(23c) Ammonia Manufacturing Box: Small Ammonia Plant Design Using Micro Processing Technology and Process Intensification Technology

Small Ammonia Plant Design using Micro Processing Technology and Process Intensification Technology

By: Richard B. Strait, Adjunct Professor, Rice University, Department of Chemical and Biomolecular Engineering, Houston, Texas

The small self-contained ammonia manufacturing box (AMB) came out of the need for farmers in remote locations containing modest amounts of natural gas and water to produce enough fertilizer for their local needs.

Presently ammonia plants are getting larger and larger. The future however, is to make small highly automated plants that are portable, use readily available inputs and produce the products where they are needed. To this end the new small scale plant will include all the latest leading edge technologies that apply such as Micro Processing Technology (MPT), Process Intensification (PI) and automated safety systems. The ammonia plant of the future is contained on one rail car, shop fabricated and contains all the latest technology.

Recent developments in micro reactor designs are applied to the ammonia plant reactions; with special attention to: A) steam methane reforming, B) water gas shift and C) ammonia synthesis.

1. Steam methane reforming occurs at high temperatures, is endothermic and an equilibrium reaction. Alternatives are evaluated including: 1) electric reformer, 2) fired heater reformer and 3) auto thermal reformer.
2. Water gas shift occurs at high temperatures with one catalyst for optimum rate and at lower temperatures with a different catalyst to reach a more complete conversion for this endothermic equilibrium reaction. Alternatives are evaluated including: 1) two shift reactors with precise temperature control along the flow path and 2) one reactor with a changing catalyst formulation along the reactor tube length.
3. Ammonia synthesis occurs at high pressures and high temperatures, is exothermic and an equilibrium reaction. Alternatives are evaluated including: 1) precise reactor temperature control following the equilibrium curve and 2) micro channel liquid separation of product ammonia.

Process intensification is applied to CO2 removal, compression, refrigeration and heat integration as well as alternative energy sources.

Safety, operability and maintenance are improved over the traditional stick built plant and these important issues are addressed.

R. B. Strait

October 24, 2018