SYSTEM AND METHOD FOR STACK HEAT RECOVERY

A system and method are presented for recovering heat from flue gas produced by a recovery boiler in a pulp and paper mill, the recovery boiler having a flue stack. Flue gas is drawn from the flue stack and passed through a first and second condensing heat exchangers before exiting through a separate stack. The first heat exchanger is used to heat boiler feedwater whereas the second heat exchanger is used to produce process hot water for use in the pulp and paper mill. Steam previously used to heat the boiler feedwater and produce the process hot water can now be used to generate electricity that can be used for the pulp and paper mill operations or to export to the electrical power grid.

TECHNICAL FIELD

The present disclosure is related to the field of recovering heat from flue gas produced from a recovery boiler used in a pulp and paper mill.

BACKGROUND

In the production of chemical pulp, lignin and other organic non-cellulosic material can be separated from the raw material of chemical pulp by cooking using cooking chemicals. Cooking liquor used in chemical digestion, that is, waste liquor is recovered. The waste liquor (also referred to as “black liquor”), which is separated mechanically from the chemical pulp, has a high combustion value due to carbonaceous and other organic, combustible material contained therein and separated from the chemical pulp. The waste liquor also contains inorganic chemicals, which do not react in chemical digestion. Several different methods have been developed for recovering heat and chemicals from waste liquor.

Black liquor obtained in kraft pulp production is combusted in a recovery boiler. As the organic and carbonaceous materials contained in black liquor burn, inorganic components in the black liquor are converted into chemicals, which can be recycled and further utilized in the cooking process.

Hot flue gases are generated in black liquor combustion, which are led into contact with various heat exchangers within the recovery boiler. Flue gas conveys heat into water or vapor, or a mixture of water and vapor, flowing inside the heat exchangers, simultaneously cooling itself. Usually, flue gases contain abundantly of ash. Main part of the ash is sodium sulfate, and the next largest part is usually sodium-carbonate. Ash contains other components, too. The ash entrained in flue gases is in the furnace mainly in vaporized form and starts to convert into fine dust or smelt droplets mainly in the parts of the boiler downstream of the furnace. The salts contained in the ash melt can be sticky particles even at relatively low temperatures. Molten and sticky particles stick easily onto heat transfer surfaces and even corrode them. Deposits of sticky ash have caused a clogging risk of the flue gas ducts, and also corrosion and wearing of the heat surfaces in the boiler. A recovery boiler in a pulp and paper mill, thus, can produce hot flue gas that is released to the atmosphere through a flue gas stack, as well known to those skilled in the art.

Recovery boiler flue gas, however, contains acid, especially sulfuric acid vapour inside of flue gas that has been known to cause acid corrosion. As a result, dry heat exchangers are typically used (where temperatures are above the sulfuric acid dew point) and considered to be a common sense or standard type of heat exchanger as used in pulp and paper mill industries. In addition, flue gas particulates contain chloride and this is known to cause stress crack corrosion in normal stainless steel

A typical material used for heat exchangers is carbon steel because it is a low-cost material and provides better heat exchange efficiency. Carbon steel can also be used in the construction of dry heat exchangers to avoid concerns of acid corrosion therein. In some cases, titanium can be used (as is used in a majority of the Japanese mills) as well as the casing and ducts can be made off 316 stainless steel or carbon steel. However, titanium is very expensive, has low heat exchange efficiency and is difficult to fabricate. This is why, historically, pulp and paper mills have only used dry heat exchanges, or no heat exchangers at all, to avoid problem of corrosion caused by acid condensation.

Referring toFIG.1, a prior art recovery boiler system is shown. Flue gas in recovery boiler100passes through economizers104and then through ducts106into precipitator units108. Fan units110then draw flue gas from precipitator units108and direct the flue gas through flue gas ducts112to exit to the atmosphere via recovery boiler stack102. In the illustrated example, the flue gas is split through parallel paths to a pair of precipitator units108and fan units110although the flue gas can be directed through a single path or through multiple paths of these units, as well known to those skilled in the art. Recovery boiler stack102is, typically, constructed of carbon steel.

The flue gas contains sensible and latent heat that can be used to heat boiler feedwater and to produce process hot water used in the mill operations. This could be accomplished by passing the flue gas through condensing heat exchangers, however, the condensation produced in doing so prevents the heat exchangers from being placed in flue gas ducts112due to the acid condensation that causes corrosion therein.

It is, therefore, desirable to provide a system and method that can extract the heat in the flue gas with condensing heat exchangers without causing corrosion to both the heat exchanger and the recovery boiler stack.

SUMMARY

A system and method for recovering heat from the flue gas produced by a recovery boiler in a pulp and paper mill is presented. In some embodiments, the flue gas produced by the recovery boiler can be diverted and drawn from the recovery boiler stack and passed through one or more condensing heat exchangers that can be used to extract one or both of the sensible and the latent heat in the flue gas to heat the boiler feedwater used for the recovery boiler and other boilers used in the pulp and paper mill, and to produce process hot water for use in the mill operations. In doing so, the low pressure steam previously used to heat boiler feedwater and to produce process hot water can be used to generate electrical power with steam turbines coupled to electrical generators. After passing through the heat exchangers, the heat depleted flue gas can then be released to the atmosphere via a new stack. The new heat exchangers and the new stack can be made of stainless steel to prevent acid corrosion and stress cracking corrosion due to the substances in flue gas, which contains acid and chloride condensing and precipitating on the heat exchangers.

In some embodiments, the heat exchangers can be arranged such that the first exchanger is positioned above the second heat exchanger, whereby the flue gas can be drawn from the recovery boiler stack with variable frequency drive (“VFD”) electrically-operated fan that can direct the flue gas, through ducting, downward through the two heat exchangers. After passing through the heat exchangers, the flue gas can flow through ducting to the new stack for release into the atmosphere.

In some embodiments, the condensation that forms on the heat exchangers, when the flue gas flows therethrough, can fall downward and be collected in a condensation collector where the collected condensate, typically water, can be piped and stored in a holding tank or sump for use in mill operations, or disposed of in a manner as well known to those skilled in the art.

In some embodiments, a wash system can be provided to wash off precipitate and condensate that can build up on the heat exchangers. Flue gas from a recovery boiler can contain particles such as soot and minerals. As flue gas passes through the heat exchangers, the soot and minerals can deposit or precipitate onto the heat exchangers forming an accumulated precipitate layer that can degrade the heat transfer efficiency of the heat exchangers. The precipitate layer needs to be removed from the heat exchangers on a periodic basis. To wash the precipitate and condensate off of the heat exchangers, a wash system can be used. In some embodiments, the wash system can comprise spray nozzles disposed on the heat exchangers that can be used to direct pressurized fluid, such as water or collected flue gas condensate, onto the heat exchangers to break up the precipitate and wash it off along with condensate so that the heat exchangers can operate at optimum efficiency. The wash system can be configured to operate at predetermined times for predetermined periods, as necessary, to wash off the precipitate and the condensate.

Broadly stated, in some embodiments, a heat recovery system can be provided for use with a recovery boiler system in a pulp and paper mill, the recovery boiler system comprising a flue gas stack operatively coupled thereto, the heat recovery system comprising: a first fan configured to draw flue gas away from the flue gas stack; at least one first heat exchanger operatively coupled to the first fan and configured to receive the drawn flue gas to pass therethrough; at least one second heat exchanger operatively coupled to the at least one first heat exchanger and configured to receive the drawn flue gas to pass therethrough after passing through the at least one first heat exchanger; and a second flue gas stack operatively coupled to the at least one second heat exchanger and configured to receive the drawn flue gas after passing through the at least one second heat exchanger.

Broadly stated, in some embodiments, the at least one first heat exchanger can be configured to heat boiler feedwater.

Broadly stated, in some embodiments, the at least one first heat exchanger can comprise two or more boiler feedwater heat exchangers operatively coupled together sequentially.

Broadly stated, in some embodiments, the at least one second heat exchanger can be configured to heat process hot water for use in the pulp and paper mill.

Broadly stated, in some embodiments, the at least one second heat exchanger can comprise two or more process hot water heat exchangers operatively coupled together sequentially.

Broadly stated, in some embodiments, the at least one first exchanger can be disposed above the at least one second heat exchanger, and wherein the drawn flue gas can be directed downward through the at least one first heat exchanger and the at least one second heat exchanger.

Broadly stated, in some embodiments, the heat recovery system can further comprise a wash system configured to wash off one or both of precipitate and condensate off of one or both of the at least one first heat exchanger and the at least one second heat exchanger, the precipitate and the condensate forming on one or both of the at least one first heat exchanger and the at least one second heat exchanger as the drawn flue gas passes therethrough.

Broadly stated, in some embodiments, the wash system can comprise at least one spray nozzle disposed on one or both of the at least one first heat exchanger and the at least one second heat exchanger, the at least one spray nozzle configured to wash off one or both of the at least one first heat exchanger and the at least one second heat exchanger.

Broadly stated, in some embodiments, one or both of the at least one first heat exchanger and the at least one second heat exchanger can comprise a condensing heat exchanger.

Broadly stated, in some embodiments, the heat recovery system can further comprise a condensation collector disposed beneath one or both of the at least one first heat exchanger and the at least one second heat exchanger, the condensation produced by water vapour disposed in the drawn flue gas condensing on one or both of the at least one first heat exchanger and the at least one second heat exchanger as the drawn flue gas passes therethrough.

Broadly stated, in some embodiments, the heat recovery system can further comprise a wash system configured to use at least some of the collected condensation to wash off one or both of precipitate and condensate off one or both of the at least one first heat exchanger and the at least one second heat exchanger, the precipitate and the condensate forming on one or both of the at least one first heat exchanger and the at least one second heat exchanger as the drawn flue gas passes therethrough.

Broadly stated, in some embodiments, the wash system can comprise at least one spray nozzle disposed on one or both of the at least one first heat exchanger and the at least one second heat exchanger, the wash system comprising a first pump configured to pump the collected condensation through the at least one spray nozzle, thereby washing one or both of the at least one first heat exchanger and the at least one second heat exchanger.

Broadly stated, in some embodiments, one or both of the at least one first heat exchanger and the at least one second heat exchanger can be comprised of one or both of stainless steel and titanium.

Broadly stated, in some embodiments, one or both of the at least one first heat exchanger and the at least one second heat exchanger can be comprised of SAF 2205™ stainless steel.

Broadly stated, in some embodiments, a method can be provided for recovering heat from a recovery boiler system in a pulp and paper mill, the recovery boiler system comprising a flue gas stack operatively coupled thereto, the method comprising: drawing flue gas away from the flue gas stack; heating boiler feedwater with the drawn flue gas; then heating process hot water with the drawn flue gas; and then exiting the drawn flue gas to the atmosphere.

Broadly stated, in some embodiments, the method can comprise heating the boiler feedwater with at least one first heat exchanger.

Broadly stated, in some embodiments, the at least one first heat exchanger can comprise two or more boiler feedwater heat exchangers operatively coupled together sequentially.

Broadly stated, in some embodiments, the method can comprise heating the process hot water with at least one second heat exchanger.

Broadly stated, in some embodiments, the at least one second heat exchanger can comprise two or more process hot water heat exchangers operatively coupled together sequentially.

Broadly stated, in some embodiments, the method can further comprise washing one or both of precipitate and condensate off of one or both of the at least one first heat exchanger and the at least one second heat exchanger, the precipitate and the condensate having formed on one or both of the at least one first heat exchanger and the at least one second heat exchanger after the drawn flue gas has passed therethrough.

Broadly stated, in some embodiments, the method can further comprise using at least one spray nozzle for washing one or both of the at least one first heat exchanger and the at least one second heat exchanger.

Broadly stated, in some embodiments, the method can comprise washing the at least one first heat exchanger and the at least one second heat exchanger sequentially.

Broadly stated, in some embodiments, the method can further comprise collecting condensation produced by water vapour disposed in the drawn flue gas condensing on one or both of the at least one first heat exchanger and the at least one second heat exchanger as the drawn flue gas passes therethrough.

Broadly stated, in some embodiments, the method can comprise washing one or both of precipitate and condensate off of one or both of the at least one first heat exchanger and the at least one second heat exchanger with at least some of the collected condensation, the precipitate and the condensate having formed on one or both of the at least one first heat exchanger and the at least one second heat exchanger after the drawn flue gas has passed therethrough.

Broadly stated, in some embodiments, the method can further comprise pumping the at least some of the collected condensation through at least one spray nozzle to wash one or both of the at least one first heat exchanger and the at least one second heat exchanger.

Broadly stated, in some embodiments, the method can comprise washing the at least one first heat exchanger and the at least one second heat exchanger sequentially.

Broadly stated, in some embodiments, a heat recovery system can be provided for use with a recovery boiler system in a pulp and paper mill, the recovery boiler comprising a flue gas stack operatively coupled thereto, the heat recovery system comprising: means for drawing flue gas away from the flue gas stack; means for heating boiler feedwater with the drawn flue gas; means for heating process hot water with the drawn flue gas; and means for exiting the drawn flue gas to the atmosphere.

Broadly stated, in some embodiments, the heat recovery system can further comprise means for washing one or both of precipitate and condensate off of one or both of the means for heating boiler feedwater and the means for heating process hot water, the precipitate and the condensate having formed thereon after the drawn flue gas has passed therethrough.

Broadly stated, in some embodiments, the heat recovery system can further comprise means for collecting condensation produced by water vapour disposed in the drawn flue gas.

Broadly stated, in some embodiments, the heat recovery system can further comprise means for washing one or both of precipitate and condensate off of one or both of the means for heating boiler feedwater and the means for heating process hot water with the collected condensation, the precipitate and the condensate having formed thereon after the drawn flue gas has passed therethrough.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring toFIGS.2and3, simplified embodiments of stack heat recovery system10is shown. In its simplest configuration, in some embodiments, flue gas can be drawn away from recovery boiler stack102, via duct12, by fan14to force the flue gas to flow through first heat exchanger16and then through second heat exchanger18. After passing through heat exchangers16and18, the flue gas can exit to the atmosphere through second stack20.

In some embodiments, first heat exchanger16can be comprised of stainless steel and can be used to convert the sensible heat in the flue gas to heat boiler feedwater for use in recovery boiler100. In some embodiments, first heat exchanger16can be comprised of SAF 2205™ stainless steel, as manufactured by Sandvik AB of Stockholm, Sweden. SAF 2205™ stainless steel is known to have high resistance to stress corrosion cracking chloride-bearing and hydrogen sulphide environments, and high resistance to general corrosion and corrosion fatigue. The steam previously used to heat the boiler feedwater in the prior art system, as shown inFIG.1, can then be used to generate electrical power by running the steam through a steam turbine operatively coupled to an electrical generator (not shown), as well known to those skilled in the art. In a representative example, the steam previously used to heat the boiler feedwater can produce approximately 2.7 megawatts of power.

In some embodiments, second heat exchanger18can be comprised of stainless steel can be used to convert the sensible and latent heat in the flue gas to produce process hot water for use in operations in the pulp and paper mill. In some embodiments, second heat exchanger18can be comprised of SAF 2205™ stainless steel, as manufactured by Sandvik AB of Stockholm, Sweden. The steam previously used to produce the process hot water in the prior art system, as shown inFIG.1, can then be used to generate electrical power by running the steam through a steam turbine operatively coupled to an electrical generator (not shown), as well known to those skilled in the art. In a representative example, the steam previously used to produce the process hot water can produce approximately 6.0 megawatts of power. Thus, the implementation of this heat recovery system can then free up the steam previously used in the prior art system to produce approximately 8.7 megawatts of power, in the representative example. It would be obvious to those skilled in the art that amount of power produced can be scaled up or down depending on the size the recovery boiler and the amount of flue gas produced therefrom.

Referring toFIGS.4and5, a third embodiment of stack heat recovery system10is shown. In the illustrated embodiment shown inFIG.4, system10can draw flue gas away from recovery boiler stack102with VFD-operated fan14. In some embodiments, system10can comprise damper inlet guillotine valve13, which can be used to open and close the flow path from stack102to fan14to allow for operational and maintenance procedures on system10. From fan14, the flue gas can flow through ducting15to enter into stack structure17where heat exchangers16and18are disposed therein in a vertical configuration wherein first heat exchanger16is disposed above second heat exchanger18such that the flue gas flows downward from the top of first heat exchanger16through to the bottom of second heat exchanger18. From there, the flue gas can flow through ducting19and exit to atmosphere50via second stack20.

In some embodiments, system10can comprise two sets of heat exchangers16and18operatively configured in parallel vertical structures17, as shown inFIGS.4and5. Having multiple vertical structures17can be done to scale up the volume of flue gas processed by system10or can be done for practical reasons in terms of the logistics of shipping heat exchangers to a site where system10will be implemented. It can also be done for redundancy wherein one vertical structure17can be shut down for maintenance or repaid while the other vertical structure17remains in operation.

In some embodiments, boiler feedwater can enter first heat exchangers16via piping22. Boiler feedwater to be heated can be pumped into inlet pipe22ato enter heat exchanger inlets16a, wherein heated boiler feedwater can exit via heat exchanger outlets16bto be pumped via outlet pipe22bto recovery boiler100.

In some embodiments, process hot water can enter second heat exchangers18via piping26. Process hot water to be heated can be pumped into inlet pipe26ato enter heat exchanger inlets18in, wherein heated process hot water can exit via heat exchanger outlets18out to be pumped via outlet pipe26bfor use in pulp and paper mill operations.

In the illustrated embodiment shown inFIG.5, system10can comprise heat exchanger wash system30that can be configured to clean precipitate and condensate off of heat exchangers16and18that can accumulate thereon over time as flue gas passes therethrough. In some embodiments, wash system30can comprise of sump34that can be used to hold fluid, such as water or flue gas condensate that can form on heat exchangers16and18. The flue gas condensate can accumulate in condensate collectors32disposed on the lower ends of vertical structures17due to gravity. The flue gas condensate can then be directed to sump34via piping36. In some embodiments, fluid pump40can be used to draw flue gas condensate from sump34and pump it through piping44to be dispensed through spray nozzles38a-38bdisposed in heat exchangers16and18. Valves45a-45dcan be opened and closed as needed to selectively operate one of spray nozzles38a-38din accordance with a predetermined wash sequence or protocol.

As flue gas flows downward through heat exchangers16and18, the precipitate that can accumulate thereon can tend to accumulate more towards the top of heat exchangers16because of the first contact area and pressure drop as the flue gas contacts heat exchangers16. In some embodiments, a wash sequence can include first pumping fluid, such as water or flue gas condensate, through spray nozzles38ato first clean off heavy accumulation of condensate from the bottom of heat exchangers18so as to enable circulation therethrough again, and then spraying fluid sequentially through spray nozzles38d, then spray nozzles38c, then spray nozzles38band then spray nozzles38aonce again. In some embodiments, the wash sequence can occur as needed or on a pre-determined time schedule such as every 12 to 24 hours, or more, depending on how much soot and minerals are suspended in the flue gas as it exits from recovery boiler100. Once a wash sequence is completed, drain valve43can be opened to allow fluid within piping44to drain back to sump34.

Referring toFIGS.6and7, a fourth embodiment of stack heat recovery system10is shown. In the illustrated embodiment shown inFIG.5, system10can draw flue gas away from recovery boiler stack102with VFD-operated fan14. In some embodiments, system10can comprise damper inlet guillotine valve13, which can be used to open and close the flow path from stack102to fan14to allow for operational and maintenance procedures on system10. From fan14, the flue gas can flow through ducting15to enter into stack structure17where heat exchangers16and18are disposed therein in a vertical configuration wherein first heat exchanger16is disposed above second heat exchanger18such that the flue gas flows downward from the top of first heat exchangers16through to the bottom of second heat exchangers18. From there, the flue gas can flow through ducting19and exit to atmosphere50via second stack20.

In some embodiments, first heat exchangers16can comprise condensing heat exchangers comprised of material that is resistant to corrosion. In some embodiments, first heat exchangers16can be comprised of stainless steel, titanium or other corrosion-resistant materials as well known to those skilled in the art. In some embodiments, first heat exchangers16can be comprised of SAF 2205™ stainless steel, as manufactured by Sandvik AB of Stockholm, Sweden. In the illustrated embodiment shown inFIG.6, second heat exchanger18can comprise of three separate heat exchangers operatively coupled together sequentially, labelled as18a,18band18c. In some embodiments, second heat exchangers18can comprise condensing heat exchangers comprised of material that is resistant to corrosion. In some embodiments, second heat exchangers18can be comprised of stainless steel, titanium or other corrosion-resistant materials as well known to those skilled in the art. In some embodiments, second heat exchangers18can be comprised of SAF 2205™ stainless steel, as manufactured by Sandvik AB, of Stockholm, Sweden.

In some embodiments, system10can comprise two sets of heat exchangers16and18operatively configured in parallel vertical structures17, as shown inFIGS.6and7. Having multiple vertical structures17can be done to scale up the volume of flue gas processed by system10or can be done for practical reasons in terms of the logistics of shipping heat exchangers to a site where system10will be implemented. It can also be done for redundancy wherein one vertical structure17can be shut down for maintenance or repaid while the other vertical structure17remains in operation.

In some embodiments, boiler feedwater can enter first heat exchangers16via piping22. Boiler feedwater to be heated can be pumped into inlet pipe22ato enter heat exchanger inlets16a, wherein heated boiler feedwater can exit via heat exchanger outlets16bto be pumped via outlet pipe22bto recovery boiler100.

In some embodiments, process hot water can enter second heat exchangers18via piping26. Process hot water to be heated can be pumped into inlet pipe26ato enter heat exchanger inlets18in of heat exchangers18a, wherein process hot process can flow sequentially through heat exchangers18ato18cto be heated and can then exit via heat exchanger outlets18out to be pumped via outlet pipe26bfor use in pulp and paper mill operations.

In the illustrated embodiment shown inFIG.7, system10can comprise heat exchanger wash system30that can be configured to clean precipitate and condensate off of heat exchangers16and18ato18cthat can accumulate thereon over time as flue gas passes therethrough. In some embodiments, wash system30can comprise of sump34that can be used to hold fluid, such as water or flue gas condensate that can form on heat exchangers16and18ato18c. The flue gas condensate can accumulate in condensate collectors32disposed on the lower ends of vertical structures17due to gravity. The flue gas condensate can then be directed to sump34via piping36. In some embodiments, fluid pump40can be used to draw flue gas condensate from sump34and pump it through piping44to be dispensed through spray nozzles38a-38bdisposed in heat exchangers16and18ato18c, one set of spray nozzles per heat exchanger as an example. Valves45a-45dcan be opened and closed as needed to selectively operate one of spray nozzles38a-38din accordance with a predetermined wash sequence or protocol.

As flue gas flows downward through heat exchangers16and18ato18c, the precipitate that can accumulate thereon can tend to accumulate more towards the top of heat exchangers16because of the first contact area and pressure drop as the flue gas contacts heat exchangers16. In some embodiments, a wash sequence can include first pumping fluid, such as water or flue gas condensate, through spray nozzles38ato first clean off heavy accumulation of condensate from the bottom of heat exchangers18aso as to enable circulation therethrough again, and then spraying fluid sequentially through spray nozzles38d, then spray nozzles38c, then spray nozzles38band then spray nozzles38aonce again to cycle through all of heat exchanges18ato18c. In some embodiments, the wash sequence can occur as needed or on a pre-determined time schedule such as every 12 to 24 hours, or more, depending on how much soot and minerals are suspended in the flue gas as it exits from recovery boiler100. Once a wash sequence is completed, drain valve43can be opened to allow fluid within piping44to drain back to sump34.

Referring toFIG.8, a simplified block diagram for control system46is shown for controlling the operation of system10. In some embodiments, control system46can comprise computing control device48that can comprise of one or more of a programmable logic controller (“PLC”), a general purpose computer, a microcontroller and a microprocessor-based computing device configured for controlling the subcomponents let of system10. In some embodiments, computing control device48can be operatively to one or more of guillotine valve13, VFD-operated fan14, fluid pump40, drain valve43and nozzle control valves45ato45d. In some embodiments, computing control device48can be used to control the operation of guillotine valve13and VFD-operated fan14to regulate and control the volume of the flue gas flowing through system10. In some embodiments, computing control device48can be used to control wash system40through the operation of fluid pump40and the operation of spray nozzle valve45ato45din accordance with a pre-determined wash sequence of heat exchangers16and18to remove precipitate or condensate therefrom on a pre-determined time schedule for wash operations or in response to how much precipitate or condensate has accumulated on heat exchangers16and18. In some embodiments, computing control device48can be used to open drain valve43to drain piping44after a wash operation of heat exchangers16and18.

Embodiments implemented in computer software can be implemented in software, firmware, middleware, microcode, hardware description languages, or any combination thereof. A code segment or machine-executable instructions can represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment can be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. can be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.