The invention relates to a simple method for extending the service life of coal tube castable

1. Problem description and cause analysis

A company's 2 500 t/d new-type dry cement production line was overhauled in 2012. After replacing Smith coal pipe with lafarket high-thrust coal pipe, the service life of castable was reduced from 6 ~ 8 months to 2 ~ 3 months, with the minimum time of 45 days. All castable lost about 80 ~ 200 mm at the head, and the castable at the back was in good condition (see figure 1).In order to protect the coal pipe, the coal pipe has to be replaced in time, which greatly increases the cost.During the process, we have changed different levels of castable and construction methods, and the results are not good. For this, we have made the following analysis.

The reasons affecting the service life of castable are:

(1) clean the end coking damage castable.After the coal tube thrust increases, the nozzle wind speed reaches 350 ~ 430 m/s, the end coking is very frequent, a class to clean 1-2 times.The cleaning tool is the heat-resistant steel pipe. It moves the steel pipe from the horizontal coal pipe on the side of the kiln head cover. The distance is long, and the steel pipe is difficult to control.In addition, the stress will peel off part of the castable when the coking and falling off.

(2) the casting material is too thin.Since the diameter of Smith coal pipe head is 120 mm smaller than that of lafarge, the old mold is used after replacement, and the thickness of pouring material for the new coal pipe head is only 80 mm.

(3) sulfur alkali and sand erosion.The residual head of castable yellow, sampling for chemical analysis, sulfur alkali content is obviously high.At ordinary times, the head of the kiln has a large amount of sand, which has a certain abrasion on the head of the coal pipe.

2. Original processing process and effect

(1) increase the thickness of castable and knock down Angle of head.The castable thickness within the head 500 mm length increased to 120 mm, cramp Φ 60 mm x 6 mm (V cramp, thick 6 mm, 6 mm), replace Φ 80 mm x 8 mm, with floating cramp, cramp head with 3 mm plastic cap, bitumen paint is brushed coal pipe and cramp, strictly control the water content, mixing time and vibration.The head is chamfered 45°.Life expectancy increased but not by more than three months. 

(2) improve the strength grade of castable.The type of castable was changed from 75MP to a90-p240, and the effect was still not obvious when the end accumulation was frequently cleaned. 

(3) optimize the coal pipe construction method.At ordinary times, transverse pouring is carried out, 2 expansion joints are left in axial symmetry, and one expansion joint is left in every 1 m ring direction.Due to transverse pouring, it is difficult to deposit large particles of pouring material on the head, which affects the strength of pouring material to some extent. Therefore, the coal pipe is erected for construction with the head facing down, so that the pouring material with large particles can be concentrated on the head and increase the strength.Strictly control the construction quality.But the service life is still only 135d. 

(4) change the position of coal pipe.The initial position of the coal pipe is at the same level as the mouth of the kiln under the hot state. Due to the large flying sand in front of the kiln, the flying sand will cause certain abrasion on the head of the coal pipe when the secondary wind enters the kiln, shortening the service life of castable.Therefore, the coal pipe is evacuated to the place 300mm away from the mouth of the kiln in the hot state, which can not only increase the length of the kiln relatively, but also reduce the abrasion of castable material on the head of the coal pipe caused by flying sand.But the effect remains modest.

3. New processing mode and effect

The above measures are taken to strictly control the type selection and construction quality of castable, but the service life of castable of coal pipe head is still not long.Analysis of the reasons, pouring material is mainly due to frequent cleaning of coal pipe head coking often hit pouring material.Therefore, a 16mm thick Cr25Ni20 steel plate was used to weld the coal pipe head with a height of 120mm and the same height as the pouring material. It was divided into 6 sections with an expansion joint of 10mm for each section, as shown in figure 2.When welding, cut both ends, full welding on both sides.Use A402 or 132 high temperature resistant electrode.After welding with heat-resistant steel plate, the end of the coking is better, when cleaning steel pipe in the head, will not damage the castable.The service life of head castable can be extended to more than 12 months.Greatly reduce the replacement of coal tube manpower and material resources.