JPH0149191B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the recovery and reuse of sulfur from a liquefied residue in a coal liquefaction method in which an iron-based catalyst and elemental sulfur are used as catalysts and the liquefied residue is gasified in a molten metal bath. In recent years, there has been much talk of the depletion of petroleum resources, and various energy creation studies have been conducted with the aim of creating alternative energy to petroleum. Among these, coal liquefaction is seen as the most promising because it is an abundant resource, relatively ubiquitous on the earth, and can produce products similar to petroleum-based coal, and research on it has been actively conducted. . Coal liquefaction generally involves making pulverized coal into a slurry with a solvent, raising the temperature to about 430-470°C in a preheater, liquefying the coal under hydrogen at 150-300 atm in a reaction tower, and then converting it into gas in a high-temperature, high-pressure separation tower. Light oil is separated into solvent and solids, which are further depressurized in a low-pressure separation tower, and the liquefied product is separated from the solvent, liquefied oil, and solids such as ash and end-reacted carbon (hereinafter referred to as "liquefaction residue") in the solid-liquid separation process. ) and are separated into Here, the solid-liquid separation step is a step in which a liquefied product is separated into a liquid component and a solid component by distillation, centrifugation, gravity sedimentation, etc., depending on the subsequent use. There are various methods for liquefying coal, and each method is devised to improve the yield of liquefied oil.
Recent trends include a two-stage liquefaction method in which the liquefaction process is divided into a primary liquefaction process and a secondary liquefaction process, a bottom recycling method in which the vacuum distillation residue (vacuum bottom) of the liquefied product is recycled to the liquefaction process, and a liquefaction process. The mainstream method is to add a catalyst. Among these methods, the method of adding a catalyst to the liquefaction process is technically relatively easy and has recently been the subject of much research. Catalysts include Ni-Mo, Co-Mo, Ni-W, and Co-, which are used as petroleum-based hydrodesulfurization, denitrification, and decomposition catalysts such as in the H-Coal method.
Although W and Ni-Co-Mo catalysts are sometimes used, iron-based catalysts are used because they are inexpensive, have relatively high activity, and do not need to be recovered. In particular, red mud discharged from the aluminum industry is famous and has been used for a long time in Germany and other countries. These iron-based catalysts are added to the liquefaction process in the form of a powder suspension, but it is generally said that it is in the form of iron sulfide that exerts the catalytic action, and elemental sulfur is also usually added at the same time. . The catalytic action is said to be caused by the nascent hydrogen produced by the change in the form of iron sulfide as shown in the equation below, or by the hydrogen adsorbed atomically on iron sulfide, but the details are still unclear. It is unknown. [Mechanism of morphological change of iron sulfide] Fe ₂ O ₃ +3S+3H ₂ →Fe ₂ S ₃ +3H ₂ O ......(1) Fe ₂ S ₃ +H ₂ S→2FeS ₂ +2H・ ...(2) 2FeS ₂ +H ₂ →Fe ₂ S ₃ +H ₂ S ......(3) [Adsorption mechanism of hydrogen on iron sulfide] xFe ₂ O ₃ +2yS+3xH ₂ →2FexSy+3xH ₂ O ......(4) FexSy+zH ₂ →FexSyH _2z (adsorption) ...(5) FexSyH _2z +nCoal→FexSyH _(2z-o) +nH−Coal ……(6) FexSyH _(2z-o) +n/2H ₂ →FexSyH _2z ……(7) FexSyH _2z →FexS _(yz) +zH ₂ S↑(due to reduced pressure Hydrogen sulfide desorption)...(8) When examining the form of iron sulfide in the liquefaction residue, it is mostly pyrrhotite, so an adsorption mechanism seems more appropriate, but in any case, it is similar to iron. It can be seen that sulfur plays an important role. Although sulfur is important in this way, the inventors recently investigated the balance of sulfur in coal liquefaction and found that 80 to 90% of the sulfur added with iron-based catalysts is lost to unreacted coal and ash as iron sulfide. It was found that the hydrogen gas migrated to the liquefied residue along with other substances, and only about 10 to 20% remained in the circulating hydrogen gas line. Therefore, if sulfur is brought in from outside the coal liquefaction system and added, the liquefaction process will not work, so naturally it is desirable to recover sulfur or iron sulfide from the liquefaction residue. However, recovering iron sulfide from liquefaction residue has difficult problems such as separation from coal ash, carbonaceous matter on the surface of iron sulfide, and reduction in catalyst activity due to adhesion of coal ash.
It is virtually impossible. Therefore, normally it is necessary to recover sulfur from the gasification process of the liquefied residue, which is gasified to produce the hydrogen required in the liquefaction process. Since the liquefied residue is gasified in a gasification furnace similar to the converter in Fine dust also has the advantage that it can be used as a catalyst for coal liquefaction, but since CaO is added as a sludge agent for the purpose of dissolving ash in the liquefaction residue and increasing its fluidity, the sulfur content in the liquefaction residue increases. is mostly captured in the slag as CaS, with almost no migration into the gas.
The drawback is that the sulfur content cannot be recovered at all. The present invention was invented based on this viewpoint, and is used in a coal liquefaction method in which an iron-based catalyst and elemental sulfur are used as catalysts, and the liquefied residue is gasified in a molten metal bath. By adding a slag agent CaO or MgO depending on the sulfur concentration in the slag and adjusting the basicity (CaO/SiO ₂ or MgO/SiO ₂ ) of the slag to be 1 or less (weight ratio), The method is characterized in that the sulfur content in the liquefied residue is actively transferred to the generated gas, and then the sulfur content is recovered from the gas as hydrogen sulfide or elemental sulfur and reused in the liquefaction process. The basicity of slag is the basic component CaO in slag.
The basicity is adjusted by changing _{the CaO/SiO 2 ratio} , but in some cases it can also be done by converting CaO to MgO. Ru. The basicity of the formed slag is adjusted depending on the sulfur concentration in the liquefied residue or coal slurry, but for convenience, it can also be adjusted depending on the sulfur concentration of the coal used. Existing methods such as the monoethanolamine method and hot potassium carbonate method are available for recovering hydrogen sulfide from gas, and methods for recovering elemental sulfur include the Claus method. Note that when recovering the sulfur content in the gas, dust used as a catalyst necessary for liquefaction is simultaneously recovered from the gas, and both of them are put into the liquefaction process. Next, the present invention will be explained using examples. Example 1 In a molten iron bath gasifier with a coal throughput of 8 t/day, the basicity of the slag was set to a CaO/SiO ₂ ratio of 1.5 and 1.5, respectively.
The liquefied residue with the composition shown in Table 1 was crushed to 200 mesh or less while maintaining the MgO/SiO ₂ ratio of 0.8 and 0.8.
4.7Kg/hr steam and 190N at a rate of 330Kg/hr
When gasified with oxidation of m ³ /hr, each
The gases shown in Table 2 were obtained with a gasification efficiency of 98% or more.

【table】

[Table] Example 2 Hydrogenated coal with properties shown in Table 3 that was pulverized to 100 mesh or less in a continuous coal liquefaction equipment having a reaction tower with a volume of 4 was used as a solvent (absorbing oil + anthracene oil).
50 + 50) at a solvent ratio of 2 and slurried with
It was liquefied under the following conditions and the results shown in Table 6 were obtained. However, as a catalyst, Table 5 generated from the gasifier of Example 1 was used.
Dust having the composition shown in the following was used, pulverized to 200 mesh or less, and the amount added was 2.2% per coal.
The basicity of the slag was kept at a MgO/ _SiO2 ratio of 0.8.

[Table] * Dry charcoal base

【table】

【table】

[Table] As is clear from Example 1, when the basicity of the slag was adjusted to 0.8, the gasification rate of sulfur content could be significantly increased compared to when the basicity was adjusted to 1.5. The sulfur content in the liquefied residue could be recovered and reused as hydrogen sulfide from the generated gas. In Example 2, by adjusting the basicity of the slag to 0.8, recovered and reused hydrogen sulfide and Claus process sulfur were used, as in the case of commercially available sulfur, compared to when no catalyst was used. An improvement of approximately 10-13% in liquefied oil was observed. According to the present invention, a high proportion of sulfur content, which was conventionally unrecoverable, can be recovered from generated gas and reused as a catalyst, and the effect of coal liquefaction is also extremely excellent.

Claims (1)

[Claims] 1 Using an iron-based catalyst and elemental sulfur as a catalyst,
In the coal liquefaction method in which the liquefied residue is gasified in a molten metal bath, a sludge agent CaO or MgO is added depending on the sulfur concentration in the liquefied residue or coal slurry.
The basicity of the slag that forms (CaO/SiO ₂ or
By adjusting MgO/SiO ₂ ) to 1 or less (weight ratio), the sulfur content in the liquefied residue is actively transferred to the generated gas, and then the sulfur content from the gas is converted into hydrogen sulfide or simple substances. A coal liquefaction method characterized by recovering sulfur and reusing it in the liquefaction process.