WO2007066120A1

WO2007066120A1 - Electrical power generation and oilseed processing method

Info

Publication number: WO2007066120A1
Application number: PCT/GB2006/004581
Authority: WO
Inventors: Clifford Spencer; Brian Edmunds; Martin Garrood
Original assignee: Springdale Renewable Energy Ltd
Priority date: 2005-12-08
Filing date: 2006-12-07
Publication date: 2007-06-14
Also published as: GB2433073A; GB0525026D0

Abstract

A method of generating electrical power comprises: pressing oilseed to produce oil and oilseed cake, the cake having a residual oil content; combusting the cake to generate heat energy; and converting at least a portion of the generated heat energy into electrical power. In certain embodiments the combusting comprises combusting the oilseed cake in a fluidised bed combustor. Electrical power generating apparatus is also described, the apparatus comprising: pressing apparatus for pressing oilseed to produce oil and oilseed cake, the cake having a residual oil content; a combustor arranged to combust cake from the pressing apparatus to generate heat energy; and means for converting at least a portion of the generated heat energy into electrical power.

Description

Electrical Power Generation and Oilseed Processing Method

Field of the Invention

The present invention relates to the fields of electrical power generation and the processing of oilseed, in particular, although not exclusively, rapeseed.

Background to the Invention

The combustion of fossil fuels to generate electrical power is well known, as is the associated problem of resultant emission of CO2 into the atmosphere.

Combustion of biomass sources such as fast-growing wood, straw, rice husks, and bagasse, to generate electricity is also known, and such techniques provide the environmental advantage of being substantially carbon neutral (in that the quantity of CO2 emitted when the biomass is burnt corresponds to the CO2 absorbed from the atmosphere as the plant source of the biomass grew). However, problems associated with such techniques include: the amount of pre-combustion processing of the biomass (each pre-processing step increases the complexity and cost of the overall power generation technique, and reduces overall efficiency); the energy costs associated with the transport of the low-financial value (and typically low-calorific value) materials to the combustion site; and difficulties in meeting emissions standards. Also, it is envisaged that an attempt to combine one or more of the known biomass fuel sources with a fossil fuel for co-combustion would pose pre-combustion processing difficulties.

Rapeseed, the seed of the rape plant, is a well-known oilseed crop. Rapeseed oil obtained from the rapeseed is used in a variety of applications. For example, it is used in the food industry, incorporated in edible products, such as margarine and cooking oil, and also is used in the production of so-called "biodiesel" for automotive use.

Conventionally, rapeseed oil is obtained from the rapeseed in a two-step process. Firstly, a proportion of the oil in the seed is mechanically expressed, for example using a screw pressing technique. This expelling is normally carried out with the seed conditioned to 95°C and 6-7% moisture content. The products of the expelling (or pressing) process are oil and residual biomass, which is conventionally described as "cake". The pressing process is not able to remove all of the oil from the seed and hence the cake has a residual oil content. The rapeseed initially contains

approximately 43% oil and, after expelling, the "cake" typically has an oil content of 18-20%. The second step in the process is solvent extraction of oil from the cake, typically using hexane. In other words, a solvent is used to obtain yet more oil from the rapeseed. The product of this solvent extraction is conventionally described as "meal", and typically contains approximately 1.5% oil. The oil from the expelling and extraction processes is typically combined (collected together) and contains gums (mainly phospholipids), which are then partially removed in a water degumming process. If the gums remain in the oil, processing efficiency during refining (to produce oil suitable for edible foodstuffs, for example) is significantly reduced and also costs are increased. An indication of the quantity of phospholipids present can be obtained by measuring the phosphorous content of the oil. As the gums are mostly phospholipids, the phosphorous level thus gives an indication of the quantity of gums in the oil. Conventionally produced crude rape oil (i.e. the direct product of the expelling and extraction process) has a phosphorus level typically over 200ppm.

The above-mentioned two-step process is the process conventionally used to obtain oil from rapeseed because the motivation has been to get as much oil out of the rapeseed as possible. This is because the oil is the relatively high value product (because of suitability for edible foodstuffs, and its other applications) and the byproduct, the meal, has very low value in comparison. Known uses of the meal are in animal feed, and fertiliser.

It is an object of certain embodiments of the present invention to provide electrical power generation methods and apparatus which overcome, at least partially, one or more of the problems associated with the prior art. It is an object of further embodiments to provide energy-efficient methods of processing oilseed, and in particular rapeseed. It is an object of yet further embodiments to provide improved methods of obtaining oil from oilseed, in particular rapeseed. Summary of the Invention

According to a first aspect of the present invention there is provided a method of generating electrical power comprising:

pressing oilseed to produce oil and oilseed cake, the cake having a residual oil content;

combusting the cake to generate heat energy; and

converting at least a portion of the generated heat energy into electrical power.

This aspect of the invention thus provides an environmentally friendly, carbon neutral method of generating electrical power, and represents a new use for the oilseed cake. Rather than using solvent extraction to remove yet more oil from the cake, the cake is combusted. The residual oil content assists in its combustion, and contributes to the calorific value of the cake (which is substantially higher than that of meal resulting from solvent extraction).

In certain embodiments the oilseed is rapeseed, but in other embodiments alternative oilseeds are used, e.g. sunflower, crambe, linseed, hemp.

In certain embodiments the oilseed (e.g. rapeseed) has an initial oil content in the range 42% to 44%, for example approximately 43%.

The pressing step (which may also be referred to as an expressing or expelling or crushing step) in certain embodiments is arranged such that the cake has a residual oil content in the range 10.5% to 13.5%, for example approximately 12%.

Conveniently, a screw press may be used to press the oilseed.

In certain embodiments the pressing comprises pressing the oilseed at a temperature in the range 60 to 95 degrees centigrade. In other embodiments, the pressing may be performed in -a lower temperature range, e.g. 60 to 80 degrees centigrade. In other words, steps may be taken to ensure that the temperature of the oilseed during the expression of oil remains within that temperature range. This has been found to provide the advantage, when pressing rapeseed in particular, that the expressed oil has very low gum levels, as evidenced by low phosphorous content. Pressing at higher temperatures in general enables more oil (a greater percentage) to be expelled, so it will be appreciated that pressing temperature may be selected/controlled to achieve a desired balance between gum levels and throughput.

The expelling may comprise pressing the oilseed at an elevated pressure by utilising the correct combination and specification of internal worms, breaker bars etc. to maintain an adequate throughput rate commensurate with the desired residual oil. This has also been found to assist in producing oil with low gum content. In other words, a desired residual oil level and/or a desired throughput rate may be achieved by adjustment/control of various parameters, including pressing pressure, and press structure/configuration.

The method may comprise one or more of the following steps before pressing: cleaning the oilseed (e.g. by sieving); reducing the moisture content of the oilseed (e.g. by heating); and rolling the oilseed.

In certain embodiments the method also comprises mechanically processing the oilseed cake before combusting the cake, and this mechanical processing may comprise grinding the oilseed cake. The grinding may be arranged to produce a mean particle diameter in the range 0.8 to 1.2mm (e.g. approximately lmm), or even smaller. In certain embodiments it is advantageous for the grinding process to provide ground cake having a substantially uniform particle size, for combustion in a fiuidised bed combustor for example.

Thus, the combusting step may comprise combusting the oilseed cake in a fiuidised bed combustor, which may be of the pressurised or atmospheric pressure type.

The step of converting in some embodiments comprises using the generated heat energy to raise steam, and then using the steam to drive a turbine coupled to an electrical generator.

The method may further comprise: combusting oilseed meal, produced by solvent extraction of residual oil from oilseed cake produced by pressing, to generate additional heat energy, and converting at least a portion of the additional generated heat energy into electrical power. Thus, the method may utilise a second fuel supply, in addition to the cake.

Certain embodiments further comprise: mixing the oilseed cake and meal together before combusting, and combusting the mixture. The proportions of the mixture may be arranged to give a desired overall calorific value, to suit current combustor requirements.

The mixture may be mechanically processed (e.g. ground) before combustion, which may be performed in a fluidised bed combustor.

In certain embodiments the oilseed cake provides substantially all of the combustible material supplied to the fluidised bed combustor (i.e. the cake is not mixed with other combustible material).

In other embodiments the oilseed cake and meal mixture provides substantially all of the combustible material supplied to the fluidised bed combustor.

The method may further comprise the step of combusting at least a portion of the expressed oil to generate further electrical power. This may be desirable if there is low demand for the expressed oil, or depending on the relative prices for generated electrical power and for the expressed oil. The expressed oil may be combusted in a reciprocating engine, and the method may then further comprise driving an electrical generator with the reciprocating engine to generate the further electrical power.

Another aspect of the invention provides electrical power generating apparatus comprising:

pressing apparatus for pressing oilseed to produce oil and oilseed cake, the cake having a residual oil content;

a combustor arranged to combust cake from the pressing apparatus to generate heat energy; and

means for converting at least a portion of the generated heat energy into electrical power/ In certain embodiments, the pressing apparatus and combustor are separated by a distance of no more than 0.5km providing the advantage that the relatively low- value cake does not have to be transported large distances to the combustor, thereby improving the overall efficiency of the energy generation process.

The apparatus may further comprise pre-processing apparatus arranged to process the oilseed before the pressing apparatus. This pre-processing apparatus may comprise one or more of the following: cleaning apparatus (e.g. a sieve) arranged to clean the oilseed; at least one heater arranged to heat the oilseed to reduce its moisture content; and at least one roller arranged to roll the oilseed before the pressing apparatus.

The pressing apparatus in some embodiments as adapted to maintain the oilseed at a temperature in the range 60 to 95 degrees centigrade during pressing, and in certain other embodiments 60 to 80 degrees centigrade.

The pressing apparatus may comprise a screw press, operable to provide a continuous output of cake and oil.

The apparatus may comprise grinding apparatus arranged to receive the cake and provide ground cake to the combustor, and the grinding apparatus may be arranged to produce ground cake having a mean particle size in the range 0.8 to 1.2mm, or even smaller.

In some embodiments the grinding apparatus is further arranged to receive a supply of oilseed meal, and to provide a mixture of ground cake and ground meal to the combustor.

The combustor in certain embodiments is a fluidised bed combustor (FBC). It may be an atmospheric pressure FBC, but in certain embodiments is a pressurised fluidised bed combustor, hot exhaust gases from the combustor being arranged to drive a gas turbine, the gas turbine being arranged to drive an electrical generator. The means for converting may comprise a boiler system arranged to produce steam using the heat energy, the apparatus further comprising a steam turbine arranged to be driven by said steam, and an electrical generator arranged to be driven by the steam turbine.

In some embodiments the apparatus further comprises a reciprocating engine arranged to drive an electrical generator, and means for supplying at least a portion of the expressed oil to the reciprocating engine for combustion in said engine.

Another aspect of the present invention provides a method of obtaining oil from an oilseed comprising pressing the oilseed at a temperature in the range 60 to 90 degrees centigrade to produce oil and oilseed cake, the cake having a residual oil content. In certain embodiments the pressing temperature may be no higher than 85, or even 80 degrees centigrade.

Again, the oilseed may, for example, be rapeseed; the oilseed may have an initial oil content in the range 42% to 44%, such as 43%; the cake may have a residual oil content in the range 10.5% to 13.5%, such as 12%.

The pressing may be performed using a screw press operating at an elevated pressure by utilising the correct combination and specification of internal worms, breaker bars etc. to maintain an adequate throughput rate commensurate with the desired residual oil.

The method may further comprise one or more of the following steps: cleaning the oilseed before pressing; reducing the moisture content of the oilseed before pressing; rolling the oilseed before pressing.

Another aspect of the invention provides a method of processing an oilseed, comprising:

combusting the cake to generate heat energy;

converting at least a portion of the generated heat energy into electrical power; supplying a proportion of t e produced oil to the foo industry; supplying a proportion of the produced oil for biodiesel production; and combusting a proportion of the produced oil to generate further electrical power.

Yet another aspect of the invention provides a method of processing an oilseed, comprising:

combusting the cake to generate heat energy;

converting at least a portion of the generated heat energy into electrical power; incorporating a proportion of the produced oil in an edible product;

using a proportion of the produced oil to produce biodiesel; and

combusting a proportion of the produced oil to generate further electrical power.

These methods may further comprise the step of determining the respective proportions according to market prices for the produced oil and for electrical power.

The step of combusting a proportion of the produced oil may comprise combusting the oil in a reciprocating engine arranged to drive an electrical generator.

The methods may further comprise the steps of:

combusting oilseed meal, produced by solvent extraction of oil from oilseed cake, to generate further heat energy; and

converting at least a portion of the further heat energy into electrical power.

Thus, methods embodying the invention may have the flexibility to utilise a plurality of fuel sources for energy generation, the relative proportions of the different sources being utilised at a particular time being determined according to market prices to optimise the economic and energy efficiency of the overall process. Brief description of the drawings

Embodiments of the invention will now be described with reference to the accompanying drawings, of which:

Fig 1 is a schematic representation of an electrical power generation method embodying the invention;

Fig 2 is a schematic representation of another power generation method embodying the invention;

Fig 3 is a schematic representation of part of a power generation method embodying the invention;

Fig 4 is a schematic representation of part of a power generation method embodying the invention;

Fig 5 is a schematic representation of part of another power generation method embodying the invention;

Fig 6 is schematic representation of part of another power generation method embodying the invention;

Fig 7 is a schematic representation of part of another electrical power generation method embodying the invention;

Fig 8 is a schematic representation of part of another power generation method embodying the invention;

Fig 9 is a schematic representation of part of another power generation method embodying the invention;

Fig 10 is a schematic representation of electrical power generating apparatus embodying the invention;

Fig 11 is a schematic representation of power generating apparatus in accordance with another embodiment of the invention;

Fig 12 is a schematic representation of a method of obtaining oil from an oilseed in accordance with another embodiment of the invention; and

Fig 13 is a schematic representation of an oilseed processing method embodying the invention. Detailed description of embodiments of the invention

Referring now to figure 1, in an electrical power generation method embodying the invention a quantity of oilseed 1 is pressed in a pressing step S2 (which may also be referred to as a crushing step) to produce oil 2. The residue from this process is known as oilseed cake 3, and this has a residual oil content (i.e. the pressing process does not express all of the oil from the oilseed). This cake 3 is then combusted in a combusting step S3, generating heat 4. Then, in a converting step S4, a portion of this heat 4 is converted into electrical power 5.

Referring now to figure 2, this shows a more detailed power generation method embodying the invention. In this method the oilseed 1 is rapeseed and contains approximately 43% oil. Before pressing (which may also be referred to as an expressing step) the rapeseed 1 is subjected to a series of preparatory processing steps

(which may also be referred to as pre-pressing steps). These comprise a cleaning step

SlO in which the rapeseed is cleaned using sieving to remove stones and non-seed plant matter, a heating step Sl 1, a rolling step S 12, and another heating step Sl 3. The heating and rolling steps produce flaked seeds of low moisture content ready for expelling the oil in the pressing (expressing) step S2. The heating and rolling steps

SIl, Sl 2, S13 in certain embodiments are arranged such that the moisture content in the flaked seeds supplied to the pressing step S2 is in the range to 6% to 7%. In the pressing step S2, a standard commercially available screw press is used, which is operated in a novel manner. In particular, the pressing is arranged to take place at an input temperature in the range 60 to 95°C. Furthermore, the processing conditions within the expeller, particularly in relation to pressure, temperature and throughput rate (i.e. the rate at which the prepared rapeseed is processed) is different from that in conventional expelling techniques. In particular, the specification and combination of the internal worms, breaker bars etc are optimised to achieve the desired residual oil content in the cake commensurate with throughput. The expelling of oil 2 under these novel conditions leaves a concentration of oil in the cake 3 of approximately 12%.

Also, by pressing under these conditions, the produced oil 2 has markedly lower levels of gums compared with the levels in oils obtained using the standard technique of expelling and extraction, hi the present embodiment the expressed oil 2 is then filtered in a filtering step S21, before undergoing a de-gumming step S22, finally resulting in a quantity of processed rapeseed oil 200. It will be appreciated, however, that in other embodiments the lower levels of gums in the expressed oil may mean that the de-gumming step S22 is not necessary. The cake 3, which is the other product of the pressing step S2, is then ground in a grinding step S23. The ground cake is then combusted (step S3) and the generated heat is then converted to electrical power 5 in step S4.

Referring now to figure 3, in an embodiment of the invention the oilseed cake 3 from the pressing process S2 undergoes a grinding step S31 to produce biomass fuel particles of substantially uniform size. The particle diameter may, for example, be approximately lmm or smaller. These fuel particles are then combusted in a fluidised bed combustor (step S3), generating heat which in step S40 is used to raise steam (i.e. it is used to vaporise supplied water). This steam is then used in step S41 to drive a steam turbine, which in turn is arranged to drive an electrical generator. Thus, in step S42 the electrical generator is driven to produce electrical power 5. It will be appreciated that steps S40, S41 and S42 together form a converting step S4, in which heat from the biomass combustion is converted to electrical power 5.

Referring now to figure 4, this shows part of another electrical power generation method embodying the invention. In this embodiment there is a secondary fuel stream, in addition to the oilseed cake 3 from the pressing process S2. The secondary fuel stream is a supply of oilseed meal 6 (e.g. rapeseed meal). This meal is the residue obtained when solvent extraction is used to extract a portion of the residual oil from the oilseed cake. Thus, the meal 6 has lower oil content then the cake 3. In the depicted method, both the cake 3 and meal 6 are combusted in the combusting step S3, with the resultant generated heat again being converted in step S4 to electrical power 5.

Figure 5 shows part of another power generation method embodying the invention and using both cake 3 and meal 6 supplies to fuel the combusting process. In this example, the two different fuel streams undergo a mixing and/or processing step S30 before the processed mixture is combusted. In certain embodiments this mixing and/or processing step S30 comprises mixing the cake 3 and meal 6 in a ratio selected to give a desired calorific value to the resultant processed mixture. Referring now to fig 6, this shows a further modification to the power generation method. In this example, the cake 3 and meal 6 are ground together in a grinding step S31 to give a ground mixture having a desired particle size (or particle size distribution). For example, the grinding step 31 may be arranged such that the particle size is reasonable uniform, and the average particle diameter may be lmm or smaller. The ground mixture is then supplied for combustion in a fluidised bed combustor (step S4).

Referring now to fig 7, this shows additional steps performed in another embodiment of the invention, hi addition to combusting cake (and optionally meal) to generate heat and electrical power, in this embodiment at least a portion of the oil 2 obtained from the pressing process S2 is combusted in a reciprocating engine (step S23). This engine is arranged to drive an electrical generator (step S24) and thus further electrical power 5 is generated from the oil 2. Depending on the pressing conditions, the oil 2 may be supplied directly to the reciprocating engine, or some intermediate processing may be required.

Figure 8 shows another electrical power generation method embodying the invention. Here the cake 3 from the pressing process is mechanically pfocessed in processing step S30. Optionally, a supply of oilseed meal 6 can also be processed in this step S30. The processed biomass is then combusted (in step S4) and the resultant heat used to generate steam in step S40. This steam is then used to drive a steam turbine'^step 41) which in turn is arranged to drive a generator (step 42). The method comprises the additional step S410 of recovering heat from the steam used to drive the turbine. The method comprises the final step S43 of supplying the generated electricity into the national grid.

Figure 9 shows part of another electricity generating method embodying the invention. Here, the cake 3 undergoes a fuel handling step S30. This may comprise mechanical processing and/or transportation (or conveying) of the cake to a combustor. Combustion set S4 generates heat which is supplied to a boiler (in step S40) that generates steam which drives a steam turbine (step S41). Again, some heat is recovered from the steam (step S410). The steam turbine drives a generator (step S42) to generate electrical power 5 which is supplied to the national grid in step S43. In this example, hot exhaust gases from the combustion process S4 are used to drive a gas turbine in step S420, the gas turbine itself being arranged to drive a further generator (step S42). The additional electrical power generated from the hot exhaust gases is also supplied to the national grid.

Referring now to figure 10, a power generation apparatus (which may also be referred to as a plant) embodying the invention comprises pressing apparatus 20 arranged to receive a supply of oilseed 1 and press (or crush) that oilseed to produce oil 2 and cake 3 having a residual oil content. The apparatus further comprises a combustor 30 arranged to receive and combust the cake 3 (either directly, or via some intermediate cake processing). The apparatus also comprises energy conversion means 40 arranged to convert at least a portion of the heat 4 generated by combustion of the oilseed cake 3 into electrical power 5. In this example the pressing apparatus and combustor are both located within an area having a diameter of 0.5 kilometres. This is advantageous as the relatively low value cake 3 (as compared with the relatively high value oil) has only to be transported (conveyed) a short distance to the combustor, thereby increasing the energy efficiency of the overall energy production process.

Referring now to figure 11, another power generation apparatus embodying the invention comprises a store 100 for storing a quantity of oilseed and supplying oilseed from that store or reservoir to the remainder of the apparatus. The apparatus further comprises a sieve 10 arranged to clean oilseed supplied from the store 100 by removing stones and other non-oilseed plant material, for example. A first heater 11 is then arranged to heat the sieved oilseed, and the heated seed is then fed through a roller system 12. The rolled seed is then passed through another heater 13. The combined action of the heaters 11, 13 and roller system 12 is to produce flaked oilseeds having a reduced moisture content (i.e. a moisture content lower than that in the stock of oilseed held in the store 100). On a general matter, it will be appreciated that although not shown in the figure the power generation apparatus also comprises means for conveying the oilseed and oilseed products between the illustrated components. The conveying means may comprise conveyer belts and/or other material handling equipment well known in the art. Returning to the features shown in figure 11, the pre-processed oilseed from the second heater 13 is supplied to pressing apparatus in the form of a screw press 20. Such presses are well known and include a rotating screw impeller which acts on the supplied oilseed. As a result of this continuous pressing action oil 2 is pressed out of the oilseed and is collected in a suitable containment vessel 20. Oilseed cake 3 having a residual oil content (lower, of course, than the oil content in the supplied oilseed) is continuously driven out of the screw press 20. The apparatus also comprises a grinder 31 arranged to receive the cake 3 and grind it to produce ground cake having a substantially uniform particle size. The apparatus also comprises means for introducing a secondary biomass fuel into the grinder (the secondary fuel source being oilseed meal, for example). The apparatus also comprises a combustor 30 in the form of a fluidised bed combustor. Fluidised bed combustors are well known types of combustor in which a mixture of fuel particles and inert particles, such as sand, is kept in fluidised motion by a continuous steam (e.g. updraft) of air. The mixture of fuel particles, inert material and fuel ash particles is known as the bed, and the constant mixing of particles as a result of turbulence in the mixed bed caused by the continuous stream of air encourages rapid heat transfer and complete combustion. In figure 11 the mixed bed of fuel particles (the ground cake particles), inert particles and ash is denoted by reference numeral 32. This bed is fluidised by air which is supplied to the combustor 30 via air inlet 301 and which streams or bubbles up through the bed 32 via apertures (e.g. nozzles) 33. In this example, the ground cake particles (and optionally the ground meal particles) are fed directly into the fluidised bed 32 via fuel inlet 300. However, it will be appreciated that in other embodiments the fuel particles may be introduced to the combustor at different locations, for example they may be introduced into a space above the fluidised bed 32. The apparatus includes a boiler system integrated with the fluidised bed so that the heat generated by combustion of the oil mass fuel particles can be used to raise steam. In this example the boiler system comprises pipe work 37 (which may more generally be referred to as a conduit), a portion of which is immersed in the fluidised bed 32. Water 370 supplied to this immersed portion is heated to such an extent that it vaporises and produces steam 371. This steam is conveyed by the boiler system to a steam turbine 372 and drives it. The steam turbine 372 is in turn coupled to an electrical generator 373. Thus, expansion of the steam 371 through the turbine 372 drives the generator 373 and produces electrical power 5. After expansion in the turbine 372 the steam is condensed by condenser 374 back to water, and a pump 375 circulates the water back to the combustor 30. It will be appreciated that the region 34 above the hot fluidised bed 32 in the combustor 30 contains a hot gas mixture (the gaseous combustion products). In this particular example, the fluidised bed combustor operates at pressure and the hot pressurised exhaust gases are used to generate further electrical power. The hot exhaust gases 35 are conveyed to a gas turbine 350. This gas turbine 350 is arranged to drive a further electrical generator 351. Thus, as the hot exhaust gases 35 expand through the gas turbine 350 the generator 351 generates further electrical power 5. After expansion in the gas turbine 350, the exhaust gases are supplied to a heat exchanger 353 and pre-heat the water being supplied to the combustor 30. It will be appreciated that the apparatus shown in figure 11 is an example of combined cycle power generation apparatus (as it utilises both a steam turbine and a gas turbine for power generation) and is able to provide high overall efficiency. The oil 2 produced by pressing (crushing) the oilseed may be supplied to the food industry for incorporation in food products, and/or to a plant producing biodiesel. However, the apparatus of figure 11 incorporates additional components which may be used, if desired, to generate further electrical power from the oil (or a portion of it). These additional components include a reciprocating engine 202 arranged to drive a further electrical generator 203. The apparatus includes means for supplying the pressed oil 2 directly to the reciprocating engine 202 for burning as fuel, and also comprises fuel processing apparatus for optionally processing the oil 2 prior to its supply to the reciprocating engine 202.

Referring now to figure 12, this shows an oilseed processing method embodying the invention. In this embodiment, oilseed 1 is cleaned (step SlO), heated (step SI l), rolled (step S12), heated again (step S13), and then crushed at a temperature in the range 60 to 95 degrees centigrade (or 60 to 80, 85, or 90 in other embodiments) to produce oilseed cake, having a residual oil content, and oil 2. The oilseed is rapeseed containing approximately 43% oil. The crushing step is arranged such that the cake 3 has a residual oil content of approximately 12%. The oil (rape oil in this example) has a phosphorous level of lower than lOOppm. As the phosphorous content is low (indicative of a low level of gums in the oil) the method may further comprise the step S27 of supplying the oil directly to the food industry for incoiporation in edible products. Optionally the method further comprises the step S28 of supplying the oil to a biodiesel manufacturing facility. The method optionally comprises the further step S23 of combusting at least a portion of the oil in a reciprocating engine, for example to drive the generator and produce further electrical power. The method comprises the further optional step S300 of producing animal feed from the cake 3. Another optional step in the method is combustion S3 of the cake 3, with the heat generated by combustion being utilised for electrical power generation.

Referring now to figure 13, this illustrates another oilseed processing method embodying the invention. In this method the oilseed 1 is pre-processed (step SlOO, which may include at least one of the following: cleaning, reducing moisture content, rolling). The pre-processed oilseed is then crushed in step S2 to produce cake 3 and oil 2. The cake 3 is combusted to generate electrical power (steps S3 and S4). The method comprises the optional step of combusting oilseed meal 6 together with the cake 3 in combustion step S3. The method also comprises the optional steps S27 (supplying a proportion of the produced oil 2 to the food industry); step S28 (supplying a proportion of the produced oil for bio diesel production) and steps S23 and S230 (combusting a proportion of the produced oil to generate further electrical power). The proportions of the produced oil 2 assigned to the optional steps S27, S28 and S23 and S230 are determined according to market prices for the produced oil and for electrical power. It will be appreciated that, according to market conditions, the proportion for a particular one of the optional steps may be zero, or greater than zero.

It will be appreciated from the above description that certain embodiments of the invention relate to the expelling of oil from rapeseed and the subsequent uses of the seed and cake in the biomass and biofuels sectors.

In certain embodiments, the expelling of oil from rapeseed is performed under conditions that result in minimal extraction of gums (mostly phospholipids), resulting in high quality oil, worth a considerable premium, suitable for biodiesel production or food use with reduced pre-processing requirements.

In certain embodiments the subsequent combustion of the resulting rapeseed cake from the expeller (optionally with rapeseed meal from other sources) takes place in a purpose designed bio-combustor, to produce electricity (and as a by product heating and/or cooling power) from the cake, or cake and meal.

Embodiments of the invention are also concerned with overall project economics driven by rising oil and electricity prices, at a time of stable or falling oil seed cake/meal prices, which make the burning of cake or meal a viable alternative to selling for animal feed for the first time. The economic viability of the process does not rely on further changes in prices.

In certain embodiments, rapeseed is first cleaned using sieving to remove stones, and non-seed plant matter, before being heated, then rolled and then heated again to produce flaked seeds of low moisture content ready for expelling the oil. The oil is then expelled using a standard commercially available expeller but using non-standard (i.e. novel) conditions, including a throughput of seed and lower temperatures of 60- 95°C comensurate with leaving a concentration of oil in the cake of 12%. The applicant has found that expellers under these conditions produce oil with markedly lower levels of gums (mostly phospholipids, the presence of which are measured by the phosphorous content). Conventionally crude rape oil has a phosphorus level over 200ppm. With process conditions employed in embodiments of the invention, phosphorous levels below 100 ppm have been achieved. Expelled oil of this quality should attract a premium in both the food and biodiesel markets due to reduced processing costs; it contains no residual hexane as extraction of the cake is not necessary, and potentially it could be used directly for esterification in biodiesel plants, as the free fatty acid level (fatty acids present in the oil not in the form of triglycerides) would also be expected to be low. If some amount of de-gumming is required, then the gums generated during de-gumming may be combusted with the cake.

In embodiments of the invention, being able to combust rapeseed meal and cake to produce high value 'green' electricity and heat gives a major advantage over the usual route for meal into the animal feed industry, because it gives a more financially valuable end use for the cake and meal as well as the security of a second market to sell them into. The bio-combustor is arranged to achieve an adequately high efficiency for the process. In certain embodiments of the invention, the rapeseed meal and cake requires grinding after the expelling or extraction stage to ensure a consistent fuel particle size being introduced into the combustor. Fuel handling from expeller to combustor may utilize existing storage, conveying and elevating technology from the animal feed industry.

Although the use of rapeseed has been described, a range of oilseeds, cakes and meals may be suitable for use in the rapeseed combustion plant e.g. palm kernel meal, olive pulp, and crambe meal. The fluidised bed technology may be arranged to maximize combustion efficiency. In the combustor the fuel is burnt and the heat generated used to raise steam. This steam is converted into electricity using a standard steam turbine - generator set matched to the plant steam output designed for. The fuel particles are burned within a bed of inert material such as sand. Primary combustion air is forced through the bed from beneath until the particles of fuel and the bed become supported by the flow of gas and become separated from each other, with the bed resembling a liquid with a well defined free surface. This allows a high degree of turbulent mixing and so better exposure of the fuel particles to air and also improved heat transfer, resulting in improved combustion. Conversion efficiencies for fluidised beds are typically between 86%-91%.

Secondary/tertiary air flows may be added above the bed to complete the combustion process in certain embodiments. Desired particle sizes for the fuel and inert material may be below lmm. Rapeseed has a diameter of approximately 2mm and so after expelling and grinding will give a particle size in the correct range.

The net calorific value of oil seed meal and cake is higher than many commonly used biomass fuels such as straw, rice husk, bagasse (sugar cane waste) and air dried wood (20% moisture content). Depending on the oil content, the cake can have a net calorific value in excess of oven-dried wood too (0% moisture content). There may be a significant difference in calorific value depending on the oil content of the meal or cake, and mixing fuels prior to conveying to the combustor and controlling the rate of supply of fuel to the combustor may be employed. The typical moisture content of oil seed rape meal and cake at 10-15% is low enough to make it suitable for combustion without further drying being necessary. Hence, certain embodiments dispense with drying steps. The ash content at 5-7% is higher than wood and hence the combustor is designed to enable expedient ash removal. Combustor operation temperature is chosen in light of the ash fusion temperature and ash constituent analysis design of the combustor to minimise problems of combustor slagging and corrosion. The sulphur content is enough not to give any new emission/corrosion problems. The chlorine content of 100-200ppm is sufficiently high that higher gas flue temperatures than 'standard' are required to avoid increased corrosion rates of the boiler super-heater pipes.

Looking at embodiments of the invention from the viewpoint of overall process economics, the development of a new high value end use for the rapeseed cake and the consequent flexibility to sell both the oil and the cake into the most lucrative market at the time of production gives added security of income and removes reliance on a single market for project profitability. The high final oil in cake percentage is not problematic, as the majority of the value of this oil will be recovered as energy in the combustion process.

The cake may be sold into the animal feed industry conventionally, or used to produce green electricity which will attract Government support. The oil can be sold into the food or biodiesel industries at a premium rate, because of the low gum content and therefore smaller downstream processing costs. Further markets into the biomaterials and direct combustion for electricity markets are also possibilities for the oil.

Plants embodying the invention may be designed to enable a secondary fuel stream into the bio-combustor to be utilized e.g. rape meal, palm kernel, meal etc. This secondary fuel stream adds further flexibility to the economic model.

Claims

1. A method of generating electrical power comprising:

combusting the cake to generate heat energy; and

2. A method in accordance with claim 1, wherein said oilseed is rapeseed.

3. A method in accordance with any preceding claim, wherein said oilseed has an initial oil content in the range 42% to 44%.

4. A method in accordance with claim 3, wherein said oilseed has an initial oil content of approximately 43%.

5. A method in accordance with any preceding claim, wherein said cake has a residual oil content in the range 10.5% to 13.5%.

6. A method in accordance with claim 5 claim, wherein said cake has a residual oil content of approximately 12%.

7. A method in accordance with any preceding claim, wherein said pressing comprises using a screw press to press the oilseed,

8. A method in accordance with any preceding claim, wherein said pressing comprises pressing the oilseed at a temperature in the range 60 to 95 degrees centigrade.

9. A method in accordance with any preceding claim, wherein said pressing comprises pressing the oilseed at a throughput rate commensurate with achieving the desired residual oil in cake and desired gum levels in the oil.

10. A method in accordance with any preceding claim, further comprising:

cleaning the oilseed before pressing.

11. A method in accordance with any preceding claim, further comprising:

reducing the moisture content of the oilseed before pressing.

12. A method in accordance with claim 11, wherein reducing the moisture content comprises heating.

13. A method in accordance with any preceding claim, further comprising:

rolling the oilseed before pressing.

14. A method in accordance with any preceding claim, further comprising:

mechanically processing the oilseed cake before combusting the cake.

15. A method in accordance with claim 14, wherein said mechanical processing comprises grinding the oilseed cake.

16. A method in accordance with claim 15, wherein said grinding comprises grinding the oilseed cake to produce a mean particle diameter in the range 0.8 to 1.2mm .

17. A method in accordance with any preceding claim, wherein said combusting comprises combusting the oilseed cake in a fluidised bed combustor.

18. A method in accordance with any preceding claim, wherein said converting comprises using the generated heat energy to raise steam.

19. A method in accordance with claim 18, wherein said converting comprises using the steam to drive a turbine coupled to an electrical generator.

20. A method in accordance with any preceding claim, further comprising: combusting oilseed meal, produced by solvent extraction of residual oil from oilseed cake produced by pressing, to generate additional heat energy, and converting at least a portion of the additional generated heat energy into electrical power.

21. A method in accordance with claim 20, further comprising: mixing the oilseed cake and meal together before combusting, and combusting the mixture.

22. A method in accordance with claim 21, comprising: mechanically processing the mixture before combusting.

23. A method in accordance with claim 21 or claim 22, comprising: combusting the mixture in a fluidised bed combustor.

24. A method in accordance with claim 17, wherein the oilseed cake provides substantially all of the combustible material supplied to the fluidised bed combustor.

25. A method in accordance with claim 23, wherein the oilseed cake and meal mixture provides substantially all of the combustible material supplied to the fluidised bed combustor.

26. A method in accordance with any preceding claim, further comprising combusting at least a portion of the expressed oil to generate further electrical power.

27. A method in accordance with claim 26, wherein combusting at least a portion of the expressed oil comprises combusting expressed oil in a reciprocating engine, the method further comprising driving an electrical generator with the reciprocating engine to generate said further electrical power.

28. Electrical power generating apparatus comprising:

a combustor arranged to combust cake from the pressing apparatus to generate heat energy; and means for converting at least a portion of the generated heat energy into electrical power.

29. Electrical power generating apparatus in accordance with claim 28, wherein the pressing apparatus and combustor are separated by a distance of no more than 0.5km.

30. Electrical power generating apparatus in accordance with claim 28 or claim 29, further comprising pre-processing apparatus arranged to process the oilseed before the pressing apparatus.

31. Electrical power generating apparatus in accordance with claim 30, wherein the pre-processing apparatus comprises cleaning apparatus arranged to clean the oilseed.

32. Electrical power generating apparatus in accordance with claim 31, wherein the cleaning apparatus comprises a sieve.

33. Electrical power generating apparatus in accordance with any one of claims 30 to 32, wherein the pre-processing apparatus comprises at least one heater arranged to heat the oilseed to reduce its moisture content.

34. Electrical power generating apparatus in accordance with any one of claims 30 to 33, wherein the pre-processing apparatus comprises at least one roller arranged to roll the oilseed before the pressing apparatus.

35. Electrical power generating apparatus in accordance with any one of claims 28 to 34, wherein the pressing apparatus is arranged to press the oilseed at a temperature in the range 60 to 95 degrees centigrade.

36. Electrical power generating apparatus in accordance with any one of claims 28 to 35, wherein the pressing apparatus comprises a screw press.

37. Electrical power generating apparatus in accordance with any one of claims 28 to 36, further comprising grinding apparatus arranged to receive the cake and provide ground cake to the combustor.

38. Electrical power generating apparatus in accordance with claim 37, wherein the grinding apparatus is arranged to produce ground cake having a mean particle size in the range 0.8 to 1.2mm.

39. Electrical power generating apparatus in accordance with any one of claims 37 or 38, wherein the grinding apparatus is further arranged to receive a supply of oilseed meal, and to provide a mixture of ground cake and ground meal to the combustor.

40. Electrical power generating apparatus in accordance with any one of claims 28 to 39, wherein the combustor is a fluidised bed combustor.

41. Electrical power generating apparatus in accordance with claim 40, wherein the fluidised bed combustor is a pressurised fluidised bed combustor, hot exhaust gases from the combustor being arranged to drive a gas turbine, the gas turbine being arranged to drive an electrical generator.

42. Electrical power generating apparatus in accordance with any one of claims 28 to 41, wherein the means for converting comprises a boiler system arranged to produce steam using the heat energy, the apparatus further comprising a steam turbine arranged to be driven by said steam, and an electrical generator arranged to be driven by the steam turbine.

43. Electrical power generating apparatus in accordance with any one of claims 28 to 42, further comprising a reciprocating engine arranged to drive an electrical generator, and means for supplying at least a portion of the expressed oil to the reciprocating engine for combustion in said engine.

44. A method of obtaining oil from an oilseed comprising pressing the oilseed at a temperature in the range 60 to 90 degrees centigrade to produce oil and oilseed cake, the cake having a residual oil content.

45. A method in accordance with claim 44, wherein said oilseed is rapeseed.

46. A method in accordance with claim 44 or claim 45, wherein said oilseed has an initial oil content in the range 42% to 44%.

47. A method in accordance with claim 46, wherein said oilseed has an initial oil content of approximately 43%.

48. A method in accordance with any one of claims 44 to 47, wherein said cake has a residual oil content in the range 10.5% to 13.5%.

49. A method in accordance with claim 48, wherein said cake has a residual oil content of approximately 12%.

50. A method in accordance with any one of claims 44 to 49, wherein said pressing comprises using a screw press to press the oilseed.

51. A method in accordance with any one of claims 44 to 50, wherein said pressing comprises pressing the oilseed at a throughput rate commensurate with achieving the desired residual oil in cake and desired gum levels in the oil.

52. A method in accordance with any one of claims 44 to 51, further comprising: cleaning the oilseed before pressing.

53. A method in accordance with any one of claims 44 to 52, further comprising: reducing the moisture content of the oilseed before pressing.

54. A method in accordance with claim 53, wherein reducing the moisture content comprises heating.

55. A method in accordance with any one of claims 44 to 54, further comprising: rolling the oilseed before pressing.

56. A method of processing an oilseed, comprising:

combusting the cake to generate heat energy;

converting at least a portion of the generated heat energy into electrical power; supplying a proportion of the produced oil to the food industry;

supplying a proportion of the produced oil for biodiesel production; and combusting a proportion of the produced oil to generate further electrical power.

57. A method of processing an oilseed, comprising:

combusting the cake to generate heat energy;

using a proportion of the produced oil to produce biodiesel; and

58. A method in accordance with claim 56 or claim 57, further comprising the step of:

determining said respective proportions according to market prices for the produced oil and for electrical power.

59. A method in accordance with any one of claims 56 to 58, wherein the step of combusting a proportion of the produced oil comprises combusting said oil in a reciprocating engine arranged to drive an electrical generator.

60. A method in accordance with any one of claims 56 to 59, further comprising the steps of: combusting oilseed meal, produced by solvent extraction of oil from oilseed cake, to generate further heat energy; and

converting at least a portion of the further heat energy into electrical power.

61. A method of generating electrical power substantially as hereinbefore described with reference to the accompanying drawings.

62. Electrical power generating apparatus substantially as, hereinbefore described with reference to the accompanying drawings.

63. A method of obtaining oil from an oilseed substantially as hereinbefore described with reference to the accompanying drawings.

64. A method of processing an oilseed substantially as hereinbefore described with reference to the accompanying drawings.