Method and device for extracting sulfur dioxide from gas

FIELD: separation.

SUBSTANCE: device comprises inlet and outlet for gas and plate provided with openings and interposed between the gas inlet and outlet for permitting gas to flow from below. The top side of the plate is used for flowing the absorbing liquid. The inlet pipeline connects the tank with the absorbing liquid to the top of the plate. The pump transports the absorbing liquid from the tanks to the top of the plate through the inlet pipeline and over the plate. The device is additionally provided with the outlet vessel for collecting the absorbing liquid that flows over the plate with openings and at least with one means for distributing that is in a contact with the gas supplied to the device through the inlet. The liquid flows from the outlet vessel to the tank upstream of the site where gas flows through the plate with openings.

EFFECT: enhanced reliability.

16 cl, 10 dwg, 1 ex

 

The technical field

The present invention relates to a method for separation of sulfur dioxide from a gas by absorbing fluid water-based, in this method, the gas is transferred up through the essentially horizontal plate with holes, which creates a flowing layer of the absorption liquid.

The present invention also relates to a device for the separation of sulfur dioxide from a gas by absorbing fluid water-based, this device contains input gas containing sulfur dioxide and an outlet for gas from which sulfur dioxide is selected, essentially horizontal plate with holes between input and output, and the plate with the holes is thus to enable the gas containing sulfur dioxide to pass from the bottom and to maintain on its upper side a flowing layer of the absorption liquid, a container for absorbing fluid, at least one inlet pipe, which connects the container with the top plate with apertures, and at least one means for transferring the absorbing liquid from the container via the inlet pipe to the top side of the plate with the holes and along the plate with holes.

Prior art

Sulfur dioxide is a gas that is formed during the oxidation containing the ERU materials, such as coal, oil, natural gas, industrial and domestic waste, peat and the like. Sulfur dioxide may also be formed as a residual product in chemical processes, for example in metallurgical processes. As a rule, to produce large quantities of sulfur dioxide into the atmosphere is not allowed, which leads to the necessity of some sort of cleaning. One example is the cleaning of the flue gas in power plants and other combustion installations. The combustion gas that is formed during combustion, such installations are usually cleared, among other things, by absorption of the sulfur dioxide in absorbing fluid. Absorbing liquid may, for example, contain water and one or more of the following substances: lime, limestone, dolomite, sodium hydroxide solution and similar substances, which are suitable for the absorption of sulfur dioxide. Flue gases may, for example, be purified in the tower with spray irrigation, as described, for example, in European patent EP 0162536, or through perforated trays, as described, for example, in U.S. patent 5246471. However, these devices for the purification of gases, in particular flue gases from sulfur dioxide was found to require large amounts of energy, since a large amount of the absorbing liquid is pumped at a relatively high q is no.

U.S. patent 4099925, U.S. patent 5660616, U.S. patent 4239515 and international application WO 96/00122 describe the treatment system with low energy consumption. The flue gas is transferred up through a plate with holes, which creates a flowing layer of the absorption liquid. If flue gas is not saturated with water vapor, the water will evaporate from the absorbing liquid and added to the flue gas during the cleaning process. Found that the evaporation partially occurs when the flue gas passes through a plate with holes. One of the problems is that substances such as lime, limestone, natural gypsum, calcium sulfite, sodium sulfate and the like, which are dissolved or suspended in an absorbing liquid, tend to evaporation and deposition on the underside of the plate with the holes in the holes plates with holes. This increases the pressure drop across the plate with the holes and causes changes in differential pressure across the surface of the plate with holes. This leads to increased energy consumption due to increased pressure drop and decrease the absorption of sulfur dioxide due to the uneven distribution of the flue gas in the absorbing layer of liquid on the plate with the holes. Known from the literature to solve this problem consist in placing before the treatment of mouth is Euston plate with holes of the refrigerator in the form of a separate tower with spray irrigation, for example, this type is described in U.S. patent 5753012. In a separate tower with spray irrigation, which first introduced the flue gas, the injected water-based liquid ratio (also called L/G) fluid flow to the flow of the combustion gas, which typically is about 0.2 to 1 liter of liquid/m3flue gas, and when the pressure is so high that the liquid is atomized and saturates the flue gas water vapor. After saturation with water vapor of the combustion gas can pass through the plate with the holes without the risk of precipitation of solid products. However, a separate tower with spray irrigation is a complex and energy-intensive solution which includes pumps, pipes, tanks, control systems, and a separate tower. In addition, when using such a tower with spray irrigation may be formed of semi-dry particles that stick to the underside of the plate with holes. For this reason, it is sometimes necessary to position the system for intermediate washing on the underside of the plate with holes.

Brief description of the invention

Thus, the aim of the present invention is to provide an efficient method for the separation of sulphur dioxide, in this way the above disadvantages of the prior art are eliminated or cut is to a large extent.

In accordance with the present invention this objective is achieved by a method which is the method the considered type, through the introduction and characterized in that the absorption liquid is transferred over the plate with the holes from the input area to the output area in which the absorbing liquid is collected and is forced to drip down into the container for absorbing fluid, when the gas is first transferred through the contact zone in which it is brought into contact with the absorbing liquid flowing down from the outlet zone in the container, and then the gas is transferred up through the plate with otverstiyami and flowing through the layer created on it, for the separation of sulphur dioxide. The contact zone is essentially saturating the gas with water vapor, thereby reducing the risk of deposition on the plate with the holes. The contact zone also makes possible the absorption of sulfur dioxide. When there is a two-stage absorption of sulfur dioxide, that is, first, in the contact zone, and then in the layer of the absorbing liquid that is created on the plate with holes, the total absorption of sulfur dioxide can be improved. Since absorbing the liquid first flows through a plate with holes, and then reaches the contact zone will be created counterflow, which facilitates absorption.

In accordance with the preferred embodiment for absorbing the liquid is added to the adsorbent, selected from lime, limestone and their suspensions. Lime and limestone are preferred adsorbents, from an economic point of view, since the sulfur dioxide must stand out from the large stream of flue gas. Absorbing liquid containing lime or limestone, is present in the form of a suspension of solid products due to the limited solubility of the compounds, such as limestone, natural gypsum and calcium sulfite. In the method according to the present invention there is less risk that the solid products in the specified suspension will stick to the plate with holes and cause clogging.

Accordingly, the surface of the absorbing liquid in the container is located below the contact zone, and the passage through which is carried by the gas, is provided between the surface of the absorbing fluid and the output area, and a parameter which is representative of the level of the surface of the absorbing fluid and, thus, to the height of the passage is regulated so that the average velocity of the gas in the passage was in the range of 5-35 m/s Found that this range of values gives a good contact between the gas and the absorbing liquid and, thus, a satisfactory level of saturation in relation to the content of water vapor in the gas, as well as low the pressure drop. By regulation the I height of the passage is possible by varying the flow of gas to maintain the gas velocity in the specified desired range.

In a preferred method, the output area contains the output capacity of the at least one means of distribution for distribution in the contact zone of the liquid flowing from the outlet zone in the container, the ratio of hydrostatic pressure in the output capacitance to the differential pressure in the gas between the first point immediately before the contact zone and the second point above a flowing layer of the absorption liquid on the plate with the holes is adjusted so that the specified hydrostatic pressure was greater than the specified pressure difference in the gas. This leads to the fact that the gas will not flow into the output capacity and fluid will flow from the means of distribution and to enter into contact with the gas in the contact zone. Even more preferred is for the specified relationship of hydrostatic pressure to the specified pressure difference in the gas, so it was regulated so that the absorption liquid leaving the means of distribution, has acquired a speed of 0.2-3 m/s When the absorbing liquid has such speed, it turns out effective contact between the gas and the absorbing liquid in the contact zone. The hydrostatic pressure required to obtain these speeds, is relatively low, which leads to a small energy consumption. This is because high guide staticheskoe pressure in the output capacitance provides a greater height of the absorbing liquid, which should return from the container in the input area.

In accordance with a preferred embodiment of the gas is unsaturated before introduction in the contact zone and the gas becomes essentially saturated with water vapor, when it comes into contact in the zone of contact with the flowing down of the absorbing liquid. The saturation water vapor significantly reduces the risk that any of the substances dissolved or suspended in an absorbing liquid will be deposited on the underside of the plate with holes and will cause problems with increasing differential pressure across the plate with holes.

Another objective of the present invention is to provide a simple device for the separation of sulphur dioxide in this device, the above disadvantages of the prior art are eliminated or significantly reduced. In accordance with the present invention this objective is achieved by a device of this type, which is described in the section "technical field", and which differs in that it also contains at least one output reservoir for collecting the absorbing fluid flowing through the plate holes, and at least one distribution facilities, which are located in contact with the gas fed into the device through the inlet, and the fluid flows from the output capacity of the container before g is C passes through a plate with holes.

Accordingly, distribution facilities contain at least one nozzle. The nozzle, which may be constructed in various ways, often well adapted to create a stream of absorption liquid from which the main part reaches the container, and a small part is absorbed by the gas, while absorbing the liquid provides good contact with the gas. Most types of nozzles are designed to provide low pressure drop and good distribution of the liquid and low risk of clogging. It is particularly preferable that the characteristic size of nozzles, such as the smallest hole diameter or the smallest gap width was 1-8 see These sizes of nozzles result in a good distribution, low pressure drop and acceptable to the size of the droplets, which are formed in contact with the absorbing liquid. When the specified contact with the absorbing liquid drops with a wide range of sizes. Accordingly, this size range contains a certain number of droplets that quickly evaporate upon contact with the gas is not saturated with water vapor. The main part of the liquid, however, should not be captured by the gas, but should fall in the container.

Convenient to have the output capacity had lower portion, which is located below the upper side of the PLA is Tina with holes. The lower part situated thus effectively provides a hydrostatic pressure which is sufficiently high to obtain the desired velocity of the fluid from the means of distribution. In accordance with a preferred embodiment of the liquid surface in the container is located under the output capacity, but leaves a passage between the surface of the absorbing fluid and the output capacitance. This embodiment allows to change the passage by changing the level of the surface of the absorbing liquid in the container. At the same time turns out to be convenient device for collection, in which the absorbing liquid which has passed through the passage, easy going in the container. The surface of the absorbing liquid with the absorbing liquid flowing down from the means of distribution, provides effective sealing of the passage, which lowers the risk of passing gas without coming in contact with the absorbing liquid. It is particularly preferred that the surface of the absorbing liquid in the container is also stretched on the merits under the entire plate with holes. This gives the advantage that the container collects as absorption liquid flowing from the means of distribution, and absorption liquid which may flow downward through the holes of the plate with a hole the parties. In particular, when the gas flow is lower than the stream for which you designed a device with these dimensions, a significant part of the layer flowing over a flat plate with holes, will drain down through the holes plates with holes. When the liquid surface in the container extends under the entire surface of the plate with holes all absorption liquid flowing down through the means of distribution and through holes plates with holes will thus be collected in the container without the need for any auxiliary means, such as pumps and pipes.

In accordance with a preferred embodiment of the side flow is located between the plate with the holes and the output capacitance. A side flow provides a smallest thickness of the layer flowing over a flat plate with holes. This is particularly advantageous in the case of low gas flow, because otherwise there is a risk that the output capacity will drain the entire layer.

In accordance with another preferred embodiment of the output tank contains control devices, such as plates with holes to adjust the rate of fluid flow through the distribution. Control devices can be used to adjust operation output the second capacitance, for the current mode of operation in order to obtain the most efficient operation of the device at different gas flow rates.

Preferably, these means for the introduction of the absorbing fluid to the upper side of the plate with holes contain "Mammoth" pump. "Mammoth" pump makes it possible to transfer absorbing fluid and simultaneous oxidation of all oxidizable substances, such as a sulfite that may be present in it. A special advantage of the "Mammoth" pump device according to the present invention is that in the case of a large gas flow typically requires high altitude when passing and at the same time a high degree of oxidation of sulfite. Characteristics of the "Mammoth" pump also provides greater productivity oxidation at high flow of the absorbing liquid, which is necessary for obtaining high altitude when passing.

Area drain, to drain the absorbing liquid is suitably between plate with holes and means of distribution. Drainage leads to an increase in the density of the absorbing liquid, which increases the hydrostatic pressure in the output capacitance. Increased hydrostatic pressure can be used to increase the velocity of the fluid through the means of distribution. By diversion is also possible for the mind is isenia depth output capacitance at constant hydrostatic pressure.

Brief description of drawings

Now the present invention will be described in more detail by means of several embodiments and with reference to the accompanying drawings.

Figure 1 is a side view in cross section schematically depicting the device in accordance with the present invention.

Figure 2 is a side view in cross section depicting part II figure 1 on a larger scale.

Figa is a General top view depicting the lower part of the output capacitance, shown in figure 1 and 2.

Fig.3b is a General top view depicting an alternative embodiment of the lower part shown on figa.

Figa is a side view in cross section depicting the output capacity with side overflow.

Fig.4b is a General top view of the lower part, which is shown on figa and provided with a plate with holes.

Figa is a side view in cross section depicting an embodiment of the present invention in the form of a circular device.

Fig.5b is a top view in section, along the line V-V of the device depicted in figa.

Figa is a side view in cross section depicting another alternative embodiment of the present invention in the form of a circular device.

Fig.6b is a top view in section, along the line VI-VI, of the device depicted in figa.

Description of the preferred embodiments

Figure 1 depicts a device 1 in accordance with the present invention. The device 1 has an input 2 for flue gas 4 from a boiler (not shown). The lower part of the device 1 is a tank 6 which is adapted to hold the absorbing liquid 8. The device 1 also contains a "Mammoth" pump 10 to transfer absorbing fluid 8 from the tank 6 through the inlet pipe 12 to the inlet zone 14. "Mammoth" the pump 10 consists of a tube 16 which carries compressed air from a container of compressed air (not shown), and the number of nozzles 18 for compressed air intended for distribution of compressed air into the absorbing fluid 8. Input area 14 is connected to the plate 20 with holes. The plate 20 with holes adapted to support on its upper side layer 22 24 absorbing fluid 8 flowing over the top side 22. The plate 20 with the holes has a number of holes 26, which are distributed uniformly and through which can pass the flue gases 4. The projection of the entire horizontal surface of the plate 20 with the holes located on the inside walls of the tank 6, so that the absorption liquid 8, dripping down through the holes 26 of the plate 20 with the holes, effectively collected in the tank 6. In addition the group to that device 1 has an output area 28, which communicates with the upper side 22 of the plate 20 with holes. Output area 28 is located on the end plate 20 with holes opposite the entrance zone 14 at a distance L from the entrance area 14. Output area 28 contains the output capacity of 30 to collect absorbing fluid 8 flowing in the form of layer 24 in the plate 20 with holes. Output capacity 30 has a lower portion 32 which is provided with the means of distribution in the form of nozzles 34. Between the lower part 32 output capacitance 30 and the surface 36 of the absorbing liquid in the tank 6 there is a passage in the form of a gap 38 through which can pass the flue gases 4. Gas 40, which has passed through the device 1, is transferred through the exit 42 for gas for subsequent processing (not shown), which, for example, may include the separation of droplets from the gas and re-heating the gas to a temperature higher than the saturation temperature of water vapor. Absorption liquid 8 is a essentially a mixture of water, lime, served in a tank from a container (not shown) for the suspension of limestone, gypsum and calcium sulfite formed when sulfur dioxide is separated from the flue gas 4. Absorption liquid 8 can, for example, be obtained by the method described in WO 96/00122.

In the method according to the present invention the flue gas 4 is thus transferred through the input of the pipeline is od 2 to the gap 38. In connection with the gap 38 absorption liquid 8 is added through the nozzle 34. Then the absorption liquid 8 is brought into contact and mixed with the flue gas 4, resulting in the contact zone 44. In the zone 44 of the contact absorption liquid 8 partially evaporates, making the flue gas 4 is essentially saturated with water vapor. Thus, when the combustion gas 4 in the zone 44 of the contact is brought into contact at substantially all amount of absorbing fluid 8 flowing through the upper side 22 of the plate 20 with the holes in the gas is obtained a satisfactory level of saturation. Then the flue gas 4 is moved further into the space 46 between the surface 36 of the absorbing fluid and the plate 20 with holes. Flue gas 4, which is essentially saturated, after passing through the gap 38, contains also drops absorbing fluid 8, captured from the contact zone 44. These drops will be captured to give the effect of leaching on the bottom side 47 of the plate with holes, which reduces the risk of deposition of solid products on the bottom side 47 of the plate 20 holes and in holes 26. Thereafter, the combustion gas 4 passes through the holes 26 in the plate 20 with holes and dispersed, while being in contact with the flowing layer 24 absorbing fluid 8 on the upper side 22 of the plate 20 with holes, sulfur dioxide OTDELA the SJ from the flue gas 4 and dissolved in the absorbing liquid 8. Gas 40, which produces sulfur dioxide, then leaves the device through the exit 42 for gas.

Bubbles of compressed air generated by the nozzles 18 "Mammoth" of the pump 10, the lower density of the absorbing liquid 8 in the inlet piping 12. Thus, the absorption liquid 8 will flow upwards in the input pipe 12, to reach the entrance zone 14 and to flow along the upper side 22 of the plate 20 with holes, where it absorbs sulfur dioxide from the flue gas 4. The absorption of sulfur dioxide in absorbing fluid 8 are formed sulfite ions. A high concentration of sulfite ions is not desirable because it increases the risk of deposition and growth of calcium sulfite. Since the "Mammoth" pump 10 delivers air, strong oxidation of sulfite ions will be obtained in the inlet piping 12, at the same time, when the absorption liquid 8 is moved upwards. If you need additional oxidation oxidation device 48 that supplies compressed air from a container of compressed air (not shown)may be installed near the bottom of the tank 6. When absorbing the liquid flows across the plate 20 with holes, it is transferred to the output area 28. In the output area 28 of the combustion gas 4 barbatiruem through the absorption liquid 8, what can be discharged, more or less, the absorption liquid 8, which acquires Bo is its high density. Absorption liquid collected in the output capacitance 30, and then flowing out of the nozzles 34, is brought into contact with the flue gas 4 and partially evaporates. Not evaporated portion of the absorbing fluid 8 flowing from nozzles 34, reaches the surface of the liquid 36 and mixed with the absorbing liquid in the tank 6.

In the absorption liquid 8 will be moved along the upper side 22 of the plate 20 with the holes, and then return through the contact zone 44 in the tank 6 and treated with air for oxidation of sulfite before absorption liquid 8 is transferred on the upper side 22 of the plate 20 with holes. Thus, there is a countercurrent process, where the absorption liquid 8, which has absorbed sulfur dioxide on the upper side 22 of the plate 20 with holes and, thus, is in contact with the purified gas 40 is transferred to the contact zone 44 in which it is brought into contact with the untreated flue gas 4. Because untreated flue gas 4 contains higher amounts of sulfur dioxide than the cleaned gas 40, significant additional absorption of sulfur dioxide takes place in the contact zone 44 through the countercurrent process, despite the fact that the absorption liquid 8 has absorbed large quantities of sulfur dioxide on the plate 20 with holes. Thus, this is a counter-current process increases the ability of the device 1 to the absorption of sulfur dioxide in comparison with the technology, known from the literature, when the plate 20 with the holes flow comparable amounts of the absorbing liquid.

Figure 2 depicts part II figure 1 on a larger scale. As can be seen from figure 2, the flue gas 4 will act on the surface 36 of the liquid and to form sagged down surface 50 near the entrance 2 for flue gas 4. The specific appearance of this surface varies with the velocity of the gas stream 4 and the specific design of the device 1 and for this reason, the appearance of the surface 50, shown in figure 2, should be considered as a schematic example. Flue gas 4 will also affect the thread 35 of the absorbing liquid 8, which leaves the nozzle 34 so that this thread 35 is not vertical, but is rejected in its lower part. For the thread 35 is important that he was so strong, relative to the droplet size and flow rate, to a dense wall of absorbing liquid 8 was created all the way from the output capacitor 30 to the surface 36 of the absorbing liquid. The gap 38 between the surface 36 of the absorbing fluid and an output capacity of 30 has on the nozzles 34 height H, which is controlled by the level of the absorbing liquid in the tank 6, that is, level surface 36 of the liquid. At a certain flow of the combustion gas 4 certain height H will lead to is definitely the gas velocity 4 in the gap 38. It was discovered that the gas velocity should not exceed about 35 m/s At higher gas velocities the pressure drop in the gap 38 is increased. Even more important disadvantage at higher speeds is that leaving the nozzle 34, the flue gas 4 is to capture the main part of the absorbing liquid 8. This increases the pressure drop in the space 46 and fills the holes 26 of the absorbing liquid, making holes in the pressure drop also increases. The velocity of the gas in the gap 38 to exceed approximately 5 m/s, in order to ensure good contact between the flue gas 4 and the absorbing liquid 8 distributed by the nozzles 34. It was found that in the case shown in figure 2, where the surface 36 of the liquid in the tank 6 extends above the same horizontal surface as the plate 20 with holes, it is convenient that the height H was at least about 10% of the length of the pallet, i.e. the length L from the entrance area 14 to the output zone 28. The compressed air stream in "Mammoth" the pump 10 is controlled so as to set the height H at such a value that corresponds to the current mode of operation. When increasing the flow of the combustion gas 4 flow of air in a "Mammoth" the pump 10 increases, which increases the flow of the absorbing liquid 8 in the input area 14. Due to this, the thickness of the layer 24 increases, the number of Jew the barb in the tank 6 decreases and the height H increases. Thus, the velocity of the gas in the gap 38 can be maintained in the desired range. At the same time, a thicker layer 24 makes it possible for sufficient absorption of sulfur dioxide and also at higher flow of the combustion gas 4.

Output capacity 30 is constructed so that the desired flow of the absorbing liquid 8 left nozzle 34. To prevent the passage of flue gas 4 through the nozzle 34 instead of the holes 26, the output capacitor must have a certain hydrostatic pressure P1. The pressure difference dPrin the flue gas can be measured at the point A, which is located immediately before the contact zone 44, and at the point B, which is located directly above the layer 24. Then the hydrostatic pressure P1in the output capacitor 30 can be calculated as the height h1calculated from the lower part 32 output capacitance 30 to the point S on the surface of the absorbing liquid 8 directly above the lower part 32, multiplied by the density of the liquid in the output capacitance 30 and the acceleration of gravity g.

Absorption liquid 8 leaving the nozzle 34, must have a certain speed to create a good contact between the liquid and the flue gas 4 in the contact zone 44. Found that the liquid velocity equal to 0.2 to 3 m/s, is convenient. To ensure that speed fluid hydros eticheskoe pressure P 1in the output capacitance 30 should be much bómore than the value of dPr. Found that the height h1that is at least about 100 mm greater than the height required only to comply with dPris suitable for a specified velocity of the fluid. Is also clear that in the case of small height H will be a high pressure drop in the gap 38, which increases the pressure difference dPrthat, in turn, requires a large height h1in the output capacitance 30.

Absorption liquid 8 in the layer 24 will contain a relatively large amount of gas bubbles. It is desirable that the height h1was so small as possible, while satisfying the above conditions, since the difference between the levels H1 between the lower edge 47 of the plate 20 with the holes and the surface 36 of the liquid, which should be generated using the "Mammoth" pump 10 to obtain the desired height H in the gap 38, then it will be smaller, which reduces the consumption of compressed air in "Mammoth" the pump 10. When the hydrostatic pressure P1in the output capacitance 30 is proportional to the product of the height h1and density of the absorbing liquid 8 in the output capacitance 30, when the height h1decreases, it is necessary to maintain the same hydrostat the economic pressure to increase the density. For this purpose, accordingly, the speed of vertical movement of liquid down in the output capacitance 30 is approximately 0.1 to 1 m/s, preferably approximately 0.5 m/s This speed, as detected, is suitable to ensure satisfactory drainage, which increases the density of the liquid. For the same purpose creates a drainage area 51 between the hole 27 of the plate 20 with holes, which is the last hole, when viewed in the direction of flow P layer 24, and an output capacity of 30. When the absorption liquid 8 flows over the drainage area 51, the gas bubbles leaving the absorption liquid 8, which increases its density.

The entire flow of the absorbing liquid flowing over the plate, 20 holes, is used for contact with the flue gas 4 in the contact zone 44. The corresponding ratio (also called L/G) flow of the absorbing liquid on the plate 20 with the holes in the form of layer 24 to the flow of the combustion gas 4 through layer 24 that is created on the plate 20 with holes 10-50 liters absorbing fluid/m3flue gas. When this relatively large flow of the absorbing liquid is brought into contact with the flue gas 4 in the contact zone 44, in the contact zone 44 receive a satisfactory saturation water vapor and significant absorption of sulfur dioxide.

Figa depicts the lower portion 32 of the output of the second container 30, if you look along the line III-III in figure 2. The lower part 32 is supplied with the first row of nozzles 52, when viewed horizontally in the direction of flow of the combustion gas 4, and the second row of nozzles 54, when viewed in the same direction of flow. The nozzles are in the form of circular holes 55 and 56, respectively. Circular holes 55, 56 may have a cylindrical shape or they may be rounded at one end, to have a tapered chamfer or have any other form suitable for nozzles. The smallest diameter D, that is, the smallest cross-section of the holes 55, 56 should be about 1-8 cm, preferably about 1-5 see If the hole diameter is less about than 1 cm, when the contact of the absorbing liquid 8 and the combustion gas 4 drops, these drops are so small that they are taken, to a large extent, the flue gas 4, which causes the above increase in differential pressure in the space 46 and the hole 26. When used holes 55, 56 with a diameter larger around than 8 cm, there is poor contact between the absorbing liquid 8 and the flue gas 4, which leads to the insufficient saturation of the flue gas water vapor. As is clear from figa, the holes 55 in the row 52 are displaced with respect to the holes 56 in the row 54. This is done to obtain the optimal overlap and contact with the absorption of liquids is using 8 and flue gas 4, so no streams of flue gas 4 is not passed the contact zone 44 without admission of water vapor.

Fig.3b depicts an alternative embodiment of the output capacitor 30 shown in figa. Output capacity 130 depicted in fig.3b has a lower portion 132, which is provided with a first gap 152 when viewed horizontally in the direction of flow of the combustion gas 4 and the second gap 154, if you look in the same direction of flow. These two gap 152, 154 overlap with each other so that no flue gas streams 4 unable to contact zone 44 without coming in contact with the absorbing liquid 8. Gaps 152, 154 may be rectangular in cross section or may be rounded, to have a tapered chamfer or have some other shape corresponding to the nozzles on the inlet and/or outlet. The smallest width of the gap V, that is, the smallest cross-section of the gap 152, 154, should be approximately 1-5 cm for the same reason as discussed above in connection with circular holes 55, 56.

Figa depicts an alternative embodiment of the output capacitance, shown in figure 2. When working with small loads, i.e. when the flow of the combustion gas 4 becomes smaller than the flow for which the device 1 is constructed, sometimes the problem is that the layer 24 flows through the plate 20 with holes that are too high soon the flesh. This is because when the reduced gas flow decreases and the pressure difference dPr. As a result, the flow velocity in the nozzles 34 is increased and, thus, the layer 24 is quickly drained through the output capacity of 30. To create in these circumstances layer 24, which is thick enough for the desired level of absorption of sulfur dioxide, compressed air stream in "Mammoth" the pump 10 must be increased, which increases the cost of the work when working with small loads. This is the reason why the embodiment of the output capacitance 230 depicted in figa has a side 258 of the flow. When working with a normal load, i.e. when the normal flow of the combustion gas 4, the normal level 224 layer 24 will not generally be affected by a side flow 258. When working with small loads, i.e. at small flow of the combustion gas 4, level 225 layer 24 at low load will be much higher due to side flow 258 than the level 227 in the output capacitance 230. Low level 227 in the output capacitance 230, also lowers the hydrostatic pressure, and thus also the speed at which the absorption liquid 8 flows from the output capacitor 230. As a result, creates an equilibrium in which the fluid flow from the output capacitor 230 is balanced with a level 227. Thus, the fact that the layer 24 benefit is are the side flow 258 may reach 225, making it possible to reduce the consumption of compressed air in "Mammoth" the pump 10 when working with small loads.

Fig.4b depicts another alternative embodiment of the lower part shown on figa. The output capacity of 430 depicted in fig.4b, which is visible from above, has a lower portion 432, provided with circular holes 455, 456, in a manner similar to that depicted in figa. Directly on top of the bottom portion 432 output capacitor 430 is placed a plate with holes 458. Plate 458 with holes, which can move relative to the lower portion 432 has a circular hole 459 and 460, which correspond to the holes 455 and 456, respectively. By moving the plate 458 with holes is thus possible to create a greater or lesser reduction of the corresponding openings of the holes 455 and 456. When working with small loads is thus possible to reduce holes 455 and 456 to reduce the outflow of absorbing fluid 8 from the output capacitor 430.

Figa depicts a circular embodiment of the device 501 in accordance with the present invention. On fig.5b, the device 501, figa shown in cross section along the line V-V. the Device 501 has a Central entrance 502 for flue gas 504. The lower part of the device 501 is a tank 506 which is adapted for holding p is gosausee fluid 508. The device 501 additionally has a "Mammoth" pump 510 to transfer absorbing fluid 508 from the tank 506 via the inlet pipe 512 to the input area 514. Input area 514 has eight tubes 515 transferring a fluid-absorbing 508 to the plate 520 with holes of this type, which is described above. Plate 520 with holes has a multitude of uniformly distributed holes 526, of which only a few are depicted on fig.5b through which can pass the flue gas 504. The device 501, in addition, has an output area 528, which communicates with the upper side of the plate 520 with holes. Output area 528 contains the output capacity of 530 to collect absorbing fluid 508 flowing over the plate 520 with holes. Output capacity 530, which extends around the inlet 502 is constructed accordingly in the manner described above in connection with output capacities. Between the lower part of the output capacitor 530 and the surface 536 of the absorbing liquid in the tank 506, there is a passage in the form of a gap 538 through which can pass the flue gas 504. Gas 540, which passes through the device 501 is transferred through the output 542 for gas for subsequent processing (not shown). Located in the center of the pipe 512 and tube 515 may, alternatively, be replaced by a set of "Mammoth" pumps, for example six, are located along the outer PE Iveria plate 520 with holes.

Figa depicts another embodiment of the device 601 in accordance with the present invention. On fig.6b, the device 601, figa shown in cross section along the line VI-VI. The device 601 is located lateral entry 602 for flue gas 604. The lower part of the device 601 comprises a tank 606, which is adapted for holding absorbing fluid 608. The device 601 also has a "Mammoth" pump 610 to transfer absorbing fluid 608 from the tank 606 through a Central inlet pipe 612 in the input area 614. Input area 614 carries a fluid-absorbing 608 to the plate 620 with holes of this type, which is described above. Plate 620 with holes has a number of uniformly distributed holes 626, of which only a few are depicted on fig.6b through which can pass the flue gas 604. The device 601, in addition, has an output area 628, which communicates with the upper side of the plate 620 with holes. Output area 628 contains the output capacity of 630 to collect absorbing fluid 608 flowing over the plate 620 with holes. Output capacity 630 is constructed accordingly in a manner described above in connection with output capacities. Between the lower part of the output capacitor 630 and the surface 636 of the absorbing liquid in the tank 606 there is a passage in the form of a gap 638, through which can pass the flask gas 604. Gas 640, which has passed through the device 601 is transferred through the Central exit 642 for gas for subsequent processing (not shown).

It will be clear that within the framework of the present invention discusses a number of modifications of the above embodiments of the present invention, as defined in the attached claims.

The absorption of sulfur dioxide can be carried out using a number of different adsorption of liquids. Examples of substances which, when mixed with water are suitable for the separation of sulphur dioxide, are limestone, lime, dolomite, sodium hydroxide, and the like. Thus, the device is not limited to a particular composition of the absorbing liquid.

The device according to the present invention can be constructed in different ways. Along with circular structures described above can be considered as rectangular, square device and devices in the form of a sector.

"Mammoth" pumps can be replaced with another type of pump, for example a propeller pump. However, large gas-lift pumps are especially preferred due to the simultaneous oxidative stress. Also it is possible to provide a small gas-lift pumps possibilities for supplying absorption liquid to the plate with holes. Not what which embodiments of the present device, it is preferred because it is a more uniform distribution of the absorbing liquid on the upper side of the plate with holes.

Plate with holes can be constructed in many different ways and can be made of several different materials. Especially preferred method of manufacturing a plate with holes is described in application WO 96/00122. When used as a plate with holes, made of a polymeric material, the incoming gas should have a low temperature so as not to damage the plate with holes, and this can be achieved by the present invention. The contact zone can be equipped with devices that improve the contact between gas and liquid. Such devices may constitute, for example, vertical grid, or static mixers. However, often it is preferable to use an open design, i.e. a design in which the contact zone does not contain any parts that can cause clogging and thereby increase the pressure drop in the gap between the output capacitance and the surface of the absorbing liquid in the tank.

The above embodiments are used in the purification of flue gases from coal-fired boiler. It will be understood that the present invention can also be used in other processes where sulfur dioxide dalinettelals from gases. Examples of such processes include heating oil, peat, biological fuel and waste, such as industrial and domestic waste; metallurgical processes, such as processes for the production of steel and copper; processes of cement production and refining processes, such as refining and processing of natural gas. The device may also be used to absorb other substances with sulphur dioxide. Examples of such substances include hydrogen halides such as hydrogen chloride, hydrogen fluoride, hydrogen bromide and hydrogen iodide; bromine; heavy metals such as mercury; and other compounds.

As described above, the contact zone 44 allows for saturation of the flue gas 4 water vapor, as well as to absorb sulfur dioxide from the flue gas 4. The present invention can be used only when the saturation of the flue gas 4 water vapor in the contact zone 44 is desired, when the flue gas 4 is already saturated with water vapor, and only when the absorption of sulfur dioxide in the contact zone 44 is desired, and when, simultaneously, is the desired saturation of the flue gas 4 water vapor and the absorption of sulfur dioxide from the flue gas 4 in the contact zone 44.

Example

This example applies to pilot testing device of this type which is described in the above, with reference to figure 1, figure 2 and 3a.

The length of the pallet L of the device is approximately 3 meters. The plate 20 with holes, which are made of polypropylene, has a thickness of 30 mm and an area free of holes of about 3.6%, the holes 26 have a diameter of 22 mm Holes 26 have tapered chamfer on the bottom side 47 of the plate 20 with holes. Limestone with a grain size that is approximately 96% passes the mesh 44 microns, is fed into the tank 6 in the form of suspension from 25% of the mass of a water-based product. Additional amount of water added to the tank 6. During operation of the absorption liquid 8 in the tank contains approximately 13% of the mass of solid products and is set to a pH of about 4.5.

Flue gas 4 from the oil power plant is cleaned by introducing a gas which is unsaturated with water vapor having a temperature of about 191°C and the concentration of sulfur dioxide of about 732 mind Flue gas 4 is supplied through the inlet 2 into the gap 38. The surface 36 of the liquid in the tank 6 is set at such a level that the velocity of the gas in the gap 38 is 12 m/s When the gas velocity, the height H is 15% of the length of the pallet L. the pressure Difference between point a and point B is estimated as 4600 PA. The height h1in the output capacitance 30 is 700 mm, which corresponds to a hydrostatic pressure of approximately 6000 PA. Circular holes 55, 56 in the lower part o the ne containers have a diameter of about 2 cm The number of circular holes 55, 56 is selected so that the velocity of the fluid leaving holes 55, 56 at the current hydrostatic pressure is approximately 1.5 m/s as far as can be judged visually, gas 4 captures about 10% of the absorbing liquid, leaving circular holes 55, 56 in the lower portion 32 of the output capacitor 30, while the remainder of the absorbing fluid reaches the surface 36 of the liquid. While studies have not observed any clogging in the holes 26 of the plate 20 with holes and no growth of the residue on the bottom side 47 of the plate 20 with holes. Different types of wash effects, which are provided with the absorbing liquid entrained gas 4, also can be seen on the bottom side 47. The measurement shows that the gas 4 has a temperature of approximately 57°C directly below the plate 20 with holes and is essentially saturated with water vapor. Gas 40, leaving the device 1 has a temperature of about 55°C and contains approximately 6 mlnd sulfur dioxide.

1. Method for the separation of sulfur dioxide from a gas by absorbing fluid water-based, in which the gas is transferred up through the essentially horizontal plate with holes, which creates a flowing layer of the absorption liquid, characterized in that the absorbing secosteroids on the plate with the holes from the input area to the output area, in which the absorbing liquid is collected and forced to drip down into the container for absorbing fluid, the gas transported through the contact zone, first comes into contact with the absorbing liquid flowing down from the outlet zone in the container, and then is transferred up through the plate holes and the flowing layer created on it to highlight sulfur dioxide.

2. The method according to claim 1, wherein the adsorbent is selected from lime, limestone and their suspensions, add into the absorption liquid.

3. The method according to claim 1 or 2, in which the surface of the absorbing liquid in the container is located below the contact zone, and the passage through which is carried by the gas, is provided between the surface of the absorbing fluid and the output area, and a parameter which is representative of the level of the surface of the absorbing liquid, and, thus, the height (H) of the passage, adjust so that the average velocity of the gas in the passage was in the range of 5-35 m/S.

4. The method according to claim 1, in which the output area contains the output capacity of the at least one means of distribution for distribution in the contact zone of the liquid flowing from the outlet zone in the container, the ratio of hydrostatic pressure in the output capacitance to the differential pressure in the gas between the first point (A) immediately before the contact zone and vtoro the point of over flowing layer of the absorption liquid on the plate with the holes regulate so to the specified hydrostatic pressure was greater than the specified pressure difference in the gas.

5. The method according to claim 4, in which the ratio of hydrostatic pressure to the specified pressure difference in the gas adjust so that the absorption liquid leaving the means of distribution, has acquired a speed of 0.2-3 m/s

6. The method according to claim 1, in which the gas is unsaturated before introduction in the contact zone and the gas becomes essentially saturated with water vapor, when it comes into contact with the flowing down of the absorbing fluid in the contact zone.

7. Device for the separation of sulfur dioxide from a gas by absorbing fluid water-based, containing

a) the input gas containing sulfur dioxide and an outlet for gas from which the selected sulfur dioxide,

b) essentially horizontal plate with holes located between the inlet and outlet, and a plate with holes adapted to enable the gas containing sulfur dioxide to pass from the bottom, and to support on its upper side a flowing layer of the absorption liquid,

c) a container for absorbing fluid,

d) at least one inlet pipe, which connects the container with the top plate with holes, and

e) at least one means d is I transfer absorbing fluid from the container via the inlet pipe to the top side of the plate with the holes and along the plate with holes characterized in that it contains

f) at least one output reservoir for collecting the absorbing fluid flowing over the plate with holes, and

g) at least one means of distribution which are adapted to bring into contact gas fed into the device through the entrance, with the liquid flowing from the output capacity of the container before the gas passes through a plate with holes.

8. The device according to claim 7 in which the means of distribution contain at least one nozzle.

9. The device according to claim 8, in which the typical size of the nozzle, such as the smallest hole diameter (D) or the smallest width of the gap (V), is 1-8, see

10. Device according to any one of claims 7 to 9, in which the output capacity has a lower portion that is recessed below the upper side of the plate with holes.

11. The device according to claim 7, in which the surface of the liquid in the container is located under the output capacity and a passage provided between the surface of the absorbing fluid and the output capacity.

12. The device according to claim 11, in which the surface of the absorbing liquid in the container also extends essentially under the entire plate with holes.

13. The device according to claim 7, in which the side flow is located between plate with holes and an output capacity.

14. The device according to claim 7, in which the Ohm output capacity contains controls such as plates with holes to adjust the rate of fluid flow through the distribution.

15. The device according to claim 7, in which said funds for the introduction of the absorbing fluid to the upper side of the plate with holes contain "Mammoth" pump.

16. The device according to claim 7, in which the area for removal of the absorbing liquid is located between plate with holes and means of distribution.



 

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3 cl, 2 ex, 6 tbl

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