• Innovative energy-conservation concept for cardboard manufacturers

Innovative energy-conservation concept for cardboard manufacturers

The constantly escalating costs of energy are forcing companies - and particularly those that have high energy costs in their manufacturing process - to look at and engage in new concepts for improving energy efficiency. At the BHS Innovation Days, Prof. Dr. Ing. Markus Brautsch from the Amberg – Weiden Institute of Technology presented an innovative energy conservation concept for cardboard manufacturers, the introduction of which is being supported by BHS.

As part of a case study, a typical cardboard factory with halls for the production and further processing of cardboard products and smaller halls for the shipping, administrative offices and a boiler house was investigated. At this particular plant, a natural gas-fired boiler produces the process steam for the cardboard production. Part of the steam is pressure-reduced and utilised by steam fan heaters in the production base and for the water heating system. This system is very inefficient in terms of engineering technology. A prerequisite for innovative energy production is the replacement of the steam heating by a modern hot water heating system. The production areas which like the cardboard production process are actually reliant on process steam must in addition be supplied via the gas-fired boiler. Finally alternative types of energy supply are only worth considering if preliminary temperatures up to 90 °C are sufficient.

Six different energy supply solutions were investigated in terms of their economic considerations within the framework of a dynamic modernisation in accordance with the capital value method and with a sensitivity analysis. A modern gas-fired system, which covers the complete heat needs for the hot water system, serves as the reference version for the evaluation of the economic aspects and the CO2-balances of the other solutions. One solution consists of a trimmings and offcuts boiler for covering the thermal constant load together with a gas-fired peak load boiler. All of the other versions are based on different combinations of block type thermal power plants BTTP) units for the thermal constant load supply and a gas-fired peak load boiler. A standard BTTP (Fig 1) consists of an internal combustion engine, which drives an electrical power generator the waste heat from which is available for heating purposes. The electricity that is produced is either fed into the factory's power supply or in the event of there being any excess of energy into the National Grid on a reimbursement basis.

In the meantime, in many countries there is a demand for the use of renewable energy through subsidies, power savings or power reimbursements. All of the prices mentioned in the charts are based upon estimates using current market prices and the statutory framework provisions in Germany. Depending on the local fiscal and statutory framework provisions, a somewhat different picture can emerge in other countries.

Under the conditions that apply in Germany, the economic considerations have resulted in the fact that a solution with two vegetable oil-powered BTTPs can already pay for itself after just three years (Fig 2). Whilst the investment costs here may indeed be at the highest level, however by means of the use of in-house produced electricity and the income from making supplies available to the National Grid, the overall bottom line comes out with a positive result.

Similarly the most favourable result is also produced from the point of view of the CO2 balance sheet (Fig. 3): the two vegetable oil-powered BTTPs solution only produces 55% of the CO2 emissions of the reference version. In this, the power/heat combination with its overall efficiency can fully exploit its strengths. By way of a further advantage, one BTTP can work both with different bio-fuels and with fossil fuels. With this, the operator has the highest flexibility in his choice of energy sources.

Thus, the innovative energy production concept fulfils all demands with regard to pricing stability, environmental protection and flexibility. On the one hand, the heat production costs (Fig. 4) are reduced considerably and on the other hand also the CO2 emissions are reduced thanks to renewable energy in this example of an installation by an annual figure of 1600 tons.

Incidentally: this kind of innovative energy concept can be implemented both in cardboard production locations and in the production plants of other industries. BHS Corrugated will provide active support for you in the introduction of this new energy supply concept by means of comprehensive support services and close collaboration with its partners.

Figure 1: Design of a modern BTTP

Figure 2: The solution with 2 vegetable oil-powered BTTPs and peak load boiler pays for itself under the local conditions in Germany in just 3 years.

Figure 3: The solution with 2 vegetable oil BTTPs is the best way of reducing the CO2 balance sheet.

Figure 4: A quick summary of the overall annual and heat- production costs