一、冷凝原理
天然氣的成份中99%為甲(CH4),含有大量的氫(H),燃燒后的煙氣中含有大量的水蒸汽。經(jīng)理論計(jì)算,氣中的水蒸汽所占份額為18%左右；燃柴油鍋爐燃燒后的煙氣中,水蒸汽所占的份為12%左右:若將水蒸汽冷凝成水,回收其中的汽化潛熱,熱量回收的潛力非常大?；厥盏姆椒ㄊ菫殄仩t加裝冷凝器,實(shí)現(xiàn)將傳統(tǒng)鍋爐直接轉(zhuǎn)換為冷凝式鍋爐。
通常鍋爐的效率是按照低熱值來(lái)計(jì)算的,當(dāng)一個(gè)傳統(tǒng)鍋爐標(biāo)定的熱效率是90%時(shí),這個(gè)效率對(duì)應(yīng)的是低熱值。冷鍋爐也是按照低熱值來(lái)計(jì)算它的熱效率,則它的初始熱效率達(dá)到95-96%,加上冷凝釋放產(chǎn)生的大約5%的潛熱(在水蒸汽汽化潛熱被充分利用40-50%的情況下),冷凝鍋爐可將鍋爐的熱效率提高至大于100%
二、冷凝鍋爐設(shè)計(jì)理念
1、冷凝系統(tǒng)設(shè)計(jì)
冷凝式鍋爐的設(shè)計(jì)難則是控制煙氣溫度低于水露點(diǎn)溫度。
蒸汽鍋爐冷凝系統(tǒng)
①若給水溫度為20℃,給水經(jīng)冷凝器預(yù)熱后進(jìn)入鍋爐,與鍋爐串聯(lián),冷凝器作為鍋爐給水的預(yù)熱裝置;
②若給水溫度達(dá)到104℃(采用熱力除氧),冷凝器設(shè)計(jì)為獨(dú)立的系統(tǒng)形式,將未進(jìn)除氧器的軟水(20℃℃)與煙氣換熱,來(lái)達(dá)到煙氣冷凝的目的。
2、冷凝器的材料設(shè)計(jì)
油氣燃燒后的產(chǎn)物中含有SO2、NOx等有害物質(zhì),溶于煙氣中使冷凝水具有較強(qiáng)的酸性。因此冷凝余熱回收裝置須采用耐腐蝕材料。我公司冷凝器管采用理想的“耐硫酸低溫露點(diǎn)腐蝕”專用鋼材ND鋼,耐酸腐蝕性能、耐氯離子腐蝕優(yōu)良。與煙氣接觸的冷凝器煙道鋼板表面涂耐腐蝕瀝青漆。
3、冷凝水的回收排放
鍋爐排放物主要包括COx、NOx、SOx等,其中NOx、SOx可形成酸雨;CO2可形成溫室效應(yīng)。因此控制鍋爐大氣污染物的排放就顯得非常重要。冷凝式鍋爐一方面因?yàn)槠涓咝?燃料耗量減少,污染排放物也相應(yīng)減少。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?yàn)槔淠仕嵝?可以設(shè)置一中和池,將冷凝水排放到中和池中,定期檢查中和池的PH值。
三、冷凝式鍋爐結(jié)構(gòu)特點(diǎn)
鍋爐本體結(jié)構(gòu)特點(diǎn)
①WNSL冷凝型系列鍋爐整體布置采用臥式濕背結(jié)構(gòu),燃燒室中心低位布置,換熱煙管左右對(duì)稱分布的設(shè)計(jì)思想,換熱負(fù)荷均勻穩(wěn)定,有利于工質(zhì)側(cè)汽水循環(huán),大限度的減少缺水事故的發(fā)生,提高鍋爐an全性。
②波形爐膽和強(qiáng)化傳熱元件螺紋煙管的合理應(yīng)用,不僅強(qiáng)化高溫?zé)煔獾奈闪鱾鳠岫矣行諣t體的熱脹冷縮。
③鍋爐采用大爐膽大鍋殼大受熱面的設(shè)計(jì)思想,燃燒完全,不易積碳,節(jié)約燃料,具有效率高出力足,超負(fù)荷能力強(qiáng)的顯著特點(diǎn)。
冷凝器
①布置于鍋爐頂部,結(jié)構(gòu)緊湊,無(wú)占地面積。
②逆流布置結(jié)構(gòu),換熱溫差大,傳熱性能好。
③采用特殊ND鋼的材料,耐冷凝水腐蝕性好,大大提高了使用壽命。
④采用合理的煙道結(jié)構(gòu),冷凝水易于排放收集處理
自控系統(tǒng)
①采用燃燒器PID調(diào)節(jié)技術(shù),配置歐洲進(jìn)口燃燒器,實(shí)現(xiàn)空燃比的配置,從而達(dá)到燃料的充分燃燒。
②鍋爐給水采用變頻給水方式,通過(guò)改變水泵電機(jī)運(yùn)行頻率改變進(jìn)水量的同時(shí)改變水泵的功率,實(shí)現(xiàn)節(jié)能給水,降低電耗。
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.
