Since its founding in 1961, TOYO has been a world leader in urea technology and has designed and constructed more than 100 urea plants using its own licenses. To satisfy customers, enhance TOYO's competitiveness, and contribute to global environmental issues, TOYO has continued to improve its own licenses for energy conservation. Here, TOYO's latest energy-saving urea synthesis technology ACES21® and our urea process-related technologies are introduced.

Energy-saving Urea Synthesis Process ACES21®

It is no exaggeration to say that the progress made in the improvement of urea plants is a history of energy conservation. In the early 1980s, TOYO established the Advanced Process for Cost and Energy Saving (ACES) urea process, which significantly reduces energy consumption at urea plants.
in the 1990s, we jointly developed ACES21® with Pusri, Indonesia, with the aim of further reducing energy consumption.


ACES21® not only reduces plant construction costs by simplifying the urea synthesis system but also reduces operating costs by optimizing operating conditions. Major features of this technology are given below:

  • 1. Low Investment Cost

    Reduction of construction costs

    • Reactor installation on ground level thanks to the utilization of high-pressure ejector
    • Vertical Submerged type Carbamate Condenser (VSCC)
    • Simple synthesis loop and no gravity flow

    Reduction of equipment costs

    • Small equipment size by two-stage reaction
    • Less number equipment in the synthesis loop
  • 2. Low energy consumption (reduction of operating costs)

    Realizing a high CO2 conversion to urea by optimized process conditions

  • 3. Simple operation

    Forced flow of synthesis loop circulation by ejector and no gravity flow

  • 4. Maintenance Cost Saving

    Avoidance of corrosion issues by the milder operating condition in the synthesis loop and the selection of advanced and proven materials developed by TOYO.

ACES21 synthetic loop
4,000 t/d ACES21® Urea Plant
Indrama Eleme Fertilizer Company (Nigeria)

Vertical Submerged Carbamate Condenser (VSCC)

Vertical Submerged Carbamate Condenser (VSCC) in ACES21® has functions to condense NH3 and CO2 gas mixture from the stripper to form ammonium carbamate in the shell side, synthesize urea by dehydration of ammonium carbamate in the shell side and remove the reaction heat of ammonium carbamate formation by generating 5 barG steam in boiler tubes.

Advantages of the vertical submerged configuration of carbamate condenser are:

  • High gas velocity, appropriate gas hold up and sufficient liquid depth in the bubble column promote mass and heat transfer;
  • An appropriate number of baffle plates distributes gas bubbles in the column effectively without pressure loss; and
  • A vertical design inevitably requires a smaller plot area.
Vertical Submerged Carbamate Condenser(VSCC)

Optimum Selection of Synthesis Condition

Urea synthesis of ACES21® takes place in two stages: VSCC and Reactor. VSCC is operated at N/C ratio of 2.8 – 3.0 where the equilibrium vapor pressure of urea-carbamate solution gives the lowest. This optimum N/C selection allows VSCC to be operated at high temperature under relatively low synthesis pressure, rendering efficient heat transfer between the shell and the tube and a higher reaction rate of ammonium carbamate dehydration simultaneously. The reactor N/C ratio is selected at 3.7 to maximize CO2 conversion with appropriate excess pressure to that of equilibrium. Resultantly, high CO2 conversion is achieved in the Reactor at relatively low temperature and pressure.

Optimum Process for The Revamping of Total Recycle Urea Process

ACES21® also can be applied for the revamping of the existing total recycle urea process. With its advantages of achieving 50% increase in production and 30% reduction in energy while maximizing the use of existing facilities, it is possible to provide an optimum scheme for plant owners who are considering upgrading existing facilities.

Revamping scheme for total recycle process by ACES21®

DP28W™ Corrosion-Resistant Material for Urea

The urea process is well known as one of the chemical processes handling highly corrosive fluids. TOYO is a pioneer to start the application of duplex stainless steel in the urea process since the 1970s. In 2004, TOYO and Sumitomo Metal Industries (now Nippon Steel Corporation) jointly developed a new duplex stainless steel DP28W™ having the following features.

  1. Excellent corrosion resistance
    Improve reliability and maintainability/Less maintenance costs/Prolong the service life of equipment and plants
  2. Excellent passivation property
    Less passivation air injection/Improve safety and operability
  3. High mechanical properties (high mechanical strength)
    Reduce thickness & weight of pressure parts/Improve heat transfer performance thanks to thinner tubes of high-pressure equipment

Operation Assisting Technologies

As a urea technology licensor, TOYO has leveraged advanced IOT technology or big data analysis to develop the system for Digital Transformation for Plant (DX-PLANT®) and launched its service for improving customers' profitability. TOYO also has developed its own operating training simulators to train operators effectively. The dynamic model is based on the static simulator and physical properties which are utilized for actual process design. Therefore, the dynamic model is able to realize and simulate precisely the same as the actual urea plant operating condition. TOYO’s operating training simulator is contributed to the skill-up of operators by training of start-up, normal operation, shut down and emergency shut down without actual operating plant.

What’s NEW, ACES21-LP®

We are pleased to announce the release of our innovative next-generation urea process, "ACES21-LP®". ACES21-LP® is the most advanced urea process which realizes the lowest synthesis pressure together with the highest CO2 conversion among any modern urea processes, maintaining salient features of current ACES21®. ACES21-LP®, thanks to the sophisticated combination of the excellent process concept of ACES21® and the state-of-the-art low-pressure urea synthesis technology, further reduces energy consumption by reducing power requirements in pressurizing raw materials and reduces plant cost by trimming weight of synthesis equipment, and contributes to low-cost production of urea and global environmental protection.

History in Lowering Urea Synthesis Pressure

Urea Process Related Catalogues

※ACES21® is a registered trademark of Toyo Engineering Co., Ltd. in Japan.
※DP28WTM is a trademark of Toyo Engineering Co., Ltd. and Nippon Steel Corporation.
※DX-PLANT® is a registered trademark of Toyo Engineering Co., Ltd. in Japan.
※TOYO does not produce urea in-house. Please note that TOYO is unable to respond to requests for business negotiations for supply of urea or sample provision of urea product.

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