JPS6281491A - Method of dehydrating brown coal - Google Patents

Abstract

PURPOSE:To efficiently conduct the dehydration of brown coal, by conducting batchwise dehydration of brown coal with the use of a plurality of autoclaves in combination by controlling the feeding time of a fresh steam from the outside at a particular value and feeding the discharged steam into a downstream autoclave. CONSTITUTION:A plurality of autoclaves 1a-1d are used in combination. Brown coal 2 is loaded into each of the autoclave and sealed. With respect to the brown coal, a preheating step R, heating steps S1-S3, pressure reduction step D and coal discharge and introduction steps E/F are repeated in turn, thereby effecting batchwise satd. steam dehydration. At this time, when the number of autoclaves used in combination is n, steam flow heating is conducted by feeding the fresh superheated steam and/or satd. steam from the outside into the autoclave 1d only for a period of 1/n of the cycle time of the last batch in temp. elevating steps S1-S3 and concurrently discharging steam in the latter half S3. The resulting discharged gas is fed into the nearest downstream auto clave 1c.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to brown coal, lignite, subbituminous coal, etc., which have a low degree of coalification,
The present invention relates to a method for steam dehydration of organic solid materials such as high-moisture coals.

[Conventional technology]

Lignite is porous and contains a large amount of water within its capillaries, so although there are huge reserves, its use has been limited to the areas around the mountain base. In order to use it in remote areas, it is necessary to dehydrate it to reduce its weight and increase the economic efficiency of transportation.

Drying of organic solid materials is generally carried out by evaporation, but this evaporation method consumes a lot of heat because the material to be dried is heated and evaporated, and if the dehydrated product is a fine powder, it may generate dust. ,
It is not suitable for dehydrating and drying brown coal because of problems such as spontaneous combustion and coal dust explosion.

Conventionally, lignite is dehydrated by sealing it in a pressure vessel such as an autoclave and supplying high-temperature, high-pressure hot water or saturated steam without evaporating most of the water it contains.
Mainly due to the expansion of water volume and the contraction of lignite volume,
Methods of dehydration and drying without requiring latent heat are already known.

However, in the dehydration method in which lignite is heated with hot water, in order to extract the dehydrated lignite from hot water at high temperature and high pressure, it must be depressurized and cooled, and at this time some of the water is absorbed into the lignite. Because it is reabsorbed, the effect of dehydration is reduced.

The Fly Nona dehydration method, which heats brown coal with saturated steam, is
Hitherto, only the closed heating method as shown in Austrian Patent No. 190490 was known.

In this method, a condensate tank is always connected to the autoclave, and hot water consisting of liquid water separated from lignite and condensed water of steam is stored separately from lignite, and lignite is immersed in saturated steam. Since the pressure is reduced after the pressure is adjusted to a certain level, there is no re-absorption of moisture, and the remaining moisture is evaporated and reduced, making it even more effective.

However, the autoclave during the heating process was closed and not connected to other autoclaves, so steam flow within the lignite layer was poor. For this reason, if the temperature of the lignite is insufficient or the particle size of the lignite is small, the separation of the lignite and hot water is insufficient and the hot water trapped between the particles reabsorbs moisture and is thoroughly dehydrated and dried. The drawback is that it cannot be done. In this method,
Heat recovery was performed only by transferring steam or hot water from the autoclave during the depressurization process and the condensate tank integrated therewith to the autoclave during the preheating process. Therefore, the heating process in which fresh steam is supplied from outside the system is long, and sometimes two or more autoclaves in a set receive fresh steam at the same time, but in this case, heating is started later (downstream). (2) More steam flows toward the low-temperature, low-pressure autoclave, and the steam flow rate decreases during the most important final period of heating, which is one of the causes of insufficient heating of lignite and residual intergranular water. was.

Furthermore, as a characteristic of the above heat recovery method! There was a point that the depressurization time had to be equal to the preheating time. The shorter the decompression time and the more rapid the decompression, the better the dehydration rate.
In order to raise the temperature of lignite sufficiently, the preheating time could not be shortened, and the problem was not only that the dehydration rate was poor, but also that the processing time for one batch was longer than necessary.

In addition, with this closed heating method, waste heat is stored in the condensate tank as hot water without any heat recovery at the end of the heating process, which increases the capacity of the condensate tank and reduces the amount of heat that must be recovered from the depressurization process. This was one of the reasons why the decompression time had to be so long.

Therefore, since the processing capacity per autoclave is small, a large number of autoclaves are required and equipment costs are high.

Similarly, in the closed heating method, no heat is recovered until the end of heating, so the decomposition gas of lignite generated during the heating process is not discharged and is sealed inside the autoclave, reducing the partial pressure of the steam and converting it into steam. Since the temperature was lowered, it had to be extracted at the final stage of heating, which was dangerous and caused a lot of steam loss.

Among the above-mentioned problems, in order to solve the problem of residual intergranular water, the present inventors focused on the effect of intergranular water evaporation due to the flow of superheated steam, and disclosed in Japanese Patent Application Laid-Open No. 142987/1987. In this method, lignite is sealed in multiple pressure vessels, superheated steam is supplied to the first pressure vessel to dehydrate and dry the lignite, and saturated or nearly saturated steam is discharged. By supplying similar steam to the second pressure vessel or subsequent pressure vessels for saturated steam dehydration of lignite, it is possible to utilize the advantages of the conventional saturated steam dehydration method while also combining the evaporative drying method to process fine lignite. We are proposing a method of steam dehydration of lignite that makes it possible.

However, other problems remained unresolved.

[Problem that the invention seeks to solve]

The method described in JP-A-58-142987 is as follows:
Unlike the previously known closed heating method described above, this method was a flow-through heating method in which an autoclave in the temperature raising process was connected to another autoclave, but because it focused only on the effect of superheated steam, the above-mentioned (1) In the conventionally known sealed heating method, it took a long time to supply fresh steam directly to the autoclave from outside the system.

(2) There was a restriction that the decompression time must be equal to the preheating time.

(3) The amount of corpse heat that should be recovered during the decompression process was large.

(4) It was not possible to shorten the depressurization time and rapidly perform depressurization.

(5) It was not possible to minimize the processing time for 1 batch, resulting in high equipment costs.

(6) The cracked gas had to be extracted at the final stage of temperature rise.

It was not a means to solve such problems.

The present invention has discovered that in the above-mentioned flow-through heating method, fresh steam has many other excellent characteristics regardless of whether it is superheated steam or saturated steam, and has found that the above-mentioned flow-through heating method has many other excellent characteristics. In order to solve various problems, the purpose is to provide a method for dehydrating brown coal that utilizes the characteristics of the flow-through heat method.

[Means and effects for solving the problem] No. 1 of the present application
The invention provides a method for batchwise saturated steam dehydration in which a plurality of autoclaves are used as a set, and each autoclave sequentially repeats the heating process, pressure reducing process, and discharge coal process of lignite sealed therein. The number of autoclaves in the set is n, superheated steam and/or saturated steam is supplied from outside the system for a period of 1/n of the cycle time of the last batch of the heating process, and the steam is simultaneously discharged in the second half. This system is characterized in that it performs flow heating and supplies this exhaust steam to only one downstream autoclave. FIG. 1 shows an example of a time chart in this case. Note that the first
Symbols in the figures will be described later.

By limiting the supply time of fresh steam from outside the yarn to 1/n of the cycle time of one batch, more than one of a set of autoclaves is no longer supplied with fresh steam at the same time. . In the second half of the heating process, we communicated with the downstream autoclave to perform flow heating, which was the opposite of the conventional closed heating method. At the final stage of the hot process, a sufficient flow rate of steam can now be passed through the lignite layer.

Therefore, not only when this steam is superheated steam, but also when it is saturated steam, it has become possible to raise the temperature and dehydrate lignite more fully than the conventional closed heating method. By limiting the number of autoclaves to be communicated with only one downstream autoclave in the second half of heating, multiple autoclaves can be combined into one set, as shown in FIG. Autoclave operations can now be carried out without waste.

It is clear that even if the supply time of fresh steam from outside the system is shortened in this manner, a sufficient temperature raising time can be secured by heat recovery from the upstream temperature raising process.

As shown in FIG. 2, the second invention of the present application is to supply superheated steam or/and saturated steam to the autoclave IC from outside the line or from the O-I crepe located only one upstream, and at the same time supply superheated steam and/or saturated steam to the autoclave IC only one downstream. Steam is discharged to the autoclave 1b for circulation heating, and at the same time, the autoclave 1b, which is in the process of heating up one further downstream, receives the exhaust steam, and at the same time, the steam or hot water is supplied to the third autoclave 1a, which is further downstream. The feature is that it is discharged and heated through circulation. 2 is a lignite layer, and 3 is a condensate tank that stores hot water. Note that SH8 indicates superheated steam, and SS indicates saturated steam. In this case, even if the downstream autoclave rises in temperature and the steam flow rate decreases, the further downstream autoclaves are communicated, so the steam flow rate increases again, and the temperature rise and dehydration of the lignite in the most upstream autoclave is further increased. I can do it well enough.

Furthermore, when superheated steam is supplied to the uppermost autoclave from outside the thread, a high degree of superheating can be maintained in the uppermost autoclave.

Further, as shown in FIG. 3, the third invention of the present application is to supply superheated steam and/or saturated steam from outside the yarn to the autoclave 1b at the final stage of the temperature raising process, and at the same time supply steam to the downstream autoclave 1a. Discharge and conduct circulation heating,
The system is characterized in that the cracked gas that has accumulated up to that point and that has been generated during this period is not extracted from the system, but is discharged together with the steam to the downstream autoclave 1a.

It has been found through experiments that when flow heating is performed in the final stage of temperature rise, no drop in steam temperature or dehydration rate occurs even if no degassing is performed during this period. There is less danger as it does not need to be extracted during high temperature periods, and steam loss is also small. This is because the gas is sent to the downstream autoclave along with the steam97. . The gas may be removed in the downstream autoclave, or it may not be removed at this time.
It may be discharged to a lower temperature autoclave during another heating period prior to the final heating period. This discharge may be performed by circulating heating, or by accumulating gas on the liquid surface of the condensate tank and cutting off the gas. In this way, it can also be discharged together with wastewater without any degassing.

As in the first and third inventions, by performing flow heating at the final stage of the temperature raising process, it is no longer necessary to store all of the hot water as waste heat (preheating source) in the autoclave. became.

As in the second invention, by sending the waste heat sent downstream to the autoclave further downstream, the amount of waste heat to be recovered during pressure reduction can be further reduced.

Furthermore, in an autoclave that performs circulation heating, the generated hot water is sent to the downstream autoclave, eliminating the need for a condensate tank. Therefore, it becomes possible to perform heat recovery of the condensate tank separately from depressurization of the autoclave. In this way, the depressurization time is not limited by the preheating time and can be shortened considerably, reducing the cycle time of one batch by l/n.
The pressure can be reduced in a shorter time. Therefore, you can set the processing time for one batch without wasting any time.
This means that equipment costs can be significantly reduced.

As described above, by using these inventions, the aforementioned problems of the closed heating system can be solved. This will be specifically explained below using examples.

〔Example〕

Hereinafter, a case where the saturated steam dehydration method of the present invention is performed using a set of four autoclaves will be explained based on the drawings. Each autoclave is designed to repeat batch saturated steam dehydration, and the batch operations are as shown in Figure 4: preheating process (R), preheating process using condensate tank hot water (CW), and preheating process using condensate tank steam (CW). O8), a temperature raising process consisting of a heating process (St to SS), a depressurization process (D), and an exhaust coal process (E/F).

Further, as shown in FIG. 5, the condensate tank repeats batch operation in half the cycle time of the autoclave.

FIG. 6 is an operation time chart showing only a quarter of the cycle time of one batch. Condensate tanks 3a and 3b are autoclaves 1a1
The operation is different from 1b, lc, and 1cI. Next one
In the /4 cycle, condensate tank 3a operates as condensate tank 3b, and condensate tank 3b operates as condensate tank 3a, so two condensate tanks can be operated.

FIG. 7 is a partial flow sheet showing only those related to operation during this period. The first half of this period will be explained first. The autoclave 1a is an autoclave in which the temperature raising process has been completed, and the autoclave 1b is an autoclave in which raw coal has been charged. By opening pulp 8.11, steam moves from autoclave 1a to autoclave 1b, and autoclave 1a is depressurized (
D process), the autoclave 1b is preheated (R process).

The autoclave 1c is an autoclave that has completed a preheating process (CW) using condensate tank hot water, which will be described later, and the condensate tank 3a is a condensate tank that has completed receiving hot water (Sl process). pulp 10
By opening, the condensate tank is depressurized and
The hot water undergoes flash evaporation, and this steam flows into the autoclave, further preheating the autoclave.

The autoclave 1d is an autoclave that has completed the first stage heating process (S1 process) described below, and the inside is filled with high-pressure saturated steam (SS).
Superheated steam (
SHS) is supplied. However, since the pressure inside the autoclave is already high, the amount of SH8 flowing in is small. As the SS inside heats up the lignite and condenses it, the SHS increases accordingly.
However, it quickly becomes saturated due to the SS and hot water inside, which essentially becomes an SS heating process. By keeping the pulp 12 open, the hot water generated at this time flows into the condensate tank 3b and is stored there.

Next, the second half of this period will be explained. Autoclave 1a completes the depressurization process (D) and becomes atmospheric pressure, so
The dehydrated lignite is discharged, and the raw coal is then charged (to E/filtration. The autoclave 1b that has completed the preheating process (R) is transferred to the condensate tank 3a, which has been partially cooled and depressurized by flashing steam. When the lower part and the pulp 10' are opened and connected, hot water moves from the condensate tank to the autoclave, and the condensate tank is further depressurized.The hot water that flows into the autoclave passes through the lignite layer and preheats the lignite (CW process). By doing this, 100°
The wastewater becomes wastewater with a temperature of 150° C. or lower (at most 150° C. or lower) and is discharged from the pulp 13 to the outside.

The autoclave 1d is connected at its lower part to the downstream autoclave IC via pulps 11' and 8' while continuing to supply superheated steam. S in autoclave 1d
A large amount of H8 flows through the lignite layer and is heated by the SH3 flow, and SS heating quickly evaporates the water that has leached to the lignite surface and formed a water film (SS process). Then, SS is discharged from the lower part, and the lignite in the αQ autoclave 1c is heated by the SS and dehydrated without evaporation (Sl process). The hot water generated at this time is pulp 12'
is opened and allowed to flow down to the condensate tank 3b, where it is stored.

Next, the autoclave 1a performs the R process and the CW process in the same manner as described for the autoclave 1b, the autoclave 1b performs the O8 process and S1 process described for the autoclave IC, and the autoclave IC performs the S2 process and S3 process described for the autoclave 1d. In the process, the autoclave 1d is cyclically transferred to the operating state of the upstream autoclave, such as the D process described for the autoclave 1a, and E/filtration, and every autoclave repeats the same batch operation. Moreover, the condensate tank 8a is the condensate tank 3.
The hot water receiving process of the S2 process and the S1 process described for b is performed, and conversely, the condensate tank 3b performs the C81CW depressurization process described for the condensate tank 3a.

In FIG. 7, the white pulp is open in the first half of the period, the black pulp is open in the second half of the period, and the half-black valve is open in both the first half and the second half. In the second half, dehydrated coal is discharged from the autoclave 1a and raw coal is introduced.

All autoclaves mentioned above have the same configuration. That is, in any autoclave, pulp 7.8.8', 10°10', 11.1 as shown in the partial flow in Figure 7.
1', 12, 12', and 13 are provided and are connected by piping to perform the same function.

In addition, all autoclaves can be loaded with raw coal and discharged with dehydrated coal.

An example of the above connection is shown in FIG. The connection to the condensate tank through which the hot water generated in the autoclave flows is only in processes S7 and S2, and is disconnected in other processes. The hot water generated in the C8 process is stored in an autoclave and is used in the next step S.

During the process, it flows down to the condensate tank and is stored, and is finally discharged to the outside of the yarn along with other hot water during the CW process.

One condensate tank has a different original autoclave that receives hot water in the S process and the 82 process;
The main condensate tank is shared by four autoclaves. Further, the cracked gas does not need to be extracted in the S3 process, and is discharged to the 81 process together with steam. The decomposed gas may be extracted in the S1 process, or if it is not extracted in the S1 process, it will accumulate on the liquid surface of the condensate tank and will be sent to the O3 process and the CW process, so it is sufficient to extract it in these processes. Moreover, even if it is not removed at all, it will flow out with the waste water during the CW process, and there will be no problem of a decrease in the dehydration rate (however, if it is a problem if the odor is released, it is better to remove it midway). 15.16, ]7 is a valve,
] 8 is a raw coal bunker, and 20 is a dehydration diagram. As shown in the dehydration diagram, there are cases where pressure reduction is performed in two stages to improve heat recovery from waste steam. Note that F is fresh steam. Further, as shown in FIG. 10, a method may be adopted in which the first reduced pressure is communicated with the autoclave after the condex tank vapor recovery (CS). In this case, since it is communicated with a high-pressure autoclave, the depressurization time is relatively long, but the heat recovery rate of the hot water is high and the thermal efficiency is improved.

FIG. 11 shows a method of increasing the heat recovery of steam by making the second pressure reduction sufficiently long. Figure 12 shows a method of performing hot water heating before preheating the reduced pressure waste steam. Raw coal is first injected and washed with a large amount of waste hot water to prevent clogging of the waste water system. In addition to being effective, the heat recovery rate of hot water is increased, the thermal efficiency-di effect is increased, and when superheated steam is used, an example is shown in which the intergranular water evaporation effect is increased. Figure 14 shows relatively good temperature rise characteristics;
This is an example of a method that is suitable for lignite with low moisture content, has a short preheating and heating process, and can shorten the overall processing time (1 cycle time is short).

As an embodiment of the second invention, the eighth autoclave is also simultaneously sent to several autoclaves connected in series, thereby performing flow heating in three or more autoclaves at the same time, and a system for one autoclave. The supply period of fresh steam from outside is the last l/n cycle time of the Jf+ temperature process, and in this latter half (equal or unequal division), the number of autoclaves that are communicated and heated through circulation is larger than in the first half. In the first half of the final 1/n cycle time of the temperature raising process, all but three of the n autoclaves in a set of autoclaves <(n-3) are in communication. Therefore (n-4)
The first stage is the flow heating process, and in the second half, the remaining stages except for two (n
-2) A method in which the groups are in communication and therefore the (n-3) group is a flow heating process, the steam supplied (outside the system) is SH8, and the supply period is at the end of the temperature raising process. If this period is further subdivided into several periods (divided equally or unequally), the number of autoclaves connected downstream and the number of simultaneous circulation heating Here are some ways to increase the number of autoclaves.

Further, as an embodiment of the third invention, there is a method for extracting decomposed gas from the most downstream autoclave communicating with the autoclave at the final stage of the temperature raising process, The hot water generated in the most downstream autoclave and flowing down is sent from the most downstream autoclave communicating with the autoclave of A method in which the hot water in the condensate tank is sent to another autoclave together with the hot water and/or steam when heat is recovered to another autoclave as a liquid or/and flashed as steam. , a method in which decomposed gas is finally discharged to the outside together with waste water, a method in which steam and/or hot water from a condensate tank is recovered,
One example is a method in which the decomposed gas is extracted outside the yarn.

Examples and comparative examples will be described below.

Example 1 Using a dehydration apparatus consisting of four autoclaves and four condensate tanks, dehydration operation was carried out according to the time chart shown in FIG. 15. Only two of the four condensate tanks were used. Discharging coal operation (discharging dehydrated coal from the autoclave and introducing new raw coal)
The more time you take for E), the easier it will be to drive, but if E is taken by 2
The experiment was conducted with the time set to 0 minutes. In addition, the present inventors have
As shown in Publication No. 7794, pressure reduction operation (L
It is proposed that the dehydration rate can be improved by performing D + 2D) rapidly, but by determining the time allocation in this way, the decompression time was reduced to 20 minutes, making it possible to decompress rapidly. . The experimental conditions and results were as shown in the left column of the following table.

(The following is a blank space) Comparative Example 1 Using the same dehydration apparatus as in Example 1, a dehydration operation was carried out according to the time chart shown in FIG. 16. However, all four condensate tanks were used. One hour of depressurization was 40 minutes. The experimental conditions and results were as shown in the right column of my ex-husband.

From the above results, in the conventional method, the waste steam and hot water generated during the depressurization operation are recovered as a preheating source for the preheating operation of another autoclave, so as shown in the time chart of Fig. 16, ID and E are The time divisions must be the same. In other words, if the total depressurization time (ID and 2D) is longer than the coal discharge time, rapid depressurization operation cannot be achieved, or if rapid operation is shortened (only part of the ID time segment is operated). In this case, the autoclave is not operated for a long time, which reduces equipment efficiency, and the temperature cannot be raised smoothly. In the method of the present invention, the operation time distribution within the 1/4 cycle of the time chart can be adjusted, and the autoclave can be operated so that there is no idle time, so the overall processing time can be shortened.

As shown in the above experimental results, according to the method of the present invention, the total processing time could be shortened and the dehydration rate was improved.

It was confirmed that the equipment capacity was improved by more than 33% for equipment of the same scale. The first reason for the improved dehydration rate is that
This is because the depressurization time was shortened to 20 minutes as mentioned above, and the depressurization was performed rapidly.Secondly, the steam supply from the outside was reduced.
cycle/L'1/4/120, first stage heating process S
This is because, in No. 1, exhaust steam from the third stage heating step S3 was received, so the steam circulated inside the autoclave in S3, and the lignite was sufficiently heated. By the way, in experiments using the conventional method, the temperature rise time (from IR to S3t:)
was 100 minutes, whereas in the experiment using the method of the present invention, the temperature increase time (from IR to 83) was only 80 minutes. In this experiment, the coal discharge time was kept the same from the viewpoint of operability, but if the water content of the dehydrated coal was to be the same as in the conventional method, the cycle time for one batch using the method of the present invention would be even longer. It turns out that it can be short.

Example 2 Raw coal was Australian Bikul-IJ brown coal (moisture 65.5wt).
%), pressure 45 k'j/cyA G, superheat degree 20
Using superheated steam at °C, operation was performed according to the same time chart as in Example 1 (Fig.
We conducted an experiment in which all 7 diagrams were connected in half. Thereafter, the operation was returned to the time chart shown in FIG. 15, the autoclave 1 was depressurized, the dehydrated coal was discharged, and the water content was measured.

The moisture content of the dehydrated coal in this case (four stages broken) was 21.7 wt%. Furthermore, as a result of conducting a two-stage communication experiment under similar conditions, the moisture content of the dehydrated carbon was 23.6 wt%.

As mentioned above, by discharging superheated steam to the autoclave [C] which is sufficiently heated with saturated steam, and to the two downstream autoclaves ll) and la, the flow rate of superheated steam to autoclave 1d is increased. The water trapped between lignite particles was evaporated to dryness, and the dehydration rate was further improved than when the water was evacuated to only one downstream autoclave.

According to Example 2, the number of autoclaves is 4 or more, and 2
The effectiveness of a method of communicating in more than one stage, for example, the method shown in FIG. 13, is recognized.

〔Effect of the invention〕

Since the present invention is configured as described above, whether the steam supplied from outside the system is saturated steam (SS) or superheated steam (SHS), the steam is removed at the final stage of the temperature raising process. is sufficiently distributed through the lignite layer, and at this time, cracked gas does not stagnate, so the temperature of the steam increases, causing the temperature of the lignite to rise.
Sufficient dehydration occurs.

In addition, since hot water, which is a preheating source, is recovered to the autoclave far downstream during the temperature rising period, the depressurization time can be shortened, and the exhaust heat from the circulation heating process can be collected in an orderly manner.
Since it is recovered at an appropriate timing, it is possible to eliminate wasteful operating time while maintaining high thermal efficiency, and to reduce equipment costs.

Note that in FIGS. 9 to 14, the period indicated by a blank space in the condensate tank (for example, the period before the O3 period of the condensate tank 6a in FIG. 9) is a period in which nothing is performed. That is, during this period, all valves of the condensate tank are closed and it is not connected to any autoclave, to any condensate tank, or to the outside world. Therefore, the steam and hot water inside the container remain in their previous state, except for being slightly cooled by radiation from the heat-insulating surface of the container.

Of course, such wasted time should be kept to a minimum. In particular, experiments conducted by the present inventors have revealed that when such wasted time occurs in an autoclave, an adverse effect such as re-absorption of moisture occurs in the lignite occurs. On the other hand, in the case of a condensate tank, there is no significant effect other than a decrease in its utilization efficiency.

In the present invention, the autoclave in the process of increasing its temperature is supplied with steam from the upstream autoclave at a higher temperature, so that the autoclave's wasted time as described above does not occur at all. This is one of the important effects of the present invention.

Although the Mata condensate tank has some wasted time and its utilization efficiency has decreased, this has not led to an increase in the number of condensate tanks required. In other words, there is virtually no adverse effect. In fact, compared to the conventional method, wasted time is significantly reduced.

[Brief explanation of drawings]

Fig. 1 is a time chart showing an example of the first invention of the present application, Fig. 2 is a flow sheet showing an example of the second invention of the present application, and Fig. 6 is a flow sheet showing an example of the sixth invention of the present application. , FIGS. 4 to 14 show specific examples of the present invention. FIG. 4 is an explanatory diagram showing one batch operation of an autoclave, FIG. 5 is an explanatory diagram showing one batch operation of a condensate tank, and FIG. The figure shows 1/4 of the cycle time for one batch.
Operation time chart shown only for the period of 7th
The figure is a flow sheet showing the equipment related to the operation of Figure 6, Figure 8 is a flow sheet showing details of Figure 7, and Figures 9-
FIG. 14 is a time chart of a specific example, FIG. 15 is a time chart of Example 1, FIG. 16 is a time chart of Comparative Example 1, and FIG. 17 is a flow sheet of Example 2. 1a't 1b110% 1a% 1es If-・
Autoclave, 2... Lignite layer, 3.3a, 3b... Condensate tank, 4.5.6.7.8.8.10.
10.11, 14...External evaporation source, 18...Raw coal bunker, 20...Dehydrated coal bunker

Claims (1)

[Scope of Claims] 1. A set of multiple autoclaves, each autoclave is a heating process and a depressurizing process of lignite sealed inside.
In a method of batchwise saturated steam dehydration by sequentially repeating the discharge coal process, the number of autoclaves in one set is n, and the cycle time of the last batch in the heating process is 1/n.
Superheated steam and/or saturated steam is supplied from outside the system to the autoclave for a time of
A method for dewatering lignite, characterized by supplying it to only one downstream autoclave. 2 A set of multiple autoclaves is used to heat up and depressurize the lignite in which each autoclave is sealed.
In a method of batchwise saturated steam dehydration by sequentially repeating the discharge coal process, superheated steam and/or saturated steam is supplied to the autoclave from outside the system or from only one upstream autoclave, and at the same time, steam is discharged to the downstream autoclave. The dehydration of lignite is characterized in that a downstream autoclave in the temperature raising process that receives this exhaust steam also discharges steam or hot water to a third autoclave further downstream to perform circulation heating. Method. 3 A set of multiple autoclaves is used to heat up and depressurize the lignite in which each autoclave is sealed.
In a method of batchwise saturated steam dehydration by sequentially repeating the discharge coal process, at the final stage of the temperature raising process, superheated steam and/or saturated steam is supplied from outside the system to the autoclave, and at the same time steam is supplied to the downstream autoclave. A method for dehydrating brown coal, which is characterized by discharging the coal, performing circulation heating, and discharging the cracked gas that has accumulated and generated during this process to an autoclave downstream together with steam, without extracting it from the system. 4. The lignite dehydration method according to claim 1, 2 or 3, wherein the decompression time is shorter than 1/n of the cycle time of one batch.