Energy-saving optimization scheme for titanium heating tube heating systems in large continuous fermentation workshops

Title: Energy-saving optimisation scheme for titanium heating tube heating systems in large continuous fermentation operations The heating power consumption of fermentation tanks, which are equipped with pure titanium heating tubes, is a significant component of the workshop production costs. These tanks operate continuously throughout the year. Energy waste that results from unreasonable design and operation control is often overlooked by numerous enterprises, which exclusively concentrate on anti-corrosion performance. By optimising energy efficiency from four dimensions-heating tube structural design, medium circulation matching, intelligent temperature control logic, and routine maintenance management-this article reduces comprehensive power consumption by 10%–18%. The objective is to safeguard the titanium passive film and extend the service life of the equipment. ## 1. Optimisation of the structural design of titanium heating tubes for energy efficiency Designing a configuration with a low surface power density is the primary energy-saving measure. Excessive tube wall temperature, additional heat loss to tank insulation, and accelerated scaling are the consequences of high surface power density. Optimise in accordance with the production load: - Continuous fermentation at high temperatures and high viscosity: Utilise an ultra-low heat load design with a heat load of 0.3–0.5 W/cm², increase the outer diameter of the tube, and divide the multi-tube configuration to disperse the heat load. - Conventional medium-temperature fermentation: Maintain a power density of 0.5–0.8 W/cm². Effect: Decrease tube wall overheating loss by 7%–12%, and maintain long-term stable heat exchange efficiency by slowing carbon scale deposition. ### 1.2 Enhance the installation angle and flow guiding structure - To prevent bubble stagnation, corrosion, and local thermal dead zones, install heating tubes with a 10°–15° upward inclination instead of a horizontal arrangement. - Install diversion baffles around tube bundles and match arc-shaped PTFE supports to create a spiral high-speed scouring flow around the tube wall. This will increase the heat transfer coefficient by 8%–10%. ### 1.3 The wall thickness should be selected to balance the allowance for corrosion and heat conduction. Thermal resistance is enhanced by an excessively thick titanium wall, while an ultra-thin wall results in frequent maintenance closure losses. The wall thickness of a standard TA2 tube is as follows: - Wall thickness for a normal capacity tank is 1.5mm. - Wall thickness for a high-salinity, daily CIP high-corrosion tank is 1.8–2.0mm. The wall thickness should be balanced to prevent frequent tube replacements and energy loss from unanticipated shutdowns, while also ensuring that heat conduction performance and service life are considered. ## 2. Optimisation of medium circulating system matching ### 2.1 Maintain a circulating flow velocity of at least 1.0 m/s in the vicinity of the heating tubes The thermal resistance increases significantly as a result of the static liquid film that forms on the tube surface due to limited flow. Set up variable-frequency circulating pumps: - Decrease the frequency of the pump during the constant temperature holding stage; increase the frequency during the heating-up stage to guarantee scouring flow. Energy benefit: Enhance the heat exchange efficacy of titanium tubes while reducing the auxiliary power consumption of the pump by 15%. ### 2.2 A rational tank aeration layout to eliminate the gas thermal insulation layer Bubble coverage on the tube surface results in an air thermal resistance barrier due to insufficient aeration. Continuous micro-aeration during a constant temperature period eliminates stagnant air pockets, improves heat transfer, and discharges supersaturated dissolved gas. ### 2.3 Install a waste heat recovery device for the CIP cleansing liquid. The discharged high-temperature cleaning liquid is directed through heat exchangers to preheat the new clean water entering the tank, recover waste heat, and reduce the power consumption of the heating tube startup after acid-base cleaning of titanium tubes. 3. Energy-saving logic for intelligent temperature control (to prevent the consumption of invalid power) ### 3.1 Control of segmented gradient heating, which prevents continuous full-power startup 1. Heating-up stage: 70% of the rated power is used to prevent the formation of massive bubbles and a sudden temperature increase. 2. Culture stage at constant temperature: intermittent power compensation of 30%–50%, with closed-loop PID temperature difference control. 3. CIP cleaning stage: Reduce the heating power by 50% or completely cease heating to prevent the high-temperature acceleration of acid-base passive film erosion and unnecessary power waste. ### 3.2 Protection against liquid level interlock power-off To prevent dry heating vacant load power consumption and dry-out concentrated corrosion damage to titanium tubes, the heating circuit is automatically shut off when the liquid level falls below the heating tube bundle. ### 3.3 Temperature control for multi-tube groups that are independent of one another Multiple heating zones are established in large-volume fermentation vessels, each with its own temperature probe and power regulation. The heating tube group should be initiated in the low-temperature zone, and redundant heating tubes should be stopped in uniform temperature areas to prevent overheating of the local broth. ## 4. Energy-saving management through routine maintenance (prevents heat exchange attenuation induced by scaling) ### 4.1 Adhere to the standard graded descaling cycle strictly. The thermal conductivity of carbonised organic scale and inorganic mineral scale is incredibly low; a 0.1mm thick scale can reduce heat exchange efficacy by over 10%. - Low-load tank: Monthly standard CIP cleansing - High-sugar, high-viscosity tank: Deep descaling with a composite solution of hydrogen peroxide and citric acid is performed on a biweekly basis. The original metal heat transfer performance of titanium tubes is restored through the thorough removal of scale, which in turn reduces the long-term average heating power consumption. ### 4.2 Passive film damage and surface pitting require prompt repair. The effective heat exchange area is reduced by local corrosion fissures, which create stagnant liquid dead zones. Restore the smoothness of the tube surface by conducting polishing and re-passivation during the semi-annual overhaul. ### 4. Replace ageing supporting accessories in a timely manner Medium leakage and heat loss are the result of aged, deformed PTFE gaskets and fractured insulation sleeves. Continuous heat loss at flange gaps is eliminated by performing a unified replacement every six months. ## 5. Energy-saving effect comparison table of each optimisation measure | Optimisation Category | Specific Measure | Average Power Saving Rate | Additional Benefit for Titanium Heating Tubes | | ---- | ---- | ---- | ---- | | Structural design | Low surface power density + diversion baffle layout | 7%~12% | Suppress tube wall overheating, slow scaling & passive film cracking | | Circulation system | Variable frequency circulating pump + continuous micro-aeration | 5%~8% | Eliminate bubble stagnation pitting corrosion | | Intelligent control | Segmented PID heating + liquid level interlock power-off | 4%~6% | Avoid dry-out damage, reduce thermal stress cycle damage | | Maintenance management | Regular full descaling + pitting repair passivation | 10%~15% | Recover full heat exchange area, extend tube service life | | Waste heat recovery | CIP cleaning liquid heat exchanger recovery | 3%~5% | Reduce heating startup load, cut cleaning energy consumption | ## 6. Guidance on the priority of implementation for manufacturers 1. Short-term zero-cost transformation (immediate execution): Standardise gradient heating operation, optimise PID temperature control parameters, and rigorously implement monthly CIP descaling procedures. 2. Medium-term low-cost transformation (within the overhaul cycle): Install liquid level interlock protection, modify the circulating pump variable frequency, and install tank diversion baffles. 3. Long-term equipment upgrades (tank reconstruction or tube batch replacement): Implement a low-heat load multi-tube split layout and implement a CIP waste heat recovery system. Summary of the Main Points The energy efficiency of the titanium heating tube fermentation heating system cannot be solely dependent on a single equipment transformation. In conjunction with consistent descaling maintenance, segmented intelligent temperature control, variable frequency circulating matching, and low heat load structural design, the workshop's overall power consumption can be reduced by 10%–18%. All energy-saving measures simultaneously prevent tube wall overheating, bubble stagnation, and scaling corrosion, safeguard the titanium dioxide passive film, and achieve the dual benefits of extending the service life of heating tubes and reducing energy costs.