Quality control acid treatment

Brandt [200] has extracted tri(nonylphenyl) phosphite (TNPP) from a styrene-butadiene polymer using iso-octane. Brown [211] has reported US extraction of acrylic acid monomer from polyacrylates. Ultrasonication was also shown to be a fast and efficient extraction method for organophosphate ester flame retardants and plasticisers [212]. Greenpeace [213] has recently reported the concentration of phthalate esters in 72 toys (mostly made in China) using shaking and sonication extraction methods. Extraction and analytical procedures were carefully quality controlled. QC procedures and acceptance criteria were based on USEPA method 606 for the analysis of phthalates in water samples [214]. Extraction efficiency was tested by spiking blank matrix and by standard addition to phthalate-containing samples. For removal of fatty acids from the surface of EVA pellets a lmin ultrasonic bath treatment in isopropanol is sufficient [215]. It has been noticed that the experimental ultrasonic extraction conditions are often ill defined and do not allow independent verification. 

New technology developed continuous operations so that plants became much larger and could make more consistent quality products at lower cost. These new process methods were based on the use of solvents continuous selective solvent extraction for aromatic removal was the process which replaced acid treatment and continuous solvent de-waxing replaced the very labour-intensive cold-pressing technique. Technology has developed further in the last 40 years. Catalytic hydrogenation processes have become the normal method for finishing base oils and a more severe form is used as an alternative to solvent extraction to control aromatics content. 

Finding an economic method to continuously reuse 90 to 95 percent of an acid will (1) reduce incoming chemical consumption (for the factory), (2) reduce the cost to process parts (fewer rejects), (3) provide better quality control, and (4) reduce the chemicals (for example, caustic soda) required to neutralize the spent acid before discharge. Eliminating the need to handle spent acids will decrease the exposure of hazardous materials to employees and will reduce the wastewater treatment burden. This type of bath purification system may eliminate the need to dump selected concentrated wastes. 

Sandstone acidizing can be a very successful well stimulation method. However, the risk of failure is moderate to high. Fortunately, there are a limited number of reasons why acid treatments fail in sandstones. Success begins with the selection of a viable acidizing candidate well. Many poorly producing wells are not viable acidizing candidates. Conversely, many relatively prolific producers are the very best acidizing candidates. Once a viable candidate is selected, a systematic approach to the selection of fluids, additives, and acid placement technique must be taken. On-site quality control and posttreatment evaluation help to ensure successful results and improved future treatments. 

It is then necessary to determine if a treatment placement method must be employed mechanical, chemical diversion, or a combination. The final steps are taken after the design procedure is determined and the acid job is to be pumped. Proper treatment execution and quality control practices... 

In this section, the steps that should be taken in the interest of quality assurance are listed. Because quality control applies to all acid treatments, these steps are revisited in further detail in chapter 16. Safety at the job site is discussed in chapter 17. 

Incorporation of quality control measures during all aspects of an acid job can make the difference between success and failure. Quality control monitoring during the actual pumping of the treatment only is not sufficient. In addition, quality control steps must be planned and executed during rig-up of equipment, before pumping, and after pumping. 

As mentioned in chapter 6, a number of years ago. King and Holman of the Amoco Production Company authored a booklet entitled Acidizing Quality Control at the Wellsite A section of that booklet details the steps that should be taken to ensure the quality of an acidizing treatment. Their recommendations (italicized in the following sections) still apply today. This chapter presents a modified version of the quality control steps presented in that booklet, with commentary. 

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