8  CHEMICAL WATER TREATMENT SYSTEM

Chemical water treatment system includes the following subsystem:

1)  Boiler make-up water treatment system

2)  Chemical dosing system

3)  Water & steam sampling and analyzing system

4)  Industrial waste water treatment system

5) Circulating-water dosing system

6)  Laboratory

The water to be treated is from river water. According to the demineralized water quality requirement of the plant, the water treatment system process will be as follows:

Water from water supply ® clarified water tank ® clarified water pump ®multimedium filter® activated carbon filter ® cation exchanger ® decarbonator ®intermediate water tank ® intermediate water pump ® anion exchanger ® mixed-bed exchanger ® demineralized water tank ® demineralized water pump ® plant user

According to the total loss of the plant, the capacity of the water treatment system is 20t/h, adding to the self-used water, the capacity of the water treatment equipment is 22t/h.

The demineralized water at the outlet of the mixed bed will conform at all times as follows:

Conductivity (at 25^°C) �.2ms/cm

Silica                 â‰?0μg/L

In order to maintain the pH value and protect the feed-water pipe and equipment from corroding, the design proposes a set of ammonia dosing device including two(2) tanks and two(2) metering pumps for feed water.

In order to remove the oxygen within the feedwater, hydrazine as oxygen scavenger is fed continuously into boiler feedwater line. The hydrazine dosing device including two(2) tanks and two(2) metering pumps.

A phosphate dosing system including two(2) tanks and two(2) metering pumps will be designed to protect the boiler from scaling and corroding.

In order to monitor quality of water and steam cycle and ensure safety operation of unit, each unit will set one (1) water & steam sampling and analyzing device. Water and steam sampling and analyzing system includes high-temperature cooling rack and low-temperature instrument panel.

The regeneration waste of the water treatment plant, and acid washing, the cleaning water of air pre-heater etc., are drained to neutralized water basin .The waste water will be discharged when pH reaching 6~9 after neutralizing treatment .

8.5.1              The Killing Biology System

For prevent the microorganism growth in the circulating water system, one set of circulating-water killing biology system will be provided. The Main Equipment: Two (2) chemical solution tanks, Two (2) dosing pumps. The Equipment is in the circulating-water dosing room.

8.5.2              Inhibitor dosing system

One set of circulating-water inhibitor dosing system will be provided. The Main Equipment: Two (2) chemical solution tanks, Two (2) dosing pumps. The Equipment is in the circulating-water dosing room.

One set of instrument and equipment for chemical laboratory will be provided for the water, and coal analyzing.