JPS59107946A - Lime baking device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas circulation type lime calcination device for calcination of quicklime from limestone. The present invention relates to an exhaust gas circulation type lime sintering device capable of sintering quicklime.

Quicklime (Cab) is based on the reaction shown in the following formula (1),
That is, limestone (Ca CO3) is heated to about 820°C.
It is calcined by separating carbon dioxide (CO, ) from.

CaC0a-CaO+CO2-43kcal −
(1) Conventionally, an exhaust gas circulation type kiln has been used as a device for baking such quicklime. In the exhaust gas circulation type kiln, the outer periphery of the raw stone storage part through which limestone, which is the raw stone for quicklime firing, is allowed to descend and pass through is configured with a lattice, and the fuel is stored in the combustion chamber formed on the outer periphery of the lower part of the raw rock storage part. After the combustion gas obtained by burning the limestone is detoured to the opposite side of the burner installation position, it is guided into the raw stone storage section, and is passed across the inside of the raw stone storage section to contribute to the heating of the limestone passing through it. A part of the combustion exhaust gas discharged outside the raw stone storage area is sucked by the flow of auxiliary combustion air discharged from the ejector nozzle into the diffuser at a constant discharge pressure (approximately 4000 mH2O). It is circulated by being guided into the combustion chamber by the diffuser.

As the fuel, a low calorie gas can also be used since the burning of quicklime is carried out based on convective heat transfer as described above. Therefore, reflecting the recent energy situation, attempts are being made to switch from conventional heavy oil to low calorie gas such as blast furnace gas (BFG). However, burning such a low-calorie gas alone should be avoided because of the narrow flammability range, low flame temperature, and unstable ignition. Therefore, it is considered to use a gas mixed with coke gas (COG) etc. (hereinafter referred to as M gas), but when using M gas, the gas radiation will be lower than that of heavy oil, and the flame temperature will be lower. M gas cannot be used as it is as a fuel in a conventional kiln furnace designed and manufactured for heavy oil, for reasons such as lower production efficiency.

As a countermeasure to the above-mentioned problem, the applicant has found that it is effective to control the air ratio and circulating gas ratio (the ratio of the amount of combustion exhaust gas to be circulated and the amount of auxiliary combustion air) according to the unit calorific value of the fuel7. I found out that. The present invention was made based on this knowledge, and uses 200% of conventional heavy oil as fuel.
0 kcal! The present invention provides an exhaust gas circulation type lime sintering device that burns quicklime without reducing productivity while converting the gas to a low-calorie gas of /Ny+ or less.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The lime calcining apparatus according to the present invention will be described in detail below with reference to drawings showing embodiments thereof.

Reference numeral 11 denotes a raw stone storage section constituting the central portion of the lime kiln 1, which is arranged vertically and whose outer periphery is constituted by a prismatic lattice 11a. At its upper end there is a hopper 12 shaped like a forest.
However, chutes 13 each having a discharge port opening onto the conveyor 2 are connected to their lower ends. The raw stone storage section 1
Except for the through parts 14a and 14b formed in the upper and lower center to connect the single hopper 12 and the chute 13,
The surrounding area is covered with a furnace shell 14 made of a heat-resistant material. The inner diameter of the furnace outer shell 14 is designed to be larger than the outer diameter of the raw ore storage portion 11 by a predetermined dimension, and a gas flow space 15 is formed between the two.

The lower part of the gas flow space 15 corresponds to the combustion chamber 15a,
A burner 3 capable of burning gas fuel at a low air ratio is attached to the combustion chamber 15a. In other words, a flow control valve 31a and an orifice flow meter 31 are installed at the lower part of the furnace shell 14.
b in the middle of the pipe, and gas fuel (calorific value 1870 kca
A fuel supply pipe 31 and a flow rate control valve 32a for supplying M gas (1/Nrd) are arranged in the middle of the pipe, and the burner 3 to which the air supply pipe 32 for supplying main auxiliary combustion air is connected has its outlet in the furnace. It is mounted towards. Then, the fuel supplied through the fuel supply pipe 31 and the main auxiliary combustion air supplied through the air supply pipe 32 & are mixed in the burner 3, and the auxiliary combustion air, which will be described later, is also added to the mixture in the combustion chamber 15a. Burn it to generate combustion gas.

In addition, in the part of the rough stone storage section 11 where the flame of the combustion gas directly shines, a closed nine-periphery wall 11b is attached instead of the grid 11a, so that the flame of the burning gas does not directly shine into the rough stone storage section 11. It is not allowed to enter.

Further, a cylindrical diffuser 5 is arranged above the burner 3 mounting position in the gas flow space 15, and a pressure gauge 4b is arranged in the upper opening of the diffuser 5 in the middle of the pipe.
Ejector 4 connected to air supply pipe 41 that supplies air
A nozzle 4a is inserted therein, and its lower opening is located just above the burner 3. A part of the combustion exhaust gas is sucked by the flow of auxiliary auxiliary combustion air (indicated by a broken line arrow in the figure) discharged from the nozzle 4a of the ejector 4, and is guided into the combustion chamber 15a by the diffuser 5. Is it like a cycle? I'm here.

The hopper 12 and the chute 13 are also provided with exhaust gas discharge ports 6 and 7 for guiding combustion exhaust gas out of the furnace. The exhaust gas exhaust ports 6 and 7 are connected to an exhaust gas exhaust pipe 61 having an orifice flow meter 61a disposed in the middle of the pipe, and an exhaust gas exhaust pipe 71 led into the heat exchanger 8, respectively. The exhaust gas exhaust pipe 71 is connected to the exhaust gas exhaust pipe 61 via a piping system within the heat exchanger 8 for preheating the air sucked in by the proar 81 to produce the auxiliary combustion air. Also, an air supply pipe 82#-1 for supplying the air preheated by the heat exchanger 8:,, there is a temperature limit 82#-1 in the middle of the pipe.
A 2a1 flow rate control valve 82b and an orifice flowmeter 82C are arranged, the ends of which are connected to the air supply pipes 32 and 41 for supplying auxiliary combustion air.

Note that the above-mentioned orifice flowmeters 31b and 61a.

In addition to the thermometer 82a1, etc., there are also sensors for obtaining control data such as the raw ore storage part 11 and the furnace outer shell 14.
A combustion chamber 15a is located at an appropriate position in the gas flow space 15 between the
A thermometer 15b and a gas analyzer 15c are installed to measure the temperature of the 02 gas (or CO gas) and the concentration of the 02 gas (or CO gas), and a thermometer 4c is installed near the nozzle 4a of the ejector 4 to measure the temperature of the circulating combustion exhaust gas. However, thermometers 12a are further arranged at appropriate positions within the hopper 12 to measure the temperature of the combustion exhaust gas discharged. All measurement data from these sensors is input to the arithmetic and control unit 9. Furthermore, data such as circulating gas ratio r1 air ratio m1 theoretical air flow rate per unit amount of fuel Ao1 theoretical gas flow rate G and calorific value H/ etc. are also sent to the arithmetic and control unit 9. On the other hand, the control signals calculated therein are outputted to the flow control valves 31a, 32a, and 82b.

Next, the reason why it is possible to convert heavy oil to gas fuel by using the apparatus of the present invention having such a configuration will be explained. Converting fuel without changing productivity means keeping the fuel consumption rate constant before and after the conversion, which means keeping the temperature and flow rate of combustion gas constant.

Now, assuming that the temperature and specific heat at each position in the furnace of the lime calcining apparatus are constant, the following equation (2) holds true due to the heat balance.

Qtn +QA + QR= Qcao + QR+
QW , -(2) However, Q!ゎ: Sensible QA of the supplied fuel: Sensible QR of the auxiliary combustion air: Sensible heat of the circulated combustion exhaust gas Qcao: Heat of lime formation Qw: @Heat or exhaust gas balance of the combustion gas discharged from the exhaust gas exhaust pipe 7 The following equation (3) holds true from above.

However, m: Air ratio Ao: Theoretical air flow rate Go: Theoretical exhaust gas flow rate Hl: Calorific value GR: Flow rate of the circulated combustion exhaust gas Gco, : Flow rate of carbon dioxide gas Gw: Combustion discharged from the exhaust gas exhaust pipes 6 and 7 Gas flow rate Furthermore, when converting fuel from heavy oil to M gas, in order to keep the fuel consumption constant, it is necessary to satisfy the following equation (4) derived from equations (2) and (3) above. .

However, in the case of double oil firing, in the case of dash (2M) gas firing, the air ratio should be changed according to the unit calorific value of the fuel. However, when changing the air ratio, It is necessary to change the flow rate of the auxiliary combustion air.When changing the flow rate of the auxiliary combustion air, it is necessary to change the circulating gas ratio r shown in equation (5).

0゛...(5) 3 However, it is also necessary to control the GR"flow rate A3 of the combustion exhaust gas to be circulated: the flow rate of the auxiliary auxiliary combustion air, that is, the circulating gas ratio".

This circulating gas ratio is controlled by adjusting the valve opening of the flow control valve 32a while measuring with the pressure gauge 4b, and adjusting the amount of main auxiliary combustion air supplied directly to the burner 3 through the air supply pipe 32. By doing so, the amount of supplementary combustion air supplied by the air supply pipe 41 is indirectly adjusted, and the nozzle 4 of the ejector 4 is
This is done by controlling the air discharge pressure from a. Note that control can also be performed by changing the diameter of the nozzle 4a of the ejector 4. Further, the air supply pipe 41 may be provided with a flow rate control valve.

Next, the control contents of the arithmetic and control unit 9 will be explained.

First, the required fuel supply amount is calculated based on the furnace temperature and exhaust gas temperature measurement data by the thermometers 4c, 12a, and 15b, and in order to realize this, the orifice flowmeter 31 is
Using the measurement data obtained by b as a feedback signal, the opening degree of the actual flow rate control valve 31a is adjusted to control the amount of fuel supplied so that the temperature inside the furnace reaches a predetermined temperature.Next, the amount of auxiliary combustion air corresponding to the amount of fuel supplied is Calculate. This is determined by adding an amount determined by the amount of 02 gas in the combustion gas measured by the gas analyzer 15c to the product of the fuel supply amount, the theoretical air flow rate AO per unit, and the air ratio m.

The amount of auxiliary combustion air is controlled by the flow control valve 8 using the orifice flow meter 82c as a feedback signal based on the calculation result.
This is done by adjusting the opening of 2b.

The fuel supplied to the burner 3 and the auxiliary combustion air preheated by the heat exchanger 8 are mixed in the burner 3 and combusted in the combustion chamber 15a, but the resulting combustion gas is As shown by the arrow in the middle, after detouring to the gas flow space 15 on the opposite side of the burner 3 mounting position, it is guided into the raw ore storage section 11 via the grid 11a. The combustion gas traverses the raw stone storage section 11 and contributes to the heating of the limestone passing therethrough while descending therein, and then a part of it is guided to the gas flow space 15 on the side where the burner 3 is attached and is combusted. It becomes exhaust gas.

This combustion exhaust gas is sucked into the flow of auxiliary auxiliary combustion air generated by discharging the auxiliary combustion air that entered the air supply pipe 41 from the air supply pipe 82 into the diffuser 5 from the nozzle 4a of the ejector 4, and is further sucked into the flow of auxiliary auxiliary combustion air that flows into the air outlet of the burner 3. It is guided and circulated.

The circulating gas ratio is determined by the amount of auxiliary auxiliary combustion air between the The opening degree of the flow rate control valve 32a of the air supply pipe 32 through which the main auxiliary combustion air flows is adjusted so that it flows through the main combustion air.

By circulating the exhaust gas in this way, it is possible to maintain a constant gas concentration in the furnace and to maximize thermal efficiency, making it possible to use low-calorie gas as fuel without reducing productivity. It becomes possible to bake.

Note that data regarding the concentrations of O, gas, and gas in the combustion gas were measured using a gas analyzer 15c near the combustion chamber 15a, but data measured near the nozzle 4a of the ejector 4 was used. There is no problem. In addition, gases other than the combustion exhaust gas that are circulated as shown in the exhaust gas outlet 6
After being directly discharged to the outside of the furnace via the exhaust gas exhaust pipe 61, and after being fed into the heat exchanger 8 to preheat the combustion air via the exhaust gas exhaust pipe 71 from the exhaust gas exhaust lower 1-1, As usual, it is disposed of by being discharged outside the furnace.

As detailed above, the lime sintering apparatus according to the present invention includes means for changing the amount of main auxiliary combustion air and the amount of auxiliary auxiliary combustion air, a burner that can combust combustion gas at a low air ratio, and a control device thereof. Therefore, the air ratio and circulating gas ratio can be controlled according to the unit calorific value of the fuel, and quicklime can be fired without reducing productivity even though low calorie gas is used as the fuel.

[Brief explanation of drawings]

The drawings are schematic diagrams showing embodiments of the present invention. 1... Lime firing furnace 11... Raw stone storage section 11a.
...Grate 14...Furnace shell 15a...Combustion chamber 2
...Conveyor 3...Burner 4...Ejector 4
a... Nozzle 5... Diffuser 8... Heat exchanger 9... Arithmetic control unit 10... Setting device patent Applicant: 1 agent other than Sumitomo Metal Industries, Ltd. Patent attorney Noboru Kono dog

Claims (1)

[Claims] 1. An exhaust gas circulation type that supplies combustion gas to the raw ore storage area in the furnace and heats it, and circulates a part of the heated combustion exhaust gas to the combustion chamber along with the auxiliary combustion air that is blown into the furnace from the ejector. It is equipped with a lime kiln, an air supply amount control valve to the ejector, and a main auxiliary combustion air amount control valve to be supplied to the burner section of the lime kiln. The present invention is characterized by comprising a device that controls the openings of both of the control valves so as to achieve an air ratio defined according to a unit calorific value and a ratio between an amount of circulated combustion exhaust gas and an amount of auxiliary combustion air. Lime calcining equipment.