JPH04252294A - Emulsion fuel and combustion thereof - Google Patents

Abstract

PURPOSE:To provide the subject water in oil-in-water type emulsion fuel capable of ready atomization, having guaranteed excellent combustion properties and capable of realizing low NOx and low dust by combining a water-in-oil type emulsion with an oil-in-water type emulsion. CONSTITUTION:To 75-95 pts.wt. heavy oil, 25-5 pts.wt. water and 0.01-0.5wt.% nonionic surfactant are added with stirring to prepare a water-in-oil type emulsion. To 30-15 pts.wt. water and 0.01-1.0wt.% surfactant, 70-85 pts.wt. above- mentioned water-in-oil type emulsion is then added with stirring to obtain the objective water-in-oil in water type emulsion fuel. When used for combustion, the above-mentioned emulsion fuel is preheated to reduce the viscosity to <=50cSt and subsequently burnt using an atomizing burner.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emulsion fuel that suppresses the emission of air pollutants such as NOx, SOx, and soot in exhaust gas during the combustion of heavy oil, and a method of combustion thereof.

0002

[Prior Art] When a substance is burned, it inevitably produces nitrogen (N2) in the air or organic nitrogen (Fuel N) contained in the fuel or combustion target and oxygen (O2) in the air.
) to generate nitrogen oxides (NOx). The former is NO, which is produced by combining nitrogen and oxygen in the air.
x is called inorganic nitrogen oxide (thermal NOx), and the latter is called organic nitrogen oxide (fuel NOx).

[0003] The generation factors of the above-mentioned inorganic nitrogen oxides are as follows:
(1) oxygen concentration in the combustion zone, (2) combustion temperature (flame temperature), and (3) high temperature residence time of combustion gas. It is known that the production reaction of inorganic nitrogen oxides is endothermic, and the higher the temperature, the more the reaction shifts to the production side, and the longer the residence time at high temperature and the higher the oxygen concentration, the greater the amount produced. ing.

The organic nitrogen oxides are incorporated into complex aromatic nuclei in the form of pyridine, quinoline, pyrrole, indole, carbazole, etc. in nitrogen compounds contained in heavy oil and coal, and are also incorporated into sludge and garbage. is produced by the combustion of organic nitrogen in the form of ammonia and protein. It is thought that these organic nitrogens are more easily oxidized than nitrogen in the air, but the details of the pathway and intermediate products by which they are decomposed have not been elucidated. Not yet.

Accordingly, based on the above-mentioned principle of nitrogen oxide production, the production of nitrogen oxides can be suppressed by considering the following matters. (1) Keep oxygen concentration low in the combustion reaction zone by low air ratio combustion, two-stage combustion, rich flame combustion, etc. (2) Keep the flame temperature as low as possible by exhaust gas recirculation, steam or water injection, emulsion combustion, etc. (3) Shorten the residence time at high temperatures by using rapid mixed combustion, ultra-atomized spray combustion using emulsion, and the use of high-speed heat conduction type low NOx burners. (4) Reduce the nitrogen content in fuel by switching to higher quality fuel.

However, if the air ratio in (1) or the flame temperature in (2) is made too low, incomplete combustion will proceed, resulting in air pollution such as hydrocarbons (HC), carbon monoxide (CO), and soot. There is a risk of increased generation of substances, and a decrease in thermal efficiency is also a problem. Furthermore, when comparing the economic efficiency of each of the above measures, the two-stage combustion method, exhaust gas recirculation, low NOx burner, etc. require a large initial capital investment, and few small and medium-sized factories can afford it. In addition, switching to high-quality fuel will also increase the unit fuel cost, which will have a large impact on production costs.

[0007] Therefore, in recent years, attention has been focused on the emulsion combustion method, which does not require a large investment in equipment and can reduce NOx and dust.

This emulsion fuel has a water-in-oil type (
There are two types: the W/O type) and the oil-in-water type (O/W type), and research has been carried out on each type for the past 20 years.
Great results have been achieved in reducing soot and dust.

[0009]

[Problem to be solved by the invention] However, among the many studies on emulsion combustion that have been conducted to date, most of the studies on reducing NOx and reducing particulate matter have focused on light oil, whereas heavy oil has It has been shunned because of the large number of Diesel oil and kerosene, which have low emissions of NOx and soot, have little economic benefit even if they add surfactants to emulsify them, whereas heavy oil has a low organic nitrogen content. Although it is expensive, the unit price per unit of heat is much lower, and if heavy oil can be emulsified to reduce NOx and dust, extremely large benefits can be expected.

[0010] Therefore, the present inventor conducted extensive research on emulsification of heavy oil and found that in the water-in-oil type, the viscosity increases, albeit slightly, as the water content increases. and,
As the viscosity increases, it becomes difficult to atomize oil droplets during combustion. It is already known that the smaller the oil droplet size during spray combustion, the better the combustion will be, and the production of nitrogen oxides will be suppressed. I can't perform well. That is, the problem with water-in-oil emulsion of heavy oil is that the viscosity increases and good combustion cannot be guaranteed.

[0011] In addition, when trying to make an oil-in-water type emulsion of heavy oil, the viscosity of this oil-in-water type emulsion increases significantly when the water content is less than 10%, but when it exceeds 15%, the viscosity decreases rapidly. . However, although the overall viscosity of this oil-in-water emulsion can be expected to decrease depending on the water content, in the case of heavy oil, it is difficult to reduce the oil droplets to a particle size of 5μ or less, and some of them have a particle size of 100μ or more. Large oil droplets will become suspended in the water. Therefore, even if this oil-in-water emulsion is burned in a spray combustion burner, it is difficult to make it into ultra-fine particles.
OX ・The problem is that the effect of reducing soot and dust is low.

[0012] The present invention was made in view of the above, and combines a water-in-oil type and an oil-in-water type to create a new type of emulsion called a water-in-oil-in-water (W/O/W type) emulsion. The object of the present invention is to provide an emulsion combustion method that allows easy atomization using an emulsion, ensures good combustion, and achieves low NOx and soot dust.

[0013]

[Means for Solving the Problems] The present invention provides a water-in-oil type (
In order to utilize the advantages of W/O type (W/O type) emulsion fuel, a water-in-oil type (W/O type) emulsion is first obtained. but,
Due to the high viscosity of heavy oil, this water-in-oil emulsion is not suitable for combustion in a normal spray combustion burner.In order to lower the viscosity, the water-in-oil emulsion is further converted into an oil-in-water emulsion. In other words, an emulsion fuel suitable for combustion in a normal spray combustion burner is realized as a water-in-oil-in-water (W/O/W) emulsion. It is possible to lower the viscosity of heavy oil and water-in-oil emulsions by preheating, but when heavy oil is normally used as a raw material, water is required to reduce the viscosity to 50 cSt or less, which is suitable for combustion in a spray combustion burner. The boiling point of water must be preheated to 100℃ or higher, and the boiling point of water is 100℃ or higher.
If preheated to 00°C or higher, the water in the water-in-oil emulsion will evaporate during the preheating stage, making it impossible to utilize these advantages. Therefore, the present invention uses a combination of a water-in-oil emulsion and an oil-in-water emulsion to evaporate water in the water-in-oil emulsion. The present invention has realized an emulsion fuel that has a viscosity suitable for combustion in a spray combustion burner even when preheated at a relatively low temperature below the boiling point, and a method for burning the emulsion fuel.

[0014]

[Operation] Therefore, the emulsion combustion method of the present invention has a viscosity of 1
75 to 95 parts by weight of heavy oil of 50 cSt or more and 4000 cSt or less (50°C), 25 to 5 parts by weight of water, and 0 surfactant.
．． Water droplets with a diameter of 0.1 to 5μ can be uniformly dispersed in heavy oil by adding and stirring 01 to 0.5% to prepare a water-in-oil (W/O type) emulsion, and then ,
30 to 15 parts by weight of water, 0.01 to 1.0% of surfactant (
By adding and stirring 70 to 85 parts by weight of the water-in-oil emulsion (ratio to 100 parts by weight) to prepare a water-in-oil-in-water (W/O/W type) emulsion,
The above water-in-oil emulsion is made into oil droplets (including minute water droplets) with a maximum particle size of 10 to 50μ, that is, 10 to 50μ of the particle size.
A water-in-oil-in-water (W/O/W) emulsion containing water droplets with a diameter of 0.1 to 5 μm in μ-sized oil-in-water droplets is obtained.

[0015] The water-in-oil type (W/O type) emulsion has a somewhat increased viscosity compared to the raw material heavy oil, but during combustion, depending on the high temperature of 1000°C or more at the start of ignition combustion, It is known that the oil droplets burst due to instantaneous heating and evaporation of the minute water droplets they contain, becoming ultrafine particles, which exhibit the effect of reducing NOx and dust.

However, the water-in-oil emulsion described above is not suitable for spray combustion because it has a high viscosity even if it is preheated to 100° C. or less when heavy oil is used as the raw material. Therefore, by further converting this water-in-oil emulsion into an oil-in-water emulsion, that is, a water-in-oil emulsion, the viscosity is significantly lowered as shown in Figure 1, and the effect is to make spraying easier. It exhibits the following.

[0017] Even if the above oil-in-water emulsion is made into a water-in-water emulsion, the viscosity does not become suitable for combustion in a normal spray combustion burner at room temperature when the water content is 30 to 15 parts by weight. Figure 1 shows the water-in-drop type emulsion.
As is clear from the above, the viscosity becomes 50 cSt or less when the boiling point of water is below 100°C, and oil droplets can be reduced by instantaneous heating transpiration of water in the combustion atmosphere, which is an advantage of water-in-oil emulsions and water-in-oil emulsions even with preheating. The ultrafine particle formation effect is not impaired.

[0018]

[Embodiments] Next, embodiments of the present invention will be described as follows. First, the present invention has a viscosity of 150 cSt or more and 400 cSt or more.
75 to 95 parts by weight of heavy oil below 0 cSt (50°C),
25 to 5 parts by weight of water, HLB5 listed in I to IV below
~0.01~0.5% by weight of one or more surfactants selected from the group of 12 nonionic surfactants at a temperature of 30~80°C.
A water-in-oil type (W/O type) emulsion is prepared by adding and stirring at ℃.

As a specific example of the above-mentioned heavy oil, heavy oil produced in Mexico can be used, and as the surfactant, any of the nonionic surfactants listed in I to IV below may be used. I. Polyoxyethylene phenyl ether having a straight chain or branched alkyl or alkenyl group having 4 to 12 carbon atoms. II. Polyoxyethylene alkyl ether or polyoxyethylene alkenyl ether derived from a saturated or unsaturated linear or branched higher aliphatic alcohol having 8 to 20 carbon atoms. III. Polyoxyethylene alkanoyl ether or polyoxyethylene alkenoyl ether derived from a saturated or unsaturated linear or branched higher fatty acid group having 8 to 20 carbon atoms. IV. A polyoxyethylene higher fatty acid alkanolamide ether derived from a saturated or unsaturated linear or branched higher fatty acid group alkanolamide having 8 to 20 carbon atoms. Note that some conventional cationic surfactants have been proposed to be used, but these cationic surfactants are excluded from the present invention because they contain nitrogen and work against the reduction of nitrogen oxides during combustion. did.

[0020] After various trials, among the above ionic surfactants, nonyl phenol ethoxylate,
In particular, those having an HLB (lipophilicity, hydrophilicity balance) of 5 to 12 were suitable. For stirring, various mixers can be used, but one that can perform high shear stirring is desirable.

Next, 30 to 15 parts by weight of water and the following I to
In the above oil, 0.01 to 1.0% by weight (ratio to 100 parts by weight) of a surfactant containing one or more types of nonionic surfactants selected from the group of nonionic surfactants with HLB 10 to 18 listed in IV as an essential component is added. Add and stir 70 to 85 parts by weight of a water droplet emulsion at a temperature of 30 to 80°C to form a water droplet-in-oil-in-water emulsion (
W/O/W type) emulsion fuel is obtained.

[0022] In preparing the water-in-oil-in-water emulsion, first, a surfactant is mixed with water to make it homogeneous, and the water-in-oil emulsion prepared in the previous step is sequentially added dropwise into the water. Stirring was effective.

[0023] As for the surfactant used in the above process, any of the nonionic surfactants mentioned above may be used, but as in the previous step, nonionic surfactants are not particularly suitable. , one or more nonionic surfactants with HLB 10 to 18, and an anionic surfactant having -SO3 M group or -COOM group (where M is an alkali metal, alkaline earth metal, or ammonium). It is a mixture of 0.01 to 1.0% by weight of surfactants in total.
No particular difference was observed even when the ratio of nonionic surfactant to anionic surfactant was in the range of 1:5 to 50:1.

The combustion method of the present invention preheats the water-in-oil-in-water emulsion to reduce the viscosity to below the design value of a conventional spray combustion burner of 50 cSt (15 cSt in an air jet type).
~20 cSt, or 25 to 50 cSt with a steam injection type) and burn it with a spray combustion burner. A conventionally known spray combustion burner can be used as a device for this combustion, and the experimental boiler 5 shown in FIG. Furthermore, this spray combustion burner 1 is equipped with an air compressor 4.
Compressed air is fed under pressure, and the water-in-oil-in-water emulsion is sprayed into the boiler 5 together with the compressed air. Note that 6 indicates a blower that supplies air for combustion into the boiler 5, and although it is connected to the spray combustion burner 1 in the figure, it is connected to other parts of the boiler 5 near the spray combustion burner 1. You may. Further, an existing boiler may be used as the boiler 5, and if the boiler does not have the preheater 3, a boiler that can adjust the fuel temperature may be added.

[0025] Specific examples are listed below. "Specific Example 1" Mexican heavy oil A (viscosity: cSt1150 at 50°C
, asphalt content 20.02%, sulfur (S) content 3.97
%, nitrogen (N) content 0.46%, residual carbon 16.8%, L
HV9580Kcal/Kg) 84Kg was heated to 50°C, 0.3Kg of nonyl phenol ethoxylate (HLB5-12) was added as a surfactant, mixed, 15.7Kg of water was added, and high shear was applied using a line mixer. Stir to prepare water-in-oil emulsion. Next,
Nonyl phenol ethoxylate (HL) in 25 kg of water
B10-18) 0.37Kg and 0.25Kg of sodium ligninsulfonate are mixed and homogenized, then stirred for 5 minutes at 200 rpm with a paddle-type stirring blade while dropping the water-in-oil emulsion prepared in the previous step. Then, stir with a homomixer at 5000 rpm for 3 minutes.
A water-in-oil-in-water (W/O/W) emulsion weighing 25.62 kg was obtained. The viscosity of this water-in-oil-in-water emulsion was measured and was found to be 50°C as shown in Figure 1.
The cSt was 39.6, and at 70°C, the conventional cSt was 380, but the cSt was reduced to 19.5.

Then, this was burned for 3 hours under the following conditions (a) to (d) in an experimental boiler shown in "Figure 2" having a combustion chamber volume of 1.84 m3 and equipped with a flame observation window. (a) The boiler was preheated with diesel oil to a steady state for 9 hours. (b) Emulsion fuel consumption is 37
Kg/H. (c) Fuel pressure 2.15Kg/cm
2.Fuel temperature 42℃・Atomization air pressure 2.4Kg/c
m2. (d) The combustion air temperature was 32°C.

"Specific Example 2" Mexican heavy oil B (viscosity: cSt3091 at 50°C
, asphalt content 17.24%, sulfur (S) content 3.8%
, nitrogen (N) content 0.47%, residual carbon 14.61%, L
HV9660Kcal/Kg) 88Kg was heated to 55℃, 0.3Kg of nonyl phenol ethoxylate (HLB5-12) was added as a surfactant, mixed, 11.7Kg of water was added, and high shear was applied using a line mixer. Stir to prepare water-in-oil emulsion. Next,
Nonyl phenol ethoxylate (HL) in 25 kg of water
After mixing 0.37 kg of B10-18) with 0.25 kg of naphthalene sulfonic acid soda formalin condensate (degree of condensation 4.1) and homogenizing it, the water-in-oil emulsion prepared in the previous step was added dropwise using a paddle. The mixture was stirred for 5 minutes at 200 rpm using a type stirring blade, and further stirred for 3 minutes at 5000 rpm using a homomixer to obtain a water-in-oil-in-water (W/O/W type) emulsion weighing 125.62 kg. The viscosity of this water-in-oil-in-water emulsion was measured, and as shown in Figure 1, it had a cSt of 67.2 at 50°C.
, at 70℃, the conventional cSt550 becomes cSt25.
．． It dropped to 5.

Then, this was burned for 3 hours under the following conditions (a) to (d) in the same experimental boiler as in "Specific Example 1". (a) The boiler was preheated with diesel oil to a steady state for 9 hours. (b) The amount of emulsion fuel used was 35.2 Kg/H. (c) Fuel pressure 1.85
Kg/cm2 - Fuel temperature 52.52°C - Atomizing air pressure 2.4 Kg/cm2. (d) The combustion air temperature was 32°C.

In order to compare and measure the effects of both of the above specific examples, the following (( When burned for 3 hours under the conditions a) to (d), the results were as shown in the table below. (a) The boiler was preheated with diesel oil to a steady state for 9 hours. (b) Fuel consumption is 25.51 kg/h for heavy oil A: 24 kg/h for heavy oil B
Kg/H. (c) Fuel pressure is 2 for both heavy oil A and B.
．． 4Kg/cm2 - The fuel temperature was 114°C for heavy oil A and 107°C for heavy oil B. - The atomizing air pressure was 2.4Kg/cm2 for both heavy oils A and B. (d) The combustion air temperature was 30°C for heavy oil A and 32°C for heavy oil B.

[0030]

[Table 1]

[0031]

Effects of the Invention As described above, the present invention is a water-in-oil-in-water (W/O/W) emulsion, which has a low viscosity and is easy to spray.
The viscosity can be made to be 15 to 40 cSt at 80°C),
It is possible to provide an emulsion fuel that can be easily and reliably sprayed as fine particles even with an existing spray combustion device and that can perform good combustion, and a combustion method thereof.

However, in normal spray combustion, when heavy oil was preheated to a sprayable state (viscosity 50 cSt or less) and the particle size was measured with a laser, the particle size of the oil droplets was at most 30 cSt. It has a large size of ~150μ and can be sprayed with a conventionally known simple oil-in-water emulsion fuel (
Although it was possible to suppress the generation of black smoke by preheating to a viscosity of 50 cSt or less, the effect of reducing NOx was small, and it is assumed that the particle size was too large. Compared to these, in the combustion of the present invention, the particle size of the sprayed oil droplets is made smaller by the oil-in-water emulsion, and although this reduction is not sufficient, the water droplets contained in the small oil droplets are instantaneously heated and evaporated. It is possible to provide an emulsion fuel in which oil droplets burst and further become ultrafine particles, resulting in low NOx and soot and dust, and a method for burning the emulsion fuel.

[0033] As shown in Table 1 above, the improvement in combustion is remarkable, with NOx reduced by 35-41%, SO2 reduced by 22-48%, and soot reduced by 36-48%. It uses oil without a large capital investment and furthermore, without a large reforming cost, thereby reducing emissions of air pollutants.

[0034]Although the reason for the reduction in SO2 was not mentioned above, the alkali metals contained in heavy oil or surfactants react with sulfuric compounds to form sodium sulfate and potassium sulfide. It is explained that this is because sulfides such as sulfides are generated and these sulfide salts are fixed in the combustion ash, but the reason for this is not necessarily clear, and from the phenomenon perspective, a large reduction rate was confirmed as shown in "Table 1" did it.

[Brief explanation of the drawing]

FIG. 1 shows a viscosity comparison graph between raw material heavy oil and emulsion fuel of the present invention.

FIG. 2 is a partially sectional front view of an example of a boiler used in the emulsion fuel combustion method of the present invention.

Claims (3)

[Claims] Claim 1: Viscosity 150 cSt or more 4000 cSt
(50℃) or less heavy oil 75-95 parts by weight, water 25-25-95 parts by weight
Add 5 parts by weight and 0.01 to 0.5% by weight of one or more surfactants selected from the group of nonionic surfactants with HLB 5 to 12 listed in I to IV below at a temperature of 30 to 80°C. A water-in-oil type (W/O type) emulsion is prepared by stirring, and then 30 to 15 parts by weight of water and 1 selected from the group of nonionic surfactants with HLB of 10 to 18 listed in I to IV below. Surfactant with more than 1 species as essential components 0.0
70 to 85 parts by weight of the above water-in-oil emulsion was added to 1 to 1.0% by weight (ratio to 100 parts by weight) at a temperature of 30%.
Water-in-oil-in-water type obtained by addition and stirring at ~80°C (
W/O/W type) emulsion fuel. I. Polyoxyethylene phenyl ether having a straight chain or branched alkyl or alkenyl group having 4 to 12 carbon atoms. II. Polyoxyethylene alkyl ether or polyoxyethylene alkenyl ether derived from a saturated or unsaturated linear or branched higher aliphatic alcohol having 8 to 20 carbon atoms. III. Polyoxyethylene alkanoyl ether or polyoxyethylene alkenoyl ether derived from a saturated or unsaturated linear or branched higher fatty acid group having 8 to 20 carbon atoms. IV. A polyoxyethylene higher fatty acid alkanolamide ether derived from a saturated or unsaturated linear or branched higher fatty acid group alkanolamide having 8 to 20 carbon atoms. [Claim 2] In "Claim 1", after preparing a water-in-oil type (W/O type) emulsion in advance, water is added at 30 to 1
5% parts by weight and the water-in-oil emulsion 70-85
The surfactant to be mixed and stirred in parts by weight is at least one nonionic surfactant with an HLB of 10 to 18 listed in I to IV of "Claim 1" and -SO3 M group or -COOM group (However, M is alkali metal, alkaline earth metal, or ammonium), the total amount of surfactants is 0.01 to 1.0% by weight, and nonionic surfactant Claim 1, wherein the ratio of surfactant to anionic surfactant is in the range of 1:5 to 50:1.
An oil-in-water-in-water-in-water (W/O/W type) emulsion fuel described in ``W/O/W type''. 3. An emulsion fuel combustion method, characterized in that the emulsion fuel according to claims 1 and 2 is preheated to reduce the viscosity to 50 cSt or less and then burned in an atomization spray combustion burner.