CN116217099A - A double-chamber kiln using low calorific value fuel and its calcination method - Google Patents

Abstract

The invention relates to a double-chamber kiln using low calorific value fuel and a calcination method. The double-chamber kiln comprises a first kiln chamber, a second kiln chamber, a fuel pipeline and a gas waste gas heat exchanger. Waste gas suction beams are respectively arranged between the calcining section and the preheating section of the first kiln chamber and the second kiln chamber. The fuel pipeline and exhaust gas suction beam are respectively connected to the gas waste gas heat exchanger, and the low calorific value gas heated up by the gas waste gas heat exchanger is connected to the plug-in burners installed in the calcination zone of the first kiln chamber and the second kiln chamber. The invention improves the effect of calcining lime with low calorific value gas by setting waste gas suction beams in the kiln chamber, and uses the extracted high temperature waste gas to exchange heat with low calorific value gas, makes full use of low calorific value fuel, and improves the efficiency of calcined products. quality.

Description

A double-chamber kiln using low calorific value fuel and its calcination method

technical field

The invention belongs to the technical field of chemical building material production, relates to an industrial furnace, in particular to a double-chamber kiln using low calorific value fuel and a calcination method.

Background technique

Double-chamber kiln is also called double-chamber parallel-flow regenerative lime kiln. The fuel enters from the upper end of the calcination belt and flows in parallel with the raw materials. Since the fuel is injected from the upper part of the calcination zone, the raw material can absorb most of the heat released by the fuel here. Another important feature of double-chamber kiln is heat storage, which uses heat storage to preheat part of the combustion air. The thermal characteristics of co-current calcination and counter-current heat storage determine that the double-chamber kiln has high thermal efficiency, and its thermal energy consumption is the lowest among all types of lime kilns including rotary kiln and sleeve kiln.

In the production process of metallurgical enterprises, a large amount of blast furnace gas is produced, which is a valuable fuel resource. The calorific value of blast furnace gas is 3000-3400kJ/Nm ³ . Due to the low calorific value of fuel, it cannot be directly used for calcining limestone, making a large amount of low calorific value fuel Can't be fully utilized. However, the production of lime requires the purchase of fuels with high calorific value, resulting in waste of resources and affecting economic benefits.

Contents of the invention

The purpose of the present invention is to provide a double-chamber kiln and calcination method using low calorific value fuels, so that low calorific value fuels such as blast furnace gas can be used for calcining lime, making full use of low calorific value fuel resources and improving economic benefits.

According to the first aspect, the embodiment of the present application proposes a double-chamber kiln using low calorific value fuel, including a double-chamber kiln body, feeding equipment, discharging equipment, air supply system, fuel pipeline and exhaust gas discharge system; The double-chamber kiln body includes a first kiln chamber and a second kiln chamber. The first kiln chamber and the second kiln chamber are respectively equipped with a preheating zone, a calcination zone and a cooling zone; the calcination zone is provided with a plug-in burner It is characterized in that: waste gas suction beams are respectively arranged between the calcination section and the preheating section of the first kiln chamber and the second kiln chamber; the outlet of the waste gas suction beam is connected to the shell side of the gas waste gas heat exchanger, The shell side outlet of the gas waste gas heat exchanger is connected to the exhaust gas discharge system; the fuel pipeline is connected to the tube side of the gas waste gas heat exchanger, and the tube side outlet of the gas waste gas heat exchanger is connected to the plug-in burner .

Specifically, the double-chamber kiln is a double-chamber kiln with a hanging cylinder structure or a corbel structure.

Specifically, the exhaust gas suction beam has a square partition wall structure, the interior is an exhaust gas channel, and the partition wall is a cooling air channel; the outlet of the exhaust gas suction beam cooling air channel is connected to the combustion air main pipe.

Specifically, the suction port of the waste gas suction beam is arranged at the lower part of the waste gas suction beam; the number of suction holes of each waste gas suction beam is 10 to 12.

According to the second aspect, an embodiment of the present application provides a method for calcination of a double-chamber kiln using low calorific value fuel. When the first kiln chamber is calcining, the cut-off valve of the waste gas suction beam in the first kiln chamber is in a closed state , the cut-off valve of the low calorific value gas is in the open state; the cut-off valve of the waste gas suction beam in the second kiln chamber is in the open state, and the cut-off valve of the low calorific value gas is in the closed state; The device performs heat exchange on the low calorific value gas entering the first kiln chamber, and the high temperature and low calorific value gas after heat exchange enters the plug-in burner of the first kiln chamber for calcination. After the double-chamber kiln reverses the calcination, when the second kiln chamber is calcining, the cut-off valve of the waste gas suction beam in the second kiln chamber is closed, and the cut-off valve of the low calorific value gas is in an open state; the waste gas in the first kiln chamber The cut-off valve of the suction beam is in the open state, and the cut-off valve of the low calorific value gas is in the closed state; the high-temperature waste gas diverted from the first kiln chamber is used to exchange heat for the low calorific value gas entering the second kiln chamber through the gas waste gas heat exchanger; The final high-temperature and low-calorific-value gas enters the plug-in burner of the second kiln chamber for calcination.

Specifically, during the intermediate reversing process, the cut-off valves of each exhaust gas suction beam pipe and gas pipe are closed.

Specifically, during the reversing and calcination stages of the double-chamber kiln, cooling air is continuously delivered to each waste gas suction beam, thereby ensuring the service life of the waste gas suction beam.

The double-chamber kiln using low-calorific-value fuel provided by the present invention sucks a large amount of high-temperature waste gas formed after the low-calorific-value fuel is burned. The sensible heat of the high-temperature exhaust gas preheats the fuel to increase the combustion temperature of the low calorific value fuel, so that the low calorific value fuel such as blast furnace gas can be used for calcining lime, making full use of low calorific value fuel resources and improving economic benefits. In addition, the hot air discharged from the cooling exhaust air suction beam can be used to support combustion, which can not only increase the combustion temperature, save fuel, but also reduce greenhouse gas emissions, which is beneficial to environmental protection. The invention has a simple structure and is easy to implement, and can be used for the transformation of a traditional lime double-chamber kiln.

Description of drawings

Fig. 1 is the structural representation of the double-chamber kiln that uses low calorific value fuel provided by the present invention;

Among them: 1—first kiln chamber, 2—second kiln chamber, 3—plug-in burner, 4—fuel pipeline, 5—exhaust gas suction beam, 6—gas exhaust gas heat exchanger, 7—exhaust gas induced draft fan, 8—Chimney.

Implementation

The present invention will be described in detail below in conjunction with the embodiments and the accompanying drawings. The protection scope of the present invention is not limited to the embodiments, and any changes made by those skilled in the art within the scope defined in the claims also belong to the protection scope of the present invention.

Limestone calcination requires fuel to be burned in the calcination zone, releasing heat to heat the material to be calcined. The decomposition temperature of limestone is about 900°C. The higher the combustion temperature of the fuel and the greater the temperature difference from the decomposition temperature of limestone, the stronger the calcination ability. The calcination temperature of high calorific value fuel is generally 1050-1200 ℃, and the calcination temperature of low calorific value gas is less than 1000 ℃. Double-chamber kilns of the same size use fuels with different calorific values, and the output of lime is not the same, and the difference is very large. If the combustion of low calorific value fuel cannot reach the required temperature, the limestone cannot be decomposed; or if the temperature is low, the decomposition of limestone will not be complete, resulting in problems such as raw burning and poor quality of lime products. The combustion temperatures of fuels with different calorific values are shown in Table 1.

Table 1 Combustion temperature of fuels with different calorific values

fuel Calorific value (kcal/m ³ ) Theoretical combustion temperature (°C) Calcination temperature (°C) Output (t) natural gas 8400 1950 1200 600 pulverized coal 6000 1800 1190 600 converter gas 1200 1610 1050 400 blast furnace gas 840 1390 950 --

The double-chamber kiln is equipped with two kiln chambers, and each kiln chamber is equipped with a preheating zone, a calcination zone and a cooling zone. The preheating zone, calcining zone and cooling zone are arranged in sequence from top to bottom. The combustion-supporting air in one kiln chamber is heated by the preheating belt and mixed with the fuel for combustion in the calcination zone. The airflow and limestone flow downwards to heat and calcine. Entering another kiln chamber and moving upward together with the air after cooling the lime in this kiln chamber, preheating the counterflowing limestone while reducing the discharge temperature of the exhaust gas. The exhaust gas stores heat in the limestone in the preheating section of one kiln, and the combustion-supporting air takes away the heat through the preheating zone of the other kiln. Such repeated switching ensures that the exhaust gas can be reduced to below 150°C. By comparing the exhaust gas volume and exhaust gas temperature after burning fuels with different calorific values, it is known that the exhaust gas temperature of high calorific value fuel is about 110-120 °C, and the exhaust gas temperature of low calorific value gas is about 180-200 °C, the lower the calorific value The higher the exhaust gas temperature. At the same time, it can be found that the ratio of the amount of combustion-supporting air to the amount of exhaust gas of high-calorific-value gas is about 45-50%, the ratio of the amount of combustion-supporting air of low-calorific-value gas to the amount of exhaust gas is less than 30%, and the lower the calorific value of gas, the amount of combustion-supporting air is the same as that of exhaust gas. The lower the volume ratio.

There are two main reasons for the high exhaust gas temperature of double-chamber kilns burning low calorific value gas. The first is that the amount of combustion-supporting air is insufficient, and the temperature of the pre-tropical limestone cannot be sufficiently cooled. After the reversing, the limestone cannot fully absorb the heat of the exhaust gas and reduce the temperature of the exhaust gas. The second is that the calcination temperature of the low calorific value gas is low, and the heat cannot be quickly absorbed by the limestone decomposition reaction, resulting in a high temperature of the exhaust gas when it enters another kiln chamber. Table 2 lists the exhaust gas parameters of different calorific value fuels.

Table 2 Exhaust gas parameters of fuels with different calorific values

fuel Calorific value (kcal/m ³ ) Production (t/d) Combustion air volume (m ³ /h) Exhaust gas volume (m ³ /h) Exhaust gas temperature (°C) Air exhaust gas ratio/% natural gas 8400 600 29370 65900 <110 44.56 pulverized coal 6000 600 31830 68300 <120 46.6 converter gas 1200 400 14360 49300 180 29.1 blast furnace gas 840 400 14460 54960 greater than 200 26.3

The exhaust gas generated during the calcining of limestone in the double-chamber kiln lowers the temperature through the heat storage of the limestone in the preheating section, and then takes away the heat through the combustion air. In the double-chamber kiln with low calorific value fuel, the gas volume and temperature of the exhaust gas are much larger than those of the high calorific value fuel. In this way, the combustion-supporting air cannot sufficiently cool the limestone, resulting in the failure of the downstream equipment to operate normally. If a part of the waste gas is diverted out in the calcination section and the preheating section, and the ratio of the remaining waste gas to the combustion air is adjusted, the outlet temperature of the waste gas can be reduced.

The invention provides a double-chamber kiln using fuel with low calorific value. The double-chamber kiln has a hanging cylinder structure or a corbel structure. As shown in Figure 1, the double-chamber kiln includes a double-chamber kiln body, feeding equipment, discharging equipment, air supply system, fuel pipeline 4 and exhaust gas discharge system. Specifically, the double-chambered kiln body includes a first kiln chamber 1 and a second kiln chamber 2 . The first kiln chamber 1 and the second kiln chamber 2 are respectively provided with a preheating zone, a calcination zone and a cooling zone, and a plug-in burner 3 is provided in the calcination zone of each kiln chamber. Waste gas suction beams 5 are arranged between the calcining section and the preheating section of the first kiln chamber 1 and the second kiln chamber 2 respectively. Specifically, two waste gas suction beams can be arranged in the first kiln chamber, and two waste gas suction beams can be arranged in the second kiln chamber.

The outlet of the exhaust gas suction beam 5 is connected to the shell side of the gas exhaust gas heat exchanger 6 , and the shell side outlet of the gas exhaust gas heat exchanger 6 is connected to the exhaust gas discharge system composed of the exhaust gas induced fan 7 and the chimney 8 . The fuel pipeline 4 is connected to the tube side of the gas exhaust gas heat exchanger 6 , and the tube side outlet of the gas exhaust gas heat exchanger 6 is connected to the plug-in burner 3 .

Specifically, the exhaust gas suction beam 5 can be a square partition wall structure, the interior is an exhaust gas channel, and the partition wall is a cooling air channel. The outlet of the cooling air channel in the waste gas suction beam 5 is connected with the combustion air main pipe, and the temperature of the air after the partition cooling of the waste gas suction beam is raised, which can be used as the combustion air for calcining lime.

In order to prevent limestone from blocking the suction port, the suction port of the waste gas suction beam 5 can be arranged at the bottom of the waste gas suction beam. The number of suction holes in a suction beam is generally 10-12, and the size of the suction holes is determined according to the output and exhaust gas volume. In addition, the number of exhaust gas suction beams set in each kiln chamber can be determined according to the output and the amount of exhaust gas.

According to the data analysis of the 400t/d blast furnace gas-fired (calorific value 840 kcal/m3) double-chamber kiln, the combustion air volume is 14460 m ³ /h, and the main waste gas flow rate is 32000 m ³ /h according to the air waste gas ratio of 45%. The amount of exhaust gas diverted through the exhaust gas suction beam is 22960 m ³ /h. Drainage exhaust pipes need insulation protection.

An effective way to solve the problem that the double-chamber kiln cannot burn low calorific value is to increase the combustion temperature. By increasing the temperature of the low calorific value gas, the combustion temperature can be effectively increased. The gas waste gas heat exchanger 6 can effectively reduce the temperature of the waste gas and increase the temperature of the gas.

The temperature of the waste gas between the calcination section and the preheating section of the double-chamber kiln can reach 500 to 600°C, and the exhaust gas that flows out can be used to preheat low calorific value gas. According to the data analysis of 400 tons of blast furnace gas-fired double-chamber kiln (calorific value 840 kcal/m ³ ), the diversion exhaust gas volume is 22960 m ³ /h, the temperature is 600 ℃, and the blast furnace gas flow rate is 18850 m ³ /h. Heat exchange is carried out through the gas waste gas heat exchanger 6, which adopts a tube-sheet structure, the tube side passes gas, and the shell side passes high-temperature waste gas.

The preheating temperature of blast furnace gas can be calculated by formula (1).

（1）

(1)

Among them, t _m is the blast furnace gas preheating temperature, ℃; v _f is the exhaust gas flow rate, 22960m ³ /h; t _f1 is the exhaust gas inlet temperature, 600℃; c _f1 is the exhaust gas inlet specific heat capacity, 1.55kJ/(m ³ ·℃) ; t _f2 is exhaust gas outlet temperature, 150℃; c _f2 is exhaust gas outlet specific heat capacity, 1.436kJ/(m ³ ·℃); v _m is blast furnace gas flow rate, 18850m ³ /h; c _m is blast furnace gas specific heat capacity, 1.506kJ/ (m ³ ·°C).

Through calculation, the preheating temperature of blast furnace gas can reach 598°C. The combustion temperature t _i of blast furnace gas can be calculated by the theoretical combustion formula (see formula 2).

（2）

(2)

In the formula, Q is the calorific value of blast furnace gas, 840*4.18kJ/m ³ ; t _m is the preheating temperature of blast furnace gas, 598°C; c _m is the specific heat capacity of blast furnace gas, 1.506kJ/(m ³ ·°C); v _a is The amount of gas produced by unit fuel combustion under a certain air coefficient is 1.6m ³ /m ³ ; c _y is the specific heat capacity of flue gas, 1.616kJ/(m ³ ·℃).

The calculation shows that the combustion temperature of blast furnace gas is 1706°C, which is slightly lower than that of pulverized coal and higher than that of converter gas. Through the above calculation, it can be known that the calcination temperature can reach about 1100°C, which can fully meet the calcination requirements of limestone.

The operating process of the double chamber kiln using low calorific value fuel provided by the present invention is:

When the first kiln chamber 1 is calcining, the cut-off valve of the waste gas suction beam 5 in the first kiln chamber 1 is in the closed state, and the cut-off valve of the low calorific value gas is in the open state; the waste gas suction beam 5 in the second kiln chamber 2 The cut-off valve of the gas is in the open state, and the cut-off valve of the low calorific value gas is in the closed state. The high-temperature exhaust gas diverted from the second kiln chamber 2 passes through the exhaust gas heat exchanger 6 to exchange heat for the low calorific value gas entering the first kiln chamber 1, and the high temperature and low calorific value gas enters the plug-in burner of the first kiln chamber 1 after heat exchange Carry out calcination.

After the double-chamber kiln reverses the calcination, when the second kiln chamber 2 is calcining, the cut-off valve of the waste gas suction beam 5 in the second kiln chamber 2 is in the closed state, and the cut-off valve of the low calorific value gas is in the open state; the first kiln chamber The cut-off valve of the exhaust gas suction beam 5 in the chamber 1 is in an open state, and the cut-off valve of the low calorific value gas is in a closed state. The high-temperature waste gas diverted from the first kiln 1 passes through the exhaust gas heat exchanger 6 to exchange heat for the low-calorific gas entering the second kiln 2; the high-temperature low-calorific gas after heat exchange enters the plug-in burner of the second kiln 2 Carry out calcination.

During the intermediate reversing process, the shut-off valves connecting the various exhaust gas suction beam pipes and gas pipes are closed. During the reversing and calcination stages of the double-chamber kiln, cooling air is continuously delivered to each waste gas suction beam 5, thereby ensuring the service life of the waste gas suction beam 5.

Through theoretical calculation and analysis of the data of the double-chamber kiln currently in operation, after adding the suction beam and the gas heat exchanger, the output of the blast furnace gas-fired double-chamber kiln can reach 400-450 tons/day. The activity degree and raw overburning rate of lime can reach the average level of double-chamber kiln, which can fully meet various customer needs.

By adding suction beams and gas heat exchangers, the calcination temperature of low calorific value gas can be effectively enhanced, and the discharge temperature of waste gas can be reduced, so that the limestone products can meet the corresponding requirements.

Claims (7)

1. A double-chamber kiln using low calorific value fuel, comprising a double-chamber kiln body, feeding equipment, discharging equipment, air supply system, fuel pipeline (4) and exhaust gas discharge system; the double-chamber kiln body includes the first A kiln chamber (1) and a second kiln chamber (2), the first kiln chamber (1) and the second kiln chamber (2) are respectively provided with a preheating zone, a calcining zone and a cooling zone; the calcining zone A plug-in burner (3) is provided; the feature is that waste gas suction beams (5) are respectively arranged between the calcining section and the preheating section of the first kiln chamber (1) and the second kiln chamber (2); The outlet of the exhaust gas suction beam (5) is connected to the shell side of the gas exhaust gas heat exchanger (6), and the shell side outlet of the gas exhaust gas heat exchanger (6) is connected to the exhaust gas discharge system; the fuel pipeline ( 4) Connect to the tube side of the gas waste gas heat exchanger (6), and the tube side outlet of the gas waste gas heat exchanger (6) is connected to the plug-in burner (3). 2. The double-chamber kiln using low calorific value fuel according to claim 1, characterized in that: the double-chamber kiln is a double-chamber kiln with a hanging cylinder structure or a corbel structure. 3. The double-chamber kiln using low calorific value fuel according to claim 2, characterized in that: the waste gas suction beam (5) is a square partition wall structure, the interior is a waste gas channel, and the partition wall is a cooling air channel; the waste gas The outlet of the cooling air channel of the suction beam (5) is connected with the combustion air main pipe. 4. The double chamber kiln using low calorific value fuel according to claim 1, characterized in that: the suction port of the waste gas suction beam (5) is set at the lower part of the waste gas suction beam (5); each waste gas The number of suction holes of the suction beam (5) is 10 to 12. 5. The calcination method of a double-chamber kiln using low calorific value fuel according to claim 1, characterized in that: when the first kiln chamber (1) is calcining, the exhaust gas in the first kiln chamber (1) is sucked The cut-off valve of beam (5) is closed, the cut-off valve of low calorific value gas is open; Closed state; the high-temperature waste gas diverted from the second kiln chamber (2) passes through the exhaust gas heat exchanger (6) to exchange heat for the low calorific value gas entering the first kiln chamber (1), and the high temperature and low calorific value gas enters the second kiln chamber (1) after heat exchange A plug-in burner in the kiln chamber (1) for calcination; After the double-chamber kiln reverses the calcination, when the second kiln chamber (2) is calcining, the cut-off valve of the exhaust gas suction beam (5) in the second kiln chamber (2) is in the closed state, and the cut-off valve of the low calorific value gas is in the In the open state; the cut-off valve of the waste gas suction beam (5) in the first kiln chamber (1) is in the open state, and the cut-off valve of the low calorific value gas is in the closed state; the high-temperature waste gas diverted from the first kiln chamber (1) is passed The heater (6) exchanges heat for the low calorific value gas entering the second kiln chamber (2); the high temperature and low calorific value gas after heat exchange enters the plug-in burner of the second kiln chamber (2) for calcination. 6. The calcination method according to claim 5, characterized in that: during the intermediate reversing process, the cut-off valves of each exhaust gas suction beam (5) pipeline and gas pipeline are closed. 7. The calcination method according to claim 5, characterized in that: during the reversing and calcination stages of the double-chamber kiln, cooling air is continuously delivered to each exhaust gas suction beam (5), thereby ensuring that the waste gas suction beam (5) ) service life.

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