Chemical pure ammonia water preparation system and method

The invention relates to a chemical pure ammonia water preparation system and method. The system comprises a liquid ammonia gasifier, an ammonia gas buffer tank, a purifying slot A, a purifying slot B, an absorbing slot A, an absorbing slot B, an ammonia water pump, circulating water cooling equipment and a DCS control system. The method comprises the following steps: a first step of preparing a 3% potassium permanganate solution and a 2.5% barium hydroxide solution, and respectively adding the 3% potassium permanganate solution and the 2.5% barium hydroxide solution into the purifying slot Aand the purifying slot B through a solution adding valve A and a solution adding valve B; a second step of opening circulating water pipeline valves I and J, and starting circulating water equipment;and a third step of opening a deionized water pipeline pneumatic pressure-regulating valve and a valve C to add deionized water into the absorbing slot A, and then, switching off the pneumatic pressure-regulating valve and the