Method and system for zero discharge treatment of desulfurization wastewater suitable for multiple working conditions

A method for zero discharge treatment of desulfurization wastewater suitable for multiple working conditions, comprising the following steps:

• high-temperature flue gas generated by a boiler (1) passing through an economizer (2) and an air preheater (3) for heat recovery, then entering a dust collector (4) for dust removal, then entering a desulfurization absorption tower (6) to remove acidic pollutants, and finally being discharged through a chimney (7);
• gypsum slurry generated by the desulfurization absorption tower (6) entering a gypsum cyclone (9) for separation, wherein the separated overflow slurry enters a filtrate water tank (13), and the separated underflow slurry enters a gypsum dehydrator (10) for dehydration;
• the water in the slurry in the gypsum dehydrator (10) entering a gas-liquid separation tank (11) for gas-liquid separation after being filtered by a filter cloth of the dehydrator, and wherein the separated drainage water enters a wastewater collection tank (15);
• when a concentration of HCl in the flue gas is less than a preset HCl concentration value, a required amount of desulfurization wastewater is small, and when an amount of the drainage water currently output by the gas-liquid separation tank (11) is greater than the amount of the desulfurization wastewater required to be discharged, the drainage water collected by the wastewater collection tank (15) is divided into two paths one of which passes through the filtrate water tank (13) and enters the desulfurization absorption tower (6), and the other is fed into a wastewater drying tower (27) through a spray water tank (25);
• at the same time, the high-temperature flue gas is pumped through a flue gas port and fed into the wastewater drying tower (27), and the drainage water in the wastewater drying tower (27) is evaporated by the high-temperature flue gas so that the water in the drainage water evaporates into the flue gas, and the flue gas output from the wastewater drying tower (27) enters the dust collector (4) for dust removal;
• when the concentration of HCl in the flue gas is greater than or equal to the preset HCl concentration value, and a concentration ratio of SO2 to HCl in the flue gas is greater than or equal to a preset ratio, the amount of the desulfurization wastewater required to be discharged and the amount of the produced gypsum slurry are relatively large, and when the amount of the drainage water currently output by the gas-liquid separation tank (11) is greater than or equal to the amount of the desulfurization wastewater required to be discharged, part of the drainage water in the wastewater collection tank (15) is fed into the wastewater concentration tower (18), and the remaining wastewater in the wastewater collection tank (15) is fed into the filtrate water tank (13) and then into the desulfurization absorption tower (6);
• at the same time, a path of the flue gas output from the dust collector (4) is led out and fed into the wastewater concentration tower (18) for countercurrent contact with the desulfurization wastewater in the wastewater concentration tower (18), so that the desulfurization wastewater in the wastewater concentration tower (18) is reduced and solid content thereof is increased;
• the flue gas in the wastewater concentration tower (18) entering the desulfurization absorption tower (6) after being treated by a mist eliminator (19), and the slurry at the bottom of the wastewater concentration tower (18) entering a thick slurry tank (22), the slurry in the thick slurry tank (22) entering the spray water tank (25) after being clarified by a clarifier (24) and then entering the wastewater drying tower (27) for evaporation and drying treatment;
• and
• when the concentration of HCl in the flue gas is greater than or equal to the preset HCl concentration value, and the concentration ratio of SO2 to HCl in the flue gas is less than the preset ratio, the amount of the desulfurization wastewater to be discharged is large, and when the amount of the drainage water output from the gas-liquid separation tank (11) is less than the amount of the desulfurization wastewater to be discharged, all the drainage water in the wastewater collection tank (15) is transported to the wastewater concentration tower (18), and then part of the slurry in the filtrate water tank (13) is fed into the thick slurry tank (20);
• the two parts of the slurry are evaporated, reduced and concentrated in the wastewater concentration tower (18), and then enter the clarifier (24);
• the supernatant in the clarifier (24) enters the spray water tank (25), and then is fed into the wastewater drying tower (27) for evaporation.