鍋爐
施工中遇到的問題...
燃煤鍋爐，生物質鍋爐等各類鍋爐，在使用燃料燃燒過程中，會產生顆粒物和廢氣污染。
這些物質需要專用的通風/過濾系統，以確保安全的工作環境。
生物質鍋爐 & 燃煤鍋爐
鍋爐是一種大部分工廠都必備的生產工具，產生能量蒸汽為生產服務。鍋爐有各種類型，大部分都是以燃燒生物質與燃煤為主。燃料的燃燒過程中不可避免的會產生大量的顆粒物與有害氣體，造成大氣污染，破壞廠區環境，所以需要一種有效可靠的手段來抑制顆粒物與有害氣體的擴散。
危害物
鍋爐燃燒后產生的主要危害物：高溫火星，顆粒物，硫化物，氮氧化物在各種危險中。如果沒有經過處理直接排放到大氣中，將會造成嚴重污染引起霧霾酸雨，工人吸入后也有中毒風險。應及時收集到處理設備中，并為現場員工提供個人防護、通風及培訓。
設備設計思路:
確保排放達標達標，在確保達到有關污染物排放標準的前提下，將“運行可靠不影響工藝及工人的操作習慣”作為重要的設計目標考慮。
降低成本， 優化及精心設計，降低、節省一次性工程投資。 做到降低除塵電耗，減少運行成本。
確保消防安全， 確保消防安全，力求綜合效益的先進性，在確保排放濃度達標的前提下充分提高煙塵捕集率。
設備運行穩定， 保證長期穩定運行,管理簡單方便。
Each welding method and material type must be assessed to ensure appropriate filtration media are chosen. Here are some examples:
- HEPA filters are well suited for stainless steel welding.
- Nanofiber filters meet the needs for welding aluminum and parts containing high levels of manganese.
- Polyester filters are satisfactory where rust inhibitors, lubricants and coatings may generate an oily smoke.
Grinding and Deburring
Grinding and deburring activities generate airborne particulate matter that should be confined or removed from the operator’s working environment.
Typical sources include grinding, angle grinders, die grinders, automated grinding machines, deburring stations and many other abrasive processes.
Hazards
Grinding generates significant quantities of dust and sparks which require a large number of filtration media to handle the increased loading. Deburring produces submicron particles that can only be filtered with units that qualify as HEPA.
Laser & Plasma Cutting
The two main thermal cutting processes employed in industry to cut steel, metals, plastics and sometimes other materials are laser and plasma cutting.
Laser cutting
Used in serial manufacturing by directing a high-power laser light beam, with the help of laser optics and CNC (computer numerical control) to cut flat-sheet and structural steel or metal alloy components.
Operation / efficiency
The metal melts, burns, or vaporizes away by a jet of gas, leaving a remarkably clean edge with little, if any, asperities. Although principally used to cut metal, various plastics are also cut, engraved and etched with a laser. Cutting acrylic is common, but other types of plastics may be cut with a laser, such as polycarbonate, polypropylene and polyethylene.
Plasma cutting
Utilizes a gas, such as nitrogen, argon or oxygen, which is projected at high velocity through a channel / nozzle in combination with an electric arc to produce a plasma torch.
Operation / efficiency
The extremely high temperature of the plasma stream melts and projects the molten metal and slag away from the shear surface. Secondary channels on the nozzle periphery allow the constant flow of shielding gas to control the radius of the plasma beam and protect the cut from oxidation. As with other robotized equipment, CNC technology applied to plasma cutting devices provide the needed flexibility to cut a myriad of patterns, shapes and sizes with accurate cuts, leaving no metal chips. Recent technological developments allow smaller nozzles with narrow CNC plasma streams which boast near-laser precision on plasma cut edges that surprisingly require little or no finishing.
Additional Information
Hazards
Despite their unmistakable advantage in the mass production of finely cut, seemingly tailor-made manufactured parts, these technologies represent a potential threat to worker health and safety.
The IRSST (Quebec), NIOSH (USA) and research affiliates in England, France and Germany provide concerted guidance to promote worker health and safety in industry.
Laser and plasma cutting of metal creates metal dust, smoke and fumes that are unhealthful to breath. OSHA recognizes zinc, lead, beryllium, cadmium, manganese, nickel and chromium as possible hazardous elements that are released to the ambient air depending on the type of metal cut.
Coated metals
Some metals are coated, such as galvanized steel, lead or cadmium-plated steel: We recommend you remove the coating from the cutting area if possible. These coatings and any metal containing these elements give off toxic fumes when cut with a plasma arc. Of particular concern is hexavalent chromium, a coating used in metal finishing to prevent corrosion on stainless steel and other metals: plasma torch cutting of this material exposes workers to hex chrome dust, which is a heavy metal known to be a potent carcinogen when inhaled. In 2006, OSHA enforced regulatory compliance to protect employees from hexavalent chromium exposure.
Laser cutting of plastics
Laser cutting of plastics such as polypropylene, polyethylene and polycarbonate generates benzene, a carcinogen. Polystyrene gives off styrene, while PVC releases hydrogen chloride. Many plastics release submicron particles, in addition to carcinogenic PAHs (polycyclic aromatic hydrocarbons). Fluoropolymers such as PVDF, ECTFE, PFA, FEP and PTFE (used as a non-stick coating for hot plates) are sensitive and start to react at moderately high temperatures, giving off hazardous fumes.
For these reasons, we recommend capturing fumes at their source. If this is impractical, down-draft containment of rising fugitive gas emissions that escape the immediate vicinity of thermal cutting tables may be an acceptable compromise. And if these methods do not suffice, it may be necessary to design complete systems that include ventilation of open areas and thus encompass all avenues of fume propagation.
To Summarize
First and foremost
Capture the thermally generated fumes at their source. Plasma and other thermal cutting generate sparks, slag and fumes that contain different contaminants depending on the type of material cut. These heavy smoke applications require high capture velocities at source to avoid contamination of the work environment outside the enclosure.
Secondly
Down-draft containment limits propagation by encapsulating fumes that migrate to the backside and/or underneath cutting tables. Keep floating sparks at bay and avoid their dispersion upward as these may blend inconspicuously with rising smoke; uncontrolled and unmonitored, these mixtures constitute a serious fire hazard should they enter the dust collection system.
Finally
To assess available techniques that will effectively capture and filter fumes generated from large CNC plasma cutting and laser cutting machines, it may become apparent that only a large central dust collector is suited to pneumatically convey the intense smoke and vaporized metal / plastic dust in a safe and secure manner. AIREX provides an inline spark arrestor / suppression conduit along with a self-cleaning dust collector with multiple filter cartridges as a possible comprehensive solution to remove airborne contaminants from thermal cutting operations.
