JPS6281490A - Method of dehydrating brown coal - Google Patents

Abstract

PURPOSE:To effectively dehydrate brown coal, by conducting batchwise dehydration of brown coal using a plurality of autoclaves in combination by feeding steam into the upper portion of an autoclave, discharging the steam from the lower portion thereof and feeding the discharged steam into the upper portion of the downstream autoclave. CONSTITUTION:A plurality of autoclaves 1a and 1b are used in combination. Brown coal 2 is loaded into each of the autoclaves and sealed. With respect to the brown coal, temperature increase, pressure reduction and coal discharge and introduction steps are repeated in turn, thereby effecting batchwise satd. steam dehydration. At this time, superheated steam and/or satd. steam is fed into the upper portion of the autoclave 1b from the outside, caused to flow downward in the brown coal layer 2, and discharged from the lower portion of the autoclave. The steam thus discharged is fed into the upper portion of the downstream autoclave 1a of a lower temp. This causes steam to pass in a manner of descending in the brown coal layer 2, so that the water retained between particles can be purged, thereby improving the dehydration efficiency.

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 pressure, it must be depressurized and cooled, and at this time, some water is reabsorbed into the lignite. This reduces the effect of dehydration. In addition, in the saturated steam dehydration method, hot water consisting of water separated by liquid H& and steam condensed water is separated from the brown coal, and the brown coal becomes saturated.
If the pressure is reduced after the lignite is in steam, there will be no re-absorption of moisture and the remaining moisture will evaporate and reduce, making it even more effective, but if the particle size of lignite is small, it will be difficult to separate the lignite from hot water. The hot water trapped between the grains absorbs 10,000 moisture,
The drawback is that it cannot be dehydrated and dried sufficiently.

In order to eliminate the drawbacks mentioned in -, the present inventors have developed
As shown in Publication No. 8-142987, brown coal is sealed in a plurality of pressure vessels, superheated steam is supplied to the first pressure vessel to dehydrate and dry the brown coal, and saturated steam or nearly saturated steam is discharged. Then, this saturated steam or nearly saturated steam is supplied to the second pressure vessel or subsequent pressure vessels to dehydrate the lignite using saturated steam, thereby making use of the advantages of the conventional saturated steam dehydration method while achieving an evaporative drying method. We have already proposed a method for steam dehydration of lignite that makes it possible to process fine lignite by combining it with silk.

[Problem that the invention seeks to solve]

The method described in the above-mentioned patent publication No. 58-142987 has no problems in laboratory-scale experiments, but when attempting to operate continuously with multiple larger-scale autoclaves as one silk, the following steps are required: Such points remained unresolved.

(1) When an autoclave becomes large-scale and the lignite layer inside becomes thick, it is unclear how the superheated steam in the lignite layer should flow, especially the direction of flow.

(2) If the exhaust steam from the upstream autoclave alone is insufficient for saturated steam, it is necessary to supply both saturated steam and superheated steam from outside the system. It is difficult to install a steam source and switch between them when large-scale equipment is operated continuously, and countermeasures for this problem were unknown.

(]) By flowing superheated steam downward through the brown coal layer, even in a large-scale autoclave, the same effect of removing intergranular trapped water as in a laboratory scale can be obtained, and a high dewatering rate can be maintained.

(2) Conversely, if superheated steam is allowed to flow upward within the lignite layer, the intergranular water blown up by the steam and the hot water generated during the flow will stay within the lignite layer, resulting in sufficient superheated steam flow. effect cannot be obtained.

(3) Furthermore, even if saturated steam is used instead of superheated steam, if the steam is allowed to flow downward through the lignite layer, there is a purging effect of intergranular water and hot water, and the saturated The dehydration rate is improved compared to steam dehydration. Therefore, even in cases where only saturated steam can be obtained, the flow heating method using downward flow is effective.

(4) Even if superheated steam is supplied from outside the system, keep the autoclave tightly closed (do not connect it to the downstream autoclave)
If this is done, the steam temperature inside the autoclave will reach the saturation temperature. Therefore, even if only superheated steam is used as the steam source, it is possible to easily switch between saturated steam heating and superheated steam heating simply by sealing the autoclave or by connecting it to a downstream autoclave.

The present invention has been made based on the above findings, and aims to provide a dewatering method that has a better dewatering efficiency and has simplified equipment.

[Means and effects for solving the problem] No. 1 of the present application
The invention is a method for batchwise saturated steam dehydration in which a set of multiple autoclaves is used and each autoclave sequentially repeats the temperature raising process, pressure reduction process, and discharged coal process of lignite sealed therein. It is characterized by supplying superheated steam and/or saturated steam from the outside to the upper part of the autoclave, flowing it downward through the internal lignite layer and exhausting it from the lower part, and supplying this exhaust steam to the lower temperature autoclave downstream. It is said that

That is, as shown in FIG. 1, by supplying superheated steam and/or saturated steam from one or more places in the upper part of the autoclave 1b and discharging the steam from one or more places in the lower part of the autoclave 1b, lignite is produced. A flow heating process is performed in which steam flows from the top to the bottom in the layer 2, and the exhaust steam is heat-recovered to another autoclave 1a downstream which is in the process of increasing temperature at a lower temperature. 6 is a condensate tank for storing hot water, and 4.5.6 is a valve. In the drawings, SH8 indicates superheated steam and ss indicates saturated steam.

Further, as shown in FIG. 2, the second invention of the present application performs saturated steam heating using saturated steam discharged from an autoclave (not shown) in the upstream superheated steam process, and then seals the autoclave 1b to heat the lignite. By supplying only superheated steam to the upper part of autoclave 1b with no steam flowing through layer 2, heating of the autoclave 1b is substantially continued, and further, while supplying superheated steam is continued, the temperature of autoclave 1b is increased. It is characterized in that by discharging saturated steam from the lower part to the downstream autoclave 1a, steam is passed through the lignite layer 2 to perform superheated steam heating. FIG. 3 shows an example of a time chart in this case. Note that symbols in FIG. 3 will be described later. In Fig. 3, in the heating operation S of the autoclave 1d, superheated steam (S+H8) is supplied from the outside, and at the same time, saturated steam (S+H8) is supplied to another autoclave 1C in the initial stage of heating (S
SS) is communicated to ensure sufficient contact between the steam and the lignite, and the decomposed gas is exhausted downstream, increasing the steam partial pressure, ensuring sufficient temperature rise at the final stage of heating and evaporation of intergranular water. and decrease.

At this time, in the autoclave 1C, the moisture in the lignite is removed in a liquid state by the saturated steam discharged from the autoclave 1d. Subsequently, each autoclave shifts to the operating state of the upstream autoclave one by one, so that the autoclave 1c undergoes a heating process S as shown in the figure. In this heating process S, superheated steam (
S HS) is supplied, but the autoclave 1C
Since the autoclave is in a closed state, there is a saturated steam atmosphere inside the autoclave, and the liquid dehydration of the lignite continues. Since the autoclave 1c then undergoes the heating process of S8, the superheated steam dehydration described for the upstream autoclave 1d is performed.

〔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 repeats batch saturated steam dehydration, and the operation of one batch consists of a preheating process (R), a preheating process using condensate tank hot water (CW), and a preheating process using condensate tank steam (aS ), a temperature raising process consisting of a heating process (81 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 a time period that is 1/2 of one cycle time of the autoclave.

FIG. 6 is an operation time chart showing only four periods of the cycle time of one batch. Condensate tanks 3a and 3b are autoclaves 1as 1
The operation is different from bs ICN 1a. In the next four cycles, the condensate tank 3a operates as the condensate tank 6b, and the condensate tank 3b operates as the condensate tank 3a, so that 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. Autoclave 1a is an autoclave in which the temperature raising process has been completed, and autoclave 1b is an autoclave in which raw coal has been charged. By opening valve 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 (aW) using hot water in a fundensate tank, which will be described later, and the condensate tank 3a is a condensate tank that has completed receiving hot water (St process). valve 10
By opening, the condensate tank is depressurized and
The hot water flash-evaporates and this steam flows into the autoclave to further preheat it.

The autoclave 1d is an autoclave that has completed the first stage heating process (S1 process), which will be described later, and its interior is filled with high-pressure saturated steam (SS). Superheated steam (S u S) is supplied from a source 14 . However, since the pressure inside the autoclave is already high, the amount of SH3 flowing in is small. As the SS inside heats up the lignite and condenses, SHS flows in that amount, but it quickly becomes saturated due to the SS and hot water inside, and the process is essentially the same as the SS heating process. Become. By keeping the valve 12 open, the hot water generated at this time flows down to 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 6a, which has been partially cooled and depressurized by flashing steam. When the lower part and the valve 10 are opened and connected, hot water flows from the condensate tank to the autoclave, and the pressure of the condensate tank is further reduced.The hot water that flows into the autoclave passes through the lignite layer and preheats the lignite (aW process). Possibly 100
The wastewater becomes wastewater at a temperature of 150°C or lower (at most 150°C or lower) and is discharged to the outside through the valve 13.

The autoclave 1d is connected at its lower part to the downstream autoclave 1C via a valve 11.8 while continuing to supply superheated steam. SH8 in autoclave 1d
A large amount of S
S heating quickly evaporates the water that has leached onto the surface of the lignite and formed a water film (SS process). And from the bottom, S
S is discharged and heated with brown RFS in autoclave 1C for non-evaporative dehydration (St process). The hot water generated at this time is allowed to flow down to the condensate tank 6b by opening the valve 12'.
Store here.

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 C8 process and S□ process described for the autoclave 1C, and the autoclave 1C performs the S and CW processes described for the autoclave 1d. , to step S8, the autoclave 1d cyclically shifts to the operating state of the upstream autoclave sequentially to step D and E/filtration described for the autoclave 1a, and every autoclave repeats the same batch operation.

Further, the condensate tank 6a performs the hot water receiving process of S, process, and Sl process described for the condensate tank 6b, and conversely, the condensate tank 6b performs the depressurization process of O3°aw described for the condensate tank 3a.

In FIG. 7, the white valve is open in the first half of the period, the black valve 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, the dehydration level is discharged from the autoclave and raw coal is added.

All autoclaves mentioned above have the same configuration. That is, in every autoclave there are valves 7.8.8.10.10', 11.11 shown in the partial flow diagram in Figure 7.
', 12.12.16 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 Figure @8. The connection of the condensate tank for flowing down the hot water generated in the autoclave is only in the Sl and S1 processes, and is disconnected in the other processes. The hot water generated in the aS process is stored in an autoclave, and in the next process 81, it flows down to a condensate tank and is stored there, and finally it is combined with other hot water into the aW
It is discharged from the system during the process.

One condensate tank has different autoclaves for receiving and receiving hot water in the S□ process, and the two
The main condensate tank is shared by four autoclaves. Further, the cracked gas does not need to be extracted in the Ss process, and is discharged together with steam to the 80 process. The cracked 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 be sent to the O8 process and the OW process, so it is sufficient to extract it in these processes. Moreover, even if it is not extracted at all, it will flow out together with the wastewater during the OW 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 extract it midway). 15.16.17 is pulp,
18 is the raw coal bunker, 20 is the depressurized 2 as shown in the figure.
Steps may be taken to improve waste steam heat recovery. Note that F is fresh steam. Also the first
As shown in Figure 0, a method may be adopted in which the first reduced pressure is communicated with the autoclave after the condensate tank steam recovery (CS). In this case, since it is communicated with a high-pressure autoclave, the depressurization time becomes relatively long, but the heat recovery rate of the hot water increases and thermal efficiency improves.

FIG. 11 shows a method of increasing the heat recovery of the 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, which is effective in preventing clogging of the waste water system. This shows an example in which the heat recovery rate of hot water is increased, the heat-radiation effect is increased, and when superheated steam is used, the intergranular water evaporation effect is increased. Figure 14 shows a method that is suitable for brown coal with relatively good temperature rise characteristics and low moisture content, and the preheating and heating processes are short, which shortens the overall processing time.
This example shows an example in which one cycle time is small.

Examples and comparative examples will be described below.

Australian Victoria lignite (moisture 65.5 wb%) as raw coal for the example
The autoclave was operated using superheated steam at a pressure of 45" iMa and superheat degree of 20°C according to the time chart shown in FIG. 15, so that the flow of superheated steam in the autoclave was directed downward during the final heating process (S,). Superheated steam injection time is 50
It was a minute. As a result, the water content of dehydrated coal is 23.6wt.
%Met. In addition, during the S process, the temperature at the top of the autoclave was measured to be 258°C, even though superheated steam with a superheat degree of 20°C was supplied from outside the system.
This was almost the saturated temperature, indicating that saturated steam dehydration was substantially occurring during this period.

Comparative Example Under the same experimental conditions as in the Example, superheated steam was flowed upward. As a result, the moisture content of the dehydrated coal was 26.5 wt%.

〔Effect of the invention〕

As explained above, the method of the present invention allows steam to flow downward within the lignite bed, and can improve the dehydration rate by purging interparticle bound water, and also allows only superheated steam to flow. In the case of supplying steam, in addition to the above-mentioned effects, there is an effect that the equipment for supplying steam from the outside can be simplified.

[Brief explanation of drawings]

FIG. 1 is a flow sheet 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;
FIG. 3 is a time chart showing an example of the second invention;
14 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. 6 is an explanatory diagram showing one batch operation of an autoclave. An operation time chart showing only the - period of the batch cycle time, Fig. 7 is a flow sheet showing equipment related to the operation in Fig. 6, and Fig. 8 is a flow sheet showing details of Fig. 7. FIGS. 9 to 14 are time charts of specific examples. FIG. 15 is a time chart of examples and comparative examples. 1aq 1bs 1cs la,, 1es lf-・
・Auto play 11.12.12.13.15.16.1
7... Valve, 14... External steam source, 18... Raw coal bunker, 20... Dehydrated coal bunker (,---') 1, No.

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 discharged coal process, superheated steam and/or saturated steam is supplied from outside the system to the upper part of the autoclave, circulated downward through the internal lignite layer, and then dehydrated from the lower part. A method for dehydrating brown coal, which is characterized by discharging the steam and supplying this waste steam to a lower temperature autoclave downstream. 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 discharged coal process, saturated steam heating is performed using saturated steam discharged from an autoclave in the upstream superheated steam process,
Then, with the autoclave sealed to prevent steam from flowing through the lignite layer, only superheated steam is supplied to the upper part of the autoclave, essentially continuing saturated steam heating, and furthermore, while the supply of superheated steam continues. A method for dehydrating lignite, which comprises discharging saturated steam from the lower part of the autoclave to a downstream autoclave, thereby passing steam through a lignite layer to heat the lignite with superheated steam.