DEAERATOR VENT STEAM HEAT RECOVERY

The amount of steam / air mixture that needs to be released can be estimated by considering the effects of Dalton's Law of partial pressures and Henry's Law.

Consider the feasibility of installing a deaerator. Prior to installation, the boiler plant is fed by feedwater from a vented feedtank operating at 80°C. This essentially means that each 1 000 kg of feedwater contains 5 gram of air. The proposed deaerator will operate at a pressure of 0.2 bar g, which corresponds to a saturation temperature of 105°C. Assume, therefore, that all the air will be driven from the water in the deaerator. It follows that the vent must reject 5.9 gram of air per 1 000 kg of feedwater ca

The proposed deaerator will operate at a pressure of 2.75 bar g, which corresponds to a saturation temperature of 140°C. Assume, therefore, that all the air will be driven from the water in the deaerator. It follows that the vent must reject 5.9 gram of air per 1 000 kg of feedwater capacity.

Total pressure in the deaerator 3.6 bar a

Temperature of the vapour in the deaerator 130 deg C

130°C corresponds to a saturation pressure 2.73 bar a

Therefore, from Dalton's Law:-

The partial pressure caused by the non-condensable gases (air) is therefore the difference between these two figures =

The proportion to volume of air to steam in the mixture

Therfore every litre of released air acompanied by

The density of air at 130 deg C

The density of steam at 130 deg C

Therefore 0.862 grams of air release with

and, 5.9 grams of air is released with

Therfore the total mixture of air and steam released per 5.9 g of air can be calculated.5.9 g + 7.94581166493319 g =13.8458116649332 grams of air/steam mixture per 1000 kg of deaerator capacity

Although the theory suggests that 22.4 grams of steam/air mixture per tonne of deaerator capacity is required, in practice this is impossible to monitor or regulate successfully.

Therefore, based on practical experience, deaerator manufacturers will tend to recommend a venting rate of between 0.5 and 2 kg of steam/air mixture per 1 000 kg / h of deaerator capacity to be on the safe side. It is suggested that the deaerator manufacturer's advice be taken on this issue.

The practical total vent air and steam mixture is (Both HRSG's and Export in full load)

Heat loss

By dirct mixing heat exchanger the heat recovery is more than 90%

The cost of fuel saving per year in terns of IFO (Assuming Boiler eff 90% and IFO calorific value 10000kcal)

If the vapour space in the deaerator were filled with pure steam, the vapour pressure would be3.6bar a. As the vapour space has an actual temperature of130°C, the partial pressure caused by the steam is only2.73 bar a. 

Cost saving

Approx cost of heat recovery equipment

Payback period

DEAERATOR VENT STEAM HEAT RECOVERY

The amount of steam / air mixture that needs to be released can be estimated by considering the effects of Dalton's Law of partial pressures and Henry's Law.

Consider the feasibility of installing a deaerator. Prior to installation, the boiler plant is fed by feedwater from a vented feedtank operating at 80°C. This essentially means that each 1 000 kg of feedwater contains 5 gram of air. The proposed deaerator will operate at a pressure of 0.2 bar g, which corresponds to a saturation temperature of 105°C. Assume, therefore, that all the air will be driven from the water in the deaerator. It follows that the vent must reject 5.9 gram of air per 1 000 kg of feedwater ca

The proposed deaerator will operate at a pressure of 2.75 bar g, which corresponds to a saturation temperature of 140°C. Assume, therefore, that all the air will be driven from the water in the deaerator. It follows that the vent must reject 5.9 gram of air per 1 000 kg of feedwater capacity.

The partial pressure caused by the non-condensable gases (air) is therefore the difference between these two figures = 0.87 bar a

32%

2.137931 litres of steam

0.862 grams/L

0.543 grams/L

1.160897 g of steam

7.945812 g of steam

5.9 g + 7.94581166493319 g =13.8458116649332 grams of air/steam mixture per 1000 kg of deaerator capacity

Although the theory suggests that 22.4 grams of steam/air mixture per tonne of deaerator capacity is required, in practice this is impossible to monitor or regulate successfully.

Therefore, based on practical experience, deaerator manufacturers will tend to recommend a venting rate of between 0.5 and 2 kg of steam/air mixture per 1 000 kg / h of deaerator capacity to be on the safe side. It is suggested that the deaerator manufacturer's advice be taken on this issue.

The practical total vent air and steam mixture is (Both HRSG's and Export in full load) 300 Kg/hr

640.1914 Kcal/hr

576.1722 Kcal/hr

The cost of fuel saving per year in terns of IFO (Assuming Boiler eff 90% and IFO calorific value 10000kcal) 507.0316 Kg

If the vapour space in the deaerator were filled with pure steam, the vapour pressure would be3.6bar a. As the vapour space has an actual temperature of130°C, the partial pressure caused by the steam is only2.73 bar a. 

17746.11 Per year

25000

1.40876 Years

Consider the feasibility of installing a deaerator. Prior to installation, the boiler plant is fed by feedwater from a vented feedtank operating at 80°C. This essentially means that each 1 000 kg of feedwater contains 5 gram of air. The proposed deaerator will operate at a pressure of 0.2 bar g, which corresponds to a saturation temperature of 105°C. Assume, therefore, that all the air will be driven from the water in the deaerator. It follows that the vent must reject 5.9 gram of air per 1 000 kg of feedwater ca

The proposed deaerator will operate at a pressure of 2.75 bar g, which corresponds to a saturation temperature of 140°C. Assume, therefore, that all the air will be driven from the water in the deaerator. It follows that the vent must reject 5.9 gram of air per 1 000 kg of feedwater capacity.

Therefore, based on practical experience, deaerator manufacturers will tend to recommend a venting rate of between 0.5 and 2 kg of steam/air mixture per 1 000 kg / h of deaerator capacity to be on the safe side. It is suggested that the deaerator manufacturer's advice be taken on this issue.

Consider the feasibility of installing a deaerator. Prior to installation, the boiler plant is fed by feedwater from a vented feedtank operating at 80°C. This essentially means that each 1 000 kg of feedwater contains 5 gram of air. The proposed deaerator will operate at a pressure of 0.2 bar g, which corresponds to a saturation temperature of 105°C. Assume, therefore, that all the air will be driven from the water in the deaerator. It follows that the vent must reject 5.9 gram of air per 1 000 kg of feedwater ca

Consider the feasibility of installing a deaerator. Prior to installation, the boiler plant is fed by feedwater from a vented feedtank operating at 80°C. This essentially means that each 1 000 kg of feedwater contains 5 gram of air. The proposed deaerator will operate at a pressure of 0.2 bar g, which corresponds to a saturation temperature of 105°C. Assume, therefore, that all the air will be driven from the water in the deaerator. It follows that the vent must reject 5.9 gram of air per 1 000 kg of feedwater ca