Add Products to the Cart to Obtain Instant Discounts!

Fundamental Economic Justification for Boiler Blowdown Automatic Control

May 22, 2017 0 Comments

Fundamental Economic Justification for Boiler Blowdown Automatic Control

Minimize Boiler Blowdown

Minimizing your blowdown rate can substantially reduce energy losses, as the temperature of the blown-down liquid is the same as that of the steam generated in the boiler. Minimizing blowdown will also reduce makeup water and chemical treatment costs.

As water evaporates in the boiler steam drum, solids present in the feedwater are left behind. The suspended solids form sludge or sediments in the boiler, which degrades heat transfer. Dissolved solids promote foaming and carryover of boiler water into the steam. To reduce the levels of suspended and total dissolved solids (TDS) to acceptable limits, water is periodically discharged or blown down from the boiler. Mud or bottom blowdown is usually a manual procedure done for a few seconds on intervals of several hours. It is designed to remove suspended solids that settle out of the boiler water and form a heavy sludge. Surface or skimming blowdown is designed to remove the dissolved solids that concentrate near the liquid surface. Surface blowdown is often a continuous process.

Insufficient blowdown may lead to carryover of boiler water into the steam, or the formation of deposits. Excessive blowdown will waste energy, water, and chemicals. The optimum blowdown rate is determined by various factors including the boiler type, operating pressure, water treatment, and quality of makeup water. Blowdown rates typically range from 4% to 8% of boiler feedwater flow rate, but can be as high as 10% when makeup water has a high solids content.

Example

Assume that the installation of an automatic blowdown control system (see page 2) reduces your blowdown rate from 8% to 6%. This example assumes a continuously operating natural gas-fired, 150-psig, 100,000-pound-per-hour (lb/hr) steam boiler. Assume a makeup water temperature of 60°F, boiler efficiency of 80%, with fuel valued at $8.00 per million Btu ($8.00/MMBtu), and the total water, sewage, and treatment costs at $0.004 per gallon. Calculate the total annual cost savings.

Suggested Action

Review your blowdown practices to identify energy-saving opportunities.

Examine operating practices for boiler feedwater and blowdown rates developed by the American Society of Mechanical Engineers (ASME). Considerations include operating pressure, steam purity, and deposition control.

Consider an automatic blowdown control system

Example

Assume that the installation of an automatic blowdown control system (see page 2) reduces your blowdown rate from 8% to 6%. This example assumes a continuously operating natural gas-fired, 150-psig, 100,000-pound-per-hour (lb/hr) steam boiler. Assume a makeup water temperature of 60°F, boiler efficiency of 80%, with fuel valued at $8.00 per million Btu ($8.00/MMBtu), and the total water, sewage, and treatment costs at $0.004 per gallon. Calculate the total annual cost savings.

 

 

Automatic Blowdown Control Systems

These systems optimize surface blowdown by regulating water volume dis-charged in relation to amount of dissolved solids present. Conductivity, TDS, silica or chlorides concentrations, and/or alkalinity are reliable indicators of salts and other contaminants dissolved in boiler water. A probe provides feedback to a controller driving a modulating blowdown valve. An alternative is proportional control – with the blowdown rate set proportional to the makeup water flow.

 

Cycles of Concentration

“Cycles of concentration” refers to the accumulation of impurities in the boiler water. If the boiler water contains 10 times the level of impurities in the makeup water, it is said to have 10 cycles of concentration.

 


Also in Blog

Revolutionizing Water Analysis: Everything You Need to Know About the Kemio KEM10DIS
Revolutionizing Water Analysis: Everything You Need to Know About the Kemio KEM10DIS

April 19, 2023 0 Comments

The Palintest Kemio KEM10DIS is a highly accurate, fast, and easy-to-use water analysis device that offers several advantages over other methods. Its portability and wide measurement range make it ideal for use in a range of applications, from drinking water to industrial process water. With its patented Dual-Field technology and fast results, the Palintest Kemio KEM10DIS can help to improve the efficiency of water treatment processes and reduce the risk of contamination. Compared to other methods, the device is highly accurate and easy to use, making it accessible to a wide range of users. By following the simple procedure outlined above, users can quickly and easily obtain accurate results for a range of parameters, helping to ensure the safety and quality of water for various applications.

View full article →

Optimizing Cooling Tower Performance with Conductivity Controllers
Optimizing Cooling Tower Performance with Conductivity Controllers

April 17, 2023 0 Comments

Cooling towers play a critical role in industrial processes, but issues such as scaling, corrosion, and microbiological growth can cause reduced efficiency, increased maintenance costs, and even equipment failure. Fortunately, conductivity controllers like the Lakewood Instruments 1575e can help optimize cooling tower performance. A case study found that after installing the controller, a manufacturing facility was able to significantly improve the tower's performance by reducing water consumption by over 20% and saving over $10,000 per year on chemical usage. Additionally, the facility was able to reduce its environmental footprint. Overall, conductivity controllers are a worthwhile investment for any facility with a cooling tower, as they can lead to significant cost savings and environmental benefits.

View full article →

Cooling tower
Avoid this issues when starting a cooling tower

March 20, 2023 0 Comments

Conductivity controllers are critical devices in cooling tower systems, but they can develop issues when the tower has been dry for several months.

View full article →