GB2507173B - Optimising the utilisation of renewable energy from biomass resources in the palm oil industry - Google Patents

Description

OPTIMISING THE UTILISATION OF RENEWABLE ENERGY FROM BIOMASSRESOURCES IN THE PALM OIL INDUSTRY

FIELD OF THE INVENTION

The present invention relates to an arrangement for operating energy system of a crudepalm oil extraction plant and method thereof.

BACKGROUND OF THE INVENTION

Environmental considerations are increasing the economic interest in technologieswhich enable efficient energy production and energy usage coupled with low emission.Efficient use of biomass is a proven way to abate damage to the natural environmentby displacing the use of fossil fuel. But biomass is also a scarce energy resource andtherefore it is imperative that the most efficient use be found for its energy potential todisplace the maximum amount of fossil fuel and to reverse the harmful effects of fossilfuel burning on the environment.

In the Oil Palm milling industry, the electrical power required to operate a palm oil millhas steadily increased due to the additional electrically-operated machinery installedover the years for various needs, such as improving the mill process, controllingenvironmental pollution or meeting the demand for ever increasing residential electricitysupply. To cater for this progressively growing electrical power need, boilers of higherand higher steam pressure and temperature and higher efficiency steam prime moverdriven electrical generators were introduced. Existing low pressure boilers cannot bemodified for operation at higher pressure due to design constrains and thereforereplacement with new boilers with higher design pressure and temperatures were necessary. Several existing palm oil mills have circumvented installation of new boilersby resorting to operating diesel engine driven generators to supplement the steamturbine generator capacity. Others have resorted to purchasing electricity from the grid.

With reference to any thermodynamic medium as a carrier of heat energy, in particularsteam, the enthalpy of condensation provides the process heat, while the liquidenthalpy in the condensate is discharged from the local heating system.

Unit process temperatures are deliberately maintained relatively low to preventdeterioration of palm oil and kernel quality. Higher temperatures are known to causeoxidation of the palm oil and discolouration of kernels that affect subsequent bleachability of the oils. A source of heat for palm oil mill processes is steam exhausted from the steam primemover which is distributed through conduits from the source to impart its thermalenergy to various unit processes.

In prior art, the desired unit process temperatures are attained by using source steamat a pressure of about 4 bar the saturation pressure corresponding to 144 °C. Thesource steam that is conveyed to the vicinity of the unit processes in the mill is utilisedas described below: i. The source steam is let down in pressure through two control valves in seriesand de-superheated by spray of water before it is introduced into the continuoussterilizer chamber, which is maintained at atmospheric pressure. Thecondensate from the chamber is drained by siphon action with steam seal anddischarged to waste; ii. The source steam is let into the pressurised batch sterilizer through an isolatingvalve in a cycle of pressurising and depressurising to peak at about 2 barpressure. Efficient de-aeration of the vessel is effected during warm-up cyclethrough slow steam admission using the de-aeration valve and air expelledthrough the lateral pipes on either side along the length of the vessel. The largequantity of condensate during warm-up is drained quickly to prevent flooding ofthe vessel and discharged to waste; iii. The source steam is de-superheated by spray of water and directly injectedthrough nozzles into a post heating vessel for heating the fruits at atmosphericpressure; iv. The source steam is directly injected through nozzles into the digester to heatthe “Mass passing through Digester”, MPD at atmospheric pressure. Wherejacket heating is employed condensate is drained through a steam trap anddischarged to waste; v. The source steam is let into the concentric heating jacket and maintained at fullpressure to heat and facilitate moisture removal from the pressed cake passingthrough the cake breaker conveyor. Condensate is drained through a steamtrap and discharged to waste; vi. The source steam is let into the hot water tank through by means of controlvalve and sparger to heat water for process dilution; vii. The source steam is admitted into steam coils at full pressure to maintaintemperature in several tanks to clarify and purify the palm oil. Condensate isdrained through steam traps and discharged to waste; viii. The source steam is admitted through control valves and maintained at aboutfull pressure in steam coils to heat ventilation air for the nut and kernel dryingand condensate is recovered in the heating cycle.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved arrangement for operating energysystem of a crude palm oil extraction plant and improved method thereof. The improvedarrangement for operating energy system of a crude palm oil extraction plant achievesthe target of higher efficiency of energy utilisation by using heat source of a lowtemperature and having the energy system designed to operate at a design operationpoint for the low temperature of the heat source to deliver the design operation pointimproved performance and efficiency while sustaining the thermal energy needs of thepalm oil extraction process.

Palm oil mill energy systems are conventionally designed to operate at a designoperation point for heat source temperature of about 144 °C to deliver the designoperation point mechanical power output and thermal energy needs of the palm oilextraction process. Accordingly, subsystems, components, and controls are structuredto meet the design operation point for the heat source temperature that deliver thedesign operation point mechanical power output and thermal energy needs.

Heat engines incorporated into prior art energy systems to generate the mechanicalpower output are designed and configured to operate at a design operation point forspent heat temperature at about 144 °C.

In the palm oil extraction situation, observation of the various unit processes affirmsthat the process temperature requirements are relatively low, i.e., mostly no more thanabout 100 °C, except where batch sterilizers are used wherein the highest temperaturerequired may go up to about 110 °C.

Accordingly, the invention is directed to an energy system designed to operate at adesign operation point for the low temperature of the heat source to deliver the designoperation point improved performance and efficiency while sustaining the thermalenergy needs of the palm oil extraction process. As an added option the energysystem, concurrently by thermal energy communication means, provides a heat sink ofcorrespondingly low temperature for a power cycle designed to operate and dischargeits spent heat at the low sink temperature. Thus a further improvement in performanceand efficiency of the energy system is attainable with whole or part of the spent heatrejected from the power cycle supplying at least a portion of the heat demand of theheat source at the lower temperature.

Accordingly, the present invention provides, amongst others, two schemes to improvethe efficiency of energy utilisation in palm oil mills, namely: (i) the optimum utilisation of the heat energy inherent in the process heat sourcefor the palm oil mill process; and (ii) the optimal production of mechanical or electrical energy by a heat engine in thepower cycle through expanding down the thermodynamic medium to a lowertemperature heat sink provided by the heat demand of the palm oil mill process.

These objects are achieved by an incipient method characterized by using heat sourceof a low temperature feasible with the temperatures required for the palm oil extractionunit processes to impart its thermal energy to the process by an energy systemdesigned to operate at a design operation point for the low temperature of the heatsource to deliver the design operation point improved performance and efficiency.Since the process temperature in the palm oil mill is no more than about 100 °C or about 110 °C, a heat source of about 120 °C, as an example, presents sufficienttemperature differential to drive heat transfer and satisfy the operating temperatures ofthe process. Accordingly, it would be beneficial to provide an energy system for thepalm oil extraction plant that has improved performance and efficiency as compared toprior art systems.

An improvement in mechanical energy recovery from a heat engine is achieved byhaving the heat engine designed and configured to expand a thermodynamic mediumthrough the heat engine at a design operation point for a low exiting spent heattemperature to deliver its design operation point improved performance and efficiency.

Overall biomass energy utilisation in the palm oil mill is thus optimised by incorporatingheat engine optimally designed and configured to operate and discharge its spent heatat a design operation point for a correspondingly low temperature heat sink that is inthermal energy communication with the low heat source temperature brought about byan arrangement of using low heat source temperature in an energy system designed tooperate at a design operation point for the low temperature of the heat source to deliverits design operation point improved performance and efficiency while sustaining thethermal energy needs of the palm oil extraction process.

The improvement in mechanical energy recovery in the heat engine increases with thedownward divergence of the design operating point heat sink temperature which isinduced by the temperature of the heat source featuring in the energy system designoperation point.

Mechanical power output can be increased while retaining the existing boiler, byimproving the boiler steam superheat temperature, incorporating steam turbine generator optimised for the new low exit pressure, installing devices to control the backpressure vessel pressure at the new value and implementing steam distributionchanges to cater for the lower process steam source pressure.

Accordingly, the present invention provides an arrangement for operating energysystem of a crude palm oil extraction plant which includes a primary heat sourceconfigured to provide heat energy in the form of high pressure and temperature steam,a steam prime mover configured to receive high pressure and temperature steam fromthe primary heat source, a back pressure vessel configured to receive heat energy inthe form of steam exiting from the steam prime mover, at least one unit process of thecrude palm oil extraction plant requiring heat energy and at least one means configuredto convey heat energy from the back pressure vessel as source steam to the unitprocess wherein the energy system is designed and configured to operate at a designoperation point for the temperature of the source steam of the back pressure vesselcharacterized in that the temperature of the source steam of the back pressure vesselis between 100 °C and 141 °C at saturation pressure.

Furthermore, the present invention also provides a method for operating energy systemof a crude palm oil extraction plant which includes providing heat energy in the form ofhigh pressure and temperature steam from a primary heat source, reducing thepressure and temperature of steam provided by the primary heat source with a steamprime mover, providing a back pressure vessel with heat energy in the form of steamexiting from the steam prime mover and conveying heat energy from the back pressurevessel as source steam to a unit process wherein the method includes operating anenergy system designed and configured to operate at a design operation point for atemperature of the source steam of the back pressure vessel characterized in that the temperature of the source steam of the back pressure vessel is between 100 °C and141 °C at saturation pressure.

In the preferred mode, a heat engine for use in an arrangement for operating energysystem of a crude palm oil extraction plant which supplies exiting spent heat to at leasta portion of heating needs of crude palm oil extraction plant wherein the heat engine isdesigned and configured to operate at a design operation point for the spent heattemperature wherein spent heat temperature is between 115 °C and 141 °C.

The heat engine is a steam turbine and wherein the exiting spent heat is discharged assteam at a design operation pressure not greater than the saturation pressurecorresponding to the design operation temperature of the exiting spent heat.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned attributes and other features and advantages of this inventionand the manner of attaining them, will become more apparent and the invention itselfwill be better understood by reference to the following description of embodiments ofthe invention taken in conjunction with the accompanying drawings, wherein:

Figure 1 shows prior art information of design operation point temperature of the heatsource. The operating temperatures of the various unit processes of the palm oilextraction process and their respective steam usage are also indicated. The foregoingis for a typical 60 tonnes per hour fresh fruit bunches capacity mill. The typical routelengths and sizes of the steam distribution conduits to convey the source steam to theunit processes are indicated. Source steam as indicated is at about 4 bar pressure. .

Figures 2.1 and 2.2 show a prior art general arrangement using source steam at about4 bar design operating point pressure of prior art for heating in the continuous andpressurised batch sterilizers respectively.

Figures 3.1 and 3.2 show an embodiment of general arrangement using source steamat about 2 bar design operating point pressure as in the present invention for heating inthe continuous and pressurised batch sterilizers respectively.

Figures 4.1, 4.2, 4.3 and 4.4 show an embodiment of general arrangement usingsource steam at about 2 bar design operating point pressure as in the present inventionfor the various unit processes respectively.

Figure 5.1 shows a prior art embodiment of general arrangement of the source steamheader or back pressure vessel for using source steam at about 4 bar for designoperating point pressure supplying heat to the palm oil extraction processes.

Figure 5.2 shows an embodiment of general arrangement of the source steam headeror back pressure vessel for using source steam at about 2 bar for design operatingpoint pressure as in the present invention supplying heat to the palm oil extractionprocesses.

Figure 6 shows an embodiment of general arrangement consisting of heat engine orsteam turbine with exiting steam at about 2 bar for design operating point pressureconveyed to the back pressure vessel as source steam for the palm oil extractionprocesses.

Figures 7.1, 7.2, 7.3, 7.4, 7.5, 7.6 and 7.7 show embodiments of an arrangement of asteam turbine “STG” exiting steam from one or more exhaust ports where whole or partof the exiting steam at a pressure of the present invention is conveyed as source steamto impart its thermal energy to at least a portion of the palm oil mill process. A preferred embodiment of the present invention is detailed with reference to theaccompanying drawings. It is intended, however, that unless particularly specified,dimensions, material, relative positions and so forth of the constituent parts in theembodiments shall be interpreted as illustrative only and not as limitative of the scopeof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The temperature required for the various unit processes of the palm oil extractionprocess is at most about 110°C, that is, where pressurised batch sterilizers are used.Where continuous sterilizers are used, the maximum required temperature falls toabout 100°C. The foregoing provides opportunities to use low temperature heat sourceto meet the heating requirements of the palm oil extraction processes.

The energy system of a palm oil extraction plant can now be designed to operate at adesign operation point for a low temperature of the heat source to deliver the designoperation point improved performance and efficiency while sustaining the thermalenergy needs of the palm oil extraction process. Accordingly, subsystems,components, and controls are structured to meet the design operation point for the lowheat source temperature that deliver the design operation point improved performanceand energy efficiency.

The thermal energy from the heat source can preferably be conveyed by steam throughconduits to the unit processes to provide the heat required for the said processes. Thewhole process heating system comprising, the process steam distribution vesselpressure control settings, the conduits for conveying adequate process steam to thevarious unit processes from the source, flow control valves, steam traps, steam heatingcoils and steam dispersion nozzles will be designed based upon this design operationpoint for the low heat source temperature. A heat engine (for example, a steam turbine)having a design operating point of a corresponding low exiting spent heat temperaturecan be added to supply the required thermal energy for the process.

In this description the term ‘heat source’ refers to a source of heat from which anymedium gets an increase in temperature. It can refer to a place, a structure or mediafrom which heat can be extracted. In the context of the present specification ‘heatsource’ refers to the origin of the primary thermal energy for the palm oil extractionprocess heating. In prior art the origin referred to is the back pressure vessel wherein aheat source steam at a pressure of approximately 4 bar and a temperature of 144°Coriginates and this primary source of heat is then reduced in pressure and temperaturewhere necessary for supplying the heat demand of individual unit processes by way ofvarious means comprising, pressure reduction, de-superheating with water and heatingprocess water.

The back pressure vessel itself receives heat by means of two upstream supplies. Themain supply of heat is steam exiting from a steam prime mover and in the event of ashortfall, heat from a higher pressure steam available in the plant, for e.g. from a boiler,is suitably reduced in pressure and temperature and supplied from a make-up steamsupply arrangement. There are also instances of waste heat discharged at lowtemperatures from unit processes of the palm oil extraction process that are recoveredby way of energy-saving means and reused in other unit processes. But since thiswaste heat source is actually a reuse of the heat energy supplied, albeit at a lowertemperature, it should therefore not be considered as a heat source for the purposes ofthis specification. A ‘heat sink’ refers to an entity that absorbs heat without significant temperatureincrease.

The term ‘heat demand of the heat source' refers to the heat load demand the heatsource imposes onto the heat sink that is in thermal energy communication with the heat source in response to the heat source having to supply the heat load demand of aunit process of the palm oil extraction process.

The term ‘design operation point’ refers to a predetermined design operation conditioncomprising one or more parameters at various stages that can have an affect on agiven system. These parameters can include temperature, pressure and flow. Theseparameters are established at design time for optimal performance of the overallsystem for a particular plant. Accordingly, subsystems, components and controls arestructured to meet a design operation point for the one or more parameters to deliverthe design operation point performance of the system.

For example, thermal energy systems, and in particular power generation systems aretypically configured to operate at a design operation point for maximum efficiency.Thermal energy systems for heating use benefit in utilising thermal energy at higherefficiency where its heat source is of low temperature consistent with the processtemperature requirement. A heat engine, like a steam turbine gain in lower heat ratewhere it is designed for operation with low exiting spent heat temperature. An energysystem, for instance, a cogeneration system, can therefore achieve the target of higherthermal energy efficiencies and higher mechanical power output when structured tooperate at design operation point for the lower heat source temperature and lower heatengine spent heat temperature (spent heat temperature being consistent with the heatsource temperature) when operating in a combined heat and power mode.

For purposes of this specification, the terms ‘design operation point temperature’,‘design operation point pressures’ and ‘design operation point energy flow’ refer totemperature, pressure and heat energy flow respectively of such a design operation point for optimal efficiency of the energy system bearing in mind especially therelevance of heat source temperature and heat engine spent heat temperature.

The pressure value described in units of bar in the present specification refers toabsolute pressure, where the atmospheric pressure is approximately one bar.

By way of example, but not limitation, an embodiment of the invention is describedherein using heat source temperature of 120 °C and the temperature featuring in thedesign operation point of the energy system for a 60 tonnes per hour fresh fruitbunches (FFB) capacity mill. A heat source steam at about 2 bar saturation pressurethat corresponds to a heat source temperature of 120°C should be adequate to providethe heating needs of the pressurised batch sterilizer. Where continuous sterilizer isused, even lower source steam conditions can be considered to cater for its maximumrequired temperature of about 100°C. In view of this, a design operation point for 120°Cheat source temperature is recommended for efficient operation. In this instance tocater for the mill capacity, source steam of about 2 bar pressure and 27,000 kg/h flowproviding approximately 19 MW heat capacity is required in the design. The efficientuse of thermal energy in the steam at the lower pressure in the palm oil mill extractionprocess provides a conservative savings of about 10% steam usage over prior art.

Further, a source steam of about 2 bar pressure corresponding to the saturationpressure at 120 °C, offers an economic design of the steam distribution system forconveying the source steam as a carrier of heat from the source to the point of unitprocesses. Using source steam at the lower pressure improves heat utilization whilemaintaining the required process temperatures.

As a comparison, in prior art, for a similar capacity crude palm oil extraction plant,conventional energy systems have been designed with a design operation point for aheat source temperature of about 144 °C. Source steam of about 4 bar pressure and30,000 kg/h flow providing 21 MW heat capacity is made available in the design forprocess heating.

Figures 1, 2.1 and 2.2 show sections of the energy system designed to operate atdesign operation point for a heat source temperature of about 144 °C i.e temperature ofthe prior art for providing the thermal energy needs of the palm oil extraction process.The heat energy from the heat source is supplied as source steam wherein the sourcesteam is used as the medium for conveying the heat energy to the processes. Thecorresponding pressure of the source steam is about 4 bar, which is the saturationsteam pressure and sometimes the source steam is at a slight superheat. A typical sizeof the conduit conveying the source steam at 4 bar pressure to the unit processes isshown in figures.

The invention is characterised in using a heat source of a temperature lower thanabout 144 °C of the prior art and having the energy system designed to operate at adesign operation point for the low temperature of the heat source to deliver the designoperation point improved performance and efficiency while sustaining the thermalenergy needs of at least a portion of the palm oil extraction process. Accordingly, theenergy system is designed to operate at a design operation point for the heat sourcetemperature between 115 °C and 141 °C. Preferably, the energy system is designed tooperate at a design operation point for a heat source temperature between 115 °C and138 °C. The energy system designed to operate at a design operation point for a heatsource temperature between 115 °C to 130 °C is more preferred, and the energysystem designed to operate at a design operation point for a heat source temperature between greater than 100 °C and less than 115 °C is most preferred to provide thethermal energy needs of at least a portion of the palm oil extraction process. The heatsource design operation point temperatures are sufficient to permit the transfer of heatto the unit processes receiving the thermal energy.

An object of the present invention is to conserve heat energy while providing therequired process temperatures of the palm oil extraction process. By way of example,but not limitation, Figures 3.1, 3.2, 4.1, 4.2, 4.3, 4.4 and 4.5 show the embodiments ofthe invention using heat source temperature of 120 °C and the energy system designedto operate at a design operation point for the heat source temperature of 120 °C todeliver the design operation point improved performance and efficiency while sustainingthe thermal energy needs of the palm oil extraction process.

The heat energy from the source is directly conveyed by steam through conduits to theunit processes to provide the heat. The source steam is at about 2 bar pressurecorresponding to the saturation pressure at the heat source temperature.

The conduits to convey the required amount of source steam at a low pressure to theunit processes are sized such that the velocity of flow does not exceed 40 m/s and thepressure drop along the conduit satisfies the pressure required at the point ofapplication as regards its saturation temperature. At low steam pressure the specificvolume of the steam is high and this leads to increased steam flow velocity in theconduit, but this can be limited by using conduits of a larger cross sectional area. Theroute length of conduits in a palm oil mill is relatively short, of within about 100 metresand therefore the velocity of flow is the limiting factor, rather than the pressure drop, insizing steam flow conduits. The flow control valves on the circuits are similarly sized forthe higher specific volume of the steam. The steam traps in the circuits are selected based on the lower lifting pressure exerted on the condensate by the lower steampressure in the steam coils. The steam flow velocity is kept within limits to ensure noiselevels and erosion is within acceptable industry standards.

To convey the source steam at 2 bar to a continuous sterilizer having cooking capacityof 30 tonnes/ hour fresh fruit bunches, operating at atmospheric pressure andconsuming steam at an approximate 11,500 kg/h requires a 300 mm nominal diameterpipe, to keep the steam flow velocity below 40 m/s. Taking the pipe route equivalentlength at 100m, the pressure drop is small at about 0.05 bar. Critical flow (chocking atsonic velocity) occurs at a downstream pressure of approximately 1.07 bar. A flowlimiting device like an orifice plate with an orifice size of approximately 135 mmdiameter is therefore fitted at the downstream to limit the steam flow capacity and thusthe velocity in the distribution conduit. As an alternate solution two numbers of 200 mmnominal diameter pipes are provided in parallel, keeping the steam flow velocity below40 m/s.

To convey source steam at 2 bar to a batch sterilizer having cooking capacity of 30tonnes/ hour fresh fruit bunches, operating at minimum at about 1.5 bar peak steampressure and consuming steam at an approximate 15,000 kg/h, requires two numbersof 250 mm nominal diameter pipe in parallel, each conduit conveying 7,500 kg/h steamand keeping the steam flow velocity below 40 m/s. Taking the pipe route equivalentlength at 100m, the pressure drop is small at about 0.05 bar. Critical flow (chocking atsonic velocity) occurs at downstream pressure of approximately 1.07 bar. A flow limitingdevice like an orifice plate with an orifice size of approximately 115 mm diameter istherefore fitted at the downstream to limit the steam flow capacity and thus the velocityin the distribution conduit. As the pressure in the sterilizer vessel gradually rises toabout 1.5 bar corresponding to 110°C saturated steam temperature, the steam flow capacity across the orifice reduces to 6,000 kg/h and this is acceptable because at thisstage of the process cycle the steam consumption by the sterilizer is much reduced.De-aeration and condensate removal facility is adequately designed to expel copiousamount of air and condensate from the vessel.

To convey source steam at 2 bar to nut and kernel dryers operating at about 1.5 barsteam pressure in the heating coils and consuming steam at an approximate 2,500kg/h, requires 150 mm nominal diameter pipe to keep the steam flow velocity below 40m/s. Taking the pipe route equivalent length at 100m, the pressure drop is small atabout 0.08 bar. An allowance of about 0.4 bar is provided for pressure drop across flowcontrol valve.

Similar principles apply for sizing all conduits that convey source steam to the variousunit processes.

Where heat transfer to the process is by means of steam heating coils, the design ofthe steam heating coils takes into consideration the heating surface area and tube sizeto cater for the lower steam saturation temperature and higher steam specific volumecorresponding to the reduced steam pressure.

Another object of the present invention is to increase the mechanical power output andefficiency by expanding whole or part of thermodynamic medium through a heat engineas the prime mover to a low temperature heat sink that is in heat energycommunication means with the heat source for supplying at least a portion of processheating requirement of the palm oil extraction process. The heat energy communicationmay be by means of fluid communication or heat exchange communication.

An embodiment to realise the operation of the prime mover at higher mechanical poweroutput and efficiency by expanding steam as the thermodynamic medium to a heat sinkat temperature lower than 144 °C featuring in design operation point of the energysystem is shown in Figures 5.2 and 6, and herein described.

Figure 5.1 shows a schematic flow diagram of prior art typical arrangement fordistribution of the steam exiting from a prime mover as source steam for process use tothe palm oil extraction process through the back pressure vessel..

Figure 5.2 shows a schematic flow diagram of the arrangement for distribution of thesteam exiting from prime mover such as heat engine as source steam to at least aportion of the palm oil extraction process through the back pressure vessel according tothe present invention. A difference in Figure 5.2 when compared to Figure 5.1 of the prior art is the value ofthe design operation point temperature of the heat source, which is lower than the priorart design operation point temperature of 144 °C. Another difference is the lowerpressure settings of the steam make-up and relief facilities and yet another difference isthe increase in the size of conduits conveying steam to provide for the higher specificvolume of the steam at the lower pressure.

By way of example but not limitation, Figure 6 shows a schematic flow diagram of anarrangement comprising a heat engine such as steam turbine according to the presentinvention.

An energy system, including a heat engine, as depicted in Figure 6, may be designedto operate at a design operation point for the temperature of heat source, temperature of heat engine exiting spent heat, or both (spent heat temperature being consistent withthe heat source temperature and heat engine design optimised). Accordingly,subsystems, components, and controls are structured to meet the design operationpoint heat source temperature, heat engine exiting spent heat temperature, or both(spent heat temperature being consistent with the heat source temperature and heatengine design optimised) that deliver the design operation point improved performanceand efficiency.

Steam from a primary heat source at high pressure and temperature enters steamturbine (2) through conduit (1) and is expanded to generate mechanical energy, whichis converted by generator (12) into electrical energy. The steam exiting the steamturbine via exit port (3) is at low pressure and is conveyed through conduit (4) to aprocess steam distribution back pressure vessel (5) where it is used as source steamfor at least a portion of the palm oil extraction processes. The inlet steam condition tothe turbine is about 22 bar pressure and about 300°C temperature. The embodimentshows the energy system designed to operate at a design operation point for a heatsource temperature of 120 °C to deliver the design operation point improvedperformance and efficiency. The source steam for the process in the back pressurevessel is at design operation point temperature of about 120 °C and 2 bar pressure.

The conduit (4) conveying the exhaust steam from the steam turbine exit port to theback pressure vessel (5) is sized for the increased steam specific volume at the lowerworking pressure in order to limit the steam flow velocity to 25 m/s. Thus for a steamturbine exiting approximately 27,000 kg/h steam, the exhaust conduit is 600 mmnominal diameter to keep the steam flow velocity within limits. Taking the conduitequivalent length at 20m, the pressure drop is negligible.

The embodiment consists of a steam turbine designed to operate at a design operationpoint for the heat engine exiting spent heat temperature of 120 °C to deliver the designoperation point improved performance and efficiency. A steam turbine is designed andsupplied by the manufacturer for incorporation into an energy system to specificationsof its design operation point for exiting spent heat temperature and pressure, andsteam flow among others, as determined by energy system requirement. In thisinstance the steam turbine has a steam throughput about 27,000 kg/h to cater for themill capacity. The inlet steam condition at design operation point is opted to provide drysaturated steam at the turbine exhaust. The expansion of steam to lower pressure atthe turbine exhaust and higher internal efficiency of the steam turbine require a higherinlet steam temperature to maintain exit steam dry saturated. When the steam turbinegenerator is operated as described at the design operation point with an exiting spentheat temperature of 120 °C, it offers about 40% lower specific steam consumption overthe prior art arrangement. This results in about 40% more power, which is about 640kW in the present embodiment.

In this embodiment the steam turbine generator (STG) is on automatic frequencycontrol to maintain a constant electrical frequency from its coupled generator and underthis scheme of steam turbine control the exiting steam pressure is allowed to float whilemaintaining the constant frequency. The steam turbine exiting steam provides thesource steam for the process in the cogeneration configuration of the plant. In the eventof deviation from the design operation point, imbalance between the flow of steamexiting from the steam turbine and source steam consumption by the palm oil extractionprocess may occur that manifests in deviation of the steam pressure in the backpressure vessel. In order to maintain the exit steam pressure at the design operationpoint for efficient operation of the steam turbine, an external means of steam flow caters to balance the difference. It is also important to maintain the steam pressure atthe design operation point to provide stable process temperatures.

The external means to maintain design operation point pressure operates in the eventof decreasing source steam pressure, to admit high pressure steam from a primaryheat source through conduit (6) through the steam make-up with de-superheatingfacility (7). In the event of increasing source steam pressure during operation, excesssteam can be released through the steam relief facility (8). The valve arrangement (7)and the control of the back pressure vessel steam pressure is effected by anautomation control unit, which controls the positions of the valves of the valvearrangement (7) in dependency on the pressure, especially during start-up processes.Further, the control unit controls the position of a blow-off-valve (8). With efficientautomation the steam pressure in the back pressure vessel can be controlled within apredetermined range of set values. Accordingly in the embodiment, with the designoperation point exiting pressure of about 2 bar, the steam pressure can be easilymaintained within a range of about 1.85 bar to 2.15 bar providing satisfactory steamturbine and process operations. The pressure control facilities of valve arrangement (7)and blow-off-valve (8) are not expected to come into action during normal plantoperation having configured the steam turbine exit steam throughput in balance withthe process steam demand at the design operation point.

In another mode of operation, the steam turbine control can be set to maintain the backpressure by adjusting the power output to match the steam flow requirement, in whichinstance separate pressure control at the back pressure vessel is not required. Thismode of operation is efficient thermodynamically, because high pressure steam or reliefsteam does not come into action, however, a system to enable such an operation by taking up the varying power output must be in place like the steam turbine generatorelectrically tied in parallel operation with the grid or other prime mover.

The back pressure vessel (5) is fitted with a safety pressure relief device (9) to protectthe system against over pressure in the event of maloperation of the pressure controlfacilities of valve arrangement (7) and blow-off-valve (8).

It is another object of the invention that with the safety pressure relief device fitted atthe steam source, pressure vessels and devices fitted downstream on the processheating system can be designed for the low working pressure to effect cost savings.The back pressure vessel has a working pressure of about 2 bar and designed towithstand about 2.5 bar.

The source steam from the back pressure vessel (5) is conveyed to at least a portion ofthe palm oil extraction process via conduits (10).

The figures 7.1, 7.2, 7.3, 7.4, 7.5, 7.6 and 7.7 depict the embodiments of variations ofthe steam prime mover exhausting steam for use by the palm oil extraction process. Allembodiments depict whole or part of steam exiting from a heat engine designed tooperate at a design operation point for a exiting spent heat temperature of 120 °C todeliver the design operation point improved performance and efficiency while impartingthermal energy to at least a portion of a palm oil mill process to enhance overallefficiency of energy utilisation.

The depiction of the steam turbine (2) is highly simplified and would in some casescomprise more than one inlet and outlet ports operating at different inlet and outletsteam pressures and temperatures. The steam turbine in some cases comprises more than one cylinder coupled together. The steam turbine in some cases may be singlestage or multi-stage. The heat engine in some cases is a reciprocating steam engine.

According to the invention, the steam turbine (2) designed to operate at a designoperation point for a exiting spent heat temperature of 120 °C to deliver the designoperation point improved performance and efficiency imparts thermal energy to at leasta portion of the process heating requirements of the palm oil extraction process.

The present invention provides an arrangement for operating energy system of a crudepalm oil extraction plant which includes a primary heat source configured to provideheat energy in the form of high pressure and temperature steam, a steam prime moverconfigured to receive high pressure and temperature steam from the primary heatsource, a back pressure vessel configured to receive heat energy in the form of steamexiting from the steam prime mover, at least one unit process of the crude palm oilextraction plant requiring heat energy and at least one means configured to conveyheat energy from the back pressure vessel as source steam to the unit process whereinthe energy system is designed and configured to operate at a design operation point forthe temperature of the source steam of the back pressure vessel characterized in thatthe temperature of the source steam of the back pressure vessel is between 100 °Cand 141 °C at saturation pressure.

Preferably, the energy system is designed and configured to operate at a designoperation point for the temperature of the at least one heat source and wherein the atleast one heat source temperature is between 115 °C and 138 °C, and the energysystem designed and configured to operate at a design operation point for thetemperature of the at least one heat source and wherein the at least one heat sourcetemperature is between 115 °C and 130 °C is more preferred. Most preferred is where the energy system is designed and configured to operate at a design operation point forthe temperature of the at least one heat source and wherein the at least one heatsource temperature is between greater than 100 °C and less than 115 °C.

In the preferred arrangement, a heat sink is in heat energy communication with the heatsource for supplying the heat demand of the heat source and wherein the heat sink iscapable of receiving externally applied heat energy. A heat engine discharges its wholeor part of its spent heat energy to the heat sink. Accordingly, the heat engine is a steamturbine, and wherein whole or part of exiting heat from the steam turbine iscommunicated to the heat source through the exiting steam by fluid communication to aback pressure vessel.

It will be appreciated that in consistency with the heat sink temperature the heat engineis operated having the heat engine is designed and configured to operate at a designoperation point for the spent heat temperature wherein spent heat temperature isbetween 115 °C and 141 °C. Preferably, the heat engine is operated having the heatengine is designed and configured to operate at a design operation point for the spentheat temperature wherein spent heat temperature is between 115 °C and 138 °C. Morepreferred is where, the heat engine is operated having the heat engine is designed andconfigured to operate at a design operation point for the spent heat temperaturewherein spent heat temperature is between 115 °C and 130 °C. Most preferred iswhere the heat engine is operated having the heat engine is designed and configuredto operate at a design operation point for the spent heat temperature wherein spentheat temperature is between greater than 100 °C and less than 115 °C.

In the preferred mode, one of the unit processes is sterilization of fresh fruit bunches(FFB) by a continuous sterilizer or pressurised batch sterilizer. A pressure relief device is provided on the steam turbine exhaust to protect any equipment against a rise ofpressure of not more than 25% above the pre-designed operating pressure of thesteam turbine exhaust steam.

Furthermore, the present invention also provides a method for operating energy systemof a crude palm oil extraction plant which includes providing heat energy in the form ofhigh pressure and temperature steam from a primary heat source, reducing thepressure and temperature of steam provided by the primary heat source with a steamprime mover, providing a back pressure vessel with heat energy in the form of steamexiting from the steam prime mover and conveying heat energy from the back pressurevessel as source steam to a unit process wherein the method includes operating anenergy system designed and configured to operate at a design operation point for atemperature of the source steam of the back pressure vessel characterized in that thetemperature of the source steam of the back pressure vessel is between 100 °C and141 °C at saturation pressure.

Preferably, the method includes operating the energy system designed and configuredto operate at a design operation point for the temperature of the at least one heatsource and wherein the at least one heat source temperature is between 115 °C and138 °C, and the more preferred method includes operating the energy system designedand configured to operate at a design operation point for the temperature of the at leastone heat source and wherein the at least one heat source temperature is between 115°C and 130 °C. Most preferred method includes operating the energy system designedand configured to operate at a design operation point for the temperature of the at leastone heat source and wherein the at least one heat source temperature is betweengreater than 100 °C and less than 115 °C.

In the preferred method, a heat sink is in heat energy communication with the heatsource for supplying the heat demand of the heat source and wherein the heat sinkreceives externally applied heat energy. A heat engine discharges its whole or part ofits spent heat energy to the heat sink. Accordingly, the heat engine is a steam turbine,and wherein whole or part of the exiting heat from the steam turbine communicates withthe heat source by fluid communication to a back pressure vessel.

It will be appreciated that in consistency with the heat sink temperature the heat engineis operating having the heat engine designed and configured to operate at a designoperation point for the spent heat temperature wherein spent heat temperature isbetween 115 °C and 141 °C. Preferably, the heat engine is operating having the heatengine designed and configured to operate at a design operation point for the spentheat temperature wherein spent heat temperature is between 115 °C and 138 °C. Inmore preferred mode, the heat engine is operating having the heat engine designedand configured to operate at a design operation point for the spent heat temperaturewherein spent heat temperature is between 115 °C and 130 °C. In the most preferredmethod the heat engine is operating having the heat engine designed and configured tooperate at a design operation point for the spent heat temperature wherein spent heattemperature is between greater than 100 °C and less than 115 °C.

In the preferred mode, one of the unit processes is sterilization of fresh fruit bunches(FFB) by a continuous sterilizer or pressurised batch sterilizer. A pressure relief deviceprovided on the steam turbine exhaust protects any equipment against a rise ofpressure of not more than 25% above the pre-designed operating pressure of thesteam turbine exhaust steam.

In the preferred mode, a heat engine for use in an arrangement for operating energysystem of a crude palm oil extraction plant which supplies exiting spent heat to at leasta portion of heating needs of crude palm oil extraction plant wherein the heat engine isdesigned and configured to operate at a design operation point for the spent heattemperature wherein spent heat temperature is between 115 °C and 141 °C.

Preferably, the heat engine is designed and configured to operate at a designoperation point for the spent heat temperature wherein spent heat temperature isbetween 115 °C and 138 °C and in the more preferred mode the heat engine isdesigned and configured to operate at a design operation point for the spent heattemperature wherein spent heat temperature is between 115°C to 130°C. In the mostpreferred method the heat engine is designed and configured to operate at a designoperation point for the spent heat temperature wherein spent heat temperature isbetween greater than 100 °C and less than 115 °C

Accordingly, the heat engine is steam turbine and wherein the exiting spent heat isdischarged as steam at a design operation pressure not greater than the saturationpressure corresponding to the design operation temperature of the exiting spent heat.

While the present invention has been described as having a preferred design, it can befurther modified within the spirit and the scope of this disclosure. This application istherefore intended to cover any variations, uses or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover such departures fromthe present disclosure as come with a known or customer practice in the art to whichthis invention pertains.

While the preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious that such embodiments are provided by way ofexamples only. Numerous variations, changes and substitutions will occur to those ofskill in the art without departing from the invention herein. Accordingly it is intended thatthe invention be limited only by the spirit and scope of the appended claims.

Claims (3)

NEW CLAIMS 1 TO 30

1. An arrangement for operating energy system of a crude palm oil extraction plant whichincludes: a primary heat source configured to provide heat energy in the form of highpressure and temperature steam; a steam prime mover configured to receive high pressure and temperature steamfrom the primary heat source; a back pressure vessel configured to receive heat energy in the form of steamexiting from the steam prime mover; at least one unit process of the crude palm oil extraction plant requiring heatenergy; and at least one means configured to convey heat energy from the back pressurevessel as source steam to the unit process; wherein the energy system is designed and configured to operate at a design operationpoint for the temperature of the source steam of the back pressure vessel; characterized in that the temperature of the source steam of the back pressure vessel is between 100 °C and141 °C at saturation pressure.

2. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in Claim 1 further including a valve arrangement configured to reduce thepressure and temperature of steam received from the primary heat source, wherein theback pressure vessel is further configured to receive heat energy in the form of steamfrom the valve arrangement.

3. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in Claim 1 or 2, wherein the steam prime mover is a steam turbine having all orpart of its spent heat energy communicated to the back pressure vessel by exiting steamfrom the steam turbine. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in Claim 3, wherein a pressure relief device is provided on the steam turbineexhaust to protect any equipment against a rise of pressure of not more than 25% abovethe pre-designed operating pressure of the steam turbine exhaust steam. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in Claim 3 or 4, wherein the steam turbine exiting steam is discharged at apressure not greater than the saturation pressure corresponding to the temperature ofthe exiting steam. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 1 to 5, wherein the temperature of the source steam of theback pressure vessel is between 115 °C and 141 °C at saturation pressure. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 1 to 5, wherein the temperature of the source steam of theback pressure vessel is between 115 °C and 138 °C at saturation pressure. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 1 to 5, wherein the temperature of the source steam of theback pressure vessel is between 115 °C and 130 °C at saturation pressure. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 3 to 5, or as claimed in Claim 6 when dependent on anyone of Claims 3 to 5, wherein the steam turbine is designed and configured to operate ata design operation point for the temperature of the exiting steam, and wherein thetemperature of the exiting steam is between 115 °C and 141 °C at saturation pressure. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 3 to 5, or as claimed in Claim 7 when dependent on anyone of Claims 3 to 5, wherein the steam turbine is designed and configured to operate ata design operation point for the temperature of the exiting steam, and wherein thetemperature of the exiting steam is between 115 °C and 138 °C at saturation pressure. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 3 to 5, or as claimed in Claim 8 when dependent on anyone of Claims 3 to 5, wherein the steam turbine is designed and configured to operate ata design operation point for the temperature of the exiting steam, and wherein thetemperature of the exiting steam is between 115 °C and 130 °C at saturation pressure. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 6 to 11, wherein one of the unit processes is sterilization offresh fruit bunches (FFB) by a pressurised batch sterilizer. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 1 to 5, wherein the temperature of the source steam of theback pressure vessel is between greater than 100 °C and less than 115 °C at saturationpressure. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 3 to 5, or as claimed in Claim 13 when dependent on anyone of Claims 3 to 5, wherein the steam turbine is designed and configured to operate ata design operation point for the temperature of the exiting steam, and wherein thetemperature of the exiting steam is between greater than 100 °C and less than 115 °C atsaturation pressure. An arrangement for operating energy system of a crude palm oil extraction plant asclaimed in any one of Claims 6 to 11, 13 or 14, wherein one of the unit processes issterilization of fresh fruit bunches (FFB) by a continuous sterilizer. A method for operating energy system of a crude palm oil extraction plant which includes:providing heat energy in the form of high pressure and temperature steam from aprimary heat source; reducing the pressure and temperature of steam provided by the primary heatsource with a steam prime mover; providing a back pressure vessel with heat energy in the form of steam exitingfrom the steam prime mover; and conveying heat energy from the back pressure vessel as source steam to a unitprocess; wherein the method includes operating the energy system designed and configured tooperate at a design operation point for the temperature of the source steam of the backpressure vessel; characterized in that the temperature of the source steam of the back pressure vessel is between 100 °C and141 °C at saturation pressure. A method for operating energy system of a crude palm oil extraction plant as claimed inClaim 16, wherein the step of reducing the pressure and temperature of steam providedby the primary heat source also utilises a valve arrangement reducing the pressure andtemperature of steam received from the primary heat source. A method for operating energy system of a crude palm oil extraction plant as claimed inClaim 16 or 17, wherein the steam prime mover is a steam turbine having all or part of itsspent heat energy communicated to the back pressure vessel by receiving the exitingsteam from the steam turbine. A method for operating energy system of a crude palm oil extraction plant as claimed inClaim 18, wherein a pressure relief device provided on the steam turbine exhaustprotects any equipment against a rise of pressure of not more than 25% above the pre-designed operating pressure of the steam turbine exhaust steam. A method for operating energy system of a crude palm oil extraction plant as claimed inClaim 18 or 19, wherein the steam turbine exiting steam is discharged at a pressure notgreater than the saturation pressure corresponding to the temperature of the exitingsteam. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 16 to 20, wherein the temperature of the source steam of the backpressure vessel is between 115 °C and 141 °C at saturation pressure. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 16 to 20, wherein the temperature of the source steam of the backpressure vessel is between 115 °C and 138 °C at saturation pressure. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 16 to 20, wherein the temperature of the source steam of the backpressure vessel is between 115 °C and 130 °C at saturation pressure. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 18 to 20, or as claimed in Claim 21 when dependent on any one ofClaims 18 to 20, wherein the steam turbine is operated having the steam turbinedesigned and configured to operate at a design operation point for the temperature of theexiting steam, and wherein the temperature of the exiting steam is between 115 °C and141 °C at saturation pressure. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 18 to 20, or as claimed in Claim 22 when dependent on any one ofClaims 18 to 20, wherein the steam turbine is operated having the steam turbinedesigned and configured to operate at a design operation point for the temperature of theexiting steam, and wherein the temperature of the exiting steam is between 115 °C and138 °C at saturation pressure. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 18 to 20, or as claimed in Claim 23 when dependent on any one ofClaims 18 to 20, wherein the steam turbine is operated having the steam turbinedesigned and configured to operate at a design operation point for the temperature of theexiting steam, and wherein the temperature of the exiting steam is between 115 °C and130 °C at saturation pressure. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 21 to 26, wherein one of the unit processes is sterilization of fresh fruitbunches (FFB) by a pressurised batch sterilizer. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 16 to 20, wherein the temperature of the source steam of the backpressure vessel is between greater than 100 °C and less than 115 °C at saturationpressure. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 18 to 20, or as claimed in Claim 28 when dependent on any one ofClaims 18 to 20, wherein the steam turbine is operated having the steam turbinedesigned and configured to operate at a design operation point for the temperature of theexiting steam, and wherein the temperature of the exiting steam is between greater than100 °C and less than 115 °C at saturation pressure. A method for operating energy system of a crude palm oil extraction plant as claimed inany one of Claims 21 to 26, 28 or 29, wherein one of the unit processes is sterilization offresh fruit bunches (FFB) by a continuous sterilizer.