JP2016205694A - Oxygen concentration control system in drying system of drying equipment, and sludge drying equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen concentration control system in a drying system capable of estimating an oxygen concentration in the drying system of drying equipment in operation by calculation with high accuracy, and surely preventing dust explosion.SOLUTION: An oxygen concentration control system in a drying system in which water-containing organic wastes are circulated with a heated gas in drying equipment for drying the water-containing organic wastes and granulating organic powder, includes: an out-of-system discharge air amount calculation means 211 for calculating an out-of-system discharge air amount α(kNm/h) to be discharged to the outside of the drying system; a water vapor amount calculation means 212 for calculating a water vapor amount β(kNm/h) produced in the drying system; and oxygen concentration calculation means 213 for calculating an oxygen concentration C(vol.%) in the drying system from a formula (1) on the basis of the out-of-system discharge air amount α(kNm/h), the water vapor amount β(kNm/h), and the oxygen concentration γ=21(%) in the air supplied into the drying system. C={(α- β)/α}×21 ...(1)SELECTED DRAWING: Figure 3

Description

  The present invention relates to an oxygen concentration control system in a drying system in which the organic water-containing waste is circulated together with a heated gas in a drying facility for drying the organic water-containing waste to granulate organic powder. And a sludge drying facility equipped with this system.

  Conventionally, organic water-containing waste such as sewage sludge and livestock manure has been disposed of by burial or incineration. However, since solids obtained by drying organic water-containing waste are flammable, in recent years, effective use of organic water-containing waste as fuel has been actively studied.

  For example, in Patent Documents 1 and 2, sludge wastes such as sewage sludge and livestock manure are dried with an air dryer, the dried solid is separated with a solid-gas separation device such as a cyclone, and one of the separated dried solids. There has been proposed a method for drying sludge waste which is molded as a part and used as fuel or fertilizer.

  In Patent Documents 3 and 4, a process of obtaining a mixed powder by mixing and stirring the sludge cake with the air-dried sludge circulating dry powder, and using the mixed powder as a heat source for the exhaust gas from the suspension preheater of the cement baking apparatus. A step of pulverizing with a pulverizer of an air-flow dryer, a step of drying the pulverized mixed powder in a drying duct, collecting the dust with a dust collector to obtain a dry powder, and a certain amount of the dry powder. A sludge treatment method comprising: a step of blowing into a rotary kiln or / and calcining furnace to use as part of a cement clinker firing fuel and cooling the fired product together with a cement raw material fired product to obtain a cement clinker. Proposed.

JP 2000-065476 A Japanese Patent No. 3007345 Japanese Patent No. 4445147 Japanese Patent No. 4445148

  When granulating organic powder by drying organic water-containing waste, dust explosion may occur if the dust concentration and oxygen concentration in the drying facility reach a certain level and a fire source is generated as an ignition source. There is sex. Therefore, in order to granulate organic powder from organic water-containing waste safely and stably, it is necessary to surely prevent dust explosion. As measures for preventing dust explosions, for example, it is conceivable to perform gas analysis on the oxygen concentration in the drying equipment during operation to keep the oxygen concentration below a certain level.

  However, the oxygen concentration is generally measured by dry analysis. On the other hand, the drying equipment in operation is in a state of excessive moisture due to water vapor generated from organic water-containing waste, and there is a problem that sufficient accuracy cannot be obtained in the analysis results. In addition, even when taking a gas sample from a drying facility that has been shut down and measuring the oxygen concentration, pretreatment such as dehumidification and dust removal in the drying facility is necessary, and measurement cannot be performed immediately. There are concerns that measures cannot be taken.

  The present invention has been made in view of the above-mentioned problems, and can estimate the oxygen concentration in the drying system in the operating drying facility with high accuracy by calculation, and reliably prevent dust explosion. It is an object of the present invention to provide an oxygen concentration control system in a drying system that can be used, and a sludge drying facility equipped with this system.

  The inventors have found that the amount of gas present in the drying system in the drying facility converges to the ratio of the amount of water and the amount of air supplied to the drying system. And the present inventors excluded the possibility of the gas explosion by combustible gas, paid attention only to prevention of dust explosion, and assumed that the gas composition in a dry system | strain was water vapor | steam and air. Under this assumption, the inventors have found that the airflow in the dry system can be modeled into a simple cycle as shown in FIG.

  And, the present inventors, in the dry system model shown in FIG. 1, by the calculation based on the amount of exhaust air discharged outside the dry system and the amount of water vapor generated in the dry system, the inside of the dry system It was found that the oxygen concentration of can be estimated with high accuracy.

  As a result of further research, the present inventors have found that the possibility of dust explosion increases when the oxygen concentration calculated based on the amount of exhausted air outside the system and the amount of water vapor exceeds a predetermined value. That is, it is possible to reliably prevent dust explosion by controlling the oxygen concentration of the drying equipment to a predetermined value or less based on the oxygen concentration estimation method in the drying system that the inventors have conceived.

[A] In order to achieve the above object, the oxygen concentration control system in the drying system of the present invention uses a gas in the drying system in a drying facility for drying organic hydrated waste to granulate organic powder. An oxygen concentration control system in a drying system, the composition of which includes water vapor and air, and the organic water-containing waste is circulated together with a gas whose temperature has been increased. kNm ³ / h) calculating the outside exhaust air volume calculating means, calculating the steam amount β (kNm ³ / h) generated in the dry system, and calculating the outside exhaust air volume α (kNm). ³ / h), the water vapor amount β (kNm ³ / h), and the oxygen concentration γ in the air supplied into the drying system γ = 21 (%), from the following formula (1), Oxygen concentration calculation to calculate oxygen concentration C (volume%) It is constituted with a unit.
C = {(α−β) / α} × 21 (1)

[B] Preferably, in the oxygen concentration control system in the drying system of [a], the out-of-system exhaust air volume calculating means is configured to determine an air volume F (determined from a performance curve of an exhaust steam fan provided in the dry system. Based on m ³ / min), the system discharge air volume α (kNm ³ / h) at T (° C.) may be calculated from the following formula (2).
α = F × {273 / (273 + T)} × 60/1000 (2)

[C] Preferably, in the oxygen concentration control system in the drying system of [a] or [b], the water vapor amount β (kNm ³ / h) is a water vapor amount β ₁ (kNm ³ / h) derived from the organic hydrous waste. kNm ³ / h), and the water vapor amount calculation means includes the input amount A (t / h) of the organic water-containing waste, the water content X (%) of the organic water-containing waste, and the organic Based on the moisture content Y (%) of the powder, the water vapor amount β (kNm ³ / h) may be calculated from the following formula (3).
β ₁ = [A × {(XY) / 100}] × 22.4 / 18 (3)

[D] Preferably, in the oxygen concentration control system in the drying system of [c] above, the drying facility includes a watering device in the drying system, and the water vapor amount β (kNm ³ / h) is the organic Is the total of the amount of water vapor β ₁ (kNm ³ / h) derived from the water-containing waste and the amount of water vapor β ₂ (kNm ³ / h) derived from the watering device, ) To calculate the water vapor amount β ₁ (kNm ³ / h), and based on the water spray amount W (L / min) by the water sprinkler and the water content 100 (%), the following formula (4) It is preferable that the water vapor amount β ₂ (kNm ³ / h) be calculated.
β ₂ = {W × 60/1000} × 100 × 22.4 / 18 (4)

[E] Preferably, in the oxygen concentration control system in the drying system according to any one of the above [a] to [d], depending on the nature of the organic powder that is granulated by drying the organic water-containing waste Thus, a configuration may be adopted in which a threshold value that is the upper limit of the oxygen concentration C in the dry system calculated by the above equation (1) is set.

[F] Preferably, in the oxygen concentration control system in the drying system of [e], the oxygen concentration monitoring for monitoring whether the calculation result of the formula (1) is equal to or greater than the threshold during the operation of the drying facility. A configuration provided with means is preferable.

[G] Preferably, in the oxygen concentration control system in the drying system of [f] above, when the calculation result of the formula (1) becomes equal to or more than the threshold during the operation of the drying facility, a display or sound is displayed. It is good to have a structure provided with the alerting | reporting means to perform alerting | reporting.

[H] Preferably, in the oxygen concentration control system in the drying system according to any one of [f] to [g], the drying equipment includes a watering device in the drying system, and the drying equipment is in operation. In addition, it is preferable to have a configuration including watering amount control means for controlling the watering amount W (L / min) by the watering device so that the calculation result of the formula (1) is equal to or less than the threshold value.

[I] Preferably, in the oxygen concentration control system in the drying system according to any one of [e] to [h] above, the particle size of the organic powder granulated by drying the organic water-containing waste When the value is 63 μm or less, the threshold value may be set to a value of 12.5 (volume%) or less.

[J] Preferably, in the oxygen concentration control system in the drying system according to any one of [d] to [i], the water vapor amount β (kNm ³ / h) is set such that the input amount A = 4.5 (t / H) and the amount of water vapor β ₁ (kNm ³ / h) when the moisture content X = 80 (%), and calculated by the sum of the above formula (3) and the above (4). that the value of the water vapor β ^(kNm 3 / h) is, to a value of the water vapor content in the assumption β ^(kNm 3 / h), to control the water spray amount W (L / min) by the water spray device It is good to set it as the structure provided with the sprinkling amount control means.

[K] In order to achieve the above object, the sludge drying facility of the present invention is a sludge drying facility including an oxygen concentration control system in the drying system of any one of the above [a] to [j], An input system for supplying organic water-containing waste; and the drying system in which the organic water-containing waste is circulated together with a gas whose temperature has been increased, and the drying system solves the organic water-containing waste. A crusher for crushing, solid-gas separation means for separating the organic water-containing waste crushed by the crusher into solid and gas, and the organic water-containing waste in the crusher and the solid-gas separation means A waste circulation path to be circulated; a heat exchanger that raises the temperature of air circulating in the waste circulation path; an exhaust steam fan that discharges water vapor from the waste circulation path; and the circulation circuit that circulates through the waste circulation path. One or more water sprays for organic water-containing waste It is constituted including a location, a.

[L] Preferably, in the sludge drying facility of [k], one or a plurality of the watering devices are connected to the waste circulation path connected to the inlet of the crusher and / or the outlet of the crusher. It is good to have the structure provided in the said waste circulation path.

[M] Preferably, in the sludge drying facility of the above [k] or [l], an inlet of a heat source of the heat exchanger is directly or indirectly connected to a cement manufacturing facility, and waste heat of the cement manufacturing facility It is good to make it the structure which heats the air which circulates through the said waste circulation path by using as a heat source.

[N] Preferably, in the sludge drying facility according to any one of the above [k] to [m], the drying system is directly or indirectly connected to a cement manufacturing facility, and the organic powder is the cement It is good to have a configuration that becomes fuel for manufacturing equipment.

[O] Preferably, in the sludge drying facility according to any one of [k] to [n], the input system supplies a waste supply source for supplying a predetermined amount of the organic hydrous waste per unit time; A mixer for mixing the organic water-containing waste supplied from the waste supply source and the organic water-containing waste separated by the solid-gas separation means, and feeding the mixture to the side of the crusher. It is good to have a configuration.

  According to the oxygen concentration control system in the drying system in the drying equipment of the present invention and the sludge drying equipment equipped with this system, the oxygen concentration in the drying system in the operating drying equipment can be estimated with high accuracy by calculation. And can prevent dust explosion reliably.

  In particular, according to the oxygen concentration control system in the drying system in the drying facility of the present invention, and the sludge drying facility equipped with this system, the water vapor concentration, such as the start-up period immediately after the startup of the drying facility, and the failure of the drying facility. When the supply of organic hydrated waste that is the source of supply is delayed, that is, an unexpected situation occurs in which only organic powder (ignition source) circulates in the dry system. Even in such a case, it is possible to detect a dangerous state based on the estimated value of the oxygen concentration and prevent dust explosion.

It is drawing which modeled the airflow in a dry system | strain in the simple cycle. It is a mimetic diagram of the sludge drying equipment concerning this embodiment. It is a block diagram of an oxygen concentration control system according to the present embodiment. It is a table | surface which shows the result of the limiting oxygen concentration measurement test which concerns on this embodiment. It is a table | surface which shows the result of the limiting oxygen concentration measurement test which concerns on this embodiment. It is a table | surface which shows the result of the limiting oxygen concentration measurement test which concerns on this embodiment. It is a graph which shows the explosion range of the sample used for the said test. It is a table | surface which shows the result of the simulation using the said oxygen concentration control system. It is a table | surface which shows the result of the simulation using the said oxygen concentration control system.

  Hereinafter, a sludge drying facility according to an embodiment of the present invention will be described with reference to the drawings. The sludge drying facility of this embodiment described below includes an oxygen concentration control system in a drying system according to an embodiment of the present invention.

  FIG. 2 is a schematic diagram showing the sludge drying facility 1 according to the present embodiment. The sludge drying facility 1 of this embodiment is connected to the cement manufacturing facility 40. First, an organic water-containing waste applied to the sludge drying facility 1 of the present embodiment, and an organic powder granulated from the organic water-containing waste, and the sludge drying facility 1 shown in FIG. The configuration of the cement manufacturing facility 40 will be described.

<Organic water-containing waste>
The sludge drying facility 1 according to the present embodiment can be widely applied to drying organic water-containing waste including, for example, livestock manure in addition to sludge waste such as sewage sludge, food sludge, and paper sludge. The water content X of the organic water-containing waste is at least about 40 (mass%). Preferably, the moisture content X of the organic water-containing waste is about 80 (mass%), and the moisture content Y of the organic powder granulated by the sludge drying facility 1 is about 10 (mass%). .

<Organic powder>
The organic powder is a powder obtained by drying organic water-containing waste. The organic powder is granulated by transporting the organic water-containing waste in the sludge drying facility 1 together with the drying gas. The moisture content Y of the organic powder is at least 25 (mass%) or less, preferably 20 (mass%) or less, more preferably 15 (mass%) or less, and particularly preferably 10 (mass%) or less. There should be. On the other hand, the lower limit of the moisture content Y is, for example, about 5 (mass%). The organic powder granulated by the sludge drying facility 1 is used as a fuel for the cement manufacturing facility 40. The particle size of the organic powder when used as fuel is preferably about 1 to 5 (mm), for example.

<Sludge drying equipment>
Next, the sludge drying facility 1 of this embodiment will be described. In FIG. 2, the constituent elements of the sludge drying facility 1 can be divided into two systems, that is, an input system and a drying system, based on the function. Among these, the drying system is connected to the cement manufacturing facility 40. In the sludge drying facility 1 of the present embodiment, the cement manufacturing facility 40 is a heat source for raising the temperature of the drying gas for organic hydrated waste, and is an organic powder granulated from the organic hydrated waste. Is a supplier.

<< Input system >>
The input system is a component for supplying organic water-containing waste to the sludge drying facility 1. The input system of this embodiment is composed of a receiving hopper 10 as a waste supply source and a mixer 11 disposed on the outlet side thereof. The receiving hopper 10 is a part that receives organic water-containing waste before drying. The receiving hopper 10 sends a predetermined amount of organic water-containing waste to the mixer 11 per unit time. Specifically, the outlet of the receiving hopper 10 is connected to the mixer 11 via the transport path 21. The organic water-containing waste is supplied to the mixer 11 via the transport path 21.

  The mixer 11 mixes the organic water-containing waste before drying supplied from the receiving hopper 10 and the organic water-containing waste after drying supplied from cyclones (solid-gas separation means) 13 and 14 described later. Device. The configuration of the mixer 11 is not particularly limited as long as it can sufficiently stir and mix organic water-containing wastes having different dry states (moisture contents). For example, the mixer 11 having various configurations such as a configuration in which mixing is performed using a paddle or a screw, or a configuration in which mixing is performed using a stirring blade can be applied. The organic water-containing waste mixed by the mixer 11 is sent to the waste circulation path 22 of the drying system described below.

<< Dry system >>
The drying system is a component for granulating organic powder obtained by drying organic water-containing waste by circulating the organic water-containing waste with a drying gas. The drying gas in the present embodiment is air that has been heated to a high temperature.

  As shown in FIG. 2, the drying system of this embodiment mainly includes a crusher 12, cyclones (solid-gas separation means) 13, 14, a heat exchanger 16, a drying fan B1, an exhaust steam fan B2, A raw material tank 17 and watering devices 18 and 19 are included. Furthermore, the drying system of this embodiment includes waste circulation paths 22 to 25 that are piping for circulating organic water-containing waste, a gas line 31 for circulating a drying gas, and other drying gases. The circulation paths 32A, 32B, and 33 are included.

  The crusher 12 finely pulverizes the fed organic water-containing waste. The configuration of the crusher 12 is not particularly limited. For example, the crusher 12 may be configured to accompany the hot air flow while crushing the lump by rotating the cage. Further, for example, those used in Japanese Patent Laid-Open No. 2000-65476 may be used. The degree of crushing by the crusher 12 is appropriately adjusted depending on, for example, the properties of the organic water-containing waste used, the properties of the target organic powder, and the like. The organic water-containing waste crushed by the crusher 12 is sent out to the cyclones 13 and 14 via the waste circulation path 23.

  The cyclones 13 and 14 are solid-gas separation means for separating the organic water-containing waste crushed by the crusher 12 into solid and gas. In the present embodiment, two cyclones 13 and 14 are connected in parallel. Note that one or three or more cyclones 13 and 14 as solid-gas separation means may be provided. Two or more cyclones 13 and 14 are not limited to being connected in parallel but may be connected in series.

  Part of the gas separated by the cyclones 13 and 14 is circulated and used as a drying gas. On the other hand, the dry solids separated by the cyclones 13 and 14 are separated into undried organic water-containing waste and sufficiently dried organic powder. The undried organic water-containing waste is returned to the mixer 11. The organic powder is sent to the raw material tank 17 and finally used as a fuel for the cement manufacturing facility 40.

  The waste circulation paths 22 to 25 are pipes for circulating the organic water-containing waste together with the drying gas. As shown in FIG. 2, the waste circulation path 22 connects the mixer 11 and the crusher 12. Specifically, one end of the waste circulation path 22 is connected to the outlet side of the mixer 11 and the return gas line 33 of the drying gas via the connection portion P1. The other end of the waste circulation path 22 is connected to the inlet side of the crusher 12. The waste circulation path 23 connects the crusher 12 and the cyclone 13. The waste circulation paths 24 and 25 connect the outlets of the organic water-containing waste of the cyclones 13 and 14 to the mixer 11. The organic water-containing waste is gas-conveyed in the waste circulation paths 22 to 25 by high-temperature air that is a drying gas. The organic water-containing waste is circulated through the respective processing steps of the crusher 12, the cyclones 13 and 14, and the mixer 11 until the organic water-containing waste is sufficiently dried to become an organic powder.

  The heat exchanger 16 raises the temperature of the drying gas circulating in the waste circulation paths 22 to 25 using an external heat source. In the present embodiment, waste heat from the cement manufacturing facility 40 is supplied to the heat exchanger 16. That is, the heat exchanger 16 is connected to the rotary kiln 41 of the cement manufacturing facility 40 through the gas lines 34 and 35. Waste heat of the rotary kiln 41 is supplied to the heat exchanger 16 via the gas line 34. On the other hand, the outlet gas discharged from the heat exchanger 16 is returned to the rotary kiln 41 via the gas line 35.

  In addition, the heat source of the heat exchanger 16 should just be a thing which can heat up drying gas 120 degreeC or more, Preferably, what can raise 150 degreeC-250 degreeC is good. In this embodiment, the rotary kiln 41 of the cement manufacturing facility 40 is used as a heat source of the heat exchanger 16. However, the present invention is not limited to this, and other components of the cement manufacturing facility 40, such as a suspension preheater or a cooler (not shown). It is also possible to use exhaust gas or the like as a heat source.

  The heat exchanger 16 is connected to the above-described drying gas circulation path. The drying gas circulation path mainly includes a gas line 31, a heat exchange line 32A, a bypass line 32B, and a return gas line 33 shown in FIG.

  The gas line 31 connects the gas outlets of the cyclones 13 and 14 and the suction port of the drying fan B1. The discharge port of the drying fan B1 is connected to the branch part P2 of the heat exchange line 32A and the bypass line 32B. A part of the drying gas discharged from the drying fan B1 passes through the heat exchange line 32A and is sent to the heat exchanger 16. The other part of the drying gas discharged from the drying fan B1 passes through the bypass line 32B and is sent to the return gas line 33. That is, the drying gas passing through the heat exchange line 32A is heated by the heat exchanger 16, but the drying gas passing through the bypass line 32B bypasses the heat exchanger 16 and thus is not heated. Any drying gas is sent to the return gas line 33 and returned to the waste circulation paths 22 to 25 to be used for drying the organic water-containing waste.

  In addition, the details of the circulation path of the drying gas will be described. On the gas line 31, an air flow meter 15 for measuring the gas flow rate and a valve V3 for opening and closing the flow path are arranged. Also, flow path opening and closing valves V1 and V2 are arranged in each of the heat exchange line 32A and the bypass line 32B. By operating these valves V1, V2, and V3, the opening and closing of the flow path can be adjusted. The valves V1, V2, and V3 may be manually operated (opening / closing and / or opening degree adjustment) by an operator. In this embodiment, the valves V1, V2, and V3 are operated based on a signal from the control chamber 2. The configuration is controlled.

  As shown in FIG. 2, the piping connecting the drying fan B1, the heat exchange line 32A, and the bypass line 32B described above is connected to the suction port of the exhaust steam fan B2 via the valve V4. An exhaust port of the exhaust steam fan B <b> 2 is connected to the gas line 36. The exhaust steam fan B2 discharges part of the drying gas discharged from the drying fan B1 to the rotary kiln 41 of the cement manufacturing facility 40, which has not been sent to the heat exchange line 32A and the bypass line 32B. To do. That is, the exhaust steam fan B2 exhausts the drying gas containing water vapor out of the drying system through the gas line 36. The exhaust steam fan B2 will be described in detail in the description of the oxygen concentration control system according to the present embodiment.

  Here, the sludge drying facility 1 of the present embodiment includes two watering devices 18 and 19. As shown in FIG. 2, the watering device 18 is disposed in the waste circulation path 22 connected to the inlet of the crusher 12. Further, the watering device 19 is disposed in the waste circulation path 23 connected to the outlet of the crusher 12. As will be described in detail later, these water sprinklers 18 and 19 are controlled in operation based on the oxygen concentration in the drying system, and sprinkle the organic water-containing waste that passes through the waste circulation paths 22 and 23.

  The sprinklers 18 and 19 have a drive mechanism that adjusts the amount of sprinkling and a control circuit that controls the operation of the drive mechanism, and the control circuit controls the operation of the drive mechanism based on a signal from the control room 2. It has become. Watering by the watering devices 18 and 19 may be either a form in which water is jetted in a liquid state or a form in which water is sprayed in a mist form. Moreover, the place where the water sprinklers 18 and 19 are installed may be any of the waste circulation paths 22 to 25. However, it is preferable to arrange in the waste circulation path 23 connected to the outlet of the crusher 12 like the watering device 19 of the present embodiment. This is because the organic water-containing waste is dried by the crusher 12 in addition to the drying gas supplied to the drying system, so that it is in the most dry state at the outlet of the crusher 12. Thus, in the case where the watering device 19 is disposed in the waste circulation path 23 connected to the outlet of the crusher 12, in addition to reducing the oxygen concentration in the waste circulation path 23, organic water-containing waste It is possible to directly eliminate over-drying of the water and prevent self-ignition of organic water-containing waste.

<Cement production equipment>
In addition to the rotary kiln 41, the cement manufacturing facility 40 includes a suspension preheater, a calcining furnace, a cooler and the like (not shown). The suspension preheater includes a plurality of cyclones. The calcining furnace is connected to the lowermost cyclone of the suspension preheater. The rotary kiln 41 is connected to the lowest cyclone and calcining furnace of the suspension preheater. The organic powder stored in the raw material tank 17 of the sludge drying facility 1 described above is supplied to the cement manufacturing facility 40 and burned by the main burner of the rotary kiln 41. Although not shown, the organic powder supplied to the cement manufacturing facility 40 is also burned in the calcining furnace.

  In addition, the cement manufacturing equipment 40 connected to the sludge drying equipment 1 of this embodiment can utilize various conventionally well-known things, and is not limited to a specific structure. For example, the thing of the structure similar to the cement manufacturing equipment disclosed by patent 4445147 is applicable.

<Oxygen concentration control system>
Next, an embodiment of the oxygen concentration control system in the drying system, which is implemented in the above-described sludge drying facility 1, will be described. The oxygen concentration control system 210 shown in FIG. 3 is for preventing the dust explosion of the sludge drying equipment 1 beforehand. Dust explosion can occur when the concentration of dust and oxygen in the dry system reaches a certain level and a fire source is generated as an ignition source. The oxygen concentration control system 210 estimates the oxygen concentration C (volume%) in the dry system by calculation, and prevents the dust explosion when the estimated oxygen concentration C (volume%) exceeds a threshold value. Execute.

  The oxygen concentration control system 210 shown in FIG. 3 is realized, for example, when the arithmetic processing unit 201 such as a personal computer installed in the control room 2 shown in FIG. 2 executes a program. Specifically, a program for realizing the processing of the oxygen concentration control system 210 is installed in advance in storage means such as RAM or ROM of the arithmetic processing unit 201. Control means such as a CPU of the arithmetic processing unit 201 executes the processing of the program based on information from the sludge drying facility 1 received wirelessly or by wire.

  In FIG. 3, the oxygen concentration control system 210 includes an out-of-system discharge air amount calculation means 211, a water vapor amount calculation means 212, an oxygen concentration calculation means 213, an oxygen concentration monitoring means 214, a notification means 215, and a sprinkling amount control means. 216. Of these, the out-of-system exhaust air volume calculating means 211, the water vapor amount calculating means 212, and the oxygen concentration calculating means 213 are related to a calculation process for estimating the oxygen concentration C (volume%) in the dry system. On the other hand, the oxygen concentration monitoring unit 214, the notification unit 215, and the sprinkling amount control unit 216 are related to a control process based on the estimated oxygen concentration C (volume%).

<< Oxygen concentration estimation principle >>
It is considered that the dust explosion of the sludge drying facility 1 is caused by an increase in oxygen concentration due to a decrease in the amount of water vapor in the drying system. In the drying system model shown in FIG. 1, the water vapor amount β in the drying system converges to the ratio of the amount of water supplied to the drying system and the amount of air δ. Assuming that there is no combustion reaction in the dry system, the gas composition in the dry system is water vapor and air. The oxygen concentration γ in the air supplied into the drying system is 21%, and the moisture in the air is 0%.

In the dry system model described above, the amount of air δ supplied into the dry system can be regarded as a value (α−β) obtained by subtracting the amount of water vapor β in the dry system from the outside exhaust air amount α. The oxygen concentration C in the dry system is obtained by multiplying the value obtained by dividing the air amount δ by the out-of-system exhaust air amount α by the oxygen concentration γ in the air supplied into the dry system = 21%. That is, the estimated value of the oxygen concentration C in the dry system can be calculated by the following formula (1).
C = {(α−β) / α} × 21 (1)

<< Exhaust air volume calculation means >>
The extra-system exhaust air volume calculating means 211 calculates the extra-system exhaust air volume α (kNm ³ / h) exhausted outside the drying system of the sludge drying facility 1 based on the current value (A) of the exhaust steam fan B2.

Here, strictly speaking, the amount of air discharged outside the drying system of the sludge drying facility 1 is sufficiently dried in addition to the amount of air discharged outside the system α (kNm ³ / h) of the exhaust steam fan B2 shown in FIG. In order to send out the organic powder, there is an air volume discharged from the cyclones 13 and 14 to the raw material tank 17. However, the amount of air discharged from the cyclones 13 and 14 to the raw material tank 17 is very small with respect to the entire drying system. For this reason, the amount of gas discharged out of the system can be considered by approximating only the out-of-system exhaust air volume α (kNm ³ / h) of the exhaust steam fan B2.

Therefore, the system exhaust air volume calculation means 211 is based on the air volume F (m ³ / min) determined from the performance curve of the exhaust steam fan B2, and the system exhaust air volume α at T (° C.) from the following equation (2). (KNm ³ / h) is calculated.
α = F × {273 / (273 + T)} × 60/1000 (2)

  The performance curve of the exhaust steam fan B2 is a curve of a PQ diagram generally indicated by the pressure P and the air volume Q, and this curve represents the performance of the fan. The performance curve is unique to the various fans in the market. When a fan is introduced into the sludge drying facility 1, an optimum fan is selected in consideration of necessary ventilation volume and pressure loss.

Thus, the air volume F (m ³ / min) in the above formula (2) is determined by the performance curve unique to the exhaust steam fan B2. For example, the extra-system exhaust air volume calculation means 211 of the present embodiment calculates the power (kW) of the exhaust steam fan B2 based on the current value (A) of the exhaust steam fan B2, and uses this power (kW) as a performance curve. By applying this to the approximate expression, the out-of-system exhaust air volume α (kNm ³ / h) is calculated (see the following expressions (2-1) and (2-2)).
Power (kW) = √3 × 0.44 × exhaust steam fan current value (A) × 0.8 (2-1)
Air volume F (m ³ /min)=16.7×power (kW) −150.5 (2-2)

T (° C.) in the above formula (2) is a temperature correction value, and is determined based on the temperature of the drying gas (air heated to a high temperature) circulating in the drying system. In addition, “273” in the above formula (2) is for converting T (° C.) to an absolute temperature, “60” is a unit time, and “1000” is converted to a unit of “kNm ³ / h”. (The same applies to the following formulas (3) and (4)).

<< Water vapor amount calculation means >>
The water vapor amount calculation means 212 calculates the water vapor amount β (kNm ³ / h) generated in the drying system of the sludge drying facility 1. As described above, the amount of water vapor β (kNm ³ / h) generated in the dry system depends on the amount of water supplied in the dry system. In the sludge drying facility 1 of the present embodiment, the amount of water vapor β ₁ (kNm ³ / h) derived from the water contained in the organic water-containing waste and the amount of water vapor β ₂ derived from the water sprayed by the sprinklers 18 and 19 ( kNm ³ / h). Therefore, the following two methods can be selected for calculating the water vapor amount β (kNm ³ / h) generated in the dry system for the water vapor amount calculating means 212 of the present embodiment.

When the amount of water vapor β (kNm ³ / h) generated in the drying system only needs to consider the amount of water vapor β ₁ (kNm ³ / h) derived from organic water-containing waste, Based on the input amount A (t / h) of the organic water-containing waste, the water content X (%) of the organic water-containing waste, and the water content Y (%) of the organic powder, the amount of water vapor β ₁ (KNm ³ / h) is calculated from the following equation (3).
β ₁ = [A × {(XY) / 100}] × 22.4 / 18 (3)

  When performing the calculation of the above equation (3), the water vapor amount calculation means 212 acquires information on the input amount A (t / h) of the organic water-containing waste from the receiving hopper 10 of the sludge drying facility 1. The value of the moisture content X (%) of the organic water-containing waste and the value of the moisture content Y (%) of the organic powder are input in advance into the program of the oxygen concentration control system 210. In the above formula (3), “22.4” is for converting the volume of the gas into a mole, and “18” is the molecular weight of water (the same applies to the following formula (the same applies to (4) below)).

On the other hand, the amount of water vapor β (kNm ³ / h) generated in the dry system is the amount of water vapor β ₁ (kNm ³ / h) derived from organic water-containing waste, and the watering device 18 provided in the dry system, water vapor beta ₂ derived from the 19 when the sum of the ^(kNm 3 / h), the water vapor amount calculating means 212 calculates the amount of water vapor beta ₁ a ^(kNm 3 / h) from the above equation (3). In addition to this, the water vapor amount calculation means 212 calculates the water vapor amount β ₂ (kNm) from the following formula (4) based on the water spray amount W (L / min) by the water sprinklers 18 and 19 and the water content 100 (%). ³ / h).
β ₂ = {W × 60/1000} × 100 × 22.4 / 18 (4)

  When performing the calculation of the above formula (4), the water vapor amount calculation means 212 acquires information on the water spray amount W (L / min) of the water sprinklers 18 and 19 from the water spray amount control means 216 shown in FIG.

Whether the water vapor amount β (kNm ³ / h) is calculated only by the above equation (3) or the water vapor amount β (kNm ³ / h) is calculated by the combination of the above equations (3) and (4) will be described later. To be determined based on the limiting oxygen concentration (for example, 12.5 (volume%)). That is, the dust explosion is caused when the oxygen concentration C (volume%) in the dry system exceeds the limit oxygen concentration value, and the organic powder becomes a fire type. As described above, when the amount of water vapor β (kNm ³ / h) generated in the dry system decreases, the oxygen concentration C (volume%) in the dry system increases.

Therefore, if the oxygen concentration C (volume%) in the dry system can be kept below the critical oxygen concentration only with the amount of water vapor β ₁ (kNm ³ / h) derived from organic hydrous waste, the above formula What is necessary is just to make it the structure which calculates water vapor | steam amount (beta) (kNm < ³ > / h) only by (3). On the other hand, when only the amount of water vapor β ₁ (kNm ³ / h) derived from the organic water-containing waste cannot keep the oxygen concentration C (volume%) in the dry system below the critical oxygen concentration, The water spray amount 19 is essential, and the water vapor amount β (kNm ³ / h) may be calculated by the combination of the above formulas (3) and (4).

<< Oxygen concentration calculation means >>
The oxygen concentration calculation means 213 adjusts the above-described system exhaust air flow rate α (kNm ³ / h), the water vapor amount β (kNm ³ / h), and the oxygen concentration γ in the air supplied into the drying system γ = 21 (%). Based on the following formula (1), the oxygen concentration C (volume%) in the dry system is calculated.
C = {(α−β) / α} × 21 (1)

<< Oxygen concentration monitoring means >>
The oxygen concentration monitoring means 214 has a value of the above-mentioned limit oxygen concentration (for example, 12.5 (volume%)) as the threshold value of the oxygen concentration C (volume%) in the dry system calculated by the above equation (1). Is set. The oxygen concentration monitoring means 214 always acquires the calculation result of the above formula (1) from the oxygen concentration calculation means 213 and monitors whether or not the oxygen concentration C (volume%) in the dry system is equal to or higher than the limit oxygen concentration value. To do. For example, the oxygen concentration monitoring means 214 outputs a detection signal when the oxygen concentration C (volume%) in the drying system continuously exceeds the limit oxygen concentration value for a predetermined time (for example, several seconds). To do.

<< Informing means >>
The notification unit 215 is connected to an image display device 202 such as a liquid crystal display and an audio output device 203 such as a speaker. The notification unit 215 causes the image display device 202 and the sound output device 203 to perform display and sound notification based on the detection signal of the oxygen concentration monitoring unit 214.

<< Watering amount control means >>
The sprinkling amount control means 216 is connected to the sprinklers 18 and 19. The value of the above-mentioned critical oxygen concentration (for example, 12.5 (volume%)) is set in the sprinkling amount control means 216. The sprinkling amount control means 216 drives the sprinkling apparatuses 18 and 19 based on the detection signal of the oxygen concentration monitoring means 214 so that the oxygen concentration C (volume%) is equal to or lower than the limit oxygen concentration. The water spray amount W (L / min) is controlled.

Further, the water sprinkling amount control means 216 has a small input amount A (t / h) of organic water-containing waste, and only the amount of water vapor β ₁ (kNm ³ / h) derived from the organic water-containing waste In some cases, the oxygen concentration C (volume%) cannot be kept below the critical oxygen concentration. In such a case, the sprinkling amount control means 216 sets the sprinkling amount W (L / min) by the sprinklers 18 and 19 so that the oxygen concentration C (volume%) in the dry system is not more than the limit oxygen concentration value. Control.

<< Limit oxygen concentration >>
Here, the above-mentioned critical oxygen concentration will be described. The critical oxygen concentration was measured using the following samples, test conditions, and test methods. In this limiting oxygen concentration measurement, various concentrations are changed in the vicinity of the concentration estimated as the limiting oxygen concentration, and the oxygen concentration at which explosion does not occur once in three times is defined as the “limit oxygen concentration” in this embodiment. It was. The value of the critical oxygen concentration obtained by this critical oxygen concentration measurement is 12.5 (volume%).

[sample]
・ Dry sludge collected from raw material tank (see reference numeral 17 in FIG. 2) / Dry sludge particle size: 63 μm under (under sieve)

[Test conditions]
・ Name of test equipment Sealed blow-up type dust explosion test equipment (manufactured by Kashiwagi Chemical Instrument Co., Ltd.)
・ Pressure sensor Strain gauge pressure sensor ・ Temperature and humidity in the measurement chamber Temperature: 23 ℃, Humidity: 52%
・ Explosion cylinder volume 1.84L
・ Compressed air blowing pressure 2.0 × 10 ⁵ Pa (G)
・ Discharge start time 0.15 seconds

[Test method]
The sample is weighed with a balance and charged uniformly in the sample container, and the system is once evacuated. Next, a mixed gas that has been adjusted to a predetermined oxygen concentration with air and nitrogen in advance is filled into the explosion cylinder to atmospheric pressure, and charged into the blowing tank to a predetermined pressure. Then, a mixed gas is blown to form a dust cloud and ignited with an electric spark. The presence or absence of an explosion is determined by detecting the explosion pressure with a pressure sensor attached to the upper part of the explosion cylinder and using the following criteria of ○, Δ, and ×.
○ Explosion: Explosion pressure> 0.5 × 10 ⁵ Pa
Δ Explosion: 0.1 × 10 ⁵ Pa ≦ explosion pressure ≦ 0.5 × 10 ⁵ Pa
× Non-explosive: Ascending pressure <0.1 × 10 ⁵ Pa

[Test results]
The test results are shown in FIGS. Note that the “maximum pressure rise rate” in FIGS. 4 to 6 is obtained from the pressure waveform by the maximum gradient in 10 msec.

  The critical oxygen concentration 12.5 (volume%) of this embodiment is input to the program of the oxygen concentration control system 210 shown in FIG. The oxygen concentration monitoring unit 214 sequentially acquires the oxygen concentration C (volume%) in the dry system calculated by the oxygen concentration calculation unit 213 and compares it with the limit oxygen concentration 12.5 (volume%). The oxygen concentration monitoring unit 214 measures a predetermined time (for example, several seconds) when it is determined that the oxygen concentration C in the dry system is 12.5 (volume%) or more. Thereafter, the oxygen concentration monitoring means 214 outputs a detection signal when it is determined that the oxygen concentration C in the dry system is 12.5 (volume%) or more even after a predetermined time has elapsed. Based on this detection signal, notification by the notification means 215 is executed, and watering by the watering control means 216 is executed.

  In this embodiment, the threshold value of the oxygen concentration C (volume%) in the dry system calculated by the above formula (1) is set to the same value as the critical oxygen concentration of 12.5 (volume%). However, the present invention is not limited to this. The threshold value in the present invention defines the upper limit of the oxygen concentration C (volume%) in the dry system calculated by the above formula (1), and a value equal to or lower than the limit oxygen concentration can be set. For example, when a value less than 12.5 (volume%) of the critical oxygen concentration is set as the threshold value, the oxygen concentration C (volume%) in the dry system is shown in FIG. 3 before reaching the critical oxygen concentration. Control processing by the oxygen concentration control system 210 is executed, and higher safety can be ensured.

<Example>
The result of the simulation using the oxygen concentration control system 210 according to this embodiment is shown in FIG. The organic water-containing waste in this simulation is sludge waste. The numerical value in the column of FIG. 8 is the amount of sludge charged into the receiving hopper 10 (t / h). The moisture content X of the sludge waste in this example was set to 80 (%). The water content Y of the organic powder obtained by drying this sludge waste was set to 10 (%). The amount of sludge input was changed in the range of 0.0 to 7.0 (t / h) in 0.5 (t / h) increments. Moreover, the numerical value of the horizontal column of FIG. 8 is exhaust steam fan electric current (A), and was changed in the range of 33-44 (A) in 1 (A) increments. In the relationship between the sludge input amount (t / h) and the exhaust steam fan current (A) in FIG. 8, the oxygen concentration C (volume%) in the dry system is calculated using the above equations (1) to (3). did. A portion surrounded by a thick solid line in FIG. 8 indicates an actual operation range of the exhaust steam fan B2. On the other hand, the part enclosed by the thin dotted line in FIG. 8 shows the safe region where the oxygen concentration C in the dry system is less than the limit oxygen concentration 12.5 (volume%).

  According to the simulation results shown in FIG. 8, when the moisture content of sludge waste is 80 (%) and the moisture content of organic powder is 10 (%), the input amount of sludge waste per unit time is 4. 5 (t / h) or more is preferable. In the case of 4.5 (t / h) or more, the oxygen concentration C in the dry system is less than the critical oxygen concentration 12.5 (volume%) in the entire range of the current value 33 to 44 (A) of the exhaust steam fan B2. Thus, the dust explosion can be reliably prevented. For this reason, when the input amount of sludge waste per unit time is set to 4.5 (t / h) or more, the sprinklers 18 and 19 are omitted from the sludge drying facility 1 shown in FIG. It is possible to omit the control by the watering control means 216 shown in FIG.

  On the other hand, according to the result of the simulation shown in FIG. 8, when the moisture content of sludge waste is 80 (%) and the moisture content of organic powder is 10 (%), the input amount of sludge waste per unit time is 4 If it is less than 5 (t / h), the oxygen concentration C in the dry system exceeds the limit oxygen concentration of 12.5 (volume%), and there is a risk of dust explosion. Therefore, when the input amount of sludge waste per unit time is less than 4.5 (t / h), the water spraying devices 18 and 19 are controlled by the water spray control means 216 shown in FIG. An amount of water in which the oxygen concentration C is always less than or equal to the critical oxygen concentration of 12.5 (volume%) may be sprinkled. FIG. 9 shows a simulation result when watering is performed when the input amount of sludge waste per unit time is 0.0 to 4.0 (t / h). According to the simulation results shown in FIG. 9, the oxygen concentration C in the drying system is less than the critical oxygen concentration of 12.5 (volume%) within the actual operating range of the exhaust steam fan B2, and dust explosion is reliably prevented. Can be achieved.

DESCRIPTION OF SYMBOLS 1 Sludge drying equipment 2 Control room 10 Receiving hopper 11 Mixer 12 Crusher 13, 14 Cyclone 15 Air flow meter 16 Heat exchanger 17 Raw material tank 18, 19 Sprinkler 21 Transport path 22-25 Waste circulation path 31 Gas line 32A Heat Exchange line 32B Bypass line 33 Return gas line 34, 35 Gas line 36 Gas line 40 Cement production equipment 41 Rotary kiln 201 Arithmetic processing device 202 Image display device 203 Audio output device 210 Oxygen concentration control system 211 Exhaust air volume calculation means 212 Water vapor Quantity calculation means 213 Oxygen concentration calculation means 214 Oxygen concentration monitoring means 215 Notification means 216 Sprinkling control means B1 Drying fan B2 Exhaust steam fan B3 Heat source fan P1 Connection part P2 Branch part V1-V4 Valve

Claims (15)

In a drying facility for drying organic water-containing waste and granulating organic powder, the gas composition in the drying system contains water vapor and air, and the organic water-containing waste is circulated together with the heated gas. An oxygen concentration control system in a drying system,
An out-of-system exhaust air volume calculating means for calculating an out-of-system exhaust air volume α (kNm ³ / h) discharged outside the drying system;
A water vapor amount calculating means for calculating a water vapor amount β (kNm ³ / h) generated in the dry system;
Based on the outside exhaust air flow rate α (kNm ³ / h), the water vapor amount β (kNm ³ / h), and the oxygen concentration γ in the air supplied into the drying system γ = 21 (%), An oxygen concentration control system in a drying system, comprising: an oxygen concentration calculation means for calculating an oxygen concentration C (volume%) in the drying system from 1).
C = {(α−β) / α} × 21 (1) The out-of-system exhaust air volume calculation means is based on the air volume F (m ³ / min) determined from the performance curve of the exhaust steam fan provided in the drying system, and the T (° C.) in the following formula (2) The oxygen concentration control system in a dry system according to claim 1, wherein the system discharge air volume α (kNm ³ / h) is calculated.
α = F × {273 / (273 + T)} × 60/1000 (2) The water vapor amount β (kNm ³ / h) is the water vapor amount β ₁ (kNm ³ / h) derived from the organic water-containing waste,
The water vapor amount calculating means includes the input amount A (t / h) of the organic water-containing waste, the water content X (%) of the organic water-containing waste, and the water content Y (%) of the organic powder. The oxygen concentration control system in the dry system according to claim 1 or 2, wherein the water vapor amount β (kNm ³ / h) is calculated from the following formula (3) based on:
β ₁ = [A × {(XY) / 100}] × 22.4 / 18 (3) The drying facility includes a watering device in the drying system,
The total of the water vapor β ^(kNm 3 / h) is the organic-based water-containing waste water vapor from ^{_{β 1 (kNm 3 / h)}} , the water vapor from the water spraying unit beta ₂ and ^(kNm 3 / h) And
The water vapor amount calculation means calculates the water vapor amount β ₁ (kNm ³ / h) from the above formula (3), the water spray amount W (L / min) by the water sprinkler, and the water content 100 (%) The oxygen concentration control system in the drying system according to claim 3, wherein the water vapor amount β ₂ (kNm ³ / h) is calculated from the following formula (4) based on:
β ₂ = {W × 60/1000} × 100 × 22.4 / 18 (4)   The threshold which becomes the upper limit of the oxygen concentration C in the dry system calculated by the above formula (1) according to the property of the organic powder that is granulated by drying the organic water-containing waste Item 5. The oxygen concentration control system in the drying system according to any one of Items 1 to 4.   The oxygen concentration control system in the drying system according to claim 5, further comprising an oxygen concentration monitoring unit that monitors whether the calculation result of the formula (1) is equal to or greater than the threshold during operation of the drying facility.   The oxygen in the drying system according to claim 6, further comprising notification means for executing notification by display or sound when the calculation result of the formula (1) becomes equal to or greater than the threshold during operation of the drying facility. Concentration control system. The drying facility includes a watering device in the drying system,
The watering amount control means which controls the watering amount W (L / min) by the said watering apparatus so that the calculation result of said Formula (1) may become below the said threshold value during the driving | operation of the said drying equipment. Or the oxygen concentration control system in the dry system | strain of 7.   The said threshold value was set to the value of 12.5 (volume%) or less, when the particle diameter of the said organic powder granulated by drying the said organic water-containing waste is 63 micrometers or less. The oxygen concentration control system in the drying system according to any one of 8. The amount of water vapor β ^(kNm 3 / h) is the input amount A = 4.5 (t / h) and the said amount of water vapor when a water content _{X = 80 (%) β 1} (kNm 3 / h) Assuming that
The value of the water vapor amount β (kNm ³ / h) calculated by the sum of the formula (3) and the above (4) is the value of the water vapor amount β (kNm ³ / h) in the assumption. The oxygen concentration control system in the drying system according to any one of claims 4 to 9, further comprising a watering amount control means for controlling a watering amount W (L / min) by the watering device. It is the sludge drying equipment provided with the oxygen concentration control system in the drying system according to any one of claims 1 to 10,
An input system for supplying the organic water-containing waste, and the drying system in which the organic water-containing waste is circulated together with a heated gas,
The drying system is
A crusher for crushing the organic water-containing waste;
Solid-gas separation means for separating the organic water-containing waste crushed by the crusher into solid and gas;
A waste circulation path for circulating the organic water-containing waste to the crusher and the solid-gas separation means;
A heat exchanger that raises the temperature of air circulating in the waste circulation path;
An exhaust steam fan for discharging water vapor from the waste circulation path;
One or more watering devices for sprinkling the organic water-containing waste that circulates in the waste circulation path;
The sludge drying equipment characterized by including.   The one or a plurality of the watering devices are provided in the waste circulation path connected to an inlet of the crusher and / or the waste circulation path connected to an outlet of the crusher. Sludge drying equipment.   The inlet of the heat source of the heat exchanger is directly or indirectly connected to a cement manufacturing facility, and the temperature of the air circulating through the waste circulation path is increased by using waste heat of the cement manufacturing facility as a heat source. The sludge drying facility according to 11 or 12.   The sludge drying facility according to any one of claims 11 to 13, wherein the drying system is directly or indirectly connected to a cement manufacturing facility by piping, and the organic powder serves as a fuel for the cement manufacturing facility. The input system is
A waste supply source for supplying a predetermined amount of the organic water-containing waste per unit time;
A mixer for mixing the organic water-containing waste supplied from the waste supply source and the organic water-containing waste separated by the solid-gas separation means, and sending the mixture to the side of the crusher;
The sludge drying equipment according to any one of claims 11 to 14, comprising: