PAS „Daugavpils siltumtikli“

Daugavpils, Latvia

2022

Vacuum deaeration system 10 m³  

Main technical requirements for the system:

• Vacuum deaerator performance – 10 m³/h
• Deaerator working range – from 2 m³/h to 10 m³/h
• Initial concentration of dissolved oxygen in water – 2700 µg/l
• Initial condensate parameters: flow 2.5-3 m³/h, pH 4, temperature 43-48°С
• The concentration of oxygen dissolved in water after the deaerator is no more than 45 µg/l
• For water heating before the deaerator is used water with a temperature of 80 to 95°С (water is supplied from the recirculation system of the gas boiler)
• Use the existing atmospheric deaerator storage tank
• Ensure operation of the deaerator with zero discharge of cooling water from vacuum pumps into the sewer

Results:

When water temperature before the deaerator is 70-75°С, dissolved oxygen in the water after the deaerator is 25-45 µg/l; pH=7-7.5 (without adding NaOH to the condensate).

The customer wanted the pH of the make-up water to be at least 8.5, so we switched on NaOH deaeration and neutralized the condensate before the deaerator to pH=6. Since the condensing economizer (designed and supplied by UAB "Gandras energoefektas" UAB) not only increases the overall efficiency of the boiler to 105-107%, but also reduces NOx emissions from 100 to 47 mg/Nm³, we assumed that nitrogen, which the vacuum deaerator was unable to neutralizme, was also involved in addition to dissolved carbonic acid.

Conclusions:

• Prior to the installation of the vacuum deaerator, the customer used a chemical reagent - an oxygen suppressor, which cost four times more expensive than the operation of the vacuum deaerator.
• Before installing the vacuum deaerator, the customer used twice as much NaOH to neutralize the condensate from pH=4 to pH=8.5 (after installing the deaerator, it is necessary to neutralize from pH=4 to pH=6).
• During the implementation of this project, it was necessary to change the pipeline before the make-up pumps, because the atmospheric deaerator has excess pressure, and the vacuum one has a vacuum of up to 0.3 bar(a).
• The scheme proposed by UAB "Gandras energoefektas" allowed to fulfill all the customer's technical requirements.