Demonstration of non-linear model predictive control for optimal flexible operation of a CO2 capture plant

Due to the penetration of renewable intermittent energy, there is a need for coal and natural gas power plants to operate flexibly with variable load. This has resulted in an increasing interest in flexible and operational issues in the capture plant as well. In the present paper a nonlinear model predictive control (NMPC) system was tested at the Tiller pilot plant in Norway. The most important part of the NMPC software is the dynamic model representing the absorber/desorber plant. A previous first principle (mechanistic) dynamic model of the plant using MEA was modified for a solvent of AMP and piperazine, and then successfully verified by step response tests. The NMPC, which was set up to minimize the deviation from the capture rate setpoint and minimize the specific reboiler duty was then tested in a closed loop with large changes in flue gas flow and CO2 composition. Even for gas rate variations of more than 300% (110–340 m3/h) and CO2 concentration changes of 30%, the dynamic response was satisfactory. A test with frequently occurring constraints on the reboiler duty revealed a need for an extension to include direct control of the lean loading. Test of setpoint changes in total CO2 recovery showed that the control system managed to rapidly change from one capture rate to another with a time constant of typically 10 min. This might be used in a second layer of optimization, a dynamic real-time optimizer, that minimizes the capture costs during a longer horizon considering varying energy prices.publishedVersio

Dampak kebijakan IPPK dan IUPHHK terhadap perekonomian masyarakat di Kabupaten Malinau

Regional autonomy (OTDA) has opened up the opportunity for districts to manage their forest resources (SDH), however, the division of authority between district and central governments remains unclear. So, how and to what extent can this opportunity improve community livelihoods? For the research presented here, data was collected to answer these questions for the case of Malinau District, where, as in other forest-rich regions, decentralization has been marked with regional government (Pemda) policies granting IPPK (timber extraction and utilization permits) and IUPHHK (forest timber product exploitation permits, better known as mini HPHs). The research, conducted in the three villages of Long Pangin, Laban Nyarit, and Langap between April and June 2004, show these policies have not had the desired results. Communities’ lack of capital and technical capacity led them to give their permits to people with better access to capital. Communities only received fees. Communities’ lack of access to information and support when negotiating with these entrepreneurs resulted in agreements where the entrepreneurs enjoyed the greatest benefits while communities were left with very little

The importance of timber prices and other factors for harvest increase among nonindustrial private forest owners

Increased harvest is high on the forestry and climate policy agenda in several countries. We explored to what extent private non-industrial forest owners in Norway are willing to increase harvest due to elevated hypothetical prices by carrying out a national-wide survey of forest owners. The results indicate that owners who have not harvested timber for sale the last fifteen years do not respond to large price shifts. Instead, ownership objectives and knowledge of a key policy instrument predict willingness to enter the timber market among these owners. The willingness among owners who have sold timber the last fifteen years depends on these factors, in addition to price, forest area, income and gender. Female owners were significantly less willing than male owners to increase harvest. Once the decision to harvest was taken, the stated timber supply volume per area unit decreases with productive forest area both among active and inactive owners. With regard to sources of information, owners who have not harvested timber the last fifteen years use to less extent the information sources other owners do. Forest policies and extension services should acknowledge that for stimulating forest owners outside the timber market to supply wood,other factors than price are important, and that alternative information pathways should be explored for reaching these owners