Chlorine bypass device

Abstract

A chlorine bypass device which can cool exhaust gas quickly by mixing extracted exhaust gas with cooling air at high efficiency, to thereby produce fine chloride dust, and increase dust recovery efficiency.

Claims

1. A cement manufacturing facility for removing chlorine compounds from an exhaust gas stream, comprising; a preheated supply of cement raw material; a rotary kiln connected to an exhaust gas pipe having a diameter from 0.5 to 1.5 meters and adapted to heat an exhaust gas comprising a chloride; and a chlorine bypass device comprising: an extraction pipe connected to the exhaust gas pipe and adapted to extract pan of the exhaust gas comprising the chloride; a cooling means adapted to supply cooling gas for the exhaust gas into the extraction pipe; and a recovery device adapted to recover chloride dust contained in the exhaust gas extracted by the extraction pipe, wherein the cooling means comprises a cooling pipe adapted to cause cooling air to flow into the extraction pipe and a blower adapted to feed the cooling air to the cooling pipe, and the cooling pipe comprises a revolving portion and an introducing portion, where the revolving portion comprises an inner pipe configured to be cylindrical in shape and adapted to surround an outer wall of the extraction pipe via a gap and an outer pipe configured to be cylindrical in shape and placed on an outer side of the inner pipe, the revolving portion is closed between an exhaust-gas-pipe-side end of the inner pipe and the extraction pipe and closed by an annular top panel between an end of the inner pipe and an end of the outer pipe, the end of the inner pipe is on the side opposite the exhaust-gas-pipe-side end, and the introducing portion is defined by a reduced-diameter pipe which is joined at a first end to an exhaust-gas-pipe-side end of the outer pipe of the revolving portion and joined at a second end to the outer wall of the extraction pipe, the second end being reduced in diameter compared to the first end, and a cooling air duct from the blower is connected to the revolving portion so as to introduce the cooling air in a circumferential direction of the revolving portion and a flow inlet adapted to cause the cooling air from the introducing portion to flow into the extraction pipe is formed over an entire circumference of the outer wall of the extraction pipe, thereby forming a flow path for the cooling air, running from the revolving portion to the flow inlet through the introducing portion.

2. The cement manufacturing facility according to claim 1, wherein the inner pipe, the outer pipe, and the reduced-diameter pipe are placed with respective axes brought into coincidence with an axis of the extraction pipe, and the cooling pipe is formed so as to satisfy 1.0≦V.sub.S/V.sub.C, where V.sub.S is an average flow velocity of the cooling air in a longitudinal section of the flow path for the cooling air in a direction of the axis and V.sub.C is an average flow velocity of the extraction gas in a cross section orthogonal to a direction of the axis of the extraction pipe.

3. The cement manufacturing facility according to claim 1, wherein the inner pipe, the outer pipe, and the reduced-diameter pipe are placed with respective axes brought into coincidence with an axis of the extraction pipe, and the cooling pipe is formed so as to satisfy (V.sub.S.sup.2+V.sub.M.sup.2).sup.1/2≦90, where V.sub.S (m/s) is an average flow velocity of the cooling air in a longitudinal section of the flow path for the cooling air in a direction of the axis and V.sub.M (m/s) is an average flow velocity of the cooling air in a longitudinal section of the narrowest portion of the introducing portion.

4. The cement manufacturing facility according to claim 1, wherein the exhaust gas pipe is configured in the cement manufacturing facility to send exhaust gas discharged from a kiln adapted to burn cement material to a preheater adapted to preheat the cement raw material.

5. The cement manufacturing facility according to claim 2, wherein the inner pipe, the outer pipe, and the reduced-diameter pipe are placed with respective axes brought into coincidence with an axis of the extraction pipe, and the cooling pipe is formed so as to satisfy (V.sub.S.sup.2+V.sub.M.sup.2).sup.1/2≦90, where V.sub.S (m/s) is an average flow velocity of the cooling air in a longitudinal section of the flow path for the cooling air in a direction of the axis and V.sub.M (m/s) is an average flow velocity of the cooling air in a longitudinal section of the narrowest portion of the introducing portion.

6. The cement manufacturing facility according to claim 2, wherein the exhaust gas pipe is configured in the cement manufacturing facility to send exhaust gas discharged from a kiln adapted to burn cement material to a preheater adapted to preheat the cement raw material.

7. The cement manufacturing facility according to claim 3, wherein the exhaust gas pipe is configured in the cement manufacturing facility to send exhaust gas discharged from a kiln adapted to burn cement material material to a preheater adapted to preheat the cement raw material.

8. The cement manufacturing facility according to claim 1, wherein the preheated supply of cement raw material is heated in the rotary kiln to a temperature sufficient to volatilize alkali chlorides.

9. The cement manufacturing facility according to claim 1, wherein the exhaust gas is discharged from the rotary kiln at temperature of from 1200° C. to 1400° C.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a perspective view of principal part showing a cooling pipe of a chlorine bypass device according to the present invention.

(2) FIG. 2 is a longitudinal sectional view schematically showing a flow of cooling air in the cooling pipe of FIG. 1.

(3) FIG. 3 is a diagram showing results of analyzing a descent distance of the cooling air with an extraction ratio (a ratio of the extracted amount of the kiln exhaust gas) varied, in an example of the present invention.

(4) FIG. 4A is a schematic diagram showing a definition of V.sub.C according to the present invention.

(5) FIG. 4B is also a schematic diagram showing a definition of V.sub.S and is a sectional view taken along line b-b in FIG. 4A.

(6) FIG. 5 is a schematic diagram showing a definition of V.sub.M according to the present invention.

(7) FIG. 6A is a schematic view showing dimensional data on the cooling pipe used for analysis in an example of the present invention.

(8) FIG. 6B is a schematic view showing dimensional data on the cooling pipe used for analysis in an example of the present invention as in the case of FIG. 6A.

(9) FIG. 7 is a graph showing a relationship between V.sub.S/V.sub.C and gas cooling distance in analysis results of Table 1.

(10) FIG. 8 is an enlarged view of principal part in FIG. 7.

(11) FIG. 9 is a graph showing a relationship between (V.sub.S.sup.2+V.sub.M.sup.2).sup.1/2 and pressure loss in the analysis results of Table 1.

(12) FIG. 10 is a schematic diagram showing a schematic configuration of a typical conventional cement manufacturing facilities equipped with a chlorine bypass device.

(13) FIG. 11 is a longitudinal sectional view showing cooling means in the chlorine bypass device of FIG. 10.

DESCRIPTION OF EMBODIMENTS

(14) FIGS. 1 and 2 show an extraction pipe as well as a cooling pipe for exhaust gas extracted from the extraction pipe in an embodiment of a chlorine bypass device according to the present invention, wherein other components are the same as those in FIG. 10, and thus are hereinafter denoted by the same reference numerals as the corresponding components in FIG. 10, and description thereof will be simplified.

(15) In FIGS. 1 and 2, reference numeral 20 denotes the extraction pipe connected at a lower end in FIGS. 1 and 2 with an exhaust gas pipe 8 from a kiln inlet part 2 of a rotary kiln 1 and adapted to extract part of exhaust gas. Reference numeral 21 denotes a cooling pipe 21 adapted to quickly cool the exhaust gas extracted by the extraction pipe 20, using cooling air sent from a blower 10a.

(16) The cooling pipe 21 generally includes a revolving portion 22 and an introducing portion 23 formed integrally with an end 22a of the revolving portion 22 on the side of an exhaust gas pipe 8 and connected to the extraction pipe 20. The revolving portion 22 is formed into an annular shape by being made up of an inner pipe 24 configured to be cylindrical in shape, an outer pipe 25 configured to be cylindrical in shape and placed on an outer side of the inner pipe 24 with axes of the inner and outer pipes 24 and 25 brought into coincidence with each other, and a top panel 26 configured to close ends of the inner pipe 24 and outer pipe 25.

(17) In the revolving portion 22, the inner pipe 24 is placed so as to surround an outer wall of the extraction pipe 20 at a predetermined interval with coincidence of respective axes. Also, spacing between lower ends of the inner pipe 24 and extraction pipe 20 in FIGS. 1 and 2 is closed by a bottom plate 24a. Also, a cooling air duct 27 from the blower 10a is connected to the inner pipe 24 and the outer pipe 25 in a tangential direction to introduce the cooling air into the revolving portion 22 in a circumferential direction.

(18) On the other hand, the introducing portion 23 is formed so as to communicate with the revolving portion 22 via a conical pipe (reduced-diameter pipe) 28 whose tip is joined to the outer wall of the extraction pipe 20 by being gradually reduced in diameter from the end 22a of the outer pipe 25 of the revolving portion 22 toward the side of the exhaust gas pipe 8.

(19) On the other hand, in the introducing portion 23, an outer wall portion of the extraction pipe 20 facing the conical pipe 28 is open, forming a flow inlet 29 for the cooling air over an entire circumference. Consequently, a flow path 30 (see FIGS. 4A to 6) for the cooling air is formed in the cooling pipe 21, running from the revolving portion 22 to the introducing portion 23 to the flow inlet 29.

(20) If the average flow velocity of the bleed gas in the cross section orthogonal to the axial direction of the extraction pipe 20 is V.sub.C (m/s) as shown in FIG. 4A, where the average flow velocity V.sub.C (m/s) is obtained by dividing a flow rate Q.sub.C (Nm.sup.3/s) of the bleed gas passing the cross section in the direction perpendicular to the plane of the paper in FIG. 4A by the area A.sub.C (m.sup.2) of the cross section, and if the average flow velocity of the cooling air in the longitudinal section of the cooling air flow path 30 in the cooling pipe 21 along the axial direction is V.sub.S (m/s) as shown in FIG. 4B, where the average flow velocity V.sub.S (m/s) is obtained by dividing a flow rate Q (Nm.sup.3/s) of the cooling air passing the longitudinal section in the direction perpendicular to the plane of the paper in FIG. 4B by the longitudinal sectional area A.sub.S (m.sup.2), dimensional data on the cooling pipe 21 is set to satisfy
1.0≦V.sub.S/V.sub.C.

(21) Furthermore, if the average flow velocity of the cooling air in the narrowest portion 30a in the longitudinal section of the cooling air flow path 30 in the axial direction is V.sub.M (m/s) as shown in FIG. 5, where the average flow velocity V.sub.M (m/s) is obtained by dividing a flow rate of the cooling air flowing through the narrowest portion 30a from the side of the revolving portion 22 to the side of the introducing portion 23 by the circumferential area A.sub.M (m.sup.2) of the narrowest portion 30a shaped as a flank of a truncated cone, the dimensional data on the cooling pipe 21 is set such that resultant velocity [V.sub.S.sup.2+V.sub.M.sup.2).sup.1/2] (m/s) of V.sub.S and V.sub.M will satisfy
(V.sub.S.sup.2+V.sub.M.sup.2).sup.1/2≦90

(22) With the chlorine bypass device equipped with the cooling pipe 21 configured as described above, since the revolving portion 22 of the cooling pipe 21 into which the cooling air is introduced is formed into an annular shape, surrounding the extraction pipe 20 of the exhaust gas via a gap between the extraction pipe 20 and inner pipe 24, the extraction pipe 20 is not cooled by the cooling air flowing through the revolving portion 22, and thus adhesion of coatings to an inner wall of the extraction pipe 20 can be prevented reliably.

(23) Also, in the cooling pipe 21, the cooling air introduced in the circumferential direction of the revolving portion 22 through the cooling air duct 27 is supplied from the revolving portion 22 to the introducing portion 23 gradually reduced in diameter, by revolving around the entire circumference and flows into the extraction pipe 20 through the flow inlet 29 formed around the entire circumference of the outer wall of the extraction pipe 20. Thus, in the extraction pipe 20, the extracted exhaust gas and the cooling air are stirred and mixed while revolving intensely, making it possible to produce fine chloride dust by quickly cooling the exhaust gas using the cooling air.

(24) Consequently, since fine chloride dust can be produced by always cooling exhaust gas quickly by mixing extracted exhaust gas with cooling air at high efficiency even if the extraction ratio of the exhaust gas changes, chloride dust collection efficiency can be increased.

(25) Furthermore, since the dimensional data on the cooling pipe 21 is set to satisfy 1.0≦V.sub.S/V.sub.C, where V.sub.C is the average flow velocity of the bleed gas in the cross section orthogonal to the axial direction of the extraction pipe 20 and V.sub.S is the average flow velocity of the cooling air in the longitudinal section of the cooling air flow path 30 of the cooling pipe 21 in the axial direction, the gas cooling distance can be set to 1,200 mm or below at which a desired chloride dust refinement effect is obtained by quick cooling.

(26) In addition, since the dimensional data on the cooling pipe 21 is set to satisfy (V.sub.S.sup.2+V.sub.M.sup.2).sup.1/2≦90, where V.sub.M is the average flow velocity of the cooling air in the narrowest portion 30a of the cooling air flow path 30, the pressure loss of the cooling air in the cooling pipe 21 can be kept to 1,200 mmAq or below, eliminating concerns that air supply means such as the blower would become excessively large.

EXAMPLES

Analysis Example 1

(27) First, part of exhaust gas with a temperature of 1,200° C. discharged from the rotary kiln 1 to the exhaust gas pipe 8 was extracted from the extraction pipe 20 with extraction ratio (the ratio of the extracted amount of the kiln exhaust gases) of 2%, 4%, 6%, and 8%. The rotary kiln 1 had a production volume of 200 t/h. Cooling air (temperature 24° C.) with air volumes (2.7 to 3.0 times the extraction ratio) corresponding to the extraction ratio was introduced into the extraction pipe 20 from the cooling pipe 21. Then, in each case, the distance (mm) by which the cooling air descended from the connection (lower ends of the flow inlet 29) of the introducing portion 23 of the cooling pipe 21 to the side of the exhaust gas pipe 8 was calculated by analysis.

(28) FIG. 3 shows results of the analysis.

(29) As seen from FIG. 3, with the chlorine bypass device according to the present invention, even if the extraction ratio of the exhaust gas changes, the cooling pipe 21 allows the descent distance of the cooling air to remain almost constant, and thus the cooling air does not blow out into the exhaust gas pipe in spite of changes in the extraction ratio of the exhaust gas.

Analysis Example 2

(30) Next, using the cooling pipe 21 according to the present embodiment shown in FIG. 1, the gas cooling distance and the pressure loss were determined by analysis by varying data including the inside diameter size D (m) of the extraction pipe 20, the height size H (m) of the revolving portion 22, height size d (m) of the flow inlet 29 in the axial direction, and inclination angle α of the conical pipe 28 as shown in FIGS. 6A and 6B. In so doing, the interval σ between the inner pipe 24 of the cooling pipe 21 and the extraction pipe 20 was 0.01 m in all cases.

(31) Incidentally, in FIGS. 6A and 6B, the longitudinal sectional area A.sub.S of the cooling air flow path 30 in the axial direction, i.e., the sum of the areas of the revolving portion 22 and the introducing portion 23 can be expressed by
A.sub.S (m.sup.2)=d.sup.2 sin α.Math.cos α+2dσ+d.sup.2(cos.sup.3α/sin α)+2d(H/tan α).

(32) When the cooling air volume is Q (Nm.sup.3/s), the average flow velocity V.sub.S (m/s) of the cooling air in the longitudinal section is given by V.sub.S=Q/A.sub.S.

(33) Also, in the longitudinal section of the cooling air flow path 30 in the axial direction shown in FIG. 5, the circumferential area A.sub.M of the narrowest portion 30a shaped as a flank of a truncated cone can be expressed by
A.sub.M (m.sup.2)=π(2D+d sin α.Math.cos α)((d cos.sup.2α).sup.2+(d sin α.Math.cos α).sup.2).sup.1/2.

(34) Thus, the velocity V.sub.M (m/s) of the cooling air passing through the narrowest portion 30a is given by V.sub.M=Q/A.sub.M.

(35) TABLE-US-00001 TABLE 1 D A.sub.C A.sub.S A.sub.M V.sub.C V.sub.S V.sub.M (V.sub.S.sup.2 + V.sub.M.sup.2).sup.1/2 Gas cooling Pressure loss (m) (m.sup.2) (m.sup.2) (m.sup.2) (m/s) (m/s) (m/s) V.sub.S/V.sub.C (m/s) distance (mm) (mmAq) Analysis example 1 0.5 0.2 0.2 0.4 8.7 19.2 11.5 2.2 22.4 867 284 Analysis example 2 0.5 0.2 0.4 0.8 8.7 13.1 6.2 1.5 14.5 1086 319 Analysis example 3 0.5 0.2 0.2 0.5 8.7 20.0 8.8 2.3 21.9 1044 402 Analysis example 4 0.5 0.2 0.1 0.3 8.7 68.5 14.2 7.9 70.0 507 679 Analysis example 5 0.5 0.2 0.1 0.3 8.7 78.4 15.8 9.0 80.0 464 936 Analysis example 6 0.5 0.2 0.1 0.3 8.7 88.3 17.3 10.1 90.0 429 1108 Analysis example 7 0.5 0.2 0.1 0.3 8.7 43.5 17.3 5.0 46.9 535 509 Analysis example 8 0.5 0.2 0.2 0.6 4.3 10.8 3.9 2.5 11.5 857 322 Analysis example 9 0.5 0.2 0.3 0.8 8.7 15.7 5.7 1.8 16.7 1193 376 Analysis example 10 0.5 0.2 0.2 0.6 8.7 24.4 8.2 2.8 25.7 1131 397 Analysis example 11 0.5 0.2 0.1 0.3 8.7 52.3 15.8 6.0 54.6 634 411 Analysis example 12 0.7 0.4 5.3 7.2 4.4 0.9 0.7 0.2 1.1 1897 116 Analysis example 13 0.7 0.4 0.3 0.7 4.4 14.7 6.9 3.3 16.2 983 201 Analysis example 14 0.7 0.4 2.6 4.5 4.4 1.8 1.1 0.4 2.1 1842 173 Analysis example 15 0.7 0.4 0.6 1.3 4.4 7.4 3.6 1.7 8.2 1113 382 Analysis example 16 0.7 0.4 0.4 1.3 4.4 11.6 3.7 2.6 12.1 864 350 Analysis example 17 0.7 0.4 0.4 0.5 4.4 12.9 9.9 2.9 16.3 1081 407 Analysis example 18 0.7 0.4 0.3 0.9 4.4 18.2 5.3 4.1 19.0 777 325 Analysis example 19 0.7 0.4 0.3 0.6 2.2 9.1 3.9 4.1 9.9 728 197 Analysis example 20 0.7 0.4 0.3 0.6 6.6 27.2 11.8 4..1 29.6 795 537 Analysis example 21 0.7 0.4 0.3 0.6 8.9 36.4 15.8 4.1 39.7 813 705 Analysis example 22 0.7 0.4 0.0 0.1 1.2 84.0 44.1 70.3 94.9 307 1300 Analysis example 23 0.7 0.4 0.0 0.1 1.1 85.6 46.9 74.8 97.6 299 1407 Analysis example 24 0.7 0.4 0.0 0.1 1.1 89.9 42.2 79.7 99.3 251 1409 Analysis example 25 0.7 0.4 0.0 0.1 1.1 95.8 44.5 85.4 105.6 238 1534 Analysis example 26 0.7 0.4 1.3 1.8 4.4 3.6 2.6 0.8 4.4 1527 338 Analysis example 27 0.7 0.4 5.3 4.1 4.4 0.9 1.1 0.2 1.4 1778 97 Analysis example 28 0.7 0.4 0.4 0.4 4.4 10.7 10.6 24 15.0 883 273 Analysis example 29 0.7 0.4 0.1 0.2 4.4 36.0 23.8 8.1 43.2 673 439 Analysis example 30 0.7 0.4 0.5 0.7 4.4 10.2 7.1 2.3 12.4 833 466 Analysis example 31 1.5 1.8 0.4 1.4 1.0 12.2 3.4 12.6 12.6 513 613 Analysis example 32 1.5 1.8 0.2 0.8 1.0 26.9 6.1 27.8 27.6 441 794 Analysis example 33 1.5 1.8 0.0 0.2 1.0 111.4 22.5 115.1 113.6 239 1826 Analysis example 34 1.5 1.8 0.0 0.3 1.0 116.9 14.6 120.8 117.8 211 2091 Analysis example 35 1.5 1.8 2.2 3.0 1.0 2.1 1.6 2.2 2.7 936 284 Analysis example 36 1.5 1.8 1.1 1.5 1.0 4.5 3.1 4.6 5.4 748 457

(36) Table 1 is a chart of analysis results in examples of the present invention, showing results of calculating the gas cooling distance and the pressure loss based on A.sub.S and A.sub.M by varying data including the inside diameter size D of the extraction pipe 20, the height size H of the revolving portion 22, the height size d of the flow inlet 29 in the axial direction, and the inclination angle α of the conical pipe 28 as described above.

(37) The analysis results were obtained using an extraction ratio (the ratio of the extracted amount of the kiln exhaust gases) of 2.0% (bleed gas flow rate Q.sub.C=0.9 Nm.sup.3/s, cooling air flow rate Q=2.3 Nm.sup.3/s) in analysis examples 8 and 19, an extraction ratio of 4.0% (bleed gas flow rate Q.sub.C=1.7 Nm.sup.3/s, cooling air flow rate Q=4.7 Nm.sup.3/s) in analysis examples 1 to 7, 9 to 18 and 22 to 36, an extraction ratio of 6.0% (bleed gas flow rate Q.sub.C=2.6 Nm.sup.3/s, cooling air flow rate Q=7.0 Nm.sup.3/s) in analysis example 20, and an extraction ratio of 8.0% (bleed gas flow rate Q.sub.C=3.4 Nm.sup.3/s, cooling air flow rate Q=9.4 Nm.sup.3/s) in analysis example 21.

(38) FIG. 7 is the characteristic diagram of analysis results in Table 1, showing the relationship between V.sub.S/V.sub.C and the gas cooling distance. FIG. 8 is an enlarged view of that portion of FIG. 7 which satisfies V.sub.S/V.sub.C≦15.0. FIG. 9 is also the characteristic diagram of analysis results in Table 1, showing the relationship between (V.sub.S.sup.2+V.sub.M.sup.2).sup.1/2 and the pressure loss.

(39) As can be seen from FIG. 8, when the dimensional data on the cooling pipe 21 is set to satisfy 1.0≦V.sub.S/V.sub.C, the gas cooling distance can be set to 1,200 mm or below at which a desired chloride dust refinement effect is obtained by quick cooling.

(40) Also, as can be seen from FIG. 9, when the dimensional data on the cooling pipe is set to satisfy (V.sub.S.sup.2+V.sub.M.sup.2).sup.1/2≦90, the pressure loss can be set to 1,200 mmAq or below which makes blower capacity conventionally used for chlorine bypass fully applicable.

(41) Note that although in the above embodiment and examples, only the conical pipe 28 has been described as the reduced-diameter pipe which defines the outer wall of the introducing portion 23, the present invention is not limited to this and may use any of various reduced-diameter pipes as long as the pipe is joined at a first end to the exhaust-gas-pipe-side end of the outer pipe 25 and is joined at a second end further reduced in diameter compared to the first end to the outer wall of the extraction pipe 20. Even when a reduced-diameter pipe of another shape is used, the average flow velocities V.sub.S and V.sub.M can similarly be calculated by determining the areas A.sub.S and A.sub.M using drawings.

(42) Also, plural cooling air ducts 27 can be connected to the cooling pipe 21.

INDUSTRIAL APPLICABILITY

(43) The present invention provides a chlorine bypass device which can prevent adhesion of coatings to an inner wall of an extraction pipe, always cool exhaust gas quickly by mixing extracted exhaust gas with cooling air at high efficiency even if the extraction ratio of the exhaust gas changes, thereby produce fine chloride dust, and increase dust collection efficiency.

REFERENCE SIGNS LIST

(44) 1 Rotary kiln (kiln) 4 Preheater 8 Exhaust gas pipe 10a Blower 20 Extraction pipe 21 Cooling pipe 22 Revolving portion 22a Exhaust-gas-pipe-side end 23 Introducing portion 24 Inner pipe 25 Outer pipe 26 Top panel 27 Cooling air duct 28 Conical pipe (reduced-diameter pipe) 29 Flow inlet 30 Cooling air flow path 30a Narrowest portion