JPS5822510B2 - Treatment method for sulfur-containing fuel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a method for treating fuel containing sulfur or its compounds;
In particular, the present invention relates to a method for treating sulfur-containing fuel that does not involve the generation of sulfur dioxide gas during combustion.

Sulfur or its compounds contained in various fuels are released as sulfur dioxide gas when conventionally burned and become a source of pollution, so various flue gas desulfurization methods and devices are used to remove the pollution.

However, the gas to be treated contains sulfur dioxide gas (0.5-1.
5%), as well as carbon dioxide, nitrogen oxides, and excess air.For example, approximately 13 Nm of combustion gas is generated from 11 heavy oils, and the amount of gas to be processed is enormous.

Therefore, in the case of a coal-fired power plant, for example, the construction cost of the boiler, generator, and flue gas desulfurization equipment is approximately 1:1:1, which is a huge cost. , treatment of circulating fluid containing a neutralizing agent, and other post-treatment of wastewater require a large amount of expense, which inevitably increases electricity costs.

Attempts have also been made to directly inject magnesium hydroxide powder or lime carbonate powder into the combustion furnace to desulfurize during combustion, but the desulfurization efficiency remained at around 25%, failing to achieve the objective. Not good.

For this reason, fuel costs are somewhat higher, but in some cases the flue gas desulfurization operation is omitted by using fuel with reduced sulfur content through hydrodesulfurization or other methods.

On the other hand, we are entering an era in which people are trying to switch to coal from the standpoint of energy conservation.

However, although coal is cheaper than petroleum, since it is a solid, it is impossible to desulfurize the raw material by pre-treatment as it is, and attempts have been made to liquefy it for transportation and handling reasons, but this has not yet been achieved.

This invention was made in view of the above situation, and an object of the present invention is to propose a simple and inexpensive fuel treatment method that does not involve the generation of sulfur dioxide gas during combustion.

This invention applies to fuels containing sulfur or sulfur compounds.
One or more substances selected from oxides and hydroxides of alkaline earth metals in an amount equivalent to or in slight excess of the sulfur content are mixed and maintained under reducing conditions to convert sulfur or sulfur compounds into alkaline earth metals. This is a method for treating sulfur-containing fuel that does not involve the generation of sulfur dioxide gas, and is characterized by generating sulfates of alkaline earth metals by reducing them to sulfides and then burning them.

Generally, when coal is carbonized in a reduced state to produce coke, 20 to 45% of the sulfur compounds contained in the coal are transferred into gas as hydrogen sulfide.

Therefore, the gas before purification is 10-25% (4-15%) by volume.
In addition to hydrogen sulfide (g/m3), it is known to contain 0.2 to 0.7 g/m' of organic sulfur such as carbon disulfide, carbonyl sulfide, thiocyanic acid, mercaptan, and thiophene.

Of these, hydrogen sulfide is separated as iron sulfide through a mixing tank with iron oxide and sawdust.

The remainder remains in the generated gas or product coke.

However, when coal is used directly as a fuel, that is, in an oxidized state, it is difficult to remove the sulfur contained in it through preliminary treatment, and all of this is transferred to flue gas as sulfur dioxide gas. Flue gas must be desulfurized.

On the other hand, heavy oil can be subjected to a reduction treatment such as the Claus method as a preliminary treatment, but except in special cases, it is classified into A heavy oil, B heavy oil, and C heavy oil by fractional distillation. C heavy oil has the highest sulfur content, often exceeding 3%.

Therefore, combustion of this requires flue gas desulfurization without generating a large amount of sulfur dioxide gas.

The sulfur content during combustion becomes hydrogen sulfide in a reduced state, but if it is burned as is, it becomes sulfur dioxide gas.

However, when oxides or hydroxides of alkaline earth metals are present in a reduced state, these oxides are produced, and when these oxides are burned as they are, sulfates are produced and fixed.

When injecting fuel from a burner for combustion, if the fuel injection nozzle protrudes into the furnace and a heating tube is formed between the nozzle opening and the furnace wall, the area around the heating tube and nozzle is in a reduced state, so the fuel When oxides, hydroxides, etc. of alkaline earth metals coexist in the sulfur compound, the above-mentioned sulfur compounds become sulfides, and when this is injected from the nozzle and burned, it is converted and fixed to sulfuric compounds in an oxidizing atmosphere. It is possible to prevent the generation of sulfur dioxide gas.

For this reason, in the present invention, the money-making fuel is directly mixed with fine powder of alkaline earth metal oxide or hydroxide in an amount equivalent to or slightly in excess of the sulfur content contained in the fuel. When injected from a combustion burner through a heating tube protruding into the furnace and combusted, sulfide is converted to sulfide in the heating tube and reducing flame section, and further to sulfate in the oxidizing flame section, which can be collected as molten waste in the combustion furnace. .

Generally speaking, when looking at the flame of a Bunsen lamp, a reduction flame and an oxidation flame can be clearly distinguished.

Reducing flame is a relatively low-temperature part of the flame that occurs in a stabilizing zone that is formed near the burner, while oxidizing flame is a relatively high-temperature part that is generated in a diffusion flame zone that is far from the burner. It is a part.

Some sulfide is also generated in the above-mentioned reducing flame area, but the residence time in this area is short, so sulfide generation is not complete.
It immediately enters the oxidizing flame region and sulfur dioxide gas is produced.

When fuel mixed with alkaline earth metal oxides or hydroxides is injected and combusted at high speed through a heating tube protruding into the furnace from a burner, the fuel reaches 530% in the reducing flame part of the heating tube and stabilization zone. When heated to ~580°C, the hydrogen sulfide generated therein is fixed as calcium sulfide or magnesium sulfide, which becomes an oxidizing atmosphere of over 1000°C in the oxidizing flame part of the diffusion flame region, and the sulfide is converted to sulfate. It is oxidized and dissolved, and as a result, no sulfur dioxide gas is generated in the combustion gas.

These dissolved substances and the dissolved substances specific to the fuel form a mixed molten state, which has a heavy appearance and good separability, and can be sufficiently collected by a dust collector.

However, in the conventional method, the hydrogen sulfide generated in the stabilization zone is oxidized in the air in the diffusion flame zone and becomes sulfur dioxide gas, which is released outside the furnace, which requires flue gas desulfurization treatment. .

In addition, in the method of injecting calcium oxide, magnesium hydroxide, etc. directly into the furnace, the sulfur and oxides contained in the fuel have already been burned and become dilute sulfur dioxide gas, and then come into contact with the calcium oxide, magnesium hydroxide, etc. , the reactivity was poor and the desulfurization efficiency was low.

On the other hand, if alkaline salts such as sodium are used, in the case of heavy oil, they may form low-melting salts with the vanadium contained in the oil, causing the so-called "vanadium attack" phenomenon, which may cause corrosion of the iron materials that make up the furnace. However, there is no such concern with alkaline earth metal oxides or hydroxides such as water droplets.

Similarly to heavy oil, the sulfur compounds contained in coal produce calcium sulfate and magnesium sulfate, which can be collected together with the residue in the furnace.

However, in the case of coal, it is preferable to use it as pulverized coal because it facilitates mixing with additives and is injected from a burner.

When heavy oil is used, the particle size of the additive is preferably about 40 microns, that is, about 325 mesh.

In either case, by injecting the mixture with additives through a heating tube protruding into the furnace from a burner, heating it in a reducing state, and then burning it, combustion can be performed without producing sulfur dioxide gas.

Fuels to be treated in the present invention include fuels containing sulfur or sulfur compounds, such as crude oil, heavy oil, coal, bottom, oil sand, oil sail, and COM.

Experimental Example Add 1.1 equivalent of each additive to each sample based on its sulfur content, place it in a porcelain crucible, mix well with a porcelain stirring bar, cover and heat at a maximum of 850°C. When the crucible was heated for 0.5 hours, the inside of the crucible was heated in an oxygen-deficient state and maintained in a reduced state, and then ignited and combustion occurred.

After that, after confirming that there is no unburnt material, zinc chloride solution and hot water are added to it, and it is further washed with hot water to separate the residue and washing liquid, and then hydrochloric acid is added to the residue to elute the zinc sulfide. Then, iron and aluminum were filtered out from both washing liquids and 250 CC
SO4, Ca, Mg, and Zn were measured respectively.

The total amount of S corresponding to CaSO4 and S corresponding to Zn was expressed as fixed S.

The results are shown in Table 1.

This result shows that the sulfur content in each fuel is fixed at a high yield.

*Example of a mixture of coal 1 and heavy oil 1 Heavy oil to which calcium hydroxide and magnesium hydroxide were each added in an amount of 11 equivalents relative to the sulfur content as additives was heated in a heating pipe section using a torch lamp and maintained in a reduced state. After the post-injection and combustion, the generated waste gas was released through a water-cooled circular pipe, and the sulfur dioxide gas contained therein was measured using a Kitayo type detection tube. In both cases, no color was observed, indicating that sulfur dioxide gas was not present. It was 20ppI11.

In this case, the sulfur content in the heavy oil used was 2.07%.

As described above, according to the present invention, by mixing an alkaline earth metal oxide or hydroxide with fuel and burning it, the sulfur content in the fuel is converted into sulfate and heated to a reduced state. After converting into alkaline earth metal sulfide, it is fixed and has the effect of easily and inexpensively preventing the generation of sulfur dioxide gas.

Claims (1)

[Claims] 1. One or more substances selected from oxides and hydroxides of alkaline earth metals in an amount equivalent to or slightly in excess of the sulfur content are mixed with fuel containing sulfur or sulfur compounds, and the mixture is heated under cyclic conditions. A sulfur-containing fuel that does not generate sulfur dioxide gas and is characterized by producing alkaline earth metal sulfates by reducing sulfur or sulfur compounds to alkaline earth metal sulfides and then burning them. processing method.