PDF《Sulphur burning optimization》

Sulphurburningoptimization Optimum equipment for sulphur burning in sulphuric acid plants is not a trivial matter.

However, owners and operators can benefit from technology providers with deep knowledge of the process, command of cutting edge analysis tools, and the ability to integrate analytical results with robust equipment designs. Thus, when analyzed by the right industry experts, facility owners can realize improvements that meet and even exceed their goals. he sulphur furnace in a sulphur burning sulphuric acid plant is generally a large horizontal cylindrical vessel of carbon steel, lined internally with refractory brick. Air and liquid sulphur are fed into the furnace via a sulphur gun equipped with an atomizing spray nozzle or a rotary cup burner. The internals of a sulphur furnace are important to ensure complete combustion of sulphur to sulphur dioxide. The reaction is highly exothermic resulting in a large temperature increase. A waste heat boiler downstream of the furnace is used to remove much of the heat of combustion. The design of the sulphur furnace must achieve good gas mixing and full combustion of sulphur prior to leaving the furnace and entry to the boiler section. Sulphur droplets impinging on the baffle or checker walls will vaporize immediately and burn to sulphur dioxide. Any unburned sulphur that impinges on the carbon steel surfaces of downstream boilers, ducting and heat exchangers will corrode the steel. Understanding spray technology When producing sulphuric acid from molten sulphur, it is critical that the sulphur is atomized into sprayed droplets such that combustion occurs efficiently and within the design parameters of the furnace. Each furnace is designed to accommodate a particular throughput of sulphur to oxidize into sulphur dioxide;

however, the form or the size of the sprayed droplets produced becomes a major factor in determining when this combustion occurs. The spray nozzle needs to handle a bulk mass of fluid that is delivered through it at a specific pressure drop. When this mass of fluid exits the nozzle, it is then converted into a predictable drop size spectrum with a specific spray coverage or distribution inside the furnace. The drop size and coverage required depends on the performance characteristics of the furnace. These include the length and width of the furnace, heat load, amount of oxygen for combustion, placement of baffles, and flow rate of the air through the furnace. Spraying Systems Co. spray nozzle types Spray nozzles can be split into two broad categories, either hydraulic or pneumatic (also called air atomizing or two-fluid nozzles). Hydraulic spray nozzles use only the liquid back pressure to determine the flow rate, spray pattern, and droplet atomization. Pneumatic spray nozzles use an additional fluid, typically compressed air, to provide primary liquid breakup. Hydraulic spray nozzles can be further classified into spray pattern types such as hollow cone, full cone, and flat spray patterns. For sulphur burning, the most common types of nozzles are hollow cone hydraulic nozzles and pneumatic since these typically have larger free passages and create smaller droplets than the other nozzle styles. The BA sulphur burning nozzle is a commonly used hollow cone spray nozzle for sulphur burning. It produces small to medium size droplets, has a fairly large unobstructed flow passage to minimize clogging, and has a relatively low cost to operate as compared to a pneumatic nozzle since it does not require compressed air. Pneumatic spray nozzles require compressed air to provide primary atomization. The liquid and the gas can meet either inside or outside of an air cap depending on the design chosen. Pneumatic nozzles can create either a flat spray or a round spray pattern, and they produce the smallest droplets of any of the conventional spray nozzles. Common problems Common problems associated with molten sulphur spraying include spray atomization, turndown, plugged nozzles, and sulphur gun design. The reason that atomization and drop size is so important is that it directly affects the rate of heat transfer between the combustion gas and the sulphur. Too often, spray nozzles are chosen based mostly on their flow rate instead of on their performance. Drop size affects overall surface area. For example, by merely breaking up a single