JPS6139563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving the treatment efficiency of a regenerative type hazardous substance treatment furnace, and more specifically, to a process in which residual untreated gas is pushed out with clean gas in a switching type regenerative type treatment furnace, and then switching is performed. Concerning how to improve efficiency. The heat storage method of the heat storage type hazardous substance treatment furnace is a heat storage type heat exchanger that uses a fixed bed of solid as a heat medium and recovers heat by passing low temperature gas and high temperature gas alternately through the fixed bed.The basic technology is steel manufacturing. This is a well-known method that has traditionally been used in open hearths, glass tank kilns, heat storage chambers for coke ovens, and hot blast furnaces for blast furnaces. Thermal area is 10~25m ² /m ³ , brick volume porosity is
Since it was about 0.3, the device was large and expensive. The heat storage filling of the type of heat storage hazardous substance processing furnace that is the main target of the method of the present invention is the filling used in chemical equipment, and the heat transfer area per unit volume is 100 to 400.
m ² /m ³ and a space ratio of, for example, 0.7 to 0.74, the equipment can be made compact and inexpensive, and at the same time, it has a very high heat recovery rate for a direct combustion hazardous substance treatment furnace. Although it is a highly energy-saving device, it suffers from its high specific surface area and void ratio, and on the other hand, it has the disadvantage that the hazardous substance treatment efficiency cannot be increased above about 96%. The reasons for this are the backflow of the gas remaining in the packed bed and other low-temperature parts during switching, and the thermal effects of harmful substances adsorbed on the solid surface.
Swing was considered. The present invention is capable of handling 70 to 250
A method that achieves a remarkable treatment efficiency of 99.0% or more by using treated exhaust gas at ℃ or clean gas at an equivalent temperature to push out the untreated gas and adsorbed and adhered components remaining in the low-temperature part to the high-temperature combustion zone. This is what we provide. The present invention will be explained in detail below based on the drawings. The regenerative hazardous substance treatment furnace 1 includes a plurality of packed beds 2 separated by partition walls, a combustion chamber 3 connected to each packed bed at the top of each packed bed, an auxiliary combustion burner 4 disposed therein, and a lower part of each packed bed. , a lower chamber 5 provided to uniformly pass gas through the packed bed, a treated gas inlet valve 7 provided to switch the gas to be passed through each packed bed, a high temperature treated gas outlet valve 8, and extrusion gas. It is composed of an inlet valve 9. To simplify the explanation, the operation will be explained using two packed beds as shown in Figure 1, but even if two or more processing furnaces are used, the same process can be performed by repeating this operation. obtain. FIG. 2 shows the relationship between the gas temperature and the temperature of the packed material in each of the packed beds shown in FIG. 1 operating in a steady state, and the position of the packed bed. The broken line in the figure shows the temperature distribution of the gas, and α ₁ and α ₂ are the inflow side of the gas to be treated immediately before switching in Figure 1-1, respectively;
ie side and also the high temperature treated gas discharge side, ie side. Further, the solid line indicates the temperature distribution of the filling, and p ₁ and p ₂ respectively indicate the values in , in Fig. 1-1 immediately before switching. (In Figure 1-3, the same effect can be obtained by switching left and right.) In actual operation, the temperature of the gas to be treated swings from around p ₂ to α ₁ with each switch, and the temperature of the high-temperature treated gas The temperature of will swing between values around α ₂ to p ₁ and the temperature of the filling will swing between p ₂ and p ₁ . If the state immediately before switching in a certain steady state is as shown in Figure 1-1, the switching operation will be performed at a predetermined temperature using a thermometer (not shown) attached to the lower chamber 5 of the packed bed on the high temperature treated gas side. When a predetermined temperature of 70 to 250°C is reached, a valve switching signal is issued from the control panel (not shown), and the valve is opened and closed according to the valve opening/closing status shown in Figure 1-1 (white indicates open, black indicates closed). 1st-
In the state shown in Figure 3, the gas passages are reversed and switched, and such switching is performed alternately to measure heat recovery. If the untreated gas remaining in the low-temperature portion of the packed bed 1 switches to the state shown in FIGS. 1-3, it will be pushed by the reverse flow and become untreated exhaust gas, which will limit the treatment efficiency. Therefore, in order to guide the gas to be treated remaining in each of the above-mentioned parts to the high-temperature zone for treatment, it is necessary to push the residual gas to the high-temperature zone using another clean gas such as air at the time of switching. The third experiment measured the extrusion effect when air at room temperature was used as the clean gas, and a clean gas at room temperature mixed with odorless lower hydrocarbons that did not adhere to or adsorb onto solid surfaces was used. It is a diagram. Figure 3 shows the ventilation time and extrusion effect, that is, the removal rate, using the extrusion gas flow rate ratio as a parameter.
It was found that an extrusion time of 7 seconds or more at 80% or more is more than sufficient. This corresponds to more than twice the volume of one packed bed space plus the volume of lower chamber space. However, gases to be treated that contain heteroatoms such as mercaptans, amines, other organic bases, aldehydes, organic acids, alcohols, etc., or aromatic substances with a slightly high boiling point, such as naphthalene, etc. In some cases, lower hydrocarbons
It was found that even when the same conditions were used to decompose 99.9% or more, the removal rate remained at about 96-98°C, indicating a large difference. It has been found that the reason for this is that the above-mentioned odorous substances are easily attached or adsorbed to solid surfaces, and that the adhesion or adsorption differs depending on the type of odorous substance, its concentration in the gas to be treated, and temperature. Ivy. In other words, in the operation of this regenerative hazardous substance processing furnace, there is a temperature swing as illustrated in Fig. ₂ . side) and the lower chamber walls are at a relatively low temperature, and the high-temperature treated gas immediately after switching flows back at a temperature slightly higher than that temperature, but this temperature rises to α ₂ over time. It has been found that as the temperature of the packing and the lower chamber wall increases, the odorous components attached or adsorbed thereto are expelled back into the gas, resulting in a drop in the average treatment efficiency. The present invention was completed as a result of intensive research based on the above knowledge, and the method is as shown in Figures 1-1, 1-2, and 1-3 as a gas flow switching procedure.
This can be done by switching the valves in the order shown. That is, valves 7 and 8' are opened in FIG. 1-1, valves 7', 8, 9, and 9' are closed, and the gas to be treated is supplied by the suction blower 6 to p ₂ in FIG.
It is pumped (sucked) into a packed bed with a temperature distribution of . The gas to be treated is heated while recovering heat, and is finally subjected to temperature-controlled combustion treatment to a predetermined temperature (for example, 900℃) in a combustion chamber, and then proceeds to a packed bed with a temperature distribution of p ₁ , where it is heated. Meanwhile, the gas itself is gradually cooled down to a temperature of approximately 70° C. and is then released as exhaust gas through the suction blower 6. By this operation, the filling material in the packed bed is gradually cooled by heat radiation, and the filling material in the packed bed is gradually heated by heat reception. The exhaust gas temperature also gradually rises, and when it reaches a predetermined temperature of 70 to 250°C, a valve switching command is issued. If this final temperature is too high, heat loss will increase, so it is preferable to keep the temperature as low as possible in relation to the desorption and extrusion steps described below. Although it varies depending on the concentration of the odorous substance, in the case of a normal gas to be treated, the temperature is slightly higher than the temperature of the gas to be treated, i.e. 70°C or higher, preferably
From the viewpoint of processing efficiency and thermal economy, it is better to use gas at a temperature of 130°C or higher, particularly preferably around 150°C.
There is generally little effect below 70°C. Further, the upper limit of the temperature is preferably 250° C. or lower from the viewpoint of thermal economy, equipment maintenance, and cost. Then, by switching the valve, the desorption and extrusion process shown in FIGS. 1-2 begins. In this case, the opening and closing positions of the valves are the same as in FIG. 1-1, except that valve 7 is opened and valve 9 is opened. The treated gas, which has now reached its maximum temperature, is sent through the suction blower 6 from the bottom of the cooled packed bed and circulated, so that the residual gas is sent to the combustion chamber and at the same time the cooled part is heated and adsorbed and attached. The components are desorbed and passed into the circulating gas, which is also burned in the combustion chamber and almost completely processed. This desorption and extrusion process varies somewhat depending on the shape and size of the equipment, the type and composition of harmful substances in the gas to be treated, the temperature of the circulating gas, the required processing efficiency, etc.
It is sufficient that the gas amount for 15 seconds is approximately 1.5 to 4.5 times the space volume of one packed bed + the space volume of the lower chamber, and the temperature may be slightly higher than the gas to be treated. After a predetermined time the valve is switched again and the first
- The process shown in Figure 3 begins, and this time the gas to be treated flows from one packed bed to another, and when the predetermined conditions are reached, the valve is opened so that the process of the treated gas is reversed to that shown in Figures 1 and 2. (7, 7', 8'9
(closed, 8,9' open) desorption and extrusion steps are operated for a predetermined time. Then go back to the first process,
The operation will be repeated. In the above cases,
If a suction blower is installed on the treated gas discharge side, it is convenient because exhaust gas can be discharged and circulated even in the case of three or more packed beds in one blower. In the case of three or more packed beds, the temperature of the treated gas at the time of switching is not necessarily the highest temperature, but it is always higher than the temperature of the lower chamber on the inlet side of the gas to be treated immediately before switching. It can be circulated in the same way as in the case of . Note that if a high-temperature clean gas, such as heated air, having a temperature similar to or higher than the above-mentioned treated gas temperature is separately obtained, the processing efficiency can of course be improved even if this gas is used for desorption and extrusion. The present invention provides a method for dramatically improving the treatment efficiency of a heat storage type hazardous substance treatment furnace through relatively simple operations as described above, and the present invention greatly contributes to pollution prevention. The harmful substances that can be treated by the invention include all odorous components, air polluting components, etc., so the scope of its application is wide. Next, the present invention will be specifically explained using examples. Example: Using a regenerative hazardous substance processing furnace with a processing gas amount of 100Nm ³ /H, the switching cycle is approximately 60 seconds, and the combustion chamber temperature is 1100.
℃, and treated exhaust gas maximum temperature of 140℃, 50℃ odor gas discharged from the printed wiring board manufacturing process was treated. The experiment was carried out in three ways, using ordinary air, heated air, and exhaust gas from a processing furnace as the extrusion gas, as shown in FIG. 1, and the temperature of the extrusion gas was varied. The results are shown in the table below. 【table】

[Brief explanation of the drawing]

Fig. 1 is a process diagram of an embodiment of the extrusion switching method of the present invention, and the switching states are 1-1, 1-2, 1.
- Shown separately as 3. Figure 2 shows the gas temperature in Figure 1,
A graph showing the relationship between the temperature of the packed material and the position of the packed bed, and FIG. 3 is a graph showing the relationship between the extruded gas ventilation time and the removal rate. DESCRIPTION OF SYMBOLS 1... Heat storage type hazardous substance processing furnace, 2... Filler packed bed, 3... Combustion chamber, 4... Assist burner, 5...
...Lower chamber, 6...Exhaust blower, 7...
Processed gas inlet valve, 8...High temperature processing gas outlet valve,
9... Gas inlet valve for extrusion, A... Heat auxiliary, B...
... Air for auxiliary heating, C... Gas to be treated, D... Exhaust gas.

Claims (1)

[Claims] 1. It has a plurality of stationary packed beds filled with heat storage fillers made of porcelain or metal with a high-temperature combustion zone in between, and the gas to be treated containing harmful substances and its In a heat storage type hazardous substance treatment furnace that incinerates hazardous substances while recovering heat by passing high-temperature treated gas in sequence, the gas to be treated containing untreated hazardous substances that remains in the treatment furnace when the flow path is switched. A method for improving processing efficiency, characterized in that switching is performed after extruding the untreated gas to a high temperature combustion zone using a clean gas having a higher temperature than the untreated gas. 2. The method for improving treatment efficiency according to claim 1, wherein the clean gas is exhaust gas that has been subjected to high temperature treatment. 3. The method for improving processing efficiency according to claim 1 or 2, wherein the temperature of the clean gas is 70 to 250°C.