The traditional cement industry is a heavy industry with high energy consumption and high pollution. Even using the new dry process cement clinker production process, the calcining process still adopts decomposition outside the rotary kiln. The energy utilization rate in this process is obviously insufficient. There will be a large number of medium and low-temperature waste gases that do not fully participate in the combustion process, which is not only a waste of energy but also a problem of environmental pollution.
The cement plant equipped with a low-temperature waste heat power generation system can recycle the medium and low-temperature waste gas not fully utilized in the cement production line as secondary fuel, which can reduce the energy loss and production cost in the cement production process.
Because low-temperature waste heat power generation is only the simple use of waste heat and does not consume any fuel, it is more in line with the concept of green sustainable development of energy conservation and environmental protection.
The use of waste heat power generation in cement plants can reduce purchased electricity, reduce cement production costs, reduce energy consumption, and improve economic benefits. This is a new trend in the development and transformation of cement plants in the new era.
Waste Heat Recovery in Cement Plants
The waste heat recovery power generation technology in cement plants is usually applied to the preheater to fully absorb the heat energy of waste heat and waste gas and improve the utilization rate of energy. If the composition and content of waste heat and waste gas cannot be guaranteed, multiple waste gas outlets can be connected in series to collect waste gas uniformly, and the temperature can be effectively controlled within a reasonable range.
It is worth noting that the process of waste heat conversion is relatively floating. Since the actual output heat can not be applied to the electric energy conversion equipment to provide operating power every time, how to dispose of the excess waste heat and waste gas is also an issue that the cement plant enterprises need to pay attention to. We should not only rely on the waste heat power generation technology, but also combine a variety of technical methods to deal with the waste heat and waste gas.
Power Generation Scale
The scale of waste heat power generation of a cement plant is determined by the actual cement output and the energy consumption in the production process. Similarly, waste gas also plays a part in determining the production scale and technical process. The medium and low-temperature waste heat power generation system is divided into two operation parts, one is the outlet treatment device of waste gas, and the other is the preheating treatment device of waste gas. The temperature of the waste gas at the outlet of the kiln is treated by the cooler. If the cooler has a good cooling effect, then a small amount of waste gas will be generated, and the recovery rate will be low; If the cooling effect is poor, a large amount of waste gas will be discharged and the recovery rate will be high.
Waste Heat Recovery Device
The waste heat recovery device includes central exhaust type, back heat circulation type, and residual air direct type.
The central exhaust waste heat power generation is operated halfway according to the energy supply required in the production process, and the management control is carried out according to the production demand and actual recovery efficiency. Although this method has high recovery efficiency, it has high equipment demand and high capital cost.
The demand for exhaust gas temperature of the direct residual air type is low, but its equipment and materials are large and need a certain capital cost. However, the kiln tail waste heat generation process uses part of the waste heat recovered by the preheater as the drying heat source, which can discharge the excess impurities and harmful components after passing through the humidification and dust removal system, which is helpful to reduce air pollution.
It should be noted that when equipping a cement plant with the waste heat recovery device, the recovery of excess waste gas and the combination with the raw mill system should also be considered. The high-temperature waste gas is supplied to the waste heat boiler and its exhaust gas is sent to the raw mill. The waste heat boiler uses the steam generated by the temperature difference to improve the waste heat recovery efficiency. Therefore, when configuring the low-temperature waste heat power generation system in the cement plant, various influencing factors must be comprehensively considered and reasonably set according to the power consumption scale, waste gas quality, and energy recovery rate of the cement plant, so as to ensure the efficiency and quality of the waste heat power generation system.
Waste Heat Power Generation Equipment
Waste heat power generation equipment commonly used in cement plants includes steam turbine generators, waste heat boilers, and thermal equipment. Among them, the steam turbine generator is the core and key equipment of the waste heat power generation technology. It fully absorbs the waste heat in the waste gas, converts the heat energy into electric energy, and provides the operating power for the generator, so as to provide the required power for the cement production line.
Steam turbine generators are divided into two categories. One is the single pressure system steam turbine generator, which has a small power generation capacity, general power generation scale, intuitive and simple operation, and is often used in small and medium-sized cement plants; The other is the mixed pressure steam turbine generator, which can effectively meet the power generation demand through flash technology, and the power generation can reach one to two times that of the single pressure system generator, which is suitable for large-scale cement production plants.
Thermal equipment consists of evaporator, superheater, and economizer. Usually, the capacity and model of thermal equipment are determined according to the scale and quality of waste gas and combined with the steam turbine generator.
As the specifications and quality of cement production are not uniform, the technical process and equipment performance of cement plants are varied, and the composition and temperature of waste gas are different. These factors will have a certain negative impact on the normal operation of the waste heat power generation system unit. In the long run, it will cause equipment failure and affect production efficiency. Therefore, thermal equipment is required to be responsible for regulating parameters, reducing the difference of waste heat power generation materials and energy in the cement production line, and making corresponding adjustments according to the actual situation to ensure the power supply.
The waste heat power generation technology of cement plants can improve energy utilization, reduce environmental pollution, promote the sustainable development of green and environmental protection of enterprises, realize the dual development of economic and social benefits, and help to promote the production capacity and transformation of enterprises.