Experiment Research And Process Design For Acrylic Wastewater Treatment

Acrylic acid chemical industry has been rapidly developed and in recent years. The wastewater during its production process contains mainly acrylic acid, acetic acid, methanesulfonic acid, acetaldehyde, some of aromatic compounds and inorganic salts. The chemical oxygen demand (COD) of the wastewater is up to 104-105 mg/L. Therefore, the wastewater could be regarded as a kind of high concentration organic wastewater, which is toxic and contains high concentrations of complex components. It would cause great environmental harm, unless it is properly treated.In this thesis, firstly an experimental study of wet air oxidation was carried out. The effect of reaction temperature, oxygen partial pressure, organic matter concentration and sulfate catalyst on the COD removal and on the improvement of biodegradability was investigated. The results show that the best reaction conditions of wet air oxidation process is: reaction temperature 250℃, initial oxygen partial pressure 3.5MPa, reaction time 2h, diluted times 0.5 (COD of about 100000 mg/L). The COD removal rate is up to 56% and biodegradability B/C value increase from 0.13 to 0.63. The presence of CuSO4 can effectively improve the COD removal, but have some impact on the subsequent biochemical reactions.At the same time, the concentration and dry experimental study was carried out and mainly focused on the pretreatment of wastewater and acrylic vacuum evaporation process such as acrylic polymer, boiling point rise, the effluent COD changes, and studied the effect of hydroquinone on the role of acrylic acid polymerization. The method of using wastewater coagulation pretreatment can effectively remove the resin and part of the aging colloidal organic matter, but have little effect on COD removal. The hydroquinone inhibitor can effectively prevent the polymerization of acrylic and slow increase of boiling point, reduce the viscosity of concentrated liquid, and the dosage of 0.1% is appropriate. The pH value of wastewater directly determines the COD of evaporation condensate. When it was evaporated under acidic conditions, COD removal rate was only 17.5%, and evaporated under alkaline conditions, the COD removal efficiency was 98.8%.On the basis of experimental study, the process design and program comparison was carried out for 150t/d acrylic resin production wastewater of a chemical plant in Jiangsu. After comprehensive consideration, the concentration and drying method was chosen as the wastewater treatment process and four-effect evaporator and drum scraper dryer was selected as major equipment units. Operating cost analysis showed that treatment costs is about 76.96 Yuan/m~3, and the cost of the current burning process is about 400 Yuan/m~3. If considering the recycling of drying waste (calorific value of standard coal equivalent) and steam condensate, a profit of approximately 5 Yuan/m~3 can be gained and the consumer type treatment is changed to be resource recovery with small surplus.