As the market grows, more and more high-end will build their own laundry room, laundry room dryers, ironing machines and other facilities need to provide a lot of steam.

Steam will form condensate during use, and there is a large amount of heat in condensation. In the actual design process, waste heat recovery or overall recovery can be used for condensate, which accounts for 75% of the total steam energy. If condensate is not recovered and discharged directly, it needs to be cooled down by make-up water to meet the discharge requirements.

By recycling condensate, water costs can be effectively saved and water resources can be substantially conserved. The economic benefits of condensate recovery technology are remarkable, but in actual projects, most of them are not well recycled, and many more are discharged directly without any utilization. EPCB boiler combine actual cases to explain in depth the necessity of steam condensate recycling from the technical, economic and environmental perspectives.

Condensate Recovery Method and Principle

In recent years, many large laundries have attached great importance to steam condensate recovery, but how to choose the condensate recovery method, but also based on the principle of boiler steam condensate recovery to choose. According to whether the condensate recovery system is connected to the atmosphere, it can be divided into two systems: open and closed.

1.Open recovery system

Open recovery is the more conventional method of condensate recovery, which recovers steam condensate by feeding it into an open, atmosphere-connected water collection tank , a method in which about half of the heat of condensate is lost in the atmosphere. In addition, using an open condensate tank system to recover condensate, the steam generated by the boiler condenses into high-temperature water, which causes system corrosion, unqualified condensate water quality, pump cavitation and incomplete recovery of secondary steam and other technical problems that cannot be solved. Due to the increase in boiler fuel and soft water consumption, a large amount of energy and water resources are wasted, resulting in increased operating costs of boiler equipment.

2. Closed recovery system

The closed recovery system is a closed steam condensate recovery system consisting of a boiler conveying steam - steam-using equipment - hydrophobic piping network - water collection tank - feed pump anti-cavitation device - deaerator (or boiler steam package). The closed recovery system can effectively reduce heat loss by using a closed system to recover condensate as close as possible to the saturated water temperature at the pressure of the steam used, with the condensate not coming into contact with air and the collection tank and piping equipment all at constant pressure, so that the heat of steam is effectively used and heat loss and heat medium loss are reduced.

Compared with the open recovery method, the closed recovery substantially reduces the fuel consumption of the boiler and has the advantages of saving water resources, reducing the boiler discharge rate and shortening the boiler operation time, thus reducing the consumption of water and electricity for equipment operation and having an environmental effect.

3. Open versus closed benefits

As can be seen from the above, closed recovery systems are more in line with the current trend of energy conservation and environmental protection than open recovery systems, and are more practical in terms of utility. However, compared with the advantages of simple equipment, easy operation and low investment of open system, the equipment and piping of closed recovery system are relatively complex, with high operational requirements and large investment. Therefore, when choosing the steam condensate recovery method, we must analyze the energy consumption and energy saving potential, and choose the best solution according to the actual situation to ensure the balance between investment and output benefits.

Analysis of Steam Condensate Recycling in a Laundry Room

1. Project Overview

The laundry is equipped with two steam boilers, 1.5 t/h each, one for use and one for backup.

Both the laundry room and the steam heat exchanger room are located on the first basement level. After one year of operation, the operator has repeatedly suggested that the condensate discharge method of the laundry room is unreasonable.

The condensate is not recycled, but is discharged directly after mixing with cold water through the drainage cooling tank. This not only wasted heat and water resources, but also made the internal environment of the plant room foggy due to the long-term discharge of hot water with steam, which affected the safe use of the plant room. Due to the cost of renovation and the difficulty of renovation, the processing of this problem has been delayed time and again.

2. Energy consumption analysis before retrofitting

The steam line is sent to the laundry room after passing through the sub-cylinder. The condensate return pipe of the whole system is divided into three ways in total, and is mixed with cold water and discharged directly after gathering at the drainage cooling tank.

First, the current energy consumption of the system is analyzed and calculated, mainly calculating the water consumption and natural gas consumption. The water resources are calculated based on the condensate flow rate, which results in the mixed chilled water flow rate and the total discharge volume. The natural gas consumption is based on the condensate flow rate and temperature difference to derive the hourly energy consumption, which converts to the gas consumption.

Based on the original design and site conditions, the following base condition data were obtained:

(a) Steam actual operating capacity 1000 kg/h, supply pressure 1.0 MPa.

(b) The condensate recovery piping is divided into three ways, DN25, DN50 and DN32 respectively.

(c) The initial and end pressure difference between condensate 0.7 MPa.

(d) the average temperature of condensate is 80℃ (before mixing), the average temperature of tap water is 18℃ (calculated according to the average temperature of the year), and the discharge temperature after mixing is (measured on site) 45℃.

3. Retrofit program and cost input

This retrofit uses a closed condensate recovery scheme.

The original design condensate return pipeline of this project used stainless steel pipes, therefore, the pipeline, equipment and water tank of this recycling system are made of stainless steel to ensure the water quality of condensate, and the recovered condensate can be directly utilized without additional water treatment. The condensate is collected in the water tank and transported to the steam boiler soft water tank through the water pump, which is used as make-up water for the steam boiler, and the recovered heat and water resources can be fully utilized.

4. Recovery Benefits and Summary

The renovation of the condensate recovery system not only effectively controls the waste of water and heat energy, but also greatly improves the overall operating environment of the plant room, solving a major problem for the enterprise operator.

Conclusion

In summary, the recycling of steam condensate has a significant impact on energy conservation and environmental protection, and is one of the main energy-saving measures taken by the current laundry. In the choice of condensate system form, if the choice of open recovery system, although the initial investment is less, but there will be steam condensate recovery incomplete technical problems. Therefore, it is currently recommended that new laundry rooms adopt the form of closed recovery.

Based on the renovation of the condensate recovery system of this laundry, the technical problems of system corrosion, unqualified condensate water quality, pump cavitation and incomplete secondary vapor recovery have been effectively solved by adopting the closed recovery method of condensate, which has improved the efficiency of water and thermal energy resources utilization and saved the operation and maintenance costs, so that the economic benefits are guaranteed.

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