CF06_3: Development and implementation of a 200 kW functional model for load-flexible production of ammonia from up to 5 MW of regionally generated renewable energy

CAMPFIRE bundles deve­lo­p­ment acti­vi­ties for the entire hydrogen trans­port chain based on green ammonia. In subpro­ject CF06_3 of the CAMPFIRE imple­men­ta­tion project, the goal is the deve­lo­p­ment of a dynamic Haber-Bosch synthesis reactor for the seasonal storage of fluc­tua­ting rege­ne­ra­tive energy in ammonia. For this purpose, a new process tech­no­logy is being deve­loped that can be operated using fluc­tua­ting energy and allows for econo­mical opera­tion with a low full-load hour count. The deve­lo­p­ment work includes an inno­va­tive plant and reactor concept, novel and cost-effec­tively produced cata­lysts, as well as the imple­men­ta­tion of the reactor in two expan­sion stages of 15 kW and 200 kW.

In the project, KIT is leading the deve­lo­p­ment and cons­truc­tion of a reactor for flexible produc­tion of ammonia accor­ding to the Haber-Bosch process using up to 15 kW of regio­nally gene­rated rene­wable energy. The unique­ness of the reactor, based on a double pipe, lies in its reac­tion control using the coun­ter­cur­rent prin­ciple with a falling tempe­ra­ture profile. This allows follo­wing the optimal tempe­ra­ture trajec­tory to achieve the highest possible conver­sion rate. The reactor is equipped with flow guiding elements (FGE) charac­te­rized by their unique fluid dyna­mics. The deter­mi­na­tion of the optimal reac­tion path is carried out through a mathe­ma­tical model describing the FGE. The heat transfer proper­ties of the FGE are calcu­lated to accu­ra­tely deter­mine their struc­tures. These calcu­la­tions are coupled with a kinetic model accor­ding to Temkin. This enables placing the optimal trajec­tory of the reac­tion (Figure 1, marked in red, inner pipe with cata­lyst) onto the MAX-RATE curve (dashed line below the equi­li­brium line). The blue curve describes the tempe­ra­ture profile in the annular gap of the double pipe reactor. One boun­dary condi­tion is the use of a commer­cial cata­lyst based on wüstite. The design calcu­la­tions result in a highly effi­cient reactor, i.e., the smal­lest size with the best possible reac­tion control. Based on the results, a labo­ra­tory-sized reactor will be built and tested as the first step. Figure 2 shows a sche­matic of the double pipe reactor.

Figure 1: Tempe­ra­ture as a func­tion of ammonia content for an N2/H2 mixture of 1:3 for 50 bar total pressure.

Figure 2: Sketch of the double-tube reactor for ammonia synthesis by the Haber-Bosch process. The blue arrows describe the mate­rial flow in the annular gap and in the inner tube of the reactor equipped with SLE.

For the appli­ca­tion of the cata­lyst to the flow guiding elements, the selected commer­cial cata­lyst is provided by the asso­ciated partner Heraeus. A dip coating process is employed to coat the flow guiding elements (FGE) with a MgO carrier layer produced by elec­tro­pho­resis, along with the cata­lyst suspen­sion. In parallel with the use of commer­cial cata­lysts, the colla­bo­ra­tive project also deve­lops a novel synthesis method for produ­cing the cata­lyst. Using an atmo­spheric plasma process at the INP, the cata­lyst based on cesium- and potas­sium-acti­vated ruthe­nium on graphene is created from an aqueous salt solu­tion and ethanol, aiming for a ruthe­nium content of 24 weight percent. The SKZ Kunst­stoff­zen­trum was engaged as a contractor for the suspen­sion deve­lo­p­ment. The dip coating process for the new suspen­sion is opti­mized to ensure high repro­du­ci­bi­lity of the coating and a homo­ge­neous distri­bu­tion of the catalyst.

The perfor­mance of both the commer­cial and the novel cata­lysts deve­loped in the project is examined in a dedi­cated test setup at the Univer­sity of Rostock, follo­wing prede­ter­mined test proto­cols. A modular cross-flow reactor allows for adjus­ting tempe­ra­ture and concen­tra­tion profiles. Analysis is carried out using an online-coupled mass spec­tro­meter. Key ques­tions include the robust­ness of the cata­lysts under varying load condi­tions and poten­tial deac­ti­va­tion pathways. The expe­ri­mental work is comple­mented by quantum chemical calcu­la­tions by the company Crea­tive Quantum.

In the colla­bo­ra­tive project, ZBT, in close coope­ra­tion with INP at the CAMPFIRE Open Inno­va­tion Lab (COIL), is deve­lo­ping the plant concept for both expan­sion stages. In the project’s progress, all tech­no­lo­gical inter­faces, e.g., for elec­tro­lysis or nitrogen gene­ra­tion, were fina­lized for the func­tional proto­type, and from that, the para­me­ters and requi­re­ments for the compon­ents were derived. All neces­sary condi­tions, such as compo­si­tion of subs­tances, opera­ting pres­sure, tempe­ra­tures before and after the reactor, as well as ambient tempe­ra­tures, were taken into account in a simu­la­tion of the entire plant. The mass flow and design of the system are based on the elec­tro­lysis capa­city of initi­ally 15 kW in the first expan­sion stage; a capa­city of 200 kW is targeted for the second expan­sion stage. In COIL, the detailed plan­ning of the test field CF06_3 ammonia mid-load plant and the required infra­struc­ture and safety requi­re­ments were desi­gned. The imple­men­ta­tion of the plant in COIL is sche­duled to start from the end of 2024.