Economic account of flue gas waste heat recovery
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A drying and heating furnace uses natural gas as fuel, and the flue gas temperature is 500 degrees. It is currently directly discharged after water cooling. The annual natural gas cost is about 3 million yuan, and the natural gas price is 4.5 yuan per cubic meter. Waste heat recovery reduces the flue gas temperature to 150 degrees for emission. Find the economic account calculation method for waste heat recovery.
I don’t know how to calculate it, but it must be valuable
First you need to determine how much smoke you have? Judging from the natural gas consumption data you provided, the flue gas volume is approximately 8.04 million m³/a. Calculating the heat recovered from the waste heat of the flue gas is approximately 8.040000 * (500-150) * 1=2814000000KJ, and then divided by the low calorific value of natural gas of 35000KJ, it can be calculated that approximately 80400m³ of natural gas can be saved every year, and the cost can be saved by 361800 yuan.
Waste heat recovery requires a comprehensive economic account, or investment return ratio. If it is heat exchange, the efficiency will be higher. If it's a hot swap, based on your current data, it's not worth it. Then look at whether the overall investment in equipment can recover the cost within three years. If it exceeds three years, it is basically of little significance.
It is basically unnecessary to think about recycling power generation. At most, it is just to recover some hot water or low-pressure steam. The specific by-products will depend on your needs. However, the target discharge temperature is indeed a bit low. I am not sure about the quality of the by-product hot water or steam, and there are doubts about whether it can be supplied stably. In addition, if there is no stable demand, the actual economic significance is not great, and the hot water or steam produced by the by-product is often useless or unused.
Lithium bromide heat pump technology can be used to recover heat for cooling or heating
“500-150". It seems that the data you calculated is the ceiling of the amount that can be recycled. In fact, the loss rate is very high. It is estimated that only 10-30% may be effectively utilized.
The annual natural gas cost of 3 million is equivalent to 8,000 production hours, and the gas consumption per hour is about 85 cubic meters.
Your heat exchange settings are also perfect. In actual working conditions, 150-degree steam is required, and the flue gas temperature may be around 300 degrees. If the flue gas is reduced to 150 degrees, the vaporization ratio of water will not be high.