A thermal plant comprising - a thermal reactor in which a chemical process takes place during which process solid fuels being biomass or waste react with oxygen to produce an exhaust gas comprising hot flue gas - gas coolers (39, 40) cooling the exhaust gas to a temperature below the dew point of the water present in the exhaust gas thereby producing a condensate; - an exhaust gas heat exchanger arranged upstream of the gas coolers (39, 40) for extracting heat from the exhaust gas - a condensate cooler cooling condensate to extract energy from condensate - wherein the thermal plant comprises a particle separation system for separating particles from a stream of particles produced in the thermal reactor, the particle separation system comprises said gas coolers in the form of a quench and a scrubber for producing - a first stream of water having a first content of particles in the exit water of the quench, - a second stream of water having a second content of particles in the exit water of the scrubber, wherein - the ratio between the second stream of water and the first stream of water when measured in m3/h is larger than 5, - the content (kg/m3) of particles in the first stream is larger than the content (kg/m3) of particles in the second stream of water, and, wherein the plant further comprising - feeding means provided for feeding at least a fraction of the first stream of water to ash produced in the thermal reactor and/or to a fuel for the thermal reactor. - a thermal reactor in which a chemical process takes place during which process solid fuels being biomass or waste react with oxygen to produce an exhaust gas comprising hot flue gas - gas coolers (39, 40) cooling the exhaust gas to a temperature below the dew point of the water present in the exhaust gas thereby producing a condensate; - an exhaust gas heat exchanger arranged upstream of the gas coolers (39, 40) for extracting heat from the exhaust gas - a condensate cooler cooling condensate to extract energy from condensate - wherein the thermal plant comprises a particle separation system for separating particles from a stream of particles produced in the thermal reactor, the particle separation system comprises said gas coolers in the form of a quench and a scrubber for producing - a first stream of water having a first content of particles in the exit water of the quench, - a second stream of water having a second content of particles in the exit water of the scrubber, wherein - the ratio between the second stream of water and the first stream of water when measured in m3/h is larger than 5, - the content (kg/m3) of particles in the first stream is larger than the content (kg/m3) of particles in the second stream of water, and, wherein the plant further comprising - feeding means provided for feeding at least a fraction of the first stream of water to ash produced in the thermal reactor and/or to a fuel for the thermal reactor. - a first stream of water having a first content of particles in the exit water of the quench, - a second stream of water having a second content of particles in the exit water of the scrubber, - the ratio between the second stream of water and the first stream of water when measured in m3/h is larger than 5, - the content (kg/m3) of particles in the first stream is larger than the content (kg/m3) of particles in the second stream of water, - feeding means provided for feeding at least a fraction of the first stream of water to ash produced in the thermal reactor and/or to a fuel for the thermal reactor.