JPS633089A - Coal dryer - Google Patents

Abstract

PURPOSE:To obtain a coal dryer of low cost, having eliminated such problems as wet corrosion and to H2-generation type corrosion, by partitioning into three sections the longer direction coming into contact with coal of a rotary multipipe heat exchange type coal dryer with each section differing in the material from one another. CONSTITUTION:The objective rotary multipipe heat exchange a type coal dryer consisting of the following three sections in the longer direction: (A) section a... accounting for 0.2-0.3 part from the entrance, made of austenite-based acid-resistant stainless material, (B) section b... accounting for 0.4-0.6 part in the middle, made of two-phase stainless material, (C) section c... accounting for 0.2-0.3 part from the exit, made of carbon steel material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coal dryer used for drying raw coal for coke, etc.

[Conventional technology]

A rotary multi-tube heat exchange type dryer is commonly used as equipment for drying coking coal for coke. IC machines are known.

Coal used in the steel industry is imported from around the world for reasons such as stabilizing its supply.

Many minerals exhibit strong corrosive properties depending on the conditions of the soil and ore processing in the area where they are produced.

In the process of drying coal, corrosive components contained in the coal and on the surface of the coal, such as CI, SO, etc., are dissolved and dissolved out along with moisture, and these corrode the tube of the dryer mentioned above and the parts that come into contact with the coal.

Table 1 shows an example of the eluted components of coal used in steel, etc.
Shown below. As shown in the table, it can be seen that the concentration of corrosive components varies greatly depending on the brand. Furthermore, FIGS. 4 and 5 show the relationship between SO and CI and the amount of corrosion, respectively.

It can be seen from FIGS. 4 and 5 that the amount of corrosion is significant when the metal surface temperature is 100° C. or higher.

In addition, in order to satisfy these corrosion properties, SO resistance,
It is necessary to use a steel material that satisfies both CI and CI resistance.

Table 1: Eluted components by brand of raw material end As a countermeasure to this problem, conventional methods have been to use highly corrosion-resistant steel materials, such as duplex stainless steel, in the parts that come into direct contact with coal. However, since these steel materials are extremely expensive, most of the equipment cost of the dryer is accounted for by the material cost and processing cost of these steel materials. If these costs can be reduced, the value as a rationalization facility will further increase.

Furthermore, even if a highly corrosion-resistant steel material is used, the progression of corrosion is unavoidable if the environment in which it is used is considered.

Since the coke oven operates continuously, the maintenance required for the coal dryer is required to be simple. Since the current equipment is expensive as mentioned above, it is not possible to have a spare machine, and therefore the operation of the dryer must be stopped and repair work performed.

[Problem that the invention seeks to solve]

The mechanism of corrosion in the process of drying coal can be estimated as follows.

■ CI −, SO4′− eluted in the moisture adhering to coal
Due to the increase in electrical conductivity, the following reaction proceeds.

Fe-+Fe"-1-3e- 2JO+ Ot + 4e-→4 (OH) -Fe"
+ 3[OH]--"Fe (OH)

■ pH decrease due to hydrolysis and H2SO4, HCI attack Fe50. + 2H20-Fe(OH)2+ H2SO
.

Feel * + 2) tzo-4Fe (OH)
2 + 211CIFe +HxSOa→Fe504H
nl(,0+ Hz tFe+ HCl −FeCl
* ・nH*o+H*↑■ Low pH coal brings in H2-generating corrosion H2SO4, HCj, and H due to the presence of ■20
Two types of corrosion occur.

■　Nirojishin by coal particles ■　Progress of corrosion due to the combination of ■～■ etc. can be considered.

An object of the present invention is to provide a coal dryer that overcomes these corrosion mechanisms and has low equipment costs.

[Means for solving problems]

The present inventors investigated changes in the elution concentration of S04 ions and ce ions contained in raw coal and the temperature distribution in the longitudinal direction in a dryer, and arrived at the present invention.

That is, it was found from the results shown in FIGS. 1 and 2 that the above-mentioned corrosion did not occur over the entire dryer, but that corrosion progressed differently in the longitudinal direction.

Figure 1 shows So4'- and CI- in coal ore grade B.

It is a relationship graph between ion concentration (ppIo), pH, and elapsed time. FIG. 2 is a graph showing the longitudinal temperature distribution in the coal dryer when 5 kg of saturated steam is used as the heating medium.

As can be seen from FIGS. 1 and 2, the dryer inlet contains relatively many sulfate ions and is at a low temperature, so the attack is mainly caused by sulfuric acid. Also, when it comes to the center, CU-on gradually increases,
Furthermore, since the temperature becomes higher, it is assumed that the attack is mainly caused by hydrochloric acid attack in the presence of 5O4Z-.

Therefore, when selecting the constituent materials inside the dryer, 504
It is necessary to select a material that can withstand both the attacks of Balance with material prices must be considered.

That is, the present invention divides the dryer in the longitudinal direction that contacts coal into three parts, and uses a material whose material is changed in each divided part.
．． 2 to 031 part is austenitic acid-resistant stainless steel material, middle 0.4 to 0.6 part is duplex stainless steel material,
This is a rotary multi-tube heat exchange type coal dryer in which a 0.2 to 0.3 part on the outlet side is made of carbon steel material.

[Effect]

In the coal dryer of the present invention, the tube and shell in contact with coal are divided into three parts, and the material of each divided part is selected to correspond to the temperature and SO, CI-ion attack situation in the longitudinal direction of the dryer. It is characterized by having been selected.

That is, in the 0.2 to 0.3 part of the entrance of the dryer (assuming the total length of the dryer as 1; the same applies hereinafter), the temperature is below 100°C, and corrosion by sulfuric acid is the main cause. Therefore, a sulfuric acid-resistant material such as austenitic acid-resistant stainless steel is sufficient.

However, in the middle 0.4-0.6 part, the internal temperature is 100-
Since the corrosion of CI- in the presence of So and 2- rapidly accelerates at 130°C, this is the part where corrosion progresses the most, and this part is made of a material selected from two-phase stainless steel material Hastelloy: Titanium, etc. Considering the price, duplex stainless steel is preferable because it can overcome this problem.

Next, in the 0.2 to 0.3 part of the outlet, the ambient temperature is relatively high and the amount of condensed water is also relatively small. Also 5o42-, CI
−.

Most of the carbon steel exists in gaseous form and its concentration is considered to be extremely low, and the corrosive environment is considerably better than the former two parts, so ordinary carbon steel can withstand it well. The length is determined by the temperature of the drying heat medium used in the dryer, and the higher the temperature, the longer the outlet section, and the lower the equipment cost, by using low-profile carbon steel.

〔Example〕

FIG. 3 schematically shows an embodiment of the present invention.

In the figure, 1 is a rotary multi-tube heat exchange type coal dryer with a diameter of 4.5 m and a length of 23 m+ (capacity 270 T/[(), 2 is a tube, 3 is a shell, and 4 is a tube coupling.

The coal dryer 8il has an outer shell 3 and a tube group 3 through which low-pressure steam is passed, which are connected by a tube coupling 4, and a rotating device (not shown) is used to rotate the coal dryer at 2.5r, p,
The charged coking coal is rotated at a rate of 270 m from the outlet.
Process with T/H ability.

In the present invention, the total length L (assumed to be 1) of the coal dryer 1 is a
Divide into three parts: part (0,2-0.3), part b (0,4-0.6) and part C (0,2-0.3), and for each divided part, part a is austenite. Acid-resistant stainless steel material (Sus316L) The part b was made of a two-phase stainless steel material, and the part C was made of a carbon fi (SS41) material.

In conventional coal dryers, in order to cope with corrosive environments such as SO42- and Ce-, it is necessary to use extremely expensive materials such as two-phase stainless steel, dikuno, and hastelloy. If these materials are used extensively, the equipment cost of the coal dryer will be enormous.

In contrast, in the present invention, the coal dryer is divided into three parts, and the conditions of the coal dryer, that is, the heat medium, the properties of the coal, and the temperature conditions are taken into account.
Corrosion resistant materials were selected as described above.

〔Effect of the invention〕

According to the coal dryer of the present invention, (1) the use of expensive materials such as two-phase stainless steel is reduced, and equipment costs are extremely low;

■ Also, in maintenance, the overall installation cost is low, so it is possible to have a spare machine, and if checked regularly, continuous operation without I/I troubles is possible.

■ Also, because it is divided into three parts, if one part corrodes like the conventional product, it would require a tube the length of the dryer.
It only costs 4, which makes it cheaper.

It has the following effects.

[Brief explanation of drawings]

Figure 1 shows coal grade B medium (7) 50%-, Ce-,
A graph showing changes in pH and elapsed time; Fig. 2 is a graph showing the longitudinal distribution in the coal dryer; Fig. 3 is a schematic diagram showing an embodiment of the present invention; Figs. 4 and 5 are It is a graph showing the relationship between metal surface temperature and corrosion rate of iron under 5042- and CI- environments, respectively. In the figure, 1: coal dryer, 2: tube, 3 nitrogen, 4: tube coupling. Figure 1 5 Tokuton Saikan (Example: “”5 (yfi)
o, 70t. 2: Child Ave 3: She J Shi 4: Nayup ° force l prism

Claims (2)

[Claims] (1) A rotary multi-tube heat exchange type coal dryer, characterized in that the longitudinal direction of the dryer in contact with coal is divided into three parts, and the material of each divided part is changed. (2) Regarding the structural material of the dryer in the longitudinal direction, 0.2 to 0.3 part from the inlet is made of austenitic acid-resistant stainless steel, 0.4 to 0.6 part in the middle is made of duplex stainless steel, and 0.2 to 0.3 part from the inlet is made of duplex stainless steel. 2. The coal dryer according to claim 1, wherein 2 to 0.3 parts of the coal dryer are made of carbon steel material.