Pulverized coal injection

This ppt contains all information regarding PCI.

1. PULVERIZED COAL INJECTION IN BLAST FURNACE Navin Kumar Third year Metallurgy and Materials Engg . IIEST, Shibpur Id- 511115007

2. INTRODUCTION Pulverized coal injection was developed in the 19th century, but was not implemented industrially until the 1970s. Even PCI technology was available at that time in several countries but due to the economics and ease of the process oil and natural gas injection became more popular. Rises in the cost of  Coke due to increased global demand and thus more competition for the resource have made this method attractive to the iron producing industries and increased its value. In early sixties of the last century PCI was successfully implemented in AK Steel of USA and Shougang in China. TATA STEEL commissioned coal injection on there ‘F’ Blast furnace in March, 1991. This system is capable of injecting 150 kg/ thm . Currently almost all modern blast furnace all over the world use coal injection 100 – 200kg/ thm as a matter of routine practice.

3. What is PCI ? Pulverized Coal Injection (PCI) is a process that involves injecting large volumes of fine coal particles into the raceway of a blast furnace (BF ). What it does in BF :- Reduces the need of metallurgical coke for reactions in the blast furnace . Supplemental source of carbon. Speeds up the production of liquid iron. The main motive for the injection of Pulverized coal is to move away from the production of the metallurgical coke with its inherent environmental problems.

4. Concept and the process of coal injection The PCI technology is based on the simple concept of carrying the finely ground (pulverized) dried coal by a conveying gas (normally nitrogen) to the blast furnace where it is distributed to different tuyeres and injected through a lance in the blow pipe  In the blow pipe it is mixed with hot blast and then supplied to the blast  Furnace. The raceway propagates coal and coke combustion and melts the solid iron ore, releasing molten iron.

5. 1. Raw coal is screened and processed to remove tramp materials and is stored in raw coal bins 2. Raw coal is pulverized in grinder ( Pulverizer ) and Coal is dried thoroughly to prevent saltation and compaction . 3. For the drying of pulverized coal the waste gases of Blast furnace and Coke oven gases are used. 4. The pulverized coal is deposited in a single reservoir bin and stored under inert conditions . 5. The flow rate of the pulverized coal is regulated by inert gas pressure as a function of feed tank weight change. 6. The single stream of dense phase coal from a feed tank is combined with transport gas (nitrogen) at the mixing tee. 7. A single transport pipe carries the coal/gas mixture to a coal distributor located at the blast furnace. 8. At the distributor the single stream of coal/gas mixture is divided automatically into multiple equal streams and conveyed by a pipe into each tuyere for injection into the blast furnace . .

6. Flow Chart of Pci :-

7. s

8. COAL DISTRIBOTERS :-

9. The main features of the pulverized coal injection process :- Reducing the consumption of primary energy :- Blast furnace stove waste gas along with BF gases is used as source of energy for coal drying thus. The moisture of the coal can be removed from the system very effectively without the use of a gas cooler or condenser . Reduces the risk of fire and explosions :- Due to The use of inert gas during the operation of the reservoir bin. Ensure continuous flow of the coal :- Due to the parallel arrangements of the feed tanks into the blast furnace. The system ensures even distribution of the injected coal :- Due to every tuyers are attached with lance for PCI. Long life of pipe :- The coal is conveyed in the pipeline at a speed of only a few meters per second. Low conveying speed of the coal reduces the wear in the pipe thus increasing its life.

10. 6. Reduces the chances of coal dust explosions :- In the closed loop system, the emitted gas from the filter is partly recirculated to the inlet of the pulverizing mill. This creates an inert condition which minimizes the oxygen content in the system and reduces the chances of coal dust explosions .

11. THE PC INJECTION AFFECTS THE FOLLOWING FURNACE PARAMETERS :- Flame temperature Bose gas composition and volume The top gas temperature and CO/CO2 ratio and hence the efficiency Operational efficiency i.e. the proportion of direct and indirect reduction Slag volume and its basicity Overall production efficiency

12. Effect of various injectants on BF conditions Parameters Changes Change in flame temp., (degree Celsius) Change in coke rate, kg/ thm Natural gas Anthracite coal Heavy volatile coal Heavy fuel oil + 100 kg/ thm + 100 kg/ thm + 100 kg/ thm + 100 kg/ thm - 513 - 162 - 218 - 312 - 82.6 - 92.0 - 76.1 - 98.4

13. The limit of injecting PC is detected by a parameter called ‘ coal combustion potential ’ defined as CCP = Oxygen supplied to raceway (Nm^3/ hr ) Oxygen required to burn injected coal (kg/ hr ) The ideal value of CCP is 1.

14. Advantages of PCI :- 1. PCI uses non coking coal. This coal is cheaper than the metallurgical coke. In most of the blast furnaces PCI replaces 30 to 50 % of the metallurgical coke charge. This results in lower fuel cost 2. The productivity of blast furnace improves since coal injection is accompanied with oxygen injection. 3. A wide range of coals can be injected 4. Injection rates are higher than the injection rates of other fuels such as oil and natural gas. 5. Coal grinding and injection systems are non polluting systems. Hence the overall pollution from coke production for iron making gets reduced by injecting pulverized coal in the blast furnace.

15. 6. Coal supplies are relatively stable when compared with the petroleum fuels supplies. 7. Coal injection system is less costly than the cost of an additional coke oven battery. Lower capital cost means lower depreciation and interest to be charged on hot metal . disadvantage of PCI :- One of the chief problem to be faced in PCI is its effect on deadman . In case of incomplete burn of coal the PCI can give rise to suit of char formation and may decrease the permeability of the deadman .

16. REFERENCES :- Modern Iron Making by R. H. Tupkary and V. R. Tupkary Blast Furnace Phenomena and Modelling, The Iron and Steel I nstitute of Japane http://ispatguru.com/pulverized-coal-injection-in-a-blast-furnace / https://en.wikipedia.org/wiki/Pulverized_coal_injection_method