What made Milwaukee famous probably originated in Chicago. For over a hundred years, Chicago-based Fleischmann Kurth Malting (FKM), a subsidiary of Archer Daniel Midland, has produced malt, an important ingredient to the brewers of American beer. FKM is located about a half mile from the old Chicago Stockyards, and a railroad spur transports barley grain by rail car right into the facility, where it is loaded into silos. The five-story, reinforced-concrete and masonry structure covers an area of one city block and is surrounded by residential homes.

In the late eighties, FKM embarked on a multi-phase venture to modernize and update the process equipment, utilities, and various buildings of the malting facility. The overall effect was to allow the facility to be more efficient with process and in energy use since costs for natural gas and electricity play a significant role in the cost of producing a bushel of malt.

In January 1990, Ballard Engineering met with Steve Furcich, FKM’s vice president of engineering, and Larry Ritchie, the plant manager, to discuss cogeneration as a viable alternative to conventional energy use and power purchases. This meeting was the start of a partnering relationship between Ballard and FKM that to date has resulted in the design and implementation of the two cogeneration projects described in this article as well as a number of other energy-recovery projects.

The initial meeting resulted from Mr. Furcich’s having read an article on cogeneration by Ballard Engineering.* Messrs. Furcich and Ritchie felt that cogeneration would fit very well into their plans for plant modernization. They explained that the present (1990) production levels were to be used for sizing the initial system but that future production was expected to increase 30 percent, and this had to be considered to make the necessary provisions for future expansion. There was also a possibility that production could double due to the transfer of production from less efficient plants to the Chicago plant, but that decision was pending and was not a factor at this time. Mr. Furcich stressed that because the quality and consistency of the malt could not be compromised in any way, it was important that we have a clear understanding of the sequence the malting process follows before any engineering started.

The malting process

The following is a brief description of the malting process, the equipment used, and the method used for drying until January 1991

· Process. The barley grain is transported from the silos into steeping tanks where water at 60 F encourages the grain to grow (germinate). When this occurs, the grain then goes through a gradual drying process of about 18 hr in a five-floor drying kiln. The grain in the kiln is slowly sifted and moved through the various levels in the kiln by augers and elevators, after which the barley malt is ready to ship to the brewers.

· Thermal cycle. The heat for drying varies between 130 and 150 F and is supplied from a 2000 hp hydronic heater. A water/glycol liquid at 250 F is pumped in a 10-in, pipe loop from the heater through four 20-hp pumps to a stacked set of stainless steel heat exchangers positioned in the mouth of each of the four kilns.

Outside air is induced from the north end of the roof of the Kiln Building down through an air shaft into the basement area of the kiln hall where it then passes through the heat exchangers in each of the four kilns. The hot air is then pulled up through the various levels in each kiln to dry the grain by two 100-hp, variable-speed DC fan drives. A total of eight fan drives (two for each of the four kilns) are located on the fifth floor. As the air is rejected to the atmosphere by the drives, it passes across another set of heat exchangers, positioned in a duct on the roof adjacent to the inlet air shaft, where heat is recovered and used to temper the outside air as it is induced into the air shaft, additional heat is absorbed by the inlet air as it passes across another heat exchanger where hot flue gas from the hydronic heater is induced by a draft fan before it enters the exhaust stack.

Operating cycle selection

Armed with this limited-but-sufficient knowledge of the malting process, we started to gather historical data from utility bills, electric demand printouts, boiler flow records, and boiler gas use to develop an accurate thermal versus electric load profile for the sizing of a prime mover and selection of an operating cycle. The base electric load was found to be only 1429 kW with a high peak of 1921 kW whereas the thermal base load was found to be greater than 27.3 million BTU/Hr. In view of this, consideration was given to selecting a combustion gas turbine as the prime mover. A gas turbine could be sized to satisfy the thermal load; however, because of the small electric plant load, the majority of the electricity produced would have to be purchased by the electric utility, and its buy-back rates were extremely low. In addition, the estimated raw cost to produce 1 kWh with a gas turbine would have been about 4.4 cents and the off-peak cost for utility power was only 2.17 cents. Because of these factors, a combustion gas turbine was ruled out..

FKM’s historical utility data revealed that 80 percent of the total electric costs occurred during the 65 weekly peak hours, and the combined peak-hour energy cost (demand plus energy charge) was 12.7 cents per kWh whereas the remaining 20 percent off-peak energy cost was only 2.17 cents per KWH. On the basis of the significant disparity between peak and off-peak costs, we decided to select as the prime movers two high-efficiency, natural-gas fired, 1200- rpm engine-generators, each rated at 800 kW, to operate only during the peak hours. Table 1 provides a turbine versus reciprocating engine rate comparison. This decision was further supported by the fact that it would cost about 3.61 cents to produce 1 KWH using reciprocating engines (based on buying gas at $3.26 per MMBtu). By adding 1.8 cents per KWH for maintenance and standby cost, the operational cost would be 5.41 cents per KWH, significantly less than the 12.7 cents per KWH from the utility.

Based on operating the engines during the peak hours only, we calculated that electric costs for the facility would be reduced approximately 34 percent. In addition, there would be 3,830,280 BTU/Hr of useful heat available from each engine, based on a 97.4 percent engine utilization factor. Using this heat for process would give it a value of $108,000 each year, based on a boiler efficiency of 80 percent. The overall effect of this 1.6 MW cogeneration system would be to reduce FKM’s total energy costs by 24 percent. These heat-recovery figures were actually greatly exceeded (Table 2) as were the projected cost savings.  The cost to build this cogeneration facility was estimated to be $1.5 million with a projected pay-back of just over three years. This was acceptable to FKM, and the direction was given to start construction as soon as possible.

New building, systems
The next phase for Ballard Engineering was the detail design of a new building with space for future expansion, a heat-recovery system, the electrical interconnect scheme, the redesign of the electric service for primary metering, and an integrated graphic control system.
· Civil. A pre-engineered "Butler" type building was chosen as a suitable structure to house the cogen system. Since the facility was in a residential neighborhood, special consideration was given to noise attenuation by installing perforated metal panels on the interior walls with an air cavity and insulation between the interior and exterior panels. The building was sized to house the engines and a separate temperature-monitored control room. Space was allowed in both rooms for future expansion of the system. Isolated foundations were arranged for each engine to reduce vibration. Openings for intake and exhaust fans in the walls of the adjacent building air shaft were provided to allow for combustion and ventilation air in the engine room. This arrangement effectively made the cogen building acoustically tight. The only outside penetrations to the building were the control room door and an overhead door in the engine room to provide access for personnel and equipment.

· Heat recovery. The relatively low-level heat required by the malting process (maximum temperature is 250 F) allows for almost all of the rejected heat from the engines to be used for process. Radiant heat from each engine, as well as heat from engine room equipment, is reclaimed by extracting air from the air shaft into the engine room where it captures the radiant heat. This preheated air is then rejected into the kiln area through an exhaust fan. High-temperature exhaust gas heat is transferred to the air in the kiln inlet air shaft by injecting the high-temperature heat into a common stack and routing it in the shaft air stream vertically for a distance of 30 ft before the stack exits to the outside. Water jacket heat at approximately 200 F is pumped by a 5-hp booster pump (one for each engine) into the kiln basement area where it is rejected by two vertical radiators, each operated by two 5-hp motors, to preheat the process air before it enters the kilns. Lube oil and aftercooler heat is transferred in a 50/50 glycol/water mix that is pumped to a plate-and-frame heat exchanger where water is heated in a 160,000 gal cistern through a 5-hp pump. The cistern water is used for steeping the barley at 60 F to promote germination.

· Electric. A total of four separately metered 480v, three-phase electric services supplied power to FKM. To utilize effectively the electric power from the cogen as well as design a coordinated relay protection scheme, we decided that the prudent course to take would be to purchase 12-kV power from the electric utility at one source and install primary metering. This arrangement involved installing a weatherproof, two-cubicle piece of switchgear, with one section for potentials, current transformers, and metering and the second section for a 12-kV, fused load-break switch. The utility made its connections in the first section, and a feeder from the load side of the 12-kV switch supplied the primary of a new 4000 kva, 12,470/480-v delta wye transformer. A 4000-amp, 480-v, three-phase feeder connected the secondary of the transformer to a new power distribution panel through a 4000-amp, automatic motor-operated breaker. From the new distribution panel. the old 480-v services were connected to the four new circuit breakers. In addition, a 4000-amp circuit breaker in the distribution panel connected the 4000-amp motor-operated breaker in the cogen switchgear.

· Protective relay scheme. Overvoltage (59), undervoltage and phase sequence (47), frequency (8lu/o), overcurrent (51), ground overcurrent (51G), impedance (21), reverse power (32) protection was installed on the 480-v bus, and zero sequence ground fault protection (59G) was installed on the 12-kV feeder through an overvoltage relay connected to a grounded eye/broken delta potential transformer configuration. The trip sequence was arranged so that when a fault was detected by any relay, it would open the generator tie breaker (52-t), or as a backup, the utility breaker (52-u) would open.

· Integrated control and graphics. The operation of the system is set up such that a building automation system (BAS) automatically controls startup and shut-down of the system; monitors pressures, temperatures, flow, utility and generator voltage, amps, kilowatts, and power factor; reports scheduled maintenance; monitors set points for warning alarms and trends; and provides on a daily basis half hourly historical data of pressure, temperature, equipment status, electric output units, and system performance. A workstation in the control room provides local access to the BAS, and nine color screens display real-time graphics for diagnostics and operator information. The system can be accessed remotely either by modem or from a terminal in the plant manager’s office. A printer connected to the BAS logs all alarms and unscheduled outages as well as system status for diagnostics.

The system startup sequence is as follows. A start signal from the BAS to each engine auto-start module permits the engines to commence an orderly start sequence and interlocks with the operation of the cistern pump, ventilation fan and damper, and jacket water booster pumps. As each engine reaches 1200 rpm and its voltage and frequency stabilize, the automatic synchronizer for each engine starts to manipulate its respective electronic governor and voltage regulator to match the frequency and voltage of the generator to the utility. When this occurs, the generator breaker is signaled to close. Each generator, now in parallel with the utility, starts to load up. A load-share controller distributes the load equally to the generators; the load-share control is supervised by an import-export controller that regulates according to plant load the total energy produced by the generators up to the system capability (in this case, 1600 KW). Should the plant load be less than800 KW, the BAS causes one generator set to shutdown in an orderly manner. Each generator has individual relay protection for phase sequence, overcurrent, over- and undervoltage and frequency, ground fault, and reverse power. At the scheduled shut- down time, the BAS removes the operating signal, and a timed load shed occurs. The auto load control shifts the generator load to the utility, and when each generator set is down to 50 kW, each generator breaker opens. After a cooldown of approximately 5 min, the generator sets shut down. Radiator fans, exhaust fans, pumps, and dampers operate until normal shutdown temperatures and pressures are attained.

Construction

After design approval by FKM, detail drawings and specifications for the various disciplines were sent out for bids. The review process of the drawings by the City of Chicago Building Dept. was expedited in a reasonable time. However, some delay was encountered with the Electrical Dept. regarding the electrical interconnect and relay protection scheme since there was no specific reference to any requirements for parallel protection schemes in the city code. This was overcome by submitting to the City a letter from the electric utility stating that the proposed interconnect scheme com plied with its standards for parallel operation. Ground was broken in May 1990, and by the first week in August, the gas and electric rough- in, the cement work, and the building were completed and ready for the engines, heat-recovery equipment, mechanical piping, and electrical installation. By the end of December, the 1.6 MW facility was ready for checkout and startup. The system calibration and shakedown lasted until the end of January 1991, and then the system was placed into scheduled operation. The system operated extremely well, and based on its cycle efficiency, the avoided costs, as previously noted, exceeded what had been projected (Table 2). In December 1991, on the basis of the system performance as well as an increase in production level, FKM directed Ballard Engineering to add another engine to the system.

System Addition

As was stated earlier, provisions were made for adding 30 percent more capacity to the system. However, Archer Daniel Midland had purchased a number of used, 1000-KW, tandem, turbocharged, natural- gas fired, 1200-rpm engine-generators, one of which was allocated for FKM in Chicago.

The new unit was 13 ft longer than the projected one, and this meant that an addition measuring 13.5 by 12 ft had to be added to the building. An additional conduit was added between the generator and a new automatic, 1600-amp motor-operated circuit breaker on the generator automatic switchgear. A new electronic governor and a compatible voltage regulator were installed on the tandem for parallel operation. The heat recovery for the exhaust and the water jacket were arranged the same as those existing, and the radiant heat was recovered by the induction and exhaust fan arrangement.  The tandem generator set was placed into operation in June1992 and has operated well to date.

Hydrostatic cogen system

The hydrostatic drive system evolved based on site conditions rather than through direct planning. In October 1992, Mr. Furcich announced that the Chicago plant would be doubling its production levels in the near future. This meant that, apart from other equipment changes, the eight100-hp fan drives on the fifth floor would have to be replaced by eight new 400-hp units to satisfy the new increased capacity.

Ballard Engineering was directed to work with FKM to design the electrical and mechanical portion of the fan drive project. The initial plan was to replace the eight existing mechanical drives with new larger units and connect a 400-hp AC induction motor with a variable-frequency controller for speed control to each of the drives. A major problem was discovered when we found that the load-bearing capacity of the fifth floor would be severely taxed by the 6000-lb weight of each induction motor. To compound this further, we could not support the weight by vertically installing support beams due to the obstructions of the machinery in the lower floors. Another negative factor to the installation of the AC drives was that their electrical loads required an additional electrical service. After several meetings with FKM, we recommended installing a hydraulic system using lightweight hydraulic motors instead of electric motors and running high-pressure hydraulic fluid in pipes from the motors on the fifth floor to hydraulic pumps on the ground floor. This would effectively overcome the weight problem discussed above.

This hydrostatic system would also be more efficient than the electric system due to driving the hydraulic pumps through two natural-gas fired, 1200-rpm engines and recovering heat from the engines and the hydraulic system. The hydrostatic cogeneration system would also effectively cancel the need to increase the size of the electric service.

The hydraulic equipment required for each exhaust fan unit on the fifth floor consisted of two 200-hp hydraulic motors, each weighing about 125 lb, and one gearbox per fan weighing 425 lb, for a total weight of 975 lb per fan. Hydraulic piping was routed from the motors on the fifth floor to a new 40 ft wide by 60 ft long by 24 ft high pre-engineered metal building that was built next to the ground floor kiln hall. In this building, the hydraulic piping from the fan drives was individually connected to eight hydraulic pumps. These pumps are mechanically connected through gearboxes (four pumps per engine) to two 1470-hp, 12-cylinder (continuous duty), turbocharged, natural-gas fired engines. While the design fan loads total 1600 hp, fans often operate at less than design speed and volume. The engines can be operated at up to 1622 hp for brief periods during the time that fan power requirements may exceed the continuous-duty rating of the engines.

Reusable heat was recovered from the engine radiant heat, jacket water, exhaust gas, lube oil, and intercooler. The hydraulic cooler was recovered and used for heating in the malting process (Table 3). Avoided cost of the recovered heat was further enhanced by the savings of electric demand and electric energy through using natural gas as a low-cost fuel to operate the engines.

The end result is that the hydrostatic drive system cost less than the AC drive system, and its efficiency has been demonstrated since it went into operation in June 1993. However, a design problem with the engine gearbox sizing was discovered when mature failures occurred. Each engine gearbox was replaced with a heavier-duty one. The hydrostatic cogeneration system will pay for itself through the avoided cost to plant process heating and electric utility costs in about four years, and the hydrostatic drive system has a cycle efficiency of 88 percent.

Standard time-of-day rate, 1990 tariff

Summer demand charge $15.06 per KW
Non-summer demand charge $11.77 per KW
Peak energy charge 5.037 cents per KW

Effective peak hour cost (65 hr per week), 80% of 80% of 80% of total costs costs costs costs 12.7 cents per KWH