The formation of sulfate scale is related to the quality of water used. In the case of industrial circulating water, most companies generally adjust the pH of the system by adding H2SO4, but due to operational problems, some of the heat exchange equipment surface forms very hard sulfuric acid brine. Scale, the thickness is usually about 3mm. For example, in the north of China, the boiler scale sulfate scale is more common, and the sulfate scale formed by the brine pipeline is hard and the thickness can reach 30mm, which seriously affects the normal production.
The existing sulphate scale cleaning technology at home and abroad is generally converted into an alkali boiler, and then combined with pickling. This technology has a low removal rate and cannot be properly cleaned by the operating conditions. According to the national boiler chemical cleaning rules, at a certain temperature, a certain pressure, the removal rate of construction after several days is only 60%, and it has certain corrosion to the metal, and in many occasions, it does not have such construction conditions.
Therefore, the development of "rapid cleaning technology of sulfate scale under normal temperature and pressure conditions" has very important practical significance.
The scale analysis was carried out by analyzing the scale samples provided by a certain cleaning company in Shenyang and Shanxi Yangquan Chenguang Thermal Power Co., Ltd. and several brine sulphate scales. The scale is white or light yellow hard solid, the content of CaS4 is more than 60%, and some even reach 90%, which is pickled insoluble matter.
2 sulphate scale rapid cleaning agent development The development of sulphate scale rapid cleaning agent takes into account the following factors: safety and environmental protection: no corrosion or slight corrosion to equipment, safety to people or the environment; convenient construction: immersion or pump cycle cleaning Convenient inspection: Calculate the construction time by doubling the dissolution time of the sample; the cost is low: the cleaning cost is low.
The rapid cleaning of sulphate scale is carried out under normal temperature and normal pressure conditions. When cleaning, the solid phase sulphate reacts with the cleaning solution to convert the hardly soluble scale into a loose mud-like product, and the product has a certain fluidity. It can be taken out of the device with the solution.
13, the metal surface is changed from the active state to the passive state. After cleaning, the metal surface naturally forms a passivation film, and the passivation process is similar to that of the boiler, and does not cause metal corrosion.
According to the development idea, a large number of scale-dissolving tests are carried out to determine the components of the cleaning agent. In the final test, the scale is not broken, and the original sample is kept as it is, and it is placed in a special cleaning agent under normal temperature and normal pressure until it is completely Dissolved. The main components of special cleaning agent are: alkali-resistant surfactant (micro), such as: 0P-10, AES, etc., alkaline cleaning agent (main agent, mass fraction is generally 10% 15%, if alkaline cleaning agent The mass fraction is <10%, the scale dissolution effect is poor), and the strong penetrant (chelating agent, chelate the calcium ion in the scale, so that the reaction proceeds in the direction favorable for the scale dissolution).
Under normal temperature and normal pressure conditions, three methods of full immersion, immersion and cycle cleaning, and complete cycle cleaning are adopted.
During the cleaning process, the corrosion-resistant coupons were processed at the same time, which were respectively carbon steel, stainless steel and brass. The corrosion rate was measured and the cleaning time was 8 hours. The test results showed that the average corrosion rate was less than 0.0028g/(m2h). .
According to the calculation of 8h and the thickness of 1.5mm, the cleaning effect of different 3 different cleaning methods is shown in Table 1. Table 1 Different cleaning methods Different CaS04 content Cleaning effect comparison Table cleaning rate /% full soaking and soaking Circulating cycle cleaning test results: When the above content of sulfate scale is cleaned under the test conditions, the cleaning rate is 0.20.5mm/h. After the equipment is cleaned, the surface naturally forms a passivation film, which is repeatedly rinsed with clean water, and the device can be connected to the system. Running in.
5 The recovery of the cleaning solution and the use of the dirt after washing, the sludge is deposited in the lower part of the cleaning liquid, and the upper cleaning liquid can be used repeatedly; if the effect is not good, the mother liquid can be added; the lower mud material can be used for brick making.
If the special cleaning solution is accidentally splashed into the eyes, it can be washed with a large amount of water for 1015 minutes without special protection.
1) A cleaning company in Shenyang removes the sulfate scale of the boiler tube and the furnace tube. The scale is 11.5mm and the CaS4 content is >80%. It is cleaned with special cleaning solution for 5h, the removal rate is 100%, and the corrosion rate meets the national standard.
2) The sulphate scale of the Huai'an salt mine brine pipeline is cleaned, the scale thickness is 20, the CaS4 content is 70%, the cleaning time is 5 days, the pipeline 4km clearance rate is over 95%, and the transportation capacity is nearly doubled.
%, after 72h, the scale dissolved.
1) The normal temperature and pressure rapid cleaning technology of sulphate scale and the agent have the characteristics of fast cleaning speed, good effect, small corrosion to metal, and natural formation of protective film on the metal surface after cleaning.
Health and construction are very safe.
It has good promotion value for on-site use.
Chemical Analysis and Testing Technology Training Course Opening Notice In mid-May 2005, the chemical industry-specific occupational skill appraisal station will hold a 10-day chemical analysis and testing technology training course for those who have been engaged in chemical analysis or will be engaged in this work. The training takes a combination of centralized instruction and practical operations. The curriculum not only pays attention to perfecting the theoretical knowledge of the students, but also pays more attention to improving the practical operation ability of the students. After the completion of the study, the trainees can apply for the chemical cleaning (analytical testing) occupational skills appraisal test according to their actual situation. Those who pass the examination can obtain the national vocational qualification certificate issued by the Ministry of Labor and Social Security.
I. Training content 1. Chemical cleaning analysis and detection 1) Analysis of common chemical raw materials; 2) Qualitative and quantitative analysis of corrosion products and dirt; 3) Analysis and detection of acidity, alkalinity and cation of cleaning solution; 4) Corrosion inhibition of corrosion inhibitor Evaluation of efficiency and determination of corrosion efficiency.
2, industrial circulating cooling water quality analysis and detection 1) total hardness, total alkalinity, pH, conductivity, Ca2+, Mg2+ ion analysis; 2) chloride, sulfate, silicate, carbonate, bicarbonate and other anion analysis 3) Analysis of metal ions such as Fe2+, Fe3+, Cu2+.
Second, the specific arrangement will be reported on May 17, 2005, with centralized teaching on 1821 and actual operation on 2226.
May 27th Appraisal Examination (AM: Theoretical Knowledge, Afternoon: Actual Operation) Cost: The data fee, training fee, and appraisal fee total 3,500 yuan. Accommodation and food expenses are self-care (can be arranged in a unified manner).
Venue: Vocational skill appraisal station for chemical industry-specific work at No. 5, Anxiang Road, Area B, Beijing Airport Industrial Development Zone. Bus route: Dongzhimen take bus No. 915 and get off at Lasuying Station (gas station bypass) 500 meters west.
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