Chilean Mill uses PeCOD for Determination of Chemical Oxygen ...
Chilean Mill uses PeCOD COD Analyzer for Determination of Chemical Oxygen Demand (COD) for Savings in Bleaching Process Facts on the Chilean Mill Global company that produces many types of wood products Produces pulp used for: Paper Packaging material Diapers Produces board and wood used for: Furniture Construction What is COD and How is it Significant
to the Bleaching Process? COD is Chemical Oxygen Demand COD is the amount of oxygen required to fully oxidize organic matter It is used as a measurement of the oxygen-depletion capacity of a sample contaminated with organic waste It is significant to the bleaching process because it impacts the required chemical dosage of chlorine dioxide (ClO2) used for pulp bleaching Higher COD concentrations can result in greater consumption of ClO 2, which means excess bleaching chemical must be added to the process to compensate for the loss Traditional Method for Determining COD Traditional method for measuring COD in the wash water was by the SCAN:45-00 test The SCAN-test method is used for measuring the washing efficiency of the process The final equation calculates COD removal by washing in units of kg per ton oven dried pulp The test involves sample collection, COD analysis, and sample drying
COD of the wash water is measured by photometric method (~3hrs) Sample drying ~4hrs Total time of the test = ~ 7 hours Pulp Washing and Bleaching Challenges Experiencing deficiency in pulp washing Current SCAN-method for determining COD removal during washing takes too long Results arent timely for operation control Improper ClO2 dosing: Excess bleaching chemicals are used from accidental over-dosing, or to compensate for higher COD concentrations Pulp Washing and Bleaching Challenges Contd
COD concentration in the delignification stage (pre-bleaching) must be less than 12 kg COD/dry ton Knowing the deviations of the organic load in the process would allow operators to adjust ClO2 dosages, reducing excess chemical consumption, which is key to the profitability of the process Objectives and Goals to Improve the Bleaching Process Objective: Reduce the COD analysis time in the pulping process, to deliver a timely result to operations, thereby avoiding excess consumption of ClO 2 Goal: Decrease analysis time by 90%, to allow operators to respond to process deviations Mill Uses PeCOD COD Analyzer for Fast COD
Analysis Implementation in the lab: Validated the new method with respect to the standard SCAN test Implementation into operations: Faster COD results lead to closer monitoring of the wash area and improved bleaching process control What is the PeCOD COD Analyzer? A patented technology that measures COD by oxidizing organic matter by photoelectric method peCOD method eliminates the use of mercury and potassium dichromate Safe for both the environment and the analyst Results in less than 15 minutes
Accurate method with a detection limit of 0.7 mg/L, and upper range of 15,000 mg/L Nanotechnology The core of the technology is the PeCOD sensor, which consists of a UV-activated nanoparticle titanium dioxide (TiO2) photocatalyst coupled to an external circuit The powerful oxidizing potential of UV-illuminated TiO2 ensures that virtually all species will be fully oxidized giving a true measure of COD A Nanotechnology Based Approach hv ( < 400 nm) To external circuit and auxiliary
electrode e- Oxidation of organics Photocurrent Roughly 2 times the oxidizing power vs. dichromate i.e. Benzene, 1.8 by CODCr and 2.6 by PeCOD Immobilized TiO2 nanoparticle Conducting substrate (Eapp = 0.2V vs Ag/AgCl) Electrons to COD
Sample 100 mg/L COD Blank Time 5 min Area under curve = Qnet COD = k (Qnet Qblank) Chilean Mills Findings Using the peCOD Method Figure 1: peCOD (blue) versus traditional method (red) for COD analysis at Diffusor Line 2.
Figure 2: peCOD (blue) versus traditional method (red) for COD analysis at Press 2, Line 2. Findings Using the peCOD Method Contd Decreased time in analysis: 3 hours for COD analysis + 4 hours for drying Total Time: 7 hours peCOD method
0.27 hours (16 min.) for COD analysis + 0.08 hours (5 min.) for review Total time: 0.35 hours (20 min.) Time (hr) SCAN method 8 7 6 5 Review Drying Analysis
4 3 2 1 0 SCAN PeCOD Findings Using the peCOD Method Contd November 2013 December 2014
The graph shows a decrease in events for 2014 (with peCOD) compared to 2013 (pre-peCOD) Economic Evaluation Methods SCAN Method Daily 12 Daily PeCOD Method
12 Annual reagents cost for COD analysis Total Analyses Boxes Cost Monthly (USD) Monthly Annually 15 (25 vials 360 4320 30.00 per box)
Total Analyses Cost Reagent Use Reagents Monthly Annually Monthly [L] (USD/1L) 360 4320 2.5 60.00 Cost Monthly (USD)
Switching from the SCAN method to peCOD method resulted in savings in reagents costs by 66.4% Saving 3,600 USD/year Economic Evaluation Contd Excess ClO2 per event Line 2 COD [kg /ton] 10-12 13-19 ClO2 ClO2 consumption consumtion [kg/ton]
[kg/day] 16.3 23,651.3 18.6 26,988.6 Production (ton/d) Line 1 ClOClO2 [kg/day] 3,337.3 1,451
13-19 kg/ton of COD represents a COD event An increase in 3kg COD/ton = increase in 1kg of ClO2 consumption in the bleaching process Chemicals saving of approximately 2,237kg of ClO2 per day, considering an event in both lines 786 Risk Assessment of COD Test Method SCAN-test Method: Heat Hazardous chemicals Hazardous waste disposal Significant peCOD Method: No heat Reagents are safe
Waste is safe (can go down the drain) Tolerable Conclusions Safety: Decreased risk from significant to tolerable Improved health and safety for workers Environment: Reduced contamination to the effluent (eliminated excess ClO2 use) Eliminated hazardous waste, generated using the traditional COD method Savings: COD analysis time reduced by 95% Consumption of chemical reagents for COD analysis decreased by 66.4% Management of ClO2 consumption in the bleaching process resulted in bleaching chemical savings, over 2000kg of ClO2 when an event was avoided each day
Conclusions Operators have peCOD results in less than 20 minutes PeCOD generated chemical savings, which means money savings! Improved Health & Safety, and Profitability Mill receives national award for improving sustainability 5 PeCOD units now in 2 mills Thank You! Questions? Website: http://mantech-inc.com/ Email: [email protected] Maggie Grierson Email: [email protected]
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