Ammonia production by Haber-Bosch process:

Haber Bosch Ammonia production Flowsheet

The Haber-Bosch process, developed in 1913, was a groundbreaking method for large-scale ammonia production. Initially, the process utilized coke oven gas, a byproduct of coal coking, as its primary feedstock. The coke, rich in carbon and hydrogen, was gasified to produce a mixture of carbon dioxide, carbon monoxide, and hydrogen-rich gas. To purify the gas, carbon dioxide was scrubbed out, and the remaining carbon monoxide was removed using an ammoniacal cuprous solution in the scrubber. This yielded a water gas rich in hydrogen. The reaction mixture, comprising nitrogen and hydrogen, was then fed into the synthesis loop. However, this 1913-based design has become less economical in recent times. The shift conversion of CO and CO2 requires larger facilities and operating equipment for water gas, making the process less efficient and more costly. As a result, more modern and efficient methods have been developed to replace this outdated design.

The Haber-Bosch Process Steps

1. Ammonia Production,  The water gas generator produces water gas from coke using high-pressure air and steam. The resulting gas mixture, containing CO, CO2, N2, and H2, is then cooled and scrubbed to remove dust particles.
2. Gasholders ensure a continuous supply of gas and collect residual liquids and condensed particles for drainage.
3. In the shift reactor, carbon monoxide is converted to carbon dioxide and hydrogen by reacting with steam over a catalyst.
4. The gas mixture is then compressed and sent to the carbon dioxide purifier for removal of the CO2 fraction.
5. In the ammonia converter, a packed bed of catalyst converts the synthesis gas into ammonia gas. The product mixture is then fed to the ammonia absorber, where water is added from the top of the column.
6. The resulting ammonia water is cooled by the water cooler and stored. Unreacted gas is recirculated to achieve high conversion rates.

Haber-Bosch Process Conditions in the Converter: 

• Pressure: 330 atm
• Temperature: 500-550°C
• Conversion: 10-30%

Bridging to Emerging Technologies:

• Hybrid Approaches: Combining Haber-Bosch with emerging technologies can be a stepping stone towards more sustainable ammonia production. For example, using renewable energy to produce hydrogen for the Haber-Bosch process can reduce reliance on fossil fuels.
• Modularization: Developing smaller, modular Haber-Bosch units can be more suitable for integration with distributed renewable energy sources and can also be used for on-site ammonia production, reducing transportation costs.
• Gradual Transition: Instead of completely replacing Haber-Bosch, a gradual transition by incorporating elements of emerging technologies can be a more practical approach. This could involve using advanced catalysts developed for electrochemical synthesis in Haber-Bosch plants or adapting existing plants to utilize hydrogen from green sources.

Modifications and Upgrades: Project Ideas 

• Ammonia Separation: Improving the efficiency of ammonia separation from the reactor effluent can reduce energy consumption and improve overall process efficiency. Techniques like absorption or membrane separation can be explored.
• Hydrogen Production: Exploring more sustainable hydrogen production methods, such as electrolysis powered by renewable energy or biomass gasification, can reduce the reliance on fossil fuels for hydrogen feedstock.
• Waste Heat Utilization: Recovering and utilizing waste heat from the Haber-Bosch process can improve energy efficiency and reduce overall energy demand.