Long life pH sensor in brewery applications
Beer enthusiasts around the world know the unique and popular Belgian brewer, the Duvel Moortgat Brewery, from Golden Ales to Trappist. However, the ability to produce these unique flavors of beer is impossible without capital investment.
The production process of the Duwei Brewery is different from that of other breweries. It uses pH control technology, while other manufacturers use conductivity measurement technology. The Duwei Brewery has encountered some application challenges in using pH timing. The following describes how the Duwei Brewery overcomes these challenges by using new long-life pH sensors. This long-life pH sensor has achieved successful application experience in many food and beverage industries around the world.
pH control in the brewing process
pH measurement plays a very important role in many aspects of the brewing process. During the gelatinization process, the pH affects the activity of the enzyme and determines the efficiency of conversion of the starch to fermentable sugar. In brewing tanks, monitoring the pH of the malt determines the solubility of the hops, which in turn controls various factors that affect the body, taste, and transparency of the beer. In the filling process, monitoring the pH of the beer ensures the quality of the product that ultimately enters the consumer market, ie the container used to fill the beer does not contain any chemical cleaning ingredients.
The Dove beer brewing process has multiple pH check points. The measurement results of these points help the operator to determine whether the process is in the brewing stage, in the acid-base cleaning (CIP) stage, or in the beer water rinse stage. Brewing's brewing process: The malt is first heated to 90 ° C and maintained for 90 minutes. After the malt is cooled, the malt is sent to the fermentation vessel with beer water. Usually, the brewing process uses conductivity as a critical control point. Based on the change in conductivity value, it is determined when the malt enters the next process and whether a large amount of water is required. However, to optimize the process, more stringent control parameters are required. If too much water enters the fermentation vessel, more processing steps are required in order to obtain high quality beer.
However, as the Supervisor brand, there is no difference in the conductivity value of the malt and the conductivity value of the rinse water, but the pH values ​​of the two solutions are significantly different. Therefore, the pH control can correctly distinguish the two processes, ensuring that there is not a large amount of water inflow, thus ensuring the quality of the beer. In this application, since the pH sensor is exposed to a hot corrosive solution for a long time, the life of the pH sensor is shortened. This is because if the pH sensor is subjected to a strong thermal shock for a long time, the glass bulb of the sensor will be broken and the sensor will fail. In addition, if the reference electrode of the sensor has a small liquid junction area, the reference electrode is easily covered by dirt, resulting in a slow response of the sensor and a large measurement deviation. For some applications, if the solution contains sulfides, this solution can cause serious damage to the reference electrode, which can cause measurement deviations.
One sensor per 3 days
The Supervisor Brewery has encountered some problems in the past when using pH sensors. Initially, the life of the pH sensor was 2-4 weeks. Later, due to increased plant capacity, the flow rate of acid-base cleaning (CIP) increased by 33%. Since then, the life of the pH sensor has been maintained for only 2-3 days, and the technician has to stop the pH measurement and switch to conductivity measurement. In doing so, although the effects of heat and corrosion are eliminated, the difference between the conductivity of the malt and the conductivity of the rinse water is too small, so that the process cannot accurately distinguish the two processes, and the quality of the brand of the supervisor beer cannot be guaranteed. This practice was abandoned. The technicians of the Dulwich Brewery had to manually distinguish the two processes by assigning a technician to supervise the flow of the solution from the process line into the glass in the field to distinguish the two processes and manually close the valve. . As the commentator said: "Technicians are very unhappy."
Manual/manual control of production is unsustainable, and technicians at the Dulwich Brewery are looking for long-life pH sensors. Emerson's PERpH-X high performance pH sensor is a product of their choice. At the beginning of the test, the technicians were skeptical about the performance of PERpH-X, because they tested multiple brand sensors before, and the longest service life was less than a week! The technicians installed a PERpH-X sensor first, and they were pleasantly surprised to find that the sensor actually used it for more than three months! After its eventual failure, the technicians at the Dulwich Brewery contacted Emerson and asked for another sensor. What surprised them even more was that when Emerson technicians filled the sensor reference electrode with electrolyte, the sensor resumed operation. It took less than 10 minutes to complete the electrolyte and the pH control loop returned to automatic control!
No need to say anything, the Supervisor Brewery has seen considerable differences. From then on, the brewing process no longer needs to change a pH sensor every 3-7 days, which greatly reduces the operating cost of the equipment and shortens the installation time of the instrument. It is important to ensure that the process is precisely controlled by the measured parameters, saving valuable time for technicians and reducing the inefficiency of technicians.
working principle
Before the test, it was not surprising that the technicians at the Dulwich Brewery were skeptical about the so-called long-life sensor. In the past few years, although the design of pH sensors has been continuously improved, the basic principles of pH measurement have not changed in the past century. Because in most cases, the performance of the pH sensor is reliable, only in the high temperature or dirty solution, the pH sensor response is lagging and the measurement is not reliable.
The pH sensor uses a special composition of pH-sensitive glass material. When it is in contact with the solution to be tested, the glass electrode generates an electrode potential (millivolt signal) proportional to the pH of the solution being measured. There are also non-glass pH sensors on the market, but at extreme temperatures, such sensors are often inaccurately measured and, if used in an acid-base cleaning process, their lifetime is reduced. Unlike some food and beverage industries, glass sensors are used for beer brewing because there are multiple filtration steps throughout the beer brewing process.
The pH measurement also depends on the reference electrode, which acts to maintain a constant reference potential at a given temperature. The glass electrode and the reference electrode together constitute a pH measuring circuit, and the potential difference (millivolt signal) of the glass electrode and the reference electrode is proportional to the pH of the solution to be tested.
In addition, the pH varies with the temperature of the solution to be tested, and the extreme temperature accelerates the aging of the electrode, causing the filling liquid at the top of the electrode to freeze or boil, thereby causing the glass to rupture. The aging of the glass in turn causes the sensor to respond slowly.
Typically, the reference electrode is a silver-silver chloride electrode, i.e., a silver chloride is plated on the silver wire and then suspended in a potassium chloride solution. To obtain accurate pH measurements, the potassium chloride fill solution must not be contaminated. At the same time, the reference electrode is passed through the solution to be measured and connected to the glass electrode to form a measurement circuit. If the solution to be tested is viscous or contains a certain concentration of ions, the above two conditions are easily unsatisfied, thereby forming a precipitated coating on the reference electrode liquid junction (electrolyte permeable membrane), poisoning the filled electrolysis. liquid.
Long life design
The new long-life sensor design does not change the basic measurement principle of the pH sensor, but rather improves every fragile component. Researchers first studied the aging mechanism of pH-sensitive glass materials under high temperature conditions. Interestingly, they found that the vast majority of aging occurs in the gel layer of pH-sensitive glass. Based on this finding, researchers have isolated and developed a high temperature resistant gel layer. This research led them to develop ultra-high temperature (up to 155 ° C) pH glass electrodes that minimize glass breakage due to thermal stress or impact and improve sensor response. Typically, this long-life sensor maintains accurate measurements after several months of use under extreme temperature conditions. In addition, Emerson has added some protection designs, such as a grooved snap ring at the lower end of the glass electrode, which protects the glass bulb from direct impact from process fluids (including particulate matter). The above design improvement of the glass electrode has made the Supervisor Brewery deeply feel the change of the performance of the pH sensor.
Most of the failures of pH sensors are caused by the contamination of the electrolyte of the reference electrode or the blockage of the liquid junction of the reference electrode (electrolyte permeable membrane). The design of the long-life sensor solves this problem by using a specially designed porous Teflon liquid junction with a large surface area and a high porosity to ensure good contact between the reference electrode and the solution being tested. The anti-blocking ability is strong, and even if the sensor is used in a relatively dirty liquid, it can maintain a stable reference signal. Secondly, the electrolyte of the reference electrode is a potassium chloride gel solution, which has a certain chemical viscous resistance and can resist the clogging of the reference path due to temperature and pressure changes. In addition, the liquid junction of the internal reference electrode (electrolyte permeable membrane) is made of ceramic material, the pore size is small, and the porosity is low, so the anti-poisoning ability is strong, thereby reducing the loss of the liquid junction (electrolyte permeable membrane) of the main reference electrode. To extend the overall life of the sensor. In summary, the long-life pH sensor design combines the two characteristics of the reference electrode liquid junction, namely the measurement accuracy (high) of the high porosity liquid junction and the service life (long) of the low porosity liquid junction.
In order to further extend the life of the sensor, it is also considered to replace the blocked reference electrode liquid junction (electrolyte permeable membrane) and refill the electrolyte, which can regenerate most of the failed sensors. It is important that the sensor is also formulated with a variety of special electrolytes to optimize sensor performance in specific applications such as: anti-biofilm electrolyte; anti-grease electrolyte; anti-fouling electrolyte. In addition, the sensor sheath is chemically resistant, heat resistant Ryton and titanium.
The Supervised Brewery has the courage to adopt challenging process facilities and has an absolute need for accurate pH measurement. For such manufacturers, the innovative design of these long-life pH sensors is undoubtedly a godsend. As Jo Van Roy, the technical operation and maintenance staff of the Dulwich Brewery, said: “The measurement of the pH meter has been extended from the previously uncertain days to the current months, and no personnel are required to take care of it. This is indeed the financial belt of the Dulwich Brewery. A big change has been made, which helps us to ensure the quality and credibility of the unique Supermarket beer."