Calculation for Costs of Refractory Bricks In Rotary Kilns

As an important industrial kiln equipment, rotary kilns are widely used in cement, lime, metallurgy, chemical engineering industries, etc. To calculate the refractory bricks costs of a rotary kiln, it is necessary to take into account the rotary kiln’s specifications, refractory type and operating conditions.

I. First, determine the basic parameters of the rotary kiln to avoid deviations in cost estimation

• Kiln specifications: effective inner diameter (D, m), length of each functional zone (firing zone/transition zone/preheating zone) (L₁, m), and refractory thickness of the corresponding zone (δ, m). For example, δ of the firing zone is usually 15-20m, and that of the preheating zone is 15-25m.
• Refractory parameters: type (magnesia-chrome brick/high-alumina brick/castable), bulk density (ρ, t/m³, 2.8-3.2 for refractory bricks, 2.6-2.9 for castables), and size of a single brick.
• Operating condition coefficients: construction loss rate (5%-8% for bricks, 10%-15% for castables), annual maintenance frequency. A higher loss rate should be adopted when the raw materials have high hardness.

II. Calculate the actual refractory consumption and account for it by zone

Calculate the refractory volume of each zone: The kiln lining is a cylindrical ring, and the formula is V = π × (D – δ) × δ × L₁ (where π is 3.14).

Calculate the weight

• For castables/monolithic refractories: Use the formula Weight = Volume × Bulk Density;
• For refractory bricks: First calculate the volume of a single brick, then determine the total number of bricks, and finally multiply by the weight of one brick to get the total weight.

Adjust for loss: Actual Consumption = Theoretical Weight × (1 + Loss Rate)

III. Calculate costs by item.

Total refractory cost = Purchase cost + Construction cost + Maintenance cost + Indirect cost

• Purchase cost (accounting for 60%-70%): Calculated as Actual consumption × Tax-exclusive unit price of refractories, with zone-specific unit prices distinguished.
• Construction cost (10%-15%): In China, the “lump-sum price by weight” is commonly used. Brick masonry costs ¥200-500/ton (¥500-800/ton for complex parts like kiln head and kiln tail), and castable construction costs ¥300-600/ton.
• Maintenance cost (5%-10%): Includes daily repairs (annual castable consumption of 5-10 tons multiplied by unit price) and partial replacement (e.g., replacing 10 tons of transition zone bricks every 6 months, plus construction fees).
• Indirect cost (5%-8%): Covers transportation fees, storage fees, and management fees (3%-5% of total direct costs), estimated based on actual expenses or proportions.