MXPA00007571A - Low pressure drop inlet design to promote good gas flow patterns in high velocity absorbers - Google Patents

Abstract

A high velocity absorber (10) has a lower larger diameter tank section (20) for receiving a slurry at a liquid level (26) in the tank section (20), an upper smaller diameter absorber section (22) where liquid scrubbing agent is mingled with flue gas (44) from which impurities are to be absorbed, and a low pressure drop inlet assembly having a transition structure (24) between the tank section (20) and the absorber section (22) for closing a gas flow path and a liquid flow path between the tank section (20) and the absorber section (22). An inlet housing (42) is connected to and communicates with the transition structure (24) for inlet of flue gas (44) into the transition structure (24) between the tank section (20) and the absorber section (22).

Description

DESIGN OF LOW PRESSURE FALL INLET TUBE TO PROMOTE GOOD GAS FLOW PATTERNS IN ABSORBERS OF HIGH SPEED DESCRIPTION OF THE INVENTION The present invention, in general, is related to degassing absorbents of combustion gases, and in particular, with a new and novel arrangement of useful absorber having a gas inlet pipe in the transition between a section of large diameter lower tank containing a liquid mixing level, and a small diameter upper absorber section. The commercialization and development of high-speed absorbers is pursued due to the economic advantages they offer such as low capital cost, less land requirements, shorter and more compact absorbers, and improved S02 removal efficiency. On the other hand, high speed has some disadvantages, such as increased resistance to gas flow and increased sensitivity of the system to changes in the hydraulic compartment of the gas and liquid phases. "The physical model studies show that the velocity of the gas through the intake pipe of the absorber affects the distribution of the gas in the absorber and affects the performance and behavior of the absorption zone and the dew point eliminator. ± CH '~ of the absorber, the resistance to gas flow is categorized either as useful resistance or parasitic resistance. The resistance is directly and totally converted into purifying efficiency and participates in the redistribution of gas such as the pressure drop of the absorption zone. The parasitic resistance is spent to conduct the gas through the confines of the absorber without the effective participation in the chemical process. Inlet and outlet tube resistances are good examples of this type of resistance. The use of rotating vanes or other gas distribution devices is a simple solution for the resistance of the outlet pipe. However, the pressure drop of the inlet tube is not easy to reduce because it is a combination of gas and the interaction of scrubbing liquid through the absorber. The inlet tubes of traditional absorbers vary in configuration and size "although the configuration of the inlet tubes is basically the same Figure 1 shows the design of the inlet tube commonly offered (without protective awning) in this design, the liquid which flows out of the walls 12 of the absorber or sprayed by the nearby sprinkler manifolds, falls inside the inlet tube 14 and forms a solid product in the wet / dry interface causing maldistribution and greater strength. As shown in Figure 2, "protective" intrusive awnings 16 were placed on top of the inlet tube 14 (see Patent Number 5,281,402). The awning deflects the point of contact (between the hot gas and the flow of liquid curtains) from the vicinity of the inlet tube to the absorber center. The deposition of solids is prevented due to the fact that gas humidification occurs in an area where there is minimal contact between the hot gas and the surfaces of the flue inlet pipe. ~ It has been proven that this design is functional at traditional gas velocities when the spray zone resistance is large enough to affect - even the distribution before the gas reaches the spray eliminator beyond the wall 12. However, as the velocity of the gas increases, the resistance of the curtain significantly adds to the "system" a fall of pressure and distorts the gas flow pattern that becomes more critical. While the liquid curtain is necessary to humidify and aid redistribution of gas, it also has two significant disadvantages. Significantly increases the pressure drop of the inlet tube err compared to an inlet tube without awning, and distorts the flow pattern as the gas rises through the absorber. - In a new generation of high speed absorbers, the gas velocity is set between approximately 15 to 20 feet per second. The small distortion in the gas flow pattern results in high localized gas velocities approaching or exceeding the critical velocity of the de-oiler and can result in a functional failure of the de-aeration device. To solve the negative effects of high gas velocity in the inlet pipe, one can increase the inlet pipe flow area and limit the gas velocity to the conventional speed of 3,000 feet per minute. "This solution, although simple and practice, will result in a higher inlet-tube aspect ratio (height to width) • and increases the height of the absorber and inlet tube resistance.An increase in the height of the absorber minimizes the advantages obtained by the high-speed scrubber Other options include low-pressure drop gas inlet pipes developed for the new generation of high-speed absorbers, or the average use available within the system to redistribute the gas flow without a significant increase in The input tube resistance The current industry entrance tube design uses the installation of the protective awning 16 on top of the entrance tube. to 14 to divert the mixture away from the flow of hot combustion gas and avoid solid deposition at the wet / dry interface. However, at a high absorber gas velocity, extrusion of the gas path by the high density liquid curtain diverts the gas to the sides causing an increase in gas velocity and possible distortion. Model studies and the experience of operating teach. that at an absorber speed between about 1 to about 12.5 feet per second, the current inlet tube designs provide good gas distribution through the absorber at or below about 3,000 feet per minute of inlet tube velocity. The good gas distribution is partially provided by the resistance of the liquid curtain, which falls from the awning to the incoming gas. The main function of the awning is to provide protection against moisture in the inlet pipe and the deposition of solids and provide ample resistance to decrease the incoming gas, thus allowing the gas an adequate time to redistribute through the flow area of the gas. Absorber At a gas velocity of the absorber below 12.5 feet per second, a reasonable gas distortion in the absorber will not reach the critical failure rate of the de-oiler as the gas velocity increases above about 12.5 feet per second - and reaches about 20 feet per second or more, the resistance of the liquid curtain falls off the awning that becomes significant and amplifies the effects of the gas flow distortion. " Several attempts have been made to Teduce the awning strength first by reducing a new generation of non-intrusive awnings. In these designs, the awning is removed from the inlet pipe gas stream and placed above the inlet pipe. See US Patent Numbers 5,403,523; 5,558,818 and 5,648,022. "Each of these developments contributes to the reduction of the parasitic pressure drop of the inlet pipe caused by the intrusion of the original awning into the gas flow path." These designs, however, added three feet to the The height of the absorber and none of these completely eliminated the effect of the high density liquid curtain.These efforts were steps taken in the correct direction to reduce the parasitic resistance of the inlet tube, however, in each case the The resistance of the curtain remained the same, considering that one inch (water) of pressure drop is evaluated at approximately $ 1 million over the life of the power plant, the reduction of the parasitic resistance of the absorber provides a significant competitive margin. compare the pressure drop of an inlet tube with and if awning TABLE 1 Comparison of Input Pressure Drop for Designs with and without Tol do Description Intrusive Awning Non-Intrusive Awning Without awning _ _ Pressure Drop 4.59 3.50 2.50 Inlet Tube (Inch of Water) * Inlet pipe speed of approximately 3,600 feet per minute, liquid flow of approximately 60 gpm per square foot, speed of the absorber of. approximately 15 feet per second. The present invention provides a "combination of a gas inlet pipe developed with the intended protection against solids deposits in the wet / dry zone and reduces the liquid curtain to the same absorbed density in the inlet pipe design without The new inlet tube does not promote the formation of thick high-density liquid curtains in the gas path, thus reducing the parasitic pressure drop experienced with inlet tubes equipped with -thods. entry tube in the transition between the large diameter tank and the small diameter absorption zone The successful application of this invention could possibly result in a cost value of approximately $ 1,000,000 less than current designs and over approximately $ 2,000,000 in savings on the original intrusive awning design The present invention is suitable for absorbers with. The inlet tube is located at the transition between the tank and the absorber section. As a consequence of the position, the upper plate of the inlet tube extends from about 1 to about 10 feet beyond the lower plate. This "extension" provides a natural protection to the reflux inlet tube of the mixture within the hot gas zone.The smaller diameter absorption zone limits the area of liquid that falls to the center of the tank leaving a circular crown of the This mixture eliminates the need for an inlet tube busa and uses the circular crown to provide the gas with a low resistance path.The falling liquid has a suction effect on the gas Incoming, thus, promoting gas distribution along the perimeter of the transition.The side walls of the inlet tube follow the contour of the conical transition.Side protectors can be provided to protect the inlet tube from splashing, without However, it is expected that these side protectors will be added on a per-cass case basis, the uniform transition between the tank and the absorption zone. It provides means to contract the gas smoothly and uniformly within the section of the absorber. • Accordingly, an object of the present invention is to provide- ^ in an absorber having a lower-section large-diameter tank section to receive a mixture at a liquid level in the tank section, a section of absorber of small upper diameter where the liquid purifying agent is mixed with the combustion gas from which impurities must be absorbed, a low pressure inlet tube assembly comprising a transition structure between the tank section and the absorber section to close a __gas flow path and a liquid flow path between the tank section and the absorber section an inlet tube housing connected to and in communication with the transition structure for the combustion gas inlet pipe within the transition structure between the tank section and the absorber section. Another object of the present invention is to provide a low pressure inlet tube assembly for an absorber tower having a simple design, a rugged construction and onomic production. The different characteristics of novelty which characterize the invention are shown particularly in the appended claims and which form a part of this description. For a better understanding of the invention, operative advantages and specific objects obtained by their uses, reference is made to the accompanying drawings and descriptive matter in which the preferred embodiment of the invention is illustrated. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: - - Figure 1 is a partial schematic illustration of an absorber tower according to the prior art; Figure 2 is a view similar to Figure 1 of. another absorber tower according to the prior art; Figure 3 is a schematic side elevational view, partially in section of an absorbent tower according to the present invention, Figure 4 is an elevation view of the absorbent tower of the present invention, Figure 5 is a view in squematic cut taken along line 5-5 of Figure 4, Figure 6 is a view similar to Figure 4 of a prior art absorbent tower, Figure 7 is a schematic sectional view taken along the lines of FIG. along line 7-7 of Figure 6, Figure 8 is a partial sectional view showing the transition structure of an absorber tower according to the present invention, and Figure 9 is a view similar to Figure 8. of the transition structure illustrating the inlet pipe assembly of the present invention With reference to the drawings in particular, the invention contained in Figures 3 and 4 comprises an absorbent tower generally designated at ten ten or a relatively large diameter lower tank section 20 connected to an absorber section 22 of relatively smaller upper diameter by a transition structure 24 which forms a gas-tight and liquid-tight trajectory for gases and liquids between the tank section 20 and section 22 of the absorbent Consistent with the prior art, the tank section 20 contains a mixture made of a liquid absorber, particles and impurity from the absorption process, rising to a level 26 in section 20 of tank, under the transition structure 24. As with the absorbers, in particular, the gas absorbers for two desulfurization combustion gases, the section 22"of the absorber contains a perforated plate or tray 30 which helps to divide the combustion gas that rises with the liquid that falls to immediately communicate the two fluids to each other A plurality, 3 in the case of Figure 3, of absorber sprinkler manifolds 32 are separated at intervals on the tray 30 and receive absorbing fluid in the form of recycled tank mixture. 20 and fresh absorption liquid as a mixture of calcium carbonate or calcium, a primary spray eliminator 34 extends through the internal volume of the observer 22, above the collectors 32. An over-spray connector 36 can be provided. above "of the primary spray eliminator 34 and a secondary spray eliminator 38 provided on the over-spray manifold" 36. The purified gas exits through an upper gas tube outlet schematically shown at 40 in Figure 3. In accordance with the present invention, the flue gas initially enters the absorber tower 10 through a tube housing 42. inlet as shown schematically by the arrow 44. The inlet tube housing 42 has an opening communicating with the transition structure 24 for receiving gas 44 therein. tower, and has an aspect index of a typical height X and a typical width Y, the height is confined to the height of the transition structure 24 and the width extends partially around the circumference of the transition structure.

Figure 4 illustrates the recirculation ducts 46 that form part of the recycling structure - known for mixing. In comparison, Figure 6 illustrates a known absorbent tower generally identified as 100, with a lower tank 120, or a higher absorption section 122 and a transition structure 124. The recycling structure 146 is also provided to recycle the tank 120 mixture. According to the prior art, the inlet pipe 142 is connected to and communicates with the upper spray section 122 and suffers from the aforementioned prior art problems. previously. Figure 5 illustrates how gas enters through dislodging 42 from inlet tube in transition structure 24, spreads easily around the annular transition area of free liquid and distributes more evenly around the absorption section 22. This is mainly due to the fact that in the transition area in the annular space around the absorption section, very little liquid is present, in the background leaving the free gas to spread quickly and easily around the circular crown. Figure 7 is a similar view taken of the structure of Figure 6, illustrating however, how the entire gas inlet pipe through the inlet tube housing 142 is initially confined to one side of the section 142 of absorption that contains liquid. The height (X) of the housing inlet tube 42 determines the height of the transition 24 and the angle 25 at which the transition is executed. Transition angles - between about 15 and about 90 degrees are possible to use. They can be acute angles (less than about 15 degrees). The width (Y) of the inlet tube of the housing 42 and is usually limited to one sector: with an apex angle of approximately 90 degrees for structural purposes. A larger inlet tube width that expands over the entire diameter of the absorber can also be used without or with intermediate load bearing sections of the absorber cover to divide the gas inlet tube into two or more "sections as is required by a mechanical design.The essence of an awning plate projecting into the gas / liquid stream produces the density of the liquid curtain to a thickness that can be compared to the arrangement without an awning, thereby reducing the low depression-parasite liquid curtain at a level of designs without awning.In addition, the liquid-free circular crown formed along the perimeter of the tank allows the gas to spread around at a lower velocity. of gas will result in a recovery of part of the expanded velocity pressure in the previous designs, a higher pressure recovery is expected as the gas cold and humidifies, however, this gain is also experienced in current input tube designs. The following advantages are realized from the application of the new inlet pipe arrangement: 1. The location of the inlet pipe in the transition section reduces the depression drop an amount equal to the pressure drop of the liquid curtain. The additional pressure drop reduction can be realized as a result of a lower gas velocity in the ring gear and a better gas distribution. 2. A better distribution of gas in the absorption zone is needed to maximize the liquid contact and optimize the removal efficiency of the absorber. 3. A minimum height reduction of the total absorber height from approximately 2.5 to approximately 3_ feet. This height is added to accommodate the present design with awning. 4. The design is simple and eliminates the need for an external busa required by the previous high-speed input tube design. 5. When lowering the sprinkler manifolds. approximately 2 to 3 feet results in a lower pumping force and improves the design economy of the absorber. 6. Reduction in the "alloy material" 11 used to build the awning and a false bottom 7. Eliminate or use smaller side shields that will also reduce the use of high alloy materials and promote lower gas velocity in the circular crown 8. The removal of the busa is another source to reduce material requirements and the total weight of the absorber 9. The ring gear is provided to distribute the gas along the perimeter of the tank and is expected to provide a better distribution of gas at the bottom of the absorption zone 10. The suction created in the circular crown by the effect of the falling liquid mixture can create a reduction that can be measured in the resistance of the absorber. structure Transition 24 may include an upper flange or a skirt 27 extending 360 ° around the lower open end of the absorption section 22. Figure S is in a circumferentially out-of-place position compared to Figure 8 illustrating the inlet tube housing 42. The flange 27 extends through the inlet tube housing 42 in the embodiment of Figure 9. While the specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention can be exemplified in another way without departing from such principles. ~ - -

Claims (9)

1. CLAIMS 1. An absorber tower having a large diameter lower tank section to contain a liquid absorption mixture that rises to a liquid level in the tank section, a smaller-upper diameter absorber section where it is mixing the liquid scavenging agent with the combustion gas from which the impurities should be absorbed, a lower pressure drop tube assembly characterized in that it comprises: _ a transition structure between the tank section and the section of the absorber forming a gas-tight and fluid-tight trajectory for gas and liquids between the tank section and the absorber section and defines an annular transition area around the "absorber section in which very little liquid is present; and an inlet tube housing connected to and in communication with the transition structure for the combustion gas inlet pipe within the transition structure within the tank section-and the section of the absorber so that the combustion gas is Easily scatter around the annular transition area and be evenly distributed around the absorber section.
2. 2. The absorber tower according to claim 1, characterized in that the transition structure extends at an angle of approximately 15 to 90o-
3. 3. The absorber tower according to claim 1, characterized in that the inlet tube housing has a height X that is substantially equal to a vertical height of the transition structure and a width Y which extends partially around a circumference of the transition structure.
4. 4. The absorber tower according to claim 3, characterized in that the width extends from up to about 90 ° to about 180 ° around the circumference of the transition section.
5. The absorber tower according to claim 1, further characterized in that it comprises spray means in the section of the absorber for spraying a partially recycled mixture of the tank section, at least one perforated tray in the absorber section and therefore minus one spray eliminator on the spray means in the absorber section.
6. The absorbent tower according to claim 1, further characterized in that it comprises a flange extending around a lower opening of the suction of the absorber substantially at an upper end of the transition structure.
7. The absorbent tower according to claim 1, further characterized in that it comprises spraying means in the absorber section for spraying-a partially recycled liquid absorption mixture of the tank section.
8. 8. A method for absorbing pollutants from the combustion gas using an absorber tower having a smaller upper diameter absorber section and a lower larger diameter tank section, characterized in that it comprises the steps of: connecting an upper end from the tank section to a lower end of the absorber section using an angled transition structure that forms a gas-tight and liquid-tight trajectory for gases and liquids between the tank section and the absorber section and defines an area of annular transition around the absorber section in which very little liquid is present; transporting combustion gas through an inlet tube housing within the transition structure between the upper absorber section and the lower tank section so that the combustion gas spreads easily around the annular transition and is usually distributed around of the section of the absorber and moves inside the section of the absorber; and spraying absorption liquid into the combustion gas in the absorber section. The method according to claim 8, further characterized in that it comprises the steps of recycling 'absorption liquid from the lower tank section to the upper absorption section and spraying the recycled absorption liquid into the combustion gas.