Process design and optimization of green processes for the production of hydrogen and urea from glycerol

To address the production of hydrogen and urea from glycerol, a green process of a glycerol-to-green chemicals chain (GTGC) named Scheme-1 is presented, where the glycerol is a green feedstock from the production of biodiesel and the carbon capture and utilization (CCU) is involved to reuse captured carbon. The major processes in the GTGC include that (i) the glycerol steam reforming (GSR), the water gas shift reactor, and the ammonia synthesis reactor are integrated to enhance the yields of hydrogen and ammonia, (ii) the pressure swing adsorption (PSA) is added to capture CO₂ and produce the high-purity hydrogen, and (iii) CO₂ is converted into urea by means of the urea synthesis reactor. The optimal operating conditions of GSR such as glycerol (GLY) conversion and cold gas efficiency are determined by using the response surface methodology. To address the lower CO₂ emissions of GTGC, the heat integration of GTGC named Scheme-2 and the heat integration/combined cycle power generation of GTGC named Scheme-3 are proposed. For the comparisons of total CO₂ emissions of the three schemes, Scheme-2 is lower than other schemes due to using the heat integration method for reducing hot/cold utilities. For the comparisons of net CO₂ emissions of the three schemes, Scheme-3 is superior to other schemes due to no use of external utilities.