Abstract:
A heat exchange cooling system for an internal combustion engine co-generation plant, which allows exhaust recycled gas combustion while maintaining lower head temperatures to reduce thermal NO x  emissions while delivering increased process/utility heat to a proximate co-generation client, is provided. The cooling system has two cooling loops with different flow rates: one through the engine and the second through exhaust manifolds, such that higher engine block flow resulting in cooler head temperatures is provided, while allowing higher temperature coolant to flow through exhaust exchangers, such that when the two coolant flows converge at a process/utility heat exchanger for heating co-generation client liquid, the combined flows substantially increase the transferred heat. In another embodiment, a separate intercooler circuit is used to cool the compressed intake charge containing the recycled gas prior to entry into the intake engine manifold to further reduce head temperatures and control thermal NO x  emissions.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to heat transfer systems for co-generation units; and, more particularly, to heat transfer and cooling systems for internal combustion engine driven co-generation units.  
           [0003]    2. Description of Related Art  
           [0004]    Electric energy generation in this country has lagged behind demand. There are a number of reasons for this, but chief among them is failure of traditional energy producers to replace spent units and capitalize new plants. This has been, in part, due to increased air quality regulations. In addition new challenges face electric generation security. Events of Sep. 11, 2001 showed this nation its vulnerability to terrorist attack. Vital operations, such as police, medical and civil defense that relied upon the electric power “grid” for service, realized that their needs were susceptible to disruption and viewed stand-alone units as well as micro grids as a possible solution. These alternatives are fraught with their own problems. Chief among the reasons is a drastic increase in demand. Thus, while energy demand has increased, generating capabilities have not.  
           [0005]    One reason for the growth in demand is the increased use of computers and other technology for industrial and business purposes, as well as personal use. As computer usage continues to grow, the use of power-consuming peripheral technologies, such as printers, cameras, copiers, photo processors, servers, and the like, keep pace and even expand. As business use of computer based equipment continues to rise, as do the number of in-house data servers, outsourced data storage facilities, financial systems, and Internet-related companies requiring constant electrical uptime and somewhat reducing traditional peak demand times, requirement for reliable, cheap, environmentally compliant electrical power continues to grow.  
           [0006]    Other technological advances have also increased electrical energy demand. Increased use of power consuming devices in every aspect of life from medical to industrial manufacturing robots, as well as innovations in almost every-research and industrial field are supported by increasingly complex technology, which requires more electrical power to function. CAT scans, NMRs, side looking X-rays, MRIs and the like all take electrical power.  
           [0007]    As a result, the Federal Government deregulated power generation, and a number of states have begun to establish competitive retail energy markets. Unfortunately, the deregulation process has not provided adequate incentives for industry entities to construct generating facilities, upgrade the transmission grid, or provide consumers with price signals to enable intelligent demand-side management of energy consumption. With the deregulation in the utility market, energy (kWh) has become a commodity item that can be bought or sold. However, swings in supply and demand leave end users open to fluctuations in the cost of electricity.  
           [0008]    According to the ETA, to meet projected increases in demand over the next 20 years, at least 393 GW of additional generating capacity must be added. In some areas, the growth in demand is much higher than the projected two percent average (e.g., California&#39;s peak electricity demand grew by 18 percent between 1993 and 1999, while generating capacity increased by only 0.3 percent.) Despite California&#39;s highly publicized energy situation, a similar problem exists for other states as well; the New York Independent System Operator recently stated that 8600 MW of additional generating capacity (a 25 percent increase) must be added by 2005 to avoid widespread shortages that may lead to blackouts.  
           [0009]    In addition to the mismatch between demand and generating capacity, the physical transmission infrastructure necessary to deliver power from geographically remote generating facilities to the consumer&#39;s location is unable to support the increased load. Even under today&#39;s operating conditions, the transmission grid is subject to stress and occasional failure.  
           [0010]    Additionally, security and reliability of source has become of increasing concern. Vulnerability of grid systems and blackouts have become more commonplace. Strategic industries are looking to cut energy costs, increase reliability, and assure security. This has lead to an interest in distributed market technologies. The potential market for distributed generation has become vast without adequate means for fulfilling this need. Again, inefficiency, reliability, and environmental concerns are major barriers. The compelling economics are made on engine efficiency without the financial benefit of waste heat usage, yet with all of the same customer reluctance to accept hassles. Industry estimates indicate that the existing market for distributed generation is $300 billion in the United States and $800 billion worldwide.  
           [0011]    The need to leverage existing technology while transitioning to alternative energy sources is an important driver for meeting this challenge. Although most existing distributed generation sites use small gas turbine or reciprocating engines for generation, there are many alternatives that are being considered over the longer term. Technologies, such as micro turbines, are currently available, but only used at a relatively small number of sites. These newer generators offer some inherent advantages, including built-in communications capabilities. It is anticipated that fuel cells will be available in the next five years, which will provide some highly appealing, environmentally friendly options.  
           [0012]    As it stands today however, small gas turbine and reciprocating engines comprise a substantial proportion of existing generator technology in the market and will for some time to come for a number of reasons. Engines provide the best conversion efficiency (40%), and they can operate using non-pressurized gas. Micro turbines, on the other hand, require compressed gas and conversion efficiency is lower (approximately 30%). These latter generators tend to be used in wastewater and landfill and other specialty sites, where a conventional prime mover is unable to stand up to poor fuel quality. Therefore, for utilities to truly benefit from a distributed generation scheme over the short term, they must look to the existing generator technology to provide a sustainable and affordable solution.  
           [0013]    Waste heat utilization or co-generation is one way to meet this challenge. In the case of power generation, the waste heat is not used, and the economics are based largely on the cost of the electricity produced (i.e. heat rate is paramount), with little consideration for improved reliability or independence from the electric grid. The anticipated fluctuation in energy costs, reduced reliability, and increasing demand has led end users to consider maximizing efficiency through use of heat from generation of on-site generating-heat capture systems, i.e. co-generation, or “Combined Heating and Power” (CHP).  
           [0014]    Co-generation of electricity and client process/utility service heat to provide space heating and/or hot water from the same unit is one solution. Co-generation provides both electricity and usable process or utility heat from the formerly wasted energy inherent in the electricity generating process. With co-generation, two problems are solved for the price of one. In either case, the electricity generation must meet stringent local air quality standards, which are typically much tougher than EPA (nation wide) standards.  
           [0015]    On-site co-generation represents a potentially valuable resource for utilities by way of distributed generation. A utility can increase capacity by turning to a “host” site (e.g. industrial user) with an existing generator, and allow them to parallel with the grid and use their generator capacity to handle peak volumes. From the utility&#39;s point of view, the key advantages to a distributed generation solution are twofold: improved system reliability and quality; and the ability to defer capital costs for a new transformer station.  
           [0016]    For customers who can use the process/utility waste heat, the economics of co-generation are compelling. The impediment to widespread use is reliability, convenience, and trouble-free operation. Co-generation products empower industrial and commercial entities to provide their own energy supply, thus meeting their demand requirements without relying on an increasingly inadequate public supply and infrastructure.  
           [0017]    Unfortunately, to date, the most widespread and cost-effective technologies for producing distributed generation and heat require burning hydrocarbon-based fuel. Other generating technologies are in use, including nuclear and hydroelectric energy, as well as alternative technologies such as solar, wind, and geothermal energy. However, burning hydrocarbon-based fuel remains the primary method of producing electricity. Unfortunately, the emissions associated with burning hydrocarbon fuels are generally considered damaging to the environment, and the Environmental Protection Agency has consistently tightened emissions standards for new power plants. Green house gases, as well as entrained and other combustion product pollutants, are environmental challenges faced by hydrocarbon-based units.  
           [0018]    Of the fossil fuels, natural gas is the least environmentally harmful. Most natural gas is primarily composed of methane and combinations of Carbon Dioxide, Nitrogen, Ethane, Propane, Iso-Butane, N-Butane, Iso-Pentane, N-Pentane, and Hexanes Plus. Natural gas has an extremely high octane number, approximately 130, thus allowing higher compression ratios and broad flammability limits. A problem with using natural gas is reduced power output when compared to gasoline, due mostly to the loss in volumetric efficiency with gaseous fuels. Another problem area is the emissions produced by these natural gas engines. Although, the emissions are potentially less than that of gasoline engines, these engines generally require some types of emissions controls such as exhaust gas re-circulation (EGR), positive crankcase ventilation (PCV), and/or unique three-way catalyst. A still another problem with using natural gas is the slow flame speed, which requires that the fuel be ignited substantially before top dead center (BTDC). In general, most internal combustion engines, running on gasoline, operate with a spark advance of approximately 35° F. BTDC; where as, the same engine operating on natural gas will require an approximate advance of 50° F. BTDC. The slower burn rate of the fuel results in reduced thermal efficiency and poor burns characteristics. Never the less natural gas fueled engines provide a valuable power source for distributed generation.  
           [0019]    Internal combustion engines utilized for combined heat and power are designed so that engine coolant from the radiator passes through a process/utility heat exchanger so the heat from combustion can be transferred to a co-generation client. Prior art co-generation systems employing internal combustion engines, and specifically, natural gas fueled engines have suffered from the myriad of problems including elevated head temperatures and inability to deliver large quantities of process and/or utility heat to the co-generation client. Excessive head temperatures lead to inefficient operation and unacceptable environmental conditions, which include excessive use of fuel as well as significant thermal NO x  production.  
           [0020]    It is well known that emission reduction for natural gas engines can be accomplished by recycling of exhaust gases to make the engines “run lean.” Numerous systems have been devised to recycle exhaust gas into the fuel-air induction system of an internal combustion engine for the purposes of pre-heating the air-fuel mixture to facilitate its complete combustion in the combustion zone, for re-using the unignited or partially burned portions of the fuel which would otherwise pass to exhaust and into the atmosphere, and for reducing the oxides of nitrogen emitted from the exhaust system into the atmosphere. It has been found that approximately 15 to 20 percent exhaust gas recycling is required at moderate engine loads to substantially reduce the nitrogen oxide content of the exhaust gases discharged in the atmosphere, that is, to below about 1,000 parts per million.  
           [0021]    Although the prior art systems have had the desired effect of reducing nitrogen oxides in the exhaust by reducing the maximum combustion temperature as a consequence of diluting the fuel-air mixture with recycled exhaust gases during certain operating conditions of the engine, these systems have not been commercially acceptable from the standpoints of both cost and operating efficiency and have been complicated by the accumulation of gummy deposits which tend to clog the restricted bypass conduit provided for recycling the exhaust, and have also been complicated by the desirability of reducing the recycling during conditions of both engine idling when nitrogen oxide emission is a minor problem and wide open throttle when maximum power is required, while progressively increasing the recycling of exhaust gases with increasing engine load at part open throttle.  
           [0022]    The nitrogen oxide emission is a direct function of combustion temperature, and for that reason is less critical during engine idling when the rate of fuel combustion and the consequent combustion temperature are minimal but tends to be problematic during throttle up and extended full speed operation. In the usual hydrocarbon fuel type engine, fuel combustion can take place at about 1,200° F. The formation of nitrogen oxides does not become particularly objectionable until the combustion temperature exceeds about 2,200° F., but the usual engine combustion temperature, which increases with engine load or the rate of acceleration at any given speed frequently, rises to about 2,500° F. It is known that the recycling of at least one-twentieth and not more than one-fourth of the total exhaust gases through the engine, depending on the load or power demand, will reduce the combustion temperature to less than 2,200° F. Contaminants in the exhaust resulting from fuel additives desired for improved combustion characteristics normally exist in a gaseous state at combustion temperatures exceeding about 1,700° F., but tend to condense and leave a gummy residue that is particularly objectionable at the location of metering orifices and valve seats in the exhaust recycling or bypass conduit.  
           [0023]    Thus, natural gas fired internal combustion driven co-generation systems have previously suffered from one or more disadvantages. Specifically, the EGR system did not recycle exhaust gas to the intake engine manifold at sufficiently low temperature to foster low cylinder head temperatures. Simultaneously, turbo charged fuel systems, because of the compression, increased intake fuel manifold temperatures causing the same affect. Additionally, engine-cooling systems were not efficient enough to remove substantial engine heat from the cooling fluid while maintaining an inlet temperature of the coolant sufficient to reduce head temperatures to an acceptable level. This in turn reduced the heat, which was transferred to the co-generation client. However, increasing coolant flow through the engine increases parasitic load decreasing efficiency. The result was a rich burning engine, i.e. inefficient, with substantial thermal NO x  production, violating air emission standards, while not providing sufficient heat transfer to the process/heat co-generation loop to be worthwhile.  
           [0024]    A further drawback was that recycling exhaust gas increased the intake air temperature and, therefore, increased the head temperature. This is particularly true when the inlet gas is supercharged. This combination of disadvantages made natural gas fueled, internal combustion driven co-generation systems an unacceptable candidate for client based distributed generation complexes.  
           [0025]    It would be, therefore, advantageous to have a system, which reduced fuel consumption, as well as NO x  production while delivering substantial heat to the process/utility heat co-generation system. In addition, it would be advantageous to run a lean burning engine using recycled exhaust gas, which results in not only a lean burn but also reduced head temperatures leading to reduces thermal emissions and greater efficiency.  
         SUMMARY OF THE INVENTION  
         [0026]    It has now been unexpectedly discovered that a system for engine cooling and effective heat transfer to a co-generation client, reduces engine head temperature thereby reducing fuel consumption and reducing pollutants, as well as delivering substantially increased heat to a co-generation process/utility heat facility. The cooling cycles and process/utility heat radiation configurations of the inventive system maintain cylinder inlet temperature resulting in improved efficiency, reduced thermal NO x  and longer engine life. This allows operation of the engine at optimum inlet and outlet temperatures regardless of co-generation process/utility heat system requirements, without excessive parasitic pump loads.  
           [0027]    In accordance with the invention, a split flow engine cooling system includes a first coolant loop which directs coolant through the engine block, and a second loop which directs coolant through the at least one exhaust manifold in cooperation with the first loop, such that the coolant inlet temperature of the first loop is substantially reduced to maintain appropriate engine head temperatures to reduce thermal NO x  while maintaining efficiency. The two loops then merge at a process heat exchanger such that the combined output heat contained in the liquid of the two loops is effective to deliver increased heat to the co-generation process/utility heat system without an increase in parasitic load, i.e. using the engine internal pump only.  
           [0028]    Advantageously, the coolant loops each carry different quantities of coolant to assure engine performance. In one embodiment, the loops can be balanced by means of a dynamic feed back valveing to assure head temperatures within a specified range.  
           [0029]    In accordance with another aspect of the instant invention, a turbo intercooler heat exchanger is used to reduce the temperature of compressed engine intake gas, emerging from the turbocharger, prior to its entry into the intake manifold of the engine such that the inlet gas temperature is reduced to retard the formation of thermal NO x . Thus the engine driven coolant pump can be utilized exclusively for the coolant loop, reducing the parasitic load, while drastically reducing cylinder inlet temperature resulting in improved efficiency, lower thermal NO x  and longer engine life.  
           [0030]    In another aspect an EGR cooling circuit using air finned heat exchangers is used to reduce the temperature of the recycled exhaust gas, prior to its mixing with the intake gases for combustion. This further reduces cylinder inlet temperature resulting in improved efficiency, lower thermal NO x  and longer engine life.  
           [0031]    In accordance with the invention a dump/balance radiator is used to remove heat not transferred to the co-generation process/utility heat system such that engine efficiency is maintained even in the absence of the co-generation process/utility heat system load. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]    The following drawings form part of the present specification and are included to further demonstrate certain embodiments. These embodiments may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.  
         [0033]    [0033]FIG. 1 is a flow chart of the heat transfer systems for co-generation of the instant invention;  
         [0034]    [0034]FIG. 2 is a flow chart of the engine cooling loop of the heat transfer systems for co-generation of the instant invention;  
         [0035]    [0035]FIG. 3 is a flow chart of the co-generation process/utility heat delivery loop of the instant invention;  
         [0036]    [0036]FIG. 4 is a flow chart of the turbocharger intercooler loop with turbo charged intake gas interface in accordance with the instant invention; and,  
         [0037]    [0037]FIG. 5 is a flow chart detail of the interface of the turbocharger intercooler radiator loop interface with the engine intake gas system and the engine exhaust system including the exhaust recycle in accordance with the instant invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]    In accordance with the instant invention a natural gas fueled, internal combustion engine, employing exhaust gas recycle (EGR), delivers power to spin a coupled electric turbine, as well as heat of combustion, through a heat exchanger, to a co-generation process/utility heat loop for on site use as heat for process water, utility heat, space heat, potable hot water and the like. This is accomplished with the instant system by increasing the transfer of engine heat to the co-generation process/utility heat loop while maintaining the engine, and especially the head temperature low enough to increase efficiency and reduce thermal NO x  to acceptable levels, even in the presence of the recycled exhaust gas. This is accomplished with substantially no increase in parasitic power requirements, such as adding external pumps to increase the flow through the heat exchanger.  
         [0039]    In accordance with the invention an engine coolant loop flow is split so that a first portion flows through the engine block, by way of the engine oil cooler, and through a thermal valve control to the fluid process heat exchanger. A second portion flows to at least one fluid cooled exhaust manifold by way of the engine oil cooler, for example, through the inlet ports of the left and right liquid cooled exhaust manifolds and then the inlet port of the fluid cooled turbocharger where it merges with the liquid from the first loop prior to going through the fluid process heat exchanger, which delivers heat to the co-generation process/utility heat system.  
         [0040]    Thus, in accordance with one embodiment, the coolant flows through a cooling loop by way of an engine driven pump through the oil heat exchanger. Exiting the oil heat exchanger it splits into two parallel loops. One loop follows a path through the engine block and the other through the coolant manifold, and then the coolant cooled turbo-charger. Both coolant flow loops converge at the thermal control valve where they blend back together to form a single stream prior to flowing through the fluid process heat exchanger. The thermal control valve senses the blended stream temperature and by-passes the fluid process heat exchanger if the temperature is below the threshold engine block inlet tempeture of, for example, 175° F. This closed loop prohibits flow through the fluid/process heat exchanger and dump/balance radiator to retard heat loss until optimum engine block inlet temperature is achieved. When the temperature is greater than, for example, 175° F., flow through the control valve is first diverted partially to the fluid/process heat exchanger and then fully to the fluid/process heat exchanger as operating temperatures are reached.  
         [0041]    The combined flow is, thus, through the coolant/process heat exchanger for use in heat exchange with the co-generation process/utility heat system. This parallel cooling loop increases the engine cooling loop heat available to the process/utility heat system, significantly, while maintaining favorable engine operating conditions. For example, the system of instant invention can maintain engine block outlet temperature of 198° F. instead of the typical 210° F. of comparable engine designs, while heat delivered to the process/utility co-generation system increased from a typical  780 , 000  BTU/hour to 1,100,000 BTU/hour. Flow through system is nominally 106 GPM with a differential of 20° F. across the engine block. In this manner the coolant through the second loop is at a higher tempeture, but a lower flow rate, while the coolant through the first is at a slightly lower tempeture, but a higher flow rate to keep the cylinder heads cooler, thus, increasing efficiency and reducing thermal NO x  emissions.  
         [0042]    In accordance with a further aspect, the system employs a separate loop to cool supercharged engine inlet feed. This separation of the intercooler liquid coolant loop from the engine coolant loop provides a separate heat exchanger upstream of the engine intake manifold to reduce engine intake temperatures, drastically reducing head temperatures within the engine. Likewise, in a further aspect the exhaust recycle gas is cooled by at least one air cooled radiator prior to admixing it with air and fuel which is then compressed in the supercharger.  
         [0043]    The power source compatible with the instant invention is a natural gas fueled, internal combustion liquid cooled engine, wherein at least a portion of the exhaust gas is recycled to reduce NO x . For example a Deutz brand Engine Model BE 8 M 1015 GC engine manufactured by Deutz. The natural gas fired internal combustion engine is the prime mover of the electrical generation system, having liquid coolant flow system required return coolant at a temperature to the engine to reduce head temperature to less than about 1800° F. The internal engine pump moves the coolant through the various engine components and then through the process heat exchanger to transfer heat to the co-generation process/utility the system.  
         [0044]    Turning to the drawing, there is shown in FIG. 1, the system  10 , in accordance with the instant invention. An engine block  12  contains fluid cooling ports through which cooling fluid travels by means of internal fluid pump  14  located upstream of oil heat exchanger  16 , which is ideally housed within the engine. As shown, oil heat exchanger  16  is in fluid communication with the inlet port of engine block  12  by means of conduit  18  and with inlet of fluid cooled manifold  20  by means of conduit  22 . Preferably, oil heat exchanger  16  is contained within engine block  12  and is an integral part thereof. The outlet of engine block  12  communicates with the inlet of thermal control valve  24  by means of conduit  26 .  
         [0045]    The outlet of fluid cooled manifold  20  communicates with the inlet of fluid cooled turbocharger manifold  28  by means of conduit  30 . The outlet of fluid cooled turbocharger manifold  28  communicates with a second inlet of thermal control  24  through conduit  22 . In a bypass circuit for engine warm up, the outlet of thermal control valve  24  communicates through internal fluid pump  14  with oil heat exchanger  16  through conduit  34 . Alternately, during operation thermal control valve  24  communicates through internal fluid pump  14  with oil heat exchanger  16  by way of fluid process/heat exchanger  36  via conduit  38  and dump/balance radiator  40  via conduit  42  and then a T connect of conduit  44  with conduit  34 .  
         [0046]    As better seen in FIG. 2, this fluid loop comprises the coolant system  11  of the present invention. In operation, internal fluid pump  14  is driven by engine block  12  to flow coolant at a tempeture of about 175° F. and a flow rate of about 106 GPM through oil heat exchanger  16  and simultaneously through conduit  18  to the inlet of engine block  12  at a tempeture of about 182° F. and a flow rate of about 91 GPM and conduit  22  at a tempeture of about 182° F. and a flow rate of about 26 GPM to inlet of exhaust-cooled manifolds  21 .  
         [0047]    The exhaust-cooled manifolds  21  comprise the initial fluid cooled manifold  20  and the fluid cooled turbocharged manifold  28  as shown in FIG. 1., but can consist of one or more liquid cooled manifolds for removing heat from the engine exhaust. In accordance with the invention, these manifolds may comprise a single unit as shown in FIG. 2 or separate units shown in FIG. 1. The function of these manifolds is to cool exhaust and generate heat to the cooling fluid, which will be transferred to the co-generation client as described below.  
         [0048]    Coolant exiting from exhaust-cooled manifold  21  at a tempeture of about 210° F. and a flow rate of about 26 GPM, flows to thermal control valve  24 , which functions to limit fluid circulation back to inlet of the engine block  12  until operating temperature of the system is attained, and thereafter through conduit  38  to fluid process/heat exchanger  36 . Coolant exiting from engine block  12  at a tempeture of about 198° F. and a flow rate of about 91 GPM, flows to thermal control valve  24  where is merges with the coolant from exhaust-cooled manifold  21 . Dump/balance radiator  40  serves as a cooling radiator for the system to balance coolant inlet temperature to the oil heat exchanger  16  if fluid process/heat exchanger  36  removes insufficient heat or is turned off.  
         [0049]    Returning to FIG. 1, fluid process/heat exchanger  36  is a radiator which allows heat transfer from coolant system  11  (see FIG. 2) to co-generation process/utility heat system  13 , as seen in detail in FIG. 3. Co-generation process/utility system comprises a closed loop to circulate fluid, which is heated in fluid process/heat exchanger  36 , by means of pump  46 . Fluid process/heat exchanger  36  communicates with primary facility load  48  and secondary facility load  50  by means of conduit  52  and return conduit  54 .  
         [0050]    In operation, fluid process/heat exchanger  36  which contains coolant fluid at a tempeture of about 206° F. at a flow rate of about 106 GPM, provides heat exchange between coolant system  11  and co-generation process/utility heat system  13 , which provides heated liquid to the client in a co-generation configuration. Thus, the co-generation client receives transferred heat from the coolant system  11  by way of fluid process/heat exchanger  36  to the co-generation process/utility heat system  13 . The coolant in coolant system  11  is then heat balanced, if necessary, in the dump/balance radiator  40  to return through internal fluid pump  14  to oil heat exchanger  16  to loop at a tempeture of about 175° F. at a flow rate of about 106 GPM.  
         [0051]    Thus, for example heat in coolant flow, through the coolant/process heat exchanger, is captured for the co-generation client use by counter flowing process/utility water flowing through the coolant/process heat exchanger. Thermal regulating valves can be used to regulate process/utility water temperature to insure appropriate water temperature delivery to the co-generation use.  
         [0052]    In accordance with one aspect of the invention, an exhaust heat recovery silencer  56 , further cools the exhaust from the engine block  12  and communicates through client absorption chiller  58  by means of conduit  60  and return conduit  62 , as will be further described below in reference to FIG. 5.  
         [0053]    Turning to FIG. 4, a turbo intercooler cooling circuit is shown and its interface with recycled exhaust gas, fuel, and air. Turbo intercooler cooling circuit comprises a turbo intercooler  68 , which is cooled by coolant loop separate from coolant system  11  or process/utility heat system  13  and includes an intercooler radiator  70  fluidly communicating, via conduit  72  and pump  74 , in a continuous closed circuit, through intercooler coil  76  of turbo intercooler  68 . This fluid cooling system is dedicated to further reducing the inlet tempeture of the compressed fuel/air/exhaust gas mixture from the turbocharger  78  as further explained below.  
         [0054]    As better seen in FIG. 5, there are three operating systems associated with the intercooler radiator in accordance with the instant invention. FIG. 5 shows the interfaces between the turbo intercooler cooling circuit, the turbocharged, or compressed inlet gas mixture to the engine intake manifold and the recycled exhaust gas. This interaction is important in that head temperatures, gas inlet temperatures, and exhaust gas recycle temperatures can be tuned.  
         [0055]    As seen in FIG. 5, intercooler radiator  70 , pump  74 , and conduit  72  continually circulate coolant, in a closed loop, through coil  76  of turbo intercooler  68  as previously described and shown in FIG. 4. Ambient outside air passes through air filter  100  and intake conduit  102  to EGR venturi  104 , where air mixed with recycled exhaust gas from conduit  180  as will be more fully described. Mixed air and exhaust gas exists EGR venturi  104  through intake conduit  106  into fuel/air venturi  108  where the air exhaust gas mixture entrains fuel from a regulator (not shown). The fuel/air/exhaust gas mixture is compressed in turbocharger  78  via intake conduit  110 . The compressed fuel/air/recycled exhaust gas mixture exists turbocharger  78  through intake conduit  80  into turbo cooler  68  where it is cooled from 400° F. to 165° F. The cooled intake gas exists turbo intercooler  68  into engine intake manifold  112  and into engine cylinders  82  via conduit  84 . Exhaust gas from engine cylinders  82  exits into fluid cooled manifold  21  as previously described in FIG. 2 and enters turbocharger  78  through exhaust conduit  114  to power the turbocharger  78 , thus compressing the fuel/air/recycled exhaust gas mixture entering turbocharger  78  by means of intake conduit  110  as previously described.  
         [0056]    As can be seen, exhaust gas exiting turbocharger  78  is split into a recycled stream and an exhaust stream. The exhaust stream  116  enters three-way catalyst  118  and then exhaust heat recovery silencer  56  as previously described in connection with the description of FIG. 1. It will be realized, by one skilled in the art, that the exhaust heat recovery silencer  56  is on the co-generation process/utility heat system  13  and provides additional heat recovery for that system.  
         [0057]    A portion of the exhaust gas to be recycled passes through conduit  120  to primary air cooled EGR cooler  122 ; and, if necessary, secondary air cooled EGR cooler  124  by means of conduit  126  and then passes into EGR venturi  104  through conduit  180  as previously described.  
         [0058]    Thus, in accordance with the invention, ambient air (70° F.) flows through air filter to EGR venturi where it is mixed with up to 20% cooled exhaust gas (140° F.) at 100% load. The percent of recycled exhaust gas utilized is a function of engine load. This mixture (120° F.) then passes through the fuel/air venturi where fuel is drawn from a zero pressure gas regulator and mixed with the ambient air &amp; exhaust gas to be flowed to the ambient side of the turbocharger. The fuel/air/recycle exhaust gas mixture is then pressurized by an exhaust gas-powered turbine to a pressure of 15 psig of at a temperature of (400° F.) This pressurized mixture passes through the turbocharger intercooler which reduces the pressurized and high temperature mixture to about 165° F. to be introduced into the intake manifold and then to the engine cylinders.  
         [0059]    Following combustion, exhaust gas from the cylinders (1100° F.) passes through the coolant-cooled manifolds to recover heat, which reduces the exhaust gas tempeture to about 940° F. The exit exhaust gas enters the exhaust (turbine driving section) of the turbocharger and, upon exiting, passes through a “T” with about 80% of the gas being flowed through a catalyst and a heat recovery silencer or muffler as previously described, and exhausted to atmosphere. A second portion comprising about 20% of the exhaust gas is passed through air coolers as previously described to the EGR venturi for introduction to the air/fuel intake system. The recycled exhaust gas is cooled by the air coolers to about 140° F. prior to admixing with air in the EGR venturi.  
         [0060]    The foregoing discussions, and examples, describe only specific embodiments of the present invention. It should be understood that a number of changes might be made, without departing from its essence. In this regard, it is intended that such changes—to the extent that they achieve substantially the same result, in substantially the same way —would still fall within the scope and spirit of the present invention.