Recipient Organization
STATE UNIV OF NEW YORK
(N/A)
SYRACUSE,NY 13210
Performing Department
Paper & Bioprocess Engineering
Non Technical Summary
Moisture content of biomass fuel is an important factor among others that significantly affect the performance of biomass-fired thermal systems. Research shows that very high or very low moisture content increases CO and particulate emissions and decreases efficiency depending on the operating conditions [l-3]. The maximum moisture content preferred by most manufactures of two-stage combustion systems in ensuring clean and efficient combustions is 20% [4]. Improving biomass fuel characteristics and properties is becoming increasing impmiant with growing market demand for biomass thermal systems. As already stated in the PON, staged-combustion boilers can achieve high-efficiency performance if wood chip with <30% moisture content are used instead of green chips. The use of high quality fuels will result in significant reductions in emissions as well as improve efficiencies and plant availability.Removal of water by drying in most cases is required to enhance the properties of wood to be used in many applications. Typically, greed wood moisture content ranges from 45-160%, on the oven dry (OD) basis [5] and depending on summer drying, could reduce to 35-45% of the total weight. Wood can be air dried to about 25% moisture content [6]. However, the drying rate is slow and it takes longer drying times to achieve lower moisture levels. Therefore, heat and forced air are employed in various drying methods to reduce the moisture content at a faster rate and in a controlled manner; this, in effect makes drying costly. To reliably supply wood chips with lower moisture content, the drying process would have to be energy-efficient and cost-effective.Brookhaven National Laboratory (BNL) in collaboration with SUNY College of Environmental Science and Forestry (SUNY-ESF) proposes innovative process to address category F (Process development for low (<30% dry basis) moisture content wood chips) under the NYSERDA PON 2652. The overall objective of the proposed research is to explore/demonstrate hot-water extraction (HWE) and flue-gas drying technology as an alternative to conventional wood drying methods in producing low moisture wood chips with enhanced fuel quality which could consequently increase efficiency of wood-fired boilers and reduce related emissions. The goal is to employ HWE as a pre-drying treatment prior to flue gas drying, and this proposed concept should accelerate the drying rate of wood chips and consequently decrease the cost of drying. The co-production of value-added products and the use of process derived flue-gas in drying should make the integrated HWE method an-energy efficient and economical technology which could lead to near-term commercialization. The proposed scope of work incudes i) exploring RWE as a pre-drying treatment and evaluating its effect on the drying rate of wood chips, ii) assessing the effectiveness of using process derived flue gases or waste heat to reduce moisture content to 15% iii) performing microscopic characterization to understand the effect of HWE on wood cell walls andiv) investigating the effect of using HWE wood chips on boiler efficiency, carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbon and particulate matter (PM) emissions.The proposed research effort brings together capabilities and expertise at SUNY-ESF and BNL which are well-suited for the project. SUNY ESF as the Principal Investigator (PI) will be responsible for overall project coordination and will perform hot-water extraction and flue gas drying studies using the ESF pilot plant digester. BNL will conduct spectrometric characterization of wood chips and wood chip-fired boiler studies using state-of-the-aii and advanced analytical facilities at BNL. The estimated total cost for the proposed 12-month effort is $140,000 with 25% cost-share from the SUNY-ESF team.Awarded Start Date: 5/31/2013Sponsor: NYS Energy Research and Development Authority
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Overall, this innovative approach, if successful, would decrease the cost associated with drying of wood chips; increase fuel quality, increase boiler. efficiency and decrease emissions. The integration of RWE technology and process derived flue gas drying presents an opportunity for efficient and economical co production of biomass fuel and chemicals.The RWE process has been demonstrated to selectively solubilize hemicellulose and remove ash and extractives. Therefore, the extracted wood chips, which are still intact, have higher caloric value per unit of dry mass, lower ash content, increased structural stability and are less hydrophilic' (less likely to adsorb water) [27, 32-35]. These improvements in properties would render the extracted wood chips a better fuel for wood-chip fired boilers. Furthermore, this process has the potential of allowing successful use of a wide range of non-woody fuels in biomass-fired boilers. This implies that feedstock such as agricultural residues, forest residues, energy crops and waste woods which are relatively high in ash; nitrogen and sulfur contents might be improved by RWE into suitable fuels for efficient performance in biomass-fired thermal systems. This could, in effect, provide a lower cost and more reliable feedstock supply for thermal systems without leading to poor boiler efficiency and higher emissions.Besides enhancing the fuel properties of wood chips, RWE technology shifts about 20-23% of the mass of the wood into an extract stream which consists of sugars, acetic acid and other chemicals. At · commercial scale these can be profitably processed into biofuels and bio-products in the form of commodity chemicals. The co-production of these value added-products should reduce the overall cost of the proposed process with the chips near the boiling point when exiting from RWE allowing a significant reduction of the amount of additional heat from the flue gas needed for drying.The proposed process could be setup as modest-scale distributed rural operations in a short-term to create economic opportunities for rural and urban communities with new job opportunities. Currently, ABS Applied Biorefinery Sciences which is a New York state based company is dedicated to commercializing the SUNY- ESF invented and developed hot water extraction process (RWE). RWE is a patent pending, wood fractionation process developed at SUNY-ESF and licensed for commercial application by Applied Biorefinery Sciences.
Project Methods
Fuel AnalysisProximate and ultimate analysis as well as High Heat Value (HHV) of the wood chips will be performed by Galbraith Analytical Laboratory (Knoxville, TN, USA). Table 1 below shows the specific standard method for each property.Table 1. Fuel analysis methodsProperty to be measuredStandard Method to be usedProximate (Moisture, Ash, Volatile Matter, Fixed Carbon)ASTM D3172Elemental composition (CHN, Cl, S, and 0)ASTM D3 l76 I D2492High Heat Value (Btu/ lb.)ASTM D5865Microscopic characterization of wood chipsMorphological changes as a result of hot-water extraction will be investigated to gain better understanding of the role of wood cell wall structure in drying. During HWE process, the hemicellulose portion is affected to a larger extent than the lignin portion and the cellulose is largely unaffected. Scanning Electron Microscope (SEM) and Transmission electron microscopy (TEM) will be performed on wood chip samples before and after the HWE process to increase knowledge of the effects on wood structure. Established analytical protocols developed at BNL Center for Functional Nanomaterials will be used for the study.Large Scale Hot-water extraction (HWE)The HWE is a proven technology and extraction can be done up to approximately 250 kg OD wood per batch in the SUNY ESP pilot plant. Maple'wood chips obtained from ESF's Heiberg Forest in Tully, NY will be subjected to a large scale hot-water extraction in ESF's 65 ft3' pilot plant digester. The digestercontents are heated up by steam injection or with a heat exchanger to reach a desired extraction temperature of 160 °C and held there for 2 hours. The initial work in this project will be conducted in 4- 6 liter digesters holding 500-800 grams of wood chips. A range of extraction conditions will be developed and 250 kg batches will extracted at three chosen conditions. The 250 kg batches will then be evaluated for the effect on drying and combustion.Flue gas dryingFlue gas drying will be simulated in a metal pipe dtyer to be fabricated at ESP. Flue gas will be simulated by blending hot air and steam with the combined gas passed through the pipe loaded with chips. The drying rates will be documented by weighing the pipe at intervals. There will be temperature and moisture content measurements before nd after exposure to the chips. Target flue gas conditions (Temperature and moisture content) will be those for wood fired boilers. Target moisture content after drying will be 15%. Drying rates will be documented and amount of flue ·gas needed for commercial drying application will be calculated.Wooci chip boiler testingA wood-chip boiler with an operating range of 100,000-200,000 BTU/hr output will be used. Measurements of direct input output efficiency, efficiency by Stack Loss Method (SLM) carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbon, and PM emissions will be performed. A dilution tunnel sampling system at BNL in accordance to ASTM' s method E25 l 5 will be used to measure PM. Depending on the concentrations, dilution ratios of 5-10 will be used. Input- output efficiency and efficiency by the SLM method will follow BPA Method 28 WHH and the recent BNL test method for hydronic heaters with thetmal storage as closely as possible. These measurements will be made in the lab at Brookhaven which is currently setup for this type of work.