JPH05187772A - Dried material dropping port of multi-stage drying machine positioned apart from gas passage - Google Patents

Abstract

PURPOSE:To reduce occurrence of power dusts caused by dropping of dried item by a method wherein a scraper is mounted under utilization of a rotary shaft of a rake to a dried crop dropping port and the dried item is transported and dropped at a part not acting as a passage for thermal medium gas. CONSTITUTION:Some dried items are pushed against a bank 4 with the upper stage rake 1 rotating an arrow direction 13 and piled up there, thereafter they are decayed down after the rake 1 is passed. The decayed down dried items are scraped by a scraper 3 toward an outlet port 6 and pulled toward a dropping port 8. At an inlet port 7, the scraper 3 oppositely pushes back the dried items into the drying surface, i.e., a rotating range of the rake 1. In addition, a shoot 9 may prevent occurrence of powder dusts as the dried items are dropped. In this way, the scraper 3 is mounted at the dropping port 8 for the dried items under utilization of a rotary shaft 10 of the rake 1. Then, the dried items are transported to the part not acting as the passage for the thermal medium gas and dropped there, thereby the occurrence of powder dusts accompanied by the dropping of the dried items is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention aims to significantly reduce dust generation inside a multi-stage dryer.
The passages for the dry matter and the heat carrier gas to move between the steps usually use the same port. Also, the area of the mouth through which gas passes tends to be smaller than other passages due to the structure, the flow velocity of gas becomes faster, and the dry matter falling in this flow becomes dust and mixes in the gas. Will naturally increase. In order to eliminate this defect, it is intended to remove the cause of dust generation by isolating the dry matter outlet from the gas passage.

[0002]

2. Description of the Related Art In general, a dryer for drying a dried product by directly contacting it with a heat carrier gas is a parallel flow of the dried product and the heat carrier gas for the purpose of preventing alteration of the dried product by a high temperature inlet gas. There are many cases. This method is mostly used in the dryer that uses high-temperature combustion gas. Therefore,
The closer to the dryer outlet, the more dry the dried product comes into contact with the heat carrier gas. Therefore, a large amount of dry matter mixed in the heat medium gas as dust is overlooked as a fate in a dryer in which the dry matter is in direct contact with the gas. However, multi-axis multi-stage dryer (Shown in 1987, actual application No. 6
2-03119) has a structure in which a dried product is agitated and dried on a flat surface, and the amount of dust scattered on the drying surface and mixed in gas is generated by a falling port that floats in the gas flow and falls. Much less than the amount of dust. In the example of sewage sludge, the dust generated on the dry surface is about 0.5 g per cubic meter of heat carrier gas even in the almost completely dried portion. On the other hand, at the outlet where the dried product falls in the gas flow, dust of an amount exceeding 10 grams per cubic rice may be generated.
The amount of dust generated varies depending on the properties of the dried product and the degree of drying, but in most cases it could not be operated without using a dust collector in the gas system. In particular, in a system in which gas is reheated and circulated and used, dust has a great influence on the entire system, and each device of the apparatus is contaminated, which is a major factor affecting continuous operation time.

[0003]

Once dust is mixed in the heat carrier gas, even a dust collector (usually a cyclone type) has 70 to 70%.
Only about 80% can be removed. If the amount of dust generated in the dryer is reduced to about 0.5 grams per cubic meter of gas, a dust collector will not be necessary in most cases, and if a dust collector is attached, the gas system will be kept clean and each device of the equipment will be kept clean. Withstands long-term continuous operation without becoming dirty.

[0004]

The present invention will be described with reference to the drawings. FIG. 1 is a three-dimensional view of the vicinity of the outlet of a multi-stage dryer to which the present invention is applied. (1) is the upper rake. The dried product is pressed by the weir of (4) by the rake of (1) which rotates in the direction of the arrow of (13), rises, and collapses after the rake has passed. This (3)
Scraper scrapes up to the mouth of (6) and falls (8)
I will pull it to. At the mouth of (7), on the contrary, the scraper pushes the dried material back to the drying surface, that is, the rake rotating area.
(9) is a chute that prevents dust from diffusing when the dried product falls. FIG. 2 is a plan view near the outlet. The rake of (1) rotates in the direction of arrow (13) and the scrapers of (3) in the direction of arrow (11) so as not to interfere with each other. Figure 3
[Fig. 4] is an elevation view of a scraper portion. The scraper of (3) rides on the lower rake (2) and is rotated with the rake on the rake drive shaft of (10). FIG. 4 is a three-dimensional view of a drying stage to which the present invention is applied. In this example, five rakes are arranged in two rows and both diagonal positions are gas passages.
The dried product is pressed against the weir of (4) by the rake, rises, and collapses after the rake rotates. The scraper of (3) carries the falling side of (6) and drops from the mouth of (8) to the lower stage. Since this is a free fall, there is no concern that the outlet will be clogged if the chute (9) is not attached to the stage where there is a wet dry matter. The chute of (9) is attached to a dry stage where the dried product falls to wind up dust. Even if the chute of (9) is not provided, the dried product does not fall through the gas passage, so that even if particles that have been dried to some extent are mixed, they are hardly carried away by the gas and become dust.

[0005]

From the operational experience of the multi-stage dryer to which the present invention is applied, it has been known that the dust concentration of the heat carrier gas fluctuates greatly. That is, when the operation is performed with the supply of the dry matter stopped, the dust concentration contained in the gas is greatly reduced even though the dryness inside the dryer is advanced at each stage. On the contrary, when the supply load of the dry matter increases, the dust concentration of the gas increases. This indicates that most of the dust contained in the gas is generated in the falling part of the dry matter. In the experiment, the present invention was applied to the lower two stages (about 1/3 of the area) where the drying proceeded with a tester (drying area: 35 square meters, drying capacity: 500 kg / hour). In the test run, the dust concentration was
0.6 to 0.8 grams per cubic meter of gas and 3 before application
Well below 8 grams.

[Brief description of drawings]

FIG. 1 is a three-dimensional view near a gas passage (dried material outlet).

FIG. 2 is a plan view of the vicinity of a gas passage. The arrow is the rake,
The rotation of the scraper and the direction of gas flow are shown.

FIG. 3 is an elevation view of a scraper mounting portion. The scraper rides on the lower rake and is rotated on the same axis as this rake.

FIG. 4 is a three-dimensional view of a drying stage to which the present invention is applied.

[Explanation of symbols]

1. ・ Rake on the same level as the scraper 2 ・ Rake on the lower level with the scraper 3 ・ Scraper 4
• is a weir in the upper stage facing the gas passage for preventing dry matter from falling 5 · is a passage for gas 6 · is a passage for dry matter on the outlet side, that is, the scraper outlet side 7 · is the scraper inlet side 8 · Dry matter outlet 9 · Dry matter outlet chute 10 · Rake drive shaft 11 · Scraper rotation direction 12 · Gas flow direction 13 ·
Is the direction of rotation of the rake

Claims (1)

[Claims] 1. A multi-screw multi-stage dryer (Actual application No. 62 of 1987)
-031198), a scraper using a rake rotating shaft is installed at the outlet where the dried product falls to the lower stage.
A dry matter outlet of a multi-axis multi-stage dryer characterized in that the dried matter is carried to a portion which is not a passage of the heat carrier gas and dropped to reduce the generation of dust when the dried matter falls.