JPS60211216A - Method of burning coal/water slurry - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of burning a coal/water slurry, and more particularly to a process of burning a coal/water slurry in a fire chamber of a furnace, in which an oxygen-enriched - next air relates to the combustion of a coal/water slurry that is fed into the firebox of a furnace together with a flow of air and a secondary air flow.

In other words, this invention provides a method for increasing the steam generation rate of coal/water slurry Q(,?).
This improves the overall stability of the in-line operation.

BACKGROUND OF THE INVENTION A suspension of fine particles of coal in an aqueous medium (hereinafter referred to as coal/water slurry) is a relatively new fuel that has been recommended for a variety of combustion purposes. In particular, this fuel is used to generate heat that can be used directly or indirectly to meet steam energy requirements.
l) and Krishna (Kr-1ahna) in 1982.
The 9th Energy Technology Conference and Exhibition was held February 16-18, 2017 in the District of Columbia
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As stated in Rence and EXpO,)
? It has been used for irritation. This steam is then used in Ira for industrial boilers to provide heat and utilities to generate electricity. In these studies, Marnell and Krishna
The conclusion was that this fuel burns successfully and is a practically usable alternative for burning other fuels, especially liquid fuels, in boilers.

The use of coal/water slurries in new combustion facilities is being considered more seriously than in the past because of the reduced availability of petroleum fuels and natural gas. Furthermore, the use of these slurries is under very active consideration as a replacement for petroleum-based liquid fuels in boilers. One of the key problems to be solved is how to make a coal/water gas flame behave like a flame generated by a liquid. Although this problem can be addressed by new boiler design, the earthen bottleneck may occur in existing boilers designed for oil fuels, i.e. in boilers retrofitted for coal/water boilers. In this case, a coal/water slurry is used.

One particular variable, and perhaps the most important that affects boiler operation, is the ignition time. West R.

A recent study in a paper at the ARC Symposium on Conversion to Solid Fuels, pages 82-9.1-15 (1982) of J. et al.
The ignition of pulverized coal is difficult during boiler startup. The coal/water slurry will make the ignition process more difficult during startup. Furthermore, due to the longer ignition time of the coal/water slurry, the flame becomes unstable and flickering during combustion at steady state and low load levels. Once the flame is extinguished, a boiler restart operation must be performed that consumes all valuable time. Reports of stability problems with coal/water baths, particularly low-volatile coals, were reported at the 9th Energy Technology Conference and Exhibition (9T) held in February 1982 in Washington, District of Columbia.
h Energy Technology Confe
Rence and Expo,). found in literature such as A. Barsin (J. A. Barsin).

Many earlier coal/water slurry combustion tests required one or all of the following criteria: Namely, E., T., Matsukher et al. ()! ,
, T., McHale, et, al.) Combustion and Flame
+ 45 + 121 (1982), G., Farthing, J. et al.
r,, et, al, ) reported 4 (KPRI R
(1982), preheating the furnace to 1650 F (899 C), joule. Virgin (J, Barsin) Phoenix, Halifax, Nova Scotia (Phoenix) in the 1980s
of the' 8084 Halifax.

In the Procee-clings of Coal of N-ova 5cot1a (1981),
Soi. Varnish, bread, etc. (Y, S.

Pan+ et, al.) Proceedings of the 4th International Conference on Coal/Water-Solution Combustion, Volume 2, 3rd Conference (1982) (Proceedings of
the 4th inter-national
Sympo8ium on Coal / 5lurr
y Combust -1on, Vol,■+5e
The continuous ignition flame of natural gas (providing 10 to 15 calories of heat input) described in the above-mentioned authors (1982) is based on excessive combustion air preheating (400 to 500' F ) (2
04-260°C). As the state of technology has advanced, the need for these three types of thermal support has decreased, but air preheating is still necessary and is described in the AC5 Division of Fuel Chemistry Reprint.
28.2
+ 36 (1983) -1'7-L, Kay, Manfred et al.
1, ), about 250° F.
) level. This is true even when highly volatile bituminous coal, which can be easily ignited, is charged to the coal/water slurry.

Once ignited, the coal/water slurry can only burn over a relatively narrow range of operating conditions. Coal/water slurries often have relatively high carbon conversion efficiencies (90+
%), it can only be burned with excess air. Sub-computational aspects, or efficient combustion of abundant fuel, have not been successfully achieved. This fact is
This would negate all of the advantages of staged combustion for NOx control over combustion of coal/water slurries.

Due to the relatively poor ignition and stability properties of the coal/water solution, the rejection ratio (ignition rate) of the burner is between 1:1 and 2:1.
It was in the rather low range of 1. For slurries to replace petroleum fuels, the optimal rejection ratio would have to be about 421.

G, 77-'/7g, Jr. (G, Farthin
As gJr, ) recognizes in the above quotation,
Ignition and stability are good but rejection ratio is still poor. Earl, coo lately. Manfred et al.
As acknowledged by R. K. Manfred, et. it is obvious.

Another overlapping variable that affects boiler efficiency during the use of coal/water slurries is carbon conversion efficiency. Carbon conversion controls the extent to which the combustion of coal particles ends. When the carbon conversion efficiency is 100 cm, the carbon ends up as ash as a by-product. Carbon conversion efficiency in pulverized coal-fired boilers is typically 95+, and is boiler and coal specific. Older or under-performing coals with lower volatility and higher carbon conversion efficiency are lower than these percentages and 100%.
The difference between the two represents the higher cost and wasted fuel. The carbon conversion efficiency of coal/water slurries is generally lower than that of pulverized coal, ranging from about 92% to 95%.

Other problems have been experienced with boiler operation, including:
These problems arise when non-conventional granular fuels such as wood, dust, wastewater sludge, etc. are used in relatively dry form or in slurries containing water and/or oil and combinations thereof. , can be alleviated using oxygen-enriched air.

That is, the coal/water slurry ignition time and carbon conversion improvement benefits described herein can also be obtained when using these non-conventional solid fuels or slurries made therefrom.

(Problem to be Solved by the Invention) There are very few direct patent documents about burning coal/water with or without concentrating oxygen, but there are some related patents. There are examples of citations. U.S. Patent Nos. 4,394,137 and 4,326,85
No. 6 describes the generation and purification of synthesis gas produced by partial oxidation of coal. In these cases, the coal/water mixture is fed into the reaction zone with oxygen-enriched air and the C
A high BTU syngas is produced that is primarily composed of O and H2. The conditions necessary to maximize conversion to synthesis gas include very high pressures and much lower temperatures when compared to combustion. Furthermore, oxygen enrichment is primarily used to reduce the nitrogen content of the product gas' in order to maximize the BTU value of the product gas with essentially no reaction kinetics. The reaction mechanism, conditions and rationale for using oxygen are completely different in these pox 111J compared to coal combustion for boiler operation.

U.S. Pat. No. 4,211,174 shows that coal can be oxidized in a slurry medium such as water to recover heat and sulfur-containing ash byproducts. What is disclosed is
This means that oxygen-enriched air can be used to better achieve the desired oxidation results. In this method, the temperature is very low compared to combustion (-400 to 7
00"F vs. 3000~4000'F) (-240°C ~
371 °C vs. 1649-2204 °C), the reaction of oxygen within the coal is 111 during the long surface phase in the gas/liquid reactor.
This occurs with a catalyst for the total generation of an approximately equilibrium composition of oxidizable and oxidizable components. Temperature, pressure and extremely long residence times make this process very different from direct combustion of coal.

US Pat. No. 3,941.552 describes a method of burning a coal/water/oil mixture in a furnace. This reference demonstrates that many variations of finely ground solids and/or slurry media are contemplated for commercial combustion, which can benefit from oxygen enrichment.

The present invention was made to solve the problems of the prior art described above, and provides a method for burning coal/water slag using oxygen-enriched air in the fire chamber of a furnace.

SUMMARY OF THE INVENTION The furnace includes a mechanism for supplying a coal/water slurry, a secondary air flow, and a secondary air flow within its firebox. The combustion method is: (a) A combustion flame is used to feed the coal/water slurry into the furnace firebox along with a secondary air stream and a secondary air stream for substantially complete combustion of the coal to CO2 and H2O. (b) When the primary air flow and the secondary air flow converge with the coal, the oxygen concentration of the air in the flame region is greater than or equal to 21% by volume and less than or equal to % by volume of the primary air. adding a sufficient amount of oxygen into the stream; and

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Finely pulverized coal streaks IJ with particle size to 70 microns
All combinations of water and selected chemical additives were prepared. This coal/water slurry is typically between 75% and 75%
coal. These additives were mixed together to provide slurry stability. This fuel is passed through one or more injection nozzles lO as shown in FIG.
The mixture was sprayed into the firebox combustion zone Z of the furnace shown in the figure. The coal/water slurry is conveyed through a nozzle in duct 48 at a predetermined rate along with sufficient air to sustain combustion in the secondary toroid and secondary toroid 52. Typically, additional air above this amount is required to maintain optimal combustion conditions, and this additional air is commonly referred to as excess air.

As can be seen in FIG. 1, the air supplied at the passageway barrier is referred to as primary air and the air within passageway 52 is referred to as secondary air. In the experiments described in this specification, both the secondary air flow and the secondary air flow were used in conventional concentric pulverized coal burners, which are used in industrial and most utility applications.
It was used to simulate a nozzle. Therefore, the -secondary air stream does not carry the coal/water slurry as it carries the pulverized coal, but is the first air stream that first contacts the atomized coal/water slurry, and carries this stream as the primary air stream. Similarly, the air within the passageway 52 is referred to as the secondary air flow. Although it is possible to properly burn the coal/water slurry with only one air flow in the annular passage and/or to add additional air to zone Z by other mechanisms for various controls. , for purposes of this invention, the advantage of using two air flows in ducts 50 and 52 will become apparent.

As shown in FIG. 2, fuel and air combust within a combustion zone Z, within which a stable flame must exist for efficient heat transfer purposes. Typically, a single flame may be shown as in FIG. 3, with fuel and air (both secondary and secondary) ejected from the nozzle IO. Flame 12 is characterized by fuel properties, including volatility and surface area, oxidant properties, ie, partial pressure of oxygen, and temperature and oxygen-to-fuel ratio. The fuel/air mixture can be ignited at a distance known as the distance from the end of the nozzle shown in FIG. When this length is divided by the flow rate, the answer is called the ignition time.

When various fuels are combusted in the manner described in this specification, the ignition time may vary, or
This results in an ignition time delay of approximately 0 to + milliseconds. The shorter the delay, the more stable the flame will be. As the ignition time increases, the flame may even extinguish.
Becomes unstable. Generally, natural gas and high quality liquid petroleum gas have little ignition time delay. Finely ground coal, especially bituminous coal, has longer ignition time delays than gaseous and liquid fuels, and these delays are primarily due to coal particle action, volatile matter content, and burner swirl.

For a coal/water slurry containing approximately 30 M% water, the ignition time is much longer than that of pulverized raw coal. In most cases, for highly volatile bituminous coals, finely ground raw coal will have little to no ignition time delay, whereas coal-water-sulfur coal will have an ignition time of 4 to 8 milliseconds. This causes delays. To overcome this problem, it is possible to increase the temperature of the air and/or coal/water slurry prior to entering the nozzle to reduce the ignition time during ignition in the combustion zone Z. It has been proposed to either contain solid or liquid volatiles.

The combustion efficiency based on the amount of carbon delivered to zone 2 in the coal/water slurry boiler is measured by the amount of carbon remaining in the ash. As the amount of residual carbon in a given amount of ash decreases, the carbon conversion efficiency increases. For gaseous fuels and liquid petroleum fuels, the carbon conversion efficiency is very high;
Close to 00 qb.

For finely ground bituminous coal, carbon conversion efficiency can decrease to about 95% depending on the quality of the coal. The coal/water slurry is expected to yield values somewhat similar to pulverized raw coal.

(Function) According to the invention, a coal/water slurry 17-j is injected into the combustion zone Z of the firebox, and the slurry contains coal having a particle size of about 45 to 70 microns at a rate of about 100 to 75 Nk. Contains %. The airscape passing through the annular cylinder of nozzle 10 and 52 is adjusted to exceed that theoretically required for safe combustion. As a typical example, if one gallon per hour of slurry is delivered into the combustion zone Z of the firebox, the total air flow rate is approximately 965 cubic meters per hour, which is equal to The ratio is 145 cubic feet per hour of primary airflow and 820 cubic feet per hour of secondary airflow through the annular space 52. This means that approximately 2
0% excess air. It is clear that these values depend on the coal and the type of coal/water slurry assumed.

From 0 to about 7 volumes of concentrated oxygen, preferably commercially available pure oxygen, is added to the air such that the oxygen partial pressure of the total air injected into the combustion zone of the firebox is from about 0.21 to about 7. Approximately 0.28 atm, that is, 0.21 or more l/AJ0.2
This is done so that the pressure is up to 8 atmospheres. The addition of concentrated oxygen can be carried out entirely to the primary air, but especially if an oxygen enrichment of at least 0.15 volumes of the total air is achieved through the concentration of the primary air - It can also be applied to both air and secondary air. Oxygen enrichment above 7 volumes is rarely proposed, even though it has additional benefits, because the furnace temperature becomes undesirably high and such high temperatures cause the ash to sludge. This is because the temperature changes and affects the inside of the furnace.

Such oxygen enrichment significantly changed the characteristics of the coal/water sinter flame when bituminous coal was burned. Under these conditions, the flame unexpectedly became more stable due to a significant reduction in ignition time.

This resulted in higher carbon conversion efficiency9, making the coal/water slurry mixture an excellent fuel source overall. These discoveries are explained in more detail by the following.

Example 1 A quantity of finely ground dry bituminous coal as shown in Clothing I was burned in a multi-purpose horizontal burner capable of storing fuel in solid, liquid and slurry form. The pulverized coal was conveyed in a primary air stream through the tallite 50 shown in FIG.

Tact 48 was not used during these experiments and was
.

Clothes I] 39.6 5.0 53.8 3.0 13,77
02 36.0 13.2 48.5 2.3 12.
5003 35.0 6.2 58.8 2. (114
,100429,23,966,92,815,125
524,2J4.7 61.1 5.0 12.920
6 17.4 17.8 64°8 6.0 12.5
907 6.5 8.6 B4.9 0.8 13,4
808 29.9 18.1 5], 9 0.8 --
These tests were necessary to establish standards and experimental guidance for subsequent slurry research. raw coal], 2, and 3
contained crystalline volatiles and burned in air at a rate of about 4 bonds per hour with 20 tons of excess air, with no detectable ignition time delay. Raw coals 4 and 5 had ignition times of 3 milliseconds and 7 milliseconds, respectively, when burned similarly.

However, when adding 2 volumes of concentrated air to the primary air (which was 15% of the total combustion wall air), at ignition
ll! 1 was reduced to O. Only raw coals 6 and 7 continued to experience delayed ignition times.

When additional oxygen enrichment was applied to Coal 6, it was unexpectedly found that the location of oxygen addition had a significant effect on the #I rate. For example, increasing oxygen enrichment further into the primary air
The ignition time for coal 6 was reduced to 0 when the volume was reduced to 21.6 volume (resulting in a total combustion air of 21.6 volume oxygen). but,
When concentrated oxygen was added to the secondary air stream, the results were unexpectedly poor. Oxygen enrichment level of 1.1% by volume in the secondary air (22,08 m) produced a total combustion of oxygen in the secondary air, compared to a decrease to 0 when added to the secondary air flow. So, the ignition time is from 12.1 mm 17 seconds to 10.6 mm 1
It only decreased to 7 seconds. On this basis, all oxygen enrichment tests were also conducted with oxygen added to the secondary air stream to achieve maximum benefit ft for ignition time delay.

Another interesting and unexpected result of pulverized coal combustion and primary air enrichment was the effect of oxygen enrichment on slag coloration. Slag generation was measured by inserting a water-cooled probe in front of the combustor exhaust. Slag generation occurs when enriched oxygen is added to the secondary air, as measured by ash buildup on the probe, or when premixed and added to both the primary and secondary air. Slag welding was significantly reduced when increased 5,000 ml of concentrated oxygen was added to the primary air only. For example, when burning an abnormally high ash coal such as Raw Coal 8, slag welding on the probe increases by approximately 45% when the oxygen enrichment is increased to 4%.
Diminished. This unexpected result further supports concentrating only sub-air as the preferred use of condensation.

The multi-purpose horizontal burner described in Example 1 was used to burn a coal/water slurry. It was initially apparent that ignition and subsequent stabilization of the coal/water slurry flame was difficult. However, even if it is very unstable,
Once the flame is ignited, the introduction of concentrated oxygen has a significant effect on the aerodynamics of the flame, and in certain cases
I made him lick the flames. In particular, it has been found that the flame licks or does not ignite despite the addition of oxygen into the secondary air. However, when oxygen is added to the primary air, the flame not only ignites, but ignites with a much shorter delay, and produces an overall more stable flame. In conclusion, oxygen enrichment in secondary air improves ignition delay and flame stability for coal/water slurries, combustion in air alone or oxygen addition in secondary air. The instructor was surprisingly good in comparison.

Example 2 Various coal/water slurries having the properties shown in Example 1
It was combusted with the burner described in .

Table ■ Coal (heavy layer, CWS) 69.3 75.4 69.
4 69.9 Volatile matter (weight also raw coal) 32.4 17
．． 1 35.7 32.7 Volatile content (heavy layer, CWS)
24.7 13.1 24.8 22.9 ash (heavy layer,
CWS) 4,9 13.4 5.9 6.9 Sulfur (wt%, CWS) 0.66 '1.93 0,81 0
．． 77 Nitrogen (wt%, CWS) 1.22 0.83
1.12 1.41 Heating value (Btu/bond) 11.
041 9,47Q 10,180 10.180 Lump average diameter (microns) 44 48 67 48 Four different coal l water streaks IJ i prepared by various commercial vendors
Used in test program. Coal/water gas burns at a rate of 0.10 gallons per hour (calories, 10,000
BTU 7 hours) and was sprayed with an average droplet size of approximately 100 microns. The slurry is pumped through a central passage, shown as duct 48 in FIG. Jt foggy. In preparing these fuels, the secondary air was 15 parts of the total combustion air, and the total excess air was 20%. In these combustion tests, enriched air was added to the total primary air. These results are shown in Table ■.

Table nI Tuft during ignition of coal/water slurry - Next air (15%) Concentration (oxygen by volume) Coal fuel 21st 22% 23% 2E% slurry A3
．． 6000 Slurry B 00 (X) 10.5 4.5 Slurry C8
400 Slurry D4.1000 Note 2 Ignition time is displayed in IJ seconds.

It was found that when no enriched air was added, ie when the secondary air contained 21 volumes of oxygen, a very long ignition time delay was measured. The flame that ignited was quite unstable and difficult to maintain.

When oxygen was added to the primary air at % n volume, the ignition time delay was reduced, but the ignition time delay from combustion tests with pulverized coal or turbidity was unexpectedly longer than that of the prior art. Met. For slurries A and D, the ignition time is O.
showed no delay in ignition time. When the concentrated air was further increased to produce primary air' (i-23 volume i%), the ignition time of streaks IJ and C also decreased to 0.

Streak 17 B still had a slight delay in ignition time, but showed excellent stability for all flames except B.

When all these results are interpreted, the ignition time is significantly influenced by the volatile content of the raw coal. That is, the higher the volatile content, all else being constant, the shorter the ignition time. S2S B
The volatile content was so low that even after oxygen enrichment of the primary air was reduced to 6 volumes, considerable ignition time delays were experienced; It has been found to be very advantageous and rare to reduce the ignition time delay for either coal.

Various dry pulverized coals were combusted in separate experiments in the apparatus described in Example 1 using oxygen-enriched air.

When comparing the ignition times of these coals to slurries, it was found that the ignition times of slurries were always much longer than those of the same comparable raw coal volatile content. For example, when the volatile content of the coal was about 32 to 10% by weight, the pulverized coal showed no obvious ignition time delay even when burned in air, whereas slurries A, C, and D It showed a considerable delay.

Therefore, ignition time delays cannot be predicted for coal/water slurries from pulverized inebriated coal data since no delays have been measured. The unexpected role of oxygen depletion in Suhae cannot be predicted from conventional techniques for the same reason.

Example 3 In the same horizontal combustor as described in Examples 1 and 2, the same coal and coal/water streak IJ t-combustion were performed to measure carbon conversion efficiency. In these tests, secondary air was again controlled at 15% of the total combustion air, with 20% excess air being delivered to the entire combustor. In all of these tests, the oxygen enrichment of the total combustion air was increased to about 1% by volume. That is, in experiments in which oxygen was added to secondary air, the oxygen content was up to 27.7% by volume, and in experiments in which oxygen was added with secondary air in mind, the oxygen content was up to 22.1% by volume. Ta. Unlike the experiments described in Examples 1 and 2, in which the furnace was heated entirely at cold walls (room temperature), these experiments heated the furnace at approximately 900°C.
I preheated it. The pre-injection continued for the entire duration of each experiment, which lasted approximately 1 hour. Therefore, compared to example 2,
The ignition time delay was much shorter and the flame was more stable, primarily due to the higher temperature. In this way, combustion was possible with oxygen enriched in the secondary air stream, allowing studies of carbon conversion efficiency to be carried out.

Table ■ contains experimentally determined carbon conversion efficiencies for the coal/water slurries listed in Table ■.

Data for pure coal is also shown for comparison.

Carbon conversion efficiency was measured by the following two methods. That is, (
This was done 1) by monitoring the concentration of gases CO2, CO and 02 in the exhaust gas; (2) by capturing particulates (ash) in the exhaust gas and measuring carbon in the residue. At complete combustion, there is no carbon in the ash and the cog depth has reached its highest possible value based on the final analysis of the fuel.

As the data in Table 1 shows, the concentration of 1 volume of air over the total combustion air (02 - 2 volume of starved air varies from 21 volumes of starved air to 27
．． The carbon conversion efficiency of pulverized coal flames and coal/water slurry flames was surprisingly increased with secondary air O2 up to 22.1 volumes. In particular, oxygen enrichment over a single volume when oxygen was introduced into the primary air increased the carbon conversion efficiency compared to when the secondary air was enriched with oxygen. Furthermore, the primary air oxygen enrichment of 5 volumes of oxygen (total combustion air enrichment of 0.6% by volume) was rarely sufficient to yield the maximum possible carbon conversion efficiency for three of the slurries tested. . Despite the results for pure coal, the increase in carbon conversion for slurry is much lower than the increase in carbon conversion for pure coal, even when water in the slurry is involved. What I discovered was unexpected.

Table ■ Coal and coal/water/water flame carbon conversion efficiency Oxygen enrichment, no oxygen enrichment, and oxygen enrichment air introduction carbon conversion efficiency ←) Primary air (15%) Secondary observation (85%) Negative condensation Concentrated slurry B ----8694-941----Volatile content (
Received Lk%, raw coal) 29.9 ash (N child care, raw coal)
18.1 Fixed carbon (wt%, raw coal) 51.2 Moisture (wt%)
0.8 Heating Value (Btu/Bond) 12,032 The results listed in Table 3 demonstrate the importance of introducing oxygen-enriched air and the effectiveness of slightly lower levels of oxygen enrichment.

This phenomenon is a result of the devolatilization of raw coal particles being facilitated through direct contact with the primary air stream. Since devolatilization occurs significantly within the primary air stream during and immediately after ignition, the benefits of enriched air are greatest when it is added to the primary air. At a constant combustion rate, (a)
Introducing oxygen-enriched air at the wrong rate will reduce the effectiveness of this improved method of coal combustion, thus reducing the
Concentrating the oxygen partial pressure of the subair to more than 5% by volume does not result in a further significant increase in carbonation conversion efficiency. For carbon conversion efficiency, the use of higher levels of oxygen-enriched subair would be warranted if higher combustion rates were to be achieved while maintaining high carbon conversion efficiency. This effect is illustrated by data on coal/water streaks IJA, C and DK combusted using primary air with an oxygen partial pressure of 2Fl"i%. In these tests, the carbon conversion efficiency of these slurry at a rate of 0.1 gallons per hour, it was 99+. At this concentration level, the flow rate of the coal/water slurry was:
0.1 m/h while maintaining 99% carbon conversion efficiency
It was determined that this could be increased from 0.75 gallons per hour.

EFFECTS OF THE INVENTION In summary, when relatively low levels of oxygen are added to the primary air stream, combustion air has an unexpectedly improved carbon conversion efficiency, which increases the efficiency of coal-containing fuels. It represents a new usage. Oxygen addition to the secondary air stream has also been shown to be advantageous, as would be expected from oxygen addition to the combustion zone via other mechanisms such as ducts or separate directional ducts. The larger-than-expected improvement found in condensing the , -second air stream could not have been predicted or extrapolated.

Overall, the two examples above provide evidence that oxygen addition to the primary or secondary air stream improves ignition time and carbon conversion efficiency for four types of coal/water slurries. There is. Based on this data, it is preferred to add enriched oxygen to the -substance air stream for maximum benefit.

Since the mechanism of ignition time or carbon conversion efficiency is the same for granular fuels containing carbon in the slurry phase, the advantages described in this article for coal are:
It can be concluded that we have a clear understanding of other solids that are similarly combusted. Using the same rationale, we can also conclude that: That is, the optimal oxygen enrichment for a particular coal/water slurry will depend on the characteristics of the particular slurry. For the four slurries tested, the maximum overall concentration of oxygen in the combustion zone was approximately 23.0 vol fL-4. At this level, ignition and carbon conversion efficiency were surprisingly improved. However, it is reasonable to expect that: That is, a higher degree of oxygen enrichment is required for larger burner nozzles with uniquely different nozzle designs, and for coals whose volatile content and properties differ from the lime used in the above. It may happen. Approximately 28.
It is believed that oxygen contents in the total combustion air in the range up to 0.08*'lr can be utilized to achieve the advantages discussed throughout this specification.

[Brief explanation of drawings]

Figure 1 is a schematic perspective view of a typical burner and nozzle used to inject fuel and oxidant into the furnace; Figure 2 is a schematic diagram of a conventional boiler with a firebox in which the fuel is combusted; The cross-sectional view, FIG. 3, is an illustration of the flame created by the flow of fuel and oxidant from the nozzle after ignition. 10... Injection nozzle, 12... Flame, invitation... duct, blade... - secondary annular passage, 52... secondary annular passage,
2...Firebox combustion area. Patent Applicant Air, Products, &. Chemicals, Incoholated FIG, 1 ◆ <)-Hera 4 units 1- FIG, J

Claims (8)

[Claims] (1) Oxygen in the firebox of a furnace equipped with a mechanism for supplying a coal/water slurry and primary and secondary air streams into the firebox for substantially complete combustion of the coal to CO2 and HaO. using concentrated air; (0) feeding the coal/water mixture into the furnace firebox along with a primary air flow and a secondary air flow to create a combustion flame; (b) a secondary air flow; adding a sufficient amount of oxygen into the primary air stream such that when the secondary air stream converges with the coal, the oxygen concentration of the air in the flame zone is greater than or equal to 21 percent by weight; A method of combustion of a coal/water slurry consisting of: 2. A method for combustion of a coal/water slurry according to claim 1, wherein said air is about 15 inches of the total air delivered for combustion. 3. The method of claim 1, wherein the combustion is carried out with a total excess of 20% air into the firebox. (4) The method for burning a coal/water slurry according to claim 1, wherein the coal/water slurry has a volatile content of at least a weighted amount. (5) The entire air flow is n volume! A method for combustion of a coal/water slurry according to claim 1, characterized in that the slurry is enriched with oxygen to a maximum of 50%. (6) The method for burning coal/water slurry according to claim 1, wherein the firebox of the furnace is for public utility use to generate steam for power generation. (7) The second air flow has an oxygen concentration of 21 or more
The method of burning coal/water slurry according to claim 1, characterized in that the combustion rate is up to 7.7 yen. (8) The coal/water slurry combustion method according to claim 1, wherein the firebox of the furnace is an industrial boiler for generating steam for use in work. .