Waste Plastics injection in a Blast Furnace Nov14

Waste Plastics injection in a Blast Furnace...

Waste Plastics injection in a Blast Furnace The recycling of waste plastics (WP) by injecting them in a blast furnace (BF) is being practiced in few BFs especially in japan and Europe. The use of plastics in the BF also recovers energy from the WP and so it is sometimes considered as energy recovery. BF based ironmaking processes can utilize WP by any of the following methods. Carbonization with coal to produce coke. Top charging into the BF, although this generates unwanted tar from the decomposition of the plastics in the shaft. Gasifying the plastics outside the BF. The resultant synthesis gas is then injected through the tuyeres. Injection as a solid through the tuyeres in a similar way to pulverized coal (PC). Normally it is done as a co-injection of WP and coal into the BF. The first attempt for the waste plastics injection (WPI) in a BF was made at the Bremen Steel Works in 1994, with commercial injection starting a year later. The first integrated system for injecting plastic wastes was at NKK’s (now JFE Steel) Keihin Works in Japan. Injecting WP into BF has several environmental, operational and economic advantages. These include the following. Reduction in the amount of plastic wastes being landfilled or incinerated. Lower consumption of both coke and PC, thus saving coal resources. However, neither WP nor PC can completely replace coke. The amount of coke replaced in the BF is partly dependent on the quality of the WP. There is energy resource savings. The benefit of saved resources from mixed WPI is around 11 giga calories per ton (Gcal/t). There is decrease in the carbon dioxide (CO2) emissions since the combustion energy of WP is generally at least as high as that of PC normally injected,...

Hot Metal

Hot Metal Hot metal (HM) is the output of a blast furnace (BF). It is liquid iron which is produced by the reduction of descending ore burden (iron ore lump, sinter, and pellet) by the ascending reducing gases. HM gets collected in the hearth of the BF. From the hearth, the HM is tapped from the taphole of the BF after an interval of time. Normally in large BFs, HM tapping rates of 7 ton/min and liquid tapping velocities of 5 m/sec, in tap holes of 70 mm diameter and 3.5 m long, are typically encountered. The tapping rate of HM is strongly influenced by the taphole condition and taphole length. Generally the temperature of tapped HM varies in the range of 1420 deg C to 1480 deg C. The tapped HM is handled in the two stages namely (i) handling of the HM in the cast house i.e. from taphole to the hot metal ladles (open top or torpedo), and (ii) transport of HM ladles to the point of HM consumption. Presently most of the HM is consumed within integrated steel plants for steel making. The HM is transferred to the steel melting shop for making of steel. The HM which is not sent for steel making is cast into pig iron in pig casting machine for use in steel making later as cold charge or is sold to foundries or to mini steel plants having induction furnaces as merchant pig iron. HM can also be granulated by a process which is known as ‘Granshot’ process. Presently the Granshot plants for the production of GPI are working at six places namely (i) Uddeholm, Sweden, (ii) SSAB Lulea, Sweden, (iii) Voest Alpine, Donawitz, (iv) Saldanha steel, South Africa, (v) SSAB Oxelosund, Sweden, and (vi)...

Understanding Blast Furnace Ironmaking with Pulverized Coal Injection Nov04

Understanding Blast Furnace Ironmaking with Pulverized Coal Injection...

Understanding Blast Furnace Ironmaking with Pulverized Coal Injection Injection of pulverized coal in the blast furnace (BF) was initially driven by high oil prices but now the use of pulverized coal injection (PCI) has become a standard practice in the BF operation since it satisfies the requirement of reducing raw material costs, pollution and also satisfies the need to extend the life of ageing coke ovens. The injection of the pulverized coal into the BF results into (i) increase in the productivity of the BF, i.e. the amount of hot metal (HM) produced per day by the BF, (ii) reduce the consumption of the more expensive coking coals by replacing coke with cheaper soft coking or thermal coals, (iii) assist in maintaining furnace stability, (iv) improve the consistency of the quality of the HM and reduce its silicon (Si) content, and (v) reduce greenhouse gas emissions. In addition to these advantages, use of the PCI in the BF has proved to be a powerful tool in the hands of the furnace operator to adjust the thermal condition of the furnace much faster than what is possible by adjusting the burden charge from the top. Pulverized coal has basically two roles in the operation of a BF. It not only provides part of the heat required for reducing the iron ore, but also some of the reducing gases. For understanding the HM production in a BF with the injection of pulverized coal, it is necessary to understand what is happening inside the BF as well as the chemical reactions and the importance of permeability within the furnace and how the raw materials can affect this parameter. The BF is essentially a counter-current moving bed furnace with solids (iron ore, coke and flux), and later molten...

Natural gas and its Usage in Iron and Steel Industry...

Natural gas and its Usage in Iron and Steel Industry Natural gas (NG) is an environmentally friendly non-renewable gaseous fossil fuel which is extracted from deposits in the earth. It is a clean and green fuel with a high efficiency and plays a major role in helping many industries cut emissions and improve the overall air quality. It is normally supplied as (i) piped natural gas (PNG), (ii) compressed natural gas (CNG), and (iii) liquefied natural gas (LNG). Natural gas is a mixture of hydro-carbons consisting primarily of methane (CH4), generally in a percentage of over 85 % by volume. Other hydro-carbons in NG include varying amounts of various higher alkanes such as ethane, propane, and butane etc. It also contains water vapour (H2O) at varying degrees of saturation, or condensed water. It may also contain some small percentage of nitrogen (N2), carbon dioxide (CO2) and hydrogen sulphide (H2S) and helium (He) etc. NG burns with a clean blue luminous flame when mixed with the requisite amount of air and ignited. It is considered one of the cleanest burning fuels. On burning, it produces primarily heat, CO2, and water vapour. NG is a fuel found in deposits in its gas phase. It is colourless and odourless, non-toxic, and lighter than air. It does not contain olefins (hydrocarbons produced during the process of destructive distillation or reforming). It is a highly flammable and combustible gas. Its CAS number is 8006-14-2 and UN number is 1971. Quantities of natural gas are measured in normal cubic meters (corresponding to 0 deg C and 1 atmosphere pressure) or standard cubic feet (corresponding to 16 deg C and 14.73 pounds per square inch absolute pressure). The higher heat value of one cubic meter of natural gas varies from around 9500...

Understanding Pulverized Coal Injection in Blast Furnace Oct21

Understanding Pulverized Coal Injection in Blast Furnace...

Understanding Pulverized Coal Injection in Blast Furnace Pulverized coal injection (PCI) is a well-established technology for hot metal (HM) production in a blast furnace (BF). It is practiced in most of the BFs and all the new BFs are normally built with PCI capability. The composition and properties of the coal used for injection can influence the operation, stability and productivity of the BF, the quality of the HM, and the composition of the BF gas. The coals being used for the PCI are described in the article under link ‘http://ispatguru.com/coal-for-pulverized-coal-injection-in-blast-furnace/’. The critical aspects of PCI systems include coal preparation, its storage and distribution to ensure uniform feed of coal to each tuyere without fluctuations in the coal delivery rate and its combustion through lance design and oxygen (O2) injection. Coal preparation Pulverization of coal is carried out in a single or multiple grinding mills (pulverizers) depending on the requirements. Grinding and distribution of the coal to the injection lances constitute a major operating cost. Coal reclaimed from coal storage is screened for the removal of the foreign material and any large lump of coal is crushed. The coal is then fed into the mill where it is pulverized and dried. Coal of the required size is transported out of the mill by the hot gas stream, collected in a bag filter and conveyed to the storage bins. Grinding and transport are carried out under an inert atmosphere to minimize the risk of ignition of the dry coal particles. The resultant particle size distribution of the pulverized coal affects it handleability in pneumatic transport equipment and, at high injection rates, its combustibility. Pulverizers grind coal to one of the two size fractions namely (i) pulverized coal where around 70 % to 80 % of...