Cofire biomass with coal
Biomass and wood waste from the local area can be mixed in with coal up to 10 or 20%. Since the next crop of biomass will take in as much CO2 as was emitted, it is considered carbon neutral. Biomass also has very low sulfur and mercury content and reduces Nox, so cofiring also helps meet emissions limits. Fuel and maintenance costs are often significantly lowered.
Torrefaction can convert biomass to biocoal, which can be shipped, stored, pulverised and burned just like coal. Torrefaction plants along the train tracks or rivers normally used to supply coal can convert locally grown biomass to biocoal and fill the same vehicles now used to deliver coal. Torrefaction, a process similar to coffee roasting, increases the energy density of biomass to about 11,000 Btu/lb and makes it waterproof and friable.
Install biomass gasifiers
Biomass gasifiers can be located anywhere on the property to produce syngas, which is piped to burners installed in the coal boilers. As with natural gas conversion, only a brief shutdown is required for installation. Direct coal firing is still possible if desired. Fluidised bed gasifiers are extremely efficient and can work with a wide variety of feedstocks including waste.
Solar preheating of boiler water
Solar thermal preheating of boiler water efficiently captures the energy of the sun and reduces fuel consumption. Solar heating peaks in the middle of the day but is ineffective at night. By using the sun to preheat water, fuel requirements are reduced by an amount equal to the heat captured. It is particularly effective on the same bright sunny days that maximise air conditioning loads. Carbon credits and investment credits are available.
Sell waste energy
Combined Heat and Power (CHP) plants achieve up to 90% overall efficiency by selling waste power instead of disposing of it in cooling towers or streams. Existing plants can be modified to do the same thing by leasing adjacent or excess land for energy-intensive industrial use. Kilns, ethanol and drying plants can buy hot steam and then pass it on to lower temperature applications like cold storage, greenhouses and fishponds. In urban areas hot water is sold for district heating. In Denmark hot water is sent through insulated pipes 30 miles with only 10% loss.
Author: Thomas Blakeslee, The Clearlight Foundation,
Read the article online at: https://www.worldcoal.com/coal/20102009/five_ways_to_green_existing_power_plants/