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CN-122003293-A - Dynamic hydrogen dispenser from LOHC

CN122003293ACN 122003293 ACN122003293 ACN 122003293ACN-122003293-A

Abstract

Liquid Organic Hydrogen Carrier (LOHC) dehydrogenation systems are described that are capable of meeting time-varying hydrogen demands with short-term kinetics while always ensuring a high degree of dehydrogenation under all operating conditions. The system includes one or more reactors including an LOHC vessel and a recirculation loop including a recirculation pump, a preheater capable of supplying heat of reaction as sensible heat, and a cartridge containing a solid catalyst.

Inventors

  • PIETRO DELOGU
  • M. Fermelia

Assignees

  • 洛卡特有限责任公司

Dates

Publication Date
20260508
Application Date
20241003
Priority Date
20231005

Claims (14)

  1. 1. A continuous Liquid Organic Hydrogen Carrier (LOHC) dehydrogenation system comprising one or more reactors in series, characterized in that each reactor comprises a vessel containing reactant LOHC and an external drum containing dehydrogenation catalyst, a loop provided with at least one pump for circulating a liquid phase from said vessel to said drum and a heat exchanger adapted to preheat said liquid phase, wherein said vessel has a free volume for generated gas.
  2. 2. The dehydrogenation system according to claim 1 wherein the heat exchanger is adapted to preheat the liquid circulating in the loop to a temperature above the reaction temperature and sufficient to maintain the temperature of the liquid contained in the vessel at a level required to compensate for the heat demand of the reaction and the outward heat removal.
  3. 3. The dehydrogenation system of claim 1 or 2, wherein the vessel comprises a level controller for the volume of liquid present.
  4. 4. A dehydrogenation system according to one or more of claims 1-3, wherein the circulation flow rate of the reactant liquid is adjusted according to the desired temperature of the liquid in the vessel.
  5. 5. The dehydrogenation system according to one or more of claims 1-4, wherein the vessel comprises a hydrogen extraction valve for regulating the hydrogen pressure.
  6. 6. The dehydrogenation system according to one or more of claims 1-5 wherein the LOHC flow rate to the system is adjusted according to the desired hydrogen extraction rate.
  7. 7. The dehydrogenation system according to one or more of claims 1-6, wherein the LOHC feed is hydrogenated dibenzyltoluene.
  8. 8. The dehydrogenation system according to one or more of claims 1-7, wherein the vessel is adapted to contain a liquid at a temperature in the range of 250 ℃ to 350 ℃, preferably 280 ℃ to 320 ℃.
  9. 9. The dehydrogenation system according to one or more of claims 1-8, wherein the gas-liquid separation unit is interposed between the outlet of the solid catalyst cartridge and the return vessel.
  10. 10. The dehydrogenation system according to one or more of claims 1-9 comprising three or more reactors connected in series.
  11. 11. The dehydrogenation system according to one or more of the preceding claims, wherein at the outlet of the outer cylinder there is a partially dehydrogenated LOHC and hydrogen produced in the gas phase.
  12. 12. The dehydrogenation system according to one or more of the preceding claims, wherein the heat exchanger is located in the circuit upstream of the outer cartridge containing a dehydrogenation catalyst.
  13. 13. The dehydrogenation system according to one or more of the preceding claims, wherein the reactant LOHC from the outer barrel is mixed with the feed LOHC and the resulting mixture is recycled to the outer barrel.
  14. 14. The dehydrogenation system according to one or more of the preceding claims, comprising at least two reactors connected in series, and wherein the spent LOHC from a first reactor is fed to a second reactor located after the first reactor.

Description

Dynamic hydrogen dispenser from LOHC The present invention relates to a continuous liquid organic hydrogen storage carrier (LOHC) dehydrogenation system comprising one or more reactant liquid vessels having free space for containing generated gas and being connected to an external solid dehydrogenation catalyst cartridge via a circuit equipped with a pump for circulating the liquid phase. In particular, the dehydrogenation system further comprises a heat exchanger adapted to preheat the liquid phase to provide heat of reaction. Background LOHC (liquid organic hydrogen carrier) technology has become one of the main methods for storing and transporting hydrogen. This technique has many advantages over other techniques (high pressure hydrogen, liquid hydrogen, hydrogen stored as metal hydrides). In particular, this technique avoids the use of high pressure tanks, does not require expensive compression or liquefaction processes of the hydrogen itself at very low temperatures, and allows the use of the same infrastructure as the hydrocarbons, and can be stored indefinitely without progressive losses. The cycle of producing, storing and releasing hydrogen on a suitable medium has been the subject of much research, as has the manner in which the released hydrogen is used to produce thermal or electrical energy. Studies have shown that the use of LOHC is also cost effective, especially in long haul transportation. The LOHC technical cycle essentially consists of four steps, hydrogenation of the medium or support at an average pressure of 10-50 bar to produce feed LOHC, transportation of the feed LOHC in liquid form at ambient pressure and temperature, dehydrogenation of the LOHC to release hydrogen and obtain spent LOHC, and recycling of the spent LOHC back to the hydrogenation step. Both the first two steps and the last step are well defined in terms of equipment and operating conditions. The dehydrogenation stage is more problematic because the implementation of this stage depends to a large extent on the specific use of the hydrogen, the location of the dehydrogenator, whether in a fixed position or on a movable support, and the need for continuity of the hydrogen from the system used. Furthermore, the process is complicated by the fact that the dehydrogenation reaction takes place at high temperatures of 200 to 350 ℃ depending on the type of LOHC used and the reaction is endothermic, which requires the provision of heat of reaction at these temperatures. Therefore, it is necessary to determine a structure that satisfies the following requirements: 1. Hydrogen can be supplied at a variable flow rate to quickly adapt to the changing demands of the system used; 2. the energy source is autonomous, i.e. no energy supply from an external source is required; 3. Ensures a high degree of dehydrogenation of the feed LOHC under all operating conditions. Rapid adaptation to the change in demand means a transition from one steady state to another in a few seconds or tens of seconds, and high dehydrogenation means a conversion of feed LOHC to dehydrogenated LOHC of more than 50%, preferably 80%, under all operating conditions. It should also not be necessary to insert a large number of storage buffers for the resulting hydrogen between the dehydrogenator and the system used. Several types of dehydrogenation reactors have been proposed in the publications and patent literature. Most studies are based on Plug Flow Reactors (PFR) which are divided into three zones, a heating zone which increases the temperature of the feed LOHC to the reaction temperature, a zone containing solid catalyst for the reaction to take place, and a cooling zone which brings the temperature of the two-phase gas-liquid stream to a level compatible with the requirements of use. Patent US 11,383,974 describes different types of dehydrogenation reactors, i.e. fixed bed and moving bed, but always of the batch type or of the plug flow type. The patent also focuses on the use of reaction promoters, i.e. secondary alcohols or polyols, wherein the dehydrogenation reaction is carried out in two steps, the first step being by hydrogen exchange between the LOHC and the oxidized form of the promoter (i.e. the corresponding ketone), and the second step being dehydrogenation of the alcohol formed. An advantage of this solution is the ability to provide the heat of reaction to the system at a lower temperature (about 200 ℃) than is required for the direct dehydrogenation of LOHC. The document does not mention possible dynamic use. Patent US 10,350,566 describes in detail a plug flow reactor consisting of three zones, the first zone for preheating the LOHC, the second zone for the reaction to take place and the third zone for separating the gas stream from the liquid at the outlet. Also, the document does not mention dynamic behavior. Patent DE 10 2021 203 887 describes a plug flow reactor in which the vibration of the solid catalytic bed occurs, which promotes the se