Conversion of Hardness – various units
| German degree | p.p.m. | mmol/l | mval/l | mg CaO/l | mg CaCO3/l | mg Ca2+/l | grains/US galon | ||
| German degree | 1odH | 1 | 17,848 | 0,178 | 0,357 | 10 | 17,848 | 7,147 | 1,043 |
| p.p.m. | 1 ppm | 0,056 | 1 | 0,01 | 0,02 | 0,56 | 1 | 0,4 | 0,058 |
| milimoles per liter | 1 mmol/l | 5,607 | 100,087 | 1 | 2 | 56,077 | 100,087 | 40,078 | 5,847 |
| milival per liter | 1 mval/l | 2,804 | 50,044 | 0,5 | 1 | 28,039 | 50,0436 | 20,039 | 2,923 |
| mg CaO/liter | 1 mg CaO/l | 0,1 | 1,784 | 0,0178 | 0,0356 | 1 | 1,784 | 0,715 | 0,104 |
| mg CaCO3/l | 1 mg CaC03/l | 0,056 | 1 | 0,01 | 0,02 | 0,56 | 1 | 0,4 | 0,058 |
| mg Ca2+/liter | 1 mg Ca2+/l | 0,14 | 2,498 | 0,025 | 0,05 | 1,399 | 2,497 | 1 | 0,1458 |
| grains/US galon | 1 gr/gal(US) | 0,959 | 17,118 | 0,171 | 0,342 | 9,591 | 17,118 | 8,855 | 1 |
Hardness of water - classification
| Classification | mmol/l | mg CaCO3/l |
| Very soft | < 0,5 | <50 |
| Soft | 0,7 - 1,25 | 70 - 125 |
| Medium hard | 1,26 - 2,5 | 126 - 250 |
| Hard | 2,51 - 3,75 | 251 - 375 |
| Very hard | > 3,76 | > 376 |
We meet with many types of cooling towers or evaporative condensers.
Open cooling systems come up to cooling thanks to water evaporation. Cooling towers evaporate 1% (at old) and 2% (at new)of curculating water. Delta T (temperature of hot water on top of the tower minus temperature of cooled water down) is about 5 oC. Water is cooled below the current T of air just above the wet bulb temperature. In summer, 90% heat leaves by evaporation (we get on a minimum temperature 25 oC). In winter only 25% leaves by evaporation and 75% by cooling of cold air (we get on a minimum temperature between 5 oC-10 oC).
If you need to lower or negative temperatures, we can´t do it without compressor cooling (freon, ammonia). The evaporative condensers get on delta T to 10 oC. We have to look difference not at the bottom or and the top of the condenser, but at the layer of water on the tube plate. The layer is the highest at the metal top and it decreases toward the edge of the water layer.
Cooling towers
Scale causes insufficient splash, water flows only by local”trickle”. This leads to lower evaporation and cooling operation of tower. Biological slime can also cause the same problem.
The incidence of limescale on the tower is usually caused by insufficient or unsuitable treatment of water. Nowadays, we use chemicals based on organophosphates which increase solubility of calcium carbonate, and so it is maintained in solution even at concentrations which would otherwise have long been precipitated. Many suppliers of water treatment inform customers on ways to save water insufficiently. You can create economic balance, how much does water cost during current treatment and how much does water cost, for example, when the involvement of cation exchanger or better using of chemicals. Huge savings can also be achieved by measuring the evaporation. Erudite supplier of water treatment chemicals calculate you all this and ensure economical operation of your device.
Evaporative condensers
Scaled tubes have a strong influence on consumption of electric energy. In adition it´s possible that customer don´t refrigerate. Consumption of electric energy based on worsten tranfer of heat from refrigerant medium caused by scale (ammonia, freon) to water. Sufficiently, ammonia doesn´t refrigerate and higher pressure (more electric energy) is useful to it liquefaction. In comparison with clear condenser these costs can create 20% of energy consumption extra. For a year that is ten thousand till hundred thousand. Another condenser´s bogy is corrosion of zinc, called white corrosion. Steel is protected by a galvanized layer under it. It is really sensitive to pH, especially if we get over 8,5. White specks of zinc oxide can arise. It easy washes off by water so steel appears under it. There is one complication. Optimal pH of steel is higher than ph of zinc. We should get under 9 that means if we have both metals here, we are not able to meet both at a blow. Only one aprooved chance passivates surface by increased concentrations of phospate. Concentration aprooved us about 15 mg/l. This concentration provides to keep rests of zinc layer and together with it protects surface of steel tubes. Among other risks belong a corrosion caused by biocide treatment insufficiently. The best combination is shock dosage and alternating oxidizing and nonoxidizing biocide.
Dalším rizikem je koroze zaviněná nedostatečným biocidním ošetřením. Nejlepší je kombinace oxidačního (na bázi halogenů, Cl2, Br2) a neoxidačního biocidu, které se dávkují šokově a střídají se.
Closed loops have the greatest plenty of risks in the case they have low capacity, which is not permuted. Suppliers also make many mistakes during the treatment of water. Closed system treatment is often a check of qualities and supplier´s experience.
Closed systems are threatened by all problems, which can made by water. It includes scale creation , corrosion, galvanic corrosion and biological growth. In addition, you can´t use common means, as we know from boilers and refrigerating towers.
Today it is best treatment by a molybden or eventually by a means???, which combined molybden with silicates. This treatment has an excellent result in area of uniform corrosion and oxygen corrosion of iron. These problems are the biggest bogy of closed loops. Most closed systems combine more metals. Common combination is steel with copper or with it´s alloys. There is a high risk of system damage due to galvanic corrosion. We recognize it thanks to dissolved cooper ions in the system water because their concentration is higher than in supplemental water where usually occurre in minimum quantity. In this case, it is necessary to treat the system with azoles, which are very effective and long term protection protect yours system.
At the customers we meet with many types of steam, hot water and heat water devices. Against past steam is used for heating occasionally. Many companies are still using steam for production. For example food production: dairy, bakeries, breweries. Steam is needed also to produceplastics or heavy industry. Hot water and heat water pipes are mainly used for heating and for production of hot water. Nowadays, only a few companies have a portfolio of products, wich respect these differences. Chemical treatment depends on construction and pressure of steam boilers in which they are operated. Steam boilers are divided into low, medium and high pressure by the temperature and pressure ratios. By way of relief flue gases to water-tube and fire-tube. The surface of water and water-steam pipes which are surrounded by fuel gas form the heat transfer position of evaporator in the case of water-tube boilers. These boilers were used for cases of higher wattage above about 15t/hour. Today boilers are produced with high wattages and they are fire-tube. These boilers are characterized by their huge water space. Fire tubes rolled at the front of boiler (flue tubes) going through this water space. Fire tubes through which flows hot combustion gases from the fireplace, form the main heating surface of the boiler.
Schema of fire-tube boiler
If you need steam immediately, it is better to use the steam generators. They are preferred there, where the steam consumption is irregular and the long-term heat in the boiler cost a lot of money. However, they are compared to conventional boilers. They are very sensitive to perfect treatment and pre-treatment of water.
Boiler feed water:
Water quality pre-treatment is the main point for a good job. Without a good softening or osmosis boiler is not possible to operate a boiler for a long time. It is also necessary to service the pH of boiler feed water, usually in the values of 8.5 to 9.5. The temperature of boiler feed water should reach 105 oC in thermal degassing otherwise there is an opportunity of corrosion in the boiler. Chemicals dosing into supply tanks or sometimes for supply tanks have following tasks:
- chemical degassing
Although we have good thermal degassing, it is also necessary to treat it chemically. It is usually based on a sulphite as oxygen scavengers. Current sulfite is sufficient if it has enough time for the chemical reaction with oxygen. Length chemical reaction depends on the temperature, the colder supply water, the longer reaction. Reaction can take two minutes. It can happen when we have a small supply tank, sulphite abundance, reaction doesn´t have to run over and it can appear the pitting. It is therefore wise to use a form of catalyzed sulfite, which is offered by some manufacturers worldwide and eliminate this problem.
Catalyzed form of sulphite is used in smart case. It is offered by some worldwide manufacturers and the problem is eliminated.
- Removal of residual hardness
Hardness always remains even when a cation exchanger is well working. Hardness is not measurable by typical means, it thickens and precipitated calcium carbonate, limescale in a boiler. Therefore it is dosed a phosphate, which reacts with residual hardness and produces sludge which is removed regularly continuous blow down. Phosphate disadvantage is its tendency to stick to the tube sheet and create deposits that as an insulating layer prevents effective heat transfer from the flue gas into the water. Today´s advantage is using polymeric products, which contain a phosphate and simultaneously polymer particle slurry coating, put into suspension, and diverts the blow down. At the same time will clean already clogged heat transfer surfaces. Fully polymeric product is based on organophosphate, residual hardness is not precipitated, but keeps it in solution.
Boiler water:
Water is thickened in water due the evaporation and it causes increasing pH, conductivity and alkalinity, and other parameters. pH should be between 10,5 to 12. Lower pH increases the risk of corrosion. At lower alkalinity also increases the risk of low OH alkalinity, which may create a risk of the boiler magnesium phosphate (black, sticky), or magnesium silicate (like glass), which is then very difficult to get rid of. Higher pH in turn could threaten the boiler alkaline embrittlement.
Another important parameter is the M-alkalinity, which should not exceed 1000mg / l. When value is exceeded it can cause in foaming of a boiler.
Too high phosphate concentration is that mistake too. Besides the enviroment being unnecessarily burdening. They can often be a source of fines for exceeding their limits in wastewater. They are also a source of sludge, which then clog the boiler.
If you just have a trouble with high phosphates in waste waters, it is very convenient to use a fully polymer treatment where the concentration of phosphorus is very low and also immeasurable commonly used laboratory wals.
We have to pay attention to the content of silicates, in the case if the boiler has a turbine. Concentration of silicates musn´t exceed 20 mg / l.
Silicates are transferred to the steam and it can cause clogging of turbine.
In some boiler rooms are still pay low attention to the efficiency of steam production.
Heat transfer is get worse with small deposits in tenths of mm on the tube plate. We can save up several percent of the annual rates for gas or other fuel if we clean it.
The next a little control parameter is thickening, by another name cycles of concentration. They show the amount of blow down losses. We lose not only water that goes to sewage, but also the heat that goes with blow down. You can save both adjusting concentration, and utilization of the residual heat.
In the case of chemical treatment of steam generators - don´t save money! Screw feeder, which leads the water to produce steam, has a very small radius, even the smallest error in the chemical treatment leads to scaling. There is no other way than to replace it when it is fauled. Generators also don´t usually have thermal degassing, and the temperature moves up to around 90°C in the supply feed water tank. In addition, they have a small feed water tank, and beside it is often missing automatic chemical dosing synchronized with doses of boiler feed water to the boiler.
All this cause that chemical reaction runs only a few seconds to remove oxygen and oxygen is not eliminated and it occuresto oxygen corrosion. Fully polymeric product type of organophosphate and also catalysed sulphite is good solution for this case.
Chemical treatment of make-up water (boiler feed water or refill water in the other devices) is an important part of perfect operation of heat devices. Parameters of this water have to meet the parameters of the ČSN and the requirements of the supplier.
Companies usually take care of the parameters by themselves, but more often they let this job to companies which are specialized in chemical treatment of heating systems. These parameters are guaranteed in signed contract with some company.
During treating of heat system it is easy to forget to watch the efficiency of operation. It usually happens because of energy and fuels consumption (coal, gas, electricity and others), improperly set water chemistry system, unnecessary high water consumption and waste energy in form of residual heat from wastewater (flue gas, blow down, continuous blow down and other). It is often forgotten on an extending life device.
Our company deals with:
- Analysis of the current operation device in area of chemistry water and quality of using equipment
- Drafts of new programs for operating devices like:
- Supply of modern chemical products for chemical treatment of water
- Set up a dosing
- Automation, monitoring and service of this process
- Supply of equipment for pre-treatment water
- Installation of additional devices for wasted energy utilization
- Drafts and supply of new devices and complex equipment
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