JPS5880416A - Multistage incinerator - Google Patents

Abstract

PURPOSE:To make it possible to properly increase or decrease the waste gas circulation quantity and maintain the quantity of fuel at the minimum by detecting the qunatity of waste gas circulated to the combustion zone or cooling zone of the titled incinerator which burns sewage sludges, and the quntity of fuel corresponding thereto. CONSTITUTION:A part of waste gas discharged through a waste gas port 3 of the furnace top passes through a waste gas circulator 26 by a waste gas circulation quantity controlling device 29, and is circulated to a combustion zone, a cooling zone within the furnace or a hot air furnace 11. There exists a relationship shown in Fig. 2 between the waste gas circulating quantity Am<3>/h and the fuel quantity Bl/h. For this reason, beginning from the fuel qunatity B1 with respect to the waste gas circulating quantity A1, the waste gas circulating quantity is increased by a predetermined quantity (a) every predetermined time, and is successively compared with the integrated value of the fuel quantity every predetermined time. When the integrated value of the fuel quantity reaches a value B4 increased from the integrated value at the previous time, the operation is repeated at a waste gas circulating quantity between A3 and A4. In this manner, the fuel can be burnt in a range close to the minimum fuel quantity BM.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multistage incinerator, and particularly to a multistage incinerator in which the amount of exhaust gas circulation is controlled to maintain the amount of fuel at a minimum.

Conventional multi-stage incinerators that incinerate waste such as sewage sludge have a theoretical combustion air volume of . In many cases, incineration was carried out in a closed atmosphere under oxidation by introducing two to three times as much excess air, but this required a large amount of fuel for incineration, and it was easy to generate harmful substances such as NOx. Since the amount of exhaust gas is large, there are problems such as requiring large exhaust gas treatment equipment and shortening the service life due to the rapid increase in combustion concentration.

For this reason, in recent years, the low air ratio combustion method, in which incineration is performed while supplying air not exceeding twice the theoretical amount of combustion air, and the combustion exhaust gas recirculation to the combustion zone, which reduces the amount of heat in the exhaust gas and the residual oxygen in the exhaust gas, have been developed. Exhaust gas circulation has been adopted, which reduces both the amount of fuel and exhaust gas zl by making effective use of it, and controls the temperature of the combustion zone. For example, Tokkosho, t4Z-/ /j. The conventional exhaust gas circulation method described in No. 29 for controlling the amount of exhaust gas circulated in a multistage incinerator will be explained with reference to Figure 3. The detection signal is transmitted to the fuel control valve<ii4 and the primary air control valve (//7) via the setting device (ll4IO) to control the amount of fuel and air supplied to the hot blast furnace (//c). The detection signal from the needle (//3) is transmitted to the wandering gas amount control valve (lcotI) via the controller (/.υ) to control the amount of exhaust gas that is circulated into the combustion zone or cooling zone. At this time, when the combustion zone o1 leanness is low, the exhaust gas circulation amount is reduced, and when the combustion zone temperature is high, the exhaust gas circulation amount is increased to absorb excess heat and control the combustion zone temperature to be constant. However, the conventional method using only the combustion zone Ill as an indicator has problems such as the fact that the properties of waste such as sewage sludge are not constant, the transfer time from the drying zone to the combustion zone, and the drying rate in the drying zone vary considerably. Some of the exhaust gas circulation type multi-stage incinerators have the drawback that it is not possible to maintain combustion zone II within an appropriate temperature range and at the same time to maintain the minimum amount of fuel to save energy.

The present invention eliminates the above-mentioned drawbacks and reduces fuel consumption, which accounts for a large amount of running costs, by providing a multi-stage incineration system in which the amount of exhaust gas circulation can be controlled to minimize the amount of fuel supplied to the combustion zone. It was completed for the purpose of a furnace, and the illustrated embodiment will be described in detail below.

In Fig. 1, (1) is a one-stage type multistage incinerator body, and the multistage incinerator body (1) has, from above, a drying zone of three stages, a combustion zone of three stages, and a cooling zone of one stage. , multi-stage incinerator body (
The top of 1), ie, the upper part of the drying zone, is provided with a supply inlet (2) and an exhaust gas inlet (3), while the bottom, ie, the lower part of the cooling zone, is provided with an ash outlet (4). A hollow rotating shaft (6) that is rotated by the drive sweater (5) is provided in the center of the multistage incinerator body (1).
Each hearth (7
) The arm (8) is fixed so as to move once on the rotation shaft (6), and the shaft cooling air that cools the rotating shaft (6) is supplied to the shaft cooling fan (9).
The shaft-cooled air is fed into the rotary shaft (6), and the shaft-cooled air is sent as preheated combustion air directly to the lower part of the multistage incinerator main body (1) through the conduit (to) or into the hot blast furnace. aυ
Then, as a combustion control device, a hot coal meter (to) that detects the concentration in the combustion zone in the furnace is installed at the bottom of the drying zone or in the combustion zone, and its H
t total 03 + 2) The detection signal is sent to the hot air stove Q via the setting device α◆
The burner QS attached to burner 1 is connected to a fuel amount control valve αQ that controls the amount of fuel supplied. In this case, the air for fuel combustion supplied to burner (G) is ignited in proportion to the amount of fuel. The amount of secondary combustion air introduced into the hot air stove αυ via the secondary air amount control valve (to) and shaft cooling air amount control valve QQ is controlled by the intermediate air amount control valve aη. The amount of shaft cooling air is increased or decreased depending on the temperature detected by the hot-blast furnace thermometer installed in the hot-blast stove aυ, and
WA charcoal of hot air is sent inside! The amount of hot air at a nearly constant temperature introduced into the main body (1) of the multi-stage incinerator from the hot blast furnace αυ is increased or decreased depending on the internal temperature of the incinerator. The wet coal in the furnace is controlled to a predetermined setting II coal. In addition, as an exhaust gas circulation amount control device that controls the amount of circulating exhaust gas, that is, the amount of exhaust gas circulated, there is a fuel amount flow meter (c) that measures the amount of fuel supplied to the burner (to) attached to the hot air stove Ql). The detection signal of the fuel flow meter (to) is transmitted to the arithmetic controller (1), and the exhaust gas circulation amount control device increases or decreases the amount of exhaust gas circulation by a predetermined amount at predetermined intervals, thereby controlling the amount of fuel. is kept to a minimum. On the other hand, there is an exhaust gas circulation path (2) that circulates the exhaust gas discharged from the exhaust gas port (3) installed at the top of the furnace into the combustion zone or cooling zone. A circulation fan, an exhaust gas circulation amount control valve (F), and an exhaust gas circulation positional flow rate needle (C) are installed. The detection signal from the exhaust gas circulation flow meter (E) is transmitted to the arithmetic controller ■, which compares and calculates this □ detection signal with the detection signal from the fuel flow meter (E). ), a control signal is transmitted to the exhaust gas circulation amount control valve (■). Note that in the embodiment shown in Fig. 1, the circulating exhaust gas is directly fed *m into the combustion zone or the cooling zone, but it is also fed through the hot air stove αυ while being controlled by hot air 1 [in the setting device]. Alternatively, the circulating exhaust gas may be directly circulated into the combustion zone or the cooling zone and also circulated into the hot blast furnace αυ. The hot air may be circulated into the furnace and distributed to several locations in the combustion zone or cooling zone by an exhaust gas distribution valve.

In order to incinerate waste in the multi-stage incinerator configured as described above, the combustion control device (2) must control the temperature of the combustion zone of the multi-stage incinerator main body (1) to a level at which the sewage sludge burns. If waste is fed from the top of the furnace into the furnace while the temperature required for this is maintained at, for example, 600°C or higher, the waste will be dried by contact with the upward flow of Ganu in the drying zone. Combustion begins in the combustion zone. And the warm meter (
) and the set temperature (for example, 7).
00℃) is compared in the setting device α4, and if the detected coal production is less than the setting it, the fuel amount control valve 0 and the combustion position control valve aη are opened to allow fuel and primary air to flow into the burner Qf9. The air is sent to the hot air stove aυ through the air. moreover,
The hot air temperature meter installed in the hot air stove detects the hot air temperature, and the hot air temperature setting device sets the temperature to be maintained at the set hot air temperature (for example, 900"C). The secondary air amount control valve (to) and the axially cooled air amount control valve OI are controlled, and the secondary air and axially cooled air are sent to the hot blast furnace aυ.In this way, the combustion control device and the flue gas port at the top of the furnace (
A part of the exhaust gas discharged from It is controlled by the exhaust gas circulation amount control device @ to control the fuel amount to the minimum by increasing or decreasing it by a predetermined amount. Next, this exhaust gas circulation amount control method will be explained in detail. There is a relationship between the exhaust gas circulation amount A If'/h and the fuel amount BJ/h as shown in Figure 2. After the combustion zone charcoal reaches the set temperature, the exhaust gas circulation starts; Starting from a fuel amount B1'/h corresponding to the amount A1/h, the exhaust gas circulation amount is increased to a predetermined amount a/h at predetermined time intervals,
The integrated values of the fuel amount for each predetermined time period (for example, one hour) are sequentially compared.

Then, when the current integrated value is smaller than the previous integrated value, the exhaust gas circulation amount is further increased to a predetermined amount,
The exhaust gas circulation amount is increased by repeating the same operation as A2'/h and A3'/h. Increase the exhaust gas circulation amount from M3/h to A4/h.
If the integrated value of the fuel amount increases from B3゛j/h to B4 Zh, then the exhaust gas circulation amount is changed to A4 Zh.
Yoru Aa'/hK decreases. And in Figure 2,
The exhaust gas circulation amount starting from the initial value A1/h is the predetermined amount a
The optimum exhaust gas circulation amount is increased by Zh, II'/h.
Driving between Mu 311 I/h and Mu 4'/h that sandwich *
B is returned, and the fuel amount is maintained between B3 and B4J/h, which sandwich the minimum value BMJ/h, and burning continues.

It should be noted that if the predetermined amount a - h for concentrating the exhaust gas circulation amount is too large, the fluctuation in the fuel amount will be large, and if it is too small, the time required to reach the minimum value will be longer, which is a problem.
This is determined empirically depending on the amount and properties of the waste, but in order to quickly obtain the optimum exhaust gas circulation amount, the specified amount a Z
It is preferable that h is not fixed but is allowed to form into buds in stages. In other words, the predetermined amount a2 is
When the value of h is increased, after reaching the predetermined amount a, the value of Zh is decreased. Therefore, as explained in FIG.
2/), t7 and shi, when similar operations are performed, the exhaust gas circulation amount changes between A3 Zh and A4'/h, and a''/h also changes within a small range, that is, /2 Zh, When operation at this width is repeated several times, if a smaller predetermined amount, such as 1/4''/h, is performed, the exhaust gas circulation amount is '/2'/hJ: ! 0 also varies within an even smaller width, ie /4 Zh. By repeating the above operations, the exhaust gas circulation amount will gradually approach the optimal exhaust gas amount that minimizes the fuel amount, and it is possible to obtain an exhaust gas circulation amount that more precisely maintains the fuel amount at the minimum. . In addition, in the above embodiment, when the exhaust gas circulation amount is changed, the fuel amount integrated value is not instantly changed to the fuel amount corresponding to the exhaust gas circulation amount, resulting in a response delay of a predetermined time. Burnt vinegar is also unstable, so instead of integrating the entire time from immediately after switching the exhaust gas circulation rate until the next switch, we calculate only the stable state that excludes the unstable state of combustion immediately after the switch. In terms of accuracy, it is preferable to integrate the fuel amount corresponding to the time and compare it with the exhaust gas circulation amount. Note that it is of course possible to use the fuel amount at a certain point in time when the combustion is stable as a substitute for the fuel amount integrated value.

As is clear from the description of the above embodiments, the present invention has the following features:
Detects the amount of exhaust gas circulated to the combustion zone or cooling zone and the corresponding amount of fuel.

This type of conventional multistage incinerator is capable of maintaining the fuel l at a minimum by increasing or decreasing the amount of exhaust gas circulation by a predetermined amount at predetermined intervals in the direction in which the fuel amount decreases. It is extremely important that it contributes to the development of industry even if the disadvantages of

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an embodiment of the present invention, FIG. 1 is a graph showing the exhaust gas circulation amount, fuel amount, and Q relationship in the present invention, and No. 31i2I is a flow sheet of a conventional multistage incinerator. eII3: Exhaust gas circulation path, @: Exhaust gas circulation amount control device Fig. 1 Fig. 2

Claims (1)

[Claims] In a multistage incinerator equipped with a combustion zone temperature control device that detects the concentration inside the furnace and increases or decreases the amount of fuel and air supplied to the combustion zone according to the concentration, the combustion exhaust gas discharged from the top of the furnace is It is characterized by providing an exhaust gas circulation path for feeding the combustion zone or the cooling zone K11ll, and an exhaust gas circulation amount control device that maintains the fuel amount at a minimum by increasing or decreasing the amount of exhaust gas circulation by a predetermined amount at predetermined time intervals. A multi-stage incinerator.