Nithesh Mohun, senior sales engineer at thyssenkrupp Uhde, talks about the company’s alkaline water electrolysis (AWE) technology for the production of green hydrogen, ammonia and urea.
For ammonia synthesis, a 50 tpd electrolysis module is paired with a 20 MW AWE plant, while the 300 tpd module requires a 120 MW AWE plant.
Green ammonia is no longer a pipedream. What’s more, since ammonia is a high-density energy carrier, it is also suitable for offsetting the fluctuations in the availability of renewable energy sources. Traditionally, ammonia production has been based on natural gas or coal. Now, thanks to optimised technology, the economies of scale for plants producing up to 5 000 metric tons/day (mtpd) make this process very cost-competitive.
Under increasing pressure to reduce greenhouse gas emissions and decarbonise operations, companies are now prioritising climate-friendly production solutions. With this in mind, thyssenkrupp Uhde has developed an ammonia production solution based on renewable feedstocks that is 100% CO2-free, which means it can be designated as a green ammonia production solution. Besides climate considerations, other drivers include the move to distributed production of green ammonia from small-scale plants that fulfil the need for localised self-sufficiency and avoid high transportation costs along with import- or carbon-taxes.
“Whereas in conventional ammonia plants, ammonia is produced by steam reforming natural gas, thyssenkrupp Uhde’s green ammonia production is underpinned by our alkaline water electrolysis (AWE) technology,” says Nithesh Mohun, Senior Sales Engineer at thyssenkrupp Uhde. “The AWE technology for the production of green hydrogen is built on the proven chlor-alkali electrolysis technology developed by thyssenkrupp Uhde Chlorine Engineers and our EPC execution experience gained from more than 600 plants installed worldwide."
According to Mohun, the feedstocks for the green ammonia production are hydrogen, water and renewable power. The renewable power can be produced by either solar PV, wind, hydropower or a combination of these. Explaining green ammonia production, Mohun says, “Within an AWE plant, water is converted into green hydrogen by the application of direct current electricity, while nitrogen is produced in an air separation unit (ASU).”
For the production of green ammonia, thyssenkrupp Uhde has developed solutions with capacities ranging from 50 tpd up to 5 000 tpd. “Our smaller scale plants in capacity classes 50 tpd, 300 tpd, 600 tpd and 1 200 tpd are offered on a fully modularised basis," adds Mohun. The plants are fabricated, pre-assembled and pre-commissioned as skids for easy transportation. The only limitations for modularisation are typically the shipping envelope.
Larger plants are usually built using the stick-built approach. Nevertheless, these can be expanded and further developed by adding modules. Mohun adds that the key is standardisation to maximum capacity while simplifying installation.
Hydrogen and ammonia modular solutions must be matched. For example, the 50 tpd module is paired with a 20 MW AWE plant and the 300 tpd module is paired with a 120 MW AWE plant.
Modularisation also provides benefits in addition to the underlying technology. These include reduced implementation timeframes, improved quality control, reduced project investment cost through lower contingency requirements and greater risk mitigation through a significant reduction of on-site construction effort and time.
Small-scale ammonia plants have the advantage of distributed production location and reduction of logistics risks and costs. The small-scale plant can be designed to service the immediate market and thus limit capital outlay and transportation of large consignments of the product as well as logistics risks in off-loading and storage.
Small-scale green ammonia plants can compete with conventional plants under the right conditions. The key drivers for green ammonia competitiveness are reduced capital expenditure, cost effective renewable power supply and stringent CO2 taxes and penalties. In most parts of the world renewable power is now more affordable than power produced from fossil fuels. Capital costs for green ammonia plants are falling with increased research and development efforts. Governments and environmental organisations are strongly driving enforcement of CO2 taxes and penalties.
“Considering the above, green ammonia can already reach price parity with conventional ammonia production, if leveraging CO2 incentives and eliminating the need to import ammonia over long distances,” states Mohun.
When the project focus is on conventional ammonia production, thyssenkrupp Uhde offers the modular A01 and A04 series Gas Heater Reformer (GHR) solution with capacities ranging from 50 to 350 tpd. The GHR solution was developed in collaboration with Johnson Matthey. These systems are based on gas heated reforming (GHR) technology with a pressure swing adsorption (PSA) system at the front end and thyssenkrupp Uhde low-pressure synthesis loop at the back end.
The design is less complicated than a conventional primary/secondary reformer and is especially suited for small capacities with low ammonia needs and high transportation challenges. The GHR is a cost-effective solution as it eliminates the need for an externally- fired primary reformer, the elaborate waste heat-recovery section and the consequent excess steam production.
Moreover, as the reforming uses air, there is no need for an air separation unit. The modular nature of the GHR offers, amongst others, reduced implementation timeframes, improved quality control and reduced project investment. thyssenkrupp Uhde also offers conventional ammonia production plants of up to 5 000 tpd based on Uhde ammonia technology with almost a century of experience and more than 130 plants built, resulting in a total equivalent production capacity of about 50-million tons per annum.
With more than four decades of experience in the design and construction of urea plants, thyssenkrupp Uhde is regarded as one of the top international contractors in this field. “Strong relations with technology licensors grants us access to world leading urea production technologies,” confirms Mohun.
All that is needed for production of urea is ammonia and a source of CO2. Ammonia can be produced via the plant solutions above, while CO2 can be sourced from power generation, oil and gas processing and cement plants. Proven technology and operating plant references are for capacities from 600 to 5 000 tpd.