Abstract
Primetals Technologies Austria offers metallurgic plant solutions around the world. One of the company’s goals is to offer green steel solutions. The hot strip mill is a plant type which is well established. It has various waste heat streams from which the sum of all cooling water systems carries the most heat. This heat is dissipated right now. The thesis offers concepts which use large heat pumps to recover the heat of the cooling water system of a cooling line and of a re-heating furnace. The temperature is increased to a level at which a district heating system can be supplied with.
The heated return cooling water enters the water treatment plant, where it is among others filtered and cooled. The concepts foresee the placement of a large heat pump in the by-pass of the cooling aggregate. This makes sure that actual temperatures are close to maximum design temperatures which is beneficial for a heat extraction. The water temperature can be controlled by the flow control over this by-pass. The heat pump does not only supply heat to the heat sink but also cools the water. This relieves cooling power from the cooling aggregates.
Compared to the actual situation, the implementation of a heat pump in the cooling system of a hot strip mill would mean the supply of heat to the district heating network, a lower water consumption due to less evaporation in cooling aggregates and a lower 𝐶𝑂2 equivalent in the district heating system, because more expensive carbon-intensive alternatives are less needed. The overall electricity consumption for the water treatment plant would significantly rise with the installation of a heat pump. The economic viability of a realization project is evaluated for an investment case for a given steel producer. The payback period is influenced by several factors from which the heat price is the most important. Depending on the specifics of the hot strip mill, on the district heating network and on price levels, the return on investment can achieve values where it is interesting for a realization project from an economic perspective only. The payback period can be lowered if 𝐶𝑂2 pricing, savings in expenses for water or public funding are also considered.
The heated return cooling water enters the water treatment plant, where it is among others filtered and cooled. The concepts foresee the placement of a large heat pump in the by-pass of the cooling aggregate. This makes sure that actual temperatures are close to maximum design temperatures which is beneficial for a heat extraction. The water temperature can be controlled by the flow control over this by-pass. The heat pump does not only supply heat to the heat sink but also cools the water. This relieves cooling power from the cooling aggregates.
Compared to the actual situation, the implementation of a heat pump in the cooling system of a hot strip mill would mean the supply of heat to the district heating network, a lower water consumption due to less evaporation in cooling aggregates and a lower 𝐶𝑂2 equivalent in the district heating system, because more expensive carbon-intensive alternatives are less needed. The overall electricity consumption for the water treatment plant would significantly rise with the installation of a heat pump. The economic viability of a realization project is evaluated for an investment case for a given steel producer. The payback period is influenced by several factors from which the heat price is the most important. Depending on the specifics of the hot strip mill, on the district heating network and on price levels, the return on investment can achieve values where it is interesting for a realization project from an economic perspective only. The payback period can be lowered if 𝐶𝑂2 pricing, savings in expenses for water or public funding are also considered.
| Translated title of the contribution | Wärmerückgewinnung aus Kühlwasser in einer Warmbandstraße |
|---|---|
| Original language | English |
| Qualification | Dipl.-Ing. (FH) |
| Awarding Institution | |
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| Award date | 23 Aug 2023 |
| Publication status | Published - 12 Sept 2023 |
