How to reduce solvent loss
Thread Content
I’m seeking help from experts: I am working on a Lean Six Sigma project at an oil-based coatings factory. Our factory experiences significant solvent losses every month; over the course of a year, the total amount lost amounts to more than 600 tons. It accounts for 0.7% of the total amount of raw materials used; therefore, the company assigned me this project with the goal of reducing solvent losses. Since I have been working mainly with water-based coatings in the past, they contain very little volatile solvents. Regarding the area I am working with now, I’m not sure how to make improvements to reduce its losses. First: I will explain the basic details of this project. The scope of this project relates only to the storage tanks in our factory used for holding solvents. During monthly inventory checks, the pressure detected by pressure sensors is transmitted to a computer, and the readings displayed on the computer – obtained by multiplying the pressure value by predetermined coefficients to convert it into kilograms – are used as the basis for the inventory count. In fact, we are aware that these pressure sensors are the least accurate, but at present no other instruments that can more precisely determine the actual quantity of substances in the storage tanks are installed; this is one aspect we are aware of ； Another aspect is volatilization. But we don’t know yet whether there are any other factors that could affect this loss. Could the experts share some of their professional knowledge and experience? ?
To reduce solvent consumption, solutions must be found at the process and management levels. Moreover, the inventory counts at the end of each month must be accurate in order to reflect the actual process consumption accurately. The measurement methods used for tanks should be reliable and precise. For materials with high volatility, flame arresters should be installed on the vent openings or water seals should be used; these materials should be stored at low temperatures as much as possible, and the tanks should be insulated.
2# dongzhuli1999 Yes: We already know that this inventory count is inaccurate. Although it’s not possible to determine the exact true value of the items at the time of the inventory count, we do know that, within a 0.7% margin of error, the loss due to pressure sensors accounts for 0.1% of that total.
It shouldn’t be you who is responsible for reducing the unit consumption; it should be the people in the production department who come up with solutions for improvement. Calculating the weight inside the tank by multiplying the values measured by pressure sensors by a certain coefficient is a feasible approach and quite good indeed. It’s advisable to verify this coefficient; if it can be validated, the measurement of solvent consumption per month will be more accurate, which is of great importance for production management.
4# jukejuke: In fact, most of the team members working on this project are supervisors in production workshops or professionals, but no one can come up with any good methods for controlling volatilization. That’s exactly why I’ve come up to ask everyone for help.
This post was last edited by jothan on 2010-1-7 at 18:20. A consumption of 600 tons does indeed seem a bit incredible. Solvent evaporation does exist, but it is not insolvable. 1) Please identify the main sources of solvent loss; I personally do not think that metering is the cause of such losses. Vapor loss from the storage tank? Volatilization losses during the production process? 2) Address the main causes of the loss. Volatile losses from storage tanks are relatively easy to address; if this is the cause, I can offer some suggestions: use an internal floating roof tank with a nitrogen seal, which is both safe and effective in solving the problem. If there are problems in the production process, you’ll have to find solutions on your own.
6# jothan Moderator: Thank you very much for your suggestion. We also agree that measurement error is not the main factor. Therefore: Our next step is to hire a professional to test the volatility of each solvent under dynamic, static conditions, as well as at different temperatures. Additionally: the loss value here does not include losses that occur during the production process; that value is higher than this one. Reach 1.0% KNX.
7# Nicole_wei is not quite sure how your storage tanks prevent vaporization at the moment; if the existing tanks lack such protection, installing a nitrogen blanket can reduce vaporization by at least 70%.
In fact, the error of pressure sensors doesn’t make any sense when considered over a long period of time such as \"one year\". I believe that devices like return water seals in storage tanks are sufficient; the main issue lies in losses during production – a small mistake, multiplied by the number of batches produced, can result in a significant figure.
8# jothan Thank you very much for the valuable advice from the moderator; I will discuss with our team members and colleagues in the mechanical and electrical department to find ways to reduce vaporization from the storage tanks. Currently, tank evaporation occurs in both dynamic and static forms; in the dynamic case, the air currents generated inside the tank as the solvent is fed in are expelled through vents. I believe this constitutes an important part of tank evaporation, and the moderator’s opinion has been of great help to us.
Another point is that the coefficient in the inventory calculation should be temperature-dependent; different coefficients are required at various temperatures. Furthermore, the monthly consumption per unit should also be related to the local temperature. In some processes, temperature has an impact on losses.