Petcoke for jsw. pradeep
- 1. Petcoke firing in Kiln K.P.PRADEEP KUMAR
- 5. Petcoke properties The use of petcoke as a thermal energy source offers potential for reduction of thermal energy costs. However Petcoke has different properties from coal which must be take into account: • Petcoke has in general a higher sulfur content compared to normal coal which can enhance the formation of build-ups in the kiln system. • Petcoke has in general low volatiles and ash content. • The volatiles of petcoke are not released below 900°C. The volatiles of petcokeare mainly methane compared to >50% aromatic compounds in bituminous coals. The aromatic compounds present in the coal combust more easily • Petcoke burns from the outside and does not explode. This causes the problemof precalciner burnout and temperature increase in the bottom cyclone stage • The maximum petcoke substitution rate is related to the amount of the circulating elements - sulfur, alkali and chlorine - which are contained in the fuel and raw meal inputs • The Hardgrove index of petcoke is generally lower than of coal
- 6. Petcoke rules The following rules are important for the utilization of petcoke in calciner kilns: • Alkali / sulfur SO3 inputs <2.0% (clinker basis); Molar ratio of Alkali / sulfur ≥ 0.4 • Coal / petcoke preparation Controlled mixing from two feed hoppers • Coal mill o Petcoke fineness R 90µm <3% and R 200µm <1% o Determine the coal mill output by trial (Hardgrove index can be misleading, greasing effect) • Kiln feed (raw material) o Kiln feed uniformity LSF, STD <1.2 SR, STD <0.04 AR, STD <0.04 o Medium term (10 min) mass-flow fluctuations <±0.5% • Fine coal dosing o Short term mass flow fluctuations (10 sec) <±1% o Fluctuations in calorific value of coal/petcoke mixture <±1% o Pressure fluctuations in transport duct at burner <±10% of average pressure • Combustion o O2 content at kiln inlet sufficient high, o O2 target = 3-4% at kiln inlet, CO <0.1% (better CO <0.05%)
- 9. Petcoke firing 1.Grinding 2.Combustion 3.Volatile recycle 4.Influence of refractory 5.Effect on quality of cement
- 10. coal mill Table rpm =35 Table dia = 2.5 M Capacity = 50 tph for coal The hard groove of index of petcok is about 40 % And the residue of pet coke is < 3 % on 90 Microns . For this the damm ring has been Increased by 20 mm (from 120 to 140 mm) Sometimes the mill operates at 90% of the Speed to have stable bed.Water spray on the Grinding track further stabilises the bed to Improve grinding efficiency As thumb ruleresidue on 90 microns =volatiles* 0.5,( volatiles=7-8 %) 7*.5=3.5 Dam ring
- 13. Mill capacity vs HGI coal petcoke
- 14. Combustion of petcoke in pyro system
- 21. Flame impulse =10-11 N/Mw 0r Momentum = 2000 t0 2500 % m/s Coal injecction velocity =30 m/s Petcoke injection velocity= 25 m/s
- 22. Jet air in pyro jet =400 m/s Normally = 3.0 % Normally ,25 m/s
- 27. Normally 3-4 %
- 33. Modern burners are aligned parallel to kiln axis If it is parallel to kln axis it may impinge the charge If the flame is short and convergent it may not impinge the flame
- 35. Flame is parallel to kiln axis , 3.5 to 4.0 % slope
- 43. Petcoke firing in calciner
- 48. Pyroclone and low nox calciner Firing point Hgh tertiary air temperature with clnker dust laden With rich oxygen (21 % ) is more favorable for Petcoke firing than low NoX calciner ,though it Has high retention time > 5 -6 seconds.
- 52. Why we must have O 2 when we do petcoke firing
- 65. Longer flame elonagte the burning zone and transition zone where the meal Has more retention time and make it favorable for more evaporation
- 77. REFRACTORY FAILURES Refractory failures are generally very difficult to identify the root cause failure mechanism. The main reasons are: •Very few people truly understand the non-linear properties of the •refractory, the thermo-chemical reactions of the refractory with the •process environment and the thermo-mechanical interactions of the refractory and steel shell. •Correct information regarding the service conditions of the existing refractory is rarely compiled by the plant. •There are so many variables that could affect the brick reliability during a typical campaign •that it would be impossible to isolate the direct effect of any. •Most refractory (especially kiln brick) failures are a result of a complex combination of multiple variables.
- 78. Sulfur / Alkali – The most obvious affects of burning Pet Coke on cement plant refractory have been the destructive forces of sulfur / alkali. These destructive forces are seen in brick spalling, brick capping, shell corrosion, anchor corrosion, alkali penetration, expansive refractory reactions and direct damage from buildup removals. Depending on the fuel sources, pet coke can have anywhere from 1-7 wt% more sulfur and is typically in the 4-6% range. This change in fuel composition Creates a large change in the sulfur / alkali ratio and the resulting cycles.
- 79. Direct Refractory Damage – “Direct” refractory damages are of a physical nature due to mechanical forces. These damages and the failure analysis are usually easily identified and corrected in a timely manner. Examples of “direct damage” include the following: Misaligned kiln, kiln shell damage, incorrect shimming of the kiln tires, direct flame impingement of a misaligned burner, over-firing a burner, sulfur ring buildups, abrasion in high wear areas and normal wear and tear of the system. Direct Refractory Damages that are related to fuel variations might include: •Excessive temperatures (due to coke combustion) in the “burning zone” brick •which show 1 ½” to 2” of severe penetration of high liquid phase is an indication of excessive temperature. This can be accompanied with thick coating and extremely hard to remove (also indicating high liquid phase). • Deep cobbling of brick is a result of excessive temperatures which left residual stress in the brick.
- 80. •AZS castables have been found to offer excellent buildup •resistance in cement application. The AZS grain imparts great thermal shock (water blasting) resistance, low thermal expansion, low thermal conductivity and excellent abrasion resistance. The AZS fused grain products are an upgrade over the products with just the Zircon additive. Numerous trials have shown that it is more effective to utilize an AZS refractory rather than Silica Carbide. The AZS refractory has shown as good if not better results for buildup resistance, lower conductivity for better designs, and better resistance to alkali/steam reactions that limit the service life of Silicon Carbide. •Standard 50-70% alumina products can be upgraded with a zircon flour addition of 4-8% in the matrix. The zircon addition can fill interstices sites within the refractory matrix and impart a “non-wetting” type property to the system to help repeal alkali impregnation.This type of product is recommended not only in buildup areas of the Tower but also in the Cooler and Tertiary Air Ducts. •Denser spinel kiln brick with less porosity / permeability are being evaluated to help decrease kiln shell corrosion. The trade off is that this type of brick will generally have a higher modulus of elasticity and may not lead to shorter term reliability. •Monolithic materials with high percentage of calcium alumina cement should be avoided in any application above 1400 deg. F. •Any firebrick should be of the high-fired variety to avoid expansive reactions.
- 89. Thank you