Method and system for preparing compound fertilizer and sodium carbonate from fly ash

The invention discloses a method and a system for preparing a compound fertilizer and sodium carbonate from fly ash, and belongs to the technical field of chemical metallurgy, wherein the method comprises the steps: uniformly mixing collected salt-containing fly ash in steel mill production with water in proportion, and stirring and leaching to obtain a first filtrate and iron-containing slag; purifying the first filtrate with a sodium carbonate solution, and evaporating, concentrating and filtering to obtain a second filtrate and potassium chloride; adjusting the pH value of the second filtrate with ammonia water, introducing CO2, and filtering to obtain a third filtrate and sodium bicarbonate; evaporating the third filtrate to dryness to obtain a compound fertilizer containing potassiumchloride and ammonium chloride; and crushing and calcining the sodium bicarbonate to obtain sodium carbonate. According to the method, salt can be removed by water leaching; the iron-containing slag is sintered and recycled,