Did you know that the clinker cooling process can account for up to 30% of a cement plant’s total energy consumption? Traditional grate coolers often waste valuable heat and demand intensive maintenance, quietly inflating operational costs. A modern retrofit can change that. By improving heat recovery efficiency to over 70%, reducing specific fuel consumption, and cutting electricity use, upgraded grate coolers deliver measurable savings from day one. More importantly, the retrofit not only reduces costs but also enhances clinker quality and lowers CO₂ emissions—helping cement plants stay competitive in a cost-sensitive, sustainability-driven market.
AGICO CEMENT is dedicated to offering revamping solutions for single cement equipment or complete cement plant. We will show a grate cooler retrofit case to help you understand how much you can save with a grate cooler upgrade.
A company’s cement clinker plant features a rotary kiln measuring 5.2m x 78m. The grate cooler uses a JL4x7 pusher-type grate cooler. After years of continuous operation, the grate cooler’s thermal efficiency, energy consumption, and waste heat recovery efficiency have fallen below industry standards. Furthermore, issues such as equipment wear and tear and the replacement of spare parts have become prominent, resulting in high annual grate cooler maintenance costs. After multiple discussions with us, the company finalized a technical upgrade plan for the grate cooler and implemented it during off-peak production periods.
The latest fourth-generation step-type grate cooler system is used to replace the current clinker cooler. The grate bed inside the current grate cooler is removed, the shell is retained, and the core is replaced. The tail hammer crusher is changed to a roller crusher. The technical transformation goals are shown in the table below.
| Grate cooler technical transformation goals | ||
| Item | Before | After |
| Capacity(t/d) | 7600 | 8100 |
| Reliability of kilns(%) | 95 | ≥98 |
| Secondary air temperature（℃） | 1050-1100 | ≥1120 |
| Tertiary air temperature（℃） | 850-900 | ≥950 |
| Clinker temperature(℃) | 90 | Discharge temperature ≤ 65℃ + ambient temperature |
| heat recovery efficiency(%) | 60 | ≥74 |
| Clinker power consumption by step(kWh/t) | 30.5 | 28 |
| Clinker standard coal consumption(kg/t) | 108.85 | 104 |
Grate Cooler Technical Improvement Plan
The current clinker cooler will be replaced with the latest fourth-generation step-type grate cooler system. The existing grate cooler upper and lower casings, part of the hydraulic station, and part of the lubrication station will be retained. The hammer crusher will be replaced with a roller crusher. The new grate bed specifications are SCLW4-13×15 (13 rows and 15 segments), increasing the effective grate area from 161m² to 165m², meeting the clinker line’s 8,100t/d production capacity.
Retained components: The existing grate cooler upper and lower casings, part of the fan, air cannon, high-temperature camera, stairs, platform, kiln door cover, waste heat duct, and exhaust gas duct.
Removed components: The existing ramp, grate bed, transmission, seals, hydraulic station, lubrication station, hammer crusher, castables for the two side low walls, and the upper casing at the rear of the cooler.
Fan part
Since this is a technical transformation project, the original fan configuration is comprehensively considered. Under the premise of ensuring cooling performance, the existing fan is used. The fan configuration after technical transformation is shown in Table 2.
In this technical transformation, no new fans are purchased, and the original F6 and F7 fans are removed. The old fans are reused and kept in the same position. The total installed power of the cooling fans is reduced by 500kW compared with the original.
Hydraulic lubrication and control
- Hydraulic station motor: a total of 6 sets (5 in use and 1 spare) (original hydraulic pumps 8): motor 75kW, pump A3H180.
- Oil tank components are reused.
- Add 5 sets of proportional reversing valves: brand: Hawe, rated pressure: 25MPa.
- Add 39 oil cylinders (90/50), 3 for each row of grate beds, a total of 13 rows. (5) One PLC electrical control cabinet (internal components are technically transformed). The centralized dry oil lubrication system was completely newly supplied, and the existing equipment was no longer in use.
Tail Roller Crusher
- The existing hammer crusher was removed and a tail roller crusher was added.
- Roller crusher specifications: 4 rollers, 4 rpm speed, forward and reverse rotation control for the middle two rollers, and reverse rotation for the lead and tail rollers.
- Supplied motors: 4 18.5kW motors.
- Roller Crusher Foundation: The existing hammer crusher foundation was removed and a new roller crusher foundation was constructed.
Electrical
The motors for the fans and hydraulic stations involved in this technical renovation were all reused; the corresponding starter cabinets and inverters were also fully reused; the lubrication station motor cables were re-routed; some fans required re-routing, and the roller crusher reduction motor cables were re-routed. All pressure gauges in the air chamber were retained, with some relocated and re-routed. The PLC control cabinet underwent a technical renovation.
Comparison of Operational Performance Before and After the Grate Cooler Retrofit
Reduced Clinker Energy Consumption
Two grate cooler cooling fans (F6 and F7), two hydraulic pumps, and motors were removed. The original crusher power was 132 kW, but after the retrofit, the total power was 74 kW (18.5 kW x 4). The installed power of the grate cooler system decreased by 783 kW. The reduced cooling air volume of the grate cooler and the reduced kiln exhaust fan speed and current led to a significant increase in secondary and tertiary air temperatures. After the retrofit, the secondary air temperature reached 1200°C and the tertiary air temperature reached 950°C. The clinker power consumption per unit was significantly reduced, essentially achieving the expected goals. A comparison of clinker power consumption and standard coal consumption after the retrofit is shown in the following table.
| Before | After | |
| Clinker power consumption by step(kWh/t) | 30.76 | 27.03 |
| Clinker standard coal consumption(kgce/t) | 109.21 | 103.27 |
Increased Unit-Hourly Output
After the retrofit of the grate cooler, the clinker system’s operational reliability improved, conveying capacity increased, and failure rate decreased. The kiln-hourly output per kiln unit increased significantly compared to before the retrofit. A comparison of the rotary kiln’s unit-hourly output before and after the retrofit is shown in Table 4.
| Before | After | |
| Average hourly output(t/h) | 316.67 | 342.04 |
| Average daily output(t/d) | 7600 | 8208.96 |
Significantly Increased Heat Recovery Rate
Power generation has increased compared to before the technical upgrade. A comparison of power generation per ton of clinker before and after the grate cooler upgrade is shown in Table 5.
| Before | After | |
| Power generation/kW | 8309.42 | 9156.41 |
| Power generation per ton of clinker(kWh/t) | 26.24 | 26.77 |
Clinker Temperature
Before the upgrade, kiln output was 7,600 tons/day. After the upgrade, output increased to 8,200 tons/day. Despite the increased cooling area, the clinker temperature remained high. Limited by the capacity of the power generation system’s turbine and generator, as well as the size of the original grate cooler housing, the unit cross-sectional load of the upgraded grate cooler approached 50 tons/m²/day after the increase in clinker production, exceeding the rated load of the fourth-generation grate cooler. Despite the cooling fan’s unit air flow of approximately 2.2 Nm²/kg-cl, the clinker temperature still exceeded expectations. Future upgrades will focus on upgrading the grate cooler’s hot-end quenching system to further reduce clinker temperature. The clinker temperature has been reduced from 115°C before the upgrade to 90°C.
Clinker Strength
After the technical upgrade, the 3d clinker strength increased from 28.1 MPa before the upgrade to 29.1 MPa; the 28d clinker strength increased from 53.4 MPa before the upgrade to 53.7 MPa.
Equipment Operation Description
1. Significant Improvement in Operation Rate and Reliability
After the technical upgrade, the grate cooler has lower speed and oil pump pressure, resulting in better operational reliability and improved kiln system operation rate. Aside from normal kiln shutdowns, no kiln shutdowns or production reductions due to grate cooler failures occurred. A comparison of grate cooler operating parameters before and after the technical upgrade is shown in Table 6.
| Before | After | |
| Grate cooler speed(r/min) | 17-19 | 4.5-6.0 |
| Oil pump pressure MPa | 15-19 | 10-16 |
2. Comparison of Maintenance
Before the technical upgrade, the JL4×7 grate cooler required frequent replacement of wearing parts. After the technical upgrade, the fourth-generation grate cooler from Sinoma Equipment required relatively less maintenance and spare parts. Since its commissioning in April 2019, the grate cooler has undergone the main maintenance of replacing the grate plates that secure the slope. Routine maintenance primarily involves tightening the air chamber bolts, with no other maintenance required.
3. Crusher Operation
Before the technical upgrade, the hammer crusher required annual replacement of one set of hammer heads. However, these hammer heads could no longer maintain a stable clinker particle size, directly impacting clinker quality. Furthermore, hammer head replacement is difficult and time-consuming. The roller crusher, after the upgrade, offers increased reliability, fewer spare parts, and lower installed power. The clinker particle size before the upgrade was ≤55mm, while after the upgrade, it was ≤25mm.
Benefit Analysis of Grate Cooler Retrofit
Increased rotary kiln table hours, increased benefits
After the grate cooler technical transformation, the equipment reliability is improved and the kiln system operation rate is guaranteed. Except for normal kiln shutdown and maintenance, there will be no reduction in material or kiln shutdown due to grate cooler failure. The average daily increase in clinker is about 608 tons, and the annual increase in clinker output is 608 tons/day×160 days=97280 tons. The profit per ton of clinker is calculated at 50 yuan, and the increased benefits are 4.864 million yuan.
Reduced maintenance and reduced maintenance costs
Currently, the wearing parts of the grate cooler are frequently replaced. The maintenance and spare parts of the latest step-type grate cooler after the transformation are very small. Based on the maintenance costs in previous years, 1.5 million yuan can be saved each year.
Energy saving and consumption reduction
After the renovation, the installed power of the grate cooler cooling fan, hydraulic station oil pump, and crusher will be reduced, and the total installed power will be reduced. Taking into account the power consumption, the renovation will save 3.47kWh of electricity per ton of clinker. Based on an annual production of 1.2 million tons of clinker, the annual power consumption cost savings are expected to be 120×3.47×0.50=2.082 million yuan.
After the grate cooler upgrade, the secondary air temperature will increase from the current 1100℃ to 1200℃, and the tertiary air temperature will increase from the current 830℃ to over 950℃. The heat exchange efficiency will be improved, the standard coal consumption will be reduced, and 5.93kg of standard coal will be saved per ton of clinker. Calculated based on the coal consumption of 5600kcal/kg and 520 yuan/t, the cost savings are 120×5.93/1000×7000/5600×520=4.6254 million yuan. Total annual revenue generated: 486.4 million + 150 million + 208.2 million + 462.54 million = 13.0714 million yuan.
The total project investment is 16.0885 million yuan, with an estimated payback period of approximately 1.3 years.
This grate cooler upgrade project has improved the reliability and availability of the clinker cooler, enabling continuous high-speed operation of the rotary kiln. It also significantly reduced maintenance costs, energy consumption, and production costs, resulting in significant economic benefits. If you’re considering a grate cooler upgrade, we’re here to help!
