View waste heat power generation from the perspective of total energy In the cement industr

1. Reflection on the concept of waste heat power generation In the cement industry

In the cement industry, the waste heat power generation has been used as a subsidiary system of the cement kiln system. Therefore, the "Four-Not Principle" have been put forward to the waste heat power generation system, namely, it is: Do not affect the production of clinker; do not increase the heat consumption and power consumption of clinker production; do not change the original fuel drying heat source in clinker production; do not change the clinker production process and equipment.

This "Four-Not Principles" has great practical significance in the initial development stage of low-temperature waste heat power generation in China. But if we continue to pursue the "Four-Not Principle", it is likely to hinder the progress of technology, for the following reasons:

First of all, the name of "waste heat power generation" has a limit, more accurate statement should be "residual energy generation"; second, the principle is standing in the cement kiln system rather than standing in the overall field of vision, and it only takes into account the "quantity" of energy, but not take into account the "quality" of energy. At present, the power industry energy power system has already entered the third generation, the first generation was based on the first law of thermodynamics, pursuing higher total energy utilization; the second generation was based on the second law of thermodynamics, noted that the energy grade difference and the use of the cascade, began to put forward the total system; the third generation overall develops the total system, paying attention to multi-disciplinary cross. If from the view of total energy, waste heat power generation is far from its actual full ability.

2. First of all, there is still a great shortage of "quantity"

In the present production process, heat energy consumption in cement clinker production system reaching 2930kJ/kg can be said as advanced level. Now the thermal efficiency of clinker calcination is about 55% ~ 60%, the waste heat of unit clinker is about 1 172~1319kJ/kg, about 40 ~ 45kg standard coal per ton of clinker, which, according to advanced coal consumption index of thermal power generation: 350g/kWh, can generate 128 ~ 114kWh per ton of clinker. Of course, this is only a simple theoretical calculation from the view of "quantity", and in practice it is not possible to reach such a high level. Pure low temperature waste heat power generation capacity now is only about 40kWh per ton of clinker.

3. For "quality": the whole power generation system is very low efficient

At present, cement clinker production line is generally supported by pure low temperature waste heat power generation system, whose efficiency is very low. Take the 5000 TPD cement clinker plant of a company as an example, The the steam turbine its waste heat generation system has a low efficiency of only 18%, far below the 30%~45% of the power plant. If make a series of transformation on the existing basis, and even redesign the cement clinker production system and waste heat power generation system to improve the thermal efficiency of waste heat power system, so that its original low-grade energy to a higher level, you can use lower inputs achieve greater output.