I. General Provisions

1. These specifications apply to the operation and management of spray tower equipment (including waste gas washing towers and acid/alkali neutralization towers) in fertilizer production workshops, covering the entire process of pre-production preparation, production operation, and maintenance.
2. Operators must pass training before taking up their posts. Before operation, they shall become familiar with the equipment structure and the contents of these specifications. In fertilizer production, the working condition is mainly ammonia-containing alkaline waste gas, which is treated by adding acid for neutralization. The waste gas often contains process dust, and after reaction, ammonium salt crystals are easily produced, causing packing blockage and reduced treatment efficiency. Operators must understand the characteristics of this working condition and possess basic chemical safety knowledge.
3. The spray tower mainly consists of a tower body (PP/FRP material), circulating water tank (liquid storage tank), circulating water pump, spray layer (spiral nozzles/atomizing nozzles), packing layer (Pall rings/multi-faceted hollow balls), mist eliminator layer (baffle mist eliminator/wire mesh mist eliminator), induced draft fan, dosing system (online pH monitoring), piping and valves, and electrical control system. The circulating pump pressurizes the absorption liquid and sends it to the spray layer at the top of the tower. The liquid is atomized and drips from top to bottom, while the waste gas flows countercurrently from bottom to top, fully contacting and reacting in the packing layer. After purification, water mist is removed through the mist eliminator layer, and the gas is discharged up to standard.

II. Pre-Production Preparation Stage

2.1 Pre-Startup Inspection

1. Equipment integrity inspection: Check the tower body, pipes, and flange connections for cracks, deformation, or damage, and check whether sealing is good. Check whether the packing layer is evenly filled, without accumulation or voids. Check whether the spray headers are installed securely and the nozzles are not clogged. Check whether the mist eliminator layer is intact. Clear obstacles around the tower body and in the maintenance accessway.
2. Circulating system inspection: Check whether the liquid level in the circulating water tank is within the normal range (usually 70%–80% of the tank volume). Too low a water level will cause the pump to run dry and be damaged. Check whether the circulating water pump motor wiring is correct, whether the pump rotates flexibly, and whether there is jamming or abnormal noise.
3. Spray system inspection: Check whether the spray piping is unobstructed and whether each valve opens and closes flexibly without leakage. Check whether nozzles are clogged or damaged, and ensure the nozzle direction is correct so that the spray liquid can evenly cover the entire cross-section of the tower.
4. Fan system inspection: Check the wear condition of fan impeller, belts, bearings, and other parts to ensure the fan runs smoothly without abnormal vibration and noise. Check whether the fan inlet and outlet pipe connections are tight.
5. Dosing system inspection: Check whether the pH meter has been calibrated, whether the chemical storage tank (dilute sulfuric acid/sodium hydroxide solution) is sufficiently stocked, and whether the dosing pump is normal. For fertilizer working conditions, two dosing systems must be provided: the ammonia absorption system uses 5%–8% dilute sulfuric acid solution, with pH maintained at 3–5; the desulfurization and deodorization system uses 2% sodium hydroxide with a small amount of sodium hypochlorite, with pH controlled at 9–11.
6. Electrical inspection: Power connections should be firm and reliable, insulation should be good, and grounding should be correct. Motor insulation resistance should meet the standard (≥0.5 MΩ), and control switches should function normally.

2.2 Material Preparation

1. Confirm that the upstream dust removal pretreatment system is operating normally. For fertilizer working conditions, upstream dust removal pretreatment must be added. Dust-containing waste gas directly entering the tower will generate a large amount of salt crystals, quickly clogging the packing and raising the tower internal resistance.
2. Prepare spray liquid of appropriate concentration according to waste gas composition and treatment requirements. It is strictly prohibited to pour high-concentration absorption liquid directly into the water tank. This abnormal behavior will cause collapse of the packing support inside the tower and damage to the water tank.
3. Confirm that the waste gas to be treated does not contain a large amount of oil mist or viscous substances. If present, the impact on the packing must be evaluated.

III. During Production Operation

3.1 Startup Sequence

1. This machine must strictly follow the principle of “start liquid first, then gas.”
2. Start the circulating water pump and observe whether the pump operating status and outlet pressure are normal. After startup for about 60 seconds, wait until the circulating system is stable and ensure that the spray liquid is evenly sprayed to all parts inside the tower.
3. Start the fan and gradually adjust the fan air volume to the design working condition, so that the waste gas enters the spray tower uniformly and stably.
4. After confirming that the system operates normally, start the dosing system (if any) and adjust the dosing amount according to online pH monitoring data.

3.2 Operation Monitoring

1. Spray effect monitoring: Observe the atomization effect of the spray headers to ensure all nozzles spray water evenly, without interruption or spray dead zones. Nozzle clogging will reduce gas-liquid contact efficiency and must be handled promptly.
2. Circulating liquid parameter monitoring:
   • pH value: For fertilizer working conditions, the pH of the ammonia absorption system should be maintained at 3–5, and the pH of the desulfurization system should be controlled at 9–11. According to pH changes, regularly add absorbent.
   • Liquid level: Keep the circulating water tank liquid level stable. If the water level is too low, replenish water immediately to prevent the pump from running dry and burning out.
   • Water quality: Regularly test the suspended solids content of the circulating liquid. Dust carried by fertilizer waste gas easily causes turbid water quality and must be treated promptly.
3. Equipment status monitoring:
   • Check whether the fan and pump operating sounds are normal, whether there is leakage, and whether each instrument reading is stable.
   • Observe the pressure inside the tower (normal range: 100–300 Pa). Abnormal pressure increase may indicate packing blockage.
   • Check the operation of the mist eliminator. If the pressure difference before and after the mist eliminator is too large, it may be blocked by accumulated dust and needs timely cleaning.
4. Safety discipline:
   • The spray tower is pressure equipment. It is strictly prohibited to open the tower inspection door or perform other dangerous operations during equipment operation.
   • When contacting corrosive spray liquid, acid/alkali-resistant gloves, goggles, protective clothing, and other protective equipment must be worn.
   • Open flames are strictly prohibited around the equipment. Welding, cutting, and other hot work are prohibited nearby (when treating combustible waste gas).

3.3 Shutdown Operation

1. Normal shutdown (must follow the principle of “stop gas first, then stop liquid”):
   • Gradually close the gas inlet valve and stop introducing waste gas to be treated into the tower.
   • Continue running the spray system and fan for a period of time (usually 5–15 minutes) to rinse the interior of the tower.
   • Shut down the fan.
   • Shut down the circulating water pump and dosing system.
   • Cut off the main power of the control cabinet and hang a “Stopped / Do Not Operate” warning sign.
2. Emergency shutdown (abnormal shutdown): Immediately press the emergency stop button or cut off power to perform emergency shutdown.
   • Handling after emergency shutdown: The cause of the fault must be identified and eliminated before restarting according to the startup sequence. It is strictly prohibited to force startup before the fault is eliminated. At the same time, the emergency shutdown time, cause, and handling process should be recorded in detail in the Equipment Operation Record.
3. Post-shutdown on-site handling (mandatory):
   • Replenish the absorption liquid in the dosing tank, inspect the pump seal, treat sediment in the tower body, and check whether the nozzles are clogged by debris.
   • If the shutdown is long-term or maintenance is to be carried out, drain the water in the circulating water tank and clean the tower body and piping.
4. Shift-change shutdown requirements:
   • Before handover, the equipment must be stopped and cleaned, and the Equipment Operation Record and Shift Handover Record must be truthfully filled in, noting the equipment operation status during the shift (pH value, liquid level, pressure, abnormalities, and countermeasures).
   • Before startup, incoming shift personnel must re-confirm the equipment status against the inspection requirements in the “Pre-Production Preparation Stage.”

IV. Maintenance and Care

4.1 Daily Maintenance (Each Shift)

1. Liquid level inspection: Check the liquid level in the circulating water tank and replenish in time. When the water level is 200 mm below the pump inlet, the liquid preparation tank must immediately be replenished with chemical liquid to prevent the pump from running dry and burning out.
2. Water quality observation: Observe the circulating liquid quality. If it is turbid or has a large amount of floating residue, replenish or replace the water in time.
3. Spray inspection: Check whether nozzles are clogged, fallen off, or worn, and ensure the atomization effect.
4. Seal inspection: Check the sealing performance of pipes, valves, and tower body for liquid or gas leakage.
5. Operation record: Fill in the equipment operation record each shift, recording parameters such as pH value, liquid level, and pressure.

Regular Maintenance

1. Circulating liquid management:
   • Test the pH value of the circulating liquid weekly. When it is below the standard, add chemicals (such as sodium hydroxide or dilute sulfuric acid) in time.
   • Regularly replace the circulating liquid: discharge sewage and replace the washing circulating liquid on time to alleviate ammonium salt accumulation and scaling, ensure neutralization reaction effect, and maintain stable equipment operation. For fertilizer working conditions, it is recommended to replace the mixed liquid in the water tank every 7 days and discharge residue once a month.
   • Clean impurities in the water tank: Open the water tank drain outlet to discharge sediment. Manually scrub the inner wall of the water tank when necessary to prevent microbial growth.
2. Packing and mist eliminator maintenance:
   • Check monthly whether the packing is clogged, collapsed, or aged. Under fertilizer working conditions, packing is easily clogged by ammonium salt crystals. It can first be backflushed with clean water; if severe, the packing must be removed for cleaning or replacement.
   • Check whether the mist eliminator blades are intact and clean, without accumulated dust or blockage.
3. Water pump and filter maintenance:
   • Check whether the pump shaft seal and interface seals are tight, without spray liquid leakage. Replace the shaft seal in time when worn or aged.
   • Check the filter operating status. The pressure difference between inlet and outlet should not exceed 0.1 MPa. If the pressure difference is too large, the filter element is clogged and needs cleaning or replacement.
   • Check the lubrication of pump bearings and replace lubricating oil regularly (once every 3–6 months).
4. Electrical system: Regularly check whether electrical lines are damaged, aged, or short-circuited, and whether grounding is reliable.

4.3 Long-Term Shutdown Maintenance

When the equipment is out of service for more than 30 days, drain the liquid in the circulating water tank and piping to prevent accumulated liquid from corroding the equipment. Thoroughly clean the interior of the tower body and remove scale from the packing layer and mist eliminator. Before restarting, test the motor insulation with a megohmmeter, check whether safety devices are effective, trial run according to the no-load trial run requirements, and feed production only after confirming normal operation.

4.4 Fault Handling Principles

1. If spray interruption, packing blockage, abnormal pH value, equipment leakage, etc. are found, stop immediately; restart only after the cause is identified and the fault is eliminated.
2. It is strictly prohibited to run equipment with faults, and strictly prohibited to perform maintenance or cleaning while the equipment is running.
3. When entering the tower interior for maintenance, cut off power, close the gas source, and implement confined space operation procedures. At least two people are required, and a dedicated person outside the tower shall monitor.

V. Common Faults and Remedies