ENERGIÅTERVINNING I GRANSHOT® - PROCESSEN

Sammanfattning

Uvån Hagfors Teknologi AB (UHT) has developed a process ” GRANSHOT® ” for quick

solidification of metals in water baths. In the process liquid metal is splintered ” granulated ”

into small drops. The drops are rapidly cooled in a water bath where all the heat energy from the

liquid metal is transferred into the water. The granulation is often performed with great metal

flows, normally 1-4 tonnes of metal is granulated per minute. The energy that is transferred from

the liquid metal to the water is about 300 ? 400 kWh per tonne depending on type of metal and

current metal temperature in the granulation process. In normal applications the water is allowed

to gain a temperature of 60

°C before it is cooled to the surrounding temperature in cooling

towers or in heat exchangers. Because of drastically increasing energy prizes and in some cases

lack of energy resources, it is very interesting to try to recover the energy the water contains.

The purpose of the project is to perform a study of the energy flow in the GRANSHOT®-process

and analyse different methods to make use of the developed energy. The investigation contain

analyses of the economical consequences of an eventual implementation of the most suitable

method in the GRANSHOT®-process and a simple layout design of a granulation facility with

implemented energy recovery technology.

An extensive pre-study is executed to investigate different types of existing energy recovery

technologies and what they need to operate. The possibility to modify different electricity

production technologies to suit an implementation in the GRANSHOT®-process are also

investigated.

The most suitable energy recovery technology for the GRANSHOT®-process was found to be a

product built on the Organic Rankine Cycle (ORC) called Powerbox, developed by the Swedish

company Opcon. When analysing the effects of a Powerbox installation in a high capacity

granulation facility with a yearly tonnage of 3 million tonnes the big water flows results in a

need of 10 Powerbox-units. Despite an estimated efficiency of only around 4 % and investment

costs as high as around 100 million SEK, the repayment time is as short as from just over 2 years

up to around 5 years. The repayment time is depending on the electricity prizes, and thereby in

which country the facility is situated. The project has also resulted in a basic layout modelled in

a computer aided design program, displaying key components and water flow paths.