Two Methods of Boiler Blowdown

July 27, 2020

Two Methods of Boiler Blowdown

1. Continuous blowdown

Purpose:

Continuous blowdown can remove part of the salt dissolved in the boiler water. To control a suitable amount of salt and alkalinity in the boiler water. Prevent excessive concentration from affecting the quality of boiler steam.

The installation location of the blowdown hole:

Generally, the blowdown outlet for continuous blowdown is installed at 200-300mm below the normal water level of the boiler drum. The boiler water is continuously heated and concentrated so that the salt is collected on the surface of the boiler water. The blowdown outlet is installed in the boiler water. The continuous blowdown outlet is installed at the place with the highest salt content in the boiler water to discharge high-concentration saltwater for new water supply treatment.

Discharge Time:

continuous Blowdown

Blowdown Rate:

generally about 1% of boiler capacity.

Blowdown Location:

1. Direct Blowdown.

2. Blowdown through the blowdown expansion vessel.

Sewage is generally led to the continuous blowdown expansion vessel from the steam drum. The sewage from the boiler is saturated water produced under the working pressure of the boiler, and the temperature is relatively high. If the pressure is suddenly reduced, the boiling point of the water will also decrease. The original water that may need 150℃ to gasify, only 100℃ is enough gasification. Recycling the generated water vapor can have an energy-saving effect.

2. Regular Blowdown

Purpose:

Regular boiler blowdown is mainly to remove flocculent sediments such as rust slag and unsalted calcium and magnesium in the boiler drum. Reduce its adhesion to the boiler wall and improve the thermal efficiency of the boiler. It is generally intermittent, also known as intermittent blowdown or bottom blowdown.

Installation location:

The nozzle for regular blowdown is generally located at the lowest point of water circulation in the boiler.

Blowdown time:

The period of regular blowdown is intermittent, and the discharge is generally selected when the boiler load is low. The discharge volume of regular blowdown is large, and the discharge goal can be achieved by only performing sewage discharge for a short time: the time is generally 0.5-1 minutes (specifically determined by the boiler water quality). A long period of regular blowdown should be avoided so as not to affect the normal circulation of water in the boiler.

Blowdown Rate:

Generally 0.1%-0.5% of boiler evaporation.

Blowdown location:

1. Direct Blowdown

2. Blowdown through the blowdown expansion vessel.

water lead from the blowdown hole to the blowdown expansion vessel. After decompression and expansion, the secondary steam and waste hot water are separated. The secondary steam is discharged into the atmosphere or used as a heat source, and the waste hot water is generally discharged into the sewage system through the sewage cooling tank.

Blowdown rate = continuous blowdown flow during calculation period (t) / actual boiler evaporation during calculation period (t) * 100%

Boiler blowdown is an operation that must be carried out during the use of steam boilers. The correct blowdown method can improve the quality of steam and stabilize the steam supply. Improve the quality of your products.

Hope this article can bring you more help.