Wet exhaust gas desulfurization apparatus and wet exhaust gas desulfurization method using this apparatus

Abstract: A wet exhaust gas desulfurization apparatus which comprises a housing, an absorbing solution stored in the lower portion of the housing, a flue above the surface of the absorbing solution, and a partition plate for dividing the flue; and a wet exhaust gas desulfurization method which comprises the steps of introducing an untreated combustion gas from a space above one absorbing solution divided by a partition plate into the above-mentioned wet exhaust gas desulfurization apparatus, sinking the lower edge of the partition plate into the solution, bringing the exhaust gas into contact with the solution, and then discharging the gas through a space above the other absorbing solution divided by the partition plate.

Description: The present invention relates to a wet exhaust gas desulfurization apparatus and a wet exhaust gas desulfurization method using this apparatus. One embodiment of a conventional wet exhaust gas desulfurization apparatus and a wet exhaust gas desulfurization method using the conventional apparatus will first be described with reference to Fig. 17. A combustion exhaust gas A introduced into an absorption tower 51 is brought into contact with an absorbing solution sprayed through a nozzle 55 via a circulating pump 53 and a circulating line 54 from an absorbing solution tank 52, whereby SO₂ in the combustion exhaust gas A is absorbed and removed by the absorbing solution 56. The thus treated exhaust gas is then discharged as a desulfurized exhaust gas B from the system. In the above-mentioned conventional wet exhaust gas desulfurization apparatus, it is required that the solution is pumped up by the use of a pump or the like so as to spray the absorbing solution. In consequence, some facilities and additional power are necessary, and the height of the apparatus has to be high. The present invention provides a wet exhaust gas desulfurization apparatus by which the above-mentioned problems of the conventional technique can be solved and which requires neither the facilities for pumping up the absorbing solution nor the additional power and which permits decreasing the height of the apparatus. The present invention also provides a wet exhaust gas desulfurization method which utilizes this apparatus. The present invention provides a wet exhaust gas desulfurization apparatus which comprises a housing, an absorbing solution stored in the lower portion of said housing, and a partition plate whose lower end portion is immersed in the absorbing solution and whose upper portion divides a flue positioned above the surface of said absorbing solution. The present invention also provides a wet exhaust gas desulfurization method which comprises the steps of introducing an untreated combustion gas into the wet exhaust gas desulfurization apparatus from a space above one of the two sections of the absorbing solution divided by a partition plate, sinking the lower end portion of the partition plate into the solution so as to bring the exhaust gas into contact with the solution, and then discharging the gas through a space above the other section of absorbing solution divided by the partition plate. In the present invention, the partition plate is disposed so that the combustion exhaust gas may be introduced into the absorbing solution in the absorbing solution tank, whereby the combustion exhaust gas is brought into contact with the absorbing solution and SO₂ is removed from the combustion exhaust gas. Therefore, the amount of SO₂ to be removed (desulfurization ratio) and the amount of the exhaust gas to be treated can be easily adjusted by changing the arrangement conditions and the shape of the partition plate, as described hereinafter. (1) The gas-solution contact time can be adjusted by altering the immersion depth of the partition plate in the absorbing solution. (2) The length of the lower edge line of the partition plate along which the combustion exhaust gas is passed can be adjusted by folding or curving the lower end portion of the partition plate. (3) The size of bubbles in the absorbing solution or the like can be changed by forming the lower edge of the partition plate into a sawtooth shape and by altering the shape and the size of the sawteeth or altering the thickness of the edge portion, whereby the contact efficiency can be adjusted. According to the present invention, neither facilities nor power for pumping up the absorbing solution are required, and the height of the apparatus can be reduced. In addition, the desulfurization ratio and the amount of the combustion exhaust gas to be treated can also be adjusted relatively easily by changing the shape and the size of the partition plate and by altering the immersion depth of the partition plate in the absorbing solution. According to the present invention, in order to make gas stream uniform and stabilize the desulfurization ratio and eliminate pressure fluctuation, the above-mentioned wet exhaust gas desulfurization apparatus can be provided with a plurality of sectional plates crossing the partition plate so that the lower edge of each sectional plate may be at a position lower than the lower edge of the partition plate and so that the upper edge of each sectional plate may be at a position higher than the surface of the absorbing solution. According to the wet exhaust gas desulfurization apparatus of the present invention which is equipped with the above-mentioned sectional plates, it is possible to control the turbulence of the absorbing solution surface which tends to occur when the exhaust gas is introduced into the solution from one side of the flue divided by the partition plate, passed under the partition plate, and then discharged from the solution surface on the other side. In consequence, the deterioration of the desulfurization ratio and the pressure fluctuation can be eliminated which are attributable to the unbalance of the gas stream due to the turbulence of the absorbing solution surface. Moreover, in the method of the present invention, in order to make the gas stream uniform and prevent increases of the pressure loss in the gas stream and the deposition of scale which will cause the partition plate to corrode, water can be intermittently or continuously jetted to a surface of the partition plate at a position above the absorbing solution surface. In addition, water can also be jetted to the whole surface of the partition plate above the absorbing solution by the action of a water jet device. According to the present invention, by jetting water to the partition plate in this way, if splashes which occur as the combustion exhaust gas passes under the partition plate adhere to the surface of the partition plate, the splashes can be washed away intermittently or continuously. Moreover, the adhesion of the splashes can be prevented in a wide range by operating the water jet device. Accordingly, jetting water to the partition plate can solve problems such as the unbalance of the gas stream and increases of the pressure loss in the gas stream which are attributable to the scale, and a problem such as the release of the untreated combustion gas which is due to the corrosion and perforation of the partition plate. Fig. 1 shows an explanatory view illustrating the whole of one embodiment of a wet exhaust gas desulfurization apparatus according to the present invention; Fig. 2 shows an explanatory view along the arrow line X-X on a partition plate of the apparatus in Fig. 1; Fig. 3 shows an explanatory view along the arrow line X-X on another partition plate of the apparatus in Fig. 1; Fig. 4 shows an explanatory view along the arrow line X-X on still another partition plate of the apparatus in Fig. 1; Fig. 5 shows an explanatory view of one shape of the lower edge of the partition plate in the apparatus in Fig. 1; Fig. 6 shows an explanatory view of another shape of the lower edge of the partition plate in the apparatus in Fig. 1; Fig. 7 shows an explanatory view of still another shape of the lower edge of the partition plate in the apparatus in Fig. 1; Fig. 8 shows an explanatory view of a mechanism for adjusting the immersion depth of the partition plate in an absorbing solution in the apparatus of Fig. 1; Fig. 9 shows an explanatory view of another embodiment of the present invention; Fig. 10 shows a plan view of a section cut along the line A-A in Fig. 9; Fig. 11 shows an explanatory view of still another embodiment of the present invention; Fig. 12 shows a plan view of a section cut along the line B-B in Fig. 11; Fig. 13 shows an explanatory view of still another embodiment of the present invention; Fig. 14 shows an explanatory view along the line C-C in Fig. 13; Fig. 15 shows an explanatory view of one embodiment of a multi-stage type water jet device which can be used in the present invention; Fig. 16 shows an explanatory view illustrating the constitution of the multi-stage type water jet device in Fig. 15; and Fig. 17 shows an explanatory view of one embodiment of a conventional wet exhaust gas desulfurization apparatus. One embodiment of the present invention will be described in reference to Figs. 1 to 8. Fig. 1 shows the whole view of an apparatus of the present invention and a mode of operation thereof. In this drawing, reference numeral 1 is an inlet flue, numeral 2 is an outlet flue, 3 is an absorbing solution, 4 is a partition plate, and 5 is an lower edge of the partition plate. In Fig. 1, a combustion exhaust gas A pushes down a surface 6 of the absorbing solution to a lower surface 6' thereof by its pressure. The gas A passes under the lower edge of the partition plate 4, comes in contact with the absorbing solution 3, and rises through the solution, while SO₂ contained in the combustion exhaust gas A is absorbed by the absorbing solution 3. The desulfurized exhaust gas B from which SO₂ has been removed is passed through the surface 6'' of the absorbing solution on the opposite side divided by the partition plate 4, and then discharged from the system. Figs. 2, 3 and 4 show examples of the shape of the partition plate 4 along the arrow line X-X in Fig. 1. In these drawing, reference numeral 7 is a flue wall. Furthermore, Figs. 5, 6 and 7 are perspective views illustrating examples of the shape of the lower edge of the partition plate 4. Fig. 8 shows one example of the construction of the present invention in which the immersion depth of the partition plate in the absorbing solution can be adjusted by from the outside of the apparatus. In this construction, a rack gear 4' is attached to the partition plate, and this plate can be moved upward and downward on a pinion gear 4''. The movement of the partition plate can be carried out by means of a remote control device. Another embodiment of the present invention will be described in reference to Figs. 9 to 12. Fig. 9 shows the whole of the arrangement of the respective parts in the present invention, and in this drawing, the untreated exhaust gas A coming through the inlet flue 11 pushes down a surface 13' of the absorbing solution to a surface 13 of the same solution by its pressure when no gas passes through, and passes under a lower edge 16 of a partition plate 15, and comes in gas-liquid contact with the absorbing solution B, and goes through a solution surface 14 on the side of an outlet flue 12, and passes through the outlet flue 12, and then leaves the system as a treated exhaust gas A'. On the side where the untreated exhaust gas A is introduced, a plurality of sectional plates 17 crossing the partition plate 15 are disposed so that a lower edge 18 of each sectional plate 17 may be at a position lower than a lower edge 16 of the partition plate 15 and so that an upper edge 19 of the sectional plate 17 may be at a position higher than the surface 13 of the absorbing solution. Also on the side of the outlet flue 12, a plurality of similar sectional plates 17' are disposed so that a lower edge 18' of each sectional plate 17' may be at a position lower than the surface 14 of the absorbing solution and so that an upper end portion 19' of the sectional plate 17' may be at a position higher than the solution surface 14. Fig. 10 is a plan view of a section cut along the arrow line A-A in Fig. 9. Fig. 11 shows an embodiment in which the partition plate 15 is formed in a zigzag shape, and the sectional plates 17 and 17' on the exhaust gas inlet and outlet sides are arranged so as to cross the zigzag partition plate 15 at the tips thereof. Figs. 12 shows a plan view of a section cut along the arrow line B-B in Fig. 11. Still another embodiment of the present invention will be described in reference to Figs. 13 to 16. Fig. 13 is an explanatory view illustrating the whole of the arrangement of the present invention. In this drawing, the untreated exhaust gas A coming through an inlet flue 21 pushes down a surface 23' of the absorbing solution to a surface 23 of the solution by its pressure when no gas passes through, and passes under a lower edge 26 of a partition plate 25, and comes in gas-liquid contact with the absorbing solution B, and goes through a solution surface 24 on the side of an outlet flue 22, passes through the outlet flue 22, and then leaves the system as a treated exhaust gas A'. When the untreated exhaust gas A passes under the lower edge 26 of the partition plate 25 and when the treated exhaust gas A' gets out of the surface 24 of the absorbing solution, splashes take place and part of the splashes adhere to an inlet side surface 27 and an outlet side surface 28 of the partition plate 25. In order to wash away the adhered splashes, water jet devices 29 are disposed which have openings 30 facing to the inlet side surface 27 and the outlet side surface 28 of the partition plate, respectively. Washing water C coming through pipes 33 is intermittently or continuously jetted to the inlet side surface 27 and the outlet side surface 28 of the partition plate 25 through the openings 30 of the water jet devices 29. In Fig. 13, reference numeral 31 is a driving device of the partition plate, and numeral 32 is a sealing material. Fig. 14 shows an embodiment of the water jet device 29 seen from the direction of the arrow line C-C in Fig. 13. Figs. 13 and 14 show embodiments in which the washing water C is jetted in a wide range in a rising/falling manner. Fig. 15 shows an embodiment of the multi-stage type water jet device 29 which can drive in the direction of the arrow line E-E. Fig. 16 is an explanatory view illustrating the structure of driving members in Fig. 15, and in this drawing, an edge 29' of each water jet device 29 is fixed to a link 35, and this link 35 is connected to a rod 34 connected to a driving device 36. This driving device 36 is expanded and contracted in the direction of the arrow line D-D to move the water jet device 29' in the direction of the arrow line E-E.

Claims: A wet exhaust gas desulfurization apparatus which comprises a housing, an absorbing solution stored in the lower portion of said housing, and a partition plate whose lower end portion is immersed in the absorbing solution and whose upper portion divides a flue positioned above the surface of said absorbing solution so that the gas passes under the lower edge of the plate through the absorbing solution. The wet exhaust gas desulfurization apparatus according to Claim 1 wherein a plurality of sectional plates crossing said partition plate are disposed so that the lower edge of each sectional plate may be at a position lower than the lower edge of said partition plate and so that the upper edge of each sectional plate may be at a position higher than the surface of said absorbing solution. A wet exhaust gas desulfurization method which comprises the steps of introducing an untreated combustion gas from a space above one of the two section of absorbing solution divided by a partition plate into a wet exhaust gas desulfurization apparatus comprising a housing, an absorbing solution stored in the lower portion of said housing, a flue positioned above the surface of said absorbing solution and a partition plate for dividing said flue, sinking the lower edge of said partition plate into said solution so as to bring said exhaust gas into contact with said solution, and then discharging said gas through a space above the other section of the absorbing solution divided by said partition plate. The wet exhaust gas desulfurization method according to Claim 3 wherein water is intermittently or continuously jetted to a portion of said partition plate above the surface of said absorbing solution. The wet exhaust gas desulfurization method according to Claim 4 wherein water is jetted to the whole surface of said partition plate above the surface of said absorbing solution by driving a water jet device.

Inventors: OCHI EIJI C O MITSUBISHI JUKOG, OKAZOE KIYOSHI C O MITSUBISHI, OKINO SUSUMU C O HIROSHIMA TEC, ONIZUKA MASAKAZU C O HIROSHIMA, UKAWA NAOHIKO C O HIROSHIMA TE, OCHI, EIJI, C/O MITSUBISHI JUKOGYO K.K., OKAZOE, KIYOSHI C/O MITSUBISHI JUKOGYO K.K., OKINO, SUSUMU, C/O HIROSHIMA TECHNICAL INSTITUTE, ONIZUKA, MASAKAZU, C/O HIROSHIMA TECHN. INSTITUTE, UKAWA, NAOHIKO, C/O HIROSHIMA TECHNICAL INSTITUTE
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1992
Main classification: B01D53
IPC codes: B01D53