Survey of Available Biomass Fuels and Measurement of Their Gasification and Combustion Characteristics

Transcription

1 Survey of Available Biomass Fuels and Measurement of Their Gasification and Combustion Characteristics Principal Investigator: Dr. Albert Ratner Associate Professor Mechanical and Industrial Engineering University of Iowa

2 Table of Contents Abstract List of Nomenclature iii iv Sections I. Introduction 1 II. Biomass Survey 3 III. Biomass Gasification Characterization 4 Material and Experiment 5 Experimental Configuration 6 Experimental 6 Results and Discussion 7 IV. Conclusion 1 V. Acknowledgements 11 References 12 Tables 13 Figures 18 ii

3 Abstract Through co-firing of oat hulls and coal in the University of Iowa s Main Power Plant (UIMPP) boilers, the UIMPP reduces their annual coal usage by 2, tons. The success of this project demonstrates the benefits of biomass utilization and provides the impetus for continued research. Since there are various kinds of biomass available locally, this effort focused on identifying and testing new materials for use as substitutes or complements for oat hulls to decrease the fuel cost and provide resilience to change in the availability of particular biomass fuel streams. More than forty companies were contacted and 12 responded with information regarding available material. Seed corn, paper sludge, wood chips, and manure were deemed to be the leading candidates for use as fuel and chemical testing was carried out on all 4 materials. Gasification tests were conducted for seed corn and paper sludge, as these materials are both abundant and cost effective. It was found that seed corn produces more combustible gases than oat hulls or paper sludge, while the paper sludge is similar to, but slower than, the oat hulls in gas evolution. iii

4 List of Nomenclature = Time difference [s] Q = Nitrogen flow rate [L/s] = Concentration of the target gas R = Universal gas constant [L-atm/mol-k] P atm = Atmospheric pressure [atm] M w = Molar weight of the target gas [g/mol] T amb = Ambient temperature [K] iv

5 I. Introduction This report describes the work performed to enhance the ability of the University of Iowa Power Plant to utilize a broader range of biomass fuels for power production. Currently, most of the world relies on non-renewable fossil fuels. In America, fossil fuels provide more than 85% of all the energy used in the United States (DOE). However, taking into account of the reserves and environmental problem, the need of develop and use of new renewable energy is urgent. Biomass offers the United States tremendous opportunities for use as domestic and sustainable resources to provide fuel and power. By co-firing the University of Iowa s Main Power Plant (UIMPP) boilers with oat hulls and coal, the UIMPP reduces their annual coal usage by 2, tons. More importantly, the annual CO 2 emissions have been decreased by ~6, tons (the equivalent of removing 1,2 passenger vehicles from the road each year) and the University has saved over $2.45 million dollars from this project [1]. The oat hulls used at the UIMPP are a byproduct of cereal making processes and were purchased from Quaker Oats for a fraction of the cost of coal. In excess of 16 tons of oat hulls are consumed each day. The success of this project demonstrates the benefits of biomass utilization and provides the impetus for continued research. Although biomass has been used since the 19 th century, use in modern boilers still necessitates research to maximize the efficiency and minimize the pollutant production. In addition, since there are various kinds of biomass produced locally, we may be able to find substitutes for oat hulls that might decrease the acquisition, transportation, or handling cost. 1

6 Following this reasoning, the first step in our work was to conduct a biomass survey. The students contacted various organizations including nearby companies and relevant state departments to ascertain which companies produce biomass byproducts. The investigation led to the establishment of a database of relevant biomass resources available within 2-3 miles of the University. The second phase of this research focused on the lab-based characterization of biomass samples. To gain a better understanding of the various factors affecting the final gaseous products, an existing experimental system was upgraded and employed to perform the testing. Five materials were testing in regard to their chemical content and two of those materials including seed corn (both whole and crushed) and paper sludge were gasified. Gasification and pyrolysis measurements are undertaken to understand how the various material characteristics impact the exuded product gases. A heating rate of 1K/s ensured similarity with real boiler conditions while a temperature range of 4 C-8 C is employed as the primary gaseous species (C, H 2 O, CH 4, CO 2, CO, and H 2 ) are highly sensitive to the pyrolysis temperature in this temperature range. 2

7 II. Biomass Survey The aim of our survey is to find the available biomass sources near the University. So we spent the last two years contacting various companies and organizations, performing cost and availability analysis. Finally, we found that there are more than companies and organizations which have the possibility to provide the relevant sources within three hundred miles of the University. These companies covered various kinds of industries such as some food companies, tire services corporation etc. In addition, some government organizations and marketing brokers are all involved. From the diversity of the biomass market, we could indicate that biomass utilization is a prominent issue in development in Iowa. Table 2.1 shows the biomass availability survey with complete response. These 12 companies have given us detailed information about the main biomass and secondary biomass sources they produce, from which we know that several companies produce quite a few biomass sources. The biomass materials are mainly dried distillers grains (DDG), corn byproducts, several types of Iowan wood sources, recycled tires and dissolved organic liquid wastes. Based on the datum, nearly all the responsive companies have great quantity in biomass production, but only half of them have set a price for selling. Most of the companies gave positive feedback regarding long term availability. Table 2.2 shows the companies and organizations with no responses. During the last two years, we contacted these companies multiple times; however, we have not obtained detailed information either because they do not have the relevant information or they are not willing to discuss this issue with the University research groups. There is a possible chance of obtaining information if workers from the University of Iowa Power Plant contact them directly. 3

8 III. Biomass Gasification Characterization Biomass gasification is a process by which biomass or other carbonaceous materials are converted into a syngas-type fuel through incomplete combustion. The main steps in the gasification process include preprocessing, gasification, gas clean-up and reforming, and gas utilization [2]. Gasification is where the biomass is decomposed into gaseous species including: hydrogen (H 2 ), carbon monoxide (CO), carbon dioxide (CO 2 ), methane (CH 4 ), oxygen (O 2 ), water, tar, char, and ash. The gasification process can be split in three stages: Pre-heating and drying Pyrolysis Char oxidation and gasification The pyrolysis step is the main focus of this work. The experimental goal of this work is, through experimentation, to characterize the instantaneous gas concentrations (O 2, CO, CO 2, CH 4, H 2 ) during the gasification process for a range of materials (corn kernels, oat hulls, and paper sludge) and temperatures (4-8 C). The temperature ranges are directly related to the chemical reaction equations seen in Eq.1-4[3]. Equations 1 and 2, the rate of steam reforming and dry reforming reactions, are dominant at higher temperatures (6-8 C) and increase the production of CO and H 2 while breaking down heavier hydrocarbons such as CH 4 and CO 2. (1) (2) 4

9 Equations 3 and 4, the boundary and primary water-gas reactions, attribute to the increase of CO and H 2 at higher temperatures, such as those tested in this work. (3) (4) From these equations and previous research it is known that through the pyrolysis process, gases such H 2 and CO are produced in higher concentrations at higher temperatures. Many different aspects affect the products of these processes such as: temperature, equivalence ratio, heating rate, residence time, and fuel type. Materials and Experimental Four new materials including corn, paper sludge, wood chips, and manure have been examined in this work because of their local abundance and low cost. Out of the four, only corn, in both crushed and whole kernel forms, and paper sludge have been progressed through gasification tests. Corn, already used as a renewable energy source in the form of ethanol, is locally abundant in Iowa. The paper sludge is from a company in Cedar Rapids, Iowa, called Weyerhaeuser - Cedar River Paper. The paper sludge is the result of recycling cardboard and creating new cardboard pallets. The parts that can no longer be recycled or are left after the creating process are known as paper sludge. The paper sludge contains small strands of paper, sand, and a very small amount of plastic contaminant. The Cedar Rapids facility creates around 62, wet tons of paper sludge per year at around 5% moisture content. The ultimate and proximate analysis for all of the materials can be seen in Table 3.1 and Table 3.2. This information allows one to predict the gas evolution resulting from gasification. Further analysis of this information is in the results and discussion section. 5

10 Experimental Configuration The experiment used to gasify the materials is shown in Figures 3.1 and 3.2. Figure 3.1 is a schematic and illustrates most of the main components including the industrial heater, torch systems, thermocouples, flow controllers, and the spark ignition system. Figure 3.2 is a photograph of the system arrangement. Notables not seen in the schematic include the particulate filters, sensor bank, power supplies, and the working environment. A full list of the components used in the experiment is presented in Table 3.3. Procedure Fifteen conditions, 5 each for whole corn, crushed corn, and paper sludge were tested, with (typically) 5 repetitions per condition. The resulting data, at 1 C intervals from 4-8 C at 1 atm, was collected at one second intervals for the duration of the solid residence time (3 seconds). The data from each five repetitions was averaged for each temperature value. Equivalence ratio plays a vital role in the production of CO [4] and it is known that gasification rarely occurs without O 2 present. To maximize CO production in the pyrolysis gas, a concentration of excess O 2 is added to the gasification agent (N 2 ) based on the ratio of the heating torch s flow rates. Table 3.4 shows the excess O 2 volume for each material and temperature range. To determine the mass of CO produced throughout pyrolysis as well as the final yield, Equations 5 & 6 are used [4]. Using these calculations, the mass of CO and CO 2 was determined from the gas concentrations measured in the experiment. ( ) (5) ( ) (6) 6

11 Results and Discussion The gas evolution for CO can be seen for all of the tested materials in Figure 3.3. It was found that the gas evolution increased with an increase in temperature with all the three tested materials. Table 3.5 shows the approximate pyrolysis duration (identified as when the slope of the data series reaches ~) for the materials at each temperature series. The pyrolysis duration is where the majority of the volatiles are released and ends when gas evolution is negligible. For all the materials tested, the pyrolysis temperature is generally inversely proportional to the pyrolysis duration. To determine the total CO yield, each temperature series was integrated to find the total CO production throughout the pyrolysis process and are plotted in Figure 3.4. Surprisingly, the highest CO yield was produced by whole corn kernels at 7 C. For all other materials, higher temperatures yield higher results; however, for corn kernels this is true except for the temperature series at 7 C and 796 C. This anomaly could be related to the surface area exposed to heating, which is much lower than the other materials (including crushed corn kernels). Aside from the maximum yield across the materials, CO yields were highest for crushed and whole corn kernels and lowest in oat hulls and paper sludge. For each material, except corn, temperature and CO gas yield were positively related. The CO 2 gas evolution and production were determined in the same method as that used for CO, using Equations 5 and 6. As seen in Figure 3.5, the production of CO 2 is independent of temperature and no particular pattern is consistent for all materials from the gathered data. Figure 3.6 shows the cumulative CO 2 produced versus time and it can be seen that the CO 2 production is temperature independent and the slope is mostly constant. 7

12 Since O 2 present within the heated N 2 stream, pyrolysis gas yields are significantly affected. Figure 3.7 shows the evolution of O 2 throughout the pyrolysis process. Common trends can be seen for all materials including a quick initial increase in O 2 production followed by a sharp negative dip in concentrations. The sharp dip is associated with the reaction of O 2, C, and H 2 to create compounds such as CO, CO 2, and H 2 O. The largest drop in O 2 concentration occurs for corn at a temperature of 796 C, about 2 times the change of any other material. The H 2 produced from the biomass was measured during all tests; however, negligible H 2 was detected. The lack of H 2 production was found to be explained by the short hightemperature gas residence time, about.2 seconds. This gas residence time is short in comparison to modern industrial systems and other experimental configurations where it can be significantly longer [5-11]. While negligible H 2 was detected, more CH 4 was produced than was detectable by the ENMET EX-512 IR CH 4 sensor used, 5% of the total volume. There were also some wide fluctuations in the readings, so this data was deemed to be inconclusive and is not reported. From the material analysis and the gasification test results, it is apparent that both kinds of wood have similar content composition as oat hulls. The only difference is the ash content is even lower in wood than oat hull, which will generally improve efficiency. Dry paper sludge also could be a good substitute for oat hulls because of the similarity in composition. The primary concern is that the ash content in dry paper sludge is over 1%; thus, the feasibility of this as a substitute fuel depends on the requirement of the specific boiler. Co-firing the paper sludge with either corn or wood chips could be a good choice in that it would balance the ash content of these two fuels and ensure sufficient ash in a stoker boiler while not detracting from the efficiency. Manure, because of its high ash content, 4%, may be difficult to use from both an ash 8

13 handling/disposal and efficiency perspectives. As seed corn and wood have the highest BTU/lb, they will typically cost less to transport, handle, and utilize than materials with lower BTU/lb values. 9

14 IV. Conclusion The goal of the present work is to identify and characterize available biomass fuels for use in the University of Iowa s Power Plant facilities. In performing the biomass survey, various types of available biomass were identified with a few being sold in an open-market environment with competitive pricing, while most are not being utilized. This underutilization creates both opportunities for the University of Iowa from a cost perspective and difficulties in the sense that the sellers of the material are often not in a position to evaluate, transport, and sell the material of interest. The chemical characterization, from both outside lab tests and in-house gasification testing, indicated that wood chips, paper sludge and corn all appear to be viable substitutes for oat hulls. Manure, because of its high ash content, would require more extensive modification of existing utility systems before it could be utilized in significant quantities. Suggested future work includes gasification testing of more wood type and assessment of paper sludge drying on improving its cost and performance. 1

15 V. Acknowledgement Several students contributed to the work presented in this report. The biomass survey was carried out by Marta Muilenburg, the biomass gasification tests were performed by John Hennigan, Brian Sulak and James Ulstad, and the resulting data was analyzed and the report written by Yunye Shi. 11

16 Reference [1] The University of Iowa: Pioneering Technology for Utilizing Biomass Fuels. Brochure. 27. [2] Kumar, A.; Jones, D. D.; Hanna, M. A., Thermochemical Biomass Gasification: A Review of the Current Status of the Technology. Energies 29, 2 (3), [3] Dai, X. W.; Wu, C. Z.; Li, H. B.; Chen, Y., The fast pyrolysis of biomass in CFB reactor. Energy &Fuels 2, 14 (3), [4] DeCristofaro E: Gas Evolution from Biomass Gasification and Pyrolysis. Master s Thesis. The University of Iowa, 29 [5] Dupont C, Commandre J M, Gauthier P, Boissonnet G, Salvador S, Schweich D: Biomass pyrolysis experiments in an analytical entrained flow reactor between 173 K and 1273 K. Fuel 28, 87 (7), [6] Fushimi C, Araki K, Yamaguchi Y, Tsutsumi A: Effect of heating rate on steam gasification of biomass. 1. Reactivity of char. Industrial & Engineering Chemistry Research 23, 42 (17), [7] Zanzi R, Sjostrom K, Bjornbom E. Biomass and Bioenergy 23 (22): [8] Fagbemi L, Khezami L, Capart R, Applied Energy 69 (21): [9] Zanzi, Rolando, Sjostrom K, Bjornbom E, Fuel 75 (1995): [1] Kinoshita C M, Wang Y, Zhou J, Journal of Analytical and Applied Pyrolysis 29 (1994): [11] Yanik, Jale, Kornmayer C, Saglam M, Yuksel M, Fuel Processing Technology 88 (27):

17 Tables Table 2.1: Companies that responded to requests for information ADM Company Contact Steve Bowen, project engineering waste treatment Distance from UI 3 miles Main Biomass DDG, corn byproducts, dead bacteria, protozoan Cargill Sheri Rundell (HR) 3 miles Corn Fiber Sun Opta Rich Rozinek 3 miles Pierce Lumber Inc. Jim Pierce, President 6 miles Disolved Organic material (Liquid Waste) All types of Native Iowa wood sources Hackert Wood Products Craig Hackert 56 miles Wood Hammes Bros. Sawmill, Inc. Jerry Hammes, Owner 65 miles Wood Big River Resources Stan Janson 8 miles DDG Grain Processing Corp. 45 miles DDG: Turned into Feed for farmers Hawkeye Gold, LLC. Ryan Sauer DDG Tire Environmental Services Inc. Hormel Interstate Bakeries Corp. Interstate Bakeries Corp. Dennis Froelich 45 miles Tires/Rubber 22 miles 9 miles 9 miles Corregate cardboard Bread Crumples (currently hog farmer picks them up) Bread Crumples (currently hog farmer picks them up) Secondary Biomass Dried out Feed Wet distilled grain 13

18 ADM Cargill Company Amount of Material Yearly 5, - 7, lbs/month Not Documented Cost per Unit not set yet not set yet (Never sold) Long Term Availability Indefinite Indefinite Density granular similar to sugar Flakes (Varying Particle Size) Moisture Sun Opta "Tons and Tons" Never Sold Yes 1% Pierce Lumber Inc. Hackert Wood Products Hammes Bros. Sawmill, Inc. Big River Resources Depends on Production rates $2-25/ton Yes Depends on wood type Grain Processing Corp. 1,2 tons/day No set number Yes Not Constant 5% Depends on wood type If Dried: 5-12; If sold to Farmers: 2-25% Hawkeye Gold, LLC. 36, tons $2/ton Yes 35lb/ft3 1% Tire Environmental Services Inc. Hormel Interstate Bakeries Corp. 75 ton/month 6-8 lbs/week depends on market, but they get paid akin to cardboard 14

19 Table 2.2: Companies that were queried but did not provide data Company Distance from UI Company Distance from UI Quaker 3 miles Soy Innovations 13 miles Penford Corporation 3 miles Kraft Foods, INC 6 miles Bio Springer 3 miles Tyson Foods, INC 9 miles Diamond V 3 miles Nestle 13 miles Genecor 3 miles Jimmy Dean Foods 33 miles General Mills 3 miles ConAgra Foods 244 miles Heinz 3 miles Swift and Co 95 miles Red Star 3 miles Oakland Foods of OSI Group 22 miles Ag Processing Inc. 19 miles Land O'Lakes 15 miles Quality Tire 9 miles Ralcorp Holdings 3 miles Wastewater and Landfill 2 miles 1 miles Division Schwan Food Co. Landfill and Recycling Center 2 miles Pinnacle Foods 72 miles Cedar Rapids/Linn County 3 miles 145 miles Solid Waste Agency Foremost Farms, USA Farmers Corrugated Solutions 17 miles Company Distance from UI Table 3.1: Material Ultimate Analysis Seed Corn Paper Sludge Oat Hulls Manure Wood1 Wood2 Moisture 11.59% 46.99% 1.43% 2.16% 9.19% 1.6% Carbon 39.13% 22.97% 43.51% 32.% 45.1% 44.32% Hydrogen 5.5% 2.88% 4.71% 3.61% 5.42% 5.23% Nitrogen 1.28%.5%.65% 2.49%.14%.8% Chlorine.4%.1%.15%.91%.2%.1% Sulfur.1%.7%.4%.66%.1%.1% Ash.83% 7.3% 5.22% 42.14%.74%.71% Oxygen 41.53% 2% 35.44% 16.3% 39.47% 39.5% Total 1% 1% 1% 1% 1% 1% 15

20 Table 3.2: Material Proximate Analysis Seed Corn Paper Sludge Oat Hulls Manure Wood1 Wood2 Moisture 12.91% 46.99% 1.43% 2.16% 9.19% 1.6% Volatile Matter 74.42% 44.99% 67.8% 46.1% 79.15% 77.85% Fixed Carbon 7.46%.99% 16.55% % 1.84% Ash 5.21% 7.3% 5.22% 42.14%.74%.71% Total 1.% 1.% 1.% 1% 1% 1% HV [BTU/lb] 8,91 3,556 6,934 5,496 7,827 7,629 Table 3.3: Experiment components Equipment List 25 Ω resistors (4) Biomass Injection Valve Biomass Samples Chromalox Industrial Heater Computer with DASYLab Data Acquisition Card (2) DC Power Source w/ connection cables (2) Exhaust fan H2 Sensor High Precision Scale High temperature insulation Ice bath IR CH4 Sensor IR CO Sensor IR CO2 Sensor Lighter Micro air pump Nitrogen Tank Omega FMA-54 Flow Controller Omega FMA-A249 Flow Controller Oxy-acetylene torch Oxygen Tank Particle/moisture Filter (2) Lexan enclosure Quartz tube Qubit Systems Oxygen Sensor Qubit Temperature/Humidity sensor Rotameter Screen Packet Stainless steel mesh Tubing and fittings Type K thermocouples (2) 16

21 Table 3.4: Excess O 2 volume per temperature range and material Corn Crushed Corn Oat Hulls Paper Sludge ~ 8 C 7.58 % 7.58 % % 7.58 % ~ 7 C % % % % ~ 6 C % % % % ~ 5 C 5.28 % % 4.94 % % ~ 4 C 4.3 % % 4. % % Table 3.5: Approximate pyrolysis duration (in seconds) by material and temperature series Corn Crush Corn Oat Hulls Paper Sludge ~8 C ~7 C ~6 C ~5 C ~4 C

22 Figures Figure 3.1: Schematic of experimental setup 18

23 Sensor Bank Reaction Chamber Ice Bath Heater Heating Torch Figure 3.2: Actual experimental setup 19

24 Gas Evolution [gco/g Oat Hulls/s] Gas Evolution [g CO/g Paper/s] Gas Evolution [g CO/g Corn/s] Gas Evolution [g CO/g Corn/s] A ~ Corn Kernels C.3 7 C C C C C ~ Oat Hulls C C C C 41 C B ~ Crushed Corn Kernels C C C C 424 C D ~ Paper Sludge C.25 7 C 6 C C C Figure 3.3: CO gas evolution versus time for A) corn kernels, B) crush corn kernels, C) oat hulls, and D) paper sludge 2

25 Gas Production [g CO/g Oat Hulls] Gas Production [g CO/g Paper] Gas Production [g CO/g Corn] Gas Production [ g CO/g Corn] A ~ Corn 796 C 7 C C B ~ Crushed Corn 88 C 699 C C C C.8 42 C C C ~ Oat Hulls 792 C 686 C C D ~ Paper Sludge 84 C 7 C C C C.8 41 C.8 44 C Figure 3.4: CO gas production versus time for A) corn kernels, B) crush corn kernels, C) oat hulls, and D) paper sludge 21

26 Gas Evolution [g CO 2 /g Oat Hull/s] Gas Evolution [g CO 2 /g Paper/s] Gas Evolution [g CO 2 /g Corn/s] Gas Evolution [g CO 2 / g Corn/s] A ~ Corn 796 C 7 C C C 4 C C ~ Oat Hulls 791 C 686 C C 515 C C B ~ Crushed Corn 88 C 699 C C 498 C C D ~ Paper Sludge 84 C 7 C.2 6 C 521 C C Figure 3.5: CO 2 gas evolution versus time for A) corn kernels, B) crush corn kernels, C) oat hulls, and D) paper sludge 22

27 Gas Production [g CO 2 /g Oat Hull] Gas Production [g CO 2 /g Paper] Gas Production [g CO 2 /g Corn] Gas Production [g CO 2 /g Corn] A ~ Corn C ~ Oat Hulls C 7 C 614 C 522 C 42 C C 686 C 592 C 515 C 41 C B ~ Crushed Corn D ~ Paper Sludge C 699 C 612 C 498 C 424 C C 7 C 6 C 521 C 44 C Figure 3.6: CO 2 production versus time for A) corn kernels, B) crush corn kernels, C) oat hulls, and D) paper sludge 23

28 O 2 Concentration [%] O 2 Concentration [%] O 2 Concentration [%] O 2 Concentration [%] A ~ Corn B ~ Crushed Corn C 7 C C 699 C C C C 42 C C 424 C C ~ Oat Hulls D ~ Paper Sludge C 686 C 592 C 515 C 41 C C 7 C 6 C 521 C 44 C Figure 3.7: O 2 concentration evolution versus time for A) corn kernels, B) crush corn kernels, C) oat hulls, and D) paper sludge 24