Which type of heat exchanger is suitable for utilizing the waste heat from flue gas with heat transfer oil?

Consider the costs and space constraints. A plate-type system is also an option, but is your moisture content too high... (10/43=23%)... Will it drop below the dew point temperature after condensation, requiring recovery? It’s important to evaluate this carefully

This post was last edited by wiseboy on 2018-9-28 09:32. The operating conditions you described are quite typical and common; I have designed many such heat exchangers, which have operated successfully. Here is my brief response: 1. In terms of flow rate: (1) If a shell-and-tube heat exchanger is used (with a floating head or fixed tube sheet, i.e., one with a cylindrical shell), a large number of tubes need to be connected in parallel due to the high flow rate. Since heat exchangers all have a limited diameter, it is necessary to use multiple units in parallel, which is very inconvenient. (2) Using a box-type heat exchanger (with a rectangular enclosure, similar in structure to an air cooler), one unit is sufficient: it is almost the most sensible choice. (3) There is a lot of dust; plate heat exchangers are out of the question. 2. In terms of corrosion, material, and lifespan: (1) There are options that are used to cut costs, involving the use of carbon steel, which results in a very short lifespan. (2) There are also those made of tetrafluoroethylene; due to their poor heat transfer properties, the heat exchangers built with this material are much larger than those made of metal materials such as carbon steel or stainless steel. However, their cost is lower than that of stainless steel, and their lifespan is particularly long. (3) When stainless steel is used, the heat exchanger is much smaller than one made of PTFE, but it has the highest cost and a relatively long service life. 3. From a manufacturing perspective: There are numerous manufacturers of metal heat exchangers ； There are very few manufacturers of tetrafluoroethylene heat exchangers.

If a box-type heat exchanger is chosen, is it appropriate to use heat transfer oil as the medium (mainly to reduce the construction costs associated with 150-meter-long DN1600 pipes, supports, and pipe racks per journey) in order to transfer heat?

Whether it’s heat transfer oil, water, or anything else, there’s no problem. It’s just that the structural dimensions (area) of the heat exchanger are different, requiring careful design. Since this heat exchanger is so large, don’t sacrifice overall performance just to save on design costs.

Also, for flue gas at 400 °C, to what temperature do you need to recover it? 200 ℃? 100 ℃? 60 ℃? This relates to the selection of heat transfer oil. Secondly, how do you make use of the heat recovered from the heat transfer oil? That is: How is heat transfer oil cooled? Do you need a heat exchanger that requires heat transfer oil for cooling (heat application)?

Given that the flue gas dew point is only 110, indicating a high moisture content, the target flue gas temperature should be maintained between 280 and 290

This post was last edited by wiseboy on 2018-9-28 at 10:06. The inlet and outlet temperatures of the heat transfer oil: 260°C ——> 270/275°C, which is one option available. With these determined, the heat exchanger can be designed.

Flue gas volume: 34,000 Nm3/h (of which 10,000 Nm3/h is water, 1,300 Nm3/h is carbon dioxide, and 22,700 Nm3/h is air)； Such conditions are untrustworthy and too rough. Strictly speaking: this is incorrect information. Among them, “air 22700 Nm3/h” – this is impossible. Flue gas is formed after air is used for combustion; the oxygen in the air is exhausted, and what remains is mainly nitrogen, so it can no longer be called air. Therefore, the most reliable approach is to ask clearly: What is being burned to produce these smoke emissions – a coal-fired boiler? A natural gas boiler? Based on this, I can calculate a relatively accurate composition of the flue gas, rather than using the basically incorrect data you provided.

Water-tube waste heat boilers, heat-pipe waste heat boilers, and tube-type waste heat boilers are all suitable; it depends on whether you need hot water or steam.