GASIFICATION TECHNOLOGY COUNCIL CONFERENCE SAN FRANCISCO, OCTOBER 9-12, 2005 GASIFICATION TECHNOLOGIES ADVANCEMENT CONTINUES

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1 Conference Topic: GASIFICATION TECHNOLOGY COUNCIL CONFERENCE SAN FRANCISCO, OCTOBER 9-12, 2005 GASIFICATION TECHNOLOGIES ADVANCEMENT CONTINUES SUCCESSFUL CONTINUOUS INJECTION OF COAL INTO GASIFICATION AND PFBC SYSTEM OPERATING PRESSURES EXCEEDING 500 PSI - DOE FUNDED PROGRAM RESULTS Authors: Timothy Saunders, Derek Aldred - Stamet Inc 8210 Lankershim North Hollywood, CA timsaunders@stametinc.com dlaldred@stametinc.com Michael Rutkowski, Parsons Corporation, Pasadena, CA Michael.D.Rutkowski@parsons.com Abstract President Bush s energy program is focused towards commercializing power production technologies that offer improvements in efficiency and reductions in emissions while utilizing the nation s most abundant energy reserve - coal. Gasification offers such benefits. To bring this technology to full commercial acceptance, the operational issue of feeding solid fuel into the pressure environment needs to be addressed. The DOE, through the National Energy Technology Laboratory, has funded research to develop the unique Stamet Posimetric Solids Pump to feed coal into current gasification operating pressures. The project comprised design and testing to feed coal into 300 PSI and a second Phase for feeding into 500 PSI. The 300 PSI target was achieved in December In January 2005, the Posimetric feeder achieved continuous injection of coal into 560 PSI, exceeding the Phase 2 target. This paper will present a review and evaluation of the design, design optimizations and test results of the successful feeder. The paper will additionally present analysis of economic benefits to pump use and results from semi-commercial testing at gasifieroperating test facilities, which should have commenced by the date of the conference. Page 1 of 20

2 Introduction Over the past several decades there have been many attempts to build a continuous positive displacement device for solids i.e. a solids pump. There has only been one success, the unique and novel Posimetric concept developed by Stamet Inc. This technology has, in two earlier DOE-funded programs, achieved direct and continuous coal feeding into pressures exceeding 250 PSI. In the current DOE-funded program, the Posimetric device has just exceeded 500 PSI, making it the first, and to date only, mechanically powered solids pump to achieve this record pressure. The Posimetric Pump Technology The Stamet machine utilizes a radical technology known as Posimetric solids feeding. The machine relies on a simple continuously rotating element, without valves or pressure vessels, and which also provides precise flow control. The Posimetric concept (Figure 1) was originally developed as a solution to the problems of feeding crushed oil shale into retorts for a joint project between Exxon and Tosco at Parachute Creek, part of President Jimmy Carter s energy program. Figure 1 The Stamet Posimetric Pump has only one moving part; discs on a shaft forming a spool, which rotates within a housing. An abutment, extending between the discs to the hub, separates the inlet from the outlet. Material entering the pump becomes Figure 2 locked or bridged between the discs and is carried around by their rotation (Figure 2). This principle of lockup means Page 2 of 20

3 the pump experiences virtually no wear. The abutment prevents material being carried around for an entire rotation, and also makes the pump self-cleaning. Research Program The current research program specifically addresses DOE-objectives to develop technologies that improve performance of advanced combustion and gasification systems. These systems will need material handling equipment that is efficient, reliable, accurate, and cost-effective at pressures exceeding 500 PSI. Achieving the target pressure level has required two phases: Phase 1) Evaluate and Select suitable coal material specification for feeder testing to minimize material handling issue affecting the program. Design, manufacture and test a semi-scale, 300-PSI pressure capable, machine and test rig. Test and evaluate design concepts and elements for internal pump configuration including inlet and outlet arrangements to build confidence in design for higher pressures in phase 2. Phase 2) Design, manufacture and testing of a modified feeder and test rig capable of discharging at the full operating pressure of 500 PSI. Coal Evaluation and Selection The project commenced with study of gasification systems and identification of feed material properties desirable for achieving the target pressures. Coal preparation processes were reviewed to ensure final feed material specifications were consistent with coal preparation plant capabilities and systems being fed. Ultimately PRB coal samples provided by the Wilsonville PSDF facility were selected. Page 3 of 20

4 Phase I - Feeder Design The Posimetric feeder designed for this program incorporates innovations to provide flexibility in testing and minimized cost. The feeder is the minimum size able to allow reliable coal flow performance for the sample coal selected. Due to the Posimetric design fixed relationship between disc spacing and disc diameter, as the disc spacing increases so the diameter increases, consequently overall machine costs escalate as opening size increases. Figure 3 The research Posimetric feeder still consists of one moving part the spool (Figure 3). The spool comprises of two discs and a hub spacer on a shaft. The spool rotates inside the body housing (Figure 4). Unique to this design are inserts for inlet and outlet, allowing component configurations to be changed should testing indicate such need. Mounted onto the inlet side of the body is an inlet transition Figure 4 assembly which functions to direct material from the Stamet proprietary active hopper mounted above the feeder into the spacing between the discs. The active or live-wall hopper is critical for material flow, having to reliably supply coal through a 1.25 inch wide opening - its design reflects the knowledge gained over years of development in flow enhancement systems. Mounted onto the outlet side of the body is the outlet transition assembly which functions to remove the material between the discs and direct it into the discharge pipe. Due to the level of compaction in the zone between the discs, significant energy can be required for this process if design is not optimized. The Phase 1 research has focused Page 4 of 20

5 on identifying the best and most efficient configuration for this component. The feeder is mounted within a frame (Figure 5) that supports both pressure vessels. Phase I Test Results Phase 1 testing included feeding coal samples at various feed rates and pressures. These series of tests were carried out at progressively increasing pressures and speed to evaluate feeder performance up to the target pressure of 300 PSI (21 kg/cm 2 ). To confirm pump drive a mechanical load was applied to resist the coal Figure 5 flow at the pump exit. Steady flow was achieved confirming the pumps ability to deliver coal in a controlled manner against a resistance. Tests were then carried out with outlet gas pressure applied. In the initial pump configuration a stable outlet seal was not obtained. The outlet was modified to further consolidate coal in the discharge area and stabilize the outlet seal. The revised outlet geometry required significantly higher torque to feed into atmospheric conditions than the previous geometry, and resulted in excessive torque requirements as outlet gas pressure was applied. Subsequent outlet changes progressively reduced restrictions to flow until a balance was obtained of sufficient resistance to produce a stable gas seal without exceeding the torque capacity of the drive system. Substantial torque was still required, however the weight pumped was in good agreement with the calculated value, confirming throughput remained directly proportional to rotational speed (figure 6). Page 5 of 20

6 First Run to 300psi Pressure, psig / Weight, lbs Pout psi Weight lbs Calc Wt lbs Torque ft/lb 300psi Achieved Torque Time 0 Figure 6 Further outlet modifications resulted in additional torque reduction. Several runs were made with a maximum of 340 psi attained. Torque requirement for the first, last and an intermediate run illustrating the drop in torque is shown in Figure 7. Outlet Pressure vs Torque Requirements First Run Torque Final Run Intermediate Run Outlet Pressure, psi Figure 7 Page 6 of 20

7 Of particular significance was data confirming the independence of throughput relative to outlet pressure. Figure 8 shows typical comparison between measured coal flow and calculated coal flow from pump speed at constant inlet coal density. Actual Wt./Calc.Wt Comparison of Actual and Calculated Weight Pumped at Constant Inlet Conditions Outlet Pressure, psi Figure 8 Phase 2 Program The second phase focused on further optimization, particularly in the outlet to reduce loads in the pump. Instrumentation and monitoring equipment was upgraded to provide more detailed data, and visual monitoring of pump internal operation undertaken to allow better understanding of the mechanics of operation (Figure 9). This identified a number of modifications that significantly reduced torque requirements. Design and manufacture of an outlet utilizing 3D prototyping techniques enabled an optimum-for flow configuration in the transition from disc containment to outlet duct. Figure 9 Page 7 of 20

8 Figure 10 shows the outlet cross-section. During testing the outlet was progressively shortened to determine effect on torque requirements and sealing capability. The result of this process was a torque reduction of percent over the outlet used for the phase 1 tests while still maintaining a stable seal. Figure 10 Tests at increasing pressures were undertaken with minor modifications until in January 2005 a pressure level of 560 PSI was achieved, a world record for continuous feeding of solids. Figures 11 and 12 show monitoring instrumentation when the 500-PSI barrier was broken for the first time. Figure 11 Figure 12 Page 8 of 20

9 Phase 2 Results The Stamet Posimetric feeder operated successfully for several hours feeding into gas pressures at and above 500 PSI. Figure 13 shows one particular run DOE Pressure Injection - Test 216. Feeding at 500 psi 700 Weight Pumped, lbs Weight Pumped Outlet Pressure % Speed Outlet Pressure, psi / % Speed Cumulative Revs Figure 13 Make-up Gas Consumption vs Outlet Pressure 1.5 Make-up Gas Flowrate, scfm Outlet Pressure, psig Figure 14 Page 9 of 20

10 Of particular significance to practical applications, feeder operation at these pressures exhibited very low requirements for make-up gas as shown in Figure 14. This offers gasifier operations greatly reduced gas consumption over lock-hopper systems. The program has been very successful in reducing pump torque with an overall reduction from program beginning to end of over 50 percent, shown in Figure 15. Outlet Pressure vs Drive Torque Requirements Dri ve To rq ue, ft.l bs Phase 1 Start Phase 1 Final Phase 2 Current Outlet Pressure, psig Figure 15 Posimetric Feeder Flexibility Upon achieving the key program objective 500-PSI injection, other areas of feeder performance could be studied. One key target was fuel flexibility. Since current gasification systems are generally capable of burning a variety of fuels, an ideal feed system should have similar capability. Early in the program bituminous coal samples, in addition to PRB, were supplied for testing. PRB has always been considered more of a problem for handling than bituminous and so it was no surprise when testing confirmed that bituminous coal pulverized to gasifier specifications was not a problem for the Stamet feeder. Page 10 of 20

11 At the other end of the handling spectrum was lignite. DOE/NETL provided two samples, both were prepared for typical combustion applications with 50-55% passing 200 mesh. One sample was dried to 15-20% moisture and the second as-received around 30%. Both samples exhibited difficulty in flow through the very narrow Posimetric feeder entry (1.25 inch width) in initial tests. The live-wall hopper was independently tested to determine best hopper settings (vibrator energy level, frequency and duration) for maximum flow rate of each sample. After optimization, the hopper was re-installed and lignite run through the feeder. The feeder successfully achieved a maximum pressure of 530 PSI with a number of tests above 500 PSI. The feeder was able to successfully start and stop at elevated pressures. The tests did confirm the sensitivity of the inlet condition to pump operation, however for a commercial unit, the inlet dimension would be significantly larger than the test unit 1.25 inches and greatly reducing or eliminating such problems. Data for a successful high-pressure run with lignite are shown in figures 16. Figure 16 Page 11 of 20

12 Economic Comparisons The economic benefits offered by the Posimetric technology are potentially very significant compared to other feeding options. To quantify these benefits, the DOE s initiated a study by Parsons Inc., using feeder performance criteria developed from this test program and C&O costs from other DOE-funded work. The basis for the economic comparisons was to utilize the cost estimates of previously studied gasifier and IGCC configurations. Rather than attempting to modify the capital costs of the entire plant, the cost comparisons centered on the feed system equipment changes directly affected by the Stamet pump retrofit. The cost comparisons were limited to changes in feed system capital cost, for example addition of the Stamet system and removal of equipment no longer required. To accommodate changes in auxiliary power resulting from the Stamet retrofit, a power production value was placed on the auxiliary load change in the form of a $1,300 per kw capital charge. Another issue entailed the feasibility of the gasifier vessel to accept the bulk feed from the Stamet pump. The Shell gasifier requires a method of injecting the pulverized coal into the combustion zone. The transport gasifier may not require any modifications other than a means of getting the coal from the Stamet outlet to the bed. The GEE gasifier, like the Shell, requires a means of mixing the coal with oxygen and injecting it into the combustion zone. Since the design of gasifier internals was beyond the scope of the study, a capital charge was applied to each gasifier as an estimate of unspecified equipment to accept the Stamet pump outlet. Shell Gasifier Coal preparation and feeding costs, broken out from a previous Shell IGCC economic analysis are presented in Table 1. The estimate is based on a single train gasifier with sufficient capacity to fuel a GE 7FA gas turbine. The Stamet Pump retrofit consisted of removing the lock-hopper and its 350 kw N 2 compressor, the feeder and the drying capability for the Shell gasifier. In addition to the Stamet Pump, it was assumed that as the coal enters the pressure envelope of the gasifier, there would have to be an unspecified mechanism to break up any coal agglomeration before injection into the Page 12 of 20

13 combustion zone. Designing or specifying this equipment was beyond the scope of the study and, as such, an additional $2 million per gasifier was estimated and applied for internal equipment. A 40 percent contingency for project, process and engineering was applied to the bare erected capital cost for the Stamet case. Auxiliary power increased for the Stamet feed system from 770 to 1,000 kw, and was priced out at $1,300/kW. The net power for the Stamet case was estimated, and was used in the $/kw calculations. Table 1 shows comparative costs of retrofitting a Shell system with the Stamet pump. Table 1 Shell Gasifier IGCC Plant Preliminary Cost Comparisons Dry Feed Shell Gasifier Shell Gasifier w/ Stamet Pump Coal prep & Feed Bare Erected Cost, $1,000 Coal Crushing $2,852 Coal Crushing & Drying $13,003 Prepared Coal Storage & Conveyors $705 $600 Dry Coal Injection System $18,467 $3,500 Internal Gasifier Modifications $2,000 Miscellaneous Coal Prep & Feed $1,213 $964 Foundations $2,282 $1,940 Total Coal Prep & Feed $35,670 $11,856 Engineering and Contingency $8,918 $4,742 Auxiliary $1300/kW $1,001 $1,300 TOTAL CAPITAL COSTS ($1000) $45,589 $17,898 ($/kw) $176 $69 Balance of Gasifier Island $112,661 $112,661 Total Gasifier Island ($1,000) $158,249 $130,559 Total Gasifier Island ($/kw) $611 $501 Design Basis Prep & Feed Aux Power, kw 770 1,000 Plant Net Power Rating, MWe Single Shell Gasifier Train Coal Feed: EPRI Pittsburgh No ,337 lb/hr into 450 psig 163,821 lb/hr into 450 psig Page 13 of 20

14 Transport Gasifier Coal preparation and feeding costs from a previous Air-Blown Transport gasifier IGCC study were broken out and are presented in Table 2. The Transport estimate is based on a plant with dual train gasifiers. Cost estimates for the Transport Stamet retrofit were factored from the Shell feeder costs utilizing the coal feed ratios raised to the 0.7 power. Since the transport gasifier does not require pulverized injection into the combustion zone, and is assumed to be a simpler configuration than the Shell gasifier, an additional $1 million only per gasifier ($2 million total) was applied for internal equipment. A 40 percent contingency for project, process and engineering was applied to the bare erected capital cost for the Stamet retrofit. Lower installed power of the Stamet feed system reduced auxiliary power from 3,140 to 1,523 kw. However, with the additional moisture in the as-received feed coal, the air requirement to the gasifier increased substantially, resulting in a net auxiliary power increase of 4,143 kw. The total auxiliary power attributed to the Stamet retrofit was 7,283 kw, and was priced out at $1,300/kW. Net power for the Stamet transport case was estimated, and was used in the $/kw calculations. Table 2 shows comparative costs of retrofitting the Transport gasifier with the Stamet pump. Page 14 of 20

15 Table 2 Transport Gasifier IGCC Plant Preliminary Cost Comparisons Dry Feed Transport Gasifier Transport Gasifier w/ Stamet Pump Coal prep & Feed Bare Erected Cost, $1,000 Coal Crushing $4,343 Coal Crushing & Drying $22,310 Prepared Coal Storage & Conveyors $1,214 $914 Dry Coal Injection System $15,524 $5,330 Internal Gasifier Modifications $2,000 Miscellaneous Coal Prep & Feed $1,826 $1,468 Foundations $3,535 $2,954 Total Coal Prep & Feed $44,409 $17,008 Engineering and Contingency $11,102 $6,803 Allowance for Auxiliary Power Needs $4,082 $9,468 TOTAL CAPITAL COSTS ($1000) $59,594 $33,279 ($/kw) $197 $111 Balance of Gasifier Island $72,774 $72,774 Total Gasifier Island ($1,000) $132,368 $106,054 Total Gasifier Island ($/kw) $438 $352 Design Basis Aux Power Attributed to Feed System, kw 3,140 7,283 Plant Net Power Rating, MWe Dual Train Air-Blown Transport Gasifier Coal Feed: Wyodak-Anderson PRB 301,407 lb/hr into 450 psig 299,663 lb/hr into 450 psig GE Energy Gasifier The GEE gasifier operates at 1000 PSI and the base case is evaluated at this pressure level. However, the Stamet case has been evaluated at a reduced pressure level of 500 PSI, reflecting the current proven injection pressure level of the Stamet pump. Coal preparation and feeding costs were broken out from a previous GEE gasifier IGCC study and are presented in a table 3. The GEE estimate is based on a plant with a single train gasifier. Cost estimates for the GEE Stamet retrofit were factored from the Shell feeder costs utilizing the coal feed ratios raised to the 0.7 power. An additional $1 million for the single gasifier was applied for internal equipment to modify the fuel injection system from slurry feed to dry feed. A 40 percent contingency for project, process and engineering was applied to the bare erected capital cost for the Stamet case. Auxiliary power for the feed system was increased from 815 to 1,000 kw with the Page 15 of 20

16 Stamet pump. Overall plant auxiliary power was reduced 5,005 kw or a net lowering of auxiliary power of 4,190 kw. Reduction of auxiliary power is attributed primarily to the reduction in oxygen requirement associated with the dry feed. This resulted in an effective lowering of capital for the GEE gasifier of $5.5 million. Table 3 shows comparative costs of retrofitting the GEE gasifier with the Stamet pump. Table 3 GEE Gasifier IGCC Plant Preliminary Cost Comparisons GE Energy Radiant/Convective Gasifier w/ Slurry Feed GE Energy Radiant/Convective Gasifier w/ Stamet Pump Coal prep & Feed Bare Erected Cost, $1,000 Coal Crushing $2,862 $2,852 Prepared Coal Storage & Conveyors $600 $600 Slurry Preparation & Feed $2,931 Dry Coal Injection System $3,500 Internal Gasifier Modifications $1,000 Miscellaneous Coal Prep & Feed $1,032 $964 Foundations $1,940 $1,940 Total Coal Prep & Feed $9,365 $10,856 Engineering and Contingency $2,341 $4,342 Auxiliary $1300/kW $1,060 ($5,447) TOTAL CAPITAL COSTS ($1000) $12,766 $9,751 ($/kw) $46 $37 Balance of Gasifier Island $111,020 $111,020 Total Gasifier Island ($1,000) $123,786 $120,772 Total Gasifier Island ($/kw) $449 $463 Design Basis Prep & Feed Aux Power, kw 815-4,190 Plant Net Power Rating, MWe Single GEE Gasifier Train Coal Feed: EPRI Pittsburgh No ,413 lb/hr into 1,000 psig 163,821 lb/hr into 500 psig Page 16 of 20

17 Economic Study Results For the Shell gasifier IGCC case, the feed coal selected was Pittsburgh No percent contingency for project, process and engineering was applied to the bare erected capital cost for the Stamet retrofit. Specific results are summarized in Table 4. The use of the Shell gasifier with the Stamet pump has clearly advantages. These include approximately $28 million reduction in capital cost for the gasifier island along with slight improvement in the plant heat rate (efficiency) and coal consumption. Table 4 Shell Gasifier IGCC Results Summary Lock Hopper Feeder Stamet Pump Feeder Capital Cost, ($1000) Feeder Capital Cost, $/kw Coal, (lb/hr) Plant Efficiency, (%) Net Power Production, (MW) $45,589 $ , $17,898 $69 163, For the Transport reactor case, the feed coal selected was Wyodak-Anderson PRB. Again, a 40 percent contingency for project, process and engineering was applied to the bare erected capital cost for the Stamet case. It should be noted that no ASU is associated with this gasifier system. Specific results are summarized in Table 5. Table 5 Transport Gasifier IGCC Results Summary Feeder Capital Cost, ($1000) Feeder Capital Cost, $/kw Coal, (lb/hr) Plant Efficiency (%) Net Power Production, (MW) Lock Hopper $59,594 $ , Feeder Stamet Pump $33,279 $ , The air blown transport system with the Stamet pump has essentially the same advantage over the lock hopper case as was seen with the Shell gasifier. This includes approximately $26 million in capital cost reduction along with slight improvements in the Page 17 of 20

18 plant heat rate (efficiency) and coal consumption. In comparison with the Shell gasifier, the lower capital cost is essentially based on the use of an air blown gasifier, i.e., no ASU. However, with the high moisture as-received coal, the air requirement to the gasifier increased substantially. For the GEE Radiant-Convective IGCC system, the feed coal selected was Pittsburgh No. 8. A 40 percent contingency for project, process and engineering was applied to the bare erected capital cost for the Stamet case. In this case, to simplify the analysis, it was assumed that the performance of the gasifier was equal to the Shell gasifier. Specific results are summarized in Table 6 Table 6 GE Energy Gasifier IGCC Results Summary Feeder Capital Cost, ($1000) Feeder Capital Cost, $/kw Coal, (lb/hr) Plant Efficiency (%) Net Power Production, (MW) Slurry Feeder $12,766 $46 176, Stamet Pump $9,751 $37 163, The results for this case deviate from the previous cases. While the heat rate (efficiency), coal consumption and capital cost favor the Stamet pump case, the net power production is more favorable for the slurry-feed GEE gasifier. This is primarily due to the loss of net power from elimination of the high-pressure syngas expander. As a result, the feeder costs are reduced by about $3 million ($9/kW), but because of the decreased net power, the gasifier island cost is increased by $14/kW. The feeder cost with the Stamet pump shows a reduction of about $9/kW. This minor change in feeder cost results from the nearly lateral effect of converting from one low cost feed system to another. Heat rate is reduced by 120 Btu/kWh - this could be more if the clean syngas expander could be retained, but at the time of this study, the Stamet pump had not been proven capable of feeding against an 800 psi differential. Stamet, Inc. has indicated that higher-pressure operation with the pump will soon be obtained, and the GE retrofit should be re-examined at higher pressure. Page 18 of 20

19 Conclusions Based on the Parsons analysis, it can be concluded that the Stamet pump is viable from both a process economic and a plant efficiency point of view. Likewise, the simplicity of the pump leads one to ascertain that maintenance costs would be substantially lower than the complex lock hopper system currently being considered as the leading candidate. These potential benefits have been recognized by industry with requests for test installations at commercial scale operations. First in line is the DOE/NETL funded PSDF facility in Wilsonville Alabama where Stamet anticipates an installation and testing before the end of The successful operation of the Stamet Posimetric feeder at pressure well over 500 PSI is a major milestone for gasification and pressurized combustion systems. A feeder designed for commercial operation based on this technology will offer many major benefits to the acceptance of such systems. Benefits include: Major capital cost reduction (plants will require less vertical height than when using lock-hoppers, Posimetric feeders will be much less expensive than lock hoppers). Significant operating cost reduction (virtual elimination of make-up gas for lock hopper operation, elimination of a large proportion of energy cost to raise coal into plant storage bins, simplicity and ease of maintenance of a machine with one moving part). Greatly simplified control systems offering much higher reliability. Stabilized operation of combustor/gasifier owing to controlled feed rates and accurate turn down offers optimized performance. Flexible fuel handling capability while maintaining all performance benefits. The success of the program and interest of industry has prompted the DOE/NETL to move ahead with a Phase 3 research program to enable the Posimetric technology to leapfrog current commercial gasifier operating levels with a new feed pressure objective of 1000 PSI. The program commenced in July Page 19 of 20

20 Pushing the pressure envelope even further, Pratt & Whitney-Rocketdyne has requested that Stamet participate in developing an injection system to feed their planned ultra compact gasifier operating at pressure levels of 1300 PSI. This proposed project, to be undertaken with co-funding by DOE, plans for a feed system operating at this pressure within five years. Stamet is evaluating changes to pump design that will expand application of the technology to pressure letdown for ash handling, which is another area of industry concern. Page 20 of 20