JPS6032668B2 - Liquefaction method of lignite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for liquefying low-grade coals containing a large amount of water (hereinafter simply referred to as lignite) such as lignite, lignite, and sub-green coal, and more specifically, a method for effectively dehydrating lignite. The present invention relates to a method for liquefying lignite, in which the pressure and heat required for dehydration and liquefaction processes are effectively used.

Many methods have been proposed to date to liquefy coal, but these prior art methods involve evaporating water in order to remove water contained in coal as a pretreatment for liquefaction. A method was taken.

In other words, there are methods in which coal is evaporated and dried in advance using a method such as flash drying, and then mixed with the solvent necessary for the liquefaction reaction, coal is mixed with a high-temperature solvent, or coal is mixed with a solvent. A method has been used in which water is evaporated by heating a fluid mixture. These evaporative drying methods are economically disadvantageous because they require a large amount of latent heat to evaporate moisture, and are particularly problematic for coals with a low degree of coalification, such as lignite, which has a high moisture content.
For example, some types of brown coal in Australia contain as much as 2k9 of water per lk9 of anhydrous lignite, and the amount of heat required to evaporate this water is 2 times the calorific value of the lignite.
It reaches as much as 5%. In addition, coals with a low degree of coalification such as lignite contain many oxygen-containing functional groups such as carboxyl groups, hydroxyl groups, and carbonyl groups, and have a high oxygen content. Therefore, when attempting to fluidize brown coal as an oily liquid as a pretreatment for liquefaction reactions, most of the coal hydrogens that make up brown coal are lipophilic, whereas oxygen-containing functional groups such as carboxyl groups are hydrophilic. There are problems in that it is difficult to mix with oil-based liquids, making the fluid unstable, and consuming a large amount of surfactant to stabilize the fluid. Furthermore, during the liquefaction reaction, the contained oxygen reacts with hydrogen added for liquefaction or hydrogen in the solvent to form water, resulting in the problem of wasting expensive hydrogen. The present invention has been made to solve the above problems, and when coal with a low degree of coalification such as lignite is heated in an atmosphere where moisture cannot evaporate, the degree of coalification progresses and the moisture content decreases. It is an object of the present invention to provide a method for liquefying lignite, etc., which can significantly reduce heat consumption, hydrogen consumption, and additive consumption by effectively utilizing the phenomenon of dehydration while in a liquid state.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated based on drawing about the case where lignite is processed as a low grade coal. As shown in Fig. 1, raw lignite is crushed and classified by a classifier 1 such as a vibrating screen and a crusher 2 such as a green mill, and then mixed with waste water (separated water) described later and a pestle tank 3. Azusa inside,
It is mixed and prepared into a water/lignite slurry. This water/lignite slurry is pressurized to a high pressure of, for example, 50 k9/lump G by the pump 4, and then sent to the heat exchangers 5, 6 to a temperature lower than the saturation temperature at the high pressure of 50 k9/lump G, for example, 26,000 g. The temperature is raised to around 300 degrees, and the water in the lignite is dehydrated into liquid form. The water/lignite slurry, whose concentration has been reduced by dehydration and viscosity by raising the temperature, is introduced into a solid-liquid separator 7 such as a cyclone, where it is separated into separated water and a lignite-rich phase, and the separated water is subjected to heat exchange. After being introduced into the vessel 5 and subjected to heat exchange with the water and the lignite slurry pressurized by the pump 4, the mixture is introduced into the fly-azusa tank 3 and mixed with the crushed lignite to form a water supply source for the water and lignite slurry. shall be. On the other hand, the separated lignite thick phase is mixed with a solvent made of oil produced by liquefaction, which will be described later, to prepare a fluid, and the fluid is sent to the gas-liquid separator 8. The pressure inside the gas-liquid separator 8 is slightly reduced (below the saturation pressure of water at the water/brown coal slurry temperature), and the water/liquid separator 8 is
The remaining moisture in the lignite slurry is evaporated to further reduce the moisture content. When the solvent made of liquefied oil is at a high temperature, residual moisture in the water/brown coal slurry can be evaporated and dehydrated by using its retained heat as a heat source. In order to further improve the dehydration rate, the pressure inside the gas-liquid separator 8 may be slightly reduced even if the temperature of the solvent is high. The gas phase separated by the gas-liquid separator 8 is cooled by a dephlegmator 9, moisture is condensed, and volatile products (including some exhaust gas) are recovered. 1 is a gas-liquid separator, 11 is a volatile product recovery pipe, and 12 is a waste water discharge pipe.

On the other hand, the fluid from the gas-liquid separator 8, that is, the oil/brown coal slurry, is at a sufficiently high temperature and pressure, but if necessary, it is further heated and raised to a temperature and pressure suitable for the liquefaction reaction, and the hydrogen supply pipe 13 A necessary amount of hydrogen is added thereto, and the mixture is fed into the liquefaction reactor 14 and liquefied. 15 is a boost pump, 1
6 is a heater.

The liquefied reactant is introduced into the heat exchanger 6 and exchanges heat with the water/lignite slurry to raise the water/lignite slurry, and the liquefied reactant is lowered to a temperature suitable for distillation. This liquefied reactant is then introduced into a solid-liquid separator 17 and separated into a liquefied liquefied reactant, a solid liquefied residual light, and water produced during liquefaction. 18 is a liquefaction residue extraction pipe, and 19 is a wastewater extraction pipe.

The liquid liquefied reactant is fed into the distillation column 20' and distilled to obtain a liquefied reactant oil such as light oil, heavy oil, etc., and a part or all of the liquefied reactant oil, such as light oil, in short, at least a portion. is recycled as at least a portion of the solvent to prepare an oil and lignite slurry. In this way, as the solvent, only the liquefied reaction oil may be used, or the liquefied reaction oil and the solvent supplied from the liquefaction solvent supply pipe 21 may be used. 22 is a bulge oil extraction pipe, 23 is a virgin oil extraction pipe, and 24 is a boost pump.

The liquefied residual light separated by the solid-liquid separator 17 is processed using existing gasification technology. can also be produced and used as a hydrogen source for use in the liquefaction process. In the lantern tank 3,
Excess water during the preparation of the water/lignite slurry is sent to a solid-liquid separator 25 such as a cyclone to separate and collect lignite particles, and then disposed of through a wastewater extraction pipe 26. Note that if the operating temperature in the liquid dehydration step is increased, the amount of dehydration increases accordingly, and almost anhydrous dehydrated coal can be obtained. It is preferable to provide means for removing trapped water. If the operating pressure in the liquid dehydration step is the operating pressure in the liquefaction step plus the pressure drop in the gas-liquid separator 8, etc., the pressure and temperature increases before the liquefaction step can be omitted.
However, it goes without saying that heating is required to maintain the temperature. If the operating conditions are set so that dehydration is carried out at sufficiently high temperature and pressure, there is almost no need to raise the temperature during the liquefaction process. However, in the present invention, since the temperature of the liquefied product oil is recovered to perform dehydration, heat supply from the outside is necessary in the liquefaction process to maintain the temperature. In any case, since the water and lignite slurry that has gone through the liquid dehydration process maintains high temperature and high pressure, it is possible to significantly save the energy needed to reach the high temperature and pressure required in the liquefaction process. Next, two other embodiment rods of the present invention,
I will explain. In this embodiment, the gas phase separated from the fluid (oil/lignite slurry) in the gas-liquid separator 8 and the water/lignite slurry boosted to high pressure by the pump 4 are heat exchanged in the heat exchanger 27. In addition to cooling and dividing the gas phase, the water/lignite slurry is also heated, making the use of heat much more effective. Other structures and functions are the same as those shown in FIG. Since the present invention is configured as described above, when lignite is heated in a non-evaporating atmosphere in the dehydration step as a pretreatment, the water content is dehydrated in a liquid state, and is consumed in dehydration compared to the conventional evaporative drying method. In addition, since high-temperature separated moisture and high-temperature liquefied reactants are used as the heating source for the water/lignite slurry, the amount of heat that needs to be added from outside the system is extremely small, which is economically advantageous.

In addition, the water and brown coal slurry produced through this dehydration process is separated in liquid form by a field liquid separator 7 such as a cyclone, so there is no temperature drop due to evaporation, and the viscosity is low due to the high temperature. The efficiency of solid-liquid separation is high because the concentration decreases over time. Moreover, due to this high solid-liquid separation efficiency, the amount of evaporated water in the gas-liquid separator 8 following this step is small, so the drop in temperature and pressure in the gas-liquid separator 8 is small, and the gas-liquid separation is The slurry from vessel 8 maintains high temperature and pressure, requiring less energy to be added when introduced into the liquefaction process. For this reason, it is significantly advantageous compared to liquefying dehydrated coal that has been once produced by conventional evaporative drying methods or liquid dehydration methods. On the other hand, the water/lignite slurry is further returned to the Takaazusa tank 3 via the heat exchanger 5, and its sensible heat is sufficiently recovered.

Furthermore, as the solvent added during liquefaction, at least a portion of the light oil produced in the liquefaction process is used, and additional hydrogen can also be produced using the residue from the liquefaction process.
It is extremely economical as there is no need to introduce large amounts of added oil (solvent) and hydrogen from the outside. In addition, lignite that has gone through the dehydration process shows a decrease in oxygen content due to a decrease in oxygen-containing groups, which is characteristic of liquid dehydration, and the proportion of hydrogen added in the liquefaction process that is wasted by reacting with oxygen is reduced. In addition, the dehydrated coal has increased lipophilicity, and it is easy to prepare an oil/brown coal slurry. In the above embodiment, the case where the solvent extraction method is used as the liquefaction method has been described, but the same effect can be obtained by combining the liquefaction dehydration step of the present invention as a pretreatment using another liquefaction method such as a direct hydrogenation method. It is something to play.

Next, embodiments of the present invention will be described.

Example Raw lignite with a moisture content of 63% is crushed to 100k9/Hr.
The following experiment was conducted using the apparatus shown in FIG. 1.

The flow rates of each part (a to j) were as shown in the following table. As explained above, since the method of the present invention employs liquid dehydration, the heat consumption and hydrogen consumption are small, and the high temperature and pressure in the dehydration process can be maintained and used in the liquefaction process. This reduces energy consumption, and since it is used to preheat the hot water and lignite slurry produced by liquid dehydration, it has excellent thermoeconomic efficiency as it is liquid dehydration. After heat recovery, a portion of this is used as a water source for preparing water/lignite slurry, and the high-temperature liquefied reactant oil is used as an extraction solvent in the liquefaction process, so the total cost is extremely large. This has the effect of saving energy.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an example of an apparatus for implementing the method of the present invention, and FIG. 2 is a flow sheet showing another example of an apparatus for implementing the method of the present invention. 1...Classifier, 2...Crusher, 3...Takatomo tank, 4...
・Pump, 5, 6... Heat exchanger, 7... Solid-liquid separator, 8... Gas-liquid separator, 9... Decentralizer, 10... Gas-liquid separator, 13. ... Hydrogen supply pipe, 14 ... Liquefaction reactor, 15 ... Boosting pump, 16 ... Heater, 17.
... Garden liquid separator, 20 ... Distillation column, 22 ... Vertical oil withdrawal pipe, 23 ... Heavy oil withdrawal pipe, 24 ... Boosting pump, 27 ... Heat exchanger . Figure 1 Figure 2

Claims (1)

[Claims] 1. A water-lignite slurry is prepared by mixing crushed lignite and water, and the water-lignite slurry is pressurized to a high pressure, and then heated to a temperature lower than the saturation temperature at this pressure. The water in the brown coal is dehydrated to reduce the brown coal concentration in the water/brown coal slurry, and then the water/brown coal slurry is separated into solid and liquid, the separated water is heat exchanged with the pressurized water/brown coal slurry, and then the crushing The separated lignite thick phase is mixed with a solvent to prepare a fluid, and the fluid is depressurized to provide a water source for the water-lignite slurry. The remaining water is evaporated and separated by using the retained heat of After liquefying the liquefied reaction product by heating and raising the temperature to a temperature of A method for liquefying lignite, comprising distilling it to obtain a liquefied reaction oil, and recycling at least a portion of the liquefied reaction oil as at least a portion of the solvent. 2. A patent claim characterized in that the gas phase separated from the fluid and the water/lignite slurry that has been pressurized to a high pressure are subjected to heat exchange to cool and partial condense the gas phase and to preheat the water/lignite slurry. The method for liquefying lignite according to item 1.