Today ’ s modern breweries must not only produce a popular refreshing product , but they also must continuously reduce costs and their carbon footprint by tightly controlling natural gas usage , residual CO2 levels and mixed waste gases .
Figure 2
Figure 3 reactive gas and toxic pollutant . NOx often appears as a brownish gas ( remember smog ). It is a strong oxidizing agent and plays a major role in the atmospheric reactions with volatile organic compounds ( VOC ) that produce ozone on hot summer days .
# 2 Effects of Gas Composition
Natural gas composition ( Fig 3 ) differs somewhat around the world , as well as seasonally in very cold winters and hot , humid summer conditions . The primary energy components of natural gas are methane , ethane , propane , butane and condensates . The non-energy components are nitrogen , carbon dioxide , hydrogen sulfide and helium .
The mix of these components can affect gas density , the calorific value and then in turn plant instrumentation . Some thermal flow instruments , however , are available with multiple calibration groups , which can automatically switch seasonally or any time as inline gas analyzers indicate changes in the gas mixture to assure the proper air / gas ratio is maintained for heating efficiency .
# 3 Process Variability--Turndown Range
Brewery and other food or pharmaceutical batch processes often operate at variable levels of production , which means the amounts of natural gas required for heating are also variable . Some of the reasons include processing multiple products on the same line , seasonal demand , wash-down cycles , planned maintenance , shift changes , etc .
For the most accurate gas and air flow measurement , a laboratory-like steadystate flow is generally the easiest to measure . That ’ s why in the real plant world it is important to understand the potential full flow range of the gas to be measured , also known as turndown range — from the lowest to highest flows and if the flow measurement accuracy expected will be available over the entire flow range ( Fig 4 ).
# 4 Flow Meter Accuracy & Repeatability
In order to achieve the desired flow measurement accuracy level with confidence , the process or plant engineer must define the required process flow range , the desired flow measurement accuracy and the expected turndown ratio . For example , some processes require a rapid start-up with initially fast heating and then revert to a much lower steady-state or standby function in between batches . The speed of these changes in gas flow can affect measurement accuracy .
The major natural gas flow meter technologies available ( coriolis , differential pressure , thermal , ultrasonic , vortex ) all vary in specified accuracy from ± 0.5 % and up depending on their turndown ranges from 1,000:1 to 8:1 ( depending on sensing technology ). For natural gas heating , thermal flow sensing offers the advantages of a broad flow range , wide turndowns and accuracy to ± 0.75 %).
Solutions for Brewers
For the San Diego County brewer and others concerned about natural gas cost control and waste gas emission levels , the ST75 Series Flow Meter from Fluid Components Internal ( FCI ) was a simpleto-make decision ( Fig 5 ). It optimizes their complex fermentation tank steam heating
FDPP - www . fdpp . co . uk 5