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103-591: The Bell Bay Pulp Mill , also known as the Tamar Valley Pulp Mill or Gunns Pulp Mill , was a proposed $ 2.3 billion pulp mill in which the former Gunns Limited was planning to build in the Tamar Valley , near Launceston, Tasmania . Gunns Limited went into voluntary administration in 2012, and on 30 August 2017, the permits for the proposed building lapsed, signalling the end of the project. A Gunns spokesperson said they will not contest

206-513: A heat recovery steam generator (HRSG) with a live steam temperature between 420 and 580 °C. The condenser of the Rankine cycle is usually cooled by water from a lake, river, sea or cooling towers . This temperature can be as low as 15 °C. Plant size is important in the cost of the plant. The larger plant sizes benefit from economies of scale (lower initial cost per kilowatt) and improved efficiency. For large-scale power generation,

309-430: A 50.00 MJ/kg (21,500 BTU/lb) LHV: a 11% increase. Efficiency of the turbine is increased when combustion can run hotter, so the working fluid expands more. Therefore, efficiency is limited by whether the first stage of turbine blades can survive higher temperatures. Cooling and materials research are continuing. A common technique, adopted from aircraft, is to pressurise hot-stage turbine blades with coolant. This

412-634: A backup or supplementary power. It is named after American professor D. Y. Cheng who patented the design in 1976. The efficiency of a heat engine, the fraction of input heat energy that can be converted to useful work, is limited by the temperature difference between the heat entering the engine and the exhaust heat leaving the engine. In a thermal power station , water is the working medium. High pressure steam requires strong, bulky components. High temperatures require expensive alloys made from nickel or cobalt , rather than inexpensive steel . These alloys limit practical steam temperatures to 655 °C while

515-415: A business add plant capacity as it is needed. Multiple-pressure reheat steam cycles are applied to combined-cycle systems with gas turbines with exhaust gas temperatures near 600 °C. Single- and multiple-pressure non-reheat steam cycles are applied to combined-cycle systems with gas turbines that have exhaust gas temperatures of 540 °C or less. Selection of the steam cycle for a specific application

618-482: A chemist with over 20 years experience in the Kraft pulping and paper, a hiccup with a waterspray within an "integrated" process could cause the bleaching chemical chlorine dioxide to be contaminated with elemental chlorine . Elemental chlorine contamination of the chlorine dioxide bleaching chemical could in turn lead to the release of persistent organic pollutants ( dioxins ), potentially causing environmental harm and

721-449: A combined heat and power (CHP) plant. In general, combined cycle efficiencies in service are over 50% on a lower heating value and Gross Output basis. Most combined cycle units, especially the larger units, have peak, steady-state efficiencies on the LHV basis of 55 to 59%. A limitation of combined cycles is that efficiency is reduced when not running at continuous output. During start up,

824-526: A further twenty six months to complete the studies. A new condition was also placed on the mill, meaning Gunns could be liable for criminal and civil penalties if the mill breached defined "environmental limits" during operations. In early March 2011, following a one-week delay after Gunns contacted his department the day prior to the deadline requesting tougher environment standards, the Federal Environment Minister, Tony Burke , gave

927-545: A large warehouse and wharf north of and not within the Tamar River Conservation Area as well as the installation of a water supply pipe to be drilled under or 'jet trenched' into the bed of the Tamar River in order to cross it. The proposed Pulp Mill will also include on site production of chlorine dioxide and other chemicals and a steam turbine power station fed by a large Recovery boiler and

1030-520: A marine CCGT safer by permitting a ship to operate with equipment failures. A flexible stationary plant can make more money. Duct burning raises the flue temperature, which increases the quantity or temperature of the steam (e.g. to 84 bar, 525 degree Celsius). This improves the efficiency of the steam cycle. Supplementary firing lets the plant respond to fluctuations of electrical load, because duct burners can have very good efficiency with partial loads. It can enable higher steam production to compensate for

1133-552: A means of load control or load shifting since ice can be made during periods of low power demand and, potentially in the future the anticipated high availability of other resources such as renewables during certain periods. Combustion technology is a proprietary but very active area of research, because fuels, gasification and carburation all affect fuel efficiency. A typical focus is to combine aerodynamic and chemical computer simulations to find combustor designs that assure complete fuel burn up, yet minimize both pollution and dilution of

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1236-403: A mechanical mill. The conditions of the chemical treatment are much less vigorous (lower temperature, shorter time, less extreme pH) than in a chemical pulping process, since the goal is to make the fibers easier to refine, not to remove lignin as in a fully chemical process. Pulps made using these hybrid processes are known as Chemi-thermomechanical pulps (CTMP). Sometimes a CTMP mill is located on

1339-479: A mechanical treatment to separate the fibers. These hybrid methods include thermomechanical pulping (TMP) and Chemi-thermomechanical pulping (CTMP). The chemical and thermal treatments reduce the amount of energy subsequently required by the mechanical treatment, and also reduce the amount of strength loss suffered by the fibers. The earliest known methods for preparing pulp for paper making were water-powered, in 8th-century Samarkand , Abbasid Caliphate . Much of

1442-422: A more efficient steam cycle. However, a multi-shaft system is about 5% higher in initial cost. The overall plant size and the associated number of gas turbines required can also determine which type of plant is more economical. A collection of single shaft combined cycle power plants can be more costly to operate and maintain, because there are more pieces of equipment. However, it can save interest costs by letting

1545-458: A number of environmental, social activist and political groups including The Wilderness Society , and TAP into a better Tasmania (formerly Tasmanians Against the Pulpmill). There have been numerous rallies, public meetings, actions and protests around the entire state and especially in the north since the pulp mill was proposed. In September 2006, a protest rally against the proposed pulp mill

1648-400: A number of environmentally focused and other local community groups. It is not the first pulp mill proposed for Tasmania. In 1989 Wesley Vale pulp mill was proposed but did not go ahead. The Wesley Vale project was to be a kraft mill and was also subject to local opposition due to its use of elemental chlorine as the main bleaching chemical, which was a convention of that time. As a result of

1751-521: A part-time lecturer and researcher in the School of Chemistry at the University of Tasmania, states an ECF system uses chlorine dioxide instead of chlorine to bleach the pulp, which greatly reduces the levels of organochlorines that make it out into the environment through effluent released from a pulp mill. She describes this system a more environmentally friendly process. Opponents of the mill include

1854-407: A percentage of the lower heating value of the fuel consumed, can be over 60% when operating new, i.e. unaged, and at continuous output which are ideal conditions. As with single cycle thermal units, combined cycle units may also deliver low temperature heat energy for industrial processes, district heating and other uses. This is called cogeneration and such power plants are often referred to as

1957-438: A single cycle steam power plant is limited to efficiencies from 35 to 42%. Many new power plants utilize CCGTs. Stationary CCGTs burn natural gas or synthesis gas from coal . Ships burn fuel oil . Multiple stage turbine or steam cycles can also be used, but CCGT plants have advantages for both electricity generation and marine power. The gas turbine cycle can often start very quickly, which gives immediate power. This avoids

2060-434: A single electrical generator on a single shaft. This arrangement is simpler to operate, smaller, with a lower startup cost. Single-shaft arrangements can have less flexibility and reliability than multi-shaft systems. With some expense, there are ways to add operational flexibility: Most often, the operator desires to operate the gas turbine as a peaking plant. In these plants, the steam turbine's shaft can be disconnected with

2163-556: A smaller Biomass boiler. The Tasmanian Government employed the Finnish consultants, Sweco Pic , to conduct an environmental impact assessment of the proposed mill. Community groups opposed to the mill criticised the choice of this company. Gunns withdrew from Tasmania's independent planning and development assessment process (the RPDC) in March 2007 after senior RPDC panel members cited

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2266-609: A state level by the Tasmanian Government. Turnbull stated that an extra 24 conditions, beyond a series of draft departmental conditions previously published, would be imposed on the project giving a total of 48 conditions. He said the decision was based on science and recommendations made by the Australian Governments chief scientist Dr Jim Peacock. Tasmanian Premier, Paul Lennon , said the federal conditions duplicate permit conditions already mandated by

2369-546: A subsequent breach of the Stockholm Convention . The "integrated" design for chlorine dioxide generation was not selected by Gunns to proceed as it was effectively prevented from implementation by the State Permit (Condition 3GN9.1). Gunns has subsequently indicated it will move from "ECF" to "ECF-Light" bleaching, which is facilitated by moving from "Merchant alternative 1" to "Merchant alternative 2" within

2472-602: A synchro-self-shifting (SSS) clutch, for start up or for simple cycle operation of the gas turbine. Another less common set of options enable more heat or standalone operation of the steam turbine to increase reliability: Duct burning, perhaps with a fresh air blower in the duct and a clutch on the gas turbine side of the shaft. A multi-shaft system usually has only one steam system for up to three gas turbines. Having only one large steam turbine and heat sink has economies of scale and can have lower cost operations and maintenance. A larger steam turbine can also use higher pressures, for

2575-564: A thermodynamic cycle that operates between the gas-turbine's high firing temperature and the waste heat temperature from the condensers of the steam cycle. This large range means that the Carnot efficiency of the cycle is high. The actual efficiency, while lower than the Carnot efficiency, is still higher than that of either plant on its own. The electric efficiency of a combined cycle power station, if calculated as electric energy produced as

2678-470: A thick porridge-like consistency and is "blown" or squeezed from the outlet of the digester through an airlock. The sudden change in pressure results in a rapid expansion of the fibers, separating the fibers even more. The resulting fiber suspension in water solution is called "brown stock". Brown stock washers, using countercurrent flow, remove the spent cooking chemicals and degraded lignin and hemicellulose. The extracted liquid, known as black liquor in

2781-544: A trading halt since March 2012 with the share price at A$ 0.16 and have yet to relist (as of 17 September 2012). 41°9′18″S 146°55′37″E  /  41.15500°S 146.92694°E  / -41.15500; 146.92694 Pulp mill Wood and other plant materials used to make pulp contain three main components (apart from water): cellulose fibres (desired for papermaking ), lignin (a three-dimensional polymer that binds

2884-626: A typical set would be a 270 MW primary gas turbine coupled to a 130 MW secondary steam turbine, giving a total output of 400 MW. A typical power station might consist of between 1 and 6 such sets. Gas turbines for large-scale power generation are manufactured by at least four separate groups – General Electric, Siemens, Mitsubishi-Hitachi, and Ansaldo Energia. These groups are also developing, testing and/or marketing gas turbine sizes in excess of 300 MW (for 60 Hz applications) and 400 MW (for 50 Hz applications). Combined cycle units are made up of one or more such gas turbines, each with

2987-478: A waste heat steam generator arranged to supply steam to a single or multiple steam turbines, thus forming a combined cycle block or unit. Combined cycle block sizes offered by three major manufacturers (Alstom, General Electric and Siemens) can range anywhere from 50 MW to well over 1300 MW with costs approaching $ 670/kW. The heat recovery boiler is item 5 in the COGAS figure shown above. Hot gas turbine exhaust enters

3090-430: A water washing procedure. A simpler and less expensive purification system will do the same job for light crude and light distillates. A magnesium additive system may also be needed to reduce the corrosive effects if vanadium is present. Fuels requiring such treatment must have a separate fuel-treatment plant and a system of accurate fuel monitoring to assure reliable, low-maintenance operation of gas turbines. Xcel Energy

3193-508: A wider range of temperatures or heat to electric power. Systems burning low quality fuels such as brown coal or peat might use relatively expensive closed-cycle helium turbines as the topping cycle to avoid even more expensive fuel processing and gasification that would be needed by a conventional gas turbine. A typical single-shaft system has one gas turbine, one steam turbine, one generator and one heat recovery steam generator (HRSG). The gas turbine and steam turbine are both coupled in tandem to

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3296-406: Is a simplified form of combined cycle where the steam turbine is eliminated by injecting steam directly into the combustion turbine. This has been used since the mid 1970s and allows recovery of waste heat with less total complexity, but at the loss of the additional power and redundancy of a true combined cycle system. It has no additional steam turbine or generator, and therefore it cannot be used as

3399-408: Is adjacent to the industrial area known as Bell Bay which is currently zoned 'Heavy Industrial'. Industry already located at Bell Bay includes an aluminum smelter, a metallurgical plant, a gas-fired thermal power station (decommissioned), a recently commissioned combined cycle gas turbine power station and a saw-milling and wood chipping facility. Included in the proposed development is construction of

3502-471: Is also bled-off in proprietary ways to improve the aerodynamic efficiencies of the turbine blades. Different vendors have experimented with different coolants. Air is common but steam is increasingly used. Some vendors might now utilize single-crystal turbine blades in the hot section, a technique already common in military aircraft engines. The efficiency of CCGT and GT can also be boosted by pre-cooling combustion air. This increases its density, also increasing

3605-419: Is also some development of modified Rankine cycles. Two promising areas are ammonia/water mixtures, and turbines that utilize supercritical carbon dioxide. Modern CCGT plants also need software that is precisely tuned to every choice of fuel, equipment, temperature, humidity and pressure. When a plant is improved, the software becomes a moving target. CCGT software is also expensive to test, because actual time

3708-547: Is called " combined heat and power " (CHP). In stationary and marine power plants, a widely used combined cycle has a large gas turbine (operating by the Brayton cycle ). The turbine's hot exhaust powers a steam power plant (operating by the Rankine cycle ). This is a combined cycle gas turbine (CCGT) plant. These achieve a best-of-class real (see below) thermal efficiency of around 64% in base-load operation. In contrast,

3811-420: Is called a combined gas and steam (COGAS) plant. Combining two or more thermodynamic cycles improves overall efficiency, which reduces fuel costs. The principle is that after completing its cycle in the first engine, the working fluid (the exhaust) is still hot enough that a second subsequent heat engine can extract energy from the heat in the exhaust. Usually the heat passes through a heat exchanger so that

3914-418: Is determined by an economic evaluation that considers a plant's installed cost, fuel cost and quality, duty cycle, and the costs of interest, business risks, and operations and maintenance. By combining both gas and steam cycles, high input temperatures and low output temperatures can be achieved. The efficiency of the cycles add, because they are powered by the same fuel source. So, a combined cycle plant has

4017-416: Is even more difficult to remove. In chemical pulp mills, the bark introduces unwanted contaminants such as calcium , silica , and aluminum that cause scaling and give an extra loading for the chemical recovery system. Birchbark contains betulin , a terpenoid that easily creates deposits in a pulp mill. The earliest mills used sandstone grinding rollers to break up small wood logs called "bolts", but

4120-941: Is going to build two natural gas power plants in the Midwestern United States that can mix 30% hydrogen with the natural gas. Intermountain Power Plant is being retrofitted to a natural gas/hydrogen power plant that can run on 30% hydrogen as well, and is scheduled to run on pure hydrogen by 2045. However others think low-carbon hydrogen should be used for things which are harder to decarbonize , such as making fertilizer , so there may not be enough for electricity generation. Combined-cycle systems can have single-shaft or multi-shaft configurations. Also, there are several configurations of steam systems. The most fuel-efficient power generation cycles use an unfired heat recovery steam generator (HRSG) with modular pre-engineered components. These unfired steam cycles are also

4223-445: Is mixed with an aqueous solution of the pulping chemicals, then heated with steam. In the kraft process the pulping chemicals are sodium hydroxide and sodium sulfide and the solution is known as white liquor. In the sulfite process the pulping chemical is a mixture of metal (sodium, magnesium, potassium, or calcium) and ammonium sulfite or sulfite. After several hours in the digester, the chips or cut plant material breaks down into

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4326-479: Is often readily available in rural areas. Gas turbines burn mainly natural gas and light oil. Crude oil, residual, and some distillates contain corrosive components and as such require fuel treatment equipment. In addition, ash deposits from these fuels result in gas turbine deratings of up to 15%. They may still be economically attractive fuels however, particularly in combined-cycle plants. Sodium and potassium are removed from residual, crude and heavy distillates by

4429-402: Is removed by pressing the sheet of fibers, and the sheet is then dried. At this point the sheets of pulp are several millimeters thick and have a coarse surface: it is not yet paper. The dried pulp is cut, stacked, bailed and shipped to another facility for whatever further process is needed. Bleached kraft pulp and bleached sulfite pulp are used to make high quality, white printing paper. One of

4532-482: Is supplied to the low-temperature turbine. A super heater can be provided in the low-pressure circuit. Some part of the feed water from the low-pressure zone is transferred to the high-pressure economizer by a booster pump . This economizer heats up the water to its saturation temperature . This saturated water goes through the high-temperature zone of the boiler and is supplied to the high-pressure turbine . The HRSG can be designed to burn supplementary fuel after

4635-410: Is the gas turbine power plant cycle is the topping cycle. It depicts the heat and work transfer process taking place in the high temperature region. The cycle a-b-c-d-e-f-a which is the Rankine steam cycle takes place at a lower temperature and is known as the bottoming cycle. Transfer of heat energy from high temperature exhaust gas to water and steam takes place in a waste heat recovery boiler in

4738-674: The Regional Forest Agreement . In January 2010, the company told the Australian Securities Exchange that the mill would not use any old growth or other native timber, and would be 100 per cent plantation timber fed from start-up. A second legal challenge against the Federal approval process for the Pulp Mill was undertaken by a group known as Lawyers For Forests (LFF). The case questioned

4841-426: The bleach plant . Combined cycle A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy . On land, when used to make electricity the most common type is called a combined cycle gas turbine ( CCGT ) plant, which is a kind of gas-fired power plant . The same principle is also used for marine propulsion, where it

4944-429: The cellulose fibres together) and hemicelluloses , (shorter branched carbohydrate polymers). The aim of pulping is to break down the bulk structure of the fiber source, be it chips, stems or other plant parts, into the constituent fibers. Chemical pulping achieves this by degrading the lignin and hemicellulose into small, water-soluble molecules that can be washed away from the cellulose fibers without depolymerizing

5047-428: The pulp and paper industry for two primary reasons, to avoid iron contamination of the product and their corrosion resistance to the various chemicals used in the papermaking process. A wide range of stainless steels are used throughout the pulp making process. For example, duplex stainless steels are being used in digesters to convert wood chips into wood pulp and 6% Mo super austenitic stainless steels are used in

5150-408: The super heater , then passes through the evaporator and finally through the economiser section as it flows out from the boiler . Feed water comes in through the economizer and then exits after having attained saturation temperature in the water or steam circuit. Finally it flows through the evaporator and super heater. If the temperature of the gases entering the heat recovery boiler is higher, then

5253-589: The "corrupted" approval process making it forever unacceptable. This new tough stance coincided with further splits emerging between Tasmanian environmental groups over the failure to halt logging in all high-conservation-value forests in an immediate moratorium. Dr Phill Pullinger of Environment Tasmania stated in March 2011 that "It's not a proposal that we'll ever be in a position that we'll endorse or support". Gunns shares were trading at A$ 4.50 in December 2004 (announcement of Bell Bay Pulp Mill). Gunns have been in

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5356-508: The $ 2.3 billion project. Geoffrey Cousins , former adviser to John Howard , has also been a vocal opponent of the mill, comparing it to the Franklin River Dam . Paul Lennon has claimed that the wood supply agreement "will not provide for any old growth timber to be used in the pulp mill.", while Peter Garrett has said that the tracts of old growth forest that will supply the mill were already earmarked for logging under

5459-754: The $ 2.3 billion pulp mill in the Tamar Valley. It failed when Labor and the Liberals joined to vote down the bill to repeal the Pulp Mill Assessment Act, which was fast-tracked through Parliament in 2007. In addition to these, there have been numerous community meetings in Launceston including one regarding concerns surrounding the pipe line in 2008 a pulp mill information night in 2009 and No Pulp Mill public meetings in December 2010 and March 2011. There have also been protests outside

5562-545: The ANZ bank, at Gunns' AGMs at their headquarters in Launceston and at the offices of state and federal politicians. In April 2007, allegations were made that a Gunns lawyer was involved in preparing new legislation introduced by then Premier Paul Lennon which bypasses the Resource Planning and Development Commission and replaces it with a government-appointed consultant which raised questions about Gunns influence over

5665-584: The Derwent Valley and one at Burnie. The Burnie pulp mill no longer exists and the mill in the Derwent Valley (Boyer) is vastly different from that proposed for the Tamar Valley, being a smaller scale (295,000 tpa), a thermo-mechanical process and includes paper making machines (producing news print on site), in comparison to the more sophisticated kraft process producing higher value pulp for further processing into copying paper, tissues etc. by off-site customers. The State commissioned research that reported

5768-464: The Gunns pledge to improve effluent standards and promised to support them if the details released by Gunns matched the commitment, but agree that the community would never give a "Social Approval" for the mill. The Wilderness Society spokesman Vica Bayley has stated that The Wilderness Society would never approve the contentious pulp mill, regardless of any future changes to its design or operations, citing

5871-485: The Tasmanian parliament. He has also noted that one benchmark had been relaxed from draft conditions, being the monthly average concentration limit of chlorate in the effluent. In 2009, (then) Federal Environment Minister, Peter Garrett , would not grant the proposed mill the final necessary operational approval before then planned studies were completed on its potential impact on the marine environment and allowed Gunns

5974-514: The bottoming cycle. During the constant pressure process 4-1 the exhaust gases from the gas turbine reject heat. The feed water, wet and super heated steam absorb some of this heat in the process a-b, b-c and c-d. The steam power plant takes its input heat from the high temperature exhaust gases from a gas turbine power plant. The steam thus generated can be used to drive a steam turbine . The Waste Heat Recovery Boiler (WHRB) has 3 sections: Economiser, evaporator and superheater. The Cheng cycle

6077-507: The capital costs of combined cycle power is relatively low, at around $ 1000/kW, making it one of the cheapest types of generation to install. The thermodynamic cycle of the basic combined cycle consists of two power plant cycles. One is the Joule or Brayton cycle which is a gas turbine cycle and the other is the Rankine cycle which is a steam turbine cycle. The cycle 1-2-3-4-1 which

6180-501: The cellulose fibers (chemically depolymerizing the cellulose weakens the fibers). The various mechanical pulping methods, such as groundwood (GW) and refiner mechanical (RMP) pulping, physically tear the cellulose fibers one from another. Much of the lignin remains adhering to the fibers. Strength is impaired because the fibers may be cut. Related hybrid pulping methods use a combination of chemical and thermal treatment to begin an abbreviated chemical pulping process, followed immediately by

6283-414: The chips are just ground up with the plates, the pulp is called "refiner mechanical" pulp (RMP), if the chips are steamed while being refined the pulp is called "thermomechanical" pulp (TMP). Steam treatment significantly reduces the total energy needed to make the pulp and decreases the damage (cutting) to fibers. Mechanical pulp mills use large amounts of energy, mostly electricity to power motors which turn

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6386-496: The company told the Australian Securities Exchange (ASX) in February 2011 that the mill would generate between A$ 475 million and A$ 500 million in pre-tax earnings. The company has released statements (on numerous occasions – 2008, 2009 and 2010) that it was in negotiations with several partners to secure financial backing for the proposed pulp mill. A new company called Southern Star Corporation has been set up to build and operate

6489-618: The current State Labor government. There are other allegations of collusion and co-operation between the company and Tasmania's political leaders. Professor Quentin Beresford from Perth WA has written an academic paper citing the Lennon government's approval of the Gunns pulp mill in Tasmania as a case study to illustrate the notion of institutional corruption. Gunns sued 20 environmental organisations and individuals for some $ 6 million in

6592-523: The days preceding the announcement of its plans to build a pulp mill in the Tamar Valley. The proposal had been criticised for not using accepted technology for the bleaching process and instead involved the presence of elemental chlorine at an intermediate stage (rather than hydrogen peroxide or methanol ) in the production of the main bleaching chemical chlorine dioxide . This particular criticism could only refer to Gunns' original preferred chemical plant design termed and 'integrated' chemical plant, which

6695-600: The energy harvested from solar radiation with another fuel to cut fuel costs and environmental impact (See: ISCC section ). Many next generation nuclear power plants can use the higher temperature range of a Brayton top cycle, as well as the increase in thermal efficiency offered by a Rankine bottoming cycle. Where the extension of a gas pipeline is impractical or cannot be economically justified, electricity needs in remote areas can be met with small-scale combined cycle plants using renewable fuels. Instead of natural gas, these gasify and burn agricultural and forestry waste, which

6798-400: The expansion ratio of the turbine. This is practised in hot climates and also has the effect of increasing power output. This is achieved by evaporative cooling of water using a moist matrix placed in the turbine's inlet, or by using Ice storage air conditioning . The latter has the advantage of greater improvements due to the lower temperatures available. Furthermore, ice storage can be used as

6901-407: The failure of another unit. Also, coal can be burned in the steam generator as an economical supplementary fuel. Supplementary firing can raise exhaust temperatures from 600 °C (GT exhaust) to 800 or even 1000 °C. Supplemental firing does not raise the efficiency of most combined cycles. For single boilers it can raise the efficiency if fired to 700–750 °C; for multiple boilers however,

7004-712: The failure of the Wesley Vale project, a major series of scientific studies termed the National Pulp Mills Research Program was commissioned by the Commonwealth Government to support an update and strengthening of the Australian guidelines for this industry sector. At about the same time, significant changes in bleaching technology and waste water treatment in relation to kraft pulp mills were also being made throughout

7107-453: The final approval for the Gunns' proposed pulp mill, on the basis of tougher environmental conditions requested by the company itself. Burke stated that demands made by environmental groups opposed to the development, particularly with regards to the chemical process to be used in the plant , had been addressed. One of those conditions concerned the bleaching process, described by the minister as "elemental chlorine free" or ECF. Dr Karen Stack,

7210-542: The final design of the chemical plant described above. Raverty resigned from the now defunct Resource Planning and Development Commission (RPDC) panel on the mill, citing undue political interference. In July 2007, The Wilderness Society launched a legal case against the federal government, claiming the Federal Minister for the Environment and Water Resources, Malcolm Turnbull , acted illegally by allowing

7313-485: The financial viability of the proposed Tamar Valley pulp mill. Greens Senator Christine Milne was criticised for describing the report as "independent" when it was written by a Greens adviser and paid for by Senator Milne using her taxpayer-funded allowance. A January 2008 report commissioned by The Wilderness Society estimated the Bell Bay Pulp Mill may run at a $ 300 million loss to Tasmania. However

7416-470: The flexibility of the plant should be the major attraction. "Maximum supplementary firing" is the condition when the maximum fuel is fired with the oxygen available in the gas turbine exhaust. Combined cycle plants are usually powered by natural gas , although fuel oil , synthesis gas or other fuels can be used. The supplementary fuel may be natural gas, fuel oil, or coal. Biofuels can also be used. Integrated solar combined cycle power stations combine

7519-407: The gas turbine. Supplementary burners are also called duct burners . Duct burning is possible because the turbine exhaust gas (flue gas) still contains some oxygen . Temperature limits at the gas turbine inlet force the turbine to use excess air, above the optimal stoichiometric ratio to burn the fuel. Often in gas turbine designs part of the compressed air flow bypasses the burner in order to cool

7622-411: The grinders. A rough estimate of the electrical energy needed is 10,000 mega joules (MJ) per tonne of pulp (2,750  kWh per tonne ) Chemical pulping processes such as the kraft (or sulfate) process and the sulfite process remove much of the hemicelluloses and lignin. The kraft process does less damage to the cellulose fibers than the sulfite process , thereby producing stronger fibers, but

7725-607: The hot exhaust gases. Some combustors inject other materials, such air or steam, to reduce pollution by reducing the formation of nitrates and ozone. Another active area of research is the steam generator for the Rankine cycle. Typical plants already use a two-stage steam turbine, reheating the steam between the two stages. When the heat-exchangers' thermal conductivity can be improved, efficiency improves. As in nuclear reactors, tubes might be made thinner (e.g. from stronger or more corrosion-resistant steel). Another approach might use silicon carbide sandwiches, which do not corrode. There

7828-495: The information about the technology in following subsections is from the book by C.J. Biermann. The chemistry of the various pulping processes can be found in Sjöström's book. The most common fiber source for pulp mills is pulpwood . Other common sources are bagasse and fibre crops. The first step in all mills using wood (trees) as the fiber source is to remove the bark . Bark contains relatively few usable fibers and darkens

7931-426: The input temperature to the turbine (the firing temperature), is relatively high (900 to 1,400 °C). The output temperature of the flue gas is also high (450 to 650 °C). This is therefore high enough to provide heat for a second cycle which uses steam as the working fluid (a Rankine cycle ). In a combined cycle power plant, the heat of the gas turbine's exhaust is used to generate steam by passing it through

8034-445: The kraft process, and red or brown liquor in the sulfite processes, is concentrated, burned and the sodium and sulfur compounds recycled in the recovery process. Lignosulphonates is a useful byproduct recovered from the spent liquor in the sulfite process. The clean pulp (stock) can be bleached in the bleach plant or left unbleached, depending on the end-use. The stock is sprayed onto the pulp machine wire, water drains off, more water

8137-591: The lapsing of the permits. The proposed mill is to use the Kraft process , with Elemental Chlorine Free bleaching, and it is claimed it is to be fed with 100 per cent plantation grown eucalyptus feed stock, having a production capacity of 1.1 million tonnes per annum of Air Dried pulp. Construction of the mill is supported by the State Government and the Federal Government and opposed by

8240-549: The legality of the decision making process taken by former Environment Minister, Malcolm Turnbull . The LFF claimed in court that Mr Turnbull did not adequately assess the proposed mill as he was required to by law. The case was dismissed in April 2009 and costs awarded against Lawyers For Forests. The Wilderness Society, Environment Tasmania and the Australian Conservation Foundation have welcomed

8343-399: The low temperature "bottoming" cycle. Very low temperature bottoming cycles have been too costly due to the very large sizes of equipment needed to handle the large mass flows and small temperature differences. However, in cold climates it is common to sell hot power plant water for hot water and space heating. Vacuum-insulated piping can let this utility reach as far as 90 km. The approach

8446-431: The lower temperature of a steam plant is fixed by the temperature of the cooling water. With these limits, a steam plant has a fixed upper efficiency of 35–42%. An open circuit gas turbine cycle has a compressor , a combustor and a turbine . For gas turbines the amount of metal that must withstand the high temperatures and pressures is small, and lower quantities of expensive materials can be used. In this type of cycle,

8549-427: The lowest in initial cost, and they are often part of a single shaft system that is installed as a unit. Supplementary-fired and multishaft combined-cycle systems are usually selected for specific fuels, applications or situations. For example, cogeneration combined-cycle systems sometimes need more heat, or higher temperatures, and electricity is a lower priority. Multishaft systems with supplementary firing can provide

8652-408: The mill design as 'critically non-compliant'. The next day then premier Paul Lennon recalled parliament and by the end of the month new fast-track pulp mill assessment legislation was passed by both Houses of Parliament. On 4 October 2007 the then federal Minister for Environment and Water Resources, Malcolm Turnbull , gave Commonwealth approval for the mill which had previously been given approval at

8755-579: The most visible uses for unbleached kraft pulp is to make brown paper shopping bags and wrapping paper where strength is particularly important. A special grade of bleached sulfite pulp, known as dissolving pulp, is used to make cellulose derivatives such as methylcellulose which are used in a wide range of everyday products from laxatives to baked goods to wallpaper paste . Some mills pretreat wood chips or other plant material like straw with sodium carbonate , sodium hydroxide , sodium sulfite , and other chemical prior to refining with equipment similar to

8858-581: The need for separate expensive peaker plants , or lets a ship maneuver. Over time the secondary steam cycle will warm up, improving fuel efficiency and providing further power. In November 2013, the Fraunhofer Institute for Solar Energy Systems ISE assessed the levelised cost of energy for newly built power plants in the German electricity sector . They gave costs of between 78 and €100 /MWh for CCGT plants powered by natural gas. In addition

8961-407: The probability of a disturbance or breakdown. Each stage also may have different decision variables, such as steam / water / chemical input, etc. Finally, scheduling needs to consider fuel optimization and CO 2 emissions, because part of the energy requirements may be met from fossil-fuel boilers. The overall aim is to maximize production at minimum cost. Stainless steels is used extensively in

9064-479: The project will generate $ 6.7 billion in spending over 25 years and create up to 1600 temporary jobs during the construction phase. After construction, it has been estimated by consultants engaged by Gunns that approximately 3100 extra long term jobs will be created in Tasmania and that approximately one twelfth of these will be employed by the operator at the pulp mill. A report by Naomi Edwards, Economics Adviser to Australian Greens Leader Bob Brown has questioned

9167-559: The pulp mill to escape proper assessment by the independent RPDC . Turnbull agreed to withhold a decision on the approval of the mill until after 6 August conclusion of the case. The case was dismissed in August 2007. Former Gunns director, John Gay, had previously put pressure on the state government to approve the mill quickly by threatening to take the project interstate or overseas: the company has already invested an estimated $ 100 million (5% of expenditure) on plans and consultants for

9270-565: The pulp mill. It is a private company with Gunns intending to retain a 51% equity share with the remaining 49% being made available for potential investors. The proposed site had been classified as a Private Conservation Area (Sanctuary) since 1958 but this was revoked by the Tasmanian State Government in 2007 (under section 21 of the Nature Conservation Act 2002). The proposed site is at Long Reach and

9373-422: The pulp. The removed bark is burned, along with other unusable plant material, to generate steam to run the mill. Almost all wood is then chipped before being processed further in order to free the fibers. Removal of the bark is done in a barker (or debarker ). The bark adhesion is about 3–5 kg/cm in the growing season (summer) and 2-3 times higher in the dormant season (winter). The bark of frozen logs

9476-405: The pulping liquor to penetrate the pieces completely. In the case of wood, the logs are chipped and the chips screened to ensure that the feed to the digester is of a uniform size. Oversized chips are either used as fuel or run through the chipper again, while sawdust may be burned or collected for sale. The screened chips or cut plant material ( bamboo , kenaf , etc.) goes to the digester where it

9579-472: The same site as a kraft mill so that the effluent from the CTMP mill can be treated in the kraft recovery process to regenerate the inorganic pulping chemicals. The pulping process involves many production stages, usually coupled with intermediate storage tanks. As each stage has a different reliability and bottlenecks may vary from day to day, scheduling a pulp mill needs to take into account these bottlenecks and

9682-517: The second cycle can take time to start up. Thus efficiency is initially much lower until the second cycle is running, which can take an hour or more. Heat engine efficiency can be based on the fuel Higher Heating Value (HHV), including latent heat of vaporisation that would be recuperated in condensing boilers , or the Lower Heating Value (LHV), excluding it. The HHV of methane is 55.50 MJ/kg (23,860 BTU/lb), compared to

9785-417: The sulfite process makes pulp that is easier to bleach. The chemical pulping processes use a combination of high temperature and alkaline (kraft) or acidic (sulfite) chemicals to break the chemical bonds of the lignin. However, atmospheric pollution and contaminants in wastewater effluent in the kraft pulping process has been widely documented The material fed into the digester must be small enough to allow

9888-428: The temperature of the exiting gases is also high. In order to remove the maximum amount of heat from the gasses exiting the high temperature cycle, a dual pressure boiler is often employed. It has two water / steam drums. The low-pressure drum is connected to the low-pressure economizer or evaporator. The low-pressure steam is generated in the low temperature zone of the turbine exhaust gasses. The low-pressure steam

9991-413: The turbine blades. The turbine exhaust is already hot, so a regenerative air preheater is not required as in a conventional steam plant. However, a fresh air fan blowing directly into the duct permits a duct-burning steam plant to operate even when the gas turbine cannot. Without supplementary firing, the thermal efficiency of a combined cycle power plant is higher. But more flexible plant operations make

10094-494: The two engines can use different working fluids. By generating power from multiple streams of work, the overall efficiency can be increased by 50–60%. That is, from an overall efficiency of the system of say 34% for a simple cycle, to as much as 64% net for the turbine alone in specified conditions for a combined cycle. Historically successful combined cycles have used mercury vapour turbines , magnetohydrodynamic generators and molten carbonate fuel cells , with steam plants for

10197-446: The use of natural stone ended in the 1940s with the introduction of manufactured stones with embedded silicon carbide or aluminum oxide . The pulp made by this process is known as "stone groundwood" pulp (SGW). If the wood is ground in a pressurized, sealed grinder the pulp is classified as "pressure groundwood" (PGW) pulp. Most modern mills use chips rather than logs and ridged metal discs called refiner plates instead of grindstones. If

10300-404: The world. On completion of the scientific studies, the Tasmanian guidelines for any new Tasmanian mill were then developed and published in 2004, which included provisions that meant that any future project must implement either Elemental Chlorine Free or Totally Chlorine Free bleaching technology. Tasmania was an innovator in pulp and paper in the 1930s and 40s, with one pulp mill established in

10403-489: Was held at the iconic Batman Bridge in the Tamar Valley. In May 2011, another rally was held in Launceston opposing the pulp mill where Greens MP Kim Booth stated he would move a no confidence motion in the government if any more money was spent to support the pulp mill project. Protesters listened and watched outside parliament as the Tasmanian Greens attempted a last-ditch bid to revoke a law allowing Gunns to build

10506-475: Was held in Launceston with speakers, included Greens politician Christine Milne and TV gardener Peter Cundall . In June 2007, an opposition rally to the mill attracted a crowd estimated at 10 000 and Richard Flanagan made a speech at a rally in the state's capital, Hobart, in November 2007. In August 2008, approximately 5 000 people attended a protest rally in Launceston and in March 2011, a "No Pulp Mill" rally

10609-558: Was one of three chemical plant designs presented for assessment. The integrated process as then described by Gunns had not been approved by the United Nations Environment Programme as Accepted Modern Technology (AMT) for this purpose and therefore was inconsistent with Tasmanian guidelines. By comparison, the two alternative chemical plant designs, presented by Gunns as "merchant chemical plant alternative 1" and "2" were AMT. According to Dr Warwick Raverty,

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