Measuring of VOC emissions from pulping process wastewaters

Transkriptio

1 VOCless Pulping Wastewaters LIFE09 ENV/FI/568 Measuring of VOC emissions from pulping process wastewaters Work 10745Y10A On 20 th of September 2013 Kuokkamaantie 4 Box 428 FI Tampere Finland Tel CONSU LTING ENVIRONMENT

2 CONSU LTING REPORT Work 10745Y10A ENVIRONMENT Seppo Heinänen/she (9) seppo.heinanen@ax.fi Tel. direct Client Assignment Meehanite Technology Markku Tapola Kuokkamaantie 4 FI- FINLAND Measuring of VOC emissions from pulping process wastewaters Date and place of measurements: Anjalankoski , , , , and Kotka , , , and Measuring staff Reported by Marko Liikanen, Perttu Kriikku, Heikki Paukkunen, Ari Hiltunen, Pauli Pellikka and Seppo Heinänen Seppo Heinänen A X L V I C o n s u l t i n g L t d Environmental Engineering Department Seppo Heinänen Environmental Engineering Dept. Manager Marko Liikanen Chief of the Measurement Staff

3 AX-LVI Consulting Ltd 2 Table of contents 1. Wastewater treatment processes studied in LIFE project Stora Enso Anjala Mill, Anjalankoski, Finland Kotkamills, Kotka, Finland Measurement results Stora Enso Anjala Mill VOC concentrations of wastewater VOC emissions released into atmosphere Specific VOC emissions and total VOC emission balances Kotkamills, Kotka VOC-concentrations of wastewater VOC emissions released into atmosphere Specific emissions and total VOC emission balance Conclusions Stora Enso Anjalankoski Kotka Mills Kotka Specific emissions from aerobic and anaerobic system Measuring uncertainty Measurement equipment APPENDICES APPENDIX 1 Stora Enso Anjala Mill. VOC concentrations in wastewaters APPENDIX 2 Stora Enso Anjala Mill. Measured VOC concentrations in air cooling towers and MBBR1 APPENDIX 3 Stora Enso Anjala Mill. VOC compouds in air samples APPENDIX 4 Kotkamills. Measured VOC concentration and emission in wastewater APPENDIX 5 Kotkamills. Measured VOC concentrations and emissions in air APPENDIX 6 Kotkamills. Measured VOC compouds in air samples

4 AX-LVI Consulting Ltd 3 1. Wastewater treatment processes studied in LIFE project 1.1. Stora Enso Anjala Mill, Anjalankoski, Finland Stora Enso Publication Papers Oy Ltd Anjala Mill (see the Figure 1). The annual prodiction capacity is tonnes and the production in 2012 was tonnes of book paper and improved newsprint grades. There are 330 employees. Figure 1. Stora Enso Publication Papers Oy Ltd Anjala Mill, Finland Stora Enson Anjala Mill has the aerobic waste water treatment system. All wastewaters from the paper mill, board mill and mechanical pulping including TMP and PGW production as well debarking is collected to the equalization station for ph control and mixing. Alone in the mechanical pulp mill there are ten different sites from where wastewaters are led to wastewater treatment plant. Total wastewater amount is about m 3 /d. Solid suspense are settled in primary clarifier and the wastewaters are cooled in cooling tower to 37 C. The process diagram is presented in Figure 2. Nutrients, phosphor and urea will be added, and waters are pumped to the biological wastewater treatment. The objective of this process is to remove soluble and insoluble organics from wastewater stream and to convert the material into flocculant microbial suspension that is readily settleable and will permit the use of gravitational solids liquid separation techniques. The process used in this case is so called nutrient restricted MBBR

5 AX-LVI Consulting Ltd 4 (Moving Bed Biofilm Reactor) activated sludge process. The easily degradable organic materials will be degraded already in MBB reactors. The amount of organic material in wastewaters is descripted with the biological oxygen demand BOD7. In aerated reactors the microbes are cleaning the wastewater using the soluble materials as nutrition and consuming oxygen. Additional nutrients (like phosphor and urea) are needed. The yield will be carbondioxide, water, heat and new microbes. Microbes, activated sludge will be returned after the final sedimentation to the aeration basin, and the excess sludge to the sludge handling. Process conditions are restricted, ph about 7, temperature under 40 o C. After the final sedimentation clarification, the cleaned water is led to the river of Kymijoki. bioreactors MBBR equalisation neutralization pumping reserve 1 2 clarification sedimentation aeration, biology cooling Figure 2. The chart of Stora Enso Anjala Mill wastewater treatment system Kotkamills, Kotka, Finland Kotkamills is a forest products company in Finland. The company specializes in laminating paper, matt coated bulky paper and sawn products. The annual production capacity of Kotkamills is tonnes of Absorbex Kraft Paper and tonnes of Imprex products, tonnes of Solaris paper, and m 3 of sawn timber. The company employs 570 people. See Figure 3.

6 AX-LVI Consulting Ltd 5 Figure 3. Kotkamills Oy in Finland. Kotkamills has both aerobic and anaerobic wastewater treatment systems. The total wastewater amount is about m 3 /d. Only a small amount, circa 10% of all wastewater flow is treated anaerobically. Wastewaters from the mills with high COD-concentration are collected to the primary flotation. Solid suspenses are removed with the air flotation system and the clarified wastewater is led to the tank where also concentrate drains are collected from the evaporation plant and clarifiers from the mill. High COD-concentration makes it possible to use anaerobic treatment. Anaerobic wastewater will be cooled in two cooling towers to be suitable for the biological treatment (under 40 o C). The following process is anaerobic acidification stage (Figure 4). Anaerobically purified water is additionally led to the aerobic aerated basin (1500 m 3 ) together with other wastewaters from paper and pulp mills flowing via primary clarifier. After the post-sedimentation the purified wastewater is finally led to the sea of Suomenlahti.

7 AX-LVI Consulting Ltd 6 ANAEROBIC PV.evaporation Clean filtrate Unclean condensate PM2 Grid Flotation Cooling tower Acid Reactor Odourgas Aeration base AEROBIC Fiber water Grid Primary clarifivation Cooling tower Combined breath fumes Secundary clarification base Figure 4. The chart of Kotkamills wastewater treatment system. To the sea 2. Measurement results 2.1. Stora Enso Anjala Mill Table 1. Measured VOC emissions Target concentration air flow hourly emission annual emission mg/nm 3 Nm³/h kg/d kg/a Primary clarification 48, ,3 822 Cooling towers 3, , MBBR 1 17, ,0 369 MBBR 2 14, ,9 321 Secondary clarification 1, ,2 69 Sum 48, Measurements at Stora Enso Anjala Mill were carried out at the cooling tower and the moving bed bioreactors (MBBR1 and 2 ). Pilot sites were decided based on the preliminary measurement results carried out in during the first LIFE VOCless Pulping project LIFE06 ENV/FI/

8 AX-LVI Consulting Ltd VOC concentrations of wastewater VOC concentrations fluctuated greatly specially in the wastewater from the debarking plant where the fluctuation in different days may exceed the ratio of 1/5. The fluctuation was also great in the wastewater from TMP plant (thermomechanical pulping) (App1). The concentration level was descending after the sedimentation and the cooling and also the fluctuation decreased but the distinct fluctuation was still observed. This also effected on VOC emissions. Detected VOC compounds were mainly alcohols (ethanol and methanol) and some samples contained also turpentines. Additionally the samples contained several unidentified hydrocarbons VOC emissions released into atmosphere The airborne VOC concentrations of aeration air of the wastewater basins caused fluctuation also in the hydrocarbon emissions into atmosphere between various measurement days (App 2). Especially in the MBBR basins the fluctuation was significant on different measurement days. The fluctuation of VOC concentrations was at highest threefold. Detected VOC compounds were mainly same as in wastewater. Additionally also different turpentines origin from wood were detected from alcohols. Unexpectedly, emissions also contained quite a high concentration of methane. Methane most probably originates from the anaerobic bacterial activity in waste water treatment system. In the additional measurements carried out on methane portion of VOC compounds was 24 v-% in the pre-sedimentation basin, 55 v-% MBBR1 basin and 40 v-% in MBBR2 reactor.

9 AX-LVI Consulting Ltd Specific VOC emissions and total VOC emission balances Table 2. Specific VOC emission Target specific emission kg/t product From PGW to air 0,41 From TMP to air 0,38 From deparking to air 0,06 From proces to wastewater by water 0,89 From wastewater to air 0,03 From wastewater to river 0,04 Total to air 0,88 Total to water 0,04 Total sum 0,93 VOC emission balances of the PGW and TMP plants were measured in the first VOCless Pulping project (LIFE06 ENV/FI/000201) in Based on these measurement results the total annual VOC emissions from the PGW plant were 195 tons (production was tons). The total annual VOC emissions from TMP plant were 41 tons (production was tons). The total annual VOC emission balance of mechanical pulping production in Stora Enso Anjala Mill was about 236 tons in The specific VOC emissions from the process dissolved to wastewater was 0,89 kg/produced pulp ton. Based on the tentative results from the first VOCless Pulping project, the specific VOC emission was measured as 0,48 kg/produced pulp ton. According to the measurement results in this project, the amount of VOC emissions dissolved in wastewaters was almost two times higher than expected (0,89 kg/t product). In 2012 the total production in Stora Enso Anjala Pulp Mill was tons. The total VOC emissions of the aerobic wastewater treatment plant were 445 tons in VOC concentration measurements of the aerobic wastewater treatment plant result the cleaning efficiency of 91%. Annually 17 tons of VOC emissions are released to the environment.

10 AX-LVI Consulting Ltd Kotkamills, Kotka Table 3. Measured VOC emissions Point of measurement TVOC concentration CH 4 - concentration NMVOCconcentration Exhaust gas flow NMVOC hourly emission NMVOC annual emission mg/nm³ mg/nm³ mg/nm³ Nm³/h g/h kg/a Primary clarification 5,0 2,6 2,4 45,2 0,11 0,94 Flotation base 407 1, ,8 103 Wastewater tank 116 0, Cooling tower 4,3 0,04 4, Combined breath fumes to water Weak odorgas to water , Aeration basin middle , Aeration basin side , Sum Secondary clarification , ,6 17,5 153 Tolal emisiions VOC-concentrations of wastewater Effluent VOC concentrations vary highly over the time depending on the situation of the pulp production and operation of the wastewater treatment system. The strongest VOC concentration of wastewaters did origin from the anaerobic system (eg. likaislauhde). The anaerobic reactor was not working properly all the time during the project measurements because of malfunction. This also affected the measurements and it was taken into account when planning the measurement activities. VOC concentrations are equalized in the aeration basin where both the aerobic and anaerobic wastewaters are mixed. Measured VOC compounds were mainly alcohols (ethanol and methanol) and some samples contained also turpentines VOC emissions released into atmosphere The VOC concentration in wastewaters was also detected in the hydrocarbon emissions into atmosphere in various measurement days. Detected VOC compounds were mainly the same as the ones in wastewaters. In addition to alcohols also different turpentines origin from wood were detected. Unexpectedly, emissions also contained quite a high concentration of methane. It probably origin from the bottom of the sedimentation basin

11 AX-LVI Consulting Ltd 10 where anaerobic bacterial activity occurs Specific emissions and total VOC emission balance Table 4. Specific VOC emission Target specific emission kg/t product From proces to wastewater by air 2,45 From proces to wastewater by water 2,98 From wastewater to air 0,79 From wastewater to sea 0,05 In Kotkamills there are more VOC emissions are dissolved in the wastewaters from the production (2,98 kg/produced pulp ton) than in Stora Enso Anjala Mill. 90% of the wastewaters will be treated in aerobic wastewater treatment system and 10% in the anaerobic reactor (strong concentrations). At the end all wastewaters are gathered to the aerobic treatment basin and from there led to the sea. The total VOC emissions in wastewaters were 596 tons in Production was tons. Based on the project measurement results the VOC cleaning efficiency in the aerobic basin was about 85%. The annual VOC emissions of the anaerobic wastewater treatment system are an average 162 tons that are released to the environment. 3. Conclusions 3.1. Stora Enso Anjala Mill High variations of VOC concentration in wastewaters and also in air appeared in different measurement days were somewhat unexpected. It was not detected whether the fluctuations were caused because of changes in TMP process or in wastewater treatment process. Most likely the fluctuations are origin from the production. Due to the long delay time of 2,5 days of the waste water treatment plant any confident conclusions can not be made. The tentative results from the first VOCless Pulping project showed the specific emission of 0,48 kg/produced pulp ton. Based on the measurement results from this project, the amount of VOC emissions dissolved in wastewaters was almost two times higher than expected (0,89 kg/t product). Therefore an efficient wastewater treatment system

12 AX-LVI Consulting Ltd 11 is needed to abate the dissolved VOC emissions from wastewaters Kotka Mills Kotka High variations of VOC concentration in wastewaters and also in air appeared in different measurement days were somewhat unexpected. It was not detected whether the fluctuations were caused because of changes in TMP process or in wastewater treatment process. It is probable that the fluctuations are origin from the production. Due to the long delay time of one day, any confident conclusions can not be made. 4. Specific emissions from aerobic and anaerobic system the tables 5 and 6 illustrate production specific VOC emissions (kg VOC/ton production) of both sources: aerobic and anaerobic wastewater treatment systems. 5. Measuring uncertainty Table 5. Specific emission from aerobic wastewater treatment Target specific emission kg/t product From aerobic system to air 0,03 From aerobic system to water 0,04 Sum 0,08 Table 6. Specific emission from anaerobic wastewater treatment Target specific emission kg/t product From anaerobic system to air 0,10 From anaerobic system to water 0,45 From anaerobic system water to air (85 % cleaning efficiency) 0,07 Sum 0,17 Examining the results, it should be remembered that they are based on a relatively small amount of sample. The results have to be recognized as plant specific rather than general situation. The fluctuation also demonstrates the high variation in driving conditions of both TMP process and wastewater treatment systems.

13 AX-LVI Consulting Ltd 12 Uncertainty of airflow measurement is normally ± 5 %, but the measurement points were not in accordance with the standards. The uncertainty was estimated to be ± 15 %. Mainly due to low concentrations, high moisture and fluctuation of concentration of compounds the uncertainty of sampling and direct indicating FID analyser results are is estimated to be 20 %. Total uncertainty of VOC-emission was therefore ± 35 %. Temperature measurement uncertainty is ± 2 %. The uncertainty of information obtained from the factory is not estimated. 6. Measurement equipment CAI flame ionising detector (2 pcs) SKC-222 sampling pumps + active charcoal tubes Gasmet-FTIR analyser Getac computer + DasyLab 9.0 software Personal Daq/300 data logger + K-type thermocouples Testo data logger+ K-type thermocouples Mikor micromanometer + pitot tube Testo 922 thermometer Peltier dryer

14 AX-LVI Consulting Ltd 13

20 AX-LVI Consulting Ltd 19 Puhelin Y-tunnus