1 Overview
1.1 Development of filter dust removal technology
The ancient Shu Kingdom Jinsha Site Museum in Chengdu There are more than 3,000 years of "filters" on the display - exquisitely designed, non-bottomed large pots with fillers for filtering drinking water and removing sediment. This invention reveals the wonderful, romantic and rich life of the ancestors of our country. It can be regarded as the oldest technology gene for filter dust removal technology.
In 1972, I once met the thermal conductivity analyzer produced in 1956 for CO2 measurement of flue gas in the Chongqing Jiulong Power Plant. The sampling probe equipped with a filter is a de facto online analysis system. Also in 1956, Nanfen established a factory and became the origin of China's analytical instrument industry.
In 1972, when the CO2 thermal conductivity analyzer was produced, the SiC probe filter was improved from 100 mesh to 150 mesh, and the filtration accuracy was approximately 20um. In the past 40 years, the probe filters of many companies have remained at low levels of 10 to 20um. In May 2011, we visited a powerful foreign company. The filtration accuracy of the first-stage probe filter of its high-end products was 20um. The use and maintenance requirements: The entire probe was cleaned with chemical solvents for three months, and it had to be replaced within one year. Maintenance and costs will be overwhelmed.
At the end of the 1980s, the German H&B company had reached a high level of 0.3 um in the probe filter, successfully used in cement kiln kiln (sample gas temperature 1350 °C, dust content 2000g/m3) dry high temperature sampling probe, filtration Dust removal technology is already a fully mature technology. This fact confirms that the current industry is still lagging behind. It is questionable and reflective.
1.2 Reflections on the Status of Filtration and Dust Collection
Although filter dusting has long been a focus of professional attention, how can it be stagnant? Satisfaction and stay in the "can use" state, the behavior of unrestrained behavior has played a very bad block.
Experts and even senior experts rely on the technical logic of intuitive technology. One is that the accuracy of the filter is increased, the airflow resistance is necessarily greater, and certainly not applicable. The second is the use of a multi-stage filter combination technology route. The filtration accuracy can be improved, and sampling probes of several companies using three-stage filters can only reach >2um, but there is also the fear of increased airflow resistance and poor backwashing.
Chongqing Lingka Company relied on technological innovation and the coordination of many technical features of the filter to successfully advance the filter filter's filtering accuracy (single stage) to 0.3um, and the membrane filter was advanced to 0.05um without any increase in airflow resistance. Disadvantages, as well as new characteristics of nano hydrophobic properties, anti-pollution. This fact shows that the above-mentioned intuitive technical logic is not correct, and mature technologies must be extended and extended to microscopic and macroscopic technologies.
2 Analogy Revelation of Atmospheric Particulate Pollution
2.1 Haze Weather and Aerosol
The urban haze weather is the turbidity phenomenon after the air is mixed with smoke particles. Fine particles, especially ultrafine particles, have become one of the main pollutants that affect the air quality of urban environment in China. Diameter of <2.5um) pollutants suspended in the air for a long time does not settle and become a prominent pollution problem.
Aerosols generally refer to <2.5um of dry particle contamination and should also include fine droplets. Studies have shown that <1 μm of fine particles dominate the scattering and absorption of light, and the extinction of <1 μm particles in Tianjin accounts for 80% of the total extinction. [2] Therefore, it can be considered that the aerosol is a fine particle contamination of <1 μm, including dust, smoke, volatile organic compounds, water fog, etc. The so-called aerosol filter must be better than 1um, and it should be able to adapt to the conditions of the presence of fine liquid mist.
2.2 Air Quality Standards and Monitoring Examples
The United States established and implemented the air quality standard as early as in 1997 as PM2.5, <35ug/m3. WHO is also PM2.5 but <20ug/m3. There is early international consensus that particulate matter with a particle size of <2.5 μm is harmful to human health (such as cardiovascular disease).
China's air quality standards have been operating since 1996 and are PM10 (ie, particle size <10um). The criticality index is 100 (ie, <100ug/m3 is acceptable). Even at such low standards, about 58% of cities are not meeting standards. . China has not included <2.5 um of fine particulate matter in the scope of compulsory monitoring of pollutants, but it is the most toxic particulate matter. This will result in weather monitoring reports without pollution, and the public is deeply and physically surprised.
The study of fine particle pollution monitored by aerosol particle size analyzer in Tianjin shows that the particle size is less than 10um, which is a statutory monitoring target. The pollutants were mainly distributed in the range of 0.25-0.6 μm, with the highest concentration occurring in the 0.3-0.35 μm segment, accounting for 30.8%, and the particle size of <0.65 μm accounting for 98.5%. [2]
The air quality during the 2008 Olympic Games in Beijing is undoubtedly the best since it has been monitored. It is absolutely beneficial to human health. Monitoring during this period showed that the proportion of ultra-fine particles in the range of 30 to 50 nm (ie, 0.03 to 0.05 μm) was the largest, reaching 23.5%. [2]
3 Stringent requirements for sample gas processing on-line gas analyzers
Based on the core technology concept of “15-year life cycle for on-line analysis system†[3], the sample gas can best meet the standard-like excellent quality, and most engineering application projects certainly cannot meet this demanding requirement.
The most basic and important part of the analyzer's demanding requirements for sample processing is filtration dust removal. The author finds the only basis for quantity limitation from the specifications of the IR200 IR Analyzer from Yokogawa, Japan: <0.3um, <10ug/m3. The "<0.3um" value has penetrated into the peak (0.3-0.35um) of fine particulate contaminants in Tianjin, so it can be understood as an eligibility criterion. For the online analyzer and its on-line analysis system to truly achieve a long life of 10 to 15 years, the 0.3um “qualified†standard is certainly not enough. Ultrafine particles of 0.03 to 0.05 μm during the Beijing Olympics marked particularly good weather. Analogously, 0.05 μm accurate sample gas is a particularly good sample. Fortunately, this high standard can be achieved through hard work. of.
4 Air flow resistance test of LKF2 type hydrophobic microporous SiC high-efficiency filter element
As the 12th five-year outline of the national development strategy, great emphasis is placed on the application of new technologies, new components, new materials, new processes, and new devices. The technological advancement of online analytical technologies should also emphasize the research and application of new components. The research and application of advanced filter elements for filter dust removal technology of Chongqing Lingka Company has made breakthrough progress. LKF1 hydrophobic super-efficient polymeric filter membranes and LKF2 hydrophobic ultra microporous SiC high-efficiency filter elements have been successfully developed. The former is used for ultra-efficient membranes. Filter (0.05um), the latter is used for high-efficiency filtration (single stage, 0.3um) of non-clogging continuous sampling probes.
For high-efficiency probe filter elements, the biggest concern of professionals including senior experts is the failure of the airflow resistance assembly to cause the probe to clog. To this end or reduce its filtering accuracy to 10 ~ 20um, or to enlarge the filter element, a large company's large filter element size is Φ58 × Φ38 × 148, filtering surface area of ​​270cm2. Using 2 to 3 filter combinations is another type of unsuccessful effort.
The LKF2 probe filter developed by Lingka has the following comprehensive properties:
• Nano hydrophobic properties, anti-pollution and chemical corrosion, high temperature resistance;
• Efficient filtration: 0.3um 99%;
• Low airflow resistance: <100Pa (Φ42×Φ18×130 specifications, 1L/min flow rate)
Using the "LSC1-type ultra-microporous SiC high-efficiency filter element air flow resistance tester", the test results (1L/min flow rate) for six LKF2 type samples of Φ50×Φ20×135 specifications are: 74.5Pa 84.3Pa 68.6Pa 66.7Pa 80.4 Pa 82.4 Pa, the average value is 76.2 Pa. [4]
For the recommended Φ42 × Φ18 × 130 specifications, the filter surface area is only 171cm2, the maximum airflow resistance obtained by surface area conversion method is 104Pa, the average value is 94Pa.
Hopefully, the above test results can be heard positively: relying on technological innovation, relying on in-depth technical design, quality design and advanced manufacturing, advanced filter elements for processing and developing new processes, completely achieving hydrophobic characteristics, efficient filtration, and low airflow resistance The perfect coordination will reach the realm of the ultimate ideal solution in TRIZ's Invention Problem Solving Theory.
5 Technical design of non-clogging continuous sampling probes
The filter element of the probe can be integrated into the dry sampling probe system only through perfect system technology design, so as to achieve the purpose of continuous sampling without clogging. The technical elements involved are as follows:
• As little dust as possible enters the probe tube of the probe: The selection of the probe mounting position and the installation and installation must be handled with care;
• The probe structure is well-designed: it must meet the technical characteristics of fluid mechanics;
• Configure the back-flush device: it is best to have both internal and external back-sweep at the same time. The back-flush gas path and the sample gas pipeline are preferably independent of each other, the diameter of the pipe is matched properly, and the back-flush device is preferably less than 2 meters from the probe installation position;
• PLC program-controlled back-flushing: A reasonable pulse backflush program can be modified in the field according to actual needs. Non-pulse high-resistance continuous purging is technically very backward and is doomed to be ineffective.
The above-mentioned well-designed and reasonably matched dry sampling probes, such as the LKP103 medium-temperature sampling probe, can completely achieve near-maintenance, high-precision filtration, continuous sampling without clogging, and achieve satisfactory results of coordinated operation. According to a site survey conducted by a cement factory in Lafarge, the pipelines and components behind the probes did not show any pollution, and the filter membranes of the rear-stage ultra-efficient filters could not be replaced in a year. [5]
6 Patented R&D of combined demister filter separator
In addition to filter dust removal, another important topic of sample gas treatment is defogging and dehydration. The most famous and oldest Chinese medicine book in China is "The Yellow Emperor's Internal Classic." The secret to teaching people not to get sick is simply a simple two-step approach to "eat well and sleep well." The sample gas processing system technology also has two strokes that can be compared and conceived: “filtering and dust removal, and good defogging and dehydration†can make the on-line analysis system “not sickâ€, that is, less failure, less maintenance, and longer life.
Once the industry has high-profile affirmation of self-purification cyclone filters and eliminators with the exception of the alkali and liquid mist, it now appears that both have technical defects and limitations. The former filter element is stainless steel powder metallurgy, and the filtration accuracy is not high. At least 2um or more, the airflow resistance is large. In case of high humidity (especially liquid water), it is easy to block; the effect of cyclone separation of dust and droplets is also limited. Without a "threshold", separation of particles >5 um yields a separation efficiency of 90%. The latter is actually a coagulation separation acting on a loose filler, and there is also no "threshold", and it is difficult to achieve an ideal defogging effect.
LKP307 type combined demister filter separator has applied for a utility model patent. It combines the full functions of high-efficiency condensation demister, particulate matter (including droplets) high-efficiency filter, gas-water separator, and even bypass diverter. The core is a LKF2-type hydrophobic ultra-microporous SiC high-efficiency filter element with a size of Φ27×Φ16×50, a filtration accuracy of 1um 99%, and airflow resistance of 120Pa. Its biggest advantage is based on the hydrophobic nature of the lotus leaf, and there is a 1um "threshold", a variety of particle size of the liquid mist gradually increases after it condenses, after a certain degree of gravity drops to achieve self-cleaning . Due to the hydrophobicity, there are fewer liquid mists that can be traversed. The liquid water and vapor-phase water (ie, liquid mist) are trapped in front of the “valve†and separated, steam and even smaller liquid mist are trapped. It is the legal task of the sample gas condenser thereafter.
With LKP307, even if the wet desulfurization CEMS project does not need to use "water alarm."
The LKP307T can also be used as a sampling probe in the chemical industry. It completely blocks the transmission of liquid and gaseous water (>1 μm of fine liquid mist) to the downstream stage. The liquid water and the condensed liquid water are returned to the 1/2†sampling tube. In the process tube, it is not necessary to design drainage measures separately.
7 Interpretation of Filtration Mechanism of LKF1 Hydrophobic Super-efficient Polymeric Filtration Membrane
LKF1 type polymeric filter film has the following excellent comprehensive performance:
• Ultra-efficient filtration: 0.3um 99.99999%
The presumed reference value is 0.05um 99%, which is smaller than the 0.1um of the upper limit of the nanoscale (1-100nm), and better than 0.1um is called ultrafiltration (UF);
• Low airflow resistance: 120Pa (Φ50 specification, 1L/min flow rate);
• Nano hydrophobic properties: water resistance 5000Pa, anti-pollution;
• High strength: thickness 0.36±0.02mm, base material is glass fiber, corrosion resistance;
Tensile strength: longitudinal (MD) 400N/m2, lateral (ND) 250N/m2;
• The maximum use temperature: 200 °C;
• Oil mist transmission rate: 0.00001 (that is, 99.99999% filtration accuracy).
Special Note:
Data of 0.3um, 99.99999%, and 0.00001 of the oil mist transmission rate were obtained using the internationally accepted laser particle method and imported equipment.
The low airflow resistance of LKF1 ultra-efficient filtration, including professionals including senior experts, has many doubts. This is due to the misleading direct technical thinking. It only believes that the rat hole based on the interception mechanism is bigger than the mouse. Ultrafine particles have different filtering mechanisms, which is the difference in microscopic techniques.
The filtration mechanism of LKF1 is interpreted as follows:
• >0.3um: inertial collision and interception will produce particle gravity settlement, which belongs to mechanical interception;
• 0.1 to 0.3um: both diffusion and interception;
• <0.1um: Brownian diffusion, ie van Dewar, is more of a physical effect.
Its nano-hydrophobic properties are due to the hydrophobic surface with micro/nano structures.
8 Self-cleaning ultra-efficient membrane filter patent research and development
Adopt LKF1 type hydrophobic super-efficient polymerization filtration membrane, which has the following filter elements: Ф55, Ф50, Ф46.5, Ф38 and Ф30, and has developed LKP300 series ultra-efficient membrane filter on the market:
The LKP301 (Ф50mm) and LKP302 (Ф55mm) are all panel mounted and the diaphragm can be easily maintained or replaced online. The effective filter area of ​​LKP301 is 17cm2, dead volume 8cm3, airflow resistance 120Pa.
LKP303A self-cleaning ultra-efficient membrane filter (Ф50mm) is a utility model patented product. It is wall-mounted and the diaphragm can also be easily maintained or replaced online. The third joint besides the inlet and outlet of sample gas is discharge separation water. , condensate and bypass flow outlet, bypass air flow has self-cleaning function on the filter membrane.
The LKP305 compact disposable filter (Ф30mm) is used in the analyzer housing for final protection.
9 Preliminary Conclusions and Suggestions
9.1 Analogy and association are the technical thinking methods used repeatedly in this paper.
The simple solution to complex technical problems and the pursuit of simple results are the direction of this article.
"Coordination" is the key to achieving technological breakthroughs and expressing breakthroughs in this article.
9.2 A technology must reach the realm of mature technology. Professionals are only willing to adopt it. Mature technology should have the following four signs:
• Have a certain theoretical analysis and theoretical basis;
• Have accurate technical characteristics and error data;
• Coordinated performance within the technical system, there is no potential technical problem;
• Proof of long-term engineering practice.
9.3 It is possible to pursue the ultimate ideal solution
(1) In the past, the filter element was only regarded as a very intuitive and simple part. Based on the inspiration of TRIZ's Invention Problem Solving Theory, this article sees it as a living technology system (small system or sub-system). This is the first step in technological advancement.
(2) Filter elements This small system must also rely on a coordinated evolutionary principle to evolve and develop: sharp conflicts between increased filtering accuracy and reduced airflow resistance are resolved and highly coordinated. The long-term inoperability and uncontrollability have become easy to operate and completely controllable. This is a great technical advantage. In the 40 years, I couldn’t do anything. Today, I was in a cloud.
(3) The coordination of the small-technical system of filter elements facilitates and improves the coordination of the complex technology system of the online analytical instrument large-scale system and the online analytical system. This helps to achieve the overall goal of long-term coordinated operation of engineering applications.
(4) The quality design and innovative R&D of Lingka's advanced filter elements deepen the technical understanding of filter dust removal, and we have the courage to seek the ultimate ideal solution to the “TRIZ invention problem solving theoryâ€:[6]
• retains the advantages of the original system;
• Eliminate the deficiencies of the original system;
• did not complicate the new system;
• The new system did not introduce new defects.
(5) LKF1 and LKF2 advanced filter elements have core values ​​for sample gas processing systems and on-line gas analysis systems. They play an irreplaceable role in advancing technological advancement with low maintenance and high reliability.
Although the filter element is small, it has the performance of cutting-edge technology in the new century. The two major manifestations of breakthroughs in technological innovation are:
• Full control over the key parameters of the core process;
• Coordinated operation of important technical features of technical systems at all levels.
references
1 Jin Yizhong. Application and development of on-line analytical instrument sample processing system technology, Proceedings of the 2nd International Analytical Instrument Application and Development International Forum, 2007: 210-216
2 Dong Haiyan et al. A continuous online observation and analysis of fine particulate pollution in Tianjin, Environmental Monitoring Management and Technology, 2010(6): 42~45
3 Jin Yizhong, Cao Yigang. On-line Analysis of Engineering Technology Introduction, Analytical Instruments, 2008(5): 39~44
4 LKF2 Ultra Microporous SiC High Efficiency Filter Test Report, Chongqing Lingka Analytical Instrument Co., Ltd., 2011.3.26
5 Jin Yizhong. A comprehensive investigation report on the four-year operation of Lafarge Cement Optimized Control Online Analysis System, 2010
6 Yang Qingliang. How the Invention Was Born--TRIZ Theory Full Contact, Mechanical Industry Press, 2006: 30~32