NOVELTY - A composite filtering device comprises a water bath sprayer, a heat exchanger, and a dry filter. The three parts form an integrated composite structure. The water bath sprayer, i.e. a container with a spraying device, comprises a water inlet pipeline, a water outlet pipeline and a gas conveying pipeline. The heat exchanger comprises a gas inlet chamber, a gas outlet chamber and a heat exchanging area. The dry filter comprises at least two layers, where adjacent layers are separated by an interlayer and connected with the gas conveying pipeline.    USE - A composite filtering device for a biomass fuel gas (claimed).    ADVANTAGE - The composite filtering device has a compact structure; and is small in space area, and more convenient in installation. It can realize the gasification and channelization of biomass waste material in villages, and can enable villagers to use the clean and convenient fuel gas. The filter is more sufficient, so that a cleaner and pollution-free fuel gas with higher purification can be obtained with de-tarring rate of more than 99%.    DETAILED DESCRIPTION - A composite filtering device comprises a water bath sprayer, a heat exchanger, and a dry filter. The three parts form an integrated composite structure. An inside of the composite structure is orderly connected to a gas inlet chamber of the heat exchanger from an upper part of the water bath sprayer via a gas converting pipe; and then connected to a lower part of the dry filter from a gas outlet chamber of the heat exchanger. A thermal insulating course is installed between the water bath sprayer and the dry filter. The water bath sprayer which is a container with a spraying device comprises a water inlet pipeline, a water outlet pipeline and a gas conveying pipeline. An inside of the water bath sprayer is stored with water with a certain height. A gas inlet of the composite filtering device is installed on a middle part of the water batch sprayer and above the highest water level. The gas conveying pipeline of the gas inlet is inserted with water stored in the water bath sprayer from the gas inlet. The heat exchanger comprises a gas inlet chamber, a gas outlet chamber and a heat exchanging area. The heat exchanging area comprises cooling circulatory water, a water inlet and outlet pipeline, and a heat exchanging pipe steeped in the water. The gas inlet and outlet chambers are separated by two baffles on the two ends of the heat exchanging area. The two ends of the heat exchanging pipe are respectively connected with the gas inlet and outlet chambers. The dry filter comprises at least two layers, where adjacent layers are separated by an interlayer and connected with the gas conveying pipeline. Each filtering layer is installed with at least four filter screens. The fuel gas is conveyed to the next filter layer by the gas conveying pipeline after passing by the filter screen. A gas outlet of the composite filtering device is installed on the upper part of the dry filter. The composite filtering device is installed with a sludge discharging valve on a bottom of the heat exchanger.    DESCRIPTION OF DRAWING(S) - The drawing is a sectional view of the composite filtering device.