357 MMBtu/hr (105 MWth) Renewable energy from cattle manure

Panda Ethanol required a source of economical,reliable and renewable steam for its new ethanol plant in Hereford, Texas.

Using fossil fuels for the production of green ethanol was not fitting in with the eco-friendly image of ethanol production and therefore Panda Ethanol was looking to reduce the carbon footprint of the ethanol production.

Outotec bubling fluizided bed boiler is designed to convert one billion pounds of cattle manure a year into usable energy for an ethanol plant.

By using a renewable fuel (cattle manure) to create a renewable fuel (ethanol), Panda is eliminating exposure to natural gas pricing volatility, conserving the energy equivalent of 1,000 barrels of oil a day and creating a significant market advantage in their ethanol production costs.

In addition, by disposing of the manure in a clean environmentally friendly manner, Panda is addressing the environmental hazards related to field application of cattle manure in the Hereford, Texas region.

Summary

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Customer
Panda Ethanol
Location
USA
Delivery year
2008
Technology
BFB
Commodity
Biomass
Scope
EPC

Challenge

  • High fuel moisture content
  • High fuel alkaline content
  • Large amount of noncombustible “tramp” material in the fuel

Solution

  • Outotec Bubbling Fluidized Bed boiler island
  • Supplied to the client as a “metering bin-to-stack” solution

Benefits

  • Stable operation with varying fuel quality
  • Reduced slagging potential due to low operating temperatures
  • Online bed recycling system removes tramp material and re-injects clean bed media automatically.

The system is designed to operate on 100% cattle manure, or a mixture of manure and many other fuels. Outotec’s bubbling fluidized bed energy system is the first commercially successful system to operate on 100% cattle manure

In this process, relatively wet cattle manure is introduced into a bubbling sand bed which is maintained at a precise temperature. This bed effectively drives off the moisture and converts the organic materials into a usable energy in the form of hot gas. The gas is run through a specially designed boiler that produces steam for use in the ethanol process. The result is a clean, odor-free conversion of cattle manure, or other biomass materials, into clean usable steam.

Initial heat for starting up the renewable energy system is provided by overbed and underbed burners fired by natural gas. Air from the 900 HP forced draft (FD) fan fluidizes the bed media such that it bubbles like a boiling pot of water. Fuel entering this hot, bubbling bed area, first releases its moisture, then oxidizes in the combustion chamber to release its thermal energy.

Hot flue gas rises above the bed into the upper vapor space. NOx abatement occurs inside the main vessel’s upper vapor space via nozzles that spray ammonia into the flue gas, which then reacts with nitrous oxides to form nitrogen, carbon-dioxide and water.

Any remaining, inert fuel contaminants, such as metal or rock are removed from the bed continuously during normal operation via Outotec’s proprietary bed material cleaning, handling, and storage system.

Energy is recovered from the sensible heat produced via a boiler design proprietary to Outotec. This boiler produces over 267,000 lbs/hr of saturated steam at 155 psi. Any remaining energy that cannot be utilized for steam production is recovered in the economizer, which pre-heats the incoming water to the boiler.

Lastly, a 350 HP induced draft fan pulls clean flue gas from the baghouse and disperses it via the stack. Emissions are monitored via a continuous emissions monitoring system (CEMS), which measures carbon monoxide, oxygen, nitrogen oxides, sulfur dioxides, and opacity.

Flue gas cleanup is first accomplished via hydrated lime injection into a dry scrubber. The partially-cleaned flue gas continues into a pulse-jet fabric filter baghouse, in which over 99% of the particulate matter is removed.

BFB Plant facts:

Fuel Throughput 1500 tpd of cattle manure
Ash quantity Approximately 55%
Boiler Steam  
Generation capacity: 267,000 lbs/hr
Pressure: 155 psia
Temperature: 360°F
Economizer Inlet Temp: 280°F
Flue Gas Cleaning  
Gas quantity: 502,000 lbs/hr
Flue Gas Exit Temp: 293°F
Ash Silo Capacity: Approx seven (7) days of operation
Emissions: NOx, SOx, PM, HCl, CO, Opacity complies with all standards for the state of Texas.

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