is difficult to control the local air supply to the burners and leads to an unfavorable ratio of fuel gas to air.

[0008] The ratio of oxygen to fuel gas can be technically described by the so-called lambda (λ) value. When using the stoichiometric molar ratio of oxygen to fuel gas, a lambda value of 1.0 is obtained. When using a higher proportion of oxygen in the stoichiometric combustion ratio, a lambda value higher than 1.0 is obtained. Therefore, combustion is optimal when the lambda value is 1.0. Conventional constructions on individual burners receive fluctuating lambda values ​​that can be temporarily higher due to operation. [0009] This adversely affects the combustion process. The consequence may be combined greater consumption of fuel gas in relation to the reforming process. When changing fuel, it is difficult to set the air supply to the changed stoichiometry. As a result, an undesirable increase in flame temperature can occur transiently, and due to an increased air supply, an increased formation of NOx nitrogen oxides. Nitrogen oxides as harmful substances contribute to acid rain in the atmosphere.

[0010] Therefore, it is the object of the invention to find possibilities to improve the air supply to the burner system in such a way that the air supply to the burners can be optimally adjusted throughout the process. This improves the combustion of fuel gas and thus the fuel gas yield in the reforming process. Optimal lambda values ​​should always be set on individual burners so that the flame temperature always has only the necessary height. In this way, the formation of harmful nitrogen oxides can be significantly reduced or completely eliminated.

[0011] The invention solves this task through a reactor for catalytic primary reforming of hydrocarbons with steam under elevated pressure with a chamber furnace firing device for the reforming process, wherein the firing device heats the heat-insulated space of the furnace with the pipes sealed gas tight in furnace spaces that carry out the reforming process, which should be filled with a catalyst suitable for reforming processes and through which a mixture of reforming gases is carried out, and · the tanning apparatus consists of a number of burners arranged between the reforming pipes, and · the tanning apparatus is supplied with fuel gas and air, and · in each from the burners are separate, for both gases, feeding devices, arranged in both cases in series, which can be cut off individually or together, in pairs, and · the mixing of both gases is carried out respectively in the burner or directly in front of it, and wherein · the device supplying air to each burner has a main inlet channel and an additional secondary inlet channel, and · both inlet channels are equipped with devices suitable for setting the gas flow, and · wherein, each secondary inlet channel of the respective main inlet channel branches off after the gas flow setting device and the other, the downstream duct forms the primary air duct, and the ratio of the cross sectional area of ​​the secondary inlet duct to the cross sectional area of ​​the main inlet duct is between 1: 2 and 1: 100 before the secondary inlet duct branch.

[0012] Each burner is fed individually with a mixture of fuel gas and air and for both gases there are separate supply devices, and the main air supply channel allows additional air supply to the burners structure through the refractory lining of the furnace ("secondary inlet channel"). The mixing of fuel gas and air is carried out each time in the burner.

[0013] In one embodiment of the invention, the secondary inlet channels and main inlet channels are provided with delivery devices that can be cut off individually or together in pairs.

[0014] In a further embodiment of the invention, the secondary dampers can in any case be operated directly next to the associated main dampers. This allows operating personnel to set both leads in one work step.

[0015] Preferably all the supply channels are directed downwards to the tanning space and arranged in series. In order to technically guarantee the feasibility of tanning, the supply direction of the air inlet ducts can be inclined or stairs depending on the furnace design. Devices for supplying air to the burner space may be formed in the form of gaps by refractory lining of the furnace. This design allows a more accurate distribution of air in the flame space. Optionally and depending on the design of the furnace space, this form of gaps for optimization of combustion can also be realized by swirlers or bifurcated pipes with manifolds.

[0016] In further embodiments of the invention, alternatively · the secondary inlet channels are routed vertically downwards from the branching place to the furnace space, or · the secondary inlet channels are inclined or have a step, or · the secondary inlet channels in the burner inlet part are in the form of a slit or swirler or bifurcated pipes.

[0017] The invention also includes a method of catalytic primary reforming of hydrocarbons by steam under elevated pressure with a vaulted chamber furnace firing furnace for the reforming process using the device according to the invention. It is foreseen that · the tanning device heats the heat-insulated space of the furnace with the gas tight closed in the furnace space, pipes carrying out the reforming process, which need to be filled with a catalyst suitable for reforming processes and through which the reforming gas mixture is carried out, and · the tanning device consists of many burners spaced between reforming pipes, and · the tanning device is supplied with fuel gas and air, and · in each of the burners, the supply of both gases is carried out through separate supply devices arranged in series, which can be cut off individually or jointly in pairs, and · the mixing of both gases is carried out respectively in the burner or immediately in front of it, and · the supply of air to each the burners are made through the main inlet channel and an additional secondary inlet channel, which is set or cut off by appropriate devices in the gas flow, and · constant stoichiometry with a lambda value from 1.05 to set as the ratio of mixing air with fuel gas at the outlet of the primary inlet channel

1.15 and, depending on the air supply, the flame lambda value from

1.1 to 1.5. The outlet of the air-fuel gas mixture from the primary inlet channel is also referred to as the burner ceramic outlet cap.

[0018] In carrying out the original reforming process of the invention, a mixture of natural gas and air is preferably used for heating. In another embodiment of the process, the burner is heated instead of a mixture of natural gas and air, a mixture of LPG and air. LPG hydrocarbons are usually a mixture of C3 and C4 hydrocarbons, obtained from the appropriate fraction of natural gas and easily liquefiable. As fuel gas, instead of natural gas or LPG, other hydrocarbons, preferably with a boiling point below room temperature, are also suitable.

[0019] The described method of feeding the secondary air to the flame optimizes the supply of air to the burner. Depending on the control, this results in an optimal air-to-fuel gas ratio and an optimal flame control. By this action, the maximum flame temperature can be kept relatively low.

[0020] Conventional reforming synthesis structures generally set a lambda value of about 1.1 on burners. However, this value may vary depending on the operation. In the implementation of the structure according to the invention, the secondary inlet channel can be opened in particular when supplying more air , so that additional air is led past the primary outlet channel. As a result, the local lambda value from 1.05 to 1.15 can be kept constant on the ceramic outlet cap of the burner, even if the lambda value is set from 1.1 to 1.5 in the flame.

In one embodiment of the method according to the invention, the setting of the mixing ratio of fuel gas with air is made at the outlet of the primary inlet channel by setting the throttles arranged in the inlet part in the supply channels.

[0022] In a further embodiment of the method according to the invention, the reforming gas comprises methane and heated steam. In the device according to the invention, the reforming gas can be heated by the waste heat exchange devices from the burners in the tunnel to remove the waste gas outside the furnace space to a temperature of 500 to 650 ° C.

[0023] In a further embodiment of the method according to the invention, the air needed to heat the burner is heated by heat exchanging devices from the waste gas from the burners to a temperature of 250 to 450 ° C. In this case, the waste gases in the waste gas tunnel are used downstream of the heat exchange device to heat the reforming gas, so that the temperature at the outlet of the tunnel or chimney is in principle around 150-200 ° C.

[0024] The flue gas is discharged via the aforementioned flue gas tunnels from the wall. The tunnels have openings on the sides to allow exhaust gases to be drawn off the furnace space. This action guarantees effective removal of flue gases from the entire furnace space. Tunnels are usually made of wall materials.

[0025] Said implementations have the advantage of an optimized setting of the ratio of air and fuel gas on the burners and optimal combustion control in terms of setting the optimal lambda value. It is known that the content of NOx nitric oxide in the waste gas clearly decreases when using a more favorable lambda value on the burner ceramic outlet cap. It is also known that the content of NOx NOx in the waste gas clearly decreases at a lower flame temperature setting. This can be found in the respective known compendiums. For example, the theory "The John Zink Combustion Handbook", CE Baukel Jr., CRC-Press, London New York, 2001. Nitrogen oxides of NOx type contribute to acid rain.

[0026] The configuration of the burner and the fuel gas and air supply system according to the invention will be explained in more detail on the basis of two sketches showing a fragment of a reforming furnace in a side view, the method according to the invention is not limited to these embodiments.

[0027] FIG. 1 shows a diagram of supplying air and fuel gas to the burner, starting from the main air supply channel 1. In each case, individual air supply channels 2 branch off from it to individual burners, of which four are shown here, for example. The individual main air supply ducts can be controlled by individually cut-off and independent control devices 3. The secondary air inlet duct 4 according to the invention then branches off before supplying it to the burner, also having a cut-off and independent control device 5. The main air supply duct is then routed as the primary air supply duct. It is fed directly with fuel gas 6 in front of the burner. In order to guarantee the introduction of the flame 8 into the furnace space, the power supply system passes through the refractory lining of the furnace 7. The reaction tubes 9 to be reformed are then heated in this firing.

[0028] FIG. 2 again shows the delivery system in reduced form. The diagram of air and fuel gas supply on the burner is also shown, starting from the main air supply channel 1. In each case, individual air supply channels 2 branch off from it to individual burners (for example, four are shown here for clarity). The individual main air supply ducts can be controlled by individually cut-off and independent control devices 3. The secondary air intake duct 4 according to the invention then branches off before feeding to the burner, also having a single cut-off and independent control device 5. Then the main supply duct air is routed further as the primary air inlet channel. It is fed directly with fuel gas 6, upstream of the burner via control devices. In order to guarantee the introduction of flame 8 into the furnace space, the power supply system passes through the refractory lining of the furnace 7.

List of markings [0029] main duct air supply to the burner system main air duct for individual burners control device for air supply to the main inlet duct secondary inlet duct control device for air supply to the secondary inlet duct fuel gas supply passing through the refractory lining of the furnace ("ceramic outlet cap burner ") leading the flame of the reforming gas pipe