A FLEXIBLE PLANT TO PRODUCE HYDROGEN FROM AMMONIA OR NATURAL GAS

Abstract

In the present invention, a flexible installation is produced and configured to produce hydrogen using either ammonia or natural gas separately. In a preferred mode, an existing steam methane reformer is reconfigured to include new piping and equipment, allowing the operator to switch between a first operating mode in which natural gas is the feed stream and a second operating mode in which ammonia is the feed stream. (Shortcut figure: Fig. 2)

Description

Title of the invention: A FLEXIBLE PLANT FOR PRODUCING HYDROGEN AT FROM AMMONIA OR NATURAL GAS

[0001] The present invention relates to a method for producing hydrogen using non-hydrocarbon raw materials. More specifically, embodiments of the present invention relate to the use of ammonia as a raw material in a hydrogen production plant instead of hydrocarbons, in particular natural gas.

[0002] In order to reduce the effects of carbon dioxide emissions, new energy carriers are becoming increasingly important. Hydrogen is one of the main energy carriers; however, due to its small molecular size, high pressure requirements and very low boiling point, the transportation of elemental hydrogen is difficult and expensive.

[0003] Ammonia (NH3) has received some attention in the literature, since existing infrastructure can be used for storage and transportation (e.g., LPG infrastructure). Thus, hydrogen production from ammonia, rather than natural gas, is expected to play a major role in the future of hydrogen as a key molecule in the low-carbon energy transition.

[0004] Cracking of ammonia to produce hydrogen is well reported and published. Reference is made here to a combustor (or furnace) tubular ammonia cracker in which ammonia is cracked to H2+N2 over a catalyst. The thermal reaction for cracking ammonia is supplied externally via fuel combustion. Several process flowsheets are published in which the combustion load can be reduced by preheating / superheating the ammonia feed, preheating the combustion air used for combustion, partially cracking the ammonia (upstream) outside the main combustor type cracker in an adiabatic / heated precracker. Using appropriate thermal integration of the process stream and flue gases can result in a system in which steam co-production can be zero.

[0005] There are a large number of steam reforming plants (or steam reforming plants) around the world. Decarbonizing them is a challenge. One option is to convert steam reforming plants into ammonia crackers. However, from the current perspective, such a redesign is permanent. After the renovation, the plant will be able to run on ammonia, but the ability to run on natural gas will be lost.

[0006] With global ammonia and natural gas markets volatile, it is uncertain whether economic circumstances will favor ammonia. There may be periods when one or the other product is cheaper. A plant that can flexibly switch between ammonia and natural gas would therefore be beneficial.

[0007] A steam reforming plant can be converted into an ammonia cracker. Although the production of syngas (cracked gas) is quite similar, the separation of hydrogen from the syngas (cracked gas) is different. In steam reforming plants, a PSA unit is usually installed. The PSA is filled with a specific combination of adsorbents tailored to a syngas from a steam reformer. It cannot separate hydrogen from the cracked gas with the same rate and hydrogen recovery capacity because large amounts of nitrogen are present compared to the syngas.

[0008] In light of the above, no reported plant can operate efficiently in two operating modes, in which one mode operates with natural gas feedstock and a second mode operates with ammonia feedstock.

[0009] The present invention provides an apparatus and method that meet at least one of these needs. In some embodiments of the invention, a solution is provided for retrofitting an existing steam methane reforming plant to be configured to crack ammonia; however, the resulting retrofitted plant will have the ability to switch between two modes of operation: a first mode in which natural gas is the feedstock, and a second mode in which ammonia is the feedstock. In some embodiments, a PSA system for hydrogen purification useful in the present invention will have increased flexibility compared to a typical PSA system that is part of a normal SMR plant.

[0010] A method for retrofitting an existing steam methane reformer (SMR) for ammonia cracking is provided. In one embodiment, the existing SMR may include a pre-reformer, a desulfurization unit, a furnace, waste heat recovery sections, a water gas shift reactor, a pressure swing adsorption (PSA) unit, the furnace including a plurality of SMR tubes and a plurality of burners.

[0011] In a preferred embodiment, the method may comprise the steps of: providing the existing SMR; means for bypassing a first set of equipment during a first mode of operation; means for bypassing a second set of equipment during a second mode of operation; and adding means for providing a stream of gaseous ammonia to the SMR tubes; and adding an additional PSA unit.

[0012] In optional embodiments of the method of the invention:

[0013] the means for providing the gaseous ammonia stream comprises an ammonia storage container, an ammonia feed pump and means for vaporizing the ammonia from the ammonia storage container.

[0014] the ammonia vaporization means further comprise new equipment selected from the group consisting of an ammonia vaporizer, an ammonia exchanger, an ammonia preheater, an ammonia prereactor and combinations thereof, the new equipment being arranged upstream of the SMR tubes and downstream of the ammonia feed pump.

[0015] the ammonia vaporization means further comprises an existing feed superheat section which is located upstream of the SMR tubes, the existing feed superheat section being retrofitted by treating the internal surfaces of the existing feed superheat section to improve nitriding resistance.

[0016] The step of treating the internal surfaces of the existing feed superheat section comprises a process selected from the group consisting of (1) applying a protective coating material that is mechanically coupled to the internal surface, (2) applying an aluminizing layer to the internal surface, and (3) applying a diffusion barrier layer in conjunction with the aluminizing layer, the diffusion barrier layer being disposed between the internal surface and the aluminizing layer.

[0017] the first set of equipment is selected from the group consisting of the desulfurization unit, the pre-reformer, the water-gas conversion reactor and their combinations.

[0018] the second set of equipment comprises the means for supplying the gaseous ammonia flow to the SMR tubes.

[0019] the additional PSA unit operates during the first and second modes of operation.

[0020] These and other features, aspects and advantages of the present invention will be better understood in light of the following description, claims and accompanying drawings. It should be noted, however, that the drawings illustrate only several embodiments of the invention and should therefore not be considered as limiting the scope of the invention since it may admit other equally effective embodiments.

[0021] [Fig. 1] [Fig. 1] shows an embodiment of a hydrogen production plant using ammonia as feedstock in accordance with a prior art embodiment; and

[0022] [Fig.2] [Fig.2] shows an embodiment of a production facility of hydrogen using ammonia as a feedstock which comprises integrating external electrical energy in accordance with one embodiment of the present invention.

[0023] Although the invention is described in connection with several embodiments, it will be understood that it is not intended to limit the invention to these embodiments. Rather, it is intended to cover all alternatives, modifications, and equivalents that may be included within the spirit and scope of the invention defined by the appended claims.

[0024] Certain embodiments of the invention are particularly useful for users who are willing to invest in converting their steam reformer into an ammonia cracker, but are unsure of the long-term economics.

[0025] In order to convert the existing steam reforming plant into an ammonia cracker, it affects the entire plant as shown in [Fig.2].

[0026] An ammonia pretreatment system may be newly installed, which may include an ammonia pump, a vaporizer, and a superheater.

[0027] The steam reformer feed pretreatment system may be retained.

[0028] Before the feed enters the actual reformer / cracker, the feed may be further conditioned - for example, superheated with process gases or flue gases. These heat exchangers are preferably configured for both operating modes, but may optionally be replaced (Equipment C). Other equipment that is not in direct contact with the process or flue gases and is only required for one of the operating modes may be bypassed (Equipment A and B).

[0029] The steam reformer itself must be modified. For example, the tubes and catalyst must be replaced.

[0030] An ammonia scrubbing and recovery column must be installed and operates only during ammonia cracking. By means of the scrubbing column, unconverted ammonia can be removed to an extent that does not damage conventional adsorbents suitable for hydrogen recovery from the synthesis gas of the PSA unit. The ammonia concentration is preferably monitored during operation. The columns can be bypassed when operating on natural gas.

[0031] For the waste heat recovery system:

[0032] Some equipment required only for natural gas operation may be retained. Such as the HT and LT-Shift reactors (if applicable) (Equipment D). When cracking ammonia, they must be bypassed. Some equipment that can be used for operation with both ammonia and natural gas can be modified. Such as boilers or the steam system (Equipment F). In addition, new equipment that can be used to operate with ammonia must be purchased. For example, the ammonia washing and stripping column mentioned above (Equipment E). For any equipment used only for one or the other mode of operation, a bypass can be installed (Equipments D and E).

[0033] The existing PSA for the steam reformer remains in place without modification. Only this PSA will be operational if the plant is running on natural gas on the process side.

[0034] A new small PSA suitable for hydrogen recovery from cracked gas can be installed. Both PSAs will be operational if the plant is running on ammonia on the process side.

[0035] On the PSA system:

[0036] A PSA for a steam reformer contains adsorbents suitable for the recovery of hydrogen from the synthesis gas. If this PSA is fed with cracked gas, which has been cleaned of unconverted ammonia in the scrubbing column, the recovery rate and capacity decrease. A decrease in the hydrogen recovery rate from approx. 89% to approx. 77% can be expected. A capacity decrease of approx. -50% is to be expected. The existing PSA is therefore not able to provide the same hydrogen production.

[0037] To produce as much or even more hydrogen during ammonia cracking, a new small PSA can be installed in addition to compensate for the approximately 50% missing hydrogen capacity. This PSA is suitable for separating hydrogen from the cracked gas and contains adsorbents.

[0038] The advantages of such a system are: lower carbon footprint of the produced hydrogen; no local CO2 emissions; more hydrogen production if desired; flexible option to switch from ammonia to natural gas and vice versa depending on economic circumstances; lower CAPEX for the new PSA system / smaller equipment; extends the life cycle of existing adsorbents; and redundancy while operating on ammonia: two independent PSA systems are available. In case one of the two PSAs trips, hydrogen can still be produced with the other PSA.

[0039] Varieties and options:

[0040] In a steam reformer, the process and the fuel are independent of each other. It is therefore possible to:

[0041] running the process with natural gas and heating with natural gas as a backup fuel.

[0042] carry out the process with ammonia and heating with ammonia as an auxiliary fuel.

[0043] run the process with natural gas and ammonia heating as a backup fuel.

[0044] carry out the process with ammonia and heating with natural gas as a backup fuel.

[0045] Switching between these four modes allows the user to adjust the efficiency of the ammonia and CO2 hydrogen footprint as desired. In the case where natural gas operation is desired, it is possible to equip the plant with a CO2 capture unit on the process and / or fuel side. In the case of a CO2 capture unit already installed at the plant, it can be reused while operating on natural gas.

[0046] The second newly installed PSA system may share part of the volume of the gas evacuation buffer tank (to be determined) with the old PSA. The simulations carried out show that the load of the waste gas drum during operation with ammonia is lower than the load during operation with natural gas. The gaseous discharges from the second newly installed PSA may therefore be lower.

[0047] If a larger hydrogen capacity is desired, the newly installed PSA for cracked gas separation may be of a larger size than previously discussed.

[0048] This concept can also be applied to a newly constructed steam reformer / ammonia cracker and therefore should not be limited to the refurbishment of an existing SMR.

[0049] Although the invention has been described in conjunction with specific embodiments thereof, it is apparent that numerous alternatives, modifications, and variations will occur to those skilled in the art in light of the foregoing description. Accordingly, it is intended to encompass all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist of, or consist essentially of the elements disclosed and may be practiced in the absence of any element not disclosed. In addition, language referring to order, such as first and second, is to be understood in an exemplary and not a limiting sense. For example, those skilled in the art may recognize that certain steps or devices may be combined into a single step / device.

[0050] Terms relating to / approximately a particular value include that particular value plus or minus 10%, unless the context clearly dictates otherwise.

[0051] Optional or optional means that the event or circumstances described later may or may not occur. The description includes cases where the event or circumstance occurs and cases where it does not.

[0052] Ranges may be expressed herein from about one particular value and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment ranges from one particular value and / or to the other particular value, as well as all combinations within said range.

Claims

[Claim 1] Claims A method of retrofitting an existing steam methane reformer (SMR) for ammonia cracking, the existing SMR comprising a pre-reformer, a desulfurization unit, a furnace, waste heat recovery sections, a water gas shift reactor, a pressure swing adsorption unit (PSA unit), the furnace comprising a plurality of tubes and a plurality of burners, the method comprising the following steps: - provide the existing SMR; - installing a bypass to bypass a first set of equipment during a first mode of operation; - installing a bypass to bypass a second set of equipment during a second mode of operation; and - adding an ammonia storage container, an ammonia feed pump and an ammonia vaporizer to provide a stream of gaseous ammonia to the SMR tubes; and - add an additional PSA unit.