Filtration and environmental technologies group Porvair expects to exceed its cash generation expectations in the year to November 30 and achieve its sales and profit targets.Net debt is anticipated to be better than expectations and to have reduced by over £2m in the year to less than £14.5m, the firm said.The microfiltration division, which serves the aviation, energy, clean water and industrial markets, has continued to trade as expected, it said. Selee, the largest part of its metals filtration division that underwent a severe restructuring programme in the second quarter as demand collapsed, has returned to modest profitability, it added.'Looking ahead, the board's planning assumption is that the difficult economic climate will continue throughout 2010, however the near term order book is encouraging,' the company said.