Discussion on the external temperature degreasing of the outer surface of steel drum
Discussion on the external temperature degreasing of the outer surface of steel drum
Dalian Institute of Applied Technology, Ministry of Nuclear Industry
Industry and Trade Joint Venture Dalian Barrel Factory
Abstract: This paper improves the cleaning process by adding HDY-T2 degreasing additive to the pretreatment process of steel drum exterior coating. Under the premise of improving the cleaning effect, the heating cleaning is changed to the normal temperature cleaning. This article also briefly introduces the composition, formulation, application, and economic benefits of cleaning fluids.
Foreword: Degreasing cleaning is an important process in the pre-treatment process of steel drums. Although surfactants and other additives have long been widely used in the barrel industry, most of them use a strong alkaline high temperature (80 ° C) or medium temperature (60-70 ° C) degreasing process. Low degreasing efficiency and high energy consumption. Therefore, it is imperative to select a highly efficient and energy-saving degreaser for the degreasing of steel drums.
The Dalian Cooper Factory of the Industry and Trade Joint Venture and the scientific and technical personnel of the Dalian Institute of Applied Technology of the Ministry of Nuclear Industry worked together to improve the original cleaning process in response to the problems existing in the degreasing process of the factory. After selecting HDY-T2 advanced energy-saving degreasing agent, it has realized the transition from high temperature to normal temperature cleaning, thus further improving the quality of degreasing and cleaning, and has won certain economic benefits for the factory.
First, the original barrel surface cleaning process
1. Cleaning equipment
The steel barrel external degreasing cleaning equipment of the factory is a multi-chamber through jet cleaning machine. The total length of the washing machine is 24 meters, and the effective length of the washing section and the washing section is 10 meters each. 6-7 barrels per minute, each barrel running in the degreasing section for nearly 2 minutes.
2. The composition of the cleaning solution and the problems in cleaning
The degreasing cleaning solution of the plant is a strong alkaline cleaning solution. It is mainly composed of industrial caustic soda and water glass, and a small amount of agricultural emulsifier is added. Although the formula has certain removal ability for anti-rust oil, but the steel barrel material mainly depends on imported and some domestically produced plates, the type and composition of surface anti-rust oil are different, even if it is spray-washed and heated 70-80. °C, the degreasing effect is still not ideal. After testing, the adhesion of paint after painting can often only reach two grades. High energy consumption and poor cleaning quality are the main problems in the original pre-painting process. Re-selecting the formulation of the cleaning solution is the key to improving the cleaning process.
Second, the improved degreasing cleaning process
1. Cleaning equipment: use the original cleaning equipment of our factory.
2. The composition and selection of the cleaning solution.
(1) Composition and application characteristics of HDY-T2 type degreaser
HDY-T2 type degreaser is a new product developed by Dalian Institute of Applied Technology of the Ministry of Nuclear Industry in recent years. A colorless, odorless, transparent viscous liquid prepared by scientifically compounding several surfactants (anionic surfactants and nonionic surfactants); it is non-toxic and does not pollute the environment. Energy efficient degreasing additive. It cleans all types of metal surfaces. The HDY-T2 degreaser is superior to the performance of any single surfactant due to the positive synergistic effect of several surfactants.
It adapts to a wide temperature range: 15-80 °C. It can be used not only for room temperature jet cleaning, but also for normal temperature, medium and high temperature dip cleaning.
After comparing performance tests with several domestic similar degreasers, we believe that HDY-T2 degreasing agent is superior to “664†(Shanghai No. 2 Detergent Factory) and “X-1†(Shanxi Changzhi) in degreasing efficiency. ) and other products. It is superior to "664" and "agricultural milk" in terms of high temperature resistance and alkali resistance. It can be seen that it is suitable to use HDY-T2 type degreasing agent to improve the pre-coating treatment process.
(2) Selection of builders
In the surfactant-added cleaning solution, the appropriate addition of alkaline builder helps to reduce the critical capsule concentration (ie CMC) of the surfactant in the solution, and can soften, dissolve, disperse, and prevent rust. And so on. On the basis of the original process formula, we still use industrial caustic soda and water glass as a builder. After reasonable adjustment of the ratio, we have achieved better degreasing effect.
(3) Selection test of defoamer
In the jet cleaning, due to the mechanical action, the cleaning time can be shortened, the cleaning efficiency can be improved, and the cleaning temperature can be lowered. The presence of a surfactant will cause a cleaning operation to generate and accumulate a large amount of foam, which is inconvenient for cleaning. It is absolutely necessary to add an antifoaming agent to the jet cleaning.
Add silicone oil, “foaming enemy†and “strong†antifoaming agent to the graduated test tube containing sodium dodecylbenzene sulfonate solution, and shake it up and down several times to make it foam quickly, and observe defoaming in time. Anti-foaming phenomenon. Through the test, it is considered that the "Strong" brand defoamer is the best. By adding 0.2% strength "strong" defoaming agent to the test solution, satisfactory antifoaming and defoaming effects can be obtained. When the foam layer reaches 3-4cm, it can be completely eliminated within 10 seconds at room temperature.
Third, the cleaning fluid performance test
1. The preparation of the test solution is shown in Table 1.
Table 1
Add the above chemical raw materials to water and dissolve them evenly.
2. The relationship between oil removal rate and temperature. Take the imported plate test piece (δ=l.Omm, Japan “Nippon Steelâ€), put it into the test liquid of Table 1 for the immersion and oil removal test at different temperatures, see Table 2.
Table 2
* Degreasing time is the time (seconds) necessary for the test piece to be completely degreased. The fully degreased test piece should not return to the water within 5-7 seconds after being rinsed with water.
The test shows that the cleaning solution can be degreased and cleaned in the range of normal temperature to 80 °C. Good degreasing effect. short time. Due to the jet cleaning, the steel drum in the cleaning section is run for 2 minutes, which is enough to ensure complete degreasing.
3. Defoaming test
Take the test solution of Table 1 as the defoaming test according to the test method of the defoaming agent selection test. Make the foam layer up to 3-4cm thick. Tests have shown that the purpose of foam suppression and defoaming can be achieved in about 16 seconds. Suitable for jet cleaning.
4. Determination of paint adhesion: The cleaned and dried steel drum test piece shall be painted and tested for adhesion according to normal requirements. Measurement results: generally up to one level, exceeding the standard of qualified steel drums (level 2 or above).
Fourth, the jet cleaning effect display
1. Preparation of cleaning solution: Prepared according to the method of Table 1.
2. Observation of degreasing effect: The main purpose of this process is to spray cleaning the outer surface of the steel drum at normal temperature. Through the observation of the steel drum at the outlet of the washing machine, the outer water film of the steel drum is evenly distributed, and the water is not returned within 5 seconds. The dried steel drum is obviously clean and white.
3. Determination of the adhesion of paint film: the exterior coating of the steel drum of the factory mostly uses alkyd paint and phenolic paint. The steel drum cleaned by the process is painted according to the process requirements, and the adhesion is determined after drying, up to 2-1 grade, which meets the coating requirements of the steel drum.
4. Foam condition: Since 0.2% of "strong" defoamer has been added to the cleaning solution, the foam generated during spraying can be better suppressed and eliminated. Generally, the cleaning operation of one shift is completed, and the foam can accumulate up to 4-5 cm in the liquid storage tank, which does not hinder the spray cleaning, and does not cause the loss of the cleaning agent.
5. Daily control of the cleaning solution: After one stage of the cleaning operation, the cleaning liquid is gradually reduced, and the water can be appropriately added. The cleaning efficiency is lowered due to a decrease in the concentration of the active substance and other active ingredients in the lotion. In order to ensure the normal operation of degreasing and cleaning, a certain amount of degreasing agent, builder and defoaming agent should be added to the liquid storage tank according to the process formula requirements to maintain the effectiveness of the cleaning liquid and satisfactory cleaning effect. It is generally determined by the change in the total alkalinity of the solution whether or not the active ingredient is added to the washing liquid. The total alkalinity should be controlled at 0.8-1.5%.
V. Analysis of economic benefits
1. Significant energy savings and reduced costs. The improved cleaning process uses HDY-T2 high-efficiency energy-saving degreaser, which changes the formulation of the cleaning solution, and the cleaning efficiency is greatly increased, thereby achieving normal temperature cleaning. Through long-term operation assessment and economic accounting, normal temperature cleaning operations, each steel drum can save costs O.3-0.5 yuan.
2. The waste liquid discharge cycle is extended. The original process degreasing cleaning solution must be replaced once for a period of up to 2 months. When discharged, the active ingredients in the cleaning solution are also taken away when they are boring. The improved cleaning solution has an enhanced emulsification ability for mineral oil, and the operation cycle can be up to 4 months, which reduces the consumption of raw materials.
3. Improve the quality of painting and enhance the competitiveness of the market. The improved cleaning process has a good degreasing effect and the coating quality has been significantly improved. The steel drums produced by our factory are generally praised by users for their domestic or export products. Increased market competitiveness and sales are getting better.
Sixth, the conclusion
1. The industrial and trade joint venture Dalian Co., Ltd. started from the process transformation, and adopted the high-efficiency and energy-saving degreasing agent to achieve economic results in the normal temperature cleaning of the external surface of the barrel. It is advisable for enterprises to tap the potential for energy saving, increase efficiency and increase new revenue. Initiative.
2. Although the normal temperature degreasing process can greatly reduce energy consumption, it is susceptible to weather temperature in production arrangements. Since the boiler is removed from the heat, the washed steel drum cannot be dried naturally and in a rainy weather, which hinders the painting operation. The temperature in winter is low and it is not suitable for regular room cleaning.
Our work is still in the beginning and exploratory stage. Please correct me if it is inappropriate.
references:
[1] Liu Cheng, “Application Manual for Surfactantsâ€, Chemical Industry Press, 1992.
[2] Lu Xiangeng, et al., “Applicable to the technology marketâ€, 1993 (1) 3.
[3] Ma Tianzeng et al., “Barrel Craft Technologyâ€, 1991.9.
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