Research On Key Process Technology Of Coal Chemical Wastewater And Optimization Of Water System Integration

Coal chemical industry is characterized by massive water consumption and wastewater emission while coal and water resource in China is marked as “inverse distribution” with each other.Therefore water-saving and emission reduction is an important research subject in coal chemical industry development.In this thesis,it takes key technology of coal chemical wastewater treatment and integration optimization of its water system as research object.The research mainly aims at enhancing the efficiency of coal chemical wastewater treatment and its reuse and thereafter to achieve the water-saving and emission reduction goal for the whole industry water system.In this thesis,it proposes a novel water pinch design method that is used to optimize coal chemical plant water system.This method can quickly and accurately determine water pinch point and how much the wastewater is recycled.Then analyze water user unit and manage the water flows in the system to finally optimize water system.The thesis takes a coal-to-methanol plant water system optimization as an example to verify this method.After optimization,it saved 60m3/h feed water and reduced wastewater emission by 60m3/h.For advanced wastewater treatment,it takes impregnation-deposition phase inversion method to prepare active carbon catalysts that are used to treat wastewater via catalysis ozone oxidation.By experimental optimization,catalyst with a load of 5% active component Fe-Cu-Mn shows excellent catalysis performance,good stability and low cost.The ozone that was vented into wastewater has an efficiency of 59.72%.Results from scaled tests show the average treatment load in one ozone catalysis fixed bed reactor is 0.032 kg COD/kg(catalyst)·d with 20~30mg ozone per liter wastewater.Two reactor in tandem can make sure the effluent COD lower than 100mg/L.The catalyst activity in such scenario should be regenerated by a period of 30 to 38 days and the catalysts suffer a loss of 3.25% for very time shift regeneration.Then by induction crystallization,desalt the effluent water after ozone catalysis oxidation with the precipitated crystalized particles of 0.5~1mm diameter.After softening the salt water via crystallization reactor designed in this thesis,Ca,Mg,Si removal is up to 90% and the purity of CaCO3 and MgOH recycled is up to 95% and 87% respectively,which is available to be reused.In this thesis,it develops two novel kinds of biofilm carrier,biofilm contact oxidation reactor and activated sludge reactor,which are applied in biological treatment for wastewater with low and high concentration and get excellent performance.The effluent’s index can be ensured by OAO biological process and COD and NH4-N removal is 85% and 95% respectively.For low concentration coal chemical wastewater,treatment via biofilm contact oxidation and thereafter secondary activated sludge is of high efficiency and stability,and to some extent,the investment and OM cost is competitive.