Novel design and dynamic control of coal pyrolysis wastewater treatment process

The wastewater discharged by coal pyrolysis process contains ammonium, phenol and other organic compounds, which are harmful to the environment if not disposed properly. Phenol should be particularly removed because it accounts for 60-80% of organics in coal pyrolysis wastewater (CPW) and thus brings severe threaten to the human health. This paper proposes a novel generation and treatment integration system to dispose of such CPW. First, the source of CPW is simulated followed by its effect analysis on the quality of synthesis gas in coal chemical looping gasification (CLG) process with Aspen Plus software to verify the importance of CPW treatment. The simulation results show that the flow rate of phenol in CPW stream is 833 kg/h with a significant influence on the quality of synthesis gas. Second, the stable configuration and interaction energy between three extraction solvents including methyl propyl ketone (MPK), methanol, and synergistic extraction solvent of MPK and methanol with phenol molecule are studied by quantum mechanics. The interaction energy between the synergistic extraction solvent and phenol molecule is found equal to 67.7 kJ.mol(-1), higher than both 40.99 kJ.mol(-1) of MPK and 33.58 kJ.mol(-1) of methanol. Then the treatment process of CPW is comparatively simulated using the three extraction solvents. Results demonstrate that the synergistic extraction solvent behaves best for extracting organics of CPW, consistent with quantum mechanics results. Finally, one control scheme of CPW treatment is proposed and its anti-disturbance ability is verified with Aspen Dynamics software. Dynamic simulation results show that the control structure can promptly make the process back to steady state in the face of disturbance.