The hazardous waste incineration rotary kiln is a cylindrical cylinder, which is generally equipped with refractory materials. The installation line of its axis is slightly angled with the horizontal line. The complex and changeable hazardous waste is constantly tumbling in the rotary kiln for high-temperature incineration to achieve the requirements of volume reduction and harmlessness. However, due to the wide variety of hazardous wastes and the complex and changeable chemical composition, it is necessary not only to scientifically select suitable refractory materials, but also to strictly require the masonry construction methods of refractory materials. Standardized and scientific masonry methods can not only reduce the damage to refractory bricks caused by physical forces such as mechanical stress and thermal stress, but also extend the service life of refractory fire bricks and improve quality and efficiency.
Optimization of masonry technology and methods
01 Acceptance of qualified refractories bricks
Refractory fire bricks are formed by pressing the blanks into a mold and then sintered at high temperature. Therefore, the production of each batch of refractories bricks is affected by the pressing mold and sintering temperature, which may cause deviations in the actual production size. Strictly controlling the quality deviation of refractory fire bricks can effectively reduce the overall masonry quality deviation of the rotary kiln. (1) Measuring and acceptance tools: vernier caliper (division value 0.02mm), standard steel ruler (300mm), feeler gauge. (2) Qualified acceptance: The outer packaging is not obviously damaged, the surface is smooth without protrusions, and there is no obvious melting hole; the sampling ratio each time is 2% of the normal supply quantity, and the length and width deviations are required to be no more than 2mm, the size deviations are no more than 1mm, the sum of the three sides of the missing edge is less than 60mm, and the sum of the three sides of the missing corner is less than 50mm; the crack length shall not be longer than 40mm, and the width shall not be wider than 0.25mm; non-standard refractory bricks with obvious missing edges and corners are strictly prohibited from being put into use.
02 Choice of masonry process
The masonry process of refractories bricks is generally divided into dry masonry and wet masonry. Dry masonry means that refractory mud is not used. It is easy to operate and the masonry speed is fast. However, dry masonry causes tiny gaps between refractory fire bricks, which makes it easy for liquid to penetrate and increase the risk of erosion; wet masonry requires the use of high-temperature refractory mud to fill the gaps to ensure tighter bonding. Since the "disposal center" disposes of a wide variety of hazardous wastes in daily production and operation, including solid, semi-solid, and liquid forms, when hazardous wastes are incinerated at high temperatures, flue gas, powdered waste, liquid waste, etc. are easy to penetrate into the gaps between bricks, so that the four surfaces of fire bricks can be eroded to varying degrees, which may lead to safety hazards of partial or complete detachment of fire bricks. Therefore, the "disposal center" chooses the wet masonry process for rotary kiln refractory brick masonry, that is, high-temperature refractory mortar is used to fill the gaps between refractory fire bricks, so that the four surfaces of refractory firebricks are tightly combined, and completely isolated from flue gas, powdered waste, liquid waste, etc., to reduce the chance of erosion and extend the service life of refractories bricks.
03 Optimize the masonry method to reduce the impact on the thinning rate of refractory bricks
The optimized masonry methods include:
(1) Center point calibration: Use a level and a plumb bob to locate 3 points to confirm the 2 axial center lines of the cylinder, and locate 5 circumferential reference lines and roundness to calibrate the center of the cylinder. Masonry based on the center of the cylinder can effectively detect the deformation of the cylinder and ensure the uniform annular gap of the bricks during masonry.
(2) Select the flower masonry method: During masonry, the axial staggered masonry method is used to stagger the horizontal brick joints, effectively slowing down the consistency of the relative sliding of the refractorieis bricks in each ring, reducing the local stress of the bricks, and reducing the probability of damage to the brick corners. Do not choose the method of insufficient mortar fullness, because the masonry method will cause the brick joints to be consistent and prone to bending, which may cause the local stress of the firebricks to be large when they slide relative to each other, and increase the probability of damage to the local corners of the refractories bricks.
(3) Reserve expansion joints: Although refractory fire bricks are qualitative refractory products sintered at high temperatures, they will still expand to a certain extent due to heat in actual production and operation; during the construction of the "disposal center", a 5mm expansion joint is set in the circumferential direction of about 1 meter for every 5 rings of refractory firebricks to release the thermal expansion of refractories bricks, thereby reducing the extrusion and fracture between refractory fire bricks.
(4) It is strictly forbidden to use hammers for bricklaying: Refractories bricks are fired at high temperatures. Although they are hard, they are still brittle and cannot withstand the impact of rigid materials. Flexible tools such as wooden hammers and rubber hammers must be used for bricklaying. If it is really necessary to use a hammer for masonry, it is necessary to cushion it with a wooden board to avoid direct contact with the refractory bricks and cause damage.
(5) Locking bricks: a. Refractory brick masonry is constructed in rings. The masonry work must be completed on the same day. The whole ring of locking bricks must be finished without interruption in the middle, otherwise it will cause inconsistent mud coagulation time and extrusion. b. In actual masonry of designed-size refractories bricks, due to the thickness deviation of refractory mortar and the allowable deviation size of bricks, it is necessary to use processed bricks for the final masonry. Generally, the last three to five refractory fire bricks are estimated to find the appropriate size of the last refractory brick. c. When using processed bricks for locking bricks, when the processed size is less than 50% of the original size, the original brick structure may change and affect its actual strength. It may also break after being subjected to large forces and unable to withstand pressure during the rotation of the rotary kiln, which will affect the integrity of the bricks and cause safety risks such as falling off or collapse. Therefore, it is generally required that no more than 2 processed refractory firebricks should appear in each circle of refractory brick masonry; the length of the processed fire bricks shall not be less than 50% of the original refractories bricks, and the thickness shall not be less than 80% of the original refractory bricks; if 2 processed bricks are required, they need to be laid on both sides of one or two whole bricks, and 2 processed bricks cannot be laid adjacent to each other. The last lock brick of the whole kiln should be processed carefully. It is strictly forbidden to use castables to lock bricks alone, but the last lock brick can be fixed with castables. The lock bricks should be firm and not misplaced.
After optimizing the refractory brick masonry process and method, the quality of refractory brick masonry of rotary kiln is effectively improved, and the operation efficiency of refractory fire bricks is improved. In the masonry process, strictly use qualified fire bricks, and it is strictly forbidden to use broken corners and cracked defective bricks for masonry. In order to avoid the erosion of refractory brick gaps by hazardous waste, choose the flower masonry method to masonry the hazardous waste incineration rotary kiln, and use rubber hammers in masonry to reduce the hard impact on refractory fire bricks; reserve expansion joints according to the thermal expansion of refractory firebricks themselves, effectively avoid the situation where refractory fire bricks are broken by hard force; make good measurements when locking bricks to ensure that the size of the final processed bricks is moderate, so as to avoid increasing the annular pressure due to excessive size and causing annular looseness due to too small size, which will affect the overall structure of the masonry.
