Renewable energy and carbon emission reduction policies in Japan, South Korea, Canada, Western Europe and other countries support the use of particulate fuels as a substitute for coal in power stations. To date, investment in conversion of particulates has been concentrated on conventional industrial wood pellets and sometimes We call them white particles.
Due to the appearance after heat treatment, advanced wood particles, often referred to as black particles, have long been touted as fuels superior to traditional white wood particles. Black particles should address some of the potential flaws associated with white wood chips as coal Coal substitutes for powder power plants Key advantages of black particles that have been proposed for many years include: No need for dry storage and transport, better grindability, less handling, dust formation during storage and higher energy density Black particles Usually comes from two different technical methods of developing advanced wood pellets: baking and steam explosion (SE).
Baking is a form of pyrolysis that results in partial thermal decomposition in the absence of oxygen Typically, baking is done at between 200 degrees Celsius and 300 degrees Celsius to remove volatiles from the wood, and the resulting material is then densified to granules. FutureMetrics No baking technology was analyzed, but the Arbaflame technology used to produce SE particles was analyzed in detail.
This article is a stand-alone analysis of Arbaflame's (an annual output of 40,000 tons of SE particles) technology and the company has granted FutureMetrics permission to post the information in this article.
What is a steam explosion (SE)?
The SE method for wood fiber pretreatment involves exposing the material to saturated steam.The temperature and pressure of the steam as well as the time in the reaction vessel determines how much the hemicellulose will be degraded and how much of the material will be converted to volatile materials and organisms The subsequent steam explosion is a rapid release of pressure.The explosive expansion of water in the cell walls of the lignocellulosic feedstock causes the lignocelluloses to break down into very small particles.The severity of the steam treatment is controlled so that the cellulose and lignin are affected While the hemicellulose is partially degraded.While the resulting material has a higher energy density, improved grindability, harder and produces less powder when densified in a pellet press than white particles, Water affinity changes from hygroscopicity to hydrophobicity.
The steam explosion process causes lignin to appear as small beads on the surface of the fine wood fibers.When the fibers are densified in a pellet press, these beads form a film-like surface coating of broken wood fibers and produce almost Does not produce fine, hard, highly water-resistant particles.
The advantages of SE particles
SE particles of the three major advantages are:
• In contrast to white particles, SE particles do not disintegrate when wet.
• SE particles have a higher volume and weight energy density (about 31% more) than white particles, which means that more energy can be stored or transported per unit volume of particles.
• The power requirements for pulverizing SE particles at a pulverized coal plant are significantly lower than the power requirements for pulverizing white particles.
While these benefits have been proposed for several years, technical limitations and high production costs have prevented their widespread adoption.In early attempts to fabricate SE particles, energy consumption, loss of mass and energy content, and reaction with SE Relevant issues such as the nature of the gas released have outweighed the advantages of the product itself, and the reliable operation of manufacturing SE pellet equipment is also a challenge for the SE pellet industry.
Figure 1: SE particles after water changes in water content The SE particles absorb some of the water. As shown in Figure 1, after 48 hours of total immersion in water, the moisture content of the particles increased by about 6% to 14% from the average level after production. The water remained in the surface layer and evaporated from the particles. .
Figure 1: SE particles soaked Durability Variety SE particles do not lose their mechanical properties after exposure to water. The durability of Arbaflame SE particles before soaking is an average of 98.8%. As shown in Figure 2, durability is between 97.5% and 98.5% after 48 hours of total soaking. The ability to store SE pellets outdoors eliminates the need for expensive dry storage domes, silos, sheds, or covered railcars. It can also handle ships when it's raining or snowing. SE pellets can be the same as coal Are stored and processed under conditions that can be placed on the same storage site with coal without adversely affecting its function.
Arbaflame SE pellets are stored in the coal yard of Thunder Bay Power Station in Ontario. SE pellets are exposed to rain and snow without degradation. Higher specific energy content (SE about 19.5GJ/MT, white about 17.5GJ/MT) and bulk density (SE about 790kg/m 3, white about 650kg/m 3) The impact on the delivery cost of each GJ is another feature of the SE granules, which gives it an advantage over the white granules. Fully loaded 60,000 cubic meters of container (Great Handysize): White granules will contain about 682,000 GJ of energy, SE particles contain about 924,000 GJ of energy.
The energy required to run a coal power plant's crushing facility can be quite large. It takes about 45 kilowatt-hours (kWh) of electricity to grind a ton of white particles, while grinding a ton of SE particles requires only 11 kilowatt-hours (degrees). If applied above Japan's independent power producer (IPP) projects operating at net prices are particularly important for cost savings. IPPs with 200,000 tons of SE pellets can be used to burn 60 MW units for one year, and compared to smashing white granules, the plant is used to pulverize electricity every year. The cost can be reduced by nearly half a million dollars.
Are SE particles cost-effective?
Arbaflame has optimized its production process so it does not waste energy through more than a decade of R & D (research and development), combined with a biochemical recovery system to capture the valuable organic chemicals produced during the steam reaction, White particles competing SE particles.
Recent developments in Arbaflame's SE particle technology have greatly increased the competitiveness of SE particles.The most relevant and recent process improvements that have helped to reduce the cost of previously non-competing processes are: Energy recovery and recovery for feedstock drying As a gaseous by-product of the SE process, Value Organic Chemicals. Years of R & D at Arbaflame's plant in Norway have resulted in a granular plant model that operates reliably and reliably.
The Arbaflame SE pellet process, operating in Arbaflame's 40,000 tonne / year plant, is robust and energy efficient. The plant operates safely and reliably. The balance of the pre-dryer output, the moisture level between the steam reactor and the after-dryer allows the pre-drying process to be carried out Almost completely utilizing the energy generated in the process and the energy of the after-dryer, the efficient use of this energy is crucial to the economy of the operation.
The quality losses due to steam treatment and the extra energy costs for operating the reaction are offset by the value of regenerative biological compounds produced.SE fibers are more densified than white wood fibers.The running cost of the granulator is lower (about 30% ) And the dry hammer mill was eliminated (the SE process achieved the reduction in fiber size required to make the pellets), which helped to further offset the higher wood costs.
The ability to safely deliver fuel to new and co-fired power plants is crucial.While White Particle Mills generally have multiple production plants in many locations, the supply chain will not stall completely if there is a problem at one of the factories or shipping terminals. SE particle industry is not yet supply chain redundancy, may result in supply chain rupture.
According to our analysis, the only obstacle to the rapid growth of the SE particle industry is overcoming the lack of redundancy in the fuel supply chain.
Author: William Strauss, president FutureMetrics
Lorentz Schmidt FutureMetrics Senior Engineer
