一、冷凝原理

天然气的成份中99%为甲(CH4),含有大量的氢(H),燃烧后的烟气中含有大量的水蒸汽。经理论计算,气中的水蒸汽所占份额为18%左右；燃柴油锅炉燃烧后的烟气中,水蒸汽所占的份为12%左右:若将水蒸汽冷凝成水,回收其中的汽化潜热,热量回收的潜力非常大。回收的方法是为锅炉加装冷凝器,实现将传统锅炉直接转换为冷凝式锅炉。

通常锅炉的效率是按照低热值来计算的,当一个传统锅炉标定的热效率是90%时,这个效率对应的是低热值。冷锅炉也是按照低热值来计算它的热效率,则它的初始热效率达到95-96%,加上冷凝释放产生的大约5%的潜热(在水蒸汽汽化潜热被充分利用40-50%的情况下),冷凝锅炉可将锅炉的热效率提高至大于100%

二、冷凝锅炉设计理念

1、冷凝系统设计

冷凝式锅炉的设计难则是控制烟气温度低于水露点温度。

蒸汽锅炉冷凝系统

①若给水温度为20℃,给水经冷凝器预热后进入锅炉,与锅炉串联,冷凝器作为锅炉给水的预热装置;

②若给水温度达到104℃(采用热力除氧),冷凝器设计为独立的系统形式,将未进除氧器的软水(20℃℃)与烟气换热,来达到烟气冷凝的目的。

2、冷凝器的材料设计

油气燃烧后的产物中含有SO2、NOx等有害物质,溶于烟气中使冷凝水具有较强的酸性。因此冷凝余热回收装置须采用耐腐蚀材料。我公司冷凝器管采用理想的“耐硫酸低温露点腐蚀”专用钢材ND钢,耐酸腐蚀性能、耐氯离子腐蚀优良。与烟气接触的冷凝器烟道钢板表面涂耐腐蚀沥青漆。

3、冷凝水的回收排放

锅炉排放物主要包括COx、NOx、SOx等,其中NOx、SOx可形成酸雨;CO2可形成温室效应。因此控制锅炉大气污染物的排放就显得非常重要。冷凝式锅炉一方面因为其高效率,燃料耗量减少,污染排放物也相应减少。另一方面冷凝水可以吸收部分COx、NOx、SOx、大大降低了污染物的排放。因为冷凝水呈酸性,可以设置一中和池,将冷凝水排放到中和池中,定期检查中和池的PH值。

三、冷凝式锅炉结构特点

锅炉本体结构特点

①WNSL冷凝型系列锅炉整体布置采用卧式湿背结构,燃烧室中心低位布置,换热烟管左右对称分布的设计思想,换热负荷均匀稳定,有利于工质侧汽水循环,大限度的减少缺水事故的发生,提高锅炉an全性。

②波形炉胆和强化传热元件螺纹烟管的合理应用,不仅强化高温烟气的紊流传热而且有效吸收炉体的热胀冷缩。

③锅炉采用大炉胆大锅壳大受热面的设计思想,燃烧完全,不易积碳,节约燃料,具有效率高出力足,超负荷能力强的显著特点。

冷凝器

①布置于锅炉顶部,结构紧凑,无占地面积。

②逆流布置结构,换热温差大,传热性能好。

③采用特殊ND钢的材料,耐冷凝水腐蚀性好,大大提高了使用寿命。

④采用合理的烟道结构,冷凝水易于排放收集处理

自控系统

①采用燃烧器PID调节技术,配置欧洲进口燃烧器,实现空燃比的配置,从而达到燃料的充分燃烧。

②锅炉给水采用变频给水方式,通过改变水泵电机运行频率改变进水量的同时改变水泵的功率,实现节能给水,降低电耗。

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.

Condenser

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.