低氮燃燒器及脫硝改造后的影響有哪些

機組經過低氮燃燒器、脫硝系統以及相應輔機改造后，在實際運行NOx排放量均能滿足國家的環保要求，為日后機組的正常運行創造了先決條件，與此同時也給機組帶來一些負面影響。

After low nitrogen burner, denitration system and the corresponding auxiliary after modification, in the actual operation of NOx emissions can meet the national requirements of environmental protection, for the normal operation of the unit in the future created prerequisites, at the same time also bring some negative effects on unit.

一、機組最小技術出力降低，調峰能力差

1. The minimum technical output of the unit is reduced and its peak regulating capacity is poor

大部分電廠的脫硝均采用SCR脫硝反應器，催化劑的設計溫度為300℃～420℃。在機組投入脫硝系統運行后，除同步投產脫硝系統的機組外，由于早期鍋爐設計未考慮脫硝系統的運行溫度，多數機組改造后出現了鍋爐低負荷運行時，省煤器出口煙溫無法滿足脫硝系統正常運行溫度的現象，因而鍋爐最小技術出力較改造前均有不同程度的升高，機組的調峰能力下降。針對上述情況，選取山西省具有代表性的九個電廠進行了調研，綜合九個電廠的最小技術出力情況，改造后機組的最小技術出力在50%-77%之間。經加權平均，鍋爐最小技術出力平均為59%，較改造前40%的最低穩燃負荷提高了19%;僅就改造機組來計算鍋爐最小技術出力平均為62%，鍋爐最小技術出力較改造前提高了22%。其中，原設計低氮燃燒器和脫硝系統的機組效果最佳，低氮加脫硝同時改造的機組效果最差。

Most of the power plant of denitration adopt SCR denitration reactor, catalyst design temperature is 300 ℃ ~ 420 ℃. After denitration system run operation unit, in addition to the synchronous production unit of denitration system, due to early boiler design did not consider the operating temperature of the denitration system, most of the unit after transforming the low load running, the boiler economizer outlet smoke temperature can meet the phenomenon of denitration system normal operation temperature, and minimum technology before the transform of output has the varying degree to rise, the peakload ability decline. According to the above situation, choose the typical nine power plant in Shanxi Province has carried on the investigation and research, comprehensive nine power plant, the minimum technical output, after transforming unit, the minimum technical output between 50% and 77%. According to weighted average, the minimum technical output of boiler is 59%, which is 19% higher than the minimum stable combustion load of 40% before reforming. The average minimum technical output of the boiler was 62% when the unit was modified, and the minimum technical output of the boiler was 22% higher than before the reform. Among them, the original low-nitrogen combustion and denitrification system has the best effect, while the low-nitrogen and denitrification system has the worst effect.

二、AGC調節特性能差

2. Poor regulatory performance of AGC

機組在經過低氮燃燒器改造后，爐內的燃燒方式發生了明顯變化，在使用原有協調方式的情況下，機組在投入AGC控制時，主汽壓力偏差大、汽包水位波動;負荷調節速率較快時，由于脫硝噴氨反應存在滯后，容易造成NOx排放指標在短時間內超標，嚴重影響負荷調節速率;同步進行引風機改造的機組，改造后未進行引風機調節特性試驗，在低負荷時，在原有控制方式下，爐膛壓力波動大。

Unit after low nitrogen burner alteration, furnace combustion mode has changed significantly, in the case of using the original coordinate methods, unit in AGC control, big deviation main steam pressure, steam drum water level fluctuation; When the load adjustment rate is relatively fast, it is easy to exceed the standard of NOx emission in a short period of time due to the lag of denitrification ammonia injection reaction, which seriously affects the load adjustment rate. The unit that carries out the synchronous fan modification has not carried out the fan adjustment characteristic test after the modification. When the load is low, the pressure in the furnace fluctuates greatly under the original control mode.

三、運行經濟性差

3. Poor operation economy

完成低氮燃燒器和脫硝改造的機組，大部分存在經濟性降低的現象。主要體現在：

Most of the units that have completed the transformation of low nitrogen burners and denitrification have the phenomenon of economic reduction. Mainly reflected in:

1、飛灰含碳量增大

1. The carbon content of fly ash increases

機組進行低氮燃燒器改造后，由于燃燒方式的改變，如果風粉配比不佳，主燃燒區的缺氧燃燒及燃燼區的低溫燃燒均不利于煤粉的燃盡。另外，改造后機組進行的燃燒調整更多的傾向于降低NOx排放量的調整，導致飛灰含碳量增大，機組經濟性降低。

After the modification of the low-nitrogen burner of the unit, due to the change of combustion mode, if the ratio of air powder is not good, the oxygen-deficient combustion in the main combustion area and the low-temperature combustion in the embers area are not conducive to the coal combustion. In addition, after the modification, the combustion adjustment of the unit is more inclined to reduce the adjustment of NOx emission, which leads to the increase of carbon content of fly ash and the decrease of the unit economy.

2、空預器傳熱效果下降，排煙溫度升高

2. The heat transfer effect of air preheater decreases, and the exhaust temperature increases

機組脫硝系統投入運行后，脫硝副產物硫酸氫氨在低于露點溫度下，容易在空預器的受熱面上粘結，且極具粘性，流經空預器煙氣中的飛灰容易沉積在空預器受熱面上，致使空預器傳熱效果下降，排煙溫度升高，鍋爐效率降低。

After denitration system put into operation, denitration by-product ammonium hydrogen sulfate under the lower than the dew point temperature, easy bonding on air preheater of the heating surface, and highly viscous, flying through the air preheater in the flue gas ash deposits on air preheater heating surface easily, cause air preheater heat transfer effect, exhaust temperature, boiler efficiency is reduced.

3、再熱汽溫偏低

3. The reheat steam temperature is low

基于不同的改造情況，部分電廠改造后，再熱汽溫降低5℃～20℃，嚴重影響機組的經濟性。據估算再熱汽溫每降低10℃，影響機組單位煤耗約1g標準煤。

Reconstruction based on different situation, some power plants after modification, reheat steam temperature to reduce the 5 ℃ ~ 20 ℃, seriously affect the economy of the unit. According to estimate every 10 ℃ below the reheat steam temperature, affecting the unit coal consumption unit about 1 g of standard coal.

對大多數脫硝改造機組，經濟性均受到一定影響，通過調研，改造后影響機組效率約1%。以單臺600MW機組、負荷率80%、年運行小時數5500小時、標煤單價600元、鍋爐效率降低1%，單位能耗增加約3g標準煤估算，每年多消耗標煤7920噸，折合人民幣475萬元，單位電量成本增加0.18分。

The economy of most denitrification and denitrification reconstruction units is affected to a certain extent. Through investigation, the efficiency of the unit after transformation is affected by about 1%. To a single 600 mw unit, load rate of 80%, annual operating hours 5500 hours, BiaoMei unit price 600 yuan, boiler efficiency by 1%, the unit energy consumption increased about 3 g standard coal estimates that consumption BiaoMei 7920 tons a year, equivalent to 4.75 million yuan, the unit cost of electricity increased by 0.18 points.

四、鍋爐輔機的堵塞與腐蝕

4.Plug and corrosion of boiler auxiliaries

鍋爐低負荷時，由于脫硝入口溫度下降、脫硝催化劑的活性降低、氨逃逸率增大等因素，脫硝副產物NH3HSO3的生成量增加。NH3HSO3粘結性強、露點溫度高，并具有一定的腐蝕性，容易堵塞空氣預熱器，導致空氣預熱器差壓增大，傳熱效果變差，并造成冷端腐蝕。

When the boiler is under low load, the production of NH3HSO3, a byproduct of denitrification, is increased due to the decrease of temperature at the denitrification inlet, the decrease of the activity of denitrification catalyst and the increase of ammonia escape rate. NH3HSO3 has strong adhesion, high dew point temperature and certain corrosion, which is easy to block air preheater, leading to increased differential pressure of air preheater, poor heat transfer effect and cold end corrosion.

此外，如果氨逃逸率控制不好、NH3HSO4生成量較大時，還會造成布袋除塵器以及引風機葉片腐蝕。通過調研發現，個別電廠在進行機組檢修時，發現布袋除塵器\引風機均有腐蝕現象。

In addition, if the ammonia escape rate is not well controlled and the NH3HSO4 production is large, it will also cause corrosion of the cloth bag duster and the fan blade. Through investigation, it is found that some power plants have corrosion phenomenon of cloth bag duster and fan during unit maintenance.

1、液氨站的安全運行

1. Safe operation of liquid ammonia station

液氨又稱無水氨，是一種無色液體，易揮發，有腐蝕性，具有刺激性氣味。液氨揮發成氨氣，屬于易燃、易爆氣體，泄漏后可引發中毒，對眼、粘膜有刺激性，有燒傷危險。液氨在運輸、裝卸、儲存以及檢修過程存在泄漏、靜電起火、爆炸以及中毒等安全隱患。使用液氨作為還原劑的電廠，安全隱患增加，尤其臨近城市地區的電廠，采用液氨脫硝，其運輸、儲存、運行風險更大，大大增加了機組運行的危險性。

2、脫硝改造、運行成本高