JPH02289432A - Purification of exhaust gas from melting furnace - Google Patents

Abstract

PURPOSE: To decrease pollutants in flue gases by filtering the cooled waste gases obtd. by preheating a mixture composed of glass cullet, with the waste gases of a melting furnace heated with heavy oil by means of a bag filter.

CONSTITUTION: This apparatus for purification of the waste gases is obtd. by disposing a heat exchanger 13, a fan 15, a silo 1, an aperture 3, the bag filter 10, etc. Next, the waste gases of 400 to 750°C from the heat exchanger 13 are fed via the fan 15 into an adiabatic cullet preheating system 11 and are passed through a cavity outside wall 2, a cullet bed 6, a manifold 5 and the aperture 3. Next, the glass cullet 4 is supplied into the aperture 3 and the waste gases are supplied at a rate of about 0.1 m/s and are heat exchanged. The waste gases cooled to 200 to 250°C by controlling temp. with valves 18, 19 are fed into the bag filter 10 via a duct 20. The Na₂S₂O₇, etc., formed by accelerating the reaction of Na₂SO₄ and SO₃, etc., in the waste gases are filtered and separated by the filter 10, by which the waste gases from the melting furnace are purified.

COPYRIGHT: (C)1990,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION (Graduation Field of Application) The present invention is a method for cooling the exhaust gas discharged from a heavy oil-heated melting furnace for the production of all types of glass, especially soda-lime glass, and then filtering it with a bag filter. Concerning the purification process.

(Prior Art) The problem of air pollution due to exhaust gases from glass melting furnaces, especially those for the production of container or hollow glass, has recently been addressed almost exclusively by companies with experience in the field of abatement equipment. Ta.

Until now, the glass industry has only used conventional equipment, namely electrostatic precipitators. This conventional device has been modified to suppress or prevent experimentally proven negative phenomena, but not necessarily in a suitable manner.

A more detailed study of the chemical properties of the substances in the exhaust gases and their high temperature properties clearly disqualifies almost all solutions that have been adopted to date. The reason is as follows.

The exhaust gas from the soda-lime glass melting furnace is approximately 1
, discharged at a temperature of 500-1.600°C.

This exhaust gas passes through a heat recovery system. There are several types of heat recovery systems, but of course all systems have the function of transferring part of the heat of the exhaust gas to the combustion air for energy circulation in the melting furnace/s. This can be achieved using a metal heat exchanger (heat recovery device) or a regeneration chamber (heat storage device) with a The latter, in a discontinuous cycle, accumulates heat from the exhaust gas in the refractory brick or checker brick during the evacuation step and releases this heat to the combustion air during the ignition step. Such systems reduce the exhaust gas temperature to 750 to 80 °C for metal heat exchangers.
It can be lowered to 0'C, 400-500C in case of regeneration chamber.

Improved heat recovery with lower exhaust gas temperatures using metal heat exchangers with tube bundles is not possible. In addition, in the case of a regeneration chamber, the number of checker bricks must be increased, which is uneconomical as it negates the benefit of increased heat recovery, and is not only uneconomical but also There are limits.

Most glass factories, and almost all factories that produce soda-lime glass containers, use large amounts of energy at high heat levels, but virtually no energy use at low heat levels.

This limits the possibility of directly utilizing the large amount of energy remaining in the downstream exhaust gas, since the temperature of the exhaust gas downstream of the heat recovery system is too low compared to the temperatures required for the various processes. is clear.

This large amount of low-temperature energy can be converted into steam and then into mechanical or electrical energy. However, this solution is only economical for exhaust gas temperatures of the order of 750-800° C. and is therefore only applicable to furnaces with metal heat recoverers. This solution also requires a significant financial investment and causes operational problems such as particulate matter in the gas adhering to the heat exchange surfaces of the boiler.

This means that almost all glass factories have a production capacity of 450 to 800.
This is the reason why the exhaust gas is released into the atmosphere at a temperature of ℃.

During the melting process in the production of soda-lime glass, which is carried out at mass temperatures of the order of 1,350 to 1,500°C, conditions arise in which dust particles, sulfur dioxide gas, sulfur trioxide, and nitrogen oxides are produced. In particular, dust particles in the flue gas discharged from the furnace chimney are generated for the following reasons.

a) Mechanical carryover of batch raw materials This phenomenon clearly depends to a large extent on the design dimensions and operating method of the furnace. Due to their size, dust particles from mechanical carryover tend to accumulate in the regeneration chamber, and wetting the glass batch considerably suppresses this phenomenon, so that the exhaust gases released into the atmosphere usually contain only a very small amount. .

b) Production of sodium sulfate, which is produced from the melting furnace at 1.500-1.600 °C (7)
It occurs because the exhaust gas discharged at temperature contains sodium oxide vapor and sulfur dioxide and sulfur trioxide. Sodium, present in the form of sodium oxide (12-14%) in soda-lime glass, is well known to be a more adiabatic and volatile glass component than others. Therefore,
Its concentration in the exhaust gas increases as the proportion of Na and O in the glass increases or as the operating temperature of the furnace increases. The formation of solid particles from these two components (sodium oxide and sulfur trioxide) occurs as the exhaust gas cools in the regeneration chamber and these reach the temperature at which sodium sulfate is stable, i.e. 750-800 m
This occurs as long as the temperature reaches 0°C.

C) Presence of Calcium and Magnesium Sulfate These components are formed by the reaction of mechanically carried over calcium and magnesium carbonate with sulfur trioxide.

Gaseous pollutants in the exhaust gas of soda-lime glass furnaces are produced as follows.

1) Sulfur dioxide and sulfur trioxide (SOx) These are produced by the oxidation of the sulfur component of fossil fuels and the oxidation/reduction reaction of sulfates and sulfides present in the glass batch. The oxidation state of the glass and its refining mechanism depend on these reactions. Significant amounts of these gases are released by partial degassing of ecological cullet. This phenomenon can also be responsible for the generation of the majority of SOx in the flue gas, making it necessary for ecological reasons to use oxidized glass cullet in the production of reduced glass, and SOx
This occurs due to the fact that oxidized glass is much more difficult to dissolve in reduced glass than in oxidized glass.

It is clear that the difference in solubility between the two is released into the atmosphere along with the exhaust gas.

2) Nitrogen oxides (NOx) These are produced by the oxidation of nitrogen present in the combustion air and are facilitated by the operating temperature of the furnace. The favorable conditions for this secondary parasitic reaction are the excess of combustion air required for complete combustion of the fuel.

3) Fluoride and Chloride These occur when the glass batch contains traces of these anions, but these traces can be avoided. Since fluoride is not used in soda-lime glass once it has been ignited as a glidant in the glass batch, its content in the glass furnace exhaust gas decreases rapidly and continuously. These are due to the use of cullet from containers produced before fluoride was no longer used.

Chloride can be supplied to the glass furnace when using soda ash produced by the Truvay method using sodium chloride as a raw material.

As mentioned above, it is important for the glass industry to treat glass furnace exhaust gases to a level that not only complies with current legislation but also does not cause contamination as in the case of the containers produced by it. It is a complex problem that can only be approached and solved by taking all issues into account.

The problem of cleaning glass furnace flue gases was first addressed by glass factories in American states (California and New Chassis) that first regulated particulate matter emissions in flue gases to levels well below measured levels. 250℃@
Bag filters were not considered from the beginning, as there was no filter cloth that could withstand temperatures exceeding these temperatures (even today).

Therefore, there was no choice but to use an electrostatic precipitator that in principle can operate at a temperature of 400 to 600°C.

However, this solution has some limitations and problems.

The main ones are as follows.

a) The investment required for installation of this type of mitigation device is very large. An electrostatic precipitator capable of treating exhaust gas from a glass furnace with a daily production capacity of 220 tons requires an investment equivalent to 40% of the investment for the furnace itself.

b) The operating costs of electrostatic precipitators based on abatement systems are also very high due to the electrical energy consumption and the manpower required for operation and maintenance.

C) Continuous operation of the electrostatic precipitator system reduces SO in the exhaust gas.
Uncertain because of the interruption by x.

Therefore, long-term shutdowns may be necessary to regulate the quality of the emitted exhaust gas.

d) Efficiency in steady state operation significantly reduces the level of particulate matter in the exhaust gas, but does not guarantee that particulate matter concentrations required by current legislation will be reached and maintained.

e) The use of electrostatic precipitators within the above limits is only a solution for reducing particulate matter, but does not help reduce the emission levels of gaseous pollutants such as SOx, NOx, fluorides and chlorides. .

As part of the solution to problem C) above, S
To reduce Ox levels, experiments are being conducted in West Germany to treat exhaust gas with a base such as calcium oxide to neutralize the S03 contained therein before passing through an electrostatic precipitator.

This chemical treatment improves the operating conditions of the electrostatic precipitator and reduces the 5Oxfi degree in the exhaust gas. On the other hand,
Equipment becomes more complex, increasing investment and operating costs. This significantly increases the amount of particulate matter. This particulate #y
J quality cannot be reused in glass batches because of its very complex chemical composition, including calcium sulfate and calcium oxide.

Because of the challenges surrounding electrostatic precipitators, another solution was developed in California, which has very strict air pollution laws. One of the most significant is the one developed by Latchford Glass of Los Angeles, which lowers the temperature of the exhaust gas to a point where particulate matter can be removed using a conventional right-handed filter.

The reduction in temperature is obtained with a ``quench-1'' device, which is a large container into which exhaust gas and water are supplied simultaneously.

Some of the exhaust gas heat is used to evaporate water. To prevent damage to the filter material and avoid condensation caused by the increased concentration of water in the "quenching" process,
The water flow is automatically adjusted to maintain the emitted exhaust gas at a sufficiently low temperature.

Using water to reduce the temperature of wandering gases
It is possible to add a basic reagent to partially neutralize the solid sulfates forming SOx, which can be separated by filtration. Although this solution yields interesting results, it creates problems that many glass factories cannot solve. Among them, the obvious ones are:

1) This system requires a very large amount of space, about 4 times the space for the furnace.

2) The required investment is similar to that for electrostatic precipitators. This is because the cost of the cheaper filter system is offset by the cost of the quenching equipment and the expensive insulated ducts that connect the two.

3) Control of process variables (temperature, reagent supply, filtration, etc.) in equipment that is necessarily remote from the work area of the furnace personnel implies the use of specialized personnel skilled in operating the abatement system.

Quite different techniques are being tested to reduce the exhaust gas temperature to match the heat resistance of the filter cloth. One method uses cold air to dilute the furnace exhaust gases.

However, this method has the adverse effect of reducing the particulate matter concentration of the fluid being filtered, essentially increasing the flow through the filter. This reduces the efficiency of the filter system even though the concentration of particulate matter remains the same, as dilution by cold air increases the flow rate. And the total released into the atmosphere! (kg/h) inevitably increases. The filter area also needs to be increased, and therefore the investment for the reduction equipment is also high.

The second method is to use fluids (
The exhaust gas temperature is lowered by using the energy of the exhaust gas to heat water (for example, water).

This method is also unsuccessful because particulate matter in the exhaust gas adheres to the heat exchange surfaces, reducing the heat recovery rate and increasing the risk of sending the exhaust gas to the filter at a temperature high enough to damage the filter material.

Also, cooling the exhaust gas below the dew point can produce acidic condensates that can cause premature corrosion of the system. Such cooling is possible at the initial stage of operation because the heat exchange rate is high when there is no adhesion of particulate matter.

Recently, some fossil fuels have been converted into electrical energy (electric boost).
Particulate e! in the exhaust gas from the glass melting furnace by replacing it with Attempts have been made to reduce the J quality. This technology makes it possible to supply part of the required thermal energy directly to the glass melt, reducing the temperature of the furnace superstructure and reducing the evaporation of sodium oxide, thus reducing the particulate matter content of the exhaust gas. decrease. Particulate matter and NO in exhaust gas
These attempts have proven that even though the x content is improved at boost levels of 7-8% of the total thermal energy, the results are far from satisfactory. All of the above methods require large investments and therefore considerably increase the production costs of the containers.

These reduction devices provide no financial return on the associated investment in the long term.

These are the basic reasons why the European glass industry is reluctant to install furnace gas reduction systems. Such abatement systems are only installed in countries with very strict laws in place and where efficient control measures are available.

OBJECT OF THE INVENTION It is therefore an object of the invention to find an effective solution to the problem of reducing pollutants in flue gases.

(Means for Solving the Problems) The present invention preheats glass cullet or a mechanical mixture of glass cullet and glass batch using high-temperature exhaust gas of about 400 to 750°C, thereby transferring the exhaust gas to the cloth material of the bag filter. An exhaust gas purification method is provided in which glass cullet or a mechanical mixture of glass cullet and glass batch is supplied to a melting furnace, cooled to a temperature level low enough to prevent damage to the glass cullet or glass batch preheated by the exhaust gas.

(Operation and Effects) The method of the present invention solves the problem of reducing particulate matter or dust very efficiently and also reduces gaseous pollutants (SOx and NOx) in the flue gas coming out of soda-lime glass furnaces.
) to achieve control and reduction of

Additionally, cooling the filtered exhaust gas by using it to preheat the glass cullet not only reduces exhaust gas but also achieves significant energy savings and higher melting rates. These advantages, together with the recovery of sodium sulfate from the exhaust gas, result in economic advantages with a relatively short return on investment. In addition, low fIi (280 to 2 mg/rd) of particulate matter, lower SOx and NOx levels, unlimited reuse of ecological cullet, etc., which could not be achieved so far, can be achieved economically.

The ever-increasing consumption of glass cullet has opened up the possibility of its use as a means of extracting heat from furnace exhaust gases. The world's leading glass manufacturing companies have been researching the possibility of using exhaust gas heat to preheat glass batches for many years. However, to date, satisfactory results have not been achieved because the direct contact of the hot exhaust gas with the glass batch creates separation and agglomeration problems, which interfere with operation.

On the contrary, glass cullet, which is a well-defined chemical product with a large particle size, can solve all of the above problems regardless of the filtration conditions described herein.

A system has been developed to extract heat from exhaust gas by preheating glass cullet. Initially, the devices were developed to improve the thermal efficiency of new types of furnaces that used metal heat exchangers and therefore discharged hot exhaust gases into the atmosphere.

This new system is used to reduce the temperature of the exhaust gas to a level where traditional bag filters can be used downstream, and the energy obtained from that same exhaust gas is recycled by the preheated glass cullet.

(Example) FIG. 1 is a block diagram of an apparatus designed, installed, and tested from the above viewpoint.

Exhaust gas is discharged at a temperature of 400 to 750° C. from the regeneration chamber of the glass furnace or the metal heat exchanger 13 (not shown), and passes through the insulated duct 12. , is supplied to the cullet preheating system 11. This system has 15 fans
A continuous stream of glass cullet is passed through a silo 1 with a hollow outer wall 2 into which hot exhaust gases of e.g. Opening 3
Consisting of The flue gases flow across the cullet bed 6 in the cavity outer wall 20 passages 7 towards the central manifold 5.

These passages 7 are configured to allow flue gas to flow in, but not to allow glass cullet 4 to flow out. The glass cullet 4 is continuously supplied from the top, and the vibrating channel 9 is fed from the bottom.
is discharged through. The ratio of flue gas flow rate to glass cullet is determined by a mass balance taking into account the percentage of glass cullet and furnace fuel consumption based on furnace suction under normal conditions.

Glass cullet is 200-300 depending on the amount used
It is preheated to °C and fed to the furnace together with a cold glass batch stored in a separate container (not shown). Two dosing systems installed in front of the batch charger maintain the cullet to batch ratio at a predetermined level. The flue gas (exhaust gas) flowing out from the cullet preheating system is 200
Cooled to ~250°C. The gas is sent through a duct to a known bag filter lO and is discharged to the outside air via a fan 16 and a chimney 17.

The experience gained in the filtration process downstream of the cullet preheater 1 shows that in the case of exhaust gases from soda-lime glass furnaces, filtration is possible only under very strict operating conditions.

The filtration temperature can be kept constant by valves 18,19. When the temperature in the duct 20 between the cullet preheater 11 and the filter 100 exceeds a limit value, the valve 18 is opened and fresh air is introduced. If the temperature is low,
Valve 19 is opened and uncooled wandering gas is supplied from bypass path 21.

Filtration at temperatures above 200-205° C. easily produces a dense material that forms a thin film on the fabric surface of the filter.

This membrane makes filtration difficult and eventually impossible as the pressure drop across the cloth increases. When an experiment was conducted under these conditions, after 10 days of operation, the pressure decreased by 450 mm of water column across the filter, which caused a problem in the filtration process.

After stopping the experiment, visual inspection and analysis of the filter cloth revealed that approximately 75% of the particulate matter in the filtered exhaust gas
was absorbed by the filter cloth. Although the filtered gas particulate 1rfA degree was very low (less than 4+ng/Nr&), the operating conditions deteriorated below acceptable levels. Similar results were observed using another type of filter fabric. This shows that the filtration temperature is a decisive condition that influences the structure, shape and thus the filtration potential of particulate matter. In fact, at temperatures around 190'C a noticeable change occurs, with the filter deposits becoming finer and easier to remove from the filter bag. This phenomenon becomes even more pronounced at about 180'C. When we analyzed the powder and thin films collected at various filtration temperatures, we found no particular differences in chemical composition or compound structure. Chemical analysis showed that the acidity of the samples was very similar, approximately 8% in percent Hs SOa, and that the absorption of SOI was constant at the seed filtration temperature. The X-ray diffraction results show that the main compounds in both samples are Na, SO4 and Na3()130
4) Z, that is, N a 2S 0aNaH30. It was shown that

Chemical and X-ray analysis results show that filtration temperature does not affect the type of compounds deposited on the filter surface.

On the other hand, the filtration temperature has a decisive influence on the structure and shape of the powdery substance, which greatly affects the filtration ability. It is unlikely that a limited temperature change would result in such a difference in filtration capacity without resulting in a change in the chemical composition of the filtered powder material. Therefore, at higher temperatures (200-205°C),
S0 due to sodium sulfate present on the filter surface. The absorption of J results in the formation of sodium pyrosulfate (NatSzOt), which reacts with ambient moisture to form Na z S Oa and NaH30. It is reasonable to think that it was generated. At lower temperatures (180-190<0>C), this reaction would have taken place directly on the filter surface due to condensation of the water contained in the exhaust gas. Filtration at high temperatures may be difficult due to the presence of sodium pyrosulfate. A significant improvement in filtration capacity at temperatures of the order of 180-190°C is a key part of the invention, whether this relies on a simple chemical mechanism or a more complex series of chemical reactions. .

The lower limit of filtration temperature is the condensation temperature of exhaust gas, which is H, O
and 803, so the temperature is approximately 140 to 150°C.

It is clear that the operating conditions of the plant equipment must take into account the loss of heat t4, which leads to a reduction in temperature and the risk of a-condensation.

Furthermore, depending on the conditions, acidic condensate may be generated, so it is desirable to use a filter material that can withstand an acidic atmosphere.

In experiments, good results were obtained when acid-resistant polyimide material was used (although Teflon-coated filter bags lasted only 14 days due to acid corrosion).

Systems such as those described above have been tested with good results, and this has been confirmed several times over time. The main process conditions and results are shown in FIG. 2 and are as follows.

1. The quality of the exhaust gases filtered through known filter bags or filter tubes and released into the atmosphere was very high. The level of particulate matter or dust was reduced to very low values (approximately 4-5 mg /rrr). This low value was maintained for a long period of about 100 days to properly determine the heat and chemical resistance of the filter material.

2. When we analyzed the exhaust gas upstream of the cullet preheater, between the preheater and the filter bag, and downstream of the filter, we found that the 5Ox1 degree of the samples taken before and after the filter decreased by 40 to 50 degrees. %). Analysis of the material deposited in the filter bag shows that the thermodynamic conditions at exhaust gas filtration temperatures of 160-200°C produce sodium pyrosulfate (N a zs'tot), which reacts with water to form sodium bisulfate. (NaH30.) was found to be produced.

Particulate matter in the flue gas discharged from soda-lime glass furnaces has been found to be primarily (90-92%) sodium sulfate. This chloride absorbs a portion of the SOI in the exhaust gas at ambient temperatures below 300°C to form sodium pyrosulfate.

This reaction is suitably carried out under filtration conditions of 160 to 200°C, where part of the heat of the wandering gas is removed by a cullet preheater. S
The Ol-containing exhaust gas is actually forced through a layer of sodium sulfate that is always present on the filter surface. Therefore,
The mass ratio of N a , S Oa and SOl is very high (suitable for this reaction).

For the above reasons, it may be necessary to operate at temperature conditions suitable for small amounts of water condensation. This results in pyrosulfate (N
azszot) is converted to sodium bisulfate, which is much easier to filter, facilitating the filtration process.

The above reaction, which is possible by reducing the exhaust gas temperature and is therefore a key part of the present invention, results in a surprising reduction in the SOx concentration of the exhaust gas discharged into the atmosphere as described above.

3. Powdered materials periodically removed from the filter contain sodium sulfate (NatS04), sodium bisulfate (NatS04),
H30. ), contained small amounts of calcium and magnesium carbonate, and small amounts of glass dust carried over from equipment installed upstream of the filter bag.

Typical analysis results of the powdered material filtered through the filter are as follows.

NazSOa = 54.2%, S0. = 7.03% Ca50. = 3.6% NaH30. = 20.80% Mg50. = 0.6% Pb50. = 2.7% Glass = 11.0% This powder substance controls the oxidation state of the molten glass, and improves the glass blue lubrication process (gas from the molten glass (Co)).
It can be reused in glass batches to replace the sodium sulfate needed to aid in the release of This can be reused as is or after neutralizing sodium bisulfate (NaH30.) with sodium hydroxide (NaOH).

By treatment with sodium hydroxide, the S03 trapped under sodium bisulfate becomes thermally stable, increasing the control efficiency of the molten glass oxidation and fining process. Therefore, the powder material removed from the filter bag is NaH3O4+NaOH-+ NazS0. +H,0 can be added to the sodium hydroxide solution to obtain a neutral suspension of sodium sulfate by reaction. This suspension can be recycled to the furnace by pumping a measured amount to a batch mixer.

4. By preparing a neutral aqueous sodium sulfate solution by neutralizing the powder taken out from the filter bag, the method that takes advantage of the SO□ absorption effect described in item 2 above becomes possible. This advantage is also a key part of the invention and requires pumping a portion of the sodium sulfate suspension to a small "quench" located just downstream of the cullet preheater and upstream of the filter. shall be.

A small portion of the residual heat of the exhaust gas is utilized to evaporate the water added with the suspension of sodium sulfate. As a result, the exhaust gas entering the bag filter is low enough to allow long-term use of the filter material, but the condensation of water required to convert pyrosulfate (NatSxOl) to bisulfate (NaH3O4) is excessive. The temperature can be adjusted to a high enough temperature to prevent this from occurring. It is very interesting that this procedure can freely increase the proportion of sodium sulfate and SOx in the exhaust gas, making it suitable for the above reaction and reducing the SOx level in the exhaust gas released to the atmosphere. Reusing the separated pulverulent material naturally increases the i-load of the filter and therefore requires a larger filter surface. This problem occurs even when the exhaust gas has a higher concentration of particulate matter than usual as a result of recycling.
The solution is partly that the glass dust carried by the gas acts as a filtration aid that reduces the pressure drop at constant flow rates across the filter.

5. One of the main advantages of the unexpected discovery which forms the main part of the invention as described in paragraphs 2.3 and 4 above is that the use of ecological cullet, which for obvious reasons must be fed to the furnace, produces Most of the S03 that occurs can be captured by the bag filter. This cullet is a composite containing soda-lime glasses of different colors and therefore of different oxidation levels. The use of this type of cullet necessarily generates large amounts of SOx during the melting process. It is known that the solubility of SOx in soda-lime glass increases rapidly with increasing oxidation level of the glass. This level is selected based on the required spectrophotometric properties (color and UV absorption). So of oxidized glass, 4 degrees is about 0.35~0
．． It is about 38%, whereas reduced glass is 0.02%.
and low. Therefore, when producing oxidized or reduced glasses, the use of mixed ecological cullet can catalyze oxidation-reduction reactions, which change the solubility of sulfides in the glass and release a large amount of SOx in the exhaust gas. is clear. The above phenomena often create conditions that exceed the legal maximum emission concentration even when using natural gas containing only trace amounts of sulfur.

The incredible capacity of sodium sulfate to absorb So, at filter operating temperatures, allows for neutralization of the powdery material recovered with sodium hydroxide and reuse of a portion of the resulting suspension to absorb sulfuric acid on the filter. Together with its ability to add to the sodium layer, it not only lowers the SOx concentration in the exhaust gas of the filter, but also increases the SOx emission level, allowing the unlimited use of ecological cullet whose use was previously restricted. do.

6. Another important advantage of the debut cycle of the present invention is the use of preheated cullet to produce an effect on the NOx:a degree of the exhaust gas released into the atmosphere. Feeding preheated cullet has a significant advantage as far as the speed of the reaction converting the batch into glass is concerned.

This effect is of course based on the glass suction (more pronounced with higher cullet percentages, but makes it possible to maintain the same specific furnace suction at the same glass quality level and lower furnace operating temperature. As such, the reduced furnace temperature accelerates the nitrogen oxidation reaction, thus reducing NOx in the exhaust gas.
Lowers the third degree. Also, the lower operating temperature of the furnace reduces wear on the glass contacts and upper refractory structure, thus extending the life of the furnace.

7. The particulate matter or dust reduction process of the present invention and the control and reduction of gaseous pollutants in the exhaust gases released into the atmosphere from soda-lime glass melting furnaces provide the following economic advantages:

7a. The availability of unlimited amounts of ecological cullet reduces the energy consumption of the furnace and thus lowers the cost of glass production. Furthermore, there is no risk of exceeding the legal SOx emission level.

7b, it is clear that the use of preheated cullet further reduces energy consumption and glass production costs.

7c. Recycling of the sodium sulfate extracted from the flue gas into the glass batch allows for the correct disposal of the recovered pulverulent material and reduces raw material costs by eliminating the need to purchase this component.

7d, the lower operating temperature of the furnace increases the service life of the glass contact and upper refractory structure, extending the life of the furnace and lowering the reassembly cost and unit glass cost.

The above points are of great importance, and the economic advantages thereof result in savings, and the investment required in plant equipment can be recovered in 5 to 7 years, depending on the amount of cullet used.

All abatement systems prior to the present invention required much larger investments, resulting in high operating costs as well as no economic benefits.

Further advantageous features of the invention are set out in claims 2 to 21.

1 of flue gas from a glass furnace with a capacity of 210 tons per day.
Some experimental examples conducted at a test factory capable of processing 0% (1,20 ONrrf/h) are listed below, but the present invention is not limited thereto.

Example 1; 40% flow of cullet glass suction! 1.200 NrIf/h Exhaust gas analysis 2 Particulate matter level SOx reduction: 40% Powdered matter composition: Furnace energy reduction = 4% Example 2: Cullet 40% Flow rate 1.200 Nn(/h Exhaust gas analysis - particles Nation in particulate matter level filter: 1.5 times the level of SOx reduction = 60% Furnace energy reduction: 4% Example 3: Cullet 40% flow! 1,200 N/h Exhaust gas analysis: Particulate matter level filter N a , S 0.: twice the level 2 mg/rri 2 mg/rrj 2 mg/nf in flue gas Reduction of SOx in flue gas -60% Reduction in furnace energy: 4% Example 4: Cullet 50% Flow rate 1.200 N B/h N az S O4: Same level of S as in exhaust gas
Reduction in Ox: 45% Reduction in furnace energy: 5% Note that numbers are written in the claims section for convenient comparison with the drawings, but the present invention is not limited to the structure of the attached drawings by the entry. It's not something you can do.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an uninvented exhaust gas purification system, and FIG. 2 is an explanatory diagram of the operation of the purification system. 10...Bag filter, 12...Preheater.

Claims (1)

[Claims] 1. A purification method in which exhaust gas discharged from a melting furnace for producing all types of glass, especially soda-lime glass, is cooled and then filtered through a bag filter, the melting furnace being heated with heavy oil. , preheating the glass cullet or a mechanical mixture of glass cullet and glass batch using hot exhaust gases of about 400-750°C, thereby cooling the exhaust gases to a temperature level low enough to prevent damage to the bag filter fabric. and a method characterized in that glass cullet or a mechanical mixture of glass cullet and glass batch preheated by exhaust gas is fed to the melting furnace. 2. Adjust the temperature conditions of the exhaust gas in the bag filter to promote partial and moderate condensation of the water vapor contained in the exhaust gas, and generate bisulfate by reacting the condensed water with pyrosulfate, which is a component of the exhaust gas. 2. Process according to claim 1, characterized in that it is maintained at a level that promotes, in particular the reaction Na_2S_2O_7+H_2O→NaHSO_4. 3. Reaction between SOx contained in exhaust gas and at least another sulfur compound contained in exhaust gas, especially Na_2SO_4
3. Process according to claim 2, characterized in that pyrosulfate is produced by the reaction +SO_3→Na_2S_2O_7. 4. Maintain the temperature condition of the exhaust gas in the bag filter at a level that promotes the reaction of SOx contained in the exhaust gas and at least another sulfur compound contained in the exhaust gas to generate pyrosulfate, particularly the reaction of Na_2SO_4+SO_3→Na_2S_2O_7. The method according to claim 1, characterized in that: 5. Process according to any of claims 1 to 4, characterized in that the bag filter is operated at a temperature of 150-250<0>C, preferably 180-190<0>C. 6. The temperature of the exhaust gas is 300-850℃, preferably 40℃
6. Process according to any of claims 1 to 5, characterized in that the glass cullet or the mechanical mixture of glass cullet and glass batch is fed to the preheater at a temperature of 0 to 750<0>C. 7. Preheating of the glass cullet or the mechanical mixture of glass cullet and glass batch is achieved by directing the exhaust gas and the cullet or said mechanical mixture by sending the exhaust gas across or impinging on the flow of the glass cullet or said mechanical mixture. 7. Process according to claim 1, characterized in that it is carried out in a system in which heat exchange is obtained through contact. 8. The heat exchange between the exhaust gas and the glass cullet or the mechanical mixture is carried out at an exhaust gas velocity of 0.05 to 0.15 m/s, preferably about 0.1 m/s. 7. The method according to any one of 7. 9. The temperature of the exhaust gas coming out of the preheater of the glass cullet or the mechanical mixture is 150 to 350 °C, preferably 2
The method according to any one of claims 1 to 8, characterized in that the temperature is 00 to 300°C. 10. Controlling the operating temperature of the bag filter by diluting the exhaust gas coming out of the preheater of the glass cullet or the mechanical mixture with cold air or by adding hot exhaust gas thereby. Any method described. 11. A method according to any of claims 1 to 10, characterized in that the operating temperature of the bag filter is maintained high enough to avoid or suppress acidic condensation. 12. According to any one of claims 1 to 11, characterized in that the operating temperature of the bag filter is controlled by mixing the exhaust gas exiting from the preheater of the glass cullet or the mechanical mixture with water or an aqueous solution of Na_2SO_4. Method. 13. Any one of claims 1 to 12, characterized in that the exhaust gas emitted from the melting furnace is treated with an aqueous solution of calcium oxide, magnesium oxide, or NaOH, or some of these components to neutralize SO_3 in the exhaust gas. The method described in. 14. Process according to claim 13, characterized in that the neutralization of the exhaust gas takes place downstream of the glass cullet or of the mechanical mixture preheater and upstream of the bag filter. 15. The particulate matter filtered by the bag filter is taken out from the bag filter, especially NaHSO_4 + NaOH → Na_2SO_4 + H_2
ONa_2S_2O_7+2NaOH→2Na_2SO
15. Process according to any of claims 1 to 14, characterized in that it is converted into a sulphate by one or both of the reactions:_4+H_2O. 16. Process according to claim 15, characterized in that part or all of the obtained sulfate is recycled to the exhaust gas upstream of the bag filter. 17. Claim 15 or 1, characterized in that part or all of the obtained sulfate is used for glass batch preparation.
6. The method described in 6. 18. Process according to any of claims 1 to 17, characterized in that the exhaust gas temperature for the filtration step is controlled by adding water to the glass cullet or the mechanical mixture fed to the preheater. 19, in particular that calcium or magnesium or sodium sulfate or their several components produced in the neutralization reaction of SO_3 with calcium oxide, magnesium oxide or NaOH are removed from the glass cullet exiting the preheater or from said mechanical mixture. 20. The method of claim 18, characterized in that: 20. The method according to claim 19, characterized in that said removal is carried out by sieving, sorting, etc. 21. A purification device for cooling the exhaust gas discharged from a melting furnace for producing all kinds of glass, especially soda-lime glass, and then filtering it through a bag filter, said bag filter (10), said bag filter (10) discharging the exhaust gas upstream of the bag filter. a preheater (12) for preheating the glass cullet or a mechanical mixture of glass cullet and glass batch by cooling the glass cullet or the preheated mechanical mixture discharged from the preheater to the melting furnace; An apparatus comprising: means for transmitting; and means for controlling the temperature of the exhaust gas flowing into the filter (10).