COGENERATION OF ELECTRICITY AT RADFORD ARMY AMMUNITION PLANT (AAP) - A CASE STUDY

Transcription

1 COGENERATION OF ELECTRICITY AT RADD ARMY AMMUNITION PLANT (AAP) - A CASE STUDY Mohamed A. Masood, PE Value Engineer Production Base Modernization Activity Picatinny Arsenal, New Jersey ABSTRACT Oil crises, trade deficits and shrinking landfills for disposing of solid and liquid waste are all nightmares to the financial markets of the world and to the American public. Cogeneration, being an energy conservation measure, will help in solving these problems. The purpose of this paper is to look into cogeneration as it is applied to an Army Ammunition Plant and to understand its complexities. The changing scenario in the cogeneration industry is also outlined and its challenges are presented. CONSERVATION OF BY COGENERATION: The examples given are for systems that use coal and steam for driving the turbine(s). There are other systems that use natural gas as fuel to drive the turbines directly with heat recovery. The name of the game in cogeneration is conservation of energy. This is best illustrated in the graphic illustration. See Figure 4. MODERNIZATION AT RADD AAP - FIRST VE STUDY: Radford AAP is undergoing modernization. The boiler house, including the T-G's, date back to the forties. New electrical distribution system and a new control system are being installed. INTRODUCTION Radford AAP, located in Virginia, has current industrial mission to manufacture propellants, explosives and chemical materials for the Army. Its power plant, being the center of our study, has coal fired steam boilers that supply steam at 400 psig. At present, steam to the processing area is supplied at 40 psig through either Pressure Reducing Valves (PRV's) or through four turbo generators(t-g) that cogenerate electricity. The electricity thus cogenerated provides for part of the electric demand at the plant. The rest of the demand is met by a utility company. A study was done to evaluate the economics of various options available in upgrading or replacing the turbine generators to a point where life expectancy is extended an additional 40 years. In the option where replacement was considered, provisions were made for supplying the existing and future steam requirements through the turbine(s) and avoid the use of PRV's. The evaluation was done from the standpoint of initial repair/replacement cost, energy savings (loss), and future repair cost together with life cycle cost analysis to determine present net worth. The study recommended replacing all four (4) existing T-G's with new units as specified in Figure 5. Cogeneration is the simultaneous An explanation on the different types production of heat and electricity from a of turbines shown in Figure 5 is provided: single source of fuel such as coal, natural gas or diesel. Turbine #1 is a 9.25 MW condensing type with double extraction at 40 psig and A few graphic examples of cogeneration 275 psig. In these turbines up to the are given on the following page. (Figures extraction points, energy is being saved 1, 2, and 3) 73

2 Industry Electric Utility CONDENSATE (I Tl COOLING TOWER W W SPACE HEATING Figure 1: Cogeneration as Practiced at Radford Interrelating with Utility Electricity Production FUEL IN i BOILER HIGH PRESSURE STEAM L ELECTRICITY. FEEDWATER r COOL WATER RETURN Figure 2: European Cogeneration System^ 400 PSIG, TBCF, 14"0 I IO" I 142,000 PPH 2.1 KV #3 2.4 KV 2.4 KV 2.4 KV 20" «127,500 PPH 20" O 127,500 PPH 20" 135,000 PPH 20"» 135,000 PPH 40 PSIG, 350<'F, 30" 0 NOTE; THE CONDENSING UNITS, 100% CONDENSING AND EXTRACTION FLOWS CANNOT BE ACHIEVED SIMULTANEOUSLY Figure 3: Existing Cogeneration Arrangement at Radford** * Source Ref 1, pg. 6 ** Source Ref 2 74

3 CENTRAL POWER STATION BY-PRODUCT POWER GENERATION A. STEAM POWER GENERATION ADDED AVAILABLE POWER POWER B. PROCESS STEAM AVAILABLE POWER C. STEAM AT BOILING POINT ADDED POWER GENERATION WASTE ADDED PROCESS STEAM AVAILABLE AS PROCESS STEAM HEAT D. WATER AT BOILING POINT FEEDWATER I I WASTE I Figure 4: Conservation of Energy: Compare the Waste Heat in a Central Power Station and in a By-Product Power Generation (Cogeneration)* 400 PSIG, 750 F, 14" ^ NOTE: THE CONDENSING UNITS, 100% CONDENSING AND - EXTRACTION FLOWS CANNOT BE ACHIEVED SIMULTANEOUSLY Figure 5: Proposed Cogeneration Arrangement at Radford** * Source Ref 3, pg. 14 ** Source Ref 2 75

4 by way of using the extracted steam for process and heating purposes. Beyond the extraction point, heat is wasted to the condensate. The condensing portion of the turbine provides just electricity. The condensing feature of the turbine is good for taking care of the peaks in electric loads at the expense of wasting heat. If the peaks in electric load are not smoothed out, the utility company supplying electricity levies heavy penalties. Turbine #2 is a condensing turbine with one extraction to 40 psig. Turbines #3 and #4 are 40 psig back pressure turbines with an extraction port at 275 psig. The waste heat in these turbines is utilized for process and heating buildings. SECOND VE STUDY: While doing a VE Study on electrical distribution system of the boiler house, a question was raised whether all these turbines and generators were needed. Why not eliminate all cogeneration, install an additional power feeder and purchase all power from the utility company? Industrial plants commonly said, "We are not in the power business". This attitude was considered normal during the cheap fuel era prior to Because of low fuel prices before then, cogeneration was not in vogue. CURRENT TRENDS IN COGENERATION: After the 1974 oil crisis, and the greater emphasis placed on energy conservation, cogeneration is coming back with the result that central utility power companies are banking on industrial cogenerators for their future capacity. Under federal regulations drafted in 1978, power companies are required to purchase electricity from small producers at a price equal to the cost those companies can avoid by not having to produce the power themselves. This incentive can amount to 110% of the rates charged by the utilities.* In some places, artificially high avoided cost rates have led to numerous marginal and unnecessary cogeneration projects that would not have been built without the incentives that were offered. Also, some cogenerators are trying to make a fast buck by using natural gas as fuel instead of using coal - the preferred fuel by the utilities. The utilities fear that when the incentives are removed, as eventually they will, the utilities will be forced to take over failed cogeneration plants to maintain their reserve capacity margin and end up being dependent on expensive natural gas. Whether cogeneration at Radford's AAP is viable can be viewed in this changing scenario. THIRD VE STUDY: A third VE study was done to determine the most cost effective alternative for providing electric power to Radford AAP. The findings of the study, based on steam and electrical usage in peacetime and mobilization and on capital cost data, revealed cogeneration with condensing turbines to be the most cost effective, as cash flow becomes positive after four years. Besides establishing that cogeneration is preferable to all purchased power, the VE Study yielded good dividends by bringing to light overcapacity of the proposed turbogenerators during peacetime conditions. Peacetime maximum steam production in winter could support cogeneration electrical output to 13.5 MW whereas the proposed turbogenerators (T-G) had a total capacity of MW. VE SAVINGS: An Engineering Change Proposal to reduce the capacity of turbine #1, (See Figure 5), to 6 MW was approved. This resulted in a $2M hard cash savings. A VE Study on one subject led us to unexpected savings on another. The study also brought better awareness of cogeneration at Radford AAP and other Army Aminunition Plants. COGENERATION STRATEGY AT RADD AAP: Twenty-four (24) MW capacity of T-G's was s t i l l excessive when compared to the electricity that could be produced with available steam (13.5 MW). However, the plant opposed further cuts in T-G's capacity for the following reasons: - Steam production at the plant is substantially more than the average reported. Thus, more than 13.5 MW of electricity could be generated. - Besides cogenerated electrical demand, the present purchased electrical peak demand is 13 MW. A new peak demand is automatically established if the existing peak is exceeded for 30 minutes. This new peak demand, so established, increases the minimum monthly electrical charge and will remain in effect for twelve months even if the demand is *Source Ref 4 76

5 below the newly established peak. Peak demands are now held to a minimum by juggling three turbogenerators. In winter, when demand for steam is high due to heating requirements of buildings, two back pressure turbines and one condensing turbine supply steam and electricity at varying rates to satisfy the swings in steam and electrical demands. The summer season requires less steam. Therefore, in order not to establish a new peak purchased electric demand during this period, two condensing turbines and one non-condensing turbine are used. - Operating three turbines for cogeneration allows v i t a l and hazardous manufacturing areas to continue operations when the u t i l i t y tie-line is interrupted, or a turbine must be taken off line. This is accomplished by increasing power production via the condensing turbine(s) already on line and by instantly operating a pre-programmed load shedding controller for nonessential and non-hazardous areas. Thus, safety requirements are met. - As three turbines are always operating, a fourth turbine is required as a backup during turbine maintenance and inspection. There were more compelling reasons for not reducing the capacity for cogeneration. Other related projects were already far advanced and any change in specifications would have adversely affected them. The bids on the turnkey project for the modernization of the power house, due to good management, were much lower than expected. The different VE studies may have forewarned the bidders on keeping the prices low. A decision was made to stop any further cuts in cogeneration capacity and to accept the $2M savings. CONCLUSION: Poor performance of nuclear power plants and their exorbitant cost has placed extra emphasis on cogeneration.***cogeneration of electricity from abundant coal supplies seems to be the answer to limit foreign dependence on o i l. One of the drawbacks of cogeneration is i t requires heavy capital outlay. A turbine for cogeneration costs 2 to 3 times as much as an ordinary turbine. The Return On Investment (ROI) is moderate to low depending on the size of the unit. Figure 6. Fig. 6: **Incremental ROI for Coal fired Cogeneration Plants with varying Annual Utilization at Existing Manufacturing Facilities* *See definition on Fig 6 **Source Ref 3, pg. 129 *** Source Ref 1, pg

6 The ROI has to be viewed with the many advantages cogeneration gives to a plant, especially army ammunition plants like the one at Radford. At this plant, cogeneration, besides providing electricity at a cheaper rate than do the utilities, also acts as a backup power source for hazardous processes. As pointed out earlier, the Government is also giving incentives through monopolistic utility companies. District Heating is a term describing particular techniques in space and water heating. European countries are more advanced than this country in District Heating. Independent total electricity generation through Total Energy or Modular Integrated Utility Systems using solid and liquid waste as fuel and water is a multiagency effort to provide new options for supplying community utility services. There are challenges facing cogeneration, but they are not insurmountable. REFERENCES: 1. Wilkinson, Bruce W., Cogeneration of Electricity and Useful Heat, CRC Press Inc., Boca Raton, Florida. 2. Main, Chas. T., Designer Study Revisions Power House No. 1, Chas. T. Main of Virginia, Inc., Charlotte, North Carolina. 3. Noyes, Robert, Cogeneration of Steam and Electric Power, Noyes Data Corporation Park Ridge, New Jersey. 4. Ted Sherman, "JCP&L sees the outlook dimming for natural gas-driven cogeneration." The Sunday Star-Ledger, 29 November 1987, New Jersey. 5. Foster Wheeler USA Corporation, Final Report on Evaluation of Alternatives for Electric Power, Foster Wheeler USA Corporation, Clinton, New Jersey. 78