Where is the passport office in Tanggu District, Tianjin?

Go to the exit-entry administration. There is one in each district. I suggest you make an appointment in official website, the entry-exit hall of your city. You will be asked to fill in a form with the date you can handle it within one month (holidays are definitely not allowed), and another column will let you choose the location of your account or the jurisdiction where you live. You will choose the nearest jurisdiction, and the specific address will be displayed after submission. Then follow the appointment time, be sure to bring your ID card, household registration book, photo+photo receipt, money or bank card.