MU Green Technology MU Static Mixing Technologies We Are To Live Harmonious Coexistence Of Ecology And Chemistry, And To Promote Amenity for Global Environment General Catalogue-1 MU SCRUBBER High-Performance Wet-Type Exhaust Gas Treatment Equipment Mixing Scrubber System 3 Deodorization Equipment (Exhaust Gas Treatment 90,000m /h) MU COMPANY LTD.
1. Structure MU Scrubber is a static mixer having mixing blades built-in inside cylindrical towers for agitation called MU Mixing Element with a high-performance gas-liquid contact efficiency. MU Mixing Element is a right- or left-twisted blade of a helical structure. Exhaust gases containing fine particles and chemical substances are fed from the upper part of MU Scrubber while washings supplied by pumps from the tanks at the bottom part of the equipment are injected into the towers via spray nozzles installed on sprinkler tubes, which tubes are placed on the sidewall of the towers. The washings absorb chemical substances and fine particle dusts present in exhaust gases, fall from the upper part to the lower part of the towers, gather in the tanks placed in downstream and circulate again in the towers. That is to say when exhaust gases which are passing through the towers flow in parallel with circulating liquids over MU Mixing Elements installedinside, gases and liquids are mixed and contacted completely with repetition of splitting, crossing, shearing, and helical rotation in right- and left-directions. The first effect of this system is to trap contained substances from exhaust gases. As described earlier gas-liquid contact efficiency is enhanced to perform trapping at high efficiency. Chemical substances present in exhaust gases are absorbed chemically, and inactive substances are dissolved physically and absorbed into washings. Fine particles of dusts in exhaust gases grow macro-gigantic into large particles via aggregation or swelling as they flow inside the equipment. They are then trapped by fine bubbles produced inside the towers as exhaust gases are mixed strongly with circulating washings. This way fine particles are now easily trapped into and suspended in washings. With the above process the exhaust gases are cleaned. Secondly, the system performs trapping of substances from exhaust gases without clogging in the equipment. This process is based on mutual effects realized by the combination between gas-liquid mixed flow of exhaust gases and washings and MU Mixing Elements. The system prevents clogging causable due to adhesion and growth of reactionproducts on front and rear surfaces and in pores of the blades as well as growth thereof on the wall surfaces of the equipment. Thirdly, the system realizes reduction of pressure drops during fluid passage in exhaust gas treatment. This effect is to lower pressure drops on the basis of the strucure of MU Mixing Element. The system also contributes to further reduction of pressure drops by causing ejector effect via blowout of circulating washings from spray nozzles of sprinkler tubes placed on the sidewall of the towers. During the exhaust gas treatment MU Scrubber is supplied properly with makeup lquids (fresh liquids). This is for the purpose of controlling gas-liquid temperatures. Normally cooling is carried out using sensible heat and evaporation heat from makeup lquids (fresh liquids). Also there is an additional method where heat exchangers are installed on circulating liquid lines to perform cooling from outside or heating.
Multiple control methods are available to suitably meet requirements of individual processes. Another purpose of supplying makeup liquids (fresh liquids) is to control concentrations of trapped substances in circulating liquids in the towers. Exhaust liquids are discharged while the liquid level in the tanks is maintained. 2. The Mixing Principle As shown in Fig. 1 helical-form right- (right rotation) and left- (left rotation) twisted blades are installed and multiple number of rightand left- twisted blades are placed alternately with space zones in between. The blades have many openings.while exhaust gases and washings are flowing in parallel and passing through the right-twisted helical-form blades gas-liquid mixed contact is realized by actions including splitting, crossing, as well as shearing in horizontal and vertical directions in space zones. In space zones gases and liquids are crossed together and mix- contacted by re-splitting and shearing actions that are afforded by helical left-twisted blades. This way gases and liquids are completely mix-contacted via continuous repetition of actions including multi-splitting, rotation, crossing, inversion as well as shearing in radial and axial directions. 3. Mixing Test With MU Scrubber important points in achieving favorable gas-liquid mix-contact conditions are two-folds as shown below. To enhance liquid/gas ratio (under constant gas flow rate) To increase gas flow rate (under constant liquid/gas ratio) Fig. 1 Schematic mode diagram of gas-liquid contact afforded by built-in MU Mixing Element In order to experimentally confirm the above, small-size MU Mixing Elements are placed on the 72 mm- inner diameter tube as shown in Fig. 2 and tests were conducted where water flows from the upper part in downward direction and at the same time ordinary-temperature air and water flow in parallel. Transparent tubing zone photographed in Fig.3 is a space, empty and hollow, between two MU Mixing Elements. Over there mixed status of air and water can be observed visually. Test results under several conditions are shown. First, at air flow rate of 10m/sec. water/air ratio was changed from 70 to 8l/. Here if water is reduced down to water/air ratio of 8l/ mixing status turns unfavorable (Photo.(d)) while in the range of 70 to 15l/ with more amount of water (Photo.(a) to (c)) it is good. Fig. 2 Schematic mode diagram of MU Scrubber settings for observation purpose (Shown in the diagram are photographed parts) 2
(a) Flowing amount per unit area 3,500m³/m² h Gas Velocity 10m/sec Liquid/Gas ratio 70ℓ/m³ (d) Flowing amount per unit area 3,500m³/m² h (b) Flowing amount per unit area (c) Flowing amount per unit area 3,500m³/m² h 3,500m³/m² h Gas Velocity 10m/sec Gas Velocity 10m/sec Liquid/Gas ratio 45ℓ/m³ (e) Flowing amount per unit area Liquid/Gas ratio 15ℓ/m³ (f) Flowing amount per unit area 1,800m³/m² h Gas Velocity 10m/sec Gas Velocity 5m/sec Liquid/Gas ratio 8ℓ/m³ Liquid/Gas ratio 35ℓ/m³ Fig. 3 Photograph of Gas-Liquid Mixed Status Liquid/Gas ratio= 3 1,800m³/m² h Gas Velocity 5m/sec Liquid/Gas ratio 15ℓ/m³ Liquid amout(ℓ h) Gas amout(m³/h)
Next air flow rate was halved to 5m/sec.. At that time mixed status at water/air ratio of 15 l/ was poor (Photo.(e)). Contrary to this, in the case where air flow rate is 10m/sec. given the same water/air ratio of 15 l/mixed status was good as shown in Photo. (c). This indicates that higher flow rates lead to favorable mixing conditions. Now at 5m/sec., half the pervious flow rate, by raising water/air ratio up to 35 l/ mixed status turned favorable again (Photo.(f)) Results of these tests indicate that as each of liquid/gas ratio and gas flow rate is raised gas-liquid mixed status becomes favorable. It was also observed that in the reverse case the status deteriorated. 4. Features 1) MU Scrubber can be installed on exhaust lines in a compact manner The superficial gas velocity in a tower is 2 to 20m/sec. and the tower can be installed midway on exhaust pipes. Since gas-liquid is a parallel flow flooding phenomenon does not take place. The scrubber can be operated at max. flow rate of 20m/sec. inside the tower. This way based on the compact design equipment costs can be saved. 2) Pressure drop is small During the operation liquids are circulated as gases pass through the towers. Liquid/gas ratios then are in the range of 0.2 to 500 l/, while in order to achieve a favorable gasliquid contact, in the vicinity of min. gas flow rate of 2m/sec. liquid/gas ratios are set relatively higher at 50 to 500 l/. On the contrary at max. flow rate of 20m/sec., liquid/gas ratios are relatively low in the range of 0.2 to 20 l/. When low pressure drop is desired, zero-pressure drop operation is also possible by reducing in-tower flow rate and/or lowering liquid/gas ratio. Conversely under the conditions of high flow rate and high liquid/gas ratio where gas-liquid contact efficiency is raised to the max. level, pressure drop may, in some cases, rise outside of ordinal operation level of 3kPa. 3) MU Scrubber prevents clogging and is maintenance free Even at severely demanded gas-liquid mixing conditions where strongly adhesive dusts are treated and/or solids such as metal oxides deposit at gas-liquid interfaces, clogging causable due to products is prevented entirely. At the same time continuous operation of many hours is achievable (8,000 hrs/year or over is our normal performance with records of 15 year continuous operation). When equipments are washed after long-term operation dismounting and washing can be done easily. 4) MU Scrubber is capable of high-performance trapping of dust, mist and chemical substance Removal efficiency is 90 to 99.99% or over in terms of absorption of chemical substances per tower. With proper process settings even 99.999% or over is possible provided that it depends on nature of chemical substances. For dusts or mists of 1 μm or lower removal efficiency is normally 90% or over, provided that it changes depending on compatibility of dusts with washings. If further enhancement of removal efficiency is required such requirement can be easily addressed normally with increased number of mixing elements.. 4
5) MU Scrubber is suitable for treatment of both high- and low-concentration gases MU Scrubber can easily treat exhaust gases containing even high-concentration chemical substances of several tens of volume% or over. No need to dilute with air or nitrogen. Also due to high gas-liquid contact efficiency the Scrubber is suitable for treatment of low-concentration chemical substances of several tens of volume ppm. 6) Due to high gas-liquid contact efficiency MU Scrubber can be designed simply assuming achievement of gas-liquid equilibrium MU Scrubber is designed by calculating gas-liquid composition, temperature and required heat quantity on the basis of gas-liquid equilibrium data of chemical absorption, phase change of evaporation and condensation or physical absorption based on Henry s Law. During absorption and desorption of chemical substances in gas-liquids it has been confirmed in several cases that gas-liquid equilibrium is reached inside MU Scrubber. When washings are water, gas-liquid equilibrium is reached during water evaporation and condensation. 7) Functions are available for simultaneous trapping and cooling. Gas-liquid cooling can be performed simultaneously with trapping of dusts and chemical substances from exhaust gases. Provision of these concurrent functions is an advantage of MU Scrubber. 8) For certain objectives countercurrent system is available additional to parallel -current system. In some limited special cases countercurrent design is provided. There theoretical plate number is calculated by applying such ideas as distillation tower concept to multi-stage Mixing Element. At this time if absorption rate of substances is slow, MU Scrubber is designed by setting number of plates higher than the theoretical number. During absorption process concentrations of chemical substances in exhaust liquids (absorption liquids) are raised and concentrations of chemical substances in exhaust gases are reduced to very small amounts. On the other hand during stripping high-concentration chemical substances are recovered in the form of gases from absorption liquids, and concentrations of chemical substances in absorption liquids that remained after stripping are minimized to the lowest possible level. In certain cases combination of parallel-current and countercurrent may be used as the optimum design. 5. Practical usages and examples of installation MU Scruber can be used for cleaning of exhaust gases, recovery of chemical substances from exhaust gases, etc. with the following applications. Fig. 4 shows some examples of actual installation designs. Practical Usages 1) Treatment of exhaust gases containing HCl, Cl2, HF, SOx, NH3, NOx, Hg, DXN s. etc. 2) Treatment of exhaust gases which generate metal oxide solids via contact with water including silicon tetrachloride, silicon trichloride, silicon dichloride, methyl sillcon chlorido, silicon fluoride, titanium tetrachloride, etc. 3) Dust removal of metal oxides such as SiO2, ZnO, etc. present in exhaust gases. 5
4) Deodorization by absorbing trace amount of offensive odor components including ammonia, triethylamin, hydrogen sulfide, etc. 5) Sterilization and disinfection of organisms such as bacteria, virus, etc. by ozone gases, etc. 6) Recovery of chemical substances such as NH3, HCl, etc. from exhaust gases. 7) Removal and recovery of dusts in the original agents. 6. How to make inquiries of MU Scrubber To make inquiries of MU Scrubber it is necessary to disclose design conditions as shown below in order to determine adequacy of the use of MU Scrubber and review process requirements and equipment specifications. The following indicates almost fullest range of design conditions. You are requested to disclose necessary information relative to the required accuracy of the review. Design Conditions 1. Treated gas amount: N/h 2. Gas temperature: Operation Design 3. Pressure at gas source: Operation kpag Design kpag 4. Pressure at inlet to equipment: Operation kpag Design kpag 5. Exhaust gas components: Gas, liquid or solid regarding components (a), (b), (c).? 6. Concentration of exhaust gas components: Components (a), (b), (c) are indicated in clear units such as volume%, volume ppm, mg/n, etc. 7. Post-treatment concentration of exhaust gas components: Components (a), (b), (c) are indicated in clear units such as volume ppm, mg/n etc. 8. Allowable max. pressure drop: Operation kpa Design kpa 9. Location of installation: Indoor or outdoor? 10. Size of Installation: Width, depth, height 11. Anti-explosion measures: Required or not required 12. Power source: Voltage, etc. 13. Materials: Produces discretion or designated To designate please designate materials, PVC, FRP, SUS, titanium and others, for each part as shown below. Tower, mixing element, circulating liquid tank, liquid pipe, gas pipe, circulating liquid pump, exhaust blower, flange, gasket, bolts and nuts, mounting and common base 14. Spare parts: Mixing Element, spray nozzle, gasket, bolts and nuts 15. Status of operation: Hours of operation hr/day, batch or continuous? 16. Supply of fresh liquid: Name of substance, temperature, pressure, concentration of dissolving substance, PH, specific gravity, viscosity 17. Exhaust liquid: Name of substance, temperature, concentration of dissolving substance 18. Active use of available information: Flow sheet of existing facilities, problems of existing facilities, disclosure of test data 19. Status of utilities: Disclosure of utility information required for exhaust gas treatment 6
Fig. 4 Examples of Actual Installation Designs 1) Installed On Anterior And Posterior Lines Of Existing Treatment Equipment This example assumes additional processes be installed midway on the piping of the existing facilities to enhance exhaust gas treatment. (2) Installed At Final Stage Of Exhaust Gas Treatment In this example it is assumed that MU Scrubber performs final treatment of exhaust gases and cleaned gases are released into air. Here mists entrained in exhaust gases are recovered normally by mist separator (MU Separator). Shown in the Fig. is one example of well-designed installation of mist separator (MU Separator). Dusts or mists may be adhered on and grow inside exhaust gas suction blower. The flow in this Figure resolves such problems. 3) To Satisfy Requirement For Higher Removal Efficiency MU Scrubber provides several combination patterns of high removal efficiency, recovery of chemical substances and dust removal. The Fig. shows one such example assuming dust removal in parallelcurrent in the first tower and absorption of chemical substances in countercurrent to clean up exhaust gases in the second tower. In the first tower dust is removed and in the second tower chemical substances are removed from exhaust gases at high efficiency. It is also possible in the second tower to concurrently recover chemical substances into absorption liquids using high-concentration liquids. In the first tower, however, since saturated liquids of chemical substances are used for washings absorption of chemical substances does not take place.
8 Contact Contact Packed bed column A-2 Dispersed Liquid Type Jet scrubber Venturi scrubber B-1 Packed column Spray column Gas phase (Dispersed phase) MU Scrubber B-4 Parallel-current Gas-liquid contact/mixing Countercurrent Gas-liquid contact/agitation Liquid phase (Dispersed phase) Mixing Contact Gas phase (Dispersed phase) MU Scrubber A-4 Dispersed Liquid Type Fig. 5. Comparison of Gas-Liquid Contact Mechanism of MU Scrubber with Conventional Scrubbers Gas-liquid contact/agitation Gas-liquid contact/agitation Countercurrent Liquid phase (Continuous phase) Tray column Perforated-Plate column B-3 Contact Perforated-plate column Tray column A-3 Dispersed Gas Type Parallel-current Liquid phase (Dispersed phase) Liquid phase (Dispersed phase) Gas phase (Continuous phase) B-2 Contact Gas phase (Continuous phase) Spray column ② Schematic Mode Diagram of Gas - Liquid Phase Mass Transfer Venturi scrubber Jet scrubber A-1 Dispersed Liquid Type ① Schematic Mode Diagram of Gas-Liquid Contact Status
Pump Exhaust gas source Exhaust Static Mixing Scrubber (MU Scrubber) Pump Right-twisted mixing element Left-twisted mixing element Right-twisted mixing elelment Exhaust Blower Circulating liquid tank Suitable for both small and large gas flow 100L 3,000m3/min High removal efficiency No nozzle clogging by dust mixing No flooding phenomenon Suitable for simultaneous processing of gas cooling,gas absorption and dust removal High-performance mixing blades called "MU Mixing Element"are placed inside towers FEATURE OF MU SCRUBBER IN COMPARISON TO EXISTING SCRUBBER Process type Jet Scrubber Packed Scrubber Babble Column Scrubber Spray Scrubber Exhaust gas Exhaust gas Exhaust gas Exhaust gas Schematic view Gas Exhaust blower Throat Demister Gas Pump Gas Pump Gas Pump Blower Blower Blower Circulating liquid tank Circulating liquid tank Circulating liquid tank Circulating liquid tank 9 Removal efficiency(%) 99 99.5 90 99 90 99 60 90 99.999 Processable concentration several100ppm several% several100ppm several% several100ppm several% several100ppm several% several10ppm 100% Amount of gas flow Suitable for Small gas flow (10L 200L/min) Suitable for Large gas flow (severalm3/min several100m3/min) Suitable for Large gas flow (severalm3/min several100m3/min) Suitable for Large gas flow (severalm3/min several100m3/min) Clogging inside apparatus None Sometimes many due to concentrated dusts and chemicals Relatively little compared with Packed Scrubber Little None Pressure drop(kpa) 3 5 0.2 1 1 3 0.02 0.2 0.5 3 Effect on removal efficiency by change of gas flow Small (adjustable by bypass line) Small Large Large Small Space velocity(m/sec) Flow speed of throat 30 0.3 2 1 3 0.2 1 2 20 Liquid-gas ratio(l/m3) 1,000 3,000 0.5 5 1 3 0.2 1.5 0.2 500 Feature High removal efficiency No nozzle clogging by dust mixing Forced liquid-gas mixing condition can be made in throat by liquid atomization with high pressure Less pressure drop Small amount of circulating liquid Simple structure More effective than Packed Scrubber in general Simple structure Generally utilized as previous step of absorption
MU Scrubber Tower