Ammonia Emissions to Air from Sugar Beet Processing: Source Testing Results

Transcription

1 Ammonia Emissions to Air from Sugar Beet Processing: Source Testing Results Shawn Sullivan Harry Chen Anne Ogrey Environmental Engineer Environmental Engineer Environmental Engineer Holly Sugar Corporation Imperial Holly Corporation Holly Sugar Corporation PO Box 700 PO Box 9 PO Box 60 Torrington, WY Sugar Land, TX Tracy, CA Introduction and Objectives Ammonia is an important compound that can be toxic to aquatic life and human health. Annual reporting of ammonia emissions is required under the Emergency Planning and Community Right-to-Know Act as part of the Toxic Release Inventory. Several sugar beet processors appear on a state's Top Ten Toxic Polluter list because of estimated ammonia emissions. At least one stale, Wyoming, charges for ammonia emissions. Sugar beets contain amino acids, especially glutamine and asparagine, that decompose under factory conditions of high temperature and liming to form soluble salts and ammonia 1. Figure 1 shows reactions occurring under deamination of glutamine under factory operating conditions. Amino nitrogen is increased by high nitrogen fertilizers, lack of water during the beet growing period, disease and variety differences. Ammonia emissions from sugar beet factories occur vi a wastewater and vents to the atmosphere. Some companies estimate ammonia emissions based on the average amide nitrogen content in beets, (given by McGinnis as 0.02% on beets), although procedures vary greatly. Measurements of ammonia emissions are difficult due to the many potential emission points including the diffuser, prelimer, main limer, cooling towers, raw and thin juice heaters, carbonation vents, precipitated calcium carbonate filters, evaporator noncondensables, pulp dryer, condensates and crystallizers. The amount of ammonia produced at a source depends on the temperature, residence time, alkalinity and solids content of the juice. 2 Water conservation practices that recycle condensates and pressed pulp water back to the diffuser complicate the mass balance. Data exist for ammonia and nitrogen levels in wastewater flows primarily due to discharge monitoring requirements, however, very little data exists for air emissions. Measured emissions of ammonia to air would help verify existing estimates based on entering amino acid content and potentially demonstrate areas to review operation procedures to reduce ammonia generation. Holly Sugar Corporation has begun the direct measurement of ammonia emissions at its Worland, Wyoming facility by conducting stack sampling and analysis for ammonia on first carbonation, second carbonation, second carbonation heater, second and third evaporators, low, mid and high vapor thin juice heaters and the pulp dryer. 299

2 HN _ I( ~ 2 '-../' o Glutamine NHl k CcnH -H Heat or ~Ii NHl HO~OzH o Glutamic Acid O )--COzH I H u-pyrrolidone-carboxylic acid (PCC) Figure 1. Deamination of glutamine under factory operating conditions. Materials and Methods Source testing was conducted during the 1996 campaign. The factory was operating at a slice rate of about 3600 tons per day or 150 tons per hour. EPA proposed method M 206 for ammonia was used to determine the ammonia emissions. Two runs per stack were made with sample times ranging from 5 to 40 minutes. Stack samples were collected and analyzed in a laboratory for ammonia concentration using ion chromatography analysis. Sampling and analysis was performed by an outside contractor, Emission Measurement Group. Table 1 shows runs performed and sampling times. Results and Discussion McGinnis gives an average "amide" nitrogen content of 0.02% for sugar beets, however, this can vary significantly depending upon grower irrigation, fertilizer practices, growing area, variety and disease. Previous estimates of ammonia emi ssions were calculated using average amide nitrogen content of diffusion juice and estimating the amount converted to ammonia and then released to air or wastewater. Holly Sugar estimated that 45% of available amino nitrogen is capable of deamination to produce ammonia and that 60% of possible deamination occurs. The resulting estimates for ammonia emissions based on amide nitrogen content are given in Table

3 Table 1. Ammonia Sampling Points and Slice Rate During Test SOURCE TESTED DATE SLICE SAMPLE TIME TESTED tons/hour Minutes Dryer 11/6/ nd Evaporator 11/2/ nd Carb Heater - Low Vapor 11/2/ rd Evaporator A2 11 /2/ st Carbonation 10/31/ rd Evaporator A1 & B 11/2/ nd Carbonation 11/6/ Thin Juice Heater - Low Bank 11/6/ Thin Juice Heater - Mid Vapor 11/6/ Thin Juice Heater - High Bank 11/6/ Method: EPA proposed M-206 with ion chromatography analysis Table 2. Estimated Ammonia Emissions to Air Based on Amino Nitrogen Content SOURCE DAILY SLICE Tons AMMONIA EMISSIONS Ibs/day Ibs/hour Ib/ton Overall Carbonation Evaporation Units: White Pan, Hi Raw Pan, Low Raw Pan, Concentrator & Evaporator Condensers Source testing was conducted to verify emission estimates and potentially determine methods to reduce emissions. The ammonia testing locations and results are shown in Table 3. Concentrations and total emissions are given for comparison. Velocities in some stacks reached supercritical wh ich may have impacted the estimated flow rates. Testing in Holland 4 gave ammonia data with similar concentration ranges for the pulp dryer and first and second carbonation. However, it is unclear how their tests were performed or how total emissions were calculated. For example, their annual ammonia emissions for the pulp dryer are 35 tons while our measured emissions adjusted to the slice rate of 10,000 tpd give approximately 13 tons. Tables 4 & 5 compare results of current testing, previous esti mates and tests conducted in Holland and Itall. The total air emissions are very similar, however, the specific sources have widely varying values. 301

4 Table 3. Measured Ammonia Emissions to Air AM MONIA tons/500,000 SOURCE Ib/hr Ib/ton Beets Ibs/5000 tons tons of beets Pulp Dryer 1st Carbonation 2nd Carbonation 2nd Carbo Heater - Low Vapor 2nd Evaporator 3rd Evaporator Thin Juice Heater - High Vapor(1st) Thin Juice Heater - Mid Vapor(2nd) Thin Juice Heater - Low Vapor(3rd) Total Table 4. Comparison of Measured Concentrations of Ammonia Holly Test Holland Test grains/dscf grains/dscf SOURCE Low Range High Range Pulp Dryer 1 st Carbonation 2nd Carbonation 2nd Carbonation Heater-Low Vapor 2nd Evaporator 3rd Evaporator Thin Juice Heater -High Vapor Thin Juice Heater -Mid Vapor Thin Juice Heater -Low Vapor Vacuum Pump -Evaporation Vacuum Pump -Crystallization Vacuum Pump -Carbonatation lime Rotary Vacuum Filter Lime slaker Table 5. Comparison of Measured and Estimated Ammonia Emissions SOURCE Holly Test Holland Test Italian Test Adjusted to 5000 ton/day slice Ibs/hour Ibs/hour Ibs/hour Pulp Dryer st Carbonation nd Carbonation nd Carbonation Heater-Low Vapor nd Evaporator rd Evaporator Thin Juice Heater -High Vapor 1.13 Thin Juice Heater -Mid Vapor 1.91 Thin Juice Heater -Low Vapor Miscellaneous 2 Cooling Tower Lime Filtration 4 Ponds 29 TOTAL Amide Nitrogen Estimates Ibs/hour

5 The source testing results show the non-condensable vents from the third evaporator and low bank (3rd vapor) thin juice heater account for over 70% of measured ammonia emissions. This is potentially due to the continued concentration or formation of the ammonia in the juice due to the high temperatures and ph. Note that the majority of the estimated ammonia emissions were from carbonation while this source testing shows evaporation as the main emission point. Analyzing for glutamine content of juice during stack sampling would give a better comparison but this was not performed. Figure 2 shows the percent of total measured emissions for each source. Flow rates obviously affect the overall emissions in addition to the concentration. Dryer 4% Low Vapor 1st Carb 1% Mid Vapor Htr 15% 2nd Carb 0% Htr5% 2nd Carb Htr 1% High Bank Htr 3% 2nd Evap 15% 3rd Evap 56% Figure 2. Ammonia Emissions to Air: % of Total Measured Summary Ammonia emissions from sugar beet processing, both air and water, are expected to be of greater regulatory interest in the near future. Current interest is already sufficient enough to identify sugar beet processors as major toxic polluters because of ammonia. The variations in the limited data available from different locations suggests that both grower practices and processing operations affect the amount and location of ammonia generation and emissions. Additional information about where ammonia formation occurs during processing is needed to improve identification of ammonia sources and em issions and develop process control methods. Additional air source testing of all potential air and wastewater sources along with simultaneous sampling for amino nitrogen needs to be performed. A comparison of ammonia emissions to amino nitrogen of sugar beets could then be made to help correlate estimates. The ammonia going to air or water could possibly be shifted to one phase or the other, depending on which is more critical for a given site. 30 3

6 It appears from this limited data that estimates based on amide nitrogen are reasonably close to actual emissions. Methods of reducing ammonia generation or ways to capture the ammonia and convert it into a usable product would be useful to reduce emissions and regulatory concerns. Options like re-injection of evaporator non-condensables for reducing lime salts or stripping ammonia to make ferti lizer may become more practical or necessary depending on regulatory interest and economics. Literature Cited 1. McGinnis, R.A., Beet Sugar Technology, 3rd edition. Beet Sugar Development Foundation, Fort Collins, CO. 2. Buczys, et al "Glutamine Degradation in the Process of Sugar Production" Zuckerind. 118 (1993) Nr. 4 pp Bryan Tungland, Internal Imperial Holly Memorandum dated July 2, Peters, H.J. "Environmental Aspects of Beet Sugar Production in Holland: Airborne Factory Emissions - A Review" Zuckerind 11 9 (1994) Nr. 3. pp Bruno Carlesso, et al. "Recovery of Ammonia from Carbonation Vent Gases" Zuckerind. 120 (1995) Nr. 7 pp W illiam B. Kienzle, Internal Imperial Holly Memorandum dated May 8,