DESCRIPTION OF GASIFICATION EQUIPMENT AT THE ENERGY & ENVIRONMENTAL RESEARCH CENTER

Transcription

1 DESCRIPTION OF GASIFICATION EQUIPMENT AT THE ENERGY & ENVIRONMENTAL RESEARCH CENTER SUMMARY The Energy & Environmental Research Center (EERC) has multiple gasification systems capable of gasifying coal, biomass, and other solid or liquid feedstocks. Of these, five of the systems are expected to see primary use over the next couple of years. Three systems are operational, and the other two are scheduled to come online in Table 1 lists the systems and the basic characteristics of each. A detailed description of each system follows the table. The five systems each have warm-gas cleanup capabilities. The EERC has a bench-scale warm-gas cleanup train that is portable and can be placed at the back end of each gasifier. The system is capable of reducing sulfur levels to as low as ppm, particulate to less than 0.1 ppmw with ceramic/metal candle filters, and fixed-bed reactors for reducing mercury or other contaminants. Water gas shift reactors including sour, high-temperature, and low-temperature shift can be inserted at any location in the cleanup train. The EERC, through its National Center for Hydrogen Technology (NCHT), developed the warm-gas cleanup testing capability. The bench-scale cleanup train has now been tested and is fully operational. Hydrogen separation using hydrogen separation membranes can be performed at elevated temperatures without the need to quench the syngas because of the capability of the warm-gas cleanup train. The hydrogen membrane can be inserted into any point in the cleanup train to simulate the desired operating conditions but would normally be installed after the sulfur removal and shift reactors, depending on the sensitivity of the membrane to sulfur. If needed, a small slipstream of the syngas from any gasifier can be pulled for hydrogen separation testing. 1

2 2 Table 1. Gasifier Summary Gasifier Name Type Scale Continuous Fluidized Fluid-Bed bed Reactor (CFBR) Transport Reactor Development Unit (TRDU) Entrained-Flow Gasifier (EFG) Fluid-Bed Gasifier (FBG) Carbonizer Transport reactor Entrained flow Fluidized bed Nominal Feed Rate, lb/hr Syngas Production, scfm Bench 4 8 on air 1.5 to 2 on O 2 System Pressure, psi Gasifier Nominal Temp., F (metal reactor) Pilot on air 250 on O 2 Refractorylined Bench refractoryceramic lined Bench to 1800 depending on operating pressure metal reactor Warm Gas Cleanup Capability One Week Run Cost (5 days, 24hr/day)* Status/ Availability Notes Full stream Operational $85,000 Can boost quenched syngas to 800 psi Recycled syngas to eliminate N 2 dilution Slipstream, 5% Full stream Full stream Operational $225,000 Can boost quenched slipstream to 800 psi N 2 purges Under construction/ late summer 2008 Under construction/ fall 2008 Fluidized bed Pilot 100 to on air to 1800 refractorylined *Estimated cost of baseline run; cost per week will vary with duration of run and types of testing performed $110,000 Can boost quenched gas to 2500 psi Recycled syngas to eliminate N 2 dilution $110,000 Can boost quenched gas to 2500 psig Recycled syngas to eliminate N 2 dilution Slipstream Operational $150,000 Can boost quenched slipstream to 800 psi N 2 purges

3 DETAILED DESCRIPTION OF EQUIPMENT Continuous Fluid-Bed Reactor (CFBR) Figure 1 shows the 4-lb/hr CFBR used for gasification tests. The unit was originally designed as a pyrolysis unit for a U.S. Department of Energy (DOE) mild gasification program but has since been used for gasification and pyrolysis on a variety of projects. Gases used for fluidization are mixed in a gas manifold. Bottled gas, house nitrogen, house air, and any liquid desired (such as water) are first preheated, then mixed and heated to reaction temperature in a superheater (20 ft of 3/8-in. tubing coiled into an 18-in. ceramic fiber heater). Two bottled gases in combination with either house air or house nitrogen and a liquid can be used at the present time. The reactor is constructed of 316H stainless steel Schedule 80 pipe. The first (bottom) section is made of 3-in. pipe and is 33 in. in length. The next (top) reactor section is made of 4-in. pipe, in. in length. The two sections are connected with a 316H weld reducer. The unit was designed such that the top of the fluid bed lies 33 in. above the coal injection point. A solids offtake leg at the top of the bed is the primary means of solids removal from the reactor. A ball valve facilitates the collection of product while the system is operating. The reactor currently has two ceramic fiber heaters to maintain the vessel s temperature and eliminate hot spots. Using external heaters allows the evaluation of internal and external heating methods for process development and scale-up. The reactor is capable of operation at a maximum of 155 psig and 840 C (1500 F). Figure 1. Schematic of CFBR. 3

4 A 3-in.-diameter cyclone is used for solids removal from the gas stream. A ball valve allows the changing of the solids catchpot while the system is operating. The cyclone is heated with a ceramic fiber heater capable of operating at a temperature of 900 C (1650 F). An 8-in.- long section of 2-in. 316H stainless steel Schedule 80 pipe has also been utilized as a pressure vessel to either contain a fixed bed of zinc-based sorbent to reduce the H 2 S concentrations or to contain calcium-based sorbent for the removal of chlorine gases from the fuel gases. Three 4-in.-diameter vessels are used to remove all condensables from the gas stream. Two separate trains were installed: one for mass balance sampling and the other for heatup, unsteadystate conditions, and cooldown. The first condenser pot is indirectly cooled by water and typically cools the gas stream from 300 C (570 F) to 95 C (200 F). The next two condensers, also indirect, are glycol-cooled. The exit gas temperature is typically 10 C (50 F). A glass wool filter is used to capture aerosols passed through the condenser system. A wet scrubber has also been used to neutralize any chlorine still present in the gas stream before the gas is sent through a product gas meter. A Genesis software package is used for process control and data acquisition. Pressure drop across the bed is measured by two transmitters, and thermocouples throughout the unit measure temperature. Temperature and pressure readings are recorded every 30 seconds, and these data are directly transferred to Lotus spreadsheets. Online continuous emission monitors for H 2, CO, CH 4, CO 2, and H 2 S together with an online Foxboro 931C gas chromatograph are utilized for measuring gas compositions. If desired, the gas composition of the coal-derived gas stream can be adjusted slightly by adding bottled gas to the gas stream entering the reactor. Bench-Scale Hot-Gas Filter Vessel (HGFV) The design and construction of a bench-scale filter vessel that could be used in conjunction with the CFBR (for gasification/pyrolysis) was built to test hot-gas candle filters for their ability to obtain high-temperature, high-pressure operational data on various filter elements. This vessel is designed to handle all of the gas flow from the CFBR at its nominal design conditions. The vessel is 10-in. i.d. and 60-in. long (including cone, vessel, and cap) and can handle a gas flow up to 30 scfm at 843 C (1550 F) and 150 psig. The tube sheet is interchangeable to handle different-sized filters. The filters are sealed in the tube sheet by a bolted metal plate and Nextel fiber gaskets which counteract the upward force imparted across the candle filter by the filter s differential pressure. The vessel is sized such that it could handle three candle filters up to 18-in. long with a in. o.d. This would provide candle space of 3.85 in. center line to center line and enable filter face velocities as low as 2.5 ft/min to be tested in the CFBR. Higher face velocities would be achieved by using shorter candles or higher gas flow rates. Ports are added in the filter vessel for allowing temperature and pressure measurements to be obtained. The ash letdown station consists of two high-temperature valves to act as lock hoppers to isolate the ash hopper from the filter vessel. The nitrogen backpulse system is constructed from existing materials utilized from a previous hot-gas filter test system. The backpulse system is designed to supply a minimum of three candle volumes per pulse for the longest candle filters and even higher volumes for the shorter candle filters. The nitrogen is capable of being heated up to 816 C (1500 F) before 4

5 entering the filter vessel, although most tests utilize room-temperature nitrogen for backpulsing. The length and volume of nitrogen displaced into the vessel is controlled by the regulated pressure (up to 600 psig) of the cold-nitrogen reservoir and the solenoid valves used to control the timing of the cold-gas pulse, which displaces the hot nitrogen into the filter vessel. An electrically heated ½-in. pipe is used to connect the CFBR to the HGFV. Transport Reactor Development Unit (TRDU) The pilot-scale TRDU has an exit gas temperature of up to 980 C (1800 F), a gas flow rate of 400 scfm (0.153m 3 /s), and an operating pressure of 120 psig (9.3 bar). The TRDU system can be divided into three sections: the coal feed section, the TRDU, and the product recovery section. The TRDU proper, as shown in Figure 2, consists of a riser reactor with an expanded mixing zone at the bottom, a disengager, and a primary cyclone and standpipe. The standpipe is connected to the mixing section of the riser by an L-valve transfer line. All of the components in the system are refractory-lined and designed mechanically for 150 psig (11.4 bar) and an internal temperature of 1090 C (2000 F). Detailed design criteria and a comparison to actual operating conditions on the design coal are given in Table 2. The premixed coal and limestone feed to the transport reactor can be admitted through three nozzles, which are at varying elevations. Two of these nozzles are located near the top of the mixing zone (gasification), and the remaining one is near the bottom of the mixing zone (combustion). During operation of the TRDU, feed is admitted through only one nozzle at a time. The coal feed is measured by an rpm-controlled metering auger. Oxidant is fed to the reactor through two pairs of nozzles at varying elevations within the mixing zone. For the combustion mode of operation, additional nozzles are provided in the riser for feeding secondary air. Hot solids from the standpipe are circulated into the mixing zone, where they come into contact with the nitrogen and the steam being injected into the L-valve. This feature enables spent char to contact steam prior to the fresh coal feed. This staged gasification process is expected to enhance process efficiency. Gasification or combustion and desulfurization reactions are carried out in the riser as coal, sorbent, and oxidant (with steam for gasification) flow up the reactor. The solids circulation into the mixing zone is controlled by fluffing gas in the standpipe, J-leg aeration flows, and the solids level in the standpipe. The riser, disengager, standpipe, and cyclones are equipped with several internal and skin thermocouples. Nitrogen-purged pressure taps are also provided to record differential pressure across the riser, disengager, and cyclones. The data acquisition and control system scans the data points every ½ second and is saving the process data every 30 s. The bulk of entrained solids leaving the riser is separated from the gas stream in the disengager and circulated back to the riser via the standpipe. A solids stream is withdrawn from the standpipe via an auger to maintain the system s solids inventory. Gas exiting the disengager enters a primary cyclone. The dipleg solids have been recirculated back to the standpipe through a loop seal at the bottom of the dipleg. Gas exiting this cyclone enters a jacketed-pipe heat exchanger before entering the HGFV. The warm particulate-free gases leaving the HGFV are vented directly into a thermal oxidizer where they are combusted. 5

6 Figure 2. Schematic of the TRDU. 6

7 Table 2. Summary of TRDU Design and Operation on the Design Coal Parameter Design Actual Coal Illinois No. 6 Illinois No. 6 Moisture Content, % Pressure, psig 120 (9.3 bar) 120 (9.3 bar) Steam/Coal Ratio Air/Coal Ratio Ca/S Ratio, mol Air Inlet Temperature, C Steam Preheat, C Coal Feed Rate, lb/hr 198 (89.9 kg/hr) 220 (99.9 kg/hr) Gasifier Temperature, maximum C T, maximum C to 100 Carbon Conversion, 1 % > HHV 2 of Fuel Gas, Btu/scf Heat Loss as Coal Feed, % Riser Velocity, ft/sec Heat Loss, Btu/hr 252, ,000 Standpipe Superficial Velocity, ft/sec Carbon conversion = (wt carbon feed wt carbon removed)/wt carbon feed * Higher heating value. Hot-Gas Filter Vessel This vessel is designed to handle all of the gas flow from the TRDU at its expected operating conditions. The vessel is approximately 48-in. i.d. (121.9 cm) and 185 in. (470 cm) long and is designed to handle gas flows of approximately 325 scfm at temperatures up to 815 C (1500 F) and 120 psig (8.3 bar). The refractory has a 28-in. (71.1-cm) i.d. with a shroud diameter of approximately 22-in. (55.9 cm). The vessel is sized such that it could handle candle filters up to 1.5 m long; however, 1-m candles were utilized in the 540 C (1000 F) gasification tests to date. Candle filters are in. (6-cm) o.d. with a 4-in. (10.2-cm) center line-to-center line spacing. The filter design criteria are summarized in Table 3. The total number of candles that can be mounted in the current geometry of the HGFV tube sheet is 19. This enables filter face velocities as low as 2.0 ft/min to be tested using 1.5-m candles. Higher face velocities are achieved by using fewer candles. The majority of testing has been performed at a face velocity of approximately 4.0 to 4.5 ft/min. This program has tested an Industrial Filter & Pump (IF&P) ceramic tube sheet and Fibrosic and REECER SiC candles, silicon carbon-coated and SiO 2 ceramic fiber candles from the 3M company, along with sintered 7

8 Table 3. Design Criteria and Actual Operating Conditions for the Pilot-Scale HGFV Operating Conditions Design Actual Inlet Gas Temperature 540EC 450E 580EC Operating Pressure 150 psig (10.3 bar) 120 psig (8.3 bar) Volumetric Gas Flow 325 scfm (0.153 m 3 /s) 350 scfm (0.165 m 3 /s) Number of Candles 19 (1 or 1.5 meter) 13 (1 meter) Candle Spacing 4 in. 6 to 6 (10.2 cm) 4 in. 6 to 6 (10.2 cm) Filter Face Velocity ft/min (1.3 to 2.3 cm/s) 4.5 ft/min (2.3 cm/s) Particulate Loading <10,000 ppmw < 38,000 ppmw Temperature Drop Across HGFV <30EC 25EC Nitrogen Backpulse System Pressure Up to 600 psig (42 bar) 250 to 350 psig (17 to 24 bar) Backpulse Valve Open Duration Up to 1-s duration ¼-s duration metal (iron aluminide) and Vitropore silicon carbon ceramic candles from Pall Advanced Separation Systems Corporation. In addition, granular SiC candles from U.S. Filter/Schumacher and composite candle filters from McDermott Technologies and Honeywell were tested. Current testing has focused on Pall s iron aluminide metal filters. Also, candle filter fail-safes from Siemens-Westinghouse Science and Technology Center have been tested. The ash letdown system consists of two sets of alternating high-temperature valves with a conical pressure vessel to act as a lock hopper. Additionally, a preheat natural gas burner attached to a lower inlet nozzle on the filter vessel can be used to preheat the filter vessel separately from the TRDU. The hot gas from the burner enters the vessel via a nozzle inlet separate from the dirty gas. The high-pressure nitrogen backpulse system is capable of backpulsing up to four sets of four or five candle filters with ambient-temperature nitrogen in a time-controlled sequence. The pulse length and volume of nitrogen displaced into the filter vessel is controlled by regulating the pressure (up to 600 psig [42 bar]) of the nitrogen reservoir and controlling the solenoid valve pulse duration. Figure 2 also shows the filter vessel location and process piping in the EERC gasifier tower. A recently installed heat exchange surface now allows the hot-gas filter to operate in the 500 to 1200 F range instead of the higher temperature range of 800 to 1000 F utilized in previous testing. This additional heat exchange surface was added to allow gas cooling to the temperature where Hg removal is likely to occur. Ports for obtaining hot high-pressure particulate and trace metal samples both upstream and downstream of the filter vessel were added to the filter system piping. 8

9 Entrained-Flow Gasifier (EFG) A conceptual drawing of the EFG is shown in Figure 3. The EFG will be downfired and housed in an existing high-pressure vessel approximately 24 in. in diameter and 7 ft in length. It will fire nominally 8 10 lb/hr of coal and produce up to 20 scfm of fuel gas. The newly designed heating system will be capable of reaching a nominal temperature of 1500 C and will provide a consistent temperature throughout the length of the furnace. Infrared thermocouples will be used to monitor the temperature of the combustion zone, and the heat input will be automatically controlled to stay within a tight operating range. The pressure inside the alumina furnace tube will be 300 psi and will be balanced with a 300-psi nitrogen atmosphere outside the alumina tube. The reactor will have the capability to run in oxygen- or air-blown mode. Pulverized coal at a nominal rate of 8 10 lb/hr will be fed to the furnace via a twin screw feed motor contained in a pressurized vessel. The design will allow for 8 hours of continuous use at 4 lb/hr before the coal hopper would need to be refilled. The feed system will be situated on a scale so that actual feed rates can be calculated. Combustion gases consisting of air or oxygen and steam will be used to carry the solid pulverized coal into the combustion zone. A novel heating system will be used to reach the 1500 C temperature required of a slagging gasifier. Past testing on the pressurized drop-tube furnace indicated that high temperature could not be maintained when operating above 100 psig. The novel system is expected to be able to reach and maintain the flue gas at that temperature by utilizing a uniform heat input throughout the length of the furnace. Refractory will be used as insulation to help maintain the required temperature in the furnace. Refractory has the ability to withstand both high temperature and high pressure. A water-cooled jacket surrounds the outside of the vessel and is used to remove excess heat from the system. The gasifier is brought up to pressure by running gas through the main furnace tube and then allowing it to run through a pressure equalization line that balances the gas pressure on the inside and outside of the alumina furnace tube. The pressure equalization line ensures that during start-up and operation, the pressure on the inside and outside of the tube is equal. Unequal pressure will result in a broken furnace tube. Gas will exit the bottom of the furnace and pass through a 90 turn where it will then be tested in subsequent pollution control devices. A provision for a water quench will be added to the bottom of the furnace. Slag also exits the bottom of the furnace and is collected in a refractory-lined slag trap. Sulfur Reactor The transport reactor for sulfur removal is shown in Figure 4. Sulfur sorbents are introduced from the feed hopper via a screw feed motor. The sorbents contact the gas stream and are moved upward through the riser and across the top horizontal section. The sorbents and 9

10 Figure 3. Schematic of the EFG. 10

11 Figure 4. Schematic of the sulfur reactor. 11

12 flue gas are then separated in the primary cyclone. The sorbents fall into the standpipe while the syngas exits the top of the reactor and onto the HGFV for fine particulate removal. The sorbents in the standpipe are recycled back to the riser via a second screw feed motor. Temperature in the system can be adjusted from 300 to 1000 F, allowing for a wide range of testing parameters. Ceramic external heaters are used to maintain run temperature, and multiple thermocouples are used across the system for temperature monitoring. The speed of the recycle screw feeder can be adjusted, which allows for variation of the sorbent recycle rate. Pressure drop is measured in the riser, which allows for calculation of the recycle rate. Standpipe pressure drop is also measured to determine the amount of sorbent accumulated in the standpipe. Nitrogen purges are used to keep the pressure taps free of particulate. Sorbent can be removed from the system for analysis while testing is in progress via a double-valve hopper system. This also allows for removal of spent sorbent and addition of fresh sorbent while the system is running. Fluid-Bed Gasifier (FBG) This system has been designed according to American Society of Mechanical Engineers (ASME) B31.3 Process Piping Code specifications. The internal reactor dimensions are based upon the existing operational CFBR that currently operates up to a maximum operating pressure (MOP) of 1.0 MPa (150 psig). After a review of available alloys, Haynes 556 has been selected as the material most suitable for fabrication of this high-temperature, high-pressure system. The reactor has been designed with the capability to operate at a MOP of 6.9 MPa (1000 psig) at operational temperatures of 843 C (1550 F), 4.5 MPa (650 psig) at an operational temperature of 917 C (1650 F), and 2.0 MPa (300 psig) at an operational temperature of 1800 F. This system has been designed to be externally electrically heated in a similar manner to the CFBR. The 2500-lb 316H stainless steel flanged connections at the top and bottom of the reactor will be limited to a maximum operating temperature of 677 C (1250 F) for a MOP of 6.9 MPa (1000 psig), 732 C (1350 F) for a MOP of 4.5 MPa (650 psig), and an operational temperature of 816 C (1500 F) for a MOP of 2.0 MPa (300 psig). This system will be instrumented with thermocouples in all key locations to monitor that operating temperatures of the material are not exceeding their design limitations. A design drawing of the reactor is shown in Figure 5. The thicknesses required for the construction are not available in standard schedules and sizes. Reactor material has been purchased in a solid billet form and will be machined by a process called gundrilling. Additionally, all of the nozzles for fuel feed, bed drains, the gas exit, and all thermocouple and pressure taps will have to be custom-machined and drilled. Several companies have been contacted to determine if they have the capabilities for the required machining and welding of these components. Final discussions are in progress for the machining and welding requirements. Design of a solid-fuel feed system has been completed. This fuel feed system will be shared with another gasification system, the EFG, that will be located immediately adjacent to the FBG. The feed system uses a K-tron loss-in-weight feeder that will be installed inside of a pressure vessel capable of 6.9-MPa (1000-psig) operation. This system will allow an 12

13 Figure 5. Design drawing of the pressurized fluidized gasification reactor. 13

14 instantaneous measurement of the fuel feed rate to the gasification system it is connected to. The feed system electronic controls will be interfaced to a data acquisition system that will allow for local or remote computer control of the fuel feed rate. The K-tron feeder has been purchased, and bids have been obtained for the two pressure vessels required for this feed system. A side view of this feed system is shown in Figure 6. The actual feeder is located inside of the lower feeder pressure vessel. Power and electronic signals to and from the feeder will be through two isolation fittings on the pressure vessel. The upper pressure vessel is the fuel charge hopper. The fuel charge hopper is manually charged with fuel through the top valve while at atmospheric pressure. It is then sealed and pressurized. Finally, the fuel feed material is transferred by gravity feed to the weigh hopper inside through the lower dual-valve system. The weigh hopper is on an integral platform scale that provides an electronic signal of the overall weight of the fuel feed material. Hopper weights along with feed rates are recorded by the data acquisition system and can be displayed and trended as required. Additionally, two sets of three (six total) water-cooled quench pots have been designed for condensing moisture and organics from the gas stream. These quench pots have been designed for operation up to 1000 psig. The design of these quench pots is based upon what has been successfully used with the CFBR. This design has been very effective in the removal of organics and moisture while not plugging off. It has evolved over years of operation. Either water or a cooled glycol and water mixture is circulated through the outer jacket of each quench pot to cool the product gas down. Figure 7 shows a cross-sectional view of one of the quench pots. Carbonizer The carbonizer consists of the refractory-lined fluid-bed reactor, two cyclones, and a natural gas preheat burner (Figure 8). The carbonizer can be operated as a spouting- or bubblingbed reactor with a feed capacity of 100 to 150 lb/hr at temperatures from 1200 F (650 C) to 1800 F (980 C), pressures up to 150 psig, and steam partial pressures from 0% to 60%. The body of the carbonizer consists of four 5-ft-tall sections. The modular design of the carbonizer allows removal of different sections to obtain a variety of gas and char residence times. The lower two sections are constructed of 24-in. 304L SS pipe. The pipe is lined with 5.25 in. of insulating refractory and a layer of hard, abrasion-resistant refractory, resulting in a 10-in. i.d. The two upper sections are constructed of 30-in. 304L SS pipe. The pipe is lined with in. of insulating refractory and 2 in. of hard refractory, resulting in a 16-in. i.d. When operated in spouting-bed mode, the smaller diameter of the lower sections of the reactor is intended to increase the velocity and turbulence of the bed and potentially reduce agglomeration of the test coals. When the high-velocity gas jet enters the larger-diameter upper section, its velocity decreases. The char entrained in the gas jet falls back into the lower section and dilutes the fresh coal entering the bottom of the reactor, providing a longer residence time for the char. The fluidization gases can be heated by a stoichiometrically operated natural gas burner. The desired operating temperature is maintained by adding air and/or steam or nitrogen to the burner gas in the carbonizer plenum. 14

15 Figure 6. Cross-sectional view of fuel feed system. 15

16 Figure 7. Cross-sectional view of a quench pot. 16

17 Figure 8. Schematic of the carbonizer. 17

18 The char can be removed from the system and cooled in a nitrogen-purged tote bin. The char fines entrained by the gases leaving the top of the carbonizer are separated from the gas stream by a pair of cyclones. The primary cyclone removes particles greater than 10.7 μm in size with 50% efficiency. The cyclones are constructed of 304 SS pipe. Refractory was cast inside the pipes to form the cones at the bottoms of the cyclones. The fines are removed from the hot-gas stream by the cyclones and collected in a lock hopper. Modification of process outlet piping would allow the fuel gas to be fed to the existing hotgas filter system utilized on the TRDU for dry ash particulate removal to less than 0.1 ppmw. Feedstock Preparation Material can be delivered by truck. Solid feedstock is prepared to the desired specifications and stored in nitrogen-purged bunkers. The following equipment is available for feedstock preparation: C Williams coal and rock crusher Capacity 4 ton/hr of coal or rock to ¼ in. C Mikro pulverizer Capacity 1 ton/hr to 200 or 325 mesh Other bar screen sizes can be purchased C Kason classifier Capacity 4 to 5 tons/hr Screen sizes include ¾ inch, ½ inch, ¼ inch, 1/16 inch and 2, 6, 10, 20, 30, 40, 50, 60, 100, 150, 200, and 325 mesh A steam dryer is available to dry feedstocks before they enter the carbonizer or TRDU. The objective of drying the feed material is to reduce or eliminate the net production of wastewater, reduce the heat load of the feed, or reduce feed problems that are inherent with excess surface moisture. Additional processing and storage equipment is has been added to the EERC capabilities that should enable biomass processing. Pilot-Scale Solids Feed System The carbonizer and TRDU share a common coal feed system. Solids enter the system in a nonpressurized hopper with a capacity of 2500 lb. The coal is gravity-fed into two pressurized coal lock hoppers, which have a capacity of 1700 lb. A set of valves isolates the pressurized lock hoppers from an auger at the bottom of the pressurized feed hopper which meters the solids. The rotational speed of the auger is controlled to produce various feed rates. The feed auger drops the solids into a high-velocity gas stream of ambient-temperature nitrogen or air. The flow of 18

19 nitrogen entrains the material into either the carbonizer or TRDU, depending on which unit is in operation. The solids can also be augured into the carbonizer rather than by pneumatic transport. Utilities The utilities area consists of the following: C Electrical service C Natural gas C Cooling water C Nitrogen C Process air C Steam boiler and superheater C Process oxygen The boiler, which supplies steam to the carbonizer and TRDU, has the capacity to deliver 400 lb/hr of saturated steam at temperatures up to 385 F (196 C) at 200 psig. The electric superheater can heat 200 lb/hr of steam from 250 F (121 C) to 1400 F (760 C). 19