Has your business begun to pay attention to environmental protection and energy conservation? Reducing pollution and reducing costs is an important part of every enterprise's research. Enterprises using boilers can achieve cost control by reducing boiler water costs. Among them, the recycling of steam boiler condensate water is a major breakthrough.

Boilers are one of the main energy-consuming equipment in the production and operation of many enterprises, among which steam boilers and hot water boilers are the most common. Steam boilers have a wide range of uses. In the production of many enterprises, in addition to providing the steam required for production, they are also often used for heat tracing and insulation in winter such as domestic heating.

Boiler steam condensate refers to the water condensed and formed by the hot steam generated by the steam boiler after releasing heat. The condensate is generally distilled water with high purity, moderate pH and low hardness. It is an excellent water resource for steam boilers. Therefore, the reuse of condensed water has considerable economic, environmental and labor cost benefits.

However, many steam boilers do not consider the recovery of condensed water during installation and design. Due to the diversity of steam uses, the quality of condensed water is easily polluted, and the steam pipeline is long, which makes the recycling of condensed water difficult. And steam pipelines are generally cast iron and cast steel pipelines, so the content of iron ions in the condensed water is generally high, resulting in a decrease in the quality of the condensed water, and will cause accelerated corrosion of boiler tubes and other components, affecting the normal operation and service life of the steam boiler. Therefore, Generally, the good quality steam condensate is discharged in vain.

If the company wants to save fuel and water, it can recycle the condensed water that the steam turns into through the heat exchanger according to the discharge of condensed water. Through technological transformation, the purpose of cost reduction and energy saving is achieved.

The purpose and significance of condensate recycling and reuse

The winter heating water for the production posts in the living area comes from the hot water produced by the steam generated by the boiler to heat the circulating water through the exchanger. The steam produces a large amount of condensed water in the process of heat exchange. If the condensed water enters the replenishment tank and is used as the circulating water replenishment design, the heating water system is a closed circulation system, the water loss is small, and there is basically no need for replenishment. The main method is discharge, which will cause a lot of waste of water resources.

The condensed water is much higher than ordinary softened water in terms of pH, hardness and purity and other boiler water indicators, and is a high-quality steam boiler water. If the steam condensed water can be effectively used, the usage of softened water will be significantly reduced, and the production cost of steam will be greatly reduced; and since the temperature of the condensed water is generally higher than that of ordinary softened water, the condensed water will enter the steam boiler again to generate the heat required for steam. It will also be greatly reduced, which will effectively reduce the use of steam boiler fuel, and also reduce the emission of soot particles, sulfur dioxide, carbon dioxide and other harmful substances, which is an effective measure for energy saving and water saving in the heating process of boilers.

Features of the steam condensate recovery system

The steam condensate recovery system can generally be divided into two categories: open recovery system and closed recovery system.

Open condensate recovery system

The open condensate recovery system is a steam boiler condensate recovery method with a long history of use. During the recovery and reuse of the steam condensate, one end of the steam recovery pipe is open, and the collecting tank storing the condensate is connected to the atmosphere.

The pressure of the condensed water under the recovery system is low, and it cannot reach the furnace of the steam boiler by its own pressure. Generally, the condensed water needs to be pressurized and injected into the furnace of the steam boiler by a condensed water circulating pump. The open condensate recovery system has the characteristics of simple recovery process, simple equipment, convenient operation and small investment. However, because the entire recovery system is directly exposed to the air, the oxygen in the air is easily dissolved in the condensed water during the recovery process, causing the oxygen content of the condensed water to exceed the standard and unable to meet the boiler water requirements. Reduce the recovery rate of condensed water and waste heat energy, affecting economic benefits.

 Closed condensate recovery system

In the closed condensate recovery system, the water collecting tank and all the pipelines adopt a closed process, which is basically completely isolated from the air, and the whole system is under constant positive pressure. Since the system is in a closed environment and does not come into contact with air, the heat loss of the condensed water is small and the consumption of boiler fuel is reduced. At the same time, the condensed water is not in contact with the air, and the oxygen content of the water is low, which reduces the cost of deoxidizing the condensed water again. The economic benefit of the closed condensate recovery system is good, but the initial investment is large, and the operation is not very convenient.

Retrofit of condensate recovery system

In order to effectively prevent the scaling and metal corrosion of the steam boiler furnace and furnace tubes caused by the increase of iron ion content in the steam condensate water, it is necessary to improve the quality of the steam condensate water and reduce the content of O₂ and CO₂ in the condensate water, thereby reducing the condensate water. Corrosion of the recovery pipeline caused by changes in pH, thereby reducing the formation of iron ions in the pipeline and ensuring that the index of condensed water is qualified. Add chemical deoxidizer to reduce CO₂ in steam and reduce carbonate alkalinity in feed water; adopt closed recovery to completely eliminate O₂ and CO₂ in the outside air from entering the recovery system; control recovery PH value, boiler water in furnace When the environment pH > 7, it can effectively reduce metal corrosion and scaling of furnace and furnace tubes, and can also buffer the influence of condensed water pH.

The heat exchange is realized through the heat exchanger, and the water in the boiler is fully heated. The rising tube of the boiler is located in the furnace to absorb heat, and a part of the water in the tube is vaporized into steam to form a steam-water mixture. The sub-cylinder enters the steam-water heat exchanger to replace the steam, and the condensed water in the water replenishment tank is fully utilized by the condensed water recovery device to make full use of its thermal energy. The denser water flows into the boiler after deoxidizing from the unheated descending pipe outside the furnace wall, completing a complete circulation loop. Set up a condensate water recovery system for the heat exchanger, lay a recovery DN32 pipeline of more than 50 meters, set up a recovery pump, and install an automatic liquid level control device to realize automatic operation, and the condensate water directly enters the boiler deaerator water tank.

Add a float level gauge to the water supply tank. When the water tank is full, the contact of the float level gauge is turned on, and the water pump is started to pump water. A time relay is added to the control circuit of the water pump. According to the size of the water tank and the displacement of the pump, the time required The relay controls the running time of the pump and thus the water level in the make-up tank.

Conclusion 

Steam condensate is a high-quality steam boiler water source with high cleanliness, low oxygen content and low hardness. Generally, condensate has higher calorific value and brine value than ordinary softened water. In the future, the recovery of steam condensed water will also attract more and more attention from enterprises. The recovery of steam condensed water can not only reduce the cost of boiler water softening, deoxidation and other processes, but also reduce the consumption of boiler fuel and the pollution caused by enterprise sewage. costs and environmental pollution. 

In today's increasing pressure on energy and environmental protection, the research and discussion on the recovery of steam boiler condensate has strong economic potential, which is conducive to maximizing the use value of condensate.

Further Reading:

What Kind of Steam Boiler is Right For You? Your Industry Needs to Know it

Eight misunderstandings of boiler operation NO.1 you may be wrong

Boiler Guidance| Industrial Boiler Operation Optimization and Adjustment Method