Recipient Organization
STATE UNIV OF NEW YORK
(N/A)
SYRACUSE,NY 13210
Performing Department
Environmental Resources Engineering
Non Technical Summary
No significant differences in ammonia recovery were found between the distillation experiments with filtrate of undigested and digested manure. The higher dissolved ( solids content in the digested manure only slightly retarded ammonia volatilization. 96.5-99.5% of ammonia was stripped in 3 h with an ammonia half-life of 1.4-1.6 h. The cumulative ammonium sulfate formed upon complete volatilization of ammonia was 3.70-3.87 g/L manure filtrate. High-purity ammonium sulfate (::=::98%) was produced as clear granules by cooling the acid solutions pre-saturated with ammonium sulfate.Aqueous ammonium is converted to free ammonia with increasing temperature. In the experiments with anaerobically digested dairy manure, free ammonia concentration peaked after less than 1 h of heating. Free ammonia was stripped rapidly out of dairy manure, with an average liquid-phase ammonia mass transfer coefficient of 21 mm/h. After 3 h of vacuum distillation, ammonium sulfate formed was 6.13-7.92 g/L manure. Upon 5 h of vacuum distillation, ammonium sulfate formed was 6.46-8.13 g/L manure. Ammonia solubility was zero in all the combinations of temperature and vacuum. Ammonium sulfate production rate varied with total2 ammonia concentration initially in the digested manure samples. There were no significant differences in ammonia volatilization kinetics among the 4 combinations of temperature and vacuum. The insignificant differences among the combinations of temperature and vacuum could be attributed to the high fraction of free ammonia in total ammonia (more than 94%) in the tested ranges of temperature and vacuum.Vacuum distillation at a lower temperature and stronger vacuum creates greater economic profitability. Ammonia recovery at the lowest bubble point temperature and vacuum generates the greatest net present value ($10.9 million) and benefit/cost ratio (1.3) for the example dairy farm at a usable life of I 0 years and an 8% discount rate. With less than $9000 of initial capital cost, an ammonia recovery system can create 3 jobs at this large-size dairy farm. Labor cost accounts for 64-68% of the total operational cost.Awarded Start Date: 9/1/15Sponsor: Environmental Protection Agency
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The specific objectives are to 1) evaluate the combined effect of temperature and vacuum on ammonia volatilization from anaerobically digested dairy manure as well as liquid portion (filtrate) of digested and undigested dairy manure, which have different concentrations of total and dissolved solids; 2) design a vacuum distillation - acid absorption system for production of ammonium sulfate granules with dairy manure; 3) construct a pilot-scale vacuum distillation - acid absorption system and develop operational parameters; and 4) perform a farm-scale economic analysis of the developed technology.Proposed Phase II Objectives and Strategies: To fmiher develop the vacuum distillation - acid absorption technology for ammonia recovery in a recirculation line of anaerobic digestion we set the following objectives for Phase II:• To evaluate the kinetics and capacity of ammonia volatilization in vacuum distillation under temperature and vacuum lower than 70 °C 252 torr, using the pilot-scale vacuum distillation - acid absorption system;• To optimize design and operational parameters of the still's demister and absorption column in order to produce granular ammonium sulfate;• To examine the synergistic effects of integrating ammonia recovery into anaerobic codigestion of dairy manure and cheese whey; and• To assess economic sustainability of options for integrating ammonia recovery into anaerobic digestion of dairy manure and whey.
Project Methods
A laboratory vacuum distillation - acid absorption assembly was used to evaluate ammonia volatilization kinetics and ammonium sulfateformation in vacuum distillation of ammonia from digested dairy manure at four combinations of bubble point temperature and vacuum (absolute pressure), i.e., 100 °C 760 torr, 90 °C 557 torr, 80 °C 392 torr, and 70 °C 252 torr. Ammonia volatilization in distillation at the normal boiling point without vacuum was also compared between filtrate of digested and undigested dairy manure that have different concentrations of dissolved solids. A stainless steel kettle reboiler equipped with a demister and connected to a gas absorption column by a vacuum pump was designed for batch operation of the vacuum distillation - acid absorption process, featuring operational ease, technical simplicity, and low cost compared with other ammonia recovery methods. A pilot-scale vacuum distillation - acid absorption system is under construction, which can hold up to 30 L of digested dairy manure. This pilot-scale ammonia recovery system will be operated in the coming months to investigate ammonia volatilization kinetics and ammonium sulfate production capacity at four different feed depths in the still. Cost benefit assessment was performed to assess economic sustainability of the ammonia recovery technology, taking a largesizedairy farm as example. The base option was as it was, without ammonia recovery.Alternatives were to recover ammonia in the four combinations of vacuum and temperature, which allow different recirculation rates of digester effluent.This project fills a literature gap in ammonia volatilization kinetics and the combined effects of temperature, vacuum, and solids on distillation of ammonia from dairy manure. Kinetic study with a pilot-scale ammonia recovery system at different feed depths will support design for scaled-up, broader applications. Integrating vacuum distillation - acid absorption into anaerobic digestion is anticipated to make ammonia recovery an economically viable technology ..This P3 project provided an excellent platform for the students and faculty advisors to work in a multidisciplinary team. The team explored into a green technology that benefit people, prosperity and the Planet. By working on the design and experiments for ammonia recovery from dairy manure, students in this P3 team were trained in critical thinking and problem solving for sustainable solutions to waste management issues. In mid-July 2015, high school students in a Boy Scouts Engineering Camp will be guided to produce ammonium sulfate with our pilot-scale ammonia recovery system.Phase II:At the combinations of temperature and vacuum in Phase I, more than 94% of total ammonia was in free ammonia. It is possible that the temperature and vacuum could be fmiher decreased without ammonia volatilization being compromised. It is estimated that ammonia saturation concentration remains zero and free ammonia fraction is still higher, 89% at 60 °C and 79% at 50 °C with bubble point vacuum. In Phase II, ammonia volatilization kinetics and ammonium I 3 sulfate production capacity will be investigated in combinations of even lower bubble point temperature and vacuum, tentatively 70 °C 252 torr, 60 °C 150 torr, and 50 °C 93 torr, using the pilot-scale ammonia recovery system at the optimum feed depth. Ammonia mass transfer coefficient and saturation concentration will be estimated with the time series data of ammonia remaining in feed. Estimation of these kinetic constants for digested dairy manure at the combinations of lower temperature and vacuum in Phase II will support model-based design and economic analysis for scaled-up applications. By applying a stronger vacuum, a greater recirculation rate can be drawn for distillation at a lower boiling point, thus recovering more ammonia and decreasing its concentration in digester effluent.Ammonia recovered from wastewater has been mainly in liquid forms, but granular ammonium sulfate is more convenient for storage, transportation and agricultural uses. When acid solution is pre-saturated with ammonium sulfate, ammonium sulfate formed by the reaction of stripped ammonia and sulforic acid can be in fine crystals, which grow into granules due to mixing by vacuum pumping. Ammonium sulfate is highly soluble and its saturation concentration increases with temperature. To produce granular ammonium sulfate through vacuum distillation - acid absorption, mists and water sprays must be captured efficiently by the demister. Water condensation in the acid solution and solution temperature increase must be minimized. Water reflux in the still is related to the diameter and packing height of a demister. The optimum diameter and packing height will be determined experimentally with the pilot-scale system, which has changeable demister diameters and packing heights. Volume change in the reboiler and absorption column as well as production of granular ammonium sulfate will be determined during each batch experiment. When the stripped ammonia entered acid solution through a fine bubble diffuser, ammonia was quickly absorbed in the acid solution as shallow as 3 cm. The increase of temperature in the acid solution can then be controlled by increasing volume or decreasing depth of the acid solution. In Phase II, batch experiments with the pilot-scale system will be performed to identify the minimum depth and optimum volume of acid solution in the absorption column when the still is operated under the optimum distillation conditions (temperature, vacuum, feed depth, and demister diameter and packing height). Initial and final concentrations of ammonia in the feed will be determined for each batch. Ammonium sulfate granules will be collected on a sieve and weighed. Dry granules will be examined for purity, morphology, and compactness. Appropriate velocity gradient (G value) is required for effective granulation of ammonium sulfate crystals. The G value is related to effective volume of the absorption column, vapor pressure, and gas flow rate. A digital gas flowmeter and pressure gauge will be installed to record the pressure and flow rate of gas entering the absorption column. Regression analysis will be performed to identify the relationship of granule size and weight with G value. The optimum depth and volume of acid solution will finally be determined with the minimum depth and optimum G value.In Phase II, we will evaluate the synergistic effects of ammonia recovery on anaerobic digestion. Four bench-scale anaerobic digesters will be operated under 4 mesophilic conditions with dairy manure and cheese whey, two without ammonia recovery and the other two with ammonia recovery. Later on, the synergistic effects will be examined under thermophilic conditions (56 °C). Biogas production rate, methane content in biogas, pH and ammonia concentration in digester effluent, and solids removal efficiency will be determinedperiodically. Specific methane yield and ammonia concentration will be compared between the digesters with and without ammonia recovery.Similar to the economic analysis in Phase I, cost-benefit analysis will be performed to evaluate economic sustainability of integrating ammonia recovery into anaerobic digestion. In particular, costs and benefits associated with the synergistic effects of integrating ammonia recovery into anaerobic digestion will be quantified. Cost-benefit analysis of the developed technology will elucidate the potential of commercialization and market penetration.