Industrial Cleaners and Cleaning Technology

Industrial fouling and industrial fouling cleaning In industrial production, equipment, pipelines, plants, buildings, raw materials, products or semi-finished products, etc., when they are in contact with the atmosphere, environment, production raw materials, media, products, mechanical oil, etc., due to physical, chemical and electrochemical or biological effects, their surfaces will remain, deposit and generate various dirt harmful to production operation, product quality or human health, which is industrial fouling. The formation of industrial fouling is related to all aspects of industrial production, such as substances harmful to production operation, product quality or human health produced after contact with the atmosphere, production raw materials, mechanical oil, microorganisms, etc. It can come from a wide range of sources, such as gases such as sulfur dioxide in the atmosphere, ions in cooling media, raw materials and products for production, mechanical oils, microorganisms, and surface processing products and corrosion products. From the perspective of chemical composition, it can be divided into inorganic dirt and organic dirt, and the composition of different types of dirt is different. Secondly, the hazards of industrial fouling are multifaceted, which will affect the normal operation of production, increase energy consumption and cost, reduce product quality, cause accidents, affect material performance and equipment life, etc. The purpose of industrial cleaner varies in different industrial sectors, including improving the appearance of equipment, purifying the environment, maintaining production, extending equipment life, increasing production capacity and reducing production accidents. In addition, the materials to be cleaned include commonly used metal materials, such as carbon steel, corrosion-resistant carbon steel, low-alloy steel, stainless steel, etc.; Organic non-metallic materials (good corrosion resistance but low mechanical strength); Inorganic non-metallic materials, such as ceramics, cement, etc.; and composite materials. Technical measures must be taken to eliminate industrial dirt, otherwise the appearance of pollutants will be damaged, the material will be eroded and damaged, production can not be carried out normally, product quality will decline, raw material and energy consumption will increase, and production accidents will occur frequently. The process of removing dirt on a regular or irregular basis using physical, chemical, or biological methods is collectively known as industrial dirt cleaning.

Source of industrial fouling

(1) Atmosphere: sulfur dioxide, hydrogen sulfide, carbon dioxide, oxygen

(2) Cooling medium: calcium ions, magnesium ions, bicarbonate ions

(3) Production of raw materials and products

(4) Machinery oil: lubricating oil, anti-rust oil, hydraulic oil and additives, etc

(5) Microorganisms

(6) Surface processing products: old electroplating layer, patent leather, resin layer, enamel layer, etc. (7) Corrosion products: rust scale

Classification of industrial dirt According to the chemical composition, inorganic dirt includes metal oxide scale, scale, sediment, etc.; Organic dirt includes oil scale, polymer scale, carbohydrate scale, protein, etc.

Hazards of industrial fouling Materials, production equipment and pipelines, workshops, buildings, production raw materials and products are polluted to form fouling, mainly the following hazards: affecting the normal operation of production, increasing production energy consumption and cost, reducing product quality, causing various accidents, affecting material performance and equipment life, etc.

The purpose of industrial cleaner The cleaning objects of different industrial sectors are different, the purpose ofindustrial cleaner is also different, and the methods used are also different. Generally speaking, the purpose of industrial cleaner is mainly the following aspects: to improve the appearance of equipment, purify and beautify the environment; Maintain normal production and extend the life of equipment; Increase production capacity and improve product quality; Reduce production accidents.

Materials to be cleaned Commonly used metal materials: carbon steel and ordinary carbon steel, corrosion-resistant carbon steel (adding certain alloying elements to cast iron to obtain corrosion-resistant alloy cast iron with high corrosion resistance in some media, referred to as corrosion-resistant carbon steel, such as high silicon cast iron, high nickel cast iron, aluminum cast iron, etc.), low alloy steel, stainless steel, copper and copper alloys, aluminum and aluminum alloys, titanium and titanium alloys, lead and lead alloys. Organic non-metallic materials: non-metallic materials have characteristics that metals do not have, such as good corrosion resistance, abundant sources of raw materials, and relatively cheap prices; The disadvantages are low mechanical strength, less rigidity, easy to deform and damage when bearing load for a long time, poor thermal conductivity in addition to graphite, low heat resistance and thermal stability. Commonly used inorganic non-metallic materials: ceramics, cement, glass, enamel, cast stone, concrete, natural silicate materials, graphite. Composite materials: Generally refers to the combination of two or more objects with different chemical properties or different tissue phases in a microscopic or macroscopic form.

Classification of commonly used chemical cleaning agents In terms of classification of chemical cleaning agents, there are aqueous and non-aqueous solvents (water is an important solvent, and non-aqueous solvents are used to dissolve organic scale), pickling solutions (mainly hydrochloric acid, with basic composition and basic process), alkali washing solution (used to remove grease and scale, etc., with advantages and disadvantages), surfactants (with a variety of properties and uses, including many types), metal chelating agents (used to remove scale and rust on metal surfaces), dirt adsorbents (using dirt to clean the difference in the affinity of different substances on the surface), Biocides and sludge strippers (to deal with microbial growth in circulating cooling water systems), enzyme preparations (can accelerate the reaction, used for a variety of dirt cleaning), metal corrosion and inhibitors (corrosion damage should be considered when cleaning, corrosion inhibitors have many classifications), and foaming and defoaming during the cleaning process (foam has conditions, beneficial effects and hazards, and there are defoaming methods).

1. Water and non-aqueous solvents Water: Water exists in nature and is the most important solvent. In industrial cleaner, water is the solvent for most chemical cleaning agents and for many dirts. Non-aqueous solvents: The dissolution of polymers, oil scales, etc. by non-aqueous solvents includes not only the dissolution process of transforming the dissolved substances into molecular states, but also the process of swelling and dispersing the dissolved substances into smaller particle states. It includes hydrocarbons and halogenated hydrocarbons, alcohols, ethers, ketones, esters, phenols, etc. and their mixtures, which are mainly used to dissolve organic scales.

2. Pickling solution (mainly hydrochloric acid) The basic composition of pickling solution: add necessary corrosion inhibitors, wetting agents, defoamers and thickeners. Corrosion inhibitor: It is a substance that can prevent or slow down the corrosion of metals in environmental media at low concentrations. Wetting agent: It is a substance that can repel the gas adsorbed on the solid surface and accelerate or uniformly contact with the liquid, that is, surfactants, such as Pingpingjia, OP emulsifier, Tween-80, Qutong X-100, etc. Defoamer: It is a substance that can reduce the surface tension of liquids, inhibit the formation of foam, or make the original foam disappear or decrease. Thickener: It is an additive that increases the viscosity of the pickling medium to prolong the residence and action time of the pickling medium on the surface to be cleaned. The basic process of pickling: (1) The basic process of pickling to remove metal oxides Alkali washing to remove grease scale→ hot water rinsing→ pickling→ cold water rinsing→ neutralization→ cold water rinsing→ post-treatment (as needed, such as passivation, phosphating, drying, coating, etc.) → waste liquid treatment (2) The basic process of pickling to remove inorganic salt scale on the heating surface Hot alkali cleaning (making inorganic salt scale loose) → water rinsing→ pickling→ water rinsing→ passivation treatment→ waste liquid treatment

3. Caustic washing solution (mainly used to remove grease scale, protein, etc.) Compared with pickling solution, it has the following advantages and disadvantages: Advantages: It will not cause metal corrosion, will not cause obvious changes in the size of the workpiece, and will not quickly return to rust. Disadvantages: high cost, slow speed of rust removal and scale, etc.

4. Surfactant concept: also known as surfactant, it is a class of substances that aggregate at the interface of two substances and can significantly change the surface tension of the liquid and the interface properties between the two phases. It can change the interfacial state of the system, so as to produce a series of effects such as wetting or anti-wetting, emulsification or demulsification, foaming or defoaming, and solubilization. Everyday soaps, laundry detergents, shampoos, margarine, salad dressings, etc. are all surfactants. Properties of aqueous surfactant solutions: wettability, emulsification and dispersion, cleaning, foaming and foaming. Basic composition of surfactants: Any kind of surfactant is composed of non-polar lipophilic (hydrophobic) hydrocarbon chain groups and polar hydrophilic (oleophobic) groups. The surfactant molecule is an amphiphilic molecule with amphiphilic properties that are both lipophilic and hydrophilic. Uses of surfactants (mainly chemical): The dispersion and wettability of surfactants can be used to change many chemical production processes. For example, emulsification increases the reaction speed of mixed systems with insoluble substances; Surfactants can improve the yield of certain extraction processes, etc.

Main surfactants Anionic surfactants Main features: Cleanability improves with increasing temperature; Alkali addition is beneficial to increase the cleaning power; In addition to sodium alkylbenzene sulfate, the washed fabric feels good and the price is relatively low. Cationic surfactants Amphoteric surfactants Common characteristics: good surface activity, strong decontamination, wetting, emulsification, dispersion, and bactericidal, antistatic, soft and other characteristics. It has mild performance, low irritation, and has a moisturizing effect on the skin. Good compatibility and easy degradation. Soluble in water, resistant to hard water, strong foaming. It shows cationic in acidic solutions and anionic in alkaline solutions. Disadvantages: Amphoteric surfactants are more expensive, and their cleaning capacity is not as good as that of nonionic surfactants and anionic surfactants. Nonionic surfactants: polyethylene glycol type, polyol type. Special types of surfactants (including polymer surfactants, biological surfactants, silicon-containing fluorine-containing surfactants, etc.) The use of surfactants and precautions: according to the types and characteristics of different surfactants, surface adsorption residues, safety, use concentration, solubility, foaming, use temperature and cloud point, stability to hard water, correct selection of different raw materials compatibility, economy.

In terms of cleaning methods for industrial dirt, it is divided into physical methods and chemical methods. industrial cleaner agents have technical requirements, such as fast cleaning speed, small damage to the cleaning object, cheap and easy to obtain, etc. Typical examples of cleaning of chemical production equipment include cleaning before start-up (with pre-cleaning preparation, chemical cleaning procedures) and post-start-up cleaning (with different cleaning methods for different fouling).

Finally, there are separate treatment methods for the liquid waste, solid waste and exhaust gas generated by chemical cleaning, as well as general safety guidelines to ensure the safety of the cleaning process.

5. Metal chelating agent concept: metal chelating agent is an important compound used in the cleaning process. When cleaning metal, limescale and rust can be removed from the metal surface. Chelating agent is added to boiler water and circulating cooling water to prevent scale formation; The addition of a chelating agent to a scaled system can be removed by the chelating agent to loosen the scale. Inorganic metal chelating agent Ammonia: It is a cleaning agent for cleaning copper scale. Polymerized phosphate. Organometallic chelators citric acid, ethylenediaminetetraacetic acid, nitritriacetic acid, polyacrylic acid, etc.

6. Dirt adsorbent concept: using the difference in the affinity of dirt to the surface of different substances, the dirt is transferred from the surface of the originally attached object to the surface of another substance in the gas or fluid medium to achieve the purpose of removing the dirt, and this cleaning process is called adsorption cleaning. The substance used for this purpose is called an adsorbent, and the substance that is adsorbed is called an adsorbate. Classification: (according to the nature of the force, it is divided into physical and chemical adsorption) Physical adsorption: If all the chemical binding forces of the particles on the solid surface have been saturated with adjacent particles, then the particles on the solid surface and the adsorbate can only be attracted to each other by intermolecular forces (van der Waals force). Chemical adsorption: If the chemical binding of atoms on the surface of the solid is not completely saturated by adjacent atoms, and there is still the ability to form chemical bonds, electron transfer can occur between the adsorbent and the adsorbate to form chemical bonds. Commonly used dirt adsorbents: activated carbon, zeolite, diatomaceous earth (silicate after the death of diatoms), bentonite. For example: car scrub brightener formula: triethanolamine 240g, oleic acid 600g, diatomaceous earth 450g, white oil 6.15g, water 22.51g. First, triethanolamine is dissolved in water, a mixture of white oil and oleic acid is added to the water, diatomaceous earth is added after stirring, and it is completely mixed. When using, use a cotton cloth dipped in this liquid, apply it to the surface of the car body, and wipe it after it dries to remove the oil stain on the surface of the car body.

7. Biocides and sludge strippers Premise: In the open circulating cooling water system, the cooling water temperature is usually between 32 - 42 °C. The cooling water is in full contact with the air in the cooling tower, and the microorganisms in the air and the microorganisms in the make-up water continuously enter the circulating cooling water system, which is extremely suitable for microbial reproduction.

Inorganic biocides Commonly used inorganic biocides are chlorine, sodium hypochlorite, chlorine dioxide, ozone, bromine compounds (new biocides).

Organic biocides chlorophenols (easy to pollute the environment, not easy to be biodegradable, rarely used); Quaternary ammonium salts, such as: Xinjieer. It is sometimes used as a defoamer; There are: organotin compounds, organosulfur compounds, organobromine compounds, organochlorine compounds. The commonly used organochlorine biocide is sodium dichloroisocyanurate, trade name: Euchlorin. It has the characteristics of high efficacy, long-lasting efficacy, low toxicity, stable storage, low relative harm, and easy dosing.

Microbial sludge stripping agent Some biocides, such as Jieerfen, Xinjieerfen, etc., have their own stripping effect.

/ 8. Enzyme preparation (enzyme structure is amino acid) Concept: Enzyme is an organic compound existing in the organism and is a biological catalyst that can accelerate the reaction. As a biological catalyst, enzymes have the characteristics of general chemical catalysts, but also have their own characteristics. Enzyme preparations for cleaning are: lipase, protease, amylase, cellulase. Application of enzymes in water Dirt cleaning (vegetable oil, protein, cellulose), textile desizing, raw silk degumming (degumming with alkaline protein), pipeline dredging, photosensitive waste film cleaning and recycling (alkaline protein washing), agricultural product processing and food machinery cleaning, contact lens cleaning.

9. Metal corrosion and inhibitors in the metal cleaning process During the cleaning process, the cleaning agent may cause corrosion to various metal materials. When cleaning metal materials and their products (such as parts, machines, equipment, buildings, etc.), the damage that may be caused by corrosion must be fully considered and necessary technical measures must be taken.

Common metal corrosion in the cleaning process, corrosion in acidic cleaning media, corrosion in alkaline cleaning media, corrosion in neutral cleaning media, corrosion in the atmosphere.

Classification of Corrosion Inhibitors Definition: Substances that can prevent or slow down the corrosion of metals in environmental media at low concentrations are called corrosion inhibitors. Classification: According to the inhibition of the electrode process, it is divided into: cathode type, anode type, and hybrid type.

Commonly used corrosion inhibitors (1) Acid media corrosion inhibitors: urotropine, Ruoding, Shen 1 - D, blue - 5, blue - 826; (2) Corrosion inhibitors for medium alkaline media: sodium nitrite, sodium butyrate and potassium dichromate, etc.; (3) Oil-soluble corrosion inhibitors; (4) Vapor phase corrosion inhibitors.

10. Foaming and defoaming in the cleaning process Foam generation and function Conditions for foam production: A: Bubbles and liquid are in continuous and full contact, which is a necessary condition for the gas to form foam in the liquid dispersion system; B: The foam has a certain lifespan, that is, the foaming speed should be lower than the foaming speed; C: The gas is insoluble in the liquid of this dispersion system.

The beneficial role of foam in cleaning A: Foam has the effect of adsorbing and carrying oil droplets and solid dirt; B: Foam can indicate the effectiveness of the cleaning operation; C: The foam also has an indication effect on the rinsing process of the workpiece.

The harm of foam to cleaning operation The existence of foam sometimes brings trouble to the cleaning operation, especially when using strong mechanical stirring, spray washing, and ultrasonic cleaning, due to the formation of a large amount of foam, the working solution will overflow out of the tank, resulting in the loss of raw materials, delaying the cleaning operation, and polluting the environment, so defoaming treatment should be carried out.

Defoaming method (1) Prepare cleaning solution with low foaming raw materials; (2) reduce foam by changing the temperature; (3) Spray cold water onto the foam; (4) Avoid air ingress; (5) Avoid the impact of cleaning liquid; (6) Add appropriate defoamers or inhibitors.

Commonly used foam regulators: foaming agents, foam stabilizers, defoamers.

Cleaning methods of industrial dirt The cleaning of industrial dirt can be divided into physical methods and chemical methods in principle. Physical methods: with the help of mechanical force, sound waves, heat, light, etc., and simple physical dissolution. Chemical methods: including acid-base reaction, redox reaction, combination reaction and other methods to remove dirt, as well as methods for cleaning dirt with the help of electrochemical, enzyme and microbial actions.

1. Technical requirements for industrial cleaner agents (1) Clean the dirt quickly and thoroughly. (2) The damage to the cleaning object should be within the scope of the production license, and there are corresponding measures to suppress the corrosion that may be caused by the metal. (3) Cleaning chemicals are cheap and easy to obtain, and based on localization; The cleaning cost is low and does not cause excessive resource consumption. (4) The cleaning agent is non-toxic or low-toxic to organisms and the environment, and the waste gas, waste liquid and waste residue generated should be able to be treated to meet the requirements of relevant national laws and regulations. (5) The cleaning conditions are mild, and try not to rely on additional strengthening conditions, such as not too high requirements for temperature, pressure, mechanical energy, etc. (6) During the cleaning process, no insoluble matter remains on the cleaning surface, no new stains are generated, no harmful covering layer is formed to the subsequent process, and the product quality is not affected. (7) There will be no foam and odor that affect the cleaning process and on-site hygiene.

2. Typical industrial cleaner cases (mainly involving the cleaning of chemical production equipment) Cleaning of chemical production equipment before start-up Preparation before chemical cleaning A: Transformation of cleaning objects: remove the parts that are susceptible to corrosion damage by cleaning liquid, such as regulating valves, flow meters, pressure gauges, various sensor probes, filter cores (nets) and check valves, and clean the removed parts according to the requirements for installation and reset. B: Public works conditions: prepare water, electricity, steam, compressed air, nitrogen and engineering materials as required. C: Temporary cleaning system: including the selection of cleaning pumping station, the connection of cleaning circulation circuit, etc.

Chemical Cleaning Procedures and Process Conditions System Hydrostatic Leak Detection and Water Flushing - Degreasing - Water Flushing - Pickling - Water Flushing - Rinsing - Neutralization and Passivation - Inspection and Manual Treatment. A: Degreasing: The purpose is to remove the mechanical oil, graphite grease, oil coating and anti-rust oil in the system to ensure uniform pickling. B: Rinsing: The purpose is to remove the floating rust formed in the system during the washing process with water, and reduce the total iron ion concentration of the system to ensure the passivation effect. C: Neutralization and passivation: prevent secondary floating rust.

Cleaning after start-up of the production plant Dirt condition: Chemical plants that have been in operation for more than 1-2 years often have ferrous sulfide, iron oxides, copper oxide scales and oil scales. Cleaning of rust and scale: mostly pickling. Cleaning of ferrous sulfide scale: Raise the temperature sharply at a rate of 40 - 60 °C/h to 300 °C and hold for 1 - 2 hours, then let the temperature drop again, and then carry out the percussion operation. The purpose of heating is to embrittle the scale, and at the same time burn off the residual oil to improve the cracking effect caused by knocking, but care should be taken to prevent the heating tube from overheating during the heating process. After the percussion, it is cleaned with surfactant. Cleaning of oil scale: The hydrocarbon oil scale on the surface of petrochemical equipment is generally circulated with solvent oil and hot water.

3. Treatment methods of chemical cleaning waste liquid, solid waste and waste gas The treatment method of chemical cleaning waste liquid can adopt physical, chemical, physicochemical and biological methods. Treatment method of alkaline waste liquid A: Alkaline treatment: neutralize the alkaline waste liquid and the pickling waste liquid with each other to make pH = 6 - 7; The flue gas is used to neutralize the alkaline waste liquid; B: Oil treatment: demulsification - oil-water separation - water purification; C: Treatment of chemical oxygen consumption (COD).

Treatment method of acidic waste liquid A: acidic treatment; B: Treatment of chemical oxygen consumption (COD).

The treatment method of solid waste liquid adopts pretreatment technology, chemical treatment technology, incineration treatment technology, pyrolysis treatment technology and microbial decomposition technology.

At present, the domestic treatment methods for gas pollutants mainly include absorption method, adsorption method, catalytic method and combustion method. The choice of treatment method depends on the chemical and physical properties of the hazardous gas, concentration, emissions, emission standards.

General Safety Rules

1.Safety rules for on-site sampling;

2.Safety Practices for Preventing Poisoning;

3.safety codes against combustion and explosion;

4.Safety Practices against Chemical Burns, Scalds and Cuts;

5.Safety Practices for the Use of Electrical Equipment;

6.General methods of fire prevention and extinguishing of fires.