JPS61171795A - Production of pellet containing brown coal for gassification - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is intended for carrying out gasification in a reactor in a pressure range of 5 to 150 bar using oxygen, water vapor and/or carbon dioxide as gasifying agents. A method for producing strong pellets containing particulate fuel, comprising: feeding the pellets onto a fixed bed that slowly moves downward in a reactor; introducing a gasification agent into the fixed bed from below; This invention relates to a method in which mineral components are extracted from below a fixed bed as solid ash or liquid slag.

[Summary of the invention]

The present invention is a method for producing pellets used for gasification in a fixed bed, in which wet pellets are formed from a mixture containing lignite and heated and dried in an atmosphere rich in water vapor, thereby making it easier to transport, transport, and drop the pellets. The present invention enables the production of pellets that can be easily handled and endured through various gasification processing steps in a simple and economical manner.

C□. □1ゎi・Coal-containing pellets for gas and other uses in a fixed bed 7) are described in German Patent Application Publication No. 2851370 and German Patent Application No. 28533.
89 and from European Patent No. 10,792. The gasification of granular coal in fixed beds is described, for example, in Ullmann's Encyclopedia of Industrial Chemistry.
s Enzyklo-paedie der Tech
Nischen Chesie) 4th edition (1977)
It is described in Vol. 14, pages 383-386. Details of the gasification method with solidified residual ash can be found, for example, in U.S. Pat.
No. 40867, No. 3854895 and German Patent Application No. 2201278. Furthermore, GB 1,507,905, GB 1,508,671 and GB 1,512,677 disclose variations of the gasification process in which liquid slag is discharged. In these known methods, the gasification reactor is preferably charged with granular fuel, the particle size of which is approximately in the range from 3 to 60 nm.

[Problem that the invention seeks to solve]

The object of the invention is to produce gasification moldings in a simple and economical manner. This compact has sufficient shape and structural stability to meet the requirements of mechanical handling, e.g. transshipment, transport and dropping, while at the same time not collapsing during the thermal processing steps that take place during gasification. There must be.

[Means for solving problems]

According to the present invention, a pelletizing mixture is prepared in which at least 80% by weight of the particulate fuel component consists of hard lignite, and the hard lignite has a particle size of at most 1. Water content of 25% by weight and 4-1
0 wt% bentonite content and 25-35 wt% from this mixture by adding water as pelletizing liquid.
a wet pellet having a moisture content of The above-mentioned problems are solved by heating the pellets to at least 90° C. and adjusting the moisture content of the dried pellets to 1 to 4% by weight.

The wet pellets initially obtained after molding with a moisture content of 25-35% by weight exhibit a plastic behavior and do not exhibit a tendency to disintegrate during transshipment and transport operations. However, these pellets do not exhibit sufficient heat resistance when heated, which means that they disintegrate in the reactor in the upper region of the fixed bed for gasification. That is, under conditions where the gas temperature is about 350 to 600° C., structural relaxation of the pellets proceeds sufficiently, and most of the pellets disintegrate into fine particles and powder. If the wet pellets produced by pelletization are dried outside the reactor, for example on a drying belt, with a purge gas, the pellets, especially those made of lignite, will significantly lose their strength and will even disintegrate during transport.

Surprisingly, however, when the pellets are kept in a water vapor-rich atmosphere during the drying process, and the core of the pellets is also heated to at least 90°C before the actual drying process begins, the bentonite bonds are removed. Various experiments have shown that brown coal pellets can be transformed into dry pellets with a strong structure. Thus, the interior of the pellet will also reach a temperature as close as possible to the boiling point of water before significant evaporation or vaporization of water occurs. In this way, by avoiding significant humidity and temperature differences between the surface and the center of the pellet, the structure of the dried pellet becomes very strong.

Preferably, the pellets are dried in such a way that an atmosphere substantially saturated with water vapor surrounds the pellets. This is achieved by embedding the wet pellets during the drying process in a bed of hot granular solids having a temperature of about 150-300°C.

Such a bed of hot solids can for example consist of a sand bed. Instead, superheated steam at a temperature of about 110 to 180°C is used for the drying process'''hbT'1Wa
T; J>4・11ゞ<Lx 7) f)*)kt'
6 [is a maximum of 4% by weight.

According to the invention, the hard lignite contained in the pelletizing mixture has a particle size of at most 0.5 tsuru and at most 0.063
The fine particle fraction of tm accounts for 60-80% by weight. The hard lignite used is preferably hard lignite with classification numbers 10 to 12 according to the International Lignite Classification Method. In its mined state, this lignite has a total moisture content (calculated without ash) of up to 40% by weight. The fuel in the pellets preferably consists only of hard lignite without any other carbon-containing components.

As binder for the pellets, the customary bentonites such as natural sodium bentonite, activated calcium bentonite and green clay can also be used.

Either the bentonite is fed to the crushing plant along with the lignite, or
Alternatively, it may be added afterwards to the finely divided lignite already charged in the mixer; preferably bentonite and lignite are processed together in the grinding step. The reason is that in this way the binder is finely dispersed among the lignite.According to the invention, a first humidification is carried out in a subsequent mixer,
The moisture content of the mixture is 10-25% by weight, preferably 12-25% by weight.
20% by weight. This results, on the one hand, in that the mixture can be further processed without dusting, and on the other hand, the bentonite can absorb water and swell.

Forming of the pellets is carried out in the conventional manner in a pellet forming disk or, for example, in a rotary kiln. At this time, water is added as a pelletizing liquid. The infiltrated pellet thus formed is about 6 to 30 m, preferably 8 m
It has a diameter of ~20m.

If the pellets are to be gasified and the liquid slag is to be discharged, it is desirable to add fine flux, especially lime, to the pelletizing mixture in order to lower the melting point of the ash. The proportion is 2 to 15% by weight according to a conventional method. The flux-containing or non-flux-containing pellets can not only form a fixed bed by themselves in a gasification reactor, but also can be charged into a fixed bed together with granular coal having a particle size in the range of 3 to 60 m. Good too.

According to a number of experiments carried out in which dry pellets obtained according to the present invention were charged into a gasification reactor, these pellets showed satisfactory behavior not only during drying but also during coking and gasification. It was a kimono. A detailed study of the decrease in carbon that progresses from the outside to the inside during gasification of the pellets confirmed that the structure of the pellets is stable at all combustion stages;
In the case of pellets consisting primarily of lignite, this is by no means obvious.

〔Example〕

Next, a reloading test was conducted on the pellets obtained by the method of the present invention to examine the stability of the pellets during transportation and during multiple drops from different heights.

A test simulating the actual handling of pellets will be explained based on the attached drawings. The pellets are first transferred from the first conveyor belt 1 to the lower end 2 of the inclined belt 3, with a falling height A of 1.5 m. The pellets fall from the upper end 4 of the inclined belt 3 at a fall height B of 2.5 m onto the second conveyor belt 5 and from there to the third conveyor belt 6.
It falls at a height C of 2 m. The falling height D from the conveyor belt 6 to the storage container 7 is 6 m, after which the pellets pass through the accumulation height E of about 6 m in the storage container 7 and fall into the lock chamber 8 with a falling height F of 3.5 m. do. The falling height G from the lower end of the lock chamber 8 (height H=3 m) to the deposit in the reactor 9 is 1 m. A final check is made after the pellets have been discharged from the lower end 10 of the reactor 9.

EXAMPLE 1 - US hard brown coal containing 32% by weight (dry basis) was dried to a moisture content of about 8-10% by weight and milled in a ball mill to particles up to 0.315 tm.

This lignite already contains about 17% by weight of montmorillonite, the active ingredient as a binder in bentonite. Therefore, there is no need to further add a binder. The moisture content of ground lignite is approximately 18% by weight.
After the humidification treatment was carried out until reaching the desired temperature, the pellets were molded into pellets having a diameter of 8 to 161 mm using a pellet molding disk while spraying water. The moisture content of these pellets was 28% by weight, and the breaking strength per pellet was 22 to 35N.

A portion of these pellets was used in the reloading test described above, and as a result, the number of fine particles with a maximum particle size of 1 m was 0.
Less than 2% by weight was produced. However, this pellet loses its strength considerably on drying in a heated gas stream and produces a rather large amount of powder, making it unsuitable for gasification in a fixed bed. After drying treatment in an air stream with a temperature of 150 °C, the pellets are 15-25N
It showed only the strength of Further drying and carbonization of the pellets as in the fixed bed upper region of the gasification reactor
The strength of the pellet further decreased to 10-2N, so
This pellet is not suitable for gasification.

A second charge of wet pellets was dried in steam superheated to a temperature of 120°C, and in another example to a temperature of 150°C. In both cases, the dried pellets had a moisture content of about 3% by weight and a strength of 60-8 ON, and were sufficiently stable for conveyance and gasification.

The third charge of wet pellets contains 70% water vapor by volume and 3
dried at a temperature of 120 °C in a mixture with 0% by volume of air, this treatment resulted in a moisture content of 3% by weight and 50-7% by weight.
Dry pellets with a strength of ON were obtained. These pellets are likewise suitable for transport and fixed bed gasification.

A fourth charge of wet pellets was dried in a sand bed, with a pellet to sand weight ratio of 5:40 and a sand temperature of 20.
It was 0°C. The sand bed together with the pellets was placed in a drying chamber with a temperature of 200° C. and left for 2 hours. The sand was then sieved while still hot and the pellets were cooled in a closed container. The strength of the pellets thus dried to a moisture content of 1% by weight ranged between 140 and 21 ON.

The pellets were milling resistant, with less than 0.2% by weight of milled pieces having a particle size of up to 1 fl produced in a reshipment test.

The breaking strength of the coke pellets obtained by subsequent coking of the pellets under a pressure of 25 bar was 100
It was ~15ON. In reality, coking by fixed bed gasification was also carried out above the fixed bed. In this coking test, the heat resistance of the pellets dried in the sand bed was reported to be good, with no particulate formation observed. The dry pellets are therefore suitable as feedstock for gasification in fixed beds.

Daisho-1 Borland hard lignite containing 15% by weight ash (dry basis) was dried to a moisture content of 8-10% by weight, and then ground in a ball mill to a maximum particle size of 0.315 Tsuru. .

Since this lignite contains no natural binders, it was necessary to add 6% by weight of bentonite. Hard lignite and bentonite are mixed in a mixer, humidified with water,
The pellets were then molded into pellets with a diameter of 8 to 16 mm using a pellet molding disk. The moisture content of this pellet was 29% by weight, and its breaking strength was 20-3ON. This pellet showed transport resistance in a humidified state.

This first charge of pellets was dried in an air stream with a temperature of 150° C., during which some of the pellets disintegrated into fragments and powder. The strength of this dry pellet is 4~
It was only 8N. Increasing the binder content to 10% by weight and lowering the drying temperature to 60° C. only slightly improved the strength values of the pellets. This pellet is not suitable for any use.

Another charge of wet pellets was dried in a sand bed with a temperature of 150-220°C. This treatment produced transport resistant dry pellets with a moisture content of about 1.5% by weight and a strength of 80-12 ON.

The dried pellets were carbonized by fixed bed gasification under a standard pressure of 25 bar to obtain coke pellets with a strength of 60-8 ON. Therefore, these dry pellets are suitable as a charge for gasification in a fixed bed from all points of view.

It was carried out in the same manner as in Examples 1 and 2 using another hard lignite, especially hard lignite from the United States containing 5 to 35% by weight of ash (dry basis) in a sand bed or in a steam atmosphere. Similar results were obtained in a drying experiment.

The invention can be summarized as follows.

Gasification is carried out in the pressure range from 5 to 150 bar using oxygen, water vapor and/or carbon dioxide as gasification agents, with the pellets being fed onto a fixed bed slowly moving downwards in the gasification reactor. The gasifying agent is introduced into this fixed bed from below, and the mineral components are discharged from below the fixed bed as solid ash or liquid slag.

In order to produce lignite-containing pellets for gasification,
First, the content of fine granular hard lignite is at least 80% by weight.
A mixture is prepared in which the particle size of this hard lignite is at most 1 crane. This pellet mixture has a water content of 10-25% by weight and a bentonite content of 4-10% by weight. Water is added as the pelletizing liquid to form wet pellets with a water content of 25-35% by weight from this mixture. The wet pellets are dried in an atmosphere rich in water vapor, the core of the pellets being dried at least 90% before the pellets lose 1/10 or more of their moisture content.
heated to ℃. Dried pellets up to 4% by weight
indicates the moisture content of

Wet pellets may be dried, for example in a bed of sand.

〔Effect of the invention〕

The present invention provides that at least 80% by weight of the fuel component of the mixture for gasification pellets containing lignite consists of hard lignite having a particle size of 1n or less, and this mixture comprises 10 to 25% by weight of the fuel component.
and a bentonite content of 4 to 10% by weight, water is added to this mixture to form wet pellets having a moisture content of 25 to 35% by weight, and the pellets are heated in an atmosphere rich in water vapor. Before it loses more than 1/10 of its water content, the center is heated to 90°C to reduce the water content to 4% or less.

Therefore, the above mixture can be processed without producing dust, and wet pellets can be obtained by conventional methods. Before a significant burst of water due to drying begins, significant humidity and temperature differences between the surface and center of the pellet can be avoided, and the pellet can have a very strong structure in the dry state. . Therefore, the pellets meet the requirements for mechanical handling such as transshipment, transport and dropping while at the same time having satisfactory properties for gasification.

[Brief explanation of drawings]

The figure shows how to conduct a test that simulates the way pellets are actually handled. In addition, in the symbols used in the drawings, 1.5.6 ・-・・・−・−・・Conveyor belt 2
−−−−−−−−−−−−−−−−−・−・・・・・−・
・Lower end 3 ・・・・・・・・−・・・・−・・
−・−・−・−・・− Inclined belt 4−・−・・−・−・
・−−−−−−−−−1−−−−−Top end 7 ・・−・
・・・・・・・・・・・・・・・−・−・・・・−−1−
---Storage container 8 ---
−−−−−−−~ Lock chamber 9−・・・・・−・−・−
・−・・−・−・・−・・−・−・Reactor 10−・−・
・−・・−・−・・・・・・・・−・・−・Lower end.

Claims (1)

[Claims] 1. Process for producing particulate fuel-containing pellets for gasification in a reactor in a pressure range of 5 to 150 bar using oxygen, water vapor and/or carbon dioxide as gasifying agents. The pellets are fed onto a fixed bed that slowly moves downward in the reactor, the gasifying agent is introduced from below into the fixed bed, and the mineral components are transferred as solid ash or liquid slag below the fixed bed. In the method, a pelletizing mixture is prepared in which at least 80% by weight of the particulate fuel component consists of hard lignite and the hard lignite has a particle size of at most 1 mm, and the pelletizing mixture is The mixture is 1
Wet pellets having a moisture content of 0 to 25% by weight and a bentonite content of 4 to 10% by weight, and having a moisture content of 25 to 35% by weight are formed from this mixture by adding water as pelletizing liquid. , the wet pellet is dried in an atmosphere rich in water vapor, the core of the pellet being heated to at least 90° C. before the pellet loses 1/10 or more of its water content; A method characterized in that the moisture content of the pellets obtained is at most 4% by weight. 2. A method according to claim 1, characterized in that the wet pellets are dried in a bed of hot particulate solids covering the pellets and having a temperature of about 150 DEG to 300 DEG C. 3. A method according to claim 2, characterized in that the wet pellets are dried in a bed of sand. 4. A method according to claim 1, characterized in that the pellets are dried in a superheated atmosphere containing water vapor at a temperature of about 110-180C. 5. Hard lignite contained in the pelletizing mixture is at most 0.
6 fine particles with a particle size of 5 mm and a maximum of 0.063 mm.
5. A method according to any one of claims 1 to 4, characterized in that it accounts for 0 to 80% by weight. 6. Any one of claims 1 to 5, characterized in that the wet pellet has a diameter of about 6 to 30 mm.
The method described in section. 7. Any one of claims 1 to 6, characterized in that the pelletizing mixture contains a flux for lowering the melting point of ash, especially lime in a proportion of 2 to 15% by weight. The method described in Section 1. 8. According to any one of claims 1 or 2 to 7, the pellets are charged into a fixed bed together with coal having a particle size in the range of 3 to 60 mm. the method of.