The heating methods for pickling solutions generally include direct steam heating, steam jet heating, steam heating tube heating, electric heating element heating, immersion flame heating, direct hot exhaust gas heating, and hot water heating tube heating. Their advantages and disadvantages are as follows:
(1) Direct Steam Heating Method
Advantages: Simple and convenient, requiring only the placement of a steam pipe (or a rubber hose over it) directly into the pickling solution. High heat utilization efficiency of steam, which can accelerate the pickling process.
Disadvantages: High noise levels, vibrations, inadequate mixing effect, prone to damage of steel pipes and rubber hoses, and dilution of the acid solution by steam condensate.
(2) Steam Jet Heating Method
Advantages: Lower noise levels, reduced vibrations, better mixing effect, high heat utilization efficiency of steam, and improved quality of pickled steel pipes.
Disadvantages: Requires special acid-resistant metal construction, higher costs, and dilution of the acid solution by steam condensate.
(3) Steam Heating Tube Heating Method
Advantages: Avoids dilution of the pickling solution by steam condensate, reducing acid consumption.
Disadvantages: Low heat utilization efficiency of steam, high manufacturing costs for heaters, occupation of effective working volume in the pickling tank, and poor mixing effect.
(4) Electric Heating Element Heating Method
Advantages: Compact equipment structure and convenient use.
Disadvantages: High costs, potential hazards if heating elements are damaged, occupation of a certain working volume in the pickling tank.
(5) Immersion Flame Heating Method
Advantages: Rapid heating, good mixing effect of the pickling solution, and no dilution of the pickling solution.
Disadvantages: Complex equipment structure, high manufacturing costs, risk of overheating and evaporation of the pickling solution, and requirement for a gas fuel supply.
(6) Direct Hot Exhaust Gas Heating Method
Advantages: Low heating costs and high heat utilization efficiency.
Disadvantages: Potential contamination of the pickling solution and higher equipment costs.
(7) Hot Water Heating Tube Heating Method
Advantages: Prevents dilution of the pickling solution and reduces acid consumption.
Disadvantages: Poor heat utilization efficiency, occupation of a certain working volume in the pickling tank, and higher equipment costs.
Considering the above heating methods, direct steam heating is generally the primary method adopted in practice domestically.
