Design of exhaust system for industrial workshop

Exhaust system. The local exhaust system consists of local exhaust hood (dust suction hood), ventilation duct, ventilator, dust or harmful gas purification equipment and exhaust device. The local exhaust hood (dust suction hood) is a key component of the local exhaust system. Exhaust cabinet is a common partially enclosed exhaust device. When the workpieces producing harmful gas, steam or dust are large and cannot be processed in the exhaust cabinet, the side exhaust hood with one side open and the rest closed can be used, or the side exhaust hood that cannot be closed by any party, or the umbrella hood with upper exhaust can be used, including single side exhaust (slot width<=0.7m), double="" side="" exhaust="" slot="" width=""> 0.7m) and suction slot side exhaust (slot width>=2.0m). The exhaust air volume of the air inlet shall be greater than the air supply jet flow< Br/>In order to obtain a good effect of local discharge of dust, harmful gas or steam, the following requirements should be considered regardless of the type of exhaust hood used: ① The source of harmful substances should be as closed as possible, and the exhaust hood should be as close to the source of harmful substances as possible; ② The suction direction of the exhaust hood or dust hood should be consistent with the direction of harmful substances escaping as far as possible; ③ The exhaust hood shall be arranged so that the polluted air will not flow through the worker's breathing belt; ④ The air exhaust device shall not be set near the door and window to prevent the air flow entering the outdoor from interfering with the air exhaust effect; ⑤ The hood of exhaust hood shall have a certain control wind speed. Create proper air flow at the harmful emission point (i.e. control point) farthest from the hood mouth, so as to suck harmful substances into the hood. The air flow speed at the control point is called the control wind speed (also called the suction speed). That is, the speed should be greater than the speed of harmful substances escaping outward and the speed of preventing cross flow interference, so as to effectively pump harmful substances into the closed equipment. For example, when side exhaust hood is used, in case of the escape of harmful substances, it is necessary to control not only the harmful substances at a close to the hood mouth, but also the harmful substances at b far away. The control wind speed should be Vx, so as to achieve good exhaust effect. The control wind speed shall be related to the toxicity of poisons and the particle size of dust. Generally, the control wind speed for poisons is 0.7-1.0m/s, and that for dust is 1-1.5m/s< Br/>2. In general, comprehensive ventilation is to install a certain number of exhaust fans on the exterior wall, and rely on the exhaust to form a negative pressure indoors, so that outdoor fresh air can enter the room through doors and windows, so that the whole workshop can be ventilated and the concentration of harmful gases can be diluted to meet the requirements of health standards. The air exchange rate of general ventilation can be calculated as follows: L=M/(S-S0) Where: L is ventilation volume (m3/h); M is the emission of harmful gas (mg/h); S is the maximum allowable concentration of harmful gas (mg/m3); S。 Is the concentration of harmful gases in the intake air< Br/>When the vapours of several solvents or several irritating gases are emitted into the air at the same time, the ventilation volume shall be calculated according to the sum of the air volume required to dilute to the maximum allowable concentration respectively. When other harmful substances are released into the air at the same time, the ventilation volume is only calculated according to the harmful substances with the largest air demand<--= bilateral="" exhaust="" slot="" width="" --="">