C R. ombustion esources, Inc. Evaluation of Stratean Inc. Gasifier System. 18 March Consultants in Fuels, Combustion, and the Environment

Transcription

1 C R ombustion esources, Inc W. 820 N. Provo, Utah Consultants in Fuels, Combustion, and the Environment 18 March 2016 Submitted To: Stratean Inc Legend Hills Drive Clearfield, UT Submitted By: Dr. Craig Eatough President Combustion Resources, Inc West 820 North Provo, Utah 84601

2 Table of Contents Executive Summary Introduction Background Objective Approach Results Preparation of gasifier for test runs Fuel preparation and analysis Preliminary checkout tests of gasifier Initial baseline run of gasifier Conclusions and Recommendations... 11

3 EXECUTIVE SUMMARY Stratean Inc. is working towards commercializing a co-current, atmospheric pressure gasifier for processing various waste materials, including: municipal solid wastes (MSW), sewage sludge, coal, and biomass into a clean synthesis gas (syn-gas). The fuel-rich syn-gas has multiple uses including the generation of electric power and production of liquid fuels. This project represents a feasibility study to evaluate the potential performance of the gasifier. Initial system checkout runs were performed without fuel and also with coal as the feedstock. The checkout runs were followed by a baseline run with coal to demonstrate operation of the gasifier. An extended run is also planned with the gasifier, following successful completion of the baseline run. Petersen Machine and Manufacturing, Inc. (Petersen) constructed/built the Stratean Gasifier. Petersen has verified the mechanical operation of the gasifier, and has been consulted throughout the testing. The tasks for the project were: 1) fully characterize the feedstock to determine its elemental composition, proximate analysis and energy content; 2) review the design data for the gasifier to understand the design capabilities and operation of the gasifier; 3) install the gasifier at Utah State University s (USU s) Carbon Energy Innovation (CEIC) facility and prepare the gasifier for testing; 4) perform preliminary tests runs of the gasifier to better understand operation of the gasifier and to work out any issues related to initial gasifier startup, 5) perform a baseline run of the gasifier with a single feedstock to evaluate performance and demonstrate operation of the gasifier. The gasifier was operated with a subbituminous coal as feedstock. Calculations show that 96.6% of the fuel portion of the coal was converted during gasification. The syn-gas produced was determined to be high in CO and H2 with applicability for steam or electrical power generation or for use as a feedstock for liquid fuels production.

4 LIST OF FIGURES FIGURES CAPTION PAGE Figure 1 Stratean Gasifier installed at USU s CEIC facility 7 Figure 2 Heat-up curve for gasifier preheat 9 LIST OF TABLES TABLES CAPTION PAGE Table 1 Elemental analysis of feed coal 7 Table 2 Proximate analysis and Heating Value of feed coal 8 Table 3 Syn-gas properties 10 Table 4 Proximate analysis of the collected ash 10

5 1. INTRODUCTION 1.1 BACKGROUND Stratean Inc. is working towards commercializing a co-current, atmospheric pressure gasifier for processing various waste materials, including: municipal solid wastes (MSW), sewage sludge, coal, and biomass into a clean synthesis gas. In gasification, the solid material is heated to high temperatures (> 700 C) with only limited amounts of oxygen to release a combustible gas. Gasification of MSW and other solid wastes can be used to extract the energy and reduce the volume of the waste material. The processes can be used to produce liquid fuels, low-btu gases, and heat. Subsequently, the gas can be used to produce electricity or liquid fuels, and the heat can be used as process heat for a variety of applications. Gasification of solid wastes also reduces the amount of material that must be landfilled, which reduces the need for additional landfills. The Stratean gasifier actually consists of six separate vertical tubes. Each fed by a common upper chamber. A rotating mixing arm in the upper chamber ensures that each tube is continuously supplied with feed material. Each tube contains grooves that are used to distribute gas (e.g., oxygen) around the circumference of the columnar cavity. Multiple smaller tubes, rather than a single large tube, allows for rapid mixing of oxidizer and fuel as well as uniform axial temperature which appears to be unique to gasifier designs. This should provide for uniform operation, fast heat transfer and enhanced process control. An extensive sensor suite for each gasification tube form the backbone of the control system. By monitoring various sensors such as temperature sensors, pressure sensors, flow meters, and the like, the control system adjusts what is happening within the gasifier. The control system then issues appropriate commands to one or more implementation systems such as a heater suite, gas-delivery system, and the like. For example, the control system may instruct the gasdelivery system to adjust the flow of gas (e.g., oxygen, oxygen enriched air, air) to a particular columnar cavity. The control system may increase the flow to raise the temperature within the columnar cavity, decrease the flow to lower the temperature within the columnar cavity, or the like to maintain the temperature of the columnar cavity within a particular range. Ash or slag exits the individual cavities is cooled and drops onto a bed of rotating ceramic balls which acts like a ball mill, breaking up the residue for transport to a storage bin. This enables the gasifier to be operated in either slagging or non-slagging mode which appears to be another unique feature of this gasifier design. The clean synthesis gas (syn-gas) exists the gasifier to a heat exchanger for cooling. The syn-gas may then be used in dual-fuel diesel engines, gas turbines and steam boilers to create electricity, or the syn-gas may be converted by a into liquid transportation fuels such as diesel, gasoline, jet fuel or ethanol with use of various catalysts.

6 1.2 OBJECTIVE Combustion Resources, Inc. The objectives of this project were to perform gasifier system checks and to demonstrate and evaluate the Stratean gasifier using coal as a feedstock. The mechanical operation and integrity of the gasifier was evaluated after the test runs with consultation of Petersen Machine and Manufacturing, Inc. (Petersen), the manufacturer of the gasifier. 1.3 APPROACH Combustion Resources was primarily responsible to install the gasifier, perform the testing, analyze the test results, and generate this project report. Carl Wecker of EnDigit was responsible to complete the process control and data acquisition programming for the gasifier. Petersen was available to consult regarding the mechanical operation of the gasifier. 2. RESULTS 2.1 PREPARATION OF GASIFIER FOR TEST RUNS The gasifier was installed at USU s CEIC facility near Helper, UT, and prepared for operation. Electrical power was delivered to the gasifier bay. A product gas condenser, gas flow meter and variable speed exhaust fan were installed. Cooling water was routed to the gasifier and connected to an on-site chiller and water supply. The exhaust was piped to an existing flare at the facility. An inert nitrogen gas supply was installed for emergency shut-down and an oxygen supply was installed for gasifier operation. The gasifier, as installed in the CEIC facility, is shown in Figure 1.

7 Figure 1. Stratean gasifier installed at USU s CEIC facility. 2.2 FUEL PREPARATION AND ANALYSIS A bituminous coal that had been ground to about minus 3/8 inch was selected as the feedstock. The coal was analyzed using standard ASTM Elemental and Proximate analysis and Heating Value. The results are provided in Tables 1 and 2. Table 1. Elemental Analysis of feed coal. Parameter Dry Basis, Wt. % Dry, Ash Free Basis, Wt. % Ash Carbon Hydrogen Nitrogen Oxygen Sulfur

8 Table 2. Proximate Analysis and Heating Value of feed coal. Parameter As Received Basis, Wt. % Dry, Ash Free Basis, Wt. % Moisture Ash Volatile Matter Fixed Carbon Heating Value (Btu/lb) 14,151 15, PRELIMINARY CHECKOUT TESTS OF GASIFIER Non-reacting system checkout tests were performed prior to full, reacting gasifier operation. These check-out tests included motor direction checks, fuel feed system operation, ash handling, gasifier tube filling and ash grinding operations, pre-heaters, cooling water flow and leak checks, exhaust fan operation, nitrogen and oxygen flow checks, flow and temperature measurement checks, and bed level sensor operation. Most systems were determined to be in working order in preparation of the baseline test run. Electrical pre-heaters were tested to determine their ability to adequately heat the gasifier tubes in preparation for feeding fuel. Figure 2 shows the heat-up curves for the gasifier heaters. It shows heaters 1 and 4 lagging the others. Continuity checks revealed electrical contacts requiring adjustment which was performed. The maximum temperature produced within the gasification chambers using the pre-heaters was about 600 F (see Figure 2). It is desirable to preheat to around 1000 F prior to operation. Therefore, it was determined to preheat the gasifier for 24 hours prior to operation and recommended that higher wattage pre-heaters be considered for future gasifiers to shorten pre-heat time.

9 Figure 2. Heat-up curve for gasifier preheat. 2.4 INITIAL BASELINE RUN OF GASIFIER An initial baseline test run of the gasifier was performed after the system check-out tests verified that the gasifier and support equipment were working properly. The baseline test conditions were established based on discussions with Stratean personnel. The Subbituminous coal described in Section 2.2 was used as the fuel. Initially the gasifer passages were filled with diatomaceous earth to provide appropriate sealing around auger screws passages and to control the initial flow of coal into the gasifier chambers. After preheating, coal was fed to the top gasifier chamber. As gasification proceeded, the product gas composition was monitored using a Horiba in-line gas analyzer which provided guidance regarding appropriate oxygen and fuel flow rates. The object was to adjust the oxygen flow to the point where there was no oxygen in the product gas. The oxygen flow rate was then reduced further to minimize the measured carbon dioxide concentration in the product gas. These conditions were considered to represent those that would produce a high value product gas. The analyzer was not able to analyze for fuel rich gas species at the high levels being produced during gasification. As oxygen was added to the gasifier cavities the bed temperature rose very quickly signifying good mixing of fuel and oxidizer as provided by the unique cavity design. Adjustment of oxidizer flow rate created a fast response in the bed temperature. The final operating conditions

10 provided about 3% CO2 with no recorded O2 in the gas. The bed temperature was measured at 1650 C while using oxygen at atmospheric pressure. During the gasification run, resistance in the feed tube prevented the feed auger from delivering a constant supply of coal to the gasifier. It was later determined that the feed auger motor was specified to be 1 hp but it was actually equipped with a 0.5 hp motor. It is recommended that the motor be changed prior to additional gasifier operation. Sufficient information was collected during gasifier operation to estimate the product gas composition using chemical equilibrium methods. To do this, the NASA Chemical Equilibrium with Applications (NASA-CEA) model was utilized. NASA-CEA is a program which calculates chemical equilibrium product concentrations from any set of reactants and determines thermodynamic and transport properties for the product mixture. Knowing the elemental composition of the fuel and reaction temperature and pressure, code iterations with variation in fuel/o2 ratios were performed to obtain the measured O2 and CO2 concentrations. The conditions were met at an Oxygen/Fuel ratio of 1.24 (mass basis). The results for the syn-gas properties are provided in Table 3. Table 3. Syn-gas properties. Parameter Volume % (dry basis) CO CO H N H2S 0.18 SO2 (ppm) 9 Heating Value (Btu/ft 3 ) 312 Following the run, ash was collected from the inlet to the ash feed screw. A proximate analysis of the as is provided in Table 4. Table 4. Proximate Analysis of the collected ash. Parameter As Received Basis, Wt. % Dry Basis, Wt. % Moisture Ash Volatile Matter Fixed Carbon

11 Using the proximate analyses of the original coal and the resulting ash, and assuming the ash to be inert, calculations were performed to determine the percent of the original fuel in the coal that was reacted during gasification. The results show that 96.6% of the fuel portion of the coal was converted by reaction during gasification. Following the baseline test the gasifier was disassembled and inspected. Of interest was the condition of the bottom ash/slag grinding chamber. Inspection showed that the ceramic balls remained in good condition and ash was noted in the collection bin. This suggests that the ash/slag handling system performed as designed, allowing for slagging and non-slagging modes of operation. 3. CONCLUSIONS AND RECOMMENDATIONS The successfully completed initial testing of the Stratean gasifier produced significant information regarding operation as well as recommendations for moving forward. The gasifier demonstrated the ability to produce a good, clean medium-btu syn-gas with commercial application for steam or power generation and liquid fuels production. During this initial test the operating conditions were not optimized and higher heating value syn-gas could likely be obtained by operating in a fashion to maximize methane production. While the conditions used for this test demonstrated the gasifiers ability to produce a good quality syn-gas, the high temperature and Oxygen/Fuel ratio predictably produced high levels of CO and H2. The versatility of the Stratean gasifier certainly allows for lower temperature gasification ( C) which is known to help promote the production of methane. Operating with a lower Oxygen/Fuel ratio would lower the gasification temperature and most certainly produce a higher heating value gas. Also, fuels with a higher volatile content such as biomass and low-rank coals tend to favor methane production. It is therefore recommended that tests which vary Oxygen/Fuel ratio be performed on coal as well as additional fuel types. It is also recommended that higher power preheaters be installed for easier startup and that the feed auger motor be increased to 1 hp to meet the design specifications. Also, the refractory forming the gasification chambers appears to be a fused alumina or mullite material. These refractories and capable of high temperature but are very susceptible to thermal stress fracture. Other refractories are available which are resistant to thermal stress cracking. Therefore, it is recommended that refractory supply companies be consulted regarding selection of a suitable material that combines high temperature capability with thermal stress resistance.