1 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Facilitating renewable ammonia production and export via LOHC The following statement is a full description of this invention, including the best method of performing it as known to me: 2 Exporting renewable ammonia via LOHC FIELD OF THE INVENTION (01) The present invention relates broadly to a method of using a Liquid Organic Hydrogen Carrier (LOHC) storage system to facilitate the production and export of renewable ammonia. BACKGROUND TO THE INVENTION (02) In response to the need to reduce global carbon emissions, a renewable energy rich country such as Australia can convert its renewable energy into hydrogen gas and then export this gas to new and traditional export markets in countries such as Japan, Korea and China. (03) A challenge for this potential renewable energy export industry is that hydrogen is a very difficult substance to store and transport, especially via ocean going tankers. (04) One viable solution to this storage and transport problem is to convert the renewable hydrogen in Australia into readily transportable ammonia (NH 3 ) by combining the renewable hydrogen with nitrogen from the air which has been produced from nitrogen generation plants also powered by renewable energy (nitrogen is 78% of the atmosphere). (05) Traditional ammonia is currently mostly produced by combining hydrogen from a fossil fuel feedstock, with nitrogen in a chemical synthesis plant, such as the Haber Bosch process. (06) Ammonia is a globally traded commodity with world production in excess of 140 million tonnes pa with most of this being used for fertilizer and with much of it being produced using hydrogen feedstock sourced from carbon intensive, steam reforming of methane gas
(CH
4 ) or from coal gasification and reforming. (07) In addition to its use as a fertilizer, there is growing global interest in ammonia's potential role as an energy source whereby it can be used as fuel for alkaline fuel cells and for high temperature solid oxide fuel cells and as fuel for modified combustion engines driving electricity generators. (08) Ammonia can also be cracked back to its constituent elements of nitrogen and hydrogen with the hydrogen used to power fuel cell electric vehicles such as the Toyota Mirai. (09) Renewable hydrogen for ammonia production can be generated via water electrolysis powered by a renewable energy source such as solar, tidal, wind or geothermal energy.
3 (10) For many sources of renewable energy, especially wind and solar, the intermittent nature of the energy supply can make it difficult to design efficient methods for hydrogen generation and downstream processing such as ammonia production, because processes such as ammonia production work best with regular and scheduled production runs. (11) Liquid Organic Hydrogen Carriers (such as Toluene to Methylcyclohexane and Dibenzyltoluene to Perhydro-Dibenzyltoluene) present an opportunity to cost effectively store an intermittent supply of renewable hydrogen so as to smooth out its delivery into a downstream process such as a Haber Bosch plant for ammonia production. (12) A significant advantage of LOHC chemicals, such as the type referred to above, is that they have properties very similar to those of diesel in that they are liquid at ambient temperature and pressure and can hence be easily transported or stored, for up to many months, without the need for cryogenic or pressurised storage vessels. (13) By way of example, an LOHC storage system (System) can be established at a location in which, at its front end, the System is connected to a renewably powered electrolysis unit which feeds an intermittent supply of hydrogen into the System, whilst at the back end, the System is connected to a Haber Bosch plant into which the System delivers a steady scheduled stream of hydrogen for ammonia production. (14) In this way the System acts as a buffer to connect an intermittent hydrogen supply into a regularly scheduled ammonia production process. (15) The System achieves this by, at its front end, having a hydrogenation unit which draws the unloaded LOHC (such as Toluene or Dibenzyltoluene) from a holding tank (the LOHC-U tank) and chemically combines it with the hydrogen from electrolysis to produce the loaded LOHC (such as, respectively, Methylcyclohexane or Perhydro-Dibenzyltoluene) which is then stored in a separate tank (the LOHC-L tank). (16) The hydrogen now being stored in the LOHC-L tank, which is about 6% by weight or approximately 60kg of H 2 per tonne of LOHC, can be stored there for many months without loss and hence the System provides a means for not only daily and overnight storage but also weekly, monthly or seasonal storage of potentially large volumes of hydrogen at ambient pressure and temperature. (17) As and when required for ammonia production, the loaded LOHC can be drawn from the LOHC-L tank and processed through a dehydrogenation unit located at the back end of the System, which releases highly pure hydrogen for delivery to the Haber Bosch plant, whilst the now unloaded LOHC is delivered back to the LOHC-U tank for storage. (18) Some of the hydrogen released from the dehydrogenation unit can also be used to n in nmiti fiu I nil5- nr hvdrnnan nnwir-nd Mintrinitv nnarntinn qpt, whinh nrnvifi- MintrinnI 4 power to run other plant items in the renewable ammonia production process such as the nitrogen generating plant, so as to ensure that the entire ammonia production process is powered by renewable energy. (19) A major cost for the System is the heat energy required for the dehydrogenation unit so care needs to be taken in the design of the System to maximise the reuse of heat sources from the electrolysis, the hydrogenation unit, the Haber Bosch unit and other plant components, so as to maximise overall System efficiency. (20) Use of an LOHC storage System of the type described offers prospects for facilitating a large new renewable ammonia export industry for Australia which can target global demand for both sustainable food production and for zero carbon energy sources. SUMMARY OF THE INVENTION (21) According to one aspect of the present invention there is provided a method of using an LOHC storage system to facilitate the production and export of renewable ammonia, by: a. Producing renewable hydrogen (RH 2 ) via electrolysis powered by a renewable energy source such as solar, tidal, wind or geothermal power; and b. Using a hydrogenation unit to load this RH 2 , into an unloaded LOHC which is liquid at ambient temperature and pressure such as Toluene or Dibenzyltoluene which, once loaded with the hydrogen becomes a loaded LOHC which is also liquid at ambient temperature and pressure, such as, respectively, Methylcyclohexane or Perhydro-Dibenzyltoluene; and c. Storing this loaded LOHC in a tank, the LOHC-L tank, which can hold it at ambient pressure and temperature for many days or even months without losses of hydrogen; and d. When required for ammonia production, drawing such loaded LOHC from the LOHC-L tank into a dehydrogenation unit which releases a pure stream of hydrogen for delivery into an ammonia production plant such as the Haber Bosch process, whilst returning the now unloaded LOHC to a separate holding tank, the LOHC-U tank; and e. Using some of the RH 2 released from the dehydrogenation unit to run onsite fuel cells or hydrogen powered electricity generating sets which provide electrical power to run other plant items in the renewable ammonia production process such as the nitrogen generating plant; and f. Using this LOHC storage system to overcome the intermittent nature of the supplv of RH, so as to facilitate the regular and scheduled production and 5 export from Australia of renewable ammonia as a premium carbon free source of fertilizer and energy fuel. BRIEF DESCRIPTION OF DRAWING IN FIGURE 1 (22) In order to achieve a better understanding of the nature of the present invention a preferred embodiment of a method of using a Liquid Organic Hydrogen Carrier storage system to facilitate the production and export of renewable ammonia will now be described, by way of example only, with reference to the accompanying drawing in Figure 1 in which; (23) A schematic view is presented depicting a solar PV farm being used to generate electricity to power a water electrolysis plant for the production of hydrogen which is first stored in an LOHC storage system and then delivered to an ammonia production plant as both feedstock for the ammonia synthesis plant and as fuel to power other plant items within the ammonia production facility such as the nitrogen generation unit. (24) Figure 1 also depicts a PV solar farm being used to produce desalinated sea water for delivery to the electrolysis unit for hydrogen production. DETAILED DESCRIPTION OF THE PREFERRED EMBODIEMENT (25) Figure 1 depicts a method of using an LOHC storage system to facilitate the production and export of renewable ammonia involving the following steps: a. Using a solar PV farm (1) to generate desalinated water at a plant (2) located near the coast. b. Transferring via pipeline (3) that water to the PV powered (4) electrolysis plant (5) for the production of hydrogen. c. Delivering that hydrogen to the LOHC system's hydrogenation plant (6) for loading into the LOCH carrier liquid which is then stored, overnight or for longer, in the LOCH loaded tank (7). d. Drawing down the loaded carrier liquid from the LOCH loaded tank (7) into the dehydrogenation plant (9) for release of hydrogen for delivery to the Haber Bosch ammonia synthesis plant (12) and to a fuel cell (10) to power the nitrogen Air Separation Unit (11). e. Returning the unloaded LOCH liquid to the LOHC unloaded tank (8) to await recycling through the hydrogenation unit (6).
6 f. Using the renewably generated hydrogen and nitrogen delivered to the Haber Bosch plant (12) to produce renewable ammonia for delivery by pipeline (13) to a shipping tanker (14) for delivery to export markets g. Having the water pipeline (3) and the ammonia pipeline (13) share a common pipeline corridor to run between the coast line and the ammonia production facility. (26) Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. For example, both the ammonia production plant and the LOCH storage system could be located on an offshore production platform or ship whereby the renewably generated electricity to power the storage and production processes is generated on shore and delivered to the offshore platform or ship via high voltage transmission cables. (27) All such variations are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description.