GB2131829A

GB2131829A - Apparatus for drying organic solid materials

Info

Publication number: GB2131829A
Application number: GB08329377A
Authority: GB
Inventors: Alois Janusch
Original assignee: Voestalpine AG
Current assignee: Voestalpine AG
Priority date: 1982-11-03
Filing date: 1983-11-03
Publication date: 1984-06-27
Also published as: AT375387B; GB8329377D0; DE3332596C2; JPS5998195A; YU216383A; AU2091983A; DE3332596A1; ATA401282A

Abstract

For drying organic solid materials, a steam cooker (1) is provided, in which the material to be dried is dried under the action of steam and/or hot water. The process water is discharged via a conduit (4) into an appending receptacle (3). The CO2 formed during drying is withdrawn from above the liquid level within the appending receptacle (3) via a riser conduit (8), which is connected to the cover of the appending receptacle (3) or to the connecting conduit (4) between the steam cooker (1) and the appending receptacle (3). The riser conduit (8) has a first section (9) of greater internal cross-section and passes over a reduction to the discharge conduit (13) for CO2. Within the riser conduit (8) there is arranged a diaphragm (12) of variable aperture and a valve (11). (Fig. 1). <IMAGE>

Description

SPECIFICATION Apparatus for drying organic solid materials The invention refers to an apparatus for drying organic materials, in particular brown coals, comprising an autoclave within which the material to be dired is dried under the action of steam and/or hot water and comprising an appending receptacle for receiving the process water, said appending receptacle having a discharge opening for the CO2 generated during the drying process. In such apparatuses it is, as a rule, worked according to the saturated steamdrying process going back to Fleissner, noting that when drying within the autoclave brown coals rich in water, CO2 is set free at a temperature of 1 50 to 1 600C by the carbonization reaction taking place.The CO2 set free has a relatively high specific gravity and accumulates within the lower portion of the autoclave and removes the steam from this location. Depending on the coal used, the amount of CO2 produced can become so high that up to half of the volume of the autoclave becomes filled with CO2. Such removal of steam has, in combination with the extremely bad heat conductivity of CO2, as a result that the coal would only insufficiently be heated within the lower portion of said autoclave or cooker and that the process conditions required for drying the coal would not be fulfilled.

With the known apparatus of the initially mentioned type, the CO2 was discharged from the lower portion of the cooker. This known embodiment of the mentioned apparatus has, however, the disadvantage that the discharge openings easily become clogged by the coal to be dried and by contaminations, because coal dust and condensating coal resins, fats etc. are taken along with the discharged mixture of steam and CO2. A rigid throttle diaphragm connected to the bottom of the autoclave was extremely subject to becoming clogged by these entrained uonstituents and resulted in troubles in the process performance.

Now it is an object of the invention to improve an apparatus of the initially mentioned type such, that clogging of the discharge openings for the CO2 is avoided and the amount of steam in the discharged gas is reduced. To solve this task, the invention essentially consists in that the discharge opening for the CO2 is provided above the liquid level within the appending receptable, in particular in the upper portion or, respectively, in the area of the cover of the appending receptacle.

In view of the CO2 no longer being discharged from the bottom of the autoclave and, instead of this, from the upper portion of the appending receptacle, the CO2 is discharged at lower temperatures, because the temperatures prevailing within the appending receptacle are lower. Thus, a portion of the volatile constituents can condense within the appending receptacle and thus remain associated with the waste water.

The appending receptacle is located at a level below the level of the autoclave and on account of the high specific gravity of the CO2, there can accumulate nearly pure CO2, noting that on discharge of the CO2 steam losses can be avoided, To reduce steam losses further, the arrangement is, according to a preferred embodiment of the invention, such that a riser conduit is connected to the discharge openings for CO2. Additional steam can condense within this riser conduit, so that correspondingly pure CO2 can be discharged without steam losses. In this case, the riser conduit is preferably substantially vertically arranged and adapted to be closed, in particular by means of a valve, at a distance from the discharge openings for CO2.

With such an embodiment, a diaphragm may be arranged within the riser conduit such that any danger of clogging or jamming of the diaphragm is avoided. Preferably, and according to the invention, a diaphragm of variable aperture is arranged in the riser conduit, a gas analyzer being connected into or to the riser conduit and the aperture of the diaphragm being adjustable by a drive means in dependence on the measured values of the gas analyzer.

Such a discharge diaphragm of variable aperture results, in combination with the preferred open-loop control or closed-loop control of the discharge aperture of this diaphragm, in a further reduction of the steam loss, because a high proportion of condensable substances and, above all, also condensing water can be separated within the riser conduit and be returned into the appending receptacle.

For improving separation of condensable substances, the arrangement is preferably such that the riser conduit has a greater inner width along a lower section adjoining the CO2 discharge opening of the appending receptacle and passes over to the discharge conduit for CO2 via a reduction. In this manner it is achieved that the CO2 moving upward within the section having a greater diameter flows at a lower speed, thereby favoring separation of droplets of condensed water and other contaminations. It is only downstream of the reduction that the discharge speed of the CO2 is increased corresponding to the reduction in the cross-section, and the arrangement is preferably such that the shut-off valve and/or the diaphragm is arranged within the reduced section of the discharge conduit for CO2.

It is thus possible to extract already very pure CO2 from this partial section. In an advantageous manner a device for separating condensed water can be connected to the riser conduit.

The sizes of the riser conduit are selected in conformity with the expected CO2 formation of the particular coal to be dried or in dependence on the steam pressure applied. Within the lower section of the riser conduit, the internal diameter can be 50 to 1 50 mm, preferably approximately 100 mm. The length of the riser conduit is preferably at least 1 m, whereby separation of condensable constituents is improved.

The invention is further explained below with reference to an embodiment shown in the drawings.

The material to be dried can be introduced into an autoclave 1 via a closable opening 2. Within this autoclave, preheating and drying can be effected stepwisely, a corresponding process operable with such an autoclave being described in AT-PS 185 349. An appending receptacle 3 is connected to the autoclave 1. The connecting conduit is designated by 4. In the prior embodiment of the apparatus, a conduit 5, closable by means of a valve 6, was connected to the lower portion of the autoclave 1, as is shown in dashed lines. Further, a rigid throttle diaphragm 7 was provided, which was subject to becoming clogged by the emerging mixture of CO2 and steam. In contrast to this old embodiment, the appending receptacle 3 is now provided with a riser conduit 8 which opens into the upper portion or the cover area of the appending receptacle 3.

The riser conduit has an internal diameter d1 of 50 to 1 50 mm in its lower partial section 9 and passes, after a length of approximately 1 m, over into a reduced partial section 10 having a diameter d2. The flow velocity within these two partial sections 9 and 10 of the riser conduit 8 is inversely proportional to the internal diameter.

Within the reduced partial section 10 of the riser conduit 8, there is arranged a shut-off valve 11 and a diaphragm 12 of variable cross-section. A gas analyzer 14 is connected to the discharge conduit 13 for CO2, and the signals of this gas analyzer are used for varying the diameter of the aperture of the discharge diaphragm 12. The control conduit is designated by 1 5.

The CO2 expelled from the coal within the autoclave 1 during the steaming process flows downward on account of its high specific gravity and fills the connecting conduit 4 and the space within the appending receptacle 3 above the liquid level 16 of the waste liquid. The temperatures prevailing within the appending receptacle 3 are lower as compared with the temperatures prevailing within the autoclave, and volatile constituents thus condense within the appending receptacle 3 and within the first partial section 9 of the riser conduit 8, respectively. The CO2 moving upward within the riser conduit 8 is withdrawn via the discharge conduit 13 in a substantially pure condition, continuous withdrawal being made possible by correspondingly controlling the diaphragm arranged within the riser conduit.

Claims

1. Apparatus for drying organic materials, in particular brown coals, comprising an autoclave within which the material to be dried is dried under the action of steam and/or hot water and comprising an appending receptacle for receiving the process water, said appending receptacle having a discharge opening for the CO2 generated during the drying process characterized in that the discharge opening for the CO2 is provided above the liquid level within the appending receptable, in particular in the upper portion or, respectively, in the area of the cover of the appending receptacle (3).

2. Apparatus as claimed in claim 1, characterized in that a riser conduit (8) is connected to the discharge openings for CO2.

3. Apparatus as claimed in claim 1 or 2, characterized in that the riser conduit (8) is substantially vertically arranged and adapted to be closed, in particular by means of a valve (11), at a distance from the discharge openings for CO2.

4. Apparatus as claimed in any of claims 1 to 3, characterized in that a diaphragm (12) is arranged in the riser conduit (8), said diaphragm preferably having an aperture of variable cross-section.

5. Apparatus as claimed in claim 4, characterized in that a gas analyzer (14) is being connected into or to the riser conduit (8) and the aperture of the diaphragm (12) is being adjustable by a drive means in dependence on the measured values of the gas analyzer (14).

6. Apparatus as claimed in claim 4, characterized in that the riser conduit (8) has a greater inner width along a lower section (9) adjoining the CO2 discharge opening of the appending receptacle and passes over to the discharge conduit (13) for CO2 vin a reduction.

7. Apparatus as claimed in claim 1, characterized in that the shut-off Ive (11) and/or the diaphragm (12) is arranged within the reduced section of the discharge conduit for CO2

8. Apparatus as claimed in any of claims 1 to 7, characterized in that the shut-off valve (11) and/or condensed water is connected to the riser conduit (8).

9. Apparatus as claimed in any of claims 1 to 8, characterized in that the internal diameter of the lower section (9) of the riser conduit (8) is 50 to 1 50 mm, preferably approximately 100 mm, and that this section extends over an axial length of at least 1000 mm.

10. Apparatus as claimed in any of claims 1 to 9, characterized in that the discharge opening for CO2 is immediately connected to the appending receptacle (3) or to the connecting conduit (4) from the appending receptacle (3) to the autoclave (1).