System and method for treating ammonia-nitrogen wastewater

[0069] Example 1

[0070] This embodiment provides an ammonia nitrogen wastewater treatment system. The schematic structural diagram of the ammonia nitrogen wastewater treatment system is as figure 1 As shown, it includes: a filter device 1, a preheating unit 2, a three-effect countercurrent evaporator, a gas-liquid separation unit and a concentrated liquid combustion unit.

[0071] The discharge port of the preheating unit 2 is connected with the feed port of the three-effect evaporator 51 in the three-effect countercurrent evaporator, and the condensate outlet of the three-effect evaporator 51 in the three-effect countercurrent evaporator is connected with the gas-liquid separation unit , The liquid outlet of the one-effect evaporator 31 in the three-effect countercurrent evaporator is connected to the concentrated liquid combustion unit through a jacketed pipe.

[0072] The concentrated liquid combustion unit includes a direct-fired furnace 81, a heat exchanger 82, an SCR reactor 83, a spray tower 84 and a chimney 85 which are connected in sequence. The liquid outlet of the one-effect evaporator 31 in the three-effect countercurrent evaporator is connected to the direct-fired furnace 81 in the concentrated liquid combustion unit through a jacketed pipe.

[0073] The preheating unit 2 is a shell-and-tube heat exchanger.

[0074] The one-effect preheater 32 of the three-effect counterflow evaporator is connected with an external heat source heating pipe, which is connected to the one-effect preheater 32 and then connected to the preheating unit 2, so that the external heat source is After the one-effect evaporator 31 provides heat, it then provides heat for the ammonia nitrogen wastewater, thereby improving the energy utilization rate.

[0075] The filtering device 1 is a precision filter with a filtering aperture of 0.5 mm or less.

[0076] The gas-liquid separation unit includes a condensate intermediate tank 71, a gas-liquid separation tank 72, and a vacuuming device connected in sequence. The heat source outlet pipes of the two-effect preheater 42 and the three-effect preheater 52 in the three-effect countercurrent evaporator are independently connected to the condensate intermediate tank 71; the condenser in the three-effect countercurrent evaporator 6 The liquid outlet is connected to the gas-liquid separation tank 72. The vacuum pump 9 is a vacuum pump 9 for pumping non-condensable gas in the gas-liquid separation tank 72.

[0077] The ammonia nitrogen wastewater is filtered in the filter device 1, and then flows into the preheating unit 2 for preheating. The preheated ammonia nitrogen wastewater flows into the three-effect countercurrent evaporation unit for evaporation and concentration, and the concentrated liquid flows into the concentrated liquid combustion unit for combustion and combustion. The latter gas undergoes exhaust gas treatment after heat exchange to reduce the nitrogen oxide content in the exhaust gas. The evaporative gas of multi-effect evaporation is condensed and separated from gas and liquid, and then the condensate is recovered, which realizes the resource utilization of ammonia nitrogen wastewater, and the energy consumption in the treatment process is low, and the pollutant removal rate is high.

[0078] The invention adopts a three-effect countercurrent evaporator to evaporate and concentrate the preheated ammonia nitrogen wastewater, wherein the gas phase and liquid phase materials flow countercurrently. The flow direction of the liquid phase is as follows: the preheated ammonia nitrogen wastewater first enters the three-effect evaporator 51, exchanges heat in the three-effect preheater 52, and enters the separation chamber of the three-effect evaporator 51 for gas-liquid separation; After being concentrated to a certain concentration in the effect evaporator 51, the three-effect transfer pump is sent to the two-effect evaporator 41 for evaporation and concentration; after the ammonia nitrogen wastewater is concentrated to a certain degree in the two-effect evaporator 41, the two-effect transfer pump It is sent to the one-effect evaporator 31 for evaporation and concentration, and after the concentration reaches the process requirements, it is transported to the direct-fired furnace 81 in the concentrated liquid combustion unit by the one-effect transfer pump.

[0079] The gas flow direction is: saturated steam enters the first-effect preheater 32 for heat exchange and condensation, and the condensate flows into the preheating unit 2 to preheat the ammonia nitrogen wastewater; the secondary steam generated by the first-effect evaporator 31 is used as the heat source of the second-effect preheater 42 , And condense in the two-effect preheater 42; the secondary steam produced by the two-effect evaporator 41 is used as the heat source of the three-effect preheater 52, and condensed in the three-effect preheater 52; The secondary steam is condensed in the condenser 6, and the condensate flows into the gas-liquid separation unit. Among them, the condensate of the two-effect preheater 42 and the three-effect preheater 52 flows into the condensate intermediate tank 71 and then flows into the gas-liquid separation tank 72; the condensate in the condenser 6 directly flows into the gas-liquid separation tank 72 and is used in the vacuum pump The non-condensable gas is recovered under the action of 9.