How long does it take in general for business visa these days? Where to submit application?

Hi,
We need to send one of our technical persons to Tianjin, China for an inspection of steel items being produced for a hydropower project. The Chinese factory will send us the invitation letter please. We seek your guidance in finding out where to submit the visa application (online or physically to the embassy) and how long does it take to issue the business Visa please?
Thank you.