How to cut fossil fuel use by 90 per cent
Momentive Specialty Chemicals manufactures resin with little need for fossil fuels, thanks to an engineering project that has cut fuel use and CO2 emissions by nearly 90 per cent.
The company, working with Energy Plant Solutions were honoured at the EECA Awards on 28 May, picking up both the Large Business and Innovation trophies for a boiler installation that runs on waste gas from its own manufacturing process.
The project was described by judges as “comprehensive and innovative, with great teamwork”.
“All the numbers in this project are impressive – carbon savings, energy, particulates and other benefits,” the judges said.
The plant in Hornby, Christchurch, manufactures specialised resins used in the engineered wood panels industry.
A by-product of the manufacturing process is a waste gas stream containing 19 per cent hydrogen with the balance gases of nitrogen, carbon dioxide, water and a small per centage of organic compounds.
Momentive wanted to harness the low calorific value waste gas being f lared to atmosphere and use it as a fuel to generate steam in a boiler plant. This would greatly reduce the need for light fuel oil to fire the existing boiler plant. The intent was to reduce energy use, as well as CO2 and sulphur emissions, to improve the plant’s environmental footprint.
Although similar projects had been carried out at Momentive sites overseas, plant differences meant a direct copy of those designs were not possible. Momentive turned to Energy Plant Solutions to design a combustion system that would integrate with its New Zealand processes.
The project involved supplying and installing a high efficiency EPS 4 Degrees package steam boiler. In addition to the boiler, EPS designed and manufactured a burner and automated control system to combust the waste gas stream.
The waste gas is produced at a rate of up to 3,900 cubic metres an hour and is directly proportional to the production rate of the process plants. Given the nature of resin manufacture, process plant steam demand can be highly variable.
EPS and Momentive worked closely together to integrate the new boiler control system with the existing facility. The result is a boiler installation that needs little fossil fuel for continuous operation.
Completed in May 2013, the tail gas boiler plant reduced fuel use by 89.5 per cent in its first seven months, compared with 2012’s average. This reduces CO2 emissions by a projected 1300 tonnes a year. Sulphur emissions have reduced by 99 per cent and PM10 emissions by 93 per cent, assisting with air quality targets in the Christchurch urban air shed.
This project is an extremely successful industrial scale installation, centred on energy efficiency, waste minimisation and productivity gains. A chemical manufacturing facility is now able to use its own waste stream as a fuel to produce a process steam supply to manufacture.
The Momentive project differs from normal boiler installations. Typically burners fitted to boiler plants run on conventional fossil fuels and the fuel f low is regulated to maintain the steam pressure or water temperature at the set point.
At Momentive, the waste gas stream is proportional to the production rate of the manufacturing process. It is not possible to store the gas so it must be combusted as it is produced.
There was also the challenge of trying to get clean, efficient and reliable combustion when only 20 per cent of the fuel is combustible.
EPS engineered a system that measures the waste gas stream f low rate. The f low meter automatically corrects for pressure and temperature. The gas f low data is used to calculate the required air quantity to achieve the desired air/fuel ratio. An O2 sensor in the f lue gives the system feedback on the actual air/fuel ratio.
The system then trims the air f low by either increasing or decreasing the air damper and fan speed. EPS also spent time perfecting the burner head design to ensure adequate mixing of the waste gas stream and combustion air.
The results speak for themselves, and have set a new Momentive benchmark for fuel use per tonne of resin in the Australasia region.
David Early, Momentive Process Control Engineer for Australia / New Zealand region,says: “The environmental benefits were central to the project, and these were communicated clearly throughout the process.”
Energy Plant Solutions has applied the learnings from the Momentive plant to solve issues with other burner installations, operating in unusual applications.
The next step for the company is to develop burner technologies that improve the combustion of bio-gases and bio-oils derived from woody biomass – offering even more scope for CO2 emission reduction.