A method of removing particulate matter from exhaust gas stream

Abstract

The present invention relates to a method of removing particulate matter from an exhaust gas stream, the method comprising treating the exhaust gas stream with a scrubbing solution comprising a treatment composition. The treatment composition is a water-soluble polymer-based solution comprising a cationic silicate component. The present invention also relates to a scrubbing solution suitable for use in a wet scrubbing process, the scrubbing solution comprising a treatment composition in water at a concentration of from about 0.01% w / w to about 10% w / w.

Description

Technical Field

[0001] The present invention relates to a method for removing particulate matter from an exhaust gas stream using a scrubbing liquid comprising a treatment composition comprising a non-aqueous water-soluble polymer-based composition containing a cationic silicate component. In particular, but not exclusively, the present invention provides a method for removing PM10, PM4, PM2.5 and PM1 particulate matter from an exhaust gas stream. Background Art

[0002] The presence of high levels of particulate matter (particularly fine particles) in the atmosphere is associated with a large number of illnesses and even premature deaths each year. In addition, these pollutants also have significant impacts on sensitive ecosystems.

[0003] Liquid particles or solid particles can be removed from the exhaust gas stream by transferring them into a liquid. The most commonly used liquid is water. Furthermore, it is well known that the particle collection efficiency of a wet scrubber is directly related to the energy consumed in contacting the exhaust gas stream with the scrubbing liquid. Therefore, this has a direct impact on the operating costs of a particular scrubbing system.

[0004] While many conventional wet scrubber systems are common in the industry, there remains a need to improve the efficiency with which the scrubbing liquid droplets bind to the particles to be removed from the gas stream.

[0005] In particular, there is a need for improvements in these systems as they relate to the removal of fine particulate matter that is harmful to human health. There is also a need for improvements in the efficiency of the scrubber liquor, thereby reducing the volume of scrubber liquor used while maintaining the same or improved particle removal efficiency. Summary of the invention

[0006] According to a first aspect of the present invention, there is provided a method for removing particulate matter from an air flow, the method comprising the following steps:

[0007] a) provide an exhaust gas stream containing particulate matter, and

[0008] b) treating the exhaust gas stream with a scrubbing liquid to produce a treated gas stream having a particle concentration less than the particle concentration of the exhaust gas stream,

[0009] wherein the washing liquid comprises a treatment composition,

[0010] The treatment composition is a polymer-based solution containing a cationic silicate component, and the polymer is a water-soluble polymer.

[0011] In one embodiment, the wash liquor is a solution of the treatment composition in water.

[0012] In one embodiment, the wash liquor comprises from about 0.01% w / w to about 10% w / w of the treatment composition.

[0013] In another embodiment, the wash liquor comprises from about 90% w / w to about 100% w / w of the treatment composition.

[0014] In a preferred embodiment, the process is a wet scrubbing process, wherein the wet scrubbing apparatus is an apparatus selected from the group consisting of a spray tower, a cyclone spray tower, a dynamic scrubber, a tray tower, a venturi scrubber and a perforated plate scrubber.

[0015] In one embodiment, the exhaust gas stream has a PM10 concentration of about 5% w / w to about 30% w / w based on the total particulate matter content in the exhaust gas stream.

[0016] In a preferred embodiment, the removal efficiency of the PM10 fraction is increased by 10% or more compared to the removal efficiency of a process using the same process parameters but excluding the treatment composition from the scrubbing liquor.

[0017] In preferred embodiments, the removal efficiency of the PM10 fraction is increased by 15% or more, 20% or more or 30% or more compared to the removal efficiency of a method using the same process parameters but excluding the treatment composition from the scrubbing liquor.

[0018] In one embodiment, the exhaust gas stream has a PM4 concentration of about 5% w / w to about 30% w / w based on the total particulate matter content in the exhaust gas stream.

[0019] In a preferred embodiment, the removal efficiency of the PM4 fraction is increased by 10% or more compared to the removal efficiency of a process using the same process parameters but excluding the treatment composition from the scrubbing liquor.

[0020] In preferred embodiments, the removal efficiency of the PM4 fraction is increased by 15% or more, 20% or more or 30% or more compared to the removal efficiency of a method using the same process parameters but excluding the treatment composition from the scrubbing liquor.

[0021] The waste gas stream may come from a mining operation, a grinding operation, general dust control, or an incineration or digestion operation.

[0022] In one embodiment, the scrubbing liquid is located in a direction opposite to the exhaust gas flow, in the same direction as the exhaust gas flow, or perpendicular to the exhaust gas flow.

[0023] In one embodiment, the treatment composition further comprises a cationic additive component.

[0024] In one embodiment, the cationic additive component is a salt of a compound selected from the class of compounds including thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines, and aldehyde amines.

[0025] In one embodiment, the cationic additive component is a salt of a compound selected from the class of compounds comprising thiazoles, dithiocarbamates, dithiophosphates, thiuram sulfides, or combinations thereof.

[0026] In a preferred embodiment, the cationic additive component is a salt of 2-mercaptobenzothiazole (MBT), zinc dibenzyldithiocarbamate (ZBEC), zinc dialkyldithiophosphate (ZBOP), tetrabenzylthiuram disulfide (TBzTD), diisopropylxanthogen disulfide (DIXD) or diisopropylxanthogen polysulfide (AS100), or a combination thereof.

[0027] In one embodiment, the salt is a sodium salt or a potassium salt.

[0028] In one embodiment, the cations of the cationic silicate component are sodium cations or potassium cations.

[0029] In a preferred embodiment, the water-soluble polymer is an ethylene oxide polymer or a polyvinyl alcohol polymer.

[0030] In a particularly preferred embodiment, the water soluble polymer is polyethylene glycol.

[0031] In one embodiment, the molecular weight of the water-soluble polymer is between 300 g / mol and 10,000,000 g / mol, preferably between 500 g / mol and 20,000 g / mol, and more preferably between about 1,000 g / mol and 10,000 g / mol.

[0032] According to another aspect of the present invention, there is provided the use of a treatment composition for improving the particle removal efficiency of a wet scrubbing process, wherein the treatment composition comprises a polymer-based solution having a cationic silicate component, and the polymer is a water-soluble polymer.

[0033] According to another aspect of the present invention, there is provided a washing liquor suitable for a wet washing method, wherein the washing liquor is a solution of a treatment composition in water, the concentration of the treatment composition is from about 0.01% w / w to about 10% w / w of the washing liquor, the treatment composition comprises a polymer-based solution having a cationic silicate component, and the polymer is a water-soluble polymer. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will now be described in more detail with reference to the following non-limiting embodiments and the accompanying drawings, in which:

[0035] Figure 1 shows the wet scrubber test configuration used in the following examples;

[0036] Figure 2 v is the graded coal used in Experiments 2 and 3;

[0037] Figure 3 shows the coal CDF for the sensor specific area used in the experiment; and

[0038] Figure 4 The average CDFs of water and coal in the Z-neck, Z-upstream, and Z-downstream regions are shown;

[0039] Figure 5 The average CDF values ​​of water and coal relative to 10 μm in the Z neck, Z upstream, and Z downstream regions are shown;

[0040] Figure 6 The average CDFs of water and coal spiked with PEGSIL in the Z neck, Z upstream, and Z downstream regions are shown;

[0041] Figure 7 The average CDFs of water and coal doped with PEGSIL in the Z-neck, Z-upstream, and Z-downstream regions normalized to 1000 Z-neck with respect to 10 μm are shown;

[0042] Figure 8 The average CDFs of water and polyhalite at 33 LPM in the Z neck, Z upstream, and Z downstream regions are shown;

[0043] Fig. 9 The average CDFs of water and polyhalite doped with PEGSIL at 33 LPM in the Z-neck, Z-upstream, and Z-downstream regions are shown;

[0044] Fig.10 The scrubbing efficiency of the system with water and polyhalite for various particulate fractions at various flow rates is shown;

[0045] Fig.11 The washing efficiency of the system with water and polyhalite doped with PEGSIL for various particulate fractions at various flow rates is shown;

[0046] Fig.12 shows the particle diameter cumulative distribution function ("CDF") of the high silica content particles in the particle size range <75 μm in Experiment 5; and

[0047] Fig.13 The performance of various tests performed on the beta values ​​obtained in Experiment 5 for PM4, PM2.5, PM1 and PM0.5 partitions respectively is shown. DETAILED DESCRIPTION

[0048] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some non-limiting embodiments of the invention are shown.

[0049] The invention as described below is not to be construed as limited to the specific embodiments disclosed as slight modifications and other embodiments are intended to be included within the scope of the invention.

[0050] Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0051] As used herein, throughout this specification and the claims that follow, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0052] The terms and expressions used herein are for descriptive purposes only and should not be regarded as limiting. As used herein, the use of the terms "including," "comprising," "having," "comprising," and variations thereof are meant to encompass the items listed below and equivalents thereof as well as additional items.

[0053] As used in this specification, the term "particulate matter" is to be understood as a mixture of solid particles and liquid droplets suspended in the air, and in particular in this case a mixture of solid particles and liquid droplets suspended in the exhaust gas stream.

[0054] As used in this specification, the terms "PM10", "PM4", "PM2.5", "PM1" and "PM0.5" should be understood to mean particulate matter having a nominal aerodynamic diameter equal to or less than 10 micrometers (μm), equal to or less than 4 μm, equal to or less than 2.5 μm, equal to or less than 1 μm and equal to or less than 0.5 μm, respectively.

[0055] As used in this specification, the term "wet scrubber" shall be understood to mean an air pollution control device that removes particulate matter and / or acid gases from an exhaust gas stream. The pollutants are removed primarily by impaction, diffusion, interception and / or absorption of the pollutants on liquid droplets. The liquid containing the pollutants is then typically collected for further processing and / or disposal. Unless the context clearly indicates otherwise, as used herein, the term "wet scrubbing" shall be understood to mean a process for removing particulate matter and acid gases from an exhaust gas stream using a wet scrubber.

[0056] As used in this specification, the term "scrubbing liquid" is understood to mean a liquid used in a wet scrubber or wet scrubbing process to interact with particulate matter and / or acid gases in a waste stream. The scrubbing liquid may contain one or more additives to improve the efficiency of the wet scrubbing system.

[0057] As used in this specification, the term "water-soluble polymer" is understood to mean a polymer that dissolves, disperses or swells in water, including a polymer containing a hydroxyl group, such as an ethylene oxide-based polymer or a polyvinyl alcohol polymer.

[0058] As used in this specification, the term "Beta value" should be understood to mean the value of a particular washing system, which is defined as the number of particles that leave the system for every 100 particles that enter the system. For example, in a system where 15 particles leave the system for every 100 particles that enter the system, the Beta value would be 6.67. Alternatively, the efficiency of the same system could also be recorded as 85%.

[0059] The present invention provides a method for removing particulate matter from an exhaust gas stream, wherein the method uses a scrubbing liquor comprising a treatment composition. The present invention also relates to such a scrubbing liquor composition.

[0060] The present inventors have surprisingly discovered that scrubbing liquors comprising treatment compositions comprising a water-soluble polymer-based composition containing a cationic silicate component improve the particle removal efficiency of the scrubbing liquor and, therefore, the particle removal efficiency of the entire process. These treatment compositions have shown surprising and unexpected results in removing particulate matter from an exhaust gas stream, or as an additive to a scrubbing liquor used in a process for removing particulate matter from an exhaust gas stream.

[0061] The treatment composition can be dissolved in the scrubbing liquid to form a solution of the treatment composition in the scrubbing liquid at a concentration of about 0.01% or more. For example, the treatment composition can be dissolved in water to form a solution of the treatment composition in water at a concentration of about 0.01% w / w to about 10% w / w relative to the scrubbing liquid. Other examples of treatment compositions in the scrubbing liquid depend on the exhaust gas stream, the source of the particulate matter, and the standard operating parameters of the particular process. These further examples can be determined by routine experimentation by those skilled in the art who have the benefit of the teachings of the present invention.

[0062] The treatment composition may further comprise a second cationic component (in addition to the cationic silicate component), referred to herein as a cationic additive component, which is dissolved in and stabilized by the cationic silicate-polymer composition. For example, the second cationic component or cationic additive component may be a metal salt of a metal oxide (e.g., zinc oxide) or a cationic nanopowder (e.g., reduced graphene oxide).

[0063] The salt of the cationic additive component may be a salt of a compound selected from the class of compounds including thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines, aldehyde amines, or combinations thereof.

[0064] The polymer in the treatment composition is a water-soluble polymer, such as an ethylene oxide polymer, a polyvinyl alcohol polymer or any other polymer containing hydroxyl groups.

[0065] The water-soluble polymer-based treatment composition can be prepared as follows. A suitable cationic silicate component solution is synthesized by dissolving silica powder in an alkaline solution (e.g., sodium hydroxide or potassium hydroxide). The cationic silicate component thus produced can be added to a water-soluble polymer (e.g., an ethylene oxide polymer containing polyethylene glycol) and then dried to produce a stable ionic solution or ionic liquid having a specific cationic silicate component.

[0066] As an alternative to an aqueous environment, the specific combination of a cationic silicate component and a polymer (e.g., polyethylene glycol) allows for the formation of a suitably stable ionic solution. This means it has greater reactivity and potential as an active solvent medium and stabilizer for other cationic additive components that may be required in the final treatment composition.

[0067] It is contemplated that these cationic silicate solutions and the cationic silicate polymer compositions or complexes produced therefrom can be prepared by reacting selected cations with silica in varying ratios, thereby varying the surface chemistry and ionic properties of the solutions and the treatment compositions produced therefrom. In one embodiment of the invention, a stoichiometric ratio of cations to silica can be used. Alternatively, this ratio can be varied depending on the requirements of a particular system and the particulate matter to be removed from the exhaust gas stream.

[0068] The cationic silicate component may be prepared in water, or in an azeotrope of a suitable water and alcohol, preferably water and isopropanol.

[0069] In one embodiment of the present invention, as a cationic additive component, the composition may further comprise a salt of a compound dissolved in the cationic silicate component and the polymer carrier. The cationic additive complex can be prepared in a corrosive aqueous solution (e.g., sodium hydroxide solution or potassium hydroxide solution). The cationic additive complex can be prepared by dissolving sodium hydroxide or potassium hydroxide in water and then reacting with the compound.

[0070] The cationic additive complex may also be prepared in a suitable azeotrope of water and alcohol. In a preferred process of the present invention, the cationic additive complex is prepared in a water-isopropanol azeotrope.

[0071] The cationic additive may be based on a salt of a compound selected from the class of compounds including thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines, aldehyde amines, or combinations thereof.

[0072] In one embodiment, the compound for the cationic additive is a compound selected from the class of compounds including thiazoles, dithiocarbamates, dithiophosphates, thiuram sulfides, or combinations thereof. Preferably, the salt is a sodium or potassium salt of 2-mercaptobenzothiazole (MBT), zinc dibenzyldithiocarbamate (ZBEC), zinc dialkyldithiophosphate (ZBOP), tetrabenzylthiuram disulfide (TBzTD), diisopropylxanthogen disulfide (DIXD), or diisopropylxanthogen polysulfide (AS100), or a combination thereof.

[0073] The above-mentioned cationic additive or any other suitable ionic material (such as metal salt, metal oxide or nano powder) is added to the cationic silicate solution to prepare the reaction mixture, and a water-based polymer is added thereto. The resulting reaction mixture is then dried to remove the solution medium, particularly to remove any water from the system. In one embodiment, the mixture can be dried under vacuum (such as 100 millibars or lower) to remove the solution medium. The resulting composition is a non-aqueous composition based on a water-soluble polymer (such as polyethylene glycol).

[0074] The cationic additive component and the cationic silicate component may comprise up to about 50% of the total mass of the polymer-based composition, with the aqueous polymer component constituting the remainder of the detergent treating composition.

[0075] It is envisioned that the scrubbing liquid treatment composition will be applied to any wet scrubbing device, including a spray tower, a cyclone spray tower, a dynamic scrubber, a disc tower, a venturi scrubber, a perforated scrubber, or any combination of the underlying principles of these devices. In addition, the interaction of the scrubbing liquid with the exhaust gas flow (including particulate matter) can take a variety of configurations. The system can be adapted to interact in the direction opposite to the exhaust gas flow, in the same direction as the exhaust gas flow, or in a direction perpendicular to the exhaust gas flow. In the following embodiments, the interaction is substantially in the same direction as the exhaust gas flow.

[0076] The wet scrubber configuration used in the embodiments described below is as follows: Figure 1 See Figure 1 , the exhaust gas stream enters the wet scrubber 10 from an inlet point 12. A scrubbing liquid feed is provided through an orifice 20, and a particulate filter screen 30 is provided downstream of the inlet point 12 and the scrubbing liquid orifice 20. Particulate sensors 40, 42 and 44 are provided at different points in the system. Sensor 40 (hereinafter referred to as the "Z neck") is located after the inlet point 12 but before the orifice 20, in an area generally referred to as the neck of the system; sensor 42 (hereinafter referred to as "Z upstream") is located upstream of the screen 30; and sensor 44 (hereinafter referred to as "Z downstream") is located downstream of the screen 30.

[0077] The present invention will now be described in more detail with reference to the following non-limiting examples and experimental results.

[0078] Experimental Example 1: Preparation of sodium silicate / polyethylene glycol composite detergent treatment composition

[0079] In a suitable container, add 10 g of NaOH to 40 ml of water. To this solution, add 7.5 g of silica powder while stirring. Heat the solution to 60°C and see that it dissolves quickly (the reaction is exothermic, so excessive heating is not required). Stir the solution at 60°C for 5 minutes. After the reaction of NaOH and SiO2 is complete, the solution is transparent.

[0080] 2NaOH+SiO2→Na2SiO3(aq)+H2O

[0081] Sodium silicate solutions can also be prepared in a suitable azeotrope, such as a mixture of water and isopropanol.

[0082] 15 g of polyethylene glycol is added to the solution, wherein the amount of PEG is usually the same as the silicate content. The solution is stirred at 60°C for 5 minutes until the PEG is completely dissolved in the solution. The solution is dried at 105°C and below 100 mbar to obtain an amber transparent sodium silicate-polyethylene glycol composition.

[0083] In the following examples, the above sodium silicate-polyethylene glycol composition is referred to as "PEGSIL".

[0084] Experimental Example 2 (Control): Coal Particle Control (Water Only)

[0085] In this control experiment, water was used as the scrubbing liquid. The exhaust gas stream contained graded coal particles, whose particle diameter cumulative distribution function ("CDF") was as follows: Figure 2 The coal particle distribution is given as a CDF and for a specific area of ​​the Sensirion sensor (0.5 μm to 10 μm), the CDF is shown in Figure 3 Middle. Sensirion particle sensors are located in the Z-neck, Z-upstream and Z-downstream positions as described above.

[0086] Total removal for each system was determined in terms of mass flow of coal entering the system using the known mass distribution of the coal and correcting for the relative counts measured by the downstream sensors. The coal CDF for PM4 was approximately 15% of the total mass of coal particulates entering the scrubbing system.

[0087] Standard water flow rate is 15lpm to 33lpm, and air flow is 30m.s -1 .

[0088] The results obtained using water as a scrubbing liquid to remove coal particles from the flue gas stream are shown in Figure 4 and Figure 5 From these figures it can be seen that the PM10, PM4, PM2.5 and PM 1 fractions all appear to increase when the Z neck value is compared to Z upstream and even Z downstream which is located downstream of the filter screen. Without wishing to be bound by any particular theory, it is speculated that this is due to the collisions between the coal particles themselves and between the coal particles and the water droplets, resulting in a higher number of particles in these size ranges.

[0089] The total amount of coal leaving the scrubbing system is approximately 30% of the total amount of coal entering the system, so coal particles in this size range yield a beta value of 3.33 (70% efficiency).

[0090] Experimental Example 3: Coal Particle Control (Water Doped with PEGSIL)

[0091] In this experiment, the scrubbing liquid was water with PEGSIL as treatment composition (PEGSIL was added to the water system at 0.1% by mass). The exhaust gas stream contained the same graded coal particles as described in Comparative Experiment 1. The Sensirion particle sensors were located at the Z-neck, Z-upstream and Z-downstream positions as described above.

[0092] Total removal for each system was determined in terms of mass flow of coal entering the system using the known mass distribution of the coal and correcting for the relative counts measured by the downstream sensors. The coal CDF for PM4 was approximately 15% of the total mass of coal particulates entering the scrubbing system.

[0093] Standard wash fluid flow rates are 15 lpm to 33 lpm and air flow is 21 m.s -1 , measured by an anemometer directly upstream of the intake fan. Air flow is normal to the system as it determines the actual capacity and intake of particulate matter.

[0094] The results obtained for the removal of coal particulate matter from the flue gas stream using water as the scrubbing liquid are shown in Figure 6 and Figure 7 middle.

[0095] In Experiment 1 ( Figure 4 ), the particle screen removed about 39% of PM4 particles (i.e. particles of 4 μm and smaller). Figure 6 and Figure 7 As can be seen in the figure, the system with the washing liquid doped with the treatment composition reduced the PM4 particle count before the screen by about 35% ( Figure 4 and Figure 5Comparison of PM4 values ​​upstream of Z in Figure 1). Without wishing to be bound by any particular theory, it is believed that this result is obtained due to superior wetting and gravity action to remove coal particulates from the gas stream. Therefore, it can be seen that the washing liquor doped with the PEGSIL treatment composition without the use of a particulate screen is as effective as the use of a particulate screen in the control experiment, which reflects the standard water washing coal operation. In addition, the washing liquor doped with the PEGSIL treatment composition reduced the particle count after the screen by approximately 48.5% compared to the control experiment, which may be due to further interaction and wetting on the screen support. The washing liquor doped with the PEGSIL treatment composition reduced the total count of particulates by 50% compared to the water washing system.

[0096] The amount of coal leaving the scrubbing system was approximately 15% of the amount of coal entering the system, yielding a beta value of 6.66 (85% efficiency).

[0097] Experimental Example 4: Polyhalite Washing

[0098] In this series of experiments, the scrubbing performance of water was compared with that of water spiked with 0.1% w / w PEGSIL as the scrubbing liquid. The waste gas stream contained polyhalite, a mineral containing hydrated sulfates of potassium, calcium and magnesium with the formula K2Ca2Mg(SO4)4·2H2O.

[0099] The experiments were conducted at 15 liters per minute ("LPM"), 22 LPM and 33 LPM. The mass counts of particles of different particle size segments were measured at the Z neck, Z upstream and Z downstream. The beta value and efficiency Eta were then determined.

[0100] Representative graphs of measurements of water and PEGSIL-doped systems at 33 LPM are shown in Figure 8 and Fig. 9 middle.

[0101] Fig.10 and Fig.11 The results obtained are summarized along with the efficiency of the water and PEGSIL spiked washing systems. From these figures it can be seen that the system using water spiked with 0.1% w / w of the PEGSIL treatment composition as the washing liquid clearly outperforms the standard water washing system.

[0102] The efficiency of each system is represented by the beta value in Table 1 below. It is clear from the beta values ​​shown in Table 1 that for each particulate fraction, the system doped with PEGSIL provided a significant efficiency improvement over water alone at each flow rate tested. The significance of this result is that the use of a scrubbing system doped with PEGSIL can potentially allow for a significant reduction in water usage while maintaining particulate control, or can provide more efficient particulate control at the same flow rate as a standard scrubbing system.

[0103] Table 1 : Beta values ​​of different particulate fractions when water and water spiked with PEGSIL (0.1% w / w) were tested at 15 LPM, 22 LPM and 33 LPM.

[0104] Beta PM 1.0 PM 2.5 PM 4.0 PM 10 Water 15Lpm 13.76 16.00 16.47 18.18 PEGSIL 15LPM 22.50 27.99 29.30 32.38 Water 22Lpm 8.53 10.08 10.44 11.52 PEGSIL 22LPM 16.98 20.33 21.10 23.31 Water 33Lpm 1.60 1.61 1.62 1.78 PEGSIL 33LPM 2.15 2.57 2.66 2.94

[0105] Experimental Example 5: Washing of particles with high silica content (water mixed with PEGSIL)

[0106] In this experiment, the scrubbing liquid was again water with PEGSIL as the treatment composition, the dosage of PEGSIL being 0.1% w / w. The efficiency of the scrubbing system doped with PEGSIL was compared with scrubbing with water alone. The exhaust gas stream contained high silica content particulate matter obtained from a South African gold mining operation.

[0107] The particle size distribution of high silica content particles is shown in Fig.12 The critical area of ​​a wet scrubber is the airborne particulate matter, which is generally matter with a radius of less than 75 μm, often referred to as the “floating” area. Fig.12 (CDF of silica particles in the floating area) It can be seen that, expressed as total silica, about 11.5% of the particles in this sample are in the toxic inhalable range.

[0108] As previously described, high silica content particulates were introduced and the system was allowed to reach steady state. In these experiments, flushing was performed for different times using clean water as the scrubbing liquid to investigate the potential impact of PEGSIL on the scrubber net. Table 2 below shows the beta values ​​for tests 1 to 6 performed in this set of experiments.

[0109] Table 2: Beta values ​​of high silica particles with water (Test 3), water spiked with 0.1% w / w PEGSIL (Test 4) and water rinse (Tests 5 and 6)

[0110]

[0111]

[0112] From the results summarized in Table 2, it can be seen that at full steady-state saturation (Test 4), the beta values ​​when using water spiked with PEGSIL (0.1% w / w) are much higher than the beta values ​​obtained when using water as the wash liquid. Test 5 shows how the wash performance begins to decline as the PEGSIL is flushed from the system, while Test 6 shows the final performance of the water-only system when all of the PEGSIL has been flushed from the screen and there is no more PEGSIL in the system. Fig.13 The results of Tests 4, 5 and 6 are summarized, with Test 6 showing a baseline for water and Test 4 showing the best operating values ​​for the high silica content particulates with PEGSIL wash.

[0113] The above description of some illustrative embodiments of the present invention is to illustrate how to make and carry out the present invention. Those skilled in the art will appreciate that various details may be modified to produce further embodiments, but many of these embodiments are still within the scope of the present invention.

Claims

1. A method for removing particulate matter from an air flow, the method comprising the following steps: a) provide an exhaust gas stream containing particulate matter, and b) treating the exhaust gas stream with a scrubbing liquid to produce a treated gas stream having a particle concentration less than the particle concentration of the exhaust gas stream, wherein the washing liquid comprises a treatment composition, The treatment composition is a polymer-based solution comprising a cationic silicate component, and the polymer is a water-soluble polymer.

2. The method according to claim 1, wherein: The wash liquor is a solution of the treatment composition in water.

3. The method according to claim 2, wherein: The wash liquor comprises from about 0.01% w / w to about 10% w / w of the treatment composition.

4. The method according to claim 1, wherein: The wash liquor comprises from about 90% w / w to about 100% w / w of the treatment composition.

5. A method according to any one of the preceding claims, wherein: The method is a wet scrubbing method, and the wet scrubbing device is a device selected from a spray tower, a cyclone spray tower, a dynamic scrubber, a tray tower, a venturi scrubber and a perforated plate scrubber.

6. A method according to any one of the preceding claims, wherein: The exhaust gas stream has a PM10 concentration of about 5% w / w to about 30% w / w based on the total particulate matter content in the exhaust gas stream.

7. The method according to claim 6, wherein: The removal efficiency of the PM10 fraction is increased by 10% or more compared to the removal efficiency of a method using the same process parameters but excluding the treatment composition from the scrubbing liquor.

8. The method according to claim 6, wherein: The removal efficiency of the PM10 fraction is increased by 15% or more, 20% or more or 30% or more compared to the removal efficiency of a method using the same process parameters but excluding the treatment composition from the scrubbing liquor.

9. A method according to any one of the preceding claims, wherein: The exhaust gas stream has a PM4 concentration of about 5% w / w to about 30% w / w based on the total particulate matter content in the exhaust gas stream.

10. The method according to claim 9, wherein: The removal efficiency of the PM4 fraction is increased by 10% or more compared to the removal efficiency of a method using the same process parameters but excluding the treatment composition from the scrubbing liquor.

11. The method according to claim 9, wherein: The removal efficiency of the PM4 fraction is increased by 15% or more, 20% or more or 30% or more compared to the removal efficiency of a method using the same process parameters but excluding the treatment composition from the scrubbing liquor.

12. A method according to any one of the preceding claims, wherein: Exhaust gas streams may come from mining operations, grinding operations, general dust control, or incineration or digestion operations.

13. A method according to any one of the preceding claims, wherein: The scrubbing liquid is located in a direction opposite to the exhaust gas flow, in a direction identical to the exhaust gas flow, or in a direction perpendicular to the exhaust gas flow.

14. Use of a treatment composition for improving the particle removal efficiency of a wet scrubbing process, wherein: The treatment composition comprises a polymer-based solution having a cationic silicate component, and the polymer is a water-soluble polymer.

15. The use according to claim 14, wherein The treatment composition further comprises a cationic additive component.

16. The use according to claim 15, wherein The cationic additive component is a salt of a compound selected from the class of compounds including thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines and aldehyde amines.

17. The use according to claim 15, wherein The cationic additive component is a salt of a compound selected from the class of compounds including thiazoles, dithiocarbamates, dithiophosphates, thiuram sulfides, or combinations thereof.

18. The use according to any one of claims 15 to 17, wherein The cationic additive component is a salt of 2-mercaptobenzothiazole (MBT), zinc dibenzyldithiocarbamate (ZBEC), zinc dialkyldithiophosphate (ZBOP), tetrabenzylthiuram disulfide (TBzTD), diisopropylxanthogen disulfide (DIXD) or diisopropylxanthogen polysulfide (AS100), or a combination thereof.

19. The use according to any one of claims 16 to 18, wherein The salt is a sodium salt or a potassium salt.

20. The use according to any one of claims 14 to 19, wherein The cations of the cationic silicate component are sodium cations or potassium cations.

21. The use according to any one of claims 14 to 20, wherein The water-soluble polymer is an ethylene oxide polymer or a polyvinyl alcohol polymer.

22. The use according to claim 21, wherein The water-soluble polymer is polyethylene glycol.

23. The use according to any one of claims 14 to 22, wherein The molecular weight of the water-soluble polymer is between 300 g / mol and 10,000,000 g / mol, optionally between 500 g / mol and 20,000 g / mol, optionally between about 1,000 g / mol and 10,000 g / mol.

24. A washing liquid suitable for a wet washing method, wherein: The wash liquor is a solution of a treatment composition in water at a concentration of about 0.01% w / w to about 10% w / w of the wash liquor, the treatment composition comprising a polymer-based solution having a cationic silicate component, and the polymer is a water-soluble polymer.

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