WO2013056489A1 - 火力发电厂锅炉edta低温化学清洗钝化工艺 - Google Patents

火力发电厂锅炉edta低温化学清洗钝化工艺 Download PDF

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WO2013056489A1
WO2013056489A1 PCT/CN2011/083173 CN2011083173W WO2013056489A1 WO 2013056489 A1 WO2013056489 A1 WO 2013056489A1 CN 2011083173 W CN2011083173 W CN 2011083173W WO 2013056489 A1 WO2013056489 A1 WO 2013056489A1
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Prior art keywords
cleaning
edta
passivation
solution
boiler
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PCT/CN2011/083173
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English (en)
French (fr)
Inventor
陈里
宋建华
陈浩
陈兴武
王一波
吴兴生
孔胜杰
刘娜
徐伶
张翠文
张红
肖清明
陈晖�
袁从明
杨传
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宁夏电力科学研究院
宁夏回族自治区电力公司
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Publication of WO2013056489A1 publication Critical patent/WO2013056489A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/60—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using alkaline aqueous solutions with pH greater than 8
    • C23C22/62—Treatment of iron or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/088—Iron or steel solutions containing organic acids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28G—CLEANING OF INTERNAL OR EXTERNAL SURFACES OF HEAT-EXCHANGE OR HEAT-TRANSFER CONDUITS, e.g. WATER TUBES OR BOILERS
    • F28G9/00—Cleaning by flushing or washing, e.g. with chemical solvents

Definitions

  • the invention relates to the field of cleaning of a boiler in a thermal power plant, in particular to a low temperature chemical cleaning passivation process of a thermal power plant boiler EDTA.
  • the boilers, economizers and pre-furnace water supply systems should be chemically cleaned separately for the infrastructure and operation units. Chemical cleaning is a necessary measure to prevent accidents caused by corrosion and scaling on the heated surface. It is also one of the effective measures to improve the thermal efficiency of the boiler and improve the water vapor quality of the unit.
  • Thermal power plant boiler EDTA low temperature chemical cleaning passivation process taking energy saving and emission reduction as a practical point, through research and a large number of laboratory tests and field tests, the cleaning temperature is controlled at 60 ⁇ 75 °C, thus reducing the temperature constraints Sexuality reduces the impact of ambient temperature on the process, reduces insecurity in cleaning work, significantly reduces energy consumption and capital investment, and is easy to operate and promote.
  • the EDTA low-temperature chemical cleaning passivation process uses EDTA-2Na to chelate the cleaning solution against the scale on the boiler tube wall at low temperatures, and the scale is stripped off.
  • EDTA-2Na EDTA-2Na
  • the thickness of scale Degree the degree of fouling of the surface to be cleaned
  • the concentration of the cleaning agent the temperature at which the cleaning solution is heated
  • the length of the cleaning time the length of the cleaning time
  • the flow rate, head, and flow rate of the cleaning pump are selected to formulate a suitable cleaning process. Thereby achieving a satisfactory cleaning purpose.
  • the object of the present invention is to overcome the deficiencies of the prior art and to provide a low temperature chemical cleaning passivation process for a thermal power plant boiler EDTA using EDTA to perform cleaning and passivation at a low temperature.
  • thermo power plant boiler EDTA low temperature chemical cleaning passivation process the process comprising the following steps:
  • Alkaline washing and rinsing Add degreasing agent to the cleaning system for alkaline washing, control the temperature at 60 °C ⁇ 5 °C, and after 4-6 hours of alkali washing time, drain the alkali washing waste liquid and remove it with demineralized water. Rinse, rinse to effluent pH 9.0, water quality is transparent;
  • EDTA cleaning For the above-mentioned alkaline washing cleaning system, the EDTA-2Na cleaning solution is used for cleaning, and the iron content is balanced in the EDTA-2Na cleaning solution at the outlet of the cleaning system, and the cleaning is terminated without change; the above EDTA-2Na The cleaning solution is composed of EDTA-2Na solution with a concentration of 3 to 6% by mass and an appropriate amount of EDTA-2Na corrosion inhibitor and hydrazine; the temperature of the solution during the above cleaning is 60-75 ° C;
  • step D After the step D is finished, add NaOH to the above cleaning solution, adjust the pH value of the cleaning solution to be between 8.5 and 9.5, and passivate the system.
  • the pH of the cleaning solution reaches 8.5 or more, and the temperature returns to 60 °C or more, the time is started. After the passivation time is 3 hours, the monitoring tube section is removed to observe the film formation, and the passivation time is not easy to exceed 5 hours.
  • the mass concentration of the EDTA-2Na corrosion inhibitor is 0.3 to 0.5%, and the mass percentage of the hydrazine is 0.2%.
  • the solution temperature during passivation is 60 to 70 °C.
  • the degreaser is an A5 degreaser, and the mass percentage concentration of the A5 degreaser is 2 to 4%.
  • the invention has the following characteristics: 1. Energy saving and consumption reduction, shortening cleaning cycle and cost. Due to the whole Qing During the washing process, the temperature of the cleaning solution is 60 ⁇ 75 °C, and the temperature of the solution during passivation is 60 ⁇ 70 °C. This can be used to clean the tank of the cleaning equipment by auxiliary steam, and it can be cleaned with the current EDTA. Compared with the cleaning technology of the agent, when the same boiler is cleaned by the method, the cleaning cycle can be shortened by half, and the cleaning cost is reduced by about one third; the energy consumption is saved. 2.
  • the invention is capable of controlling the EDTA cleaning temperature to a very low level.
  • the main technique is to strictly calculate the amount of hydrazine added during the cleaning process to ensure that the mass percentage concentration is 0.2%, breaking the existing EDTA cleaning technology and guidelines.
  • the general passivation process the general idea of ammonium salt and sodium salt is adopted, and the pH adjustment is carried out by using strong alkali NaOH, and the passivation time is strictly controlled. 3.
  • the pH of the EDTA passivation solution is adjusted by adding strong alkali NaOH during the passivation process, and the "cleaning and passivation" of the cleaned boiler is completed in one step.
  • the cleaning process of the invention is applicable to boilers of various specifications, which is beneficial to the implementation and promotion of the site.
  • the specific conditions of the boiler are: BHW35 for steam drum and SA-210C for water wall.
  • the economizer is made of SA-210C.
  • the water supply flows from the left side of the boiler through the check valve and the electric valve to the economizer inlet header, then flows through the economizer tube set, the intermediate connection header and the suspension pipe, and then merges at the economizer outlet.
  • the tank is introduced into the drum from the economizer outlet header through three drums of ⁇ 219 ⁇ 25.
  • the feed water is injected into the large-diameter drop pipe of ⁇ 558.8 ⁇ 60 in the water distribution pipe arranged along the length of the drum, the feed water is directly mixed with the boiler water in the down pipe, and a distributor is arranged at the lower end of the four downcomers. It is connected to 96 water-cooled wall inlet pipes and sent to the lower tank of the water wall.
  • the water wall consists of 764 tubes with a diameter of ⁇ 60 and is divided into 32 loops according to heat and geometry.
  • the lower header is distributed to the lower header of each water wall through 48 ⁇ 133 10mm water connection pipes.
  • the chemical cleaning equipment used in this experiment is the XLG-400 mobile boiler chemical cleaning platform.
  • the chemical cleaning platform consists of a system consisting of a cleaning tank and two washing pumps.
  • the mobile boiler chemical cleaning platform is connected with the ring boiler to form a cleaning system consisting of a washing tank ⁇ a washing pump ⁇ an inlet mother pipe ⁇ an economizer ⁇ a steam drum ⁇ a discharge port.
  • the cleaning process is: A. After performing the hydrostatic test on the above cleaning system, flush the circulating water until the effluent reaches transparency and no impurities;
  • Alkaline washing and rinsing Add A5 degreaser to the cleaning system so that the concentration of A5 degreaser in the system is 3%. According to the foaming in the water in the washing tank, add an appropriate amount of defoaming agent.
  • the temperature is controlled at 60 °C ⁇ 5 °C, and after the alkali washing time is about 4 hours, the cleaning system solution is drained, rinsed with demineralized water, rinsed to the effluent pH 9.0, and the water quality is transparent;
  • the configured EDTA-2Na cleaning solution is put into the cleaning system for cleaning, and the iron content reaches equilibrium in the EDTA-2Na cleaning solution at the outlet of the cleaning system. The cleaning is terminated after no change; the above EDTA-2Na
  • the cleaning solution consists of a 3% by weight concentration of EDTA-2Na solution and an appropriate amount of EDTA-2Na corrosion inhibitor, hydrazine.
  • the EDTA-2Na corrosion inhibitor is an IS-136 corrosion inhibitor with a mass percent concentration of 0.3% and a hydrazine concentration of 0.2%.
  • the temperature of the solution during the above cleaning is 60 ⁇ 75 ° C ;
  • E. Passivation After the EDTA cleaning is completed, add NaOH to the above cleaning solution, adjust the pH value of the cleaning solution to about 9.0, and passivate the system. When the pH of the cleaning solution reaches 8.5 or more, and the temperature returns to 60 degrees or more, the timing starts. After the passivation time is 3 hours, the monitoring tube section is removed to observe the film formation, and the passivation time is not easy to exceed 5 hours.
  • the test piece is taken out, and the surface of the test piece is smooth and rust-free and has a silver-gray protective film.
  • the filming effect of this chemical cleaning is good.
  • EDTA low temperature chemistry 1400 m3 use starter pot 35 tons environmental pollution cleaning furnace to provide auxiliary small steam
  • the inorganic acid or organic acid is used for boiler cleaning, although the cleaning price is cheaper than the cleaning with EDTA, the inorganic acid and organic acid need to be discharged in the pre-passivation period, and the boiler should be rinsed with water to re-form the passivation reagent. It is cumbersome to treat the acid and passivation solution after cleaning to the discharge standard, and the price is high, and the discharge liquid is likely to cause environmental pollution.
  • the EDTA low-temperature chemical cleaning and passivation process can complete the "cleaning and passivation" of the boiler body in one step. Through recycling or coal-fired mixed combustion, the power plant can be discharged to "zero", which is conducive to environmental protection.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Cleaning By Liquid Or Steam (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Abstract

本发明涉及一种火力发电厂锅炉的化学清洗方法，特别是采用EDTA进行低温化学清洗钝化工艺，该工艺包括以下步骤：A、将化学清洗平台与需清洗的系统连接后形成清洗系统，对连接后的清洗系统进行水压试验后，打循环水冲洗至出水达到透明无杂质止；B、将清洗系统循环升温；C、碱洗及冲洗；D、EDTA清洗；钝化。本发明具有如下特点：1、节能降耗，缩短清洗周期及费用。2、使锅炉的清洗、钝化一步完成。在利用EDTA低温清洗后，增加了钝化过程。通过在EDTA清洗液中加入NaOH物质，调节EDTA清洗液的PH值，实现对被清洗锅炉的钝化。本发明的清洗工艺，适用于各种规格锅炉，有利于现场的实施和推广。

Description

火力发电厂锅炉 EDTA低温化学清洗钝化工艺
技术领域
本发明涉及一种火力发电厂锅炉的清洗领域， 特别是火力发电厂锅炉 EDTA低温化学清洗钝化工艺。
背景技术
据《火力发电厂锅炉化学清洗导则》的要求， 对基建和运行机组， 都应对 锅炉本体、 省煤器、 炉前给水系统分别进行化学清洗。 化学清洗是可以防止受 热面因腐蚀和结垢引起事故的必要措施， 同时也是提高锅炉热效率、 改善机组 水汽品质的有效措施之一。
随着电力工业的发展,高参数、 大容量机组的不断投产 ,以及环保意识的不 断增强， 对锅炉化学清洗提出了愈来愈高的要求。 EDTA清洗法以其临时系统 和清洗工艺筒单、 清洗时间短、 安全可靠、 清洗效果好、 废液可回收、 环保型 药剂等优点，在电力工业中得到了愈来愈广泛的关注，
《火力发电厂锅炉化学清洗导则》规定： 要求在 135 ~ 140°C进行 EDTA 清洗工艺。 有些科研机构通过研究， 将 EDTA清洗温度降低到为 80 ~ 90°C , 但是在中国北方和西北地区， 以及高海拔地区的冬季进行锅炉清洗， 80 ~ 90 ° 的温度只能通过辅助蒸汽对设备罐体加热，很难达到预期效果， 这就要启用 临炉加热（或其它辅助设备）及要求更高的保暖措施，无形中增加了经济成本。 火力发电厂锅炉 EDTA低温化学清洗钝化工艺， 以节能减排为切实点，通过研 究及大量实验室试验和现场试验， 将清洗温度控制在 60 ~ 75°C , 从而减小了 温度上的制约性， 减少了环境温度对工艺的影响， 减少了清洗工作中的不安全 性， 大幅度降低了能源消耗及资金投入， 易于操作和推广。
发明内容
EDTA低温化学清洗钝化工艺是通过 EDTA-2Na在低温状态下使清洗药液 与锅炉管壁上的垢起螯合作用， 结垢被剥离下来。 ^据污垢的种类、 结垢的厚 度、 被清洗表面的结垢复杂程度， 选定清洗剂浓度、 清洗液被加热的温度， 清 洗时间的长短以及选用清洗泵的流量、扬程、 流速等， 据以制定出相适应的清 洗工艺， 从而达到满意的清洗目的。
本发明的目的是克服现有技术的缺陷，提供一种利用 EDTA在低温度状态 下一次完成清洗、 钝化的火力发电厂锅炉 EDTA低温化学清洗钝化工艺。
为实现本发明的目的， 所采用的技术方案是： 一种火力发电厂锅炉 EDTA 低温化学清洗钝化工艺， 该工艺包括以下步骤：
A、 将化学清洗平台与需清洗的系统连接后形成清洗系统， 对连接后的清 洗系统进行水压试验后， 打循环水沖洗至出水达到透明无杂质止；
B、 将清洗系统循环升温至回液温度达到 40 ± 5 °C后， 进行碱洗；
C、 碱洗及沖洗： 在清洗系统中加入除油剂进行碱洗， 控制温度 60°C ± 5 °C , 碱洗时间 4 ~ 6小时后， 将碱洗废液排空， 用除盐水进行沖洗， 沖洗至出 水 PH 9.0, 水质透明止；
D、 EDTA清洗： 对上述碱洗后的清洗系统， 采用 EDTA-2Na清洗溶液进 行清洗， 至清洗系统出口的 EDTA-2Na清洗溶液中， 铁含量达到平衡， 无变化 后清洗终止； 上述 EDTA-2Na 清洗溶液是由质量百分比浓度为 3 ~ 6%的 EDTA-2Na溶液和适量 EDTA-2Na緩蚀剂、联胺组成； 上述清洗时溶液的温度 为 60 ~ 75°C ;
E、 钝化： 步骤 D结束后， 在上述清洗溶液中加入 NaOH, , 调节清洗溶 液的 PH值在 8.5 ~ 9.5之间， 对系统进行钝化处理。 当清洗溶液 PH达到 8.5 以上， 同时回液温度达到 60 °C以上后开始计时， 钝化时间在 3小时后， 取下 监视管段进行观察成膜情况， 钝化时间不易超过 5个小时。 上述步骤 D的清 洗溶液中， EDTA-2Na緩蚀剂的质量百分比浓度为 0.3 ~ 0.5%, 联胺的质量百 分比浓度为 0.2%。
上述步骤 E中， 钝化时的溶液温度为 60 ~ 70°C。
上述步 C中除油剂为 A5除油剂， A5除油剂的质量百分比浓度为 2 ~ 4%。 本发明具有如下特点： 1、 节能降耗， 缩短清洗周期及费用。 由于整个清 洗过程中清洗液的温度在 60 ~ 75°C , 钝化时的溶液温度为 60 ~ 70 °C , 这样通 过辅助蒸汽对清洗设备的罐体加热就可以满足清洗需要，与现用 EDTA为清洗 剂的清洗技术相比， 利用本方法对同样锅炉进行清洗时， 可有效可缩短清洗周 期一半， 降低清洗费用三分之一左右； 节约能源消耗。 2、本发明能够将 EDTA 清洗温度控制很低主要技术在于，在清洗过程中，对加入联胺量要严格进行计 算， 确保其的质量百分比浓度为 0.2%, 打破现有 EDTA清洗技术和导则上一 般钝化过程采用铵盐及钠盐常规想法， 采用强碱 NaOH进行 PH调节， 严格控 制钝化时间。 3、通过在 EDTA清洗液中加入联氨，钝化过程中加入强碱 NaOH 调节 EDTA钝化液的 PH值， 实现对被清洗锅炉的 "清洗、 钝化" 一步完成。 本发明的清洗工艺， 适用于各种规格锅炉， 有利于现场的实施和推广。
具体实施方式
在对上海锅炉厂有限公司制造的型号 SG-1166/17.47-M892 的亚临界压力 自然循环锅炉进行清洗实验时， 该锅炉的具体情况为： 汽包材质为 BHW35, 水冷壁材质为 SA-210C,省煤器材质为 SA-210C。给水由锅炉左侧单路经过止 回阀和电动阀后进入省煤器进口集箱后， 流经省煤器管组、 中间连接集箱和悬 吊管， 然后汇合在由省煤器出口集箱， 通过 3根 Φ219χ25的锅筒给水管道从 省煤器出口集箱引入锅筒。 给水在沿锅筒长度布置的给水分配管分别注入 4 根 Φ558.8χ60的大直径下降管座，给水直接在下降管中与炉水混合，在 4根下 降管的下端设有一分配器。 与 96根水冷壁引入管连接送入水冷壁的四周下集 箱。 水冷壁由 764根直径 Φ60的管子组成， 按受热情况和几何形状划分为 32 个循环回路。 下集箱， 经 48根 Φ 133 10mm的下水连接管分配到每个水冷壁 的下集箱。
本次实验所采用的化学清洗设备为 XLG-400型移动式锅炉化学清洗平台， 该化学清洗平台包括由一个清洗箱和 2台清洗泵组成的系统。
将移动式锅炉化学清洗平台与环锅相连， 形成由清洗箱→清洗泵→进液母 管→省煤器→汽包→排放口组成的清洗系统。
清洗过程为： A、 对上述清洗系统进行水压试验后， 打循环水沖洗至出水达到透明无杂 质止；
B、 利用辅助蒸汽对清洗系统进行循环加热至回液温度达到 40°C后， 进行 碱洗；
C、碱洗及沖洗： 在清洗系统中加入 A5除油剂，使系统中 A5除油剂的质 量百分比浓度为 3%。 根据清洗箱水体中起泡沫情况， 加入适量消泡剂。 碱洗 过程中控制温度 60°C ± 5°C , 碱洗时间 4小时左右后， 将清洗系统溶液排空， 用除盐水进行沖洗， 沖洗至出水 PH 9.0, 水质透明止；
D、 EDTA清洗： 将配置好的 EDTA-2Na清洗溶液打入清洗系统中， 进行 清洗， 至清洗系统出口的 EDTA-2Na清洗溶液中， 铁含量达到平衡， 无变化后 清洗终止； 上述 EDTA-2Na清洗溶液是由质量百分比浓度为 3%的 EDTA-2Na 溶液和适量 EDTA-2Na緩蚀剂、 联胺组成。 EDTA-2Na緩蚀剂是采用 IS-136 緩蚀剂， 其质量百分比浓度为 0.3%, 联胺的质量百分比浓度为 0.2%。 上述清 洗时溶液的温度为 60 ~ 75°C ;
E、 钝化： 在 EDTA清洗结束后， 在上述清洗溶液中加入 NaOH, 调节清 洗溶液的 PH值在 9.0左右， 对系统进行钝化处理。， 当清洗溶液 PH达到 8.5 以上， 同时回液温度达到 60度以上后开始计时， 钝化时间在 3小时后， 取下 监视管段进行观察成膜情况， 钝化时间不易超过 5个小时。
清洗结束后打开各系统排放门， 将清洗系统排空， 完成清洗。
清洗完成后取出试片观察，试片表面上光滑无锈且有一层银灰色的保护膜。 通过对试片成膜效果点滴试验检测， 本次化学清洗成膜效果 4艮好。
以上述机组为例
在标准大气压下， 1吨水升温 1度要花 1000千卡， 约为 41900千焦， 而 一公斤标准煤的燃烧值是 29302千焦。 以一台锅炉容积为 300立方米而言，在 理想状况下， 标准煤的燃烧值完全转化为热量，锅炉每升高一度需要标准煤约 0.428吨。 而现实生产过程中热量转化率 4艮低， 一般电厂启备锅炉的热量转化 率在 45%左右。 由于本专利采用的是清洗和钝化一步完成，所以水耗也相对其 它锅炉化学清洗技术较低。本专利技术减少了资金投入， 大幅度降低了能源消 耗。
表 1:以上述 300m3容积锅炉为例 EDTA低温化学清洗工艺与其它工艺的 对比
\ 费 用 耗水量 化学清洗所 耗煤量（以 环境污染 目 须条件 标准煤计， 情况 清洗工 不计算其它 消耗）
EDTA低温化学 1400 m3 利用启备锅 35吨 环境污染 清洗 炉提供辅助 小 蒸汽
EDTA高温化学 2800 m3 锅炉本体具 136吨 C02 、 CO 清洗（ 135 ~ 140 备油枪点火 及其它有
°C ) 条件、炉膛内 害气体污 具备保温措 染， 产生高 施 温污染。
EDTA化学清洗 2100 m3 锅炉具备临 64 屯 固体废弃 现有技术（ 80 ~ 炉加热条件， 物污染、
90 °C ) 临时系统及 炉膛内要有
保温措施 如果采用无机酸或者有机酸进行锅炉清洗， 清洗价格上虽然比使用 EDTA 进行清洗便宜，但在钝化前期无机酸和有机酸需要排放， 同时还要对锅炉进行 水沖洗，重新配制钝化试剂，对清洗后酸液和钝化液处理到排放标准比较繁瑣， 价格费用较高，排放液容易造成环境污染。 而 EDTA低温化学清洗钝化工艺可 以使锅炉本体 "清洗、 钝化" 一步完成， 通过回收或者燃煤混合燃烧， 可以让 电厂作到 "零"排放， 有利于环境保护。

Claims

权 利 要 求
1. 一种火力发电厂锅炉 EDTA低温化学清洗钝化工艺， 该工艺包括一下 步骤：
A、 将化学清洗平台与需清洗的系统连接后形成清洗系统， 对连接后的清 洗系统进行水压试验后， 打循环水沖洗至出水达到透明无杂质止；
B、 将清洗系统循环升温至回液温度达到 40 ± 5 °C后， 进行碱洗；
C、 碱洗及沖洗： 在清洗系统中加入除油剂进行碱洗， 控制回液温度 60 ± 5°C , 碱洗时间 4 ~ 6小时后， 将碱洗液排空， 用除盐水进行沖洗， 沖洗至出 水 PH 9.0, 水质透明止；
D、 EDTA清洗： 对上述碱洗后的清洗系统， 采用 EDTA-2Na清洗溶液进 行清洗， 至清洗系统出口的 EDTA-2Na清洗溶液中， 铁含量达到平衡， 无变化 后清洗终止； 上述 EDTA-2Na 清洗溶液是由质量百分比浓度为 3 ~ 6%的 EDTA-2Na溶液和适量 EDTA-2Na緩蚀剂、联胺组成； 上述清洗时溶液的回液 温度为 60 ~ 75°C ;
E、 钝化： 步骤 D结束后， 在上述清洗溶液中加入 NaOH, 调节清洗溶液 的 PH值在 8.5 ~ 9.5之间， 对系统进行钝化处理。 当清洗溶液 PH达到 8.5以 上， 同时温度达到 60度以上后开始计时， 钝化时间在 3小时后， 取下监视管 段进行观察成膜情况， 钝化时间不易超过 5个小时。
2.根据权利要求 1所述的火力发电厂锅炉 EDTA低温化学清洗钝化工艺， 其特征在于上述步骤 D的清洗溶液中， EDTA-2Na緩蚀剂的质量百分比浓度为
0.3 - 0.5%, 联胺的质量百分比浓度为 0.2%。
3.根据权利要求 1或 2所述的火力发电厂锅炉 EDTA低温化学清洗钝化 工艺， 其特征在于上述步骤 E中， 钝化时的溶液温度为 60 ~ 70 °C。
4.根据权利要求 3所述的火力发电厂锅炉 EDTA低温化学清洗钝化工艺， 其特征在于上述步 C中除油剂为 A5除油剂， A5除油剂的质量百分比浓度为 2 ~ 4%。
5.根据权利要求 4所诉的火力发电厂锅炉 EDTA低温化学清洗钝化工艺， 其特征在于上述步 E中调节 PH试剂为 NaOH, 钝化时间不超过 5个小时。
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