Seeking advice on plant ventilation + RTO issues
Thread Content
I would like to ask for some advice. We are planning to install an RTO system to handle waste gas, specifically the gas collected in exhaust hoods installed at the loading and unloading points of the production lines within enclosed factories, as well as the unorganized waste gas present throughout the factory. I have a question: how is the air volume or wind speed determined in this case? What is the basis for this?
Determined based on the number of air changes in the confined space
It depends on your financial resources and operating costs. If all unorganized emissions and plant ventilation are connected to an RTO, the air flow rate will need to be at least 100,000 cubic meters per hour; the investment cost will be around 8 to 10 million yuan. The concentration of waste gases will be quite low, and the cost of natural gas per hour will be at least 400 to 1,000 yuan. It is necessary to carefully separate waste gases with low and high concentrations: those with low concentration are adsorbed and concentrated before being sent to the RTO, while those with high concentration go directly to the RTO, and so on.
Hello, thank you for the reply. That’s the current thinking: high-concentration gases are sent directly to the RTO, while low-concentration gases are concentrated using a zeolite wheel before being sent to the RTO. The issue now is related to the volume of air flow. I’ve consulted several RTO suppliers, and the settings for the RTO at the back end have been roughly determined in this way; however, it’s difficult to determine the volume of air required for ventilation in the factory building as well as for other uncontrolled emissions. If the gas collection at the front end isn’t proper, that will also be a major problem
Consider the equipment size, the size of the factory, and the estimated capital investment. And what level of management effectiveness is required on-site.
According to the GB50019-2015 Code for Design of Heating, Ventilation and Air Conditioning in Industrial Buildings, when the height of a workshop is greater than 6 meters, the air exchange rate is calculated at 6 m3/(h·m2); this results in a required air exchange volume of 7134 cubic meters per hour. This air needs to be treated after being concentrated to low concentrations. There is also air with high concentrations collected by exhaust hoods installed on things such as the vent valves of reaction vessels. As for the exhaust hoods used at areas where packaging or unloading takes place, what volume of air is required there?
Are you going to do it yourself, or have the manufacturer do it?
Find a design firm to provide you with consultation
{:3_54:} We use variable-frequency fans. For exhaust ventilation in your case, it’s possible to separate the systems: use a large fan for rooms, work areas, and areas where air needs to be released; for areas with strong odors resulting from unloading, use a separate fan. You can determine the appropriate size of these fans on your own – just set the frequency accordingly. The key factors are the processing capacity of your RTO unit as well as the way in which gases are collected. As long as you seal off areas with strong odors, reduce the number of intake and exhaust openings, and ensure that these odor-causing areas are along the same airflow path, a moderate volume of air flow will suffice. What’s important is proper sealing – a few hundred cubic feet per hour is enough
{:3_65:} Another thing is to minimize the points where leaks can occur; by controlling the pressure at the inlet and outlet of the fan, it’s possible to prevent a lot of material from being carried away through the vents