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低氮燃烧器及脱硝改造后的影响有哪些

时间:2018-07-16 18:26    作者:admin 返回列表

机组经过低氮燃烧器、脱硝系统以及相应辅机改造后,在实际运行NOx排放量均能满足国家的环保要求,为日后机组的正常运行创造了先决条件,与此同时也给机组带来一些负面影响。
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、机组最小技术出力降低,调峰能力差
1. The minimum technical output of the unit is reduced and its peak regulating capacity is poor

大部分电厂的脱硝均采用SCR脱硝反应器,催化剂的设计温度为300℃~420℃。在机组投入脱硝系统运行后,除同步投产脱硝系统的机组外,由于早期锅炉设计未考虑脱硝系统的运行温度,多数机组改造后出现了锅炉低负荷运行时,省煤器出口烟温无法满足脱硝系统正常运行温度的现象,因而锅炉最小技术出力较改造前均有不同程度的升高,机组的调峰能力下降。针对上述情况,选取山西省具有代表性的九个电厂进行了调研,综合九个电厂的最小技术出力情况,改造后机组的最小技术出力在50%-77%之间。经加权平均,锅炉最小技术出力平均为59%,较改造前40%的最低稳燃负荷提高了19%;仅就改造机组来计算锅炉最小技术出力平均为62%,锅炉最小技术出力较改造前提高了22%。其中,原设计低氮燃烧器和脱硝系统的机组效果最佳,低氮加脱硝同时改造的机组效果最差。
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调节特性能差
2. Poor regulatory performance of AGC

机组在经过低氮燃烧器改造后,炉内的燃烧方式发生了明显变化,在使用原有协调方式的情况下,机组在投入AGC控制时,主汽压力偏差大、汽包水位波动;负荷调节速率较快时,由于脱硝喷氨反应存在滞后,容易造成NOx排放指标在短时间内超标,严重影响负荷调节速率;同步进行引风机改造的机组,改造后未进行引风机调节特性试验,在低负荷时,在原有控制方式下,炉膛压力波动大。
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.

低氮燃烧器


三、运行经济性差
3. Poor operation economy

完成低氮燃烧器和脱硝改造的机组,大部分存在经济性降低的现象。主要体现在:
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、飞灰含碳量增大
1. The carbon content of fly ash increases

机组进行低氮燃烧器改造后,由于燃烧方式的改变,如果风粉配比不佳,主燃烧区的缺氧燃烧及燃烬区的低温燃烧均不利于煤粉的燃尽。另外,改造后机组进行的燃烧调整更多的倾向于降低NOx排放量的调整,导致飞灰含碳量增大,机组经济性降低。
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、空预器传热效果下降,排烟温度升高
2. The heat transfer effect of air preheater decreases, and the exhaust temperature increases

机组脱硝系统投入运行后,脱硝副产物硫酸氢氨在低于露点温度下,容易在空预器的受热面上粘结,且极具粘性,流经空预器烟气中的飞灰容易沉积在空预器受热面上,致使空预器传热效果下降,排烟温度升高,锅炉效率降低。
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、再热汽温偏低
3. The reheat steam temperature is low

基于不同的改造情况,部分电厂改造后,再热汽温降低5℃~20℃,严重影响机组的经济性。据估算再热汽温每降低10℃,影响机组单位煤耗约1g标准煤。
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.

对大多数脱硝改造机组,经济性均受到一定影响,通过调研,改造后影响机组效率约1%。以单台600MW机组、负荷率80%、年运行小时数5500小时、标煤单价600元、锅炉效率降低1%,单位能耗增加约3g标准煤估算,每年多消耗标煤7920吨,折合人民币475万元,单位电量成本增加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、锅炉辅机的堵塞与腐蚀
4.Plug and corrosion of boiler auxiliaries

锅炉低负荷时,由于脱硝入口温度下降、脱硝催化剂的活性降低、氨逃逸率增大等因素,脱硝副产物NH3HSO3的生成量增加。NH3HSO3粘结性强、露点温度高,并具有一定的腐蚀性,容易堵塞空气预热器,导致空气预热器差压增大,传热效果变差,并造成冷端腐蚀。
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生成量较大时,还会造成布袋除尘器以及引风机叶片腐蚀。通过调研发现,个别电厂在进行机组检修时,发现布袋除尘器\引风机均有腐蚀现象。
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、液氨站的安全运行
1. Safe operation of liquid ammonia station

液氨又称无水氨,是一种无色液体,易挥发,有腐蚀性,具有刺激性气味。液氨挥发成氨气,属于易燃、易爆气体,泄漏后可引发中毒,对眼、粘膜有刺激性,有烧伤危险。液氨在运输、装卸、储存以及检修过程存在泄漏、静电起火、爆炸以及中毒等安全隐患。使用液氨作为还原剂的电厂,安全隐患增加,尤其临近城市地区的电厂,采用液氨脱硝,其运输、储存、运行风险更大,大大增加了机组运行的危险性。

Liquid ammonia, also known as anhydrous ammonia, is a colorless liquid, volatile, corrosive, irritating smell。 The liquid ammonia volatilizes into ammonia gas, belongs to inflammable and explosive gas, which can cause poisoning after leakage, irritate eyes and mucous membrane, and is in danger of burns。 There are safety hazards such as leakage, electrostatic fire, explosion and poisoning in transportation, loading, unloading, storage and maintenance of liquid ammonia。 Using liquid ammonia as a reducing agent of power plant, potential safety hazard, especially near the urban areas of power plant, using liquid ammonia denitration, the transportation, storage, operation risk bigger, greatly increases the risk of unit operation。


2、脱硝改造、运行成本高

2。 Denitrification and transformation, high operating cost

脱硝改造增加了原风烟系统的阻力,脱硝副产物有堵塞和腐蚀空预器、除尘器、引风机等设备的情况,需配套进行空预器以及引风机的改造,改造幅度大,成本高。

Denitration modification increases the resistance of the original specific systems, denitration by-products have blockage and corrosion of air preheater, dust collector, induced draft fan and other equipment, to form a complete set of air preheater and induced draft fan renovation, a large range transform, high cost.

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