Patent Publication Number: US-8973535-B2

Title: Steam-generator temperature control and optimization

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 11/787,100, filed Apr. 13, 2007, which application is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Power generation plants often use steam turbines that are powered by steam generated in boilers from fuels such as coal, oil or gas. Both superheated and reheated steam are used in a steam turbine cycle. Steam temperatures are affected by the steam-heating facilities such as from a boiler. Power-generation conditions can also vary, however, based upon the actual state of the power-generation equipment, and in particular based upon the state of the boiler system and the steam turbines. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments of this disclosure are illustrated by way of example and not limitation in the Figures of the accompanying drawings in which: 
         FIG. 1  shows a schematic diagram of a power-generation system that uses steam according to an embodiment; 
         FIG. 2  shows a schematic diagram of a steam-generation system that uses control and optimization modules according to an embodiment; 
         FIG. 3  shows a graph of the affect of desuperheater cooling water flow with minimum mean flow, as it is used to control superheated steam temperature within a desuperheater according to an embodiment; 
         FIG. 4  shows a graph of the affect of desuperheater cooling water flow, as the control action is limited and within a fully closed valve range within a desuperheater according to an embodiment; 
         FIG. 5  shows a graph of the affect of desuperheater cooling water flow with maximum mean flow, as it is used to control superheated steam temperature above a more useful proportional valve range within a desuperheater according to an embodiment; 
         FIG. 6  shows a graph of the affect of desuperheater cooling water flow, as it control action is limited and within a fully open valve range within a desuperheater according to an embodiment; 
         FIG. 7  shows a graph of the affect of desuperheater cooling water flow range, as it can be used to control superheated steam temperature without a limitation inside a more useful range within a desuperheater according to an embodiment; 
         FIG. 8  shows a schematic diagram of control and optimization modules for the steam-generation system according to an embodiment; 
         FIG. 9  is a method flowchart that illustrates method embodiment of this disclosure; 
         FIG. 10  is a schematic diagram illustrating a media having an instruction set, according to an example embodiment; and 
         FIG. 11  illustrates an example computer system used in conjunction with certain example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     A system and method for controlling and optimizing steam generation system is described herein. In method embodiments, the operation of a steam generation system includes manipulating system conditions to influence desuperheater cooling water control, to usually operate where symmetrical control action can be assured. Cooling water flow can only be positive, i.e. a negative flow cannot be realized to control a desuperheater. The method embodiments influence the steam generation system to operate in a region where a proportional-valve action for desuperheater cooling water is virtually assured to stabilize a steam output temperature. 
     In an embodiment, control is focused upon reheater (RH) desuperheater control, upon final superheater (SH) desuperheater control, and upon burner tilt control, to effect a proportional desuperheater cooling water valve action that can stabilize a steam output temperature. Further, optimization of the steam generation system includes addressing changing conditions such as overall boiler and turbine status. 
     In the following description, numerous specific details are set forth. The following description and the drawing figures illustrate aspects and embodiments sufficiently to enable those skilled in the art. Other embodiments may incorporate structural, logical, electrical, process, and other changes; e.g., functions described as software may be performed in hardware and vice versa. Examples merely typify possible variations, and are not limiting. Individual components and functions may be optional, and the sequence of operations may vary or run in parallel. Portions and features of some embodiments may be included in, substituted for or added to those of others. The scope of the embodied subject matter encompasses the full ambit of the claims and substantially all available equivalents. 
     The embodiments and their art-recognized equivalents of this description are divided into three sections. In the first section, an embodiment of a system-level overview is presented. In the second section, methods for using example embodiments are described. In the third section, an embodiment of a hardware and operating environment is described. 
     System-Level Overview 
     This section provides a system level overview of example embodiments. 
       FIG. 1  shows a schematic diagram of an electrical power-generation system  100  that uses steam according to an embodiment. The electrical power-generation system  100  includes steam-generated electricity that is attached to a power grid  120 , according to an example embodiment. 
     The power-generation system  100  includes all the resources available to an entity to produce steam. For example, an entity may have a large power plant such as a coal-fired plant that generates boiler steam and electrical power, and an atomic power plant that produces energy and generates power and steam in another locale as well as smaller diesel fueled power plants. In other words, the power-generation system includes all of the various individual steam generating plants available to an entity. Various resources have various costs associated with the production of steam generation as it is being generated. 
     The electrical power-generation system  100  is connected to the power grid  120 . The power grid  120  has all the various equipment necessary to distribute power from a power plant to individual businesses and home owners and the like. The power grid  120  includes transmission substations, high voltage transmission lines, power substations, switching towers, distribution busses, transformers and regulator banks as well as the power poles and various power lines. In some applications, the distributions lines are underground and there are transformer boxes located near the curve at every house or two. 
     Although conditions may vary within the steam-generation system  100 , the disclosed embodiments teach a desuperheater cooling water system that achieves a proportional control action to treat superheated steam output temperatures. While the boiler system has control capabilities to meet changing duty, it also has optimization capabilities to meet changing boiler-system conditions. The proportional control action is achieved by restricting control and optimization of the boiler to achieve proportional valve action in the desuperheater cooling water flow. 
     The various embodiment of the steam-generation system  100  therefore include a separation between control of the desuperheater and reheater system with its unique control actions, and the control and optimization of the boiler system. 
       FIG. 2  shows a schematic diagram of a steam-generation system  200  that uses control and optimization modules according to an embodiment. The steam-generation system  200  can be a steam-generation system such as that shown in  FIG. 1 . 
     A desuperheater system is depicted within the dashed line  206 . An independently controlled and optimized boiler system is depicted within the dashed line  208 . 
     A boiler  210  such as a coal-fired or an oil-fired boiler is depicted. Although the steam-generation system  200  depicts a boiler  210 , embodiments are also applicable to other steam-generation systems such as a nuclear-fuel steam-generation system. 
     The boiler  210  has inputs such as fuel type  212 , burner intensity  214 , and burner tilt  216 . Another input for the boiler  210  is a flue-gas recycle  218  functionality. According to an embodiment, the flue-gas recycle  218  functionality is controllable by a high-temperature ventilation system such as a fan that operates in harsh combustion-product environments. 
     Variability in the boiler system  208  can cause a changing boiler output status. Such variability can occur such as when a different fuel grade such as coal is used, or when different flue emission limits are imposed upon the boiler system  208 . In an embodiment, variability is addressed by a cautious-optimization strategy that, for example, control emissions of carbon monoxide (CO) or nitrides of oxygen (NOx), and that operates the boiler system within specific emission limits. This cautious-optimization strategy can be one aspect of control and optimization for the boiler system. U.S. Pat. No. 6,712,604, by the inventor discloses various cautious-optimization strategies for such CO and NOx controls, and is incorporated herein by reference. 
     Another input for the boiler  210  includes a platen superheater  220  according to an embodiment. The platen superheater  220  can also be referred to as a superheat- 1  (SH 1 )  220 . Another input for the boiler  210  includes a final superheater  222 . The final superheater  222  can also be referred to as a superheat- 2  (SH 2 )  222 , or as an outlet superheater  222 . 
     Another input for the boiler  210  includes a reheat (RH) superheater  224  according to an embodiment. The RH superheater  224  can also be referred to as a reheater  224 . 
     Another input for the boiler  210  is an economizer  226  that can pre-heat feed water to the boiler. Another input for the boiler  210  is an air heater  228  that can pre-heat combustion air that mixes with the fuel. The economizer  226  and the air heater  228  are depicted in  FIG. 2  as being upstream from the flue-gas recycle functionality  218 . In an embodiment, however, the location of the flue-gas recycle functionality  218  can be upstream from either or both of the economizer  226  and the air heater  228 . 
     A related input is desuperheating cooling water flow to desuperheaters. An SH 1  desuperheater  230  (also referred to as DSH SH 1   230 ) depicts a cooling water flow  232 . Steam flows to the RS desuperheater  230  include a DSH SH 1  inlet flow  234  and a DSH SH 1  outlet steam flow  236 . 
     An SH 2  desuperheater  238  (also referred to as DSH SH 2   238 ) depicts a cooling water flow  240 . Steam flows to the SH 2  desuperheater  238  are DSH SH 2  inlet steam flow  242  and DSH SH 2  outlet steam flow  244 . After the post-DSH SH 2  flow  244  enters and exits the confines of the boiler  210 , it is referred to as an turbine admission steam flow  246 . 
     An RH desuperheater  248  (also referred to as a DSH RH  248 ) depicts a cooling water flow  250 . Steam flows to the RH desuperheater  248  are DSH RH inlet steam flow  252  and DSH RH outlet steam flow  254 . The post-DSH RH flow  254  is depicted as entering the confines of the boiler  210 , passing through the RH tube bundle  224 , and exiting the boiler  210  as an intermediate-pressure (IP) turbine feed flow  258 . 
     A high-pressure (HP) turbine  260  and an IP and LP turbine  262  are also depicted. The HP turbine  260  receives the HP turbine steam flow  246 , extracts enthalpy therefrom, and returns lower temperature steam as the HP-turbine exit flow  252 . The IP and LP turbine  262  receives the IP turbine feed flow  258 , extracts enthalpy therefrom, and LP outlet steam is condensed to water in condenser as the LP-turbine exit flow  264 . 
       FIG. 3  shows a graph of the affect of desuperheater cooling water flow with minimum mean flow, as it is used to control superheated steam temperature within a desuperheater according to an embodiment. DSH valve flow is depicted by a fully closed valve region  310 , a proportional region  312 , and a fully open valve region  314 . The vertical axis represents desuperheater cooling water flow amounts, and the horizontal axis represents a cooling water flow set point as required for temperature correction for superheated steam as it exits a desuperheater. 
     The symmetry line  316  represents mean value of DSH water flow as it enters a desuperheater. The curved line represents required cooling water flow trajectory  318  of a given desuperheater, and it is depicted in arbitrary shape and amplitude. 
       FIG. 4  shows a graph of the affect of desuperheater cooling water flow, as the control action is limited and within a fully closed valve range within a desuperheater according to an embodiment. DSH valve flow is depicted by a fully closed valve region  410 , a proportional valve region  412 , and a fully open valve region  414 . The vertical axis represents desuperheater cooling water flow amounts, and the horizontal axis represents a cooling water flow set point as required for temperature correction for superheated steam as it exits a desuperheater. 
     The symmetry line  416  represents a mean value of the DSH water flow as it enters a desuperheater. The curved line represents required cooling water flow trajectory  418  of a given desuperheater, and it is depicted in arbitrary shape and amplitude. As the set point trajectory results in valve actions that include fully closed  410 , a control limit  420  is noted. In this case, the steady state value is too low, and the minimum cooling will be limited, because a fully closed  410  valve action limits control-action. This would result in a decrease of a reheater DSH temperature, and a subsequent reduction of achievable cycle efficiency. 
     In an embodiment, equipment stress or thermodynamic inefficiencies are experienced. Such stresses and inefficiencies can be thermal shock of equipment from combining streams of significantly disparate temperature, or from feeding a stream to a unit where the temperatures are significantly disparate. In this embodiment, a desuperheater system is depicted at a state seen in  FIG. 4 , and a method of controlling the desuperheater system changes the location of the symmetry line  416  and the set point trajectory  418  from what is seen in  FIG. 4 , to what is seen in  FIG. 3 . In this method embodiment, controlling the desuperheater system includes affecting cooling water flow rates while avoiding a fully closed cooling water valve action, as seen by the observation at  FIG. 4 , followed by the response at  FIG. 3 . 
       FIG. 5  shows a graph of the affect of desuperheater cooling water flow with maximum mean flow, as it is used to control superheated steam temperature above a proportional valve range within a desuperheater according to an embodiment. DSH valve flow is depicted by a fully closed valve region  510 , a proportional valve region  512 , and a fully open valve region  514 . The vertical axis represents desuperheater cooling water flow amounts, and the horizontal axis represents a cooling water flow set point as required for temperature correction for superheated steam as it exits a desuperheater. 
     The symmetry line  516  represents a mean value of the DSH cooling water flow as it enters a desuperheater. The curved line represents a set point trajectory  518  of a given desuperheater, and it is depicted in arbitrary shape and amplitude. In this case, the steady state valve setting is higher than an optimal setting, and a discrepancy  520  is noted. 
     In this embodiment, a desuperheater system is depicted at a state seen in  FIG. 5 , and a method of controlling the desuperheater system changes the location of the symmetry line  516  and the set point trajectory  518  from what is seen in  FIG. 5 , to what is seen in  FIG. 3 . 
       FIG. 6  shows a graph of the affect of desuperheater cooling water flow, as it control action is limited and within a fully open valve range within a desuperheater according to an embodiment. DSH valve flow is depicted by a fully closed valve region  610 , a proportional valve region  612 , and a fully open valve region  614 . The vertical axis represents desuperheater cooling water flow amounts, and the horizontal axis represents a cooling water flow set point as required for temperature correction for superheated steam as it exits a desuperheater. 
     The symmetry line  616  represents a mean value of DSH cooling water flow as it enters a desuperheater. The curved line represents a set point trajectory  619  of a given desuperheater, and it is depicted in arbitrary shape and amplitude. In this case, the steady state valve setting is higher than an optimal setting, such that a fully open valve has reach a control limit boundary, and a control limit  621  is noted. 
     In this embodiment, a desuperheater system is depicted at a state seen in  FIG. 6 , and a method of controlling the desuperheater system changes the location of the symmetry line  616  and the set point trajectory  619  from what is seen in  FIG. 6 , to what is seen in  FIG. 3 . It should be clear that a new set point trajectory could be established that is neater to the fully open cooling water valve setting, rather than nearer to the fully closed cooling water valve setting that is seen in  FIG. 3 . 
       FIG. 7  shows a graph of the affect of desuperheater cooling water flow range, as it can be used to control superheated steam temperature without a limitation inside a more useful range within a desuperheater according to an embodiment. DSH valve flow is depicted by a fully closed valve region  710 , proportional valve region  712 , and a fully open valve region  714 . The vertical axis represents desuperheater cooling water flow amounts, and the horizontal axis represents a cooling water flow set point as required temperature correction for superheated steam as it exits a desuperheater. 
     A first symmetry line  716  represents minimum mean value of DSH cooling water as it enters a given desuperheater within the desuperheater system. A second symmetry line  717  represents maximum of DSH cooling water as it enters a given desuperheater within the desuperheater system. The depicted range  722  between the minimum and maximum flow lines  716 ,  717  is optimized to provide sufficient space to avoid DSH water flow limitation by lower and upper limit  720 ,  721  (feasible interval  722  amounts to a proportional valve action) as well as to provide maximum range within which boiler performance optimization can be done. 
       FIG. 7  therefore represents in an embodiment, a two-operating-zone model with a feasible interval  722  for a desuperheater system that has a single desuperheater.  FIG. 7  can also represent in an embodiment, however, a two-desuperheater-unit, feasible interval  722  operating-zone for a desuperheater system. It can be appreciated that a feasible interval for a three-desuperheater-unit operating-zone can also be modeled in an embodiment, for a steam-generating system such as the steam-generation system  200  depicted in  FIG. 2 . 
     It can now be seen that a complex steam-generating system can have many disturbances, loads, and duties that may affect a feasible interval operating zone for a cooling water desuperheater system. 
     In an embodiment, control of the desuperheater system  206  includes optimization of RH desuperheater cooling water flow (typically minimization). During a given control action, burner tilt  216  may result in a too-low steam temperature for the final superheater  222 , and some RH desuperheater cooling water flow may be needed. 
       FIG. 8  shows a schematic diagram of control and optimization modules for the steam-generation system according to an embodiment. The control and optimization modules  800  include a desuperheater control module  810  and a steam-generation control and optimization module  830 . 
     Within the desuperheater control module  810 , a first data bus  812  is used to communitively couple desuperheater control submodules, which include a desuperheater modeling submodule  814 , a desuperheater monitoring submodule  816 , and a desuperheater data acquisition submodule  818 . Data can be transferred amongst the several submodules over the data bus  812  during the control process. 
     The modeling submodule  814  is used to model the process of spraying cooling water into a given desuperheater to adjust the temperature of superheated steam. The thermodynamics of such spraying processes are well understood. As illustrated in  FIGS. 3-7 , a symmetrical steam-temperature response is achievable by operating the boiler system  208  within parameters that assure desuperheater steam-temperature responses to be controllable within the feasible interval  720 . The modeling submodule  814  also is used to describe heat-transfer conditions for a given desuperheater as external conditions affect the overall spraying process. 
     The monitoring submodule  816  monitors the overall conditions of a given desuperheater. The overall conditions include actual spraying-process data such as enthalpy changes and heat-transfer changes. The data-acquisition submodule  818  acquires a desuperheater duty for a selected period of time. 
     Within the steam-generation control module  820 , a second data bus  822  is used to communitively couple steam-generation control submodules, which include a modeling submodule  824 , a monitoring submodule  826 , a data acquisition submodule  828 , a data diagnostic submodule  830 , and a prediction submodule  832 . Data can be transferred amongst the several submodules over the second data bus  812  during the steam-generation control and optimization process. 
     The modeling submodule  814  is used to model a power generation apparatus in which it can also be used to model the various steam generation aspects of the power generation apparatus and, more particularly, the generation range for different equipment configurations and steam-generation duties. The monitoring submodule  824  monitors the internal consumption of power for a steam-generation system such as the boiler  210  depicted in  FIG. 2 . The monitoring submodule  824  also monitors the generation of a total amount of power from the steam-generation system such as the steam-generation system  100  depicted in  FIG. 1 . The total amount of power, in some embodiments, includes all the power that is generated over a selected time, such as a particular hour for a particular day. The data-acquisition submodule  828  acquires a power generation requirement for a selected period of time. The diagnostic submodule  830  operates several and various diagnostic tests of the steam-generation system  100 . 
     In an embodiment, a diagnostic test that is directed by the diagnostic submodule  830  includes varying fuel type  212  as depicted in  FIG. 2 . Differences in fuel type  212  can be unavoidable when, for example a given grade of coal or fuel oil is what the market offers. Differences in fuel type  212  can also be selected, based upon optimization data that has been logged by the data-acquisition submodule  828 . In an example embodiment, the boiler  210  is near to a scheduled down time for maintenance and cleaning, and boiler fouling is significant. A fuel grade can be selected based upon known diagnostics that will make heat transfer to the boiler more efficient, despite the pre-down time boiler fouling. 
     In an embodiment, a diagnostic test that is directed by the diagnostic submodule  830  includes varying burner intensity  214  as depicted in  FIG. 2 . Burner intensity  214  can be independent of boiler fouling, or it can be dependent upon boiler fouling. In an embodiment, the steam-generation system  100  has a significantly decreased duty, such as when a power company that is purchasing turbine-generated electricity, has an off-peak period. In such a time, burner intensity  214  can be reduced. Other example embodiments are convention as when to vary burner intensity  214 . 
     In an embodiment, estimation of internal boiler parameters are monitored such as boiler fouling. 
     In an embodiment, a diagnostic test that is directed by the diagnostic submodule  830  is burner tilt  216 . Burner tilt  216  can be a sub-function of burner intensity  214 . 
     In an embodiment, a diagnostic test that is directed by the diagnostic submodule  830  is the flue-gas recycle  218  functionality. According to an embodiment, the diagnostic test evaluates the flue-gas recycle rate upon the overall efficiency of the boiler  210 . In an embodiment, the diagnostic test evaluates the position near the economizer  226  and the air heater  228 . The position from which the flue-gas is removed, whether it is upstream from the economizer  226  and the air heater, between them, or downstream from them, is logged into the diagnostic test. 
     Other data that are able to be acquired and evaluated within the diagnostic module  830 , include superheater platen temperatures, such as the RS superheater platen  220 , the outlet superheater platen  222 , and the RH superheater  224 . 
     The prediction submodule  832  predicts an optimal power execution trajectory over a remaining portion of time which is needed to meet a projected amount of power. The prediction submodule  832  utilizes data from all the other submodules in the steam-generation control module  820 . 
     In an embodiment, the steam-generation control module  820  uses real-time control and optimization during the generation of steam. This real-time control and optimization is carried out independently of actions being effected within the desuperheater control module  810 . Information from the desuperheater control module  810 , however, can be acquired by the data-acquisition submodule  828  with the steam-generation control module  820 , such as by a hard line  834 , or through wireless communication. 
     As shown, each of the modules discussed above can be implemented in software, hardware or a combination of both hardware and software. Furthermore, each of the modules can be implemented as an instruction set on a microprocessor associated with a computer system or can be implemented as a set of instructions associated with any form of media, such as a set of instructions on a disk drive, a set of instructions on tape, a set of instructions transmitted over an Internet connection or the like. 
     Methods of Embodiments 
     This section describes methods embodiments. In certain embodiments, the methods are performed by machine-readable media (e.g., software), while in other embodiments, the methods are performed by hardware or other logic (e.g., digital logic). 
       FIG. 9  is a method flowchart  900  that illustrates method embodiment of this disclosure. At  910 , a desuperheater control action is carried out in a given desuperheater by controlling at least one steam temperature by a predictive, feed-forward control action that is based upon a system disturbance. In a non-limiting example, a look-up database of saturated and superheated steam data is referenced while a corrective action is taken to cause conditions of the given desuperheater to change from the output depicted in  FIG. 4 , to the output depicted in  FIG. 3 . In a nonlimiting example, a corrective action is taken to assure desuperheater cooling water flow to remain within a feasible interval, such as the feasible interval  720  depicted in  FIG. 7 . 
     At  912 , the method includes sending a control statement to the boiler system, such that a corrective action is taken within the boiler system to cause cooling water control valve action to remain proportional and/or within the feasible interval that has been established. 
     At  914 , the method includes sending a control statement within either of the boiler system or the desuperheater system, to minimize desuperheater cooling water flow in a reheater. 
     It should be clear that the control actions depicted in  910 ,  912 , and  914 , can be carried out singly, or in combination. 
     At  920 , a boiler system control action is carried out. In an embodiment the boiler-system control action originates in the modeling submodule  824  such as by a feedback data statement that results in a control statement. 
     At  930 , a boiler system control action is carried out. In an embodiment the boiler-system control action originates in the monitoring submodule  826  such as by a feedback data statement that results in a control statement. 
     At  940 , a boiler system control action is carried out. In an embodiment the boiler-system control action originates in the data diagnostic submodule  830  such as by a feedback data statement that results in a control statement. 
     At  950 , a boiler system control action is carried out. In an embodiment the boiler-system control action originates in the prediction submodule  832  such as by a database-lookup statement that results in a control statement. 
       FIG. 10  is a schematic diagram illustrating a media having an instruction set, according to an example embodiment. A machine-readable medium  1000  includes any type of medium such as a link to the internet or other network, or a disk drive or a solid state memory device, or the like. A machine-readable medium  1000  includes instructions within and instruction set  1050 . The instructions, when executed by a machine such as an information handling system or a processor, cause the machine to perform operations that include the control methods, such as the ones discussed in  FIGS. 2-9 . 
     In an example embodiment, a machine-readable medium  1000  that includes a set of instructions  1050 , the instructions, when executed by a machine, cause the machine to perform operations including modeling the desuperheater system embodiments and also the steam-generation system embodiments. 
     Hardware and Operating Environment 
     This section provides an overview of the example hardware and the operating environment in which embodiments of the can be practiced. 
       FIG. 11  illustrates an example computer system used in conjunction with desuperheater and steam-generation embodiments set forth in this disclosure. As illustrated in  FIG. 10 , computer system  1100  comprises processor(s)  1102 . The computer system  1100  also includes a memory unit  1130 , processor bus  1122 , and Input/Output controller hub (ICH)  1124 . The processor(s)  1102 , memory unit  1130 , and ICH  1124  are coupled to the processor bus  1122 . The processor(s)  1102  may comprise any suitable processor architecture. The computer system  1100  may comprise one, two, three, or more processors, any of which may execute a set of instructions in accordance with desuperheater and steam-generation embodiments. 
     The memory unit  1130  includes an operating system  1140 , which includes an I/O scheduling policy manager  1132  and I/O schedulers  1134 . The memory unit  1130  stores data and/or instructions, and may comprise any suitable memory, such as a dynamic random access memory (DRAM), for example. The computer system  1100  also includes IDE drive(s)  1108  and/or other suitable storage devices. A graphics controller  1104  controls the display of information on a display device  1106 , according to disclosed embodiments. 
     The Input/Output controller hub (ICH)  1124  provides an interface to I/O devices or peripheral components for the computer system  1100 . The ICH  1124  may comprise any suitable interface controller to provide for any suitable communication link to the processor(s)  1102 , memory unit  1130  and/or to any suitable device or component in communication with the ICH  1124 . For one embodiment, the ICH  1124  provides suitable arbitration and buffering for each interface. 
     In an embodiment, the ICH  1124  provides an interface to one or more suitable integrated drive electronics (IDE) drives  1108 , such as a hard disk drive (HDD) or compact disc read-only memory (CD ROM) drive, or to suitable universal serial bus (USB) devices through one or more USB ports  1110 . In an embodiment, the ICH  1124  also provides an interface to a keyboard  1112 , a mouse  1114 , a CD-ROM drive  1118 , and one or more suitable devices through one or more firewire ports  1116 . The ICH  1124  also provides a network interface  1120  though which the computer system  1100  can communicate with other computers and/or devices. 
     In one embodiment, the computer system  1100  includes a machine-readable medium that stores a set of instructions (e.g., software) embodying any one, or all, of the methodologies for desuperheater and steam-generation systems described herein. Furthermore, software can reside, completely or at least partially, within memory unit  1130  and/or within the processor(s)  1102 . 
     Thus, a system, method, and machine-readable medium including instructions for Input/Output scheduling have been described. Although the various desuperheater and steam-generation control and optimization systems has been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader scope of the disclosed subject matter. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.