First, the principle of condensation
99% of the natural gas composition is A (CH4), containing a large amount of hydrogen (H), and the combustion flue gas contains a large amount of water vapor. The theoretical calculation shows that the share of water vapor in the gas is about 18%; in the combustion gas of a diesel-fired boiler, the proportion of water vapor is about 12%: if the steam is condensed into water, the vaporization of the gas is recovered. Latent heat, the potential for heat recovery is very large. The recycling method is to add a condenser to the boiler and realize the conversion of the conventional boiler directly to a condensing boiler.
Usually the efficiency of the boiler is calculated according to the low heating value. When the thermal efficiency of a conventional boiler calibration is 90%, this efficiency corresponds to the low calorific value. The cold boiler also calculates its thermal efficiency according to the low calorific value, and its initial thermal efficiency reaches 95-96%, plus about 5% of the latent heat generated by the condensation release (under the condition that the latent heat of steam vaporization is fully utilized 40-50%. ), The condensing boiler can increase the thermal efficiency of the boiler to more than 100%
Second, the condensing boiler design concept
1. Condensate system design
The difficulty in designing a condensing boiler is to control the flue gas temperature below the water dew point temperature.
Steam boiler condensing system
1 If the feed water temperature is 20 °C, the feed water is preheated by the condenser and then enters the boiler, in series with the boiler, and the condenser is used as a preheating device for the boiler feed water;
2 If the feedwater temperature reaches 104°C (using heat to remove oxygen), the condenser is designed as an independent system, and the soft water (20°C°C) that has not entered the deaerator is heat exchanged with the flue gas to achieve the purpose of flue gas condensation.
2, the material design of the condenser
The products after oil and gas combustion contain harmful substances such as SO2, NOx, etc., dissolved in the flue gas so that the condensed water has a strong acidity. Therefore, the condensing waste heat recovery device must be made of corrosion-resistant materials. The condenser tube of our company adopts the best “sulfuric acid-resistant low-temperature dew point corrosion” special steel ND steel, which is excellent in acid corrosion resistance and chloride ion corrosion resistance. The condenser flue steel plate in contact with the flue gas is coated with a corrosion-resistant bituminous paint.
3, recycling of condensed water
Boiler emissions mainly include COx, NOx, SOx, etc. Among them, NOx, SOx can form acid rain; CO2 can form greenhouse effect. Therefore, it is very important to control the emission of boiler air pollutants. On the one hand, condensing boilers have reduced fuel consumption due to their high efficiency, resulting in a corresponding reduction in pollutant emissions. On the other hand, condensed water can absorb part of COx, NOx, SOx and greatly reduce the emission of pollutants. Because the condensate is acidic, a neutralization tank can be set up to discharge the condensate into the neutralization tank and periodically check the pH of the neutralization tank.
Third, the condensing boiler structure features
Boiler body structure features
1WNSL condensing boiler series adopts the horizontal wet back structure, the center of the combustion chamber is arranged in a low position, and the design idea of symmetrical symmetry distribution of the heat-exchanger flue tubes ensures that the heat transfer load is uniform and stable, which is conducive to the circulation of soda water in the working medium and minimizes the shortages. Water accidents increase boiler safety.
2 The rational application of the spiral furnace tube and the enhanced heat transfer element of the wave form furnace not only enhances the turbulent heat transfer of the high temperature flue gas but also effectively absorbs the thermal expansion and contraction of the furnace body.
3 The boiler adopts the design idea of the largest heating surface of the large furnace shell of the large furnace, which is characterized by complete combustion, low carbon deposition, fuel saving, high efficiency, and high overload capacity.
1 arranged on the top of the boiler, compact structure, no floor space.
2 countercurrent arrangement structure, heat exchange temperature difference, good heat transfer performance.
3 The use of special ND steel materials, corrosion resistance of condensate water is good, greatly improving the service life.
4 Using a reasonable flue structure, the condensate is easily discharged for collection and treatment
Automatic control system
1 The burner PID adjustment technology is adopted to configure the burners imported from Europe to achieve the best configuration of the air-fuel ratio so as to achieve full combustion of the fuel.
2 Boiler feed water adopts variable frequency water supply method. By changing the water pump motor operating frequency and changing the water intake, the power of the water pump can be changed to realize energy saving water supply and reduce power consumption.