ELIMINATION OF SODIUM HYDROXIDE IN CEHMICAL BAGASSE STREET OXYGEN DELIGNIFICATION STAGE IN TNPL

Transcription

1 ELIMINATION OF SODIUM HYDROXIDE IN CEHMICAL BAGASSE STREET OXYGEN DELIGNIFICATION STAGE IN TNPL Date of commencement: October 2015 Date of completion : on going Presented by Dr. S. SUBRAMANIAN DGM (Lab and R&D) TAMIL NADU NEWSPRINT AND PAPERS LIMITED-TNPL UNIT-1 KAGITHAPURAM UNIT-2 MONDIPATTI 2 1

2 PAPER AND BOARD PRODUCTION CAPACITY GROWTH,TPA Writing &Printing paper,mt Board,MT SELF SUFFICIENT IN POWER (100%) About 2.0MW of surplus power is exported to TANGEDCO Wind power is exported to state grid 2 No s of 3 KW Solar Panel installed in Wind Farm Thermal power,mw Wind Power,MW Solar Power,KW

3 PULP AND PAPER PRODUCTION PROCESS IN TNPL UNIT-1 - TAPCON - Captive Plantation - Farm Forestry - Global procurement - Procurement from all educational institution Baggase Hard Wood Waste Paper Sugar Sugarcane crop Sugarcane Sugar mill Bagasse Paper loading Paper Bagasse pulp Bagasse storage Forest Preservation COMPANY PROFILE World s largest bagasse based paper plant promoted by Governemnt of Tamil Nadu in early 80 s Exporting over MT of Writing and printing paper to more than 30 countries per annum IMS (ISO 14001:2015, ISO 9001:2015), ISO 27001:2013 and CW/COC Certified TNPL Cement - First of its kind in pulp and paper industry in India by using Lime Sludge and Fly Ash Over one lakh acres of pulp wood plantation since 2004 involving more than 22,200 farmers Commissioned multilayer double coated board machine 2.0lakh MT per annum for folding box and solid bleached sulphite board 6 3

4 CBECF PLANT PROCESS FLOW DIAGRAM 5 NUNMBER OF CONTINUOUS DIGESTER FOR BAGASSE PULPING DELTA COMBI SCREENING THREE STAGE (TRP) WASHING ODL STAGE POST ODL WASHING NO.1 POST ODL WASHING NO.2 D0 STAGE EOP STAGE D1 STAGE PULP TO MACHINE CHEMISTRY OF OXYGEN DELIGNIFICATION Using oxygen and alkali to remove the residual and dissolved lignin in the unbleached pulp that remains after cooking in order to improve the brightness of the pulp. Oxygen is weak oxidizing agent, but its power is promoted by an increase in temperature under alkaline conditions. During ODL, oxygen reacts predominantly with residual lignin and soluble the lignin in dissolved form. 4

5 OXYGEN DELIGNIFICATION(ODL)PROCESS The Bagasse pulp from the digester is screened, washed in three stage Twin Roll Press (TRP) and mixed with sodium hydroxide. The pulp is deposited in the oxygen reactor, steam heated and injected with gaseous oxygen to undergoes oxidative delignification. After ODL, pulp is washed to remove the dissolved lignin before moving to the bleaching plant. The lignin content in Bagasse ODL pulp is reduced by maximum 20%, resulting in marginal reduction in bleaching chemicals and chlorinated compounds. Effluent from the oxygen reactor is recycled in pulp mill and recovery cycle, further reducing the dissolved solids going to the bleaching plant, as well as effluent load from the bleach plant. The net effect is reduced effluent flows and less solids generation. BEFORE CONCEPTION IN CBECF : (ODL) STAGE Third stage washed BSW pulp NaOH O 2 STEAM ODL Stage 5

6 UNIQUENESS OF THE PROJECT Concept : Normally oxygen delignification in CBECF is carried out in alkaline ph range of above 10.5 to control effective solubility of dissolved lignin from Kraft pulping. This higher ph >10.5 increases the delignification efficiency but simultaneously decreases the dissolved lignin content in bagasse washed pulp. Application : In this project through extensive Laboratory studies and kappa number reduction data were carried out before implementation. In plant trial, sodium hydroxide is eliminated in ODL stage without any process modification. Decreased alkali carry over to post oxygen pulp for bleaching stage was observed. DISADVANTAGE OF OXYGEN DELIGNIFICATION IN BAGASSE PULP Bagasse pulp contains more pith fines, which surface area were higher than bagasse fiber. Pith fines holds more residual cooking chemicals from pulping, which removal is very difficult in Twin Roll Press (TRP) washing even at higher press load. Due to sponging nature of the pith fines, swelling with alkali is happened during sodium hydroxide addition in ODL stage. Therefore, residual active alkali carrying over from washed pulp is sufficient to maintain the alkaline ph in ODL stage. 6

7 IMPROVED ODL STAGE IN CBECF PULP This project was implemented in CBECF from October 2015 onwards. Oxygen delignified pulp without NaOH shows minor change in kappa number with decreased alkali loss. Post oxygen washer number-2 filtrate contains lower dissolved solids and residual alkali, which is used as counter current washing liquor of previous stage pulp. This lower alkali carrying over ODL pulp requires lower sulphuric acid in D 0 stage to maintain the pulp ph for chlorine dioxide bleaching. Bleach filtrate ph is observed as on higher side in D 0 stage and contains lower COD and BOD. AFTER CONCEPTION IN CBECF : (ODL) STAGE Third stage washed BSW pulp O 2 STEAM ODL Stage 7

8 BEFORE IMPLEMENTATION IN ODL STAGE CHEMICAL CONSUMPTION & COST S. No. Chemicals kg/t of pulp cost / t of pulp 1 Sodium hydroxide Sulphuric acid Total PULP PROPERTIES OF POST OXYGEN WASHER NUMBER (POW2) S. No. Properties Unit Alkali loss Kg/t Kappa number

9 CHEMICAL REUCTION PER TON OF BLEACHED PULP S. No. Chemical Before Implementation Kg/MT After Implementation Kg/MT Chemical saving Kg/MT NaOH H 2 SO Total * 7.69* * Open Market bagasse S. COST REUCTION IN Rs. PER TON OF BLEACHED PULP No. Chemical Before Implementat ion After Implementation Cost saving in Rs NaOH H 2 SO TOTAL

10 ANNUAL TANGIBLE BENEFITS (chemical and cost saving) S. No. Chemi cals (Oct.15-Mar.16) T / Cost Rs. / annum annum T / annum cost Rs./ annum T / annum cost Rs./ annum 1 NaOH ,00,60, ,85,71, ,23,40,900 2 H 2 SO ,78, ,33, ,65,210 Total ,26,39, ,17,05, ,43,76,110 ANNUAL COST ECONOIMICS FOR IMPLEMENTATION OF THIS PROJECT S. No. Cost Investment made nil nil nil 2 Cost saving per annum 126*Lakhs (Oct.-Mar) 217 Lakhs 144* Lakhs 3 Payback period IMMEDIATE * Plant stopped due to water crisis 10

11 PULP PROPERTIES OF POST OXYGEN WASHER NUMBER 2 AFTER IMPLEMENTATION S. No. Properties unit (Oct.-March) Alkali loss Kg/t Kappa number STRTENGTH PROPERTIES OF BLEACHED PULP S. No. Parameters Unit Before implement ation After implementation CSF ml * 2 Bulk cc/ g * 3 Breaking length M * 4 Tear Factor * 5 Burst Factor * *Open market bagasse 11

12 S. No. REUCTION OF BLEACHING EFFLUENT LOAD PER TON OF BLEACHED PULP Filtrate parameters Before Implementa tion mg/l After Implementation mg/l Pollution load Reduction % COD, kg/t BOD, kg/t Total * Water crisis period COST ECONOMICS OF THE PROJECT S. No. Parameters Benefit 1 Project cost (INR Lakhs) NIL 2 Intangible benefits ENCLSOED 3 Tangible benefits ENCLOSED 4 Savings ( in MT) Savings ( INR Lakhs) Pay Back (Years) Immediate 12

13 INTANGIBLE BENEFITS Improvement in initial alkali loss carried over to bleaching stage. Decreased alkali loss carry over to bleaching stage, require lower sulphuric acid to maintain the D 0 stage ph with same bleaching chemicals. Decreased suphuric acid addition in D 0 stage is increased pulp ph and thereby reduce the organic acid generation in bleaching filtrate and pulp. Higher end ph in chlorine dioxide bleaching is decrease the residual chlorine content in pulp, which eliminate the sulphur dioxide usage. Reducing sulphuric acid addition in D 0 stage is reducing caustic consumption in extraction stage and thereby reduces the recycling filtrate dissolved solids. CHALLENGES / BOTTLENECKS Before implementing of this project, R&D officials called for meeting with top management and pulp mill executives to discuss about the Laboratory trial results of bagasse pulp properties before and after ODL, pollution load reduction and cost saving etc. Machinery supplier cautioned us, elimination of sodium hydroxide will increase ODL outlet kappa number and require more bleaching chemical. There is no significant bottlenecks observed for implement this project. 13

14 REPLICATION POTENTIAL OF THIS PROJECT This project can be implemented in any Bagasse pulp mill having ODL stage immediately without using any modification or material cost. This project can be implemented in agro based pulp and paper Industry. ACHIEVING NATIONAL / INTERNATIONAL BENCHMARK / STANDARDS After elimination of sodium hydroxide in ODL stage, discharge CBECF effluent contains lesser pollution load is helps to meet the pollution control board standards. Decreased pollution load and raised end ph is an advantage for effluent treatment plant. At source chemical reduction or elimination is to decrease the pollution load at source itself. After implementation, the treated effluent COD and BOD values are decreased below to the National and International discharge standard. 14

15 EMPLOYEE INVOLVEMENT, TRAINING AND CAPACITY BUILDING Before implementation, process personnel were thoroughly educated the advantages of this project. Process personnel are well versed of this project objectives and after implemention it is running continuously. To reduce the pulp deposition in press part and feed lines were cleaned periodically and run the plant with maximum production rate. Continuous process monitoring of plant and if any process parameter deviation is attended immediately without time delay. FUTURE TARGETS AND ACTION PLANS This project is not implemented in HWECF plant due to the usage of oxidized white liquor (OWL) instead of sodium hydroxide. Two stage oxygen delignification is carried out in HWECF plant instead of one stage ODL stage in CBECF plant. Unbleached kappa number in Hard wood pulp is higher than Bagasse pulp. Laboratory trail is carried out to reduce the OWL addition in HWECF ODL stage. 15

16 June2018 Thanking you for listening our achievements 16