## 3 Materials and Production
### Industrial Products and By-Products Suitable as Bed Material
#### 3.2.1 Iron Ore and Steel Production  
The iron ore- and steel industry is one of Sweden's largest industries. In 2019, the total amount of ore mined in Sweden was 47.5 Mton, being refined into 27.3 Mton ore-products [70]. A smaller amount of iron ore is also mined in Norway, where the amount has varied a lot historically due to the closing and reopening of mines [71]. Ore-production quantities for Sweden and Norway between 2004 and 2017 are presented in Figure 5a. Steel production in Sweden amounts to approximately 4.5-5 Mton crude steel, including both ore-based and scrap-based steel production. A similar amount of crude steel is produced in Finland. The crude steel production in Sweden and Finland between the years 2004 and 2017 is presented in Figure 5b. The large drop in production in 2009 was due to the financial crisis. Approximately 600 kton scrap-based steel is also produced in Norway (not included in the graph). Swedish ore is produced by Luossavaara-Kirunavaara Aktiebolag (LKAB) as pellets and fines. Pellets are the main product produced by LKAB by quantity (around 80-90% of the products are pellets). There is some flexibility in the production process, so that the ratio between pellets and fines production can adapt to the current demand. However, only a fraction of the raw ore has properties making it possible to turn into sinter fines, while the requirements for pellets production is less strict [73]. Figure 6 presents the production by type of products between the years 2014-2017. Due to their high iron content and a size interval of 0-2 mm, hematite and magnetite fines are of interest to use in OCAC. Iron ore from LKAB has not been a subject for OCAC or CLC experiments, but other samples of iron ores have shown good bed material properties in CLC experiments. Crushed iron ore has been used in experiments using coal and wood char as fuel (e.g., [74; 75]). However, due to the high purity, the MAF-product produced by LKAB more closely resembles iron mill scales in composition [65]. Figure 5: Iron ore and steel production between the years 2004–2017, in kton. (**a**): Iron ore production in Sweden and Norway. (**b**): Crude steel production in Sweden and Finland. Data from [72]. A major by-product emerging in the ore beneficiation process is concentrator tailings, which is essentially crushed silica rock with approximately 8% iron content. According to environmental reports from LKAB, the production of concentrator tailings in the year 2018 was in total around 5 Mton from the three mines [76; 77; 78]. Even though the iron content in this fraction is low, it could be expected to have some oxygen-carrying properties and it should be of interest to evaluate it as a bed material. The main advantage is that it is produced in large quantities and has no current applications, thus, it is practically a waste fraction. A challenge with concentrator tailings could be the relatively high concentration of phosphorous, which is known to potentially cause agglomeration when alkali is present in FBC. Preliminary inspection of concentrator tailings samples from LKAB suggested that it could have a large fraction of fine or fragile material. However, due to the good availability and the fact that it currently is regarded as end-of-life waste material, a large material loss can be accepted for the production of bed material from concentrator tailings. Production of low-carbon steel generates LD-slag, which has been a subject for OCAC and CLC experiments. As seen in Table 4, LD-slag contains both iron and a few percent manganese, which gives it its oxygen-carrying properties. LD-slag is also naturally rich in CaO, which suggests that it could be resistant to agglomeration [3]. Indeed, Ca-phases in LD-slag have been seen to react with and capture alkali components without causing agglomeration in fixed bed experiments [79]. A lower agglomeration tendency than silica sand was also concluded by dedicated agglomeration tests in connection with the OCAC experiment at Chalmers University's CFB [46].