JP2016087565A - Exhaust gas treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas treatment method capable of preventing dust discharged from a melting furnace and containing a Na compound from adhering to a water pipe of a waste heat boiler and from solidifying.SOLUTION: An exhaust gas treatment method of the present invention is an exhaust gas treatment method for an exhaust gas treatment facility comprising a waste heat boiler 30 provided in a gas duct 20 for exhaust gas containing a Na compound in dust discharged from a melting furnace 12, comprises supplying powder containing an alkaline component into the gas duct 20 before the exhaust gas is introduced into the waste heat boiler 30 so as to prevent sodium hydrogensulfate from solidifying on a water pipe 32 of the waste heat boiler 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas treatment method for an exhaust gas treatment facility equipped with a waste heat boiler that generates steam with waste heat of exhaust gas in a flue of exhaust gas containing Na compound in dust discharged from a melting furnace.

FIG. 3 is an explanatory diagram of a treatment facility for exhaust gas discharged from a melting furnace.
As shown in the figure, an exhaust gas treatment facility 10 for a melting furnace is provided with a waste heat boiler 30, a bag filter 40, and a fan 50 in the flue 20 of the exhaust gas generated from the melting furnace 12 from upstream to downstream in the flow direction of the exhaust gas. Is arranged.
In the melting furnace 12, for example, in the case of a glass melting furnace, glass raw materials such as silica sand and Na ₂ SO ₄ supplied into the furnace are melted at 1000 ° C. or more by a combustion burner. And glass products, such as a glass bottle and illumination, are shape | molded by the latter shaping | molding machine.

  The waste heat boiler 30 is installed in the flue 20 of the exhaust gas discharged from the melting furnace 12. The waste heat boiler 30 is mainly composed of a water pipe and a pump. A plurality of water pipes are arranged at predetermined intervals in a direction orthogonal to the flow direction of the exhaust gas flowing through the flue 20, and water is supplied into the pipes by a pump. The waste heat boiler 30 having such a configuration heats the water flowing in the pipe of the water pipe by the exhaust gas flowing through the flue 20 to generate steam. The generated steam is used for, for example, soot blowing for cleaning dust adhering to the surface of the water pipe.

The bag filter 40 is a dust collector that collects dust (raw material scattered matter) contained in the exhaust gas.
The fan 50 sucks the exhaust gas generated from the melting furnace 12 downstream of the flue 20 and discharges it to the outside.
Since exhaust gas contains air pollutants such as SO _X (sulfur oxide), NO _X (nitrogen oxide), PM (particulate matter), etc., exhaust gas that has been provided with desulfurization equipment and denitration equipment in the past There are treatment facilities.

  The exhaust gas treatment facility disclosed in Patent Document 1 is an alkaline powder that supplies alkaline powder to a region where a waste heat recovery boiler is installed in order to remove sulfur oxides contained in exhaust gas discharged from a gas turbine. Body supply means is provided. And the sulfur oxide is removed suitably with the desulfurization apparatus provided in the downstream of the waste heat recovery boiler, and the durability of an apparatus is made high.

  In the glass melting furnace exhaust gas treatment method disclosed in Patent Document 2, the exhaust gas generated in the glass melting furnace is cooled to a temperature of 200 ° C. to 300 ° C., and the sulfur oxide in the exhaust gas is conveyed with an alkali neutralizer to sulfate. A compound is generated. Sulfate compounds are removed with an electrostatic precipitator.

JP 2014-128775 A JP 2006-75764 A

  In the glass raw material supplied to the glass melting furnace described above, various metal substances are contained depending on the use of the glass product. For this reason, the component in the dust of the exhaust gas discharged from the glass melting furnace is different from the component contained in the dust of the exhaust gas generated from a general combustion furnace. As an example, Na (sodium): 30 wt%, S (sulfur) : 40 wt%, K (potassium): 10 wt%, Cr (chromium): 10 wt%, and others containing a large amount of Na compound.

When the applicant operates an exhaust gas treatment experimental device for exhaust gas containing a large amount of Na compounds and sulfur oxides generated from a melting furnace, dust adheres to the water pipe of a waste heat boiler provided in the flue The phenomenon of caking was confirmed. The consolidated dust could not be removed by washing with soot blow. When this dust was collected and components were examined, it was found that it contained NaHSO ₄ , Na ₃ H (SO ₄ ) ₂ , Na ₂ SO _{4, and the} like.

  If dust adheres to and accumulates on the water pipe of a waste heat boiler, the flue is blocked, and an excessive load is applied to the suction fan or the inside of the flue is in an excessively negative pressure state. In this case, it is necessary to stop the operation of the glass melting furnace and remove dust adhering to the water pipe of the waste heat boiler. When the glass melting furnace is stopped, there is a problem that it takes a long time to return to manufacture and the operating efficiency is remarkably lowered.

The exhaust gas treatment facility disclosed in Patent Document 1 is disposed between heat exchangers in which a plurality of alkali powder supply devices are installed. For this reason, when processing the exhaust gas which contains many Na compounds in dust, adhesion to the water pipe provided in the upstream heat exchanger with the most dust adhesion amount cannot be prevented.
In the glass melting furnace exhaust gas treatment method disclosed in Patent Document 2, since the exhaust gas temperature is cooled to 200 ° C. to 300 ° C. by the gas cooling device before supplying the alkali neutralizer, the sodium hydrogen sulfate is melted and liquefied. However, there was a risk of adhering to the gas cooling device.

  In view of the above-mentioned problems of the conventional technology, the present invention aims to provide an exhaust gas treatment method capable of preventing dust containing Na compound discharged from a melting furnace from adhering to a water pipe of a waste heat boiler and solidifying. Yes.

  As a first means for solving the above-mentioned problems, the present invention provides an exhaust gas treatment method for an exhaust gas treatment facility provided with a waste heat boiler in an exhaust gas flue containing Na compound in dust discharged from a melting furnace. Supplying powder containing alkali components to the flue before the exhaust gas is introduced into the waste heat boiler (hereinafter sometimes simply referred to as powder) on the water pipe of the waste heat boiler Another object of the present invention is to provide an exhaust gas treatment method characterized by preventing caking of sodium hydrogen sulfate.

  The present invention provides, as a second means for solving the above-mentioned problems, in the first means, when the powder is supplied from a supply pipe protruding from the outside to the inside of the flue. An object of the present invention is to provide an exhaust gas treatment method characterized in that the pipe surface of the supply pipe inside the road is kept warm.

  According to the present invention as described above, the sulfur oxide contained in the exhaust gas is removed, so that the sodium hydrogen sulfate dust does not adhere to the waste heat boiler and solidify to block the flue. In addition, the exhaust gas treatment facility can be stably operated over a long period of time.

  In addition, since powder containing an alkaline component is supplied into the flue between the melting furnace and the waste heat boiler, sodium hydrogen sulfate dust is most likely to adhere to the water pipe on the upstream side of the waste heat boiler. It can be effectively prevented.

  In addition, since the surface of the tube in the flue of the supply pipe that supplies the powder is kept warm, supplying the powder by pneumatic transportation cools the tube surface of the supply pipe in the flue and causes condensation. Can be prevented.

It is explanatory drawing of the waste gas processing method of this invention. It is a graph which shows the relationship between the pressure loss ratio of a flue, and time. It is explanatory drawing of the processing equipment of the waste gas discharged | emitted from a melting furnace.

  Embodiments of an exhaust gas treatment method of the present invention will be described below in detail with reference to the accompanying drawings.

溶解炉で発生した排ガスは、煙道に導入されるとガス温度が約４００℃まで低下する。 [Dust consolidation mechanism]
Examples of the Na compound of the exhaust gas containing Na compound in the dust discharged from the melting furnace include glass raw material Na ₂ SO ₄ .
Na ₂ SO ₄ is decomposed in the melting furnace 12 at 1000 ° C. or more as shown by the following formula to generate SO ₃ .

When the exhaust gas generated in the melting furnace is introduced into the flue, the gas temperature decreases to about 400 ° C.

Circulating water flows in the water pipe of the waste heat boiler placed in the flue. The water pipe exposed in the flue is heated by the waste heat of the exhaust gas, and the surface temperature of the water pipe is about 160 ° C. For this reason, the temperature distribution of 160-400 degreeC has arisen in the dust layer adhering to the water pipe. On the other hand, when SO ₃ is contained in the exhaust gas, it is known that the electrical resistivity of the dust is significantly reduced by condensation of SO ₃ on the surface of the dust at a temperature of about 220 ° C. or less. Accordingly, the _Na 2 SO ₄ a temperature of about 220 ° C. or less of the area of the dust layer deposited on the surface of the water pipe, SO ₃ condenses reacts as moisture and the formula in the exhaust gas, sodium bisulfate (NaHSO ₄ ) Occurs.

生成したＮａ_３Ｈ（ＳＯ_４）_２は融点が約２７０℃であり、水管表面のダスト層内の温度が約２７０℃以下の領域で固結したものと推定される。 Since the generated sodium hydrogen sulfate has a melting point of 180 ° C. to 190 ° C., the dust in the region above the melting point in the dust layer adhering to the surface of the water tube is melted to serve as a binder to adhere Na ₂ SO _{4 to} each other. .
Then, the contacted or mixed Na ₂ SO ₄ and sodium hydrogen sulfate react as shown in the following formula.

The produced Na ₃ H (SO ₄ ) ₂ has a melting point of about 270 ° C., and is presumed to be consolidated in a region where the temperature in the dust layer on the surface of the water tube is about 270 ° C. or less.

[Powder supply means 60]
FIG. 1 is an explanatory view of the exhaust gas treatment method of the present invention. As shown in the figure, in the flue 20 connected to the outlet of the melting furnace 12, powder supply means 60 for powder containing an alkali component is attached upstream of the waste heat boiler 30.

The powder supply means 60 of this embodiment has a supply pipe 62, a hopper 64, a blower 66, and a heat retaining means 68 as the main basic configuration.
The supply pipe 62 is inserted from the outside to the inside of the flue 20 (the cross-sectional direction of the flue 20), one end is arranged in parallel with the flow direction of the exhaust gas, and the other end is arranged outside the flue 20. The blower 66 is connected. One end of the supply pipe 62 can have an end face directed upstream or downstream. When the end surface is directed upstream, the powder supply direction is opposite to the flow direction of the exhaust gas, so that the powder can be supplied while being diffused. In addition, the supply pipe 62 may have a configuration in which a plurality of branch pipes provided with powder discharge ports are connected to one end side at equal intervals.

  A hopper 64 is attached to the supply pipe 62 between the blower 66 and the flue 20. The hopper 64 is filled with powder. In the supply pipe 62 of this embodiment, the surface of the pipe inserted into the flue 20 by the heat retaining means 68 is heated and kept at a predetermined temperature. The heat retaining means 68 is a heater formed so as to cover the pipe surface of the supply pipe 62 in the flue 20. The temperature of the tube surface is set to 40 ° C. to 50 ° C., for example. By performing such heat insulation, when the powder is supplied into the flue 20, the temperature of the pipe surface exposed in the flue 20 is reduced due to the temperature of the pipe wall being lowered by the powder that is pneumatically transported. It is possible to prevent condensation from occurring due to a decrease. This is because when hydrogen condensation occurs, sodium hydrogen sulfate may be easily consolidated.

The powder containing an alkali component may be any powder that can neutralize acidic sulfur oxides. For example, Ca (OH) ₂ , CaCO ₃ , CaO, MgO, Mg (OH) ₂ , sodium compound, barium Compounds and the like can be applied. As the powder of the present embodiment, a powder having a particle size of 100 μm or less is used. If it is such a particle size, when it supplies in the flue 20, it can mix with waste gas easily and can accelerate | stimulate reaction with a sulfur oxide.

The powder is measured in advance for the concentration of sulfur oxide in the exhaust gas, and a predetermined amount is supplied based on the measured value. In the present embodiment, the molar ratio of the sulfur oxide and the powder in the exhaust gas is set in the range of 1: 1 to 1:10 and supplied. When the molar ratio is more than 1:10, there is a risk that the load of the subsequent bag filter may be applied by the sulfur oxide and the unreacted excessive powder. For example, when the concentration of sulfur oxide in the exhaust gas is 10 ppm and Ca (OH) ₂ is powder, the supply amount of powder when the molar ratio of sulfur oxide is 1 is about 300 g / h. Can be set.

このように煙道内に供給されたアルカリ性の粉体が排ガス中のＳＯ_３と反応して、ＳＯ_３を除去することができる。 The powder supply means 60 having such a configuration supplies the powder filled in the hopper 64 to the flue 20 by air transportation from the supply pipe 62 by the blower 66.
When the alkali component is Ca (OH) ₂ , it reacts with SO _{3 in} the exhaust gas as follows.

In this way, the alkaline powder supplied into the flue reacts with SO ₃ in the exhaust gas to remove SO ₃ .

  In addition, when the wind speed of the exhaust gas in the flue is 5 to 6 m / s, the powder supply means 60 is installed on the upstream side of the waste heat boiler 30 and supplies the powder into the flue 20 to form sulfur. It is sufficient that the time for reacting with the oxide is at least 0.5 seconds or more, and as an example, it is attached to the flue 20 upstream from the waste heat boiler 30 by several meters. Further, the powder supply means 60 of this embodiment is provided on the upstream side of the water pipe 32 on the upstream side of the waste heat boiler 30 and is not provided on the downstream side of the water pipe 32 on the upstream side. In the waste heat boiler 30, the most dust-attached portion is the upstream water pipe 32, and if the powder supply means 60 is not installed on the upstream side, the dust on the upstream water pipe 32 is prevented. This is because it cannot be done.

  The powder supply means 60 may be configured so that the powder can be supplied from the outside to the inside of the flue 20, and in addition to the above configuration, other uses such as supply using the negative pressure of the flue without using a blower. Configurations are also applicable.

[Action]
The operation of the exhaust gas treatment method of the present invention having the above configuration will be described below.
In the flue 20 connected to the outlet of the melting furnace 12, powder is supplied into the flue 20 from the powder supply means 60 provided on the upstream side of the waste heat boiler 30 by pneumatic transportation.
When the powder is Ca (OH) ₂ , it reacts with sulfur oxide in the exhaust gas to become calcium sulfate, and the concentration of sulfur oxide can be reduced. The waste heat boiler 30 is provided with a soot blow 70, and dust attached to the water pipe 32 is periodically removed. Since the produced calcium sulfate does not melt at the flue gas temperature in the flue (about 400 ° C. or less), it can be collected by the subsequent bag filter 40. And since the density | concentration of a sulfur oxide is low in the waste heat boiler 30, almost no sodium hydrogen sulfate is produced | generated. For this reason, sodium hydrogen sulfate does not solidify in the water pipe 32. Therefore, the melting furnace 12 and the exhaust gas treatment facility 10 can be stably operated over a long period of time.

[Example]
Next, JIS special slaked lime is sprayed as powder from the powder supply means 60 onto the flue 20 between the melting furnace 12 and the waste heat boiler 30, and the change in the pressure loss ratio of the waste heat boiler 30 over time is examined. It was. The pressure loss ratio represents the pressure loss of the waste heat boiler at the initial stage of operation as 1 and the pressure loss of the subsequent waste heat boiler as a ratio. At this time, the supply amount of slaked lime is 0.1 to 1 g / m ³ _N with respect to the exhaust gas.

  FIG. 2 is a graph showing the relationship between the pressure loss ratio of the flue and time. The horizontal axis of the graph shows the test time (h), and the vertical axis shows the pressure loss ratio (−) of the flue. Further, a shows the case where the powder containing the alkali component is supplied, and b shows the case where the powder containing the alkali component is not supplied.

  According to FIG. 2, when no powder is supplied into the flue of b, the pressure rises with time, and the pressure loss ratio rises significantly from 3 to 4 around the test time of 2000 hours. On the other hand, when the powder was supplied into the flue a, the pressure loss ratio was 1.5 or less even after the test time of 4000 hours, and the increase in pressure loss over time could be suppressed.

  According to the exhaust gas treatment method of the present invention, by removing sulfur oxides contained in the exhaust gas, the sodium hydrogen sulfate dust does not adhere to the waste heat boiler and solidify to block the flue. The melting furnace and the exhaust gas treatment facility can be stably operated over a long period of time.

  The present invention is particularly useful in the field of treating exhaust gas containing a large amount of Na compound in dust such as a glass melting furnace.

10 ......... Exhaust gas treatment equipment, 12 ......... Smelting furnace, 20 ......... Smoke, 30 ......... Waste heat boiler, 32 ......... Water pipe, 40 ...... Bug filter, 50 ...... Fan, 60 ......... powder supply means containing an alkali component, 62 ......... supply pipe, 64 ......... hopper, 66 ......... blower, 70 ... soot blow.

Claims (2)

In the exhaust gas treatment method of an exhaust gas treatment facility equipped with a waste heat boiler in the flue of the exhaust gas containing Na compound in the dust discharged from the melting furnace,
Supplying powder containing an alkali component to the flue before the exhaust gas is introduced into the waste heat boiler to prevent caking of sodium hydrogen sulfate on the water pipe of the waste heat boiler Exhaust gas treatment method.   The tube surface of the supply pipe inside the flue is kept warm when the powder is supplied from a supply pipe protruding from the outside to the inside of the flue. Exhaust gas treatment method.

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