Date of Award

1-1-2012

Document Type

Campus Access Dissertation

Department

Chemical Engineering

First Advisor

James A Ritter

Abstract

Ammonia has long been an essential raw material for manufacture of chemical compounds of vital importance. Recent DOE-EERE-ITP Chemicals Subprogram studies have consistently ranked ethylene and ammonia as the top two most energy intensive processes. Ammonia production consumes a total energy of 750 Trillion BTU. New innovative methods are needed to address and improve (the chemistry and separation methods of) older processes that are not energy efficient. The goal of this dissertation is to design, develop and demonstrate a technically feasible and commercially viable system to produce ammonia along with recovery of the products by adsorption separation method and significantly decrease the energy requirement in ammonia production.

Pressure swing adsorption (PSA) technology enables the energy-efficient recovery of specific compounds from a gas under pressure. In this study, an ammonia production process that incorporates PSA technology for the recovery of ammonia from reactor-off gas is developed. Conventionally, ammonia is recovered via energy-intensive refrigeration and condensation from the reactor-off gas. The new approach is expected to increase ammonia yield and reduce natural gas feedstock and fuel consumption. The improved ammonia process will find application in the U.S. chemical industry, which produced 23.7 billion pounds of ammonia in 2004.

The presentation will discuss many of the key results and findings. In particular it will focus on an in-depth bench scale experiments and analysis on adsorbent(s) performance and stability at similar temperature conditions for the ammonia recovery section. Experimental cyclic steady state PSA results using different cycles from a full functional 4-bed PSA system will be provided along with the model prediction. The construction of such a complete and functional PSA system for ammonia recovery is important to enable successful commencement of further studies for model validation, experimental data gathering and process optimization for the prototype design and scale up operation. A parametric study will also be presented using an in-house developed PSA simulator to evaluate the effects of various parameters on the cyclic steady state PSA performance. Finally, the presentation will showcase an adsorption enhanced catalytic hybrid process via simulation that justifies the development of a proprietary ammonia synthesis reactor in order to operate together with PSA process to produce purified ammonia out of nitrogen and hydrogen.

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