JP4321797B2 - Hydrous substance combustion treatment equipment and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a combustion treatment facility for hydrated matter such as sewage sludge and garbage that requires drying prior to treatment, and a method thereof .
[0002]
[Prior art]
In recent waste treatment facilities, in response to a request for energy saving, exhaust heat generated by incineration or melting is recovered and effectively used as a heat source in the facility or as electric energy by a generator.
[0003]
For example, there is a technique disclosed in Japanese Patent Publication No. 7-24733 as an effective utilization of exhaust heat in a hydrous waste treatment facility. This prior art includes a steam direct dryer that performs drying by directly contacting steam and water-containing waste, and a combustion furnace that burns dry waste dried by the dryer, and is dried using a heat exchanger. The used steam used by the machine is heated by heat exchange with the exhaust gas of the combustion furnace, and is circulated again to the dryer.
[0004]
Moreover, as a combustion furnace in such a processing facility, a natural cooling type is generally used.
[0005]
[Problems to be solved by the invention]
However, the natural cooling type combustion furnace has a problem that the amount of heat release is extremely small, and the refractory material in the furnace is easily damaged due to being easily overheated.
[0006]
Then, the main subject of this invention is providing the technique which reduces the furnace temperature efficiently and protects a refractory material effectively.
[0007]
[Means for Solving the Problems]
The present invention that has solved the above problems includes a steam direct dryer that performs drying by directly contacting steam and a water-containing material, and a natural cooling type combustion furnace that burns the dried material dried by the dryer, A hydrous combustion treatment facility configured to heat used steam used by a dryer by heat exchange with the exhaust gas of the combustion furnace and to circulate and supply again to the dryer,
A part of the circulating steam was supplied to the combustion furnace to prevent overheating of the combustion furnace.
It is water incineration treatment facility according to claim.
[0008]
In the present invention, it is desirable that a part of the steam supplied to the dryer after the heat exchange is supplied to the combustion furnace. It is also preferable that a part of the circulating steam is supplied to the combustion furnace after being mixed with preheated air. In particular, a pressure gauge for measuring the internal pressure of the dryer and means for controlling the amount of circulating steam supplied to the combustion furnace according to the measurement result of the pressure gauge are preferably provided.
[0009]
On the other hand, in the hydrated material combustion treatment method of the present invention, the steam and the hydrated material are directly contacted to perform drying, and the dried dried material is combusted in a combustion furnace, while the used steam used for the drying is changed to the above-described drying method. It is a combustion treatment method that is heated by heat exchange with exhaust gas from a combustion furnace and used again for the drying,
Supplying a portion of the circulating steam to the combustion furnace to prevent overheating of the combustion furnace;
It is characterized by this.
[0010]
(Function and effect)
In the case where drying is performed by directly contacting the hydrated material with steam, the circulating steam increases with time due to evaporation of moisture during drying, and therefore it is necessary to discharge it outside the system as necessary. On the other hand, when the combustion furnace is naturally cooled, a large amount of air must be supplied into the furnace to prevent overheating. However, by blowing a part of the circulating steam into the furnace according to the present invention, not only can the amount of circulating steam be adjusted, but the specific heat of the steam is about twice that of air, so that it is remarkably compared with the case of air alone. The furnace temperature can be adjusted with a small amount of blowing. In particular, waste such as sludge contains a large amount of malodorous components in the circulating steam, but there is also a secondary advantage that the malodorous components are thermally decomposed when blown into the combustion furnace. However, if the steam blown into the combustion furnace is at a low temperature, the temperature in the furnace will drop rapidly, making it difficult to adjust the temperature. In such a case, after mixing with preheated air as described above, the furnace It is preferable to blow in.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to an example of sewage sludge treatment equipment.
FIG.1 and FIG.2 has shown the flowchart of the example of the sewage sludge processing equipment to which this invention is applied. Reference numeral 1 in FIG. 1 denotes a sludge pit, and the sludge S stored therein is transferred to a hopper (not shown) by a crane (not shown) and supplied to a dryer 3 by a sludge supply pump 2 attached thereto. The
[0012]
Oite the dryer 3, the sludge is dried to the heated about 400 ° C. of about steam as a heat source for drying by heat exchange with the exhaust gas to be described later. As the dryer 3, a steam direct drying type that performs drying by directly contacting the steam and the hydrated waste according to the present invention is used.
[0013]
The steam reduced in temperature by heat exchange with the sludge is supplied to the dust collector 3C at about 150 ° C. After the dried sludge dust is separated and recovered here, the first-stage steam described later by the steam circulation fan 3F. It is supplied to the heater 8. Note that it is preferable to provide a plurality of stages of bag filters or cyclones as the dust collector 3C.
[0014]
The dried sludge dried and discharged by the dryer 3 and the dried sludge dust collected by the dust collector 3C are then supplied to the melting furnace 5 by pneumatic transportation by the dried sludge transportation blower 4, and are burned and melted. Although the combustion melting furnace 5 is not particularly limited in the present invention, in the illustrated example, a vertical swirl type preliminary combustion furnace 50, a horizontal main combustion furnace 51 having one end connected to the lower end, and a slag chute at the other end. This is a naturally-cooled type composed of a saddle-type mixing cooler 53 connected via 52, and the dried sludge is blown into the upper portion of the preliminary combustion furnace 50. A burner 54 is provided in the upper portion of the pre-combustion furnace 50, and fuel such as city gas, heavy oil, kerosene, waste oil, and combustion air from the fan 55 are supplied to the burner 54. The dried sludge blown into the pre-combustion furnace 50 along the swirl direction is burned and melted by the combustion frame by the burner 54 while swirling down, and is discharged from the slag chute 52 as molten slag through the main combustion furnace 51. . The discharged molten slag is taken out after being cooled and solidified by the water-cooled slag conveyor 6.
[0015]
On the other hand, the exhaust gas from the melting furnace 5 is about 1350 to 1450 ° C., and after this is cooled to about 850 ° C. through the mixing cooler 53, the air preheater 7 and the multistage steam heaters 8 to 10 are cooled. It is sent to the exhaust heat recovery unit consisting of In this example, the air preheater 7 and the first stage steam heater 8 are each composed of a radiant heat exchanger, and the second and third stage steam heaters 9 and 10 are each composed of a shell and tube heat exchanger. However, the present invention is not limited to such types and combinations, and other known heat exchangers can also be used.
[0016]
The air preheater 7 is preheated by heat exchange with the melting furnace exhaust gas in advance in order to avoid an extreme temperature drop when blowing air of about 20 to 200 ° C. into the main combustion furnace 51 to prevent overheating in the furnace. More specifically, as shown in FIG. 3, a vertically-arranged cylindrical portion 7T (for example, an inner diameter 1500) through which melting furnace exhaust gas is circulated from the upper supply port 7i toward the lower end discharge port 7e. ˜2500 mm) and a cylindrical jacket portion 7J which is provided so as to surround the circulating exhaust gas in the cylindrical portion 7T and through which combustion air flows from the upper end supply port 7m to the lower end discharge port 7n. . For example, as shown in the drawing, the atmospheric air is directly supplied to the air preheater 7, and the supplied air flows in the jacket portion 7J in the downward direction, and the melting furnace exhaust gas flows in parallel in the cylindrical portion 7T. Is preheated to about 500 ° C. by indirect heat exchange, and then sent to the main combustion furnace 51 to suppress the furnace temperature to an appropriate temperature. This preheated air can also be supplied to the precombustion furnace 50. Further, the cooling air of about 200 ° C. taken out from the upper cooling jacket of the pre-combustion furnace 50 can be supplied to the air preheater 7 alone or in place of the air.
[0017]
The melting furnace exhaust gas that has passed through the air preheater 7 reaches about 811 ° C. and is supplied to the first stage steam heater 8 via the exhaust gas communication passage 70. The first stage steam heater 8 has basically the same structure as the air preheater 7. That is, as shown in detail in FIG. 3, the first stage steam heater 8 includes a vertically disposed cylindrical portion 8 </ b> T through which melting furnace exhaust gas flows from the lower end supply port 8 i to the upper discharge port 8 e, and the cylindrical portion. It arrange | positions so that the distribution | circulation waste gas in 8T may be surrounded, and it is comprised from the cylindrical jacket part 8J through which the vapor | steam discharged | emitted from the dryer 3 distribute | circulates from the lower end part supply port 8m toward the upper end part discharge port 8n. The steam of about 150 ° C. discharged from the dryer 3 is heated to about 181 ° C. by indirect heat exchange with the melting furnace exhaust gas flowing in the cylindrical portion 8T in the process of circulating in the jacket portion 8J. . On the other hand, the melting furnace exhaust gas is cooled to about 750 degrees.
[0018]
Next, in this example, the steam that has passed through the first stage steam heater 8 is circulated in the order of the second stage steam heater 9 and the third stage steam heater 10, and conversely, the melting furnace exhaust gas is the third stage steam. The heater 10 and the second-stage steam heater 9 are circulated in this order, and indirect heat exchange is performed in such a manner that they flow backward to each other. These second-stage and third-stage steam heaters 9 and 10 are, as shown in detail in FIG. 3, a so-called shell-and-tube heat exchange having a large number of tubes 9T and 10T in the shells 9S and 10S. Steam is circulated between the inner surface of the shell 9S, 10S and the outer surface of the tubes 9T, 10T, and the melting furnace exhaust gas is circulated in the tubes 9T, 10T. In the process, the steam is indirectly heat exchanged with the melting furnace exhaust gas. Is heated by.
[0019]
To explain in detail along the flow of the steam, first, with respect to the second stage steam heater 9, the steam of about 181 ° C. that has been heated in the first stage steam heater 8 is passed through the steam communication path 80. The melting furnace exhaust gas at about 400 ° C. after the heat exchange in the third stage steam heater 10 is supplied through the exhaust gas communication path 72. Thereby, the vapor | steam which distribute | circulates the inside of the shell 9S is heated to about 232 degreeC by indirect heat exchange with the waste gas which distribute | circulates the inside of the tube 9T. The melting furnace exhaust gas is cooled to about 250 ° C. Next, in the third stage steam heater 10, the steam of about 232 ° C. that has been heated in the second stage steam heater 9 passes through the steam communication path 81 and the first stage steam heater 8. The melting furnace exhaust gas at about 750 ° C. after the heat exchange is supplied through the exhaust gas communication passage 71. Thereby, the vapor | steam which distribute | circulates the inside of the shell 10S is heated to about 369 degreeC by indirect heat exchange with the waste gas which distribute | circulates the inside of the tube 10T. The melting furnace exhaust gas is cooled to about 400 ° C.
[0020]
On the other hand, the dust contained in the melting furnace exhaust gas accumulates and collects at the lower end of the air preheater 7 and the first to third steam heaters 8 to 10, and removes foreign matter etc. with a fly ash treatment facility (not shown). It stabilizes after processing, and it disposes outside or returns to the entrance side of dry sludge transport blower 4, and mixes in dry sludge.
[0021]
As described above, among the plurality of stages of heat exchangers 7 to 10 that sequentially recover the exhaust heat of the melting furnace exhaust gas, the front stage heat exchanger (the air preheater 7 and the first stage) that easily generates dust due to re-solidification of the evaporated metal. As a steam heater 8), the radiation heat exchanger having the above-described configuration is used, so that even if some dust adheres to the inner peripheral surface of the cylindrical portion, the situation in which the flow of exhaust gas is hindered or blocked. Are not easily reached, are easy to clean, and sufficiently resistant to high temperatures. Moreover, simply using such a radiant heat exchanger results in a low heat exchange efficiency, and therefore the installation space of the entire exhaust heat recovery unit becomes excessive. In this example, the latter stage is further difficult to generate dust due to evaporated metal. Combined as a side heat exchanger (second and third stage steam heaters 9 and 10) is a shell and tube heat exchanger with very high heat exchange efficiency per unit installation area and sufficient high-temperature resistance As a result, it is possible to minimize the installation space of the exhaust heat recovery unit while reducing the risk of blockage of the exhaust gas circulation system due to dust.
[0022]
However, even if the above combined configuration is adopted, dust cannot be completely prevented from adhering in the heat exchangers 7 to 10, and regular cleaning is required. However, even if cleaning is necessary, cleaning work becomes very complicated if dust adheres to all of the heat exchangers in a plurality of stages. Therefore, preferably, as shown in FIG. 4, the exhaust gas from the heat exchanger (air preheater 7) on the most upstream side where dust due to evaporated metal is likely to be generated is used as the heat exchanger (first stage steam heater) at the next stage. the exhaust gas communication passage 70 for feeding to 8), so that the interior of the exhaust gas flow rate becomes slower than the heat exchanger 7 on the upstream side, for example, also the cross-sectional area with respect to exhaust gas flow direction than the heat exchanger 7 on the upstream side It is desirable to form large dust capture spaces 70S, 70S. Particularly preferably, the flow rates in the dust trapping spaces 70S and 70S are all exhaust gas passages upstream of the dust trapping spaces 70S and 70S (that is, in this example, the heat exchanger 7 and the mixed cooler). It is desirable that the speed is lower than that in the communication path 72) with 53. The degree of decrease in the flow velocity in the dust trapping spaces 70S and 70S cannot be generally specified, but is preferably about 2 to 5 m / second, for example. More specifically, the flow velocity in the communication path 72 is 5 to 10 m / second, the flow velocity in the heat exchanger 7 is 3 to 6 m / second, and the flow velocity in the dust trapping space 70S is 2 to 5 m / second. It is desirable to design.
[0023]
Thereby, the flow velocity of the exhaust gas accompanied by dust generated by cooling in the heat exchanger 7 on the most upstream side is lowered in the dust trapping spaces 70S and 70S in the exhaust gas communication passage 70 to the next stage, and the dust contained therein is reduced. The trapping spaces 70S and 70S are trapped in a concentrated manner. Therefore, some dust may adhere to the heat exchanger 7 on the most upstream side, but dust is less likely to be generated / attached in the heat exchangers 8 to 10 after the exhaust gas communication path 70, and the flow path is blocked. The risk is also reduced and the cleaning work is greatly facilitated.
[0024]
Further, as shown in the drawing, a sideways exhaust gas communication path (duct) 70 connecting the air preheater 7 and the steam heater 8 is provided at the lower end discharge port 7e of the cylindrical portion of the air preheater 7 at the supply port 70i on the upper end wall. When the exhaust port 70e is connected to the lower end supply port 8i of the tubular portion of the steam heater 8 at the discharge port 70e on the upper wall of the other end, there is an advantage that the exhaust gas communication passage 70 can be easily cleaned. .
[0025]
In particular, as shown in detail in FIG. 4, the exhaust gas communication passage 70 has a cylindrical upper portion t1 connected in series with the lower end discharge port 7e of the air preheater 7, and a conical lower side having a dust discharge port x1 at the lower end vertex. A conical lower portion c2 having an inlet side cylindrical portion 70A composed of a portion c1, a cylindrical upper portion t2 connected in series to the lower end supply port 8i of the steam heater 8, and a dust discharge port x2 at the lower end apex portion. The entrance side saddle-shaped cylindrical portion 70B is connected to the side of the entrance-side saddle-shaped cylindrical portion 70A and the exit side is connected to the side of the exit-side saddle-shaped cylindrical portion 70B. A lateral duct portion 70C in which the lower surface en is continuously inclined downward to the lower end discharge port x1 of the entry side saddle-shaped cylindrical portion and the lower surface ex in the exit side portion is continuously inclined downward to the lower end discharge port x2 of the exit side saddle-shaped cylindrical portion; Are preferably formed integrally. In the exhaust gas communication passage 70, the entire sides of the reduced diameter portion ce at the center of the lateral duct portion 70C serve as dust capturing spaces. With this configuration, not only the entire communication path 70 excluding the reduced diameter portion ce becomes a dust capturing space, but also substantially all of the lower portion c1, en, ex, c2 are formed with downward inclined surfaces. Therefore, there is no horizontal surface over substantially the entire lower surface, and almost all of the dust that has fallen due to a decrease in the flow velocity slides down to one of the discharge ports x1 and x2. Therefore, the dust capturing ability in the exhaust gas communication passage 70 is further increased, and substantially all of the descending dust can be collected and discharged at the discharge ports x1 and x2.
[0026]
On the other hand, the steam heated by heat exchange with the melting furnace exhaust gas is circulated and supplied to the dryer 3. At this time, in the auxiliary heater 11 (indirect heat exchanger) as necessary, after heating to a predetermined temperature, for example, 400 ° C. by heat exchange with the clean exhaust gas from the auxiliary furnace 12 that burns fuel such as city gas, It is desirable to supply to the dryer 3. For this reason, although not shown, a temperature measuring device for measuring the temperature of the steam returned to the dryer 3 is provided, and the amount of clean exhaust gas blown to the heater 11 and the auxiliary furnace 12 based on the measurement result by the temperature measuring device. The degree of combustion can be adjusted. Reference numeral 13 denotes an auxiliary furnace fan that feeds combustion air to the auxiliary furnace.
[0027]
In this example, a part of the steam returned to the dryer 3 according to the present invention is supplied into the melting furnace 5 according to the present invention to prevent overheating. In this way, by blowing part of the circulating steam into the furnace 5 according to the present invention, not only can the amount of circulating steam be adjusted, but the specific heat of the steam is about four times that of air, In comparison, the furnace temperature can be adjusted with a remarkably small blowing amount. The circulating steam contains a large amount of malodorous components, but there is a secondary advantage that when the steam is blown into the melting furnace 5, the malodorous components are thermally decomposed. However, when the steam blown into the melting furnace 5 is at a low temperature (about 370 ° C.) as in this example, the temperature in the furnace is drastically lowered and the temperature adjustment is hindered. Thus, it is preferable to mix with the air blown into the melting furnace 5 from the preheater 7 and then blow it into the furnace. In the case of the melting furnace 5 of this example, in order to obtain the above advantages, it is desirable to blow the circulating steam into the main combustion furnace 51 and the remainder into the mixing cooler 53. Although not shown, a pressure gauge for measuring the internal pressure of the dryer 3 and means for controlling the amount of the circulating steam supplied to the melting furnace 5 according to the measurement result of the pressure gauge are provided for adjusting the amount of the circulating steam. Is desirable.
[0028]
On the other hand, the melting furnace exhaust gas cooled to about 250 ° C. by heat exchange with steam is cooled to about 200 ° C. by spraying cooling water and cooling air in the exhaust gas cooler 100, and then removed by the bag filter 101. . The dust collected by the exhaust gas cooler 100 and the bag filter 101 is also stabilized and disposed of after being subjected to foreign matter removal or the like in a fly ash treatment facility (not shown), or on the inlet side of the dry sludge transport blower 4 And mix with dry sludge. The exhaust gas that has passed through the bag filter 101 is then supplied to the flue gas treatment tower 102 (scrubber) and cleaned and collected with cleaning water. Further, after being cooled to about 50 ° C. in the process, it is introduced into the denitration processing unit 110 by the induction fan 103.
[0029]
The denitration processing unit 110 preheats the melting furnace exhaust gas to about 250 ° C. in advance by heat exchange with exhaust heat in a denitration preheater (indirect heat exchanger) 111, and then heats about 350 by the heating furnace 112 using a fuel such as city gas. After heating to the reaction tower supply temperature of 0 ° C., urea water, air, dilution water, and the like are added, and denitration treatment by denitration reaction is performed in the reaction tower 113. As the exhaust heat medium used in the preheater 111, in this example, the clean exhaust gas used in the auxiliary heater 11 of the steam circulation system has an appropriate temperature (about 400 ° C.), all of which (or a part thereof), and denitration treatment. Since the later exhaust gas has an appropriate temperature (about 350 ° C.), all of the exhaust gas is combined and mixed for use. Of course, either one is ok. The mixed gas is released into the atmosphere from the chimney 114 after heat exchange in the preheater 111. In particular, by mixing the clean exhaust gas used in the auxiliary heater 11 into the exhaust gas after the denitration treatment, there is an advantage that the generation of white smoke when released into the atmosphere can be prevented. Reference numeral 115 denotes an air fan that feeds air into the heating furnace.
[0030]
<Others>
(B) In the above example, four stages of heat exchangers using the melting furnace exhaust gas as a heating medium are provided, but the number of stages of the heat exchanger can be appropriately determined according to the degree of exhaust heat recovery.
[0031]
(B) In the present invention, when the air to be mixed with the steam supplied to the combustion furnace is preheated, it is not always necessary to preheat by heat exchange with the melting furnace exhaust gas as in the above example. For example, the steam auxiliary heater in the above example Similarly to 11, heating may be performed using a heating device that uses fuel.
[0032]
(C) In the above example, a part of the heated circulating steam is supplied to the melting furnace 5 by heat exchange with the melting furnace exhaust gas, but in the present invention, before heating (taken out of the dryer 3) It is also possible to supply the molten steam to the melting furnace 5 immediately after heating) or during the heating.
[0033]
(D) Further, the above example is a sewage sludge melting treatment facility, but the present invention is not limited to this, and it can be applied to treatment of other wastes and non-wastes as long as it contains water. It can also be applied to combustion treatment equipment such as incineration equipment that is not performed.
[0034]
【The invention's effect】
As described above, according to the present invention, the temperature inside the combustion furnace can be efficiently reduced to effectively protect the refractory material.
[Brief description of the drawings]
FIG. 1 is a front-stage flow diagram of an example of a sludge treatment facility according to the present invention.
FIG. 2 is a latter-stage flow diagram.
FIG. 3 is an enlarged view of an exhaust heat recovery unit.
FIG. 4 is an enlarged perspective view of an exhaust gas communication path.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sludge pit, 2 ... Sludge supply pump, 3 ... Dryer, 4 ... Dry sludge transport blower, 5 ... Melting furnace, 6 ... Water-cooled slag conveyor, 7 ... Air preheater, 8, 9, 10 ... Steam heater, DESCRIPTION OF SYMBOLS 11 ... Auxiliary heater, 12 ... Auxiliary furnace, 70, 71, 72 ... Exhaust gas communication path, 80, 81 ... Steam communication path, 100 ... Exhaust gas cooler, 101 ... Bag filter, 102 ... Smoke treatment tower, 111 ... Denitration Preheater, 112 ... heating furnace, 113 ... reaction tower, 114 ... chimney.

Claims (5)

A steam direct dryer for drying by directly contacting the steam and the water-containing material, and a natural cooling furnace for burning the dried material dried by the dryer, and the used steam used by the dryer is Heated by heat exchange with the exhaust gas of the combustion furnace, hydrated combustion treatment equipment configured to circulate again to the dryer,
A part of the circulating steam was supplied to the combustion furnace to prevent overheating of the combustion furnace.
A hydrated substance combustion treatment facility characterized by that. The hydrous combustion treatment facility according to claim 1, wherein a part of the steam supplied to the dryer after the heat exchange is supplied to the combustion furnace. The hydrated material combustion treatment facility according to claim 1 or 2, wherein a part of the circulating steam is mixed with preheated air and then supplied to the combustion furnace. The pressure gauge for measuring the dryer internal pressure, and means for controlling the amount of circulating steam supplied to the combustion furnace according to the measurement result of the pressure gauge, The hydrated substance combustion treatment facility according to claim 1. The steam and water-containing material are directly contacted to perform drying, and the dried product is burned in a combustion furnace, while the used steam used for the drying is heated by heat exchange with the exhaust gas of the combustion furnace, A combustion treatment method used again for the drying,
Supplying a portion of the circulating steam to the combustion furnace to prevent overheating of the combustion furnace;
A hydrated combustion method characterized by the above.

Images