Final effluent-fully automatic generator now in operation at the Heidelberg Schlossquell Brewery. This is a new brewery, built in 1999. This system features a neutralization system that allows for pH corrected flow into the municipal waste system.
In 1999, this famous brewery was relocated from the city center to the outskirts of Heidelberg. This move gave the brewery more room to operate, yet, it still allowed for central operation within its main market areas.
The major component of the effluent comes from the regeneration of the brewing water treatment and, from the CIP (Clean in Place) generator. The CIP purification comprises cleaning effluents from the brew containers, the fermentation and yeast tanks, piping and a filtration generator. The generator uses 2 % sodium hydroxide solution with additives and detergents for the clean in place. The regeneration effluents from the brewing water treatment include hydrochloric acid. The regeneration water along with pre-rinsing and rinse water and the production outlet make up the effluent that is treated at the neutralization generator. The specific effluent flow rate can reach up to 2,640 gph (10 m³/h).
Neutralization generator
The task of the neutralization generator is to stabilize the pH value of the effluents that reach the neutralization inlet at about a ph level between 2 and 12. The objective is that the pH range before disposal is between pH 6.5 to 9.5.
The influent waste to the neutralization system is first mixed in a 529 ft³ (15 m³) stainless steel advanced stabilization tank. In that way, some natural pH adjustment takes place by balancing the acidic and alkaline influents. Once the pH is stabilized, the pH of the tank contents can still vary between pH 4 and pH 12.
From the advanced stabilization tank, an outlet overflow at the 247 ft³ (7 m³) fill level allows flow to the actual neutralization tank. The tank is made of polypropylene and has a total volume of 70 ft³ (2m³). If the advance stabilization tank is not filled sufficiently to the outlet level, the tank can be emptied via progressive cavity pump that flows at 2,113 gph (8m³/h) to the neutralization tank. A high-speed stirrer provides the homogeneous mixing of the dosed neutralization reagents to the contents of the neutralization tank. The decrease of pH is attained with concentrated nitric acid (53 %), or alternatively, a pH increase is a result of addition of 15% sodium hydroxide solution.
PH value measurement is controlled in the homogenous mixing zone of the neutralization tank. The measuring value is transmitted to a controller with PID control function that is installed at site. The limit values of the pH control are situated between pH 6.8 and pH 9.2 There is a second pH and temperature measuring point monitoring the proper operation of the neutralization system. All measuring signals and operation status are transmitted to the central control room of the brewery.
In case of extreme pH values or given high effluent flow rates, the integrated volume flow control constitutes an additional safety step for the proper neutralization. In critical cases, the flow regulation from the advance stabilization tank can be controlled.
In order to provide the best design, reliability and accountability, the brewery decided to give the contract for the neutralization system to one manufacturer, which was ProMinent Fluid Controls.
Critical to Operation is the Sensor
The sensor used for pH adjustment and control is a pH electrode type PHEX 112 SE. It can be used in a measuring range between pH 1 and pH 12 up to a temperature of 212 ° F (100 ° C) and a maximum pressure of 87 psig (6 bar). The electrode has a large surface ring diaphragm and a gel electrolyte. Thus, this electrode has a very long operating life even when used for polluted effluents. In addition, since the distance from the sensor to the controller was greater than 50 m, a plug-in measuring transducer PHV1 transforms the primary voltage signal into the 4-20mA standard signal was used. This ensured the signal integrity over longer distances and protected the signal from electrical interference.
Controller
The control device type D1Ca applied in the control circuit enables the following functions:
- processing, display and analysis of the 4-20 mA standard signal
- PID control device
- control of two metering pumps
- programming of one alarm and two limit value relays
- 2 free programmable 4-20mA standard signal outputs
- control input “pause” for engaging/disconnecting the entire control
- connection of a further D1Ca device (see final pH control)
Metering pumps
The neutralization reagents (53% nitric acid and 15% sodium hydroxide solution) and therefore the selection of the metering pump liquid end material was extremely important. For exact and maintenance-free continuous dosing, diaphragm metering pumps type Beta 4 and Beta 5 are used with special material for liquid end and seal material. Both pumps are equipped with an automatic degassing of the chemicals. The pumps were also supplied with a no-chemical-flow dosing alarm, variable length suction lances that are equipped with a two-stage level switch (PVDF). These provide the brewery with information on low and empty chemical containers so that replacement chemicals are provided when needed. This again ensures the operation of the system is continuous.
Final pH control
The measuring station for the final pH control consists of the pH electrode PHEX 112SE and a Pt100 temperature sensor. This is important because of the varying temperatures of the effluent effect the pH ready and temperature compensation is essential for good operation.
Summary
To operate a complex neutralization system with varying flow and varying influent character, an ideal control circuit is necessary. The correct equipment and execution of the project is as important for reliable and maintenance-free operation as is the high quality of the components itself is. The customer benefit is always the primary objective, as it was for the Heidelberg Schlossquell Brewery.