Feed Water Specification

These items are highly site specific. Power cost is low because the salinity removed by the selected plant is low. The quality of the feed water, its sahnity, turbidity, and concentration of problematic ionic and fouhng solutes, is a major variable in pretreatment and in conver-... 

The effluent obtained after solids removal and microbiological disinfection could be reused as cooling water, cleaning water or industrial process water in many industrial uses. A final polishing step may be necessary if higher quality requirements are needed in some specific industrial uses, e.g., cooling and boiler feed-water. Membrane processes such as NF or RO eliminate inorganic ions and reduce parameters like conductivity, alkalinity or salinity, etc. 

Utility functions such as the supply of steam and cooling water generally are set up to service several processes. Boiler feed water is prepared and steam is generated in a single boiler house. Noncontact steam used for surface heating is circulated through a closed loop, whereby various quantities are made available for the specific requirements of the different processes. The condensate is nearly always recycled to the boiler house, where a certain portion is discharged as blowdown. 

Installation qualification (IQ) is a process used to ensure that the environmental chamber was delivered or built as ordered and is installed properly. The room where the chamber will be installed should have the proper utilities (e.g., power supply, feed water) and conditions (e.g., temperature) available to ensure that the chamber will operate according to the manufacturer s specifications during normal use. The review of the installation should include, but is not limited to, the following ... 

The utilities check is used to verify that the utility supplied fulfills the chamber requirements as specified by the manufacturer. During IQ, the as found parameters are verified against the as specified parameters on the checklist. If the as found results are significantly different from the as specified parameters, it will be necessary to determine the cause of this discrepancy and to implement corrective actions. The utilities check is a part of the site preparation for the installation of the chamber and should include verification of the power supply, such as the voltage, amperage, and wire size and the quality, pressure, and flow rate of the feed water supply. The quality of the feed water supply is a critical component of proper operation of the chamber. Experience has shown that if the quality of the feed water does not meet the manufacturer s specifications, this will lead to premature corrosion within the humidification and/or dehumidification system and subsequent problems with maintaining the humidity in the chamber within the specified limits. 

When assessing the potential for RO as an industrial water treatment option and reviewing standard plant specifications, it is important to compare the rated membrane capacity against the available water source to be treated. Reported RO membrane capacity may be based on a temperature of 77°F (25°C) and perhaps only a 1000 ppm TDS feed-water. This level of TDS is probably much lower than the potential source of cooling system makeup water, and the temperature may also vary, making corrections necessary. At lower water temperatures, the viscosity increases and the RO flux decreases (output decreases). This increases the number of membranes required to provide the desired flow. 

Formulations for these problems tend to require higher dose rates, which can prove expensive for some applications. An example is a 2 ppm dose rate to RO feed-water of specific silica polymer product for every 10 to 12 ppm Si02, and a 10 to 20 ppm dose rate for blended products that incorporate an iron control terpolymer. 

The boiler feed water deaerator reduced oxygen content to less than 7 ppb by the use of exhaust steam (low pressure). This system operated at lower temperature (110°C), used lower-pressure steam (0.05-MPa gauge), and achieved the oxygen specification without the use of chemical reducing agents as compared to conventional thermal desorption in a packed tower (7). 

Water supplied to industry has to meet stringent specifications. For example, process water for the chemical and biotechnology industries is routinely purified beyond potable water standards. Boiler feed water for steam generation must contain a minimum of silica. Reverse osmosis units designed specifically for these purposes are in widespread use today. For example, reverse osmosis/distillation hybrid systems have been designed to separate organic liquids. For semiconductor manufacture, reverse osmosis is combined with ultrafiltration, ion exchange, and activated carbon adsorption to produce the extremely clean water required. 

Rejection is a property of the specific feed water component and the membrane of interest. Table 3.2 lists the general rejection ability of the most common polyamide composite RO membranes. Note that ionic charge of the component of interest plays a role its rejection by an RO membrane the rejection of multi-valent ions is generally greater than for mono-valent ions. 

The SDI filter pads can also be sent into a lab for analysis of the deposit. The results of the deposit analysis will aid in the development of an appropriate pretreatment scheme, as specific species contributing to the suspended solids loading can be targeted for treatment to reduce their concentration in the feed water to the RO. 

Table 16.7 General feed water quality requirements for CEDI systems. Adapted from specification sheets for various manufacturers.

Two hypotheses are assumed in each case the first one assumes specific (exergy-based) cost for boiler-feeding water equal to zero the second one considers this cost equal to process steam cost (exergy-based) [1]. Results are shown in Table 1. Table 1 Energy costs for the chosen sugar/alcohol plant... 

The catalyst consisted of an alumina plate coated with V205/Ti02 mixtures on both sides. The mass specific reaction rate decreased with increasing thickness of the catalyst layer. Intrinsic kinetics was obtained for catalyst layers with a thickness lower than 20 mm. A power law dependence of the main reaction rate on the concentration of NO was found in the absence of water in the feed. Water reduces the activity slightly at temperatures lower than 663 K however, it increases the selectivity with respect to nitrogen. 

The RO machine consists of 78 sepralators using SEPA -97 membrane. A 50 Hp motor is the only energy required and it runs a pump supplying pressure to the membranes at 50 to 480 psig (3041-3243 kPa). The most common feed water temperature to the RO is 80-8S°F (27-30°C) but the temperature will fluctuate depending on the specific time of the year. The machine is running... 

Here, V is the voltage, and R is the resistance, which must be obtained experimentally and are specific for certain stack and feed water conditions. 

Energy integration is achieved by using steam produced by the reactor effluent heat exchanger (4) in the methanol evaporator (10) and in the boiler feed water preheater (11). Typical product specifications are given in Table 3.20. Twelve commercial units based on this process technology have been built, while three additional units are under construction [9]. 

---