JPS60110787A - Fine fuel powder - Google Patents

Abstract

PURPOSE:To enable petroleum coke having poor combustibility as fuel to be burnt in oil-fored boilers, by mixing petroleum coke with pitch, crushing the mixtue and adjusting its ash content and volatile matter content. CONSTITUTION:Petroleum coke is mixed with pitch in such a proportion that petroleum coke accounts for not more than 80wt% of the mixture. The mixture is crushed into a powder having such a particle size distribution that at least 70% of particles is passed through a 200-mesh sieve. The ash content and the volatile matter content of the powder are then adjusted so that the ash content is 2wt% or below and the volatile matter content is 20wt% or above. Examples of the petroleum coke are fluid coke, flexi coke and delayed coke abtd. by thermally cracking heavy oil by a coking process. Examples of the pitch are asphalt as solvent deasphalting residue, coal pitch and petroleum pitch obtd. by thermally cracking heavy petroleum oil with superheated steam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pulverized fuel, and particularly to a pulverized fuel that uses petroleum coke, which has poor combustibility, as fuel and can be combusted in an oil-fired boiler.

[Background of the invention]

Heavy oil has been mainly used as a fuel for combustion furnaces such as boilers, but due to the deterioration of the oil situation in recent years, research is being conducted on technology for using solid fuel in combustion furnaces. Pulverized coal or a mixed fuel of heavy oil and pulverized coal are generally known as solid fuels, but since treatment of the large amount of ash contained in coal is a problem, recently they have become virtually free of ash, resulting in lower fuel costs. Residues from the low-impact oil refining process are attracting attention.

However, although pitch with a high volatile content among petroleum refinery residues can be pulverized to achieve combustibility comparable to that of heavy oil, petroleum coke such as delayed coke and flute coke with a high 4F content cannot be used as fuel for cement kilns, etc. However, due to its low volatile content, it has poor combustibility, and therefore it is difficult to use it as a fuel for heavy oil-fired boilers.

From this point of view, as a method to efficiently burn petroleum coke by mixing petroleum coke with poor combustibility and fuel with good combustibility, it is possible to create a slurry fuel of pulverized coke and heavy oil, or to mix pulverized coke with gas or heavy oil. One possible method is to use it as a combustion improver. However, in the former case, when the heavy oil is atomized into the furnace, it adheres to the surface of the fine coke, and the heavy oil on the surface of the coke starts to burn first, and after the heavy oil has finished burning, the coke combustion starts. It will be started. Also, in the latter method, the combustion speed of the combustion improver is extremely fast compared to the combustion speed of coke. Therefore, no matter which method is used, since the combustion of highly combustible fuel such as heavy oil or gas has been completed by the time the fixed carbon component of coke is combusted, it is not possible to effectively increase the combustion rate of the fixed carbon component of coke. The drawback is that it cannot be done. Therefore, the current situation is that the combustion technology for using petroleum coke in ordinary combustion furnaces has not yet been established, and there has been a problem that petroleum coke cannot be used as a fuel.

[Purpose of the invention]

The present invention focuses on the above-mentioned conventional problems and provides a pulverized fuel that can be used as fuel for ordinary furnaces by imparting desired combustibility to petroleum coke, which has low volatility and poor combustibility. The purpose is to

[Summary of the invention]

The present invention is based on the discovery that a composition obtained by mixing petroleum coke, which has poor combustibility, with pitch, which contains a large amount of volatile matter and has excellent combustibility, has the desired combustibility.

That is, the pulverized fuel according to the present invention includes petroleum coke and pitch in a mixing ratio of petroleum coke of 80% by weight.
Mixed with the following, the particle size is 70 tons under a 200 mesh sieve
% or more, and the composition was adjusted to have an ash content of 2 weight % or less and a volatile content of 20 weight % or more.

Petroleum coke, which is the first component of pulverized fuel, has a low volatile content, and as it is, it has poor combustibility in normal combustion furnaces such as heavy oil or coal-fired fuel.
The amount of M is % or less. Furthermore, the ash content is about 2% or less. As the petroleum coke, delayed coke, fluid coke, flexi coke, etc. obtained by thermally decomposing heavy oil by a corking method may be used.

In addition, pitch, which is the second component of pulverized fuel, has an auxiliary combustion effect on coke, and has a volatile content of 30M%.
In the above, a material having an ash content of about 2% by weight or less is used. Specifically, petroleum pitch obtained by thermally decomposing petroleum-based heavy oil using superheated steam, solvent deasphalted asphalt, coal liquefied pitch, etc. are used.

The pulverized fuel according to the present invention is prepared by mixing the petroleum coke as the first component and the pitch as the second component. This mixing ratio is not uniquely determined depending on the types of both components, but in short, the volatile content of the mixed pulverized fuel is 20%.
They are mixed in an amount of at least 25% by weight, preferably 25 to 35% by weight. More specifically, petroleum coke is 80~zoo
m%. This is because if the volatile content is less than 20% by weight, the combustion rate will be slow, stable ignition and flame maintenance will be difficult, and char will also increase. In addition, increasing the mixing ratio of pitch increases the volatile content, which improves flammability and results in sifting, but this conversely decreases the monthly premium for petroleum coke, so petroleum coke with poor combustibility This does not meet the purpose of the present invention, which is to increase the combustion efficiency of ordinary furnaces.

The ash content of the blended pulverized fuel is primarily limited by the combustion equipment. That is, the ash content of the mixed fuel composition may be 2% by weight or less, preferably 1% by weight or less. If fuel with an ash content of 2M% or less is used in an oil-fired boiler, the amount of ash deposited in the furnace will be small, and it will be sufficient to remove it during regular inspections, and heat transfer will not be inhibited by the deposited ash. This eliminates the effect on heat generation and the circulation of heated materials, and reduces the noise of boiler operation. In addition, when there is a large amount of ash in the fuel, it is necessary to lower the flow rate of combustion gas in the boiler to a speed that does not cause heat transfer tubes to become sluggish due to ash, or to lower the furnace outlet gas temperature to below the ash sag degree. It may be necessary to install the boiler to maintain a sufficiently low level or to change the specifications to a coal-fired boiler. Therefore, having an ash content of 2% by weight or less is an extremely significant practical advantage.

The fuel, which consists of petroleum coke and pitch, is mixed and pulverized into a fine powder, but there are no restrictions on the mixing or pulverizing method (each component may be pulverized and mixed, or it may be mixed in the desired ratio). They may be crushed later. However, if the petroleum coke has poor crushability, coarse particles of petroleum coke with poor combustibility will remain if crushed after mixing, so it is preferable to crush them separately and then mix them. There are no particular restrictions on the pulverizer, but if the softening point of the pitch used is low, an impact-type one may be used, for example, to prevent softening and fusion during pulverization.

Here, the particle size of the pulverized pulverized fuel is 70% by weight or more under 200 mesh, preferably 8ON amount % or more. If the particle size is less than 703i% below the 200 mesh surface, it means that large particles are included.In particular, if large particles of petroleum coke are included, it will take a long combustion time and a large amount will be in the exhaust gas. This is because it would be undesirable for Char to step on it. If the particle size is extremely small, for example, 10 microns or less, although this is preferable in terms of combustion, the equipment load on the pulverizer becomes large and this is not necessarily advantageous. From the viewpoint of combustibility, it is preferable that the petroleum coke is ground finer than pitch when the components are individually ground.

The pulverized fuel having such a structure is a solid composition in which petroleum coke and pitch are uniformly mixed, and since it contains an appropriate amount of volatile matter, it has excellent combustibility and exhibits good combustion characteristics in a normal furnace. In particular, since pitch is mixed with petroleum coke, which has poor ignitability, a pulverized fuel with excellent ignitability as a whole can be obtained.

In combustion of such pulverized fuel, when it is supplied from the burner to the furnace, the temperature of the fuel increases due to radiant heat and the volatile matter is gasified.This generated gas surrounds the particles, and due to the presence of oxygen, they are immediately ignited. and combustion begins. Following the combustion of the volatile matter, the combustion of the fixed coal begins. Here,
The combustion rate of solid fuel is mainly determined by the oxidation reaction rate on the surface of the fuel, and therefore, it is thought that if the temperature of the top surface of the particles is increased, the combustion rate will be reduced. Therefore, compared to petroleum coke which has a high increase temperature and a slow burning rate, since it contains a large amount of volatile matter and is mixed with pitch which has a fast burning rate, the combustion heat of the pitch that burns first causes the petroleum coke to burn. It is possible to increase the surface temperature and increase the combustion rate, thereby making it possible to effectively burn petroleum coke in a normal furnace.In particular, pitch
Unlike combustion improvers such as heavy oil and gas, which burn at extremely high speeds, it has the characteristic that its combustion speed is relatively close to that of petroleum coke6, so it can effectively improve the combustibility of petroleum coke. .

Furthermore, since the ash content of the pulverized fuel is extremely low at 2 M%, ash treatment in the furnace poses almost no problem, and the equipment used for conventional heavy oil firing can be used as is, making it economically and practically possible. The benefits are great.

[Embodiments of the invention]

Examples of the pulverized fuel according to the present invention will be described in detail below.

Example 1 Petroleum coke containing 9.7% by weight of volatile matter was used as the first component, and petroleum coke containing 40.8% by weight of volatile matter was used as the second component. The properties of each are shown in Table 1.

Figure 1 shows a combustion test device for a mixed fuel of petroleum coke and petroleum pitch. First, there is a bunker 10 which separately accommodates petroleum coke as a first component and petroleum pinch as a second component.
12, the flow rate is adjusted by each feeder so as to achieve a desired mixing ratio, and the fuel is sent to a fuel tanker 16 via a belt conveyor 14. The fuel bunker 16 is connected to a crusher 18 to crush the mixed fuel.

The finely pulverized fuel is transferred to a 77-ton 2 built-in pulverizer 18.
0 through the primary air stream to the burner 22;
It is injected into the furnace 24. The burner 22 used was a horizontally installed fine powder type burner. In addition, in order to supply secondary air to the injected fuel, a secondary air fan 26 is arranged, and after exchanging heat with the exhaust gas in an air preheater 28 provided on the outlet side of the furnace 24, the secondary air is supplied. Raise the temperature to an appropriate temperature and turn on burner 22.
It is supplied into the furnace 24 via the surrounding wind box 30. The furnace 24 imitates a water tube boiler, and a portion of the furnace wall is a water-cooled wall. The exhaust gas from the furnace 24 passes through the air preheater 28 and is then sent to the flue gas desulfurization device 3.
After being desulfurized in step 2, it is released into the atmosphere from the chimney 34.

Using the above device, combustion was started in advance with a petroleum pitch of 1oox'i'% to preheat the furnace 24, and then the fuel was switched to a mixture of petroleum coke and petroleum pitch, the mixing ratio was changed, and the combustion state was observed. . In addition, the gas inside P is sampled by a sample gas sampling probe installed at the inlet of the preheater 28,
5CO temperature and amount of soot in gas and combustion rate calculated from unburned part of soot and dust Q. Mixing ratio of mixed fuel of petroleum coke and petroleum pitch used in combustion test, industrial analysis values, measurement results of particle size and combustion rate are shown in Table 2 below.

The combustion status of the mixed fuel can be determined by changing the mixing ratio of petroleum coke (
As the flame length increases, the oil pinch 1
00% by weight (approximately 1.5m at 40.8% by weight volatile content)
It was observed that for petroleum coke 50% by weight (volatile content 25.6% by weight), the length was approximately 2 m, and for petroleum coke 0% by weight (volatile content 19.3% by weight) it was approximately 3 m. At this time, the flame was maintained stably even with 0.0% petroleum powder, and the flame at the tip was clear. However, although petroleum coke can maintain combustion up to 80% by weight (volatile content: 15.9% by weight), flame cannot be maintained when it exceeds 80% by weight (volatile content: 15.9% by weight).
became. On the other hand, the combustion rate showed a high value of 99% or more up to 70% by weight of petroleum coke, as shown in Table 2, and was 78% for the mixed fuel containing i% of BO by weight.

Example 2 Petroleum coke with a volatile content of 1 g and 9 M% by weight was used as the first component, and petroleum pitch with a volatile content of 50.4% by weight was used as the second component. Each property is as shown in Table @3.

Using petroleum coke and petroleum pitch with the above properties,
A combustion test was conducted using the apparatus shown in Figure 1 in the same manner as in the example. Table 4 shows the mixing ratio, industrial analysis value, particle size, and combustion rate measurement results of the mixed fuel used in the combustion test.

The combustion conditions of the mixed fuel were as follows: As in Example-J, the flame length became longer (as the proportion of petroleum coke became higher).
% by weight), petroleum pitch is 100% by weight (volatile content 50.
6% by weight), but a stable flame was maintained and a good combustion state was achieved. Moreover, the combustion rate at this time was 99% or more. Furthermore, when the mixing ratio of petroleum coke was increased to 90% by weight (volatile content: 18.0% by weight), combustion was able to continue, but the flame was not stable, a state of oscillating combustion was observed, and the combustion rate was 94%. %Met.

[Effect of ejection ψ]

As described above, according to the present invention, it is possible to obtain a pulverized fuel that can be burned in an oil-fired boiler using petroleum coke as fuel.

[Brief explanation of the drawing]

The drawing is a configuration diagram of a pulverized fuel combustion test apparatus according to this embodiment. lO・12...Bunker, 18...Crusher, 22...
...burner, 24...furnace. Agent Tatsuyuki Unuma (and 1 other person)

Claims (1)

[Claims] (11 Petroleum coke and pitch are mixed so that the mixing ratio of the petroleum coke is 80% by weight or less, and the resulting mixture is pulverized to a particle size of 70% or more under a 200 mesh sieve, and the ash content is 2% by weight.
A pulverized fuel characterized by having a volatile content adjusted to 20% by weight or more as follows.