SNCR和SCR脱硝技术与装置

适用范围：水泥、钢钢、电力、化工、冶金等行业。

定义：SNCR:选择性非催化还原技术SNCR是向炉窑合适部位喷入氨基还原剂，在850~1100°C的温度条件下,与烟气中的N0x发生还原反应，形成无害的Nz和H20,脱硝效率30~70%。还原剂主要以
尿素、氨水为主。主要用于水泥、钢铁、电力、化工、治金等行业。SCR: SCR和SCNR不同的是，反应过程中有了催化剂的参与，催化剂的参与降低了反应温度至
300~380°C，并提高了反应效率。混合SNCR-SCR:混合SNCR-SCR烟气脱硝技术是结合了SCR技术高效、SNCR技术投资省的特点而发展起来的一种新型工艺。

工艺流程：SNCR:SNCR工艺就是把含有氨基的还原剂喷入到锅炉炉膛中850~1100°C的区域内，该还原剂快速热解成NH3并和烟气中的NOX进行还原反应，将N0x还原成Nz和H20。SCR:采用氨气或无水液氨作为还原介质,把符合要求的氨气喷入烟道中,与原烟气充分混合后进入反应塔,在催化剂的作用下，并在有氧气存在的条件下，选择性地与烟气中的NOx发生反应,生成N2H20。混合SNCR-SCR:混合SNCR-SCR工艺具有两个反应区，通过布置在锅炉炉墙上的喷射系统，首先将还原剂喷入第一个反应区--炉膛，在高温下，还原剂与烟气中的N0x发生非催化还原反应,实现初步脱氮.然后，未反应完的还原剂进入混合工艺的第二个反应区--反应器,进-步脱氮.

工艺优点：SNCR:具有 最大灵活性，系统简单，施工周期短，可以根据运行状况灵活处理，不受机组燃料和负荷的变化影响。SCR:脱硝效率最高，可达50~85%，但投资较高。
混合SNCR-SCR :脱硝效率高，催化剂用量小，反应塔体积小、空间适应性强,脱硝系统阻力小，降低腐蚀危害,省去SCR旁路，催化剂的回收处理量减少，简化还原剂喷射系统，提高SNCR阶段的脱硝效率，方便地使用尿素作为脱硝还原剂，减小N20的生成，降低由于煤种引起催化剂大量失效的压力。

Socope:Cement, steel, power, chemical, metallurgical and other industries.

Definition:

SNCR: Selective non-catalytic reduction technology SNCR is to provide a suitable site within the kiln, from which is injected in to the amino reductant. At the temperature of 850-1100C，reduction reaction occurs between amino reductantand NOx in the flue gas, then generates harmless N2 and H2O, the denitrification efficiency is from 30 to 70%. Reductant mainly composes of urea and ammonia

SCR: SCR is different with SCNR, With the participation of the catalyst during the reaction leads to a reduction.in the reaction temperature to 300~ 380C, and improving the reaction efficiency.
Hybrid SNCR-SCR: Hybrid SNCR-SCR flue gas denitrification technology is a new developed process which has combined the characteristics of SCR technical efficiency and SNCR technology investment savign.

Process:

SNCR: SNCR Process sprays the reductant which contains amino into the boiler furnace at the temperature of 850~1 100C region, The reductant Pyrolyzes quickly into NH3, and reduction reaction occurs between NH3 and NOx in the flue gas, the NOx dioxides into N2 and H2O.

SCR: Using ammonia or anhydrous ammonia as a reducing medium, to meet the requirements of ammonia injected into the flue, and after mixing with the orininal gas goes into the reaction tower In the of a catalyst and in the presence of oxygen, ammonia reacts witrh NOx in the flue gas selectively, then generates N2 and H2O.

Hybrid SNCR-SCR: Hybrid SNCR-SCR Process has two reaction zones. First, through the injection system which arranges on the wall of the boiler furnace, the reductant is sprayed into the first reaction zone--Furnace. At high temperatures, non-catalytic reduction reaction occurs between reductant with NOx in the flue gas, achieves preliminary denitrification. Then, the unreacted reductant goes into the mixing process of the mixing process of the second rdaction zone -Reactor ,further denitrification occurs.

Process Advantages:

SNCR: It has maximum flexibility, simple system, short construction period, It can depend of the operating Conditions flexibly and it isn't affected by unit fuel and load changes.

SCR: It has the highest denitration efficiency up to 50~ 85 %, however, the investment is higher.

Hybrid SNCR-SCR: Higher denitrification efficiency, small amount of catalyst, small reaction toewr, space adaptable, deitrification system small resiatance, reduce the corrosion hazard, eliminate SCR bypass, reduce catalyst recovery process, simplify the reductant injection system, iumprove the efficiency of denitrification in SNCR stages, easy to urea as a reductant for denitrification, reduce the production of N2O, reduce stress from coal causes catalyst amount of failure.