The Uhde process and design for ammonia plants is based on reliable and proven process steps. The main features are a top-fired primary reformer with a cold outlet manifold, a secondary reformer with a circumferential vortex burner and a magnetite-based three-bed radial heat exchange synthesis with one or two synthesis converters.

The feedstock (natural gas for example) is desulphurized, mixed with steam and converted to synthesis gas over nickel catalysts at approximately 40 bar and 800°C in the primary reformer. The Uhde steam reformer is a top-fired reformer which has tubes made of centrifugally-cast alloy steel and a proprietary cold outlet manifold system to enhance reliability.

Efficient, reliable, durable

The process gas leaving the primary reformer enters the secondary reformer, where process air is admitted to the syngas via a special nozzle system that provides a perfect mixture of air and gas. Subsequent high pressure steam generation and superheating permit maximum process heat exploitation to achieve optimized energy efficiency. Since its introduction in 1968, the Uhde secondary reformer has proved to be a reliable item of equipment with a long service life.

Emission reduction

Carbon monoxide is converted to carbon dioxide in the HT and LT shift over standard catalysts. Carbon dioxide is removed in a scrubbing unit, which normally uses the BASF-OASE or the UOP-Benfield process. Remaining carbon oxides are reconverted to methane by catalytic methanation at trace ppm levels.

The flowsheet diagram of an Uhde ammonia plant shows the conventional sequence of process steps that form the basis of most present-day ammonia processes. However, a more detailed scrutiny of the facts and figures shows that what appears to be a conventional set-up is in fact a most up-to-date ammonia plant concept. The total consumption figure (feed + fuel + electric power) per metric ton of ammonia produced is in the range of 6.6 to 7.2 Gcal (27.6 - 30.1 GJ), depending on local conditions (e.g. cooling water temperature) and project-specific requirements (such as the natural gas price, etc.).

The following process areas have undergone major modifications in order to achieve these figures:

• the steam reforming section including its waste heat recovery system;

• the CO₂ removal unit;

• the ammonia synthesis unit.

thyssenkrupp Uhde and Johnson Matthey’s new ammonia plant concept for 300 to 600 stpd

The chemical and fertilizer industries have relied upon large-scale ammonia plants during the past four dec-ades because economies of scale favor the lower specific construction and production costs. The business model for these larger plants was partly based on the fact that the ammonia product not consumed on-site could be exported, calling for straightforward transportation to other users at economically attractive costs. However, increasing safety and security concerns for transporting hazardous chemicals have led to higher freight rates and insurance premiums for the transportation of anhydrous ammonia. This affects most small-scale ammonia consumers who depend on importing ammonia by rail, barge or road.

A viable alternative is to co-locate a small-scale ammonia production facility with a consuming facility and thus to eliminate the transport risk and costs. Conventional plant designs face technical and economic chal-lenges below plant capacities of 600 short tons per day (550 metric tons per day). thyssenkrupp Uhde and Johnson Matthey have addressed this concern, developing an economic concept for smaller plants based on gas heated reformer technology.

As a consequence, thyssenkrupp Uhde can now offer a plant capacity range of 270 to 550 met-ric tons per day (300 to 600 short tons per day) and has a standard design of 360 short tons per day available and ready to go. This plant uses a gas heated reformer (GHR) and a pressure swing adsorption (PSA) system in the front end and an Uhde low pressure synthesis loop in the back end

Special solutions for ammonia plants that meet your needs

The technology presented here focuses on ammonia production from steam reforming of natural gas. Of course we can also offer other technologies and processes for other feedstocks for ammonia production, including:

• autothermal reforming of natural gas

• naphtha reforming

• ammonia production using hydrogen from other sources, e.g. water electrolysis, refinery offgas, etc.

We have solutions available for many other requirements arising in connection with ammonia plant projects, including:

• capturing of sulfur from natural gas for sulfur export

• increase of CO₂ export to a urea plant or CO₂ recovery from flue gas

• special requirements for waste water treatment

• ammonia storage tanks

• and many more

Contact us – we will be glad to discuss your requirements.

thyssenkrupp Uhde - technology service

Continuous improvement using high-tech solutions

Would you like your plant to be permanently operating to the highest possible efficiency and safety standards, not just at start-up but throughout its entire lifetime?

As a technological leader with around 90 years of experience in the fertilizer business thyssenkrupp Uhde can accompany you on the entire journey of your plant.

Who we are

As a professional service provider to the ammonia & urea industry we offer you a comprehensive service portfolio for continuous improvement of your plant in the fields of a minimized power consumption, increased capacity, plant availability & safety as well as product quality in order to support you on your way to becoming "best in class".

What we offer

In addition to engineering, operation and maintenance, inspection and repairs, consulting and assessments, troubleshooting and training, we can support you with the following services:

Revamps:

Based on our extensive experience in designing, constructing and commissioning new plants, thyssenkrupp Uhde has developed a wide-ranging strategy for the revamping of ammonia and urea plants to meet the requirements and objectives of our customers, such as:

• Improve annual production

• Improve energy efficiency

• Extend remaining lifetime

• Improve plant reliability

• Reduce emissions

Engineering and supply of equipment and spare parts:

If you choose thyssenkrupp Uhde as a supplier of equipment, you benefit from the thyssenkrupp Uhde global procurement organization of an international EPC contractor. By combining engineering skills and procurement skills for equipment supply we provide our customers a comprehensive service package including mechanical and performance guarantees as well as commissioning services for the supplied equipment and machinery.

Ammonia synthesis catalyst & cartridge replacement:

Due to the high complexity of catalyst and cartridge replacement in the ammonia converter we offer our customers a full-service package. As general contractor, Uhde not only ensures competent project execution and fixed-price catalyst and cartridge replacement under observance of a set time schedule, but also performance reliability once the plant has been restarted.The full-service package for catalyst and cartridge replacement in an ammonia converter includes:

• Project management incl. site management

• Procedures and method statements

• Supervision of all working steps

• Inspection Services

• Supply of catalyst, cartridge, spare parts & tools

• Mechanical works

• Catalyst handling

• Start-up supervision

• Performance optimization