KR20140092244A - Feed ratio control for hter - Google Patents

Abstract

The invention provides a method for designing the construction of a heat exchange reformer (HER) to minimize metal dusting, and a method for improved thermal control in the HER. By analysis of various parameters related to a main reforming unit (MRU) and the HER, improved thermal control and reduced metal dusting is achieved.

Description

Feed Ratio Control for HTER {FEED RATIO CONTROL FOR HTER}

With regard to syngas production by steam reforming, high temperatures are required to achieve realistic conversion of hydrocarbons to syngas.

In conventional syngas plants, sensible heat in syngas is used to generate steam. By conducting a pinch point analysis on this, it will be concluded that the temperature difference in the hot end is typically in the range of 650-750 ° C, and the heat in the gas from the reformer is typically better utilized. However, it is difficult to design heat exchangers in a manner that does not degrade plant reliability due to corrosion phenomena known as metal dusting. In the waste heat boiler used in conventional syngas plants, where the possibility of a high temperature metal surface having affinity for metal dusting is considerably reduced due to the relatively low temperature and high heat transfer coefficient on the steam / water side, .

Therefore, when designing a device that uses direct heat from a steam reforming zone, it is most important to take advantage of the considerable knowledge and experience of the metal dusting phenomenon.

Pinch point analysis and / or CAPEX / OPEX (enterprise / operational cost) evaluations typically show that the temperature approximation must be between 10 and 150 ° C to achieve an optimal balance between investment and operating costs. Higher values are generally associated with more "toxic" materials in environments with high temperature and / or high corrosion potential.

The outlet temperature of the main reforming zone for synthesis gas production is in the range of 850-1050 ° C, which means that the process stream can be heated to 600-900 ° C using direct heat. This stream is not present in the syngas process other than the reforming process itself. Thus, other concepts for the use of direct heat in syngas from the main reformer for further steam reforming have been considered, such as Aasberg-Petersen K., Dybkjaer I., Ovesen C.V., Schjodt N. C., Sehested J., Thomsen S.G. "Natural gas to synthesis gas - Catalysts and catalytic processes", Journal of Natural Gas Science and Engineering,

The gas-heated steam reformer may be located in line with the main reformer (HTER-s) and in parallel with the main reformer (HTER-p). The main reformer may be a tubular reformer, a secondary reformer, or a string reformer. HTER-s has the advantage that a higher average outlet temperature can be obtained, which is beneficial in relation to the overall conversion of the feedstock and is particularly beneficial for higher CO / H ₂ ratios for syngas for synthetic fuels , The overall pressure drop in the front-end is lower in the HTER-p concept. Only then will HTER-p be discussed, and in Figures 1-3 an embodiment of HTER-p in different plant types is shown.

Typical operating parameters from the main reformer are shown in Table 1.

week Reformer  Typical conditions H ₂ plant NH ₃ plant ATR-based plant Steam to carbon ratio 1.8-2.5 2.5-3.6 0.6-0.9 Secondary reformer no Yes - Outlet temperature
(Main reformer), ° C 850-930 950-1000 1000-1050 H ₂ / CO ratio 3.3-4.5 ~ 4 ~ 2

The duty of HTER-p can typically be up to 40-50% of the duty of the waste heat boiler (and, if applicable, steam superheater) applied to the standard plant configuration, and the reforming capacity corresponds to 25-30% of the capacity of the main reformer . In ammonia, methanol and hydrogen plants this means that the duty of the tubular / primary reformer can be correspondingly reduced. In addition to the reduction in reformer size, the fuel consumption and recovered waste heat are also considerably reduced, resulting in lower overall raw material + fuel consumption and reduced size of the waste heat section of the tubular reformer. In the case of a plant employing an autoregressor (ATR), the oxygen requirement for ATR is reduced, resulting in lower operating costs of the air separation unit and reduced unit size. The implementation of HTER-p (and HTER-s) can enhance overall plant capacity for the same O ₂ consumption, since economies of scale are particularly relevant in synthetic fuel plants and air separation unit capacity is a major bottleneck.

As discussed above, the efficiency associated with raw material and fuel consumption of the syngas plant is improved, and CO ₂ emissions are reduced. However, in some cases, the vapors produced in the syngas plant may have significant values in the overall composite, in which case it is important to determine the steam export from the synthesis gas plant. Andersen NU, Olsson H., "The hydrogen generation game", Hydrocarbon Engineering 2011. Generally, the steam generation efficiency in syngas plants can be as high as 94%, but the typical efficiency of the auxiliary boiler is 92.5%. However, as the efficiency of the auxiliary boiler improves (e.g., by the implementation of force generation from low temperature heat by the use of an organic Rankine cycle), the main advantage of HTER is that as pumps and compressors drive the change of electric furnace It becomes important.

In HTER-p, a higher heat transfer coefficient is obtained compared to the total heat transfer obtained in the ignited tubular reformer, which results in a very small plot area for HTER-p compared to the tubular reformer (see Table 2).

In the reformer  The reactor volume and delivered Duty
(For example Essar Oil H ₂  plant) HTER-p Tubular reformer Transferred duty, Gcal / h 23 96 Reactor / volume, m ³ 48 2900 "Heat Strength" kcal / h per m ³ 480,000 33,000

The thermal strength of HTER-p appears to be 10 times higher than the strength of a typical tubular reformer, which is more complicated in HTER-p configuration and HTER-p is a new or existing tubular reformer Which is a realistic way to add a modifying capacity.

It is important to know the important parameters in the entire plant to minimize the overall cost of the entire plant. Topsoe has two types of HTER-p for commercial operation: 1) bayonet tube HTER-p, and 2) double tube HTER-p.

The bayonet tube HTER-p (see FIG. 4) consists of tube bundles each consisting of three concentric tubes. In the outer ring flow, the heating gas flows upward from the main reformer, and in the middle loop, the feed gas flows down through the catalyst bed, from which it is directed and directed to the center tube (bayonet tube) Where the cooled reformed gas is mixed with the cooled heated gas from the outer ring.

The double tube HTER-p (see Figure 5) consists of tube bundles with double tubes. The catalyst is loaded inside the center tube and outside the outer tube. The raw gas passes through the catalyst inside the tube and flows downward through the catalyst outside the tube. The reformed gas from the catalyst bed mixes with the heated gas from the main reformer and flows upward from the loop between the dual tube assemblies exchanging heat with the gas flowing through the catalyst bed.

In plants where high conversion is critical, typically the outlet temperature of the catalyst bed should be as high as possible to ensure minimal methane leaks in the syngas. This is a situation where, for example, the fuel balance occurs mainly in ammonia plants and hydrogen plants, which operate at low steam to carbon ratios. In this case, the heating gas from the main reformer (tubular reformer or secondary reformer) is not mixed with the HTER-p catalyst effluent gas before heat exchange occurs, so Bayonet type HTER-p is optimal. This results in a higher reforming temperature (approximately 30-40 ° C) in HTER-p at the same temperature approximation at the high temperature end of HTER-p than in the double tube HTER-p case. When the methane slip is less, the double tube HTER-p has the advantage that the space between the tube assemblies is used as a catalyst layer, making the HTER-p more compact and more compact. The dual tube HTER-p is the most realistic solution in ATR-based plants and hydrogen plants, where the main reformer outlet temperature is typically relatively high, where fuel balancing allows this design (mainly due to the steam to carbon ratio being dependent on the type of feedstock Lt; / RTI >

The criteria are typically part of, and many other factors may affect the final and most realistic layout of the HTER-p.

The main tubing associated with a heat exchanger reformer heated by a modified process gas is corrosion by metal dusting, which can typically occur in a temperature range of 400-800 [deg.] C in an atmosphere enriched with CO and / or hydrocarbons.

The precursors for metal dusting are carbon formation, and possible mechanisms for carbon formation in the reformed gas are described in Aguero A., Gutierrez M., Korcakova L., Nguyen TTM, Hinnemann B., Saadi S. "Metal Dusting Protective Coatings. A Literature Review ", Oxidation of Metals, 2011:

<Buda reaction>

(1) 2 CO <-> C + CO ₂

<CO reduction>

_{(2) CO + H 2 <} -> C + H 2 O

<Methane decomposition>

(3) CH ₄ <-> C + 2 H ₂

Both the Buda reaction (1) and the CO reduction reaction (2) are exothermic, ie they have an affinity for carbon formation from the two reactions when the actual temperature is below the equilibrium temperature. However, at a certain temperature, that is, at 400-450 ° C, the reaction rate is too slow, resulting in very slight corrosion. The methane decomposition reaction (3) is an endothermic reaction, that is, there is an affinity for carbon formation above the equilibrium temperature. Table 3 shows typical equilibrium temperatures for the carbon forming reaction.

For the carbon-forming reaction in different plant types
Typical Equilibrium Temperature H ₂ plant NH ₃ plant ATR-based plant Equilibrium temperature Buda reaction, T _eq , ° C 790-800 800-810 CO reduction, T _eq , ° C 750-780 760-770 Methane decomposition, T _eq , ° C > 950 > 1200

It is seen that the process gas crosses the critical temperature range and there is a possibility of affinity for carbon formation and metal dusting. It is not necessarily (but often) the same as having metal dusting corrosion that is not allowed to have affinity for carbon. Some commercial alloys have long incubation times and low corrosion rates and are therefore suitable for operation under conditions with affinity for metal dusting. However, operation in the presence of affinity for carbon formation requires extensive testing prior to use in commercial units, and Topsoe continues to test materials and operating conditions to map metal dusting attacks in the laboratory, And has extensive partnerships with leading companies in the development of Finally, however, Topsoe has had decades of successful industrial experience in the operation of convection reformers in the field of metal dusting.

Haldor Topsoe A / S (Topsoe) has been operating a convection reformer since 1990. The original heat exchanger reformer was based on convection from flue gas (Haldor Topsoe convection reformer "HTCR"). Operating (more than 30) HTCRs are mostly bayonet-type (see FIG. 6) and have relatively complex heat transfer mechanisms. Extensive experience and feedback on heat transfer in convection reformers has been obtained from these units, which have been used to optimize the design of other types of convection reformers.

In 2003, the first HTER was successfully commissioned at Sasol's Synfuel Plant in Secunda, South Africa and continues to operate since then (Thomsen SG, Han PA, Loock S., Ernst W. "The First Industrial Experience with the Haldor Topsoe Exchanger Reformer ", AIChE Ammonia Safety Symposium, 2006). The HTER is a double tube type, and the synthesis of syngas has been increased to more than 30% by the application of HTER. The operating conditions for this reformer are relatively harsh with respect to metal dusting due to the high temperature and low steam to carbon ratios. This first tube bundle had been in service for more than seven years, and metal dusting corrosion was within the expected rate, so there was no reason to replace the tube bundle.

In 2010, Bayonet type HTER was launched at Numaligarh Refinery Limited in India (Konwar S., Thakuria A .. "New Paradigms in Revamp Options for Hydrogen Units - The HTERP in NRL" 16th Refinery Technology Meet., 2011). The HTER was a modification of the refinery complex, related to the overall H ₂ demand, due to the more stringent environmental requirements for fuel products. Was originally capacity 38000 MTPY (52,400N㎥ / h) of hydrogen existing units, additional H ₂ production is provided by the HTER N㎥ 14,600 / h, an increase of over 25% capacity. Essar Oil Vadinar Limited and Haldor Topsoe agreed in 2007 to design a hydrogen unit with a capacity of 130,000 Nm3 / h of hydrogen.

In view of the operating costs and benefits associated with the raw material and fuel consumption of this hydrogen unit, Essar Oil decided to implement a dual-tube HTER. The configuration of this hydrogen unit is shown in Fig. The plant is designed for both high flexibility and feedstock for both natural gas, refinery fugitive gas, LPG and naphtha. To accommodate the high flexibility in the feedstock, a steam to carbon ratio of 2.5 was selected for the preliminary and tubular reformers and ensures that the preliminary reformer operation is optimized.

The tubular reformer was designed with a maximum operating outlet temperature of 915 ° C to achieve peak efficiency and conversion, which also allows for better utilization of the HTER-p. The duty of HTER-p is approximately 23 Gcal / h, which corresponds to approximately 40% of the heat in syngas when cooled to approximately 280 ° C (the typical outlet temperature from the waste heat boiler). In addition, this duty corresponds to a reduction of raw materials and fuel to about 5% hydrogen unit (and steam exports are therefore reduced).

As mentioned above, it is very important to ensure that the temperature of the metal surface is within certain limits in order to avoid excessive corrosion caused by metal dusting. For HTER-p in the Essar Oil H ₂ plant, the most important parameter is the CO reduction temperature. It is important that a material with sufficient resistance to metal dusting is selected for the relevant portions of the tube bundle, since the syngas passes the critical temperature with affinity for metal dusting while transferring heat to the catalyst bed. The choice of material is optimized in terms of cost and operating flexibility. Since the Essar Oil H ₂ plant is designed to have a pre-reformer and the feed to HTER-p is taken downstream of the pre-reformer, the feed composition (at a constant steam to carbon ratio) , LPG or naphtha), other parameters are important for the temperature profile in HTER.

- Ratio of raw material relative to HTER as compared to tubular reformer

- tubular reformer outlet temperature

- steam to carbon ratio

The effect of these variables on the temperature profile is shown in Fig.

Material selection is made to ensure a robust design that allows for variations in plant operating parameters, to facilitate control, minimize corrosion caused by metal dusting, and ensure that the plant controls the flow of raw material to the HTER in an optimal manner Lt; / RTI &gt;

8, the important parameters for the temperature profile are HTER feed flow rate and tubular reformer outlet temperature. Since the tubular reformer outlet temperature can be determined by other requirements (reformer tube metal temperature, tube ignition speed, etc.), it was chosen to manipulate the feed flow rate according to feed flow to HTER to have an optimal temperature profile in HTER.

_{F HTER = f (F tub.} . Ref, T out, tub ref, S / C)

here,

F _HTER : Raw material flow rate to HTER

F _{tub . ref} : Raw material flow rate to tubular reformer

T _{out , tub . ref} : outlet temperature from tubular reformer

S / C: steam to carbon ratio to the reforming zone

Steam to carbon (S / C) means the molar ratio of H ₂ O to carbon in a given process stream.

The equilibrium temperature for the carbon-forming reaction is affected by the outlet temperature from the tubular reformer and the vapor to carbon ratio. The equilibrium temperature is reduced for a reduced outlet temperature and increased steam to carbon ratio, whereby operating conditions that are more moderately considered for the tubular reformer are also more benign for HTER and therefore the ratio of feed to HTER and tubular reformer is One type of self-regulation is given as long as it remains constant. However, it is always recommended to use advanced algorithms as it will ease control and minimize the risk of premature failure due to malfunction.

HTER-p was designed and procured by Topsoe. The pressure shell was lined with fire retardant and the fire retardant was dried on site in August 2011 before commissioning of the plant. Since the flow is not intended to pass along the refractory during the commissioning (or operation), the topping agent in the pressure shell can not be dried during the preliminary commissioning / commissioning (as refractory of the exit collector).

In September 2011, the pressure shell was launched and the tube bundle was installed.

The HTER-p was loaded with a Topsoe catalyst in a heat exchanger reformer at 16x8 mm in November 2011, which proceeded smoothly and resulted in a very low deviation (+ 3.1 / -2.2%) between loading density and pressure drop in the tube . This ensures a good flow distribution between the tubes. The overall catalyst loading time for both in-tube catalyst and tube-external catalyst was 10 days on a weekly basis. This time is expected to be reduced and compared to conventional tubular reformers with similar H ₂ production capacity (~ 32,000 Nm 3 / h corresponding to 80-100 reformer tubes), the loading time of HTER is only 3 It is only four days longer, which can be considered reasonable considering the compactness of the HTER and the loading of the HTER is not typically a critical path.

The H ₂ plant was mechanically completed in January 2012 and was fully commissioned, commissioning commenced shortly after. Heating of the reforming zone (pre-reformer, tubular reformer and HTER-p) in the circulating nitrogen started on January 12, and on January 15 the raw material was introduced into the reforming zone.

The Essar Oil H ₂ plant is designed to have an intermediate temperature shift (MTS), and the MTS catalyst is reduced by H ₂ produced by the H2 plant itself, with the intermediate temperature shift bypassed due to the utilization rate of imported hydrogen in the start- . This can be done by operating the reforming zone at a reduced capacity, at a reduced outlet temperature from the reformer (tubular reformer and HTER) and at an increased steam to carbon ratio, and is thus suitable for feeding into a pressure swing adsorption (PSA) unit Syngas is produced, and H ₂ for MTS catalytic reduction is produced in this manner.

The MTS catalytic reduction was completed on January 20 and the mid-temperature switch was inserted on the same day, reaching 60% capacity on January 21, 2012 and reaching 85% capacity on January 22, 2012 . The H ₂ plant was operated according to H ₂ requirements at the refinery complex.

The H ₂ plant was restarted early in the second quarter of 2012 and piloted at 100% capacity in May 2012. Operational data was analyzed using a data combination program, which ensures that the analysis of the plant and HTER is done on a consistent dataset without errors on heat and mass balance. Operating and consumption figures were in the 130,130 Nm3 / hdml capacity as expected and better consumption figures could be obtained than expected and guaranteed by site optimization (see Table 4).

Specific net energy consumption ( Gcal / 1000 Nm ³ H ₂ )
("Fuel optimized" in the column represents an optimized period of 4 hours of pilot operation) low  data Combined data design Demonstration
driving (fuel
optimal) Pilot driving (Fuel optimum) Raw materials + fuel - steam 3.15 3.15 3.12 3.17 3.14 Raw material + fuel 3.39 3.42 3.39 3.45 3.42 Raw material 3.16 3.04 3.04 3.06 3.06

Also, the operation and performance of the HTER-p was evaluated during the trial run, and the temperature was measured in good agreement with the simulated temperature by the Topsoe reformer model (see FIG. 9) Which is slightly better than heat transfer.

The evaluation of the temperature profile compared to the direct result from the simulated reformer model using the combined termination temperature shifts the position of the critical temperature by only about 0.5m, and in this case (and generally in the case of the double tube HTER-p) Position indicates that it moves further toward the top, i. E. Toward the portion of the tube assembly comprised of the material with high resistance to metal dusting. See FIG. 10, for example.

In conclusion, the installation of the Haldor Topsoe exchange reformer significantly reduces raw material and fuel consumption in the H ₂ plant and thus also reduces CO ₂ emissions from the plant. The HTER-p is a very compact reformer and has a very high thermal strength, which makes it possible for both ordinary plant and retrofit projects.

It is important to accurately predict both heat transfer and catalytic activity, and to consider the interaction between thermal design and catalytic performance, as a design tool for sizing the reformer. Excessive estimates of heat transfer and catalytic activity will lead to devices that can not meet design capacity, but application of "design margins" can lead to too much heat transfer and / or catalytic activity to play a critical role with metal dusting attacks It is not a solution.

The commissioning and operation of the Essar Oil H ₂ plant shows that the implementation of HTER-p does not negatively affect commissioning and start-up time, HTER-p operation is robust and stable, and does not affect plant reliability. The evaluation of the operational data from the Essar Oil H ₂ plant shows that the model used to predict heat transfer and catalyst is very accurate and ensures a proper and safe design of the HTER-p.

It is anticipated that nine units with HTER-p designed by Topsoe will start up in 2013-1015.

U.S. Patent No. 6224789 describes a method for producing syngas comprising a self-heat reformer and a heat exchange reformer placed in parallel, wherein the effluent from the autothermal reformer is used to heat the heat exchange reformer.

According to the present invention, metals resistant to metal dusting are used at a distance from the inlet of the heat exchange reformer, and this distance is determined by the steam-to-carbon ratio, effluent outlet temperature and hydrocarbon flow of the main reformer, To carbon ratio and hydrocarbon flow rate.

Figure 1: HTER at the NH ₃ plant front end
2: ATR-based front end for synthetic fuel
Figure 3: HTER &lt; _{RTI ID} = 0.0 &gt;
Figure 4: Bayonet tube HTER
5: Double tube HTER
Figure 6: Heat transfer in HTCR
Figure 7: Essar Oil hydrogen plant
Figure 8: Temperature profile in HTER
Figure 9: Evaluation of HTER-p termination temperature
Figure 10: Simulated and estimated actual temperature profile

An aspect of the present invention that follows and in accordance with the appended claims is as follows:

Embodiment 1: A method for designing a configuration of a heat exchange reformer (HER) for minimizing metal dusting, the HER being part of a syngas production unit comprising a main reforming unit (MRU) (HER), the effluent from the MRU being arranged to provide heat to the HER, the hydrocarbon feedstock being arranged to pass both the MRU and the HER in parallel,

a. MRU hydrocarbon feedstock with MRU steam to carbon ratio (MRU _{S / C} ), effluent outlet temperature (T _MRU ) and MRU hydrocarbon flow rate (F _MRU )

b. Provides a HER hydrocarbon feed having a HER steam to carbon ratio (HER _{S / C} ) and a HER hydrocarbon flow rate (F _HER )

The method

- the temperature profile within the _{HER indicates} the ratio of F _HER / F _MRU , MRU outlet temperature (T _MRU ), MRU steam to carbon ratio (MRU _{S / C} ), HER steam to carbon ratio (HER _{S / C} ) (F _MRU + F _HER ) as a function of distance from the entrance of the HER to a certain extent;

- determining a distance (A) from the entrance of the HER where less metal dusting occurs from said temperature profile;

- constructing a HER from a first metal having a high resistance to metal dusting at a distance exceeding said distance (A) from the inlet of the HER; And

- constructing a HER from a second metal having a lower resistance to metal dusting than said first metal at a distance less than said distance (A) from the entrance of the HER.

Aspect 2: A method for improving thermal control in a heat exchange reformer (HER) of a syngas production unit, said syngas production unit comprising a main reforming unit (MRU) and a heat exchange reformer (HER) The water is arranged to provide heat to the HER and the hydrocarbon feedstock is arranged to pass both MRU and HER in parallel,

a. MRU hydrocarbon feedstock with MRU steam to carbon ratio (MRU _{S / C} ), effluent outlet temperature (T _MRU ) and MRU hydrocarbon flow rate (F _MRU )

b. Provides a HER hydrocarbon feed having a HER hydrocarbon flow rate (F _HER )

The method adjusts the ratio of F _HER / F _MRU by adjusting the hydrocarbon flow to MRU and HER based on MRU _{S / C} , T _MRU , HER _{S / C} and total hydrocarbon flow (F _MRU + F _HER ) And maintaining a stable temperature profile in a heat exchange reformer (HER).

Embodiment 3: The method according to embodiment 2, wherein the method comprises the step of increasing or decreasing the ratio of F _HER / F _MRU , preferably decreasing the ratio of F _HER / F _MRU .

Embodiment 4: The method of embodiment 2, wherein said method increases or decreases the MRU steam to carbon ratio (MRU _{S / C} ), increases or decreases the MRU effluent outlet temperature (T _MRU ) _{S / C} ) and / or increasing or decreasing the total hydrocarbon flow (F _MRU + F _HER ).

Embodiment 5: The method of embodiment 4, wherein the method comprises increasing the TR vapor-to-carbon ratio (TR _{S / C} ).

Embodiment 6: A method according to any one of the preceding embodiments, wherein the HER is bayonet type HER or double tube type HER.

Mode 7: The method according to any one of the preceding aspects, wherein the method comprises reducing the ratio of F _HER / F _MRU .

Embodiment 8: A method according to any one of the preceding embodiments, wherein the MRU provides syngas to a hydrogen plant, an ammonia plant, a methanol plant, and / or a synthetic fuel plant.

Embodiment 9: A method according to any one of the preceding embodiments, wherein the MSR is selected from a tubular reformer, an air-blown secondary reformer, an oxygen-blown secondary reformer, and an autothermal reformer.

Embodiment 10: A method according to any one of the preceding embodiments, wherein the effluent from the MRU is arranged to flow in the same or opposite direction as the HER hydrocarbons fed to the HER.

Embodiment 11: A method according to any one of the preceding embodiments, wherein the hydrocarbon feedstock comprises natural gas, LPG, naphtha, redistilled gasoline (RFG) or a mixture of LPG and naphtha.

Embodiment 12: The method of any of the preceding embodiments, wherein the syngas production unit further comprises a pre-reformer disposed upstream of the MRU and / or the HER.

Mode 13: Use of the method according to any one of aspects 2-11 for reducing metal dusting in HER.

Claims (13)

A method for designing a configuration of a heat exchange reformer (HER) for minimizing metal dusting, the HER being part of a syngas production unit, the syngas production unit comprising a main reforming unit (MRU) and a heat exchange reformer Wherein the effluent from the MRU is arranged to provide heat to the HER and the hydrocarbon feedstock is arranged to pass both the MRU and the HER in parallel,
a. MRU hydrocarbon feedstock with MRU steam to carbon ratio (MRU _{S / C} ), effluent outlet temperature (T _MRU ) and MRU hydrocarbon flow rate (F _MRU )
b. Providing a HER hydrocarbon feed having a HER steam to carbon ratio (HER _{S / C} ) and a HER hydrocarbon flow rate (F _HER )
The method
- the temperature profile within the _{HER indicates} the ratio of F _HER / F _MRU , MRU outlet temperature (T _MRU ), MRU steam to carbon ratio (MRU _{S / C} ), HER steam to carbon ratio (HER _{S / C} ) (F _MRU + F _HER ) as a function of distance from the entrance of the HER to a certain extent;
- determining a distance (A) from the entrance of the HER where less metal dusting occurs from said temperature profile;
- constructing a HER from a first metal having a high resistance to metal dusting at a distance exceeding said distance (A) from the inlet of the HER; And
- constructing a HER from a second metal having a lower resistance to metal dusting than said first metal at a distance less than said distance (A) from the entrance of the HER. A method for improving thermal control in a heat exchange reformer (HER) of a syngas production unit, said syngas production unit comprising a main reforming unit (MRU) and a heat exchange reformer (HER) And the hydrocarbon feedstock is arranged to pass both the MRU and the HER in parallel,
a. MRU hydrocarbon feedstock with MRU steam to carbon ratio (MRU _{S / C} ), effluent outlet temperature (T _MRU ) and MRU hydrocarbon flow rate (F _MRU )
b. Providing a HER hydrocarbon feed having a HER hydrocarbon flow rate (F _HER )
The method adjusts the ratio of F _HER / F _MRU by adjusting the hydrocarbon flow to MRU and HER based on MRU _{S / C} , T _MRU , HER _{S / C} and total hydrocarbon flow (F _MRU + F _HER ) And maintaining a stable temperature profile in a heat exchange reformer (HER). 3. The method of claim 2, wherein the method comprises increasing or decreasing the ratio of F _HER / F _MRUs , preferably decreasing the ratio of F _HER / F _MRUs . The method of claim 2, wherein the method MRU steam-to-carbon ratio (MRU _{S / C)} increasing or decreasing the, increase or decrease the MRU effluent outlet temperature (T _MRU) and, HER steam-to-carbon ratio (HER _{S / C} ), and / or increasing or decreasing the total hydrocarbon flow (F _MRU + F _HER ). 5. The method of claim 4, wherein the method comprises increasing the TR vapor to carbon ratio (TR _{S / C} ). 6. The method according to any one of claims 1 to 5, wherein the HER is bayonet type HER or double tube type HER. 7. A method according to any one of claims 1 to 6, characterized in that the method comprises reducing the ratio of the F _HER / F _MRU . 8. The method according to any one of claims 1 to 7, wherein the MRU provides synthesis gas to a hydrogen plant, an ammonia plant, a methanol plant and / or a synthetic fuel plant. 9. The method according to any one of claims 1 to 8, wherein the MSR is selected from a tubular reformer, an air-blown secondary reformer, an oxygen-blown secondary reformer and an autothermal reformer. 10. A process according to any one of claims 1 to 9, characterized in that the effluent from the MRU is arranged to flow in the same or opposite direction as the HER hydrocarbons fed to the HER. 11. A process according to any one of the preceding claims, characterized in that the hydrocarbon feedstock comprises a mixture of natural gas, LPG, naphtha, redistilled gasoline (RFG) or LPG and naphtha. 12. A process according to any one of the preceding claims, characterized in that the syngas production unit further comprises a pre-reformer located upstream of the MRU and / or the HER. Use of a method according to any one of claims 2 to 12 for reducing metal dusting in HER.

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