WO2012108756A1

WO2012108756A1 - Optimising the utilisation of renewable energy from biomass resources in the palm oil industry

Info

Publication number: WO2012108756A1
Application number: PCT/MY2012/000021
Authority: WO
Inventors: Krishna Moorthy PALANISAMY
Original assignee: Palanisamy Krishna Moorthy
Priority date: 2011-02-07
Filing date: 2012-02-03
Publication date: 2012-08-16
Also published as: DOP2013000173A; GB2507173A; MY178140A; CR20130383A; BR112013019721B1; AP3481A; PE20140822A1; ECSP13013000A; MX362776B; MX2013009108A; GB201315817D0; GT201300195A; CR20130382A; BR112013019721A2; GB2507173B

Abstract

The invention provides an arrangement for operating energy system of a crude palm oil extraction plant and method thereof. The arrangement for operating energy system of a crude palm oil extraction plant achieves the target of higher efficiency of energy utilisation by using heat source at a low temperature featuring in the design operation point of the energy system providing thermal energy to the palm oil extraction process. Accordingly, the present invention provides an arrangement for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the energy system is designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 115 °C and 141 °C. Preferably, the temperature of the at least one heat source is between 115 °C and 138 °C and the temperature of the at least one heat source is between 115 °C and 130 °C is more preferred. Most preferred is where the temperature of the at least one heat source is between greater than 100 °C and less than 115 °C.

Description

OPTIMISING THE UTILISATION OF RENEWABLE ENERGY FROM BIOMASS RESOURCES IN THE PALM OIL INDUSTRY

FIELD OF THE INVENTION

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

BACKGROUND OF THE INVENTION

Environmental considerations are increasing the economic interest in technologies which 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 environment by displacing the use of fossil fuel. But biomass is also a scarce energy resource and therefore it is imperative that the most efficient use be found for its energy potential to displace the maximum amount of fossil fuel and to reverse the harmful effects of fossil fuel burning on the environment.

In the Oil Palm milling industry, the electrical power required to operate a palm oil mill has steadily increased due to the additional electrically-operated machinery installed over the years for various needs, such as improving the mill process, controlling environmental pollution or meeting the demand for ever increasing residential electricity supply. To cater for this progressively growing electrical power need, boilers of higher and higher steam pressure and temperature and higher efficiency steam prime mover driven electrical generators were introduced. Existing low pressure boilers cannot be modified for operation at higher pressure due to design constrains and therefore replacement with new boilers with higher design pressure and temperatures were necessary. Several existing palm oil mills have circumvented installation of new boilers by resorting to operating diesel engine driven generators to supplement the steam turbine generator capacity. Others have resorted to purchasing electricity from the grid. With reference to any thermodynamic medium as a carrier of heat energy, in particular steam, the enthalpy of condensation provides the process heat, while the liquid enthalpy in the condensate is discharged from the local heating system.

Unit process temperatures are deliberately maintained relatively low to prevent deterioration of palm oil and kernel quality. Higher temperatures are known to cause oxidation of the palm oil and discolouration of kernels that affect subsequent bleach ability of the oils.

A source of heat for palm oil mill processes is steam exhausted from the steam prime mover which is distributed through conduits from the source to impart its thermal energy to various unit processes.

In prior art, the desired unit process temperatures are attained by using source steam at a pressure of about 4 bar the saturation pressure corresponding to 144 °C. The source steam that is conveyed to the vicinity of the unit processes in the mill is utilised as described below: i. The source steam is let down in pressure through two control valves in series and de-superheated by spray of water before it is introduced into the continuous sterilizer chamber, which is maintained at atmospheric pressure. The condensate from the chamber is drained by siphon action with steam seal and discharged to waste; The source steam is let into the pressurised batch sterilizer through an isolating valve in a . cycle of pressurising and depressurising to peak at about 2 bar pressure. Efficient de-aeration of the vessel is effected during warm-up cycle through slow steam admission using the de-aeration valve and air expelled through the lateral pipes on either side along the length of the vessel. The large quantity of condensate during warm-up is drained quickly to prevent flooding of the vessel and discharged to waste;

The source steam is de-superheated by spray of water and directly injected through nozzles into a post heating vessel for heating the fruits at atmospheric pressure;

The source steam is directly injected through nozzles into the digester to heat the "Mass passing through Digester", MPD at atmospheric pressure. Where jacket heating is employed condensate is drained through a steam trap and discharged to waste;

The source steam is let into the concentric heating jacket and maintained at full pressure to heat and facilitate moisture removal from the pressed cake passing through the cake breaker conveyor. Condensate is drained through a steam trap and discharged to waste;

The source steam is let into the hot water tank through by means of control valve and sparger to heat water for process dilution; The source steam is admitted into steam coils at full pressure to maintain temperature in several tanks to clarify and purify the palm oil. Condensate is drained through steam traps and discharged to waste;

The source steam is admitted through control valves and maintained at about full pressure in steam coils to heat ventilation air for the nut and kernel drying and 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 energy system of a crude palm oil extraction plant and improved method thereof. The improved arrangement for operating energy system of a crude palm oil extraction plant achieves the target of higher efficiency of energy utilisation by using heat source of a low temperature and having the energy system designed to operate at a design operation point for the low temperature of the heat source to deliver the design operation point improved performance and efficiency while sustaining the thermal energy needs of the palm oil extraction process.

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

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

In the palm oil extraction situation, observation of the various unit processes affirms that the process temperature requirements are relatively low, i.e., mostly no more than about 100 °C, except where batch sterilizers are used wherein the highest temperature required may go up to about 1 10 °C. Accordingly, the invention is directed to an energy system designed to operate at a design operation point for the low temperature of the heat source to deliver the design operation point improved performance and efficiency while sustaining the thermal energy needs of the palm oil extraction process. As an added option the energy system, concurrently by thermal energy communication means, provides a heat sink of correspondingly low temperature for a power cycle designed to operate and discharge its spent heat at the low sink temperature. Thus a further improvement in performance and efficiency of the energy system is attainable with whole or part of the spent heat rejected from the power cycle supplying at least a portion of the heat demand of the heat source at the lower temperature.

Accordingly, the present invention provides, amongst others, two schemes to improve the efficiency of energy utilisation in palm oil mills, namely: (i) the optimum utilisation of the heat energy inherent in the process heat source for the palm oil mill process; and

(ii) the optimal production of mechanical or electrical energy by a heat engine in the power cycle through expanding down the thermodynamic medium to a lower temperature 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 source of a low temperature feasible with the temperatures required for the palm oil extraction unit processes to impart its thermal energy to the process by an energy system designed to operate at a design operation point for the low temperature of the heat source 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 1 10 "C, a heat source of about 120 °C, as an example, presents sufficient temperature differential to drive heat transfer and satisfy the operating temperatures of the process. Accordingly, it would be beneficial to provide an energy system for the palm oil extraction plant that has improved performance and efficiency as compared to prior art systems.

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

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

The improvement in mechanical energy recovery in the heat engine increases with the downward divergence of the design operating point heat sink temperature which is induced by the temperature of the heat source featuring in the energy system design operation point.

Mechanical power output can be increased while retaining the existing boiler, by improving the boiler steam superheat temperature, incorporating steam turbine generator optimised for the new low exit pressure, installing devices to control the back pressure vessel pressure at the new value and implementing steam distribution changes to cater for the lower process steam source pressure. Accordingly, the present invention provides an arrangement for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the energy system is designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ^SC and 141 ⁵C.

Furthermore, the present invention also provides a method for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the method includes operating the energy system designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 115 ⁸C and 141 ⁸C.

In the preferred mode, a heat engine for use in an arrangement for operating energy system of a crude palm oil extraction plant which supplies exiting spent heat to at least a portion of heating needs of crude palm oil extraction plant wherein the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^QC and 141 ^SC. The heat engine is a steam turbine and wherein the exiting spent heat is discharged as steam at a design operation pressure not greater than the saturation pressure corresponding 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 invention and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

Figure 1 shows prior art information of design operation point temperature of the heat source. The operating temperatures of the various unit processes of the palm oil extraction process and their respective steam usage are also indicated. The foregoing is for a typical 60 tonnes per hour fresh fruit bunches capacity mill. The typical route lengths and sizes of the steam distribution conduits to convey the source steam to the unit 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 about 4 bar design operating point pressure of prior art for heating in the continuous and pressurised batch sterilizers respectively.

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

Figures 4.1 , 4.2, 4.3 and 4.4 show an embodiment of general arrangement using source steam at about 2 bar design operating point pressure as in the present invention for the various unit processes respectively. Figure 5.1 shows a prior art embodiment of general arrangement of the source steam header or back pressure vessel for using source steam at about 4 bar for design operating point pressure supplying heat to the palm oil extraction processes. Figure 5.2 shows an embodiment of general arrangement of the source steam header or back pressure vessel for using source steam at about 2 bar for design operating point pressure as in the present invention supplying heat to the palm oil extraction processes. Figure 6 shows an embodiment of general arrangement consisting of heat engine or steam turbine with exiting steam at about 2 bar for design operating point pressure conveyed to the back pressure vessel as source steam for the palm oil extraction processes. Figures 7.1 , 7.2, 7.3, 7.4, 7.5, 7.6 and 7.7 show embodiments of an arrangement of a steam turbine "STG" exiting steam from one or more exhaust ports where whole or part of the exiting steam at a pressure of the present invention is conveyed as source steam to 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 the accompanying drawings. It is intended, however, that unless particularly specified, dimensions, material, relative positions and so forth of the constituent parts in the embodiments shall be interpreted as illustrative only and not as limitative of the scope of the present invention. DETAILED DESCRIPTION OF THE INVENTION

The temperature required for the various unit processes of the palm oil extraction process is at most about 1 10^°C, that is, where pressurised batch sterilizers are used. Where continuous sterilizers are used, the maximum required temperature falls to about 100°C. The foregoing provides opportunities to use low temperature heat source to 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 a design operation point for a low temperature of the heat source to deliver the design operation point improved performance and efficiency while sustaining the thermal energy needs of the palm oil extraction process. Accordingly, subsystems, components, and controls are structured to meet the design operation point for the low heat source temperature that deliver the design operation point improved performance and energy efficiency.

The thermal energy from the heat source can preferably be conveyed by steam through conduits to the unit processes to provide the heat required for the said processes. The whole process heating system comprising, the process steam distribution vessel pressure control settings, the conduits for conveying adequate process steam to the various unit processes from the source, flow control valves, steam traps, steam heating coils and steam dispersion nozzles will be designed based upon this design operation point 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 temperature can 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 any medium gets an increase in temperature. It can refer to a place, a structure or media from which heat can be extracted. In the context of the present specification 'heat source' refers to the origin of the primary thermal energy for the palm oil extraction process heating. In prior art the origin referred to is the back pressure vessel wherein a heat source steam at a pressure of approximately 4 bar and a temperature of 144°C originates and this primary source of heat is then reduced in pressure and temperature where necessary for supplying the heat demand of individual unit processes by way of various means comprising, pressure reduction, de-superheating with water and heating process water.

The back pressure vessel itself receives heat by means of two upstream supplies. The main supply of heat is steam exiting from a steam prime mover and in the event of a shortfall, 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 steam supply arrangement. There are also instances of waste heat discharged at low temperatures from unit processes of the palm oil extraction process that are recovered by way of energy-saving means and reused in other unit processes. But since this waste heat source is actually a reuse of the heat energy supplied, albeit at a lower temperature, it should therefore not be considered as a heat source for the purposes of this specification.

A 'heat sink' refers to an entity that absorbs heat without significant temperature increase.

The term 'heat demand of the heat source' refers to the heat load demand the heat source 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 a unit process of the palm oil extraction process.

The term 'design operation point' refers to a predetermined design operation condition comprising one or more parameters at various stages that can have an affect on a given system. These parameters can include temperature, pressure and flow. These parameters are established at design time for optimal performance of the overall system for a particular plant. Accordingly, subsystems, components and controls are structured to meet a design operation point for the one or more parameters to deliver the design operation point performance of the system.

For example, thermal energy systems, and in particular power generation systems are typically configured to operate at a design operation point for maximum efficiency. Thermal energy systems for heating use benefit in utilising thermal energy at higher efficiency where its heat source is of low temperature consistent with the process temperature requirement. A heat engine, like a steam turbine gain in lower heat rate where it is designed for operation with low exiting spent heat temperature. An energy system, for instance, a cogeneration system, can therefore achieve the target of higher thermal energy efficiencies and higher mechanical power output when structured to operate at design operation point for the lower heat source temperature and lower heat engine spent heat temperature (spent heat temperature being consistent with the heat source 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 to temperature, pressure and heat energy flow respectively of such a design operation point for optimal efficiency of the energy system bearing in mind especially the relevance of heat source temperature and heat engine spent heat temperature.

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

By way of example, but not limitation, an embodiment of the invention is described herein using heat source temperature of 120 °C and the temperature featuring in the design operation point of the energy system for a 60 tonnes per hour fresh fruit bunches (FFB) capacity mill. A heat source steam at about 2 bar saturation pressure that corresponds to a heat source temperature of 120 °C should be adequate to provide the heating needs of the pressurised batch sterilizer. Where continuous sterilizer is used, even lower source steam conditions can be considered to cater for its maximum required temperature of about 100 °C. In view of this, a design operation point for 120 °C heat source temperature is recommended for efficient operation. In this instance to cater for the mill capacity, source steam of about 2 bar pressure and 27,000 kg/h flow providing approximately 19 W heat capacity is required in the design. The efficient use of thermal energy in the steam at the lower pressure in the palm oil mill extraction process provides a conservative savings of about 10% steam usage over prior art.

Further, a source steam of about 2 bar pressure corresponding to the saturation pressure at 120 °C, offers an economic design of the steam distribution system for conveying the source steam as a carrier of heat from the source to the point of unit processes. Using source steam at the lower pressure improves heat utilization while maintaining 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 a heat source temperature of about 144 °C. Source steam of about 4 bar pressure and 30,000 kg/h flow providing 21 W heat capacity is made available in the design for process heating.

Figures 1 , 2.1 and 2.2 show sections of the energy system designed to operate at design operation point for a heat source temperature of about 144 °C i.e temperature of the 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 source steam is used as the medium for conveying the heat energy to the processes. The corresponding pressure of the source steam is about 4 bar, which is the saturation steam pressure and sometimes the source steam is at a slight superheat. A typical size of the conduit conveying the source steam at 4 bar pressure to the unit processes is shown in figures.

The invention is characterised in using a heat source of a temperature lower than about 144 °C of the prior art and having the energy system designed to operate at a design operation point for the low temperature of the heat source to deliver the design operation point improved performance and efficiency while sustaining the thermal energy needs of at least a portion of the palm oil extraction process. Accordingly, the energy system is designed to operate at a design operation point for the heat source temperature between 1 15 ⁸C and 141 ^aC. Preferably, the energy system is designed to operate at a design operation point for a heat source temperature between 1 15 ^SC and 138 ^aC. The energy system designed to operate at a design operation point for a heat source temperature between 115 ^QC to 130 ^SC is more preferred, and the energy system designed to operate at a design operation point for a heat source temperature between greater than 100 ^eC and less than 1 15 ^SC is most preferred to provide the thermal energy needs of at least a portion of the palm oil extraction process. The heat source design operation point temperatures are sufficient to permit the transfer of heat to the unit processes receiving the thermal energy.

An object of the present invention is to conserve heat energy while providing the required 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 of the invention using heat source temperature of 120 °C and the energy system designed to operate at a design operation point for the heat source temperature of 120 °C to deliver the design operation point improved performance and efficiency while sustaining the thermal energy needs of the palm oil extraction process.

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

The conduits to convey the required amount of source steam at a low pressure to the unit processes are sized such that the velocity of flow does not exceed 40 m/s and the pressure drop along the conduit satisfies the pressure required at the point of application as regards its saturation temperature. At low steam pressure the specific volume of the steam is high and this leads to increased steam flow velocity in the conduit, but this can be limited by using conduits of a larger cross sectional area. The route length of conduits in a palm oil mill is relatively short, of within about 100 metres and therefore the velocity Of flow is the limiting factor, rather than the pressure drop, in sizing steam flow conduits. The flow control valves on the circuits are similarly sized for the 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 steam pressure in the steam coils. The steam flow velocity is kept within limits to ensure noise levels and erosion is within acceptable industry standards. To convey the source steam at 2 bar to a continuous sterilizer having cooking capacity of 30 tonnes/ hour fresh fruit bunches, operating at atmospheric pressure and consuming steam at an approximate 1 1 ,500 kg/h requires a 300 mm nominal diameter pipe, to keep the steam flow velocity below 40 m/s. Taking the pipe route equivalent length at 100m, the pressure drop is small at about 0.05 bar. Critical flow (chocking at sonic velocity) occurs at a downstream pressure of approximately 1 .07 bar. A flow limiting device like an orifice plate with an orifice size of approximately 135 mm diameter is therefore fitted at the downstream to limit the steam flow capacity and thus the velocity in the distribution conduit. As an alternate solution two numbers of 200 mm nominal diameter pipes are provided in parallel, keeping the steam flow velocity below 40 m/s.

To convey source steam at 2 bar to a batch sterilizer having cooking capacity of 30 tonnes/ hour fresh fruit bunches, operating at minimum at about 1 .5 bar peak steam pressure and consuming steam at an approximate 15,000 kg/h, requires two numbers of 250 mm nominal diameter pipe in parallel, each conduit conveying 7,500 kg/h steam and keeping the steam flow velocity below 40 m/s. Taking the pipe route equivalent length at 100m, the pressure drop is small at about 0.05 bar. Critical flow (chocking at sonic velocity) occurs at downstream pressure of approximately 1 .07 bar. A flow limiting device like an orifice plate with an orifice size of approximately 115 mm diameter is therefore fitted at the downstream to limit the steam flow capacity and thus the velocity in the distribution conduit. As the pressure in the sterilizer vessel gradually rises to about 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 this stage of the process cycle the steam consumption by the sterilizer is much reduced. De-aeration and condensate removal facility is adequately designed to expel copious amount of air and condensate from the vessel.

To convey source steam at 2 bar to nut and kernel dryers operating at about 1 .5 bar steam pressure in the heating coils and consuming steam at an approximate 2,500 kg/h, requires 150 mm nominal diameter pipe to keep the steam flow velocity below 40 m/s. Taking the pipe route equivalent length at 100m, the pressure drop is small at about 0.08 bar. An allowance of about 0.4 bar is provided for pressure drop across flow control valve.

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

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

Another object of the present invention is to increase the mechanical power output and efficiency by expanding whole or part of thermodynamic medium through a heat engine as the prime mover to a low temperature heat sink that is in heat energy communication means with the heat source for supplying at least a portion of process heating requirement of the palm oil extraction process. The heat energy communication may be by means of fluid communication or heat exchange communication. An embodiment to realise the operation of the prime mover at higher mechanical power output and efficiency by expanding steam as the thermodynamic medium to a heat sink at temperature lower than 144 ^SC featuring in design operation point of the energy system is shown in Figures 5.2 and 6, and herein described.

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

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

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

Steam from a primary heat source at high pressure and temperature enters steam turbine (2) through conduit (1 ) and is expanded to generate mechanical energy, which is converted by generator (12) into electrical energy. The steam exiting the steam turbine via exit port (3) is at low pressure and is conveyed through conduit (4) to a process steam distribution back pressure vessel (5) where it is used as source steam for at least a portion of the palm oil extraction processes. The inlet steam condition to the turbine is about 22 bar pressure and about 300°C temperature. The embodiment shows the energy system designed to operate at a design operation point for a heat source temperature of 120 °C to deliver the design operation point improved performance and efficiency. The source steam for the process in the back pressure vessel 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 the back pressure vessel (5) is sized for the increased steam specific volume at the lower working pressure in order to limit the steam flow velocity to 25 m/s. Thus for a steam turbine exiting approximately 27,000 kg/h steam, the exhaust conduit is 600 mm nominal diameter to keep the steam flow velocity within limits. Taking the conduit equivalent length at 20m, the pressure drop is negligible. The embodiment consists of a steam turbine designed to operate at a design operation point for the heat engine exiting spent heat temperature of 120 °C to deliver the design operation point improved performance and efficiency. A steam turbine is designed and supplied by the manufacturer for incorporation into an energy system to specifications of its design operation point for exiting spent heat temperature and pressure, and steam flow among others, as determined by energy system requirement. In this instance the steam turbine has a steam throughput about 27,000 kg/h to cater for the mill capacity. The inlet steam condition at design operation point is opted to provide dry saturated steam at the turbine exhaust. The expansion of steam to lower pressure at the turbine exhaust and higher internal efficiency of the steam turbine require a higher inlet steam temperature to maintain exit steam dry saturated. When the steam turbine generator is operated as described at the design operation point with an exiting spent heat temperature of 120 °C, it offers about 40% lower specific steam consumption over the prior art arrangement. This results in about 40% more power, which is about 640 kW in the present embodiment.

In this embodiment the steam turbine generator (STG) is on automatic frequency control to maintain a constant electrical frequency from its coupled generator and under this scheme of steam turbine control the exiting steam pressure is allowed to float while maintaining the constant frequency. The steam turbine exiting steam provides the source steam for the process in the cogeneration configuration of the plant. In the event of deviation from the design operation point, imbalance between the flow of steam exiting from the steam turbine and source steam consumption by the palm oil extraction process may occur that manifests in deviation of the steam pressure in the back pressure vessel. In order to maintain the exit steam pressure at the design operation point 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 at the design operation point to provide stable process temperatures.

The external means to maintain design operation point pressure operates in the event of decreasing source steam pressure, to admit high pressure steam from a primary heat source through conduit (6) through the steam make-up with de-superheating facility (7). In the event of increasing source steam pressure during operation, excess steam 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 an automation control unit, which controls the positions of the valves of the valve arrangement (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 efficient automation the steam pressure in the back pressure vessel can be controlled within a predetermined range of set values. Accordingly in the embodiment, with the design operation point exiting pressure of about 2 bar, the steam pressure can be easily maintained within a range of about 1.85 bar to 2.15 bar providing satisfactory steam turbine 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 plant operation having configured the steam turbine exit steam throughput in balance with the process steam demand at the design operation point. in another mode of operation, the steam turbine control can be set to maintain the back pressure by adjusting the power output to match the steam flow requirement, in which instance separate pressure control at the back pressure vessel is not required. This mode of operation is efficient thermodynamically, because high pressure steam or relief steam 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 generator electrically 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 protect the system against over pressure in the event of maloperation of the pressure control facilities of valve arrangement (7) and blow-off-valve (8).

It is another object of the invention that with the safety pressure relief device fitted at the steam source, pressure vessels and devices fitted downstream on the process heating 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 to withstand about 2.5 bar.

The source steam from the back pressure vessel (5) is conveyed to at least a portion of the 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 of the steam prime mover exhausting steam for use by the palm oil extraction process. All embodiments depict whole or part of steam exiting from a heat engine designed to operate at a design operation point for a exiting spent heat temperature of 120 °C to deliver the design operation point improved performance and efficiency while imparting thermal energy to at least a portion of a palm oil mill process to enhance overall efficiency of energy utilisation. The depiction of the steam turbine (2) is highly simplified and would in some cases comprise more than one inlet and outlet ports operating at different inlet and outlet steam pressures and temperatures. The steam turbine in some cases comprises more than one cylinder coupled together. The steam turbine in some cases may be single stage 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 design operation point for a exiting spent heat temperature of 120 °C to deliver the design operation point improved performance and efficiency imparts thermal energy to at least a portion of the process heating requirements of the palm oil extraction process.

In most preferred mode, the present invention provides an arrangement for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the energy system is designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 115 ⁹C and 141 ⁸C.

Preferably, the energy system is designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ^SC and 138 ^SC, and the energy system designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ^SC and 130 ^SC is more preferred. Most preferred is where the energy system is designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between greater than 100 °C and less than 1 15 °C. In the preferred arrangement, a heat sink is in heat energy communication with the heat source for supplying the heat demand of the heat source and wherein the heat sink is capable of receiving externally applied heat energy. A heat engine discharges its whole or part of its spent heat energy to the heat sink. Accordingly, the heat engine is a steam turbine, and wherein whole or part of exiting heat from the steam turbine is communicated to the heat source through the exiting steam by fluid communication to a back pressure vessel.

It will be appreciated that in consistency with the heat sink temperature the heat engine is operated having the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^QC and 141 ⁸C. Preferably, the heat engine is operated having the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^BC and 138 ⁸C. More preferred is where, the heat engine is operated having the heat engine is designed and configured to Operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^SC and 130 ⁵C. Most preferred is where the heat engine is operated having the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between greater than 100 °C and less than 1 15 ^SC.

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 of pressure of not more than 25% above the pre-designed operating pressure of the steam turbine exhaust steam. Furthermore, the present invention also provides a method for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the method includes operating the energy system designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ^flC and 141 ^SC.

Preferably, the method includes operating the energy system designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ^SC and 138 ^SC, and the more preferred method includes operating the energy system designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ^SC and 130 ⁸C. Most preferred method includes operating the energy system designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between greater than 100 °C and less than 1 15 °C. In the preferred method, a heat sink is in heat energy communication with the heat source for supplying the heat demand of the heat source and wherein the heat sink receives externally applied heat energy. A heat engine discharges its whole or part of its 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 with the heat source by fluid communication to a back pressure vessel. It will be appreciated that in consistency with the heat sink temperature the heat engine is operating having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 °C and 141 ^SC. Preferably, the heat engine is operating having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^SC and 138 ^SC. In more preferred mode, the heat engine is operating having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^SC and 130 ^BC. In the most preferred method the heat engine is operating having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between greater than 100 °C and less than 1 15 °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 provided on the steam turbine exhaust protects any equipment against a rise of pressure of not more than 25% above the pre-designed operating pressure of the steam turbine exhaust steam. In the preferred mode, a heat engine for use in an arrangement for operating energy system of a crude palm oil extraction plant which supplies exiting spent heat to at least a portion of heating needs of crude palm oil extraction plant wherein the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^SC and 141 ⁸C.

Preferably, the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^SC and 138 ^SC and in the more preferred mode the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 115^SC to 130^SC. In the most preferred method the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between greater than 100 °C and less than 1 15 °C

Accordingly, the heat engine is steam turbine and wherein the exiting spent heat is discharged as steam at a design operation pressure not greater than the saturation pressure 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 be further modified within the spirit and the scope of this disclosure. This application is therefore intended to cover any variations, uses or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come with a known or customer practice ίη the art to which this invention pertains.

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

Claims

CLAIMS:

1. An arrangement for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the energy system is designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ^SC and 141 ^SC. 2. An arrangement for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat wherein the energy system is designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ^SC and 138 ^SC.

An arrangement for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at one means to communicate heat from the at one heat source to a unit process requiring wherein the energy system is designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ⁸C and 130 ⁵C.

An arrangement for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at one means to communicate heat from the at one heat source to a unit process requiring wherein the energy system is designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between greater than 100 ^SC and less than 1 15 ^SC.

An arrangement for operating energy system of a crude palm oil extraction plant as claimed in any of Claims 1 , 2, 3 or 4, wherein a heat sink is in thermal energy communication with the heat source and wherein the heat sink is capable of receiving externally applied heat energy.

An arrangement for operating energy system of a crude palm oil extraction plant as claimed in Claim 5, wherein a heat engine discharges its whole or part of its spent heat energy to the heat sink.

An arrangement for operating energy system of a crude palm oil extraction plant as claimed in Claim 6, wherein the heat engine is a steam turbine, and wherein whole or part of exiting steam from the steam turbine is communicated to the heat source through the exiting steam by fluid communication to a back pressure vessel.

8. An arrangement for operating energy system of a crude palm oil extraction plant as claimed in any of Claims 1 , 2, 3, or 4, wherein one of the unit processes is sterilization of fresh fruit bunches (FFB) by a continuous sterilizer or pressurised batch sterilizer.

An arrangement for operating energy system of a crude palm oil extraction plant as claimed in Claim 7, wherein a pressure relief device is provided on the steam turbine exhaust to protect any equipment against a rise of pressure of not more than 25% above the pre-designed operating pressure of the steam turbine exhaust steam.

10. A method for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the method includes using operating a energy system designed and configured to operate at a design operation point for a temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ⁸C and 141 ²C.

A method for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the method includes operating the energy system designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ^SC and 138 ⁸C. 12. A method for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the method includes operating the energy system designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between 1 15 ⁸C and 130 ^aC.

13. A method for operating energy system of a crude palm oil extraction plant which includes at least one heat source and at least one means to communicate heat from the at least one heat source to a unit process requiring heat energy wherein the method includes operating the energy system designed and configured to operate at a design operation point for the temperature of the at least one heat source and wherein the at least one heat source temperature is between greater than 100 ^SC and less than 1 15 ²C.

14. A method for operating energy system of a crude palm oil extraction plant as claimed in any of Claims 10, 1 1 , 12 or 13, wherein a heat sink is in thermal energy communication with the heat source and wherein the heat sink receives externally applied heat energy.

15. A method for operating energy system of a crude palm oil extraction plant as claimed in Claim 14, wherein a heat engine is discharging its whole or part of its spent heat energy to the heat sink.

16. A method for operating energy system of a crude palm oil extraction plant as claimed in Claim 15, wherein the heat engine is a steam turbine, and wherein whole or part of exiting steam from the steam turbine is communicating with the heat source through the exiting steam by fluid communication to a back pressure vessel.

17. A method for operating energy system of a crude palm oil extraction plant as claimed in any of Claims 10, 1 1 , 12, or 13, wherein one of the unit processes is sterilization of fresh fruit bunches (FFB) by a continuous sterilizer or pressurised batch sterilizer.

18. An method for operating energy system of a crude palm oil extraction plant as claimed in Claim 16, wherein a pressure relief device provided on the steam turbine exhaust is protecting any equipment against a rise of pressure of not more than 25% above the pre-designed operating pressure of the steam turbine exhaust steam.

19. A heat engine for use in an arrangement for operating energy system of a crude palm oil extraction plant which supplies spent exiting heat to at least a portion of heating needs of crude palm oil extraction plant wherein the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^aC and 141 ⁸C.

20. A heat engine for use in an arrangement for operating energy system of a crude palm oil extraction plant which supplies spent exiting heat to at least a portion of heating needs of crude palm oil extraction plant wherein the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^BC and 138 ^aC.

A heat engine for use in an arrangement for operating energy system of a crude palm oil extraction plant which supplies spent exiting heat to at least a portion of heating needs of crude palm oil extraction plant wherein the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15^SC and 130^SC. 22. A heat engine for use in an arrangement for operating energy system of a crude palm oil extraction plant which supplies spent exiting heat to at least a portion of heating needs of crude palm oil extraction plant wherein the heat engine is designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between greater than 100^SC and less than 1 15^SC. 23. A heat engine for use in an arrangement for operating energy system of a crude palm oil extraction plant as claimed in any of Claims 19, 20, 21 or 22, wherein the heat engine is steam turbine and wherein the spent exiting heat is discharged as steam at a pressure equal to or lower than the saturation pressure corresponding to the temperature of the spent exiting heat.

24. An arrangement for operating energy system of a crude palm oil extraction plant as claimed in Claim 6, wherein the heat engine is operated having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^SC and 41 ⁸C.

25. An arrangement for operating energy system of a crude palm oil extraction plant as claimed in Claim 6, wherein the heat engine is operated having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^SC and 138 ⁸C.

26. An arrangement for operating energy system of a crude palm oil extraction plant as claimed in Claim 6, wherein the heat engine is operated having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^SC and 130 ⁵C.

27. An arrangement for operating energy system of a crude palm oil extraction plant as claimed in Claim 6, wherein the heat engine is operated having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between greater than 100 ^SC and less than 1 15 ^BC. 28. A method for operating energy system of a crude palm oil extraction plant as claimed in Claim 15, wherein the heat engine is operated having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^SC and 141 ^SC 29. A method for operating energy system of a crude palm oil extraction plant as claimed in Claim 15, wherein the heat engine operated having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ⁸C and 138 ²C. 30. A method for operating energy system of a crude palm oil extraction plant as claimed in Claim 15, wherein the heat engine is operated having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between 1 15 ^eC and 130 ⁸C 31 . A method for operating energy system of a crude palm oil extraction plant as claimed in Claim 15, wherein the heat engine is operated having the heat engine designed and configured to operate at a design operation point for the spent heat temperature wherein spent heat temperature is between greater than 100 ^SC and less than 1 15 ^BC.

32. An arrangement for operating energy system of a crude palm oil extraction plant as claimed in Claim 7, wherein the steam turbine spent exiting heat is discharged as steam at a pressure not greater than the saturation pressure corresponding to the temperature of the spent exiting heat.

A method for operating energy system of a crude palm oil extraction plant as claimed in Claim 16, wherein the steam turbine spent exiting heat is discharged as steam at a pressure not greater than the saturation pressure corresponding to the temperature of the spent exiting heat.