Technology Sharing] 4 Construction Quality Problems Affecting The Use Of Kilns

Furnace as an indispensable core equipment in industrial production, its construction quality is directly related to production efficiency, product quality and equipment life. In the process of construction and maintenance of kiln, the following four construction quality issues are particularly critical, need to pay great attention to and take effective measures to control.

Problem Description:

Refractory material is the furnace against high temperature erosion of the first line of defense, its selection of improper or masonry process is not standardized, easy to cause the refractory layer cracking, spalling or even collapse. For example, the use of refractory bricks that do not match the working temperature of the kiln, or uneven masonry, leaving too large a gap, will reduce the overall strength of the refractory layer and thermal insulation properties.

Impact:

Shortens the service life of the kiln and increases maintenance costs.

Leads to heat dissipation and higher energy consumption.

In serious cases, it may trigger furnace shutdown, affecting the production schedule.

Response:

 Precise selection of materials: according to the working temperature of the kiln, atmosphere conditions and material characteristics, select the appropriate refractory materials.

 Standardized construction: Strictly control the thickness of masonry mortar joints (usually ≤3mm) and adopt the "staggered masonry" method to ensure the structural stability of the refractory layer.

 Quality inspection: After the construction is completed, key indexes such as compressive strength and thermal shock resistance are inspected to ensure compliance with the design requirements.

Problem Description:

The steel structure of the kiln is the foundation to support the refractory layer and the operation of the equipment. Insufficient installation accuracy (e.g., deviation in verticality, uneven tightening torque of the bolts) will lead to the overall deformation of the kiln and even cause safety accidents. For example, the cylinder welding does not strictly follow the welding process specification, which is prone to welding residual stress and leads to cylinder cracking after long-term operation.

Impact:

Kiln operation becomes less stable and vibration increases.

Refractory materials are damaged prematurely by stress.

In severe cases, structural collapse may be triggered, resulting in significant losses.

Response:

 Precision Measurement: High-precision equipments such as laser range finder and total station are adopted to ensure that the error of steel structure installation is controlled within ±1mm.

 Standardized welding: Strictly implement the welding process evaluation, control the welding current, voltage and interlayer temperature, and carry out non-destructive testing after welding.

 Bolt fastening: Fasten the bolts in stages according to the designed torque value to avoid over-tightening or loosening.

Problem Description:

Kiln sealing directly affects thermal efficiency and product quality. If the sealing material is not properly selected or the installation process is rough, it will easily lead to cold air infiltration or hot flue gas leakage. For example, the kiln head and kiln tail sealing device is seriously worn and not replaced in time, which will lead to unstable negative pressure in the kiln and affect the combustion efficiency.

Impact:

Heat loss increases, energy consumption rises.

Kiln atmosphere fluctuation, affecting product quality (e.g. uneven firing temperature).

Increased environmental pollution, flue gas emission exceeds the standard.

Response:

 Optimize sealing design: According to the operating characteristics of the kiln, select sealing materials (e.g. graphite packing, ceramic fiber blanket) that are resistant to high temperature and abrasion.

 Fine installation: sealing surface machining accuracy should reach Ra3.2 or above, and ensure that the seals and contact surfaces are closely fitted during installation.

 Regular maintenance: establish a sealing system inspection system, find wear and tear timely replacement, and record the replacement cycle.

Problem Description:

Thermal instrumentation (such as temperature sensors, pressure transmitters) and control system (PLC / DCS) is the furnace automation operation of the "nerve center". If the commissioning is not appropriate, it is easy to lead to data distortion, control failure. For example, the temperature sensor installation position is not reasonable or calibration is not accurate, will lead to the actual temperature and display value deviation is too large, affecting the process parameters adjustment.

Impact:

Fluctuating product quality and increased rate of defective products.

Increased risk of kiln operation (e.g. over-temperature, under-temperature).

Failure of automation control, reliance on manual intervention, and inefficiency.

Response:

 Accurate calibration: Thermal instrumentation needs to be strictly calibrated before installation to ensure that the measurement error is ≤ ± 0.5%.

 Reasonable layout: the sensor installation position should avoid the high temperature radiation area and material washout area, and take protective measures (such as installing protective casing).

 System tuning: In the trial operation stage of the kiln, carry out the whole process tuning of the control system, optimize the PID parameters to ensure the control accuracy.

Kiln in the working process is not good operation control so of course with the design is reasonable, the operator's technical level and practical experience has a lot to do, but with the kiln masonry construction quality is also closely related. The main reason is:

① the construction of the ruler only large errors, such as section size and shape, position size (including horizontal and vertical), etc., which is equivalent to a certain degree of change in the design, so it can not reach. The purpose of the design requirements, so that the calculation of accurate things into inaccurate, which, of course, brings difficulties in operational control.

② Ash joints are too large, the masonry is not dense. The result is that the kiln body is poor airtight, resulting in air leakage, leakage of fire, so that the kiln body is easy to damage, deformation, displacement, so that the geometry of the kiln body to produce a large error, will inevitably affect the firing process or even lead to serious accidents.

For example, if the masonry size error of the kiln car is large, the curve seal between the car and the car is not tight, and if the curve seal size error of the kiln body is large, the curve seal between the car and the kiln body is not tight, which will produce air leakage, affect the firing process and thermal efficiency, and even lead to truck accidents. Therefore, in order to ensure that the advanced kiln design intention can be realized, so that the firing operation can flexibly and accurately control the pressure, temperature, atmosphere system, and improve the thermal efficiency of the dense, it is necessary to improve the quality of the construction, especially pay attention to the above two main aspects.

The quality of kiln construction is the core factor determining its long-term stable operation. By strictly controlling the construction quality of the four key aspects of refractory materials, steel structure, sealing system and thermal instrumentation, the thermal efficiency, service life and safety of the kiln can be significantly improved. It is recommended that enterprises introduce a third-party quality supervision mechanism during the construction and maintenance of the kiln, and carry out regular technical training to improve the professionalism of the construction personnel, so as to escort the efficient operation of the kiln.

Zinfon Refractory Technology Co.,Ltd

We are a refractory material supplier integrating R&D,production,construction,warehousing and commerce.

We are offering various magnesia and alumina refractories including both shaped and unshaped products, raw materials and related chemical products.

We are certified to ISO9001, ISO14001, ISO45001 and other national and local certifications as follows:

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